add more tests

src/test/ui/const-generics/unused-substs/unused-substs-1.rs

@@ -0,0 +1,12 @@
+#![feature(const_generics)] //~ WARN the feature `const_generics` is incomplete
+trait Bar<const M: usize> {}
+impl<const N: usize> Bar<N> for A<{ 6 + 1 }> {}
+
+struct A<const N: usize>
+where
+    A<N>: Bar<N>;
+
+fn main() {
+    let _ = A;
+    //~^ ERROR mismatched types
+}

src/test/ui/const-generics/unused-substs/unused-substs-2.rs

@@ -0,0 +1,26 @@
+#![feature(const_generics)] //~ WARN the feature `const_generics` is incomplete
+
+// The goal is is to get an unevaluated const `ct` with a `Ty::Infer(TyVar(_#1t)` subst.
+//
+// If we are then able to infer `ty::Infer(TyVar(_#1t) := Ty<ct>` we introduced an
+// artificial inference cycle.
+struct Foo<const N: usize>;
+
+trait Bind<T> {
+    fn bind() -> (T, Self);
+}
+
+// `N` has to be `ConstKind::Unevaluated`.
+impl<T> Bind<T> for Foo<{ 6 + 1 }> {
+    fn bind() -> (T, Self) {
+        (panic!(), Foo)
+    }
+}
+
+fn main() {
+    let (mut t, foo) = Foo::bind();
+    // `t` is `ty::Infer(TyVar(_#1t))`
+    // `foo` contains `ty::Infer(TyVar(_#1t))` in its substs
+    t = foo;
+    //~^ ERROR mismatched types
+}

src/test/ui/const-generics/unused-substs/unused-substs-2.stderr

@@ -0,0 +1,18 @@
+warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/unused-substs-2.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
+
+error[E0308]: mismatched types
+  --> $DIR/unused-substs-2.rs:24:9
+   |
+LL |     t = foo;
+   |         ^^^ cyclic type of infinite size
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/const-generics/unused-substs/unused-substs-3.rs

@@ -0,0 +1,18 @@
+
+#![feature(const_generics)] //~ WARN the feature `const_generics` is incomplete
+
+// The goal is is to get an unevaluated const `ct` with a `Ty::Infer(TyVar(_#1t)` subst.
+//
+// If we are then able to infer `ty::Infer(TyVar(_#1t) := Ty<ct>` we introduced an
+// artificial inference cycle.
+fn bind<T>() -> (T, [u8; 6 + 1]) {
+    todo!()
+} 
+
+fn main() {
+    let (mut t, foo) = bind();
+    // `t` is `ty::Infer(TyVar(_#1t))`
+    // `foo` contains `ty::Infer(TyVar(_#1t))` in its substs
+    t = foo;
+    //~^ ERROR mismatched types
+}

src/test/ui/const-generics/unused-substs/unused-substs-3.stderr

@@ -0,0 +1,21 @@
+warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/unused-substs-3.rs:2:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
+
+error[E0308]: mismatched types
+  --> $DIR/unused-substs-3.rs:16:9
+   |
+LL |     t = foo;
+   |         ^^^
+   |         |
+   |         cyclic type of infinite size
+   |         help: try using a conversion method: `foo.to_vec()`
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0308`.