Don't ICE because recomputing overflow goals during find_best_leaf_obligation causes inference side-effects

17 files changed, 81 insertions, 179 deletions

diff --git a/tests/ui/traits/next-solver/coherence/coherence-fulfill-overflow.stderr b/tests/ui/traits/next-solver/coherence/coherence-fulfill-overflow.stderr
index 6e68646fbe4..57cba790b55 100644
--- a/tests/ui/traits/next-solver/coherence/coherence-fulfill-overflow.stderr
+++ b/tests/ui/traits/next-solver/coherence/coherence-fulfill-overflow.stderr
@@ -1,12 +1,12 @@
-error[E0119]: conflicting implementations of trait `Trait` for type `W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<_>>>>>>>>>>>>>>>>>>>>>>`
+error[E0119]: conflicting implementations of trait `Trait` for type `W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<_>>>>>>>>>>>>>>>>>>>>>`
   --> $DIR/coherence-fulfill-overflow.rs:12:1
    |
 LL | impl<T: ?Sized + TwoW> Trait for W<T> {}
    | ------------------------------------- first implementation here
 LL | impl<T: ?Sized + TwoW> Trait for T {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<_>>>>>>>>>>>>>>>>>>>>>>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<_>>>>>>>>>>>>>>>>>>>>>`
    |
-   = note: overflow evaluating the requirement `W<W<W<W<_>>>>: TwoW`
+   = note: overflow evaluating the requirement `W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<W<_>>>>>>>>>>>>>>>>>>>>>: TwoW`
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "20"]` attribute to your crate (`coherence_fulfill_overflow`)
 
 error: aborting due to 1 previous error
diff --git a/tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.stderr b/tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.stderr
index df25150c21f..8d7d8cee08a 100644
--- a/tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.stderr
+++ b/tests/ui/traits/next-solver/cycles/coinduction/fixpoint-exponential-growth.stderr
@@ -1,16 +1,9 @@
-error[E0275]: overflow evaluating the requirement `_: Sized`
+error[E0275]: overflow evaluating the requirement `W<_>: Trait`
   --> $DIR/fixpoint-exponential-growth.rs:33:13
    |
 LL |     impls::<W<_>>();
    |             ^^^^
    |
-note: required for `W<(W<_>, W<_>)>` to implement `Trait`
-  --> $DIR/fixpoint-exponential-growth.rs:23:12
-   |
-LL | impl<T, U> Trait for W<(W<T>, W<U>)>
-   |      -     ^^^^^     ^^^^^^^^^^^^^^^
-   |      |
-   |      unsatisfied trait bound introduced here
 note: required by a bound in `impls`
   --> $DIR/fixpoint-exponential-growth.rs:30:13
    |
diff --git a/tests/ui/traits/next-solver/cycles/double-cycle-inductive-coinductive.stderr b/tests/ui/traits/next-solver/cycles/double-cycle-inductive-coinductive.stderr
index 86c71ad92ff..7cedb4d36c9 100644
--- a/tests/ui/traits/next-solver/cycles/double-cycle-inductive-coinductive.stderr
+++ b/tests/ui/traits/next-solver/cycles/double-cycle-inductive-coinductive.stderr
@@ -1,53 +1,21 @@
-error[E0275]: overflow evaluating the requirement `(): Inductive`
+error[E0275]: overflow evaluating the requirement `(): Trait`
   --> $DIR/double-cycle-inductive-coinductive.rs:32:19
    |
 LL |     impls_trait::<()>();
    |                   ^^
    |
-note: required for `()` to implement `Trait`
-  --> $DIR/double-cycle-inductive-coinductive.rs:9:34
-   |
-LL | impl<T: Inductive + Coinductive> Trait for T {}
-   |         ---------                ^^^^^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-note: required for `()` to implement `Inductive`
-  --> $DIR/double-cycle-inductive-coinductive.rs:12:16
-   |
-LL | impl<T: Trait> Inductive for T {}
-   |         -----  ^^^^^^^^^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-   = note: 7 redundant requirements hidden
-   = note: required for `()` to implement `Trait`
 note: required by a bound in `impls_trait`
   --> $DIR/double-cycle-inductive-coinductive.rs:17:19
    |
 LL | fn impls_trait<T: Trait>() {}
    |                   ^^^^^ required by this bound in `impls_trait`
 
