Rollup merge of #88602 - BoxyUwU:tests-uwu-nya, r=lcnr

Add tests for some const generics issues

closes #82956
closes #84659
closes #86530
closes #86535

there is also a random test in here about array repeat expressions that I already had on this branch but it seems to fit the theme of this PR so kept it...

r? `@lcnr`

src/test/ui/const-generics/issues/issue-82956.rs

+#![feature(generic_const_exprs, array_map)]
+#![allow(incomplete_features)]
+
+pub struct ConstCheck<const CHECK: bool>;
+
+pub trait True {}
+impl True for ConstCheck<true> {}
+
+pub trait OrdesDec {
+    type Newlen;
+    type Output;
+
+    fn pop(self) -> (Self::Newlen, Self::Output);
+}
+
+impl<T, const N: usize> OrdesDec for [T; N]
+where
+    ConstCheck<{N > 1}>: True,
+    [T; N - 1]: Sized,
+{
+    type Newlen = [T; N - 1];
+    type Output = T;
+
+    fn pop(self) -> (Self::Newlen, Self::Output) {
+        let mut iter = IntoIter::new(self);
+        //~^ ERROR: failed to resolve: use of undeclared type `IntoIter`
+        let end = iter.next_back().unwrap();
+        let new = [(); N - 1].map(move |()| iter.next().unwrap());
+        (new, end)
+    }
+}
+
+fn main() {}

src/test/ui/const-generics/issues/issue-82956.stderr

+error[E0433]: failed to resolve: use of undeclared type `IntoIter`
+  --> $DIR/issue-82956.rs:25:24
+   |
+LL |         let mut iter = IntoIter::new(self);
+   |                        ^^^^^^^^ not found in this scope
+   |
+help: consider importing one of these items
+   |
+LL | use std::array::IntoIter;
+   |
+LL | use std::collections::binary_heap::IntoIter;
+   |
+LL | use std::collections::btree_map::IntoIter;
+   |
+LL | use std::collections::btree_set::IntoIter;
+   |
+     and 8 other candidates
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0433`.

src/test/ui/const-generics/issues/issue-84659.rs

+#![allow(incomplete_features)]
+#![feature(generic_const_exprs)]
+
+trait Bar<const N: usize> {}
+
+trait Foo<'a> {
+    const N: usize;
+    type Baz: Bar<{ Self::N }>;
+    //~^ ERROR: unconstrained generic constant
+}
+
+fn main() {}

src/test/ui/const-generics/issues/issue-84659.stderr

+error: unconstrained generic constant
+  --> $DIR/issue-84659.rs:8:15
+   |
+LL |     type Baz: Bar<{ Self::N }>;
+   |               ^^^^^^^^^^^^^^^^
+   |
+   = help: try adding a `where` bound using this expression: `where [(); { Self::N }]:`
+
+error: aborting due to previous error
+

src/test/ui/const-generics/issues/issue-86530.rs

+#![feature(generic_const_exprs)]
+#![allow(incomplete_features)]
+
+pub trait X {
+    const Y: usize;
+}
+
+fn z<T>(t: T)
+where
+    T: X,
+    [(); T::Y]: ,
+{
+}
+
+fn unit_literals() {
+    z(" ");
+    //~^ ERROR: the trait bound `&str: X` is not satisfied
+}
+
+fn main() {}

src/test/ui/const-generics/issues/issue-86530.stderr

+error[E0277]: the trait bound `&str: X` is not satisfied
+  --> $DIR/issue-86530.rs:16:7
+   |
+LL |     z(" ");
+   |       ^^^ the trait `X` is not implemented for `&str`
+   |
+note: required by a bound in `z`
+  --> $DIR/issue-86530.rs:10:8
+   |
+LL | fn z<T>(t: T)
+   |    - required by a bound in this
+LL | where
+LL |     T: X,
+   |        ^ required by this bound in `z`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/const-generics/issues/issue-86535-2.rs

+// run-pass
+#![feature(adt_const_params, generic_const_exprs)]
+#![allow(incomplete_features)]
+
+pub trait Foo {
+    const ASSOC_C: usize;
+    fn foo() where [(); Self::ASSOC_C]:;
+}
+
+struct Bar<const N: &'static ()>;
+impl<const N: &'static ()> Foo for Bar<N> {
+    const ASSOC_C: usize = 3;
+
+    fn foo() where [u8; Self::ASSOC_C]: {
+        let _: [u8; Self::ASSOC_C] = loop {};
+    }
+}
+
+fn main() {}

src/test/ui/const-generics/issues/issue-86535.rs

+// run-pass
+#![feature(adt_const_params, generic_const_exprs)]
+#![allow(incomplete_features, unused_variables)]
+
+struct F<const S: &'static str>;
+impl<const S: &'static str> X for F<{ S }> {
+    const W: usize = 3;
+
+    fn d(r: &[u8; Self::W]) -> F<{ S }> {
+        let x: [u8; Self::W] = [0; Self::W];
+        F
+    }
+}
+
+pub trait X {
+    const W: usize;
+    fn d(r: &[u8; Self::W]) -> Self;
+}
+
+fn main() {}

src/test/ui/const-generics/sneaky-array-repeat-expr.rs

+trait Trait<const N: usize> {
+    const Assoc: usize;
+}
+
+impl<const N: usize> Trait<N> for () {
+    const Assoc: usize = 1;
+}
+
+
+pub const fn foo<const N: usize>() where (): Trait<N> {
+    let bar = [(); <()>::Assoc];
+    //~^ error: constant expression depends on a generic parameter
+}
+
+trait Trait2<const N: usize> {
+    const Assoc2: usize;
+}
+
+impl<const N: usize> Trait2<N> for () {
+    const Assoc2: usize = N - 1;
+}
+
+
+pub const fn foo2<const N: usize>() where (): Trait2<N> {
+    let bar2 = [(); <()>::Assoc2];
+    //~^ error: constant expression depends on a generic parameter
+}
+
+fn main() {
+    foo::<0>();
+    foo2::<0>();
+}

src/test/ui/const-generics/sneaky-array-repeat-expr.stderr

+error: constant expression depends on a generic parameter
+  --> $DIR/sneaky-array-repeat-expr.rs:11:20
+   |
+LL |     let bar = [(); <()>::Assoc];
+   |                    ^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: constant expression depends on a generic parameter
+  --> $DIR/sneaky-array-repeat-expr.rs:25:21
+   |
+LL |     let bar2 = [(); <()>::Assoc2];
+   |                     ^^^^^^^^^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to 2 previous errors
+