Class ASDLParser

Parser/asdl.py:267–399

Parser for ASDL files. Create, then call the parse method on a buffer containing ASDL. This is a simple recursive descent parser that uses tokenize_asdl for the lexing.

                yield Token(op_kind, c, lineno)

class ASDLParser:
    """Parser for ASDL files.

    Create, then call the parse method on a buffer containing ASDL.
    This is a simple recursive descent parser that uses tokenize_asdl for the
    lexing.
    """
    def __init__(self):
        self._tokenizer = None
        self.cur_token = None

    def parse(self, buf):
        """Parse the ASDL in the buffer and return an AST with a Module root.
        """
        self._tokenizer = tokenize_asdl(buf)
        self._advance()
        return self._parse_module()

    def _parse_module(self):
        if self._at_keyword('module'):
            self._advance()
        else:
            raise ASDLSyntaxError(
                'Expected "module" (found {})'.format(self.cur_token.value),
                self.cur_token.lineno)
        name = self._match(self._id_kinds)
        self._match(TokenKind.LBrace)
        defs = self._parse_definitions()
        self._match(TokenKind.RBrace)
        return Module(name, defs)

    def _parse_definitions(self):
        defs = []
        while self.cur_token.kind == TokenKind.TypeId:
            typename = self._advance()
            self._match(TokenKind.Equals)
            type = self._parse_type()
            defs.append(Type(typename, type))
        return defs

    def _parse_type(self):
        if self.cur_token.kind == TokenKind.LParen:
            # If we see a (, it's a product
            return self._parse_product()
        else:
            # Otherwise it's a sum. Look for ConstructorId
            sumlist = [Constructor(self._match(TokenKind.ConstructorId),
                                   self._parse_optional_fields())]
            while self.cur_token.kind  == TokenKind.Pipe:
                # More constructors
                self._advance()
                sumlist.append(Constructor(
                                self._match(TokenKind.ConstructorId),
                                self._parse_optional_fields()))
            return Sum(sumlist, self._parse_optional_attributes())

    def _parse_product(self):
        return Product(self._parse_fields(), self._parse_optional_attributes())