gopls/internal/doc/generate: convert Analyzer.Doc to Markdown
The format of Analyzer.Doc fields is not specified, but in
practice all of gopls' analyzers (from x/tools and staticcheck)
use go/doc/comment form. Although this is similar to a subset
of Markdown, strictly it should be passed through the
comment.{Parser,Printer} machinery, for example to quote
Markdown metacharacters (*, [, etc) when they do not have
special meanings in the go/doc/comment subset.
This change adds this step to the doc generator.
A consequence is that ##, when used as a subheading in a
Go doc comment, will be escaped so that it appears literally.
This makes the rendering of analyzers.md consistent with
pkg.go.dev and gopls' internal doc viewer.
Unlike Markdown, Go doc comments have no concept of
subheadings (at least today), yet there are occasions
when a subheading is warranted, such as the docs for
internal/gofix. The meaning of a literal ## is clear enough,
even though it won't render as a heading nor appear in the ToC.
(Staticcheck's SA9004 analyzer also uses subheadings in its
doc string literal, but of the pre-go1.19 legacy variety.
However, internal/gofix cannot use this approach because,
in a doc comment, gofmt will helpfully convert it to a #
heading. Consequently, staticcheck gets to add subheadings
in the ToC, but our own analyzers do not.)
The output was verified in go doc, go doc -http (pkgsite),
and analyzers.md as rendered by go.dev/gopls/analyzers.
We should probably specify the form of Analyzer.Doc comments
more precisely.
Fixes golang/go#75199
Change-Id: I44f3e0fad9cdd5bdc77b34fa23147f4e0dce8a09
Reviewed-on: https://go-review.googlesource.com/c/tools/+/704735
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
diff --git a/gopls/doc/analyzers.md b/gopls/doc/analyzers.md
index 60c5bed..0adeaa9 100644
--- a/gopls/doc/analyzers.md
+++ b/gopls/doc/analyzers.md
@@ -42,9 +42,9 @@
<a id='QF1001'></a>
## `QF1001`: Apply De Morgan's law
-
Available since
- 2021.1
+
+ 2021.1
Default: off. Enable by setting `"analyses": {"QF1001": true}`.
@@ -54,34 +54,33 @@
<a id='QF1002'></a>
## `QF1002`: Convert untagged switch to tagged switch
-
-An untagged switch that compares a single variable against a series of
-values can be replaced with a tagged switch.
+An untagged switch that compares a single variable against a series of values can be replaced with a tagged switch.
Before:
- switch {
- case x == 1 || x == 2, x == 3:
- ...
- case x == 4:
- ...
- default:
- ...
- }
+ switch {
+ case x == 1 || x == 2, x == 3:
+ ...
+ case x == 4:
+ ...
+ default:
+ ...
+ }
After:
- switch x {
- case 1, 2, 3:
- ...
- case 4:
- ...
- default:
- ...
- }
+ switch x {
+ case 1, 2, 3:
+ ...
+ case 4:
+ ...
+ default:
+ ...
+ }
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -91,33 +90,32 @@
<a id='QF1003'></a>
## `QF1003`: Convert if/else-if chain to tagged switch
-
-A series of if/else-if checks comparing the same variable against
-values can be replaced with a tagged switch.
+A series of if/else-if checks comparing the same variable against values can be replaced with a tagged switch.
Before:
- if x == 1 || x == 2 {
- ...
- } else if x == 3 {
- ...
- } else {
- ...
- }
+ if x == 1 || x == 2 {
+ ...
+ } else if x == 3 {
+ ...
+ } else {
+ ...
+ }
After:
- switch x {
- case 1, 2:
- ...
- case 3:
- ...
- default:
- ...
- }
+ switch x {
+ case 1, 2:
+ ...
+ case 3:
+ ...
+ default:
+ ...
+ }
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -127,9 +125,9 @@
<a id='QF1004'></a>
## `QF1004`: Use strings.ReplaceAll instead of strings.Replace with n == -1
-
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -139,19 +137,19 @@
<a id='QF1005'></a>
## `QF1005`: Expand call to math.Pow
-
Some uses of math.Pow can be simplified to basic multiplication.
Before:
- math.Pow(x, 2)
+ math.Pow(x, 2)
After:
- x * x
+ x * x
Available since
- 2021.1
+
+ 2021.1
Default: off. Enable by setting `"analyses": {"QF1005": true}`.
@@ -161,24 +159,24 @@
<a id='QF1006'></a>
## `QF1006`: Lift if+break into loop condition
-
Before:
- for {
- if done {
- break
- }
- ...
- }
+ for {
+ if done {
+ break
+ }
+ ...
+ }
After:
- for !done {
- ...
- }
+ for !done {
+ ...
+ }
Available since
- 2021.1
+
+ 2021.1
Default: off. Enable by setting `"analyses": {"QF1006": true}`.
@@ -188,20 +186,20 @@
<a id='QF1007'></a>
## `QF1007`: Merge conditional assignment into variable declaration
-
Before:
- x := false
- if someCondition {
- x = true
- }
+ x := false
+ if someCondition {
+ x = true
+ }
After:
- x := someCondition
+ x := someCondition
Available since
- 2021.1
+
+ 2021.1
Default: off. Enable by setting `"analyses": {"QF1007": true}`.
@@ -211,9 +209,9 @@
<a id='QF1008'></a>
## `QF1008`: Omit embedded fields from selector expression
-
Available since
- 2021.1
+
+ 2021.1
Default: off. Enable by setting `"analyses": {"QF1008": true}`.
@@ -223,9 +221,9 @@
<a id='QF1009'></a>
## `QF1009`: Use time.Time.Equal instead of == operator
-
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -235,9 +233,9 @@
<a id='QF1010'></a>
## `QF1010`: Convert slice of bytes to string when printing it
-
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -247,9 +245,9 @@
<a id='QF1011'></a>
## `QF1011`: Omit redundant type from variable declaration
-
Available since
- 2021.1
+
+ 2021.1
Default: off. Enable by setting `"analyses": {"QF1011": true}`.
@@ -259,9 +257,9 @@
<a id='QF1012'></a>
## `QF1012`: Use fmt.Fprintf(x, ...) instead of x.Write(fmt.Sprintf(...))
-
Available since
- 2022.1
+
+ 2022.1
Default: on.
@@ -271,24 +269,23 @@
<a id='S1000'></a>
## `S1000`: Use plain channel send or receive instead of single-case select
-
-Select statements with a single case can be replaced with a simple
-send or receive.
+Select statements with a single case can be replaced with a simple send or receive.
Before:
- select {
- case x := <-ch:
- fmt.Println(x)
- }
+ select {
+ case x := <-ch:
+ fmt.Println(x)
+ }
After:
- x := <-ch
- fmt.Println(x)
+ x := <-ch
+ fmt.Println(x)
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -298,22 +295,21 @@
<a id='S1001'></a>
## `S1001`: Replace for loop with call to copy
-
-Use copy() for copying elements from one slice to another. For
-arrays of identical size, you can use simple assignment.
+Use copy() for copying elements from one slice to another. For arrays of identical size, you can use simple assignment.
Before:
- for i, x := range src {
- dst[i] = x
- }
+ for i, x := range src {
+ dst[i] = x
+ }
After:
- copy(dst, src)
+ copy(dst, src)
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -323,17 +319,17 @@
<a id='S1002'></a>
## `S1002`: Omit comparison with boolean constant
-
Before:
- if x == true {}
+ if x == true {}
After:
- if x {}
+ if x {}
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"S1002": true}`.
@@ -343,17 +339,17 @@
<a id='S1003'></a>
## `S1003`: Replace call to strings.Index with strings.Contains
-
Before:
- if strings.Index(x, y) != -1 {}
+ if strings.Index(x, y) != -1 {}
After:
- if strings.Contains(x, y) {}
+ if strings.Contains(x, y) {}
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -363,17 +359,17 @@
<a id='S1004'></a>
## `S1004`: Replace call to bytes.Compare with bytes.Equal
-
Before:
- if bytes.Compare(x, y) == 0 {}
+ if bytes.Compare(x, y) == 0 {}
After:
- if bytes.Equal(x, y) {}
+ if bytes.Equal(x, y) {}
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -383,23 +379,23 @@
<a id='S1005'></a>
## `S1005`: Drop unnecessary use of the blank identifier
-
In many cases, assigning to the blank identifier is unnecessary.
Before:
- for _ = range s {}
- x, _ = someMap[key]
- _ = <-ch
+ for _ = range s {}
+ x, _ = someMap[key]
+ _ = <-ch
After:
- for range s{}
- x = someMap[key]
- <-ch
+ for range s{}
+ x = someMap[key]
+ <-ch
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"S1005": true}`.
@@ -409,11 +405,11 @@
<a id='S1006'></a>
## `S1006`: Use 'for { ... }' for infinite loops
-
For infinite loops, using for { ... } is the most idiomatic choice.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"S1006": true}`.
@@ -423,24 +419,21 @@
<a id='S1007'></a>
## `S1007`: Simplify regular expression by using raw string literal
+Raw string literals use backticks instead of quotation marks and do not support any escape sequences. This means that the backslash can be used freely, without the need of escaping.
-Raw string literals use backticks instead of quotation marks and do not support
-any escape sequences. This means that the backslash can be used
-freely, without the need of escaping.
-
-Since regular expressions have their own escape sequences, raw strings
-can improve their readability.
+Since regular expressions have their own escape sequences, raw strings can improve their readability.
Before:
- regexp.Compile("\\A(\\w+) profile: total \\d+\\n\\z")
+ regexp.Compile("\\A(\\w+) profile: total \\d+\\n\\z")
After:
- regexp.Compile(`\A(\w+) profile: total \d+\n\z`)
+ regexp.Compile(`\A(\w+) profile: total \d+\n\z`)
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -450,20 +443,20 @@
<a id='S1008'></a>
## `S1008`: Simplify returning boolean expression
-
Before:
- if <expr> {
- return true
- }
- return false
+ if <expr> {
+ return true
+ }
+ return false
After:
- return <expr>
+ return <expr>
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"S1008": true}`.
@@ -473,21 +466,19 @@
<a id='S1009'></a>
## `S1009`: Omit redundant nil check on slices, maps, and channels
-
-The len function is defined for all slices, maps, and
-channels, even nil ones, which have a length of zero. It is not necessary to
-check for nil before checking that their length is not zero.
+The len function is defined for all slices, maps, and channels, even nil ones, which have a length of zero. It is not necessary to check for nil before checking that their length is not zero.
Before:
- if x != nil && len(x) != 0 {}
+ if x != nil && len(x) != 0 {}
After:
- if len(x) != 0 {}
+ if len(x) != 0 {}
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -497,12 +488,11 @@
<a id='S1010'></a>
## `S1010`: Omit default slice index
-
-When slicing, the second index defaults to the length of the value,
-making s[n:len(s)] and s[n:] equivalent.
+When slicing, the second index defaults to the length of the value, making s\[n:len(s)] and s\[n:] equivalent.
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -512,30 +502,30 @@
<a id='S1011'></a>
## `S1011`: Use a single append to concatenate two slices
-
Before:
- for _, e := range y {
- x = append(x, e)
- }
-
- for i := range y {
- x = append(x, y[i])
- }
-
- for i := range y {
- v := y[i]
- x = append(x, v)
- }
+ for _, e := range y {
+ x = append(x, e)
+ }
+
+ for i := range y {
+ x = append(x, y[i])
+ }
+
+ for i := range y {
+ v := y[i]
+ x = append(x, v)
+ }
After:
- x = append(x, y...)
- x = append(x, y...)
- x = append(x, y...)
+ x = append(x, y...)
+ x = append(x, y...)
+ x = append(x, y...)
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"S1011": true}`.
@@ -545,20 +535,19 @@
<a id='S1012'></a>
## `S1012`: Replace time.Now().Sub(x) with time.Since(x)
-
-The time.Since helper has the same effect as using time.Now().Sub(x)
-but is easier to read.
+The time.Since helper has the same effect as using time.Now().Sub(x) but is easier to read.
Before:
- time.Now().Sub(x)
+ time.Now().Sub(x)
After:
- time.Since(x)
+ time.Since(x)
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -568,28 +557,24 @@
<a id='S1016'></a>
## `S1016`: Use a type conversion instead of manually copying struct fields
-
-Two struct types with identical fields can be converted between each
-other. In older versions of Go, the fields had to have identical
-struct tags. Since Go 1.8, however, struct tags are ignored during
-conversions. It is thus not necessary to manually copy every field
-individually.
+Two struct types with identical fields can be converted between each other. In older versions of Go, the fields had to have identical struct tags. Since Go 1.8, however, struct tags are ignored during conversions. It is thus not necessary to manually copy every field individually.
Before:
- var x T1
- y := T2{
- Field1: x.Field1,
- Field2: x.Field2,
- }
+ var x T1
+ y := T2{
+ Field1: x.Field1,
+ Field2: x.Field2,
+ }
After:
- var x T1
- y := T2(x)
+ var x T1
+ y := T2(x)
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"S1016": true}`.
@@ -599,25 +584,21 @@
<a id='S1017'></a>
## `S1017`: Replace manual trimming with strings.TrimPrefix
-
-Instead of using strings.HasPrefix and manual slicing, use the
-strings.TrimPrefix function. If the string doesn't start with the
-prefix, the original string will be returned. Using strings.TrimPrefix
-reduces complexity, and avoids common bugs, such as off-by-one
-mistakes.
+Instead of using strings.HasPrefix and manual slicing, use the strings.TrimPrefix function. If the string doesn't start with the prefix, the original string will be returned. Using strings.TrimPrefix reduces complexity, and avoids common bugs, such as off-by-one mistakes.
Before:
- if strings.HasPrefix(str, prefix) {
- str = str[len(prefix):]
- }
+ if strings.HasPrefix(str, prefix) {
+ str = str[len(prefix):]
+ }
After:
- str = strings.TrimPrefix(str, prefix)
+ str = strings.TrimPrefix(str, prefix)
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -627,23 +608,21 @@
<a id='S1018'></a>
## `S1018`: Use 'copy' for sliding elements
-
-copy() permits using the same source and destination slice, even with
-overlapping ranges. This makes it ideal for sliding elements in a
-slice.
+copy() permits using the same source and destination slice, even with overlapping ranges. This makes it ideal for sliding elements in a slice.
Before:
- for i := 0; i < n; i++ {
- bs[i] = bs[offset+i]
- }
+ for i := 0; i < n; i++ {
+ bs[i] = bs[offset+i]
+ }
After:
- copy(bs[:n], bs[offset:])
+ copy(bs[:n], bs[offset:])
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -653,13 +632,11 @@
<a id='S1019'></a>
## `S1019`: Simplify 'make' call by omitting redundant arguments
-
-The 'make' function has default values for the length and capacity
-arguments. For channels, the length defaults to zero, and for slices,
-the capacity defaults to the length.
+The 'make' function has default values for the length and capacity arguments. For channels, the length defaults to zero, and for slices, the capacity defaults to the length.
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -669,17 +646,17 @@
<a id='S1020'></a>
## `S1020`: Omit redundant nil check in type assertion
-
Before:
- if _, ok := i.(T); ok && i != nil {}
+ if _, ok := i.(T); ok && i != nil {}
After:
- if _, ok := i.(T); ok {}
+ if _, ok := i.(T); ok {}
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -689,18 +666,18 @@
<a id='S1021'></a>
## `S1021`: Merge variable declaration and assignment
-
Before:
- var x uint
- x = 1
+ var x uint
+ x = 1
After:
- var x uint = 1
+ var x uint = 1
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"S1021": true}`.
@@ -710,16 +687,13 @@
<a id='S1023'></a>
## `S1023`: Omit redundant control flow
+Functions that have no return value do not need a return statement as the final statement of the function.
-Functions that have no return value do not need a return statement as
-the final statement of the function.
-
-Switches in Go do not have automatic fallthrough, unlike languages
-like C. It is not necessary to have a break statement as the final
-statement in a case block.
+Switches in Go do not have automatic fallthrough, unlike languages like C. It is not necessary to have a break statement as the final statement in a case block.
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -729,20 +703,19 @@
<a id='S1024'></a>
## `S1024`: Replace x.Sub(time.Now()) with time.Until(x)
-
-The time.Until helper has the same effect as using x.Sub(time.Now())
-but is easier to read.
+The time.Until helper has the same effect as using x.Sub(time.Now()) but is easier to read.
Before:
- x.Sub(time.Now())
+ x.Sub(time.Now())
After:
- time.Until(x)
+ time.Until(x)
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -752,37 +725,34 @@
<a id='S1025'></a>
## `S1025`: Don't use fmt.Sprintf("%s", x) unnecessarily
-
-In many instances, there are easier and more efficient ways of getting
-a value's string representation. Whenever a value's underlying type is
-a string already, or the type has a String method, they should be used
-directly.
+In many instances, there are easier and more efficient ways of getting a value's string representation. Whenever a value's underlying type is a string already, or the type has a String method, they should be used directly.
Given the following shared definitions
- type T1 string
- type T2 int
+ type T1 string
+ type T2 int
- func (T2) String() string { return "Hello, world" }
+ func (T2) String() string { return "Hello, world" }
- var x string
- var y T1
- var z T2
+ var x string
+ var y T1
+ var z T2
we can simplify
- fmt.Sprintf("%s", x)
- fmt.Sprintf("%s", y)
- fmt.Sprintf("%s", z)
+ fmt.Sprintf("%s", x)
+ fmt.Sprintf("%s", y)
+ fmt.Sprintf("%s", z)
to
- x
- string(y)
- z.String()
+ x
+ string(y)
+ z.String()
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"S1025": true}`.
@@ -792,17 +762,17 @@
<a id='S1028'></a>
## `S1028`: Simplify error construction with fmt.Errorf
-
Before:
- errors.New(fmt.Sprintf(...))
+ errors.New(fmt.Sprintf(...))
After:
- fmt.Errorf(...)
+ fmt.Errorf(...)
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -812,23 +782,19 @@
<a id='S1029'></a>
## `S1029`: Range over the string directly
-
-Ranging over a string will yield byte offsets and runes. If the offset
-isn't used, this is functionally equivalent to converting the string
-to a slice of runes and ranging over that. Ranging directly over the
-string will be more performant, however, as it avoids allocating a new
-slice, the size of which depends on the length of the string.
+Ranging over a string will yield byte offsets and runes. If the offset isn't used, this is functionally equivalent to converting the string to a slice of runes and ranging over that. Ranging directly over the string will be more performant, however, as it avoids allocating a new slice, the size of which depends on the length of the string.
Before:
- for _, r := range []rune(s) {}
+ for _, r := range []rune(s) {}
After:
- for _, r := range s {}
+ for _, r := range s {}
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"S1029": true}`.
@@ -838,16 +804,13 @@
<a id='S1030'></a>
## `S1030`: Use bytes.Buffer.String or bytes.Buffer.Bytes
+bytes.Buffer has both a String and a Bytes method. It is almost never necessary to use string(buf.Bytes()) or \[]byte(buf.String()) – simply use the other method.
-bytes.Buffer has both a String and a Bytes method. It is almost never
-necessary to use string(buf.Bytes()) or []byte(buf.String()) – simply
-use the other method.
-
-The only exception to this are map lookups. Due to a compiler optimization,
-m[string(buf.Bytes())] is more efficient than m[buf.String()].
+The only exception to this are map lookups. Due to a compiler optimization, m\[string(buf.Bytes())] is more efficient than m\[buf.String()].
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -857,27 +820,25 @@
<a id='S1031'></a>
## `S1031`: Omit redundant nil check around loop
-
-You can use range on nil slices and maps, the loop will simply never
-execute. This makes an additional nil check around the loop
-unnecessary.
+You can use range on nil slices and maps, the loop will simply never execute. This makes an additional nil check around the loop unnecessary.
Before:
- if s != nil {
- for _, x := range s {
- ...
- }
- }
+ if s != nil {
+ for _, x := range s {
+ ...
