type ParseError* = enum
  #TODO write a description for all error codes
  ABRUPT_CLOSING_OF_EMPTY_COMMENT
  ABRUPT_DOCTYPE_PUBLIC_IDENTIFIER
  ABRUPT_DOCTYPE_SYSTEM_IDENTIFIER
  ABSENCE_OF_DIGITS_IN_NUMERIC_CHARACTER_REFERENCE
  CDATA_IN_HTML_CONTENT
  CHARACTER_REFERENCE_OUTSIDE_UNICODE_RANGE
  CONTROL_CHARACTER_IN_INPUT_STREAM
  CONTROL_CHARACTER_REFERENCE
  END_TAG_WITH_ATTRIBUTES
  DUPLICATE_ATTRIBUTE
  END_TAG_WITH_TRAILING_SOLIDUS
  EOF_BEFORE_TAG_NAME
  EOF_IN_CDATA
  EOF_IN_COMMENT
  EOF_IN_DOCTYPE
  EOF_IN_SCRIPT_HTML_COMMENT_LIKE_TEXT
  EOF_IN_TAG
  INCORRECTLY_CLOSED_COMMENT
  INCORRECTLY_OPENED_COMMENT
  INVALID_CHARACTER_SEQUENCE_AFTER_DOCTYPE_NAME
  INVALID_FIRST_CHARACTER_OF_TAG_NAME
  MISSING_ATTRIBUTE_VALUE
  MISSING_DOCTYPE_NAME
  MISSING_DOCTYPE_PUBLIC_IDENTIFIER
  MISSING_DOCTYPE_SYSTEM_IDENTIFIER
  MISSING_END_TAG_NAME
  MISSING_QUOTE_BEFORE_DOCTYPE_PUBLIC_IDENTIFIER
  MISSING_QUOTE_BEFORE_DOCTYPE_SYSTEM_IDENTIFIER
  MISSING_SEMICOLON_AFTER_CHARACTER_REFERENCE
  MISSING_WHITESPACE_AFTER_DOCTYPE_PUBLIC_KEYWORD
  MISSING_WHITESPACE_AFTER_DOCTYPE_SYSTEM_KEYWORD
  MISSING_WHITESPACE_BEFORE_DOCTYPE_NAME
  MISSING_WHITESPACE_BETWEEN_ATTRIBUTES
  MISSING_WHITESPACE_BETWEEN_DOCTYPE_PUBLIC_AND_SYSTEM_IDENTIFIERS
  NESTED_COMMENT
  NONCHARACTER_CHARACTER_REFERENCE
  NONCHARACTER_IN_INPUT_STREAM
  NON_VOID_HTML_ELEMENT_START_TAG_WITH_TRAILING_SOLIDUS
  NULL_CHARACTER_REFERENCE
  SURROGATE_CHARACTER_REFERENCE
  SURROGATE_IN_INPUT_STREAM
  UNEXPECTED_CHARACTER_AFTER_DOCTYPE_SYSTEM_IDENTIFIER
  UNEXPECTED_CHARACTER_IN_ATTRIBUTE_NAME
  UNEXPECTED_CHARACTER_IN_UNQUOTED_ATTRIBUTE_VALUE
  UNEXPECTED_EQUALS_SIGN_BEFORE_ATTRIBUTE_NAME
  UNEXPECTED_NULL_CHARACTER
  UNEXPECTED_QUESTION_MARK_INSTEAD_OF_TAG_NAME
  UNEXPECTED_SOLIDUS_IN_TAG
  UNKNOWN_NAMED_CHARACTER_REFERENCE
  LAST_SPECIFIED_ERROR # never returned
  # From here on, error code names have not been specified by the standard.
  MISMATCHED_TAGS = "Mismatched start and end tags"
  INVALID_DOCTYPE = "Unrecognized document type"
  UNEXPECTED_DOCTYPE = "Unexpected document type"
  UNEXPECTED_INITIAL_TOKEN = "Unexpected token in initial state"
  UNEXPECTED_START_TAG = "Unexpected start tag"
  UNEXPECTED_END_TAG = "Unexpected end tag"
  ELEMENT_NOT_IN_OPEN_ELEMENTS = "Element has not been added to open elements"
  ELEMENT_NOT_IN_SCOPE = "Element not in appropriate scope"
  ELEMENT_NOT_CURRENT_NODE = "Element is not current node"
  #TODO merge with UNEXPECTED_NULL_CHARACTER?
  UNEXPECTED_NULL = "Unexpected null character"
  NESTED_TAGS = "Non-nestable nested tags"
  UNEXPECTED_SPECIAL_ELEMENT = "Unexpected special element on open elements"
  UNEXPECTED_EOF = "Unexpected end of file"
  INVALID_TEXT_PARENT = "Invalid parent element for text node"
  NON_SPACE_TABLE_TEXT = "Non-space table text"
  UNEXPECTED_AFTER_BODY_TOKEN = "Unexpected token after body"