add regression test for #71169

Author: lcnr

src/test/ui/const-generics/issues/issue-71169.rs

@@ -0,0 +1,10 @@
+#![feature(const_generics)]
+#![allow(incomplete_features)]
+
+fn foo<const LEN: usize, const DATA: [u8; LEN]>() {}
+//~^ ERROR the type of const parameters must not
+fn main() {
+    const DATA: [u8; 4] = *b"ABCD";
+    foo::<4, DATA>();
+    //~^ ERROR constant expression depends on
+}

src/test/ui/const-generics/issues/issue-71169.stderr

@@ -0,0 +1,17 @@
+error[E0770]: the type of const parameters must not depend on other generic parameters
+  --> $DIR/issue-71169.rs:4:43
+   |
+LL | fn foo<const LEN: usize, const DATA: [u8; LEN]>() {}
+   |                                           ^^^ the type must not depend on the parameter `LEN`
+
+error: constant expression depends on a generic parameter
+  --> $DIR/issue-71169.rs:8:14
+   |
+LL |     foo::<4, DATA>();
+   |              ^^^^
+   |
+   = note: this may fail depending on what value the parameter takes
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0770`.