syntax_data: {"ast_node_type":"other","tokens":[{"end":51,"kind":"keyword","start":0,"text":"ty::ClosureKind::FnMut"}]}
source_snippet:                         ty::ClosureKind::FnMut => {
context_before:                         }
context_after:                             Ty::new_mut_ref(tcx, tcx.lifetimes.re_erased, closure_ty)