cmd/gc: inlining unparenthesizes struct literals in if statements.

[anacrolix]

Importing a module containing syntax like the following:

type bleh struct {
    hi int
}

func (me bleh) meh() string {
    if me == (bleh{}) { // <- this is bad
        return "0"
    }

Will give an error at the point of import, instead of during compilation at the line of
the actual syntax error.

I've boiled down the problem as small as I can get it here:
https://bitbucket.org/anacrolix/goplay/src/a2ffccb08ad0/bug

What is the expected output?
D:\gopath\src\bitbucket.org\anacrolix\goplay\bug>go build
bitbucket.org/anacrolix/goplay/bug
# bitbucket.org/anacrolix/goplay/bug/dep
d:\gopath\src\bitbucket.org\anacrolix\goplay\bug\dep\dep.go:8: syntax error: unexpected
{ at end of statement

What do you see instead?

D:\gopath\src\bitbucket.org\anacrolix\goplay\bug>go build
bitbucket.org/anacrolix/goplay/bug
# bitbucket.org/anacrolix/goplay/bug
d:\gopath\src\bitbucket.org\anacrolix\goplay\bug\main.go:4: syntax error: unexpected {
at end of statement

Which compiler are you using (5g, 6g, 8g, gccgo)?
8g, go version devel +bc50fc903d6e Thu Oct 11 01:34:26 2012 +0800

Which operating system are you using?
Windoze

[remyoudompheng]

Comment 1:

This is not a syntax error. What happens is that the inlining information is missing the
parentheses that make the if statement grammatically correct.
See the spec:
A parsing ambiguity arises when a composite literal using the TypeName form of the
LiteralType appears between the keyword and the opening brace of the block of an "if",
"for", or "switch" statement, because the braces surrounding the expressions in the
literal are confused with those introducing the block of statements. To resolve the
ambiguity in this rare case, the composite literal must appear within parentheses.

Labels changed: added priority-later, compilerbug, removed priority-triage.

Status changed to Accepted.

[remyoudompheng]

Comment 2:

This issue was closed by revision 319131f.

Status changed to Fixed.

[remyoudompheng]

Comment 3:

This issue was closed by revision 20ebee2.

[ianlancetaylor]

Comment 4:

Labels changed: added go1.1.2, removed go1.1.

[adg]

Comment 5:

This issue was closed by revision 31a32150a72b.