text: from fontTools.feaLib.error import FeatureLibError
  from fontTools.feaLib.lexer import Lexer, IncludingLexer, NonIncludingLexer
  from fontTools.misc.encodingTools import getEncoding
  from fontTools.misc.py23 import *
  import fontTools.feaLib.ast as ast
  import logging
  import os
  import re
  
  
  log = logging.getLogger(__name__)
  
  
  class Parser(object):
      """Initializes a Parser object.
  
      Example:
  
          .. code:: python
  
              from fontTools.feaLib.parser import Parser
              parser = Parser(file, font.getReverseGlyphMap())
              parsetree = parser.parse()
  
      Note: the ``glyphNames`` iterable serves a double role to help distinguish
      glyph names from ranges in the presence of hyphens and to ensure that glyph
      names referenced in a feature file are actually part of a font's glyph set.
      If the iterable is left empty, no glyph name in glyph set checking takes
      place, and all glyph tokens containing hyphens are treated as literal glyph
      names, not as ranges. (Adding a space around the hyphen can, in any case,
      help to disambiguate ranges from glyph names containing hyphens.)
  
      By default, the parser will follow ``include()`` statements in the feature
      file. To turn this off, pass ``followIncludes=False``. Pass a directory string as
      ``includeDir`` to explicitly declare a directory to search included feature files
      in.
      """
      extensions = {}
      ast = ast
      SS_FEATURE_TAGS = {"ss%02d" % i for i in range(1, 20+1)}
      CV_FEATURE_TAGS = {"cv%02d" % i for i in range(1, 99+1)}
  
      def __init__(self, featurefile, glyphNames=(), followIncludes=True,
                   includeDir=None, **kwargs):
  
          if "glyphMap" in kwargs:
              from fontTools.misc.loggingTools import deprecateArgument
              deprecateArgument("glyphMap", "use 'glyphNames' (iterable) instead")
              if glyphNames:
                  raise TypeError("'glyphNames' and (deprecated) 'glyphMap' are "
                                  "mutually exclusive")
              glyphNames = kwargs.pop("glyphMap")
          if kwargs:
              raise TypeError("unsupported keyword argument%s: %s"
                              % ("" if len(kwargs) == 1 else "s",
                                 ", ".join(repr(k) for k in kwargs)))
  
          self.glyphNames_ = set(glyphNames)
          self.doc_ = self.ast.FeatureFile()
          self.anchors_ = SymbolTable()
          self.glyphclasses_ = SymbolTable()
          self.lookups_ = SymbolTable()
          self.valuerecords_ = SymbolTable()
          self.symbol_tables_ = {
              self.anchors_, self.valuerecords_
          }
          self.next_token_type_, self.next_token_ = (None, None)
          self.cur_comments_ = []
          self.next_token_location_ = None
          lexerClass = IncludingLexer if followIncludes else NonIncludingLexer
          self.lexer_ = lexerClass(featurefile, includeDir=includeDir)
          self.advance_lexer_(comments=True)
  
      def parse(self):
          """Parse the file, and return a :class:`fontTools.feaLib.ast.FeatureFile`
          object representing the root of the abstract syntax tree containing the
          parsed contents of the file."""
          statements = self.doc_.statements
          while self.next_token_type_ is not None or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(
                      self.ast.Comment(self.cur_token_,
                                       location=self.cur_token_location_))
              elif self.is_cur_keyword_("include"):
                  statements.append(self.parse_include_())
              elif self.cur_token_type_ is Lexer.GLYPHCLASS:
                  statements.append(self.parse_glyphclass_definition_())
              elif self.is_cur_keyword_(("anon", "anonymous")):
                  statements.append(self.parse_anonymous_())
              elif self.is_cur_keyword_("anchorDef"):
                  statements.append(self.parse_anchordef_())
              elif self.is_cur_keyword_("languagesystem"):
                  statements.append(self.parse_languagesystem_())
              elif self.is_cur_keyword_("lookup"):
                  statements.append(self.parse_lookup_(vertical=False))
              elif self.is_cur_keyword_("markClass"):
                  statements.append(self.parse_markClass_())
              elif self.is_cur_keyword_("feature"):
                  statements.append(self.parse_feature_block_())
              elif self.is_cur_keyword_("table"):
                  statements.append(self.parse_table_())
              elif self.is_cur_keyword_("valueRecordDef"):
                  statements.append(
                      self.parse_valuerecord_definition_(vertical=False))
              elif self.cur_token_type_ is Lexer.NAME and self.cur_token_ in self.extensions:
                  statements.append(self.extensions[self.cur_token_](self))
              elif self.cur_token_type_ is Lexer.SYMBOL and self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError(
                      "Expected feature, languagesystem, lookup, markClass, "
                      "table, or glyph class definition, got {} \"{}\"".format(self.cur_token_type_, self.cur_token_),
                      self.cur_token_location_)
          return self.doc_
  
      def parse_anchor_(self):
          # Parses an anchor in any of the four formats given in the feature
          # file specification (2.e.vii).
          self.expect_symbol_("<")
          self.expect_keyword_("anchor")
          location = self.cur_token_location_
  
          if self.next_token_ == "NULL": # Format D
              self.expect_keyword_("NULL")
              self.expect_symbol_(">")
              return None
  
          if self.next_token_type_ == Lexer.NAME: # Format E
              name = self.expect_name_()
              anchordef = self.anchors_.resolve(name)
              if anchordef is None:
                  raise FeatureLibError(
                      'Unknown anchor "%s"' % name,
                      self.cur_token_location_)
              self.expect_symbol_(">")
              return self.ast.Anchor(anchordef.x, anchordef.y,
                                     name=name,
                                     contourpoint=anchordef.contourpoint,
                                     xDeviceTable=None, yDeviceTable=None,
                                     location=location)
  
          x, y = self.expect_number_(), self.expect_number_()
  
          contourpoint = None
          if self.next_token_ == "contourpoint": # Format B
              self.expect_keyword_("contourpoint")
              contourpoint = self.expect_number_()
  
          if self.next_token_ == "<": # Format C
              xDeviceTable = self.parse_device_()
              yDeviceTable = self.parse_device_()
          else:
              xDeviceTable, yDeviceTable = None, None
  
          self.expect_symbol_(">")
          return self.ast.Anchor(x, y, name=None,
                                 contourpoint=contourpoint,
                                 xDeviceTable=xDeviceTable,
                                 yDeviceTable=yDeviceTable,
                                 location=location)
  
      def parse_anchor_marks_(self):
          # Parses a sequence of ``[<anchor> mark @MARKCLASS]*.``
          anchorMarks = []  # [(self.ast.Anchor, markClassName)*]
          while self.next_token_ == "<":
              anchor = self.parse_anchor_()
              if anchor is None and self.next_token_ != "mark":
                  continue  # <anchor NULL> without mark, eg. in GPOS type 5
              self.expect_keyword_("mark")
              markClass = self.expect_markClass_reference_()
              anchorMarks.append((anchor, markClass))
          return anchorMarks
  
      def parse_anchordef_(self):
          # Parses a named anchor definition (`section 2.e.viii <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#2.e.vii>`_).
          assert self.is_cur_keyword_("anchorDef")
          location = self.cur_token_location_
          x, y = self.expect_number_(), self.expect_number_()
          contourpoint = None
          if self.next_token_ == "contourpoint":
              self.expect_keyword_("contourpoint")
              contourpoint = self.expect_number_()
          name = self.expect_name_()
          self.expect_symbol_(";")
          anchordef = self.ast.AnchorDefinition(name, x, y,
                                                contourpoint=contourpoint,
                                                location=location)
          self.anchors_.define(name, anchordef)
          return anchordef
  
      def parse_anonymous_(self):
          # Parses an anonymous data block (`section 10 <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#10>`_).
          assert self.is_cur_keyword_(("anon", "anonymous"))
          tag = self.expect_tag_()
          _, content, location = self.lexer_.scan_anonymous_block(tag)
          self.advance_lexer_()
          self.expect_symbol_('}')
          end_tag = self.expect_tag_()
          assert tag == end_tag, "bad splitting in Lexer.scan_anonymous_block()"
          self.expect_symbol_(';')
          return self.ast.AnonymousBlock(tag, content, location=location)
  
      def parse_attach_(self):
          # Parses a GDEF Attach statement (`section 9.b <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#9.b>`_)
          assert self.is_cur_keyword_("Attach")
          location = self.cur_token_location_
          glyphs = self.parse_glyphclass_(accept_glyphname=True)
          contourPoints = {self.expect_number_()}
          while self.next_token_ != ";":
              contourPoints.add(self.expect_number_())
          self.expect_symbol_(";")
          return self.ast.AttachStatement(glyphs, contourPoints,
                                          location=location)
  
