go: proposal: cmd/vet: warning on a special case of switch code block use.

What version of Go are you using (`go version`)?

go version go1.9.3 linux/amd64

Does this issue reproduce with the latest release?

Yes

What did you do?

package main

func alwaysFalse() bool {
	return false
}

func main() {
	switch alwaysFalse() {
	case true: println("1: true")
	case false: println("1: false")
	}
	
	switch alwaysFalse() // vet should warn here.
	{
	case true: println("2: true")
	case false: println("2: false")
	}
}

What did you expect to see?

go vet should warn on the second switch code block use.

What did you see instead?

go vet reports nothing.

About this issue

Original URL
State: closed
Created 6 years ago
Comments: 16 (13 by maintainers)

Most upvoted comments

The second block is the same as

switch alwaysFalse(); {
case true: println("2: true")
case false: println("2: false")
}

cznic on Feb 1, 2018

To be honest, I was surprised to learn that that compiles. I doubt that it hits the “frequency” criterion for vet, but making gofmt put that on a single line would probably make the bug obvious enough.

josharian on Feb 1, 2018

maybe it shouldn’t compile, https://golang.org/ref/spec#ExprSwitchStmt specifies the “;”

It’s valid Go code, the semicolon is injected at EOL after ) being the last token on the line