syntax_data: {"ast_node_type":"variable","tokens":[{"end":75,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let explicit_params = cx.explicit_params(owner_id, fn_decl, &body);
context_before:         let closure_env_param = cx.closure_env_param(owner_def, owner_id);
context_after:         cx.thir.params = closure_env_param.into_iter().chain(explicit_params).collect();