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+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date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() {}

tests/crashes/133066.rs

@@ -0,0 +1,58 @@
+error[E0277]: the trait bound `(dyn Sized + 'static): ConstDefault` is not satisfied
+  --> $DIR/wf_before_evaluate-2.rs:14:14
+   |
+LL | fn user() -> impl Owner<dyn Sized, C = 0> {}
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `ConstDefault` is not implemented for `(dyn Sized + 'static)`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/wf_before_evaluate-2.rs:10:1
+   |
+LL | trait ConstDefault {
+   | ^^^^^^^^^^^^^^^^^^
+note: required for `()` to implement `Owner<(dyn Sized + 'static)>`
+  --> $DIR/wf_before_evaluate-2.rs:6:23
+   |
+LL | impl<K: ConstDefault> Owner<K> for () {
+   |         ------------  ^^^^^^^^     ^^
+   |         |
+   |         unsatisfied trait bound introduced here
+
+error[E0277]: the size for values of type `(dyn Sized + 'static)` cannot be known at compilation time
+  --> $DIR/wf_before_evaluate-2.rs:14:14
+   |
+LL | fn user() -> impl Owner<dyn Sized, C = 0> {}
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Sized + 'static)`
+   = help: the trait `Owner<K>` is implemented for `()`
+note: required for `()` to implement `Owner<(dyn Sized + 'static)>`
+  --> $DIR/wf_before_evaluate-2.rs:6:23
+   |
+LL | impl<K: ConstDefault> Owner<K> for () {
+   |      -                ^^^^^^^^     ^^
+   |      |
+   |      unsatisfied trait bound introduced here
+
+error[E0038]: the trait `Sized` is not dyn compatible
+  --> $DIR/wf_before_evaluate-2.rs:14:40
+   |
+LL | fn user() -> impl Owner<dyn Sized, C = 0> {}
+   |                                        ^ `Sized` is not dyn compatible
+   |
+   = note: the trait is not dyn compatible because it requires `Self: Sized`
+   = note: for a trait to be dyn compatible it needs to allow building a vtable
+           for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
+
+error[E0308]: mismatched types
+  --> $DIR/wf_before_evaluate-2.rs:14:40
+   |
+LL | fn user() -> impl Owner<dyn Sized, C = 0> {}
+   |                                        ^ expected `dyn Sized`, found integer
+   |
+   = note: expected trait object `(dyn Sized + 'static)`
+                      found type `{integer}`
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0038, E0277, E0308.
+For more information about an error, try `rustc --explain E0038`.

tests/crashes/133199.rs

@@ -0,0 +1,24 @@
+#![feature(associated_const_equality, generic_const_items)]
+#![expect(incomplete_features)]
+
+// When we type check `main` we wind up having to prove `<() as Trait>::C<128_u64> = 128_u64`
+// doing this requires normalizing `<() as Trait>::C<128_u64>`. Previously we did not check
+// that consts are well formed before evaluating them (rust-lang/project-const-generics#37) so
+// in attempting to get the normalized form of `<() as Trait>::C<128_u64>` we would invoke the
+// ctfe machinery on a not-wf type system constant.
+
+trait Trait {
+    const C<const N: u32>: u32;
+}
+
+impl Trait for () {
+    const C<const N: u32>: u32 = N;
+}
+
+fn ice<const N: u64, T: Trait<C<N> = { N }>>(_: T) {}
+//~^ ERROR: the constant `N` is not of type `u32`
+
+fn main() {
+    ice::<128, _>(());
+    //~^ ERROR: type mismatch resolving `<() as Trait>::C<128> == 128`
+}

tests/crashes/136894.rs

@@ -0,0 +1,31 @@
+error: the constant `N` is not of type `u32`
+  --> $DIR/wf_before_evaluate.rs:18:31
+   |
+LL | fn ice<const N: u64, T: Trait<C<N> = { N }>>(_: T) {}
+   |                               ^^^^^^^^^^^^ expected `u32`, found `u64`
+   |
+note: required by a const generic parameter in `Trait::C`
+  --> $DIR/wf_before_evaluate.rs:11:13
+   |
+LL |     const C<const N: u32>: u32;
+   |             ^^^^^^^^^^^^ required by this const generic parameter in `Trait::C`
+
+error[E0271]: type mismatch resolving `<() as Trait>::C<128> == 128`
+  --> $DIR/wf_before_evaluate.rs:22:19
+   |
+LL |     ice::<128, _>(());
+   |     ------------- ^^ expected `128`, found `<() as Trait>::C::<128>`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = note: expected constant `128`
+              found constant `<() as Trait>::C::<128>`
+note: required by a bound in `ice`
+  --> $DIR/wf_before_evaluate.rs:18:31
+   |
+LL | fn ice<const N: u64, T: Trait<C<N> = { N }>>(_: T) {}
+   |                               ^^^^^^^^^^^^ required by this bound in `ice`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0271`.

