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// Copyright 2022 The Fuchsia Authors
//
// Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
// This file may not be copied, modified, or distributed except according to
// those terms.
include!("../../zerocopy-derive/tests/include.rs");
extern crate zerocopy;
use util::NotZerocopy;
use zerocopy::{Immutable, IntoBytes};
fn main() {
// This is adapted from #1296, which includes the following text:
//
// The compiler errors when a type is missing Immutable are somewhat
// misleading, although I'm not sure there's much zerocopy can do about
// this. An example where the compiler recommends adding a reference
// rather than implementing Immutable (some were even more confusing than
// this):
//
// error[E0277]: the trait bound `virtio::wl::CtrlVfdNewDmabuf: zerocopy::Immutable` is not satisfied
// --> devices/src/virtio/wl.rs:317:20
// |
// 317 | .write_obj(ctrl_vfd_new_dmabuf)
// | --------- ^^^^^^^^^^^^^^^^^^^ the trait `zerocopy::Immutable` is not implemented for `virtio::wl::CtrlVfdNewDmabuf`
// | |
// | required by a bound introduced by this call
// |
// note: required by a bound in `virtio::descriptor_utils::Writer::write_obj`
// --> devices/src/virtio/descriptor_utils.rs:536:25
// |
// 536 | pub fn write_obj<T: Immutable + IntoBytes>(&mut self, val: T) -> io::Result<()> {
// | ^^^^^^^^^ required by this bound in `Writer::write_obj`
// help: consider borrowing here
// |
// 317 | .write_obj(&ctrl_vfd_new_dmabuf)
// | +
// 317 | .write_obj(&mut ctrl_vfd_new_dmabuf)
// | ++++
//
// Taking the compiler's suggestion results in a different error with a
// recommendation to remove the reference (back to the original code).
//
// As of this writing, the described problem is still happening thanks to
// https://github.com/rust-lang/rust/issues/130563. We include this test so
// that we can capture the current behavior, but we will update it once that
// Rust issue is fixed.
Foo.write_obj(NotZerocopy(()));
}
struct Foo;
impl Foo {
fn write_obj<T: Immutable + IntoBytes>(&mut self, _val: T) {}
}
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