diff --git a/.rustfmt.toml b/.rustfmt.toml
new file mode 100644
index 00000000..faa3d5a3
--- /dev/null
+++ b/.rustfmt.toml
@@ -0,0 +1,3 @@
+# Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+max_width = 80
+tab_spaces = 2
diff --git a/src/main.rs b/src/main.rs
index a363b483..9f29639f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,246 +1,249 @@
 mod channel {
-    use super::util;
+  use super::util;
 
-    extern "C" {
-        // Call a method/destructor; virtual methods use C++ dynamic dispatch.
-        fn Channel__DTOR(this: &mut Channel) -> ();
-        fn Channel__a(this: &mut Channel) -> ();
-        fn Channel__b(this: &Channel) -> i32;
+  extern "C" {
+    // Call a method/destructor; virtual methods use C++ dynamic dispatch.
+    fn Channel__DTOR(this: &mut Channel) -> ();
+    fn Channel__a(this: &mut Channel) -> ();
+    fn Channel__b(this: &Channel) -> i32;
 
-        // Call a method of a specific class implementation, bypassing dynamic
-        // dispatch. C++ equivalent: `my_channel.Channel::a()`.
-        fn Channel__Channel__a(this: &mut Channel) -> ();
+    // Call a method of a specific class implementation, bypassing dynamic
+    // dispatch. C++ equivalent: `my_channel.Channel::a()`.
+    fn Channel__Channel__a(this: &mut Channel) -> ();
 
-        // Constructs a special class derived from Channel that forwards all
-        // virtual method invocations to rust. It is assumed that this subclass
-        // has the same size and memory layout as the class it's deriving from.
-        fn Channel__OVERRIDE__CTOR(this: &mut std::mem::MaybeUninit<Channel>) -> ();
+    // Constructs a special class derived from Channel that forwards all
+    // virtual method invocations to rust. It is assumed that this subclass
+    // has the same size and memory layout as the class it's deriving from.
+    fn Channel__OVERRIDE__CTOR(this: &mut std::mem::MaybeUninit<Channel>)
+      -> ();
+  }
+
+  #[repr(C)]
+  pub struct Channel {
+    _cxx_vtable: *const [usize; 0],
+  }
+
+  #[allow(dead_code)]
+  impl Channel {
+    pub fn a(&mut self) {
+      unsafe { Channel__a(self) }
+    }
+    pub fn b(&self) -> i32 {
+      unsafe { Channel__b(self) }
+    }
+  }
+
+  impl Drop for Channel {
+    fn drop(&mut self) {
+      unsafe { Channel__DTOR(self) }
+    }
+  }
+
+  pub struct ChannelDefaults;
+  impl ChannelDefaults {
+    pub fn a(this: &mut Channel) {
+      unsafe { Channel__Channel__a(this) }
+    }
+  }
+
+  pub trait ChannelOverrides {
+    fn extender(&self) -> &ChannelExtender;
+    fn extender_mut(&mut self) -> &mut ChannelExtender;
+
+    fn a(&mut self) {
+      ChannelDefaults::a(self.extender_mut())
+    }
+    fn b(&self) -> i32;
+  }
+
+  pub struct ChannelExtender {
+    cxx_channel: Channel,
+    extender_offset: usize,
+    rust_vtable: util::RustVTable<&'static dyn ChannelOverrides>,
+  }
+
+  #[no_mangle]
+  unsafe extern "C" fn Channel__OVERRIDE__a__DISPATCH(this: &mut Channel) {
+    ChannelExtender::dispatch_mut(this).a()
+  }
+  #[no_mangle]
+  unsafe extern "C" fn Channel__OVERRIDE__b__DISPATCH(this: &Channel) -> i32 {
+    ChannelExtender::dispatch(this).b()
+  }
+
+  impl ChannelExtender {
+    fn construct_cxx_channel() -> Channel {
+      unsafe {
+        let mut buf = std::mem::MaybeUninit::<Channel>::uninit();
+        Channel__OVERRIDE__CTOR(&mut buf);
+        buf.assume_init()
+      }
     }
 
-    #[repr(C)]
-    pub struct Channel {
-        _cxx_vtable: *const [usize; 0],
+    fn get_extender_offset<T>() -> usize
+    where
+      T: ChannelOverrides,
+    {
+      let buf = std::mem::MaybeUninit::<T>::uninit();
+      let embedder_ptr: *const T = buf.as_ptr();
+      let self_ptr: *const Self = unsafe { (*embedder_ptr).extender() };
+      util::FieldOffset::from_ptrs(embedder_ptr, self_ptr).offset()
     }
 
