Generate safe stable code for derives on empty enums #113770
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Generate `match *self {}` instead of `unsafe { core::intrinsics::unreachable() }`.
This is:
1. safe
2. stable
for the benefit of everyone looking at these derived impls through `cargo expand`.
Both expansions compile to the same code at all optimization levels (including `0`).
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r? @b-naber (rustbot has picked a reviewer for you, use r? to override) |
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Changes to the code generated for builtin derived traits. cc @nnethercote |
compiler-errors
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very nice r? @compiler-errors @bors r+ |
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I was just about to request a tiny change. @bors r- |
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| // There is no sensible code to be generated for *any* deriving on a | ||
| // zero-variant enum. So we just generate a failing expression. | ||
| // For zero-variant enum, this function body is unreachable. | ||
| // Generate `match *self {}`. |
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Can you add something like this: "This results in the same generated code as unsafe { core::intrinsics::unreachable() } while also being safe and stable."
Thanks.
@bors delegate=dtolnay
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✌️ @dtolnay, you can now approve this pull request! If @nnethercote told you to " |
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@bors r=compiler-errors,nnethercote |
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@bors rollup |
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…ors,nnethercote
Generate safe stable code for derives on empty enums
Generate `match *self {}` instead of `unsafe { core::intrinsics::unreachable() }`.
This is:
1. safe
2. stable
for the benefit of everyone looking at these derived impls through `cargo expand`.
[Both expansions compile to the same code at all optimization levels (including `0`).](https://rust.godbolt.org/z/P79joGMh3)
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…iaskrgr Rollup of 4 pull requests Successful merges: - rust-lang#112741 (fix typo in `rustdoc/src/what-is-rustdoc.md`) - rust-lang#113535 (Add a sparc-unknown-none-elf target.) - rust-lang#113651 (self type param infer, avoid ICE) - rust-lang#113770 (Generate safe stable code for derives on empty enums) r? `@ghost` `@rustbot` modify labels: rollup
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Generate
match *self {}instead ofunsafe { core::intrinsics::unreachable() }.This is:
for the benefit of everyone looking at these derived impls through
cargo expand.Both expansions compile to the same code at all optimization levels (including
0).