syntax_data: {"ast_node_type":"other","tokens":[{"end":59,"kind":"keyword","start":0,"text":"//!"}]}
source_snippet: //! custom fold operations that are specific to the folder.
context_before: //! This means each fold is a mixture of (a) generic folding operations, and (b)
context_after: //! - The `TypeFoldable` impls handle most of the traversal, and call into