fn trailer_expr(
begin: ParseBuffer<'_>,
attrs: Vec<Attribute>,
input: ParseStream<'_>,
allow_struct: AllowStruct,
) -> Result<Expr>
fn trailer_expr(
begin: ParseBuffer<'_>,
attrs: Vec<Attribute>,
input: ParseStream<'_>,
allow_struct: AllowStruct,
) -> Result<Expr>