syntax_data: {"ast_node_type":"variable","tokens":[{"end":21,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let mut builder =
context_before:     let infcx = tcx.infer_ctxt().build(TypingMode::non_body_analysis());
context_after:         Builder::new(thir, infcx, def, hir_id, span, 0, const_ty, const_ty_span, None);