add regression test for rust-lang#73491

Author: lcnr

src/test/ui/const-generics/issues/issue-73491.rs

@@ -0,0 +1,9 @@
+// check-pass
+#![feature(const_generics)]
+#![allow(incomplete_features)]
+
+const LEN: usize = 1024;
+
+fn hoge<const IN: [u32; LEN]>() {}
+
+fn main() {}