Fix dereference of temporary immediate newtype structs

src/librustc/middle/trans/datum.rs

@@ -690,7 +690,14 @@ impl Datum {
                     }
                     ByValue => {
                         assert!(ty::type_is_immediate(bcx.tcx(), ty));
-                        (Some(Datum {ty: ty, ..*self}), bcx)
+                        (
+                            Some(Datum {
+                                val: ExtractValue(bcx, self.val, 0),
+                                ty: ty,
+                                mode: ByValue
+                            }),
+                            bcx
+                        )
                     }
                 }
             }

src/test/run-pass/newtype-temporary.rs

@@ -0,0 +1,19 @@
+// 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.
+
+struct Foo(uint);
+
+fn foo() -> Foo {
+    Foo(42)
+}
+
+fn main() {
+    assert_eq!(*foo(), 42);
+}