go/types, types2: make the new comparable semantics the default
Ordinary interface types now satisfy comparable constraints.
This change makes the new comparable semantics the default behavior,
depending on the Go -lang version.
It also renames the flag types2.Config.AltComparableSemantics to
types2.Config.OldComparableSemantics and inverts its meaning
(or types.Config.oldComparableSemantics respectively).
Adjust some existing tests by setting -oldComparableSemantics
and add some new tests that verify version-dependent behavior.
The compiler flag -oldcomparable may be used to temporarily
switch back to the Go 1.18/1.19 behavior should this change
cause problems, or to identify that a problem is unrelated
to this change. The flag will be removed for Go 1.21.
For #52509.
For #56548.
Change-Id: Ic2b22db9433a8dd81dc1ed9d30835f0395fb7205
Reviewed-on: https://go-review.googlesource.com/c/go/+/453978 Reviewed-by: Robert Findley <rfindley@google.com> Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Robert Griesemer <gri@google.com>