[flow] Remove attached error in SpeculationSingletonError

Summary:
Mostly a revert of D80179072, since it's unused.

Changelog: [internal]

Reviewed By: panagosg7

Differential Revision: D84386554

fbshipit-source-id: 383e63ad568e70b91a3accc19545b31d9b78f217

Author: SamChou19815

src/typing/flow_js.ml

@@ -175,7 +175,7 @@ struct
         l
         (UseT (unknown_use, u))
     with
-    | exception Flow_js_utils.SpeculationSingletonError _ -> false
+    | exception Flow_js_utils.SpeculationSingletonError -> false
     | _ -> true
 
   (* get prop *)
@@ -6789,7 +6789,7 @@ struct
                   evaluate_type_destructor cx ~trace use_op reason t d tvar
               )
             with
-            | Flow_js_utils.SpeculationSingletonError _ ->
+            | Flow_js_utils.SpeculationSingletonError ->
               let opaque_type_args =
                 Base.List.mapi stuck_eval_targs ~f:(fun i t ->
                     ( Subst_name.Synthetic { name = string_of_int i; op_kind = None; ts = [] },
@@ -7760,7 +7760,7 @@ struct
         && not (TvarVisitors.has_unresolved_tvars cx t2)
       then
         try SpeculationKit.try_unify cx trace t1 use_op t2 with
-        | Flow_js_utils.SpeculationSingletonError _ ->
+        | Flow_js_utils.SpeculationSingletonError ->
           let explanation =
             let open Flow_intermediate_error_types in
             match unify_cause with

src/typing/flow_js_utils.ml

@@ -484,7 +484,7 @@ let use_op_of_lookup_action = function
 
 exception SpeculativeError of Error_message.t
 
-exception SpeculationSingletonError of Error_message.t
+exception SpeculationSingletonError
 
 (* [src_cx] is the context in which the error is created, and [dst_cx] the context
  * in which it is recorded. *)

src/typing/implicit_instantiation.ml

@@ -160,7 +160,7 @@ module Make (Observer : OBSERVER) (Flow : Flow_common.S) : S = struct
 
   let speculative_subtyping_succeeds cx trace use_op l u =
     match SpeculationKit.try_singleton_throw_on_failure cx trace l (UseT (use_op, u)) with
-    | exception Flow_js_utils.SpeculationSingletonError _ -> false
+    | exception Flow_js_utils.SpeculationSingletonError -> false
     | _ -> true
 
   (* This visitor records the polarities at which BoundTs are found. We follow the bounds of each
@@ -1775,7 +1775,7 @@ module Kit (FlowJs : Flow_common.S) (Instantiation_helper : Flow_js_utils.Instan
                  any_substituted_check_t
                  (UseT (use_op, any_substituted_extends_t))
              with
-            | exception Flow_js_utils.SpeculationSingletonError _ ->
+            | exception Flow_js_utils.SpeculationSingletonError ->
               (* When all the GenericT and infer types are replaced with any, and subtyping
                  check still cannot succeed, then we can safely conclude that, in every possible
                  instantiation, we will always take the false branch *)

src/typing/speculation_flow.ml

@@ -13,12 +13,10 @@ let try_custom = SpeculationKit.try_custom
 let flow_t_unsafe cx (l, u) =
   SpeculationKit.try_singleton_throw_on_failure cx DepthTrace.dummy_trace l (UseT (unknown_use, u))
 
-let speculation_error_opt cx t u =
+let is_flow_successful cx t u =
   match SpeculationKit.try_singleton_throw_on_failure cx DepthTrace.dummy_trace t u with
-  | exception Flow_js_utils.SpeculationSingletonError e -> Some e
-  | () -> None
-
-let is_flow_successful cx t u = Base.Option.is_none (speculation_error_opt cx t u)
+  | exception Flow_js_utils.SpeculationSingletonError -> false
+  | () -> true
 
 let is_subtyping_successful cx l u = is_flow_successful cx l (UseT (unknown_use, u))
 