-    #[allow(dead_code)]
-    impl Channel {
-        pub fn a(&mut self) {
-            unsafe { Channel__a(self) }
-        }
-        pub fn b(&self) -> i32 {
-            unsafe { Channel__b(self) }
-        }
+    fn get_rust_vtable<T>() -> util::RustVTable<&'static dyn ChannelOverrides>
+    where
+      T: ChannelOverrides,
+    {
+      let buf = std::mem::MaybeUninit::<T>::uninit();
+      let embedder_ptr = buf.as_ptr();
+      let trait_object: *const dyn ChannelOverrides = embedder_ptr;
+      let (data_ptr, vtable): (*const T, util::RustVTable<_>) =
+        unsafe { std::mem::transmute(trait_object) };
+      assert_eq!(data_ptr, embedder_ptr);
+      vtable
     }
 
-    pub struct ChannelDefaults;
-    impl ChannelDefaults {
-        pub fn a(this: &mut Channel) {
-            unsafe { Channel__Channel__a(this) }
-        }
+    pub fn new<T>() -> Self
+    where
+      T: ChannelOverrides,
+    {
+      Self {
+        cxx_channel: Self::construct_cxx_channel(),
+        extender_offset: Self::get_extender_offset::<T>(),
+        rust_vtable: Self::get_rust_vtable::<T>(),
+      }
     }
 
-    pub trait ChannelOverrides {
-        fn base(&self) -> &Override;
-        fn base_mut(&mut self) -> &mut Override;
-
-        fn a(&mut self) {
-            ChannelDefaults::a(self.base_mut())
-        }
-        fn b(&self) -> i32;
+    fn channel_offset() -> util::FieldOffset<Self, Channel> {
+      let buf = std::mem::MaybeUninit::<Self>::uninit();
+      util::FieldOffset::from_ptrs(buf.as_ptr(), unsafe {
+        &(*buf.as_ptr()).cxx_channel
+      })
     }
 
-    pub struct Override {
-        cxx_channel: Channel,
-        base_offset: usize,
-        rust_vtable: util::RustVTable<&'static dyn ChannelOverrides>,
+    fn embedder_offset(&self) -> util::FieldOffset<util::Opaque, Self> {
+      util::FieldOffset::<util::Opaque, Self>::from_offset(self.extender_offset)
     }
 
-    #[no_mangle]
-    unsafe extern "C" fn Channel__OVERRIDE__a__DISPATCH(this: &mut Channel) {
-        Override::dispatch_mut(this).a()
-    }
-    #[no_mangle]
-    unsafe extern "C" fn Channel__OVERRIDE__b__DISPATCH(this: &Channel) -> i32 {
-        Override::dispatch(this).b()
+    unsafe fn dispatch(channel: &Channel) -> &dyn ChannelOverrides {
+      let this = Self::channel_offset().to_outer(channel);
+      let embedder = this.embedder_offset().to_outer(this);
+      std::mem::transmute((embedder, this.rust_vtable))
     }
 
-    impl Drop for Channel {
-        fn drop(&mut self) {
-            unsafe { Channel__DTOR(self) }
-        }
+    unsafe fn dispatch_mut(channel: &mut Channel) -> &mut dyn ChannelOverrides {
+      let this = Self::channel_offset().to_outer_mut(channel);
+      let vtable = this.rust_vtable;
+      let embedder = this.embedder_offset().to_outer_mut(this);
+      std::mem::transmute((embedder, vtable))
     }
+  }
 
