Move mutable::Mut to cell::RefCell

6 files changed, 320 insertions, 335 deletions

diff --git a/src/libstd/cell.rs b/src/libstd/cell.rs
index b33a18ed95d..019cd53be55 100644
--- a/src/libstd/cell.rs
+++ b/src/libstd/cell.rs
@@ -8,12 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! Runtime move semantics
+//! Types dealing with dynamic mutability
 
 #[missing_doc];
 
-use cast::transmute_mut;
 use prelude::*;
+use cast;
+use util::NonCopyable;
+
 
 /*
 A dynamic, mutable location.
@@ -36,7 +38,7 @@ impl<T> Cell<T> {
 
     /// Yields the value, failing if the cell is empty.
     pub fn take(&self) -> T {
-        let this = unsafe { transmute_mut(self) };
+        let this = unsafe { cast::transmute_mut(self) };
         if this.is_empty() {
             fail!("attempt to take an empty cell");
         }
@@ -46,7 +48,7 @@ impl<T> Cell<T> {
 
     /// Yields the value if the cell is full, or `None` if it is empty.
     pub fn take_opt(&self) -> Option<T> {
-        let this = unsafe { transmute_mut(self) };
+        let this = unsafe { cast::transmute_mut(self) };
         this.value.take()
     }
 
