From 6876916a45f14973897dd05fe4dfdd2b47ac9607 Mon Sep 17 00:00:00 2001
From: Huon Wilson <dbau.pp+github@gmail.com>
Date: Wed, 18 Dec 2013 00:06:20 +1100
Subject: [PATCH] rustc: Allow `return` to return from a closure.

With the old `for` gone, this behaviour is no longer conflicting with
that use of `return` in closures, and this allows shortcircuiting in a
closure.
---
 src/librustc/middle/check_loop.rs             |  6 ---
 .../compile-fail/return-in-block-function.rs  | 15 -------
 src/test/run-pass/return-from-closure.rs      | 41 +++++++++++++++++++
 3 files changed, 41 insertions(+), 21 deletions(-)
 delete mode 100644 src/test/compile-fail/return-in-block-function.rs
 create mode 100644 src/test/run-pass/return-from-closure.rs

diff --git a/src/librustc/middle/check_loop.rs b/src/librustc/middle/check_loop.rs
index a08884857a6..332e63288a1 100644
--- a/src/librustc/middle/check_loop.rs
+++ b/src/librustc/middle/check_loop.rs
@@ -47,12 +47,6 @@ impl Visitor<Context> for CheckLoopVisitor {
             }
             ast::ExprBreak(_) => self.require_loop("break", cx, e.span),
             ast::ExprAgain(_) => self.require_loop("continue", cx, e.span),
-            ast::ExprRet(oe) => {
-                if cx == Closure {
-                    self.tcx.sess.span_err(e.span, "`return` in a closure");
-                }
-                visit::walk_expr_opt(self, oe, cx);
-            }
             _ => visit::walk_expr(self, e, cx)
         }
     }
diff --git a/src/test/compile-fail/return-in-block-function.rs b/src/test/compile-fail/return-in-block-function.rs
deleted file mode 100644
index f231810cbf1..00000000000
--- a/src/test/compile-fail/return-in-block-function.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-// 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 = || {
-        return //~ ERROR: `return` in a closure
-    };
-}
diff --git a/src/test/run-pass/return-from-closure.rs b/src/test/run-pass/return-from-closure.rs
new file mode 100644
index 00000000000..1756d74a81e
--- /dev/null
+++ b/src/test/run-pass/return-from-closure.rs
@@ -0,0 +1,41 @@
+// Copyright 2013 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.
+
+// just to make sure that `return` is only returning from the closure,
+// not the surrounding function.
+static mut calls: uint = 0;
+
+fn surrounding() {
+    let return_works = |n: int| {
+        unsafe { calls += 1 }
+
+        if n >= 0 { return; }
+        fail!()
+    };
+
+    return_works(10);
+    return_works(20);
+
+
+    let return_works_proc = proc(n: int) {
+        unsafe { calls += 1 }
+
+        if n >= 0 { return; }
+        fail!()
+    };
+
+    return_works_proc(10);
+}
+
+pub fn main() {
+    surrounding();
+
+    assert_eq!(unsafe {calls}, 3);
+}