-    impl Override {
-        fn construct_cxx_channel() -> Channel {
-            unsafe {
-                let mut buf = std::mem::MaybeUninit::<Channel>::uninit();
-                Channel__OVERRIDE__CTOR(&mut buf);
-                buf.assume_init()
-            }
-        }
-
-        fn get_base_offset<T>() -> usize
-        where
-            T: ChannelOverrides,
-        {
-            let buf = std::mem::MaybeUninit::<T>::uninit();
-            let top_ptr: *const T = buf.as_ptr();
-            let self_ptr: *const Self = unsafe { (*top_ptr).base() };
-            util::FieldOffset::from_ptrs(top_ptr, self_ptr).offset()
-        }
-
-        fn get_rust_vtable<T>() -> util::RustVTable<&'static dyn ChannelOverrides>
-        where
-            T: ChannelOverrides,
-        {
-            let buf = std::mem::MaybeUninit::<T>::uninit();
-            let embedder_ptr = buf.as_ptr();
-            let trait_object: *const dyn ChannelOverrides = embedder_ptr;
-            let (data_ptr, vtable): (*const T, util::RustVTable<_>) =
-                unsafe { std::mem::transmute(trait_object) };
-            assert_eq!(data_ptr, embedder_ptr);
-            vtable
-        }
-
-        pub fn new<T>() -> Self
-        where
-            T: ChannelOverrides,
-        {
-            Self {
-                cxx_channel: Self::construct_cxx_channel(),
-                base_offset: Self::get_base_offset::<T>(),
-                rust_vtable: Self::get_rust_vtable::<T>(),
-            }
-        }
-
-        fn channel_offset() -> util::FieldOffset<Self, Channel> {
-            let buf = std::mem::MaybeUninit::<Self>::uninit();
-            util::FieldOffset::from_ptrs(buf.as_ptr(), unsafe { &(*buf.as_ptr()).cxx_channel })
-        }
-
-        fn embedder_offset(&self) -> util::FieldOffset<util::Opaque, Self> {
-            util::FieldOffset::<util::Opaque, Self>::from_offset(self.base_offset)
-        }
-
-        unsafe fn dispatch(channel: &Channel) -> &dyn ChannelOverrides {
-            let this = Self::channel_offset().to_outer(channel);
-            let embedder = this.embedder_offset().to_outer(this);
-            std::mem::transmute((embedder, this.rust_vtable))
-        }
-
-        unsafe fn dispatch_mut(channel: &mut Channel) -> &mut dyn ChannelOverrides {
-            let this = Self::channel_offset().to_outer_mut(channel);
-            let vtable = this.rust_vtable;
-            let embedder = this.embedder_offset().to_outer_mut(this);
-            std::mem::transmute((embedder, vtable))
-        }
+  impl std::ops::Deref for ChannelExtender {
+    type Target = Channel;
+    fn deref(&self) -> &Channel {
+      &self.cxx_channel
     }
+  }
 
-    impl std::ops::Deref for Override {
-        type Target = Channel;
-        fn deref(&self) -> &Channel {
-            &self.cxx_channel
-        }
-    }
-
-    impl std::ops::DerefMut for Override {
-        fn deref_mut(&mut self) -> &mut Channel {
-            &mut self.cxx_channel
-        }
+  impl std::ops::DerefMut for ChannelExtender {
+    fn deref_mut(&mut self) -> &mut Channel {
+      &mut self.cxx_channel
     }
+  }
 }
 
 mod trying {
-    use super::channel::*;
+  use super::channel::*;
 
-    #[allow(dead_code)]
-    pub struct Session {
-        a: i32,
-        b: String,
-        c: Override,
-    }
+  #[allow(dead_code)]
+  pub struct Session {
+    a: i32,
+    b: String,
+    c: ChannelExtender,
+  }
 
-    impl ChannelOverrides for Session {
-        fn base(&self) -> &Override {
-            &self.c
-        }
-        fn base_mut(&mut self) -> &mut Override {
-            &mut self.c
-        }
-        fn a(&mut self) {
-            println!("Override a!");
-        }
-        fn b(&self) -> i32 {
-            println!("Override b!");
-            42
-        }
+  impl ChannelOverrides for Session {
+    fn extender(&self) -> &ChannelExtender {
+      &self.c
     }
+    fn extender_mut(&mut self) -> &mut ChannelExtender {
+      &mut self.c
+    }
+    fn a(&mut self) {
+      println!("ChannelExtender a!");
+    }
+    fn b(&self) -> i32 {
+      println!("ChannelExtender b!");
+      42
+    }
+  }
 
-    impl Session {
-        pub fn new() -> Self {
-            Self {
-                a: 1,
-                b: "abc".to_owned(),
-                c: Override::new::<Self>(),
-            }
-        }
+  impl Session {
+    pub fn new() -> Self {
+      Self {
+        a: 1,
+        b: "abc".to_owned(),
+        c: ChannelExtender::new::<Self>(),
+      }
     }
+  }
 }
 
 mod util {
-    use std::marker::PhantomData;
-    use std::mem::size_of;
+  use std::marker::PhantomData;
+  use std::mem::size_of;
 