-error[E0275]: overflow evaluating the requirement `(): CoinductiveRev`
+error[E0275]: overflow evaluating the requirement `(): TraitRev`
   --> $DIR/double-cycle-inductive-coinductive.rs:35:23
    |
 LL |     impls_trait_rev::<()>();
    |                       ^^
    |
-note: required for `()` to implement `TraitRev`
-  --> $DIR/double-cycle-inductive-coinductive.rs:21:40
-   |
-LL | impl<T: CoinductiveRev + InductiveRev> TraitRev for T {}
-   |         --------------                 ^^^^^^^^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-note: required for `()` to implement `CoinductiveRev`
-  --> $DIR/double-cycle-inductive-coinductive.rs:27:19
-   |
-LL | impl<T: TraitRev> CoinductiveRev for T {}
-   |         --------  ^^^^^^^^^^^^^^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-   = note: 7 redundant requirements hidden
-   = note: required for `()` to implement `TraitRev`
 note: required by a bound in `impls_trait_rev`
   --> $DIR/double-cycle-inductive-coinductive.rs:29:23
    |
diff --git a/tests/ui/traits/next-solver/cycles/inductive-fixpoint-hang.stderr b/tests/ui/traits/next-solver/cycles/inductive-fixpoint-hang.stderr
index ea46c0fea97..a2a5c028cf8 100644
--- a/tests/ui/traits/next-solver/cycles/inductive-fixpoint-hang.stderr
+++ b/tests/ui/traits/next-solver/cycles/inductive-fixpoint-hang.stderr
@@ -1,19 +1,9 @@
-error[E0275]: overflow evaluating the requirement `W<W<_>>: Trait`
+error[E0275]: overflow evaluating the requirement `W<_>: Trait`
   --> $DIR/inductive-fixpoint-hang.rs:31:19
    |
 LL |     impls_trait::<W<_>>();
    |                   ^^^^
    |
-note: required for `W<W<W<_>>>` to implement `Trait`
-  --> $DIR/inductive-fixpoint-hang.rs:22:17
-   |
-LL | impl<T: ?Sized> Trait for W<W<T>>
-   |                 ^^^^^     ^^^^^^^
-LL | where
-LL |     W<T>: Trait,
-   |           ----- unsatisfied trait bound introduced here
-   = note: 8 redundant requirements hidden
-   = note: required for `W<W<W<W<W<W<W<W<W<W<W<_>>>>>>>>>>>` to implement `Trait`
 note: required by a bound in `impls_trait`
   --> $DIR/inductive-fixpoint-hang.rs:28:19
    |
diff --git a/tests/ui/traits/next-solver/cycles/inductive-not-on-stack.rs b/tests/ui/traits/next-solver/cycles/inductive-not-on-stack.rs
index 9d0ea51b1b2..78683372580 100644
--- a/tests/ui/traits/next-solver/cycles/inductive-not-on-stack.rs
+++ b/tests/ui/traits/next-solver/cycles/inductive-not-on-stack.rs
@@ -39,7 +39,7 @@ fn impls_ar<T: AR>() {}
 
 fn main() {
     impls_a::<()>();
-    //~^ ERROR overflow evaluating the requirement `(): B`
+    //~^ ERROR overflow evaluating the requirement `(): A`
 
