Missing => infix operator escape

formatTest/unit_tests/expected_output/infix.re

@@ -1311,3 +1311,10 @@ let not = x => !x;
 let other = x => not(x);
 
 let derefInsideArray = [|a^|];
+
+/* #1941: infix `=>` */
+let (\=>) = (a, b) => a + b;
+
+let x = a \=> b;
+
+let (=>>) = (a, b) => a + b;

formatTest/unit_tests/input/infix.re

@@ -1004,3 +1004,10 @@ let not = (x) => !x;
 let other = (x) => not(x);
 
 let derefInsideArray = [|a^|];
+
+/* #1941: infix `=>` */
+let (\=>) = (a, b) => a + b;
+
+let x = a \=> b;
+
+let (=>>) = (a, b) => a + b;

src/reason-parser/reason_lexer.mll

@@ -612,9 +612,7 @@ rule token = parse
   | '\\'? ['~' '?' '!'] operator_chars+
             { PREFIXOP(lexeme_operator lexbuf) }
   | '\\'? ['=' '<' '>' '|' '&' '$'] operator_chars*
-            {
-              INFIXOP0(lexeme_operator lexbuf)
-            }
+            { INFIXOP0(lexeme_operator lexbuf) }
   | '\\'? '@' operator_chars*
             { INFIXOP1(lexeme_operator lexbuf) }
   | '\\'? '^' ('\\' '.')? operator_chars*

src/reason-parser/reason_syntax_util.ml

@@ -148,6 +148,11 @@ let escape_string str =
     ) str;
   Buffer.contents buf
 
+let remove_backslashes_for_ml s =
+  if s.[0] == '\\' then
+    String.sub s 1 (String.length s - 1)
+  else s
+
 (* the stuff below contains side-effects and are not used by BuckleScript's
   vendored version of reason_syntax_util.ml. So we can neglect it *)
 
@@ -393,6 +398,8 @@ let remove_literal_attrs_mapper_maker super =
 let remove_literal_attrs_mapper =
   remove_literal_attrs_mapper_maker Ast_mapper.default_mapper
 
+let remove_backslashes_for_ml_mapper = identifier_mapper remove_backslashes_for_ml
+
 (** escape_stars_slashes_mapper escapes all stars and slashes in an AST *)
 let escape_stars_slashes_mapper =
   let escape_stars_slashes str =

src/reason-parser/reason_syntax_util.mli

@@ -47,6 +47,9 @@ val reason_to_ml_swap_operator_mapper :
 val ml_to_reason_swap_operator_mapper :
   Ast_404.Ast_mapper.mapper -> Ast_404.Ast_mapper.mapper
 
+val remove_backslashes_for_ml_mapper :
+  Ast_404.Ast_mapper.mapper -> Ast_404.Ast_mapper.mapper
+
 val attribute_exists : 'a -> ('a Ast_404.Asttypes.loc * 'b) list -> bool
 
 val attributes_conflicted :

src/reason-parser/reason_toolchain.ml

@@ -484,8 +484,10 @@ module OCaml_syntax = struct
     Pprintast.signature formatter
       (To_current.copy_signature signature)
   let format_implementation_with_comments (structure, _) formatter =
+    let mapper = Reason_syntax_util.(remove_literal_attrs_mapper |> remove_backslashes_for_ml_mapper)
+    in
     let structure =
-      Reason_syntax_util.(apply_mapper_to_structure structure remove_literal_attrs_mapper)
+      Reason_syntax_util.(apply_mapper_to_structure structure mapper)
     in
     Pprintast.structure formatter
       (To_current.copy_structure structure)

src/refmt/reason_implementation_printer.ml

@@ -50,8 +50,10 @@ let print printtype filename parsedAsML output_chan output_formatter =
     );
   )
   | `Binary -> fun (ast, _) ->
+    let mapper = Reason_syntax_util.(remove_literal_attrs_mapper |> remove_backslashes_for_ml_mapper)
+    in
     let ast =
-      Reason_syntax_util.(apply_mapper_to_structure ast remove_literal_attrs_mapper)
+      Reason_syntax_util.(apply_mapper_to_structure ast mapper)
     in
     Ast_io.to_channel output_chan filename
       (Ast_io.Impl ((module OCaml_current),