go/types, types2: do not abort constraint type inference eagerly
During constraint type inference, unification may fail because it
operates with limited information (core types) even if the actual
type argument satisfies the type constraint in question.
On the other hand, it is safe to ignore failing unification during
constraint type inference because if the failure is true, an error
will be reported when checking instantiation.
Fixes #53650.
Change-Id: Ia76b21ff779bfb1282c1c55f4174847b29cc6f3a
Reviewed-on: https://go-review.googlesource.com/c/go/+/454655
Auto-Submit: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com> Reviewed-by: Robert Griesemer <gri@google.com> Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>