Detect method not being present that is present in other tuple types #142034
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When a method is not present because of a trait bound not being met, and that trait bound is on a tuple, we check if making the tuple have no borrowed types makes the method to be found and highlight it if it does. This is a common problem for Bevy in particular and ORMs in general.
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Jun 6, 2025
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| if let Some(impl_span) = self | ||
| .tcx | ||
| .all_impls(def_id) | ||
| .filter(|&impl_def_id| { | ||
| let header = self.tcx.impl_trait_header(impl_def_id).unwrap(); | ||
| let trait_ref = header.trait_ref.instantiate( | ||
| self.tcx, | ||
| self.infcx.fresh_args_for_item(DUMMY_SP, impl_def_id), | ||
| ); | ||
|
|
||
| let value = ty::fold_regions(self.tcx, ty, |_, _| { | ||
| self.tcx.lifetimes.re_erased | ||
| }); | ||
| // FIXME: Don't bother dealing with non-lifetime binders here... | ||
| if value.has_escaping_bound_vars() { | ||
| return false; | ||
| } | ||
| self.infcx.can_eq(ty::ParamEnv::empty(), trait_ref.self_ty(), value) | ||
| && header.polarity == ty::ImplPolarity::Positive | ||
| }) | ||
| .map(|impl_def_id| self.tcx.def_span(impl_def_id)) | ||
| .next() |
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This is a smell blatantly taken from another diagnostic. This seems to be a recurring useful need: assert if a certain (trait) predicate would be fulfilled with a different type, and if so, get the span for that specific impl. We should probably add a mechanism of doing that to TyCtxt.
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When a method is not present because of a trait bound not being met, and that trait bound is on a tuple, we check if making the tuple have no borrowed types makes the method to be found and highlight it if it does. This is a common problem for Bevy in particular and ORMs in general.
Address #141258. I believe that more combination of cases in the tuple types should be handled (like adding borrows and checking when a specific type needs to not be a borrow while the rest stay the same), but for now this handles the most common case.