+ }
+ }
After:
- for _, x := range s {
- ...
- }
+ for _, x := range s {
+ ...
+ }
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -887,21 +848,19 @@
<a id='S1032'></a>
## `S1032`: Use sort.Ints(x), sort.Float64s(x), and sort.Strings(x)
-
-The sort.Ints, sort.Float64s and sort.Strings functions are easier to
-read than sort.Sort(sort.IntSlice(x)), sort.Sort(sort.Float64Slice(x))
-and sort.Sort(sort.StringSlice(x)).
+The sort.Ints, sort.Float64s and sort.Strings functions are easier to read than sort.Sort(sort.IntSlice(x)), sort.Sort(sort.Float64Slice(x)) and sort.Sort(sort.StringSlice(x)).
Before:
- sort.Sort(sort.StringSlice(x))
+ sort.Sort(sort.StringSlice(x))
After:
- sort.Strings(x)
+ sort.Strings(x)
Available since
- 2019.1
+
+ 2019.1
Default: on.
@@ -911,11 +870,11 @@
<a id='S1033'></a>
## `S1033`: Unnecessary guard around call to 'delete'
-
Calling delete on a nil map is a no-op.
Available since
- 2019.2
+
+ 2019.2
Default: on.
@@ -925,9 +884,9 @@
<a id='S1034'></a>
## `S1034`: Use result of type assertion to simplify cases
-
Available since
- 2019.2
+
+ 2019.2
Default: on.
@@ -937,12 +896,11 @@
<a id='S1035'></a>
## `S1035`: Redundant call to net/http.CanonicalHeaderKey in method call on net/http.Header
-
-The methods on net/http.Header, namely Add, Del, Get
-and Set, already canonicalize the given header name.
+The methods on net/http.Header, namely Add, Del, Get and Set, already canonicalize the given header name.
Available since
- 2020.1
+
+ 2020.1
Default: on.
@@ -952,37 +910,35 @@
<a id='S1036'></a>
## `S1036`: Unnecessary guard around map access
-
-When accessing a map key that doesn't exist yet, one receives a zero
-value. Often, the zero value is a suitable value, for example when
-using append or doing integer math.
+When accessing a map key that doesn't exist yet, one receives a zero value. Often, the zero value is a suitable value, for example when using append or doing integer math.
The following
- if _, ok := m["foo"]; ok {
- m["foo"] = append(m["foo"], "bar")
- } else {
- m["foo"] = []string{"bar"}
- }
+ if _, ok := m["foo"]; ok {
+ m["foo"] = append(m["foo"], "bar")
+ } else {
+ m["foo"] = []string{"bar"}
+ }
can be simplified to
- m["foo"] = append(m["foo"], "bar")
+ m["foo"] = append(m["foo"], "bar")
and
- if _, ok := m2["k"]; ok {
- m2["k"] += 4
- } else {
- m2["k"] = 4
- }
+ if _, ok := m2["k"]; ok {
+ m2["k"] += 4
+ } else {
+ m2["k"] = 4
+ }
can be simplified to
- m["k"] += 4
+ m["k"] += 4
Available since
- 2020.1
+
+ 2020.1
Default: on.
@@ -992,13 +948,11 @@
<a id='S1037'></a>
## `S1037`: Elaborate way of sleeping
-
-Using a select statement with a single case receiving
-from the result of time.After is a very elaborate way of sleeping that
-can much simpler be expressed with a simple call to time.Sleep.
+Using a select statement with a single case receiving from the result of time.After is a very elaborate way of sleeping that can much simpler be expressed with a simple call to time.Sleep.
Available since
- 2020.1
+
+ 2020.1
Default: on.
@@ -1008,11 +962,11 @@
<a id='S1038'></a>
## `S1038`: Unnecessarily complex way of printing formatted string
-
Instead of using fmt.Print(fmt.Sprintf(...)), one can use fmt.Printf(...).
Available since
- 2020.1
+
+ 2020.1
Default: on.
@@ -1022,12 +976,11 @@
<a id='S1039'></a>
## `S1039`: Unnecessary use of fmt.Sprint
-
-Calling fmt.Sprint with a single string argument is unnecessary
-and identical to using the string directly.
+Calling fmt.Sprint with a single string argument is unnecessary and identical to using the string directly.
Available since
- 2020.1
+
+ 2020.1
Default: on.
@@ -1037,16 +990,11 @@
<a id='S1040'></a>
## `S1040`: Type assertion to current type
-
-The type assertion x.(SomeInterface), when x already has type
-SomeInterface, can only fail if x is nil. Usually, this is
-left-over code from when x had a different type and you can safely
-delete the type assertion. If you want to check that x is not nil,
-consider being explicit and using an actual if x == nil comparison
-instead of relying on the type assertion panicking.
+The type assertion x.(SomeInterface), when x already has type SomeInterface, can only fail if x is nil. Usually, this is left-over code from when x had a different type and you can safely delete the type assertion. If you want to check that x is not nil, consider being explicit and using an actual if x == nil comparison instead of relying on the type assertion panicking.
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -1056,9 +1004,9 @@
<a id='SA1000'></a>
## `SA1000`: Invalid regular expression
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1000": true}`.
@@ -1068,9 +1016,9 @@
<a id='SA1001'></a>
## `SA1001`: Invalid template
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1080,9 +1028,9 @@
<a id='SA1002'></a>
## `SA1002`: Invalid format in time.Parse
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1002": true}`.
@@ -1092,16 +1040,13 @@
<a id='SA1003'></a>
## `SA1003`: Unsupported argument to functions in encoding/binary
-
-The encoding/binary package can only serialize types with known sizes.
-This precludes the use of the int and uint types, as their sizes
-differ on different architectures. Furthermore, it doesn't support
-serializing maps, channels, strings, or functions.
+The encoding/binary package can only serialize types with known sizes. This precludes the use of the int and uint types, as their sizes differ on different architectures. Furthermore, it doesn't support serializing maps, channels, strings, or functions.
Before Go 1.8, bool wasn't supported, either.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1003": true}`.
@@ -1111,22 +1056,15 @@
<a id='SA1004'></a>
## `SA1004`: Suspiciously small untyped constant in time.Sleep
+The time.Sleep function takes a time.Duration as its only argument. Durations are expressed in nanoseconds. Thus, calling time.Sleep(1) will sleep for 1 nanosecond. This is a common source of bugs, as sleep functions in other languages often accept seconds or milliseconds.
-The time.Sleep function takes a time.Duration as its only argument.
-Durations are expressed in nanoseconds. Thus, calling time.Sleep(1)
-will sleep for 1 nanosecond. This is a common source of bugs, as sleep
-functions in other languages often accept seconds or milliseconds.
+The time package provides constants such as time.Second to express large durations. These can be combined with arithmetic to express arbitrary durations, for example 5 \* time.Second for 5 seconds.
-The time package provides constants such as time.Second to express
-large durations. These can be combined with arithmetic to express
-arbitrary durations, for example 5 * time.Second for 5 seconds.
-
-If you truly meant to sleep for a tiny amount of time, use
-n * time.Nanosecond to signal to Staticcheck that you did mean to sleep
-for some amount of nanoseconds.
+If you truly meant to sleep for a tiny amount of time, use n \* time.Nanosecond to signal to Staticcheck that you did mean to sleep for some amount of nanoseconds.
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1136,28 +1074,21 @@
<a id='SA1005'></a>
## `SA1005`: Invalid first argument to exec.Command
+os/exec runs programs directly (using variants of the fork and exec system calls on Unix systems). This shouldn't be confused with running a command in a shell. The shell will allow for features such as input redirection, pipes, and general scripting. The shell is also responsible for splitting the user's input into a program name and its arguments. For example, the equivalent to
-os/exec runs programs directly (using variants of the fork and exec
-system calls on Unix systems). This shouldn't be confused with running
-a command in a shell. The shell will allow for features such as input
-redirection, pipes, and general scripting. The shell is also
-responsible for splitting the user's input into a program name and its
-arguments. For example, the equivalent to
-
- ls / /tmp
+ ls / /tmp
would be
- exec.Command("ls", "/", "/tmp")
+ exec.Command("ls", "/", "/tmp")
-If you want to run a command in a shell, consider using something like
-the following – but be aware that not all systems, particularly
-Windows, will have a /bin/sh program:
+If you want to run a command in a shell, consider using something like the following – but be aware that not all systems, particularly Windows, will have a /bin/sh program:
- exec.Command("/bin/sh", "-c", "ls | grep Awesome")
+ exec.Command("/bin/sh", "-c", "ls | grep Awesome")
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1167,9 +1098,9 @@
<a id='SA1007'></a>
## `SA1007`: Invalid URL in net/url.Parse
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1007": true}`.
@@ -1179,30 +1110,23 @@
<a id='SA1008'></a>
## `SA1008`: Non-canonical key in http.Header map
+Keys in http.Header maps are canonical, meaning they follow a specific combination of uppercase and lowercase letters. Methods such as http.Header.Add and http.Header.Del convert inputs into this canonical form before manipulating the map.
-Keys in http.Header maps are canonical, meaning they follow a specific
-combination of uppercase and lowercase letters. Methods such as
-http.Header.Add and http.Header.Del convert inputs into this canonical
-form before manipulating the map.
+When manipulating http.Header maps directly, as opposed to using the provided methods, care should be taken to stick to canonical form in order to avoid inconsistencies. The following piece of code demonstrates one such inconsistency:
-When manipulating http.Header maps directly, as opposed to using the
-provided methods, care should be taken to stick to canonical form in
-order to avoid inconsistencies. The following piece of code
-demonstrates one such inconsistency:
+ h := http.Header{}
+ h["etag"] = []string{"1234"}
+ h.Add("etag", "5678")
+ fmt.Println(h)
- h := http.Header{}
- h["etag"] = []string{"1234"}
- h.Add("etag", "5678")
- fmt.Println(h)
+ // Output:
+ // map[Etag:[5678] etag:[1234]]
- // Output:
- // map[Etag:[5678] etag:[1234]]
-
-The easiest way of obtaining the canonical form of a key is to use
-http.CanonicalHeaderKey.
+The easiest way of obtaining the canonical form of a key is to use http.CanonicalHeaderKey.
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1212,12 +1136,11 @@
<a id='SA1010'></a>
## `SA1010`: (*regexp.Regexp).FindAll called with n == 0, which will always return zero results
-
-If n >= 0, the function returns at most n matches/submatches. To
-return all results, specify a negative number.
+If n >= 0, the function returns at most n matches/submatches. To return all results, specify a negative number.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1010": true}`.
@@ -1227,9 +1150,9 @@
<a id='SA1011'></a>
## `SA1011`: Various methods in the 'strings' package expect valid UTF-8, but invalid input is provided
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1011": true}`.
@@ -1239,9 +1162,9 @@
<a id='SA1012'></a>
## `SA1012`: A nil context.Context is being passed to a function, consider using context.TODO instead
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1251,9 +1174,9 @@
<a id='SA1013'></a>
## `SA1013`: io.Seeker.Seek is being called with the whence constant as the first argument, but it should be the second
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1263,9 +1186,9 @@
<a id='SA1014'></a>
## `SA1014`: Non-pointer value passed to Unmarshal or Decode
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1014": true}`.
@@ -1275,15 +1198,13 @@
<a id='SA1015'></a>
## `SA1015`: Using time.Tick in a way that will leak. Consider using time.NewTicker, and only use time.Tick in tests, commands and endless functions
-
-Before Go 1.23, time.Tickers had to be closed to be able to be garbage
-collected. Since time.Tick doesn't make it possible to close the underlying
-ticker, using it repeatedly would leak memory.
+Before Go 1.23, time.Tickers had to be closed to be able to be garbage collected. Since time.Tick doesn't make it possible to close the underlying ticker, using it repeatedly would leak memory.
Go 1.23 fixes this by allowing tickers to be collected even if they weren't closed.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1015": true}`.
@@ -1293,14 +1214,11 @@
<a id='SA1016'></a>
## `SA1016`: Trapping a signal that cannot be trapped
-
-Not all signals can be intercepted by a process. Specifically, on
-UNIX-like systems, the syscall.SIGKILL and syscall.SIGSTOP signals are
-never passed to the process, but instead handled directly by the
-kernel. It is therefore pointless to try and handle these signals.
+Not all signals can be intercepted by a process. Specifically, on UNIX-like systems, the syscall.SIGKILL and syscall.SIGSTOP signals are never passed to the process, but instead handled directly by the kernel. It is therefore pointless to try and handle these signals.
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1310,16 +1228,11 @@
<a id='SA1017'></a>
## `SA1017`: Channels used with os/signal.Notify should be buffered
-
-The os/signal package uses non-blocking channel sends when delivering
-signals. If the receiving end of the channel isn't ready and the
-channel is either unbuffered or full, the signal will be dropped. To
-avoid missing signals, the channel should be buffered and of the
-appropriate size. For a channel used for notification of just one
-signal value, a buffer of size 1 is sufficient.
+The os/signal package uses non-blocking channel sends when delivering signals. If the receiving end of the channel isn't ready and the channel is either unbuffered or full, the signal will be dropped. To avoid missing signals, the channel should be buffered and of the appropriate size. For a channel used for notification of just one signal value, a buffer of size 1 is sufficient.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1017": true}`.
@@ -1329,12 +1242,11 @@
<a id='SA1018'></a>
## `SA1018`: strings.Replace called with n == 0, which does nothing
-
-With n == 0, zero instances will be replaced. To replace all
-instances, use a negative number, or use strings.ReplaceAll.
+With n == 0, zero instances will be replaced. To replace all instances, use a negative number, or use strings.ReplaceAll.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1018": true}`.
@@ -1344,9 +1256,9 @@
<a id='SA1020'></a>
## `SA1020`: Using an invalid host:port pair with a net.Listen-related function
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1020": true}`.
@@ -1356,15 +1268,11 @@
<a id='SA1021'></a>
## `SA1021`: Using bytes.Equal to compare two net.IP
-
-A net.IP stores an IPv4 or IPv6 address as a slice of bytes. The
-length of the slice for an IPv4 address, however, can be either 4 or
-16 bytes long, using different ways of representing IPv4 addresses. In
-order to correctly compare two net.IPs, the net.IP.Equal method should
-be used, as it takes both representations into account.
+A net.IP stores an IPv4 or IPv6 address as a slice of bytes. The length of the slice for an IPv4 address, however, can be either 4 or 16 bytes long, using different ways of representing IPv4 addresses. In order to correctly compare two net.IPs, the net.IP.Equal method should be used, as it takes both representations into account.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1021": true}`.
@@ -1374,11 +1282,11 @@
<a id='SA1023'></a>
## `SA1023`: Modifying the buffer in an io.Writer implementation
-
Write must not modify the slice data, even temporarily.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1023": true}`.
@@ -1388,20 +1296,17 @@
<a id='SA1024'></a>
## `SA1024`: A string cutset contains duplicate characters
+The strings.TrimLeft and strings.TrimRight functions take cutsets, not prefixes. A cutset is treated as a set of characters to remove from a string. For example,
-The strings.TrimLeft and strings.TrimRight functions take cutsets, not
-prefixes. A cutset is treated as a set of characters to remove from a
-string. For example,
+ strings.TrimLeft("42133word", "1234")
- strings.TrimLeft("42133word", "1234")
-
-will result in the string "word" – any characters that are 1, 2, 3 or
-4 are cut from the left of the string.
+will result in the string "word" – any characters that are 1, 2, 3 or 4 are cut from the left of the string.
In order to remove one string from another, use strings.TrimPrefix instead.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA1024": true}`.
@@ -1411,9 +1316,9 @@
<a id='SA1025'></a>
## `SA1025`: It is not possible to use (*time.Timer).Reset's return value correctly
-
Available since
- 2019.1
+
+ 2019.1
Default: off. Enable by setting `"analyses": {"SA1025": true}`.
@@ -1423,9 +1328,9 @@
<a id='SA1026'></a>
## `SA1026`: Cannot marshal channels or functions
-
Available since
- 2019.2
+
+ 2019.2
Default: off. Enable by setting `"analyses": {"SA1026": true}`.
@@ -1435,17 +1340,13 @@
<a id='SA1027'></a>
## `SA1027`: Atomic access to 64-bit variable must be 64-bit aligned
+On ARM, x86-32, and 32-bit MIPS, it is the caller's responsibility to arrange for 64-bit alignment of 64-bit words accessed atomically. The first word in a variable or in an allocated struct, array, or slice can be relied upon to be 64-bit aligned.
-On ARM, x86-32, and 32-bit MIPS, it is the caller's responsibility to
-arrange for 64-bit alignment of 64-bit words accessed atomically. The
-first word in a variable or in an allocated struct, array, or slice
-can be relied upon to be 64-bit aligned.
-
-You can use the structlayout tool to inspect the alignment of fields
-in a struct.
+You can use the structlayout tool to inspect the alignment of fields in a struct.
Available since
- 2019.2
+
+ 2019.2
Default: off. Enable by setting `"analyses": {"SA1027": true}`.
@@ -1455,11 +1356,11 @@
<a id='SA1028'></a>
## `SA1028`: sort.Slice can only be used on slices
-
The first argument of sort.Slice must be a slice.
Available since
- 2020.1
+
+ 2020.1
Default: off. Enable by setting `"analyses": {"SA1028": true}`.
@@ -1469,19 +1370,13 @@
<a id='SA1029'></a>
## `SA1029`: Inappropriate key in call to context.WithValue
+The provided key must be comparable and should not be of type string or any other built-in type to avoid collisions between packages using context. Users of WithValue should define their own types for keys.
-The provided key must be comparable and should not be
-of type string or any other built-in type to avoid collisions between
-packages using context. Users of WithValue should define their own
-types for keys.
-
-To avoid allocating when assigning to an interface{},
-context keys often have concrete type struct{}. Alternatively,
-exported context key variables' static type should be a pointer or
-interface.
+To avoid allocating when assigning to an interface{}, context keys often have concrete type struct{}. Alternatively, exported context key variables' static type should be a pointer or interface.
Available since
- 2020.1
+
+ 2020.1
Default: off. Enable by setting `"analyses": {"SA1029": true}`.
@@ -1491,12 +1386,11 @@
<a id='SA1030'></a>
## `SA1030`: Invalid argument in call to a strconv function
-
-This check validates the format, number base and bit size arguments of
-the various parsing and formatting functions in strconv.
+This check validates the format, number base and bit size arguments of the various parsing and formatting functions in strconv.
Available since
- 2021.1
+
+ 2021.1
Default: off. Enable by setting `"analyses": {"SA1030": true}`.
@@ -1506,14 +1400,11 @@
<a id='SA1031'></a>
## `SA1031`: Overlapping byte slices passed to an encoder
-
-In an encoding function of the form Encode(dst, src), dst and
-src were found to reference the same memory. This can result in
-src bytes being overwritten before they are read, when the encoder
-writes more than one byte per src byte.
+In an encoding function of the form Encode(dst, src), dst and src were found to reference the same memory. This can result in src bytes being overwritten before they are read, when the encoder writes more than one byte per src byte.
Available since
- 2024.1
+
+ 2024.1
Default: off. Enable by setting `"analyses": {"SA1031": true}`.
@@ -1523,21 +1414,17 @@
<a id='SA1032'></a>
## `SA1032`: Wrong order of arguments to errors.Is
-
-The first argument of the function errors.Is is the error
-that we have and the second argument is the error we're trying to match against.
-For example:
+The first argument of the function errors.Is is the error that we have and the second argument is the error we're trying to match against. For example:
if errors.Is(err, io.EOF) { ... }
-This check detects some cases where the two arguments have been swapped. It
-flags any calls where the first argument is referring to a package-level error
-variable, such as
+This check detects some cases where the two arguments have been swapped. It flags any calls where the first argument is referring to a package-level error variable, such as
if errors.Is(io.EOF, err) { /* this is wrong */ }
Available since
- 2024.1
+
+ 2024.1
Default: off. Enable by setting `"analyses": {"SA1032": true}`.
