syntax_data: {"ast_node_type":"other","tokens":[{"end":82,"kind":"keyword","start":0,"text":"//!"}]}
source_snippet: //! - A `TypeFolder`/`FallibleTypeFolder` may also call into a `TypeSuperFoldable`
context_before: //!   other types of interest.
context_after: //!   impl, because each folder might provide custom handling only for some types