can borrow mut in proc Fixes #10617

src/test/run-pass/kindck-implicit-close-over-mut-var.rs

@@ -1,4 +1,4 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// 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.
 //
@@ -13,38 +13,41 @@ use std::task;
 fn user(_i: int) {}
 
 fn foo() {
-    // Here, i is *moved* into the closure: Not actually OK
+    // Here, i is *copied* into the proc (heap closure).
+    // Requires allocation.  The proc's copy is not mutable.
     let mut i = 0;
     do task::spawn {
-        user(i); //~ ERROR mutable variables cannot be implicitly captured
+        user(i);
+        println!("spawned {}", i)
     }
+    i += 1;
+    println!("original {}", i)
 }
 
 fn bar() {
-    // Here, i would be implicitly *copied* but it
-    // is mutable: bad
+    // Here, the original i has not been moved, only copied, so is still
+    // mutable outside of the proc.
     let mut i = 0;
     while i < 10 {
         do task::spawn {
-            user(i); //~ ERROR mutable variables cannot be implicitly captured
+            user(i);
         }
         i += 1;
     }
 }
 
 fn car() {
-    // Here, i is mutable, but *explicitly* shadowed copied:
+    // Here, i must be shadowed in the proc to be mutable.
     let mut i = 0;
     while i < 10 {
-        {
-            let i = i;
-            do task::spawn {
-                user(i);
-            }
+        do task::spawn {
+            let mut i = i;
+            i += 1;
+            user(i);
         }
         i += 1;
     }
 }
 
-fn main() {
-}
+pub fn main() {}
+