Remove the legacy %re source extension

Signed-off-by: Christoph Knittel <ck@cca.io>

Author: cknitt

CHANGELOG.md

@@ -14,6 +14,7 @@
 
 #### :boom: Breaking Change
 
+- Remove `%re`; use regexp literals instead. https://github.com/rescript-lang/rescript/pull/8610
 - Reject malformed UTF-8 in documentation comments and invalid string or template literal escapes that were previously accepted, including empty or out-of-range braced Unicode escapes (`\u{}`, `\u{110000}`) and legacy decimal or octal escapes in templates (`\1`, `\01`, `\8`). These inputs now produce syntax diagnostics instead of compiling to invalid or inconsistent JavaScript. https://github.com/rescript-lang/rescript/pull/8606
 - Reject tagged template literals in patterns. Patterns cannot invoke their tag; previously their raw payload was compiled as a plain string comparison. https://github.com/rescript-lang/rescript/pull/8606
 - Remove runtime APIs that were deprecated for removal in ReScript 13, including the `Char` module, unsafe `Obj` operations, legacy `Pervasives` helpers, and `Array.unsafe_get`. https://github.com/rescript-lang/rescript/pull/8564

compiler/frontend/ast_exp_extension.ml

@@ -56,11 +56,7 @@ let handle_extension e (_self : Ast_mapper.mapper)
                | Some msg -> " - Todo: " ^ msg)) );
       ]
   | "ffi" -> Ast_exp_handle_external.handle_ffi ~loc ~payload
-  | "raw" -> Ast_exp_handle_external.handle_raw ~kind:Raw_exp loc payload
-  | "re" ->
-    Exp.constraint_ ~loc
-      (Ast_exp_handle_external.handle_raw ~kind:Raw_re loc payload)
-      (Ast_comb.to_regexp_type loc)
+  | "raw" -> Ast_exp_handle_external.handle_raw loc payload
   | "debugger" ->
     {e with pexp_desc = Ast_exp_handle_external.handle_debugger loc payload}
   | _ -> e

compiler/frontend/ast_exp_handle_external.ml

@@ -34,20 +34,13 @@ let handle_debugger loc (payload : Ast_payload.t) =
   | _ ->
     Location.raise_errorf ~loc "%%debugger extension doesn't accept arguments"
 
-let handle_raw ~kind loc payload =
+let handle_raw loc payload =
   let is_function = ref None in
-  match Ast_payload.raw_as_string_exp_exn ~kind ~is_function payload with
-  | None -> (
-    match kind with
-    | Raw_re ->
-      Location.raise_errorf ~loc
-        "%%re extension can only be applied to a string"
-    | Raw_exp ->
-      Location.raise_errorf ~loc
-        "%%raw extension can only be applied to a string"
-    | Raw_program ->
-      Location.raise_errorf ~loc
-        "%%%%raw extension can only be applied to a string")
+  match
+    Ast_payload.raw_as_string_exp_exn ~kind:Raw_exp ~is_function payload
+  with
+  | None ->
+    Location.raise_errorf ~loc "%%raw extension can only be applied to a string"
   | Some exp ->
     {
       exp with

compiler/frontend/ast_exp_handle_external.mli

@@ -26,11 +26,7 @@ val handle_debugger : Location.t -> Ast_payload.t -> Parsetree.expression_desc
 
 val handle_ffi : loc:Location.t -> payload:Ast_payload.t -> Parsetree.expression
 
-val handle_raw :
-  kind:Js_raw_info.raw_kind ->
-  Location.t ->
-  Ast_payload.t ->
-  Parsetree.expression
+val handle_raw : Location.t -> Ast_payload.t -> Parsetree.expression
 
 val handle_raw_structure :
   Location.t -> Ast_payload.t -> Parsetree.structure_item

compiler/ml/ast_mapper_to0.ml

@@ -653,6 +653,7 @@ module E = struct
         (sub.pat sub pat) start_expr end_expr Asttypes.Upto
         (sub.expr sub body_expr)
     | Pexp_regexp {pattern; flags} ->
+      (* %re is only a frozen PPX wire encoding, not source syntax. *)
       extension ~loc ~attrs
         ( Location.mkloc "re" loc,
           Pt.PStr

