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Auto merge of rust-lang#110204 - compiler-errors:new-solver-hir-typec…
…k-hacks, r=lcnr Deal with unnormalized projections when structurally resolving types with new solver 1. Normalize types in `structurally_resolved_type` when the new solver is enabled 2. Normalize built-in autoderef targets in `Autoderef` when the new solver is enabled 3. Normalize-erasing-regions in `resolve_type` in writeback This is motivated by the UI test provided, which currently fails with: ``` error[E0609]: no field `x` on type `<usize as SliceIndex<[Foo]>>::Output` --> <source>:9:11 | 9 | xs[0].x = 1; | ^ ``` I'm pretty happy with the approach in (1.) and (2.) and think we'll inevitably need something like this in the long-term, but (3.) seems like a hack to me. It's a *lot* of work to add tons of new calls to every user of these typeck results though (mir build, late lints, etc). Happy to discuss further. r? `@lcnr`
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55 changes: 55 additions & 0 deletions
55
compiler/rustc_trait_selection/src/traits/structural_normalize.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,55 @@ | ||
| use rustc_infer::infer::at::At; | ||
| use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; | ||
| use rustc_infer::traits::{FulfillmentError, TraitEngine}; | ||
| use rustc_middle::ty::{self, Ty}; | ||
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| use crate::traits::{query::evaluate_obligation::InferCtxtExt, NormalizeExt, Obligation}; | ||
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| pub trait StructurallyNormalizeExt<'tcx> { | ||
| fn structurally_normalize( | ||
| &self, | ||
| ty: Ty<'tcx>, | ||
| fulfill_cx: &mut dyn TraitEngine<'tcx>, | ||
| ) -> Result<Ty<'tcx>, Vec<FulfillmentError<'tcx>>>; | ||
| } | ||
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| impl<'tcx> StructurallyNormalizeExt<'tcx> for At<'_, 'tcx> { | ||
| fn structurally_normalize( | ||
| &self, | ||
| mut ty: Ty<'tcx>, | ||
| fulfill_cx: &mut dyn TraitEngine<'tcx>, | ||
| ) -> Result<Ty<'tcx>, Vec<FulfillmentError<'tcx>>> { | ||
| assert!(!ty.is_ty_var(), "should have resolved vars before calling"); | ||
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| if self.infcx.tcx.trait_solver_next() { | ||
| while let ty::Alias(ty::Projection, projection_ty) = *ty.kind() { | ||
| let new_infer_ty = self.infcx.next_ty_var(TypeVariableOrigin { | ||
| kind: TypeVariableOriginKind::NormalizeProjectionType, | ||
| span: self.cause.span, | ||
| }); | ||
| let obligation = Obligation::new( | ||
| self.infcx.tcx, | ||
| self.cause.clone(), | ||
| self.param_env, | ||
| ty::Binder::dummy(ty::ProjectionPredicate { | ||
| projection_ty, | ||
| term: new_infer_ty.into(), | ||
| }), | ||
| ); | ||
| if self.infcx.predicate_may_hold(&obligation) { | ||
| fulfill_cx.register_predicate_obligation(self.infcx, obligation); | ||
| let errors = fulfill_cx.select_where_possible(self.infcx); | ||
| if !errors.is_empty() { | ||
| return Err(errors); | ||
| } | ||
| ty = self.infcx.resolve_vars_if_possible(new_infer_ty); | ||
| } else { | ||
| break; | ||
| } | ||
| } | ||
| Ok(ty) | ||
| } else { | ||
| Ok(self.normalize(ty).into_value_registering_obligations(self.infcx, fulfill_cx)) | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,25 @@ | ||
| // compile-flags: -Ztrait-solver=next | ||
| // check-pass | ||
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| // Verify that we can assemble inherent impl candidates on a possibly | ||
| // unnormalized self type. | ||
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| trait Foo { | ||
| type Assoc; | ||
| } | ||
| impl Foo for i32 { | ||
| type Assoc = Bar; | ||
| } | ||
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| struct Bar; | ||
| impl Bar { | ||
| fn method(&self) {} | ||
| } | ||
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| fn build<T: Foo>(_: T) -> T::Assoc { | ||
| todo!() | ||
| } | ||
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| fn main() { | ||
| build(1i32).method(); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,13 @@ | ||
| // compile-flags: -Ztrait-solver=next | ||
| // check-pass | ||
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| #[derive(Default)] | ||
| struct Foo { | ||
| x: i32, | ||
| } | ||
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| fn main() { | ||
| let mut xs = <[Foo; 1]>::default(); | ||
| xs[0].x = 1; | ||
| (&mut xs[0]).x = 2; | ||
| } |