Add new tests covering various cases.

src/test/compile-fail/impl-unused-tps-inherent.rs

@@ -0,0 +1,35 @@
+// 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.
+
+struct MyType;
+
+struct MyType1<T>(T);
+
+trait Bar {
+    type Out;
+}
+
+impl<T> MyType {
+    //~^ ERROR  the type parameter `T` is not constrained
+}
+
+impl<T> MyType1<T> {
+    // OK, T is used in `Foo<T>`.
+}
+
+impl<T,U> MyType1<T> {
+    //~^ ERROR  the type parameter `U` is not constrained
+}
+
+impl<T,U> MyType1<T> where T: Bar<Out=U> {
+    // OK, T is used in `Foo<T>`.
+}
+
+fn main() { }

src/test/compile-fail/impl-unused-tps.rs

@@ -0,0 +1,72 @@
+// 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.
+
+trait Foo<A> {
+    fn get(&self, A: &A) { }
+}
+
+trait Bar {
+    type Out;
+}
+
+impl<T> Foo<T> for [int;0] {
+    // OK, T is used in `Foo<T>`.
+}
+
+impl<T,U> Foo<T> for [int;1] {
+    //~^ ERROR the type parameter `U` is not constrained
+}
+
+impl<T,U> Foo<T> for [int;2] where T : Bar<Out=U> {
+    // OK, `U` is now constrained by the output type parameter.
+}
+
+impl<T:Bar<Out=U>,U> Foo<T> for [int;3] {
+    // OK, same as above but written differently.
+}
+
+impl<T,U> Foo<T> for U {
+    // OK, T, U are used everywhere. Note that the coherence check
+    // hasn't executed yet, so no errors about overlap.
+}
+
+impl<T,U> Bar for T {
+    //~^ ERROR the type parameter `U` is not constrained
+
+    type Out = U;
+
+    // Using `U` in an associated type within the impl is not good enough!
+}
+
+impl<T,U> Bar for T
+    where T : Bar<Out=U>
+{
+    //~^^^ ERROR the type parameter `U` is not constrained
+
+    // This crafty self-referential attempt is still no good.
+}
+
+impl<T,U,V> Foo<T> for T
+    where (T,U): Bar<Out=V>
+{
+    //~^^^ ERROR the type parameter `U` is not constrained
+    //~|   ERROR the type parameter `V` is not constrained
+
+    // Here, `V` is bound by an output type parameter, but the inputs
+    // are not themselves constrained.
+}
+
+impl<T,U,V> Foo<(T,U)> for T
+    where (T,U): Bar<Out=V>
+{
+    // As above, but both T and U ARE constrained.
+}
+
+fn main() { }