auto merge of #9090 : jbclements/rust/let-var-hygiene, r=luqmana

This appears to fix issue #9049. It also re-enables the ICE check on comparing idents for equality; it appears that ICEs are better than seg faults.

src/test/run-pass/match-in-macro.rs

@@ -0,0 +1,25 @@
+// 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.
+
+enum Foo {
+    B { b1: int, bb1: int},
+}
+
+macro_rules! match_inside_expansion(
+    () => (
+        match B { b1:29 , bb1: 100} {
+            B { b1:b2 , bb1:bb2 } => b2+bb2
+        }
+    )
+)
+
+fn main() {
+    assert_eq!(match_inside_expansion!(),129);
+}