add ice test for 46511

Fixes #46511

src/test/ui/const-generics/issue-46511.rs

@@ -0,0 +1,8 @@
+// check-fail
+
+struct Foo<'a> //~ ERROR parameter `'a` is never used [E0392]
+{
+    _a: [u8; std::mem::size_of::<&'a mut u8>()] //~ ERROR  a non-static lifetime is not allowed in a `const`
+}
+
+pub fn main() {}

src/test/ui/const-generics/issue-46511.stderr

@@ -0,0 +1,21 @@
+error[E0658]: a non-static lifetime is not allowed in a `const`
+  --> $DIR/issue-46511.rs:5:35
+   |
+LL |     _a: [u8; std::mem::size_of::<&'a mut u8>()]
+   |                                   ^^
+   |
+   = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
+   = help: add `#![feature(generic_const_exprs)]` to the crate attributes to enable
+
+error[E0392]: parameter `'a` is never used
+  --> $DIR/issue-46511.rs:3:12
+   |
+LL | struct Foo<'a>
+   |            ^^ unused parameter
+   |
+   = help: consider removing `'a`, referring to it in a field, or using a marker such as `PhantomData`
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0392, E0658.
+For more information about an error, try `rustc --explain E0392`.