syntax_data: {"ast_node_type":"other","tokens":[{"end":71,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // FIXME: Represent the above fact in the trait system somehow.
context_before:         // SAFETY: This is never called when `Self` is not `Ty<'tcx>`.
context_after:         unsafe { std::mem::transmute::<Ty<'tcx>, Ty<'_>>(Ty::new_error(tcx, guar)) }