Class DefinedVisitor

mypyc/analysis/dataflow.py:302–345

Visitor for finding defined registers. Note that this only deals with registers and not temporaries, on the assumption that we never access temporaries when they might be undefined. If strict_errors is True, then we regard any use of LoadErrorValue as making a register undefine

class DefinedVisitor(BaseAnalysisVisitor[Value]):
    """Visitor for finding defined registers.

    Note that this only deals with registers and not temporaries, on
    the assumption that we never access temporaries when they might be
    undefined.

    If strict_errors is True, then we regard any use of LoadErrorValue
    as making a register undefined. Otherwise we only do if
    `undefines` is set on the error value.

    This lets us only consider the things we care about during
    uninitialized variable checking while capturing all possibly
    undefined things for refcounting.
    """

    def __init__(self, strict_errors: bool = False) -> None:
        self.strict_errors = strict_errors

    def visit_branch(self, op: Branch) -> GenAndKill[Value]:
        return _EMPTY

    def visit_return(self, op: Return) -> GenAndKill[Value]:
        return _EMPTY

    def visit_unreachable(self, op: Unreachable) -> GenAndKill[Value]:
        return _EMPTY

    def visit_register_op(self, op: RegisterOp) -> GenAndKill[Value]:
        return _EMPTY

    def visit_assign(self, op: Assign) -> GenAndKill[Value]:
        # Loading an error value may undefine the register.
        if isinstance(op.src, LoadErrorValue) and (op.src.undefines or self.strict_errors):
            return set(), {op.dest}
        else:
            return {op.dest}, set()

    def visit_assign_multi(self, op: AssignMulti) -> GenAndKill[Value]:
        # Array registers are special and we don't track the definedness of them.
        return _EMPTY

    def visit_set_mem(self, op: SetMem) -> GenAndKill[Value]:
        return _EMPTY


def analyze_maybe_defined_regs(