      def parse_enumerate_(self, vertical):
          # Parse an enumerated pair positioning rule (`section 6.b.ii <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#6.b.ii>`_).
          assert self.cur_token_ in {"enumerate", "enum"}
          self.advance_lexer_()
          return self.parse_position_(enumerated=True, vertical=vertical)
  
      def parse_GlyphClassDef_(self):
          # Parses 'GlyphClassDef @BASE, @LIGATURES, @MARKS, @COMPONENTS;'
          assert self.is_cur_keyword_("GlyphClassDef")
          location = self.cur_token_location_
          if self.next_token_ != ",":
              baseGlyphs = self.parse_glyphclass_(accept_glyphname=False)
          else:
              baseGlyphs = None
          self.expect_symbol_(",")
          if self.next_token_ != ",":
              ligatureGlyphs = self.parse_glyphclass_(accept_glyphname=False)
          else:
              ligatureGlyphs = None
          self.expect_symbol_(",")
          if self.next_token_ != ",":
              markGlyphs = self.parse_glyphclass_(accept_glyphname=False)
          else:
              markGlyphs = None
          self.expect_symbol_(",")
          if self.next_token_ != ";":
              componentGlyphs = self.parse_glyphclass_(accept_glyphname=False)
          else:
              componentGlyphs = None
          self.expect_symbol_(";")
          return self.ast.GlyphClassDefStatement(baseGlyphs, markGlyphs,
                                                 ligatureGlyphs, componentGlyphs,
                                                 location=location)
  
      def parse_glyphclass_definition_(self):
          # Parses glyph class definitions such as '@UPPERCASE = [A-Z];'
          location, name = self.cur_token_location_, self.cur_token_
          self.expect_symbol_("=")
          glyphs = self.parse_glyphclass_(accept_glyphname=False)
          self.expect_symbol_(";")
          glyphclass = self.ast.GlyphClassDefinition(name, glyphs,
                                                     location=location)
          self.glyphclasses_.define(name, glyphclass)
          return glyphclass
  
      def split_glyph_range_(self, name, location):
          # Since v1.20, the OpenType Feature File specification allows
          # for dashes in glyph names. A sequence like "a-b-c-d" could
          # therefore mean a single glyph whose name happens to be
          # "a-b-c-d", or it could mean a range from glyph "a" to glyph
          # "b-c-d", or a range from glyph "a-b" to glyph "c-d", or a
          # range from glyph "a-b-c" to glyph "d".Technically, this
          # example could be resolved because the (pretty complex)
          # definition of glyph ranges renders most of these splits
          # invalid. But the specification does not say that a compiler
          # should try to apply such fancy heuristics. To encourage
          # unambiguous feature files, we therefore try all possible
          # splits and reject the feature file if there are multiple
          # splits possible. It is intentional that we don't just emit a
          # warning; warnings tend to get ignored. To fix the problem,
          # font designers can trivially add spaces around the intended
          # split point, and we emit a compiler error that suggests
          # how exactly the source should be rewritten to make things
          # unambiguous.
          parts = name.split("-")
          solutions = []
          for i in range(len(parts)):
              start, limit = "-".join(parts[0:i]), "-".join(parts[i:])
              if start in self.glyphNames_ and limit in self.glyphNames_:
                  solutions.append((start, limit))
          if len(solutions) == 1:
              start, limit = solutions[0]
              return start, limit
          elif len(solutions) == 0:
              raise FeatureLibError(
                  "\"%s\" is not a glyph in the font, and it can not be split "
                  "into a range of known glyphs" % name, location)
          else:
              ranges = " or ".join(["\"%s - %s\"" % (s, l) for s, l in solutions])
              raise FeatureLibError(
                  "Ambiguous glyph range \"%s\"; "
                  "please use %s to clarify what you mean" % (name, ranges),
                  location)
  
      def parse_glyphclass_(self, accept_glyphname):
          # Parses a glyph class, either named or anonymous, or (if
          # ``bool(accept_glyphname)``) a glyph name.
          if (accept_glyphname and
                  self.next_token_type_ in (Lexer.NAME, Lexer.CID)):
              glyph = self.expect_glyph_()
              self.check_glyph_name_in_glyph_set(glyph)
              return self.ast.GlyphName(glyph, location=self.cur_token_location_)
          if self.next_token_type_ is Lexer.GLYPHCLASS:
              self.advance_lexer_()
              gc = self.glyphclasses_.resolve(self.cur_token_)
              if gc is None:
                  raise FeatureLibError(
                      "Unknown glyph class @%s" % self.cur_token_,
                      self.cur_token_location_)
              if isinstance(gc, self.ast.MarkClass):
                  return self.ast.MarkClassName(
                      gc, location=self.cur_token_location_)
              else:
                  return self.ast.GlyphClassName(
                      gc, location=self.cur_token_location_)
  
          self.expect_symbol_("[")
          location = self.cur_token_location_
          glyphs = self.ast.GlyphClass(location=location)
          while self.next_token_ != "]":
              if self.next_token_type_ is Lexer.NAME:
                  glyph = self.expect_glyph_()
                  location = self.cur_token_location_
                  if '-' in glyph and self.glyphNames_ and glyph not in self.glyphNames_:
                      start, limit = self.split_glyph_range_(glyph, location)
                      self.check_glyph_name_in_glyph_set(start, limit)
                      glyphs.add_range(
                          start, limit,
                          self.make_glyph_range_(location, start, limit))
                  elif self.next_token_ == "-":
                      start = glyph
                      self.expect_symbol_("-")
                      limit = self.expect_glyph_()
                      self.check_glyph_name_in_glyph_set(start, limit)
                      glyphs.add_range(
                          start, limit,
                          self.make_glyph_range_(location, start, limit))
                  else:
                      if '-' in glyph and not self.glyphNames_:
                          log.warning(str(FeatureLibError(
                              f"Ambiguous glyph name that looks like a range: {glyph!r}",
                              location
                          )))
                      self.check_glyph_name_in_glyph_set(glyph)
                      glyphs.append(glyph)
              elif self.next_token_type_ is Lexer.CID:
                  glyph = self.expect_glyph_()
                  if self.next_token_ == "-":
                      range_location = self.cur_token_location_
                      range_start = self.cur_token_
                      self.expect_symbol_("-")
                      range_end = self.expect_cid_()
                      self.check_glyph_name_in_glyph_set(
                          f"cid{range_start:05d}",
                          f"cid{range_end:05d}",
                      )
                      glyphs.add_cid_range(range_start, range_end,
                                           self.make_cid_range_(range_location,
                                                                range_start, range_end))
                  else:
                      glyph_name = f"cid{self.cur_token_:05d}"
                      self.check_glyph_name_in_glyph_set(glyph_name)
                      glyphs.append(glyph_name)
              elif self.next_token_type_ is Lexer.GLYPHCLASS:
                  self.advance_lexer_()
                  gc = self.glyphclasses_.resolve(self.cur_token_)
                  if gc is None:
                      raise FeatureLibError(
                          "Unknown glyph class @%s" % self.cur_token_,
                          self.cur_token_location_)
                  if isinstance(gc, self.ast.MarkClass):
                      gc = self.ast.MarkClassName(
                          gc, location=self.cur_token_location_)
                  else:
                      gc = self.ast.GlyphClassName(
                          gc, location=self.cur_token_location_)
                  glyphs.add_class(gc)
              else:
                  raise FeatureLibError(
                      "Expected glyph name, glyph range, "
                      f"or glyph class reference, found {self.next_token_!r}",
                      self.next_token_location_)
          self.expect_symbol_("]")
          return glyphs
  
      def parse_class_name_(self):
          # Parses named class - either a glyph class or mark class.
          name = self.expect_class_name_()
          gc = self.glyphclasses_.resolve(name)
          if gc is None:
              raise FeatureLibError(
                  "Unknown glyph class @%s" % name,
                  self.cur_token_location_)
          if isinstance(gc, self.ast.MarkClass):
              return self.ast.MarkClassName(
                  gc, location=self.cur_token_location_)
          else:
              return self.ast.GlyphClassName(
                  gc, location=self.cur_token_location_)
  
