Tidy-up witness rendering

Summary: Adds specific details for all flavors of `Pessimised_[...]` decl witnesses and remove rendering of the reason name in fallthrough cases

Reviewed By: mheiber

Differential Revision: D64824202

fbshipit-source-id: de607b5c532136b3c20fc88a9d1b025dab3b5c40

hphp/hack/src/typing/typing_reason.ml

@@ -4039,25 +4039,23 @@ module Derivation = struct
       | No_return pos ->
         Explanation.Witness (Pos_or_decl.of_raw_pos pos, "declaration")
       | Shape_literal pos ->
-        Explanation.Witness (Pos_or_decl.of_raw_pos pos, "shape literal")
+        Explanation.Witness (Pos_or_decl.of_raw_pos pos, "`shape` literal")
       | Destructure pos ->
         Explanation.Witness
           (Pos_or_decl.of_raw_pos pos, "destructure expression")
       | Join_point pos ->
         Explanation.Witness (Pos_or_decl.of_raw_pos pos, "join point")
-      | _ ->
-        Explanation.Witness
-          ( witness_locl_to_raw_pos witness,
-            Format.sprintf
-              "element (`%s`)"
-              (constructor_string_of_witness_locl witness) )
+      | _ -> Explanation.Witness (witness_locl_to_raw_pos witness, "element")
 
     and explain_witness_decl witness =
       match witness with
       | Hint pos -> Explanation.Witness (pos, "hint")
       | Witness_from_decl pos -> Explanation.Witness (pos, "declaration")
       | Support_dynamic_type pos ->
         Explanation.Witness (pos, "function or method declaration")
+      | Pessimised_inout pos -> Explanation.Witness (pos, "`inout` parameter")
+      | Pessimised_prop pos -> Explanation.Witness (pos, "property")
+      | Pessimised_this pos -> Explanation.Witness (pos, "`this` hint")
       | Pessimised_return pos -> Explanation.Witness (pos, "return hint")
       | Var_param_from_decl pos ->
         Explanation.Witness (pos, "variadic parameter declaration")
@@ -4079,10 +4077,7 @@ module Derivation = struct
               nm )
       | _ ->
         Explanation.Witness
-          ( witness_decl_to_raw_pos witness,
-            Format.sprintf
-              "element (`%s`)"
-              (constructor_string_of_witness_decl witness) )
+          (witness_decl_to_raw_pos witness, Format.sprintf "declaration")
 
     and explain_def (pos, reason) ~st ~cfg ~ctxt =
       let (expl_reason, st) = explain_reason reason ~st ~cfg ~ctxt in

hphp/hack/test/extended_reasons/bad_inout_lvalue9.php.exp

@@ -156,7 +156,7 @@ Here's why:
 
 I started by checking this subtype relationship.
 
-The subtype comes from this element (Rpessimised_inout)
+The subtype comes from this inout parameter
 
 File bad_inout_lvalue9.php, line 3, character 30 - line 3, character 31:
 
@@ -180,7 +180,7 @@ File bad_inout_lvalue9.php, line 6, character 11 - line 6, character 23:
  6 |   f(inout »tuple($x, $y)«);
  7 | }
 
-and flows into this element (Rpessimised_inout)
+and flows into this inout parameter
 
 File bad_inout_lvalue9.php, line 3, character 30 - line 3, character 31:
 
@@ -276,7 +276,7 @@ Here's why:
 
 I started by checking this subtype relationship.
 
-The subtype comes from this element (Rpessimised_inout)
+The subtype comes from this inout parameter
 
 File bad_inout_lvalue9.php, line 3, character 30 - line 3, character 31:
 
@@ -300,7 +300,7 @@ File bad_inout_lvalue9.php, line 6, character 11 - line 6, character 23:
  6 |   f(inout »tuple($x, $y)«);
  7 | }
 
-and flows into this element (Rpessimised_inout)
+and flows into this inout parameter
 
 File bad_inout_lvalue9.php, line 3, character 30 - line 3, character 31:
 
@@ -319,7 +319,7 @@ via an assignment
 
 The subtype is a union type so next I checked the subtype constraint is satisfied for all its elements.
 
-The subtype comes from this element (Rpessimised_inout)
+The subtype comes from this inout parameter
 
 File bad_inout_lvalue9.php, line 3, character 30 - line 3, character 31: