go/types, types2: report type mismatch error when conversion is impossible
Rather than reporting an impossible conversion error when mixing an
untyped value with a pointer type in an operation, report a type
mismatch error. This fixes a regression in error quality compared
to pre-1.18.
For the fix, clean up the implementation of canMix, add documentation,
and give it a better name.
Adjust test case for corresponding error code bacause we now get a
better error message (and error code) for the old error code example.
Fixes #57160.
Change-Id: Ib96ce7cbc44db6905fa2f1c90a3769af609e101b
Reviewed-on: https://go-review.googlesource.com/c/go/+/457055 Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@google.com>