Bless (and add) some tests

Author: BoxyUwU

tests/crashes/127643.rs

@@ -0,0 +1,26 @@
+// regression test for #137813 where we would assume all constants in the type system
+// cannot contain inference variables, even though associated const equality syntax
+// was still lowered without the feature gate enabled.
+
+trait AssocConst {
+    const A: u8;
+}
+
+impl<T> AssocConst for (T,) {
+    const A: u8 = 0;
+}
+
+trait Trait {}
+
+impl<U> Trait for () where (U,): AssocConst<A = { 0 }> {}
+//~^ ERROR associated const equality is incomplete
+//~| ERROR the type parameter `U` is not constrained by the impl trait
+
+fn foo()
+where
+    (): Trait,
+    //~^ ERROR type mismatch resolving
+{
+}
+
+fn main() {}

tests/crashes/131046.rs

@@ -0,0 +1,39 @@
+error[E0658]: associated const equality is incomplete
+  --> $DIR/unconstrained_impl_param.rs:15:45
+   |
+LL | impl<U> Trait for () where (U,): AssocConst<A = { 0 }> {}
+   |                                             ^^^^^^^^^
+   |
+   = note: see issue #92827 <https://github.com/rust-lang/rust/issues/92827> for more information
+   = help: add `#![feature(associated_const_equality)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0207]: the type parameter `U` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unconstrained_impl_param.rs:15:6
+   |
+LL | impl<U> Trait for () where (U,): AssocConst<A = { 0 }> {}
+   |      ^ unconstrained type parameter
+
+error[E0271]: type mismatch resolving `<(_,) as AssocConst>::A == 0`
+  --> $DIR/unconstrained_impl_param.rs:21:5
+   |
+LL |     (): Trait,
+   |     ^^^^^^^^^ expected `0`, found `<(_,) as AssocConst>::A`
+   |
+   = note: expected constant `0`
+              found constant `<(_,) as AssocConst>::A`
+note: required for `()` to implement `Trait`
+  --> $DIR/unconstrained_impl_param.rs:15:9
+   |
+LL | impl<U> Trait for () where (U,): AssocConst<A = { 0 }> {}
+   |         ^^^^^     ^^                        --------- unsatisfied trait bound introduced here
+   = help: see issue #48214
+help: add `#![feature(trivial_bounds)]` to the crate attributes to enable
+   |
+LL + #![feature(trivial_bounds)]
+   |
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0207, E0271, E0658.
+For more information about an error, try `rustc --explain E0207`.

tests/crashes/131406.rs

@@ -0,0 +1,20 @@
+#![feature(associated_const_equality)]
+
+trait Owner<K> {
+    const C: K;
+}
+impl<K: ConstDefault> Owner<K> for () {
+    const C: K = K::DEFAULT;
+}
+
+trait ConstDefault {
+    const DEFAULT: Self;
+}
+
+fn user() -> impl Owner<dyn Sized, C = 0> {}
+//~^ ERROR: the trait bound `(dyn Sized + 'static): ConstDefault` is not satisfied
+//~| ERROR: the size for values of type `(dyn Sized + 'static)` cannot be known at compilation time
+//~| ERROR: the trait `Sized` is not dyn compatible
+//~| ERROR: mismatched types
+
+fn main() {}