go/types, types2: implement alternative comparable semantics
This is an experiment to see the impact of a potential spec change:
As an exception to the rule that constraint satisfaction is the same
as interface implementation, if the flag Config.AltComparableSemantics
is set, an ordinary (non-type parameter) interface satisfies the
comparable constraint. (In go/types, the flag is not exported to
avoid changing the API.)
Disabled by default. Test files can set the flag by adding
// -altComparableSemantics
as the first line in the file.
For #52509.
Change-Id: Ib491b086feb5563920eaddefcebdacb2c5b72d61
Reviewed-on: https://go-review.googlesource.com/c/go/+/444635 Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>