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cmd/compile: regressed and non-informative error messages when return call site doesn't match return signature #48834

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odeke-em opened this issue Oct 7, 2021 · 3 comments
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@odeke-em
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@odeke-em odeke-em commented Oct 7, 2021

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

GoTip at 6f74ed0 aka Go1.18

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)? Not Applicable

What did you do?

Ran this program https://play.golang.org/p/uUOlQ-99Wx_y or inlined below

package main

func foo() (int, error) {
	return nil
}

func main() {}

What did you expect to see?

./main.go:4:2: not enough arguments to return
	have (nil)
	want (int, error)

What did you see instead?

./main.go:4:2: wrong number of return values (want 2, got 1)

This is a regression from Go1.8 and it is unique in the upcoming Go1.18; I understand there have been compiler rewrites but just a count of arguments takes us back to square 0 where we were, yet we had worked on improving the user experience of these messages. This was one of my first contributions to the compiler driven after getting feedback from users at Gophercon 2016 fixing at least 2 issues #4215 and #6750.

Kindly cc-ing @mdempsky @griesemer

@odeke-em odeke-em added this to the Go1.18 milestone Oct 7, 2021
@odeke-em odeke-em self-assigned this Oct 7, 2021
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@gopherbot gopherbot commented Oct 7, 2021

Change https://golang.org/cl/354490 mentions this issue: cmd/compile/internal/types2: report types in mismatched call arguments

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@gopherbot gopherbot commented Nov 17, 2021

Change https://golang.org/cl/364874 mentions this issue: cmd/compile/internal/types2: report types for mismatched call and return statements

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@gopherbot gopherbot commented Nov 26, 2021

Change https://golang.org/cl/367196 mentions this issue: go/types: report types for mismatched call and return statements

gopherbot pushed a commit that referenced this issue Nov 29, 2021
This is a port of CL 364874 from types2 to go/types with various
adjustments:

- the error position for "not enough arguments" in calls is the
  closing ) rather than the position of the last provided argument

- the ERROR comments in tests are positioned accordingly

- the reg. expression for matching error strings accepts newlines
  for the . pattern (added s flag)

For #48834.
For #48835.

Change-Id: I64362ecf605bcf9d89b8dc121432e0131bd5da1b
Reviewed-on: https://go-review.googlesource.com/c/go/+/367196
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
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