syntax_data: {"ast_node_type":"variable","tokens":[{"end":31,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let label_msg =
context_before:                 let note_msg = "matching on a reference type with a non-reference pattern changes the default binding mode";
context_after:                     format!("this matches on type `{}_`", def_br_mutbl.ref_prefix_str());