test: Make borrowck-assign-to-subfield into a run-pass test, now that

it no longer has boxes in it

src/test/compile-fail/borrowck-assign-to-subfield.rs

@@ -1,41 +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.
-
-#[feature(managed_boxes)];
-
-fn main() {
-    struct A {
-        a: int,
-        w: B,
-        x: @B,
-        z: @mut B
-    }
-    struct B {
-        a: int
-    }
-    let mut p = A {
-        a: 1,
-        w: B {a: 1},
-        x: @B {a: 1},
-        z: @mut B {a: 1}
-    };
-
-    // even though `x` is not declared as a mutable field,
-    // `p` as a whole is mutable, so it can be modified.
-    p.a = 2;
-
-    // this is true for an interior field too
-    p.w.a = 2;
-
-    // in these cases we pass through a box, so the mut
-    // of the box is dominant
-    p.x.a = 2;     //~ ERROR cannot assign to immutable field
-    p.z.a = 2;
-}