@@ -1547,26 +1434,21 @@
<a id='SA2001'></a>
## `SA2001`: Empty critical section, did you mean to defer the unlock?
-
Empty critical sections of the kind
- mu.Lock()
- mu.Unlock()
+ mu.Lock()
+ mu.Unlock()
are very often a typo, and the following was intended instead:
- mu.Lock()
- defer mu.Unlock()
+ mu.Lock()
+ defer mu.Unlock()
-Do note that sometimes empty critical sections can be useful, as a
-form of signaling to wait on another goroutine. Many times, there are
-simpler ways of achieving the same effect. When that isn't the case,
-the code should be amply commented to avoid confusion. Combining such
-comments with a //lint:ignore directive can be used to suppress this
-rare false positive.
+Do note that sometimes empty critical sections can be useful, as a form of signaling to wait on another goroutine. Many times, there are simpler ways of achieving the same effect. When that isn't the case, the code should be amply commented to avoid confusion. Combining such comments with a //lint:ignore directive can be used to suppress this rare false positive.
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1576,9 +1458,9 @@
<a id='SA2002'></a>
## `SA2002`: Called testing.T.FailNow or SkipNow in a goroutine, which isn't allowed
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA2002": true}`.
@@ -1588,9 +1470,9 @@
<a id='SA2003'></a>
## `SA2003`: Deferred Lock right after locking, likely meant to defer Unlock instead
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA2003": true}`.
@@ -1600,16 +1482,11 @@
<a id='SA3000'></a>
## `SA3000`: TestMain doesn't call os.Exit, hiding test failures
-
-Test executables (and in turn 'go test') exit with a non-zero status
-code if any tests failed. When specifying your own TestMain function,
-it is your responsibility to arrange for this, by calling os.Exit with
-the correct code. The correct code is returned by (*testing.M).Run, so
-the usual way of implementing TestMain is to end it with
-os.Exit(m.Run()).
+Test executables (and in turn 'go test') exit with a non-zero status code if any tests failed. When specifying your own TestMain function, it is your responsibility to arrange for this, by calling os.Exit with the correct code. The correct code is returned by (\*testing.M).Run, so the usual way of implementing TestMain is to end it with os.Exit(m.Run()).
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1619,14 +1496,11 @@
<a id='SA3001'></a>
## `SA3001`: Assigning to b.N in benchmarks distorts the results
-
-The testing package dynamically sets b.N to improve the reliability of
-benchmarks and uses it in computations to determine the duration of a
-single operation. Benchmark code must not alter b.N as this would
-falsify results.
+The testing package dynamically sets b.N to improve the reliability of benchmarks and uses it in computations to determine the duration of a single operation. Benchmark code must not alter b.N as this would falsify results.
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1636,9 +1510,9 @@
<a id='SA4000'></a>
## `SA4000`: Binary operator has identical expressions on both sides
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1648,9 +1522,9 @@
<a id='SA4001'></a>
## `SA4001`: &*x gets simplified to x, it does not copy x
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1660,9 +1534,9 @@
<a id='SA4003'></a>
## `SA4003`: Comparing unsigned values against negative values is pointless
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1672,9 +1546,9 @@
<a id='SA4004'></a>
## `SA4004`: The loop exits unconditionally after one iteration
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1684,9 +1558,9 @@
<a id='SA4005'></a>
## `SA4005`: Field assignment that will never be observed. Did you mean to use a pointer receiver?
-
Available since
- 2021.1
+
+ 2021.1
Default: off. Enable by setting `"analyses": {"SA4005": true}`.
@@ -1696,9 +1570,9 @@
<a id='SA4006'></a>
## `SA4006`: A value assigned to a variable is never read before being overwritten. Forgotten error check or dead code?
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA4006": true}`.
@@ -1708,14 +1582,11 @@
<a id='SA4008'></a>
## `SA4008`: The variable in the loop condition never changes, are you incrementing the wrong variable?
-
For example:
for i := 0; i < 10; j++ { ... }
-This may also occur when a loop can only execute once because of unconditional
-control flow that terminates the loop. For example, when a loop body contains an
-unconditional break, return, or panic:
+This may also occur when a loop can only execute once because of unconditional control flow that terminates the loop. For example, when a loop body contains an unconditional break, return, or panic:
func f() {
panic("oops")
@@ -1729,7 +1600,8 @@
}
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA4008": true}`.
@@ -1739,9 +1611,9 @@
<a id='SA4009'></a>
## `SA4009`: A function argument is overwritten before its first use
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA4009": true}`.
@@ -1751,9 +1623,9 @@
<a id='SA4010'></a>
## `SA4010`: The result of append will never be observed anywhere
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA4010": true}`.
@@ -1763,9 +1635,9 @@
<a id='SA4011'></a>
## `SA4011`: Break statement with no effect. Did you mean to break out of an outer loop?
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1775,9 +1647,9 @@
<a id='SA4012'></a>
## `SA4012`: Comparing a value against NaN even though no value is equal to NaN
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA4012": true}`.
@@ -1787,9 +1659,9 @@
<a id='SA4013'></a>
## `SA4013`: Negating a boolean twice (!!b) is the same as writing b. This is either redundant, or a typo.
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1799,9 +1671,9 @@
<a id='SA4014'></a>
## `SA4014`: An if/else if chain has repeated conditions and no side-effects; if the condition didn't match the first time, it won't match the second time, either
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1811,9 +1683,9 @@
<a id='SA4015'></a>
## `SA4015`: Calling functions like math.Ceil on floats converted from integers doesn't do anything useful
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA4015": true}`.
@@ -1823,9 +1695,9 @@
<a id='SA4016'></a>
## `SA4016`: Certain bitwise operations, such as x ^ 0, do not do anything useful
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1835,9 +1707,9 @@
<a id='SA4017'></a>
## `SA4017`: Discarding the return values of a function without side effects, making the call pointless
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA4017": true}`.
@@ -1847,9 +1719,9 @@
<a id='SA4018'></a>
## `SA4018`: Self-assignment of variables
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA4018": true}`.
@@ -1859,9 +1731,9 @@
<a id='SA4019'></a>
## `SA4019`: Multiple, identical build constraints in the same file
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -1871,76 +1743,69 @@
<a id='SA4020'></a>
## `SA4020`: Unreachable case clause in a type switch
-
In a type switch like the following
- type T struct{}
- func (T) Read(b []byte) (int, error) { return 0, nil }
+ type T struct{}
+ func (T) Read(b []byte) (int, error) { return 0, nil }
- var v any = T{}
+ var v any = T{}
- switch v.(type) {
- case io.Reader:
- // ...
- case T:
- // unreachable
- }
+ switch v.(type) {
+ case io.Reader:
+ // ...
+ case T:
+ // unreachable
+ }
-the second case clause can never be reached because T implements
-io.Reader and case clauses are evaluated in source order.
+the second case clause can never be reached because T implements io.Reader and case clauses are evaluated in source order.
Another example:
- type T struct{}
- func (T) Read(b []byte) (int, error) { return 0, nil }
- func (T) Close() error { return nil }
+ type T struct{}
+ func (T) Read(b []byte) (int, error) { return 0, nil }
+ func (T) Close() error { return nil }
- var v any = T{}
+ var v any = T{}
- switch v.(type) {
- case io.Reader:
- // ...
- case io.ReadCloser:
- // unreachable
- }
+ switch v.(type) {
+ case io.Reader:
+ // ...
+ case io.ReadCloser:
+ // unreachable
+ }
-Even though T has a Close method and thus implements io.ReadCloser,
-io.Reader will always match first. The method set of io.Reader is a
-subset of io.ReadCloser. Thus it is impossible to match the second
-case without matching the first case.
+Even though T has a Close method and thus implements io.ReadCloser, io.Reader will always match first. The method set of io.Reader is a subset of io.ReadCloser. Thus it is impossible to match the second case without matching the first case.
+### Structurally equivalent interfaces {#hdr-Structurally_equivalent_interfaces}
-Structurally equivalent interfaces
+A special case of the previous example are structurally identical interfaces. Given these declarations
-A special case of the previous example are structurally identical
-interfaces. Given these declarations
+ type T error
+ type V error
- type T error
- type V error
+ func doSomething() error {
+ err, ok := doAnotherThing()
+ if ok {
+ return T(err)
+ }
- func doSomething() error {
- err, ok := doAnotherThing()
- if ok {
- return T(err)
- }
-
- return U(err)
- }
+ return U(err)
+ }
the following type switch will have an unreachable case clause:
- switch doSomething().(type) {
- case T:
- // ...
- case V:
- // unreachable
- }
+ switch doSomething().(type) {
+ case T:
+ // ...
+ case V:
+ // unreachable
+ }
-T will always match before V because they are structurally equivalent
-and therefore doSomething()'s return value implements both.
+T will always match before V because they are structurally equivalent and therefore doSomething()'s return value implements both.
Available since
- 2019.2
+
+ 2019.2
Default: on.
@@ -1950,11 +1815,11 @@
<a id='SA4022'></a>
## `SA4022`: Comparing the address of a variable against nil
-
Code such as 'if &x == nil' is meaningless, because taking the address of a variable always yields a non-nil pointer.
Available since
- 2020.1
+
+ 2020.1
Default: on.
@@ -1964,67 +1829,38 @@
<a id='SA4023'></a>
## `SA4023`: Impossible comparison of interface value with untyped nil
+Under the covers, interfaces are implemented as two elements, a type T and a value V. V is a concrete value such as an int, struct or pointer, never an interface itself, and has type T. For instance, if we store the int value 3 in an interface, the resulting interface value has, schematically, (T=int, V=3). The value V is also known as the interface's dynamic value, since a given interface variable might hold different values V (and corresponding types T) during the execution of the program.
-Under the covers, interfaces are implemented as two elements, a
-type T and a value V. V is a concrete value such as an int,
-struct or pointer, never an interface itself, and has type T. For
-instance, if we store the int value 3 in an interface, the
-resulting interface value has, schematically, (T=int, V=3). The
-value V is also known as the interface's dynamic value, since a
-given interface variable might hold different values V (and
-corresponding types T) during the execution of the program.
+An interface value is nil only if the V and T are both unset, (T=nil, V is not set), In particular, a nil interface will always hold a nil type. If we store a nil pointer of type \*int inside an interface value, the inner type will be \*int regardless of the value of the pointer: (T=\*int, V=nil). Such an interface value will therefore be non-nil even when the pointer value V inside is nil.
-An interface value is nil only if the V and T are both
-unset, (T=nil, V is not set), In particular, a nil interface will
-always hold a nil type. If we store a nil pointer of type *int
-inside an interface value, the inner type will be *int regardless
-of the value of the pointer: (T=*int, V=nil). Such an interface
-value will therefore be non-nil even when the pointer value V
-inside is nil.
+This situation can be confusing, and arises when a nil value is stored inside an interface value such as an error return:
-This situation can be confusing, and arises when a nil value is
-stored inside an interface value such as an error return:
+ func returnsError() error {
+ var p *MyError = nil
+ if bad() {
+ p = ErrBad
+ }
+ return p // Will always return a non-nil error.
+ }
- func returnsError() error {
- var p *MyError = nil
- if bad() {
- p = ErrBad
- }
- return p // Will always return a non-nil error.
- }
+If all goes well, the function returns a nil p, so the return value is an error interface value holding (T=\*MyError, V=nil). This means that if the caller compares the returned error to nil, it will always look as if there was an error even if nothing bad happened. To return a proper nil error to the caller, the function must return an explicit nil:
-If all goes well, the function returns a nil p, so the return
-value is an error interface value holding (T=*MyError, V=nil).
-This means that if the caller compares the returned error to nil,
-it will always look as if there was an error even if nothing bad
-happened. To return a proper nil error to the caller, the
-function must return an explicit nil:
+ func returnsError() error {
+ if bad() {
+ return ErrBad
+ }
+ return nil
+ }
- func returnsError() error {
- if bad() {
- return ErrBad
- }
- return nil
- }
+It's a good idea for functions that return errors always to use the error type in their signature (as we did above) rather than a concrete type such as \*MyError, to help guarantee the error is created correctly. As an example, os.Open returns an error even though, if not nil, it's always of concrete type \*os.PathError.
-It's a good idea for functions that return errors always to use
-the error type in their signature (as we did above) rather than a
-concrete type such as *MyError, to help guarantee the error is
-created correctly. As an example, os.Open returns an error even
-though, if not nil, it's always of concrete type *os.PathError.
+Similar situations to those described here can arise whenever interfaces are used. Just keep in mind that if any concrete value has been stored in the interface, the interface will not be nil. For more information, see The Laws of Reflection at [https://golang.org/doc/articles/laws\_of\_reflection.html](https://golang.org/doc/articles/laws_of_reflection.html).
-Similar situations to those described here can arise whenever
-interfaces are used. Just keep in mind that if any concrete value
-has been stored in the interface, the interface will not be nil.
-For more information, see The Laws of
-Reflection at https://golang.org/doc/articles/laws_of_reflection.html.
-
-This text has been copied from
-https://golang.org/doc/faq#nil_error, licensed under the Creative
-Commons Attribution 3.0 License.
+This text has been copied from [https://golang.org/doc/faq#nil\_error](https://golang.org/doc/faq#nil_error), licensed under the Creative Commons Attribution 3.0 License.
Available since
- 2020.2
+
+ 2020.2
Default: off. Enable by setting `"analyses": {"SA4023": true}`.
@@ -2034,19 +1870,19 @@
<a id='SA4024'></a>
## `SA4024`: Checking for impossible return value from a builtin function
-
Return values of the len and cap builtins cannot be negative.
-See https://golang.org/pkg/builtin/#len and https://golang.org/pkg/builtin/#cap.
+See [https://golang.org/pkg/builtin/#len](https://golang.org/pkg/builtin/#len) and [https://golang.org/pkg/builtin/#cap](https://golang.org/pkg/builtin/#cap).
Example:
- if len(slice) < 0 {
- fmt.Println("unreachable code")
- }
+ if len(slice) < 0 {
+ fmt.Println("unreachable code")
+ }
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -2056,23 +1892,18 @@
<a id='SA4025'></a>
## `SA4025`: Integer division of literals that results in zero
-
-When dividing two integer constants, the result will
-also be an integer. Thus, a division such as 2 / 3 results in 0.
-This is true for all of the following examples:
+When dividing two integer constants, the result will also be an integer. Thus, a division such as 2 / 3 results in 0. This is true for all of the following examples:
_ = 2 / 3
const _ = 2 / 3
const _ float64 = 2 / 3
_ = float64(2 / 3)
-Staticcheck will flag such divisions if both sides of the division are
-integer literals, as it is highly unlikely that the division was
-intended to truncate to zero. Staticcheck will not flag integer
-division involving named constants, to avoid noisy positives.
+Staticcheck will flag such divisions if both sides of the division are integer literals, as it is highly unlikely that the division was intended to truncate to zero. Staticcheck will not flag integer division involving named constants, to avoid noisy positives.
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -2082,19 +1913,15 @@
<a id='SA4026'></a>
## `SA4026`: Go constants cannot express negative zero
+In IEEE 754 floating point math, zero has a sign and can be positive or negative. This can be useful in certain numerical code.
-In IEEE 754 floating point math, zero has a sign and can be positive
-or negative. This can be useful in certain numerical code.
+Go constants, however, cannot express negative zero. This means that the literals -0.0 and 0.0 have the same ideal value (zero) and will both represent positive zero at runtime.
-Go constants, however, cannot express negative zero. This means that
-the literals -0.0 and 0.0 have the same ideal value (zero) and
-will both represent positive zero at runtime.
-
-To explicitly and reliably create a negative zero, you can use the
-math.Copysign function: math.Copysign(0, -1).
+To explicitly and reliably create a negative zero, you can use the math.Copysign function: math.Copysign(0, -1).
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -2104,17 +1931,13 @@
<a id='SA4027'></a>
## `SA4027`: (*net/url.URL).Query returns a copy, modifying it doesn't change the URL
+(\*net/url.URL).Query parses the current value of net/url.URL.RawQuery and returns it as a map of type net/url.Values. Subsequent changes to this map will not affect the URL unless the map gets encoded and assigned to the URL's RawQuery.
-(*net/url.URL).Query parses the current value of net/url.URL.RawQuery
-and returns it as a map of type net/url.Values. Subsequent changes to
-this map will not affect the URL unless the map gets encoded and
-assigned to the URL's RawQuery.
-
-As a consequence, the following code pattern is an expensive no-op:
-u.Query().Add(key, value).
+As a consequence, the following code pattern is an expensive no-op: u.Query().Add(key, value).
Available since
- 2021.1
+
+ 2021.1
Default: on.
@@ -2124,9 +1947,9 @@
<a id='SA4028'></a>
## `SA4028`: x % 1 is always zero
-
Available since
- 2022.1
+
+ 2022.1
Default: on.
@@ -2136,16 +1959,11 @@
<a id='SA4029'></a>
## `SA4029`: Ineffective attempt at sorting slice
-
-sort.Float64Slice, sort.IntSlice, and sort.StringSlice are
-types, not functions. Doing x = sort.StringSlice(x) does nothing,
-especially not sort any values. The correct usage is
-sort.Sort(sort.StringSlice(x)) or sort.StringSlice(x).Sort(),
-but there are more convenient helpers, namely sort.Float64s,
-sort.Ints, and sort.Strings.
+sort.Float64Slice, sort.IntSlice, and sort.StringSlice are types, not functions. Doing x = sort.StringSlice(x) does nothing, especially not sort any values. The correct usage is sort.Sort(sort.StringSlice(x)) or sort.StringSlice(x).Sort(), but there are more convenient helpers, namely sort.Float64s, sort.Ints, and sort.Strings.
Available since
- 2022.1
+
+ 2022.1
Default: on.
@@ -2155,15 +1973,11 @@
<a id='SA4030'></a>
## `SA4030`: Ineffective attempt at generating random number
-
-Functions in the math/rand package that accept upper limits, such
-as Intn, generate random numbers in the half-open interval [0,n). In
-other words, the generated numbers will be >= 0 and < n – they
-don't include n. rand.Intn(1) therefore doesn't generate 0
-or 1, it always generates 0.
+Functions in the math/rand package that accept upper limits, such as Intn, generate random numbers in the half-open interval \[0,n). In other words, the generated numbers will be >= 0 and \< n – they don't include n. rand.Intn(1) therefore doesn't generate 0 or 1, it always generates 0.
Available since
- 2022.1
+
+ 2022.1
Default: on.
@@ -2173,9 +1987,9 @@
<a id='SA4031'></a>
## `SA4031`: Checking never-nil value against nil
-
Available since
- 2022.1
+
+ 2022.1
Default: off. Enable by setting `"analyses": {"SA4031": true}`.
@@ -2185,9 +1999,9 @@
<a id='SA4032'></a>
## `SA4032`: Comparing runtime.GOOS or runtime.GOARCH against impossible value
-
Available since
- 2024.1
+
+ 2024.1
Default: on.
@@ -2197,9 +2011,9 @@
<a id='SA5000'></a>
## `SA5000`: Assignment to nil map
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA5000": true}`.
@@ -2209,9 +2023,9 @@
<a id='SA5001'></a>
## `SA5001`: Deferring Close before checking for a possible error
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -2221,9 +2035,9 @@
<a id='SA5002'></a>
## `SA5002`: The empty for loop ('for {}') spins and can block the scheduler
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA5002": true}`.
@@ -2233,13 +2047,11 @@
<a id='SA5003'></a>
## `SA5003`: Defers in infinite loops will never execute
-
-Defers are scoped to the surrounding function, not the surrounding
-block. In a function that never returns, i.e. one containing an
-infinite loop, defers will never execute.
+Defers are scoped to the surrounding function, not the surrounding block. In a function that never returns, i.e. one containing an infinite loop, defers will never execute.
