diff --git a/serde/src/ser/impls.rs b/serde/src/ser/impls.rs
index d0ac49bc..a8876c95 100644
--- a/serde/src/ser/impls.rs
+++ b/serde/src/ser/impls.rs
@@ -64,8 +64,6 @@ use super::{
     Error,
     Serialize,
     Serializer,
-    SeqVisitor,
-    MapVisitor,
 };
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -133,26 +131,6 @@ impl<T> Serialize for Option<T> where T: Serialize {
     }
 }
 
-impl<T> SeqVisitor for Option<T> where T: Serialize {
-    #[inline]
-    fn visit<S>(&mut self, serializer: &mut S) -> Result<Option<()>, S::Error>
-        where S: Serializer,
-    {
-        match self.take() {
-            Some(value) => {
-                try!(serializer.serialize_seq_elt(value));
-                Ok(Some(()))
-            }
-            None => Ok(None),
-        }
-    }
-
-    #[inline]
-    fn len(&self) -> Option<usize> {
-        Some(if self.is_some() { 1 } else { 0 })
-    }
-}
-
 ///////////////////////////////////////////////////////////////////////////////
 
 impl<T> Serialize for PhantomData<T> {
@@ -164,69 +142,6 @@ impl<T> Serialize for PhantomData<T> {
     }
 }
 
-///////////////////////////////////////////////////////////////////////////////
-
-/// A `serde::Visitor` for sequence iterators.
-///
-/// # Examples
-///
-/// ```
-/// use serde::{Serialize, Serializer};
-/// use serde::ser::impls::SeqIteratorVisitor;
-///
-/// struct Seq(Vec<u32>);
-///
-/// impl Serialize for Seq {
-///     fn serialize<S>(&self, ser: &mut S) -> Result<(), S::Error>
-///         where S: Serializer,
-///     {
-///         ser.serialize_seq(SeqIteratorVisitor::new(
-///             self.0.iter(),
-///             Some(self.0.len()),
-///         ))
-///     }
-/// }
-/// ```
-pub struct SeqIteratorVisitor<Iter> {
-    iter: Iter,
-    len: Option<usize>,
-}
-
-impl<T, Iter> SeqIteratorVisitor<Iter>
-    where Iter: Iterator<Item=T>
-{
-    /// Construct a new `SeqIteratorVisitor<Iter>`.
-    #[inline]
-    pub fn new(iter: Iter, len: Option<usize>) -> SeqIteratorVisitor<Iter> {
-        SeqIteratorVisitor {
-            iter: iter,
-            len: len,
-        }
-    }
-}
-
-impl<T, Iter> SeqVisitor for SeqIteratorVisitor<Iter>
-    where T: Serialize,
-          Iter: Iterator<Item=T>,
-{
-    #[inline]
-    fn visit<S>(&mut self, serializer: &mut S) -> Result<Option<()>, S::Error>
-        where S: Serializer,
-    {
-        match self.iter.next() {
-            Some(value) => {
-                try!(serializer.serialize_seq_elt(value));
-                Ok(Some(()))
-            }
-            None => Ok(None),
-        }
-    }
-
-    #[inline]
-    fn len(&self) -> Option<usize> {
-        self.len
-    }
-}
 
 ///////////////////////////////////////////////////////////////////////////////
 
@@ -237,7 +152,11 @@ impl<T> Serialize for [T]
     fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
         where S: Serializer,
     {
-        serializer.serialize_seq(SeqIteratorVisitor::new(self.iter(), Some(self.len())))
+        let mut state = try!(serializer.serialize_seq(Some(self.len())));
+        for e in self.iter() {
+            try!(serializer.serialize_seq_elt(&mut state, e));
+        }
+        serializer.serialize_seq_end(state)
     }
 }
 
@@ -250,8 +169,11 @@ macro_rules! array_impls {
             fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
                 where S: Serializer,
             {
-                let visitor = SeqIteratorVisitor::new(self.iter(), Some($len));
-                serializer.serialize_fixed_size_array(visitor)
+                let mut state = try!(serializer.serialize_seq_fixed_size($len));
+                for e in self.iter() {
+                    try!(serializer.serialize_seq_elt(&mut state, e));
+                }
+                serializer.serialize_seq_end(state)
             }
         }
     }
@@ -293,40 +215,40 @@ array_impls!(32);
 
 ///////////////////////////////////////////////////////////////////////////////
 
+macro_rules! serialize_seq {
+    () => {
+        #[inline]
+        fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+            where S: Serializer,
+        {
+            let mut state = try!(serializer.serialize_seq(Some(self.len())));
+            for e in self {
+                try!(serializer.serialize_seq_elt(&mut state, e));
+            }
+            serializer.serialize_seq_end(state)
+        }
+    }
+}
+
 #[cfg(any(feature = "std", feature = "collections"))]
 impl<T> Serialize for BinaryHeap<T>
     where T: Serialize + Ord
 {
-    #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
-        where S: Serializer,
-    {
-        serializer.serialize_seq(SeqIteratorVisitor::new(self.iter(), Some(self.len())))
-    }
+    serialize_seq!();
 }
 
 #[cfg(any(feature = "std", feature = "collections"))]
 impl<T> Serialize for BTreeSet<T>
     where T: Serialize + Ord,
 {
-    #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
-        where S: Serializer,
-    {
-        serializer.serialize_seq(SeqIteratorVisitor::new(self.iter(), Some(self.len())))
-    }
+    serialize_seq!();
 }
 
 #[cfg(all(feature = "nightly", feature = "collections"))]
 impl<T> Serialize for EnumSet<T>
     where T: Serialize + CLike
 {
-    #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
-        where S: Serializer,
-    {
-        serializer.serialize_seq(SeqIteratorVisitor::new(self.iter(), Some(self.len())))
-    }
+    serialize_seq!();
 }
 
 #[cfg(feature = "std")]
@@ -334,24 +256,24 @@ impl<T, H> Serialize for HashSet<T, H>
     where T: Serialize + Eq + Hash,
           H: BuildHasher,
 {
-    #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
-        where S: Serializer,
-    {
-        serializer.serialize_seq(SeqIteratorVisitor::new(self.iter(), Some(self.len())))
-    }
+    serialize_seq!();
 }
 
 #[cfg(any(feature = "std", feature = "collections"))]
 impl<T> Serialize for LinkedList<T>
     where T: Serialize,
 {
-    #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
-        where S: Serializer,
-    {
-        serializer.serialize_seq(SeqIteratorVisitor::new(self.iter(), Some(self.len())))
-    }
+    serialize_seq!();
+}
+
+#[cfg(any(feature = "std", feature = "collections"))]
+impl<T> Serialize for Vec<T> where T: Serialize {
+    serialize_seq!();
+}
+
+#[cfg(any(feature = "std", feature = "collections"))]
+impl<T> Serialize for VecDeque<T> where T: Serialize {
+    serialize_seq!();
 }
 
 #[cfg(feature = "nightly")]
@@ -364,27 +286,11 @@ impl<A> Serialize for ops::Range<A>
         where S: Serializer,
     {
         let len = iter::Step::steps_between(&self.start, &self.end, &A::one());
-        serializer.serialize_seq(SeqIteratorVisitor::new(self.clone(), len))
-    }
-}
-
-#[cfg(any(feature = "std", feature = "collections"))]
-impl<T> Serialize for Vec<T> where T: Serialize {
-    #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
-        where S: Serializer,
-    {
-        (&self[..]).serialize(serializer)
-    }
-}
-
-#[cfg(any(feature = "std", feature = "collections"))]
-impl<T> Serialize for VecDeque<T> where T: Serialize {
-    #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
-        where S: Serializer,
-    {
-        serializer.serialize_seq(SeqIteratorVisitor::new(self.iter(), Some(self.len())))
+        let mut state = try!(serializer.serialize_seq(len));
+        for e in self.clone() {
+            try!(serializer.serialize_seq_elt(&mut state, e));
+        }
+        serializer.serialize_seq_end(state)
     }
 }
 
@@ -413,52 +319,18 @@ macro_rules! tuple_impls {
         }
     )+) => {
         $(
-            /// A tuple visitor.
-            pub struct $TupleVisitor<'a, $($T: 'a),+> {
-                tuple: &'a ($($T,)+),
-                state: u8,
-            }
-
-            impl<'a, $($T: 'a),+> $TupleVisitor<'a, $($T),+> {
-                /// Construct a new, empty `TupleVisitor`.
-                pub fn new(tuple: &'a ($($T,)+)) -> $TupleVisitor<'a, $($T),+> {
-                    $TupleVisitor {
-                        tuple: tuple,
-                        state: 0,
-                    }
-                }
-            }
-
-            impl<'a, $($T),+> SeqVisitor for $TupleVisitor<'a, $($T),+>
-                where $($T: Serialize),+
-            {
-                fn visit<S>(&mut self, serializer: &mut S) -> Result<Option<()>, S::Error>
-                    where S: Serializer,
-                {
-                    match self.state {
-                        $(
-                            $state => {
-                                self.state += 1;
-                                Ok(Some(try!(serializer.serialize_tuple_elt(&e!(self.tuple.$idx)))))
-                            }
-                        )+
-                        _ => {
-                            Ok(None)
-                        }
-                    }
-                }
-
-                fn len(&self) -> Option<usize> {
-                    Some($len)
-                }
-            }
-
             impl<$($T),+> Serialize for ($($T,)+)
                 where $($T: Serialize),+
             {
                 #[inline]
-                fn serialize<S: Serializer>(&self, serializer: &mut S) -> Result<(), S::Error> {
-                    serializer.serialize_tuple($TupleVisitor::new(self))
+                fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+                    where S: Serializer,
+                {
+                    let mut state = try!(serializer.serialize_tuple($len));
+                    $(
+                        try!(serializer.serialize_tuple_elt(&mut state, &e!(self.$idx)));
+                    )+
+                    serializer.serialize_tuple_end(state)
                 }
             }
         )+
@@ -638,83 +510,27 @@ tuple_impls! {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-/// A `serde::Visitor` for (key, value) map iterators.
-///
-/// # Examples
-///
-/// ```
-/// use std::collections::HashMap;
-/// use serde::{Serialize, Serializer};
-/// use serde::ser::impls::MapIteratorVisitor;
-///
-/// struct Map(HashMap<u32, u32>);
-///
-/// impl Serialize for Map {
-///     fn serialize<S>(&self, ser: &mut S) -> Result<(), S::Error>
-///         where S: Serializer,
-///     {
-///         ser.serialize_map(MapIteratorVisitor::new(
-///             self.0.iter(),
-///             Some(self.0.len()),
-///         ))
-///     }
-/// }
-/// ```
-pub struct MapIteratorVisitor<Iter> {
-    iter: Iter,
-    len: Option<usize>,
-}
-
-impl<K, V, Iter> MapIteratorVisitor<Iter>
-    where Iter: Iterator<Item=(K, V)>
-{
-    /// Construct a new `MapIteratorVisitor<Iter>`.
-    #[inline]
-    pub fn new(iter: Iter, len: Option<usize>) -> MapIteratorVisitor<Iter> {
-        MapIteratorVisitor {
-            iter: iter,
-            len: len,
-        }
-    }
-}
-
-impl<K, V, I> MapVisitor for MapIteratorVisitor<I>
-    where K: Serialize,
-          V: Serialize,
-          I: Iterator<Item=(K, V)>,
-{
-    #[inline]
-    fn visit<S>(&mut self, serializer: &mut S) -> Result<Option<()>, S::Error>
-        where S: Serializer,
-    {
-        match self.iter.next() {
-            Some((key, value)) => {
-                try!(serializer.serialize_map_elt(key, value));
-                Ok(Some(()))
+macro_rules! serialize_map {
+    () => {
+        #[inline]
+        fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+            where S: Serializer,
+        {
+            let mut state = try!(serializer.serialize_map(Some(self.len())));
+            for (k, v) in self {
+                try!(serializer.serialize_map_elt(&mut state, k, v));
             }
-            None => Ok(None)
+            serializer.serialize_map_end(state)
         }
     }
-
-    #[inline]
-    fn len(&self) -> Option<usize> {
-        self.len
-    }
 }
 
-///////////////////////////////////////////////////////////////////////////////
-
 #[cfg(any(feature = "std", feature = "collections"))]
 impl<K, V> Serialize for BTreeMap<K, V>
     where K: Serialize + Ord,
           V: Serialize,
 {
-    #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
-        where S: Serializer,
-    {
-        serializer.serialize_map(MapIteratorVisitor::new(self.iter(), Some(self.len())))
-    }
+    serialize_map!();
 }
 
