Class Frame

mypy/binder.py:51–82

A Frame represents a specific point in the execution of a program. It carries information about the current types of expressions at that point, arising either from assignments to those expressions or the result of isinstance checks and other type narrowing operations. It also record

class Frame:
    """A Frame represents a specific point in the execution of a program.

    It carries information about the current types of expressions at
    that point, arising either from assignments to those expressions
    or the result of isinstance checks and other type narrowing
    operations. It also records whether it is possible to reach that
    point at all.

    We add a new frame wherenever there is a new scope or control flow
    branching.

    This information is not copied into a new Frame when it is pushed
    onto the stack, so a given Frame only has information about types
    that were assigned in that frame.

    Expressions are stored in dicts using 'literal hashes' as keys (type
    "Key"). These are hashable values derived from expression AST nodes
    (only those that can be narrowed). literal_hash(expr) is used to
    calculate the hashes. Note that this isn't directly related to literal
    types -- the concept predates literal types.
    """

    def __init__(self, id: int, conditional_frame: bool = False) -> None:
        self.id = id
        self.types: dict[Key, CurrentType] = {}
        self.unreachable = False
        self.conditional_frame = conditional_frame
        self.suppress_unreachable_warnings = False

    def __repr__(self) -> str:
        return f"Frame({self.id}, {self.types}, {self.unreachable}, {self.conditional_frame})"


Assigns = defaultdict[Expression, list[tuple[Type, Type | None]]]