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -2249,9 +2061,9 @@
<a id='SA5004'></a>
## `SA5004`: 'for { select { ...' with an empty default branch spins
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -2261,21 +2073,13 @@
<a id='SA5005'></a>
## `SA5005`: The finalizer references the finalized object, preventing garbage collection
+A finalizer is a function associated with an object that runs when the garbage collector is ready to collect said object, that is when the object is no longer referenced by anything.
-A finalizer is a function associated with an object that runs when the
-garbage collector is ready to collect said object, that is when the
-object is no longer referenced by anything.
-
-If the finalizer references the object, however, it will always remain
-as the final reference to that object, preventing the garbage
-collector from collecting the object. The finalizer will never run,
-and the object will never be collected, leading to a memory leak. That
-is why the finalizer should instead use its first argument to operate
-on the object. That way, the number of references can temporarily go
-to zero before the object is being passed to the finalizer.
+If the finalizer references the object, however, it will always remain as the final reference to that object, preventing the garbage collector from collecting the object. The finalizer will never run, and the object will never be collected, leading to a memory leak. That is why the finalizer should instead use its first argument to operate on the object. That way, the number of references can temporarily go to zero before the object is being passed to the finalizer.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA5005": true}`.
@@ -2285,19 +2089,13 @@
<a id='SA5007'></a>
## `SA5007`: Infinite recursive call
+A function that calls itself recursively needs to have an exit condition. Otherwise it will recurse forever, until the system runs out of memory.
-A function that calls itself recursively needs to have an exit
-condition. Otherwise it will recurse forever, until the system runs
-out of memory.
-
-This issue can be caused by simple bugs such as forgetting to add an
-exit condition. It can also happen "on purpose". Some languages have
-tail call optimization which makes certain infinite recursive calls
-safe to use. Go, however, does not implement TCO, and as such a loop
-should be used instead.
+This issue can be caused by simple bugs such as forgetting to add an exit condition. It can also happen "on purpose". Some languages have tail call optimization which makes certain infinite recursive calls safe to use. Go, however, does not implement TCO, and as such a loop should be used instead.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA5007": true}`.
@@ -2307,9 +2105,9 @@
<a id='SA5008'></a>
## `SA5008`: Invalid struct tag
-
Available since
- 2019.2
+
+ 2019.2
Default: on.
@@ -2319,25 +2117,15 @@
<a id='SA5010'></a>
## `SA5010`: Impossible type assertion
+Some type assertions can be statically proven to be impossible. This is the case when the method sets of both arguments of the type assertion conflict with each other, for example by containing the same method with different signatures.
-Some type assertions can be statically proven to be
-impossible. This is the case when the method sets of both
-arguments of the type assertion conflict with each other, for
-example by containing the same method with different
-signatures.
+The Go compiler already applies this check when asserting from an interface value to a concrete type. If the concrete type misses methods from the interface, or if function signatures don't match, then the type assertion can never succeed.
-The Go compiler already applies this check when asserting from an
-interface value to a concrete type. If the concrete type misses
-methods from the interface, or if function signatures don't match,
-then the type assertion can never succeed.
-
-This check applies the same logic when asserting from one interface to
-another. If both interface types contain the same method but with
-different signatures, then the type assertion can never succeed,
-either.
+This check applies the same logic when asserting from one interface to another. If both interface types contain the same method but with different signatures, then the type assertion can never succeed, either.
Available since
- 2020.1
+
+ 2020.1
Default: off. Enable by setting `"analyses": {"SA5010": true}`.
@@ -2347,72 +2135,59 @@
<a id='SA5011'></a>
## `SA5011`: Possible nil pointer dereference
+A pointer is being dereferenced unconditionally, while also being checked against nil in another place. This suggests that the pointer may be nil and dereferencing it may panic. This is commonly a result of improperly ordered code or missing return statements. Consider the following examples:
-A pointer is being dereferenced unconditionally, while
-also being checked against nil in another place. This suggests that
-the pointer may be nil and dereferencing it may panic. This is
-commonly a result of improperly ordered code or missing return
-statements. Consider the following examples:
+ func fn(x *int) {
+ fmt.Println(*x)
- func fn(x *int) {
- fmt.Println(*x)
+ // This nil check is equally important for the previous dereference
+ if x != nil {
+ foo(*x)
+ }
+ }
- // This nil check is equally important for the previous dereference
- if x != nil {
- foo(*x)
- }
- }
+ func TestFoo(t *testing.T) {
+ x := compute()
+ if x == nil {
+ t.Errorf("nil pointer received")
+ }
- func TestFoo(t *testing.T) {
- x := compute()
- if x == nil {
- t.Errorf("nil pointer received")
- }
+ // t.Errorf does not abort the test, so if x is nil, the next line will panic.
+ foo(*x)
+ }
- // t.Errorf does not abort the test, so if x is nil, the next line will panic.
- foo(*x)
- }
+Staticcheck tries to deduce which functions abort control flow. For example, it is aware that a function will not continue execution after a call to panic or log.Fatal. However, sometimes this detection fails, in particular in the presence of conditionals. Consider the following example:
-Staticcheck tries to deduce which functions abort control flow.
-For example, it is aware that a function will not continue
-execution after a call to panic or log.Fatal. However, sometimes
-this detection fails, in particular in the presence of
-conditionals. Consider the following example:
+ func Log(msg string, level int) {
+ fmt.Println(msg)
+ if level == levelFatal {
+ os.Exit(1)
+ }
+ }
- func Log(msg string, level int) {
- fmt.Println(msg)
- if level == levelFatal {
- os.Exit(1)
- }
- }
+ func Fatal(msg string) {
+ Log(msg, levelFatal)
+ }
- func Fatal(msg string) {
- Log(msg, levelFatal)
- }
+ func fn(x *int) {
+ if x == nil {
+ Fatal("unexpected nil pointer")
+ }
+ fmt.Println(*x)
+ }
- func fn(x *int) {
- if x == nil {
- Fatal("unexpected nil pointer")
- }
- fmt.Println(*x)
- }
+Staticcheck will flag the dereference of x, even though it is perfectly safe. Staticcheck is not able to deduce that a call to Fatal will exit the program. For the time being, the easiest workaround is to modify the definition of Fatal like so:
-Staticcheck will flag the dereference of x, even though it is perfectly
-safe. Staticcheck is not able to deduce that a call to
-Fatal will exit the program. For the time being, the easiest
-workaround is to modify the definition of Fatal like so:
+ func Fatal(msg string) {
+ Log(msg, levelFatal)
+ panic("unreachable")
+ }
- func Fatal(msg string) {
- Log(msg, levelFatal)
- panic("unreachable")
- }
-
-We also hard-code functions from common logging packages such as
-logrus. Please file an issue if we're missing support for a
-popular package.
+We also hard-code functions from common logging packages such as logrus. Please file an issue if we're missing support for a popular package.
Available since
- 2020.1
+
+ 2020.1
Default: off. Enable by setting `"analyses": {"SA5011": true}`.
@@ -2422,14 +2197,11 @@
<a id='SA5012'></a>
## `SA5012`: Passing odd-sized slice to function expecting even size
-
-Some functions that take slices as parameters expect the slices to have an even number of elements.
-Often, these functions treat elements in a slice as pairs.
-For example, strings.NewReplacer takes pairs of old and new strings,
-and calling it with an odd number of elements would be an error.
+Some functions that take slices as parameters expect the slices to have an even number of elements. Often, these functions treat elements in a slice as pairs. For example, strings.NewReplacer takes pairs of old and new strings, and calling it with an odd number of elements would be an error.
Available since
- 2020.2
+
+ 2020.2
Default: off. Enable by setting `"analyses": {"SA5012": true}`.
@@ -2439,9 +2211,9 @@
<a id='SA6000'></a>
## `SA6000`: Using regexp.Match or related in a loop, should use regexp.Compile
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA6000": true}`.
@@ -2451,34 +2223,26 @@
<a id='SA6001'></a>
## `SA6001`: Missing an optimization opportunity when indexing maps by byte slices
+Map keys must be comparable, which precludes the use of byte slices. This usually leads to using string keys and converting byte slices to strings.
-Map keys must be comparable, which precludes the use of byte slices.
-This usually leads to using string keys and converting byte slices to
-strings.
+Normally, a conversion of a byte slice to a string needs to copy the data and causes allocations. The compiler, however, recognizes m\[string(b)] and uses the data of b directly, without copying it, because it knows that the data can't change during the map lookup. This leads to the counter-intuitive situation that
-Normally, a conversion of a byte slice to a string needs to copy the data and
-causes allocations. The compiler, however, recognizes m[string(b)] and
-uses the data of b directly, without copying it, because it knows that
-the data can't change during the map lookup. This leads to the
-counter-intuitive situation that
-
- k := string(b)
- println(m[k])
- println(m[k])
+ k := string(b)
+ println(m[k])
+ println(m[k])
will be less efficient than
- println(m[string(b)])
- println(m[string(b)])
+ println(m[string(b)])
+ println(m[string(b)])
-because the first version needs to copy and allocate, while the second
-one does not.
+because the first version needs to copy and allocate, while the second one does not.
-For some history on this optimization, check out commit
-f5f5a8b6209f84961687d993b93ea0d397f5d5bf in the Go repository.
+For some history on this optimization, check out commit f5f5a8b6209f84961687d993b93ea0d397f5d5bf in the Go repository.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA6001": true}`.
@@ -2488,22 +2252,15 @@
<a id='SA6002'></a>
## `SA6002`: Storing non-pointer values in sync.Pool allocates memory
+A sync.Pool is used to avoid unnecessary allocations and reduce the amount of work the garbage collector has to do.
-A sync.Pool is used to avoid unnecessary allocations and reduce the
-amount of work the garbage collector has to do.
+When passing a value that is not a pointer to a function that accepts an interface, the value needs to be placed on the heap, which means an additional allocation. Slices are a common thing to put in sync.Pools, and they're structs with 3 fields (length, capacity, and a pointer to an array). In order to avoid the extra allocation, one should store a pointer to the slice instead.
-When passing a value that is not a pointer to a function that accepts
-an interface, the value needs to be placed on the heap, which means an
-additional allocation. Slices are a common thing to put in sync.Pools,
-and they're structs with 3 fields (length, capacity, and a pointer to
-an array). In order to avoid the extra allocation, one should store a
-pointer to the slice instead.
-
-See the comments on https://go-review.googlesource.com/c/go/+/24371
-that discuss this problem.
+See the comments on [https://go-review.googlesource.com/c/go/+/24371](https://go-review.googlesource.com/c/go/+/24371) that discuss this problem.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA6002": true}`.
@@ -2513,27 +2270,21 @@
<a id='SA6003'></a>
## `SA6003`: Converting a string to a slice of runes before ranging over it
+You may want to loop over the runes in a string. Instead of converting the string to a slice of runes and looping over that, you can loop over the string itself. That is,
-You may want to loop over the runes in a string. Instead of converting
-the string to a slice of runes and looping over that, you can loop
-over the string itself. That is,
-
- for _, r := range s {}
+ for _, r := range s {}
and
- for _, r := range []rune(s) {}
+ for _, r := range []rune(s) {}
-will yield the same values. The first version, however, will be faster
-and avoid unnecessary memory allocations.
+will yield the same values. The first version, however, will be faster and avoid unnecessary memory allocations.
-Do note that if you are interested in the indices, ranging over a
-string and over a slice of runes will yield different indices. The
-first one yields byte offsets, while the second one yields indices in
-the slice of runes.
+Do note that if you are interested in the indices, ranging over a string and over a slice of runes will yield different indices. The first one yields byte offsets, while the second one yields indices in the slice of runes.
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA6003": true}`.
@@ -2543,29 +2294,21 @@
<a id='SA6005'></a>
## `SA6005`: Inefficient string comparison with strings.ToLower or strings.ToUpper
-
Converting two strings to the same case and comparing them like so
- if strings.ToLower(s1) == strings.ToLower(s2) {
- ...
- }
+ if strings.ToLower(s1) == strings.ToLower(s2) {
+ ...
+ }
-is significantly more expensive than comparing them with
-strings.EqualFold(s1, s2). This is due to memory usage as well as
-computational complexity.
+is significantly more expensive than comparing them with strings.EqualFold(s1, s2). This is due to memory usage as well as computational complexity.
-strings.ToLower will have to allocate memory for the new strings, as
-well as convert both strings fully, even if they differ on the very
-first byte. strings.EqualFold, on the other hand, compares the strings
-one character at a time. It doesn't need to create two intermediate
-strings and can return as soon as the first non-matching character has
-been found.
+strings.ToLower will have to allocate memory for the new strings, as well as convert both strings fully, even if they differ on the very first byte. strings.EqualFold, on the other hand, compares the strings one character at a time. It doesn't need to create two intermediate strings and can return as soon as the first non-matching character has been found.
-For a more in-depth explanation of this issue, see
-https://blog.digitalocean.com/how-to-efficiently-compare-strings-in-go/
+For a more in-depth explanation of this issue, see [https://blog.digitalocean.com/how-to-efficiently-compare-strings-in-go/](https://blog.digitalocean.com/how-to-efficiently-compare-strings-in-go/)
Available since
- 2019.2
+
+ 2019.2
Default: on.
@@ -2575,17 +2318,15 @@
<a id='SA6006'></a>
## `SA6006`: Using io.WriteString to write []byte
-
Using io.WriteString to write a slice of bytes, as in
- io.WriteString(w, string(b))
+ io.WriteString(w, string(b))
-is both unnecessary and inefficient. Converting from []byte to string
-has to allocate and copy the data, and we could simply use w.Write(b)
-instead.
+is both unnecessary and inefficient. Converting from \[]byte to string has to allocate and copy the data, and we could simply use w.Write(b) instead.
Available since
- 2024.1
+
+ 2024.1
Default: on.
@@ -2595,9 +2336,9 @@
<a id='SA9001'></a>
## `SA9001`: Defers in range loops may not run when you expect them to
-
Available since
- 2017.1
+
+ 2017.1
Default: off. Enable by setting `"analyses": {"SA9001": true}`.
@@ -2607,9 +2348,9 @@
<a id='SA9002'></a>
## `SA9002`: Using a non-octal os.FileMode that looks like it was meant to be in octal.
-
Available since
- 2017.1
+
+ 2017.1
Default: on.
@@ -2619,9 +2360,9 @@
<a id='SA9003'></a>
## `SA9003`: Empty body in an if or else branch
-
Available since
- 2017.1, non-default
+
+ 2017.1, non-default
Default: off. Enable by setting `"analyses": {"SA9003": true}`.
@@ -2631,96 +2372,88 @@
<a id='SA9004'></a>
## `SA9004`: Only the first constant has an explicit type
-
In a constant declaration such as the following:
- const (
- First byte = 1
- Second = 2
- )
+ const (
+ First byte = 1
+ Second = 2
+ )
-the constant Second does not have the same type as the constant First.
-This construct shouldn't be confused with
+the constant Second does not have the same type as the constant First. This construct shouldn't be confused with
- const (
- First byte = iota
- Second
- )
+ const (
+ First byte = iota
+ Second
+ )
-where First and Second do indeed have the same type. The type is only
-passed on when no explicit value is assigned to the constant.
+where First and Second do indeed have the same type. The type is only passed on when no explicit value is assigned to the constant.
-When declaring enumerations with explicit values it is therefore
-important not to write
+When declaring enumerations with explicit values it is therefore important not to write
- const (
- EnumFirst EnumType = 1
- EnumSecond = 2
- EnumThird = 3
- )
+ const (
+ EnumFirst EnumType = 1
+ EnumSecond = 2
+ EnumThird = 3
+ )
-This discrepancy in types can cause various confusing behaviors and
-bugs.
+This discrepancy in types can cause various confusing behaviors and bugs.
+### Wrong type in variable declarations {#hdr-Wrong_type_in_variable_declarations}
-Wrong type in variable declarations
+The most obvious issue with such incorrect enumerations expresses itself as a compile error:
-The most obvious issue with such incorrect enumerations expresses
-itself as a compile error:
+ package pkg
- package pkg
+ const (
+ EnumFirst uint8 = 1
+ EnumSecond = 2
+ )
- const (
- EnumFirst uint8 = 1
- EnumSecond = 2
- )
-
- func fn(useFirst bool) {
- x := EnumSecond
- if useFirst {
- x = EnumFirst
- }
- }
+ func fn(useFirst bool) {
+ x := EnumSecond
+ if useFirst {
+ x = EnumFirst
+ }
+ }
fails to compile with
- ./const.go:11:5: cannot use EnumFirst (type uint8) as type int in assignment
+ ./const.go:11:5: cannot use EnumFirst (type uint8) as type int in assignment
+### Losing method sets {#hdr-Losing_method_sets}
-Losing method sets
+A more subtle issue occurs with types that have methods and optional interfaces. Consider the following:
-A more subtle issue occurs with types that have methods and optional
-interfaces. Consider the following:
+ package main
- package main
+ import "fmt"
- import "fmt"
+ type Enum int
- type Enum int
+ func (e Enum) String() string {
+ return "an enum"
+ }
- func (e Enum) String() string {
- return "an enum"
- }
+ const (
+ EnumFirst Enum = 1
+ EnumSecond = 2
+ )
- const (
- EnumFirst Enum = 1
- EnumSecond = 2
- )
-
- func main() {
- fmt.Println(EnumFirst)
- fmt.Println(EnumSecond)
- }
+ func main() {
+ fmt.Println(EnumFirst)
+ fmt.Println(EnumSecond)
+ }
This code will output
- an enum
- 2
+ an enum
+ 2
as EnumSecond has no explicit type, and thus defaults to int.
Available since
- 2019.1
+
+ 2019.1
Default: on.
@@ -2730,17 +2463,13 @@
<a id='SA9005'></a>
## `SA9005`: Trying to marshal a struct with no public fields nor custom marshaling
+The encoding/json and encoding/xml packages only operate on exported fields in structs, not unexported ones. It is usually an error to try to (un)marshal structs that only consist of unexported fields.
-The encoding/json and encoding/xml packages only operate on exported
-fields in structs, not unexported ones. It is usually an error to try
-to (un)marshal structs that only consist of unexported fields.
-
-This check will not flag calls involving types that define custom
-marshaling behavior, e.g. via MarshalJSON methods. It will also not
-flag empty structs.
+This check will not flag calls involving types that define custom marshaling behavior, e.g. via MarshalJSON methods. It will also not flag empty structs.
Available since
- 2019.2
+
+ 2019.2
Default: off. Enable by setting `"analyses": {"SA9005": true}`.
@@ -2750,29 +2479,27 @@
<a id='SA9006'></a>
## `SA9006`: Dubious bit shifting of a fixed size integer value
-
Bit shifting a value past its size will always clear the value.
For instance:
- v := int8(42)
- v >>= 8
+ v := int8(42)
+ v >>= 8
will always result in 0.
-This check flags bit shifting operations on fixed size integer values only.
-That is, int, uint and uintptr are never flagged to avoid potential false
-positives in somewhat exotic but valid bit twiddling tricks:
+This check flags bit shifting operations on fixed size integer values only. That is, int, uint and uintptr are never flagged to avoid potential false positives in somewhat exotic but valid bit twiddling tricks:
- // Clear any value above 32 bits if integers are more than 32 bits.
- func f(i int) int {
- v := i >> 32
- v = v << 32
- return i-v
- }
+ // Clear any value above 32 bits if integers are more than 32 bits.
+ func f(i int) int {
+ v := i >> 32
+ v = v << 32
+ return i-v
+ }
Available since
- 2020.2
+
+ 2020.2
Default: on.
@@ -2782,29 +2509,22 @@
<a id='SA9007'></a>
## `SA9007`: Deleting a directory that shouldn't be deleted
-
-It is virtually never correct to delete system directories such as
-/tmp or the user's home directory. However, it can be fairly easy to
-do by mistake, for example by mistakenly using os.TempDir instead
-of ioutil.TempDir, or by forgetting to add a suffix to the result
-of os.UserHomeDir.
