Disallow shadowing const parameters

src/test/ui/resolve/issue-85348.rs

@@ -0,0 +1,12 @@
+// Checks whether shadowing a const parameter leads to an ICE (#85348).
+
+impl<const N: usize> ArrayWindowsExample {
+//~^ ERROR: cannot find type `ArrayWindowsExample` in this scope [E0412]
+    fn next() {
+        let mut N;
+        //~^ ERROR: let bindings cannot shadow const parameters [E0530]
+        //~| ERROR: type annotations needed [E0282]
+    }
+}
+
+fn main() {}

src/test/ui/resolve/issue-85348.stderr

@@ -0,0 +1,25 @@
+error[E0530]: let bindings cannot shadow const parameters
+  --> $DIR/issue-85348.rs:6:17
+   |
+LL | impl<const N: usize> ArrayWindowsExample {
+   |            - the const parameter `N` is defined here
+...
+LL |         let mut N;
+   |                 ^ cannot be named the same as a const parameter
+
+error[E0412]: cannot find type `ArrayWindowsExample` in this scope
+  --> $DIR/issue-85348.rs:3:22
+   |
+LL | impl<const N: usize> ArrayWindowsExample {
+   |                      ^^^^^^^^^^^^^^^^^^^ not found in this scope
+
+error[E0282]: type annotations needed
+  --> $DIR/issue-85348.rs:6:13
+   |
+LL |         let mut N;
+   |             ^^^^^ consider giving `N` a type
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0282, E0412, E0530.
+For more information about an error, try `rustc --explain E0282`.

src/test/ui/resolve/shadow-const-param.rs

@@ -0,0 +1,20 @@
+// Checks that const parameters cannot be shadowed with fresh bindings
+// even in syntactically unambiguous contexts. See
+// https://github.com/rust-lang/rust/issues/33118#issuecomment-233962221
+
+fn foo<const N: i32>(i: i32) -> bool {
+    match i {
+        N @ _ => true,
+        //~^ ERROR: match bindings cannot shadow const parameters [E0530]
+    }
+}
+
+fn bar<const N: i32>(i: i32) -> bool {
+    let N @ _ = 0;
+    //~^ ERROR: let bindings cannot shadow const parameters [E0530]
+    match i {
+        N @ _ => true,
+    }
+}
+
+fn main() {}

src/test/ui/resolve/shadow-const-param.stderr

@@ -0,0 +1,20 @@
+error[E0530]: match bindings cannot shadow const parameters
+  --> $DIR/shadow-const-param.rs:7:9
+   |
+LL | fn foo<const N: i32>(i: i32) -> bool {
+   |              - the const parameter `N` is defined here
+LL |     match i {
+LL |         N @ _ => true,
+   |         ^ cannot be named the same as a const parameter
+
+error[E0530]: let bindings cannot shadow const parameters
+  --> $DIR/shadow-const-param.rs:13:9
+   |
+LL | fn bar<const N: i32>(i: i32) -> bool {
+   |              - the const parameter `N` is defined here
+LL |     let N @ _ = 0;
+   |         ^ cannot be named the same as a const parameter
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0530`.