Function class_member_sigs 

pub fn class_member_sigs(
    ta: &TypedAst,
    dependencies: &[&PackageDeclaration],
) -> Result<Vec<ClosureSig>, CompilerFailure>

Closure signatures for each local class’s members — its own, and the ones it inherits from a dependency class. An instance flowing through an interface-typed receiver carries every method in its chain as a $closure_<sig> value in the object-fields payload.