syntax_data: {"ast_node_type":"other","tokens":[{"end":76,"kind":"keyword","start":0,"text":"///"}]}
source_snippet: /// whether the `a` type is the type that we should label as "expected" when
context_before: /// Encodes that `a` must be a subtype of `b`. The `a_is_expected` flag indicates
context_after: /// presenting user diagnostics.