Add blanket impls to allow the various Fn traits to be interconverted.
#18388
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nikomatsakis
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| impl<F,A,R> FnMut<A,R> for F | ||
| where F : Fn<A,R> | ||
| { | ||
| #[rust_call_abi_hack] |
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Is this still needed? I thought it was only needed until a snapshot landed and could be replaced with extern "rust-call"
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@luqmana I think you are correct.
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Hmm, I still think this approach is right, but it does yield many more inference failures, due to a similar situation as described in #17901. It is likely that using an associated type for the fn return would help here, but I'd prefer not to couple these two features. I'll ponder for a bit if there's a way to improve the situation. |
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OK, this version of the branch passes tests. It also fixes #17901 along the way, although I think there may be a more comprehensive fix (this version does cause the example there to compile successfully, however). |
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r? @aturon for these latest changes, since he and I discussed them at a high-level. |
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…type variables in the intracrate case. This requires a deeper distinction between inter- and intra-crate so as to keep coherence working. I suspect the best fix is to generalize the recursion check that exists today, but this requires a bit more refactoring to achieve. (In other words, where today it says OK for an exact match, we'd want to not detect exact matches but rather skolemize each trait-reference fresh and return AMBIG -- but that requires us to make builtin bounds work shallowly like everything else and move the cycle detection into the fulfillment context.)
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Add blanket impls to allow the various `Fn` traits to be interconverted. Fixes #18387.
Fix checking for `false` `labelDetailsSupport` value.
Add blanket impls to allow the various
Fntraits to be interconverted.Fixes #18387.