-    pub type Opaque = [usize; 0];
+  pub type Opaque = [usize; 0];
 
-    #[repr(transparent)]
-    #[derive(Copy, Clone, Debug)]
-    pub struct RustVTable<DynT>(pub *const Opaque, pub PhantomData<DynT>);
+  #[repr(transparent)]
+  #[derive(Copy, Clone, Debug)]
+  pub struct RustVTable<DynT>(pub *const Opaque, pub PhantomData<DynT>);
 
-    #[derive(Copy, Clone, Debug)]
-    #[repr(transparent)]
-    pub struct FieldOffset<O, I>(isize, PhantomData<(O, I)>);
+  #[derive(Copy, Clone, Debug)]
+  #[repr(transparent)]
+  pub struct FieldOffset<O, I>(isize, PhantomData<(O, I)>);
 
-    impl<O, I> FieldOffset<O, I> {
-        pub fn from_ptrs(o_ptr: *const O, i_ptr: *const I) -> Self {
-            let o_addr = o_ptr as usize;
-            let i_addr = i_ptr as usize;
-            assert!(i_addr >= o_addr);
-            assert!((i_addr + size_of::<I>()) <= (o_addr + size_of::<O>()));
-            let offset = (o_addr - i_addr) as isize;
-            assert!(offset > 0);
-            Self(offset, PhantomData)
-        }
-
-        pub fn from_offset(offset: usize) -> Self {
-            assert!((offset as isize) > 0);
-            Self(offset as isize, PhantomData)
-        }
-
-        pub fn offset(self) -> usize {
-            self.0 as usize
-        }
-
-        fn shift<PI, PO>(ptr: *const PI, delta: isize) -> *mut PO {
-            (ptr as isize + delta) as *mut PO
-        }
-        pub unsafe fn to_outer<'a>(&self, inner: &'a I) -> &'a O {
-            Self::shift::<I, O>(inner, -self.0).as_ref().unwrap()
-        }
-        #[allow(dead_code)]
-        pub unsafe fn to_outer_mut<'a>(&self, inner: &'a mut I) -> &'a mut O {
-            Self::shift::<I, O>(inner, -self.0).as_mut().unwrap()
-        }
+  impl<O, I> FieldOffset<O, I> {
+    pub fn from_ptrs(o_ptr: *const O, i_ptr: *const I) -> Self {
+      let o_addr = o_ptr as usize;
+      let i_addr = i_ptr as usize;
+      assert!(i_addr >= o_addr);
+      assert!((i_addr + size_of::<I>()) <= (o_addr + size_of::<O>()));
+      let offset = (o_addr - i_addr) as isize;
+      assert!(offset > 0);
+      Self(offset, PhantomData)
     }
 
-    impl<O, M, I> std::ops::Add<FieldOffset<M, I>> for FieldOffset<O, M> {
-        type Output = FieldOffset<O, I>;
-        fn add(self, that: FieldOffset<M, I>) -> Self::Output {
-            FieldOffset::<O, I>::from_offset(self.offset() + that.offset())
-        }
+    pub fn from_offset(offset: usize) -> Self {
+      assert!((offset as isize) > 0);
+      Self(offset as isize, PhantomData)
     }
+
+    pub fn offset(self) -> usize {
+      self.0 as usize
+    }
+
+    fn shift<PI, PO>(ptr: *const PI, delta: isize) -> *mut PO {
+      (ptr as isize + delta) as *mut PO
+    }
+    pub unsafe fn to_outer<'a>(&self, inner: &'a I) -> &'a O {
+      Self::shift::<I, O>(inner, -self.0).as_ref().unwrap()
+    }
+    #[allow(dead_code)]
+    pub unsafe fn to_outer_mut<'a>(&self, inner: &'a mut I) -> &'a mut O {
+      Self::shift::<I, O>(inner, -self.0).as_mut().unwrap()
+    }
+  }
+
+  impl<O, M, I> std::ops::Add<FieldOffset<M, I>> for FieldOffset<O, M> {
+    type Output = FieldOffset<O, I>;
+    fn add(self, that: FieldOffset<M, I>) -> Self::Output {
+      FieldOffset::<O, I>::from_offset(self.offset() + that.offset())
+    }
+  }
 }
 
 fn main() {
-    trying::Session::new();
+  trying::Session::new();
 }