Add regression test for rust-lang#61422

Author: varkor

src/test/ui/const-generics/issue-61422.rs

@@ -0,0 +1,15 @@
+// run-pass
+
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+use std::mem;
+
+fn foo<const SIZE: usize>() {
+    let arr: [u8; SIZE] = unsafe {
+        let mut array: [u8; SIZE] = mem::uninitialized();
+        array
+    };
+}
+
+fn main() {}

src/test/ui/const-generics/issue-61422.stderr

@@ -0,0 +1,6 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/issue-61422.rs:3:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+