Test cases for issue #20055.

Note that I have not yet managed to expose any bug in
`trans::expr::into_fat_ptr`; it would be good to try to do so (or show
that the use of `.to_lvalue_datum` there is sound).

Author: pnkfelix

src/test/run-pass/issue-20055-box-trait.rs

@@ -0,0 +1,40 @@
+// 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.
+
+trait Boo { }
+
+impl Boo for [i8; 1] { }
+impl Boo for [i8; 2] { }
+impl Boo for [i8; 3] { }
+impl Boo for [i8; 4] { }
+
+pub fn foo(box_1: fn () -> Box<[i8; 1]>,
+           box_2: fn () -> Box<[i8; 20]>,
+           box_3: fn () -> Box<[i8; 300]>,
+           box_4: fn () -> Box<[i8; 4000]>,
+            ) {
+    println!("Hello World 1");
+    let _: Box<[i8]> = match 3 {
+        1 => box_1(),
+        2 => box_2(),
+        3 => box_3(),
+        _ => box_4(),
+    };
+    println!("Hello World 2");
+}
+
+pub fn main() {
+    fn box_1() -> Box<[i8; 1]> { Box::new( [1i8] ) }
+    fn box_2() -> Box<[i8; 20]> { Box::new( [1i8; 20] ) }
+    fn box_3() -> Box<[i8; 300]> { Box::new( [1i8; 300] ) }
+    fn box_4() -> Box<[i8; 4000]> { Box::new( [1i8; 4000] ) }
+
+    foo(box_1, box_2, box_3, box_4);
+}

src/test/run-pass/issue-20055-box-unsized-array.rs

@@ -0,0 +1,33 @@
+// 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.
+
+pub fn foo(box_1: fn () -> Box<[i8; 1]>,
+           box_2: fn () -> Box<[i8; 20]>,
+           box_3: fn () -> Box<[i8; 300]>,
+           box_4: fn () -> Box<[i8; 4000]>,
+            ) {
+    println!("Hello World 1");
+    let _: Box<[i8]> = match 3 {
+        1 => box_1(),
+        2 => box_2(),
+        3 => box_3(),
+        _ => box_4(),
+    };
+    println!("Hello World 2");
+}
+
+pub fn main() {
+    fn box_1() -> Box<[i8; 1]> { Box::new( [1i8] ) }
+    fn box_2() -> Box<[i8; 20]> { Box::new( [1i8; 20] ) }
+    fn box_3() -> Box<[i8; 300]> { Box::new( [1i8; 300] ) }
+    fn box_4() -> Box<[i8; 4000]> { Box::new( [1i8; 4000] ) }
+
+    foo(box_1, box_2, box_3, box_4);
+}