@@ -27,18 +25,13 @@ let resolved_lower_flow_unsafe cx r (l, u) =
   | [] -> ()
   | [l] -> Flow_js.flow cx (l, u)
   | l0 :: ls ->
-    let error_opt =
-      Base.List.fold ls ~init:(speculation_error_opt cx l0 u) ~f:(fun acc l ->
-          let r = speculation_error_opt cx l u in
-          match (acc, r) with
-          | (None, _) -> None
-          | (_, None) -> None
-          | (Some e, Some _) -> Some e
+    let successful =
+      Base.List.fold ls ~init:(is_flow_successful cx l0 u) ~f:(fun acc l ->
+          let r = is_flow_successful cx l u in
+          acc || r
       )
     in
-    (match error_opt with
-    | None -> ()
-    | Some e -> raise (Flow_js_utils.SpeculationSingletonError e))
+    if not successful then raise Flow_js_utils.SpeculationSingletonError
 
 let resolved_lower_flow_t_unsafe cx r (l, u) =
   resolved_lower_flow_unsafe cx r (l, UseT (unknown_use, u))
@@ -48,20 +41,15 @@ let resolved_upper_flow_t_unsafe cx r (l, u) =
   | [] -> ()
   | [u] -> Flow_js.flow_t cx (l, u)
   | u0 :: us ->
-    let error_opt =
+    let successful =
       Base.List.fold
         us
-        ~init:(speculation_error_opt cx l (UseT (unknown_use, u0)))
+        ~init:(is_flow_successful cx l (UseT (unknown_use, u0)))
         ~f:(fun acc u ->
-          let r = speculation_error_opt cx l (UseT (unknown_use, u)) in
-          match (acc, r) with
-          | (None, _) -> None
-          | (_, None) -> None
-          | (Some e, Some _) -> Some e)
+          let r = is_flow_successful cx l (UseT (unknown_use, u)) in
+          acc || r)
     in
-    (match error_opt with
-    | None -> ()
-    | Some e -> raise (Flow_js_utils.SpeculationSingletonError e))
+    if not successful then raise Flow_js_utils.SpeculationSingletonError
 
 let get_method_type_unsafe cx t reason propref =
   Tvar.mk_where cx reason (fun prop_t ->
@@ -76,5 +64,5 @@ let get_method_type_opt cx t reason propref =
         resolved_lower_flow_unsafe cx reason (t, use_t)
     )
   with
-  | exception Flow_js_utils.SpeculationSingletonError _ -> None
+  | exception Flow_js_utils.SpeculationSingletonError -> None
   | t -> Some t

src/typing/speculation_kit.ml

@@ -348,7 +348,7 @@ module Make (Flow : INPUT) : OUTPUT = struct
       | SingletonCustomCase _
       | SingletonUnifyCase _ ->
         (match msgs with
-        | [msg] -> raise (SpeculationSingletonError msg)
+        | [_msg] -> raise SpeculationSingletonError
         | _ ->
           failwith
             ("SingletonCase should not have exactly one error, but we got "

src/typing/subtyping_kit.ml

@@ -309,7 +309,7 @@ module Make (Flow : INPUT) : OUTPUT = struct
                         SpeculationKit.try_unify cx trace lt use_op ut;
                         false
                       with
-                      | Flow_js_utils.SpeculationSingletonError _ -> true
+                      | Flow_js_utils.SpeculationSingletonError -> true
                     then
                       (name, lt, ut) :: invariant_subtyping_failed_prop_names
                     else
@@ -1081,7 +1081,7 @@ module Make (Flow : INPUT) : OUTPUT = struct
                flow_type_args cx trace ~use_op lreason ureason ltargs utargs
            )
          with
-        | SpeculationSingletonError _ ->
+        | SpeculationSingletonError ->
           add_output
             cx
             (Error_message.EIncompatibleWithUseOp

src/typing/type_hint.ml

@@ -43,7 +43,7 @@ let in_sandbox_cx cx t ~f =
       in
       Context.reset_errors cx Flow_error.ErrorSet.empty;
       match f (Tvar_resolver.resolved_t cx ~no_lowers ~filter_empty:false t) with
-      | (exception Flow_js_utils.SpeculationSingletonError _)
+      | (exception Flow_js_utils.SpeculationSingletonError)
       | (exception UnconstrainedTvarException)
       | (exception DecompFuncParamOutOfBoundsException) ->
         Context.reset_errors cx original_errors;