Handle supertrait calls in default methods

Add a new method_super origin for supertrait methods. Also make
coherence create a table that maps pairs of trait IDs and self types
to impl IDs, so that it's possible to check a supertrait method
knowing only its index in its trait's methods (without knowing all
supertraits for a given trait).

r=nmatsakis and graydon -- with hope, we'll revamp all of this code as
per #4678, but for now this fixes the bug.

Closes #3979

src/test/auxiliary/issue_3979_traits.rs

@@ -0,0 +1,26 @@
+// Copyright 2012 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.
+
+#[link(name = "issue_3979_traits",
+       vers = "0.1")];
+
+#[crate_type = "lib"];
+
+trait Positioned {
+  fn SetX(&self, int);
+  fn X(&self) -> int;
+}
+
+#[allow(default_methods)]
+trait Movable: Positioned {
+  fn translate(&self, dx: int) {
+    self.SetX(self.X() + dx);
+  }
+}

src/test/run-pass/issue-3979-2.rs

@@ -0,0 +1,26 @@
+// Copyright 2012 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 A {
+    fn a_method();
+}
+
+trait B: A {
+    fn b_method();
+}
+
+trait C: B {
+    fn c_method() {
+        self.a_method();
+    }
+}
+
+fn main() {}
+

src/test/run-pass/issue-3979-generics.rs

@@ -0,0 +1,41 @@
+// Copyright 2012 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.
+
+// xfail-test
+trait Positioned<S> {
+  fn SetX(&self, S);
+  fn X(&self) -> S;
+}
+
+#[allow(default_methods)]
+trait Movable<S, T>: Positioned<T> {
+  fn translate(&self, dx: T) {
+    self.SetX(self.X() + dx);
+  }
+}
+
+struct Point { mut x: int, mut y: int }
+
+impl Point: Positioned<int> {
+    fn SetX(&self, x: int) {
+        self.x = x;
+    }
+    fn X(&self) -> int {
+        self.x
+    }
+}
+
+impl Point: Movable<int, int>;
+
+fn main() {
+    let p = Point{ x: 1, y: 2};
+    p.translate(3);
+    assert p.X() == 4;
+}

src/test/run-pass/issue-3979-xcrate.rs

@@ -0,0 +1,33 @@
+// Copyright 2012 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.
+
+// xfail-test // tjc: ???
+// aux-build:issue_3979_traits.rs
+extern mod issue_3979_traits;
+use issue_3979_traits::*;
+
+struct Point { mut x: int, mut y: int }
+
+impl Point: Positioned {
+    fn SetX(&self, x: int) {
+        self.x = x;
+    }
+    fn X(&self) -> int {
+        self.x
+    }
+}
+
+impl Point: Movable;
+
+fn main() {
+    let p = Point{ x: 1, y: 2};
+    p.translate(3);
+    assert p.X() == 4;
+}

src/test/run-pass/issue-3979.rs

@@ -8,15 +8,33 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// xfail-test
 trait Positioned {
-  fn SetX(int);
+  fn SetX(&self, int);
+  fn X(&self) -> int;
 }
 
+#[allow(default_methods)]
 trait Movable: Positioned {
-  fn translate(dx: int) {
+  fn translate(&self, dx: int) {
     self.SetX(self.X() + dx);
   }
 }
 
-fn main() {}
+struct Point { mut x: int, mut y: int }
+
+impl Point: Positioned {
+    fn SetX(&self, x: int) {
+        self.x = x;
+    }
+    fn X(&self) -> int {
+        self.x
+    }
+}
+
+impl Point: Movable;
+
+fn main() {
+    let p = Point{ x: 1, y: 2};
+    p.translate(3);
+    assert p.X() == 4;
+}