[release-branch.go1.12] go/analysis/passes/printf: fix big.Int false positive
It's possible to use a type which implements fmt.Formatter without
importing fmt directly, if the type is imported from another package
such as math/big.
On top of that, it's possible to use printf-like functions without
importing fmt directly, such as using testing.T.Logf.
These two scenarios combined can lead to the printf check not finding
the fmt.Formatter type, since it's not a direct dependency of the root
package.
fmt must still be in the import graph somewhere, so we could search for
it via types.Package.Imports. However, at that point it's simpler to
just look for the Format method manually via go/types.
Fixes #30399.
Change-Id: Id78454bb6a51b3c5e1bcb1984a7fbfb4a29a5be0
Reviewed-on: https://go-review.googlesource.com/c/163817
Run-TryBot: Daniel Martà <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
(cherry picked from commit 589c23e65e65055d47b9ad4a99723bc389136265)
Reviewed-on: https://go-review.googlesource.com/c/tools/+/164657
Run-TryBot: Alan Donovan <adonovan@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/go/analysis/passes/printf/printf.go b/go/analysis/passes/printf/printf.go
index c0265aa..b73ff5e 100644
--- a/go/analysis/passes/printf/printf.go
+++ b/go/analysis/passes/printf/printf.go
@@ -453,15 +453,23 @@
}
// isFormatter reports whether t satisfies fmt.Formatter.
-// Unlike fmt.Stringer, it's impossible to satisfy fmt.Formatter without importing fmt.
-func isFormatter(pass *analysis.Pass, t types.Type) bool {
- for _, imp := range pass.Pkg.Imports() {
- if imp.Path() == "fmt" {
- formatter := imp.Scope().Lookup("Formatter").Type().Underlying().(*types.Interface)
- return types.Implements(t, formatter)
- }
+// The only interface method to look for is "Format(State, rune)".
+func isFormatter(typ types.Type) bool {
+ obj, _, _ := types.LookupFieldOrMethod(typ, false, nil, "Format")
+ fn, ok := obj.(*types.Func)
+ if !ok {
+ return false
}
- return false
+ sig := fn.Type().(*types.Signature)
+ return sig.Params().Len() == 2 &&
+ sig.Results().Len() == 0 &&
+ isNamed(sig.Params().At(0).Type(), "fmt", "State") &&
+ types.Identical(sig.Params().At(1).Type(), types.Typ[types.Rune])
+}
+
+func isNamed(T types.Type, pkgpath, name string) bool {
+ named, ok := T.(*types.Named)
+ return ok && named.Obj().Pkg().Path() == pkgpath && named.Obj().Name() == name
}
// formatState holds the parsed representation of a printf directive such as "%3.*[4]d".
@@ -753,7 +761,7 @@
formatter := false
if state.argNum < len(call.Args) {
if tv, ok := pass.TypesInfo.Types[call.Args[state.argNum]]; ok {
- formatter = isFormatter(pass, tv.Type)
+ formatter = isFormatter(tv.Type)
}
}
@@ -831,7 +839,7 @@
typ := pass.TypesInfo.Types[e].Type
// It's unlikely to be a recursive stringer if it has a Format method.
- if isFormatter(pass, typ) {
+ if isFormatter(typ) {
return false
}
diff --git a/go/analysis/passes/printf/printf_test.go b/go/analysis/passes/printf/printf_test.go
index 937bbe7..6845326 100644
--- a/go/analysis/passes/printf/printf_test.go
+++ b/go/analysis/passes/printf/printf_test.go
@@ -10,5 +10,5 @@
func Test(t *testing.T) {
testdata := analysistest.TestData()
printf.Analyzer.Flags.Set("funcs", "Warn,Warnf")
- analysistest.Run(t, testdata, printf.Analyzer, "a", "b")
+ analysistest.Run(t, testdata, printf.Analyzer, "a", "b", "nofmt")
}
diff --git a/go/analysis/passes/printf/testdata/src/nofmt/nofmt.go b/go/analysis/passes/printf/testdata/src/nofmt/nofmt.go
new file mode 100644
index 0000000..c323796
--- /dev/null
+++ b/go/analysis/passes/printf/testdata/src/nofmt/nofmt.go
@@ -0,0 +1,10 @@
+package b
+
+import (
+ "math/big"
+ "testing"
+)
+
+func formatBigInt(t *testing.T) {
+ t.Logf("%d\n", big.NewInt(4))
+}
diff --git a/go/analysis/passes/printf/types.go b/go/analysis/passes/printf/types.go
index 2eb6dc7..12286fd 100644
--- a/go/analysis/passes/printf/types.go
+++ b/go/analysis/passes/printf/types.go
@@ -38,7 +38,7 @@
}
}
// If the type implements fmt.Formatter, we have nothing to check.
- if isFormatter(pass, typ) {
+ if isFormatter(typ) {
return true
}
// If we can use a string, might arg (dynamically) implement the Stringer or Error interface?
