syntax_data: {"ast_node_type":"variable","tokens":[{"end":35,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let temp = cx.temp(
context_before:                 // FIXME(deref_patterns): dedup temporaries to avoid multiple `deref()` calls?
context_after:                     Ty::new_ref(cx.tcx, cx.tcx.lifetimes.re_erased, subpattern.ty, mutability),