Reject use of open tuples in is or as tests

Summary: As the title says. We don't yet support this in HHVM, so should reject it for Hack.

Differential Revision: D68208091

fbshipit-source-id: 80d93a81052822055ad8b2e0d26aac59fcbdbfaa

hphp/hack/src/typing/typing_enforceable_hint.ml

@@ -162,13 +162,19 @@ let validator =
                ( Typing_defs_core.get_reason ty,
                  "_ in a " ^ s ^ " (use `mixed` instead)" )))
 
-    method! on_ttuple acc _ { t_required; t_extra } =
+    method! on_ttuple acc r { t_required; t_extra } =
       let acc = List.fold_left t_required ~f:this#on_type ~init:acc in
       match t_extra with
-      | Textra { t_optional; t_variadic = _ } ->
-        let acc = List.fold_left t_optional ~f:this#on_type ~init:acc in
-        this#check_for_wildcards acc t_required "tuple"
-      | Tsplat t_splat -> this#on_type acc t_splat
+      | Textra { t_optional; t_variadic } ->
+        (* HHVM doesn't currently support is/as on open tuples, so let's reject it in Hack *)
+        if (not (is_nothing t_variadic)) || not (List.is_empty t_optional) then
+          this#invalid acc r
+          @@ "a tuple type with optional or variadic elements"
+        else
+          this#check_for_wildcards acc t_required "tuple"
+      | Tsplat _ ->
+        (* HHVM doesn't currently support is/as on type splats, so let's reject it in Hack *)
+        this#invalid acc r @@ "a tuple type with a splat element"
 
     method! on_tshape acc _ { s_fields = fdm; _ } =
       let tyl = TShapeMap.values fdm |> List.map ~f:(fun s -> s.sft_ty) in

hphp/hack/test/typecheck/open_tuples/splat/tuple_splat_is_as_test_bad.php

@@ -0,0 +1,6 @@
+<?hh
+<<file: __EnableUnstableFeatures('open_tuples', 'type_splat')>>
+
+function test2<<<__Enforceable>> reify T as (mixed...)>(mixed $m): void {
+  $m as (int, ...T);
+}

hphp/hack/test/typecheck/open_tuples/splat/tuple_splat_is_as_test_bad.php.exp

@@ -0,0 +1,4 @@
+ERROR: File "tuple_splat_is_as_test_bad.php", line 5, characters 9-19:
+Invalid `as` expression hint (Typing[4195])
+  File "tuple_splat_is_as_test_bad.php", line 5, characters 9-19:
+  The `as` operator cannot be used with a tuple type with a splat element

hphp/hack/test/typecheck/open_tuples/tuple_open_is_as_test_bad.php

@@ -0,0 +1,14 @@
+<?hh
+<<file: __EnableUnstableFeatures('open_tuples')>>
+
+function test1(mixed $m): string {
+  $m as (nonnull...);
+  if ($m is (int, optional string)) {
+    return $m[1] ?? "default";
+  }
+  if ($m is (int, string...)) {
+    return $m[1] ?? "default";
+  }
+  $m as (optional bool, optional int);
+  return "fail";
+}

hphp/hack/test/typecheck/open_tuples/tuple_open_is_as_test_bad.php.exp

@@ -0,0 +1,20 @@
+WARN: File "tuple_open_is_as_test_bad.php", line 6, characters 7-34:
+This `is` check is always `false`. The expression on the left has type `(nonnull...)` which shares no values with `(int, optional string)`. (Warn[12010])
+WARN: File "tuple_open_is_as_test_bad.php", line 9, characters 7-28:
+This `is` check is always `false`. The expression on the left has type `(nonnull...)` which shares no values with `(int, string...)`. (Warn[12010])
+ERROR: File "tuple_open_is_as_test_bad.php", line 5, characters 9-20:
+Invalid `as` expression hint (Typing[4195])
+  File "tuple_open_is_as_test_bad.php", line 5, characters 9-20:
+  The `as` operator cannot be used with a tuple type with optional or variadic elements
+ERROR: File "tuple_open_is_as_test_bad.php", line 6, characters 13-34:
+Invalid `is` expression hint (Typing[4195])
+  File "tuple_open_is_as_test_bad.php", line 6, characters 13-34:
+  The `is` operator cannot be used with a tuple type with optional or variadic elements
+ERROR: File "tuple_open_is_as_test_bad.php", line 9, characters 13-28:
+Invalid `is` expression hint (Typing[4195])
+  File "tuple_open_is_as_test_bad.php", line 9, characters 13-28:
+  The `is` operator cannot be used with a tuple type with optional or variadic elements
+ERROR: File "tuple_open_is_as_test_bad.php", line 12, characters 9-37:
+Invalid `as` expression hint (Typing[4195])
+  File "tuple_open_is_as_test_bad.php", line 12, characters 9-37:
+  The `as` operator cannot be used with a tuple type with optional or variadic elements

hphp/hack/test/typecheck/open_tuples/tuple_open_is_as_test_bad.php.imp_pess_exp

@@ -0,0 +1,16 @@
+ERROR: File "tuple_open_is_as_test_bad.php", line 5, characters 9-20:
+Invalid `as` expression hint (Typing[4195])
+  File "tuple_open_is_as_test_bad.php", line 5, characters 9-20:
+  The `as` operator cannot be used with a tuple type with optional or variadic elements
+ERROR: File "tuple_open_is_as_test_bad.php", line 6, characters 13-34:
+Invalid `is` expression hint (Typing[4195])
+  File "tuple_open_is_as_test_bad.php", line 6, characters 13-34:
+  The `is` operator cannot be used with a tuple type with optional or variadic elements
+ERROR: File "tuple_open_is_as_test_bad.php", line 9, characters 13-28:
+Invalid `is` expression hint (Typing[4195])
+  File "tuple_open_is_as_test_bad.php", line 9, characters 13-28:
+  The `is` operator cannot be used with a tuple type with optional or variadic elements
+ERROR: File "tuple_open_is_as_test_bad.php", line 12, characters 9-37:
+Invalid `as` expression hint (Typing[4195])
+  File "tuple_open_is_as_test_bad.php", line 12, characters 9-37:
+  The `as` operator cannot be used with a tuple type with optional or variadic elements