mypy.types.PlaceholderType

Temporary, yet-unknown type during semantic analysis. This is needed when there's a reference to a type before the real symbol table entry of the target type is available (specifically, we use a temporary PlaceholderNode symbol node). Consider this example: class str(Sequence[str]): ... We use a PlaceholderType for the 'str' in 'Sequence[str]' since we can't create a TypeInfo for 'str' until all base classes have been resolved. We'll soon perform another analysis iteration which replaces the base class with a complete type without any placeholders. After semantic analysis, no placeholder types must exist.