syntax: add a custom owned smart pointer in ptr::P.

Author: eddyb

src/libsyntax/ast.rs

@@ -25,16 +25,6 @@ use std::rc::Rc;
 use std::gc::{Gc, GC};
 use serialize::{Encodable, Decodable, Encoder, Decoder};
 
-/// A pointer abstraction.
-// FIXME(eddyb) #10676 use Rc<T> in the future.
-pub type P<T> = Gc<T>;
-
-#[allow(non_snake_case)]
-/// Construct a P<T> from a T value.
-pub fn P<T: 'static>(value: T) -> P<T> {
-    box(GC) value
-}
-
 // FIXME #6993: in librustc, uses of "ident" should be replaced
 // by just "Name".
 

src/libsyntax/lib.rs

@@ -63,6 +63,7 @@ pub mod diagnostic;
 pub mod fold;
 pub mod owned_slice;
 pub mod parse;
+pub mod ptr;
 pub mod visit;
 
 pub mod print {

src/libsyntax/ptr.rs

@@ -0,0 +1,81 @@
+// 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.
+
+use std::fmt;
+use std::fmt::Show;
+use std::hash::Hash;
+use serialize::{Encodable, Decodable, Encoder, Decoder};
+
+/// An owned smart pointer.
+pub struct P<T> {
+    ptr: Box<T>
+}
+
+#[allow(non_snake_case)]
+/// Construct a P<T> from a T value.
+pub fn P<T: 'static>(value: T) -> P<T> {
+    P {
+        ptr: box value
+    }
+}
+
+impl<T: 'static> P<T> {
+    pub fn and_then<U>(self, f: |T| -> U) -> U {
+        f(*self.ptr)
+    }
+
+    pub fn map(self, f: |T| -> T) -> P<T> {
+        self.and_then(|x| P(f(x)))
+    }
+}
+
+impl<T> Deref<T> for P<T> {
+    fn deref<'a>(&'a self) -> &'a T {
+        &*self.ptr
+    }
+}
+
+impl<T: 'static + Clone> Clone for P<T> {
+    fn clone(&self) -> P<T> {
+        P((**self).clone())
+    }
+}
+
+impl<T: PartialEq> PartialEq for P<T> {
+    fn eq(&self, other: &P<T>) -> bool {
+        **self == **other
+    }
+}
+
+impl<T: Eq> Eq for P<T> {}
+
+impl<T: Show> Show for P<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<S, T: Hash<S>> Hash<S> for P<T> {
+    fn hash(&self, state: &mut S) {
+        (**self).hash(state);
+    }
+}
+
+impl<E, D: Decoder<E>, T: 'static + Decodable<D, E>> Decodable<D, E> for P<T> {
+    fn decode(d: &mut D) -> Result<P<T>, E> {
+        Decodable::decode(d).map(P)
+    }
+}
+
+impl<E, S: Encoder<E>, T: Encodable<S, E>> Encodable<S, E> for P<T> {
+    fn encode(&self, s: &mut S) -> Result<(), E> {
+        (**self).encode(s)
+    }
+}