syntax_data: {"ast_node_type":"variable","tokens":[{"end":95,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let valtree = match self.tcx.const_eval_resolve_for_typeck(typing_env, uv, self.span) {
context_before:         // evaluate the const.
context_after:             Ok(Ok(c)) => c,