diff --git a/serde/src/de/content.rs b/serde/src/de/content.rs
new file mode 100644
index 00000000..fa8875c8
--- /dev/null
+++ b/serde/src/de/content.rs
@@ -0,0 +1,743 @@
+// This module is doc(hidden) and nothing here should be used outside of
+// generated code.
+//
+// We will iterate on the implementation for a few releases and only have to
+// worry about backward compatibility for the `untagged` and `tag` attributes
+// rather than for this entire mechanism.
+//
+// This issue is tracking making some of this stuff public:
+// https://github.com/serde-rs/serde/issues/741
+
+#![doc(hidden)]
+
+use core::fmt;
+use core::marker::PhantomData;
+
+#[cfg(all(not(feature = "std"), feature = "collections"))]
+use collections::{String, Vec};
+
+#[cfg(all(feature = "alloc", not(feature = "std")))]
+use alloc::boxed::Box;
+
+use de::{
+    self,
+    Deserialize,
+    DeserializeSeed,
+    Deserializer,
+    Visitor,
+    SeqVisitor,
+    MapVisitor,
+    EnumVisitor,
+};
+
+/// Used from generated code to buffer the contents of the Deserializer when
+/// deserializing untagged enums and internally tagged enums.
+///
+/// Not public API. Use serde-value instead.
+#[derive(Debug)]
+pub enum Content<E> {
+    // Don't mind the PhantomData, just need to use E somewhere.
+    Bool(bool, PhantomData<E>),
+
+    U8(u8),
+    U16(u16),
+    U32(u32),
+    U64(u64),
+
+    I8(i8),
+    I16(i16),
+    I32(i32),
+    I64(i64),
+
+    F32(f32),
+    F64(f64),
+
+    Char(char),
+    String(String),
+    Bytes(Vec<u8>),
+
+    None,
+    Some(Box<Content<E>>),
+
+    Unit,
+    Newtype(Box<Content<E>>),
+    Seq(Vec<Content<E>>),
+    Map(Vec<(Content<E>, Content<E>)>),
+}
+
+impl<E> Deserialize for Content<E> {
+    fn deserialize<D: Deserializer>(deserializer: D) -> Result<Self, D::Error> {
+        // Untagged and internally tagged enums are only supported in
+        // self-describing formats.
+        deserializer.deserialize(ContentVisitor::new())
+    }
+}
+
+struct ContentVisitor<E> {
+    err: PhantomData<E>,
+}
+
+impl<E> ContentVisitor<E> {
+    fn new() -> Self {
+        ContentVisitor {
+            err: PhantomData,
+        }
+    }
+}
+
+impl<E> Visitor for ContentVisitor<E> {
+    type Value = Content<E>;
+
+    fn expecting(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.write_str("any value")
+    }
+
+    fn visit_bool<F>(self, value: bool) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::Bool(value, PhantomData))
+    }
+
+    fn visit_i8<F>(self, value: i8) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::I8(value))
+    }
+
+    fn visit_i16<F>(self, value: i16) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::I16(value))
+    }
+
+    fn visit_i32<F>(self, value: i32) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::I32(value))
+    }
+
+    fn visit_i64<F>(self, value: i64) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::I64(value))
+    }
+
+    fn visit_u8<F>(self, value: u8) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::U8(value))
+    }
+
+    fn visit_u16<F>(self, value: u16) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::U16(value))
+    }
+
+    fn visit_u32<F>(self, value: u32) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::U32(value))
+    }
+
+    fn visit_u64<F>(self, value: u64) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::U64(value))
+    }
+
+    fn visit_f32<F>(self, value: f32) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::F32(value))
+    }
+
+    fn visit_f64<F>(self, value: f64) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::F64(value))
+    }
+
+    fn visit_char<F>(self, value: char) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::Char(value))
+    }
+
+    fn visit_str<F>(self, value: &str) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::String(value.into()))
+    }
+
+    fn visit_string<F>(self, value: String) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::String(value))
+    }
+
+    fn visit_bytes<F>(self, value: &[u8]) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::Bytes(value.into()))
+    }
+
+    fn visit_byte_buf<F>(self, value: Vec<u8>) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::Bytes(value))
+    }
+
+    fn visit_unit<F>(self) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::Unit)
+    }
+
+    fn visit_none<F>(self) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        Ok(Content::None)
+    }
+
+    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+        where D: Deserializer
+    {
+        Deserialize::deserialize(deserializer).map(|v| Content::Some(Box::new(v)))
+    }
+
+    fn visit_newtype_struct<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+        where D: Deserializer
+    {
+        Deserialize::deserialize(deserializer).map(|v| Content::Newtype(Box::new(v)))
+    }
+
+    fn visit_seq<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
+        where V: SeqVisitor
+    {
+        let mut vec = Vec::with_capacity(visitor.size_hint().0);
+        while let Some(e) = try!(visitor.visit()) {
+            vec.push(e);
+        }
+        Ok(Content::Seq(vec))
+    }
+
+    fn visit_map<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
+        where V: MapVisitor
+    {
+        let mut vec = Vec::with_capacity(visitor.size_hint().0);
+        while let Some(kv) = try!(visitor.visit()) {
+            vec.push(kv);
+        }
+        Ok(Content::Map(vec))
+    }
+
+    fn visit_enum<V>(self, _visitor: V) -> Result<Self::Value, V::Error>
+        where V: EnumVisitor
+    {
+        Err(de::Error::custom("untagged and internally tagged enums do not support enum input"))
+    }
+}
+
+/// This is the type of the map keys in an internally tagged enum.
+///
+/// Not public API.
+pub enum TagOrContent<E> {
+    Tag,
+    Content(Content<E>),
+}
+
+struct TagOrContentVisitor<E> {
+    name: &'static str,
+    err: PhantomData<E>,
+}
+
+impl<E> TagOrContentVisitor<E> {
+    fn new(name: &'static str) -> Self {
+        TagOrContentVisitor {
+            name: name,
+            err: PhantomData,
+        }
+    }
+}
+
+impl<E> DeserializeSeed for TagOrContentVisitor<E> {
+    type Value = TagOrContent<E>;
+
+    fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+        where D: Deserializer
+    {
+        // Internally tagged enums are only supported in self-describing
+        // formats.
+        deserializer.deserialize(self)
+    }
+}
+
+impl<E> Visitor for TagOrContentVisitor<E> {
+    type Value = TagOrContent<E>;
+
+    fn expecting(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "a type tag `{}` or any other value", self.name)
+    }
+
+    fn visit_bool<F>(self, value: bool) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_bool(value).map(TagOrContent::Content)
+    }
+
+    fn visit_i8<F>(self, value: i8) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_i8(value).map(TagOrContent::Content)
+    }
+
+    fn visit_i16<F>(self, value: i16) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_i16(value).map(TagOrContent::Content)
+    }
+
+    fn visit_i32<F>(self, value: i32) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_i32(value).map(TagOrContent::Content)
+    }
+
+    fn visit_i64<F>(self, value: i64) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_i64(value).map(TagOrContent::Content)
+    }
+
+    fn visit_u8<F>(self, value: u8) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_u8(value).map(TagOrContent::Content)
+    }
+
+    fn visit_u16<F>(self, value: u16) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_u16(value).map(TagOrContent::Content)
+    }
+
+    fn visit_u32<F>(self, value: u32) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_u32(value).map(TagOrContent::Content)
+    }
+
+    fn visit_u64<F>(self, value: u64) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_u64(value).map(TagOrContent::Content)
+    }
+
+    fn visit_f32<F>(self, value: f32) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_f32(value).map(TagOrContent::Content)
+    }
+
+    fn visit_f64<F>(self, value: f64) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_f64(value).map(TagOrContent::Content)
+    }
+
+    fn visit_char<F>(self, value: char) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_char(value).map(TagOrContent::Content)
+    }
+
+    fn visit_str<F>(self, value: &str) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        if value == self.name {
+            Ok(TagOrContent::Tag)
+        } else {
+            ContentVisitor::new().visit_str(value).map(TagOrContent::Content)
+        }
+    }
+
+    fn visit_string<F>(self, value: String) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        if value == self.name {
+            Ok(TagOrContent::Tag)
+        } else {
+            ContentVisitor::new().visit_string(value).map(TagOrContent::Content)
+        }
+    }
+
+    fn visit_bytes<F>(self, value: &[u8]) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        if value == self.name.as_bytes() {
+            Ok(TagOrContent::Tag)
+        } else {
+            ContentVisitor::new().visit_bytes(value).map(TagOrContent::Content)
+        }
+    }
+
+    fn visit_byte_buf<F>(self, value: Vec<u8>) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        if value == self.name.as_bytes() {
+            Ok(TagOrContent::Tag)
+        } else {
+            ContentVisitor::new().visit_byte_buf(value).map(TagOrContent::Content)
+        }
+    }
+
+    fn visit_unit<F>(self) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_unit().map(TagOrContent::Content)
+    }
+
+    fn visit_none<F>(self) -> Result<Self::Value, F>
+        where F: de::Error
+    {
+        ContentVisitor::new().visit_none().map(TagOrContent::Content)
+    }
+
+    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+        where D: Deserializer
+    {
+        ContentVisitor::new().visit_some(deserializer).map(TagOrContent::Content)
+    }
+
+    fn visit_newtype_struct<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+        where D: Deserializer
+    {
+        ContentVisitor::new().visit_newtype_struct(deserializer).map(TagOrContent::Content)
+    }
+
+    fn visit_seq<V>(self, visitor: V) -> Result<Self::Value, V::Error>
+        where V: SeqVisitor
+    {
+        ContentVisitor::new().visit_seq(visitor).map(TagOrContent::Content)
+    }
+
+    fn visit_map<V>(self, visitor: V) -> Result<Self::Value, V::Error>
+        where V: MapVisitor
+    {
+        ContentVisitor::new().visit_map(visitor).map(TagOrContent::Content)
+    }
+
+    fn visit_enum<V>(self, visitor: V) -> Result<Self::Value, V::Error>
+        where V: EnumVisitor
+    {
+        ContentVisitor::new().visit_enum(visitor).map(TagOrContent::Content)
+    }
+}
+
+/// Used by generated code to deserialize an internally tagged enum.
+///
+/// Not public API.
+pub struct TaggedContent<T, E> {
+    pub tag: T,
+    pub content: Content<E>,
+}
+
+/// Not public API.
+pub struct TaggedContentVisitor<T, E> {
+    tag_name: &'static str,
+    tag: PhantomData<T>,
+    err: PhantomData<E>,
+}
+
+impl<T, E> TaggedContentVisitor<T, E> {
+    /// Visitor for the content of an internally tagged enum with the given tag
+    /// name.
+    pub fn new(name: &'static str) -> Self {
+        TaggedContentVisitor {
+            tag_name: name,
+            tag: PhantomData,
+            err: PhantomData,
+        }
+    }
+}
+
+impl<T, E> DeserializeSeed for TaggedContentVisitor<T, E>
+    where T: Deserialize
+{
+    type Value = TaggedContent<T, E>;
+
+    fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+        where D: Deserializer
+    {
+        // Internally tagged enums are only supported in self-describing
+        // formats.
+        deserializer.deserialize(self)
+    }
+}
+
+impl<T, E> Visitor for TaggedContentVisitor<T, E>
+    where T: Deserialize
+{
+    type Value = TaggedContent<T, E>;
+
+    fn expecting(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.write_str("any value")
+    }
+
+    fn visit_map<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
+        where V: MapVisitor
+    {
+        let mut tag = None;
+        let mut vec = Vec::with_capacity(visitor.size_hint().0);
+        while let Some(k) = try!(visitor.visit_key_seed(TagOrContentVisitor::new(self.tag_name))) {
+            match k {
+                TagOrContent::Tag => {
+                    if tag.is_some() {
+                        return Err(de::Error::duplicate_field(self.tag_name));
+                    }
+                    tag = Some(try!(visitor.visit_value()));
+                }
+                TagOrContent::Content(k) => {
+                    let v = try!(visitor.visit_value());
+                    vec.push((k, v));
+                }
+            }
+        }
+        match tag {
+            None => {
+                Err(de::Error::missing_field(self.tag_name))
+            }
+            Some(tag) => {
+                Ok(TaggedContent {
+                    tag: tag,
+                    content: Content::Map(vec),
+                })
+            }
+        }
+    }
+}
+
+/// Used when deserializing an internally tagged enum because the content will
+/// be used exactly once.
+impl<E> Deserializer for Content<E>
+    where E: de::Error
+{
+    type Error = E;
+
+    fn deserialize<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+        where V: Visitor
+    {
+        match self {
+            Content::Bool(v, _) => visitor.visit_bool(v),
+            Content::U8(v) => visitor.visit_u8(v),
+            Content::U16(v) => visitor.visit_u16(v),
+            Content::U32(v) => visitor.visit_u32(v),
+            Content::U64(v) => visitor.visit_u64(v),
+            Content::I8(v) => visitor.visit_i8(v),
+            Content::I16(v) => visitor.visit_i16(v),
+            Content::I32(v) => visitor.visit_i32(v),
+            Content::I64(v) => visitor.visit_i64(v),
+            Content::F32(v) => visitor.visit_f32(v),
+            Content::F64(v) => visitor.visit_f64(v),
+            Content::Char(v) => visitor.visit_char(v),
+            Content::String(v) => visitor.visit_string(v),
+            Content::Unit => visitor.visit_unit(),
+            Content::None => visitor.visit_none(),
+            Content::Some(v) => visitor.visit_some(*v),
+            Content::Newtype(v) => visitor.visit_newtype_struct(*v),
+            Content::Seq(v) => {
+                let seq = v.into_iter();
+                let mut seq_visitor = de::value::SeqDeserializer::new(seq);
+                let value = try!(visitor.visit_seq(&mut seq_visitor));
+                try!(seq_visitor.end());
+                Ok(value)
+            },
+            Content::Map(v) => {
+                let map = v.into_iter();
+                let mut map_visitor = de::value::MapDeserializer::new(map);
+                let value = try!(visitor.visit_map(&mut map_visitor));
+                try!(map_visitor.end());
+                Ok(value)
+            },
+            Content::Bytes(v) => visitor.visit_byte_buf(v),
+        }
+    }
+
+    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+        where V: Visitor
+    {
+        match self {
+            Content::None => visitor.visit_none(),
+            Content::Some(v) => visitor.visit_some(*v),
+            Content::Unit => visitor.visit_unit(),
+            _ => visitor.visit_some(self)
+        }
+    }
+
+    fn deserialize_newtype_struct<V>(self, _name: &str, visitor: V) -> Result<V::Value, Self::Error>
+        where V: Visitor
+    {
+        visitor.visit_newtype_struct(self)
+    }
+
+    forward_to_deserialize! {
+        bool u8 u16 u32 u64 i8 i16 i32 i64 f32 f64 char str string unit seq
+        seq_fixed_size bytes byte_buf map unit_struct tuple_struct struct
+        struct_field tuple enum ignored_any
+    }
+}
+
+impl<E> de::value::ValueDeserializer<E> for Content<E>
+    where E: de::Error
+{
+    type Deserializer = Self;
+
+    fn into_deserializer(self) -> Self {
+        self
+    }
+}
+
+/// Used when deserializing an untagged enum because the content may need to be
+/// used more than once.
+impl<'a, E> Deserializer for &'a Content<E>
+    where E: de::Error
+{
+    type Error = E;
+
+    fn deserialize<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+        where V: Visitor
+    {
+        match *self {
+            Content::Bool(v, _) => visitor.visit_bool(v),
+            Content::U8(v) => visitor.visit_u8(v),
+            Content::U16(v) => visitor.visit_u16(v),
+            Content::U32(v) => visitor.visit_u32(v),
+            Content::U64(v) => visitor.visit_u64(v),
+            Content::I8(v) => visitor.visit_i8(v),
+            Content::I16(v) => visitor.visit_i16(v),
+            Content::I32(v) => visitor.visit_i32(v),
+            Content::I64(v) => visitor.visit_i64(v),
+            Content::F32(v) => visitor.visit_f32(v),
+            Content::F64(v) => visitor.visit_f64(v),
+            Content::Char(v) => visitor.visit_char(v),
+            Content::String(ref v) => visitor.visit_str(v),
+            Content::Unit => visitor.visit_unit(),
+            Content::None => visitor.visit_none(),
+            Content::Some(ref v) => visitor.visit_some(&**v),
+            Content::Newtype(ref v) => visitor.visit_newtype_struct(&**v),
+            Content::Seq(ref v) => {
+                let seq = v.into_iter();
+                let mut seq_visitor = de::value::SeqDeserializer::new(seq);
+                let value = try!(visitor.visit_seq(&mut seq_visitor));
+                try!(seq_visitor.end());
+                Ok(value)
+            },
+            Content::Map(ref v) => {
+                let map = v.into_iter().map(|&(ref k, ref v)| (k, v));
+                let mut map_visitor = de::value::MapDeserializer::new(map);
+                let value = try!(visitor.visit_map(&mut map_visitor));
+                try!(map_visitor.end());
+                Ok(value)
+            },
+            Content::Bytes(ref v) => visitor.visit_bytes(v),
+        }
+    }
+
+    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+        where V: Visitor
+    {
+        match *self {
+            Content::None => visitor.visit_none(),
+            Content::Some(ref v) => visitor.visit_some(&**v),
+            Content::Unit => visitor.visit_unit(),
+            _ => visitor.visit_some(self)
+        }
+    }
+
+    fn deserialize_newtype_struct<V>(self, _name: &str, visitor: V) -> Result<V::Value, Self::Error>
+        where V: Visitor
+    {
+        visitor.visit_newtype_struct(self)
+    }
+
+    forward_to_deserialize! {
+        bool u8 u16 u32 u64 i8 i16 i32 i64 f32 f64 char str string unit seq
+        seq_fixed_size bytes byte_buf map unit_struct tuple_struct struct
+        struct_field tuple enum ignored_any
+    }
+}
+
+impl<'a, E> de::value::ValueDeserializer<E> for &'a Content<E>
+    where E: de::Error
+{
+    type Deserializer = Self;
+
+    fn into_deserializer(self) -> Self {
+        self
+    }
+}
+
+/// Visitor for deserializing an internally tagged unit variant.
+///
+/// Not public API.
+pub struct InternallyTaggedUnitVisitor<'a> {
+    type_name: &'a str,
+    variant_name: &'a str,
+}
+
+impl<'a> InternallyTaggedUnitVisitor<'a> {
+    /// Not public API.
+    pub fn new(type_name: &'a str, variant_name: &'a str) -> Self {
+        InternallyTaggedUnitVisitor {
+            type_name: type_name,
+            variant_name: variant_name,
+        }
+    }
+}
+
+impl<'a> Visitor for InternallyTaggedUnitVisitor<'a> {
+    type Value = ();
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "unit variant {}::{}", self.type_name, self.variant_name)
+    }
+
+    fn visit_map<V>(self, _: V) -> Result<(), V::Error>
+        where V: MapVisitor
+    {
+        Ok(())
+    }
+}
+
+/// Visitor for deserializing an untagged unit variant.
+///
+/// Not public API.
+pub struct UntaggedUnitVisitor<'a> {
+    type_name: &'a str,
+    variant_name: &'a str,
+}
+
+impl<'a> UntaggedUnitVisitor<'a> {
+    /// Not public API.
+    pub fn new(type_name: &'a str, variant_name: &'a str) -> Self {
+        UntaggedUnitVisitor {
+            type_name: type_name,
+            variant_name: variant_name,
+        }
+    }
+}
+
+impl<'a> Visitor for UntaggedUnitVisitor<'a> {
+    type Value = ();
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "unit variant {}::{}", self.type_name, self.variant_name)
+    }
+
+    fn visit_unit<E>(self) -> Result<(), E>
+        where E: de::Error
+    {
+        Ok(())
+    }
+}
diff --git a/serde/src/de/mod.rs b/serde/src/de/mod.rs
index ce86ce1e..8471c995 100644
--- a/serde/src/de/mod.rs
+++ b/serde/src/de/mod.rs
@@ -115,6 +115,8 @@ mod from_primitive;
 // Helpers used by generated code. Not public API.
 #[doc(hidden)]
 pub mod private;
+#[cfg(any(feature = "std", feature = "collections"))]
+mod content;
 