@@ -72,3 +74,295 @@ fn test_take_empty() {
     value_cell.take();
     value_cell.take();
 }
+
+
+/// A mutable memory location with dynamically checked borrow rules
+#[no_freeze]
+pub struct RefCell<T> {
+    priv value: T,
+    priv borrow: BorrowFlag,
+    priv nc: NonCopyable
+}
+
+// Values [1, MAX-1] represent the number of `Ref` active
+// (will not outgrow its range since `uint` is the size of the address space)
+type BorrowFlag = uint;
+static UNUSED: BorrowFlag = 0;
+static WRITING: BorrowFlag = -1;
+
+impl<T> RefCell<T> {
+    /// Create a new `RefCell` containing `value`
+    pub fn new(value: T) -> RefCell<T> {
+        RefCell {
+            value: value,
+            borrow: UNUSED,
+            nc: NonCopyable
+        }
+    }
+
+    /// Consumes the `RefCell`, returning the wrapped value.
+    pub fn unwrap(self) -> T {
+        assert!(self.borrow == UNUSED);
+        self.value
+    }
+
+    unsafe fn as_mut<'a>(&'a self) -> &'a mut RefCell<T> {
+        cast::transmute_mut(self)
+    }
+
+    /// Attempts to immutably borrow the wrapped value.
+    ///
+    /// The borrow lasts until the returned `Ref` exits scope. Multiple
+    /// immutable borrows can be taken out at the same time.
+    ///
+    /// Returns `None` if the value is currently mutably borrowed.
+    pub fn try_borrow<'a>(&'a self) -> Option<Ref<'a, T>> {
+        match self.borrow {
+            WRITING => None,
+            _ => {
+                unsafe { self.as_mut().borrow += 1; }
+                Some(Ref { parent: self })
+            }
+        }
+    }
+
+    /// Immutably borrows the wrapped value.
+    ///
+    /// The borrow lasts until the returned `Ref` exits scope. Multiple
+    /// immutable borrows can be taken out at the same time.
+    ///
+    /// # Failure
+    ///
+    /// Fails if the value is currently mutably borrowed.
+    pub fn borrow<'a>(&'a self) -> Ref<'a, T> {
+        match self.try_borrow() {
+            Some(ptr) => ptr,
+            None => fail!("RefCell<T> already mutably borrowed")
+        }
+    }
+
+    /// Mutably borrows the wrapped value.
+    ///
+    /// The borrow lasts untile the returned `RefMut` exits scope. The value
+    /// cannot be borrowed while this borrow is active.
+    ///
+    /// Returns `None` if the value is currently borrowed.
+    pub fn try_borrow_mut<'a>(&'a self) -> Option<RefMut<'a, T>> {
+        match self.borrow {
+            UNUSED => unsafe {
+                let mut_self = self.as_mut();
+                mut_self.borrow = WRITING;
+                Some(RefMut { parent: mut_self })
+            },
+            _ => None
+        }
+    }
+
+    /// Mutably borrows the wrapped value.
+    ///
+    /// The borrow lasts untile the returned `RefMut` exits scope. The value
+    /// cannot be borrowed while this borrow is active.
+    ///
+    /// # Failure
+    ///
+    /// Fails if the value is currently borrowed.
+    pub fn borrow_mut<'a>(&'a self) -> RefMut<'a, T> {
+        match self.try_borrow_mut() {
+            Some(ptr) => ptr,
+            None => fail!("RefCell<T> already borrowed")
+        }
+    }
+
+    /// Immutably borrows the wrapped value and applies `blk` to it.
+    ///
+    /// # Failure
+    ///
+    /// Fails if the value is currently mutably borrowed.
+    #[inline]
+    pub fn with<U>(&self, blk: |&T| -> U) -> U {
+        let ptr = self.borrow();
+        blk(ptr.get())
+    }
+
+    /// Mutably borrows the wrapped value and applies `blk` to it.
+    ///
+    /// # Failure
+    ///
+    /// Fails if the value is currently borrowed.
+    #[inline]
+    pub fn with_mut<U>(&self, blk: |&mut T| -> U) -> U {
+        let mut ptr = self.borrow_mut();
+        blk(ptr.get())
+    }
+}
+
+impl<T: Clone> Clone for RefCell<T> {
+    fn clone(&self) -> RefCell<T> {
+        let x = self.borrow();
+        RefCell::new(x.get().clone())
+    }
+}
+
+impl<T: DeepClone> DeepClone for RefCell<T> {
