Implement allow-by-default multiple_supertrait_upcastable lint
#105484
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This implementation looks good. Given that the lint is gated behind a feature gate, I don't think it needs an FCP. r? @compiler-errors @bors r+ |
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| // check-pass | ||
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| #![deny(multiple_supertrait_upcastable)] | ||
| //~^ WARNING unknown lint: `multiple_supertrait_upcastable` |
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Why are there so many copies of this error being emitted lol
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Dec 28, 2022
…fee1-dead Rollup of 9 pull requests Successful merges: - rust-lang#94145 (Test leaking of BinaryHeap Drain iterators) - rust-lang#103945 (Remove `iter::Empty` hack) - rust-lang#104024 (Fix `unused_must_use` warning for `Box::from_raw`) - rust-lang#104708 (Fix backoff doc to match implementation) - rust-lang#105347 (Account for `match` expr in single line) - rust-lang#105484 (Implement allow-by-default `multiple_supertrait_upcastable` lint) - rust-lang#106184 (Fix `core::any` docs) - rust-lang#106201 (Emit fewer errors on invalid `#[repr(transparent)]` on `enum`) - rust-lang#106205 (Remove some totally duplicated files in `rustc_infer`) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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Dec 31, 2022
Revert "Implement allow-by-default `multiple_supertrait_upcastable` lint" This is a clean revert of rust-lang#105484. I confirmed that reverting that PR fixes the regression reported in rust-lang#106247. ~~I can't say I understand what this code is doing, but maybe it can be re-landed with a different implementation.~~ **Edit:** rust-lang#106247 (comment) has an explanation of why rust-lang#105484 ends up surfacing spurious `where_clause_object_safety` errors. The implementation of `where_clause_object_safety` assumes we only check whether a trait is object safe when somebody actually uses that trait with `dyn`. However the implementation of `multiple_supertrait_upcastable` added in the problematic PR involves checking *every* trait for whether it is object-safe. FYI `@nbdd0121` `@compiler-errors`
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The lint detects when an object-safe trait has multiple supertraits.
Enabled in libcore and liballoc as they are low-level enough that many embedded programs will use them.
r? @nikomatsakis