      def parse_glyph_pattern_(self, vertical):
          # Parses a glyph pattern, including lookups and context, e.g.::
          #
          #    a b
          #    a b c' d e
          #    a b c' lookup ChangeC d e
          prefix, glyphs, lookups, values, suffix = ([], [], [], [], [])
          hasMarks = False
          while self.next_token_ not in {"by", "from", ";", ","}:
              gc = self.parse_glyphclass_(accept_glyphname=True)
              marked = False
              if self.next_token_ == "'":
                  self.expect_symbol_("'")
                  hasMarks = marked = True
              if marked:
                  if suffix:
                      # makeotf also reports this as an error, while FontForge
                      # silently inserts ' in all the intervening glyphs.
                      # https://github.com/fonttools/fonttools/pull/1096
                      raise FeatureLibError(
                          "Unsupported contextual target sequence: at most "
                          "one run of marked (') glyph/class names allowed",
                          self.cur_token_location_)
                  glyphs.append(gc)
              elif glyphs:
                  suffix.append(gc)
              else:
                  prefix.append(gc)
  
              if self.is_next_value_():
                  values.append(self.parse_valuerecord_(vertical))
              else:
                  values.append(None)
  
              lookuplist = None
              while self.next_token_ == "lookup":
                  if lookuplist is None:
                      lookuplist = []
                  self.expect_keyword_("lookup")
                  if not marked:
                      raise FeatureLibError(
                          "Lookups can only follow marked glyphs",
                          self.cur_token_location_)
                  lookup_name = self.expect_name_()
                  lookup = self.lookups_.resolve(lookup_name)
                  if lookup is None:
                      raise FeatureLibError(
                          'Unknown lookup "%s"' % lookup_name,
                          self.cur_token_location_)
                  lookuplist.append(lookup)
              if marked:
                  lookups.append(lookuplist)
  
          if not glyphs and not suffix:  # eg., "sub f f i by"
              assert lookups == []
              return ([], prefix, [None] * len(prefix), values, [], hasMarks)
          else:
              assert not any(values[:len(prefix)]), values
              format1 = values[len(prefix):][:len(glyphs)]
              format2 = values[(len(prefix) + len(glyphs)):][:len(suffix)]
              values = format2 if format2 and isinstance(format2[0], self.ast.ValueRecord) else format1
              return (prefix, glyphs, lookups, values, suffix, hasMarks)
  
      def parse_chain_context_(self):
          location = self.cur_token_location_
          prefix, glyphs, lookups, values, suffix, hasMarks = \
              self.parse_glyph_pattern_(vertical=False)
          chainContext = [(prefix, glyphs, suffix)]
          hasLookups = any(lookups)
          while self.next_token_ == ",":
              self.expect_symbol_(",")
              prefix, glyphs, lookups, values, suffix, hasMarks = \
                  self.parse_glyph_pattern_(vertical=False)
              chainContext.append((prefix, glyphs, suffix))
              hasLookups = hasLookups or any(lookups)
          self.expect_symbol_(";")
          return chainContext, hasLookups
  
      def parse_ignore_(self):
          # Parses an ignore sub/pos rule.
          assert self.is_cur_keyword_("ignore")
          location = self.cur_token_location_
          self.advance_lexer_()
          if self.cur_token_ in ["substitute", "sub"]:
              chainContext, hasLookups = self.parse_chain_context_()
              if hasLookups:
                  raise FeatureLibError(
                      "No lookups can be specified for \"ignore sub\"",
                      location)
              return self.ast.IgnoreSubstStatement(chainContext,
                                                   location=location)
          if self.cur_token_ in ["position", "pos"]:
              chainContext, hasLookups = self.parse_chain_context_()
              if hasLookups:
                  raise FeatureLibError(
                      "No lookups can be specified for \"ignore pos\"",
                      location)
              return self.ast.IgnorePosStatement(chainContext,
                                                 location=location)
          raise FeatureLibError(
              "Expected \"substitute\" or \"position\"",
              self.cur_token_location_)
  
      def parse_include_(self):
          assert self.cur_token_ == "include"
          location = self.cur_token_location_
          filename = self.expect_filename_()
          # self.expect_symbol_(";")
          return ast.IncludeStatement(filename, location=location)
  
      def parse_language_(self):
          assert self.is_cur_keyword_("language")
          location = self.cur_token_location_
          language = self.expect_language_tag_()
          include_default, required = (True, False)
          if self.next_token_ in {"exclude_dflt", "include_dflt"}:
              include_default = (self.expect_name_() == "include_dflt")
          if self.next_token_ == "required":
              self.expect_keyword_("required")
              required = True
          self.expect_symbol_(";")
          return self.ast.LanguageStatement(language,
                                            include_default, required,
                                            location=location)
  
      def parse_ligatureCaretByIndex_(self):
          assert self.is_cur_keyword_("LigatureCaretByIndex")
          location = self.cur_token_location_
          glyphs = self.parse_glyphclass_(accept_glyphname=True)
          carets = [self.expect_number_()]
          while self.next_token_ != ";":
              carets.append(self.expect_number_())
          self.expect_symbol_(";")
          return self.ast.LigatureCaretByIndexStatement(glyphs, carets,
                                                        location=location)
  
      def parse_ligatureCaretByPos_(self):
          assert self.is_cur_keyword_("LigatureCaretByPos")
          location = self.cur_token_location_
          glyphs = self.parse_glyphclass_(accept_glyphname=True)
          carets = [self.expect_number_()]
          while self.next_token_ != ";":
              carets.append(self.expect_number_())
          self.expect_symbol_(";")
          return self.ast.LigatureCaretByPosStatement(glyphs, carets,
                                                      location=location)
  
      def parse_lookup_(self, vertical):
          # Parses a ``lookup`` - either a lookup block, or a lookup reference
          # inside a feature.
          assert self.is_cur_keyword_("lookup")
          location, name = self.cur_token_location_, self.expect_name_()
  
          if self.next_token_ == ";":
              lookup = self.lookups_.resolve(name)
              if lookup is None:
                  raise FeatureLibError("Unknown lookup \"%s\"" % name,
                                        self.cur_token_location_)
              self.expect_symbol_(";")
              return self.ast.LookupReferenceStatement(lookup,
                                                       location=location)
  
          use_extension = False
          if self.next_token_ == "useExtension":
              self.expect_keyword_("useExtension")
              use_extension = True
  
          block = self.ast.LookupBlock(name, use_extension, location=location)
          self.parse_block_(block, vertical)
          self.lookups_.define(name, block)
          return block
  
      def parse_lookupflag_(self):
          # Parses a ``lookupflag`` statement, either specified by number or
          # in words.
          assert self.is_cur_keyword_("lookupflag")
          location = self.cur_token_location_
  
          # format B: "lookupflag 6;"
          if self.next_token_type_ == Lexer.NUMBER:
              value = self.expect_number_()
              self.expect_symbol_(";")
              return self.ast.LookupFlagStatement(value, location=location)
  
          # format A: "lookupflag RightToLeft MarkAttachmentType @M;"
          value_seen = False
          value, markAttachment, markFilteringSet = 0, None, None
          flags = {
              "RightToLeft": 1, "IgnoreBaseGlyphs": 2,
              "IgnoreLigatures": 4, "IgnoreMarks": 8
          }
          seen = set()
          while self.next_token_ != ";":
              if self.next_token_ in seen:
                  raise FeatureLibError(
                      "%s can be specified only once" % self.next_token_,
                      self.next_token_location_)
              seen.add(self.next_token_)
              if self.next_token_ == "MarkAttachmentType":
                  self.expect_keyword_("MarkAttachmentType")
                  markAttachment = self.parse_class_name_()
              elif self.next_token_ == "UseMarkFilteringSet":
                  self.expect_keyword_("UseMarkFilteringSet")
                  markFilteringSet = self.parse_class_name_()
              elif self.next_token_ in flags:
                  value_seen = True
                  value = value | flags[self.expect_name_()]
              else:
                  raise FeatureLibError(
                      '"%s" is not a recognized lookupflag' % self.next_token_,
                      self.next_token_location_)
          self.expect_symbol_(";")
  
          if not any([value_seen, markAttachment, markFilteringSet]):
              raise FeatureLibError(
                  'lookupflag must have a value', self.next_token_location_)
  
          return self.ast.LookupFlagStatement(value,
                                              markAttachment=markAttachment,
                                              markFilteringSet=markFilteringSet,
                                              location=location)
  
      def parse_markClass_(self):
          assert self.is_cur_keyword_("markClass")
          location = self.cur_token_location_
          glyphs = self.parse_glyphclass_(accept_glyphname=True)
          anchor = self.parse_anchor_()
          name = self.expect_class_name_()
          self.expect_symbol_(";")
          markClass = self.doc_.markClasses.get(name)
          if markClass is None:
              markClass = self.ast.MarkClass(name)
              self.doc_.markClasses[name] = markClass
              self.glyphclasses_.define(name, markClass)
          mcdef = self.ast.MarkClassDefinition(markClass, anchor, glyphs,
                                               location=location)
          markClass.addDefinition(mcdef)
          return mcdef
  
