auto merge of #15489 : jakub-/rust/issue-15488, r=pcwalton

Fixes #15488.

Author: bors

src/librustc/middle/check_match.rs

@@ -411,14 +411,7 @@ fn is_useful(cx: &MatchCheckCtxt, matrix @ &Matrix(ref rows): &Matrix,
         return NotUseful;
     }
     let real_pat = match rows.iter().find(|r| r.get(0).id != 0) {
-        Some(r) => {
-            match r.get(0).node {
-                // An arm of the form `ref x @ sub_pat` has type
-                // `sub_pat`, not `&sub_pat` as `x` itself does.
-                PatIdent(BindByRef(_), _, Some(sub)) => sub,
-                _ => *r.get(0)
-            }
-        }
+        Some(r) => raw_pat(*r.get(0)),
         None if v.len() == 0 => return NotUseful,
         None => v[0]
     };

src/librustc/middle/trans/_match.rs

@@ -413,26 +413,25 @@ fn expand_nested_bindings<'a, 'b>(
     let _indenter = indenter();
 
     m.iter().map(|br| {
-        match br.pats.get(col).node {
-            ast::PatIdent(_, ref path1, Some(inner)) => {
-                let pats = Vec::from_slice(br.pats.slice(0u, col))
-                           .append((vec!(inner))
-                                   .append(br.pats.slice(col + 1u, br.pats.len())).as_slice());
-
-                let mut bound_ptrs = br.bound_ptrs.clone();
-                bound_ptrs.push((path1.node, val));
-                Match {
-                    pats: pats,
-                    data: &*br.data,
-                    bound_ptrs: bound_ptrs
-                }
-            }
-            _ => Match {
-                pats: br.pats.clone(),
-                data: &*br.data,
-                bound_ptrs: br.bound_ptrs.clone()
+        let mut bound_ptrs = br.bound_ptrs.clone();
+        let mut pat = *br.pats.get(col);
+        loop {
+            pat = match pat.node {
+                ast::PatIdent(_, ref path, Some(inner)) => {
+                    bound_ptrs.push((path.node, val));
+                    inner.clone()
+                },
+                _ => break
             }
         }
+
+        let mut pats = br.pats.clone();
+        *pats.get_mut(col) = pat;
+        Match {
+            pats: pats,
+            data: &*br.data,
+            bound_ptrs: bound_ptrs
+        }
     }).collect()
 }
 

src/test/run-pass/match-pattern-bindings.rs

@@ -0,0 +1,38 @@
+// Copyright 2014 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 value = Some(1i);
+    assert_eq!(match value {
+        ref a @ Some(_) => a,
+        ref b @ None => b
+    }, &Some(1i));
+    assert_eq!(match value {
+        ref a @ ref _c @ Some(_) => a,
+        ref b @ None => b
+    }, &Some(1i));
+    assert_eq!(match value {
+        _a @ ref c @ Some(_) => c,
+        ref b @ None => b
+    }, &Some(1i));
+    assert_eq!(match "foobarbaz" {
+        _a @ b @ _ => b
+    }, "foobarbaz");
+
+    let a @ b @ c = "foobarbaz";
+    assert_eq!(a, "foobarbaz");
+    assert_eq!(b, "foobarbaz");
+    assert_eq!(c, "foobarbaz");
+    let value = Some(true);
+    let ref a @ b @ ref c = value;
+    assert_eq!(a, &Some(true));
+    assert_eq!(b, Some(true));
+    assert_eq!(c, &Some(true));
+}