Auto merge of #29243 - skeleten:issue-29184, r=alexcrichton

Fixes #29184 

This adds an error message for the use of the reserved `typeof` keyword, instead of reporting an ICE.
Also adds a `compile-fail` test.

I chose to add a `span_err` instead of removing to parser code, as to preserve the reservation of `typeof`.

src/test/compile-fail/issue-29184.rs

@@ -0,0 +1,13 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    let x: typeof(92) = 92; //~ ERROR `typeof` is a reserved keyword
+}