mypy.nodes.PlaceholderNode

Temporary symbol node that will later become a real SymbolNode. These are only present during semantic analysis when using the new semantic analyzer. These are created if some essential dependencies of a definition are not yet complete. A typical use is for names imported from a module which is still incomplete (within an import cycle): from m import f # Initially may create PlaceholderNode This is particularly important if the imported shadows a name from an enclosing scope or builtins: from m import int # Placeholder avoids mixups with builtins.int Another case where this is useful is when there is another definition or assignment: from m import f def f() -> None: ... In the above example, the presence of PlaceholderNode allows us to handle the second definition as a redefinition. They are also used to create PlaceholderType instances for types that refer to incomplete types. Example: class C(Sequence[C]): ... We create a PlaceholderNode (with becomes_typeinfo=True) for C so that the type C in Sequence[C] can be bound. Attributes: fullname: Full name of the PlaceholderNode. node: AST node that contains the definition that caused this to be created. This is useful for tracking order of incomplete definitions and for debugging. becomes_typeinfo: If True, this refers something that could later become a TypeInfo. It can't be used with type variables, in particular, as this would cause issues with class type variable detection. The long-term purpose of placeholder nodes/types is to evolve into something that can support general recursive types.