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