 ///////////////////////////////////////////////////////////////////////////////
 
diff --git a/serde/src/de/private.rs b/serde/src/de/private.rs
index 1ff206cd..750eecdc 100644
--- a/serde/src/de/private.rs
+++ b/serde/src/de/private.rs
@@ -2,6 +2,14 @@ use core::marker::PhantomData;
 
 use de::{Deserialize, Deserializer, Error, Visitor};
 
+#[cfg(any(feature = "std", feature = "collections"))]
+pub use de::content::{
+    Content,
+    TaggedContentVisitor,
+    InternallyTaggedUnitVisitor,
+    UntaggedUnitVisitor,
+};
+
 /// If the missing field is of type `Option<T>` then treat is as `None`,
 /// otherwise it is an error.
 pub fn missing_field<V, E>(field: &'static str) -> Result<V, E>
diff --git a/serde/src/de/value.rs b/serde/src/de/value.rs
index 32b69d5f..85d15267 100644
--- a/serde/src/de/value.rs
+++ b/serde/src/de/value.rs
@@ -428,7 +428,9 @@ impl<I, E> SeqDeserializer<I, E>
         }
     }
 
-    fn end(&mut self) -> Result<(), E> {
+    /// Check for remaining elements after passing a `SeqDeserializer` to
+    /// `Visitor::visit_seq`.
+    pub fn end(mut self) -> Result<(), E> {
         let mut remaining = 0;
         while self.iter.next().is_some() {
             remaining += 1;
@@ -610,17 +612,9 @@ impl<I, E> MapDeserializer<I, E>
         }
     }
 
-    fn next_pair(&mut self) -> Option<(<I::Item as private::Pair>::First, <I::Item as private::Pair>::Second)> {
-        match self.iter.next() {
-            Some(kv) => {
-                self.count += 1;
-                Some(private::Pair::split(kv))
-            }
-            None => None,
-        }
-    }
-
-    fn end(&mut self) -> Result<(), E> {
+    /// Check for remaining elements after passing a `MapDeserializer` to
+    /// `Visitor::visit_map`.
+    pub fn end(mut self) -> Result<(), E> {
         let mut remaining = 0;
         while self.iter.next().is_some() {
             remaining += 1;
@@ -633,6 +627,16 @@ impl<I, E> MapDeserializer<I, E>
             Err(de::Error::invalid_length(self.count + remaining, &ExpectedInMap(self.count)))
         }
     }
+
+    fn next_pair(&mut self) -> Option<(<I::Item as private::Pair>::First, <I::Item as private::Pair>::Second)> {
+        match self.iter.next() {
+            Some(kv) => {
+                self.count += 1;
+                Some(private::Pair::split(kv))
+            }
+            None => None,
+        }
+    }
 }
 
 impl<I, E> de::Deserializer for MapDeserializer<I, E>
diff --git a/serde/src/ser/mod.rs b/serde/src/ser/mod.rs
index a18346ce..42ccd169 100644
--- a/serde/src/ser/mod.rs
+++ b/serde/src/ser/mod.rs
@@ -106,6 +106,10 @@ use core::fmt::Display;
 mod impls;
 mod impossible;
 
+// Helpers used by generated code. Not public API.
+#[doc(hidden)]
+pub mod private;
+
 pub use self::impossible::Impossible;
 
