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Rework negative coherence to properly consider impls that only partly overlap #112875

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Merged
merged 7 commits into from
Oct 26, 2023
Merged

Rework negative coherence to properly consider impls that only partly overlap #112875

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b706b9d
pre-cleanups
compiler-errors Jun 21, 2023
66d7cfd
Remove FnPtr hack from trait_ref_is_knowable
compiler-errors May 6, 2023
7f3c2c7
Rework negative coherence
compiler-errors Jun 21, 2023
8597bf1
Make things work by using the new solver
compiler-errors Jun 21, 2023
1d99ddb
Consider regions
compiler-errors Jul 19, 2023
e1edefc
coherence doesn't like region constraints
compiler-errors Aug 2, 2023
0626f2e
nits
compiler-errors Oct 17, 2023
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Consider regions
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@compiler-errors
compiler-errors committed Oct 23, 2023
commit 1d99ddbfe81b7d766c6e6f54dbc722c70d0b6be7
11 changes: 9 additions & 2 deletions compiler/rustc_trait_selection/src/traits/coherence.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -434,12 +434,19 @@ fn impl_intersection_has_negative_obligation(
param_env,
negative_predicate,
));

if !ocx.select_all_or_error().is_empty() {
continue;
}

// FIXME: regions here too...
// FIXME: We could use the assumed_wf_types from both impls, I think,
// if that wasn't implemented just for LocalDefId, and we'd need to do
//the normalization ourselves since this is totally fallible...
let outlives_env = OutlivesEnvironment::new(param_env);

let errors = infcx.resolve_regions(&outlives_env);
if !errors.is_empty() {
continue;
}

return true;
}
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12 changes: 12 additions & 0 deletions tests/ui/coherence/negative-coherence-considering-regions.any_lt.stderr
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@@ -0,0 +1,12 @@
error[E0119]: conflicting implementations of trait `Bar` for type `&_`
--> $DIR/negative-coherence-considering-regions.rs:22:1
|
LL | impl<T> Bar for T where T: Foo {}
| ------------------------------ first implementation here
...
LL | impl<T> Bar for &T {}
| ^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0119`.
23 changes: 23 additions & 0 deletions tests/ui/coherence/negative-coherence-considering-regions.rs
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@@ -0,0 +1,23 @@
// revisions: any_lt static_lt
//[static_lt] check-pass

#![feature(negative_impls)]
#![feature(with_negative_coherence)]

trait Foo {}

impl<T> !Foo for &'static T {}

trait Bar {}

impl<T> Bar for T where T: Foo {}

#[cfg(any_lt)]
impl<T> Bar for &T {}
//[any_lt]~^ ERROR conflicting implementations of trait `Bar` for type `&_`

#[cfg(static_lt)]
impl<T> Bar for &'static T {}


fn main() {}