     impls_ar::<()>();
     //~^ ERROR overflow evaluating the requirement `(): AR`
diff --git a/tests/ui/traits/next-solver/cycles/inductive-not-on-stack.stderr b/tests/ui/traits/next-solver/cycles/inductive-not-on-stack.stderr
index fe02d3c407c..e9cc6bc6c81 100644
--- a/tests/ui/traits/next-solver/cycles/inductive-not-on-stack.stderr
+++ b/tests/ui/traits/next-solver/cycles/inductive-not-on-stack.stderr
@@ -1,25 +1,9 @@
-error[E0275]: overflow evaluating the requirement `(): B`
+error[E0275]: overflow evaluating the requirement `(): A`
   --> $DIR/inductive-not-on-stack.rs:41:15
    |
 LL |     impls_a::<()>();
    |               ^^
    |
-note: required for `()` to implement `A`
-  --> $DIR/inductive-not-on-stack.rs:21:16
-   |
-LL | impl<T: B + C> A for T {}
-   |         -      ^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-note: required for `()` to implement `B`
-  --> $DIR/inductive-not-on-stack.rs:22:12
-   |
-LL | impl<T: A> B for T {}
-   |         -  ^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-   = note: 7 redundant requirements hidden
-   = note: required for `()` to implement `A`
 note: required by a bound in `impls_a`
   --> $DIR/inductive-not-on-stack.rs:25:15
    |
@@ -32,29 +16,6 @@ error[E0275]: overflow evaluating the requirement `(): AR`
 LL |     impls_ar::<()>();
    |                ^^
    |
-note: required for `()` to implement `BR`
-  --> $DIR/inductive-not-on-stack.rs:35:13
-   |
-LL | impl<T: AR> BR for T {}
-   |         --  ^^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-note: required for `()` to implement `CR`
-  --> $DIR/inductive-not-on-stack.rs:36:13
-   |
-LL | impl<T: BR> CR for T {}
-   |         --  ^^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-note: required for `()` to implement `AR`
-  --> $DIR/inductive-not-on-stack.rs:34:18
-   |
-LL | impl<T: CR + BR> AR for T {}
-   |         --       ^^     ^
-   |         |
-   |         unsatisfied trait bound introduced here
-   = note: 6 redundant requirements hidden
-   = note: required for `()` to implement `AR`
 note: required by a bound in `impls_ar`
   --> $DIR/inductive-not-on-stack.rs:38:16
    |
diff --git a/tests/ui/traits/next-solver/cycles/mixed-cycles-1.rs b/tests/ui/traits/next-solver/cycles/mixed-cycles-1.rs
index b90a354be1b..6d75d241864 100644
--- a/tests/ui/traits/next-solver/cycles/mixed-cycles-1.rs
+++ b/tests/ui/traits/next-solver/cycles/mixed-cycles-1.rs
@@ -35,5 +35,5 @@ fn impls_a<T: A>() {}
 
 fn main() {
     impls_a::<()>();
-    //~^ ERROR overflow evaluating the requirement `(): CInd`
+    //~^ ERROR overflow evaluating the requirement `(): A`
 }
diff --git a/tests/ui/traits/next-solver/cycles/mixed-cycles-1.stderr b/tests/ui/traits/next-solver/cycles/mixed-cycles-1.stderr
index 03e61dbf99c..17544eb1da5 100644
--- a/tests/ui/traits/next-solver/cycles/mixed-cycles-1.stderr
+++ b/tests/ui/traits/next-solver/cycles/mixed-cycles-1.stderr
@@ -1,46 +1,9 @@
-error[E0275]: overflow evaluating the requirement `(): CInd`
+error[E0275]: overflow evaluating the requirement `(): A`
   --> $DIR/mixed-cycles-1.rs:37:15
    |
 LL |     impls_a::<()>();
    |               ^^
    |
-note: required for `()` to implement `B`
-  --> $DIR/mixed-cycles-1.rs:31:28
-   |
-LL | impl<T: ?Sized + CInd + C> B for T {}
-   |                  ----      ^     ^
-   |                  |
-   |                  unsatisfied trait bound introduced here
-note: required for `()` to implement `C`
-  --> $DIR/mixed-cycles-1.rs:32:25
-   |
-LL | impl<T: ?Sized + B + A> C for T {}
-   |                  -      ^     ^
-   |                  |
-   |                  unsatisfied trait bound introduced here
-note: required for `()` to implement `CInd`
-  --> $DIR/mixed-cycles-1.rs:28:21
-   |
-LL | impl<T: ?Sized + C> CInd for T {}
-   |                  -  ^^^^     ^
-   |                  |
-   |                  unsatisfied trait bound introduced here
-   = note: 4 redundant requirements hidden
-   = note: required for `()` to implement `B`
-note: required for `()` to implement `BInd`
-  --> $DIR/mixed-cycles-1.rs:23:21
-   |
-LL | impl<T: ?Sized + B> BInd for T {}
-   |                  -  ^^^^     ^
-   |                  |
-   |                  unsatisfied trait bound introduced here
-note: required for `()` to implement `A`
-  --> $DIR/mixed-cycles-1.rs:30:28
-   |
-LL | impl<T: ?Sized + BInd + C> A for T {}
-   |                  ----      ^     ^
-   |                  |
-   |                  unsatisfied trait bound introduced here
 note: required by a bound in `impls_a`
   --> $DIR/mixed-cycles-1.rs:34:15
    |
diff --git a/tests/ui/traits/next-solver/cycles/mixed-cycles-2.rs b/tests/ui/traits/next-solver/cycles/mixed-cycles-2.rs
index a3ffcaafb37..c939a6e5ef2 100644
--- a/tests/ui/traits/next-solver/cycles/mixed-cycles-2.rs
+++ b/tests/ui/traits/next-solver/cycles/mixed-cycles-2.rs
@@ -28,5 +28,5 @@ fn impls_a<T: A>() {}
 
