Merged migrated compile-fail tests and ui tests. Fixes #46841.

src/test/ui/feature-gates/feature-gate-alloc-error-handler.rs

@@ -0,0 +1,21 @@
+// Copyright 2018 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.
+
+// compile-flags:-C panic=abort
+
+#![no_std]
+#![no_main]
+
+use core::alloc::Layout;
+
+#[alloc_error_handler] //~ ERROR #[alloc_error_handler] is an unstable feature (see issue #51540)
+fn oom(info: Layout) -> ! {
+    loop {}
+}