bind: needWrapType - preliminary support for interfaces+namedtypes

Change-Id: Ia4ef5bcf3ef36eecb02cd63e5beadc1177ef1484

bind/types.go

@@ -22,18 +22,28 @@ type Type interface {
 
 func needWrapType(typ types.Type) bool {
 	switch typ.(type) {
+	case *types.Basic:
+		return false
 	case *types.Struct:
 		return true
 	case *types.Named:
-		switch typ.Underlying().(type) {
-		case *types.Struct:
-			return true
+		switch ut := typ.Underlying().(type) {
+		case *types.Basic:
+			return false
+		default:
+			return needWrapType(ut)
 		}
 	case *types.Array:
 		return true
 	case *types.Slice:
 		return true
 	case *types.Interface:
+		wrap := true
+		if typ.Underlying() == universe.syms["error"].GoType().Underlying() {
+			wrap = false
+		}
+		return wrap
+	case *types.Signature:
 		return true
 	}
 	return false