auto merge of #12338 : edwardw/rust/hygienic-break-continue, r=cmr

Makes labelled loops hygiene by performing renaming of the labels defined in e.g. `'x: loop { ... }` and then used in break and continue statements within loop body so that they act hygienically when used with macros.
    
Closes #12262.

src/test/compile-fail/hygienic-label-1.rs

@@ -0,0 +1,19 @@
+// Copyright 2012-2014 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.
+
+#[feature(macro_rules)];
+
+macro_rules! foo {
+    () => { break 'x; }
+}
+
+pub fn main() {
+    'x: loop { foo!() } //~ ERROR use of undeclared label `x`
+}

src/test/compile-fail/hygienic-label-2.rs

@@ -0,0 +1,19 @@
+// Copyright 2012-2014 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.
+
+#[feature(macro_rules)];
+
+macro_rules! foo {
+    ($e: expr) => { 'x: loop { $e } }
+}
+
+pub fn main() {
+    foo!(break 'x); //~ ERROR use of undeclared label `x`
+}

src/test/compile-fail/hygienic-label-3.rs

@@ -0,0 +1,21 @@
+// Copyright 2012-2014 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.
+
+#[feature(macro_rules)];
+
+macro_rules! foo {
+    () => { break 'x; }
+}
+
+pub fn main() {
+    'x: for _ in range(0,1) {
+        foo!() //~ ERROR use of undeclared label `x`
+    };
+}

src/test/compile-fail/hygienic-label-4.rs

@@ -0,0 +1,19 @@
+// Copyright 2012-2014 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.
+
+#[feature(macro_rules)];
+
+macro_rules! foo {
+    ($e: expr) => { 'x: for _ in range(0,1) { $e } }
+}
+
+pub fn main() {
+    foo!(break 'x); //~ ERROR use of undeclared label `x`
+}

src/test/run-pass/hygienic-labels-in-let.rs

@@ -0,0 +1,59 @@
+// Copyright 2012-2014 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.
+
+#[feature(macro_rules)];
+
+macro_rules! loop_x {
+    ($e: expr) => {
+        // $e shouldn't be able to interact with this 'x
+        'x: loop { $e }
+    }
+}
+
+macro_rules! run_once {
+    ($e: expr) => {
+        // ditto
+        'x: for _ in range(0, 1) { $e }
+    }
+}
+
+pub fn main() {
+    let mut i = 0i;
+
+    let j = {
+        'x: loop {
+            // this 'x should refer to the outer loop, lexically
+            loop_x!(break 'x);
+            i += 1;
+        }
+        i + 1
+    };
+    assert_eq!(j, 1i);
+
+    let k = {
+        'x: for _ in range(0, 1) {
+            // ditto
+            loop_x!(break 'x);
+            i += 1;
+        }
+        i + 1
+    };
+    assert_eq!(k, 1i);
+
+    let n = {
+        'x: for _ in range(0, 1) {
+            // ditto
+            run_once!(continue 'x);
+            i += 1;
+        }
+        i + 1
+    };
+    assert_eq!(n, 1i);
+}

src/test/run-pass/hygienic-labels.rs

@@ -0,0 +1,45 @@
+// Copyright 2012-2014 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.
+
+#[feature(macro_rules)];
+
+macro_rules! loop_x {
+    ($e: expr) => {
+        // $e shouldn't be able to interact with this 'x
+        'x: loop { $e }
+    }
+}
+
+macro_rules! run_once {
+    ($e: expr) => {
+        // ditto
+        'x: for _ in range(0, 1) { $e }
+    }
+}
+
+pub fn main() {
+    'x: for _ in range(0, 1) {
+        // this 'x should refer to the outer loop, lexically
+        loop_x!(break 'x);
+        fail!("break doesn't act hygienically inside for loop");
+    }
+
+    'x: loop {
+        // ditto
+        loop_x!(break 'x);
+        fail!("break doesn't act hygienically inside infinite loop");
+    }
+
+    'x: for _ in range(0, 1) {
+        // ditto
+        run_once!(continue 'x);
+        fail!("continue doesn't act hygienically inside for loop");
+    }
+}