      def parse_position_(self, enumerated, vertical):
          assert self.cur_token_ in {"position", "pos"}
          if self.next_token_ == "cursive":  # GPOS type 3
              return self.parse_position_cursive_(enumerated, vertical)
          elif self.next_token_ == "base":   # GPOS type 4
              return self.parse_position_base_(enumerated, vertical)
          elif self.next_token_ == "ligature":   # GPOS type 5
              return self.parse_position_ligature_(enumerated, vertical)
          elif self.next_token_ == "mark":   # GPOS type 6
              return self.parse_position_mark_(enumerated, vertical)
  
          location = self.cur_token_location_
          prefix, glyphs, lookups, values, suffix, hasMarks = \
              self.parse_glyph_pattern_(vertical)
          self.expect_symbol_(";")
  
          if any(lookups):
              # GPOS type 8: Chaining contextual positioning; explicit lookups
              if any(values):
                  raise FeatureLibError(
                      "If \"lookup\" is present, no values must be specified",
                      location)
              return self.ast.ChainContextPosStatement(
                  prefix, glyphs, suffix, lookups, location=location)
  
          # Pair positioning, format A: "pos V 10 A -10;"
          # Pair positioning, format B: "pos V A -20;"
          if not prefix and not suffix and len(glyphs) == 2 and not hasMarks:
              if values[0] is None:  # Format B: "pos V A -20;"
                  values.reverse()
              return self.ast.PairPosStatement(
                  glyphs[0], values[0], glyphs[1], values[1],
                  enumerated=enumerated,
                  location=location)
  
          if enumerated:
              raise FeatureLibError(
                  '"enumerate" is only allowed with pair positionings', location)
          return self.ast.SinglePosStatement(list(zip(glyphs, values)),
                                             prefix, suffix, forceChain=hasMarks,
                                             location=location)
  
      def parse_position_cursive_(self, enumerated, vertical):
          location = self.cur_token_location_
          self.expect_keyword_("cursive")
          if enumerated:
              raise FeatureLibError(
                  '"enumerate" is not allowed with '
                  'cursive attachment positioning',
                  location)
          glyphclass = self.parse_glyphclass_(accept_glyphname=True)
          entryAnchor = self.parse_anchor_()
          exitAnchor = self.parse_anchor_()
          self.expect_symbol_(";")
          return self.ast.CursivePosStatement(
              glyphclass, entryAnchor, exitAnchor, location=location)
  
      def parse_position_base_(self, enumerated, vertical):
          location = self.cur_token_location_
          self.expect_keyword_("base")
          if enumerated:
              raise FeatureLibError(
                  '"enumerate" is not allowed with '
                  'mark-to-base attachment positioning',
                  location)
          base = self.parse_glyphclass_(accept_glyphname=True)
          marks = self.parse_anchor_marks_()
          self.expect_symbol_(";")
          return self.ast.MarkBasePosStatement(base, marks, location=location)
  
      def parse_position_ligature_(self, enumerated, vertical):
          location = self.cur_token_location_
          self.expect_keyword_("ligature")
          if enumerated:
              raise FeatureLibError(
                  '"enumerate" is not allowed with '
                  'mark-to-ligature attachment positioning',
                  location)
          ligatures = self.parse_glyphclass_(accept_glyphname=True)
          marks = [self.parse_anchor_marks_()]
          while self.next_token_ == "ligComponent":
              self.expect_keyword_("ligComponent")
              marks.append(self.parse_anchor_marks_())
          self.expect_symbol_(";")
          return self.ast.MarkLigPosStatement(ligatures, marks, location=location)
  
      def parse_position_mark_(self, enumerated, vertical):
          location = self.cur_token_location_
          self.expect_keyword_("mark")
          if enumerated:
              raise FeatureLibError(
                  '"enumerate" is not allowed with '
                  'mark-to-mark attachment positioning',
                  location)
          baseMarks = self.parse_glyphclass_(accept_glyphname=True)
          marks = self.parse_anchor_marks_()
          self.expect_symbol_(";")
          return self.ast.MarkMarkPosStatement(baseMarks, marks,
                                               location=location)
  
      def parse_script_(self):
          assert self.is_cur_keyword_("script")
          location, script = self.cur_token_location_, self.expect_script_tag_()
          self.expect_symbol_(";")
          return self.ast.ScriptStatement(script, location=location)
  
      def parse_substitute_(self):
          assert self.cur_token_ in {"substitute", "sub", "reversesub", "rsub"}
          location = self.cur_token_location_
          reverse = self.cur_token_ in {"reversesub", "rsub"}
          old_prefix, old, lookups, values, old_suffix, hasMarks = \
              self.parse_glyph_pattern_(vertical=False)
          if any(values):
              raise FeatureLibError(
                  "Substitution statements cannot contain values", location)
          new = []
          if self.next_token_ == "by":
              keyword = self.expect_keyword_("by")
              while self.next_token_ != ";":
                  gc = self.parse_glyphclass_(accept_glyphname=True)
                  new.append(gc)
          elif self.next_token_ == "from":
              keyword = self.expect_keyword_("from")
              new = [self.parse_glyphclass_(accept_glyphname=False)]
          else:
              keyword = None
          self.expect_symbol_(";")
          if len(new) == 0 and not any(lookups):
              raise FeatureLibError(
                  'Expected "by", "from" or explicit lookup references',
                  self.cur_token_location_)
  
          # GSUB lookup type 3: Alternate substitution.
          # Format: "substitute a from [a.1 a.2 a.3];"
          if keyword == "from":
              if reverse:
                  raise FeatureLibError(
                      'Reverse chaining substitutions do not support "from"',
                      location)
              if len(old) != 1 or len(old[0].glyphSet()) != 1:
                  raise FeatureLibError(
                      'Expected a single glyph before "from"',
                      location)
              if len(new) != 1:
                  raise FeatureLibError(
                      'Expected a single glyphclass after "from"',
                      location)
              return self.ast.AlternateSubstStatement(
                  old_prefix, old[0], old_suffix, new[0], location=location)
  
          num_lookups = len([l for l in lookups if l is not None])
  
          # GSUB lookup type 1: Single substitution.
          # Format A: "substitute a by a.sc;"
          # Format B: "substitute [one.fitted one.oldstyle] by one;"
          # Format C: "substitute [a-d] by [A.sc-D.sc];"
          if (not reverse and len(old) == 1 and len(new) == 1 and
                  num_lookups == 0):
              glyphs = list(old[0].glyphSet())
              replacements = list(new[0].glyphSet())
              if len(replacements) == 1:
                  replacements = replacements * len(glyphs)
              if len(glyphs) != len(replacements):
                  raise FeatureLibError(
                      'Expected a glyph class with %d elements after "by", '
                      'but found a glyph class with %d elements' %
                      (len(glyphs), len(replacements)), location)
              return self.ast.SingleSubstStatement(
                  old, new,
                  old_prefix, old_suffix,
                  forceChain=hasMarks,
                  location=location
              )
  
          # GSUB lookup type 2: Multiple substitution.
          # Format: "substitute f_f_i by f f i;"
          if (not reverse and
                  len(old) == 1 and len(old[0].glyphSet()) == 1 and
                  len(new) > 1 and max([len(n.glyphSet()) for n in new]) == 1 and
                  num_lookups == 0):
              return self.ast.MultipleSubstStatement(
                  old_prefix, tuple(old[0].glyphSet())[0], old_suffix,
                  tuple([list(n.glyphSet())[0] for n in new]),
                  forceChain=hasMarks, location=location)
  
          # GSUB lookup type 4: Ligature substitution.
          # Format: "substitute f f i by f_f_i;"
          if (not reverse and
                  len(old) > 1 and len(new) == 1 and
                  len(new[0].glyphSet()) == 1 and
                  num_lookups == 0):
              return self.ast.LigatureSubstStatement(
                  old_prefix, old, old_suffix,
                  list(new[0].glyphSet())[0], forceChain=hasMarks,
                  location=location)
  
