Experimental scanner: keep track of which strings / identifiers contain an escape.

src/lexer/lexer_py.re

 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 178 matching lines @@
   if (V8_UNLIKELY(!ValidIdentifierStart())) {
     goto default_action;
   }
 }|token(IDENTIFIER)|Identifier>
 
 eos             <|terminate|>
 default_action  <do_token_and_go_forward(ILLEGAL)>
 
 <<DoubleQuoteString>>
 "\\" line_terminator_sequence <||continue>
-/\\[x][:hex_digit:]{2}/       <||continue>
-/\\[u][:hex_digit:]{4}/       <||continue>
-/\\[^xu:line_terminator:]/    <||continue>
+/\\[x][:hex_digit:]{2}/       <set_has_escapes||continue>
+/\\[u][:hex_digit:]{4}/       <set_has_escapes||continue>
+/\\[^xu:line_terminator:]/    <set_has_escapes||continue>
 "\\"                          <|token(ILLEGAL)|>
 line_terminator               <|token(ILLEGAL)|>
 "\""                          <|token(STRING)|>
 eos                           <|terminate_illegal|>
 catch_all                     <||continue>
 
 <<SingleQuoteString>>
 # TODO subgraph for '\'
 "\\" line_terminator_sequence <||continue>
-/\\[x][:hex_digit:]{2}/       <||continue>
-/\\[u][:hex_digit:]{4}/       <||continue>
-/\\[^xu:line_terminator:]/    <||continue>
+/\\[x][:hex_digit:]{2}/       <set_has_escapes||continue>
+/\\[u][:hex_digit:]{4}/       <set_has_escapes||continue>
+/\\[^xu:line_terminator:]/    <set_has_escapes||continue>
 "\\"                          <|token(ILLEGAL)|>
 line_terminator               <|token(ILLEGAL)|>
 "'"                           <|token(STRING)|>
 eos                           <|terminate_illegal|>
 catch_all                     <||continue>
 
 <<Identifier>>
 identifier_char <|token(IDENTIFIER)|continue>
 /\\u[:hex_digit:]{4}/ <{
   if (V8_UNLIKELY(!ValidIdentifierPart())) {
     goto default_action;
   }
+  next_.has_escapes = true;
 }|token(IDENTIFIER)|continue>
 
 <<SingleLineComment>>
 line_terminator  <|line_terminator|>
 eos              <|skip_and_terminate|>
 catch_all        <||continue>
 
 <<MultiLineComment>>
 /\*+\//          <|skip|>
 # TODO find a way to generate the below rule
 /\*+[^\/*]/      <||continue>
 line_terminator  <line_terminator||continue>
 eos              <|terminate_illegal|>
 catch_all        <||continue>