+It is virtually never correct to delete system directories such as /tmp or the user's home directory. However, it can be fairly easy to do by mistake, for example by mistakenly using os.TempDir instead of ioutil.TempDir, or by forgetting to add a suffix to the result of os.UserHomeDir.
Writing
- d := os.TempDir()
- defer os.RemoveAll(d)
+ d := os.TempDir()
+ defer os.RemoveAll(d)
in your unit tests will have a devastating effect on the stability of your system.
This check flags attempts at deleting the following directories:
-- os.TempDir
-- os.UserCacheDir
-- os.UserConfigDir
-- os.UserHomeDir
+\- os.TempDir - os.UserCacheDir - os.UserConfigDir - os.UserHomeDir
Available since
- 2022.1
+
+ 2022.1
Default: off. Enable by setting `"analyses": {"SA9007": true}`.
@@ -2814,25 +2534,19 @@
<a id='SA9008'></a>
## `SA9008`: else branch of a type assertion is probably not reading the right value
+When declaring variables as part of an if statement (like in 'if foo := ...; foo {'), the same variables will also be in the scope of the else branch. This means that in the following example
-When declaring variables as part of an if statement (like in 'if
-foo := ...; foo {'), the same variables will also be in the scope of
-the else branch. This means that in the following example
+ if x, ok := x.(int); ok {
+ // ...
+ } else {
+ fmt.Printf("unexpected type %T", x)
+ }
- if x, ok := x.(int); ok {
- // ...
- } else {
- fmt.Printf("unexpected type %T", x)
- }
-
-x in the else branch will refer to the x from x, ok
-:=; it will not refer to the x that is being type-asserted. The
-result of a failed type assertion is the zero value of the type that
-is being asserted to, so x in the else branch will always have the
-value 0 and the type int.
+x in the else branch will refer to the x from x, ok :=; it will not refer to the x that is being type-asserted. The result of a failed type assertion is the zero value of the type that is being asserted to, so x in the else branch will always have the value 0 and the type int.
Available since
- 2022.1
+
+ 2022.1
Default: off. Enable by setting `"analyses": {"SA9008": true}`.
@@ -2842,12 +2556,11 @@
<a id='SA9009'></a>
## `SA9009`: Ineffectual Go compiler directive
-
-A potential Go compiler directive was found, but is ineffectual as it begins
-with whitespace.
+A potential Go compiler directive was found, but is ineffectual as it begins with whitespace.
Available since
- 2024.1
+
+ 2024.1
Default: on.
@@ -2857,13 +2570,11 @@
<a id='ST1000'></a>
## `ST1000`: Incorrect or missing package comment
-
-Packages must have a package comment that is formatted according to
-the guidelines laid out in
-https://go.dev/wiki/CodeReviewComments#package-comments.
+Packages must have a package comment that is formatted according to the guidelines laid out in [https://go.dev/wiki/CodeReviewComments#package-comments](https://go.dev/wiki/CodeReviewComments#package-comments).
Available since
- 2019.1, non-default
+
+ 2019.1, non-default
Default: off. Enable by setting `"analyses": {"ST1000": true}`.
@@ -2873,37 +2584,21 @@
<a id='ST1001'></a>
## `ST1001`: Dot imports are discouraged
-
Dot imports that aren't in external test packages are discouraged.
-The dot_import_whitelist option can be used to whitelist certain
-imports.
+The dot\_import\_whitelist option can be used to whitelist certain imports.
Quoting Go Code Review Comments:
-> The import . form can be useful in tests that, due to circular
-> dependencies, cannot be made part of the package being tested:
->
-> package foo_test
->
-> import (
-> "bar/testutil" // also imports "foo"
-> . "foo"
-> )
->
-> In this case, the test file cannot be in package foo because it
-> uses bar/testutil, which imports foo. So we use the import .
-> form to let the file pretend to be part of package foo even though
-> it is not. Except for this one case, do not use import . in your
-> programs. It makes the programs much harder to read because it is
-> unclear whether a name like Quux is a top-level identifier in the
-> current package or in an imported package.
+> The import . form can be useful in tests that, due to circular > dependencies, cannot be made part of the package being tested: > > package foo\_test > > import ( > "bar/testutil" // also imports "foo" > . "foo" > ) > > In this case, the test file cannot be in package foo because it > uses bar/testutil, which imports foo. So we use the import . > form to let the file pretend to be part of package foo even though > it is not. Except for this one case, do not use import . in your > programs. It makes the programs much harder to read because it is > unclear whether a name like Quux is a top-level identifier in the > current package or in an imported package.
Available since
- 2019.1
+
+ 2019.1
Options
- dot_import_whitelist
+
+ dot_import_whitelist
Default: off. Enable by setting `"analyses": {"ST1001": true}`.
@@ -2913,21 +2608,19 @@
<a id='ST1003'></a>
## `ST1003`: Poorly chosen identifier
-
Identifiers, such as variable and package names, follow certain rules.
See the following links for details:
-- https://go.dev/doc/effective_go#package-names
-- https://go.dev/doc/effective_go#mixed-caps
-- https://go.dev/wiki/CodeReviewComments#initialisms
-- https://go.dev/wiki/CodeReviewComments#variable-names
+\- [https://go.dev/doc/effective\_go#package-names](https://go.dev/doc/effective_go#package-names) - [https://go.dev/doc/effective\_go#mixed-caps](https://go.dev/doc/effective_go#mixed-caps) - [https://go.dev/wiki/CodeReviewComments#initialisms](https://go.dev/wiki/CodeReviewComments#initialisms) - [https://go.dev/wiki/CodeReviewComments#variable-names](https://go.dev/wiki/CodeReviewComments#variable-names)
Available since
- 2019.1, non-default
+
+ 2019.1, non-default
Options
- initialisms
+
+ initialisms
Default: off. Enable by setting `"analyses": {"ST1003": true}`.
@@ -2937,21 +2630,15 @@
<a id='ST1005'></a>
## `ST1005`: Incorrectly formatted error string
-
-Error strings follow a set of guidelines to ensure uniformity and good
-composability.
+Error strings follow a set of guidelines to ensure uniformity and good composability.
Quoting Go Code Review Comments:
-> Error strings should not be capitalized (unless beginning with
-> proper nouns or acronyms) or end with punctuation, since they are
-> usually printed following other context. That is, use
-> fmt.Errorf("something bad") not fmt.Errorf("Something bad"), so
-> that log.Printf("Reading %s: %v", filename, err) formats without a
-> spurious capital letter mid-message.
+> Error strings should not be capitalized (unless beginning with > proper nouns or acronyms) or end with punctuation, since they are > usually printed following other context. That is, use > fmt.Errorf("something bad") not fmt.Errorf("Something bad"), so > that log.Printf("Reading %s: %v", filename, err) formats without a > spurious capital letter mid-message.
Available since
- 2019.1
+
+ 2019.1
Default: off. Enable by setting `"analyses": {"ST1005": true}`.
@@ -2961,23 +2648,13 @@
<a id='ST1006'></a>
## `ST1006`: Poorly chosen receiver name
-
Quoting Go Code Review Comments:
-> The name of a method's receiver should be a reflection of its
-> identity; often a one or two letter abbreviation of its type
-> suffices (such as "c" or "cl" for "Client"). Don't use generic
-> names such as "me", "this" or "self", identifiers typical of
-> object-oriented languages that place more emphasis on methods as
-> opposed to functions. The name need not be as descriptive as that
-> of a method argument, as its role is obvious and serves no
-> documentary purpose. It can be very short as it will appear on
-> almost every line of every method of the type; familiarity admits
-> brevity. Be consistent, too: if you call the receiver "c" in one
-> method, don't call it "cl" in another.
+> The name of a method's receiver should be a reflection of its > identity; often a one or two letter abbreviation of its type > suffices (such as "c" or "cl" for "Client"). Don't use generic > names such as "me", "this" or "self", identifiers typical of > object-oriented languages that place more emphasis on methods as > opposed to functions. The name need not be as descriptive as that > of a method argument, as its role is obvious and serves no > documentary purpose. It can be very short as it will appear on > almost every line of every method of the type; familiarity admits > brevity. Be consistent, too: if you call the receiver "c" in one > method, don't call it "cl" in another.
Available since
- 2019.1
+
+ 2019.1
Default: off. Enable by setting `"analyses": {"ST1006": true}`.
@@ -2987,11 +2664,11 @@
<a id='ST1008'></a>
## `ST1008`: A function's error value should be its last return value
-
A function's error value should be its last return value.
Available since
- 2019.1
+
+ 2019.1
Default: off. Enable by setting `"analyses": {"ST1008": true}`.
@@ -3001,15 +2678,11 @@
<a id='ST1011'></a>
## `ST1011`: Poorly chosen name for variable of type time.Duration
-
-time.Duration values represent an amount of time, which is represented
-as a count of nanoseconds. An expression like 5 * time.Microsecond
-yields the value 5000. It is therefore not appropriate to suffix a
-variable of type time.Duration with any time unit, such as Msec or
-Milli.
+time.Duration values represent an amount of time, which is represented as a count of nanoseconds. An expression like 5 \* time.Microsecond yields the value 5000. It is therefore not appropriate to suffix a variable of type time.Duration with any time unit, such as Msec or Milli.
Available since
- 2019.1
+
+ 2019.1
Default: off. Enable by setting `"analyses": {"ST1011": true}`.
@@ -3019,12 +2692,11 @@
<a id='ST1012'></a>
## `ST1012`: Poorly chosen name for error variable
-
-Error variables that are part of an API should be called errFoo or
-ErrFoo.
+Error variables that are part of an API should be called errFoo or ErrFoo.
Available since
- 2019.1
+
+ 2019.1
Default: off. Enable by setting `"analyses": {"ST1012": true}`.
@@ -3034,19 +2706,15 @@
<a id='ST1013'></a>
## `ST1013`: Should use constants for HTTP error codes, not magic numbers
-
-HTTP has a tremendous number of status codes. While some of those are
-well known (200, 400, 404, 500), most of them are not. The net/http
-package provides constants for all status codes that are part of the
-various specifications. It is recommended to use these constants
-instead of hard-coding magic numbers, to vastly improve the
-readability of your code.
+HTTP has a tremendous number of status codes. While some of those are well known (200, 400, 404, 500), most of them are not. The net/http package provides constants for all status codes that are part of the various specifications. It is recommended to use these constants instead of hard-coding magic numbers, to vastly improve the readability of your code.
Available since
- 2019.1
+
+ 2019.1
Options
- http_status_code_whitelist
+
+ http_status_code_whitelist
Default: off. Enable by setting `"analyses": {"ST1013": true}`.
@@ -3056,9 +2724,9 @@
<a id='ST1015'></a>
## `ST1015`: A switch's default case should be the first or last case
-
Available since
- 2019.1
+
+ 2019.1
Default: off. Enable by setting `"analyses": {"ST1015": true}`.
@@ -3068,9 +2736,9 @@
<a id='ST1016'></a>
## `ST1016`: Use consistent method receiver names
-
Available since
- 2019.1, non-default
+
+ 2019.1, non-default
Default: off. Enable by setting `"analyses": {"ST1016": true}`.
@@ -3080,15 +2748,11 @@
<a id='ST1017'></a>
## `ST1017`: Don't use Yoda conditions
-
-Yoda conditions are conditions of the kind 'if 42 == x', where the
-literal is on the left side of the comparison. These are a common
-idiom in languages in which assignment is an expression, to avoid bugs
-of the kind 'if (x = 42)'. In Go, which doesn't allow for this kind of
-bug, we prefer the more idiomatic 'if x == 42'.
+Yoda conditions are conditions of the kind 'if 42 == x', where the literal is on the left side of the comparison. These are a common idiom in languages in which assignment is an expression, to avoid bugs of the kind 'if (x = 42)'. In Go, which doesn't allow for this kind of bug, we prefer the more idiomatic 'if x == 42'.
Available since
- 2019.2
+
+ 2019.2
Default: off. Enable by setting `"analyses": {"ST1017": true}`.
@@ -3098,9 +2762,9 @@
<a id='ST1018'></a>
## `ST1018`: Avoid zero-width and control characters in string literals
-
Available since
- 2019.2
+
+ 2019.2
Default: off. Enable by setting `"analyses": {"ST1018": true}`.
@@ -3110,31 +2774,22 @@
<a id='ST1019'></a>
## `ST1019`: Importing the same package multiple times
+Go allows importing the same package multiple times, as long as different import aliases are being used. That is, the following bit of code is valid:
-Go allows importing the same package multiple times, as long as
-different import aliases are being used. That is, the following
-bit of code is valid:
+ import (
+ "fmt"
+ fumpt "fmt"
+ format "fmt"
+ _ "fmt"
+ )
- import (
- "fmt"
- fumpt "fmt"
- format "fmt"
- _ "fmt"
- )
+However, this is very rarely done on purpose. Usually, it is a sign of code that got refactored, accidentally adding duplicate import statements. It is also a rarely known feature, which may contribute to confusion.
-However, this is very rarely done on purpose. Usually, it is a
-sign of code that got refactored, accidentally adding duplicate
-import statements. It is also a rarely known feature, which may
-contribute to confusion.
-
-Do note that sometimes, this feature may be used
-intentionally (see for example
-https://github.com/golang/go/commit/3409ce39bfd7584523b7a8c150a310cea92d879d)
-– if you want to allow this pattern in your code base, you're
-advised to disable this check.
+Do note that sometimes, this feature may be used intentionally (see for example [https://github.com/golang/go/commit/3409ce39bfd7584523b7a8c150a310cea92d879d](https://github.com/golang/go/commit/3409ce39bfd7584523b7a8c150a310cea92d879d)) – if you want to allow this pattern in your code base, you're advised to disable this check.
Available since
- 2020.1
+
+ 2020.1
Default: off. Enable by setting `"analyses": {"ST1019": true}`.
@@ -3144,21 +2799,15 @@
<a id='ST1020'></a>
## `ST1020`: The documentation of an exported function should start with the function's name
+Doc comments work best as complete sentences, which allow a wide variety of automated presentations. The first sentence should be a one-sentence summary that starts with the name being declared.
-Doc comments work best as complete sentences, which
-allow a wide variety of automated presentations. The first sentence
-should be a one-sentence summary that starts with the name being
-declared.
+If every doc comment begins with the name of the item it describes, you can use the doc subcommand of the go tool and run the output through grep.
-If every doc comment begins with the name of the item it describes,
-you can use the doc subcommand of the go tool and run the output
-through grep.
-
-See https://go.dev/doc/effective_go#commentary for more
-information on how to write good documentation.
+See [https://go.dev/doc/effective\_go#commentary](https://go.dev/doc/effective_go#commentary) for more information on how to write good documentation.
Available since
- 2020.1, non-default
+
+ 2020.1, non-default
Default: off. Enable by setting `"analyses": {"ST1020": true}`.
@@ -3168,21 +2817,15 @@
<a id='ST1021'></a>
## `ST1021`: The documentation of an exported type should start with type's name
+Doc comments work best as complete sentences, which allow a wide variety of automated presentations. The first sentence should be a one-sentence summary that starts with the name being declared.
-Doc comments work best as complete sentences, which
-allow a wide variety of automated presentations. The first sentence
-should be a one-sentence summary that starts with the name being
-declared.
+If every doc comment begins with the name of the item it describes, you can use the doc subcommand of the go tool and run the output through grep.
-If every doc comment begins with the name of the item it describes,
-you can use the doc subcommand of the go tool and run the output
-through grep.
-
-See https://go.dev/doc/effective_go#commentary for more
-information on how to write good documentation.
+See [https://go.dev/doc/effective\_go#commentary](https://go.dev/doc/effective_go#commentary) for more information on how to write good documentation.
Available since
- 2020.1, non-default
+
+ 2020.1, non-default
Default: off. Enable by setting `"analyses": {"ST1021": true}`.
@@ -3192,21 +2835,15 @@
<a id='ST1022'></a>
## `ST1022`: The documentation of an exported variable or constant should start with variable's name
+Doc comments work best as complete sentences, which allow a wide variety of automated presentations. The first sentence should be a one-sentence summary that starts with the name being declared.
-Doc comments work best as complete sentences, which
-allow a wide variety of automated presentations. The first sentence
-should be a one-sentence summary that starts with the name being
-declared.
+If every doc comment begins with the name of the item it describes, you can use the doc subcommand of the go tool and run the output through grep.
-If every doc comment begins with the name of the item it describes,
-you can use the doc subcommand of the go tool and run the output
-through grep.
-
-See https://go.dev/doc/effective_go#commentary for more
-information on how to write good documentation.
+See [https://go.dev/doc/effective\_go#commentary](https://go.dev/doc/effective_go#commentary) for more information on how to write good documentation.
Available since
- 2020.1, non-default
+
+ 2020.1, non-default
Default: off. Enable by setting `"analyses": {"ST1022": true}`.
@@ -3216,9 +2853,9 @@
<a id='ST1023'></a>
## `ST1023`: Redundant type in variable declaration
-
Available since
- 2021.1, non-default
+
+ 2021.1, non-default
Default: off. Enable by setting `"analyses": {"ST1023": true}`.
@@ -3228,10 +2865,8 @@
<a id='any'></a>
## `any`: replace interface{} with any
+The any analyzer suggests replacing uses of the empty interface type, \`interface{}\`, with the \`any\` alias, which was introduced in Go 1.18. This is a purely stylistic change that makes code more readable.
-The any analyzer suggests replacing uses of the empty interface type,
-`interface{}`, with the `any` alias, which was introduced in Go 1.18.
-This is a purely stylistic change that makes code more readable.
Default: on.
@@ -3240,25 +2875,14 @@
<a id='appendclipped'></a>
## `appendclipped`: simplify append chains using slices.Concat
+The appendclipped analyzer suggests replacing chains of append calls with a single call to slices.Concat, which was added in Go 1.21. For example, append(append(s, s1...), s2...) would be simplified to slices.Concat(s, s1, s2).
-The appendclipped analyzer suggests replacing chains of append calls with a
-single call to slices.Concat, which was added in Go 1.21. For example,
-append(append(s, s1...), s2...) would be simplified to slices.Concat(s, s1, s2).
+In the simple case of appending to a newly allocated slice, such as append(\[]T(nil), s...), the analyzer suggests the more concise slices.Clone(s). For byte slices, it will prefer bytes.Clone if the "bytes" package is already imported.
-In the simple case of appending to a newly allocated slice, such as
-append([]T(nil), s...), the analyzer suggests the more concise slices.Clone(s).
-For byte slices, it will prefer bytes.Clone if the "bytes" package is
-already imported.
+This fix is only applied when the base of the append tower is a "clipped" slice, meaning its length and capacity are equal (e.g. x\[:0:0] or \[]T{}). This is to avoid changing program behavior by eliminating intended side effects on the base slice's underlying array.
-This fix is only applied when the base of the append tower is a
-"clipped" slice, meaning its length and capacity are equal (e.g.
-x[:0:0] or []T{}). This is to avoid changing program behavior by
-eliminating intended side effects on the base slice's underlying
-array.
+This analyzer is currently disabled by default as the transformation does not preserve the nilness of the base slice in all cases; see [https://go.dev/issue/73557](https://go.dev/issue/73557).
-This analyzer is currently disabled by default as the
-transformation does not preserve the nilness of the base slice in
-all cases; see https://go.dev/issue/73557.
Default: off. Enable by setting `"analyses": {"appendclipped": true}`.
@@ -3267,15 +2891,13 @@
<a id='appends'></a>
## `appends`: check for missing values after append
-
-This checker reports calls to append that pass
-no values to be appended to the slice.
+This checker reports calls to append that pass no values to be appended to the slice.
s := []string{"a", "b", "c"}
_ = append(s)
-Such calls are always no-ops and often indicate an
-underlying mistake.
+Such calls are always no-ops and often indicate an underlying mistake.
+
Default: on.
@@ -3293,10 +2915,8 @@
<a id='assign'></a>
## `assign`: check for useless assignments
+This checker reports assignments of the form x = x or a\[i] = a\[i]. These are almost always useless, and even when they aren't they are usually a mistake.