          # GSUB lookup type 8: Reverse chaining substitution.
          if reverse:
              if len(old) != 1:
                  raise FeatureLibError(
                      "In reverse chaining single substitutions, "
                      "only a single glyph or glyph class can be replaced",
                      location)
              if len(new) != 1:
                  raise FeatureLibError(
                      'In reverse chaining single substitutions, '
                      'the replacement (after "by") must be a single glyph '
                      'or glyph class', location)
              if num_lookups != 0:
                  raise FeatureLibError(
                      "Reverse chaining substitutions cannot call named lookups",
                      location)
              glyphs = sorted(list(old[0].glyphSet()))
              replacements = sorted(list(new[0].glyphSet()))
              if len(replacements) == 1:
                  replacements = replacements * len(glyphs)
              if len(glyphs) != len(replacements):
                  raise FeatureLibError(
                      'Expected a glyph class with %d elements after "by", '
                      'but found a glyph class with %d elements' %
                      (len(glyphs), len(replacements)), location)
              return self.ast.ReverseChainSingleSubstStatement(
                  old_prefix, old_suffix, old, new, location=location)
  
          if len(old) > 1 and len(new) > 1:
              raise FeatureLibError(
                  'Direct substitution of multiple glyphs by multiple glyphs '
                  'is not supported',
                  location)
  
          # If there are remaining glyphs to parse, this is an invalid GSUB statement
          if len(new) != 0:
              raise FeatureLibError(
                  'Invalid substitution statement',
                  location
              )
  
          # GSUB lookup type 6: Chaining contextual substitution.
          rule = self.ast.ChainContextSubstStatement(
              old_prefix, old, old_suffix, lookups, location=location)
          return rule
  
      def parse_subtable_(self):
          assert self.is_cur_keyword_("subtable")
          location = self.cur_token_location_
          self.expect_symbol_(";")
          return self.ast.SubtableStatement(location=location)
  
      def parse_size_parameters_(self):
          # Parses a ``parameters`` statement used in ``size`` features. See
          # `section 8.b <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#8.b>`_.
          assert self.is_cur_keyword_("parameters")
          location = self.cur_token_location_
          DesignSize = self.expect_decipoint_()
          SubfamilyID = self.expect_number_()
          RangeStart = 0
          RangeEnd = 0
          if self.next_token_type_ in (Lexer.NUMBER, Lexer.FLOAT) or \
                  SubfamilyID != 0:
              RangeStart = self.expect_decipoint_()
              RangeEnd = self.expect_decipoint_()
  
          self.expect_symbol_(";")
          return self.ast.SizeParameters(DesignSize, SubfamilyID,
                                         RangeStart, RangeEnd,
                                         location=location)
  
      def parse_size_menuname_(self):
          assert self.is_cur_keyword_("sizemenuname")
          location = self.cur_token_location_
          platformID, platEncID, langID, string = self.parse_name_()
          return self.ast.FeatureNameStatement("size", platformID,
                                               platEncID, langID, string,
                                               location=location)
  
      def parse_table_(self):
          assert self.is_cur_keyword_("table")
          location, name = self.cur_token_location_, self.expect_tag_()
          table = self.ast.TableBlock(name, location=location)
          self.expect_symbol_("{")
          handler = {
              "GDEF": self.parse_table_GDEF_,
              "head": self.parse_table_head_,
              "hhea": self.parse_table_hhea_,
              "vhea": self.parse_table_vhea_,
              "name": self.parse_table_name_,
              "BASE": self.parse_table_BASE_,
              "OS/2": self.parse_table_OS_2_,
          }.get(name)
          if handler:
              handler(table)
          else:
              raise FeatureLibError('"table %s" is not supported' % name.strip(),
                                    location)
          self.expect_symbol_("}")
          end_tag = self.expect_tag_()
          if end_tag != name:
              raise FeatureLibError('Expected "%s"' % name.strip(),
                                    self.cur_token_location_)
          self.expect_symbol_(";")
          return table
  
      def parse_table_GDEF_(self, table):
          statements = table.statements
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.is_cur_keyword_("Attach"):
                  statements.append(self.parse_attach_())
              elif self.is_cur_keyword_("GlyphClassDef"):
                  statements.append(self.parse_GlyphClassDef_())
              elif self.is_cur_keyword_("LigatureCaretByIndex"):
                  statements.append(self.parse_ligatureCaretByIndex_())
              elif self.is_cur_keyword_("LigatureCaretByPos"):
                  statements.append(self.parse_ligatureCaretByPos_())
              elif self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError(
                      "Expected Attach, LigatureCaretByIndex, "
                      "or LigatureCaretByPos",
                      self.cur_token_location_)
  
      def parse_table_head_(self, table):
          statements = table.statements
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.is_cur_keyword_("FontRevision"):
                  statements.append(self.parse_FontRevision_())
              elif self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError("Expected FontRevision",
                                        self.cur_token_location_)
  
      def parse_table_hhea_(self, table):
          statements = table.statements
          fields = ("CaretOffset", "Ascender", "Descender", "LineGap")
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.cur_token_type_ is Lexer.NAME and self.cur_token_ in fields:
                  key = self.cur_token_.lower()
                  value = self.expect_number_()
                  statements.append(
                      self.ast.HheaField(key, value,
                                         location=self.cur_token_location_))
                  if self.next_token_ != ";":
                      raise FeatureLibError("Incomplete statement", self.next_token_location_)
              elif self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError("Expected CaretOffset, Ascender, "
                                        "Descender or LineGap",
                                        self.cur_token_location_)
  
      def parse_table_vhea_(self, table):
          statements = table.statements
          fields = ("VertTypoAscender", "VertTypoDescender", "VertTypoLineGap")
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.cur_token_type_ is Lexer.NAME and self.cur_token_ in fields:
                  key = self.cur_token_.lower()
                  value = self.expect_number_()
                  statements.append(
                      self.ast.VheaField(key, value,
                                         location=self.cur_token_location_))
                  if self.next_token_ != ";":
                      raise FeatureLibError("Incomplete statement", self.next_token_location_)
              elif self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError("Expected VertTypoAscender, "
                                        "VertTypoDescender or VertTypoLineGap",
                                        self.cur_token_location_)
  
      def parse_table_name_(self, table):
          statements = table.statements
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.is_cur_keyword_("nameid"):
                  statement = self.parse_nameid_()
                  if statement:
                      statements.append(statement)
              elif self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError("Expected nameid",
                                        self.cur_token_location_)
  
      def parse_name_(self):
          """Parses a name record. See `section 9.e <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#9.e>`_."""
          platEncID = None
          langID = None
          if self.next_token_type_ in Lexer.NUMBERS:
              platformID = self.expect_any_number_()
              location = self.cur_token_location_
              if platformID not in (1, 3):
                  raise FeatureLibError("Expected platform id 1 or 3", location)
              if self.next_token_type_ in Lexer.NUMBERS:
                  platEncID = self.expect_any_number_()
                  langID = self.expect_any_number_()
          else:
              platformID = 3
              location = self.cur_token_location_
  
          if platformID == 1:                # Macintosh
              platEncID = platEncID or 0     # Roman
              langID = langID or 0           # English
          else:                              # 3, Windows
              platEncID = platEncID or 1     # Unicode
              langID = langID or 0x0409      # English
  
          string = self.expect_string_()
          self.expect_symbol_(";")
  
          encoding = getEncoding(platformID, platEncID, langID)
          if encoding is None:
              raise FeatureLibError("Unsupported encoding", location)
          unescaped = self.unescape_string_(string, encoding)
          return platformID, platEncID, langID, unescaped
  
      def parse_nameid_(self):
          assert self.cur_token_ == "nameid", self.cur_token_
          location, nameID = self.cur_token_location_, self.expect_any_number_()
          if nameID > 32767:
              raise FeatureLibError("Name id value cannot be greater than 32767",
                                    self.cur_token_location_)
          if 1 <= nameID <= 6:
              log.warning("Name id %d cannot be set from the feature file. "
                          "Ignoring record" % nameID)
              self.parse_name_()  # skip to the next record
              return None
  
          platformID, platEncID, langID, string = self.parse_name_()
          return self.ast.NameRecord(nameID, platformID, platEncID,
                                     langID, string, location=location)
  
      def unescape_string_(self, string, encoding):
          if encoding == "utf_16_be":
              s = re.sub(r"\\[0-9a-fA-F]{4}", self.unescape_unichr_, string)
          else:
              unescape = lambda m: self.unescape_byte_(m, encoding)
              s = re.sub(r"\\[0-9a-fA-F]{2}", unescape, string)
          # We now have a Unicode string, but it might contain surrogate pairs.
          # We convert surrogates to actual Unicode by round-tripping through
          # Python's UTF-16 codec in a special mode.
          utf16 = tobytes(s, "utf_16_be", "surrogatepass")
          return tounicode(utf16, "utf_16_be")
  
