Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

2 files changed, 766 insertions, 0 deletions

diff --git a/third_party/rust/lazycell/src/lib.rs b/third_party/rust/lazycell/src/lib.rs
new file mode 100644
index 0000000000..53bee073bf
--- /dev/null
+++ b/third_party/rust/lazycell/src/lib.rs
@@ -0,0 +1,680 @@
+// Original work Copyright (c) 2014 The Rust Project Developers
+// Modified work Copyright (c) 2016-2020 Nikita Pekin and the lazycell contributors
+// See the README.md file at the top-level directory of this distribution.
+//
+// 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.
+
+#![cfg_attr(not(test), no_std)]
+
+#![deny(missing_docs)]
+#![cfg_attr(feature = "nightly", feature(plugin))]
+#![cfg_attr(feature = "clippy", plugin(clippy))]
+
+//! This crate provides a `LazyCell` struct which acts as a lazily filled
+//! `Cell`.
+//!
+//! With a `RefCell`, the inner contents cannot be borrowed for the lifetime of
+//! the entire object, but only of the borrows returned. A `LazyCell` is a
+//! variation on `RefCell` which allows borrows to be tied to the lifetime of
+//! the outer object.
+//!
+//! # Example
+//!
+//! The following example shows a quick example of the basic functionality of
+//! `LazyCell`.
+//!
+//! ```
+//! use lazycell::LazyCell;
+//!
+//! let lazycell = LazyCell::new();
+//!
+//! assert_eq!(lazycell.borrow(), None);
+//! assert!(!lazycell.filled());
+//! lazycell.fill(1).ok();
+//! assert!(lazycell.filled());
+//! assert_eq!(lazycell.borrow(), Some(&1));
+//! assert_eq!(lazycell.into_inner(), Some(1));
+//! ```
+//!
+//! `AtomicLazyCell` is a variant that uses an atomic variable to manage
+//! coordination in a thread-safe fashion. The limitation of an `AtomicLazyCell`
+//! is that after it is initialized, it can't be modified.
+
+
+#[cfg(not(test))]
+#[macro_use]
+extern crate core as std;
+#[cfg(feature = "serde")]
+extern crate serde;
+
+#[cfg(feature = "serde")]
+mod serde_impl;
+
+use std::cell::UnsafeCell;
+use std::mem;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+/// A lazily filled `Cell`, with mutable contents.
+///
+/// A `LazyCell` is completely frozen once filled, **unless** you have `&mut`
+/// access to it, in which case `LazyCell::borrow_mut` may be used to mutate the
+/// contents.
+#[derive(Debug)]
+pub struct LazyCell<T> {
+    inner: UnsafeCell<Option<T>>,
+}
+
+impl<T> LazyCell<T> {
+    /// Creates a new, empty, `LazyCell`.
+    pub fn new() -> LazyCell<T> {
+        LazyCell { inner: UnsafeCell::new(None) }
+    }
+
+    /// Put a value into this cell.
+    ///
+    /// This function will return `Err(value)` if the cell is already full.
+    pub fn fill(&self, value: T) -> Result<(), T> {
+        let slot = unsafe { &*self.inner.get() };
+        if slot.is_some() {
+            return Err(value);
+        }
+        let slot = unsafe { &mut *self.inner.get() };
+        *slot = Some(value);
+
+        Ok(())
+    }
+
+    /// Put a value into this cell.
+    ///
+    /// Note that this function is infallible but requires `&mut self`. By
+    /// requiring `&mut self` we're guaranteed that no active borrows to this
+    /// cell can exist so we can always fill in the value. This may not always
+    /// be usable, however, as `&mut self` may not be possible to borrow.
+    ///
+    /// # Return value
+    ///
+    /// This function returns the previous value, if any.
+    pub fn replace(&mut self, value: T) -> Option<T> {
+        mem::replace(unsafe { &mut *self.inner.get() }, Some(value))
+    }
+
+    /// Test whether this cell has been previously filled.
+    pub fn filled(&self) -> bool {
+        self.borrow().is_some()
+    }
+
+    /// Borrows the contents of this lazy cell for the duration of the cell
+    /// itself.
+    ///
+    /// This function will return `Some` if the cell has been previously
+    /// initialized, and `None` if it has not yet been initialized.