 #[cfg(feature = "std")]
@@ -723,12 +539,7 @@ impl<K, V, H> Serialize for HashMap<K, V, H>
           V: Serialize,
           H: BuildHasher,
 {
-    #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
-        where S: Serializer,
-    {
-        serializer.serialize_map(MapIteratorVisitor::new(self.iter(), Some(self.len())))
-    }
+    serialize_map!();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/serde/src/ser/mod.rs b/serde/src/ser/mod.rs
index 6040ea11..3e6bc244 100644
--- a/serde/src/ser/mod.rs
+++ b/serde/src/ser/mod.rs
@@ -45,339 +45,323 @@ pub trait Serializer {
     /// The error type that can be returned if some error occurs during serialization.
     type Error: Error;
 
+    /// A state object that is initialized by `serialize_seq`, passed to
+    /// `serialize_seq_elt`, and consumed by `serialize_seq_end`. Use `()` if no
+    /// state is required.
+    type SeqState;
+    /// A state object that is initialized by `serialize_tuple`, passed to
+    /// `serialize_tuple_elt`, and consumed by `serialize_tuple_end`. Use `()`
+    /// if no state is required.
+    type TupleState;
+    /// A state object that is initialized by `serialize_tuple_struct`, passed
+    /// to `serialize_tuple_struct_elt`, and consumed by
+    /// `serialize_tuple_struct_end`. Use `()` if no state is required.
+    type TupleStructState;
+    /// A state object that is initialized by `serialize_tuple_variant`, passed
+    /// to `serialize_tuple_variant_elt`, and consumed by
+    /// `serialize_tuple_variant_end`. Use `()` if no state is required.
+    type TupleVariantState;
+    /// A state object that is initialized by `serialize_map`, passed to
+    /// `serialize_map_elt`, and consumed by `serialize_map_end`. Use `()` if no
+    /// state is required.
+    type MapState;
+    /// A state object that is initialized by `serialize_struct`, passed to
+    /// `serialize_struct_elt`, and consumed by `serialize_struct_end`. Use `()`
+    /// if no state is required.
+    type StructState;
+    /// A state object that is initialized by `serialize_struct_variant`, passed
+    /// to `serialize_struct_variant_elt`, and consumed by
+    /// `serialize_struct_variant_end`. Use `()` if no state is required.
+    type StructVariantState;
+
     /// Serializes a `bool` value.
     fn serialize_bool(&mut self, v: bool) -> Result<(), Self::Error>;
 
-    /// Serializes a `isize` value. By default it casts the value to a `i64` and
-    /// passes it to the `serialize_i64` method.
-    #[inline]
-    fn serialize_isize(&mut self, v: isize) -> Result<(), Self::Error> {
-        self.serialize_i64(v as i64)
-    }
+    /// Serializes an `isize` value. If the format does not differentiate
+    /// between `isize` and `i64`, a reasonable implementation would be to cast
+    /// the value to `i64` and forward to `serialize_i64`.
+    fn serialize_isize(&mut self, v: isize) -> Result<(), Self::Error>;
 
-    /// Serializes a `i8` value. By default it casts the value to a `i64` and
-    /// passes it to the `serialize_i64` method.
-    #[inline]
-    fn serialize_i8(&mut self, v: i8) -> Result<(), Self::Error> {
-        self.serialize_i64(v as i64)
-    }
+    /// Serializes an `i8` value. If the format does not differentiate between
+    /// `i8` and `i64`, a reasonable implementation would be to cast the value
+    /// to `i64` and forward to `serialize_i64`.
+    fn serialize_i8(&mut self, v: i8) -> Result<(), Self::Error>;
 
-    /// Serializes a `i16` value. By default it casts the value to a `i64` and
-    /// passes it to the `serialize_i64` method.
-    #[inline]
-    fn serialize_i16(&mut self, v: i16) -> Result<(), Self::Error> {
-        self.serialize_i64(v as i64)
-    }
+    /// Serializes an `i16` value. If the format does not differentiate between
+    /// `i16` and `i64`, a reasonable implementation would be to cast the value
+    /// to `i64` and forward to `serialize_i64`.
+    fn serialize_i16(&mut self, v: i16) -> Result<(), Self::Error>;
 
-    /// Serializes a `i32` value. By default it casts the value to a `i64` and
-    /// passes it to the `serialize_i64` method.
-    #[inline]
-    fn serialize_i32(&mut self, v: i32) -> Result<(), Self::Error> {
-        self.serialize_i64(v as i64)
-    }
+    /// Serializes an `i32` value. If the format does not differentiate between
+    /// `i32` and `i64`, a reasonable implementation would be to cast the value
+    /// to `i64` and forward to `serialize_i64`.
+    fn serialize_i32(&mut self, v: i32) -> Result<(), Self::Error>;
 
-    /// Serializes a `i64` value.
-    #[inline]
+    /// Serializes an `i64` value.
     fn serialize_i64(&mut self, v: i64) -> Result<(), Self::Error>;
 
-    /// Serializes a `usize` value. By default it casts the value to a `u64` and
-    /// passes it to the `serialize_u64` method.
-    #[inline]
-    fn serialize_usize(&mut self, v: usize) -> Result<(), Self::Error> {
-        self.serialize_u64(v as u64)
-    }
+    /// Serializes a `usize` value. If the format does not differentiate between
+    /// `usize` and `u64`, a reasonable implementation would be to cast the
+    /// value to `u64` and forward to `serialize_u64`.
+    fn serialize_usize(&mut self, v: usize) -> Result<(), Self::Error>;
 
-    /// Serializes a `u8` value. By default it casts the value to a `u64` and passes
-    /// it to the `serialize_u64` method.
-    #[inline]
-    fn serialize_u8(&mut self, v: u8) -> Result<(), Self::Error> {
-        self.serialize_u64(v as u64)
-    }
+    /// Serializes a `u8` value. If the format does not differentiate between
+    /// `u8` and `u64`, a reasonable implementation would be to cast the value
+    /// to `u64` and forward to `serialize_u64`.
+    fn serialize_u8(&mut self, v: u8) -> Result<(), Self::Error>;
 
-    /// Serializes a `u32` value. By default it casts the value to a `u64` and passes
-    /// it to the `serialize_u64` method.
-    #[inline]
-    fn serialize_u16(&mut self, v: u16) -> Result<(), Self::Error> {
-        self.serialize_u64(v as u64)
-    }
+    /// Serializes a `u16` value. If the format does not differentiate between
+    /// `u16` and `u64`, a reasonable implementation would be to cast the value
+    /// to `u64` and forward to `serialize_u64`.
+    fn serialize_u16(&mut self, v: u16) -> Result<(), Self::Error>;
 
-    /// Serializes a `u32` value. By default it casts the value to a `u64` and passes
-    /// it to the `serialize_u64` method.
-    #[inline]
-    fn serialize_u32(&mut self, v: u32) -> Result<(), Self::Error> {
-        self.serialize_u64(v as u64)
-    }
+    /// Serializes a `u32` value. If the format does not differentiate between
+    /// `u32` and `u64`, a reasonable implementation would be to cast the value
+    /// to `u64` and forward to `serialize_u64`.
+    fn serialize_u32(&mut self, v: u32) -> Result<(), Self::Error>;
 
     /// `Serializes a `u64` value.
-    #[inline]
     fn serialize_u64(&mut self, v: u64) -> Result<(), Self::Error>;
 
-    /// Serializes a `f32` value. By default it casts the value to a `f64` and passes
-    /// it to the `serialize_f64` method.
-    #[inline]
-    fn serialize_f32(&mut self, v: f32) -> Result<(), Self::Error> {
-        self.serialize_f64(v as f64)
-    }
+    /// Serializes an `f32` value. If the format does not differentiate between
+    /// `f32` and `f64`, a reasonable implementation would be to cast the value
+    /// to `f64` and forward to `serialize_f64`.
+    fn serialize_f32(&mut self, v: f32) -> Result<(), Self::Error>;
 
-    /// Serializes a `f64` value.
+    /// Serializes an `f64` value.
     fn serialize_f64(&mut self, v: f64) -> Result<(), Self::Error>;
 
-    /// Serializes a character. By default it serializes it as a `&str` containing a
-    /// single character.
-    #[inline]
-    fn serialize_char(&mut self, v: char) -> Result<(), Self::Error> {
-        self.serialize_str(::utils::encode_utf8(v).as_str())
-    }
+    /// Serializes a character.
+    fn serialize_char(&mut self, v: char) -> Result<(), Self::Error>;
 
     /// Serializes a `&str`.
     fn serialize_str(&mut self, value: &str) -> Result<(), Self::Error>;
 
-    /// Enables those serialization formats that support serializing
-    /// byte slices separately from generic arrays. By default it serializes as a regular array.
-    #[inline]
-    fn serialize_bytes(&mut self, value: &[u8]) -> Result<(), Self::Error> {
-        self.serialize_seq(impls::SeqIteratorVisitor::new(value.iter(), Some(value.len())))
-    }
+    /// Enables serializers to serialize byte slices more compactly or more
+    /// efficiently than other types of slices. If no efficient implementation
+    /// is available, a reasonable implementation would be to forward to
+    /// `serialize_seq`.
+    fn serialize_bytes(&mut self, value: &[u8]) -> Result<(), Self::Error>;
 
     /// Serializes a `()` value.
     fn serialize_unit(&mut self) -> Result<(), Self::Error>;
 
-    /// Serializes a unit struct value.
-    ///
-    /// By default, unit structs are serialized as a `()`.
-    #[inline]
-    fn serialize_unit_struct(&mut self, _name: &'static str) -> Result<(), Self::Error> {
-        self.serialize_unit()
-    }
+    /// Serializes a unit struct value. A reasonable implementation would be to
+    /// forward to `serialize_unit`.
+    fn serialize_unit_struct(
+        &mut self,
+        name: &'static str,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a unit variant, otherwise known as a variant with no arguments.
-    ///
-    /// By default, unit variants are serialized as a `()`.
-    #[inline]
-    fn serialize_unit_variant(&mut self,
-                              _name: &'static str,
-                              _variant_index: usize,
-                              _variant: &'static str) -> Result<(), Self::Error> {
-        self.serialize_unit()
-    }
+    /// Serializes a unit variant, otherwise known as a variant with no
+    /// arguments. A reasonable implementation would be to forward to
+    /// `serialize_unit`.
+    fn serialize_unit_variant(
+        &mut self,
+        name: &'static str,
+        variant_index: usize,
+        variant: &'static str,
+    ) -> Result<(), Self::Error>;
 
-    /// Allows a tuple struct with a single element, also known as a
-    /// newtyped value, to be more efficiently serialized than a tuple struct with multiple items.
-    /// By default it just serializes the value as a tuple struct sequence.
-    #[inline]
-    fn serialize_newtype_struct<T>(&mut self,
-                                   name: &'static str,
-                                   value: T) -> Result<(), Self::Error>
-        where T: Serialize,
-    {
-        self.serialize_tuple_struct(name, Some(value))
-    }
+    /// Allows a tuple struct with a single element, also known as a newtype
+    /// struct, to be more efficiently serialized than a tuple struct with
+    /// multiple items. A reasonable implementation would be to forward to
+    /// `serialize_tuple_struct`.
+    fn serialize_newtype_struct<T: Serialize>(
+        &mut self,
+        name: &'static str,
+        value: T,
+    ) -> Result<(), Self::Error>;
 
-    /// Allows a variant with a single item to be more efficiently
-    /// serialized than a variant with multiple items. By default it just serializes the value as a
-    /// tuple variant sequence.
-    #[inline]
-    fn serialize_newtype_variant<T>(&mut self,
-                                    name: &'static str,
-                                    variant_index: usize,
-                                    variant: &'static str,
-                                    value: T) -> Result<(), Self::Error>
-        where T: Serialize,
-    {
-        self.serialize_tuple_variant(
-            name,
-            variant_index,
-            variant,
-            Some(value))
-    }
+    /// Allows a variant with a single item to be more efficiently serialized
+    /// than a variant with multiple items. A reasonable implementation would be
+    /// to forward to `serialize_tuple_variant`.
+    fn serialize_newtype_variant<T: Serialize>(
+        &mut self,
+        name: &'static str,
+        variant_index: usize,
+        variant: &'static str,
+        value: T,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a `None` value..serialize
+    /// Serializes a `None` value.
     fn serialize_none(&mut self) -> Result<(), Self::Error>;
 
