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diff --git a/‎src/cmd/compile/internal/gc/reflect.go‎
Lines changed: 8 additions & 2 deletions b/‎src/cmd/compile/internal/gc/reflect.go‎
Lines changed: 8 additions & 2 deletions
@@ -320,7 +320,12 @@ func hiter(t *types.Type) *types.Type {
 // f is method type, with receiver.
 // return function type, receiver as first argument (or not).
 func methodfunc(f *types.Type, receiver *types.Type) *types.Type {
-	var in []*Node
+	inLen := f.Params().Fields().Len()
+	if receiver != nil {
+		inLen++
+	}
+	in := make([]*Node, 0, inLen)
+
 	if receiver != nil {
 		d := anonfield(receiver)
 		in = append(in, d)
@@ -332,7 +337,8 @@ func methodfunc(f *types.Type, receiver *types.Type) *types.Type {
 		in = append(in, d)
 	}
 
-	var out []*Node
+	outLen := f.Results().Fields().Len()
+	out := make([]*Node, 0, outLen)
 	for _, t := range f.Results().Fields().Slice() {
 		d := anonfield(t.Type)
 		out = append(out, d)