feat: add raw identifier syntax

CHANGES.md

@@ -4,6 +4,8 @@
   [#2800](https://github.com/reasonml/reason/pull/2800))
 - Fix: don't print all extension strings as quoted extensions (@anmonteiro,
   [#2809](https://github.com/reasonml/reason/pull/2809))
+- Add support for raw identifier syntax (@anmonteiro,
+  [#2796](https://github.com/reasonml/reason/pull/2796))
 
 ## 3.13.0
 

src/reason-parser/reason_declarative_lexer.mll

@@ -385,6 +385,7 @@ let hex_float_literal =
   (['p' 'P'] ['+' '-']? ['0'-'9'] ['0'-'9' '_']* )?
 
 let literal_modifier = ['G'-'Z' 'g'-'z']
+let raw_ident_escape = "\\#"
 
 rule token state = parse
   | "\\" newline {
@@ -408,6 +409,8 @@ rule token state = parse
     { QUESTION }
   | "=?"
     { set_lexeme_length lexbuf 1; EQUAL }
+  | raw_ident_escape (lowercase identchar * as name)
+      { LIDENT name }
   | lowercase identchar *
     { let s = Lexing.lexeme lexbuf in
       try Hashtbl.find keyword_table s
@@ -521,7 +524,7 @@ rule token state = parse
     { CHAR (char_for_decimal_code lexbuf 2) }
   | "'\\" 'x' ['0'-'9' 'a'-'f' 'A'-'F'] ['0'-'9' 'a'-'f' 'A'-'F'] "'"
     { CHAR (char_for_hexadecimal_code lexbuf 3) }
-  | "'" (("\\" _) as esc)
+  | "'" (("\\" [^ '#']) as esc)
     { raise_error (Location.curr lexbuf) (Illegal_escape esc);
       token state lexbuf
     }

src/reason-parser/reason_pprint_ast.ml

@@ -718,11 +718,15 @@ type construct =
   | `normal
   | `simple of Longident.t
   | `tuple
+  | `btrue
+  | `bfalse
   ]
 
 let view_expr x =
   match x.pexp_desc with
   | Pexp_construct ({ txt = Lident "()" }, _) -> `tuple
+  | Pexp_construct ({ txt = Lident "true"; _ }, _) -> `btrue
+  | Pexp_construct ({ txt = Lident "false"; _ }, _) -> `bfalse
   | Pexp_construct ({ txt = Lident "[]" }, _) -> `nil
   | Pexp_construct ({ txt = Lident "::" }, Some _) ->
     let rec loop exp acc =
@@ -745,7 +749,7 @@ let is_simple_list_expr x =
   match view_expr x with `list _ | `cons _ -> true | _ -> false
 
 let is_simple_construct : construct -> bool = function
-  | `nil | `tuple | `list _ | `simple _ | `cons _ -> true
+  | `nil | `tuple | `list _ | `simple _ | `btrue | `bfalse | `cons _ -> true
   | `normal -> false
 
 let uncurriedTable = Hashtbl.create 42
@@ -2062,14 +2066,22 @@ let createFormatter () =
         settings.funcApplicationLabelStyle
         typeApplicationItems
 