     /// Serializes a `Some(...)` value.
-    fn serialize_some<V>(&mut self, value: V) -> Result<(), Self::Error>
-        where V: Serialize;
+    fn serialize_some<T: Serialize>(
+        &mut self,
+        value: T,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a sequence.
-    ///
-    /// Callees of this method need to construct a `SeqVisitor`, which iterates through each item
-    /// in the sequence.
-    fn serialize_seq<V>(&mut self, visitor: V) -> Result<(), Self::Error>
-        where V: SeqVisitor;
+    /// Begins to serialize a sequence. This call must be followed by zero or
+    /// more calls to `serialize_seq_elt`, then a call to `serialize_seq_end`.
+    fn serialize_seq(
+        &mut self,
+        len: Option<usize>,
+    ) -> Result<Self::SeqState, Self::Error>;
 
-    /// Serializes a sequence element.
-    fn serialize_seq_elt<T>(&mut self, value: T) -> Result<(), Self::Error>
-        where T: Serialize;
+    /// Serializes a sequence element. Must have previously called
+    /// `serialize_seq`.
+    fn serialize_seq_elt<T: Serialize>(
+        &mut self,
+        state: &mut Self::SeqState,
+        value: T,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a tuple.
-    ///
-    /// By default this serializes a tuple as a sequence.
-    #[inline]
-    fn serialize_tuple<V>(&mut self, visitor: V) -> Result<(), Self::Error>
-        where V: SeqVisitor,
-    {
-        self.serialize_seq(visitor)
-    }
+    /// Finishes serializing a sequence.
+    fn serialize_seq_end(
+        &mut self,
+        state: Self::SeqState,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a tuple element.
-    ///
-    /// By default, tuples are serialized as a sequence.
-    #[inline]
-    fn serialize_tuple_elt<T>(&mut self, value: T) -> Result<(), Self::Error>
-        where T: Serialize
-    {
-        self.serialize_seq_elt(value)
-    }
+    /// Begins to serialize a sequence whose length will be known at
+    /// deserialization time. This call must be followed by zero or more calls
+    /// to `serialize_seq_elt`, then a call to `serialize_seq_end`. A reasonable
+    /// implementation would be to forward to `serialize_seq`.
+    fn serialize_seq_fixed_size(
+        &mut self,
+        size: usize,
+    ) -> Result<Self::SeqState, Self::Error>;
 
-    /// Serializes a fixed-size array.
-    ///
-    /// By default this serializes an array as a sequence.
-    #[inline]
-    fn serialize_fixed_size_array<V>(&mut self, visitor: V) -> Result<(), Self::Error>
-        where V: SeqVisitor,
-    {
-        self.serialize_seq(visitor)
-    }
+    /// Begins to serialize a tuple. This call must be followed by zero or more
+    /// calls to `serialize_tuple_elt`, then a call to `serialize_tuple_end`. A
+    /// reasonable implementation would be to forward to `serialize_seq`.
+    fn serialize_tuple(
+        &mut self,
+        len: usize,
+    ) -> Result<Self::TupleState, Self::Error>;
 
-    /// Serializes a tuple struct.
-    ///
-    /// By default, tuple structs are serialized as a tuple.
-    #[inline]
-    fn serialize_tuple_struct<V>(&mut self,
-                                 _name: &'static str,
-                                 visitor: V) -> Result<(), Self::Error>
-        where V: SeqVisitor,
-    {
-        self.serialize_tuple(visitor)
-    }
+    /// Serializes a tuple element. Must have previously called
+    /// `serialize_tuple`.
+    fn serialize_tuple_elt<T: Serialize>(
+        &mut self,
+        state: &mut Self::TupleState,
+        value: T,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a tuple struct element.
-    ///
-    /// By default, tuple struct elements are serialized as a tuple element.
-    #[inline]
-    fn serialize_tuple_struct_elt<T>(&mut self, value: T) -> Result<(), Self::Error>
-        where T: Serialize
-    {
-        self.serialize_tuple_elt(value)
-    }
+    /// Finishes serializing a tuple.
+    fn serialize_tuple_end(
+        &mut self,
+        state: Self::TupleState,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a tuple variant.
-    ///
-    /// By default, tuple variants are serialized as a tuple struct.
-    #[inline]
-    fn serialize_tuple_variant<V>(&mut self,
-                                  _name: &'static str,
-                                  _variant_index: usize,
-                                  variant: &'static str,
-                                  visitor: V) -> Result<(), Self::Error>
-        where V: SeqVisitor,
-    {
-        self.serialize_tuple_struct(variant, visitor)
-    }
+    /// Begins to serialize a tuple struct. This call must be followed by zero
+    /// or more calls to `serialize_tuple_struct_elt`, then a call to
+    /// `serialize_tuple_struct_end`. A reasonable implementation would be to
+    /// forward to `serialize_tuple`.
+    fn serialize_tuple_struct(
+        &mut self,
+        name: &'static str,
+        len: usize,
+    ) -> Result<Self::TupleStructState, Self::Error>;
 
-    /// Serializes a tuple element.
-    ///
-    /// By default, tuples are serialized as a sequence.
-    #[inline]
-    fn serialize_tuple_variant_elt<T>(&mut self, value: T) -> Result<(), Self::Error>
-        where T: Serialize
-    {
-        self.serialize_tuple_struct_elt(value)
-    }
+    /// Serializes a tuple struct element. Must have previously called
+    /// `serialize_tuple_struct`.
+    fn serialize_tuple_struct_elt<T: Serialize>(
+        &mut self,
+        state: &mut Self::TupleStructState,
+        value: T,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a map.
-    ///
-    /// Callees of this method need to construct a `MapVisitor`, which iterates through each item
-    /// in the map.
-    fn serialize_map<V>(&mut self, visitor: V) -> Result<(), Self::Error>
-        where V: MapVisitor;
+    /// Finishes serializing a tuple struct.
+    fn serialize_tuple_struct_end(
+        &mut self,
+        state: Self::TupleStructState,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a map element (key-value pair).
-    fn serialize_map_elt<K, V>(&mut self, key: K, value: V) -> Result<(), Self::Error>
-        where K: Serialize,
-              V: Serialize;
+    /// Begins to serialize a tuple variant. This call must be followed by zero
+    /// or more calls to `serialize_tuple_variant_elt`, then a call to
+    /// `serialize_tuple_variant_end`. A reasonable implementation would be to
+    /// forward to `serialize_tuple_struct`.
+    fn serialize_tuple_variant(
+        &mut self,
+        name: &'static str,
+        variant_index: usize,
+        variant: &'static str,
+        len: usize,
+    ) -> Result<Self::TupleVariantState, Self::Error>;
 
-    /// Serializes a struct.
-    ///
-    /// By default, structs are serialized as a map with the field name as the key.
-    #[inline]
-    fn serialize_struct<V>(&mut self,
-                           _name: &'static str,
-                           visitor: V) -> Result<(), Self::Error>
-        where V: MapVisitor,
-    {
-        self.serialize_map(visitor)
-    }
+    /// Serializes a tuple variant element. Must have previously called
+    /// `serialize_tuple_variant`.
+    fn serialize_tuple_variant_elt<T: Serialize>(
+        &mut self,
+        state: &mut Self::TupleVariantState,
+        value: T,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes an element of a struct.
-    ///
-    /// By default, struct elements are serialized as a map element with the field name as the key.
-    #[inline]
-    fn serialize_struct_elt<V>(&mut self,
-                               key: &'static str,
-                               value: V) -> Result<(), Self::Error>
-        where V: Serialize,
-    {
-        self.serialize_map_elt(key, value)
-    }
+    /// Finishes serializing a tuple variant.
+    fn serialize_tuple_variant_end(
+        &mut self,
+        state: Self::TupleVariantState,
+    ) -> Result<(), Self::Error>;
 
-    /// Serializes a struct variant.
-    ///
-    /// By default, struct variants are serialized as a struct.
-    #[inline]
-    fn serialize_struct_variant<V>(&mut self,
-                                   _name: &'static str,
-                                   _variant_index: usize,
-                                   variant: &'static str,
-                                   visitor: V) -> Result<(), Self::Error>
-        where V: MapVisitor,
-    {
-        self.serialize_struct(variant, visitor)
-    }
+    /// Begins to serialize a map. This call must be followed by zero or more
+    /// calls to `serialize_map_elt`, then a call to `serialize_map_end`.
+    fn serialize_map(
+        &mut self,
+        len: Option<usize>,
+    ) -> Result<Self::MapState, Self::Error>;
 
-    /// Serializes an element of a struct variant.
-    ///
-    /// By default, struct variant elements are serialized as a struct element.
-    #[inline]
-    fn serialize_struct_variant_elt<V>(&mut self,
-                                       key: &'static str,
-                                       value: V) -> Result<(), Self::Error>
-        where V: Serialize,
-    {
-        self.serialize_struct_elt(key, value)
-    }
-}
-
-/// A trait that is used by a `Serialize` to iterate through a sequence.
-#[cfg_attr(feature = "nightly-testing", allow(len_without_is_empty))]
-pub trait SeqVisitor {
-    /// Serializes a sequence item in the serializer.
-    ///
-    /// This returns `Ok(Some(()))` when there are more items to serialize, or `Ok(None)` when
-    /// complete.
-    fn visit<S>(&mut self, serializer: &mut S) -> Result<Option<()>, S::Error>
-        where S: Serializer;
-
-    /// Return the length of the sequence if known.
-    #[inline]
-    fn len(&self) -> Option<usize> {
-        None
-    }
-}
-
-/// A trait that is used by a `Serialize` to iterate through a map.
-#[cfg_attr(feature = "nightly-testing", allow(len_without_is_empty))]
-pub trait MapVisitor {
-    /// Serializes a map item in the serializer.
-    ///
-    /// This returns `Ok(Some(()))` when there are more items to serialize, or `Ok(None)` when
-    /// complete.
-    fn visit<S>(&mut self, serializer: &mut S) -> Result<Option<()>, S::Error>
-        where S: Serializer;
-
-    /// Return the length of the map if known.
-    #[inline]
-    fn len(&self) -> Option<usize> {
-        None
-    }
+    /// Serialize a map element. Must have previously called `serialize_map`.
+    fn serialize_map_elt<K: Serialize, V: Serialize>(
+        &mut self,
+        state: &mut Self::MapState,
+        key: K,
+        value: V,
+    ) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a map.
+    fn serialize_map_end(
+        &mut self,
+        state: Self::MapState,
+    ) -> Result<(), Self::Error>;
+
+    /// Begins to serialize a struct. This call must be followed by zero or more
+    /// calls to `serialize_struct_elt`, then a call to `serialize_struct_end`.
+    fn serialize_struct(
+        &mut self,
+        name: &'static str,
+        len: usize,
+    ) -> Result<Self::StructState, Self::Error>;
+
+    /// Serializes a struct field. Must have previously called
+    /// `serialize_struct`.
+    fn serialize_struct_elt<V: Serialize>(
+        &mut self,
+        state: &mut Self::StructState,
+        key: &'static str,
+        value: V,
+    ) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a struct.
+    fn serialize_struct_end(
+        &mut self,
+        state: Self::StructState,
+    ) -> Result<(), Self::Error>;
+
+    /// Begins to serialize a struct variant. This call must be followed by zero
+    /// or more calls to `serialize_struct_variant_elt`, then a call to
+    /// `serialize_struct_variant_end`.
+    fn serialize_struct_variant(
+        &mut self,
+        name: &'static str,
+        variant_index: usize,
+        variant: &'static str,
+        len: usize,
+    ) -> Result<Self::StructVariantState, Self::Error>;
+
+    /// Serialize a struct variant element. Must have previously called
+    /// `serialize_struct_variant`.
+    fn serialize_struct_variant_elt<V: Serialize>(
+        &mut self,
+        state: &mut Self::StructVariantState,
+        key: &'static str,
+        value: V,
+    ) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a struct variant.
+    fn serialize_struct_variant_end(
+        &mut self,
+        state: Self::StructVariantState,
+    ) -> Result<(), Self::Error>;
 }
diff --git a/serde_codegen/src/ser.rs b/serde_codegen/src/ser.rs
index 3f549c0f..9937c33b 100644
--- a/serde_codegen/src/ser.rs
+++ b/serde_codegen/src/ser.rs
@@ -216,30 +216,23 @@ fn serialize_tuple_struct(
     fields: &[Field],
     item_attrs: &attr::Item,
 ) -> P<ast::Expr> {
-    let (visitor_struct, visitor_impl) = serialize_tuple_struct_visitor(
+    let serialize_stmts = serialize_tuple_struct_visitor(
         cx,
         builder,
         ty.clone(),
-        builder.ty()
-            .ref_()
-            .lifetime("'__a")
-            .build_ty(ty.clone()),
-        builder.id("serialize_tuple_struct_elt"),
         fields,
         impl_generics,
         false,
+        cx.ident_of("serialize_tuple_struct_elt"),
     );
 
     let type_name = name_expr(builder, item_attrs.name());
+    let len = serialize_stmts.len();
 
     quote_expr!(cx, {
-        $visitor_struct
-        $visitor_impl
-        _serializer.serialize_tuple_struct($type_name, Visitor {
-            value: self,
-            state: 0,
-            _structure_ty: ::std::marker::PhantomData::<&$ty>,
-        })
+        let mut state = try!(_serializer.serialize_tuple_struct($type_name, $len));
+        $serialize_stmts
+        _serializer.serialize_tuple_struct_end(state)
     })
 }
 
