Implement tuple and tuple struct indexing

This allows code to access the fields of tuples and tuple structs:

    let x = (1i, 2i);
    assert_eq!(x.1, 2);

    struct Point(int, int);
    let origin = Point(0, 0);
    assert_eq!(origin.0, 0);
    assert_eq!(origin.1, 0);

src/test/compile-fail/borrow-tuple-fields.rs

@@ -0,0 +1,42 @@
+// 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.
+
+#![feature(tuple_indexing)]
+
+struct Foo(Box<int>, int);
+
+struct Bar(int, int);
+
+fn main() {
+    let x = (box 1i, 2i);
+    let r = &x.0;
+    let y = x; //~ ERROR cannot move out of `x` because it is borrowed
+
+    let mut x = (1i, 2i);
+    let a = &x.0;
+    let b = &mut x.0; //~ ERROR cannot borrow `x.0` as mutable because it is also borrowed as
+
+    let mut x = (1i, 2i);
+    let a = &mut x.0;
+    let b = &mut x.0; //~ ERROR cannot borrow `x.0` as mutable more than once at a time
+
+
+    let x = Foo(box 1i, 2i);
+    let r = &x.0;
+    let y = x; //~ ERROR cannot move out of `x` because it is borrowed
+
+    let mut x = Bar(1i, 2i);
+    let a = &x.0;
+    let b = &mut x.0; //~ ERROR cannot borrow `x.0` as mutable because it is also borrowed as
+
+    let mut x = Bar(1i, 2i);
+    let a = &mut x.0;
+    let b = &mut x.0; //~ ERROR cannot borrow `x.0` as mutable more than once at a time
+}

src/test/compile-fail/move-out-of-tuple-field.rs

@@ -0,0 +1,23 @@
+// 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.
+
+#![feature(tuple_indexing)]
+
+struct Foo(Box<int>);
+
+fn main() {
+    let x = (box 1i,);
+    let y = x.0;
+    let z = x.0; //~ ERROR use of moved value: `x.0`
+
+    let x = Foo(box 1i);
+    let y = x.0;
+    let z = x.0; //~ ERROR use of moved value: `x.0`
+}

src/test/compile-fail/tuple-index-not-tuple.rs

@@ -0,0 +1,22 @@
+// 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.
+
+#![feature(tuple_indexing)]
+
+struct Point { x: int, y: int }
+struct Empty;
+
+fn main() {
+    let origin = Point { x: 0, y: 0 };
+    origin.0;
+    //~^ ERROR attempted tuple index `0` on type `Point`, but the type was not
+    Empty.0;
+    //~^ ERROR attempted tuple index `0` on type `Empty`, but the type was not
+}

src/test/compile-fail/tuple-index-out-of-bounds.rs

@@ -0,0 +1,26 @@
+// 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.
+
+#![feature(tuple_indexing)]
+
+struct Point(int, int);
+
+fn main() {
+    let origin = Point(0, 0);
+    origin.0;
+    origin.1;
+    origin.2;
+    //~^ ERROR attempted out-of-bounds tuple index `2` on type `Point`
+    let tuple = (0i, 0i);
+    tuple.0;
+    tuple.1;
+    tuple.2;
+    //~^ ERROR attempted out-of-bounds tuple index `2` on type `(int,int)`
+}

src/test/run-pass/borrow-tuple-fields.rs

@@ -0,0 +1,48 @@
+// 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.
+
+#![feature(tuple_indexing)]
+
+struct Foo(int, int);
+
+fn main() {
+    let x = (1i, 2i);
+    let a = &x.0;
+    let b = &x.0;
+    assert_eq!(*a, 1);
+    assert_eq!(*b, 1);
+
+    let mut x = (1i, 2i);
+    {
+        let a = &x.0;
+        let b = &mut x.1;
+        *b = 5;
+        assert_eq!(*a, 1);
+    }
+    assert_eq!(x.0, 1);
+    assert_eq!(x.1, 5);
+
+
+    let x = Foo(1i, 2i);
+    let a = &x.0;
+    let b = &x.0;
+    assert_eq!(*a, 1);
+    assert_eq!(*b, 1);
+
+    let mut x = Foo(1i, 2i);
+    {
+        let a = &x.0;
+        let b = &mut x.1;
+        *b = 5;
+        assert_eq!(*a, 1);
+    }
+    assert_eq!(x.0, 1);
+    assert_eq!(x.1, 5);
+}

src/test/run-pass/tuple-index-fat-types.rs

@@ -0,0 +1,23 @@
+// 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.
+
+#![feature(tuple_indexing)]
+
+struct Foo<'a>(&'a [int]);
+
+fn main() {
+    let x: &[int] = &[1i, 2, 3];
+    let y = (x,);
+    assert_eq!(y.0, x);
+
+    let x: &[int] = &[1i, 2, 3];
+    let y = Foo(x);
+    assert_eq!(y.0, x);
+}

src/test/run-pass/tuple-index.rs

@@ -0,0 +1,42 @@
+// 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.
+
+#![feature(tuple_indexing)]
+
+struct Point(int, int);
+
+fn main() {
+    let mut x = Point(3, 2);
+    assert_eq!(x.0, 3);
+    assert_eq!(x.1, 2);
+    x.0 += 5;
+    assert_eq!(x.0, 8);
+    {
+        let ry = &mut x.1;
+        *ry -= 2;
+        x.0 += 3;
+        assert_eq!(x.0, 11);
+    }
+    assert_eq!(x.1, 0);
+
+    let mut x = (3i, 2i);
+    assert_eq!(x.0, 3);
+    assert_eq!(x.1, 2);
+    x.0 += 5;
+    assert_eq!(x.0, 8);
+    {
+        let ry = &mut x.1;
+        *ry -= 2;
+        x.0 += 3;
+        assert_eq!(x.0, 11);
+    }
+    assert_eq!(x.1, 0);
+
+}