+    fn deep_clone(&self) -> RefCell<T> {
+        let x = self.borrow();
+        RefCell::new(x.get().deep_clone())
+    }
+}
+
+impl<T: Eq> Eq for RefCell<T> {
+    fn eq(&self, other: &RefCell<T>) -> bool {
+        let a = self.borrow();
+        let b = other.borrow();
+        a.get() == b.get()
+    }
+}
+
+/// Wraps a borrowed reference to a value in a `RefCell` box.
+pub struct Ref<'box, T> {
+    priv parent: &'box RefCell<T>
+}
+
+#[unsafe_destructor]
+impl<'box, T> Drop for Ref<'box, T> {
+    fn drop(&mut self) {
+        assert!(self.parent.borrow != WRITING && self.parent.borrow != UNUSED);
+        unsafe { self.parent.as_mut().borrow -= 1; }
+    }
+}
+
+impl<'box, T> Ref<'box, T> {
+    /// Retrieve an immutable reference to the stored value.
+    #[inline]
+    pub fn get<'a>(&'a self) -> &'a T {
+        &self.parent.value
+    }
+}
+
+/// Wraps a mutable borrowed reference to a value in a `RefCell` box.
+pub struct RefMut<'box, T> {
+    priv parent: &'box mut RefCell<T>
+}
+
+#[unsafe_destructor]
+impl<'box, T> Drop for RefMut<'box, T> {
+    fn drop(&mut self) {
+        assert!(self.parent.borrow == WRITING);
+        self.parent.borrow = UNUSED;
+    }
+}
+
+impl<'box, T> RefMut<'box, T> {
+    /// Retrieve a mutable reference to the stored value.
+    #[inline]
+    pub fn get<'a>(&'a mut self) -> &'a mut T {
+        &mut self.parent.value
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn double_imm_borrow() {
+        let x = RefCell::new(0);
+        let _b1 = x.borrow();
+        x.borrow();
+    }
+
+    #[test]
+    fn no_mut_then_imm_borrow() {
+        let x = RefCell::new(0);
+        let _b1 = x.borrow_mut();
+        assert!(x.try_borrow().is_none());
+    }
+
+    #[test]
+    fn no_imm_then_borrow_mut() {
+        let x = RefCell::new(0);
+        let _b1 = x.borrow();
+        assert!(x.try_borrow_mut().is_none());
+    }
+
+    #[test]
+    fn no_double_borrow_mut() {
+        let x = RefCell::new(0);
+        let _b1 = x.borrow_mut();
+        assert!(x.try_borrow_mut().is_none());
+    }
+
+    #[test]
+    fn imm_release_borrow_mut() {
+        let x = RefCell::new(0);
+        {
+            let _b1 = x.borrow();
+        }
+        x.borrow_mut();
+    }
+
+    #[test]
+    fn mut_release_borrow_mut() {
+        let x = RefCell::new(0);
+        {
+            let _b1 = x.borrow_mut();
+        }
+        x.borrow();
+    }
+
+    #[test]
+    fn double_borrow_single_release_no_borrow_mut() {
+        let x = RefCell::new(0);
+        let _b1 = x.borrow();
+        {
+            let _b2 = x.borrow();
+        }
+        assert!(x.try_borrow_mut().is_none());
+    }
+
+    #[test]
+    fn with_ok() {
+        let x = RefCell::new(0);
+        assert_eq!(1, x.with(|x| *x+1));
+    }
+
+    #[test]
+    #[should_fail]
+    fn mut_borrow_with() {
+        let x = RefCell::new(0);
+        let _b1 = x.borrow_mut();
+        x.with(|x| *x+1);
+    }
+
+    #[test]
+    fn borrow_with() {
+        let x = RefCell::new(0);
+        let _b1 = x.borrow();
+        assert_eq!(1, x.with(|x| *x+1));
+    }
+
+    #[test]
+    fn with_mut_ok() {
+        let x = RefCell::new(0);
+        x.with_mut(|x| *x += 1);
+        let b = x.borrow();
+        assert_eq!(1, *b.get());
+    }
+
+    #[test]
+    #[should_fail]
+    fn borrow_with_mut() {
+        let x = RefCell::new(0);
+        let _b = x.borrow();
+        x.with_mut(|x| *x += 1);
+    }
+
+    #[test]
+    #[should_fail]
+    fn discard_doesnt_unborrow() {
+        let x = RefCell::new(0);
+        let _b = x.borrow();
+        let _ = _b;
+        let _b = x.borrow_mut();
+    }
+}
diff --git a/src/libstd/gc.rs b/src/libstd/gc.rs
index 5e2ba808d31..5fe11d310d4 100644
--- a/src/libstd/gc.rs
+++ b/src/libstd/gc.rs
@@ -55,26 +55,26 @@ impl<T: DeepClone + Send + 'static> DeepClone for Gc<T> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use cell::Cell;
+    use cell::RefCell;
 
