Eagerly instantiate closure/coroutine-like bounds with placeholders to deal with binders correctly #122267
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…r=<try> Eagerly instantiate closure/coroutine-like bounds with placeholders to deal with binders correctly A follow-up to rust-lang#119849, however it aims to fix a different set of issues. Currently, we have trouble confirming goals where built-in closure/fnptr/coroutine signatures are compared against higher-ranked goals. Currently, we don't support goals like `for<'a> fn(&'a ()): Fn(&'a ())` because we don't expect the self type of goal to reference any bound regions from the goal, because we don't really know how to deal with the double binder of predicate + self type. However, this definitely can be reached (rust-lang#121653) -- and in fact, it results in post-mono errors in the case of rust-lang#112347 where the builtin type (e.g. a coroutine) is hidden behind a TAIT. The proper fix here is to instantiate the goal before trying to extract the signature from the self type. See final two commits. r? lcnr
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lcnr
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this prevents an codegen ICE. Please add it as a test trait Trait {
type Assoc<'a>: FnOnce(&'a ());
}
impl Trait for () {
type Assoc<'a> = fn(&'a ());
}
trait Indir {
fn break_me() {}
}
impl<F: Trait> Indir for F
where
for<'a> F::Assoc<'a>: FnOnce(&'a ()),
{
fn break_me() {}
}
fn foo<F: Trait>() {
F::break_me()
}
fn main() {
foo::<()>();
}@rust-lang/types we previously failed to handle builtin This PR allows more code to pass and can in likely very artificial cases be breaking (by fixing coherence/changing candidate selection). I am confident enough that this won't break anything that I am going to start the FCP right away, even before we've finished the crater run. We can always reconsider if any breakage is found @rfcbot fcp merge |
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Team member @lcnr has proposed to merge this. The next step is review by the rest of the tagged team members: No concerns currently listed. Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up! See this document for info about what commands tagged team members can give me. |
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The final comment period, with a disposition to merge, as per the review above, is now complete. As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed. This will be merged soon. |
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| trait Trait { |
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| trait Trait { | |
| // Regression test for incomplete handling of Fn-trait goals, | |
| // fixed in #122267. | |
| trait Trait { |
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Finished benchmarking commit (e2cf2cb): comparison URL. Overall result: no relevant changes - no action needed@rustbot label: -perf-regression Instruction countThis benchmark run did not return any relevant results for this metric. Max RSS (memory usage)ResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesThis benchmark run did not return any relevant results for this metric. Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 668.516s -> 667.053s (-0.22%) |
No need to instantiate binder in `confirm_async_closure_candidate` Removes a FIXME that is redundant. No longer needed since rust-lang#122267.
No need to instantiate binder in `confirm_async_closure_candidate` Removes a FIXME that is redundant. No longer needed since rust-lang#122267.
Rollup merge of rust-lang#132486 - compiler-errors:no-binder, r=lcnr No need to instantiate binder in `confirm_async_closure_candidate` Removes a FIXME that is redundant. No longer needed since rust-lang#122267.
A follow-up to #119849, however it aims to fix a different set of issues. Currently, we have trouble confirming goals where built-in closure/fnptr/coroutine signatures are compared against higher-ranked goals.
Currently, we don't support goals like
for<'a> fn(&'a ()): Fn(&'a ())because we don't expect the self type of goal to reference any bound regions from the goal, because we don't really know how to deal with the double binder of predicate + self type. However, this definitely can be reached (#121653) -- and in fact, it results in post-mono errors in the case of #112347 where the builtin type (e.g. a coroutine) is hidden behind a TAIT.The proper fix here is to instantiate the goal before trying to extract the signature from the self type. See final two commits.
r? lcnr