tests/crashes/137813.rs

@@ -23,6 +23,9 @@ where
     for<'a> (): Unimplemented<'a>,
 {
     let _a: [(); 1] = [(); <u8 as Trait<()>>::ASSOC];
+    //~^ WARN: cannot use constants which depend on trivially-false where clauses
+    //~| WARN: this was previously accepted by the compiler
+    //~^^^ ERROR: mismatched types
 }
 
 struct Foo<const N: usize>;

tests/ui/const-generics/associated_const_equality/unconstrained_impl_param.rs

@@ -1,5 +1,23 @@
+warning: cannot use constants which depend on trivially-false where clauses
+  --> $DIR/impossible_preds_repeat_expr_hack.rs:25:28
+   |
+LL |     let _a: [(); 1] = [(); <u8 as Trait<()>>::ASSOC];
+   |                            ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #76200 <https://github.com/rust-lang/rust/issues/76200>
+   = note: `#[warn(const_evaluatable_unchecked)]` on by default
+
+error[E0308]: mismatched types
+  --> $DIR/impossible_preds_repeat_expr_hack.rs:25:23
+   |
+LL |     let _a: [(); 1] = [(); <u8 as Trait<()>>::ASSOC];
+   |             -------   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected an array with a size of 1, found one with a size of <u8 as Trait<()>>::ASSOC
+   |             |
+   |             expected due to this
+
 error[E0277]: the trait bound `for<'a> (): Unimplemented<'a>` is not satisfied
-  --> $DIR/impossible_preds_repeat_expr_hack.rs:34:43
+  --> $DIR/impossible_preds_repeat_expr_hack.rs:37:43
    |
 LL |     let _a: Foo<1> = Foo::<{ <u8 as Trait<()>>::ASSOC }>;
    |                                           ^^ the trait `for<'a> Unimplemented<'a>` is not implemented for `()`
@@ -19,7 +37,7 @@ LL |     const ASSOC: usize;
    |           ----- required by a bound in this associated constant
 
 error[E0277]: the trait bound `for<'a> (): Unimplemented<'a>` is not satisfied
-  --> $DIR/impossible_preds_repeat_expr_hack.rs:34:31
+  --> $DIR/impossible_preds_repeat_expr_hack.rs:37:31
    |
 LL |     let _a: Foo<1> = Foo::<{ <u8 as Trait<()>>::ASSOC }>;
    |                               ^^ the trait `for<'a> Unimplemented<'a>` is not implemented for `()`
@@ -38,6 +56,7 @@ LL | where
 LL |     for<'a> T: Unimplemented<'a>,
    |                ----------------- unsatisfied trait bound introduced here
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors; 1 warning emitted
 
-For more information about this error, try `rustc --explain E0277`.
+Some errors have detailed explanations: E0277, E0308.
+For more information about an error, try `rustc --explain E0277`.

tests/ui/const-generics/associated_const_equality/unconstrained_impl_param.stderr

@@ -1,9 +1,9 @@
 #![allow(incomplete_features)]
 #![feature(generic_const_exprs)]
 
-pub struct FixedBitSet<const N: usize>;
+pub struct Foo<const N: usize>;
 
-impl<const N: usize> FixedBitSet<N>
+impl<const N: usize> Foo<N>
 where
     [u8; N.div_ceil(8)]: Sized,
 {

tests/ui/const-generics/associated_const_equality/wf_before_evaluate-2.rs

@@ -0,0 +1,10 @@
+//@ check-pass
+//@ aux-build: cross-crate-2.rs
+
+extern crate cross_crate_2;
+
+use cross_crate_2::Foo;
+
+fn main() {
+    Foo::<7>::new();
+}