Class TypeChecker

mypy/checker.py:383–8450

Mypy type checker. Type check mypy source files that have been semantically analyzed. You must create a separate instance for each source file.

class TypeChecker(NodeVisitor[None], TypeCheckerSharedApi, SplittingVisitor):
    """Mypy type checker.

    Type check mypy source files that have been semantically analyzed.

    You must create a separate instance for each source file.
    """

    # Are we type checking a stub?
    is_stub = False
    # Error message reporter
    errors: Errors
    # Utility for generating messages
    msg: MessageBuilder
    # Types of type checked nodes. The first item is the "master" type
    # map that will store the final, exported types. Additional items
    # are temporary type maps used during type inference, and these
    # will be eventually popped and either discarded or merged into
    # the master type map.
    #
    # Avoid accessing this directly, but prefer the lookup_type(),
    # has_type() etc. helpers instead.
    _type_maps: list[dict[Expression, Type]]

    # Helper for managing conditional types
    binder: ConditionalTypeBinder
    # Helper for type checking expressions
    _expr_checker: mypy.checkexpr.ExpressionChecker

    pattern_checker: PatternChecker

    tscope: Scope
    scope: CheckerScope
    # Stack of function return types
    return_types: list[Type]
    # Flags; true for dynamically typed functions
    dynamic_funcs: list[bool]
    # Stack of collections of variables with partial types
    partial_types: list[PartialTypeScope]
    # Vars for which partial type errors are already reported
    # (to avoid logically duplicate errors with different error context).
    partial_reported: set[Var]
    # Short names of Var nodes whose previous inferred type has been widened via assignment.
    # NOTE: The names might not be unique, they are only for debugging purposes.
    widened_vars: list[str]
    # Global variables widened inside a function body, to be propagated to
    # the module-level binder after the function is type checked (with --allow-redefinition-new).
    _globals_widened_in_func: list[tuple[NameExpr, Type]]
    globals: SymbolTable
    modules: dict[str, MypyFile]
    # Nodes that couldn't be checked because some types weren't available. We'll run
    # another pass and try these again.
    deferred_nodes: list[DeferredNode]
    # Type checking pass number (0 = first pass)
    pass_num = 0
    # Last pass number to take
    last_pass = DEFAULT_LAST_PASS
    # Have we deferred the current function? If yes, don't infer additional