+    pub fn borrow(&self) -> Option<&T> {
+        unsafe { &*self.inner.get() }.as_ref()
+    }
+
+    /// Borrows the contents of this lazy cell mutably for the duration of the cell
+    /// itself.
+    ///
+    /// This function will return `Some` if the cell has been previously
+    /// initialized, and `None` if it has not yet been initialized.
+    pub fn borrow_mut(&mut self) -> Option<&mut T> {
+        unsafe { &mut *self.inner.get() }.as_mut()
+    }
+
+    /// Borrows the contents of this lazy cell for the duration of the cell
+    /// itself.
+    ///
+    /// If the cell has not yet been filled, the cell is first filled using the
+    /// function provided.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the cell becomes filled as a side effect of `f`.
+    pub fn borrow_with<F: FnOnce() -> T>(&self, f: F) -> &T {
+        if let Some(value) = self.borrow() {
+            return value;
+        }
+        let value = f();
+        if self.fill(value).is_err() {
+            panic!("borrow_with: cell was filled by closure")
+        }
+        self.borrow().unwrap()
+    }
+
+    /// Borrows the contents of this `LazyCell` mutably for the duration of the
+    /// cell itself.
+    ///
+    /// If the cell has not yet been filled, the cell is first filled using the
+    /// function provided.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the cell becomes filled as a side effect of `f`.
+    pub fn borrow_mut_with<F: FnOnce() -> T>(&mut self, f: F) -> &mut T {
+        if !self.filled() {
+            let value = f();
+            if self.fill(value).is_err() {
+                panic!("borrow_mut_with: cell was filled by closure")
+            }
+        }
+
+        self.borrow_mut().unwrap()
+    }
+
+    /// Same as `borrow_with`, but allows the initializing function to fail.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the cell becomes filled as a side effect of `f`.
+    pub fn try_borrow_with<E, F>(&self, f: F) -> Result<&T, E>
+        where F: FnOnce() -> Result<T, E>
+    {
+        if let Some(value) = self.borrow() {
+            return Ok(value);
+        }
+        let value = f()?;
+        if self.fill(value).is_err() {
+            panic!("try_borrow_with: cell was filled by closure")
+        }
+        Ok(self.borrow().unwrap())
+    }
+
+    /// Same as `borrow_mut_with`, but allows the initializing function to fail.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the cell becomes filled as a side effect of `f`.
+    pub fn try_borrow_mut_with<E, F>(&mut self, f: F) -> Result<&mut T, E>
+        where F: FnOnce() -> Result<T, E>
+    {
+        if self.filled() {
+            return Ok(self.borrow_mut().unwrap());
+        }
+        let value = f()?;
+        if self.fill(value).is_err() {
+            panic!("try_borrow_mut_with: cell was filled by closure")
+        }
+        Ok(self.borrow_mut().unwrap())
+    }
+
+    /// Consumes this `LazyCell`, returning the underlying value.
+    pub fn into_inner(self) -> Option<T> {
+        // Rust 1.25 changed UnsafeCell::into_inner() from unsafe to safe
+        // function. This unsafe can be removed when supporting Rust older than
+        // 1.25 is not needed.
+        #[allow(unused_unsafe)]
+        unsafe { self.inner.into_inner() }
+    }
+}
+
+impl<T: Copy> LazyCell<T> {
+    /// Returns a copy of the contents of the lazy cell.
+    ///
+    /// This function will return `Some` if the cell has been previously initialized,
+    /// and `None` if it has not yet been initialized.
+    pub fn get(&self) -> Option<T> {
+        unsafe { *self.inner.get() }
+    }
+}
+
+impl<T> Default for LazyCell<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl <T: Clone> Clone for LazyCell<T> {
+    /// Create a clone of this `LazyCell`
+    ///
+    /// If self has not been initialized, returns an uninitialized `LazyCell`
+    /// otherwise returns a `LazyCell` already initialized with a clone of the
+    /// contents of self.
+    fn clone(&self) -> LazyCell<T> {
+        LazyCell { inner: UnsafeCell::new(self.borrow().map(Clone::clone) ) }
+    }
+}
+
+// Tracks the AtomicLazyCell inner state
+const NONE: usize = 0;
+const LOCK: usize = 1;
+const SOME: usize = 2;
+
+/// A lazily filled and thread-safe `Cell`, with frozen contents.