@@ -251,30 +244,34 @@ fn serialize_struct(
     fields: &[Field],
     item_attrs: &attr::Item,
 ) -> P<ast::Expr> {
-    let (visitor_struct, visitor_impl) = serialize_struct_visitor(
+    let serialize_fields = serialize_struct_visitor(
         cx,
         builder,
         ty.clone(),
-        builder.ty()
-            .ref_()
-            .lifetime("'__a")
-            .build_ty(ty.clone()),
-        builder.id("serialize_struct_elt"),
         fields,
         impl_generics,
         false,
+        cx.ident_of("serialize_struct_elt"),
     );
 
     let type_name = name_expr(builder, item_attrs.name());
+    let len = fields.iter()
+        .filter(|&field| !field.attrs.skip_serializing())
+        .map(|field| {
+            let ident = field.ident.expect("struct has unnamed fields");
+            let field_expr = quote_expr!(cx, &self.$ident);
+
+            match field.attrs.skip_serializing_if() {
+                Some(path) => quote_expr!(cx, if $path($field_expr) { 0 } else { 1 }),
+                None => quote_expr!(cx, 1),
+            }
+         })
+        .fold(quote_expr!(cx, 0), |sum, expr| quote_expr!(cx, $sum + $expr));
 
     quote_expr!(cx, {
-        $visitor_struct
-        $visitor_impl
-        _serializer.serialize_struct($type_name, Visitor {
-            value: self,
-            state: 0,
-            _structure_ty: ::std::marker::PhantomData::<&$ty>,
-        })
+        let mut state = try!(_serializer.serialize_struct($type_name, $len));
+        $serialize_fields
+        _serializer.serialize_struct_end(state)
     })
 }
 
@@ -377,7 +374,6 @@ fn serialize_variant(
                 generics,
                 ty,
                 &variant.fields,
-                field_names,
             );
 
             quote_arm!(cx,
@@ -385,27 +381,19 @@ fn serialize_variant(
             )
         }
         Style::Struct => {
-            let field_names: Vec<_> = (0 .. variant.fields.len())
-                .map(|i| builder.id(format!("__field{}", i)))
-                .collect();
-
-            let pat = builder.pat().struct_()
-                .id(type_ident).id(variant_ident).build()
-                .with_pats(
-                    field_names.iter()
-                        .zip(variant.fields.iter())
-                        .map(|(id, field)| {
-                            let name = match field.ident {
-                                Some(name) => name,
-                                None => {
-                                    cx.span_bug(field.span, "struct variant has unnamed fields")
-                                }
-                            };
-
-                            (name, builder.pat().ref_id(id))
-                        })
-                )
-                .build();
+            let mut pat = builder.pat().struct_().id(type_ident).id(variant_ident).build();
+            for field in variant.fields.iter() {
+                let name = match field.ident {
+                    Some(name) => name,
+                    None => cx.span_bug(field.span, "struct variant has unnamed fields"),
+                };
+                pat = pat.with_field_pat(ast::FieldPat {
+                    ident: name,
+                    pat: builder.pat().ref_id(name),
+                    is_shorthand: true,
+                });
+            }
+            let pat = pat.build();
 
             let expr = serialize_struct_variant(
                 cx,
@@ -415,7 +403,6 @@ fn serialize_variant(
                 generics,
                 ty,
                 &variant.fields,
-                field_names,
                 item_attrs,
             );
 
@@ -462,46 +449,23 @@ fn serialize_tuple_variant(
     generics: &ast::Generics,
     structure_ty: P<ast::Ty>,
     fields: &[Field],
-    field_names: Vec<Ident>,
 ) -> P<ast::Expr> {
-    let variant_ty = builder.ty().tuple()
-        .with_tys(
-            fields.iter().map(|field| {
-                builder.ty()
-                    .ref_()
-                    .lifetime("'__a")
-                    .build_ty(field.ty.clone())
-            })
-        )
-        .build();
-
-    let (visitor_struct, visitor_impl) = serialize_tuple_struct_visitor(
+    let serialize_stmts = serialize_tuple_struct_visitor(
         cx,
         builder,
-        structure_ty.clone(),
-        variant_ty,
-        builder.id("serialize_tuple_variant_elt"),
+        structure_ty,
         fields,
         generics,
         true,
+        cx.ident_of("serialize_tuple_variant_elt"),
     );
 
-    let value_expr = builder.expr().tuple()
-        .with_exprs(
-            field_names.iter().map(|field| {
-                builder.expr().id(field)
-            })
-        )
-        .build();
+    let len = serialize_stmts.len();
 
     quote_expr!(cx, {
-        $visitor_struct
-        $visitor_impl
-        _serializer.serialize_tuple_variant($type_name, $variant_index, $variant_name, Visitor {
-            value: $value_expr,
-            state: 0,
-            _structure_ty: ::std::marker::PhantomData::<&$structure_ty>,
-        })
+        let mut state = try!(_serializer.serialize_tuple_variant($type_name, $variant_index, $variant_name, $len));
+        $serialize_stmts
+        _serializer.serialize_tuple_variant_end(state)
     })
 }
 
@@ -513,83 +477,42 @@ fn serialize_struct_variant(
     generics: &ast::Generics,
     ty: P<ast::Ty>,
     fields: &[Field],
-    field_names: Vec<Ident>,
     item_attrs: &attr::Item,
 ) -> P<ast::Expr> {
-    let variant_generics = builder.generics()
-        .with(generics.clone())
-        .add_lifetime_bound("'__serde_variant")
-        .lifetime_name("'__serde_variant")
-        .build();
 
-    let variant_struct = builder.item().struct_("__VariantStruct")
-        .with_generics(variant_generics.clone())
-        .with_fields(
-            fields.iter().map(|field| {
-                builder.struct_field(field.ident.expect("struct has unnamed fields"))
-                    .ty()
-                    .ref_()
-                    .lifetime("'__serde_variant")
-                    .build_ty(field.ty.clone())
-            })
-        )
-        .field("__serde_container_ty")
-            .ty().phantom_data().build(ty.clone())
-        .build();
-
-    let variant_expr = builder.expr().struct_id("__VariantStruct")
-        .with_id_exprs(
-            fields.iter()
-                .zip(field_names.iter())
-                .map(|(field, field_name)| {
-                    (
-                        field.ident.expect("struct has unnamed fields"),
-                        builder.expr().id(field_name),
-                    )
-                })
-        )
-        .field("__serde_container_ty").path()
-            .global()
-            .id("std").id("marker")
-            .segment("PhantomData")
-                .with_ty(ty.clone())
-                .build()
-            .build()
-        .build();
-
-    let variant_ty = builder.ty().path()
-        .segment("__VariantStruct")
-            .with_generics(variant_generics.clone())
-            .build()
-        .build();
-
-    let (visitor_struct, visitor_impl) = serialize_struct_visitor(
+    let serialize_fields = serialize_struct_visitor(
         cx,
         builder,
-        variant_ty.clone(),
-        variant_ty.clone(),
-        builder.id("serialize_struct_variant_elt"),
+        ty.clone(),
         fields,
-        &variant_generics,
+        &generics,
         true,
+        cx.ident_of("serialize_struct_variant_elt"),
     );
 
     let item_name = name_expr(builder, item_attrs.name());
+    let len = fields.iter()
+        .filter(|&field| !field.attrs.skip_serializing())
+        .map(|field| {
+            let ident = field.ident.expect("struct has unnamed fields");
+            let field_expr = quote_expr!(cx, $ident);
+
+            match field.attrs.skip_serializing_if() {
+                Some(path) => quote_expr!(cx, if $path($field_expr) { 0 } else { 1 }),
+                None => quote_expr!(cx, 1),
+            }
+         })
+        .fold(quote_expr!(cx, 0), |sum, expr| quote_expr!(cx, $sum + $expr));
 
     quote_expr!(cx, {
-        $variant_struct
-        $visitor_struct
-        $visitor_impl
-        _serializer.serialize_struct_variant(
+        let mut state = try!(_serializer.serialize_struct_variant(
             $item_name,
             $variant_index,
             $variant_name,
-            Visitor {
-                value: $variant_expr,
-                state: 0,
-                _structure_ty: ::std::marker::PhantomData,
-            },
-        )
+            $len,
+        ));
+        $serialize_fields
+        _serializer.serialize_struct_variant_end(state)
     })
 }
 
@@ -597,187 +520,75 @@ fn serialize_tuple_struct_visitor(
     cx: &ExtCtxt,
     builder: &aster::AstBuilder,
     structure_ty: P<ast::Ty>,
-    variant_ty: P<ast::Ty>,
-    serializer_method: ast::Ident,
     fields: &[Field],
     generics: &ast::Generics,
     is_enum: bool,
-) -> (P<ast::Item>, P<ast::Item>) {
-    let arms: Vec<_> = fields.iter()
+    func: ast::Ident,
+) -> Vec<ast::Stmt> {
+    fields.iter()
         .enumerate()
         .map(|(i, field)| {
-            let mut field_expr = builder.expr().tup_field(i).field("value").self_();
-            if !is_enum {
-                field_expr = quote_expr!(cx, &$field_expr);
-            }
+            let mut field_expr = if is_enum {
+                builder.expr().path().id(format!("__field{}", i)).build()
+            } else {
+                builder.expr().ref_().tup_field(i).self_()
+            };
 
-            let continue_if_skip = field.attrs.skip_serializing_if()
-                .map(|path| quote_stmt!(cx, if $path($field_expr) { continue }));
+            let skip = field.attrs.skip_serializing_if()
+                .map(|path| quote_expr!(cx, $path($field_expr)))
+                .unwrap_or(quote_expr!(cx, false));
 
             if let Some(path) = field.attrs.serialize_with() {
                 field_expr = wrap_serialize_with(cx, builder,
                     &structure_ty, generics, &field.ty, path, field_expr);
             }
 
