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cmd/go2go: compile error in some cases of method expressions on type parameters #39662

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Carrotman42 opened this issue Jun 17, 2020 · 2 comments
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@Carrotman42
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@Carrotman42 Carrotman42 commented Jun 17, 2020

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

The Go 2 dev playground at https://go2goplay.golang.org/

What did you do?

Full example: https://go2goplay.golang.org/p/U43Cljg2tvj

Excerpt:

type I interface {
	F()
}

func takesI(type T I)(t T) {
	_ = T.F
}

func workaround(type T I)(t T) {
	_ = (T).F
}

As shown in the full example in the playground link above, calling takesI with T = *SomeType results in compilation failing. Calling workaround is fine, and since the only difference is the manual wrapping of parenthesis this indicates to me that the generated code is just missing grouping of its own which is causing the errors.

What did you see instead?

Error messages during compilation:

./prog.go2:4: invalid method expression P.F (needs pointer receiver: (*P).F)
./prog.go2:4: invalid indirect of V.F (type func(V))
@gopherbot
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@gopherbot gopherbot commented Jun 17, 2020

Change https://golang.org/cl/238557 mentions this issue: [dev.go2go] go/go2go: parenthesize type strings

gopherbot pushed a commit that referenced this issue Jun 17, 2020
Fixes #39662

Change-Id: Id176ec00474d66a24e95f2db092f3b4245a93cfb
Reviewed-on: https://go-review.googlesource.com/c/go/+/238557
Reviewed-by: Ian Lance Taylor <iant@golang.org>
@ianlancetaylor
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@ianlancetaylor ianlancetaylor commented Jun 17, 2020

Thanks. Should be fixed now.

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