+#[derive(Debug)]
+pub struct AtomicLazyCell<T> {
+    inner: UnsafeCell<Option<T>>,
+    state: AtomicUsize,
+}
+
+impl<T> AtomicLazyCell<T> {
+    /// An empty `AtomicLazyCell`.
+    pub const NONE: Self = Self {
+        inner: UnsafeCell::new(None),
+        state: AtomicUsize::new(NONE),
+    };
+
+    /// Creates a new, empty, `AtomicLazyCell`.
+    pub fn new() -> AtomicLazyCell<T> {
+        Self::NONE
+    }
+
+    /// Put a value into this cell.
+    ///
+    /// This function will return `Err(value)` if the cell is already full.
+    pub fn fill(&self, t: T) -> Result<(), T> {
+        if NONE != self.state.compare_and_swap(NONE, LOCK, Ordering::Acquire) {
+            return Err(t);
+        }
+
+        unsafe { *self.inner.get() = Some(t) };
+
+        if LOCK != self.state.compare_and_swap(LOCK, SOME, Ordering::Release) {
+            panic!("unable to release lock");
+        }
+
+        Ok(())
+    }
+
+    /// Put a value into this cell.
+    ///
+    /// Note that this function is infallible but requires `&mut self`. By
+    /// requiring `&mut self` we're guaranteed that no active borrows to this
+    /// cell can exist so we can always fill in the value. This may not always
+    /// be usable, however, as `&mut self` may not be possible to borrow.
+    ///
+    /// # Return value
+    ///
+    /// This function returns the previous value, if any.
+    pub fn replace(&mut self, value: T) -> Option<T> {
+        match mem::replace(self.state.get_mut(), SOME) {
+            NONE | SOME => {}
+            _ => panic!("cell in inconsistent state"),
+        }
+        mem::replace(unsafe { &mut *self.inner.get() }, Some(value))
+    }
+
+    /// Test whether this cell has been previously filled.
+    pub fn filled(&self) -> bool {
+        self.state.load(Ordering::Acquire) == SOME
+    }
+
+    /// Borrows the contents of this lazy cell for the duration of the cell
+    /// itself.
+    ///
+    /// This function will return `Some` if the cell has been previously
+    /// initialized, and `None` if it has not yet been initialized.
+    pub fn borrow(&self) -> Option<&T> {
+        match self.state.load(Ordering::Acquire) {
+            SOME => unsafe { &*self.inner.get() }.as_ref(),
+            _ => None,
+        }
+    }
+
+    /// Consumes this `LazyCell`, returning the underlying value.
+    pub fn into_inner(self) -> Option<T> {
+        // Rust 1.25 changed UnsafeCell::into_inner() from unsafe to safe
+        // function. This unsafe can be removed when supporting Rust older than
+        // 1.25 is not needed.
+        #[allow(unused_unsafe)]
+        unsafe { self.inner.into_inner() }
+    }
+}
+
+impl<T: Copy> AtomicLazyCell<T> {
+    /// Returns a copy of the contents of the lazy cell.
+    ///
+    /// This function will return `Some` if the cell has been previously initialized,
+    /// and `None` if it has not yet been initialized.
+    pub fn get(&self) -> Option<T> {
+        match self.state.load(Ordering::Acquire) {
+            SOME => unsafe { *self.inner.get() },
+            _ => None,
+        }
+    }
+}
+
+impl<T> Default for AtomicLazyCell<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<T: Clone> Clone for AtomicLazyCell<T> {
+    /// Create a clone of this `AtomicLazyCell`
+    ///
+    /// If self has not been initialized, returns an uninitialized `AtomicLazyCell`
+    /// otherwise returns an `AtomicLazyCell` already initialized with a clone of the
+    /// contents of self.