 fn main() {
     impls_a::<()>();
-    //~^ ERROR overflow evaluating the requirement `(): BInd`
+    //~^ ERROR overflow evaluating the requirement `(): A`
 }
diff --git a/tests/ui/traits/next-solver/cycles/mixed-cycles-2.stderr b/tests/ui/traits/next-solver/cycles/mixed-cycles-2.stderr
index 892426abe82..a9be1016c74 100644
--- a/tests/ui/traits/next-solver/cycles/mixed-cycles-2.stderr
+++ b/tests/ui/traits/next-solver/cycles/mixed-cycles-2.stderr
@@ -1,32 +1,9 @@
-error[E0275]: overflow evaluating the requirement `(): BInd`
+error[E0275]: overflow evaluating the requirement `(): A`
   --> $DIR/mixed-cycles-2.rs:30:15
    |
 LL |     impls_a::<()>();
    |               ^^
    |
-note: required for `()` to implement `B`
-  --> $DIR/mixed-cycles-2.rs:25:24
-   |
-LL | impl<T: ?Sized + BInd> B for T {}
-   |                  ----  ^     ^
-   |                  |
-   |                  unsatisfied trait bound introduced here
-note: required for `()` to implement `BInd`
-  --> $DIR/mixed-cycles-2.rs:22:21
-   |
-LL | impl<T: ?Sized + B> BInd for T {}
-   |                  -  ^^^^     ^
-   |                  |
-   |                  unsatisfied trait bound introduced here
-   = note: 6 redundant requirements hidden
-   = note: required for `()` to implement `BInd`
-note: required for `()` to implement `A`
-  --> $DIR/mixed-cycles-2.rs:24:28
-   |
-LL | impl<T: ?Sized + BInd + B> A for T {}
-   |                  ----      ^     ^
-   |                  |
-   |                  unsatisfied trait bound introduced here
 note: required by a bound in `impls_a`
   --> $DIR/mixed-cycles-2.rs:27:15
    |
diff --git a/tests/ui/traits/next-solver/diagnostics/ambiguous-fail.rs b/tests/ui/traits/next-solver/diagnostics/ambiguous-fail.rs
new file mode 100644
index 00000000000..4094ab84166
--- /dev/null
+++ b/tests/ui/traits/next-solver/diagnostics/ambiguous-fail.rs
@@ -0,0 +1,21 @@
+//@ compile-flags: -Znext-solver
+
+trait Trait {
+    type Assoc;
+}
+
+struct W<T>(*mut T);
+impl<T> Trait for W<W<T>>
+where
+    W<T>: Trait,
+{
+    type Assoc = ();
+}
+
+trait NoOverlap {}
+impl<T: Trait> NoOverlap for T {}
+
+impl<T: Trait<Assoc = u32>> NoOverlap for W<T> {}
+//~^ ERROR conflicting implementations of trait `NoOverlap` for type `W<_>`
+
+fn main() {}
diff --git a/tests/ui/traits/next-solver/diagnostics/ambiguous-fail.stderr b/tests/ui/traits/next-solver/diagnostics/ambiguous-fail.stderr
new file mode 100644
index 00000000000..42be1960563
--- /dev/null
+++ b/tests/ui/traits/next-solver/diagnostics/ambiguous-fail.stderr
@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `NoOverlap` for type `W<_>`
+  --> $DIR/ambiguous-fail.rs:18:1
+   |
+LL | impl<T: Trait> NoOverlap for T {}
+   | ------------------------------ first implementation here
+LL |
+LL | impl<T: Trait<Assoc = u32>> NoOverlap for W<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `W<_>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0119`.
diff --git a/tests/ui/traits/next-solver/diagnostics/ambiguous-pass.rs b/tests/ui/traits/next-solver/diagnostics/ambiguous-pass.rs
new file mode 100644
index 00000000000..2d40ba37a89
--- /dev/null
+++ b/tests/ui/traits/next-solver/diagnostics/ambiguous-pass.rs
@@ -0,0 +1,21 @@
+//@ compile-flags: -Znext-solver
+
+trait Trait {
+    type Assoc;
+}
+
+struct W<T>(*mut T);
+impl<T> Trait for W<W<T>>
+where
+    W<T>: Trait,
+{
+    type Assoc = ();
+}
+
+trait NoOverlap {}
+impl<T: Trait> NoOverlap for T {}
+
+impl<T: Trait<Assoc = ()>> NoOverlap for W<T> {}
+//~^ ERROR conflicting implementations of trait `NoOverlap` for type `W<_>`
+
+fn main() {}
diff --git a/tests/ui/traits/next-solver/diagnostics/ambiguous-pass.stderr b/tests/ui/traits/next-solver/diagnostics/ambiguous-pass.stderr
new file mode 100644
index 00000000000..5c77fc71e55
--- /dev/null
+++ b/tests/ui/traits/next-solver/diagnostics/ambiguous-pass.stderr
@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `NoOverlap` for type `W<_>`
+  --> $DIR/ambiguous-pass.rs:18:1
+   |
+LL | impl<T: Trait> NoOverlap for T {}
+   | ------------------------------ first implementation here
+LL |
+LL | impl<T: Trait<Assoc = ()>> NoOverlap for W<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `W<_>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0119`.
diff --git a/tests/ui/traits/next-solver/overflow/exponential-trait-goals.rs b/tests/ui/traits/next-solver/overflow/exponential-trait-goals.rs
index 052d803765d..186d0e8be56 100644
--- a/tests/ui/traits/next-solver/overflow/exponential-trait-goals.rs
+++ b/tests/ui/traits/next-solver/overflow/exponential-trait-goals.rs
@@ -15,5 +15,5 @@ fn impls<T: Trait>() {}
 