compiler/ml/parsetree.ml

@@ -54,8 +54,8 @@ type constant =
      otherwise the frontend rejects it. The string is JavaScript source, not a
      decoded ReScript string value. *)
   | Pconst_raw_source of string
-  (* JavaScript source carried by a compiler extension such as [raw], [ffi], or
-     [re]. For example, [%raw("x + 1")] stores ["x + 1"]. The extension
+  (* JavaScript source carried by a compiler extension such as [raw] or [ffi].
+     For example, [%raw("x + 1")] stores ["x + 1"]. The extension
      interprets the string as JavaScript source rather than as a ReScript
      runtime string value. *)
   | Pconst_float of string * char option

compiler/syntax/src/res_core.ml

@@ -2153,14 +2153,12 @@ and parse_atomic_expr p =
       Parser.next_regex_token p;
       match p.token with
       | Regex (pattern, flags) -> parse_regex ~start_pos p pattern flags
-      | _ -> Ast_helper.Exp.extension (Location.mknoloc "re", Parsetree.PStr [])
-      )
+      | _ -> assert false (* next_regex_token always returns Regex. *))
     | ForwardslashDot -> (
       Parser.next_regex_token p;
       match p.token with
       | Regex (pattern, flags) -> parse_regex ~start_pos p ("." ^ pattern) flags
-      | _ -> Ast_helper.Exp.extension (Location.mknoloc "re", Parsetree.PStr [])
-      )
+      | _ -> assert false (* next_regex_token always returns Regex. *))
     | token -> (
       let err_pos = p.prev_end_pos in
       Parser.err ~start_pos:err_pos p
@@ -7672,9 +7670,14 @@ and parse_extension ?(module_language = false) p =
   else Parser.expect Percent p;
   let attr_id = parse_attribute_id ~start_pos p in
   let payload = parse_payload p in
+  if attr_id.txt = "re" then
+    Parser.err ~start_pos:attr_id.loc.loc_start ~end_pos:attr_id.loc.loc_end p
+      (Diagnostics.message
+         "The %re extension has been removed. Use a regexp literal such as \
+          /abc/i.");
   let payload =
     match (attr_id.txt, payload) with
-    | ( ("raw" | "ffi" | "re"),
+    | ( ("raw" | "ffi"),
         Parsetree.PStr
           [
             ({

compiler/syntax/src/res_printer.ml

@@ -3462,20 +3462,8 @@ and print_expression ~state (e : Parsetree.expression) cmt_tbl =
              Doc.soft_line;
              Doc.rbrace;
            ])
-    | Pexp_extension extension -> (
-      match extension with
-      | ( {txt = "re"},
-          PStr
-            [
-              {
-                pstr_desc =
-                  Pstr_eval
-                    ({pexp_desc = Pexp_constant (Pconst_raw_source expr)}, []);
-              };
-            ] ) ->
-        Doc.text expr
-      | extension ->
-        print_extension ~state ~at_module_lvl:false extension cmt_tbl)
+    | Pexp_extension extension ->
+      print_extension ~state ~at_module_lvl:false extension cmt_tbl
     | Pexp_regexp {pattern; flags} -> Doc.text ("/" ^ pattern ^ "/" ^ flags)
     | Pexp_template {source_segments; values} ->
       print_template_literal ~state ~source_segments ~values cmt_tbl

tests/build_tests/super_errors/expected/syntaxErrorsRemovedReExtension.res.expected

@@ -0,0 +1,9 @@
+
+  Syntax error!
+  /.../fixtures/syntaxErrorsRemovedReExtension.res:1:10-12
+
+  1 │ let re = %re("/abc/i")
+  2 │ // Use the literal syntax instead.
+  3 │ let literal = /abc/i
+
+  The %re extension has been removed. Use a regexp literal such as /abc/i.

tests/build_tests/super_errors/fixtures/syntaxErrorsRemovedReExtension.res

@@ -0,0 +1,3 @@
+let re = %re("/abc/i")
+// Use the literal syntax instead.
+let literal = /abc/i