+    fn clone(&self) -> AtomicLazyCell<T> {
+        self.borrow().map_or(
+            Self::NONE,
+            |v| AtomicLazyCell {
+                inner: UnsafeCell::new(Some(v.clone())),
+                state: AtomicUsize::new(SOME),
+            }
+        )
+    }
+}
+
+unsafe impl<T: Sync + Send> Sync for AtomicLazyCell<T> {}
+
+unsafe impl<T: Send> Send for AtomicLazyCell<T> {}
+
+#[cfg(test)]
+mod tests {
+    use super::{AtomicLazyCell, LazyCell};
+
+    #[test]
+    fn test_borrow_from_empty() {
+        let lazycell: LazyCell<usize> = LazyCell::new();
+
+        let value = lazycell.borrow();
+        assert_eq!(value, None);
+
+        let value = lazycell.get();
+        assert_eq!(value, None);
+    }
+
+    #[test]
+    fn test_fill_and_borrow() {
+        let lazycell = LazyCell::new();
+
+        assert!(!lazycell.filled());
+        lazycell.fill(1).unwrap();
+        assert!(lazycell.filled());
+
+        let value = lazycell.borrow();
+        assert_eq!(value, Some(&1));
+
+        let value = lazycell.get();
+        assert_eq!(value, Some(1));
+    }
+
+    #[test]
+    fn test_borrow_mut() {
+        let mut lazycell = LazyCell::new();
+        assert!(lazycell.borrow_mut().is_none());
+
+        lazycell.fill(1).unwrap();
+        assert_eq!(lazycell.borrow_mut(), Some(&mut 1));
+
+        *lazycell.borrow_mut().unwrap() = 2;
+        assert_eq!(lazycell.borrow_mut(), Some(&mut 2));
+
+        // official way to reset the cell
+        lazycell = LazyCell::new();
+        assert!(lazycell.borrow_mut().is_none());
+    }
+
+    #[test]
+    fn test_already_filled_error() {
+        let lazycell = LazyCell::new();
+
+        lazycell.fill(1).unwrap();
+        assert_eq!(lazycell.fill(1), Err(1));
+    }
+
+    #[test]
+    fn test_borrow_with() {
+        let lazycell = LazyCell::new();
+
+        let value = lazycell.borrow_with(|| 1);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    fn test_borrow_with_already_filled() {
+        let lazycell = LazyCell::new();
+        lazycell.fill(1).unwrap();
+
+        let value = lazycell.borrow_with(|| 1);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    fn test_borrow_with_not_called_when_filled() {
+        let lazycell = LazyCell::new();
+
+        lazycell.fill(1).unwrap();
+
+        let value = lazycell.borrow_with(|| 2);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_borrow_with_sound_with_reentrancy() {
+        // Kudos to dbaupp for discovering this issue
+        // https://www.reddit.com/r/rust/comments/5vs9rt/lazycell_a_rust_library_providing_a_lazilyfilled/de527xm/
+        let lazycell: LazyCell<Box<i32>> = LazyCell::new();
+
+        let mut reference: Option<&i32> = None;
+
+        lazycell.borrow_with(|| {
+            let _ = lazycell.fill(Box::new(1));
+            reference = lazycell.borrow().map(|r| &**r);
+            Box::new(2)
+        });
+    }
+
+    #[test]
+    fn test_borrow_mut_with() {
+        let mut lazycell = LazyCell::new();
+
+        {
+            let value = lazycell.borrow_mut_with(|| 1);
+            assert_eq!(&mut 1, value);
+            *value = 2;
+        }
+        assert_eq!(&2, lazycell.borrow().unwrap());
+    }
+
+    #[test]
+    fn test_borrow_mut_with_already_filled() {
+        let mut lazycell = LazyCell::new();
+        lazycell.fill(1).unwrap();
+
+        let value = lazycell.borrow_mut_with(|| 1);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    fn test_borrow_mut_with_not_called_when_filled() {
+        let mut lazycell = LazyCell::new();
+
+        lazycell.fill(1).unwrap();
+
+        let value = lazycell.borrow_mut_with(|| 2);
+        assert_eq!(&1, value);
+    }
+
+    #[test]
+    fn test_try_borrow_with_ok() {
+        let lazycell = LazyCell::new();
+        let result = lazycell.try_borrow_with::<(), _>(|| Ok(1));
+        assert_eq!(result, Ok(&1));
+    }
+
+    #[test]
+    fn test_try_borrow_with_err() {
+        let lazycell = LazyCell::<()>::new();
+        let result = lazycell.try_borrow_with(|| Err(1));