     #[test]
     fn test_clone() {
-        let x = Gc::new(Cell::new(5));
+        let x = Gc::new(RefCell::new(5));
         let y = x.clone();
-        do x.borrow().with_mut_ref |inner| {
+        do x.borrow().with_mut |inner| {
             *inner = 20;
         }
-        assert_eq!(y.borrow().take(), 20);
+        assert_eq!(y.borrow().with(|x| *x), 20);
     }
 
     #[test]
     fn test_deep_clone() {
-        let x = Gc::new(Cell::new(5));
+        let x = Gc::new(RefCell::new(5));
         let y = x.deep_clone();
-        do x.borrow().with_mut_ref |inner| {
+        do x.borrow().with_mut |inner| {
             *inner = 20;
         }
-        assert_eq!(y.borrow().take(), 5);
+        assert_eq!(y.borrow().with(|x| *x), 5);
     }
 
     #[test]
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 10887369b15..ffa91df4e8a 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -164,7 +164,6 @@ pub mod result;
 pub mod either;
 pub mod hashmap;
 pub mod cell;
-pub mod mutable;
 pub mod trie;
 
 
diff --git a/src/libstd/mutable.rs b/src/libstd/mutable.rs
deleted file mode 100644
index 44efbc149c1..00000000000
--- a/src/libstd/mutable.rs
+++ /dev/null
@@ -1,307 +0,0 @@
-// Copyright 2013 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.
-
-//! A mutable memory location with dynamically checked borrow rules
-
-use prelude::*;
-
-use cast;
-use util::NonCopyable;
-
-/// A mutable memory location with dynamically checked borrow rules
-#[no_freeze]
-pub struct Mut<T> {
-    priv value: T,
-    priv borrow: BorrowFlag,
-    priv nc: NonCopyable
-}
-
-// Values [1, MAX-1] represent the number of `Ref` active
-// (will not outgrow its range since `uint` is the size of the address space)
-type BorrowFlag = uint;
-static UNUSED: BorrowFlag = 0;
-static WRITING: BorrowFlag = -1;
-
-impl<T> Mut<T> {
-    /// Create a new `Mut` containing `value`
-    pub fn new(value: T) -> Mut<T> {
-        Mut {
-            value: value,
-            borrow: UNUSED,
-            nc: NonCopyable
-        }
-    }
-
-    /// Consumes the `Mut`, returning the wrapped value.
-    pub fn unwrap(self) -> T {
-        assert!(self.borrow == UNUSED);
-        self.value
-    }
-
-    unsafe fn as_mut<'a>(&'a self) -> &'a mut Mut<T> {
-        cast::transmute_mut(self)
-    }
-
-    /// Attempts to immutably borrow the wrapped value.
-    ///
-    /// The borrow lasts until the returned `Ref` exits scope. Multiple
-    /// immutable borrows can be taken out at the same time.
-    ///
-    /// Returns `None` if the value is currently mutably borrowed.
-    pub fn try_borrow<'a>(&'a self) -> Option<Ref<'a, T>> {
-        match self.borrow {
-            WRITING => None,
-            _ => {
-                unsafe { self.as_mut().borrow += 1; }
-                Some(Ref { parent: self })
-            }
-        }
-    }
-
-    /// Immutably borrows the wrapped value.
-    ///
-    /// The borrow lasts until the returned `Ref` exits scope. Multiple
-    /// immutable borrows can be taken out at the same time.
-    ///
-    /// # Failure
-    ///
-    /// Fails if the value is currently mutably borrowed.
-    pub fn borrow<'a>(&'a self) -> Ref<'a, T> {
-        match self.try_borrow() {
-            Some(ptr) => ptr,
-            None => fail!("Mut<T> already mutably borrowed")
-        }
-    }
-
-    /// Mutably borrows the wrapped value.
-    ///
-    /// The borrow lasts untile the returned `RefMut` exits scope. The value
-    /// cannot be borrowed while this borrow is active.
-    ///
-    /// Returns `None` if the value is currently borrowed.
-    pub fn try_borrow_mut<'a>(&'a self) -> Option<RefMut<'a, T>> {
-        match self.borrow {
-            UNUSED => unsafe {
-                let mut_self = self.as_mut();
-                mut_self.borrow = WRITING;
-                Some(RefMut { parent: mut_self })
-            },
-            _ => None
-        }
-    }
-
-    /// Mutably borrows the wrapped value.
-    ///
-    /// The borrow lasts untile the returned `RefMut` exits scope. The value
-    /// cannot be borrowed while this borrow is active.
-    ///
-    /// # Failure
-    ///
-    /// Fails if the value is currently borrowed.
-    pub fn borrow_mut<'a>(&'a self) -> RefMut<'a, T> {
-        match self.try_borrow_mut() {
-            Some(ptr) => ptr,
-            None => fail!("Mut<T> already borrowed")
-        }
-    }
-
-    /// Immutably borrows the wrapped value and applies `blk` to it.
-    ///
-    /// # Failure
-    ///
-    /// Fails if the value is currently mutably borrowed.
