[dev.typeparams] cmd/compile/internal/types2: replace optype() with under() in various cases (cleanup)

This makes the behavior for type parameter operands explicit
in those cases.

Change-Id: I38438af67de4432f1a691dc4947e4576445f031b
Reviewed-on: https://go-review.googlesource.com/c/go/+/332555
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/src/cmd/compile/internal/types2/builtins.go b/src/cmd/compile/internal/types2/builtins.go
index 7ba26509e8..83d1743ee2 100644
--- a/src/cmd/compile/internal/types2/builtins.go
+++ b/src/cmd/compile/internal/types2/builtins.go
@@ -332,13 +332,15 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 			return
 		}
 		var src Type
-		switch t := optype(y.typ).(type) {
+		switch t := under(y.typ).(type) {
 		case *Basic:
 			if isString(y.typ) {
 				src = universeByte
 			}
 		case *Slice:
 			src = t.elem
+		case *TypeParam:
+			check.error(x, "copy on generic operands not yet implemented")
 		}
 
 		if dst == nil || src == nil {
@@ -455,12 +457,12 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 		var valid func(t Type) bool
 		valid = func(t Type) bool {
 			var m int
-			switch t := optype(t).(type) {
+			switch t := under(t).(type) {
 			case *Slice:
 				m = 2
 			case *Map, *Chan:
 				m = 1
-			case *Union:
+			case *TypeParam:
 				return t.underIs(valid)
 			default:
 				return false