 fn main() {
     impls::<W<_>>();
-    //~^ ERROR overflow evaluating the requirement `_: Sized`
+    //~^ ERROR overflow evaluating the requirement `W<_>: Trait`
 }
diff --git a/tests/ui/traits/next-solver/overflow/exponential-trait-goals.stderr b/tests/ui/traits/next-solver/overflow/exponential-trait-goals.stderr
index 6583cae8bb9..b032ae3e740 100644
--- a/tests/ui/traits/next-solver/overflow/exponential-trait-goals.stderr
+++ b/tests/ui/traits/next-solver/overflow/exponential-trait-goals.stderr
@@ -1,16 +1,9 @@
-error[E0275]: overflow evaluating the requirement `_: Sized`
+error[E0275]: overflow evaluating the requirement `W<_>: Trait`
   --> $DIR/exponential-trait-goals.rs:17:13
    |
 LL |     impls::<W<_>>();
    |             ^^^^
    |
-note: required for `W<(W<_>, W<_>)>` to implement `Trait`
-  --> $DIR/exponential-trait-goals.rs:7:12
-   |
-LL | impl<T, U> Trait for W<(W<T>, W<U>)>
-   |      -     ^^^^^     ^^^^^^^^^^^^^^^
-   |      |
-   |      unsatisfied trait bound introduced here
 note: required by a bound in `impls`
   --> $DIR/exponential-trait-goals.rs:14:13
    |
diff --git a/tests/ui/traits/next-solver/overflow/global-cache.stderr b/tests/ui/traits/next-solver/overflow/global-cache.stderr
index 9e467721e83..67616619384 100644
--- a/tests/ui/traits/next-solver/overflow/global-cache.stderr
+++ b/tests/ui/traits/next-solver/overflow/global-cache.stderr
@@ -5,15 +5,6 @@ LL |     impls_trait::<Four<Four<Four<Four<()>>>>>();
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "18"]` attribute to your crate (`global_cache`)
-note: required for `Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<()>>>>>>>>>>>` to implement `Trait`
-  --> $DIR/global-cache.rs:12:16
-   |
-LL | impl<T: Trait> Trait for Inc<T> {}
-   |         -----  ^^^^^     ^^^^^^
-   |         |
-   |         unsatisfied trait bound introduced here
-   = note: 5 redundant requirements hidden
-   = note: required for `Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<Inc<()>>>>>>>>>>>>>>>>` to implement `Trait`
 note: required by a bound in `impls_trait`
   --> $DIR/global-cache.rs:15:19
    |