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cmd/vet: assume that no builtin funcs are pure

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That was the intention with the existing code, but it was buggy; builtin
functions aren't treated as values by types.TypeAndVal. Thus, we should
use the IsBuiltin method instead of IsValue.

Teaching vet what builtin funcs are pure is already being tracked as a
separate issue, #22851.

While at it, also add a test with methods, just to be sure that the
current logic doesn't break with that edge case either.

Fixes #25303.

Change-Id: Ic18402b22cceeabf76641c02f575b194b9a536cc
Reviewed-on: https://go-review.googlesource.com/112177
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Daniel Martí 2018-05-09 11:11:49 +07:00
parent 23e9dc7994
commit 2486ebfb63
2 changed files with 19 additions and 6 deletions
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16
src/cmd/vet/bool.go
View File

@ -147,12 +147,18 @@ func hasSideEffects(f *File, e ast.Expr) bool {
// conversion as a *types.Named. // conversion as a *types.Named.
typVal := f.pkg.types[n.Fun] typVal := f.pkg.types[n.Fun]
_, isSig := typVal.Type.(*types.Signature) _, isSig := typVal.Type.(*types.Signature)
if typVal.IsValue() && isSig { switch {
case typVal.IsValue() && isSig:
// If we have a value of unnamed signature type, // If we have a value of unnamed signature type,
// this CallExpr is a func call and not a type // this CallExpr is a non-builtin func call and
// conversion. Conservatively assume that all // not a type conversion. Conservatively assume
// function and method calls have side effects // that all function and method calls have side
// for now. // effects for now.
safe = false
return false
case typVal.IsBuiltin():
// For now, conservatively assume that all
// built-in functions have side effects.
safe = false safe = false
return false return false
} }

9
src/cmd/vet/testdata/bool.go vendored
View File

@ -10,12 +10,18 @@ import "io"
type T int type T int
func (t T) Foo() int { return int(t) }
type FT func() int type FT func() int
var S []int
func RatherStupidConditions() { func RatherStupidConditions() {
var f, g func() int var f, g func() int
if f() == 0 || f() == 0 { // OK f might have side effects if f() == 0 || f() == 0 { // OK f might have side effects
} }
var t T
_ = t.Foo() == 2 || t.Foo() == 2 // OK Foo might have side effects
if v, w := f(), g(); v == w || v == w { // ERROR "redundant or: v == w || v == w" if v, w := f(), g(); v == w || v == w { // ERROR "redundant or: v == w || v == w"
} }
_ = f == nil || f == nil // ERROR "redundant or: f == nil || f == nil" _ = f == nil || f == nil // ERROR "redundant or: f == nil || f == nil"
@ -25,9 +31,10 @@ func RatherStupidConditions() {
_ = FT(f) == nil || FT(f) == nil // ERROR "redundant or: FT(f) == nil || FT(f) == nil" _ = FT(f) == nil || FT(f) == nil // ERROR "redundant or: FT(f) == nil || FT(f) == nil"
_ = (func() int)(f) == nil || (func() int)(f) == nil // ERROR "redundant or: (func() int)(f) == nil || (func() int)(f) == nil" _ = (func() int)(f) == nil || (func() int)(f) == nil // ERROR "redundant or: (func() int)(f) == nil || (func() int)(f) == nil"
_ = append(S, 3) == nil || append(S, 3) == nil // OK append has side effects
var namedFuncVar FT var namedFuncVar FT
_ = namedFuncVar() == namedFuncVar() // OK; still func calls _ = namedFuncVar() == namedFuncVar() // OK still func calls
var c chan int var c chan int
_ = 0 == <-c || 0 == <-c // OK subsequent receives may yield different values _ = 0 == <-c || 0 == <-c // OK subsequent receives may yield different values