librustc_trans: Remove misoptimization in treating derefs of Box as rvalues.

src/test/run-pass/issue-18845.rs

@@ -0,0 +1,25 @@
+// Copyright 2015 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.
+
+// This used to generate invalid IR in that even if we took the
+// `false` branch we'd still try to free the Box from the other
+// arm. This was due to treating `*Box::new(9)` as an rvalue datum
+// instead of as an lvalue.
+
+fn test(foo: bool) -> u8 {
+    match foo {
+        true => *Box::new(9),
+        false => 0
+    }
+}
+
+fn main() {
+    assert_eq!(9, test(true));
+}

src/test/run-pass/issue-25497.rs

@@ -0,0 +1,28 @@
+// Copyright 2015 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.
+
+#[derive(Clone, Debug, PartialEq)]
+enum Expression {
+    Dummy,
+    Add(Box<Expression>),
+}
+
+use Expression::*;
+
+fn simplify(exp: Expression) -> Expression {
+    match exp {
+        Add(n) => *n.clone(),
+        _ => Dummy
+    }
+}
+
+fn main() {
+    assert_eq!(simplify(Add(Box::new(Dummy))), Dummy);
+}