syntax_data: {"ast_node_type":"variable","tokens":[{"end":71,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// let b: Canonical<I, (T, Ty<I>)> = a.unchecked_map(|v| (v, ty));
context_before:     /// let ty: Ty<I> = ...;
context_after:     /// ```