      @staticmethod
      def unescape_unichr_(match):
          n = match.group(0)[1:]
          return unichr(int(n, 16))
  
      @staticmethod
      def unescape_byte_(match, encoding):
          n = match.group(0)[1:]
          return bytechr(int(n, 16)).decode(encoding)
  
      def parse_table_BASE_(self, table):
          statements = table.statements
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.is_cur_keyword_("HorizAxis.BaseTagList"):
                  horiz_bases = self.parse_base_tag_list_()
              elif self.is_cur_keyword_("HorizAxis.BaseScriptList"):
                  horiz_scripts = self.parse_base_script_list_(len(horiz_bases))
                  statements.append(
                          self.ast.BaseAxis(horiz_bases,
                                            horiz_scripts, False,
                                            location=self.cur_token_location_))
              elif self.is_cur_keyword_("VertAxis.BaseTagList"):
                  vert_bases = self.parse_base_tag_list_()
              elif self.is_cur_keyword_("VertAxis.BaseScriptList"):
                  vert_scripts = self.parse_base_script_list_(len(vert_bases))
                  statements.append(
                          self.ast.BaseAxis(vert_bases,
                                            vert_scripts, True,
                                            location=self.cur_token_location_))
              elif self.cur_token_ == ";":
                  continue
  
      def parse_table_OS_2_(self, table):
          statements = table.statements
          numbers = ("FSType", "TypoAscender", "TypoDescender", "TypoLineGap",
                     "winAscent", "winDescent", "XHeight", "CapHeight",
                     "WeightClass", "WidthClass", "LowerOpSize", "UpperOpSize")
          ranges = ("UnicodeRange", "CodePageRange")
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.cur_token_type_ is Lexer.NAME:
                  key = self.cur_token_.lower()
                  value = None
                  if self.cur_token_ in numbers:
                      value = self.expect_number_()
                  elif self.is_cur_keyword_("Panose"):
                      value = []
                      for i in range(10):
                          value.append(self.expect_number_())
                  elif self.cur_token_ in ranges:
                      value = []
                      while self.next_token_ != ";":
                           value.append(self.expect_number_())
                  elif self.is_cur_keyword_("Vendor"):
                      value = self.expect_string_()
                  statements.append(
                      self.ast.OS2Field(key, value,
                                        location=self.cur_token_location_))
              elif self.cur_token_ == ";":
                  continue
  
      def parse_base_tag_list_(self):
          # Parses BASE table entries. (See `section 9.a <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#9.a>`_)
          assert self.cur_token_ in ("HorizAxis.BaseTagList",
                                     "VertAxis.BaseTagList"), self.cur_token_
          bases = []
          while self.next_token_ != ";":
              bases.append(self.expect_script_tag_())
          self.expect_symbol_(";")
          return bases
  
      def parse_base_script_list_(self, count):
          assert self.cur_token_ in ("HorizAxis.BaseScriptList",
                                     "VertAxis.BaseScriptList"), self.cur_token_
          scripts = [(self.parse_base_script_record_(count))]
          while self.next_token_ == ",":
              self.expect_symbol_(",")
              scripts.append(self.parse_base_script_record_(count))
          self.expect_symbol_(";")
          return scripts
  
      def parse_base_script_record_(self, count):
          script_tag = self.expect_script_tag_()
          base_tag = self.expect_script_tag_()
          coords = [self.expect_number_() for i in range(count)]
          return script_tag, base_tag, coords
  
      def parse_device_(self):
          result = None
          self.expect_symbol_("<")
          self.expect_keyword_("device")
          if self.next_token_ == "NULL":
              self.expect_keyword_("NULL")
          else:
              result = [(self.expect_number_(), self.expect_number_())]
              while self.next_token_ == ",":
                  self.expect_symbol_(",")
                  result.append((self.expect_number_(), self.expect_number_()))
              result = tuple(result)  # make it hashable
          self.expect_symbol_(">")
          return result
  
      def is_next_value_(self):
          return self.next_token_type_ is Lexer.NUMBER or self.next_token_ == "<"
  
      def parse_valuerecord_(self, vertical):
          if self.next_token_type_ is Lexer.NUMBER:
              number, location = self.expect_number_(), self.cur_token_location_
              if vertical:
                  val = self.ast.ValueRecord(yAdvance=number,
                                             vertical=vertical,
                                             location=location)
              else:
                  val = self.ast.ValueRecord(xAdvance=number,
                                             vertical=vertical,
                                             location=location)
              return val
          self.expect_symbol_("<")
          location = self.cur_token_location_
          if self.next_token_type_ is Lexer.NAME:
              name = self.expect_name_()
              if name == "NULL":
                  self.expect_symbol_(">")
                  return self.ast.ValueRecord()
              vrd = self.valuerecords_.resolve(name)
              if vrd is None:
                  raise FeatureLibError("Unknown valueRecordDef \"%s\"" % name,
                                        self.cur_token_location_)
              value = vrd.value
              xPlacement, yPlacement = (value.xPlacement, value.yPlacement)
              xAdvance, yAdvance = (value.xAdvance, value.yAdvance)
          else:
              xPlacement, yPlacement, xAdvance, yAdvance = (
                  self.expect_number_(), self.expect_number_(),
                  self.expect_number_(), self.expect_number_())
  
          if self.next_token_ == "<":
              xPlaDevice, yPlaDevice, xAdvDevice, yAdvDevice = (
                  self.parse_device_(), self.parse_device_(),
                  self.parse_device_(), self.parse_device_())
              allDeltas = sorted([
                  delta
                  for size, delta
                  in (xPlaDevice if xPlaDevice else ()) +
                  (yPlaDevice if yPlaDevice else ()) +
                  (xAdvDevice if xAdvDevice else ()) +
                  (yAdvDevice if yAdvDevice else ())])
              if allDeltas[0] < -128 or allDeltas[-1] > 127:
                  raise FeatureLibError(
                      "Device value out of valid range (-128..127)",
                      self.cur_token_location_)
          else:
              xPlaDevice, yPlaDevice, xAdvDevice, yAdvDevice = (
                  None, None, None, None)
  
          self.expect_symbol_(">")
          return self.ast.ValueRecord(
              xPlacement, yPlacement, xAdvance, yAdvance,
              xPlaDevice, yPlaDevice, xAdvDevice, yAdvDevice,
              vertical=vertical, location=location)
  
      def parse_valuerecord_definition_(self, vertical):
          # Parses a named value record definition. (See section `2.e.v <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#2.e.v>`_)
          assert self.is_cur_keyword_("valueRecordDef")
          location = self.cur_token_location_
          value = self.parse_valuerecord_(vertical)
          name = self.expect_name_()
          self.expect_symbol_(";")
          vrd = self.ast.ValueRecordDefinition(name, value, location=location)
          self.valuerecords_.define(name, vrd)
          return vrd
  
      def parse_languagesystem_(self):
          assert self.cur_token_ == "languagesystem"
          location = self.cur_token_location_
          script = self.expect_script_tag_()
          language = self.expect_language_tag_()
          self.expect_symbol_(";")
          return self.ast.LanguageSystemStatement(script, language,
                                                  location=location)
  
      def parse_feature_block_(self):
          assert self.cur_token_ == "feature"
          location = self.cur_token_location_
          tag = self.expect_tag_()
          vertical = (tag in {"vkrn", "vpal", "vhal", "valt"})
  
          stylisticset = None
          cv_feature = None
          size_feature = False
          if tag in self.SS_FEATURE_TAGS:
              stylisticset = tag
          elif tag in self.CV_FEATURE_TAGS:
              cv_feature = tag
          elif tag == "size":
              size_feature = True
  
          use_extension = False
          if self.next_token_ == "useExtension":
              self.expect_keyword_("useExtension")
              use_extension = True
  
          block = self.ast.FeatureBlock(tag, use_extension=use_extension,
                                        location=location)
          self.parse_block_(block, vertical, stylisticset, size_feature,
                            cv_feature)
          return block
  
      def parse_feature_reference_(self):
          assert self.cur_token_ == "feature", self.cur_token_
          location = self.cur_token_location_
          featureName = self.expect_tag_()
          self.expect_symbol_(";")
          return self.ast.FeatureReferenceStatement(featureName,
                                                    location=location)
  