-            quote_arm!(cx,
-                $i => {
-                    self.state += 1;
-                    $continue_if_skip
-                    Ok(Some(try!(_serializer.$serializer_method($field_expr))))
+            quote_stmt!(cx,
+                if !$skip {
+                    try!(_serializer.$func(&mut state, $field_expr));
                 }
-            )
+            ).unwrap()
         })
-        .collect();
-
-    let visitor_impl_generics = builder.from_generics(generics.clone())
-        .add_lifetime_bound("'__a")
-        .lifetime_name("'__a")
-        .build();
-
-    let where_clause = &visitor_impl_generics.where_clause;
-
-    let visitor_generics = builder.from_generics(visitor_impl_generics.clone())
-        .strip_bounds()
-        .build();
-
-    let nfields = fields.len();
-
-    (
-        quote_item!(cx,
-            struct Visitor $visitor_impl_generics $where_clause {
-                state: usize,
-                value: $variant_ty,
-                _structure_ty: ::std::marker::PhantomData<&'__a $structure_ty>,
-            }
-        ).unwrap(),
-
-        quote_item!(cx,
-            impl $visitor_impl_generics _serde::ser::SeqVisitor
-            for Visitor $visitor_generics
-            $where_clause {
-                #[inline]
-                fn visit<__S>(&mut self, _serializer: &mut __S) -> ::std::result::Result<Option<()>, __S::Error>
-                    where __S: _serde::ser::Serializer
-                {
-                    match self.state {
-                        $arms
-                        _ => Ok(None)
-                    }
-                }
-
-                #[inline]
-                fn len(&self) -> Option<usize> {
-                    Some($nfields)
-                }
-            }
-        ).unwrap(),
-    )
+        .collect()
 }
 
 fn serialize_struct_visitor(
     cx: &ExtCtxt,
     builder: &aster::AstBuilder,
     structure_ty: P<ast::Ty>,
-    variant_ty: P<ast::Ty>,
-    serializer_method: ast::Ident,
     fields: &[Field],
     generics: &ast::Generics,
     is_enum: bool,
-) -> (P<ast::Item>, P<ast::Item>) {
-    let arms: Vec<ast::Arm> = fields.iter()
+    func: ast::Ident,
+) -> Vec<ast::Stmt> {
+    fields.iter()
         .filter(|&field| !field.attrs.skip_serializing())
-        .enumerate()
-        .map(|(i, field)| {
+        .map(|field| {
             let ident = field.ident.expect("struct has unnamed field");
-            let mut field_expr = quote_expr!(cx, self.value.$ident);
-            if !is_enum {
-                field_expr = quote_expr!(cx, &$field_expr);
-            }
+            let mut field_expr = if is_enum {
+                quote_expr!(cx, $ident)
+            } else {
+                quote_expr!(cx, &self.$ident)
+            };
 
             let key_expr = name_expr(builder, field.attrs.name());
 
-            let continue_if_skip = field.attrs.skip_serializing_if()
-                .map(|path| quote_stmt!(cx, if $path($field_expr) { continue }));
+            let skip = field.attrs.skip_serializing_if()
+                .map(|path| quote_expr!(cx, $path($field_expr)))
+                .unwrap_or(quote_expr!(cx, false));
 
             if let Some(path) = field.attrs.serialize_with() {
                 field_expr = wrap_serialize_with(cx, builder,
                     &structure_ty, generics, &field.ty, path, field_expr)
             }
 
-            let expr = quote_expr!(cx,
-                _serializer.$serializer_method($key_expr, $field_expr)
-            );
-
-            quote_arm!(cx,
-                $i => {
-                    self.state += 1;
-                    $continue_if_skip
-                    return Ok(Some(try!($expr)));
+            quote_stmt!(cx,
+                if !$skip {
+                    try!(_serializer.$func(&mut state, $key_expr, $field_expr));
                 }
-            )
+            ).unwrap()
         })
-        .collect();
-
-    let visitor_impl_generics = builder.from_generics(generics.clone())
-        .add_lifetime_bound("'__a")
-        .lifetime_name("'__a")
-        .build();
-
-    let where_clause = &visitor_impl_generics.where_clause;
-
-    let visitor_generics = builder.from_generics(visitor_impl_generics.clone())
-        .strip_bounds()
-        .build();
-
-    let len = fields.iter()
-        .filter(|&field| !field.attrs.skip_serializing())
-        .map(|field| {
-            let ident = field.ident.expect("struct has unnamed fields");
-            let mut field_expr = quote_expr!(cx, self.value.$ident);
-            if !is_enum {
-                field_expr = quote_expr!(cx, &$field_expr);
-            }
-
-            match field.attrs.skip_serializing_if() {
-                Some(path) => quote_expr!(cx, if $path($field_expr) { 0 } else { 1 }),
-                None => quote_expr!(cx, 1),
-            }
-        })
-        .fold(quote_expr!(cx, 0), |sum, expr| quote_expr!(cx, $sum + $expr));
-
-    (
-        quote_item!(cx,
-            struct Visitor $visitor_impl_generics $where_clause {
-                state: usize,
-                value: $variant_ty,
-                _structure_ty: ::std::marker::PhantomData<&'__a $structure_ty>,
-            }
-        ).unwrap(),
-
-        quote_item!(cx,
-            impl $visitor_impl_generics
-            _serde::ser::MapVisitor
-            for Visitor $visitor_generics
-            $where_clause {
-                #[inline]
-                fn visit<__S>(&mut self, _serializer: &mut __S) -> ::std::result::Result<Option<()>, __S::Error>
-                    where __S: _serde::ser::Serializer,
-                {
-                    loop {
-                        match self.state {
-                            $arms
-                            _ => { return Ok(None); }
-                        }
-                    }
-                }
-
-                #[inline]
-                fn len(&self) -> Option<usize> {
-                    Some($len)
-                }
-            }
-        ).unwrap(),
-    )
+        .collect()
 }
 
 fn wrap_serialize_with(
diff --git a/serde_test/src/de.rs b/serde_test/src/de.rs
index a2d4c3d7..24dabe19 100644
--- a/serde_test/src/de.rs
+++ b/serde_test/src/de.rs
@@ -135,15 +135,18 @@ impl<I> de::Deserializer for Deserializer<I>
             Some(Token::Option(true)) => visitor.visit_some(self),
             Some(Token::Unit) => visitor.visit_unit(),
             Some(Token::UnitStruct(name)) => visitor.visit_unit_struct(name),
-            Some(Token::SeqStart(len)) | Some(Token::TupleStructStart(_, len)) => {
+            Some(Token::SeqStart(len)) => {
                 self.visit_seq(len, visitor)
             }
-            Some(Token::SeqArrayStart(len)) => {
+            Some(Token::SeqArrayStart(len))| Some(Token::TupleStructStart(_, len)) => {
                 self.visit_seq(Some(len), visitor)
             }
-            Some(Token::MapStart(len)) | Some(Token::StructStart(_, len)) => {
+            Some(Token::MapStart(len)) => {
                 self.visit_map(len, visitor)
             }
+            Some(Token::StructStart(_, len)) => {
+                self.visit_map(Some(len), visitor)
+            }
             Some(token) => Err(Error::UnexpectedToken(token)),
             None => Err(Error::EndOfStream),
         }
@@ -745,7 +748,7 @@ impl<'a, I> VariantVisitor for DeserializerVariantVisitor<'a, I>
         where V: Visitor,
     {
         match self.de.tokens.peek() {
-            Some(&Token::EnumSeqStart(_, _, Some(enum_len))) => {
+            Some(&Token::EnumSeqStart(_, _, enum_len)) => {
                 let token = self.de.tokens.next().unwrap();
 
                 if len == enum_len {
@@ -776,7 +779,7 @@ impl<'a, I> VariantVisitor for DeserializerVariantVisitor<'a, I>
         where V: Visitor,
     {
         match self.de.tokens.peek() {
-            Some(&Token::EnumMapStart(_, _, Some(enum_len))) => {
+            Some(&Token::EnumMapStart(_, _, enum_len)) => {
                 let token = self.de.tokens.next().unwrap();
 
                 if fields.len() == enum_len {
diff --git a/serde_test/src/ser.rs b/serde_test/src/ser.rs
index 2f028d3b..aa0f8186 100644
--- a/serde_test/src/ser.rs
+++ b/serde_test/src/ser.rs
@@ -2,8 +2,6 @@ use std::marker::PhantomData;
 
 use serde::ser::{
     self,
-    MapVisitor,
-    SeqVisitor,
     Serialize,
 };
 
@@ -30,32 +28,19 @@ impl<'a, I> Serializer<'a, I>
     pub fn next_token(&mut self) -> Option<&'a Token<'a>> {
         self.tokens.next()
     }
-
-    fn visit_seq<V>(&mut self, mut visitor: V) -> Result<(), Error>
-        where V: SeqVisitor
-    {
-        while let Some(()) = try!(visitor.visit(self)) { }
-
-        assert_eq!(self.tokens.next(), Some(&Token::SeqEnd));
-
-        Ok(())
-    }
-
-    fn visit_map<V>(&mut self, mut visitor: V) -> Result<(), Error>
-        where V: MapVisitor
-    {
-        while let Some(()) = try!(visitor.visit(self)) { }
-
-        assert_eq!(self.tokens.next(), Some(&Token::MapEnd));
-
-        Ok(())
-    }
 }
 
 impl<'a, I> ser::Serializer for Serializer<'a, I>
     where I: Iterator<Item=&'a Token<'a>>,
 {
     type Error = Error;
+    type MapState = ();
+    type SeqState = ();
+    type TupleState = ();
+    type TupleStructState = ();
+    type TupleVariantState = ();
+    type StructState = ();
+    type StructVariantState = ();
 
     fn serialize_unit(&mut self) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::Unit));
@@ -174,177 +159,162 @@ impl<'a, I> ser::Serializer for Serializer<'a, I>
         value.serialize(self)
     }
 
-
-    fn serialize_seq<V>(&mut self, visitor: V) -> Result<(), Error>
-        where V: SeqVisitor
+    fn serialize_seq<'b>(&'b mut self, len: Option<usize>) -> Result<(), Error>
     {
-        let len = visitor.len();
-
         assert_eq!(self.tokens.next(), Some(&Token::SeqStart(len)));
-
-        self.visit_seq(visitor)
+        Ok(())
     }
 
-    fn serialize_fixed_size_array<V>(&mut self, visitor: V) -> Result<(), Error>
-        where V: SeqVisitor
-    {
-        let len = visitor.len().expect("arrays must have a length");
-
-        assert_eq!(self.tokens.next(), Some(&Token::SeqArrayStart(len)));
-
-        self.visit_seq(visitor)
-    }
-
-    fn serialize_seq_elt<T>(&mut self, value: T) -> Result<(), Error>
+    fn serialize_seq_elt<T>(&mut self, _: &mut (), value: T) -> Result<(), Error>
         where T: Serialize
     {
         assert_eq!(self.tokens.next(), Some(&Token::SeqSep));
         value.serialize(self)
     }
 
-    fn serialize_tuple<V>(&mut self, mut visitor: V) -> Result<(), Error>
-        where V: SeqVisitor
-    {
-        let len = visitor.len().expect("arrays must have a length");
-
-        assert_eq!(self.tokens.next(), Some(&Token::TupleStart(len)));
-
-        while let Some(()) = try!(visitor.visit(self)) { }
-
-        assert_eq!(self.tokens.next(), Some(&Token::TupleEnd));
-
+    fn serialize_seq_end(&mut self, _: ()) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::SeqEnd));
         Ok(())
     }
 
-    fn serialize_tuple_elt<T>(&mut self, value: T) -> Result<(), Error>
+    fn serialize_seq_fixed_size(&mut self, len: usize) -> Result<(), Error>
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::SeqArrayStart(len)));
+        Ok(())
+    }
+
+    fn serialize_tuple(&mut self, len: usize) -> Result<(), Error>
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleStart(len)));
+        Ok(())
+    }
+
+    fn serialize_tuple_elt<T>(&mut self, _: &mut (), value: T) -> Result<(), Error>
         where T: Serialize
     {
         assert_eq!(self.tokens.next(), Some(&Token::TupleSep));
         value.serialize(self)
     }
 
+    fn serialize_tuple_end(&mut self, _: ()) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleEnd));
+        Ok(())
+    }
+
     fn serialize_newtype_struct<T>(&mut self,
-                               name: &'static str,
-                               value: T) -> Result<(), Error>
+                                   name: &'static str,
+                                   value: T) -> Result<(), Error>
         where T: Serialize,
     {
         assert_eq!(self.tokens.next(), Some(&Token::StructNewType(name)));
         value.serialize(self)
     }
 
-    fn serialize_tuple_struct<V>(&mut self, name: &str, mut visitor: V) -> Result<(), Error>
-        where V: SeqVisitor
+    fn serialize_tuple_struct(&mut self, name: &'static str, len: usize) -> Result<(), Error>
     {
-        let len = visitor.len();
-
         assert_eq!(self.tokens.next(), Some(&Token::TupleStructStart(name, len)));
 
-        while let Some(()) = try!(visitor.visit(self)) { }
-
-        assert_eq!(self.tokens.next(), Some(&Token::TupleStructEnd));
-
         Ok(())
     }
 
-    fn serialize_tuple_struct_elt<T>(&mut self, value: T) -> Result<(), Error>
-        where T: Serialize,
+    fn serialize_tuple_struct_elt<T>(&mut self, _: &mut (), value: T) -> Result<(), Error>
+        where T: Serialize
     {
         assert_eq!(self.tokens.next(), Some(&Token::TupleStructSep));
         value.serialize(self)
     }
 