+        assert_eq!(result, Err(1));
+    }
+
+    #[test]
+    fn test_try_borrow_with_already_filled() {
+        let lazycell = LazyCell::new();
+        lazycell.fill(1).unwrap();
+        let result = lazycell.try_borrow_with::<(), _>(|| unreachable!());
+        assert_eq!(result, Ok(&1));
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_try_borrow_with_sound_with_reentrancy() {
+        let lazycell: LazyCell<Box<i32>> = LazyCell::new();
+
+        let mut reference: Option<&i32> = None;
+
+        let _ = lazycell.try_borrow_with::<(), _>(|| {
+            let _ = lazycell.fill(Box::new(1));
+            reference = lazycell.borrow().map(|r| &**r);
+            Ok(Box::new(2))
+        });
+    }
+
+    #[test]
+    fn test_try_borrow_mut_with_ok() {
+        let mut lazycell = LazyCell::new();
+        {
+            let result = lazycell.try_borrow_mut_with::<(), _>(|| Ok(1));
+            assert_eq!(result, Ok(&mut 1));
+            *result.unwrap() = 2;
+        }
+        assert_eq!(&mut 2, lazycell.borrow().unwrap());
+    }
+
+    #[test]
+    fn test_try_borrow_mut_with_err() {
+        let mut lazycell = LazyCell::<()>::new();
+        let result = lazycell.try_borrow_mut_with(|| Err(1));
+        assert_eq!(result, Err(1));
+    }
+
+    #[test]
+    fn test_try_borrow_mut_with_already_filled() {
+        let mut lazycell = LazyCell::new();
+        lazycell.fill(1).unwrap();
+        let result = lazycell.try_borrow_mut_with::<(), _>(|| unreachable!());
+        assert_eq!(result, Ok(&mut 1));
+    }
+
+    #[test]
+    fn test_into_inner() {
+        let lazycell = LazyCell::new();
+
+        lazycell.fill(1).unwrap();
+        let value = lazycell.into_inner();
+        assert_eq!(value, Some(1));
+    }
+
+    #[test]
+    fn test_atomic_borrow_from_empty() {
+        let lazycell: AtomicLazyCell<usize> = AtomicLazyCell::new();
+
+        let value = lazycell.borrow();
+        assert_eq!(value, None);
+
+        let value = lazycell.get();
+        assert_eq!(value, None);
+    }
+
+    #[test]
+    fn test_atomic_fill_and_borrow() {
+        let lazycell = AtomicLazyCell::new();
+
+        assert!(!lazycell.filled());
+        lazycell.fill(1).unwrap();
+        assert!(lazycell.filled());
+
+        let value = lazycell.borrow();
+        assert_eq!(value, Some(&1));
+
+        let value = lazycell.get();
+        assert_eq!(value, Some(1));
+    }
+
+    #[test]
+    fn test_atomic_already_filled_panic() {
+        let lazycell = AtomicLazyCell::new();
+
+        lazycell.fill(1).unwrap();
+        assert_eq!(1, lazycell.fill(1).unwrap_err());
+    }
+
+    #[test]
+    fn test_atomic_into_inner() {
+        let lazycell = AtomicLazyCell::new();
+
+        lazycell.fill(1).unwrap();
+        let value = lazycell.into_inner();
+        assert_eq!(value, Some(1));
+    }
+
+    #[test]
+    fn normal_replace() {
+        let mut cell = LazyCell::new();
+        assert_eq!(cell.fill(1), Ok(()));
+        assert_eq!(cell.replace(2), Some(1));
+        assert_eq!(cell.replace(3), Some(2));
+        assert_eq!(cell.borrow(), Some(&3));
+
+        let mut cell = LazyCell::new();
+        assert_eq!(cell.replace(2), None);
+    }
+
+    #[test]
+    fn atomic_replace() {
+        let mut cell = AtomicLazyCell::new();
+        assert_eq!(cell.fill(1), Ok(()));
+        assert_eq!(cell.replace(2), Some(1));
+        assert_eq!(cell.replace(3), Some(2));
+        assert_eq!(cell.borrow(), Some(&3));
+    }
+
+    #[test]
+    fn clone() {
+        let mut cell = LazyCell::new();
+        let clone1 = cell.clone();
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(cell.fill(1), Ok(()));
+        let mut clone2 = cell.clone();
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(clone2.borrow(), Some(&1));
+        assert_eq!(cell.replace(2), Some(1));
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(clone2.borrow(), Some(&1));
+        assert_eq!(clone1.fill(3), Ok(()));
+        assert_eq!(clone2.replace(4), Some(1));
