python-typing-reference

Assignability rules are defined in the typing specification's concepts and class compatibility sections. Consult the vendored specification files rather than relying on a single checker's behavior, since checkers may implement extensions or deviate from the normative rules.

Variance for generics is defined in the generics and class compatibility sections of the typing specification. Type parameters are invariant by default, and covariant or contravariant behavior requires explicit declaration, with protocols following structural variance rules.

Checkers can implement extensions, differ in inference strategies, or deviate from the specification. Comparing their behavior against the normative typing specification identifies which checker follows the standard and which applies an implementation-specific rule.

Yes, the specification includes dedicated sections for TypedDict, protocols, dataclasses, namedtuples, and tuples. Cross-category questions, such as generic protocols, require reading multiple files like generics.rst and protocol.rst together.

Consult the specification for normative questions about what the type system requires, such as assignability, narrowing, or overload resolution semantics. Checker documentation is appropriate for tool-specific configuration, flags, and implementation extensions.