{"ast_node_type":"variable","tokens":[{"end":47,"kind":"keyword","start":0,"text":"let"}]}
    let field_tys = db.field_types(def.into());
fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
    let params = field_tys.iter().map(|(_, ty)| ty.skip_binders().clone());