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/serde/src/ser/private.rs b/serde/src/ser/private.rs
new file mode 100644
index 00000000..9d17ec78
--- /dev/null
+++ b/serde/src/ser/private.rs
@@ -0,0 +1,235 @@
+use core::fmt::{self, Display};
+
+use ser::{self, Serialize, Serializer, SerializeMap, SerializeStruct};
+
+/// Not public API.
+pub fn serialize_tagged_newtype<S, T>(
+    serializer: S,
+    type_ident: &'static str,
+    variant_ident: &'static str,
+    tag: &'static str,
+    variant_name: &'static str,
+    value: T,
+) -> Result<S::Ok, S::Error>
+    where S: Serializer,
+          T: Serialize
+{
+    value.serialize(TaggedSerializer {
+        type_ident: type_ident,
+        variant_ident: variant_ident,
+        tag: tag,
+        variant_name: variant_name,
+        delegate: serializer,
+    })
+}
+
+struct TaggedSerializer<S> {
+    type_ident: &'static str,
+    variant_ident: &'static str,
+    tag: &'static str,
+    variant_name: &'static str,
+    delegate: S,
+}
+
+enum Unsupported {
+    Boolean,
+    Integer,
+    Float,
+    Char,
+    String,
+    ByteArray,
+    Optional,
+    Unit,
+    UnitStruct,
+    Sequence,
+    Tuple,
+    TupleStruct,
+    Enum,
+}
+
+impl Display for Unsupported {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Unsupported::Boolean => formatter.write_str("a boolean"),
+            Unsupported::Integer => formatter.write_str("an integer"),
+            Unsupported::Float => formatter.write_str("a float"),
+            Unsupported::Char => formatter.write_str("a char"),
+            Unsupported::String => formatter.write_str("a string"),
+            Unsupported::ByteArray => formatter.write_str("a byte array"),
+            Unsupported::Optional => formatter.write_str("an optional"),
+            Unsupported::Unit => formatter.write_str("unit"),
+            Unsupported::UnitStruct => formatter.write_str("a unit struct"),
+            Unsupported::Sequence => formatter.write_str("a sequence"),
+            Unsupported::Tuple => formatter.write_str("a tuple"),
+            Unsupported::TupleStruct => formatter.write_str("a tuple struct"),
+            Unsupported::Enum => formatter.write_str("an enum"),
+        }
+    }
+}
+
+struct Error {
+    type_ident: &'static str,
+    variant_ident: &'static str,
+    ty: Unsupported,
+}
+
+impl Display for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter,
+               "cannot serialize tagged newtype variant {}::{} containing {}",
+               self.type_ident, self.variant_ident, self.ty)
+    }
+}
+
+impl<S> TaggedSerializer<S>
+    where S: Serializer
+{
+    fn bad_type(self, what: Unsupported) -> S::Error {
+        ser::Error::custom(Error {
+            type_ident: self.type_ident,
+            variant_ident: self.variant_ident,
+            ty: what,
+        })
+    }
+}
+
+impl<S> Serializer for TaggedSerializer<S>
+    where S: Serializer
+{
+    type Ok = S::Ok;
+    type Error = S::Error;
+
+    type SerializeSeq = S::SerializeSeq;
+    type SerializeTuple = S::SerializeTuple;
+    type SerializeTupleStruct = S::SerializeTupleStruct;
+    type SerializeTupleVariant = S::SerializeTupleVariant;
+    type SerializeMap = S::SerializeMap;
+    type SerializeStruct = S::SerializeStruct;
+    type SerializeStructVariant = S::SerializeStructVariant;
+
+    fn serialize_bool(self, _: bool) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Boolean))
+    }
+
+    fn serialize_i8(self, _: i8) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Integer))
+    }
+
+    fn serialize_i16(self, _: i16) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Integer))
+    }
+
+    fn serialize_i32(self, _: i32) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Integer))
+    }
+
+    fn serialize_i64(self, _: i64) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Integer))
+    }
+
+    fn serialize_u8(self, _: u8) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Integer))
+    }
+
+    fn serialize_u16(self, _: u16) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Integer))
+    }
+
+    fn serialize_u32(self, _: u32) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Integer))
+    }
+
+    fn serialize_u64(self, _: u64) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Integer))
+    }
+
+    fn serialize_f32(self, _: f32) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Float))
+    }
+
+    fn serialize_f64(self, _: f64) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Float))
+    }
+
+    fn serialize_char(self, _: char) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Char))
+    }
+
+    fn serialize_str(self, _: &str) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::String))
+    }
+
+    fn serialize_bytes(self, _: &[u8]) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::ByteArray))
+    }
+
+    fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Optional))
+    }
+
+    fn serialize_some<T: ?Sized>(self, _: &T) -> Result<Self::Ok, Self::Error>
+        where T: Serialize
+    {
+        Err(self.bad_type(Unsupported::Optional))
+    }
+
+    fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Unit))
+    }
+
+    fn serialize_unit_struct(self, _: &'static str) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::UnitStruct))
+    }
+
+    fn serialize_unit_variant(self, _: &'static str, _: usize, _: &'static str) -> Result<Self::Ok, Self::Error> {
+        Err(self.bad_type(Unsupported::Enum))
+    }
+
+    fn serialize_newtype_struct<T: ?Sized>(self, _: &'static str, value: &T) -> Result<Self::Ok, Self::Error>
+        where T: Serialize
+    {
+        value.serialize(self)
+    }
+
+    fn serialize_newtype_variant<T: ?Sized>(self, _: &'static str, _: usize, _: &'static str, _: &T) -> Result<Self::Ok, Self::Error>
+        where T: Serialize
+    {
+        Err(self.bad_type(Unsupported::Enum))
+    }
+
+    fn serialize_seq(self, _: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
+        Err(self.bad_type(Unsupported::Sequence))
+    }
+
+    fn serialize_seq_fixed_size(self, _: usize) -> Result<Self::SerializeSeq, Self::Error> {
+        Err(self.bad_type(Unsupported::Sequence))
+    }
+
+    fn serialize_tuple(self, _: usize) -> Result<Self::SerializeTuple, Self::Error> {
+        Err(self.bad_type(Unsupported::Tuple))
+    }
+
+    fn serialize_tuple_struct(self, _: &'static str, _: usize) -> Result<Self::SerializeTupleStruct, Self::Error> {
+        Err(self.bad_type(Unsupported::TupleStruct))
+    }
+
+    fn serialize_tuple_variant(self, _: &'static str, _: usize, _: &'static str, _: usize) -> Result<Self::SerializeTupleVariant, Self::Error> {
+        Err(self.bad_type(Unsupported::Enum))
+    }
+
+    fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
+        let mut map = try!(self.delegate.serialize_map(len.map(|len| len + 1)));
+        try!(map.serialize_entry(self.tag, self.variant_name));
+        Ok(map)
+    }
+
+    fn serialize_struct(self, name: &'static str, len: usize) -> Result<Self::SerializeStruct, Self::Error> {
+        let mut state = try!(self.delegate.serialize_struct(name, len + 1));
+        try!(state.serialize_field(self.tag, self.variant_name));
+        Ok(state)
+    }
+
+    fn serialize_struct_variant(self, _: &'static str, _: usize, _: &'static str, _: usize) -> Result<Self::SerializeStructVariant, Self::Error> {
+        Err(self.bad_type(Unsupported::Enum))
+    }
+}
diff --git a/serde_codegen_internals/src/attr.rs b/serde_codegen_internals/src/attr.rs
index 575dad5a..97fa4650 100644
--- a/serde_codegen_internals/src/attr.rs
+++ b/serde_codegen_internals/src/attr.rs
@@ -92,6 +92,32 @@ pub struct Item {
     deny_unknown_fields: bool,
     ser_bound: Option<Vec<syn::WherePredicate>>,
     de_bound: Option<Vec<syn::WherePredicate>>,
+    tag: EnumTag,
+}
+
+/// Styles of representing an enum.
+#[derive(Debug)]
+pub enum EnumTag {
+    /// The default.
+    ///
+    /// ```json
+    /// {"variant1": {"key1": "value1", "key2": "value2"}}
+    /// ```
+    External,
+
+    /// `#[serde(tag = "type")]`
+    ///
+    /// ```json
+    /// {"type": "variant1", "key1": "value1", "key2": "value2"}
+    /// ```
+    Internal(String),
+
+    /// `#[serde(untagged)]`
+    ///
+    /// ```json
+    /// {"key1": "value1", "key2": "value2"}
+    /// ```
+    None,
 }
 
 impl Item {
@@ -102,6 +128,8 @@ impl Item {
         let mut deny_unknown_fields = BoolAttr::none(cx, "deny_unknown_fields");
         let mut ser_bound = Attr::none(cx, "bound");
         let mut de_bound = Attr::none(cx, "bound");
+        let mut untagged = BoolAttr::none(cx, "untagged");
+        let mut internal_tag = Attr::none(cx, "tag");
 
         for meta_items in item.attrs.iter().filter_map(get_serde_meta_items) {
             for meta_item in meta_items {
@@ -143,6 +171,32 @@ impl Item {
                         }
                     }
 
+                    // Parse `#[serde(untagged)]`
+                    MetaItem(Word(ref name)) if name == "untagged" => {
+                        match item.body {
+                            syn::Body::Enum(_) => {
+                                untagged.set_true();
+                            }
+                            syn::Body::Struct(_) => {
+                                cx.error("#[serde(untagged)] can only be used on enums")
+                            }
+                        }
+                    }
+
+                    // Parse `#[serde(tag = "type")]`
+                    MetaItem(NameValue(ref name, ref lit)) if name == "tag" => {
+                        if let Ok(s) = get_string_from_lit(cx, name.as_ref(), name.as_ref(), lit) {
+                            match item.body {
+                                syn::Body::Enum(_) => {
+                                    internal_tag.set(s);
+                                }
+                                syn::Body::Struct(_) => {
+                                    cx.error("#[serde(tag = \"...\")] can only be used on enums")
+                                }
+                            }
+                        }
+                    }
+
                     MetaItem(ref meta_item) => {
                         cx.error(format!("unknown serde container attribute `{}`",
                                          meta_item.name()));
@@ -155,6 +209,32 @@ impl Item {
             }
         }
 
+        let tag = match (untagged.get(), internal_tag.get()) {
+            (false, None) => EnumTag::External,
+            (true, None) => EnumTag::None,
+            (false, Some(tag)) => {
+                // Check that there are no tuple variants.
+                if let syn::Body::Enum(ref variants) = item.body {
+                    for variant in variants {
+                        match variant.data {
+                            syn::VariantData::Struct(_) | syn::VariantData::Unit => {}
+                            syn::VariantData::Tuple(ref fields) => {
+                                if fields.len() != 1 {
+                                    cx.error("#[serde(tag = \"...\")] cannot be used with tuple variants");
+                                    break;
+                                }
+                            }
+                        }
+                    }
+                }
+                EnumTag::Internal(tag)
+            }
+            (true, Some(_)) => {
+                cx.error("enum cannot be both untagged and internally tagged");
+                EnumTag::External // doesn't matter, will error
+            }
+        };
+
         Item {
             name: Name {
                 serialize: ser_name.get().unwrap_or_else(|| item.ident.to_string()),
@@ -163,6 +243,7 @@ impl Item {
             deny_unknown_fields: deny_unknown_fields.get(),
             ser_bound: ser_bound.get(),
             de_bound: de_bound.get(),
+            tag: tag,
         }
     }
 
@@ -181,6 +262,10 @@ impl Item {
     pub fn de_bound(&self) -> Option<&[syn::WherePredicate]> {
         self.de_bound.as_ref().map(|vec| &vec[..])
     }
+
+    pub fn tag(&self) -> &EnumTag {
+        &self.tag
+    }
 }
 
