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trait_sel: resolve vars in host effects - #137604
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In the standard library, the `Extend` impl for `Iterator` (specialised with `TrustedLen`) has a parameter which is constrained by a projection predicate. This projection predicate provides a value for an inference variable but host effect evaluation wasn't resolving variables first. Adding the extra resolve can the number of errors in some tests when they gain host effect predicates, but this is not unexpected as calls to `resolve_vars_if_possible` can cause more error tainting to happen. Co-authored-by: Boxy <rust@boxyuwu.dev>
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jieyouxu
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Feb 25, 2025
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r? types |
oli-obk
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Feb 25, 2025
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On nightly this emits
error[E0283]: type annotations needed: cannot satisfy `Iter: Tr`
--> src/lib.rs:31:33
|
31 | impl<A: const Foo, Iter> Tr for Iter
| ^^^^
|
note: multiple `impl`s satisfying `Iter: Tr` found
--> src/lib.rs:24:1
|
24 | / impl<A: const Foo, Iter> Tr for Iter
25 | | where
26 | | Iter: Iterator<Item = A>,
| |_________________________________^
...
31 | / impl<A: const Foo, Iter> Tr for Iter
32 | | where
33 | | Iter: MoreSpecificThanIterator<Item = A>,
| |_________________________________________________^
oli-obk
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davidtwcoforce-pushed
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21d41b0Comparedavidtwco
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Feb 25, 2025
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Also added @BoxyUwU as a co-author on the commit as I wouldn't have solved this one without their help at Rust Nation. |
compiler-errors
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Feb 25, 2025
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Yeah, the implementation of the old trait solver's const predicates kinda sucks. r? compiler-errors @bors r+ rollup |
bors
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Feb 25, 2025
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…, r=compiler-errors trait_sel: resolve vars in host effects In the standard library, the `Extend` impl for `Iterator` (specialised with `TrustedLen`) has a parameter which is constrained by a projection predicate. This projection predicate provides a value for an inference variable but - if the default bound is `const Sized` instead of `Sized` - host effect evaluation wasn't resolving variables first. Added a test that doesn't depend on a rust-lang/rfcs#3729 implementation. Adding the extra resolve can the number of errors in some tests when they gain host effect predicates, but this is not unexpected as calls to `resolve_vars_if_possible` can cause more error tainting to happen.
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Rollup of 13 pull requests Successful merges: - rust-lang#136576 (pass optimization level to llvm-bitcode-linker) - rust-lang#137320 (fix(rustdoc): Fixed stability version in rustdoc) - rust-lang#137502 (Don't include global asm in `mir_keys`, fix error body synthesis) - rust-lang#137529 (remove few unused args) - rust-lang#137544 (tests: Add regression test for derive token invalidation (rust-lang#81099)) - rust-lang#137559 (run some tests on emscripten again) - rust-lang#137601 (ssa/mono: deduplicate `type_has_metadata`) - rust-lang#137603 (codegen_llvm: avoid `Deref` impls w/ extern type) - rust-lang#137604 (trait_sel: resolve vars in host effects) - rust-lang#137609 (Complete the list of resources used in rustdoc output) - rust-lang#137613 (hir_analysis: skip self type of host effect preds in variances_of) - rust-lang#137614 (fix doc in library/core/src/pin.rs) - rust-lang#137622 (fix attribute-related ICE when parsing macro on the rhs of a name-value attribute) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup of 14 pull requests Successful merges: - rust-lang#136576 (pass optimization level to llvm-bitcode-linker) - rust-lang#137154 (Add UTF-8 validation fast paths in `Wtf8Buf`) - rust-lang#137311 (Enable `f16` for MIPS) - rust-lang#137320 (fix(rustdoc): Fixed stability version in rustdoc) - rust-lang#137529 (remove few unused args) - rust-lang#137544 (tests: Add regression test for derive token invalidation (rust-lang#81099)) - rust-lang#137559 (run some tests on emscripten again) - rust-lang#137601 (ssa/mono: deduplicate `type_has_metadata`) - rust-lang#137603 (codegen_llvm: avoid `Deref` impls w/ extern type) - rust-lang#137604 (trait_sel: resolve vars in host effects) - rust-lang#137609 (Complete the list of resources used in rustdoc output) - rust-lang#137613 (hir_analysis: skip self type of host effect preds in variances_of) - rust-lang#137614 (fix doc in library/core/src/pin.rs) - rust-lang#137622 (fix attribute-related ICE when parsing macro on the rhs of a name-value attribute) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#137604 - davidtwco:host-effect-resolve-vars, r=compiler-errors trait_sel: resolve vars in host effects In the standard library, the `Extend` impl for `Iterator` (specialised with `TrustedLen`) has a parameter which is constrained by a projection predicate. This projection predicate provides a value for an inference variable but - if the default bound is `const Sized` instead of `Sized` - host effect evaluation wasn't resolving variables first. Added a test that doesn't depend on a rust-lang/rfcs#3729 implementation. Adding the extra resolve can the number of errors in some tests when they gain host effect predicates, but this is not unexpected as calls to `resolve_vars_if_possible` can cause more error tainting to happen.
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In the standard library, the
Extendimpl forIterator(specialised withTrustedLen) has a parameter which is constrained by a projection predicate. This projection predicate provides a value for an inference variable but - if the default bound isconst Sizedinstead ofSized- host effect evaluation wasn't resolving variables first. Added a test that doesn't depend on a rust-lang/rfcs#3729 implementation.Adding the extra resolve can the number of errors in some tests when they gain host effect predicates, but this is not unexpected as calls to
resolve_vars_if_possiblecan cause more error tainting to happen.