[dev.typeparams] cmd/compile/internal/types2: use comparable bit rather than ==() method

This removes the special "==" methods from comparable interfaces in
favor of a "comparable" flag in TypeSets indicating that the interface
is or embeds comparable. Fixes various related implementation
inaccuracies.

While at it, fix setup of the predeclared error and comparable
interface types by associating their respective type name objects
with them.

For #47411.

Change-Id: I409f880c8c8f2fe345621401267e4aaabd17124d
Reviewed-on: https://go-review.googlesource.com/c/go/+/337354
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 4 insertions, 8 deletions

diff --git a/src/cmd/compile/internal/types2/universe.go b/src/cmd/compile/internal/types2/universe.go
index 0f711a6b68..a3dd4bd0d6 100644
--- a/src/cmd/compile/internal/types2/universe.go
+++ b/src/cmd/compile/internal/types2/universe.go
@@ -88,23 +88,19 @@ func defPredeclaredTypes() {
 		res := NewVar(nopos, nil, "", Typ[String])
 		sig := NewSignature(nil, nil, NewTuple(res), false)
 		err := NewFunc(nopos, nil, "Error", sig)
-		ityp := NewInterfaceType([]*Func{err}, nil)
+		ityp := &Interface{obj, []*Func{err}, nil, nil, true, nil}
 		computeTypeSet(nil, nopos, ityp) // prevent races due to lazy computation of tset
 		typ := NewNamed(obj, ityp, nil)
 		sig.recv = NewVar(nopos, nil, "", typ)
 		def(obj)
 	}
 
-	// type comparable interface{ ==() }
+	// type comparable interface{ /* type set marked comparable */ }
 	{
 		obj := NewTypeName(nopos, nil, "comparable", nil)
 		obj.setColor(black)
-		sig := NewSignature(nil, nil, nil, false)
-		eql := NewFunc(nopos, nil, "==", sig)
-		ityp := NewInterfaceType([]*Func{eql}, nil)
-		computeTypeSet(nil, nopos, ityp) // prevent races due to lazy computation of tset
-		typ := NewNamed(obj, ityp, nil)
-		sig.recv = NewVar(nopos, nil, "", typ)
+		ityp := &Interface{obj, nil, nil, nil, true, &TypeSet{true, nil, nil}}
+		NewNamed(obj, ityp, nil)
 		def(obj)
 	}
 }