cmd/compile/internal/noder: qualify identifiers for generic methods

Generic methods will be hoisted to objects so that they can get their
own dictionaries. We need to avoid name collisions, so within a
package, we qualify generic methods using their defining type.

We don't differentiate method identifiers by whether they have a pointer
or value receiver for simplicity.

Change-Id: Ied06c5e4a4c5a6f8de8027358ddbe38fc40ae452
Reviewed-on: https://go-review.googlesource.com/c/go/+/761263
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Mark Freeman <markfreeman@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/src/cmd/compile/internal/noder/writer.go b/src/cmd/compile/internal/noder/writer.go
index 2632e14e31..06264f5f87 100644
--- a/src/cmd/compile/internal/noder/writer.go
+++ b/src/cmd/compile/internal/noder/writer.go
@@ -993,8 +993,8 @@ func (w *writer) method(wext *writer, meth *types2.Func) {
 	wext.funcExt(meth)
 }
 
-// qualifiedIdent writes out the name of an object declared at package
-// scope. (For now, it's also used to refer to local defined types.)
+// qualifiedIdent writes out the name of an object typically declared at package
+// scope. It's also used to refer to generic methods and locally defined types.
 func (w *writer) qualifiedIdent(obj types2.Object) {
 	w.Sync(pkgbits.SyncSym)
 
@@ -1012,6 +1012,13 @@ func (w *writer) qualifiedIdent(obj types2.Object) {
 		}
 	}
 
+	// Generic methods are promoted to objects and thus need qualified identifiers.
+	// They must be contextualized by their defining type.
+	if isGenericMethod(obj.Type()) {
+		recv := types2.Unalias(deref2(obj.Type().(*types2.Signature).Recv().Type()))
+		name = fmt.Sprintf("%s.%s", recv.(*types2.Named).Obj().Name(), name)
+	}
+
 	w.pkg(obj.Pkg())
 	w.String(name)
 }