 /// Represents variant attribute information
diff --git a/serde_derive/src/de.rs b/serde_derive/src/de.rs
index 3d7b5d1f..b72d78ad 100644
--- a/serde_derive/src/de.rs
+++ b/serde_derive/src/de.rs
@@ -110,7 +110,8 @@ fn deserialize_body(
                 impl_generics,
                 ty,
                 fields,
-                &item.attrs)
+                &item.attrs,
+                None)
         }
         Body::Struct(Style::Tuple, ref fields) |
         Body::Struct(Style::Newtype, ref fields) => {
@@ -124,7 +125,8 @@ fn deserialize_body(
                 impl_generics,
                 ty,
                 fields,
-                &item.attrs)
+                &item.attrs,
+                None)
         }
         Body::Struct(Style::Unit, _) => {
             deserialize_unit_struct(
@@ -238,6 +240,7 @@ fn deserialize_tuple(
     ty: syn::Ty,
     fields: &[Field],
     item_attrs: &attr::Item,
+    deserializer: Option<Tokens>,
 ) -> Tokens {
     let where_clause = &impl_generics.where_clause;
 
@@ -274,7 +277,9 @@ fn deserialize_tuple(
         false,
     );
 
-    let dispatch = if is_enum {
+    let dispatch = if let Some(deserializer) = deserializer {
+        quote!(_serde::Deserializer::deserialize(#deserializer, #visitor_expr))
+    } else if is_enum {
         quote!(_serde::de::VariantVisitor::visit_tuple(visitor, #nfields, #visitor_expr))
     } else if nfields == 1 {
         let type_name = item_attrs.name().deserialize_name();
@@ -424,7 +429,11 @@ fn deserialize_struct(
     ty: syn::Ty,
     fields: &[Field],
     item_attrs: &attr::Item,
+    deserializer: Option<Tokens>,
 ) -> Tokens {
+    let is_enum = variant_ident.is_some();
+    let is_untagged = deserializer.is_some();
+
     let where_clause = &impl_generics.where_clause;
 
     let (visitor_item, visitor_ty, visitor_expr) = deserialize_visitor(impl_generics);
@@ -454,8 +463,11 @@ fn deserialize_struct(
         item_attrs,
     );
 
-    let is_enum = variant_ident.is_some();
-    let dispatch = if is_enum {
+    let dispatch = if let Some(deserializer) = deserializer {
+        quote! {
+            _serde::Deserializer::deserialize(#deserializer, #visitor_expr)
+        }
+    } else if is_enum {
         quote! {
             _serde::de::VariantVisitor::visit_struct(visitor, FIELDS, #visitor_expr)
         }
@@ -473,6 +485,20 @@ fn deserialize_struct(
         quote!(mut visitor)
     };
 
+    let visit_seq = if is_untagged {
+        // untagged struct variants do not get a visit_seq method
+        None
+    } else {
+        Some(quote! {
+            #[inline]
+            fn visit_seq<__V>(self, #visitor_var: __V) -> _serde::export::Result<#ty, __V::Error>
+                where __V: _serde::de::SeqVisitor
+            {
+                #visit_seq
+            }
+        })
+    };
+
     quote!({
         #field_visitor
 
@@ -485,12 +511,7 @@ fn deserialize_struct(
                 _serde::export::fmt::Formatter::write_str(formatter, #expecting)
             }
 
-            #[inline]
-            fn visit_seq<__V>(self, #visitor_var: __V) -> _serde::export::Result<#ty, __V::Error>
-                where __V: _serde::de::SeqVisitor
-            {
-                #visit_seq
-            }
+            #visit_seq
 
             #[inline]
             fn visit_map<__V>(self, mut visitor: __V) -> _serde::export::Result<#ty, __V::Error>
@@ -512,6 +533,45 @@ fn deserialize_item_enum(
     ty: syn::Ty,
     variants: &[Variant],
     item_attrs: &attr::Item
+) -> Tokens {
+    match *item_attrs.tag() {
+        attr::EnumTag::External => {
+            deserialize_externally_tagged_enum(
+                type_ident,
+                impl_generics,
+                ty,
+                variants,
+                item_attrs,
+            )
+        }
+        attr::EnumTag::Internal(ref tag) => {
+            deserialize_internally_tagged_enum(
+                type_ident,
+                impl_generics,
+                ty,
+                variants,
+                item_attrs,
+                tag,
+            )
+        }
+        attr::EnumTag::None => {
+            deserialize_untagged_enum(
+                type_ident,
+                impl_generics,
+                ty,
+                variants,
+                item_attrs,
+            )
+        }
+    }
+}
+
+fn deserialize_externally_tagged_enum(
+    type_ident: &syn::Ident,
+    impl_generics: &syn::Generics,
+    ty: syn::Ty,
+    variants: &[Variant],
+    item_attrs: &attr::Item,
 ) -> Tokens {
     let where_clause = &impl_generics.where_clause;
 
@@ -545,7 +605,7 @@ fn deserialize_item_enum(
         .map(|(i, variant)| {
             let variant_name = field_i(i);
 
-            let block = deserialize_variant(
+            let block = deserialize_externally_tagged_variant(
                 type_ident,
                 impl_generics,
                 ty.clone(),
@@ -604,7 +664,111 @@ fn deserialize_item_enum(
     })
 }
 
-fn deserialize_variant(
+fn deserialize_internally_tagged_enum(
+    type_ident: &syn::Ident,
+    impl_generics: &syn::Generics,
+    ty: syn::Ty,
+    variants: &[Variant],
+    item_attrs: &attr::Item,
+    tag: &str,
+) -> Tokens {
+    let variant_names_idents: Vec<_> = variants.iter()
+        .enumerate()
+        .filter(|&(_, variant)| !variant.attrs.skip_deserializing())
+        .map(|(i, variant)| (variant.attrs.name().deserialize_name(), field_i(i)))
+        .collect();
+
+    let variants_stmt = {
+        let variant_names = variant_names_idents.iter().map(|&(ref name, _)| name);
+        quote! {
+            const VARIANTS: &'static [&'static str] = &[ #(#variant_names),* ];
+        }
+    };
+
+    let variant_visitor = deserialize_field_visitor(
+        variant_names_idents,
+        item_attrs,
+        true,
+    );
+
+    // Match arms to extract a variant from a string
+    let variant_arms = variants.iter()
+        .enumerate()
+        .filter(|&(_, variant)| !variant.attrs.skip_deserializing())
+        .map(|(i, variant)| {
+            let variant_name = field_i(i);
+
+            let block = deserialize_internally_tagged_variant(
+                type_ident,
+                impl_generics,
+                ty.clone(),
+                variant,
+                item_attrs,
+                quote!(_tagged.content),
+            );
+
+            quote! {
+                __Field::#variant_name => #block
+            }
+        });
+
+    quote!({
+        #variant_visitor
+
+        #variants_stmt
+
+        let _tagged = try!(_serde::Deserializer::deserialize(
+            deserializer,
+            _serde::de::private::TaggedContentVisitor::<__Field, __D::Error>::new(#tag)));
+
+        match _tagged.tag {
+            #(#variant_arms)*
+        }
+    })
+}
+
+fn deserialize_untagged_enum(
+    type_ident: &syn::Ident,
+    impl_generics: &syn::Generics,
+    ty: syn::Ty,
+    variants: &[Variant],
+    item_attrs: &attr::Item,
+) -> Tokens {
+    let attempts = variants.iter()
+        .filter(|variant| !variant.attrs.skip_deserializing())
+        .map(|variant| {
+            deserialize_untagged_variant(
+                type_ident,
+                impl_generics,
+                ty.clone(),
+                variant,
+                item_attrs,
+                quote!(&_content),
+            )
+        });
+
+    // TODO this message could be better by saving the errors from the failed
+    // attempts. The heuristic used by TOML was to count the number of fields
+    // processed before an error, and use the error that happened after the
+    // largest number of fields. I'm not sure I like that. Maybe it would be
+    // better to save all the errors and combine them into one message that
+    // explains why none of the variants matched.
+    let fallthrough_msg = format!("data did not match any variant of untagged enum {}", type_ident);
+
+    quote!({
+        let _content = try!(<_serde::de::private::Content<__D::Error> as _serde::Deserialize>::deserialize(deserializer));
+
+        #(
+            if let _serde::export::Ok(ok) = #attempts {
+                return _serde::export::Ok(ok);
+            }
+        )*
+
+        _serde::export::Err(_serde::de::Error::custom(#fallthrough_msg))
+    })
+}
+
+fn deserialize_externally_tagged_variant(
     type_ident: &syn::Ident,
     generics: &syn::Generics,
     ty: syn::Ty,
@@ -621,7 +785,7 @@ fn deserialize_variant(
             })
         }
         Style::Newtype => {
-            deserialize_newtype_variant(
+            deserialize_externally_tagged_newtype_variant(
                 type_ident,
                 variant_ident,
                 generics,
@@ -636,6 +800,7 @@ fn deserialize_variant(
                 ty,
                 &variant.fields,
                 item_attrs,
+                None,
             )
         }
         Style::Struct => {
@@ -646,22 +811,115 @@ fn deserialize_variant(
                 ty,
                 &variant.fields,
                 item_attrs,
+                None,
             )
         }
     }
 }
 
-fn deserialize_newtype_variant(
+fn deserialize_internally_tagged_variant(
+    type_ident: &syn::Ident,
+    generics: &syn::Generics,
+    ty: syn::Ty,
+    variant: &Variant,
+    item_attrs: &attr::Item,
+    deserializer: Tokens,
+) -> Tokens {
+    let variant_ident = &variant.ident;
+
+    match variant.style {
+        Style::Unit => {
+            let type_name = type_ident.as_ref();
+            let variant_name = variant.ident.as_ref();
+            quote!({
+                try!(_serde::Deserializer::deserialize(#deserializer, _serde::de::private::InternallyTaggedUnitVisitor::new(#type_name, #variant_name)));
+                _serde::export::Ok(#type_ident::#variant_ident)
+            })
+        }
+        Style::Newtype | Style::Struct => {
+            deserialize_untagged_variant(
+                type_ident,
+                generics,
+                ty,
+                variant,
+                item_attrs,
+                deserializer,
+            )
+        }
+        Style::Tuple => unreachable!("checked in serde_codegen_internals"),
+    }
+}
+
+fn deserialize_untagged_variant(
+    type_ident: &syn::Ident,
+    generics: &syn::Generics,
+    ty: syn::Ty,
+    variant: &Variant,
+    item_attrs: &attr::Item,
+    deserializer: Tokens,
+) -> Tokens {
+    let variant_ident = &variant.ident;
+
+    match variant.style {
+        Style::Unit => {
+            let type_name = type_ident.as_ref();
+            let variant_name = variant.ident.as_ref();
+            quote! {
+                _serde::export::Result::map(
+                    _serde::Deserializer::deserialize(
+                        #deserializer,
+                        _serde::de::private::UntaggedUnitVisitor::new(#type_name, #variant_name)
+                    ),
+                    |()| #type_ident::#variant_ident)
+            }
+        }
+        Style::Newtype => {
+            deserialize_untagged_newtype_variant(
+                type_ident,
+                variant_ident,
+                generics,
+                &variant.fields[0],
+                deserializer,
+            )
+        }
+        Style::Tuple => {
+            deserialize_tuple(
+                type_ident,
+                Some(variant_ident),
+                generics,
+                ty,
+                &variant.fields,
+                item_attrs,
+                Some(deserializer),
+            )
+        }
+        Style::Struct => {
+            deserialize_struct(
+                type_ident,
+                Some(variant_ident),
+                generics,
+                ty,
+                &variant.fields,
+                item_attrs,
+                Some(deserializer),
+            )
+        }
+    }
+}
+
+fn deserialize_externally_tagged_newtype_variant(
     type_ident: &syn::Ident,
     variant_ident: &syn::Ident,
     impl_generics: &syn::Generics,
     field: &Field,
 ) -> Tokens {
-    let visit = match field.attrs.deserialize_with() {
+    match field.attrs.deserialize_with() {
         None => {
             let field_ty = &field.ty;
             quote! {
-                try!(_serde::de::VariantVisitor::visit_newtype::<#field_ty>(visitor))
+                _serde::export::Result::map(
+                    _serde::de::VariantVisitor::visit_newtype::<#field_ty>(visitor),
+                    #type_ident::#variant_ident),
             }
         }
         Some(path) => {
@@ -670,12 +928,41 @@ fn deserialize_newtype_variant(
             quote!({
                 #wrapper
                 #wrapper_impl
-                try!(_serde::de::VariantVisitor::visit_newtype::<#wrapper_ty>(visitor)).value
+                _serde::export::Result::map(
+                    _serde::de::VariantVisitor::visit_newtype::<#wrapper_ty>(visitor),
+                    |_wrapper| #type_ident::#variant_ident(_wrapper.value))
+            })
+        }
+    }
+}
+
+fn deserialize_untagged_newtype_variant(
+    type_ident: &syn::Ident,
+    variant_ident: &syn::Ident,
+    impl_generics: &syn::Generics,
+    field: &Field,
+    deserializer: Tokens,
+) -> Tokens {
+    match field.attrs.deserialize_with() {
+        None => {
+            let field_ty = &field.ty;
+            quote!({
+                _serde::export::Result::map(
+                    <#field_ty as _serde::Deserialize>::deserialize(#deserializer),
+                    #type_ident::#variant_ident)
+            })
+        }
+        Some(path) => {
+            let (wrapper, wrapper_impl, wrapper_ty) = wrap_deserialize_with(
+                type_ident, impl_generics, field.ty, path);
+            quote!({
+                #wrapper
+                #wrapper_impl
+                _serde::export::Result::map(
+                    <#wrapper_ty as _serde::Deserialize>::deserialize(#deserializer),
+                    |_wrapper| #type_ident::#variant_ident(_wrapper.value))
             })
         }
-    };
-    quote! {
-        _serde::export::Ok(#type_ident::#variant_ident(#visit)),
     }
 }
 