-    #[inline]
-    pub fn with<U>(&self, blk: |&T| -> U) -> U {
-        let ptr = self.borrow();
-        blk(ptr.get())
-    }
-
-    /// Mutably borrows the wrapped value and applies `blk` to it.
-    ///
-    /// # Failure
-    ///
-    /// Fails if the value is currently borrowed.
-    #[inline]
-    pub fn with_mut<U>(&self, blk: |&mut T| -> U) -> U {
-        let mut ptr = self.borrow_mut();
-        blk(ptr.get())
-    }
-}
-
-impl<T: Clone> Clone for Mut<T> {
-    fn clone(&self) -> Mut<T> {
-        let x = self.borrow();
-        Mut::new(x.get().clone())
-    }
-}
-
-impl<T: DeepClone> DeepClone for Mut<T> {
-    fn deep_clone(&self) -> Mut<T> {
-        let x = self.borrow();
-        Mut::new(x.get().deep_clone())
-    }
-}
-
-impl<T: Eq> Eq for Mut<T> {
-    fn eq(&self, other: &Mut<T>) -> bool {
-        let a = self.borrow();
-        let b = other.borrow();
-        a.get() == b.get()
-    }
-}
-
-/// Wraps a borrowed reference to a value in a `Mut` box.
-pub struct Ref<'box, T> {
-    priv parent: &'box Mut<T>
-}
-
-#[unsafe_destructor]
-impl<'box, T> Drop for Ref<'box, T> {
-    fn drop(&mut self) {
-        assert!(self.parent.borrow != WRITING && self.parent.borrow != UNUSED);
-        unsafe { self.parent.as_mut().borrow -= 1; }
-    }
-}
-
-impl<'box, T> Ref<'box, T> {
-    /// Retrieve an immutable reference to the stored value.
-    #[inline]
-    pub fn get<'a>(&'a self) -> &'a T {
-        &self.parent.value
-    }
-}
-
-/// Wraps a mutable borrowed reference to a value in a `Mut` box.
-pub struct RefMut<'box, T> {
-    priv parent: &'box mut Mut<T>
-}
-
-#[unsafe_destructor]
-impl<'box, T> Drop for RefMut<'box, T> {
-    fn drop(&mut self) {
-        assert!(self.parent.borrow == WRITING);
-        self.parent.borrow = UNUSED;
-    }
-}
-
-impl<'box, T> RefMut<'box, T> {
-    /// Retrieve a mutable reference to the stored value.
-    #[inline]
-    pub fn get<'a>(&'a mut self) -> &'a mut T {
-        &mut self.parent.value
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-
-    #[test]
-    fn double_imm_borrow() {
-        let x = Mut::new(0);
-        let _b1 = x.borrow();
-        x.borrow();
-    }
-
-    #[test]
-    fn no_mut_then_imm_borrow() {
-        let x = Mut::new(0);
-        let _b1 = x.borrow_mut();
-        assert!(x.try_borrow().is_none());
-    }
-
-    #[test]
-    fn no_imm_then_borrow_mut() {
-        let x = Mut::new(0);
-        let _b1 = x.borrow();
-        assert!(x.try_borrow_mut().is_none());
-    }
-
-    #[test]
-    fn no_double_borrow_mut() {
-        let x = Mut::new(0);
-        let _b1 = x.borrow_mut();
-        assert!(x.try_borrow_mut().is_none());
-    }
-
-    #[test]
-    fn imm_release_borrow_mut() {
-        let x = Mut::new(0);
-        {
-            let _b1 = x.borrow();
-        }
-        x.borrow_mut();
-    }
-
-    #[test]
-    fn mut_release_borrow_mut() {
-        let x = Mut::new(0);
-        {
-            let _b1 = x.borrow_mut();
-        }
-        x.borrow();
-    }
-
-    #[test]
-    fn double_borrow_single_release_no_borrow_mut() {
-        let x = Mut::new(0);
-        let _b1 = x.borrow();
-        {
-            let _b2 = x.borrow();
-        }
-        assert!(x.try_borrow_mut().is_none());
-    }
-
-    #[test]
-    fn with_ok() {
-        let x = Mut::new(0);
-        assert_eq!(1, x.with(|x| *x+1));
-    }
-
-    #[test]
-    #[should_fail]
-    fn mut_borrow_with() {
-        let x = Mut::new(0);
-        let _b1 = x.borrow_mut();
-        x.with(|x| *x+1);
-    }
-
-    #[test]
-    fn borrow_with() {
-        let x = Mut::new(0);
-        let _b1 = x.borrow();
-        assert_eq!(1, x.with(|x| *x+1));
-    }
-
-    #[test]
-    fn with_mut_ok() {
-        let x = Mut::new(0);
-        x.with_mut(|x| *x += 1);
-        let b = x.borrow();
-        assert_eq!(1, *b.get());
-    }
-
-    #[test]
-    #[should_fail]
-    fn borrow_with_mut() {
-        let x = Mut::new(0);
-        let _b = x.borrow();
-        x.with_mut(|x| *x += 1);
-    }
-
-    #[test]
-    #[should_fail]
-    fn discard_doesnt_unborrow() {
-        let x = Mut::new(0);
-        let _b = x.borrow();
-        let _ = _b;
-        let _b = x.borrow_mut();
-    }
-}
diff --git a/src/libstd/rc.rs b/src/libstd/rc.rs
index 24e7decfb82..242533773d7 100644
--- a/src/libstd/rc.rs
+++ b/src/libstd/rc.rs
@@ -21,7 +21,7 @@ use unstable::intrinsics::transmute;
 use ops::Drop;
 use kinds::{Freeze, Send};
 use clone::{Clone, DeepClone};
-use mutable::Mut;
+use cell::RefCell;
 
