Implement handling of arrow functions in the parser

src/token.h

 // Copyright 2012 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 47 matching lines @@
   T(LBRACK, "[", 0)                                                     \
   T(RBRACK, "]", 0)                                                     \
   T(LBRACE, "{", 0)                                                     \
   T(RBRACE, "}", 0)                                                     \
   T(COLON, ":", 0)                                                      \
   T(SEMICOLON, ";", 0)                                                  \
   T(PERIOD, ".", 0)                                                     \
   T(CONDITIONAL, "?", 3)                                                \
   T(INC, "++", 0)                                                       \
   T(DEC, "--", 0)                                                       \
+  T(ARROW, "=>", 0)                                                     \
                                                                         \
   /* Assignment operators. */                                           \
   /* IsAssignmentOp() and Assignment::is_compound() relies on */        \
   /* this block of enum values being contiguous and sorted in the */    \
   /* same order! */                                                     \
   T(INIT_VAR, "=init_var", 2)  /* AST-use only. */                      \
   T(INIT_LET, "=init_let", 2)  /* AST-use only. */                      \
   T(INIT_CONST, "=init_const", 2)  /* AST-use only. */                  \
   T(INIT_CONST_LEGACY, "=init_const_legacy", 2)  /* AST-use only. */    \
   T(ASSIGN, "=", 2)                                                     \
@@ skipping 228 matching lines @@
  private:
   static const char* const name_[NUM_TOKENS];
   static const char* const string_[NUM_TOKENS];
   static const int8_t precedence_[NUM_TOKENS];
   static const char token_type[NUM_TOKENS];
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_TOKEN_H_