+        assert_eq!(clone1.borrow(), Some(&3));
+        assert_eq!(clone2.borrow(), Some(&4));
+        assert_eq!(cell.borrow(), Some(&2));
+    }
+
+    #[test]
+    fn clone_atomic() {
+        let mut cell = AtomicLazyCell::new();
+        let clone1 = cell.clone();
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(cell.fill(1), Ok(()));
+        let mut clone2 = cell.clone();
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(clone2.borrow(), Some(&1));
+        assert_eq!(cell.replace(2), Some(1));
+        assert_eq!(clone1.borrow(), None);
+        assert_eq!(clone2.borrow(), Some(&1));
+        assert_eq!(clone1.fill(3), Ok(()));
+        assert_eq!(clone2.replace(4), Some(1));
+        assert_eq!(clone1.borrow(), Some(&3));
+        assert_eq!(clone2.borrow(), Some(&4));
+        assert_eq!(cell.borrow(), Some(&2));
+    }
+
+    #[test]
+    fn default() {
+        #[derive(Default)]
+        struct Defaultable;
+        struct NonDefaultable;
+
+        let _: LazyCell<Defaultable> = LazyCell::default();
+        let _: LazyCell<NonDefaultable> = LazyCell::default();
+
+        let _: AtomicLazyCell<Defaultable> = AtomicLazyCell::default();
+        let _: AtomicLazyCell<NonDefaultable> = AtomicLazyCell::default();
+    }
+}
diff --git a/third_party/rust/lazycell/src/serde_impl.rs b/third_party/rust/lazycell/src/serde_impl.rs
new file mode 100644
index 0000000000..8f08f7b03e
--- /dev/null
+++ b/third_party/rust/lazycell/src/serde_impl.rs
@@ -0,0 +1,86 @@
+// Copyright (c) 2020 Nikita Pekin and the lazycell contributors
+// See the README.md file at the top-level directory of this distribution.
+//
+// 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 serde::ser::{Serialize, Serializer};
+use serde::ser::{Serialize, Serializer};
+use serde::de::{self, Deserialize, Deserializer, Visitor};
+
+use std::fmt;
+use std::marker::PhantomData;
+
+use super::{LazyCell, AtomicLazyCell};
+
+impl<T: Serialize> Serialize for LazyCell<T> {
+    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+        match self.borrow() {
+            Some(val) => serializer.serialize_some(val),
+            None => serializer.serialize_none()
+        }
+    }
+}
+
+
+impl<T: Serialize> Serialize for AtomicLazyCell<T> {
+    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+        match self.borrow() {
+            Some(val) => serializer.serialize_some(val),
+            None => serializer.serialize_none()
+        }
+    }
+}
+
+struct LazyCellVisitor<T>(PhantomData<*const T>);
+impl<'de, T: Deserialize<'de>> Visitor<'de> for LazyCellVisitor<T> {
+    type Value = LazyCell<T>;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("a LazyCell")
+    }
+
+    fn visit_some<D: Deserializer<'de>>(self, deserializer: D) -> Result<Self::Value, D::Error> {
+        let mut cell = LazyCell::new();
+        cell.replace(T::deserialize(deserializer)?);
+        Ok(cell)
+    }
+
+    fn visit_none<E: de::Error>(self) -> Result<Self::Value, E> {
+        Ok(LazyCell::new())
+    }
+}
+
+impl<'de, T: Deserialize<'de>> Deserialize<'de> for LazyCell<T> {
+    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        deserializer.deserialize_option(LazyCellVisitor(PhantomData))
+    }
+}
+
+
+struct AtomicLazyCellVisitor<T>(PhantomData<*const T>);
+impl<'de, T: Deserialize<'de>> Visitor<'de> for AtomicLazyCellVisitor<T> {
+    type Value = AtomicLazyCell<T>;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("an AtomicLazyCell")
+    }
+
+    fn visit_some<D: Deserializer<'de>>(self, deserializer: D) -> Result<Self::Value, D::Error> {
+        let mut cell = AtomicLazyCell::new();
+        cell.replace(T::deserialize(deserializer)?);
+        Ok(cell)
+    }
+
+    fn visit_none<E: de::Error>(self) -> Result<Self::Value, E> {
+        Ok(AtomicLazyCell::new())
+    }
+}
+
+
+impl<'de, T: Deserialize<'de>> Deserialize<'de> for AtomicLazyCell<T> {
+    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        deserializer.deserialize_option(AtomicLazyCellVisitor(PhantomData))
+    }
+}