-    fn serialize_tuple_variant<V>(&mut self,
-                                  name: &str,
-                                  _variant_index: usize,
-                                  variant: &str,
-                                  mut visitor: V) -> Result<(), Error>
-        where V: SeqVisitor
+    fn serialize_tuple_struct_end(&mut self, _: ()) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleStructEnd));
+        Ok(())
+    }
+
+    fn serialize_tuple_variant(&mut self,
+                               name: &str,
+                               _variant_index: usize,
+                               variant: &str,
+                               len: usize) -> Result<(), Error>
     {
-        let len = visitor.len();
-
         assert_eq!(self.tokens.next(), Some(&Token::EnumSeqStart(name, variant, len)));
 
-        while let Some(()) = try!(visitor.visit(self)) { }
-
-        assert_eq!(self.tokens.next(), Some(&Token::EnumSeqEnd));
-
         Ok(())
     }
 
-    fn serialize_tuple_variant_elt<T>(&mut self, value: T) -> Result<(), Error>
-        where T: Serialize,
+    fn serialize_tuple_variant_elt<T>(&mut self, _: &mut (), value: T) -> Result<(), Error>
+        where T: Serialize
     {
         assert_eq!(self.tokens.next(), Some(&Token::EnumSeqSep));
         value.serialize(self)
     }
 
-    fn serialize_map<V>(&mut self, visitor: V) -> Result<(), Error>
-        where V: MapVisitor
-    {
-        let len = visitor.len();
+    fn serialize_tuple_variant_end(&mut self, _: ()) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::EnumSeqEnd));
+        Ok(())
+    }
 
+    fn serialize_map(&mut self, len: Option<usize>) -> Result<(), Error>
+    {
         assert_eq!(self.tokens.next(), Some(&Token::MapStart(len)));
 
-        self.visit_map(visitor)
+        Ok(())
     }
 
-    fn serialize_map_elt<K, V>(&mut self, key: K, value: V) -> Result<(), Error>
-        where K: Serialize,
-              V: Serialize,
-    {
+    fn serialize_map_elt<K, V>(&mut self, _: &mut (), key: K, value: V) -> Result<(), Self::Error> where K: Serialize, V: Serialize {
         assert_eq!(self.tokens.next(), Some(&Token::MapSep));
-
         try!(key.serialize(self));
         value.serialize(self)
     }
 
-    fn serialize_struct<V>(&mut self, name: &str, mut visitor: V) -> Result<(), Error>
-        where V: MapVisitor
-    {
-        let len = visitor.len();
+    fn serialize_map_end(&mut self, _: ()) -> Result<(), Self::Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::MapEnd));
+        Ok(())
+    }
 
+    fn serialize_struct(&mut self, name: &str, len: usize) -> Result<(), Error>
+    {
         assert_eq!(self.tokens.next(), Some(&Token::StructStart(name, len)));
 
-        while let Some(()) = try!(visitor.visit(self)) { }
-
-        assert_eq!(self.tokens.next(), Some(&Token::StructEnd));
-
         Ok(())
     }
 
-    fn serialize_struct_elt<T>(&mut self, key: &'static str, value: T) -> Result<(), Error>
-        where T: Serialize,
-    {
+    fn serialize_struct_elt<V>(&mut self, _: &mut (), key: &'static str, value: V) -> Result<(), Self::Error> where V: Serialize {
         assert_eq!(self.tokens.next(), Some(&Token::StructSep));
-
         try!(key.serialize(self));
         value.serialize(self)
     }
 
-    fn serialize_struct_variant<V>(&mut self,
-                                   name: &str,
-                                   _variant_index: usize,
-                                   variant: &str,
-                                   mut visitor: V) -> Result<(), Error>
-        where V: MapVisitor
-    {
-        let len = visitor.len();
+    fn serialize_struct_end(&mut self, _: ()) -> Result<(), Self::Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::StructEnd));
+        Ok(())
+    }
 
+    fn serialize_struct_variant(&mut self,
+                                name: &str,
+                                _variant_index: usize,
+                                variant: &str,
+                                len: usize) -> Result<(), Error>
+    {
         assert_eq!(self.tokens.next(), Some(&Token::EnumMapStart(name, variant, len)));
 
-        while let Some(()) = try!(visitor.visit(self)) { }
-
-        assert_eq!(self.tokens.next(), Some(&Token::EnumMapEnd));
-
         Ok(())
     }
 
-    fn serialize_struct_variant_elt<T>(&mut self, key: &'static str, value: T) -> Result<(), Error>
-        where T: Serialize,
-    {
+    fn serialize_struct_variant_elt<V>(&mut self, _: &mut (), key: &'static str, value: V) -> Result<(), Self::Error> where V: Serialize {
         assert_eq!(self.tokens.next(), Some(&Token::EnumMapSep));
-
         try!(key.serialize(self));
         value.serialize(self)
     }
+
+    fn serialize_struct_variant_end(&mut self, _: ()) -> Result<(), Self::Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::EnumMapEnd));
+        Ok(())
+    }
+
+    fn serialize_bytes(&mut self, value: &[u8]) -> Result<(), Self::Error> {
+        let mut state = try!(self.serialize_seq(Some(value.len())));
+        for c in value {
+            try!(self.serialize_seq_elt(&mut state, c));
+        }
+        self.serialize_seq_end(state)
+    }
 }
diff --git a/serde_test/src/token.rs b/serde_test/src/token.rs
index dcb1137f..e4b3a825 100644
--- a/serde_test/src/token.rs
+++ b/serde_test/src/token.rs
@@ -38,7 +38,7 @@ pub enum Token<'a> {
     TupleSep,
     TupleEnd,
 
-    TupleStructStart(&'a str, Option<usize>),
+    TupleStructStart(&'a str, usize),
     TupleStructSep,
     TupleStructEnd,
 
@@ -46,15 +46,15 @@ pub enum Token<'a> {
     MapSep,
     MapEnd,
 
-    StructStart(&'a str, Option<usize>),
+    StructStart(&'a str, usize),
     StructSep,
     StructEnd,
 
-    EnumSeqStart(&'a str, &'a str, Option<usize>),
+    EnumSeqStart(&'a str, &'a str, usize),
     EnumSeqSep,
     EnumSeqEnd,
 
-    EnumMapStart(&'a str, &'a str, Option<usize>),
+    EnumMapStart(&'a str, &'a str, usize),
     EnumMapSep,
     EnumMapEnd,
 }
diff --git a/testing/tests/test_annotations.rs b/testing/tests/test_annotations.rs
index a18a4b82..ba77f8f9 100644
--- a/testing/tests/test_annotations.rs
+++ b/testing/tests/test_annotations.rs
@@ -82,7 +82,7 @@ fn test_default_struct() {
     assert_de_tokens(
         &DefaultStruct { a1: 1, a2: 2, a3: 3, a4: 0, a5: 123 },
         &[
-            Token::StructStart("DefaultStruct", Some(3)),
+            Token::StructStart("DefaultStruct", 3),
 
             Token::StructSep,
             Token::Str("a1"),
@@ -111,7 +111,7 @@ fn test_default_struct() {
     assert_de_tokens(
         &DefaultStruct { a1: 1, a2: 0, a3: 123, a4: 0, a5: 123 },
         &[
-            Token::StructStart("DefaultStruct", Some(1)),
+            Token::StructStart("DefaultStruct", 1),
 
             Token::StructSep,
             Token::Str("a1"),
@@ -145,7 +145,7 @@ fn test_default_enum() {
     assert_de_tokens(
         &DefaultEnum::Struct { a1: 1, a2: 2, a3: 3, a4: 0, a5: 123 },
         &[
-            Token::EnumMapStart("DefaultEnum", "Struct", Some(5)),
+            Token::EnumMapStart("DefaultEnum", "Struct", 5),
 
             Token::EnumMapSep,
             Token::Str("a1"),
@@ -174,7 +174,7 @@ fn test_default_enum() {
     assert_de_tokens(
         &DefaultEnum::Struct { a1: 1, a2: 0, a3: 123, a4: 0, a5: 123 },
         &[
-            Token::EnumMapStart("DefaultEnum", "Struct", Some(5)),
+            Token::EnumMapStart("DefaultEnum", "Struct", 5),
 
             Token::EnumMapSep,
             Token::Str("a1"),
@@ -208,7 +208,7 @@ fn test_no_std_default() {
     assert_de_tokens(
         &ContainsNoStdDefault { a: NoStdDefault(123) },
         &[
-            Token::StructStart("ContainsNoStdDefault", Some(1)),
+            Token::StructStart("ContainsNoStdDefault", 1),
             Token::StructEnd,
         ]
     );
@@ -216,7 +216,7 @@ fn test_no_std_default() {
     assert_de_tokens(
         &ContainsNoStdDefault { a: NoStdDefault(8) },
         &[
-            Token::StructStart("ContainsNoStdDefault", Some(1)),
+            Token::StructStart("ContainsNoStdDefault", 1),
 
             Token::StructSep,
             Token::Str("a"),
@@ -281,7 +281,7 @@ fn test_elt_not_deserialize() {
             e: NotDeserializeEnum::Trouble,
         },
         &[
-            Token::StructStart("ContainsNotDeserialize", Some(3)),
+            Token::StructStart("ContainsNotDeserialize", 3),
             Token::StructEnd,
         ]
     );
@@ -299,7 +299,7 @@ fn test_ignore_unknown() {
     assert_de_tokens(
         &DefaultStruct { a1: 1, a2: 2, a3: 3, a4: 0, a5: 123 },
         &[
-            Token::StructStart("DefaultStruct", Some(5)),
+            Token::StructStart("DefaultStruct", 5),
 
             Token::StructSep,
             Token::Str("whoops1"),
@@ -334,7 +334,7 @@ fn test_ignore_unknown() {
 
     assert_de_tokens_error::<DenyUnknown>(
         &[
-            Token::StructStart("DenyUnknown", Some(2)),
+            Token::StructStart("DenyUnknown", 2),
 
             Token::StructSep,
             Token::Str("a1"),
@@ -368,7 +368,7 @@ fn test_rename_struct() {
     assert_tokens(
         &RenameStruct { a1: 1, a2: 2 },
         &[
-            Token::StructStart("Superhero", Some(2)),
+            Token::StructStart("Superhero", 2),
 
             Token::StructSep,
             Token::Str("a1"),
@@ -385,7 +385,7 @@ fn test_rename_struct() {
     assert_ser_tokens(
         &RenameStructSerializeDeserialize { a1: 1, a2: 2 },
         &[
-            Token::StructStart("SuperheroSer", Some(2)),
+            Token::StructStart("SuperheroSer", 2),
 
             Token::StructSep,
             Token::Str("a1"),
@@ -402,7 +402,7 @@ fn test_rename_struct() {
     assert_de_tokens(
         &RenameStructSerializeDeserialize { a1: 1, a2: 2 },
         &[
-            Token::StructStart("SuperheroDe", Some(2)),
+            Token::StructStart("SuperheroDe", 2),
 
             Token::StructSep,
             Token::Str("a1"),
@@ -465,7 +465,7 @@ fn test_rename_enum() {
     assert_tokens(
         &RenameEnum::WonderWoman(0, 1),
         &[
-            Token::EnumSeqStart("Superhero", "diana_prince", Some(2)),
+            Token::EnumSeqStart("Superhero", "diana_prince", 2),
 
             Token::EnumSeqSep,
             Token::I8(0),
@@ -480,7 +480,7 @@ fn test_rename_enum() {
     assert_tokens(
         &RenameEnum::Flash { a: 1 },
         &[
-            Token::EnumMapStart("Superhero", "barry_allan", Some(1)),
+            Token::EnumMapStart("Superhero", "barry_allan", 1),
 
             Token::EnumMapSep,
             Token::Str("b"),
@@ -496,7 +496,7 @@ fn test_rename_enum() {
             b: String::new(),
         },
         &[
-            Token::EnumMapStart("SuperheroSer", "dick_grayson", Some(2)),
+            Token::EnumMapStart("SuperheroSer", "dick_grayson", 2),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -516,7 +516,7 @@ fn test_rename_enum() {
             b: String::new(),
         },
         &[
-            Token::EnumMapStart("SuperheroDe", "jason_todd", Some(2)),
+            Token::EnumMapStart("SuperheroDe", "jason_todd", 2),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -550,7 +550,7 @@ fn test_skip_serializing_struct() {
             c: 3,
         },
         &[
-            Token::StructStart("SkipSerializingStruct", Some(2)),
+            Token::StructStart("SkipSerializingStruct", 2),
 