-This checker reports assignments of the form x = x or a[i] = a[i].
-These are almost always useless, and even when they aren't they are
-usually a mistake.
Default: on.
@@ -3305,13 +2925,13 @@
<a id='atomic'></a>
## `atomic`: check for common mistakes using the sync/atomic package
-
The atomic checker looks for assignment statements of the form:
x = atomic.AddUint64(&x, 1)
which are not atomic.
+
Default: on.
Package documentation: [atomic](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/atomic)
@@ -3328,18 +2948,12 @@
<a id='bloop'></a>
## `bloop`: replace for-range over b.N with b.Loop
+The bloop analyzer suggests replacing benchmark loops of the form \`for i := 0; i \< b.N; i++\` or \`for range b.N\` with the more modern \`for b.Loop()\`, which was added in Go 1.24.
-The bloop analyzer suggests replacing benchmark loops of the form
-`for i := 0; i < b.N; i++` or `for range b.N` with the more modern
-`for b.Loop()`, which was added in Go 1.24.
+This change makes benchmark code more readable and also removes the need for manual timer control, so any preceding calls to b.StartTimer, b.StopTimer, or b.ResetTimer within the same function will also be removed.
-This change makes benchmark code more readable and also removes the need for
-manual timer control, so any preceding calls to b.StartTimer, b.StopTimer,
-or b.ResetTimer within the same function will also be removed.
+Caveats: The b.Loop() method is designed to prevent the compiler from optimizing away the benchmark loop, which can occasionally result in slower execution due to increased allocations in some specific cases.
-Caveats: The b.Loop() method is designed to prevent the compiler from
-optimizing away the benchmark loop, which can occasionally result in
-slower execution due to increased allocations in some specific cases.
Default: on.
@@ -3366,13 +2980,8 @@
<a id='cgocall'></a>
## `cgocall`: detect some violations of the cgo pointer passing rules
+Check for invalid cgo pointer passing. This looks for code that uses cgo to call C code passing values whose types are almost always invalid according to the cgo pointer sharing rules. Specifically, it warns about attempts to pass a Go chan, map, func, or slice to C, either directly, or via a pointer, array, or struct.
-Check for invalid cgo pointer passing.
-This looks for code that uses cgo to call C code passing values
-whose types are almost always invalid according to the cgo pointer
-sharing rules.
-Specifically, it warns about attempts to pass a Go chan, map, func,
-or slice to C, either directly, or via a pointer, array, or struct.
Default: on.
@@ -3381,11 +2990,7 @@
<a id='composites'></a>
## `composites`: check for unkeyed composite literals
-
-This analyzer reports a diagnostic for composite literals of struct
-types imported from another package that do not use the field-keyed
-syntax. Such literals are fragile because the addition of a new field
-(even if unexported) to the struct will cause compilation to fail.
+This analyzer reports a diagnostic for composite literals of struct types imported from another package that do not use the field-keyed syntax. Such literals are fragile because the addition of a new field (even if unexported) to the struct will cause compilation to fail.
As an example,
@@ -3403,10 +3008,8 @@
<a id='copylocks'></a>
## `copylocks`: check for locks erroneously passed by value
+Inadvertently copying a value containing a lock, such as sync.Mutex or sync.WaitGroup, may cause both copies to malfunction. Generally such values should be referred to through a pointer.
-Inadvertently copying a value containing a lock, such as sync.Mutex or
-sync.WaitGroup, may cause both copies to malfunction. Generally such
-values should be referred to through a pointer.
Default: on.
@@ -3415,13 +3018,12 @@
<a id='deepequalerrors'></a>
## `deepequalerrors`: check for calls of reflect.DeepEqual on error values
-
The deepequalerrors checker looks for calls of the form:
- reflect.DeepEqual(err1, err2)
+ reflect.DeepEqual(err1, err2)
-where err1 and err2 are errors. Using reflect.DeepEqual to compare
-errors is discouraged.
+where err1 and err2 are errors. Using reflect.DeepEqual to compare errors is discouraged.
+
Default: on.
@@ -3430,10 +3032,7 @@
<a id='defers'></a>
## `defers`: report common mistakes in defer statements
-
-The defers analyzer reports a diagnostic when a defer statement would
-result in a non-deferred call to time.Since, as experience has shown
-that this is nearly always a mistake.
+The defers analyzer reports a diagnostic when a defer statement would result in a non-deferred call to time.Since, as experience has shown that this is nearly always a mistake.
For example:
@@ -3445,6 +3044,7 @@
defer func() { recordLatency(time.Since(start)) }()
+
Default: on.
Package documentation: [defers](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/defers)
@@ -3452,12 +3052,10 @@
<a id='deprecated'></a>
## `deprecated`: check for use of deprecated identifiers
+The deprecated analyzer looks for deprecated symbols and package imports.
-The deprecated analyzer looks for deprecated symbols and package
-imports.
+See [https://go.dev/wiki/Deprecated](https://go.dev/wiki/Deprecated) to learn about Go's convention for documenting and signaling deprecated identifiers.
-See https://go.dev/wiki/Deprecated to learn about Go's convention
-for documenting and signaling deprecated identifiers.
Default: on.
@@ -3466,19 +3064,13 @@
<a id='directive'></a>
## `directive`: check Go toolchain directives such as //go:debug
+This analyzer checks for problems with known Go toolchain directives in all Go source files in a package directory, even those excluded by //go:build constraints, and all non-Go source files too.
-This analyzer checks for problems with known Go toolchain directives
-in all Go source files in a package directory, even those excluded by
-//go:build constraints, and all non-Go source files too.
-
-For //go:debug (see https://go.dev/doc/godebug), the analyzer checks
-that the directives are placed only in Go source files, only above the
-package comment, and only in package main or *_test.go files.
+For //go:debug (see [https://go.dev/doc/godebug](https://go.dev/doc/godebug)), the analyzer checks that the directives are placed only in Go source files, only above the package comment, and only in package main or \*\_test.go files.
Support for other known directives may be added in the future.
-This analyzer does not check //go:build, which is handled by the
-buildtag analyzer.
+This analyzer does not check //go:build, which is handled by the buildtag analyzer.
Default: on.
@@ -3488,13 +3080,10 @@
<a id='embed'></a>
## `embed`: check //go:embed directive usage
+This analyzer checks that the embed package is imported if //go:embed directives are present, providing a suggested fix to add the import if it is missing.
-This analyzer checks that the embed package is imported if //go:embed
-directives are present, providing a suggested fix to add the import if
-it is missing.
+This analyzer also checks that //go:embed directives precede the declaration of a single variable.
-This analyzer also checks that //go:embed directives precede the
-declaration of a single variable.
Default: on.
@@ -3503,9 +3092,8 @@
<a id='errorsas'></a>
## `errorsas`: report passing non-pointer or non-error values to errors.As
+The errorsas analysis reports calls to errors.As where the type of the second argument is not a pointer to a type implementing error.
-The errorsas analysis reports calls to errors.As where the type
-of the second argument is not a pointer to a type implementing error.
Default: on.
@@ -3514,9 +3102,7 @@
<a id='fillreturns'></a>
## `fillreturns`: suggest fixes for errors due to an incorrect number of return values
-
-This checker provides suggested fixes for type errors of the
-type "wrong number of return values (want %d, got %d)". For example:
+This checker provides suggested fixes for type errors of the type "wrong number of return values (want %d, got %d)". For example:
func m() (int, string, *bool, error) {
return
@@ -3528,7 +3114,8 @@
return 0, "", nil, nil
}
-This functionality is similar to https://github.com/sqs/goreturns.
+This functionality is similar to [https://github.com/sqs/goreturns](https://github.com/sqs/goreturns).
+
Default: on.
@@ -3537,11 +3124,8 @@
<a id='fmtappendf'></a>
## `fmtappendf`: replace []byte(fmt.Sprintf) with fmt.Appendf
+The fmtappendf analyzer suggests replacing \`\[]byte(fmt.Sprintf(...))\` with \`fmt.Appendf(nil, ...)\`. This avoids the intermediate allocation of a string by Sprintf, making the code more efficient. The suggestion also applies to fmt.Sprint and fmt.Sprintln.
-The fmtappendf analyzer suggests replacing `[]byte(fmt.Sprintf(...))` with
-`fmt.Appendf(nil, ...)`. This avoids the intermediate allocation of a string
-by Sprintf, making the code more efficient. The suggestion also applies to
-fmt.Sprint and fmt.Sprintln.
Default: on.
@@ -3550,14 +3134,10 @@
<a id='forvar'></a>
## `forvar`: remove redundant re-declaration of loop variables
+The forvar analyzer removes unnecessary shadowing of loop variables. Before Go 1.22, it was common to write \`for \_, x := range s { x := x ... }\` to create a fresh variable for each iteration. Go 1.22 changed the semantics of \`for\` loops, making this pattern redundant. This analyzer removes the unnecessary \`x := x\` statement.
-The forvar analyzer removes unnecessary shadowing of loop variables.
-Before Go 1.22, it was common to write `for _, x := range s { x := x ... }`
-to create a fresh variable for each iteration. Go 1.22 changed the semantics
-of `for` loops, making this pattern redundant. This analyzer removes the
-unnecessary `x := x` statement.
+This fix only applies to \`range\` loops.
-This fix only applies to `range` loops.
Default: on.
@@ -3575,18 +3155,16 @@
<a id='gofix'></a>
## `gofix`: apply fixes based on go:fix comment directives
-
The gofix analyzer inlines functions and constants that are marked for inlining.
-## Functions
+\## Functions
Given a function that is marked for inlining, like this one:
//go:fix inline
func Square(x int) int { return Pow(x, 2) }
-this analyzer will recommend that calls to the function elsewhere, in the same
-or other packages, should be inlined.
+this analyzer will recommend that calls to the function elsewhere, in the same or other packages, should be inlined.
Inlining can be used to move off of a deprecated function:
@@ -3594,8 +3172,7 @@
//go:fix inline
func Square(x int) int { return Pow(x, 2) }
-It can also be used to move off of an obsolete package,
-as when the import path has changed or a higher major version is available:
+It can also be used to move off of an obsolete package, as when the import path has changed or a higher major version is available:
package pkg
@@ -3604,30 +3181,17 @@
//go:fix inline
func F() { pkg2.F(nil) }
-Replacing a call pkg.F() by pkg2.F(nil) can have no effect on the program,
-so this mechanism provides a low-risk way to update large numbers of calls.
-We recommend, where possible, expressing the old API in terms of the new one
-to enable automatic migration.
+Replacing a call pkg.F() by pkg2.F(nil) can have no effect on the program, so this mechanism provides a low-risk way to update large numbers of calls. We recommend, where possible, expressing the old API in terms of the new one to enable automatic migration.
-The inliner takes care to avoid behavior changes, even subtle ones,
-such as changes to the order in which argument expressions are
-evaluated. When it cannot safely eliminate all parameter variables,
-it may introduce a "binding declaration" of the form
+The inliner takes care to avoid behavior changes, even subtle ones, such as changes to the order in which argument expressions are evaluated. When it cannot safely eliminate all parameter variables, it may introduce a "binding declaration" of the form
var params = args
-to evaluate argument expressions in the correct order and bind them to
-parameter variables. Since the resulting code transformation may be
-stylistically suboptimal, such inlinings may be disabled by specifying
-the -gofix.allow_binding_decl=false flag to the analyzer driver.
+to evaluate argument expressions in the correct order and bind them to parameter variables. Since the resulting code transformation may be stylistically suboptimal, such inlinings may be disabled by specifying the -gofix.allow\_binding\_decl=false flag to the analyzer driver.
-(In cases where it is not safe to "reduce" a call—that is, to replace
-a call f(x) by the body of function f, suitably substituted—the
-inliner machinery is capable of replacing f by a function literal,
-func(){...}(). However, the gofix analyzer discards all such
-"literalizations" unconditionally, again on grounds of style.)
+(In cases where it is not safe to "reduce" a call—that is, to replace a call f(x) by the body of function f, suitably substituted—the inliner machinery is capable of replacing f by a function literal, func(){...}(). However, the gofix analyzer discards all such "literalizations" unconditionally, again on grounds of style.)
-## Constants
+\## Constants
Given a constant that is marked for inlining, like this one:
@@ -3636,14 +3200,11 @@
this analyzer will recommend that uses of Ptr should be replaced with Pointer.
-As with functions, inlining can be used to replace deprecated constants and
-constants in obsolete packages.
+As with functions, inlining can be used to replace deprecated constants and constants in obsolete packages.
-A constant definition can be marked for inlining only if it refers to another
-named constant.
+A constant definition can be marked for inlining only if it refers to another named constant.
-The "//go:fix inline" comment must appear before a single const declaration on its own,
-as above; before a const declaration that is part of a group, as in this case:
+The "//go:fix inline" comment must appear before a single const declaration on its own, as above; before a const declaration that is part of a group, as in this case:
const (
C = 1
@@ -3659,14 +3220,14 @@
Val = Value
)
-The proposal https://go.dev/issue/32816 introduces the "//go:fix" directives.
+The proposal [https://go.dev/issue/32816](https://go.dev/issue/32816) introduces the "//go:fix" directives.
You can use this (officially unsupported) command to apply gofix fixes en masse:
$ go run golang.org/x/tools/internal/gofix/cmd/gofix@latest -test ./...
-(Do not use "go get -tool" to add gopls as a dependency of your
-module; gopls commands must be built from their release branch.)
+(Do not use "go get -tool" to add gopls as a dependency of your module; gopls commands must be built from their release branch.)
+
Default: on.
@@ -3675,20 +3236,17 @@
<a id='hostport'></a>
## `hostport`: check format of addresses passed to net.Dial
+This analyzer flags code that produce network address strings using fmt.Sprintf, as in this example:
-This analyzer flags code that produce network address strings using
-fmt.Sprintf, as in this example:
+ addr := fmt.Sprintf("%s:%d", host, 12345) // "will not work with IPv6"
+ ...
+ conn, err := net.Dial("tcp", addr) // "when passed to dial here"
- addr := fmt.Sprintf("%s:%d", host, 12345) // "will not work with IPv6"
- ...
- conn, err := net.Dial("tcp", addr) // "when passed to dial here"
+The analyzer suggests a fix to use the correct approach, a call to net.JoinHostPort:
-The analyzer suggests a fix to use the correct approach, a call to
-net.JoinHostPort:
-
- addr := net.JoinHostPort(host, "12345")
- ...
- conn, err := net.Dial("tcp", addr)
+ addr := net.JoinHostPort(host, "12345")
+ ...
+ conn, err := net.Dial("tcp", addr)
A similar diagnostic and fix are produced for a format string of "%s:%s".
@@ -3700,10 +3258,7 @@
<a id='httpresponse'></a>
## `httpresponse`: check for mistakes using HTTP responses
-
-A common mistake when using the net/http package is to defer a function
-call to close the http.Response Body before checking the error that
-determines whether the response is valid:
+A common mistake when using the net/http package is to defer a function call to close the http.Response Body before checking the error that determines whether the response is valid:
resp, err := http.Head(url)
defer resp.Body.Close()
@@ -3712,8 +3267,8 @@
}
// (defer statement belongs here)
-This checker helps uncover latent nil dereference bugs by reporting a
-diagnostic for such mistakes.
+This checker helps uncover latent nil dereference bugs by reporting a diagnostic for such mistakes.
+
Default: on.
@@ -3722,19 +3277,15 @@
<a id='ifaceassert'></a>
## `ifaceassert`: detect impossible interface-to-interface type assertions
-
-This checker flags type assertions v.(T) and corresponding type-switch cases
-in which the static type V of v is an interface that cannot possibly implement
-the target interface T. This occurs when V and T contain methods with the same
-name but different signatures. Example:
+This checker flags type assertions v.(T) and corresponding type-switch cases in which the static type V of v is an interface that cannot possibly implement the target interface T. This occurs when V and T contain methods with the same name but different signatures. Example:
var v interface {
Read()
}
_ = v.(io.Reader)
-The Read method in v has a different signature than the Read method in
-io.Reader, so this assertion cannot succeed.
+The Read method in v has a different signature than the Read method in io.Reader, so this assertion cannot succeed.
+
Default: on.
@@ -3743,12 +3294,10 @@
<a id='infertypeargs'></a>
## `infertypeargs`: check for unnecessary type arguments in call expressions
-
-Explicit type arguments may be omitted from call expressions if they can be
-inferred from function arguments, or from other type arguments:
+Explicit type arguments may be omitted from call expressions if they can be inferred from function arguments, or from other type arguments:
func f[T any](T) {}
-
+
func _() {
f[string]("foo") // string could be inferred
}
@@ -3761,18 +3310,11 @@
<a id='loopclosure'></a>
## `loopclosure`: check references to loop variables from within nested functions
+This analyzer reports places where a function literal references the iteration variable of an enclosing loop, and the loop calls the function in such a way (e.g. with go or defer) that it may outlive the loop iteration and possibly observe the wrong value of the variable.
-This analyzer reports places where a function literal references the
-iteration variable of an enclosing loop, and the loop calls the function
-in such a way (e.g. with go or defer) that it may outlive the loop
-iteration and possibly observe the wrong value of the variable.
+Note: An iteration variable can only outlive a loop iteration in Go versions \<=1.21. In Go 1.22 and later, the loop variable lifetimes changed to create a new iteration variable per loop iteration. (See go.dev/issue/60078.)
-Note: An iteration variable can only outlive a loop iteration in Go versions <=1.21.
-In Go 1.22 and later, the loop variable lifetimes changed to create a new
-iteration variable per loop iteration. (See go.dev/issue/60078.)
-
-In this example, all the deferred functions run after the loop has
-completed, so all observe the final value of v [<go1.22].
+In this example, all the deferred functions run after the loop has completed, so all observe the final value of v \[\<go1.22].
for _, v := range list {
defer func() {
@@ -3789,12 +3331,9 @@
}()
}
-After Go version 1.22, the previous two for loops are equivalent
-and both are correct.
+After Go version 1.22, the previous two for loops are equivalent and both are correct.
-The next example uses a go statement and has a similar problem [<go1.22].
-In addition, it has a data race because the loop updates v
-concurrent with the goroutines accessing it.
+The next example uses a go statement and has a similar problem \[\<go1.22]. In addition, it has a data race because the loop updates v concurrent with the goroutines accessing it.
for _, v := range elem {
go func() {
@@ -3802,9 +3341,7 @@
}()
}
-A fix is the same as before. The checker also reports problems
-in goroutines started by golang.org/x/sync/errgroup.Group.
-A hard-to-spot variant of this form is common in parallel tests:
+A fix is the same as before. The checker also reports problems in goroutines started by golang.org/x/sync/errgroup.Group. A hard-to-spot variant of this form is common in parallel tests:
func Test(t *testing.T) {
for _, test := range tests {
@@ -3815,16 +3352,12 @@
}
}
-The t.Parallel() call causes the rest of the function to execute
-concurrent with the loop [<go1.22].
+The t.Parallel() call causes the rest of the function to execute concurrent with the loop \[\<go1.22].
-The analyzer reports references only in the last statement,
-as it is not deep enough to understand the effects of subsequent
-statements that might render the reference benign.
-("Last statement" is defined recursively in compound
-statements such as if, switch, and select.)
+The analyzer reports references only in the last statement, as it is not deep enough to understand the effects of subsequent statements that might render the reference benign. ("Last statement" is defined recursively in compound statements such as if, switch, and select.)
-See: https://golang.org/doc/go_faq.html#closures_and_goroutines
+See: [https://golang.org/doc/go\_faq.html#closures\_and\_goroutines](https://golang.org/doc/go_faq.html#closures_and_goroutines)
+
Default: on.
@@ -3833,11 +3366,8 @@
<a id='lostcancel'></a>
## `lostcancel`: check cancel func returned by context.WithCancel is called
+The cancellation function returned by context.WithCancel, WithTimeout, WithDeadline and variants such as WithCancelCause must be called, or the new context will remain live until its parent context is cancelled. (The background context is never cancelled.)