diff --git a/serde_derive/src/ser.rs b/serde_derive/src/ser.rs
index 6478de41..52c86c7e 100644
--- a/serde_derive/src/ser.rs
+++ b/serde_derive/src/ser.rs
@@ -251,14 +251,11 @@ fn serialize_variant(
     variant_index: usize,
     item_attrs: &attr::Item,
 ) -> Tokens {
-    let type_name = item_attrs.name().serialize_name();
-
     let variant_ident = variant.ident.clone();
-    let variant_name = variant.attrs.name().serialize_name();
 
     if variant.attrs.skip_serializing() {
         let skipped_msg = format!("the enum variant {}::{} cannot be serialized",
-                                type_ident, variant_ident);
+                                  type_ident, variant_ident);
         let skipped_err = quote! {
             _serde::export::Err(_serde::ser::Error::custom(#skipped_msg))
         };
@@ -271,140 +268,351 @@ fn serialize_variant(
             #type_ident::#variant_ident #fields_pat => #skipped_err,
         }
     } else { // variant wasn't skipped
-        match variant.style {
+        let case = match variant.style {
             Style::Unit => {
                 quote! {
-                    #type_ident::#variant_ident =>
-                        _serde::Serializer::serialize_unit_variant(
-                            _serializer,
-                            #type_name,
-                            #variant_index,
-                            #variant_name,
-                        ),
+                    #type_ident::#variant_ident
                 }
-            },
+            }
             Style::Newtype => {
-                let block = serialize_newtype_variant(
-                    type_name,
-                    variant_index,
-                    variant_name,
-                    ty,
-                    generics,
-                    &variant.fields[0],
-                );
-
                 quote! {
-                    #type_ident::#variant_ident(ref __simple_value) => #block,
+                    #type_ident::#variant_ident(ref __simple_value)
                 }
-            },
+            }
             Style::Tuple => {
                 let field_names = (0 .. variant.fields.len())
                     .map(|i| Ident::new(format!("__field{}", i)));
-
-                let block = serialize_tuple_variant(
-                    type_name,
-                    variant_index,
-                    variant_name,
-                    generics,
-                    ty,
-                    &variant.fields,
-                );
-
                 quote! {
-                    #type_ident::#variant_ident(#(ref #field_names),*) => { #block }
+                    #type_ident::#variant_ident(#(ref #field_names),*)
                 }
             }
             Style::Struct => {
                 let fields = variant.fields.iter()
                     .map(|f| f.ident.clone().expect("struct variant has unnamed fields"));
+                quote! {
+                    #type_ident::#variant_ident { #(ref #fields),* }
+                }
+            }
+        };
 
-                let block = serialize_struct_variant(
-                    variant_index,
-                    variant_name,
+        let body = match *item_attrs.tag() {
+            attr::EnumTag::External => {
+                serialize_externally_tagged_variant(
                     generics,
                     ty,
-                    &variant.fields,
+                    variant,
+                    variant_index,
                     item_attrs,
-                );
+                )
+            }
+            attr::EnumTag::Internal(ref tag) => {
+                serialize_internally_tagged_variant(
+                    type_ident.as_ref(),
+                    variant_ident.as_ref(),
+                    generics,
+                    ty,
+                    variant,
+                    item_attrs,
+                    tag,
+                )
+            }
+            attr::EnumTag::None => {
+                serialize_untagged_variant(
+                    generics,
+                    ty,
+                    variant,
+                    item_attrs,
+                )
+            }
+        };
 
-                quote! {
-                    #type_ident::#variant_ident { #(ref #fields),* } => { #block }
-                }
+        quote! {
+            #case => #body
+        }
+    }
+}
+
+fn serialize_externally_tagged_variant(
+    generics: &syn::Generics,
+    ty: syn::Ty,
+    variant: &Variant,
+    variant_index: usize,
+    item_attrs: &attr::Item,
+) -> Tokens {
+    let type_name = item_attrs.name().serialize_name();
+    let variant_name = variant.attrs.name().serialize_name();
+
+    match variant.style {
+        Style::Unit => {
+            quote! {
+                _serde::Serializer::serialize_unit_variant(
+                    _serializer,
+                    #type_name,
+                    #variant_index,
+                    #variant_name,
+                ),
+            }
+        }
+        Style::Newtype => {
+            let field = &variant.fields[0];
+            let mut field_expr = quote!(__simple_value);
+            if let Some(path) = field.attrs.serialize_with() {
+                field_expr = wrap_serialize_with(
+                    &ty, generics, field.ty, path, field_expr);
+            }
+
+            quote! {
+                _serde::Serializer::serialize_newtype_variant(
+                    _serializer,
+                    #type_name,
+                    #variant_index,
+                    #variant_name,
+                    #field_expr,
+                ),
+            }
+        }
+        Style::Tuple => {
+            let block = serialize_tuple_variant(
+                TupleVariant::ExternallyTagged {
+                    type_name: type_name,
+                    variant_index: variant_index,
+                    variant_name: variant_name,
+                },
+                generics,
+                ty,
+                &variant.fields,
+            );
+
+            quote! {
+                { #block }
+            }
+        }
+        Style::Struct => {
+            let block = serialize_struct_variant(
+                StructVariant::ExternallyTagged {
+                    variant_index: variant_index,
+                    variant_name: variant_name,
+                },
+                generics,
+                ty,
+                &variant.fields,
+                item_attrs,
+            );
+
+            quote! {
+                { #block }
             }
         }
     }
 }
 
-fn serialize_newtype_variant(
-    type_name: String,
-    variant_index: usize,
-    variant_name: String,
-    item_ty: syn::Ty,
+fn serialize_internally_tagged_variant(
+    type_ident: &str,
+    variant_ident: &str,
     generics: &syn::Generics,
-    field: &Field,
+    ty: syn::Ty,
+    variant: &Variant,
+    item_attrs: &attr::Item,
+    tag: &str,
 ) -> Tokens {
-    let mut field_expr = quote!(__simple_value);
-    if let Some(path) = field.attrs.serialize_with() {
-        field_expr = wrap_serialize_with(
-            &item_ty, generics, field.ty, path, field_expr);
-    }
+    let type_name = item_attrs.name().serialize_name();
+    let variant_name = variant.attrs.name().serialize_name();
 
-    quote! {
-        _serde::Serializer::serialize_newtype_variant(
-            _serializer,
-            #type_name,
-            #variant_index,
-            #variant_name,
-            #field_expr,
-        )
+    match variant.style {
+        Style::Unit => {
+            quote!({
+                let mut __struct = try!(_serde::Serializer::serialize_struct(
+                    _serializer, #type_name, 1));
+                try!(_serde::ser::SerializeStruct::serialize_field(
+                    &mut __struct, #tag, #variant_name));
+                _serde::ser::SerializeStruct::end(__struct)
+            })
+        }
+        Style::Newtype => {
+            let field = &variant.fields[0];
+            let mut field_expr = quote!(__simple_value);
+            if let Some(path) = field.attrs.serialize_with() {
+                field_expr = wrap_serialize_with(
+                    &ty, generics, field.ty, path, field_expr);
+            }
+
+            quote! {
+                _serde::ser::private::serialize_tagged_newtype(
+                    _serializer,
+                    #type_ident,
+                    #variant_ident,
+                    #tag,
+                    #variant_name,
+                    #field_expr,
+                ),
+            }
+        }
+        Style::Struct => {
+            let block = serialize_struct_variant(
+                StructVariant::InternallyTagged {
+                    tag: tag,
+                    variant_name: variant_name,
+                },
+                generics,
+                ty,
+                &variant.fields,
+                item_attrs,
+            );
+
+            quote! {
+                { #block }
+            }
+        }
+        Style::Tuple => unreachable!("checked in serde_codegen_internals"),
     }
 }
 
+fn serialize_untagged_variant(
+    generics: &syn::Generics,
+    ty: syn::Ty,
+    variant: &Variant,
+    item_attrs: &attr::Item,
+) -> Tokens {
+    match variant.style {
+        Style::Unit => {
+            quote! {
+                _serde::Serializer::serialize_unit(_serializer),
+            }
+        }
+        Style::Newtype => {
+            let field = &variant.fields[0];
+            let mut field_expr = quote!(__simple_value);
+            if let Some(path) = field.attrs.serialize_with() {
+                field_expr = wrap_serialize_with(
+                    &ty, generics, field.ty, path, field_expr);
+            }
+
+            quote! {
+                _serde::Serialize::serialize(#field_expr, _serializer),
+            }
+        }
+        Style::Tuple => {
+            let block = serialize_tuple_variant(
+                TupleVariant::Untagged,
+                generics,
+                ty,
+                &variant.fields,
+            );
+
+            quote! {
+                { #block }
+            }
+        }
+        Style::Struct => {
+            let block = serialize_struct_variant(
+                StructVariant::Untagged,
+                generics,
+                ty,
+                &variant.fields,
+                item_attrs,
+            );
+
+            quote! {
+                { #block }
+            }
+        }
+    }
+}
+
+enum TupleVariant {
+    ExternallyTagged {
+        type_name: String,
+        variant_index: usize,
+        variant_name: String,
+    },
+    Untagged,
+}
+
 fn serialize_tuple_variant(
-    type_name: String,
-    variant_index: usize,
-    variant_name: String,
+    context: TupleVariant,
     generics: &syn::Generics,
     structure_ty: syn::Ty,
     fields: &[Field],
 ) -> Tokens {
+    let method = match context {
+        TupleVariant::ExternallyTagged{..} => {
+            quote!(_serde::ser::SerializeTupleVariant::serialize_field)
+        }
+        TupleVariant::Untagged => {
+            quote!(_serde::ser::SerializeTuple::serialize_element)
+        }
+    };
+
     let serialize_stmts = serialize_tuple_struct_visitor(
         structure_ty,
         fields,
         generics,
         true,
-        quote!(_serde::ser::SerializeTupleVariant::serialize_field),
+        method,
     );
 
     let len = serialize_stmts.len();
     let let_mut = mut_if(len > 0);
 