      def parse_featureNames_(self, tag):
          """Parses a ``featureNames`` statement found in stylistic set features.
          See section `8.c <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#8.c>`_."""
          assert self.cur_token_ == "featureNames", self.cur_token_
          block = self.ast.NestedBlock(tag, self.cur_token_,
                                       location=self.cur_token_location_)
          self.expect_symbol_("{")
          for symtab in self.symbol_tables_:
              symtab.enter_scope()
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  block.statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.is_cur_keyword_("name"):
                  location = self.cur_token_location_
                  platformID, platEncID, langID, string = self.parse_name_()
                  block.statements.append(
                      self.ast.FeatureNameStatement(tag, platformID,
                                                    platEncID, langID, string,
                                                    location=location))
              elif self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError('Expected "name"',
                                        self.cur_token_location_)
          self.expect_symbol_("}")
          for symtab in self.symbol_tables_:
              symtab.exit_scope()
          self.expect_symbol_(";")
          return block
  
      def parse_cvParameters_(self, tag):
          # Parses a ``cvParameters`` block found in Character Variant features.
          # See section `8.d <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#8.d>`_.
          assert self.cur_token_ == "cvParameters", self.cur_token_
          block = self.ast.NestedBlock(tag, self.cur_token_,
                                       location=self.cur_token_location_)
          self.expect_symbol_("{")
          for symtab in self.symbol_tables_:
              symtab.enter_scope()
  
          statements = block.statements
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.is_cur_keyword_({"FeatUILabelNameID",
                                         "FeatUITooltipTextNameID",
                                         "SampleTextNameID",
                                         "ParamUILabelNameID"}):
                  statements.append(self.parse_cvNameIDs_(tag, self.cur_token_))
              elif self.is_cur_keyword_("Character"):
                  statements.append(self.parse_cvCharacter_(tag))
              elif self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError(
                      "Expected statement: got {} {}".format(
                          self.cur_token_type_, self.cur_token_),
                      self.cur_token_location_)
  
          self.expect_symbol_("}")
          for symtab in self.symbol_tables_:
              symtab.exit_scope()
          self.expect_symbol_(";")
          return block
  
      def parse_cvNameIDs_(self, tag, block_name):
          assert self.cur_token_ == block_name, self.cur_token_
          block = self.ast.NestedBlock(tag, block_name,
                                       location=self.cur_token_location_)
          self.expect_symbol_("{")
          for symtab in self.symbol_tables_:
              symtab.enter_scope()
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  block.statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.is_cur_keyword_("name"):
                  location = self.cur_token_location_
                  platformID, platEncID, langID, string = self.parse_name_()
                  block.statements.append(
                      self.ast.CVParametersNameStatement(
                          tag, platformID, platEncID, langID, string,
                          block_name, location=location))
              elif self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError('Expected "name"',
                                        self.cur_token_location_)
          self.expect_symbol_("}")
          for symtab in self.symbol_tables_:
              symtab.exit_scope()
          self.expect_symbol_(";")
          return block
  
      def parse_cvCharacter_(self, tag):
          assert self.cur_token_ == "Character", self.cur_token_
          location, character = self.cur_token_location_, self.expect_any_number_()
          self.expect_symbol_(";")
          if not (0xFFFFFF >= character >= 0):
              raise FeatureLibError("Character value must be between "
                                    "{:#x} and {:#x}".format(0, 0xFFFFFF),
                                    location)
          return self.ast.CharacterStatement(character, tag, location=location)
  
      def parse_FontRevision_(self):
          # Parses a ``FontRevision`` statement found in the head table. See
          # `section 9.c <https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#9.c>`_.
          assert self.cur_token_ == "FontRevision", self.cur_token_
          location, version = self.cur_token_location_, self.expect_float_()
          self.expect_symbol_(";")
          if version <= 0:
              raise FeatureLibError("Font revision numbers must be positive",
                                    location)
          return self.ast.FontRevisionStatement(version, location=location)
  
      def parse_block_(self, block, vertical, stylisticset=None,
                       size_feature=False, cv_feature=None):
          self.expect_symbol_("{")
          for symtab in self.symbol_tables_:
              symtab.enter_scope()
  
          statements = block.statements
          while self.next_token_ != "}" or self.cur_comments_:
              self.advance_lexer_(comments=True)
              if self.cur_token_type_ is Lexer.COMMENT:
                  statements.append(self.ast.Comment(
                      self.cur_token_, location=self.cur_token_location_))
              elif self.cur_token_type_ is Lexer.GLYPHCLASS:
                  statements.append(self.parse_glyphclass_definition_())
              elif self.is_cur_keyword_("anchorDef"):
                  statements.append(self.parse_anchordef_())
              elif self.is_cur_keyword_({"enum", "enumerate"}):
                  statements.append(self.parse_enumerate_(vertical=vertical))
              elif self.is_cur_keyword_("feature"):
                  statements.append(self.parse_feature_reference_())
              elif self.is_cur_keyword_("ignore"):
                  statements.append(self.parse_ignore_())
              elif self.is_cur_keyword_("language"):
                  statements.append(self.parse_language_())
              elif self.is_cur_keyword_("lookup"):
                  statements.append(self.parse_lookup_(vertical))
              elif self.is_cur_keyword_("lookupflag"):
                  statements.append(self.parse_lookupflag_())
              elif self.is_cur_keyword_("markClass"):
                  statements.append(self.parse_markClass_())
              elif self.is_cur_keyword_({"pos", "position"}):
                  statements.append(
                      self.parse_position_(enumerated=False, vertical=vertical))
              elif self.is_cur_keyword_("script"):
                  statements.append(self.parse_script_())
              elif (self.is_cur_keyword_({"sub", "substitute",
                                          "rsub", "reversesub"})):
                  statements.append(self.parse_substitute_())
              elif self.is_cur_keyword_("subtable"):
                  statements.append(self.parse_subtable_())
              elif self.is_cur_keyword_("valueRecordDef"):
                  statements.append(self.parse_valuerecord_definition_(vertical))
              elif stylisticset and self.is_cur_keyword_("featureNames"):
                  statements.append(self.parse_featureNames_(stylisticset))
              elif cv_feature and self.is_cur_keyword_("cvParameters"):
                  statements.append(self.parse_cvParameters_(cv_feature))
              elif size_feature and self.is_cur_keyword_("parameters"):
                  statements.append(self.parse_size_parameters_())
              elif size_feature and self.is_cur_keyword_("sizemenuname"):
                  statements.append(self.parse_size_menuname_())
              elif self.cur_token_type_ is Lexer.NAME and self.cur_token_ in self.extensions:
                  statements.append(self.extensions[self.cur_token_](self))
              elif self.cur_token_ == ";":
                  continue
              else:
                  raise FeatureLibError(
                      "Expected glyph class definition or statement: got {} {}".format(self.cur_token_type_, self.cur_token_),
                      self.cur_token_location_)
  
          self.expect_symbol_("}")
          for symtab in self.symbol_tables_:
              symtab.exit_scope()
  
          name = self.expect_name_()
          if name != block.name.strip():
              raise FeatureLibError("Expected \"%s\"" % block.name.strip(),
                                    self.cur_token_location_)
          self.expect_symbol_(";")
  
          # A multiple substitution may have a single destination, in which case
          # it will look just like a single substitution. So if there are both
          # multiple and single substitutions, upgrade all the single ones to
          # multiple substitutions.
  
          # Check if we have a mix of non-contextual singles and multiples.
          has_single = False
          has_multiple = False
          for s in statements:
              if isinstance(s, self.ast.SingleSubstStatement):
                  has_single = not any([s.prefix, s.suffix, s.forceChain])
              elif isinstance(s, self.ast.MultipleSubstStatement):
                  has_multiple = not any([s.prefix, s.suffix, s.forceChain])
  
