clean up issue-2284 (core marker trait name shadowing)

Author: omskscream

tests/ui/issues/issue-2284.rs

@@ -0,0 +1,21 @@
+//@ run-pass
+#![allow(dead_code)]
+
+//! Tests that user-defined trait is prioritized in compile time over
+//! the core::marker trait with the same name, allowing shadowing core traits.
+//!
+//! # Context
+//! Original issue: https://github.com/rust-lang/rust/issues/2284
+//! Original fix pull request: https://github.com/rust-lang/rust/pull/3792
+
+
+trait Send {
+    fn f(&self);
+}
+
+fn f<T:Send>(t: T) {
+    t.f();
+}
+
+pub fn main() {
+}