+    let add_raw_identifier_prefix txt =
+      let prefix =
+        match Hashtbl.find Reason_declarative_lexer.keyword_table txt with
+        | _ -> "\\#"
+        | exception Not_found -> ""
+      in
+      prefix ^ txt
+
     (* add parentheses to binders when they are in fact infix or prefix
        operators *)
     let protectIdentifier txt =
       let needs_parens = needs_parens txt in
       let txt =
         if Reason_syntax_util.is_andop txt || Reason_syntax_util.is_letop txt
         then Reason_syntax_util.compress_letop_identifier txt
-        else txt
+        else txt |> add_raw_identifier_prefix
       in
       if not needs_parens
       then atom txt
@@ -2926,7 +2938,9 @@ let createFormatter () =
             let itm =
               self#formatOneTypeDef
                 prepend
-                (atom ~loc:td.ptype_name.loc td.ptype_name.txt)
+                (atom
+                   ~loc:td.ptype_name.loc
+                   (add_raw_identifier_prefix td.ptype_name.txt))
                 (atom eq_symbol)
                 td
             in
@@ -3099,9 +3113,8 @@ let createFormatter () =
           let recordRow pld =
             let hasPunning = recordRowIsPunned pld in
             let name =
-              if hasPunning
-              then [ atom pld.pld_name.txt ]
-              else [ atom pld.pld_name.txt; atom ":" ]
+              let name = add_raw_identifier_prefix pld.pld_name.txt in
+              if hasPunning then [ atom name ] else [ atom name; atom ":" ]
             in
             let name = source_map ~loc:pld.pld_name.loc (makeList name) in
             let withMutable =
@@ -3412,6 +3425,9 @@ let createFormatter () =
                 let variant_helper i rf =
                   match rf.prf_desc with
                   | Rtag (label, opt_ampersand, ctl) ->
+                    let label =
+                      { label with txt = add_raw_identifier_prefix label.txt }
+                    in
                     let pcd_args = Pcstr_tuple ctl in
                     let all_attrs =
                       List.concat [ pcd_attributes; rf.prf_attributes ]
@@ -3599,6 +3615,9 @@ let createFormatter () =
                      ~arityIsClear:true)
             | Ppat_lazy p ->
               label (atom "lazy") (formatPrecedence (self#simple_pattern p))
+            | Ppat_construct
+                ({ txt = Lident (("true" | "false") as txt); _ }, None) ->
+              atom txt
             | Ppat_construct (({ txt } as li), po) when not (txt = Lident "::")
               ->
               (* FIXME The third field always false *)
@@ -3747,8 +3766,9 @@ let createFormatter () =
           else
             let itm =
               match x.ppat_desc with
-              | Ppat_construct ({ loc; txt = Lident (("()" | "[]") as x) }, _)
-                ->
+              | Ppat_construct
+                  ( { loc; txt = Lident (("()" | "[]" | "true" | "false") as x) }
+                  , _ ) ->
                 (* Patterns' locations might include a leading bar depending on the
                  * context it was parsed in. Therefore, we need to include further
                  * information about the contents of the pattern such as tokens etc,
@@ -5007,7 +5027,7 @@ let createFormatter () =
                         ~polyVariant:true
                         ~arityIsClear:true
                         stdAttrs
-                        (atom ("`" ^ l))
+                        (atom ("`" ^ add_raw_identifier_prefix l))
                         eo
                     ]
               (* TODO: Should protect this identifier *)
@@ -7657,6 +7677,8 @@ let createFormatter () =
                   (match view_expr x with
                   | `nil -> atom "[]"
                   | `tuple -> atom "()"
+                  | `btrue -> atom "true"
+                  | `bfalse -> atom "false"
                   | `list xs ->
                     (* LIST EXPRESSION *)
                     self#unparseSequence ~construct:`List xs
@@ -7712,7 +7734,9 @@ let createFormatter () =
                          (self#core_type ct)
                      ])
               | Pexp_variant (l, None) ->
-                Some (ensureSingleTokenSticksToLabel (atom ("`" ^ l)))
+                Some
+                  (ensureSingleTokenSticksToLabel
+                     (atom ("`" ^ add_raw_identifier_prefix l)))
               | Pexp_record (l, eo) -> Some (self#unparseRecord l eo)
               | Pexp_array l -> Some (self#unparseSequence ~construct:`Array l)
               | Pexp_let _ | Pexp_sequence _ | Pexp_letmodule _
@@ -8233,12 +8257,13 @@ let createFormatter () =
             in
 
             let upToName =
+              let name = add_raw_identifier_prefix pci_name.txt in
               if ls == []
-              then label ~space:true (atom opener) (atom pci_name.txt)
+              then label ~space:true (atom opener) (atom name)
               else
                 label
                   ~space:true
-                  (label ~space:true (atom opener) (atom pci_name.txt))
+                  (label ~space:true (atom opener) (atom name))
                   (self#class_params_def ls)
             in
             let includingEqual =
@@ -8807,14 +8832,17 @@ let createFormatter () =
             ()
 
