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go/parser: emits invalid ast for Decl with missing type. #9639

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barnex opened this issue Jan 19, 2015 · 1 comment
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go/parser: emits invalid ast for Decl with missing type. #9639

barnex opened this issue Jan 19, 2015 · 1 comment
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@barnex
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@barnex barnex commented Jan 19, 2015

The following code
var x;
is invalid and rejected by gc (http://play.golang.org/p/gIxpWYiElI).

However, go/parser parses it without returning an error. Code: http://play.golang.org/p/F2J2uFWvDu.

I expected to receive a syntax error like "unexpected semicolon or newline". Instead, no error and an ast containing a Decl with Type nil is emited.

Go version in playground at time of report: go1.3.2
My local go version at time of report: go version devel +1757b5c Thu Dec 11 07:31:32 2014 +0000 linux/amd64

@ianlancetaylor ianlancetaylor added this to the Go1.5 milestone Jan 20, 2015
@griesemer
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@griesemer griesemer commented Jan 20, 2015

The go/parser deliberately accepts a larger language than what the spec permits, for more lenient parsing which permits better error messages later. If you run through go/types, you will get the error:

$ gotype z.go
z.go:5:9: missing type or init expr
z.go:5:9: x declared but not used

Perhaps in this case the parser could be tightened a bit.

It's trivial to add a verification pass if this is required. This is issue is not urgent.

@griesemer griesemer closed this in dcb37f9 Jan 23, 2015
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