syntax_data: {"ast_node_type":"other","tokens":[{"end":94,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 // Extract `TailField<T>` and `TailField<U>` from `Struct<T>` and `Struct<U>`,
context_after:                 // normalizing in the process, since `type_of` returns something directly from