Stop making any assumption about the projections applied to the upvars in the ByMoveBody pass
#123658
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Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt |
compiler-errors
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Apr 8, 2024
| @@ -302,20 +302,18 @@ impl<'tcx> MutVisitor<'tcx> for MakeByMoveBody<'tcx> { | |||
| projection | |||
| }; | |||
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| // The only thing that should be left is a deref, if the parent captured | |||
| // an upvar by-ref. | |||
| std::assert_matches::assert_matches!(final_deref, [] | [mir::ProjectionElem::Deref]); | |||
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This assertion only makes sense when we assume that captures are going to be as precise as they can be. This is not true when we truncate captures when they don't give us anything (truncate_capture_for_optimization), and also I'm pretty sure that edition 2018 doesn't even work like that at all.
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ByMoveBody passByMoveBody pass
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@bors r+ rollup |
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Apr 9, 2024
…llaumeGomez Rollup of 8 pull requests Successful merges: - rust-lang#123254 (Do not allocate for ZST ThinBox (attempt 2 using const_allocate)) - rust-lang#123626 (Add MC/DC support to coverage test tools) - rust-lang#123638 (rustdoc: synthetic auto: filter out clauses from the implementor's ParamEnv) - rust-lang#123653 (Split `non_local_definitions` lint tests in separate test files) - rust-lang#123658 (Stop making any assumption about the projections applied to the upvars in the `ByMoveBody` pass) - rust-lang#123662 (Don't rely on upvars being assigned just because coroutine-closure kind is assigned) - rust-lang#123665 (Fix typo in `Future::poll()` docs) - rust-lang#123672 (compiletest: unset `RUSTC_LOG_COLOR`) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#123658 - compiler-errors:stop-assuming, r=oli-obk Stop making any assumption about the projections applied to the upvars in the `ByMoveBody` pass So it turns out that because of subtle optimizations like [`truncate_capture_for_optimization`](https://github.com/rust-lang/rust/blob/ab5bda1aa70f707014e2e691e43bc37a8819252a/compiler/rustc_hir_typeck/src/upvar.rs#L2351), we simply cannot make any assumptions about the shape of the projections applied to the upvar locals in a coroutine body. So stop doing that -- the code is resilient to such projections, so the assertion really existed only to "protect against the unknown". r? oli-obk Fixes rust-lang#123650
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So it turns out that because of subtle optimizations like
truncate_capture_for_optimization, we simply cannot make any assumptions about the shape of the projections applied to the upvar locals in a coroutine body.So stop doing that -- the code is resilient to such projections, so the assertion really existed only to "protect against the unknown".
r? oli-obk
Fixes #123650