Make Texp_coerce compatible with old runtime representation.

By adding a unit argument to the payload.

Author: cristianoc

CHANGELOG.md

@@ -42,6 +42,7 @@
 - Refactor uppercase exotic ident handling. https://github.com/rescript-lang/rescript-compiler/pull/6779
 - Fix `-nostdlib` internal compiler option. https://github.com/rescript-lang/rescript-compiler/pull/6824
 - Remove a number of ast nodes never populated by the .res parser, and resulting dead code. https://github.com/rescript-lang/rescript-compiler/pull/6830
+- Remove internal coercion with 2 types from internal representation. Coercion `e : t1 :> t2` was only supported in `.ml` syntax and never by the `.res` parser. https://github.com/rescript-lang/rescript-compiler/pull/6829 
 
 #### :nail_care: Polish
 

jscomp/ml/printtyped.ml

@@ -270,7 +270,7 @@ and expression_extra i ppf x attrs =
       line i ppf "Texp_constraint\n";
       attributes i ppf attrs;
       core_type i ppf ct;
-  | Texp_coerce cto2 ->
+  | Texp_coerce ((), cto2) ->
       line i ppf "Texp_coerce\n";
       attributes i ppf attrs;
       core_type i ppf cto2;

jscomp/ml/tast_mapper.ml

@@ -190,8 +190,8 @@ let expr sub x =
   let extra = function
     | Texp_constraint cty ->
         Texp_constraint (sub.typ sub cty)
-    | Texp_coerce cty2 ->
-        Texp_coerce (sub.typ sub cty2)
+    | Texp_coerce ((), cty2) ->
+        Texp_coerce ((), (sub.typ sub cty2))
     | Texp_open (ovf, path, loc, env) ->
         Texp_open (ovf, path, loc, sub.env sub env)
     | Texp_newtype _ as d -> d

jscomp/ml/typecore.ml

@@ -2626,7 +2626,7 @@ and type_expect_ ?type_clash_context ?in_function ?(recarg=Rejected) env sexp ty
         exp_type = ty';
         exp_attributes = arg.exp_attributes;
         exp_env = env;
-        exp_extra = (Texp_coerce cty', loc, sexp.pexp_attributes) ::
+        exp_extra = (Texp_coerce ((), cty'), loc, sexp.pexp_attributes) ::
                        arg.exp_extra;
       }
   | Pexp_send (e, {txt=met}) ->

jscomp/ml/typedtree.ml

@@ -68,7 +68,7 @@ and expression =
 
 and exp_extra =
   | Texp_constraint of core_type
-  | Texp_coerce of core_type
+  | Texp_coerce of unit * core_type
   | Texp_open of override_flag * Path.t * Longident.t loc * Env.t
   | Texp_poly of core_type option
   | Texp_newtype of string

jscomp/ml/typedtree.mli

@@ -119,7 +119,7 @@ and expression =
 and exp_extra =
   | Texp_constraint of core_type
         (** E : T *)
-  | Texp_coerce of core_type
+  | Texp_coerce of unit * core_type
         (** E :> T           [Texp_coerce T]
          *)
   | Texp_open of override_flag * Path.t * Longident.t loc * Env.t

jscomp/ml/typedtreeIter.ml

@@ -236,7 +236,7 @@ module MakeIterator(Iter : IteratorArgument) : sig
         match cstr with
           Texp_constraint ct ->
             iter_core_type ct
-        | Texp_coerce cty2 ->
+        | Texp_coerce ((), cty2) ->
             iter_core_type cty2
         | Texp_open _ -> ()
         | Texp_poly cto -> option iter_core_type cto

jscomp/ml/typedtreeMap.ml

@@ -362,8 +362,8 @@ module MakeMap(Map : MapArgument) = struct
     match desc with
       | Texp_constraint ct ->
         Texp_constraint (map_core_type ct), loc, attrs
-      | Texp_coerce ct ->
-        Texp_coerce (map_core_type ct), loc, attrs
+      | Texp_coerce ((), ct) ->
+        Texp_coerce ((), map_core_type ct), loc, attrs
       | Texp_poly (Some ct) ->
         Texp_poly (Some ( map_core_type ct )), loc, attrs
       | Texp_newtype _

jscomp/ml/untypeast.ml

@@ -305,7 +305,7 @@ let exp_extra sub (extra, loc, attrs) sexp =
   let attrs = sub.attributes sub attrs in
   let desc =
     match extra with
-      Texp_coerce cty2 ->
+      Texp_coerce ((), cty2) ->
         Pexp_coerce (sexp,
                      (),
                      sub.typ sub cty2)