Better typing for bitwise operations

Summary:
Bitwise operations (`&`, `|` and `^`) are currently typed incorrectly in two ways:

(1) When applied to arguments both of type `~int`, we produce `int`. This is wrong, because HHVM still accepts strings, so the `~` might hide a string type.
(2) In the dynamic pass, we produce `dynamic` regardless of the argument types, because of a call to `Typing_utils.is_dynamic` that is interpreted as dynamic-aware subtyping in the dynamic pass.

Instead, we now use a different approach of reusing the logic from SDT function calls, as though the bitwise op is a call to

  <<__SupportDynamicType>> function bitwise(int $x, int $y):int

If interpreted strictly, this would produce `~int` if *either* of the operands is `~int` or `dynamic`. We can do slightly better, as we know that the operation will throw if one operand is `int` but the other is `string`. So a like is added only if *both* operands are `~int` or `dynamic`.

Reviewed By: mheiber

Differential Revision: D83841630

fbshipit-source-id: 57a12acbcf82d25eba632ee4ee50798b0071afa8

Author: Andrew Kennedy

hphp/hack/src/typing/typing_arithmetic.ml

@@ -48,7 +48,7 @@ let check_dynamic_or_enforce_int env p t r err =
   in
   Option.iter ty_err_opt ~f:(Typing_error_utils.add_typing_error ~env);
   let ty_mismatch = Option.map ty_err_opt ~f:Fn.(const (t, ty)) in
-  (env, Typing_utils.is_dynamic env t, ty_mismatch)
+  (env, Typing_defs.is_dynamic t, ty_mismatch)
 
 (** [check_like_num p_exp p env ty] ensures that [ty] is a subtype of num or ~num.
   In the former case, it returns false and the type, in the latter, it returns
@@ -364,29 +364,38 @@ let binop p env bop p1 te1 ty1 p2 te2 ty2 =
   | Ast_defs.Amp
   | Ast_defs.Bar
     when not contains_any ->
-    let (env, is_dynamic1, err_opt1) =
-      check_dynamic_or_enforce_int
+    (* Type-check a bitwise operation as if it's a call to a function of type
+     *   <<__SupportDynamicType>> function bitwise_math(int $x, int $y): int
+     * With one samll improvement: if checking of *either* argument succeeds against int
+     * rather than ~int, then return int, because we know that it will simply throw if
+     * the other argument is not int at runtime.
+     *)
+    let (env, err_opt1, used_dynamic1) =
+      Typing_argument.check_argument_type_against_parameter_type
+        ~ignore_readonly:false
+        ~dynamic_func:(Some Typing_argument.Supportdyn_function)
         env
-        p
+        (Typing_make_type.int (Reason.bitwise p1))
+        p1
         ty1
-        (Reason.bitwise p1)
-        Typing_error.Callback.bitwise_math_invalid_argument
     in
-    let (env, is_dynamic2, err_opt2) =
-      check_dynamic_or_enforce_int
+    let (env, err_opt2, used_dynamic2) =
+      Typing_argument.check_argument_type_against_parameter_type
+        ~ignore_readonly:false
+        ~dynamic_func:(Some Typing_argument.Supportdyn_function)
         env
-        p
+        (Typing_make_type.int (Reason.bitwise p2))
+        p2
         ty2
-        (Reason.bitwise p2)
-        Typing_error.Callback.bitwise_math_invalid_argument
     in
-    let result_ty =
-      if is_dynamic1 && is_dynamic2 then
-        MakeType.dynamic (Reason.bitwise_dynamic p)
-      else
-        MakeType.int (Reason.bitwise_ret p)
-    in
-    make_result env te1 err_opt1 te2 err_opt2 result_ty
+    make_result
+      ~is_like:(used_dynamic1 && used_dynamic2)
+      env
+      te1
+      err_opt1
+      te2
+      err_opt2
+      (MakeType.int (Reason.bitwise_ret p))
   | Ast_defs.Eqeq
   | Ast_defs.Diff ->
     begin

hphp/hack/test/holes/compound_assign_bitwise_and.php

@@ -1,6 +1,6 @@
 <?hh
 
 function compound_assign_bitwise_and(Vector<int> $xs) : void {
-  /* HH_FIXME[4423] */
+  /* HH_FIXME[4110] */
   $xs[0] &= 1.0;
 }

hphp/hack/test/typecheck/dynamic/bad_math.php.exp

@@ -82,20 +82,20 @@ Typing error (Typing[4423])
   Expected `int` because this is used in an arithmetic operation
   File "bad_math.php", line 5, characters 33-33:
   But got `C`
-ERROR: File "bad_math.php", line 18, characters 3-8:
-Typing error (Typing[4423])
+ERROR: File "bad_math.php", line 18, characters 3-4:
+Invalid argument (Typing[4110])
   File "bad_math.php", line 18, characters 3-4:
   Expected `int` because this is used in a bitwise operation
   File "bad_math.php", line 5, characters 33-33:
   But got `C`
-ERROR: File "bad_math.php", line 19, characters 3-8:
-Typing error (Typing[4423])
+ERROR: File "bad_math.php", line 19, characters 3-4:
+Invalid argument (Typing[4110])
   File "bad_math.php", line 19, characters 3-4:
   Expected `int` because this is used in a bitwise operation
   File "bad_math.php", line 5, characters 33-33:
   But got `C`
-ERROR: File "bad_math.php", line 20, characters 3-8:
-Typing error (Typing[4423])
+ERROR: File "bad_math.php", line 20, characters 3-4:
+Invalid argument (Typing[4110])
   File "bad_math.php", line 20, characters 3-4:
   Expected `int` because this is used in a bitwise operation
   File "bad_math.php", line 5, characters 33-33:

hphp/hack/test/typecheck/dynamic/bitwise.php

@@ -1,17 +1,17 @@
 <?hh
 
 function testBitwise(dynamic $x): void {
-  $y = $x & 5; // $y : num
+  $y = $x & 5; // $y : int
   hh_show($y);
-  $y = $x | 5; // $y : num
+  $y = $x | 5; // $y : int
   hh_show($y);
-  $y = $x ^ 5; // $y : num
+  $y = $x ^ 5; // $y : int
   hh_show($y);
-  $y = $x >> 5; // $y : num
+  $y = $x >> 5; // $y : int
   hh_show($y);
-  $y = $x << 5; // $y : num
+  $y = $x << 5; // $y : int
   hh_show($y);
-  $y = $x ^ $x; // $y : dynamic
+  $y = $x ^ $x; // $y : ~int
   hh_show($y);
   $y = ~$x; // $y : dynamic
   hh_show($y);

hphp/hack/test/typecheck/dynamic/bitwise.php.exp

@@ -9,7 +9,7 @@ File "bitwise.php", line 11, characters 3-13:
 File "bitwise.php", line 13, characters 3-13:
   int
 File "bitwise.php", line 15, characters 3-13:
-  dynamic
+  ~int
 File "bitwise.php", line 17, characters 3-13:
   dynamic
 No errors

hphp/hack/test/typecheck/xor_bad1.php.exp

@@ -1,5 +1,5 @@
-ERROR: File "xor_bad1.php", line 13, characters 3-9:
-Typing error (Typing[4423])
+ERROR: File "xor_bad1.php", line 13, characters 8-9:
+Invalid argument (Typing[4110])
   File "xor_bad1.php", line 13, characters 8-9:
   Expected `int` because this is used in a bitwise operation
   File "xor_bad1.php", line 12, characters 22-25:

hphp/hack/test/typecheck/xor_bad2.php.exp

@@ -1,5 +1,5 @@
-ERROR: File "xor_bad2.php", line 13, characters 3-9:
-Typing error (Typing[4423])
+ERROR: File "xor_bad2.php", line 13, characters 3-4:
+Invalid argument (Typing[4110])
   File "xor_bad2.php", line 13, characters 3-4:
   Expected `int` because this is used in a bitwise operation
   File "xor_bad2.php", line 12, characters 14-17:

hphp/hack/test/typecheck/xor_bad3.php.exp

@@ -1,11 +1,11 @@
-ERROR: File "xor_bad3.php", line 13, characters 3-9:
-Typing error (Typing[4423])
+ERROR: File "xor_bad3.php", line 13, characters 3-4:
+Invalid argument (Typing[4110])
   File "xor_bad3.php", line 13, characters 3-4:
   Expected `int` because this is used in a bitwise operation
   File "xor_bad3.php", line 12, characters 14-19:
   But got `string`
-ERROR: File "xor_bad3.php", line 13, characters 3-9:
-Typing error (Typing[4423])
+ERROR: File "xor_bad3.php", line 13, characters 8-9:
+Invalid argument (Typing[4110])
   File "xor_bad3.php", line 13, characters 8-9:
   Expected `int` because this is used in a bitwise operation
   File "xor_bad3.php", line 12, characters 25-30: