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a0640c8524
This change makes changes to allow Servo to compile with the 1.78 version of Rust: - Dead code is removd (Rust seems to have gotten better at detecting it). - The `FlowRef` `DerefMut` is updated according to @SimonSapin's advice [^1]. - The `imports.rs` now explicitly silences warnings about unused imports. [^1]: https://github.com/servo/servo/issues/6503#issuecomment-2066088179 <!-- Please describe your changes on the following line: --> --- <!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: --> - [x] `./mach build -d` does not report any errors - [x] `./mach test-tidy` does not report any errors - [x] These changes do not require tests because they should not change behavior. <!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.--> <!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
66 lines
2.3 KiB
Rust
66 lines
2.3 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
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//! Reference-counted pointers to flows.
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//!
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//! Eventually, with dynamically sized types in Rust, much of this code will
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//! be superfluous. This design is largely duplicating logic of `Arc<T>` and
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//! `Weak<T>`; please see comments there for details.
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use std::ops::Deref;
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use std::sync::{Arc, Weak};
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use crate::flow::Flow;
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#[derive(Clone, Debug)]
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pub struct FlowRef(Arc<dyn Flow>);
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impl Deref for FlowRef {
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type Target = dyn Flow;
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fn deref(&self) -> &dyn Flow {
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self.0.deref()
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}
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}
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impl FlowRef {
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/// `FlowRef`s can only be made available to the traversal code.
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/// See <https://github.com/servo/servo/issues/14014> for more details.
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pub fn new(mut r: Arc<dyn Flow>) -> Self {
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// This assertion checks that this `FlowRef` does not alias normal `Arc`s.
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// If that happens, we're in trouble.
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assert!(Arc::get_mut(&mut r).is_some());
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FlowRef(r)
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}
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pub fn get_mut(this: &mut FlowRef) -> Option<&mut dyn Flow> {
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Arc::get_mut(&mut this.0)
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}
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pub fn downgrade(this: &FlowRef) -> WeakFlowRef {
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WeakFlowRef(Arc::downgrade(&this.0))
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}
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pub fn into_arc(mut this: FlowRef) -> Arc<dyn Flow> {
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// This assertion checks that this `FlowRef` does not alias normal `Arc`s.
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// If that happens, we're in trouble.
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assert!(FlowRef::get_mut(&mut this).is_some());
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this.0
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}
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/// WARNING: This should only be used when there is no aliasing:
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/// when the traversal ensures that no other threads accesses the same flow at the same time.
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/// See <https://github.com/servo/servo/issues/6503>.
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/// Use Arc::get_mut instead when possible (e.g. on an Arc that was just created).
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#[allow(unsafe_code)]
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#[allow(clippy::should_implement_trait)]
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pub fn deref_mut(this: &mut FlowRef) -> &mut dyn Flow {
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let ptr: *const dyn Flow = Arc::as_ptr(&this.0);
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unsafe { &mut *(ptr as *mut dyn Flow) }
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}
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}
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#[derive(Clone, Debug)]
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pub struct WeakFlowRef(Weak<dyn Flow>);
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impl WeakFlowRef {
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pub fn upgrade(&self) -> Option<FlowRef> {
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self.0.upgrade().map(FlowRef)
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}
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}
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