Slight refactoring to share logic between echo -e and $''.

core/lexer.py

@@ -256,6 +256,7 @@ def Tokens(self, line):
      if not matches:
        raise AssertionError(
            'no match at position %d: %r (%r)' % (pos, line, line[pos]))
      # NOTE: Need longest-match semantics to find \377 vs \.
      end_pos, tok_type, tok_val = max(matches, key=lambda m: m[0])
      yield tok_type, line[pos:end_pos]
      pos = end_pos

osh/lex.py

@@ -405,6 +405,10 @@ def IsKeyword(name):

  # Backslash that ends a line.  Note '.' doesn't match a newline character.
  C('\\\n', Id.Char_Literals),

  # e.g. \A is not an escape, and \x doesn't match a hex escape.  This could be
  # an error.
  C('\\', Id.Char_Literals),
]

# Used by ECHO_LEXER in core/builtin.py.
@@ -415,12 +419,6 @@ def IsKeyword(name):

  C(r'\c', Id.Char_Stop),

  # e.g. \A -> \A, is not a backslash escape.
  # This has to come AFTER the \c and so forth.
  #
  # This includes embedded \n?  Is that possible with echo -e?
  R(r'\\.', Id.Char_Literals),

  # Backslash that ends the string.
  R(r'\\$', Id.Char_Literals),

@@ -443,9 +441,6 @@ def IsKeyword(name):
  # well.
  R(r"[^\\'\0]+", Id.Char_Literals),

  # e.g. \x doesn't match a hex escape.  This could be an error.
  C('\\', Id.Char_Literals),

  C("'", Id.Right_SingleQuote),

  # Backslash that ends the file!  Caught by re2c exhaustiveness check.  Parser