Add error for const parameters depending on type parameters

Co-Authored-By: Gabriel Smith <yodaldevoid@users.noreply.github.com>

src/librustc_resolve/diagnostics.rs

@@ -414,8 +414,8 @@ https://doc.rust-lang.org/reference.html#use-declarations
 "##,
 
 E0401: r##"
-Inner items do not inherit type parameters from the functions they are embedded
+Inner items do not inherit type or const parameters from the functions
-in.
+they are embedded in.
 
 Erroneous code example:
 
@@ -1642,6 +1642,17 @@ fn main() {
 ```
 "##,
 
+E0670: r##"
+Const parameters cannot depend on type parameters.
+The following is therefore invalid:
+
+```
+fn const_id<T, const N: T>() -> T {
+    N
+}
+```
+"##,
+
 }
 
 register_diagnostics! {