             Token::StructSep,
             Token::Str("a"),
@@ -571,7 +571,7 @@ fn test_skip_serializing_struct() {
             c: 123,
         },
         &[
-            Token::StructStart("SkipSerializingStruct", Some(1)),
+            Token::StructStart("SkipSerializingStruct", 1),
 
             Token::StructSep,
             Token::Str("a"),
@@ -603,7 +603,7 @@ fn test_skip_serializing_enum() {
             c: 3,
         },
         &[
-            Token::EnumMapStart("SkipSerializingEnum", "Struct", Some(2)),
+            Token::EnumMapStart("SkipSerializingEnum", "Struct", 2),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -624,7 +624,7 @@ fn test_skip_serializing_enum() {
             c: 123,
         },
         &[
-            Token::EnumMapStart("SkipSerializingEnum", "Struct", Some(1)),
+            Token::EnumMapStart("SkipSerializingEnum", "Struct", 1),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -671,7 +671,7 @@ fn test_elt_not_serialize() {
             d: NotSerializeEnum::Trouble,
         },
         &[
-            Token::StructStart("ContainsNotSerialize", Some(2)),
+            Token::StructStart("ContainsNotSerialize", 2),
 
             Token::StructSep,
             Token::Str("a"),
@@ -703,7 +703,7 @@ fn test_serialize_with_struct() {
             b: 2,
         },
         &[
-            Token::StructStart("SerializeWithStruct", Some(2)),
+            Token::StructStart("SerializeWithStruct", 2),
 
             Token::StructSep,
             Token::Str("a"),
@@ -723,7 +723,7 @@ fn test_serialize_with_struct() {
             b: 123,
         },
         &[
-            Token::StructStart("SerializeWithStruct", Some(2)),
+            Token::StructStart("SerializeWithStruct", 2),
 
             Token::StructSep,
             Token::Str("a"),
@@ -756,7 +756,7 @@ fn test_serialize_with_enum() {
             b: 2,
         },
         &[
-            Token::EnumMapStart("SerializeWithEnum", "Struct", Some(2)),
+            Token::EnumMapStart("SerializeWithEnum", "Struct", 2),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -776,7 +776,7 @@ fn test_serialize_with_enum() {
             b: 123,
         },
         &[
-            Token::EnumMapStart("SerializeWithEnum", "Struct", Some(2)),
+            Token::EnumMapStart("SerializeWithEnum", "Struct", 2),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -806,7 +806,7 @@ fn test_deserialize_with_struct() {
             b: 2,
         },
         &[
-            Token::StructStart("DeserializeWithStruct", Some(2)),
+            Token::StructStart("DeserializeWithStruct", 2),
 
             Token::StructSep,
             Token::Str("a"),
@@ -826,7 +826,7 @@ fn test_deserialize_with_struct() {
             b: 123,
         },
         &[
-            Token::StructStart("DeserializeWithStruct", Some(2)),
+            Token::StructStart("DeserializeWithStruct", 2),
 
             Token::StructSep,
             Token::Str("a"),
@@ -858,7 +858,7 @@ fn test_deserialize_with_enum() {
             b: 2,
         },
         &[
-            Token::EnumMapStart("DeserializeWithEnum", "Struct", Some(2)),
+            Token::EnumMapStart("DeserializeWithEnum", "Struct", 2),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -878,7 +878,7 @@ fn test_deserialize_with_enum() {
             b: 123,
         },
         &[
-            Token::EnumMapStart("DeserializeWithEnum", "Struct", Some(2)),
+            Token::EnumMapStart("DeserializeWithEnum", "Struct", 2),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -897,7 +897,7 @@ fn test_deserialize_with_enum() {
 fn test_missing_renamed_field_struct() {
     assert_de_tokens_error::<RenameStruct>(
         &[
-            Token::StructStart("Superhero", Some(2)),
+            Token::StructStart("Superhero", 2),
 
             Token::StructSep,
             Token::Str("a1"),
@@ -910,7 +910,7 @@ fn test_missing_renamed_field_struct() {
 
     assert_de_tokens_error::<RenameStructSerializeDeserialize>(
         &[
-            Token::StructStart("SuperheroDe", Some(2)),
+            Token::StructStart("SuperheroDe", 2),
 
             Token::StructSep,
             Token::Str("a1"),
@@ -926,7 +926,7 @@ fn test_missing_renamed_field_struct() {
 fn test_missing_renamed_field_enum() {
     assert_de_tokens_error::<RenameEnum>(
         &[
-            Token::EnumMapStart("Superhero", "barry_allan", Some(1)),
+            Token::EnumMapStart("Superhero", "barry_allan", 1),
 
             Token::EnumMapEnd,
         ],
@@ -935,7 +935,7 @@ fn test_missing_renamed_field_enum() {
 
     assert_de_tokens_error::<RenameEnumSerializeDeserialize<i8>>(
         &[
-            Token::EnumMapStart("SuperheroDe", "jason_todd", Some(2)),
+            Token::EnumMapStart("SuperheroDe", "jason_todd", 2),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -957,7 +957,7 @@ enum InvalidLengthEnum {
 fn test_invalid_length_enum() {
     assert_de_tokens_error::<InvalidLengthEnum>(
         &[
-            Token::EnumSeqStart("InvalidLengthEnum", "A", Some(3)),
+            Token::EnumSeqStart("InvalidLengthEnum", "A", 3),
                 Token::EnumSeqSep,
                 Token::I32(1),
             Token::EnumSeqEnd,
@@ -966,7 +966,7 @@ fn test_invalid_length_enum() {
     );
     assert_de_tokens_error::<InvalidLengthEnum>(
         &[
-            Token::EnumSeqStart("InvalidLengthEnum", "B", Some(3)),
+            Token::EnumSeqStart("InvalidLengthEnum", "B", 3),
                 Token::EnumSeqSep,
                 Token::I32(1),
             Token::EnumSeqEnd,
diff --git a/testing/tests/test_bytes.rs b/testing/tests/test_bytes.rs
index 7a9906a4..b2e21b2e 100644
--- a/testing/tests/test_bytes.rs
+++ b/testing/tests/test_bytes.rs
@@ -52,15 +52,62 @@ impl BytesSerializer {
 
 impl serde::Serializer for BytesSerializer {
     type Error = Error;
+    type SeqState = ();
+    type MapState = ();
+    type TupleState = ();
+    type TupleStructState = ();
+    type TupleVariantState = ();
+    type StructState = ();
+    type StructVariantState = ();
 
     fn serialize_unit(&mut self) -> Result<(), Error> {
         Err(Error)
     }
 
+    fn serialize_unit_struct(&mut self, _name: &'static str) -> Result<(), Error> {
+        Err(Error)
+    }
+
+    fn serialize_unit_variant(&mut self, _: &'static str, _: usize, _: &'static str) -> Result<(), Error> {
+        Err(Error)
+    }
+
     fn serialize_bool(&mut self, _v: bool) -> Result<(), Error> {
         Err(Error)
     }
 
+    fn serialize_isize(&mut self, _v: isize) -> Result<(), Error> {
+        Err(Error)
+    }
+
+    fn serialize_usize(&mut self, _v: usize) -> Result<(), Error> {
+        Err(Error)
+    }
+
+    fn serialize_i8(&mut self, _v: i8) -> Result<(), Error> {
+        Err(Error)
+    }
+
+    fn serialize_u8(&mut self, _v: u8) -> Result<(), Error> {
+        Err(Error)
+    }
+
+    fn serialize_i16(&mut self, _v: i16) -> Result<(), Error> {
+        Err(Error)
+    }
+
+    fn serialize_u16(&mut self, _v: u16) -> Result<(), Error> {
+        Err(Error)
+    }
+
+    fn serialize_i32(&mut self, _v: i32) -> Result<(), Error> {
+        Err(Error)
+    }
+
+    fn serialize_u32(&mut self, _v: u32) -> Result<(), Error> {
+        Err(Error)
+    }
+
     fn serialize_i64(&mut self, _v: i64) -> Result<(), Error> {
         Err(Error)
     }
@@ -95,31 +142,136 @@ impl serde::Serializer for BytesSerializer {
         Err(Error)
     }
 
-    fn serialize_seq<V>(&mut self, _visitor: V) -> Result<(), Error>
-        where V: serde::ser::SeqVisitor,
+    fn serialize_newtype_struct<V>(&mut self, _: &'static str, _value: V) -> Result<(), Error>
+        where V: serde::Serialize,
     {
         Err(Error)
     }
 
-    fn serialize_seq_elt<T>(&mut self, _value: T) -> Result<(), Error>
+    fn serialize_newtype_variant<V>(&mut self, _: &'static str, _: usize, _: &'static str, _value: V) -> Result<(), Error>
+        where V: serde::Serialize,
+    {
+        Err(Error)
+    }
+
+    fn serialize_seq(&mut self, _len: Option<usize>) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_seq_fixed_size(&mut self, _len: usize) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_seq_elt<T>(&mut self, _: &mut (), _value: T) -> Result<(), Error>
         where T: serde::Serialize
     {
         Err(Error)
     }
 
-    fn serialize_map<V>(&mut self, _visitor: V) -> Result<(), Error>
-        where V: serde::ser::MapVisitor,
+    fn serialize_seq_end(&mut self, _: ()) -> Result<(), Error>
     {
         Err(Error)
     }
 
-    fn serialize_map_elt<K, V>(&mut self, _key: K, _value: V) -> Result<(), Error>
+    fn serialize_tuple(&mut self, _len: usize) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_tuple_elt<T>(&mut self, _: &mut (), _value: T) -> Result<(), Error>
+        where T: serde::Serialize
+    {
+        Err(Error)
+    }
+
+    fn serialize_tuple_end(&mut self, _: ()) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_tuple_struct(&mut self, _: &'static str, _len: usize) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_tuple_struct_elt<T>(&mut self, _: &mut (), _value: T) -> Result<(), Error>
+        where T: serde::Serialize
+    {
+        Err(Error)
+    }
+
+    fn serialize_tuple_struct_end(&mut self, _: ()) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_tuple_variant(&mut self, _: &'static str, _: usize, _: &'static str, _len: usize) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_tuple_variant_elt<T>(&mut self, _: &mut (), _value: T) -> Result<(), Error>
+        where T: serde::Serialize
+    {
+        Err(Error)
+    }
+
+    fn serialize_tuple_variant_end(&mut self, _: ()) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_map(&mut self, _: Option<usize>) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_map_elt<K, V>(&mut self, _: &mut (), _key: K, _value: V) -> Result<(), Error>
         where K: serde::Serialize,
               V: serde::Serialize,
     {
         Err(Error)
     }
 
+    fn serialize_map_end(&mut self, _: ()) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_struct(&mut self, _: &'static str, _: usize) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_struct_elt<V>(&mut self, _: &mut (), _key: &'static str, _value: V) -> Result<(), Error>
+        where V: serde::Serialize,
+    {
+        Err(Error)
+    }
+
+    fn serialize_struct_end(&mut self, _: ()) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_struct_variant(&mut self, _: &'static str, _: usize, _: &'static str, _: usize) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
+    fn serialize_struct_variant_elt<V>(&mut self, _: &mut (), _key: &'static str, _value: V) -> Result<(), Error>
+        where V: serde::Serialize,
+    {
+        Err(Error)
+    }
+
+    fn serialize_struct_variant_end(&mut self, _: ()) -> Result<(), Error>
+    {
+        Err(Error)
+    }
+
     fn serialize_bytes(&mut self, bytes: &[u8]) -> Result<(), Error> {
         assert_eq!(self.bytes, bytes);
         Ok(())
diff --git a/testing/tests/test_de.rs b/testing/tests/test_de.rs
index fcd17448..08c06af6 100644
--- a/testing/tests/test_de.rs
+++ b/testing/tests/test_de.rs
@@ -81,9 +81,9 @@ fn assert_de_tokens_ignore(ignorable_tokens: &[Token<'static>]) {
     struct IgnoreBase {
         a: i32,
     }
- 
+
     let expected = IgnoreBase{a: 1};
- 
+
     // Embed the tokens to be ignored in the normal token
     // stream for an IgnoreBase type
     let concated_tokens : Vec<Token<'static>> = vec![
@@ -91,7 +91,7 @@ fn assert_de_tokens_ignore(ignorable_tokens: &[Token<'static>]) {
                 Token::MapSep,
                 Token::Str("a"),
                 Token::I32(1),
- 
+
                 Token::MapSep,
                 Token::Str("ignored")
         ]
@@ -101,17 +101,17 @@ fn assert_de_tokens_ignore(ignorable_tokens: &[Token<'static>]) {
             Token::MapEnd,
         ].into_iter())
         .collect();
- 
+
     let mut de = serde_test::Deserializer::new(concated_tokens.into_iter());
     let v: Result<IgnoreBase, Error> = Deserialize::deserialize(&mut de);
- 
+
     // We run this test on every token stream for convenience, but
     // some token streams don't make sense embedded as a map value,
     // so we ignore those. SyntaxError is the real sign of trouble.
     if let Err(Error::UnexpectedToken(_)) = v {
         return;
     }
- 
+
     assert_eq!(v.as_ref(), Ok(&expected));
     assert_eq!(de.next_token(), None);
 }
@@ -197,7 +197,7 @@ declare_tests! {
             Token::SeqEnd,
         ],
         () => &[
-            Token::TupleStructStart("Anything", Some(0)),
+            Token::TupleStructStart("Anything", 0),
             Token::SeqEnd,
         ],
     }
@@ -241,7 +241,7 @@ declare_tests! {
             Token::SeqEnd,
         ],
         TupleStruct(1, 2, 3) => &[
-            Token::TupleStructStart("TupleStruct", Some(3)),
+            Token::TupleStructStart("TupleStruct", 3),
                 Token::TupleStructSep,
                 Token::I32(1),
 
