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::Binder<'tcx, ty::FnSig<'tcx>>`.
context_after:         unsafe { std::mem::transmute::<ty::PolyFnSig<'tcx>, ty::Binder<'_, ty::FnSig<'_>>>(fn_sig) }