add a test for rust-lang#70408

Author: TaKO8Ki

src/test/ui/const-generics/issue-70408.rs

@@ -0,0 +1,13 @@
+// build-pass
+
+#![feature(adt_const_params)]
+#![allow(incomplete_features)]
+
+pub fn function_with_bytes<const BYTES: &'static [u8; 4]>() -> &'static [u8] {
+    BYTES
+}
+
+pub fn main() {
+    assert_eq!(function_with_bytes::<b"AAAA">(), &[0x41, 0x41, 0x41, 0x41]);
+    assert_eq!(function_with_bytes::<{ &[0x41, 0x41, 0x41, 0x41] }>(), b"AAAA");
+}