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go/format: Source mishandles parens on malformed input #29593

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josharian opened this issue Jan 7, 2019 · 2 comments
Closed

go/format: Source mishandles parens on malformed input #29593

josharian opened this issue Jan 7, 2019 · 2 comments
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@josharian
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josharian commented Jan 7, 2019

Found by go-fuzz, unlikely to occur in real code. Very low priority.

func main() {
	in := []byte("g(func()())")
	out, err := format.Source(in)
	if err != nil {
		panic(err)
	}
	fmt.Printf("in : %q\nout: %q\n", in, out)
	return
}

Result:

in : "g(func()())"
out: "g(func())"

Observe the dropped parens pair.

If input is "g(func()()())" instead (extra parens pair), the result instead has misplaced parens:

in : "g(func()()())"
out: "g((func())())"
@josharian josharian added this to the Unplanned milestone Jan 7, 2019
@josharian josharian added the NeedsFix The path to resolution is known, but the work has not been done. label Jan 7, 2019
@bcmills
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bcmills commented Jan 9, 2019

Compare https://play.golang.org/p/jmef0XQwDn3.

The error in the example source is that the function passed to g is missing its FunctionBody, but other than that it seems that go/format is correctly parsing func()() as the type of a function with empty Parameters and an empty (but parenthesized) Result.

For g(func()()()), the initial func()() is similarly parsed as a bodiless function, and the parentheses are added to invoke that function with empty Arguments.

@bcmills bcmills added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jan 9, 2019
@gopherbot gopherbot removed the NeedsFix The path to resolution is known, but the work has not been done. label Jan 9, 2019
@josharian
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Thanks, Bryan. Given that observation I’m going to call this one not worth investigating and close it.

@golang golang locked and limited conversation to collaborators Jan 9, 2020
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