@@ -253,7 +253,7 @@ declare_tests! {
             Token::TupleStructEnd,
         ],
         TupleStruct(1, 2, 3) => &[
-            Token::TupleStructStart("TupleStruct", None),
+            Token::TupleStructStart("TupleStruct", 3),
                 Token::TupleStructSep,
                 Token::I32(1),
 
@@ -299,7 +299,7 @@ declare_tests! {
             Token::UnitStruct("Anything"),
         ],
         BTreeSet::<isize>::new() => &[
-            Token::TupleStructStart("Anything", Some(0)),
+            Token::TupleStructStart("Anything", 0),
             Token::SeqEnd,
         ],
     }
@@ -327,7 +327,7 @@ declare_tests! {
             Token::UnitStruct("Anything"),
         ],
         HashSet::<isize>::new() => &[
-            Token::TupleStructStart("Anything", Some(0)),
+            Token::TupleStructStart("Anything", 0),
             Token::SeqEnd,
         ],
         hashset![FnvHasher @ 1, 2, 3] => &[
@@ -377,7 +377,7 @@ declare_tests! {
             Token::UnitStruct("Anything"),
         ],
         Vec::<isize>::new() => &[
-            Token::TupleStructStart("Anything", Some(0)),
+            Token::TupleStructStart("Anything", 0),
             Token::SeqEnd,
         ],
     }
@@ -441,7 +441,7 @@ declare_tests! {
             Token::UnitStruct("Anything"),
         ],
         [0; 0] => &[
-            Token::TupleStructStart("Anything", Some(0)),
+            Token::TupleStructStart("Anything", 0),
             Token::SeqEnd,
         ],
     }
@@ -533,7 +533,7 @@ declare_tests! {
             Token::UnitStruct("Anything"),
         ],
         BTreeMap::<isize, isize>::new() => &[
-            Token::StructStart("Anything", Some(0)),
+            Token::StructStart("Anything", 0),
             Token::MapEnd,
         ],
     }
@@ -587,7 +587,7 @@ declare_tests! {
             Token::UnitStruct("Anything"),
         ],
         HashMap::<isize, isize>::new() => &[
-            Token::StructStart("Anything", Some(0)),
+            Token::StructStart("Anything", 0),
             Token::MapEnd,
         ],
         hashmap![FnvHasher @ 1 => 2, 3 => 4] => &[
@@ -615,7 +615,7 @@ declare_tests! {
             Token::MapEnd,
         ],
         Struct { a: 1, b: 2, c: 0 } => &[
-            Token::StructStart("Struct", Some(3)),
+            Token::StructStart("Struct", 3),
                 Token::StructSep,
                 Token::Str("a"),
                 Token::I32(1),
@@ -656,7 +656,7 @@ declare_tests! {
             Token::MapEnd,
         ],
         Struct { a: 1, b: 2, c: 0 } => &[
-            Token::StructStart("Struct", Some(3)),
+            Token::StructStart("Struct", 3),
                 Token::StructSep,
                 Token::Str("a"),
                 Token::I32(1),
@@ -688,7 +688,7 @@ declare_tests! {
     }
     test_enum_seq {
         Enum::Seq(1, 2, 3) => &[
-            Token::EnumSeqStart("Enum", "Seq", Some(3)),
+            Token::EnumSeqStart("Enum", "Seq", 3),
                 Token::EnumSeqSep,
                 Token::I32(1),
 
@@ -702,7 +702,7 @@ declare_tests! {
     }
     test_enum_map {
         Enum::Map { a: 1, b: 2, c: 3 } => &[
-            Token::EnumMapStart("Enum", "Map", Some(3)),
+            Token::EnumMapStart("Enum", "Map", 3),
                 Token::EnumMapSep,
                 Token::Str("a"),
                 Token::I32(1),
@@ -803,7 +803,7 @@ declare_error_tests! {
     }
     test_duplicate_field_enum<Enum> {
         &[
-            Token::EnumMapStart("Enum", "Map", Some(3)),
+            Token::EnumMapStart("Enum", "Map", 3),
                 Token::EnumMapSep,
                 Token::Str("a"),
                 Token::I32(1),
diff --git a/testing/tests/test_macros.rs b/testing/tests/test_macros.rs
index ca4dffaa..58ddfeab 100644
--- a/testing/tests/test_macros.rs
+++ b/testing/tests/test_macros.rs
@@ -174,7 +174,7 @@ fn test_ser_named_tuple() {
     assert_ser_tokens(
         &SerNamedTuple(&a, &mut b, c),
         &[
-            Token::TupleStructStart("SerNamedTuple", Some(3)),
+            Token::TupleStructStart("SerNamedTuple", 3),
             Token::TupleStructSep,
             Token::I32(5),
 
@@ -211,7 +211,7 @@ fn test_de_named_tuple() {
     assert_de_tokens(
         &DeNamedTuple(5, 6, 7),
         &[
-            Token::TupleStructStart("DeNamedTuple", Some(3)),
+            Token::TupleStructStart("DeNamedTuple", 3),
             Token::TupleStructSep,
             Token::I32(5),
 
@@ -239,7 +239,7 @@ fn test_ser_named_map() {
             c: c,
         },
         &[
-            Token::StructStart("SerNamedMap", Some(3)),
+            Token::StructStart("SerNamedMap", 3),
 
             Token::StructSep,
             Token::Str("a"),
@@ -267,7 +267,7 @@ fn test_de_named_map() {
             c: 7,
         },
         &[
-            Token::StructStart("DeNamedMap", Some(3)),
+            Token::StructStart("DeNamedMap", 3),
 
             Token::StructSep,
             Token::Str("a"),
@@ -315,7 +315,7 @@ fn test_ser_enum_seq() {
             //f,
         ),
         &[
-            Token::EnumSeqStart("SerEnum", "Seq", Some(4)),
+            Token::EnumSeqStart("SerEnum", "Seq", 4),
 
             Token::EnumSeqSep,
             Token::I8(1),
@@ -353,7 +353,7 @@ fn test_ser_enum_map() {
             //f: f,
         },
         &[
-            Token::EnumMapStart("SerEnum", "Map", Some(4)),
+            Token::EnumMapStart("SerEnum", "Map", 4),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -405,7 +405,7 @@ fn test_de_enum_seq() {
             //f,
         ),
         &[
-            Token::EnumSeqStart("DeEnum", "Seq", Some(4)),
+            Token::EnumSeqStart("DeEnum", "Seq", 4),
 
             Token::EnumSeqSep,
             Token::I8(1),
@@ -443,7 +443,7 @@ fn test_de_enum_map() {
             //f: f,
         },
         &[
-            Token::EnumMapStart("DeEnum", "Map", Some(4)),
+            Token::EnumMapStart("DeEnum", "Map", 4),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -489,7 +489,7 @@ fn test_lifetimes() {
     assert_ser_tokens(
         &Lifetimes::LifetimeMap { a: &value },
         &[
-            Token::EnumMapStart("Lifetimes", "LifetimeMap", Some(1)),
+            Token::EnumMapStart("Lifetimes", "LifetimeMap", 1),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -502,7 +502,7 @@ fn test_lifetimes() {
     assert_ser_tokens(
         &Lifetimes::NoLifetimeMap { a: 5 },
         &[
-            Token::EnumMapStart("Lifetimes", "NoLifetimeMap", Some(1)),
+            Token::EnumMapStart("Lifetimes", "NoLifetimeMap", 1),
 
             Token::EnumMapSep,
             Token::Str("a"),
@@ -518,7 +518,7 @@ fn test_generic_struct() {
     assert_tokens(
         &GenericStruct { x: 5u32 },
         &[
-            Token::StructStart("GenericStruct", Some(1)),
+            Token::StructStart("GenericStruct", 1),
 
             Token::StructSep,
             Token::Str("x"),
@@ -545,7 +545,7 @@ fn test_generic_tuple_struct() {
     assert_tokens(
         &GenericTupleStruct(5u32, 6u32),
         &[
-            Token::TupleStructStart("GenericTupleStruct", Some(2)),
+            Token::TupleStructStart("GenericTupleStruct", 2),
 
             Token::TupleStructSep,
             Token::U32(5),
@@ -584,7 +584,7 @@ fn test_generic_enum_seq() {
     assert_tokens(
         &GenericEnum::Seq::<u32, u32>(5, 6),
         &[
-            Token::EnumSeqStart("GenericEnum", "Seq", Some(2)),
+            Token::EnumSeqStart("GenericEnum", "Seq", 2),
 
             Token::EnumSeqSep,
             Token::U32(5),
@@ -602,7 +602,7 @@ fn test_generic_enum_map() {
     assert_tokens(
         &GenericEnum::Map::<u32, u32> { x: 5, y: 6 },
         &[
-            Token::EnumMapStart("GenericEnum", "Map", Some(2)),
+            Token::EnumMapStart("GenericEnum", "Map", 2),
 
             Token::EnumMapSep,
             Token::Str("x"),
@@ -622,7 +622,7 @@ fn test_default_ty_param() {
     assert_tokens(
         &DefaultTyParam::<i32> { phantom: PhantomData },
         &[
-            Token::StructStart("DefaultTyParam", Some(1)),
+            Token::StructStart("DefaultTyParam", 1),
 
             Token::StructSep,
             Token::Str("phantom"),
diff --git a/testing/tests/test_ser.rs b/testing/tests/test_ser.rs
index 981ddb86..e772e05e 100644
--- a/testing/tests/test_ser.rs
+++ b/testing/tests/test_ser.rs
@@ -256,7 +256,7 @@ declare_ser_tests! {
     }
     test_tuple_struct {
         TupleStruct(1, 2, 3) => &[
-            Token::TupleStructStart("TupleStruct", Some(3)),
+            Token::TupleStructStart("TupleStruct", 3),
                 Token::TupleStructSep,
                 Token::I32(1),
 
@@ -270,7 +270,7 @@ declare_ser_tests! {
     }
     test_struct {
         Struct { a: 1, b: 2, c: 3 } => &[
-            Token::StructStart("Struct", Some(3)),
+            Token::StructStart("Struct", 3),
                 Token::StructSep,
                 Token::Str("a"),
                 Token::I32(1),
@@ -289,7 +289,7 @@ declare_ser_tests! {
         Enum::Unit => &[Token::EnumUnit("Enum", "Unit")],
         Enum::One(42) => &[Token::EnumNewType("Enum", "One"), Token::I32(42)],
         Enum::Seq(1, 2) => &[
-            Token::EnumSeqStart("Enum", "Seq", Some(2)),
+            Token::EnumSeqStart("Enum", "Seq", 2),
                 Token::EnumSeqSep,
                 Token::I32(1),
 
@@ -298,7 +298,7 @@ declare_ser_tests! {
             Token::EnumSeqEnd,
         ],
         Enum::Map { a: 1, b: 2 } => &[
-            Token::EnumMapStart("Enum", "Map", Some(2)),
+            Token::EnumMapStart("Enum", "Map", 2),
                 Token::EnumMapSep,
                 Token::Str("a"),
                 Token::I32(1),