HACK unknowable goal, don't compute other candidates

Author: lcnr

Diff for: compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

@@ -304,6 +304,17 @@ where
 
         let mut candidates = vec![];
 
+        match self.solver_mode() {
+            SolverMode::Normal => {}
+            SolverMode::Coherence => {
+                self.assemble_coherence_unknowable_candidates(goal, &mut candidates)
+            }
+        }
+
+        if !candidates.is_empty() {
+            return candidates;
+        }
+
         self.assemble_impl_candidates(goal, &mut candidates);
 
         self.assemble_builtin_impl_candidates(goal, &mut candidates);
@@ -316,9 +327,7 @@ where
 
         match self.solver_mode() {
             SolverMode::Normal => self.discard_impls_shadowed_by_env(goal, &mut candidates),
-            SolverMode::Coherence => {
-                self.assemble_coherence_unknowable_candidates(goal, &mut candidates)
-            }
+            SolverMode::Coherence => {}
         }
 
         candidates

Diff for: tests/ui/coherence/coherence-negative-outlives-lifetimes.stock.stderr

@@ -6,6 +6,7 @@ LL | impl<'a, T: MyPredicate<'a>> MyTrait<'a> for T {}
 LL | impl<'a, T> MyTrait<'a> for &'a T {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `&_`
    = note: downstream crates may implement trait `MyPredicate<'_>` for type `&_`
 
 error: aborting due to 1 previous error

Diff for: tests/ui/coherence/coherence-negative-outlives-lifetimes.with_negative_coherence.stderr

@@ -6,6 +6,7 @@ LL | impl<'a, T: MyPredicate<'a>> MyTrait<'a> for T {}
 LL | impl<'a, T> MyTrait<'a> for &'a T {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `&_`
    = note: downstream crates may implement trait `MyPredicate<'_>` for type `&_`
 
 error: aborting due to 1 previous error

Diff for: tests/ui/coherence/coherence-overlap-issue-23516-inherent.stderr

@@ -7,6 +7,7 @@ LL |
 LL | impl<U:Sugar> Cake<Box<U>> { fn dummy(&self) { } }
    |                              --------------- other definition for `dummy`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `std::boxed::Box<_>`
    = note: downstream crates may implement trait `Sugar` for type `std::boxed::Box<_>`
 
 error: aborting due to 1 previous error

Diff for: tests/ui/coherence/coherence-overlap-issue-23516.stderr

@@ -6,6 +6,7 @@ LL | impl<T:Sugar> Sweet for T { }
 LL | impl<U:Sugar> Sweet for Box<U> { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Box<_>`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `std::boxed::Box<_>`
    = note: downstream crates may implement trait `Sugar` for type `std::boxed::Box<_>`
 
 error: aborting due to 1 previous error

Diff for: tests/ui/coherence/coherence-overlap-negate-not-use-feature-gate.stderr

@@ -6,6 +6,8 @@ LL | impl<T: DerefMut> Foo for T {}
 LL | impl<U> Foo for &U {}
    | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `&_`
+   = note: downstream crates may implement trait `std::ops::Deref` for type `&_`
    = note: downstream crates may implement trait `std::ops::DerefMut` for type `&_`
 
 error: aborting due to 1 previous error

Diff for: tests/ui/coherence/coherence-overlap-unnormalizable-projection-0.stderr

@@ -11,6 +11,7 @@ LL | |     for<'a> <T as WithAssoc<'a>>::Assoc: WhereBound,
 LL |   impl<T> Trait for Box<T> {}
    |   ^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Box<_>`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `std::boxed::Box<_>`
    = note: downstream crates may implement trait `WithAssoc<'a>` for type `std::boxed::Box<_>`
 
 error: aborting due to 1 previous error

Diff for: tests/ui/coherence/coherence-overlap-unnormalizable-projection-1.stderr

@@ -11,6 +11,7 @@ LL | |     for<'a> Box<<T as WithAssoc<'a>>::Assoc>: WhereBound,
 LL |   impl<T> Trait for Box<T> {}
    |   ^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Box<_>`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `std::boxed::Box<_>`
    = note: downstream crates may implement trait `WithAssoc<'a>` for type `std::boxed::Box<_>`
    = note: downstream crates may implement trait `WhereBound` for type `std::boxed::Box<_>`
 

