mypy.server.astdiff.SnapshotTypeVisitor

Creates a read-only, self-contained snapshot of a type object. Properties of a snapshot: - Contains (nested) tuples and other immutable primitive objects only. - References to AST nodes are replaced with full names of targets. - Has no references to mutable or non-primitive objects. - Two snapshots represent the same object if and only if they are equal. - Results must be sortable. It's important that tuples have consistent types and can't arbitrarily mix str and None values, for example, since they can't be compared.