cmd/compile: method expressions are misprinted

[mdempsky]

On the dev.regabi branch, the error message for this source file:

package p

import "bytes"

var x int = (*bytes.Buffer).Len

mentions *bytes.Buffer.Len. That's incorrect: it should be (*bytes.Buffer).Len, as it appears in the source.

(I suspect this is related to the ir/fmt.go changes in 4629f6a. Though it turns out we're printing it incorrectly even on master, where it prints as bytes.(*Buffer).Len.)

/cc @cuonglm

[ianlancetaylor]

We've printed the bytes.(*Buffer).Len version since at least Go 1.1.

[mdempsky]

@ianlancetaylor Thanks, that sounds believable. You aren't suggesting cmd/compile should continue printing it incorrectly though, are you?

In case it wasn't clear, the linker symbols used for pointer-receiver methods (including as they appear in runtime stack traces) are unchanged on dev.regabi; and while I believe the parentheses are superfluous there, I don't intend to remove them either. This issue is only about how method expressions are printed in Go-syntax compiler diagnostics, like error messages and -m output.

go/types correctly prints (*bytes.Buffer).Len in its diagnostics.

[gopherbot]

Change https://golang.org/cl/280735 mentions this issue: cmd/compile: increase prec for StarExpr in SelectorExpr

[gopherbot]

Change https://golang.org/cl/280873 mentions this issue: [dev.regabi] cmd/compile: fix printing of method expressions

[mdempsky]

cmd/compile now prints diagnostics using Go syntax for method expressions on dev.regabi.