Add failing allocator submodule test

Author: mark-i-m

src/test/ui/allocator-submodule.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.
+
+// Tests that it is possible to create a global allocator in a submodule, rather than in the crate
+// root.
+
+#![feature(global_allocator, alloc, allocator_api)]
+
+extern crate alloc;
+
+mod mymod {
+    use alloc::heap::Global;
+
+    #[global_allocator]
+    static MY_HEAP: Global = Global::default(); //~ ERROR
+}
+
+fn main() {}