Support append() and delete() built-ins for type params.

nevkontakte · nevkontakte · commit c0dc2983591b · 2023-11-12T18:53:58.000Z
Instead of interrogating the type of the slice or map expression passed
to the built-in, we interrogate types of the computed built-in
signature. In case of append(), it will be a slice of element types due
to variadic nature of the built-in. For map it will be the plain key
type. We can then use that type to translate expressing with implicit
conversion.
diff --git a/compiler/expressions.go b/compiler/expressions.go
@@ -1099,11 +1099,11 @@ func (fc *funcContext) translateBuiltin(name string, sig *types.Signature, args
 			argStr := fc.translateArgs(sig, args, ellipsis)
 			return fc.formatExpr("$appendSlice(%s, %s)", argStr[0], argStr[1])
 		}
-		sliceType := sig.Results().At(0).Type().Underlying().(*types.Slice)
-		return fc.formatExpr("$append(%e, %s)", args[0], strings.Join(fc.translateExprSlice(args[1:], sliceType.Elem()), ", "))
+		elType := sig.Params().At(1).Type().(*types.Slice).Elem()
+		return fc.formatExpr("$append(%e, %s)", args[0], strings.Join(fc.translateExprSlice(args[1:], elType), ", "))
 	case "delete":
 		args = fc.expandTupleArgs(args)
-		keyType := fc.pkgCtx.TypeOf(args[0]).Underlying().(*types.Map).Key()
+		keyType := sig.Params().At(1).Type()
 		return fc.formatExpr(
 			`$mapDelete(%1e, %2s.keyFor(%3s))`,
 			args[0],
diff --git a/tests/typeparams/builtins_test.go b/tests/typeparams/builtins_test.go
@@ -198,3 +198,30 @@ func TestNew(t *testing.T) {
 		})
 	}
 }
+
+func _append[E any, S []E](s S, e E) S {
+	return append(s, e)
+}
+
+func TestAppend(t *testing.T) {
+	got := _append([]int{1, 2}, 3)
+	want := []int{1, 2, 3}
+
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Got: append(...) = %#v. Want: %#v", got, want)
+	}
+}
+
+func _delete[K comparable, M map[K]string | map[K]int](m M, k K) {
+	delete(m, k)
+}
+
+func TestDelete(t *testing.T) {
+	got := map[int]string{1: "a", 2: "b"}
+	delete(got, 1)
+	want := map[int]string{2: "b"}
+
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Got: delete(...) = %#v. Want: %#v", got, want)
+	}
+}
