add and move trait solver cycle tests

Author: lcnr

tests/ui/traits/new-solver/runaway-impl-candidate-selection.rs renamed to tests/ui/traits/new-solver/assembly/runaway-impl-candidate-selection.rs

@@ -0,0 +1,37 @@
+// compile-flags: -Ztrait-solver=next
+#![feature(rustc_attrs)]
+
+// Test that having both an inductive and a coinductive cycle
+// is handled correctly.
+
+#[rustc_coinductive]
+trait Trait {}
+impl<T: Inductive + Coinductive> Trait for T {}
+
+trait Inductive {}
+impl<T: Trait> Inductive for T {}
+#[rustc_coinductive]
+trait Coinductive {}
+impl<T: Trait> Coinductive for T {}
+
+fn impls_trait<T: Trait>() {}
+
+#[rustc_coinductive]
+trait TraitRev {}
+impl<T: CoinductiveRev + InductiveRev> TraitRev for T {}
+
+trait InductiveRev {}
+impl<T: TraitRev> InductiveRev for T {}
+#[rustc_coinductive]
+trait CoinductiveRev {}
+impl<T: TraitRev> CoinductiveRev for T {}
+
+fn impls_trait_rev<T: TraitRev>() {}
+
+fn main() {
+    impls_trait::<()>();
+    //~^ ERROR overflow evaluating the requirement
+
+    impls_trait_rev::<()>();
+    //~^ ERROR overflow evaluating the requirement
+}

tests/ui/traits/new-solver/runaway-impl-candidate-selection.stderr renamed to tests/ui/traits/new-solver/assembly/runaway-impl-candidate-selection.stderr

@@ -0,0 +1,29 @@
+error[E0275]: overflow evaluating the requirement `(): Trait`
+  --> $DIR/double-cycle-inductive-coinductive.rs:32:5
+   |
+LL |     impls_trait::<()>();
+   |     ^^^^^^^^^^^^^^^^^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`double_cycle_inductive_coinductive`)
+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 `(): TraitRev`
+  --> $DIR/double-cycle-inductive-coinductive.rs:35:5
+   |
+LL |     impls_trait_rev::<()>();
+   |     ^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`double_cycle_inductive_coinductive`)
+note: required by a bound in `impls_trait_rev`
+  --> $DIR/double-cycle-inductive-coinductive.rs:29:23
+   |
+LL | fn impls_trait_rev<T: TraitRev>() {}
+   |                       ^^^^^^^^ required by this bound in `impls_trait_rev`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0275`.

tests/ui/traits/new-solver/coinduction/fixpoint-exponential-growth.rs renamed to tests/ui/traits/new-solver/cycles/coinduction/fixpoint-exponential-growth.rs

@@ -0,0 +1,48 @@
+// compile-flags: -Ztrait-solver=next
+#![feature(trivial_bounds, marker_trait_attr)]
+#![allow(trivial_bounds)]
+// This previously triggered a bug in the provisional cache.
+//
+// This has the proof tree
+// - `MultipleCandidates: Trait` proven via impl-one
+//   - `MultipleNested: Trait` via impl
+//     - `MultipleCandidates: Trait` (inductive cycle ~> OVERFLOW)
+//     - `DoesNotImpl: Trait` (ERR)
+// - `MultipleCandidates: Trait` proven via impl-two
+//   - `MultipleNested: Trait` (in provisional cache ~> OVERFLOW)
+//
+// We previously incorrectly treated the `MultipleCandidates: Trait` as
+// overflow because it was in the cache and reached via an inductive cycle.
+// It should be `NoSolution`.
+
+struct MultipleCandidates;
+struct MultipleNested;
+struct DoesNotImpl;
+
+#[marker]
+trait Trait {}
+
+// impl-one
+impl Trait for MultipleCandidates
+where
+    MultipleNested: Trait
+{}
+
+// impl-two
+impl Trait for MultipleCandidates
+where
+    MultipleNested: Trait,
+{}
+
+impl Trait for MultipleNested
+where
+    MultipleCandidates: Trait,
+    DoesNotImpl: Trait,
+{}
+
+fn impls_trait<T: Trait>() {}
+
+fn main() {
+    impls_trait::<MultipleCandidates>();
+    //~^ ERROR the trait bound `MultipleCandidates: Trait` is not satisfied
+}

tests/ui/traits/new-solver/coinduction/fixpoint-exponential-growth.stderr renamed to tests/ui/traits/new-solver/cycles/coinduction/fixpoint-exponential-growth.stderr

@@ -0,0 +1,16 @@
+error[E0277]: the trait bound `MultipleCandidates: Trait` is not satisfied
+  --> $DIR/inductive-cycle-but-err.rs:46:19
+   |
+LL |     impls_trait::<MultipleCandidates>();
+   |                   ^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `MultipleCandidates`
+   |
+   = help: the trait `Trait` is implemented for `MultipleCandidates`
+note: required by a bound in `impls_trait`
+  --> $DIR/inductive-cycle-but-err.rs:43:19
+   |
+LL | fn impls_trait<T: Trait>() {}
+   |                   ^^^^^ required by this bound in `impls_trait`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.