          # Upgrade all single substitutions to multiple substitutions.
          if has_single and has_multiple:
              statements = []
              for s in block.statements:
                  if isinstance(s, self.ast.SingleSubstStatement):
                      glyphs = s.glyphs[0].glyphSet()
                      replacements = s.replacements[0].glyphSet()
                      if len(replacements) == 1:
                          replacements *= len(glyphs)
                      for i, glyph in enumerate(glyphs):
                          statements.append(
                              self.ast.MultipleSubstStatement(
                                  s.prefix, glyph, s.suffix, [replacements[i]],
                                  s.forceChain, location=s.location))
                  else:
                      statements.append(s)
              block.statements = statements
  
      def is_cur_keyword_(self, k):
          if self.cur_token_type_ is Lexer.NAME:
              if isinstance(k, type("")):  # basestring is gone in Python3
                  return self.cur_token_ == k
              else:
                  return self.cur_token_ in k
          return False
  
      def expect_class_name_(self):
          self.advance_lexer_()
          if self.cur_token_type_ is not Lexer.GLYPHCLASS:
              raise FeatureLibError("Expected @NAME", self.cur_token_location_)
          return self.cur_token_
  
      def expect_cid_(self):
          self.advance_lexer_()
          if self.cur_token_type_ is Lexer.CID:
              return self.cur_token_
          raise FeatureLibError("Expected a CID", self.cur_token_location_)
  
      def expect_filename_(self):
          self.advance_lexer_()
          if self.cur_token_type_ is not Lexer.FILENAME:
              raise FeatureLibError("Expected file name",
                                    self.cur_token_location_)
          return self.cur_token_
  
      def expect_glyph_(self):
          self.advance_lexer_()
          if self.cur_token_type_ is Lexer.NAME:
              self.cur_token_ = self.cur_token_.lstrip("\\")
              if len(self.cur_token_) > 63:
                  raise FeatureLibError(
                      "Glyph names must not be longer than 63 characters",
                      self.cur_token_location_)
              return self.cur_token_
          elif self.cur_token_type_ is Lexer.CID:
              return "cid%05d" % self.cur_token_
          raise FeatureLibError("Expected a glyph name or CID",
                                self.cur_token_location_)
  
      def check_glyph_name_in_glyph_set(self, *names):
          """Raises if glyph name (just `start`) or glyph names of a
          range (`start` and `end`) are not in the glyph set.
  
          If no glyph set is present, does nothing.
          """
          if self.glyphNames_:
              missing = [name for name in names if name not in self.glyphNames_]
              if missing:
                  raise FeatureLibError(
                      "The following glyph names are referenced but are missing from the "
                      f"glyph set: {', '.join(missing)}",
                      self.cur_token_location_
                  )
  
      def expect_markClass_reference_(self):
          name = self.expect_class_name_()
          mc = self.glyphclasses_.resolve(name)
          if mc is None:
              raise FeatureLibError("Unknown markClass @%s" % name,
                                    self.cur_token_location_)
          if not isinstance(mc, self.ast.MarkClass):
              raise FeatureLibError("@%s is not a markClass" % name,
                                    self.cur_token_location_)
          return mc
  
      def expect_tag_(self):
          self.advance_lexer_()
          if self.cur_token_type_ is not Lexer.NAME:
              raise FeatureLibError("Expected a tag", self.cur_token_location_)
          if len(self.cur_token_) > 4:
              raise FeatureLibError("Tags can not be longer than 4 characters",
                                    self.cur_token_location_)
          return (self.cur_token_ + "    ")[:4]
  
      def expect_script_tag_(self):
          tag = self.expect_tag_()
          if tag == "dflt":
              raise FeatureLibError(
                  '"dflt" is not a valid script tag; use "DFLT" instead',
                  self.cur_token_location_)
          return tag
  
      def expect_language_tag_(self):
          tag = self.expect_tag_()
          if tag == "DFLT":
              raise FeatureLibError(
                  '"DFLT" is not a valid language tag; use "dflt" instead',
                  self.cur_token_location_)
          return tag
  
      def expect_symbol_(self, symbol):
          self.advance_lexer_()
          if self.cur_token_type_ is Lexer.SYMBOL and self.cur_token_ == symbol:
              return symbol
          raise FeatureLibError("Expected '%s'" % symbol,
                                self.cur_token_location_)
  
      def expect_keyword_(self, keyword):
          self.advance_lexer_()
          if self.cur_token_type_ is Lexer.NAME and self.cur_token_ == keyword:
              return self.cur_token_
          raise FeatureLibError("Expected \"%s\"" % keyword,
                                self.cur_token_location_)
  
      def expect_name_(self):
          self.advance_lexer_()
          if self.cur_token_type_ is Lexer.NAME:
              return self.cur_token_
          raise FeatureLibError("Expected a name", self.cur_token_location_)
  
      def expect_number_(self):
          self.advance_lexer_()
          if self.cur_token_type_ is Lexer.NUMBER:
              return self.cur_token_
          raise FeatureLibError("Expected a number", self.cur_token_location_)
  
      def expect_any_number_(self):
          self.advance_lexer_()
          if self.cur_token_type_ in Lexer.NUMBERS:
              return self.cur_token_
          raise FeatureLibError("Expected a decimal, hexadecimal or octal number",
                                self.cur_token_location_)
  
      def expect_float_(self):
          self.advance_lexer_()
          if self.cur_token_type_ is Lexer.FLOAT:
              return self.cur_token_
          raise FeatureLibError("Expected a floating-point number",
                                self.cur_token_location_)
  
      def expect_decipoint_(self):
          if self.next_token_type_ == Lexer.FLOAT:
              return self.expect_float_()
          elif self.next_token_type_ is Lexer.NUMBER:
              return self.expect_number_() / 10
          else:
              raise FeatureLibError("Expected an integer or floating-point number",
                                    self.cur_token_location_)
  
      def expect_string_(self):
          self.advance_lexer_()
          if self.cur_token_type_ is Lexer.STRING:
              return self.cur_token_
          raise FeatureLibError("Expected a string", self.cur_token_location_)
  
      def advance_lexer_(self, comments=False):
          if comments and self.cur_comments_:
              self.cur_token_type_ = Lexer.COMMENT
              self.cur_token_, self.cur_token_location_ = self.cur_comments_.pop(0)
              return
          else:
              self.cur_token_type_, self.cur_token_, self.cur_token_location_ = (
                  self.next_token_type_, self.next_token_, self.next_token_location_)
          while True:
              try:
                  (self.next_token_type_, self.next_token_,
                   self.next_token_location_) = next(self.lexer_)
              except StopIteration:
                  self.next_token_type_, self.next_token_ = (None, None)
              if self.next_token_type_ != Lexer.COMMENT:
                  break
              self.cur_comments_.append((self.next_token_, self.next_token_location_))
  
      @staticmethod
      def reverse_string_(s):
          """'abc' --> 'cba'"""
          return ''.join(reversed(list(s)))
  
      def make_cid_range_(self, location, start, limit):
          """(location, 999, 1001) --> ["cid00999", "cid01000", "cid01001"]"""
          result = list()
          if start > limit:
              raise FeatureLibError(
                  "Bad range: start should be less than limit", location)
          for cid in range(start, limit + 1):
              result.append("cid%05d" % cid)
          return result
  
      def make_glyph_range_(self, location, start, limit):
          """(location, "a.sc", "d.sc") --> ["a.sc", "b.sc", "c.sc", "d.sc"]"""
          result = list()
          if len(start) != len(limit):
              raise FeatureLibError(
                  "Bad range: \"%s\" and \"%s\" should have the same length" %
                  (start, limit), location)
  
          rev = self.reverse_string_
          prefix = os.path.commonprefix([start, limit])
          suffix = rev(os.path.commonprefix([rev(start), rev(limit)]))
          if len(suffix) > 0:
              start_range = start[len(prefix):-len(suffix)]
              limit_range = limit[len(prefix):-len(suffix)]
          else:
              start_range = start[len(prefix):]
              limit_range = limit[len(prefix):]
  
          if start_range >= limit_range:
              raise FeatureLibError(
                  "Start of range must be smaller than its end",
                  location)
  
          uppercase = re.compile(r'^[A-Z]$')
          if uppercase.match(start_range) and uppercase.match(limit_range):
              for c in range(ord(start_range), ord(limit_range) + 1):
                  result.append("%s%c%s" % (prefix, c, suffix))
              return result
  
          lowercase = re.compile(r'^[a-z]$')
          if lowercase.match(start_range) and lowercase.match(limit_range):
              for c in range(ord(start_range), ord(limit_range) + 1):
                  result.append("%s%c%s" % (prefix, c, suffix))
              return result
  
          digits = re.compile(r'^[0-9]{1,3}$')
          if digits.match(start_range) and digits.match(limit_range):
              for i in range(int(start_range, 10), int(limit_range, 10) + 1):
                  number = ("000" + str(i))[-len(start_range):]
                  result.append("%s%s%s" % (prefix, number, suffix))
              return result
  
          raise FeatureLibError("Bad range: \"%s-%s\"" % (start, limit),
                                location)
  
  
  class SymbolTable(object):
      def __init__(self):
          self.scopes_ = [{}]
  
      def enter_scope(self):
          self.scopes_.append({})
  
      def exit_scope(self):
          self.scopes_.pop()
  
      def define(self, name, item):
          self.scopes_[-1][name] = item
  
      def resolve(self, name):
          for scope in reversed(self.scopes_):
              item = scope.get(name)
              if item:
                  return item
          return None
  