-    quote! {
-        let #let_mut __serde_state = try!(_serde::Serializer::serialize_tuple_variant(
-            _serializer,
-            #type_name,
-            #variant_index,
-            #variant_name,
-            #len));
-        #(#serialize_stmts)*
-        _serde::ser::SerializeTupleVariant::end(__serde_state)
+    match context {
+        TupleVariant::ExternallyTagged { type_name, variant_index, variant_name } => {
+            quote! {
+                let #let_mut __serde_state = try!(_serde::Serializer::serialize_tuple_variant(
+                    _serializer,
+                    #type_name,
+                    #variant_index,
+                    #variant_name,
+                    #len));
+                #(#serialize_stmts)*
+                _serde::ser::SerializeTupleVariant::end(__serde_state)
+            }
+        }
+        TupleVariant::Untagged => {
+            quote! {
+                let #let_mut __serde_state = try!(_serde::Serializer::serialize_tuple(
+                    _serializer,
+                    #len));
+                #(#serialize_stmts)*
+                _serde::ser::SerializeTuple::end(__serde_state)
+            }
+        }
     }
 }
 
-fn serialize_struct_variant(
-    variant_index: usize,
-    variant_name: String,
+enum StructVariant<'a> {
+    ExternallyTagged {
+        variant_index: usize,
+        variant_name: String,
+    },
+    InternallyTagged {
+        tag: &'a str,
+        variant_name: String,
+    },
+    Untagged,
+}
+
+fn serialize_struct_variant<'a>(
+    context: StructVariant<'a>,
     generics: &syn::Generics,
     ty: syn::Ty,
     fields: &[Field],
     item_attrs: &attr::Item,
 ) -> Tokens {
+    let method = match context {
+        StructVariant::ExternallyTagged{..} => {
+            quote!(_serde::ser::SerializeStructVariant::serialize_field)
+        }
+        StructVariant::InternallyTagged{..} | StructVariant::Untagged => {
+            quote!(_serde::ser::SerializeStruct::serialize_field)
+        }
+    };
+
     let serialize_fields = serialize_struct_visitor(
         ty.clone(),
         fields,
         generics,
         true,
-        quote!(_serde::ser::SerializeStructVariant::serialize_field),
+        method,
     );
 
     let item_name = item_attrs.name().serialize_name();
@@ -426,16 +634,47 @@ fn serialize_struct_variant(
          })
         .fold(quote!(0), |sum, expr| quote!(#sum + #expr));
 
-    quote! {
-        let #let_mut __serde_state = try!(_serde::Serializer::serialize_struct_variant(
-            _serializer,
-            #item_name,
-            #variant_index,
-            #variant_name,
-            #len,
-        ));
-        #(#serialize_fields)*
-        _serde::ser::SerializeStructVariant::end(__serde_state)
+    match context {
+        StructVariant::ExternallyTagged { variant_index, variant_name } => {
+            quote! {
+                let #let_mut __serde_state = try!(_serde::Serializer::serialize_struct_variant(
+                    _serializer,
+                    #item_name,
+                    #variant_index,
+                    #variant_name,
+                    #len,
+                ));
+                #(#serialize_fields)*
+                _serde::ser::SerializeStructVariant::end(__serde_state)
+            }
+        }
+        StructVariant::InternallyTagged { tag, variant_name } => {
+            quote! {
+                let mut __serde_state = try!(_serde::Serializer::serialize_struct(
+                    _serializer,
+                    #item_name,
+                    #len + 1,
+                ));
+                try!(_serde::ser::SerializeStruct::serialize_field(
+                    &mut __serde_state,
+                    #tag,
+                    #variant_name,
+                ));
+                #(#serialize_fields)*
+                _serde::ser::SerializeStruct::end(__serde_state)
+            }
+        }
+        StructVariant::Untagged => {
+            quote! {
+                let #let_mut __serde_state = try!(_serde::Serializer::serialize_struct(
+                    _serializer,
+                    #item_name,
+                    #len,
+                ));
+                #(#serialize_fields)*
+                _serde::ser::SerializeStruct::end(__serde_state)
+            }
+        }
     }
 }
 
diff --git a/serde_test/src/de.rs b/serde_test/src/de.rs
index 8bdfdcee..138ed0cd 100644
--- a/serde_test/src/de.rs
+++ b/serde_test/src/de.rs
@@ -47,91 +47,29 @@ impl<I> Deserializer<I>
         }
     }
 
-    fn visit_seq<V>(&mut self, len: Option<usize>, visitor: V) -> Result<V::Value, Error>
+    fn visit_seq<V>(&mut self, len: Option<usize>, sep: Token<'static>, end: Token<'static>, visitor: V) -> Result<V::Value, Error>
         where V: Visitor,
     {
         let value = try!(visitor.visit_seq(DeserializerSeqVisitor {
             de: self,
             len: len,
+            sep: sep,
+            end: end.clone(),
         }));
-        try!(self.expect_token(Token::SeqEnd));
+        try!(self.expect_token(end));
         Ok(value)
     }
 
-    fn visit_array<V>(&mut self, len: usize, visitor: V) -> Result<V::Value, Error>
-        where V: Visitor,
-    {
-        let value = try!(visitor.visit_seq(DeserializerArrayVisitor {
-            de: self,
-            len: len,
-        }));
-        try!(self.expect_token(Token::SeqEnd));
-        Ok(value)
-    }
-
-    fn visit_tuple<V>(&mut self, len: usize, visitor: V) -> Result<V::Value, Error>
-        where V: Visitor,
-    {
-        let value = try!(visitor.visit_seq(DeserializerTupleVisitor {
-            de: self,
-            len: len,
-        }));
-        try!(self.expect_token(Token::TupleEnd));
-        Ok(value)
-    }
-
-    fn visit_tuple_struct<V>(&mut self, len: usize, visitor: V) -> Result<V::Value, Error>
-        where V: Visitor,
-    {
-        let value = try!(visitor.visit_seq(DeserializerTupleStructVisitor {
-            de: self,
-            len: len,
-        }));
-        try!(self.expect_token(Token::TupleStructEnd));
-        Ok(value)
-    }
-
-    fn visit_variant_seq<V>(&mut self, len: Option<usize>, visitor: V) -> Result<V::Value, Error>
-        where V: Visitor,
-    {
-        let value = try!(visitor.visit_seq(DeserializerVariantSeqVisitor {
-            de: self,
-            len: len,
-        }));
-        try!(self.expect_token(Token::EnumSeqEnd));
-        Ok(value)
-    }
-
-    fn visit_map<V>(&mut self, len: Option<usize>, visitor: V) -> Result<V::Value, Error>
+    fn visit_map<V>(&mut self, len: Option<usize>, sep: Token<'static>, end: Token<'static>, visitor: V) -> Result<V::Value, Error>
         where V: Visitor,
     {
         let value = try!(visitor.visit_map(DeserializerMapVisitor {
             de: self,
             len: len,
+            sep: sep,
+            end: end.clone(),
         }));
-        try!(self.expect_token(Token::MapEnd));
-        Ok(value)
-    }
-
-    fn visit_struct<V>(&mut self, fields: &'static [&'static str], visitor: V) -> Result<V::Value, Error>
-        where V: Visitor,
-    {
-        let value = try!(visitor.visit_map(DeserializerStructVisitor {
-            de: self,
-            len: fields.len(),
-        }));
-        try!(self.expect_token(Token::StructEnd));
-        Ok(value)
-    }
-
-    fn visit_variant_map<V>(&mut self, len: Option<usize>, visitor: V) -> Result<V::Value, Error>
-        where V: Visitor,
-    {
-        let value = try!(visitor.visit_map(DeserializerVariantMapVisitor {
-            de: self,
-            len: len,
-        }));
-        try!(self.expect_token(Token::EnumMapEnd));
+        try!(self.expect_token(end));
         Ok(value)
     }
 }
@@ -141,89 +79,9 @@ impl<'a, I> de::Deserializer for &'a mut Deserializer<I>
 {
     type Error = Error;
 
-    fn deserialize_seq<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_struct_field<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_map<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_unit<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_bytes<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_byte_buf<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_ignored_any<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_string<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_str<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_char<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_i64<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_i32<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_i16<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_i8<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_u64<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_u32<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_u16<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_u8<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_f32<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_f64<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
-    }
-    fn deserialize_bool<__V>(self, visitor: __V) -> Result<__V::Value, Self::Error>
-        where __V: de::Visitor {
-        self.deserialize(visitor)
+    forward_to_deserialize! {
+        bool u8 u16 u32 u64 i8 i16 i32 i64 f32 f64 char str string unit
+        seq bytes byte_buf map struct_field ignored_any
     }
 
     fn deserialize<V>(self, visitor: V) -> Result<V::Value, Error>
@@ -251,16 +109,22 @@ impl<'a, I> de::Deserializer for &'a mut Deserializer<I>
             Some(Token::Unit) => visitor.visit_unit(),
             Some(Token::UnitStruct(_name)) => visitor.visit_unit(),
             Some(Token::SeqStart(len)) => {
-                self.visit_seq(len, visitor)
+                self.visit_seq(len, Token::SeqSep, Token::SeqEnd, visitor)
             }
-            Some(Token::SeqArrayStart(len))| Some(Token::TupleStructStart(_, len)) => {
-                self.visit_seq(Some(len), visitor)
+            Some(Token::SeqArrayStart(len)) => {
+                self.visit_seq(Some(len), Token::SeqSep, Token::SeqEnd, visitor)
+            }
+            Some(Token::TupleStart(len)) => {
+                self.visit_seq(Some(len), Token::TupleSep, Token::TupleEnd, visitor)
+            }
+            Some(Token::TupleStructStart(_, len)) => {
+                self.visit_seq(Some(len), Token::TupleStructSep, Token::TupleStructEnd, visitor)
             }
             Some(Token::MapStart(len)) => {
-                self.visit_map(len, visitor)
+                self.visit_map(len, Token::MapSep, Token::MapEnd, visitor)
             }
             Some(Token::StructStart(_, len)) => {
-                self.visit_map(Some(len), visitor)
+                self.visit_map(Some(len), Token::StructSep, Token::StructEnd, visitor)
             }
             Some(token) => Err(Error::UnexpectedToken(token)),
             None => Err(Error::EndOfTokens),
@@ -360,7 +224,7 @@ impl<'a, I> de::Deserializer for &'a mut Deserializer<I>
         match self.tokens.peek() {
             Some(&Token::SeqArrayStart(_)) => {
                 self.tokens.next();
-                self.visit_array(len, visitor)
+                self.visit_seq(Some(len), Token::SeqSep, Token::SeqEnd, visitor)
             }
             Some(_) => self.deserialize(visitor),
             None => Err(Error::EndOfTokens),
@@ -379,19 +243,19 @@ impl<'a, I> de::Deserializer for &'a mut Deserializer<I>
             }
             Some(&Token::SeqStart(_)) => {
                 self.tokens.next();
-                self.visit_seq(Some(len), visitor)
+                self.visit_seq(Some(len), Token::SeqSep, Token::SeqEnd, visitor)
             }
             Some(&Token::SeqArrayStart(_)) => {
                 self.tokens.next();
-                self.visit_array(len, visitor)
+                self.visit_seq(Some(len), Token::SeqSep, Token::SeqEnd, visitor)
             }
             Some(&Token::TupleStart(_)) => {
                 self.tokens.next();
-                self.visit_tuple(len, visitor)
+                self.visit_seq(Some(len), Token::TupleSep, Token::TupleEnd, visitor)
             }
             Some(&Token::TupleStructStart(_, _)) => {
                 self.tokens.next();
-                self.visit_tuple_struct(len, visitor)
+                self.visit_seq(Some(len), Token::TupleStructSep, Token::TupleStructEnd, visitor)
             }
             Some(_) => self.deserialize(visitor),
             None => Err(Error::EndOfTokens),
@@ -419,20 +283,20 @@ impl<'a, I> de::Deserializer for &'a mut Deserializer<I>
             }
             Some(&Token::SeqStart(_)) => {
                 self.tokens.next();
-                self.visit_seq(Some(len), visitor)
+                self.visit_seq(Some(len), Token::SeqSep, Token::SeqEnd, visitor)
             }
             Some(&Token::SeqArrayStart(_)) => {
                 self.tokens.next();
-                self.visit_array(len, visitor)
+                self.visit_seq(Some(len), Token::SeqSep, Token::SeqEnd, visitor)
             }
             Some(&Token::TupleStart(_)) => {
                 self.tokens.next();
-                self.visit_tuple(len, visitor)
+                self.visit_seq(Some(len), Token::TupleSep, Token::TupleEnd, visitor)
             }
             Some(&Token::TupleStructStart(n, _)) => {
                 self.tokens.next();
                 if name == n {
-                    self.visit_tuple_struct(len, visitor)
+                    self.visit_seq(Some(len), Token::TupleStructSep, Token::TupleStructEnd, visitor)
                 } else {
                     Err(Error::InvalidName(n))
                 }
@@ -452,14 +316,14 @@ impl<'a, I> de::Deserializer for &'a mut Deserializer<I>
             Some(&Token::StructStart(n, _)) => {
                 self.tokens.next();
                 if name == n {
-                    self.visit_struct(fields, visitor)
+                    self.visit_map(Some(fields.len()), Token::StructSep, Token::StructEnd, visitor)
                 } else {
                     Err(Error::InvalidName(n))
                 }
             }
             Some(&Token::MapStart(_)) => {
                 self.tokens.next();
-                self.visit_map(Some(fields.len()), visitor)
+                self.visit_map(Some(fields.len()), Token::MapSep, Token::MapEnd, visitor)
             }
             Some(_) => self.deserialize(visitor),
             None => Err(Error::EndOfTokens),
@@ -472,6 +336,8 @@ impl<'a, I> de::Deserializer for &'a mut Deserializer<I>
 struct DeserializerSeqVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
     de: &'a mut Deserializer<I>,
     len: Option<usize>,
+    sep: Token<'static>,
+    end: Token<'static>,
 }
 