-The cancellation function returned by context.WithCancel, WithTimeout,
-WithDeadline and variants such as WithCancelCause must be called,
-or the new context will remain live until its parent context is cancelled.
-(The background context is never cancelled.)
Default: on.
@@ -3846,7 +3376,6 @@
<a id='maprange'></a>
## `maprange`: checks for unnecessary calls to maps.Keys and maps.Values in range statements
-
Consider a loop written like this:
for val := range maps.Values(m) {
@@ -3859,8 +3388,7 @@
fmt.Println(val)
}
-golang.org/x/exp/maps returns slices for Keys/Values instead of iterators,
-but unnecessary calls should similarly be removed:
+golang.org/x/exp/maps returns slices for Keys/Values instead of iterators, but unnecessary calls should similarly be removed:
for _, key := range maps.Keys(m) {
fmt.Println(key)
@@ -3872,6 +3400,7 @@
fmt.Println(key)
}
+
Default: on.
Package documentation: [maprange](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/maprange)
@@ -3879,18 +3408,14 @@
<a id='mapsloop'></a>
## `mapsloop`: replace explicit loops over maps with calls to maps package
-
The mapsloop analyzer replaces loops of the form
for k, v := range x { m[k] = v }
-with a single call to a function from the `maps` package, added in Go 1.23.
-Depending on the context, this could be `maps.Copy`, `maps.Insert`,
-`maps.Clone`, or `maps.Collect`.
+with a single call to a function from the \`maps\` package, added in Go 1.23. Depending on the context, this could be \`maps.Copy\`, \`maps.Insert\`, \`maps.Clone\`, or \`maps.Collect\`.
-The transformation to `maps.Clone` is applied conservatively, as it
-preserves the nilness of the source map, which may be a subtle change in
-behavior if the original code did not handle a nil map in the same way.
+The transformation to \`maps.Clone\` is applied conservatively, as it preserves the nilness of the source map, which may be a subtle change in behavior if the original code did not handle a nil map in the same way.
+
Default: on.
@@ -3899,9 +3424,7 @@
<a id='minmax'></a>
## `minmax`: replace if/else statements with calls to min or max
-
-The minmax analyzer simplifies conditional assignments by suggesting the use
-of the built-in `min` and `max` functions, introduced in Go 1.21. For example,
+The minmax analyzer simplifies conditional assignments by suggesting the use of the built-in \`min\` and \`max\` functions, introduced in Go 1.21. For example,
if a < b { x = a } else { x = b }
@@ -3909,9 +3432,8 @@
x = min(a, b).
-This analyzer avoids making suggestions for floating-point types,
-as the behavior of `min` and `max` with NaN values can differ from
-the original if/else statement.
+This analyzer avoids making suggestions for floating-point types, as the behavior of \`min\` and \`max\` with NaN values can differ from the original if/else statement.
+
Default: on.
@@ -3920,9 +3442,9 @@
<a id='nilfunc'></a>
## `nilfunc`: check for useless comparisons between functions and nil
-
A useless comparison is one like f == nil as opposed to f() == nil.
+
Default: on.
Package documentation: [nilfunc](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/nilfunc)
@@ -3930,13 +3452,7 @@
<a id='nilness'></a>
## `nilness`: check for redundant or impossible nil comparisons
-
-The nilness checker inspects the control-flow graph of each function in
-a package and reports nil pointer dereferences, degenerate nil
-pointers, and panics with nil values. A degenerate comparison is of the form
-x==nil or x!=nil where x is statically known to be nil or non-nil. These are
-often a mistake, especially in control flow related to errors. Panics with nil
-values are checked because they are not detectable by
+The nilness checker inspects the control-flow graph of each function in a package and reports nil pointer dereferences, degenerate nil pointers, and panics with nil values. A degenerate comparison is of the form x==nil or x!=nil where x is statically known to be nil or non-nil. These are often a mistake, especially in control flow related to errors. Panics with nil values are checked because they are not detectable by
if r := recover(); r != nil {
@@ -3964,10 +3480,7 @@
panic(p)
}
-Sometimes the control flow may be quite complex, making bugs hard
-to spot. In the example below, the err.Error expression is
-guaranteed to panic because, after the first return, err must be
-nil. The intervening loop is just a distraction.
+Sometimes the control flow may be quite complex, making bugs hard to spot. In the example below, the err.Error expression is guaranteed to panic because, after the first return, err must be nil. The intervening loop is just a distraction.
...
err := g.Wait()
@@ -3991,6 +3504,7 @@
...
+
Default: on.
Package documentation: [nilness](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/nilness)
@@ -3998,9 +3512,7 @@
<a id='nonewvars'></a>
## `nonewvars`: suggested fixes for "no new vars on left side of :="
-
-This checker provides suggested fixes for type errors of the
-type "no new vars on left side of :=". For example:
+This checker provides suggested fixes for type errors of the type "no new vars on left side of :=". For example:
z := 1
z := 2
@@ -4010,6 +3522,7 @@
z := 1
z = 2
+
Default: on.
Package documentation: [nonewvars](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/nonewvars)
@@ -4017,10 +3530,7 @@
<a id='noresultvalues'></a>
## `noresultvalues`: suggested fixes for unexpected return values
-
-This checker provides suggested fixes for type errors of the
-type "no result values expected" or "too many return values".
-For example:
+This checker provides suggested fixes for type errors of the type "no result values expected" or "too many return values". For example:
func z() { return nil }
@@ -4028,6 +3538,7 @@
func z() { return }
+
Default: on.
Package documentation: [noresultvalues](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/noresultvalues)
@@ -4035,16 +3546,10 @@
<a id='omitzero'></a>
## `omitzero`: suggest replacing omitempty with omitzero for struct fields
+The omitzero analyzer identifies uses of the \`omitempty\` JSON struct tag on fields that are themselves structs. The \`omitempty\` tag has no effect on struct-typed fields. The analyzer offers two suggestions: either remove the tag, or replace it with \`omitzero\` (added in Go 1.24), which correctly omits the field if the struct value is zero.
-The omitzero analyzer identifies uses of the `omitempty` JSON struct tag on
-fields that are themselves structs. The `omitempty` tag has no effect on
-struct-typed fields. The analyzer offers two suggestions: either remove the
-tag, or replace it with `omitzero` (added in Go 1.24), which correctly
-omits the field if the struct value is zero.
+Replacing \`omitempty\` with \`omitzero\` is a change in behavior. The original code would always encode the struct field, whereas the modified code will omit it if it is a zero-value.
-Replacing `omitempty` with `omitzero` is a change in behavior. The
-original code would always encode the struct field, whereas the
-modified code will omit it if it is a zero-value.
Default: on.
@@ -4053,15 +3558,10 @@
<a id='printf'></a>
## `printf`: check consistency of Printf format strings and arguments
+The check applies to calls of the formatting functions such as [fmt.Printf](/fmt#Printf) and [fmt.Sprintf](/fmt#Sprintf), as well as any detected wrappers of those functions such as [log.Printf](/log#Printf). It reports a variety of mistakes such as syntax errors in the format string and mismatches (of number and type) between the verbs and their arguments.
-The check applies to calls of the formatting functions such as
-[fmt.Printf] and [fmt.Sprintf], as well as any detected wrappers of
-those functions such as [log.Printf]. It reports a variety of
-mistakes such as syntax errors in the format string and mismatches
-(of number and type) between the verbs and their arguments.
+See the documentation of the fmt package for the complete set of format operators and their operand types.
-See the documentation of the fmt package for the complete set of
-format operators and their operand types.
Default: on.
@@ -4070,9 +3570,7 @@
<a id='rangeint'></a>
## `rangeint`: replace 3-clause for loops with for-range over integers
-
-The rangeint analyzer suggests replacing traditional for loops such
-as
+The rangeint analyzer suggests replacing traditional for loops such as
for i := 0; i < n; i++ { ... }
@@ -4080,10 +3578,8 @@
for i := range n { ... }
-This transformation is applied only if (a) the loop variable is not
-modified within the loop body and (b) the loop's limit expression
-is not modified within the loop, as `for range` evaluates its
-operand only once.
+This transformation is applied only if (a) the loop variable is not modified within the loop body and (b) the loop's limit expression is not modified within the loop, as \`for range\` evaluates its operand only once.
+
Default: on.
@@ -4092,14 +3588,9 @@
<a id='recursiveiter'></a>
## `recursiveiter`: check for inefficient recursive iterators
+This analyzer reports when a function that returns an iterator (iter.Seq or iter.Seq2) calls itself as the operand of a range statement, as this is inefficient.
-This analyzer reports when a function that returns an iterator
-(iter.Seq or iter.Seq2) calls itself as the operand of a range
-statement, as this is inefficient.
-
-When implementing an iterator (e.g. iter.Seq[T]) for a recursive
-data type such as a tree or linked list, it is tempting to
-recursively range over the iterator for each child element.
+When implementing an iterator (e.g. iter.Seq\[T]) for a recursive data type such as a tree or linked list, it is tempting to recursively range over the iterator for each child element.
Here's an example of a naive iterator over a binary tree:
@@ -4128,44 +3619,25 @@
}
}
-Though it correctly enumerates the elements of the tree, it hides a
-significant performance problem--two, in fact. Consider a balanced
-tree of N nodes. Iterating the root node will cause All to be
-called once on every node of the tree. This results in a chain of
-nested active range-over-func statements when yield(t.value) is
-called on a leaf node.
+Though it correctly enumerates the elements of the tree, it hides a significant performance problem--two, in fact. Consider a balanced tree of N nodes. Iterating the root node will cause All to be called once on every node of the tree. This results in a chain of nested active range-over-func statements when yield(t.value) is called on a leaf node.
-The first performance problem is that each range-over-func
-statement must typically heap-allocate a variable, so iteration of
-the tree allocates as many variables as there are elements in the
-tree, for a total of O(N) allocations, all unnecessary.
+The first performance problem is that each range-over-func statement must typically heap-allocate a variable, so iteration of the tree allocates as many variables as there are elements in the tree, for a total of O(N) allocations, all unnecessary.
-The second problem is that each call to yield for a leaf of the
-tree causes each of the enclosing range loops to receive a value,
-which they then immediately pass on to their respective yield
-function. This results in a chain of log(N) dynamic yield calls per
-element, a total of O(N*log N) dynamic calls overall, when only
-O(N) are necessary.
+The second problem is that each call to yield for a leaf of the tree causes each of the enclosing range loops to receive a value, which they then immediately pass on to their respective yield function. This results in a chain of log(N) dynamic yield calls per element, a total of O(N\*log N) dynamic calls overall, when only O(N) are necessary.
-A better implementation strategy for recursive iterators is to
-first define the "every" operator for your recursive data type,
-where every(f) reports whether an arbitrary predicate f(x) is true
-for every element x in the data type. For our tree, the every
-function would be:
+A better implementation strategy for recursive iterators is to first define the "every" operator for your recursive data type, where every(f) reports whether an arbitrary predicate f(x) is true for every element x in the data type. For our tree, the every function would be:
func (t *tree) every(f func(int) bool) bool {
return t == nil ||
t.left.every(f) && f(t.value) && t.right.every(f)
}
-For example, this use of the every operator prints whether every
-element in the tree is an even number:
+For example, this use of the every operator prints whether every element in the tree is an even number:
even := func(x int) bool { return x&1 == 0 }
println(t.every(even))
-Then the iterator can be simply expressed as a trivial wrapper
-around the every operator:
+Then the iterator can be simply expressed as a trivial wrapper around the every operator:
func (t *tree) All() iter.Seq[int] {
return func(yield func(int) bool) {
@@ -4173,13 +3645,10 @@
}
}
-In effect, tree.All computes whether yield returns true for each
-element, short-circuiting if it ever returns false, then discards
-the final boolean result.
+In effect, tree.All computes whether yield returns true for each element, short-circuiting if it ever returns false, then discards the final boolean result.
-This has much better performance characteristics: it makes one
-dynamic call per element of the tree, and it doesn't heap-allocate
-anything. It is also clearer.
+This has much better performance characteristics: it makes one dynamic call per element of the tree, and it doesn't heap-allocate anything. It is also clearer.
+
Default: on.
@@ -4188,15 +3657,9 @@
<a id='shadow'></a>
## `shadow`: check for possible unintended shadowing of variables
+This analyzer check for shadowed variables. A shadowed variable is a variable declared in an inner scope with the same name and type as a variable in an outer scope, and where the outer variable is mentioned after the inner one is declared.
-This analyzer check for shadowed variables.
-A shadowed variable is a variable declared in an inner scope
-with the same name and type as a variable in an outer scope,
-and where the outer variable is mentioned after the inner one
-is declared.
-
-(This definition can be refined; the module generates too many
-false positives and is not yet enabled by default.)
+(This definition can be refined; the module generates too many false positives and is not yet enabled by default.)
For example:
@@ -4212,6 +3675,7 @@
return err
}
+
Default: off. Enable by setting `"analyses": {"shadow": true}`.
Package documentation: [shadow](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/shadow)
@@ -4228,13 +3692,13 @@
<a id='sigchanyzer'></a>
## `sigchanyzer`: check for unbuffered channel of os.Signal
-
This checker reports call expression of the form
signal.Notify(c <-chan os.Signal, sig ...os.Signal),
where c is an unbuffered channel, which can be at risk of missing the signal.
+
Default: on.
Package documentation: [sigchanyzer](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/sigchanyzer)
@@ -4242,7 +3706,6 @@
<a id='simplifycompositelit'></a>
## `simplifycompositelit`: check for composite literal simplifications
-
An array, slice, or map composite literal of the form:
[]T{T{}, T{}}
@@ -4255,6 +3718,7 @@
This analyzer ignores generated code.
+
Default: on.
Package documentation: [simplifycompositelit](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/simplifycompositelit)
@@ -4262,7 +3726,6 @@
<a id='simplifyrange'></a>
## `simplifyrange`: check for range statement simplifications
-
A range of the form:
for x, _ = range v {...}
@@ -4283,6 +3746,7 @@
This analyzer ignores generated code.
+
Default: on.
Package documentation: [simplifyrange](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/simplifyrange)
@@ -4290,7 +3754,6 @@
<a id='simplifyslice'></a>
## `simplifyslice`: check for slice simplifications
-
A slice expression of the form:
s[a:len(s)]
@@ -4303,6 +3766,7 @@
This analyzer ignores generated code.
+
Default: on.
Package documentation: [simplifyslice](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/simplifyslice)
@@ -4310,14 +3774,10 @@
<a id='slicescontains'></a>
## `slicescontains`: replace loops with slices.Contains or slices.ContainsFunc
+The slicescontains analyzer simplifies loops that check for the existence of an element in a slice. It replaces them with calls to \`slices.Contains\` or \`slices.ContainsFunc\`, which were added in Go 1.21.
-The slicescontains analyzer simplifies loops that check for the existence of
-an element in a slice. It replaces them with calls to `slices.Contains` or
-`slices.ContainsFunc`, which were added in Go 1.21.
+If the expression for the target element has side effects, this transformation will cause those effects to occur only once, not once per tested slice element.
-If the expression for the target element has side effects, this
-transformation will cause those effects to occur only once, not
-once per tested slice element.
Default: on.
@@ -4326,7 +3786,6 @@
<a id='slicesdelete'></a>
## `slicesdelete`: replace append-based slice deletion with slices.Delete
-
The slicesdelete analyzer suggests replacing the idiom
s = append(s[:i], s[j:]...)
@@ -4337,10 +3796,8 @@
introduced in Go 1.21.
-This analyzer is disabled by default. The `slices.Delete` function
-zeros the elements between the new length and the old length of the
-slice to prevent memory leaks, which is a subtle difference in
-behavior compared to the append-based idiom; see https://go.dev/issue/73686.
+This analyzer is disabled by default. The \`slices.Delete\` function zeros the elements between the new length and the old length of the slice to prevent memory leaks, which is a subtle difference in behavior compared to the append-based idiom; see [https://go.dev/issue/73686](https://go.dev/issue/73686).
+
Default: off. Enable by setting `"analyses": {"slicesdelete": true}`.
@@ -4349,13 +3806,12 @@
<a id='slicessort'></a>
## `slicessort`: replace sort.Slice with slices.Sort for basic types
-
-The slicessort analyzer simplifies sorting slices of basic ordered
-types. It replaces
+The slicessort analyzer simplifies sorting slices of basic ordered types. It replaces
sort.Slice(s, func(i, j int) bool { return s[i] < s[j] })
-with the simpler `slices.Sort(s)`, which was added in Go 1.21.
+with the simpler \`slices.Sort(s)\`, which was added in Go 1.21.
+
Default: on.
@@ -4364,12 +3820,7 @@
<a id='slog'></a>
## `slog`: check for invalid structured logging calls
-
-The slog checker looks for calls to functions from the log/slog
-package that take alternating key-value pairs. It reports calls
-where an argument in a key position is neither a string nor a
-slog.Attr, and where a final key is missing its value.
-For example,it would report
+The slog checker looks for calls to functions from the log/slog package that take alternating key-value pairs. It reports calls where an argument in a key position is neither a string nor a slog.Attr, and where a final key is missing its value. For example,it would report
slog.Warn("message", 11, "k") // slog.Warn arg "11" should be a string or a slog.Attr
@@ -4377,6 +3828,7 @@
slog.Info("message", "k1", v1, "k2") // call to slog.Info missing a final value
+
Default: on.
Package documentation: [slog](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/slog)
@@ -4384,9 +3836,8 @@
<a id='sortslice'></a>
## `sortslice`: check the argument type of sort.Slice
+sort.Slice requires an argument of a slice type. Check that the interface{} value passed to sort.Slice is actually a slice.
-sort.Slice requires an argument of a slice type. Check that
-the interface{} value passed to sort.Slice is actually a slice.
Default: on.
@@ -4395,18 +3846,12 @@
<a id='stdmethods'></a>
## `stdmethods`: check signature of methods of well-known interfaces
-
-Sometimes a type may be intended to satisfy an interface but may fail to
-do so because of a mistake in its method signature.
-For example, the result of this WriteTo method should be (int64, error),
-not error, to satisfy io.WriterTo:
+Sometimes a type may be intended to satisfy an interface but may fail to do so because of a mistake in its method signature. For example, the result of this WriteTo method should be (int64, error), not error, to satisfy io.WriterTo:
type myWriterTo struct{...}
func (myWriterTo) WriteTo(w io.Writer) error { ... }
-This check ensures that each method whose name matches one of several
-well-known interface methods from the standard library has the correct
-signature for that interface.
+This check ensures that each method whose name matches one of several well-known interface methods from the standard library has the correct signature for that interface.
Checked method names include:
@@ -4415,6 +3860,7 @@
UnmarshalJSON UnreadByte UnreadRune WriteByte
WriteTo
+
Default: on.
Package documentation: [stdmethods](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/stdmethods)
@@ -4422,17 +3868,9 @@
<a id='stdversion'></a>
## `stdversion`: report uses of too-new standard library symbols
+The stdversion analyzer reports references to symbols in the standard library that were introduced by a Go release higher than the one in force in the referring file. (Recall that the file's Go version is defined by the 'go' directive its module's go.mod file, or by a "//go:build go1.X" build tag at the top of the file.)
-The stdversion analyzer reports references to symbols in the standard
-library that were introduced by a Go release higher than the one in
-force in the referring file. (Recall that the file's Go version is
-defined by the 'go' directive its module's go.mod file, or by a
-"//go:build go1.X" build tag at the top of the file.)
-
-The analyzer does not report a diagnostic for a reference to a "too
-new" field or method of a type that is itself "too new", as this may
-have false positives, for example if fields or methods are accessed
-through a type alias that is guarded by a Go version constraint.
+The analyzer does not report a diagnostic for a reference to a "too new" field or method of a type that is itself "too new", as this may have false positives, for example if fields or methods are accessed through a type alias that is guarded by a Go version constraint.
