syntax_data: {"ast_node_type":"import","tokens":[{"end":71,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// region `'a` is in a universe U2 that extends U1, because we can
context_before:     /// of `bar`, we cannot name `T`. Then, within the type of `y`, the
context_after:     /// name it inside the fn type but not outside.