 impl<'a, I> SeqVisitor for DeserializerSeqVisitor<'a, I>
@@ -482,158 +348,15 @@ impl<'a, I> SeqVisitor for DeserializerSeqVisitor<'a, I>
     fn visit_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Error>
         where T: DeserializeSeed,
     {
-        match self.de.tokens.peek() {
-            Some(&Token::SeqSep) => {
-                self.de.tokens.next();
-                self.len = self.len.map(|len| len - 1);
-                seed.deserialize(&mut *self.de).map(Some)
-            }
-            Some(&Token::SeqEnd) => Ok(None),
-            Some(_) => {
-                let token = self.de.tokens.next().unwrap();
-                Err(Error::UnexpectedToken(token))
-            }
-            None => Err(Error::EndOfTokens),
+        if self.de.tokens.peek() == Some(&self.end) {
+            return Ok(None);
         }
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        let len = self.len.unwrap_or(0);
-        (len, self.len)
-    }
-}
-
-//////////////////////////////////////////////////////////////////////////
-
-struct DeserializerArrayVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
-    de: &'a mut Deserializer<I>,
-    len: usize,
-}
-
-impl<'a, I> SeqVisitor for DeserializerArrayVisitor<'a, I>
-    where I: Iterator<Item=Token<'static>>,
-{
-    type Error = Error;
-
-    fn visit_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Error>
-        where T: DeserializeSeed,
-    {
-        match self.de.tokens.peek() {
-            Some(&Token::SeqSep) => {
-                self.de.tokens.next();
-                self.len -= 1;
+        match self.de.tokens.next() {
+            Some(ref token) if *token == self.sep => {
+                self.len = self.len.map(|len| len.saturating_sub(1));
                 seed.deserialize(&mut *self.de).map(Some)
             }
-            Some(&Token::SeqEnd) => Ok(None),
-            Some(_) => {
-                let token = self.de.tokens.next().unwrap();
-                Err(Error::UnexpectedToken(token))
-            }
-            None => Err(Error::EndOfTokens),
-        }
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        (self.len, Some(self.len))
-    }
-}
-
-//////////////////////////////////////////////////////////////////////////
-
-struct DeserializerTupleVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
-    de: &'a mut Deserializer<I>,
-    len: usize,
-}
-
-impl<'a, I> SeqVisitor for DeserializerTupleVisitor<'a, I>
-    where I: Iterator<Item=Token<'static>>,
-{
-    type Error = Error;
-
-    fn visit_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Error>
-        where T: DeserializeSeed,
-    {
-        match self.de.tokens.peek() {
-            Some(&Token::TupleSep) => {
-                self.de.tokens.next();
-                self.len -= 1;
-                seed.deserialize(&mut *self.de).map(Some)
-            }
-            Some(&Token::TupleEnd) => Ok(None),
-            Some(_) => {
-                let token = self.de.tokens.next().unwrap();
-                Err(Error::UnexpectedToken(token))
-            }
-            None => Err(Error::EndOfTokens),
-        }
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        (self.len, Some(self.len))
-    }
-}
-
-//////////////////////////////////////////////////////////////////////////
-
-struct DeserializerTupleStructVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
-    de: &'a mut Deserializer<I>,
-    len: usize,
-}
-
-impl<'a, I> SeqVisitor for DeserializerTupleStructVisitor<'a, I>
-    where I: Iterator<Item=Token<'static>>,
-{
-    type Error = Error;
-
-    fn visit_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Error>
-        where T: DeserializeSeed,
-    {
-        match self.de.tokens.peek() {
-            Some(&Token::TupleStructSep) => {
-                self.de.tokens.next();
-                self.len -= 1;
-                seed.deserialize(&mut *self.de).map(Some)
-            }
-            Some(&Token::TupleStructEnd) => Ok(None),
-            Some(_) => {
-                let token = self.de.tokens.next().unwrap();
-                Err(Error::UnexpectedToken(token))
-            }
-            None => Err(Error::EndOfTokens),
-        }
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        (self.len, Some(self.len))
-    }
-}
-
-//////////////////////////////////////////////////////////////////////////
-
-struct DeserializerVariantSeqVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
-    de: &'a mut Deserializer<I>,
-    len: Option<usize>,
-}
-
-impl<'a, I> SeqVisitor for DeserializerVariantSeqVisitor<'a, I>
-    where I: Iterator<Item=Token<'static>>,
-{
-    type Error = Error;
-
-    fn visit_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Error>
-        where T: DeserializeSeed,
-    {
-        match self.de.tokens.peek() {
-            Some(&Token::EnumSeqSep) => {
-                self.de.tokens.next();
-                self.len = self.len.map(|len| len - 1);
-                seed.deserialize(&mut *self.de).map(Some)
-            }
-            Some(&Token::EnumSeqEnd) => Ok(None),
-            Some(_) => {
-                let token = self.de.tokens.next().unwrap();
-                Err(Error::UnexpectedToken(token))
-            }
+            Some(other) => Err(Error::UnexpectedToken(other)),
             None => Err(Error::EndOfTokens),
         }
     }
@@ -649,6 +372,8 @@ impl<'a, I> SeqVisitor for DeserializerVariantSeqVisitor<'a, I>
 struct DeserializerMapVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
     de: &'a mut Deserializer<I>,
     len: Option<usize>,
+    sep: Token<'static>,
+    end: Token<'static>,
 }
 
 impl<'a, I> MapVisitor for DeserializerMapVisitor<'a, I>
@@ -659,17 +384,15 @@ impl<'a, I> MapVisitor for DeserializerMapVisitor<'a, I>
     fn visit_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Error>
         where K: DeserializeSeed,
     {
-        match self.de.tokens.peek() {
-            Some(&Token::MapSep) => {
-                self.de.tokens.next();
-                self.len = self.len.map(|len| if len > 0 { len - 1} else { 0 });
+        if self.de.tokens.peek() == Some(&self.end) {
+            return Ok(None);
+        }
+        match self.de.tokens.next() {
+            Some(ref token) if *token == self.sep => {
+                self.len = self.len.map(|len| len.saturating_sub(1));
                 seed.deserialize(&mut *self.de).map(Some)
             }
-            Some(&Token::MapEnd) => Ok(None),
-            Some(_) => {
-                let token = self.de.tokens.next().unwrap();
-                Err(Error::UnexpectedToken(token))
-            }
+            Some(other) => Err(Error::UnexpectedToken(other)),
             None => Err(Error::EndOfTokens),
         }
     }
@@ -688,47 +411,6 @@ impl<'a, I> MapVisitor for DeserializerMapVisitor<'a, I>
 
 //////////////////////////////////////////////////////////////////////////
 
-struct DeserializerStructVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
-    de: &'a mut Deserializer<I>,
-    len: usize,
-}
-
-impl<'a, I> MapVisitor for DeserializerStructVisitor<'a, I>
-    where I: Iterator<Item=Token<'static>>,
-{
-    type Error = Error;
-
-    fn visit_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Error>
-        where K: DeserializeSeed,
-    {
-        match self.de.tokens.peek() {
-            Some(&Token::StructSep) => {
-                self.de.tokens.next();
-                self.len = self.len.saturating_sub(1);
-                seed.deserialize(&mut *self.de).map(Some)
-            }
-            Some(&Token::StructEnd) => Ok(None),
-            Some(_) => {
-                let token = self.de.tokens.next().unwrap();
-                Err(Error::UnexpectedToken(token))
-            }
-            None => Err(Error::EndOfTokens),
-        }
-    }
-
-    fn visit_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Error>
-        where V: DeserializeSeed,
-    {
-        seed.deserialize(&mut *self.de)
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        (self.len, Some(self.len))
-    }
-}
-
-//////////////////////////////////////////////////////////////////////////
-
 struct DeserializerEnumVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
     de: &'a mut Deserializer<I>,
 }
@@ -803,7 +485,7 @@ impl<'a, I> VariantVisitor for DeserializerEnumVisitor<'a, I>
                 let token = self.de.tokens.next().unwrap();
 
                 if len == enum_len {
-                    self.de.visit_variant_seq(Some(len), visitor)
+                    self.de.visit_seq(Some(len), Token::EnumSeqSep, Token::EnumSeqEnd, visitor)
                 } else {
                     Err(Error::UnexpectedToken(token))
                 }
@@ -812,7 +494,7 @@ impl<'a, I> VariantVisitor for DeserializerEnumVisitor<'a, I>
                 let token = self.de.tokens.next().unwrap();
 
                 if len == enum_len {
-                    self.de.visit_seq(Some(len), visitor)
+                    self.de.visit_seq(Some(len), Token::SeqSep, Token::SeqEnd, visitor)
                 } else {
                     Err(Error::UnexpectedToken(token))
                 }
@@ -834,7 +516,7 @@ impl<'a, I> VariantVisitor for DeserializerEnumVisitor<'a, I>
                 let token = self.de.tokens.next().unwrap();
 
                 if fields.len() == enum_len {
-                    self.de.visit_variant_map(Some(fields.len()), visitor)
+                    self.de.visit_map(Some(fields.len()), Token::EnumMapSep, Token::EnumMapEnd, visitor)
                 } else {
                     Err(Error::UnexpectedToken(token))
                 }
@@ -843,7 +525,7 @@ impl<'a, I> VariantVisitor for DeserializerEnumVisitor<'a, I>
                 let token = self.de.tokens.next().unwrap();
 