 struct RcBox<T> {
     value: T,
@@ -55,10 +55,10 @@ impl<T: Send> Rc<T> {
     }
 }
 
-impl<T: Freeze> Rc<Mut<T>> {
-    /// Construct a new reference-counted box from a `Mut`-wrapped `Freeze` value
+impl<T: Freeze> Rc<RefCell<T>> {
+    /// Construct a new reference-counted box from a `RefCell`-wrapped `Freeze` value
     #[inline]
-    pub fn from_mut(value: Mut<T>) -> Rc<Mut<T>> {
+    pub fn from_mut(value: RefCell<T>) -> Rc<RefCell<T>> {
         unsafe {
             Rc::new_unchecked(value)
         }
@@ -116,11 +116,11 @@ impl<T> Drop for Rc<T> {
 #[cfg(test)]
 mod test_rc {
     use super::*;
-    use mutable::Mut;
+    use cell::RefCell;
 
     #[test]
     fn test_clone() {
-        let x = Rc::from_send(Mut::new(5));
+        let x = Rc::from_send(RefCell::new(5));
         let y = x.clone();
         do x.borrow().with_mut |inner| {
             *inner = 20;
@@ -130,7 +130,7 @@ mod test_rc {
 
     #[test]
     fn test_deep_clone() {
-        let x = Rc::from_send(Mut::new(5));
+        let x = Rc::from_send(RefCell::new(5));
         let y = x.deep_clone();
         do x.borrow().with_mut |inner| {
             *inner = 20;
@@ -161,6 +161,6 @@ mod test_rc {
     #[test]
     fn test_from_mut() {
         let a = 10;
-        let _x = Rc::from_mut(Mut::new(&a));
+        let _x = Rc::from_mut(RefCell::new(&a));
     }
 }
diff --git a/src/libstd/rt/comm.rs b/src/libstd/rt/comm.rs
index 7441d0d3edc..8635f9372c4 100644
--- a/src/libstd/rt/comm.rs
+++ b/src/libstd/rt/comm.rs
@@ -25,10 +25,9 @@ use unstable::sync::UnsafeArc;
 use util;
 use util::Void;
 use comm::{GenericChan, GenericSmartChan, GenericPort, Peekable, SendDeferred};
-use cell::Cell;
+use cell::{Cell, RefCell};
 use clone::Clone;
 use tuple::ImmutableTuple;
-use mutable::Mut;
 
 /// A combined refcount / BlockedTask-as-uint pointer.
 ///
@@ -433,20 +432,20 @@ type StreamPortOne<T> = PortOne<StreamPayload<T>>;
 
 /// A channel with unbounded size.
 pub struct Chan<T> {
-    // FIXME #5372. Using Mut because we don't take &mut self
-    next: Mut<StreamChanOne<T>>
+    // FIXME #5372. Using RefCell because we don't take &mut self
+    next: RefCell<StreamChanOne<T>>
 }
 
 /// An port with unbounded size.
 pub struct Port<T> {
-    // FIXME #5372. Using Mut because we don't take &mut self
-    next: Mut<Option<StreamPortOne<T>>>
+    // FIXME #5372. Using RefCell because we don't take &mut self
+    next: RefCell<Option<StreamPortOne<T>>>
 }
 
 pub fn stream<T: Send>() -> (Port<T>, Chan<T>) {
     let (pone, cone) = oneshot();
-    let port = Port { next: Mut::new(Some(pone)) };
-    let chan = Chan { next: Mut::new(cone) };
+    let port = Port { next: RefCell::new(Some(pone)) };
+    let chan = Chan { next: RefCell::new(cone) };
     return (port, chan);
 }