         method modtype x ~delim =
-          let name = atom x.pmtd_name.txt in
-          let letPattern =
-            makeList ~postSpace:true [ atom "module type"; name; atom delim ]
-          in
+          let name = atom (add_raw_identifier_prefix x.pmtd_name.txt) in
           let main =
             match x.pmtd_type with
             | None -> makeList ~postSpace:true [ atom "module type"; name ]
-            | Some mt -> self#module_type letPattern mt
+            | Some mt ->
+              let letPattern =
+                makeList
+                  ~postSpace:true
+                  [ atom "module type"; name; atom delim ]
+              in
+              self#module_type letPattern mt
           in
           let { Reason_attributes.stdAttrs; docAttrs } =
             Reason_attributes.partitionAttributes
@@ -9381,6 +9409,7 @@ let createFormatter () =
               , None )
 
         method class_opening class_keyword name pci_virt ls =
+          let name = add_raw_identifier_prefix name in
           let firstToken = if class_keyword then "class" else "and" in
           match pci_virt, ls with
           (* When no class params, it's a very simple formatting for the
@@ -9436,14 +9465,17 @@ let createFormatter () =
               self#attach_std_item_attrs binding.pmb_attributes module_binding
             | Pstr_open od -> self#pstr_open od
             | Pstr_modtype x ->
-              let name = atom x.pmtd_name.txt in
-              let letPattern =
-                makeList ~postSpace:true [ atom "module type"; name; atom "=" ]
-              in
+              let name = atom (add_raw_identifier_prefix x.pmtd_name.txt) in
               let main =
                 match x.pmtd_type with
                 | None -> makeList ~postSpace:true [ atom "module type"; name ]
-                | Some mt -> self#module_type letPattern mt
+                | Some mt ->
+                  let letPattern =
+                    makeList
+                      ~postSpace:true
+                      [ atom "module type"; name; atom "=" ]
+                  in
+                  self#module_type letPattern mt
               in
               self#attach_std_item_attrs x.pmtd_attributes main
             | Pstr_class l -> self#class_declaration_list l

test/raw-identifiers.t/input.re

@@ -0,0 +1,43 @@
+
+let \#let = 2;
+let \#let = \#let
+and \#and = \#let;
+
+/* labeled arguments */
+let \#let = (~\#let) => {
+  \#let;
+};
+
+let \#let = (~\#let: \#let = \#let) => {
+  \#let;
+};
+
+/* Types */
+type \#type = \#type;
+
+module type \#module = \#module;
+
+class \#class = \#class;
+
+class type \#class = \#class;
+
+type x = [ | `\#module ]
+type y = [ | \#module ]
+let x = `\#module
+
+external \#external: unit => unit = "external";
+
+type \#rec = {
+  \#type: \#type,
+  \#module: module_
+};
+
+let \#rec = {
+  \#type: \#type,
+  \#module: module_
+}
+
+let true = x => x;
+
+let \#true = x => x;
+

test/raw-identifiers.t/run.t

@@ -0,0 +1,49 @@
+Test raw identifiers in Reason syntax
+
+  $ refmt ./input.re | tee input2.re
+  let \#let = 2;
+  let \#let = \#let
+  and \#and = \#let;
+
+  /* labeled arguments */
+  let \#let = (~\#let) => {
+    \#let;
+  };
+
+  let \#let = (~\#let: \#let=\#let) => {
+    \#let;
+  };
+
+  /* Types */
+  type \#type = \#type;
+
+  module type \#module = \#module;
+
+  class \#class = class \#class;
+
+  class type \#class = \#class;
+
+  type x = [ | `\#module];
+  type y = [ \#module];
+  let x = `\#module;
+
+  external \#external: unit => unit = "external";
+
+  type \#rec = {
+    \#type,
+    \#module: module_,
+  };
+
+  let \#rec = {
+    \#type,
+    \#module: module_,
+  };
+
+  let true = x => x;
+
+  let \#true = x => x;
+
+Check idempotency
+
+  $ refmt ./input2.re > out.re
+