go/analysis/passes/shift: update for generics
Warn about shifts that exceed the width of a type in the type parameter
type set.
For golang/go#48704
Change-Id: If16650b0c7214415f650884014eda9690d8da11a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/357758
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Tim King <taking@google.com>
diff --git a/go/analysis/passes/shift/shift.go b/go/analysis/passes/shift/shift.go
index 1f3df07..640de28 100644
--- a/go/analysis/passes/shift/shift.go
+++ b/go/analysis/passes/shift/shift.go
@@ -14,11 +14,13 @@
"go/ast"
"go/constant"
"go/token"
+ "math"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
"golang.org/x/tools/go/ast/inspector"
+ "golang.org/x/tools/internal/typeparams"
)
const Doc = "check for shifts that equal or exceed the width of the integer"
@@ -93,9 +95,27 @@
if t == nil {
return
}
- size := 8 * pass.TypesSizes.Sizeof(t)
- if amt >= size {
+ terms, err := typeparams.StructuralTerms(t)
+ if err != nil {
+ return // invalid type
+ }
+ sizes := make(map[int64]struct{})
+ for _, term := range terms {
+ size := 8 * pass.TypesSizes.Sizeof(term.Type())
+ sizes[size] = struct{}{}
+ }
+ minSize := int64(math.MaxInt64)
+ for size := range sizes {
+ if size < minSize {
+ minSize = size
+ }
+ }
+ if amt >= minSize {
ident := analysisutil.Format(pass.Fset, x)
- pass.ReportRangef(node, "%s (%d bits) too small for shift of %d", ident, size, amt)
+ qualifier := ""
+ if len(sizes) > 1 {
+ qualifier = "may be "
+ }
+ pass.ReportRangef(node, "%s (%s%d bits) too small for shift of %d", ident, qualifier, minSize, amt)
}
}
diff --git a/go/analysis/passes/shift/shift_test.go b/go/analysis/passes/shift/shift_test.go
index 8b41b60..e60943e 100644
--- a/go/analysis/passes/shift/shift_test.go
+++ b/go/analysis/passes/shift/shift_test.go
@@ -9,9 +9,14 @@
"golang.org/x/tools/go/analysis/analysistest"
"golang.org/x/tools/go/analysis/passes/shift"
+ "golang.org/x/tools/internal/typeparams"
)
func Test(t *testing.T) {
testdata := analysistest.TestData()
- analysistest.Run(t, testdata, shift.Analyzer, "a")
+ pkgs := []string{"a"}
+ if typeparams.Enabled {
+ pkgs = append(pkgs, "typeparams")
+ }
+ analysistest.Run(t, testdata, shift.Analyzer, pkgs...)
}
diff --git a/go/analysis/passes/shift/testdata/src/typeparams/typeparams.go b/go/analysis/passes/shift/testdata/src/typeparams/typeparams.go
new file mode 100644
index 0000000..a76df88
--- /dev/null
+++ b/go/analysis/passes/shift/testdata/src/typeparams/typeparams.go
@@ -0,0 +1,32 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeparams
+
+import "unsafe"
+
+func GenericShiftTest[DifferentSize ~int8|int16|int64, SameSize int8|byte]() {
+ var d DifferentSize
+ _ = d << 7
+ _ = d << 8 // want "d .may be 8 bits. too small for shift of 8"
+ _ = d << 15 // want "d .may be 8 bits. too small for shift of 15"
+ _ = (d + 1) << 8 // want ".d . 1. .may be 8 bits. too small for shift of 8"
+ _ = (d + 1) << 16 // want ".d . 1. .may be 8 bits. too small for shift of 16"
+ _ = d << (7 + 1) // want "d .may be 8 bits. too small for shift of 8"
+ _ = d >> 8 // want "d .may be 8 bits. too small for shift of 8"
+ d <<= 8 // want "d .may be 8 bits. too small for shift of 8"
+ d >>= 8 // want "d .may be 8 bits. too small for shift of 8"
+
+ // go/types does not compute constant sizes for type parameters, so we do not
+ // report a diagnostic here.
+ _ = d << (8 * DifferentSize(unsafe.Sizeof(d)))
+
+ var s SameSize
+ _ = s << 7
+ _ = s << 8 // want "s .8 bits. too small for shift of 8"
+ _ = s << (7 + 1) // want "s .8 bits. too small for shift of 8"
+ _ = s >> 8 // want "s .8 bits. too small for shift of 8"
+ s <<= 8 // want "s .8 bits. too small for shift of 8"
+ s >>= 8 // want "s .8 bits. too small for shift of 8"
+}