Default: on.
@@ -4442,16 +3880,10 @@
<a id='stringintconv'></a>
## `stringintconv`: check for string(int) conversions
+This checker flags conversions of the form string(x) where x is an integer (but not byte or rune) type. Such conversions are discouraged because they return the UTF-8 representation of the Unicode code point x, and not a decimal string representation of x as one might expect. Furthermore, if x denotes an invalid code point, the conversion cannot be statically rejected.
-This checker flags conversions of the form string(x) where x is an integer
-(but not byte or rune) type. Such conversions are discouraged because they
-return the UTF-8 representation of the Unicode code point x, and not a decimal
-string representation of x as one might expect. Furthermore, if x denotes an
-invalid code point, the conversion cannot be statically rejected.
+For conversions that intend on using the code point, consider replacing them with string(rune(x)). Otherwise, strconv.Itoa and its equivalents return the string representation of the value in the desired base.
-For conversions that intend on using the code point, consider replacing them
-with string(rune(x)). Otherwise, strconv.Itoa and its equivalents return the
-string representation of the value in the desired base.
Default: on.
@@ -4460,9 +3892,7 @@
<a id='stringsbuilder'></a>
## `stringsbuilder`: replace += with strings.Builder
-
-This analyzer replaces repeated string += string concatenation
-operations with calls to Go 1.10's strings.Builder.
+This analyzer replaces repeated string += string concatenation operations with calls to Go 1.10's strings.Builder.
For example:
@@ -4487,14 +3917,10 @@
This avoids quadratic memory allocation and improves performance.
-The analyzer requires that all references to s except the final one
-are += operations. To avoid warning about trivial cases, at least one
-must appear within a loop. The variable s must be a local
-variable, not a global or parameter.
+The analyzer requires that all references to s except the final one are += operations. To avoid warning about trivial cases, at least one must appear within a loop. The variable s must be a local variable, not a global or parameter.
-The sole use of the finished string must be the last reference to the
-variable s. (It may appear within an intervening loop or function literal,
-since even s.String() is called repeatedly, it does not allocate memory.)
+The sole use of the finished string must be the last reference to the variable s. (It may appear within an intervening loop or function literal, since even s.String() is called repeatedly, it does not allocate memory.)
+
Default: on.
@@ -4503,12 +3929,7 @@
<a id='stringscutprefix'></a>
## `stringscutprefix`: replace HasPrefix/TrimPrefix with CutPrefix
-
-The stringscutprefix analyzer simplifies a common pattern where code first
-checks for a prefix with `strings.HasPrefix` and then removes it with
-`strings.TrimPrefix`. It replaces this two-step process with a single call
-to `strings.CutPrefix`, introduced in Go 1.20. The analyzer also handles
-the equivalent functions in the `bytes` package.
+The stringscutprefix analyzer simplifies a common pattern where code first checks for a prefix with \`strings.HasPrefix\` and then removes it with \`strings.TrimPrefix\`. It replaces this two-step process with a single call to \`strings.CutPrefix\`, introduced in Go 1.20. The analyzer also handles the equivalent functions in the \`bytes\` package.
For example, this input:
@@ -4522,8 +3943,7 @@
use(after)
}
-The analyzer also offers fixes to use CutSuffix in a similar way.
-This input:
+The analyzer also offers fixes to use CutSuffix in a similar way. This input:
if strings.HasSuffix(s, suffix) {
use(strings.TrimSuffix(s, suffix))
@@ -4535,6 +3955,7 @@
use(before)
}
+
Default: on.
Package documentation: [stringscutprefix](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/modernize#stringscutprefix)
@@ -4542,9 +3963,7 @@
<a id='stringsseq'></a>
## `stringsseq`: replace ranging over Split/Fields with SplitSeq/FieldsSeq
-
-The stringsseq analyzer improves the efficiency of iterating over substrings.
-It replaces
+The stringsseq analyzer improves the efficiency of iterating over substrings. It replaces
for range strings.Split(...)
@@ -4552,9 +3971,8 @@
for range strings.SplitSeq(...)
-which was added in Go 1.24 and avoids allocating a slice for the
-substrings. The analyzer also handles strings.Fields and the
-equivalent functions in the bytes package.
+which was added in Go 1.24 and avoids allocating a slice for the substrings. The analyzer also handles strings.Fields and the equivalent functions in the bytes package.
+
Default: on.
@@ -4563,9 +3981,9 @@
<a id='structtag'></a>
## `structtag`: check that struct field tags conform to reflect.StructTag.Get
-
Also report certain struct tags (json, xml) used with unexported fields.
+
Default: on.
Package documentation: [structtag](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/structtag)
@@ -4573,17 +3991,15 @@
<a id='testingcontext'></a>
## `testingcontext`: replace context.WithCancel with t.Context in tests
-
-The testingcontext analyzer simplifies context management in tests. It
-replaces the manual creation of a cancellable context,
+The testingcontext analyzer simplifies context management in tests. It replaces the manual creation of a cancellable context,
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
with a single call to t.Context(), which was added in Go 1.24.
-This change is only suggested if the `cancel` function is not used
-for any other purpose.
+This change is only suggested if the \`cancel\` function is not used for any other purpose.
+
Default: on.
@@ -4592,11 +4008,7 @@
<a id='testinggoroutine'></a>
## `testinggoroutine`: report calls to (*testing.T).Fatal from goroutines started by a test
-
-Functions that abruptly terminate a test, such as the Fatal, Fatalf, FailNow, and
-Skip{,f,Now} methods of *testing.T, must be called from the test goroutine itself.
-This checker detects calls to these functions that occur within a goroutine
-started by the test. For example:
+Functions that abruptly terminate a test, such as the Fatal, Fatalf, FailNow, and Skip{,f,Now} methods of \*testing.T, must be called from the test goroutine itself. This checker detects calls to these functions that occur within a goroutine started by the test. For example:
func TestFoo(t *testing.T) {
go func() {
@@ -4604,6 +4016,7 @@
}()
}
+
Default: on.
Package documentation: [testinggoroutine](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/testinggoroutine)
@@ -4611,13 +4024,10 @@
<a id='tests'></a>
## `tests`: check for common mistaken usages of tests and examples
+The tests checker walks Test, Benchmark, Fuzzing and Example functions checking malformed names, wrong signatures and examples documenting non-existent identifiers.
-The tests checker walks Test, Benchmark, Fuzzing and Example functions checking
-malformed names, wrong signatures and examples documenting non-existent
-identifiers.
+Please see the documentation for package testing in golang.org/pkg/testing for the conventions that are enforced for Tests, Benchmarks, and Examples.
-Please see the documentation for package testing in golang.org/pkg/testing
-for the conventions that are enforced for Tests, Benchmarks, and Examples.
Default: on.
@@ -4626,10 +4036,8 @@
<a id='timeformat'></a>
## `timeformat`: check for calls of (time.Time).Format or time.Parse with 2006-02-01
+The timeformat checker looks for time formats with the 2006-02-01 (yyyy-dd-mm) format. Internationally, "yyyy-dd-mm" does not occur in common calendar date standards, and so it is more likely that 2006-01-02 (yyyy-mm-dd) was intended.
-The timeformat checker looks for time formats with the 2006-02-01 (yyyy-dd-mm)
-format. Internationally, "yyyy-dd-mm" does not occur in common calendar date
-standards, and so it is more likely that 2006-01-02 (yyyy-mm-dd) was intended.
Default: on.
@@ -4638,9 +4046,8 @@
<a id='unmarshal'></a>
## `unmarshal`: report passing non-pointer or non-interface values to unmarshal
+The unmarshal analysis reports calls to functions such as json.Unmarshal in which the argument type is not a pointer or an interface.
-The unmarshal analysis reports calls to functions such as json.Unmarshal
-in which the argument type is not a pointer or an interface.
Default: on.
@@ -4649,10 +4056,8 @@
<a id='unreachable'></a>
## `unreachable`: check for unreachable code
+The unreachable analyzer finds statements that execution can never reach because they are preceded by a return statement, a call to panic, an infinite loop, or similar constructs.
-The unreachable analyzer finds statements that execution can never reach
-because they are preceded by a return statement, a call to panic, an
-infinite loop, or similar constructs.
Default: on.
@@ -4661,12 +4066,8 @@
<a id='unsafeptr'></a>
## `unsafeptr`: check for invalid conversions of uintptr to unsafe.Pointer
+The unsafeptr analyzer reports likely incorrect uses of unsafe.Pointer to convert integers to pointers. A conversion from uintptr to unsafe.Pointer is invalid if it implies that there is a uintptr-typed word in memory that holds a pointer value, because that word will be invisible to stack copying and to the garbage collector.
-The unsafeptr analyzer reports likely incorrect uses of unsafe.Pointer
-to convert integers to pointers. A conversion from uintptr to
-unsafe.Pointer is invalid if it implies that there is a uintptr-typed
-word in memory that holds a pointer value, because that word will be
-invisible to stack copying and to the garbage collector.
Default: on.
@@ -4675,53 +4076,30 @@
<a id='unusedfunc'></a>
## `unusedfunc`: check for unused functions, methods, etc
+The unusedfunc analyzer reports functions and methods that are never referenced outside of their own declaration.
-The unusedfunc analyzer reports functions and methods that are
-never referenced outside of their own declaration.
+A function is considered unused if it is unexported and not referenced (except within its own declaration).
-A function is considered unused if it is unexported and not
-referenced (except within its own declaration).
+A method is considered unused if it is unexported, not referenced (except within its own declaration), and its name does not match that of any method of an interface type declared within the same package.
-A method is considered unused if it is unexported, not referenced
-(except within its own declaration), and its name does not match
-that of any method of an interface type declared within the same
-package.
+The tool may report false positives in some situations, for example:
-The tool may report false positives in some situations, for
-example:
+ - for a declaration of an unexported function that is referenced from another package using the go:linkname mechanism, if the declaration's doc comment does not also have a go:linkname comment.
- - for a declaration of an unexported function that is referenced
- from another package using the go:linkname mechanism, if the
- declaration's doc comment does not also have a go:linkname
- comment.
+ (Such code is in any case strongly discouraged: linkname annotations, if they must be used at all, should be used on both the declaration and the alias.)
- (Such code is in any case strongly discouraged: linkname
- annotations, if they must be used at all, should be used on both
- the declaration and the alias.)
-
- - for compiler intrinsics in the "runtime" package that, though
- never referenced, are known to the compiler and are called
- indirectly by compiled object code.
+ - for compiler intrinsics in the "runtime" package that, though never referenced, are known to the compiler and are called indirectly by compiled object code.
- for functions called only from assembly.
- - for functions called only from files whose build tags are not
- selected in the current build configuration.
+ - for functions called only from files whose build tags are not selected in the current build configuration.
-Since these situations are relatively common in the low-level parts
-of the runtime, this analyzer ignores the standard library.
-See https://go.dev/issue/71686 and https://go.dev/issue/74130 for
-further discussion of these limitations.
+Since these situations are relatively common in the low-level parts of the runtime, this analyzer ignores the standard library. See [https://go.dev/issue/71686](https://go.dev/issue/71686) and [https://go.dev/issue/74130](https://go.dev/issue/74130) for further discussion of these limitations.
-The unusedfunc algorithm is not as precise as the
-golang.org/x/tools/cmd/deadcode tool, but it has the advantage that
-it runs within the modular analysis framework, enabling near
-real-time feedback within gopls.
+The unusedfunc algorithm is not as precise as the golang.org/x/tools/cmd/deadcode tool, but it has the advantage that it runs within the modular analysis framework, enabling near real-time feedback within gopls.
-The unusedfunc analyzer also reports unused types, vars, and
-constants. Enums--constants defined with iota--are ignored since
-even the unused values must remain present to preserve the logical
-ordering.
+The unusedfunc analyzer also reports unused types, vars, and constants. Enums--constants defined with iota--are ignored since even the unused values must remain present to preserve the logical ordering.
+
Default: on.
@@ -4730,32 +4108,21 @@
<a id='unusedparams'></a>
## `unusedparams`: check for unused parameters of functions
-
-The unusedparams analyzer checks functions to see if there are
-any parameters that are not being used.
+The unusedparams analyzer checks functions to see if there are any parameters that are not being used.
To ensure soundness, it ignores:
- - "address-taken" functions, that is, functions that are used as
- a value rather than being called directly; their signatures may
- be required to conform to a func type.
- - exported functions or methods, since they may be address-taken
- in another package.
- - unexported methods whose name matches an interface method
- declared in the same package, since the method's signature
- may be required to conform to the interface type.
- - functions with empty bodies, or containing just a call to panic.
- - parameters that are unnamed, or named "_", the blank identifier.
-The analyzer suggests a fix of replacing the parameter name by "_",
-but in such cases a deeper fix can be obtained by invoking the
-"Refactor: remove unused parameter" code action, which will
-eliminate the parameter entirely, along with all corresponding
-arguments at call sites, while taking care to preserve any side
-effects in the argument expressions; see
-https://github.com/golang/tools/releases/tag/gopls%2Fv0.14.
+ - "address-taken" functions, that is, functions that are used as a value rather than being called directly; their signatures may be required to conform to a func type.
+ - exported functions or methods, since they may be address-taken in another package.
+ - unexported methods whose name matches an interface method declared in the same package, since the method's signature may be required to conform to the interface type.
+ - functions with empty bodies, or containing just a call to panic.
+ - parameters that are unnamed, or named "\_", the blank identifier.
+
+The analyzer suggests a fix of replacing the parameter name by "\_", but in such cases a deeper fix can be obtained by invoking the "Refactor: remove unused parameter" code action, which will eliminate the parameter entirely, along with all corresponding arguments at call sites, while taking care to preserve any side effects in the argument expressions; see [https://github.com/golang/tools/releases/tag/gopls%2Fv0.14](https://github.com/golang/tools/releases/tag/gopls%2Fv0.14).
This analyzer ignores generated code.
+
Default: on.
Package documentation: [unusedparams](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/unusedparams)
@@ -4763,15 +4130,11 @@
<a id='unusedresult'></a>
## `unusedresult`: check for unused results of calls to some functions
-
-Some functions like fmt.Errorf return a result and have no side
-effects, so it is always a mistake to discard the result. Other
-functions may return an error that must not be ignored, or a cleanup
-operation that must be called. This analyzer reports calls to
-functions like these when the result of the call is ignored.
+Some functions like fmt.Errorf return a result and have no side effects, so it is always a mistake to discard the result. Other functions may return an error that must not be ignored, or a cleanup operation that must be called. This analyzer reports calls to functions like these when the result of the call is ignored.
The set of functions may be controlled using flags.
+
Default: on.
Package documentation: [unusedresult](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/unusedresult)
@@ -4788,12 +4151,7 @@
<a id='unusedwrite'></a>
## `unusedwrite`: checks for unused writes
-
-The analyzer reports instances of writes to struct fields and
-arrays that are never read. Specifically, when a struct object
-or an array is copied, its elements are copied implicitly by
-the compiler, and any element write to this copy does nothing
-with the original object.
+The analyzer reports instances of writes to struct fields and arrays that are never read. Specifically, when a struct object or an array is copied, its elements are copied implicitly by the compiler, and any element write to this copy does nothing with the original object.
For example:
@@ -4813,6 +4171,7 @@
t.x = i // unused write to field x
}
+
Default: on.
Package documentation: [unusedwrite](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/unusedwrite)
@@ -4820,9 +4179,7 @@
<a id='waitgroup'></a>
## `waitgroup`: check for misuses of sync.WaitGroup
-
-This analyzer detects mistaken calls to the (*sync.WaitGroup).Add
-method from inside a new goroutine, causing Add to race with Wait:
+This analyzer detects mistaken calls to the (\*sync.WaitGroup).Add method from inside a new goroutine, causing Add to race with Wait:
// WRONG
var wg sync.WaitGroup
@@ -4844,6 +4201,7 @@
}()
wg.Wait()
+
Default: on.
Package documentation: [waitgroup](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/waitgroup)
@@ -4851,9 +4209,7 @@
<a id='waitgroup'></a>
## `waitgroup`: replace wg.Add(1)/go/wg.Done() with wg.Go
-
-The waitgroup analyzer simplifies goroutine management with `sync.WaitGroup`.
-It replaces the common pattern
+The waitgroup analyzer simplifies goroutine management with \`sync.WaitGroup\`. It replaces the common pattern
wg.Add(1)
go func() {
@@ -4867,6 +4223,7 @@
which was added in Go 1.25.
+
Default: on.
Package documentation: [waitgroup](https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/modernize#waitgroup)
@@ -4874,13 +4231,9 @@
<a id='yield'></a>
## `yield`: report calls to yield where the result is ignored
+After a yield function returns false, the caller should not call the yield function again; generally the iterator should return promptly.
-After a yield function returns false, the caller should not call
-the yield function again; generally the iterator should return
-promptly.
-
-This example fails to check the result of the call to yield,
-causing this analyzer to report a diagnostic:
+This example fails to check the result of the call to yield, causing this analyzer to report a diagnostic:
yield(1) // yield may be called again (on L2) after returning false
yield(2)
@@ -4893,14 +4246,13 @@
_ = yield(1) && yield(2)
-It is not always a mistake to ignore the result of yield.
-For example, this is a valid single-element iterator:
+It is not always a mistake to ignore the result of yield. For example, this is a valid single-element iterator:
yield(1) // ok to ignore result
return
-It is only a mistake when the yield call that returned false may be
-followed by another call.
+It is only a mistake when the yield call that returned false may be followed by another call.
+
Default: on.
diff --git a/gopls/internal/doc/api.go b/gopls/internal/doc/api.go
index 52101dd..8448639 100644
--- a/gopls/internal/doc/api.go
+++ b/gopls/internal/doc/api.go
@@ -67,7 +67,7 @@
type Analyzer struct {
Name string
- Doc string // from analysis.Analyzer.Doc ("title: summary\ndescription"; not Markdown)
+ Doc string // from analysis.Analyzer.Doc ("title: summary\ndescription"; go/doc/comment, not Markdown)
URL string
Default bool
}
diff --git a/gopls/internal/doc/generate/generate.go b/gopls/internal/doc/generate/generate.go
index 5b1acc9..63eb999 100644
--- a/gopls/internal/doc/generate/generate.go
+++ b/gopls/internal/doc/generate/generate.go
@@ -20,6 +20,7 @@
"errors"
"fmt"
"go/ast"
+ "go/doc/comment"
"go/token"
"go/types"
"maps"
@@ -760,7 +761,23 @@
title, doc, _ := strings.Cut(analyzer.Doc, "\n")
title = strings.TrimPrefix(title, analyzer.Name+": ")
fmt.Fprintf(&buf, "## `%s`: %s\n\n", analyzer.Name, title)
- fmt.Fprintf(&buf, "%s\n\n", doc)
+
+ // Convert Analyzer.Doc from go/doc/comment form to Markdown.
+ // Headings in doc comments are converted to ### (HeadingLevel=3).
+ //
+ // Some Analyzers (e.g. internal/gofix) use ## to indicate subheadings
+ // Although this is valid Markdown, it is not valid go/doc/comment,
+ // nor is it rendered as a subheading by pkg.go.dev or gopls's doc viewer.
+ // Perhaps it will be supported in future; see
+ // https://github.com/golang/go/issues/51082#issuecomment-1033116430 et seq.
+ //
+ // In the meantime, the go/doc/comment processing will escape them so
+ // that the ## appears literally in analyzers.md just as it does in
+ // the two viewers mentioned above. The meaning is clear enough.
+ doctree := new(comment.Parser).Parse(doc)
+ buf.Write((&comment.Printer{HeadingLevel: 3}).Markdown(doctree))
+ buf.WriteString("\n\n")
+
fmt.Fprintf(&buf, "Default: %s.", onOff(analyzer.Default))
if !analyzer.Default {
fmt.Fprintf(&buf, " Enable by setting `\"analyses\": {\"%s\": true}`.", analyzer.Name)
