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diff --git a/third_party/rust/smart-default/src/lib.rs b/third_party/rust/smart-default/src/lib.rs
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+++ b/third_party/rust/smart-default/src/lib.rs
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+extern crate proc_macro;
+extern crate proc_macro2;
+extern crate syn;
+
+extern crate quote;
+
+use syn::{parse_macro_input, DeriveInput};
+
+mod body_impl;
+mod default_attr;
+mod util;
+
+/// # Smart Default
+///
+/// This crate provides a custom derive for `SmartDefault`. `SmartDefault` is not a real type -
+/// deriving it will actually `impl Default`. The difference from regular `#[derive(Default)]` is
+/// that `#[derive(SmartDefault)]` allows you to use `#[default = "..."]` attributes to customize
+/// the `::default()` method and to support `struct`s that don't have `Default` for all their
+/// fields - and even `enum`s!
+///
+/// # Examples
+///
+/// ```
+/// #[macro_use]
+/// extern crate smart_default;
+///
+/// # fn main() {
+/// #[derive(SmartDefault)]
+/// # #[derive(PartialEq)]
+/// # #[allow(dead_code)]
+/// enum Foo {
+///     Bar,
+///     #[default]
+///     Baz {
+///         #[default = 12]
+///         a: i32,
+///         b: i32,
+///         #[default(Some(Default::default()))]
+///         c: Option<i32>,
+///         #[default(_code = "vec![1, 2, 3]")]
+///         d: Vec<u32>,
+///         #[default = "four"]
+///         e: String,
+///     },
+///     Qux(i32),
+/// }
+///
+/// assert!(Foo::default() == Foo::Baz {
+///     a: 12,
+///     b: 0,
+///     c: Some(0),
+///     d: vec![1, 2, 3],
+///     e: "four".to_owned(),
+/// });
+/// # }
+/// ```
+///
+/// * `Baz` has the `#[default]` attribute. This means that the default `Foo` is a `Foo::Baz`. Only
+///   one variant may have a `#[default]` attribute, and that attribute must have no value.
+/// * `a` has a `#[default = 12]` attribute. This means that it's default value is `12`.
+/// * `b` has no `#[default = ...]` attribute. It's default value will `i32`'s default value
+///   instead - `0`.
+/// * `c` is an `Option<i32>`, and it's default is `Some(Default::default())`. Rust cannot (currently)
+///   parse `#[default = Some(Default::default())]` and therefore we have to use a special syntax:
+///   `#[default(Some(Default::default))]`
+/// * `d` has the `!` token in it, which cannot (currently) be parsed even with `#[default(...)]`,
+///   so we have to encode it as a string and mark it as `_code = `.
+/// * `e` is a `String`, so the string literal "four" is automatically converted to it. This
+///   automatic conversion **only** happens to string (or byte string) literals - and only if
+///   `_code` is not used.
+/// * Documentation for the `impl Default` section is generated automatically, specifying the
+///   default value returned from `::default()`.
+#[proc_macro_derive(SmartDefault, attributes(default))]
+pub fn derive_smart_default(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    match body_impl::impl_my_derive(&input) {
+        Ok(output) => {
+            output.into()
+        },
+        Err(error) =>{
+            error.to_compile_error().into()
+        }
+    }
+}