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cmd/compile: typed struct name not shown in error #48784

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rsc opened this issue Oct 5, 2021 · 5 comments
Closed

cmd/compile: typed struct name not shown in error #48784

rsc opened this issue Oct 5, 2021 · 5 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. release-blocker
Milestone
Go1.18

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@rsc
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rsc commented Oct 5, 2021 

% cat /tmp/x.go
package p

type T struct {
	x int
	y int
	z int
}

var t T

var _ = t == nil
% go tool compile /tmp/x.go
/tmp/x.go:11:14: cannot convert untyped nil to struct{x int; y int; z int}
% go tool compile -G=0 /tmp/x.go
/tmp/x.go:11:11: invalid operation: t == nil (mismatched types T and nil)
%

The old error, using the name and showing the == operation, was clearer.

In the real example I just hit, I had an os.Process instead of T, and the error was showing me the contents of os.Process instead of the name os.Process, which meant very little to me. I wasn't even sure whether it was the contents of os.Process and had to look it up.

/cc @griesemer @findleyr
@rsc rsc added NeedsFix The path to resolution is known, but the work has not been done. release-blocker labels Oct 5, 2021
@rsc rsc added this to the Go1.18 milestone Oct 5, 2021
@findleyr
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findleyr commented Oct 5, 2021

Thanks for the report, and the repro.

This is one of the areas where the go/types error messages differ from types2. go/types reports cannot use nil (untyped nil value) as T value in variable declaration.

I think this is just an oversight where we're taking the underlying and don't need to. I'll send a fix.

@findleyr findleyr self-assigned this Oct 5, 2021
@gopherbot
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Change https://golang.org/cl/353976 mentions this issue: cmd/compile/internal/types2: identify defined types in conversion errors

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Change https://golang.org/cl/354049 mentions this issue: cmd/compile: better error message for invalid untyped nil conversion

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Change https://golang.org/cl/354050 mentions this issue: go/types: better error message for invalid untyped nil conversion

gopherbot pushed a commit that referenced this issue Oct 7, 2021
@cuonglm
go/types: better error message for invalid untyped nil conversion
ebeab63 
This is port of CL 354049 for types2 to go/type.

The change is identical, but for some tweaks to the error message/position
in tests, since when go/types reports the exact operation "cannot convert"
instead of the general "invalid operation" like types2.

Updates #48784

Change-Id: I3e99f2721501d23187fd0a8970eb1de28e0c41d8
Reviewed-on: https://go-review.googlesource.com/c/go/+/354050
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
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Change https://golang.org/cl/354631 mentions this issue: test/fixedbugs: fix issue48784.go to pass with -G=0

gopherbot pushed a commit that referenced this issue Oct 7, 2021
test/fixedbugs: fix issue48784.go to pass with -G=0
7286502 
This test is currently failing in the longtest builders.

I do not know how or why the builders are adding the -G=0 parameter.

Updates #48784

Change-Id: I62248d3fbc47567a8c73b4868a2d4aeb0bc47bc3
Reviewed-on: https://go-review.googlesource.com/c/go/+/354631
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
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