This makes it clearer when changes in test results
are due to changes in the standard library.

Read through as many aliases as possible before getting
the underlying type.

Use object like we do for named types.

…on extracting an alias

… cache

… 'comparable'

This means that there is a target for defs and refs to refer to after the original fields go away because their corresponding structs have also gone away on a database downgrade.

…exported methods defined in different packages

They are only used by private predicates. They can be made public in
future if needed.