std: rewrite Hash to make it more generic

This patch merges IterBytes and Hash traits, which clears up the
confusion of using `#[deriving(IterBytes)]` to support hashing.
Instead, it now is much easier to use the new `#[deriving(Hash)]`
for making a type hashable with a stream hash.

Furthermore, it supports custom non-stream-based hashers, such as
if a value's hash was cached in a database.

This does not yet replace the old IterBytes-hash with this new
version.

src/test/compile-fail/deriving-span-Hash-enum-struct-variant.rs

@@ -0,0 +1,27 @@
+// 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.
+
+// This file was auto-generated using 'src/etc/generate-keyword-span-tests.py'
+
+#[feature(struct_variant)];
+extern crate extra;
+
+use std::hash::Hash;
+
+struct Error;
+
+#[deriving(Hash)]
+enum Enum {
+   A {
+     x: Error //~ ERROR
+   }
+}
+
+fn main() {}

src/test/compile-fail/deriving-span-Hash-enum.rs

@@ -0,0 +1,27 @@
+// 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.
+
+// This file was auto-generated using 'src/etc/generate-keyword-span-tests.py'
+
+#[feature(struct_variant)];
+extern crate extra;
+
+use std::hash::Hash;
+
+struct Error;
+
+#[deriving(Hash)]
+enum Enum {
+   A(
+     Error //~ ERROR
+     )
+}
+
+fn main() {}

src/test/compile-fail/deriving-span-Hash-struct.rs

@@ -0,0 +1,25 @@
+// 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.
+
+// This file was auto-generated using 'src/etc/generate-keyword-span-tests.py'
+
+#[feature(struct_variant)];
+extern crate extra;
+
+use std::hash::Hash;
+
+struct Error;
+
+#[deriving(Hash)]
+struct Struct {
+    x: Error //~ ERROR
+}
+
+fn main() {}

src/test/compile-fail/deriving-span-Hash-tuple-struct.rs

@@ -0,0 +1,25 @@
+// 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.
+
+// This file was auto-generated using 'src/etc/generate-keyword-span-tests.py'
+
+#[feature(struct_variant)];
+extern crate extra;
+
+use std::hash::Hash;
+
+struct Error;
+
+#[deriving(Hash)]
+struct Struct(
+    Error //~ ERROR
+);
+
+fn main() {}

src/test/run-pass/deriving-hash.rs

@@ -0,0 +1,28 @@
+// 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.
+
+// ignore-fast
+
+use std::hash;
+use std::hash::Hash;
+
+#[deriving(Hash)]
+struct Person {
+    id: uint,
+    name: ~str,
+    phone: uint,
+}
+
+fn main() {
+    let person1 = Person { id: 5, name: ~"Janet", phone: 555_666_7777 };
+    let person2 = Person { id: 5, name: ~"Bob", phone: 555_666_7777 };
+    assert!(hash::hash(&person1) == hash::hash(&person1));
+    assert!(hash::hash(&person1) != hash::hash(&person2));
+}

src/test/run-pass/deriving-meta-multiple.rs

@@ -10,6 +10,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use std::hash_old::Hash;
+
 #[deriving(Eq)]
 #[deriving(Clone)]
 #[deriving(IterBytes)]

src/test/run-pass/deriving-meta.rs

@@ -10,6 +10,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use std::hash_old::Hash;
+
 #[deriving(Eq, Clone, IterBytes)]
 struct Foo {
     bar: uint,

src/test/run-pass/typeid-intrinsic.rs

@@ -15,6 +15,7 @@
 extern crate other1 = "typeid-intrinsic";
 extern crate other2 = "typeid-intrinsic2";
 
+use std::hash_old::Hash;
 use std::unstable::intrinsics;
 use std::unstable::intrinsics::TypeId;