rustdoc: add a couple of regression tests

tests/rustdoc-ui/synthetic-auto-trait-impls/const-in-super-trait-and-item-bound.rs

@@ -0,0 +1,23 @@
+// We used to ICE here while trying to synthesize auto trait impls.
+// issue: 107715
+//@ check-pass
+
+pub const N: usize = 1;
+
+pub struct MapType<K: Supertrait<V>, V> {
+    _array: K::Array,
+}
+
+pub trait Subtrait: Supertrait<[u8; N]> {}
+
+pub trait Supertrait<V> {
+    type Array: AnotherTrait<V>;
+}
+
+pub trait AnotherTrait<V> {
+    const LENGTH: usize;
+}
+
+pub struct Container<S: Subtrait> {
+    _x: MapType<S, [u8; N]>,
+}

tests/rustdoc-ui/synthetic-auto-trait-impls/projections-in-super-trait-bound-unsatisfied.rs

@@ -0,0 +1,18 @@
+// We used to ICE here while trying to synthesize auto trait impls.
+// issue: 114657
+
+pub trait Foo {
+    type FooType;
+}
+
+pub trait Bar<const A: usize>: Foo<FooType = <Self as Bar<A>>::BarType> {
+    type BarType;
+}
+
+pub(crate) const B: usize = 5;
+
+pub trait Tec: Bar<B> {}
+
+pub struct Structure<C: Tec> { //~ ERROR the trait bound `C: Bar<5>` is not satisfied
+    _field: C::BarType, //~ ERROR the trait bound `C: Bar<5>` is not satisfied
+}

tests/rustdoc-ui/synthetic-auto-trait-impls/projections-in-super-trait-bound-unsatisfied.stderr

@@ -0,0 +1,25 @@
+error[E0277]: the trait bound `C: Bar<5>` is not satisfied
+  --> $DIR/projections-in-super-trait-bound-unsatisfied.rs:16:1
+   |
+LL | pub struct Structure<C: Tec> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Bar<5>` is not implemented for `C`
+   |
+help: consider further restricting this bound
+   |
+LL | pub struct Structure<C: Tec + Bar<5>> {
+   |                             ++++++++
+
+error[E0277]: the trait bound `C: Bar<5>` is not satisfied
+  --> $DIR/projections-in-super-trait-bound-unsatisfied.rs:17:13
+   |
+LL |     _field: C::BarType,
+   |             ^^^^^^^^^^ the trait `Bar<5>` is not implemented for `C`
+   |
+help: consider further restricting this bound
+   |
+LL | pub struct Structure<C: Tec + Bar<5>> {
+   |                             ++++++++
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

tests/rustdoc-ui/synthetic-auto-trait-impls/unconstrained-param-in-impl-ambiguity.rs

@@ -0,0 +1,10 @@
+// We used to ICE here while trying to synthesize auto trait impls.
+// issue: 112828
+
+struct Outer(Inner);
+struct Inner;
+
+unsafe impl<Q: Trait> Send for Inner {}
+//~^ ERROR the type parameter `Q` is not constrained by the impl trait, self type, or predicates
+
+trait Trait {}

tests/rustdoc-ui/synthetic-auto-trait-impls/unconstrained-param-in-impl-ambiguity.stderr

@@ -0,0 +1,9 @@
+error[E0207]: the type parameter `Q` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unconstrained-param-in-impl-ambiguity.rs:7:13
+   |
+LL | unsafe impl<Q: Trait> Send for Inner {}
+   |             ^ unconstrained type parameter
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0207`.