Rollup merge of #47104 - matthewjasper:dont-panic-on-generic-drop, r=estebank

Delay panic from incoherent drop implementation

Closes #41974

src/test/compile-fail/issue-41974.rs

@@ -0,0 +1,24 @@
+// Copyright 2017 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.
+
+#[derive(Copy, Clone)]
+struct Flags;
+
+trait A {
+}
+
+impl<T> Drop for T where T: A { //~ ERROR E0119
+                                //~^ ERROR E0120
+                                //~| ERROR E0210
+    fn drop(&mut self) {
+    }
+}
+
+fn main() {}