Add test case for #119778

Author: Nadrieril

tests/ui/pattern/usefulness/issue-119778-type-error-ice.rs

@@ -0,0 +1,13 @@
+fn main() {}
+
+fn foo() {
+    #[derive(Copy, Clone)]
+    struct Foo([u8; S]);
+    //~^ ERROR cannot find value `S`
+    //~| ERROR cannot find value `S`
+
+    type U = impl Copy;
+    //~^ ERROR `impl Trait` in type aliases is unstable
+    let foo: U = Foo(());
+    let Foo(()) = foo;
+}

tests/ui/pattern/usefulness/issue-119778-type-error-ice.stderr

@@ -0,0 +1,35 @@
+error[E0425]: cannot find value `S` in this scope
+  --> $DIR/issue-119778-type-error-ice.rs:5:21
+   |
+LL |     struct Foo([u8; S]);
+   |                     ^ not found in this scope
+   |
+help: you might be missing a const parameter
+   |
+LL |     struct Foo<const S: /* Type */>([u8; S]);
+   |               +++++++++++++++++++++
+
+error[E0425]: cannot find value `S` in this scope
+  --> $DIR/issue-119778-type-error-ice.rs:5:21
+   |
+LL |     struct Foo([u8; S]);
+   |                     ^ not found in this scope
+   |
+help: you might be missing a const parameter
+   |
+LL |     struct Foo<const S: /* Type */>([u8; S]);
+   |               +++++++++++++++++++++
+
+error[E0658]: `impl Trait` in type aliases is unstable
+  --> $DIR/issue-119778-type-error-ice.rs:9:14
+   |
+LL |     type U = impl Copy;
+   |              ^^^^^^^^^
+   |
+   = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
+   = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0425, E0658.
+For more information about an error, try `rustc --explain E0425`.