Diff for: tests/ui/coherence/coherence-wasm-bindgen.stderr

@@ -15,6 +15,7 @@ LL | |     R: ReturnWasmAbi,
    |
    = warning: the behavior may change in a future release
    = note: for more information, see issue #56105 <https://github.com/rust-lang/rust/issues/56105>
+   = note: downstream crates may implement trait `std::marker::Sized` for type `&_`
    = note: downstream crates may implement trait `FromWasmAbi` for type `&_`
    = note: this behavior recently changed as a result of a bug fix; see rust-lang/rust#56105 for details
 note: the lint level is defined here

Diff for: tests/ui/coherence/negative-coherence-check-placeholder-outlives.stderr

@@ -6,6 +6,7 @@ LL | impl<T> Bar for T where T: Foo {}
 LL | impl<T> Bar for Box<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Box<_>`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `std::boxed::Box<_>`
    = note: downstream crates may implement trait `Foo` for type `std::boxed::Box<_>`
 
 error: aborting due to 1 previous error

Diff for: tests/ui/coherence/negative-coherence-considering-regions.any_lt.stderr

@@ -7,6 +7,7 @@ LL | impl<T> Bar for T where T: Foo {}
 LL | impl<T> Bar for &T {}
    | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `&_`
    = note: downstream crates may implement trait `Foo` for type `&_`
 
 error: aborting due to 1 previous error

Diff for: tests/ui/coherence/normalize-for-errors.rs

@@ -14,6 +14,6 @@ impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {}
 //~^ ERROR conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>,
 //~| NOTE conflicting implementation for `(Box<(MyType,)>,
 //~| NOTE upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions
-//~| NOTE upstream crates may add a new impl of trait `std::clone::Clone` for type `(MyType,)` in future versions
+//~| NOTE upstream crates may add a new impl of trait `std::clone::Clone` for type `std::boxed::Box<(MyType,)>` in future versions
 
 fn main() {}

Diff for: tests/ui/coherence/normalize-for-errors.stderr

@@ -7,7 +7,7 @@ LL |
 LL | impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(Box<(MyType,)>, <_ as Iterator>::Item)`
    |
-   = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `(MyType,)` in future versions
+   = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `std::boxed::Box<(MyType,)>` in future versions
    = note: upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions
 
 error: aborting due to 1 previous error

Diff for: tests/ui/coherence/occurs-check/associated-type.next.stderr

@@ -14,6 +14,8 @@ LL | | where
 LL | |     for<'a> *const T: ToUnit<'a>,
    | |_________________________________^ conflicting implementation for `for<'a> fn(&'a (), ())`
    |
+   = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `for<'a> fn(&'a (), ())` in future versions
+   = note: upstream crates may add a new impl of trait `std::marker::Copy` for type `for<'a> fn(&'a (), ())` in future versions
    = note: this behavior recently changed as a result of a bug fix; see rust-lang/rust#56105 for details
 
 error[E0284]: type annotations needed: cannot normalize `<for<'a> fn(&'a (), ()) as Overlap<for<'a> fn(&'a (), ())>>::Assoc`

Diff for: tests/ui/coherence/occurs-check/associated-type.old.stderr

@@ -14,6 +14,8 @@ LL | | where
 LL | |     for<'a> *const T: ToUnit<'a>,
    | |_________________________________^ conflicting implementation for `for<'a> fn(&'a (), ())`
    |
+   = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `for<'a> fn(&'a (), ())` in future versions
+   = note: upstream crates may add a new impl of trait `std::marker::Copy` for type `for<'a> fn(&'a (), ())` in future versions
    = note: this behavior recently changed as a result of a bug fix; see rust-lang/rust#56105 for details
 
 error: aborting due to 1 previous error

Diff for: tests/ui/feature-gates/feature-gate-with_negative_coherence.stderr

@@ -7,6 +7,8 @@ LL |
 LL | impl<T> Foo for &T { }
    | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
    |
+   = note: downstream crates may implement trait `std::marker::Sized` for type `&_`
+   = note: downstream crates may implement trait `std::ops::Deref` for type `&_`
    = note: downstream crates may implement trait `std::ops::DerefMut` for type `&_`
 
 error: aborting due to 1 previous error