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cmd/vet: extra args if any formats are indexed are ok

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For example, the following program is valid:

	func main() {
		fmt.Printf("%[1]d", 1, 2, 3)
	}

If any of the formats are indexed, fmt will not complain about unused
extra arguments. See #22867 for more detail.

Make vet follow the same logic, to avoid erroring on programs that would
run without fmt complaining.

Fixes #23564.

Change-Id: Ic9dede5d4c37d1cd4fa24714216944897b5bb7cc
Reviewed-on: https://go-review.googlesource.com/90495
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Daniel Martí 2018-01-29 10:35:39 +00:00 committed by Ian Lance Taylor
parent 4072608b58
commit 14f8027a10
2 changed files with 12 additions and 1 deletions
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10
src/cmd/vet/print.go
View file

@ -295,6 +295,7 @@ type formatState struct {
file *File
call *ast.CallExpr
argNum int // Which argument we're expecting to format now.
hasIndex bool // Whether the argument is indexed.
indexPending bool // Whether we have an indexed argument that has not resolved.
nbytes int // number of bytes of the format string consumed.
}
@ -319,6 +320,7 @@ func (f *File) checkPrintf(call *ast.CallExpr, name string) {
// Hard part: check formats against args.
argNum := firstArg
maxArgNum := firstArg
anyIndex := false
for i, w := 0, 0; i < len(format); i += w {
w = 1
if format[i] != '%' {
@ -332,6 +334,9 @@ func (f *File) checkPrintf(call *ast.CallExpr, name string) {
if !f.okPrintfArg(call, state) { // One error per format is enough.
return
}
if state.hasIndex {
anyIndex = true
}
if len(state.argNums) > 0 {
// Continue with the next sequential argument.
argNum = state.argNums[len(state.argNums)-1] + 1
@ -346,6 +351,10 @@ func (f *File) checkPrintf(call *ast.CallExpr, name string) {
if call.Ellipsis.IsValid() && maxArgNum >= len(call.Args)-1 {
return
}
// If any formats are indexed, extra arguments are ignored.
if anyIndex {
return
}
// There should be no leftover arguments.
if maxArgNum != len(call.Args) {
expect := maxArgNum - firstArg
@ -404,6 +413,7 @@ func (s *formatState) parseIndex() bool {
arg := int(arg32)
arg += s.firstArg - 1 // We want to zero-index the actual arguments.
s.argNum = arg
s.hasIndex = true
s.indexPending = true
return true
}

3
src/cmd/vet/testdata/print.go vendored
View file

@ -270,8 +270,9 @@ func PrintfTests() {
Printf("%d %[3]d %d %[-2]d x", 1, 2, 3, 4) // ERROR "Printf format has invalid argument index \[-2\]"
Printf("%d %[3]d %d %[2234234234234]d x", 1, 2, 3, 4) // ERROR "Printf format has invalid argument index \[2234234234234\]"
Printf("%d %[3]d %-10d %[2]d x", 1, 2, 3) // ERROR "Printf format %-10d reads arg #4, but call has only 3 args"
Printf("%d %[3]d %d %[2]d x", 1, 2, 3, 4, 5) // ERROR "Printf call needs 4 args but has 5 args"
Printf("%[1][3]d x", 1, 2) // ERROR "Printf format %\[1\]\[ has unknown verb \["
Printf("%[1]d x", 1, 2) // OK
Printf("%d %[3]d %d %[2]d x", 1, 2, 3, 4, 5) // OK
// wrote Println but meant Fprintln
Printf("%p\n", os.Stdout) // OK