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Do not consider elaborated projection predicates for objects in new solver

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This commit is contained in:
Michael Goulet 2023-03-27 19:41:15 +00:00
parent cf32b9de1e
commit d62238d6a8
4 changed files with 37 additions and 9 deletions
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19
compiler/rustc_trait_selection/src/solve/assembly.rs
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@ -6,6 +6,7 @@ use super::trait_goals::structural_traits::*;
use super::{EvalCtxt, SolverMode};
use crate::traits::coherence;
use itertools::Itertools;
use rustc_data_structures::fx::FxIndexSet;
use rustc_hir::def_id::DefId;
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::util::elaborate_predicates;
@ -489,9 +490,21 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
};
let tcx = self.tcx();
for assumption in
elaborate_predicates(tcx, bounds.iter().map(|bound| bound.with_self_ty(tcx, self_ty)))
{
let own_bounds: FxIndexSet<_> =
bounds.iter().map(|bound| bound.with_self_ty(tcx, self_ty)).collect();
for assumption in elaborate_predicates(tcx, own_bounds.iter().copied()) {
// FIXME: Predicates are fully elaborated in the object type's existential bounds
// list. We want to only consider these pre-elaborated projections, and not other
// projection predicates that we reach by elaborating the principal trait ref,
// since that'll cause ambiguity.
//
// We can remove this when we have implemented intersections in responses.
if assumption.to_opt_poly_projection_pred().is_some()
&& !own_bounds.contains(&assumption)
{
continue;
}
match G::consider_object_bound_candidate(self, goal, assumption) {
Ok(result) => {
candidates.push(Candidate { source: CandidateSource::BuiltinImpl, result })

12
tests/ui/traits/new-solver/dont-elaborate-for-projections.rs Normal file
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@ -0,0 +1,12 @@
// compile-flags: -Ztrait-solver=next
// check-pass
trait Iter<'a, I: 'a>: Iterator<Item = &'a I> {}
fn needs_iter<'a, T: Iter<'a, I> + ?Sized, I: 'a>(_: &T) {}
fn test(x: &dyn Iter<'_, ()>) {
needs_iter(x);
}
fn main() {}

2
tests/ui/traits/new-solver/more-object-bound.rs
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@ -10,7 +10,7 @@ trait Trait: SuperTrait<A = <Self as SuperTrait>::B> {}
fn transmute<A, B>(x: A) -> B {
foo::<A, B, dyn Trait<A = A, B = B>>(x)
//~^ ERROR type annotations needed: cannot satisfy `dyn Trait<A = A, B = B>: Trait`
//~^ ERROR the trait bound `dyn Trait<A = A, B = B>: Trait` is not satisfied
}
fn foo<A, B, T: ?Sized>(x: T::A) -> B

13
tests/ui/traits/new-solver/more-object-bound.stderr
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@ -1,10 +1,9 @@
error[E0283]: type annotations needed: cannot satisfy `dyn Trait<A = A, B = B>: Trait`
--> $DIR/more-object-bound.rs:12:5
error[E0277]: the trait bound `dyn Trait<A = A, B = B>: Trait` is not satisfied
--> $DIR/more-object-bound.rs:12:17
|
LL | foo::<A, B, dyn Trait<A = A, B = B>>(x)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `dyn Trait<A = A, B = B>`
|
= note: cannot satisfy `dyn Trait<A = A, B = B>: Trait`
note: required by a bound in `foo`
--> $DIR/more-object-bound.rs:18:8
|
@ -13,7 +12,11 @@ LL | fn foo<A, B, T: ?Sized>(x: T::A) -> B
LL | where
LL | T: Trait<B = B>,
| ^^^^^^^^^^^^ required by this bound in `foo`
help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
|
LL | fn transmute<A, B>(x: A) -> B where dyn Trait<A = A, B = B>: Trait {
| ++++++++++++++++++++++++++++++++++++
error: aborting due to previous error
For more information about this error, try `rustc --explain E0283`.
For more information about this error, try `rustc --explain E0277`.