Method customize_grammar_rules

uncompyle6/parsers/parse2.py:238–679

The base grammar we start out for a Python version even with the subclassing is, well, is pretty base. And we want it that way: lean and mean so that parsing will go faster. Here, we add additional grammar rules based on specific instructions that are in the instruc

(self, tokens, customize)

        """

    def customize_grammar_rules(self, tokens, customize):
        """The base grammar we start out for a Python version even with the
        subclassing is, well, is pretty base.  And we want it that way: lean and
        mean so that parsing will go faster.

        Here, we add additional grammar rules based on specific instructions
        that are in the instruction/token stream. In classes that
        inherit from from here and other versions, grammar rules may
        also be removed.

        For example if we see a pretty rare JUMP_IF_NOT_DEBUG
        instruction we'll add the grammar for that.

        More importantly, here we add grammar rules for instructions
        that may access a variable number of stack items. CALL_FUNCTION,
        BUILD_LIST and so on are like this.

        Without custom rules, there can be an super-exponential number of
        derivations. See the deparsing paper for an elaboration of
        this.
        """

        if "PyPy" in customize:
            # PyPy-specific customizations
            self.addRule(
                """
                        stmt ::= assign3_pypy
                        stmt ::= assign2_pypy
                        assign3_pypy ::= expr expr expr store store store
                        assign2_pypy ::= expr expr store store
                        list_comp    ::= expr  BUILD_LIST_FROM_ARG for_iter store list_iter
                                         JUMP_BACK
                        """,
                nop_func,
            )

        # For a rough break out on the first word. This may
        # include instructions that don't need customization,
        # but we'll do a finer check after the rough breakout.
        customize_instruction_basenames = frozenset(
            (
                "BUILD",
                "CALL",
                "CONTINUE",
                "DELETE",
                "DUP",
                "EXEC",
                "GET",
                "JUMP",
                "LOAD",
                "LOOKUP",
                "MAKE",
                "SETUP",
                "RAISE",
                "UNPACK",
            )
        )