                 if fields.len() == enum_len {
-                    self.de.visit_map(Some(fields.len()), visitor)
+                    self.de.visit_map(Some(fields.len()), Token::MapSep, Token::MapEnd, visitor)
                 } else {
                     Err(Error::UnexpectedToken(token))
                 }
@@ -855,45 +537,3 @@ impl<'a, I> VariantVisitor for DeserializerEnumVisitor<'a, I>
         }
     }
 }
-
-//////////////////////////////////////////////////////////////////////////
-
-struct DeserializerVariantMapVisitor<'a, I: 'a> where I: Iterator<Item=Token<'static>> {
-    de: &'a mut Deserializer<I>,
-    len: Option<usize>,
-}
-
-impl<'a, I> MapVisitor for DeserializerVariantMapVisitor<'a, I>
-    where I: Iterator<Item=Token<'static>>,
-{
-    type Error = Error;
-
-    fn visit_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Error>
-        where K: DeserializeSeed,
-    {
-        match self.de.tokens.peek() {
-            Some(&Token::EnumMapSep) => {
-                self.de.tokens.next();
-                self.len = self.len.map(|len| if len > 0 { len - 1} else { 0 });
-                seed.deserialize(&mut *self.de).map(Some)
-            }
-            Some(&Token::EnumMapEnd) => Ok(None),
-            Some(_) => {
-                let token = self.de.tokens.next().unwrap();
-                Err(Error::UnexpectedToken(token))
-            }
-            None => Err(Error::EndOfTokens),
-        }
-    }
-
-    fn visit_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Error>
-        where V: DeserializeSeed,
-    {
-        seed.deserialize(&mut *self.de)
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        let len = self.len.unwrap_or(0);
-        (len, self.len)
-    }
-}
diff --git a/serde_test/src/lib.rs b/serde_test/src/lib.rs
index 945262c0..53f966f6 100644
--- a/serde_test/src/lib.rs
+++ b/serde_test/src/lib.rs
@@ -1,3 +1,4 @@
+#[macro_use]
 extern crate serde;
 
 mod assert;
diff --git a/test_suite/tests/compile-fail/enum-representation/internal-tuple-variant.rs b/test_suite/tests/compile-fail/enum-representation/internal-tuple-variant.rs
new file mode 100644
index 00000000..950e8d02
--- /dev/null
+++ b/test_suite/tests/compile-fail/enum-representation/internal-tuple-variant.rs
@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)] //~ ERROR: custom derive attribute panicked
+#[serde(tag = "type")] //~^ HELP: #[serde(tag = "...")] cannot be used with tuple variants
+enum E {
+    Tuple(u8, u8),
+}
+
+fn main() {}
diff --git a/test_suite/tests/compile-fail/enum-representation/internally-tagged-struct.rs b/test_suite/tests/compile-fail/enum-representation/internally-tagged-struct.rs
new file mode 100644
index 00000000..358dfde4
--- /dev/null
+++ b/test_suite/tests/compile-fail/enum-representation/internally-tagged-struct.rs
@@ -0,0 +1,8 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)] //~ ERROR: custom derive attribute panicked
+#[serde(tag = "type")] //~^ HELP: #[serde(tag = "...")] can only be used on enums
+struct S;
+
+fn main() {}
diff --git a/test_suite/tests/compile-fail/enum-representation/untagged-and-internal.rs b/test_suite/tests/compile-fail/enum-representation/untagged-and-internal.rs
new file mode 100644
index 00000000..7442679c
--- /dev/null
+++ b/test_suite/tests/compile-fail/enum-representation/untagged-and-internal.rs
@@ -0,0 +1,12 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)] //~ ERROR: custom derive attribute panicked
+#[serde(untagged)]
+#[serde(tag = "type")] //~^^ HELP: enum cannot be both untagged and internally tagged
+enum E {
+    A(u8),
+    B(String),
+}
+
+fn main() {}
diff --git a/test_suite/tests/compile-fail/enum-representation/untagged-struct.rs b/test_suite/tests/compile-fail/enum-representation/untagged-struct.rs
new file mode 100644
index 00000000..611f8416
--- /dev/null
+++ b/test_suite/tests/compile-fail/enum-representation/untagged-struct.rs
@@ -0,0 +1,8 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)] //~ ERROR: custom derive attribute panicked
+#[serde(untagged)] //~^ HELP: #[serde(untagged)] can only be used on enums
+struct S;
+
+fn main() {}
diff --git a/test_suite/tests/test_de.rs b/test_suite/tests/test_de.rs
index b748bb12..6ae92129 100644
--- a/test_suite/tests/test_de.rs
+++ b/test_suite/tests/test_de.rs
@@ -225,7 +225,7 @@ declare_tests! {
         ],
         () => &[
             Token::TupleStructStart("Anything", 0),
-            Token::SeqEnd,
+            Token::TupleStructEnd,
         ],
     }
     test_unit_struct {
@@ -330,7 +330,7 @@ declare_tests! {
         ],
         BTreeSet::<isize>::new() => &[
             Token::TupleStructStart("Anything", 0),
-            Token::SeqEnd,
+            Token::TupleStructEnd,
         ],
     }
     test_hashset {
@@ -358,7 +358,7 @@ declare_tests! {
         ],
         HashSet::<isize>::new() => &[
             Token::TupleStructStart("Anything", 0),
-            Token::SeqEnd,
+            Token::TupleStructEnd,
         ],
         hashset![FnvHasher @ 1, 2, 3] => &[
             Token::SeqStart(Some(3)),
@@ -408,7 +408,7 @@ declare_tests! {
         ],
         Vec::<isize>::new() => &[
             Token::TupleStructStart("Anything", 0),
-            Token::SeqEnd,
+            Token::TupleStructEnd,
         ],
     }
     test_array {
@@ -472,7 +472,7 @@ declare_tests! {
         ],
         [0; 0] => &[
             Token::TupleStructStart("Anything", 0),
-            Token::SeqEnd,
+            Token::TupleStructEnd,
         ],
     }
     test_tuple {
@@ -564,7 +564,7 @@ declare_tests! {
         ],
         BTreeMap::<isize, isize>::new() => &[
             Token::StructStart("Anything", 0),
-            Token::MapEnd,
+            Token::StructEnd,
         ],
     }
     test_hashmap {
@@ -618,7 +618,7 @@ declare_tests! {
         ],
         HashMap::<isize, isize>::new() => &[
             Token::StructStart("Anything", 0),
-            Token::MapEnd,
+            Token::StructEnd,
         ],
         hashmap![FnvHasher @ 1 => 2, 3 => 4] => &[
             Token::MapStart(Some(2)),
diff --git a/test_suite/tests/test_macros.rs b/test_suite/tests/test_macros.rs
index 6e5e1d82..21185412 100644
--- a/test_suite/tests/test_macros.rs
+++ b/test_suite/tests/test_macros.rs
@@ -1,11 +1,14 @@
 extern crate serde_test;
 use self::serde_test::{
+    Error,
     Token,
     assert_tokens,
     assert_ser_tokens,
     assert_de_tokens,
+    assert_de_tokens_error,
 };
 
+use std::collections::BTreeMap;
 use std::marker::PhantomData;
 
 // That tests that the derived Serialize implementation doesn't trigger
@@ -625,3 +628,256 @@ fn test_enum_state_field() {
         ]
     );
 }
+
+#[test]
+fn test_untagged_enum() {
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    #[serde(untagged)]
+    enum Untagged {
+        A {
+            a: u8,
+        },
+        B {
+            b: u8,
+        },
+        C,
+        D(u8),
+        E(String),
+        F(u8, u8),
+    }
+
+    assert_tokens(
+        &Untagged::A { a: 1 },
+        &[
+            Token::StructStart("Untagged", 1),
+
+            Token::StructSep,
+            Token::Str("a"),
+            Token::U8(1),
+
+            Token::StructEnd,
+        ]
+    );
+
+    assert_tokens(
+        &Untagged::B { b: 2 },
+        &[
+            Token::StructStart("Untagged", 1),
+
+            Token::StructSep,
+            Token::Str("b"),
+            Token::U8(2),
+
+            Token::StructEnd,
+        ]
+    );
+
+    assert_tokens(
+        &Untagged::C,
+        &[
+            Token::Unit,
+        ]
+    );
+
+    assert_tokens(
+        &Untagged::D(4),
+        &[
+            Token::U8(4),
+        ]
+    );
+    assert_tokens(
+        &Untagged::E("e".to_owned()),
+        &[
+            Token::Str("e"),
+        ]
+    );
+
+    assert_tokens(
+        &Untagged::F(1, 2),
+        &[
+            Token::TupleStart(2),
+
+            Token::TupleSep,
+            Token::U8(1),
+
+            Token::TupleSep,
+            Token::U8(2),
+
+            Token::TupleEnd,
+        ]
+    );
+
+    assert_de_tokens_error::<Untagged>(
+        &[
+            Token::Option(false),
+        ],
+        Error::Message("data did not match any variant of untagged enum Untagged".to_owned()),
+    );
+
+    assert_de_tokens_error::<Untagged>(
+        &[
+            Token::TupleStart(1),
+
+            Token::TupleSep,
+            Token::U8(1),
+
+            Token::TupleEnd,
+        ],
+        Error::Message("data did not match any variant of untagged enum Untagged".to_owned()),
+    );
+
+    assert_de_tokens_error::<Untagged>(
+        &[
+            Token::TupleStart(3),
+
+            Token::TupleSep,
+            Token::U8(1),
+
+            Token::TupleSep,
+            Token::U8(2),
+
+            Token::TupleSep,
+            Token::U8(3),
+
+            Token::TupleEnd,
+        ],
+        Error::Message("data did not match any variant of untagged enum Untagged".to_owned()),
+    );
+}
+
+#[test]
+fn test_internally_tagged_enum() {
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    struct Newtype(BTreeMap<String, String>);
+
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    struct Struct {
+        f: u8,
+    }
+
+    #[derive(Debug, PartialEq, Serialize, Deserialize)]
+    #[serde(tag = "type")]
+    enum InternallyTagged {
+        A {
+            a: u8,
+        },
+        B {
+            b: u8,
+        },
+        C,
+        D(BTreeMap<String, String>),
+        E(Newtype),
+        F(Struct),
+    }
+
+    assert_tokens(
+        &InternallyTagged::A { a: 1 },
+        &[
+            Token::StructStart("InternallyTagged", 2),
+
+            Token::StructSep,
+            Token::Str("type"),
+            Token::Str("A"),
+
+            Token::StructSep,
+            Token::Str("a"),
+            Token::U8(1),
+
+            Token::StructEnd,
+        ]
+    );
+
+    assert_tokens(
+        &InternallyTagged::B { b: 2 },
+        &[
+            Token::StructStart("InternallyTagged", 2),
+
+            Token::StructSep,
+            Token::Str("type"),
+            Token::Str("B"),
+
+            Token::StructSep,
+            Token::Str("b"),
+            Token::U8(2),
+
+            Token::StructEnd,
+        ]
+    );
+
+    assert_tokens(
+        &InternallyTagged::C,
+        &[
+            Token::StructStart("InternallyTagged", 1),
+
+            Token::StructSep,
+            Token::Str("type"),
+            Token::Str("C"),
+
+            Token::StructEnd,
+        ]
+    );
+
+    assert_tokens(
+        &InternallyTagged::D(BTreeMap::new()),
+        &[
+            Token::MapStart(Some(1)),
+
+            Token::MapSep,
+            Token::Str("type"),
+            Token::Str("D"),
+
+            Token::MapEnd,
+        ]
+    );
+
+    assert_tokens(
+        &InternallyTagged::E(Newtype(BTreeMap::new())),
+        &[
+            Token::MapStart(Some(1)),
+
+            Token::MapSep,
+            Token::Str("type"),
+            Token::Str("E"),
+
+            Token::MapEnd,
+        ]
+    );
+
+    assert_tokens(
+        &InternallyTagged::F(Struct { f: 6 }),
+        &[
+            Token::StructStart("Struct", 2),
+
+            Token::StructSep,
+            Token::Str("type"),
+            Token::Str("F"),
+
+            Token::StructSep,
+            Token::Str("f"),
+            Token::U8(6),
+
+            Token::StructEnd,
+        ]
+    );
+
+    assert_de_tokens_error::<InternallyTagged>(
+        &[
+            Token::MapStart(Some(0)),
+            Token::MapEnd,
+        ],
+        Error::Message("missing field `type`".to_owned()),
+    );
+
+    assert_de_tokens_error::<InternallyTagged>(
+        &[
+            Token::MapStart(Some(1)),
+
+            Token::MapSep,
+            Token::Str("type"),
+            Token::Str("Z"),
+
+            Token::MapEnd,
+        ],
+        Error::Message("unknown variant `Z`, expected one of `A`, `B`, `C`, `D`, `E`, `F`".to_owned()),
+    );
+}