Report unreachable subpatterns consistently #120097
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| match res_void { | ||
| Ok(_x) => {} | ||
| Err(!), |
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Ok, just double checking my understanding -- with exhaustive patterns, we don't need to care about never patterns b/c the scrutinee already disqualifies those patterns?
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Yes. Said differently, never patterns are shorthand syntax: Err(!) is short for Err(_) => unreachable_unchecked!(). The rules for which arms are required are orthogonal, and here exhaustive_patterns says "we don't need that arm". I've updated the tracking issue to clarify that while I was at it
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For T-lang: The following stable code now lints: I assume this should deserve as much scrutiny from the compiler as the same pattern in a match arm, so it's totally justified to lint here. Just double checking that y'all agree with this. |
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…ubpats, r=compiler-errors Report unreachable subpatterns consistently We weren't reporting unreachable subpatterns in function arguments and `let` expressions. This wasn't very important, but never patterns make it more relevant: a user might write `let (Ok(x) | Err(!)) = ...` in a case where `let Ok(x) = ...` is accepted, so we should report the `Err(!)` as redundant. r? `@compiler-errors`
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…ubpats, r=compiler-errors Report unreachable subpatterns consistently We weren't reporting unreachable subpatterns in function arguments and `let` expressions. This wasn't very important, but never patterns make it more relevant: a user might write `let (Ok(x) | Err(!)) = ...` in a case where `let Ok(x) = ...` is accepted, so we should report the `Err(!)` as redundant. r? ``@compiler-errors``
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…iaskrgr Rollup of 11 pull requests Successful merges: - rust-lang#117910 (Refactor uses of `objc_msgSend` to no longer have clashing definitions) - rust-lang#118639 (Undeprecate lint `unstable_features` and make use of it in the compiler) - rust-lang#119801 (Fix deallocation with wrong allocator in (A)Rc::from_box_in) - rust-lang#120058 (bootstrap: improvements for compiler builds) - rust-lang#120059 (Make generic const type mismatches not hide trait impls from the trait solver) - rust-lang#120097 (Report unreachable subpatterns consistently) - rust-lang#120137 (Validate AggregateKind types in MIR) - rust-lang#120164 (`maybe_lint_impl_trait`: separate `is_downgradable` from `is_object_safe`) - rust-lang#120181 (Allow any `const` expression blocks in `thread_local!`) - rust-lang#120204 (Builtin macros effectively have implicit #[collapse_debuginfo(yes)]) - rust-lang#120218 (rustfmt: Check that a token can begin a nonterminal kind before parsing it as a macro arg) r? `@ghost` `@rustbot` modify labels: rollup
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…iaskrgr Rollup of 10 pull requests Successful merges: - rust-lang#117910 (Refactor uses of `objc_msgSend` to no longer have clashing definitions) - rust-lang#118639 (Undeprecate lint `unstable_features` and make use of it in the compiler) - rust-lang#119801 (Fix deallocation with wrong allocator in (A)Rc::from_box_in) - rust-lang#120058 (bootstrap: improvements for compiler builds) - rust-lang#120059 (Make generic const type mismatches not hide trait impls from the trait solver) - rust-lang#120097 (Report unreachable subpatterns consistently) - rust-lang#120137 (Validate AggregateKind types in MIR) - rust-lang#120164 (`maybe_lint_impl_trait`: separate `is_downgradable` from `is_object_safe`) - rust-lang#120181 (Allow any `const` expression blocks in `thread_local!`) - rust-lang#120218 (rustfmt: Check that a token can begin a nonterminal kind before parsing it as a macro arg) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#120097 - Nadrieril:consistent_unreachable_subpats, r=compiler-errors Report unreachable subpatterns consistently We weren't reporting unreachable subpatterns in function arguments and `let` expressions. This wasn't very important, but never patterns make it more relevant: a user might write `let (Ok(x) | Err(!)) = ...` in a case where `let Ok(x) = ...` is accepted, so we should report the `Err(!)` as redundant. r? ```@compiler-errors```
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We weren't reporting unreachable subpatterns in function arguments and
letexpressions. This wasn't very important, but never patterns make it more relevant: a user might writelet (Ok(x) | Err(!)) = ...in a case wherelet Ok(x) = ...is accepted, so we should report theErr(!)as redundant.r? @compiler-errors