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cmd/compile: compiler allows unreachable statements #12920

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shoenig opened this issue Oct 13, 2015 · 3 comments
Closed

cmd/compile: compiler allows unreachable statements #12920

shoenig opened this issue Oct 13, 2015 · 3 comments
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@shoenig
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shoenig commented Oct 13, 2015

I noticed this in some badly re-factored complex code, but it reduces nicely into this toy program. Basically the compiler allows unreachable statements that could be detected statically at compile time. It would be nice if code like this failed to compile.

package main

import "fmt"

func main() {
    fmt.Println("foo", foo())
}

func foo() int {
    fmt.Println("now you see me")
    return 0
    fmt.Println("now you don't")
    return 1
}
@mdempsky
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While questionable, that's technically valid Go 1 code, so it has to be accepted by the compiler. It's also already caught by cmd/vet:

$ go vet issue12920.go
issue12920.go:12: unreachable code

@ianlancetaylor
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Let me add that to try to ensure that all Go compilers agree on which programs can be compiled, the notion of an unreachable statement is actually defined by the language spec: https://golang.org/ref/spec#Terminating_statements .

@minux
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minux commented Oct 13, 2015 via email

@golang golang locked and limited conversation to collaborators Oct 12, 2016
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@mdempsky @minux @shoenig @ianlancetaylor @gopherbot