Traits that reference Self in the supertrait list are not object-safe. Fixes #22040.

src/test/compile-fail/object-safety-issue-22040.rs

@@ -0,0 +1,50 @@
+// 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.
+
+// Regression test for #22040.
+
+use std::fmt::Debug;
+
+trait Expr: Debug + PartialEq {
+    fn print_element_count(&self);
+}
+
+//#[derive(PartialEq)]
+#[derive(Debug)]
+struct SExpr<'x> {
+    elements: Vec<Box<Expr+ 'x>>,
+}
+
+impl<'x> PartialEq for SExpr<'x> {
+    fn eq(&self, other:&SExpr<'x>) -> bool {
+        println!("L1: {} L2: {}", self.elements.len(), other.elements.len());
+        let result = self.elements.len() == other.elements.len();
+
+        println!("Got compare {}", result);
+        return result;
+    }
+}
+
+impl <'x> SExpr<'x> {
+    fn new() -> SExpr<'x> { return SExpr{elements: Vec::new(),}; }
+}
+
+impl <'x> Expr for SExpr<'x> {
+    fn print_element_count(&self) {
+        println!("element count: {}", self.elements.len());
+    }
+}
+
+fn main() {
+    let a: Box<Expr> = Box::new(SExpr::new()); //~ ERROR trait `Expr` is not object-safe
+    let b: Box<Expr> = Box::new(SExpr::new()); //~ ERROR trait `Expr` is not object-safe
+
+    assert_eq!(a , b);
+}

src/test/compile-fail/object-safety-supertrait-mentions-Self.rs

@@ -0,0 +1,32 @@
+// Copyright 2014 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.
+
+// Check that we correctly prevent users from making trait objects
+// form traits that make use of `Self` in an argument or return position.
+
+trait Bar<T> {
+    fn bar(&self, x: &T);
+}
+
+trait Baz : Bar<Self> {
+}
+
+fn make_bar<T:Bar<u32>>(t: &T) -> &Bar<u32> {
+    t
+}
+
+fn make_baz<T:Baz>(t: &T) -> &Baz {
+    t
+        //~^ ERROR `Baz` is not object-safe
+        //~| NOTE the trait cannot use `Self` as a type parameter in the supertrait listing
+}
+
+fn main() {
+}