if let Some(variant) = get_variant(adt_def, qpath) {
let field_defs = &variant.fields;
return find_first_mismatch_in_struct(cx, field_pats, field_defs, substs_ref);
if let Some(variant) = get_variant(adt_def, qpath) {
let field_defs = &variant.fields;
return find_first_mismatch_in_struct(cx, field_pats, field_defs, substs_ref);