syntax_data: {"ast_node_type":"other","tokens":[{"end":56,"kind":"keyword","start":0,"text":"///"}]}
source_snippet: ///   in scope on the function that defined the closure,
context_before: /// - 'l0...'li and T0...Tj are the generic parameters
context_after: /// - CK represents the *closure kind* (Fn vs FnMut vs FnOnce). This