Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 1720 insertions, 0 deletions

diff --git a/third_party/rust/serde/src/de/value.rs b/third_party/rust/serde/src/de/value.rs
new file mode 100644
index 0000000000..b229ebab77
--- /dev/null
+++ b/third_party/rust/serde/src/de/value.rs
@@ -0,0 +1,1720 @@
+//! Building blocks for deserializing basic values using the `IntoDeserializer`
+//! trait.
+//!
+//! ```edition2021
+//! use serde::de::{value, Deserialize, IntoDeserializer};
+//! use serde_derive::Deserialize;
+//! use std::str::FromStr;
+//!
+//! #[derive(Deserialize)]
+//! enum Setting {
+//!     On,
+//!     Off,
+//! }
+//!
+//! impl FromStr for Setting {
+//!     type Err = value::Error;
+//!
+//!     fn from_str(s: &str) -> Result<Self, Self::Err> {
+//!         Self::deserialize(s.into_deserializer())
+//!     }
+//! }
+//! ```
+
+use crate::lib::*;
+
+use self::private::{First, Second};
+use crate::de::{self, size_hint, Deserializer, Expected, IntoDeserializer, SeqAccess, Visitor};
+use crate::ser;
+
+////////////////////////////////////////////////////////////////////////////////
+
+// For structs that contain a PhantomData. We do not want the trait
+// bound `E: Clone` inferred by derive(Clone).
+macro_rules! impl_copy_clone {
+    ($ty:ident $(<$lifetime:tt>)*) => {
+        impl<$($lifetime,)* E> Copy for $ty<$($lifetime,)* E> {}
+
+        impl<$($lifetime,)* E> Clone for $ty<$($lifetime,)* E> {
+            fn clone(&self) -> Self {
+                *self
+            }
+        }
+    };
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A minimal representation of all possible errors that can occur using the
+/// `IntoDeserializer` trait.
+#[derive(Clone, PartialEq)]
+pub struct Error {
+    err: ErrorImpl,
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+type ErrorImpl = Box<str>;
+#[cfg(not(any(feature = "std", feature = "alloc")))]
+type ErrorImpl = ();
+
+impl de::Error for Error {
+    #[cfg(any(feature = "std", feature = "alloc"))]
+    #[cold]
+    fn custom<T>(msg: T) -> Self
+    where
+        T: Display,
+    {
+        Error {
+            err: msg.to_string().into_boxed_str(),
+        }
+    }
+
+    #[cfg(not(any(feature = "std", feature = "alloc")))]
+    #[cold]
+    fn custom<T>(msg: T) -> Self
+    where
+        T: Display,
+    {
+        let _ = msg;
+        Error { err: () }
+    }
+}
+
+impl ser::Error for Error {
+    #[cold]
+    fn custom<T>(msg: T) -> Self
+    where
+        T: Display,
+    {
+        de::Error::custom(msg)
+    }
+}
+
+impl Display for Error {
+    #[cfg(any(feature = "std", feature = "alloc"))]
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str(&self.err)
+    }
+
+    #[cfg(not(any(feature = "std", feature = "alloc")))]
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Serde deserialization error")
+    }
+}
+
+impl Debug for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut debug = formatter.debug_tuple("Error");
+        #[cfg(any(feature = "std", feature = "alloc"))]
+        debug.field(&self.err);
+        debug.finish()
+    }
+}
+
+#[cfg(feature = "std")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
+impl error::Error for Error {
+    fn description(&self) -> &str {
+        &self.err
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+impl<'de, E> IntoDeserializer<'de, E> for ()
+where
+    E: de::Error,
+{
+    type Deserializer = UnitDeserializer<E>;
+
+    fn into_deserializer(self) -> UnitDeserializer<E> {
+        UnitDeserializer::new()
+    }
+}
+
+/// A deserializer holding a `()`.
+pub struct UnitDeserializer<E> {
+    marker: PhantomData<E>,
+}
+
+impl_copy_clone!(UnitDeserializer);
+
+impl<E> UnitDeserializer<E> {
+    #[allow(missing_docs)]
+    pub fn new() -> Self {
+        UnitDeserializer {
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<'de, E> de::Deserializer<'de> for UnitDeserializer<E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf unit unit_struct newtype_struct seq tuple tuple_struct
+        map struct enum identifier ignored_any
+    }
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_unit()
+    }
+
+    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_none()
+    }
+}
+
+impl<E> Debug for UnitDeserializer<E> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.debug_struct("UnitDeserializer").finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer that cannot be instantiated.
+#[cfg(feature = "unstable")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "unstable")))]
+pub struct NeverDeserializer<E> {
+    never: !,
+    marker: PhantomData<E>,
+}
+
+#[cfg(feature = "unstable")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "unstable")))]
+impl<'de, E> IntoDeserializer<'de, E> for !
+where
+    E: de::Error,
+{
+    type Deserializer = NeverDeserializer<E>;
+
+    fn into_deserializer(self) -> Self::Deserializer {
+        self
+    }
+}
+
+#[cfg(feature = "unstable")]
+impl<'de, E> de::Deserializer<'de> for NeverDeserializer<E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        self.never
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+macro_rules! primitive_deserializer {
+    ($ty:ty, $doc:tt, $name:ident, $method:ident $($cast:tt)*) => {
+        #[doc = "A deserializer holding"]
+        #[doc = $doc]
+        pub struct $name<E> {
+            value: $ty,
+            marker: PhantomData<E>
+        }
+
+        impl_copy_clone!($name);
+
+        impl<'de, E> IntoDeserializer<'de, E> for $ty
+        where
+            E: de::Error,
+        {
+            type Deserializer = $name<E>;
+
+            fn into_deserializer(self) -> $name<E> {
+                $name::new(self)
+            }
+        }
+
+        impl<E> $name<E> {
+            #[allow(missing_docs)]
+            pub fn new(value: $ty) -> Self {
+                $name {
+                    value,
+                    marker: PhantomData,
+                }
+            }
+        }
+
+        impl<'de, E> de::Deserializer<'de> for $name<E>
+        where
+            E: de::Error,
+        {
+            type Error = E;
+
+            forward_to_deserialize_any! {
+                bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str
+                string bytes byte_buf option unit unit_struct newtype_struct seq
+                tuple tuple_struct map struct enum identifier ignored_any
+            }
+
+            fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+            where
+                V: de::Visitor<'de>,
+            {
+                visitor.$method(self.value $($cast)*)
+            }
+        }
+
+        impl<E> Debug for $name<E> {
+            fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter
+                    .debug_struct(stringify!($name))
+                    .field("value", &self.value)
+                    .finish()
+            }
+        }
+    }
+}
+
+primitive_deserializer!(bool, "a `bool`.", BoolDeserializer, visit_bool);
+primitive_deserializer!(i8, "an `i8`.", I8Deserializer, visit_i8);
+primitive_deserializer!(i16, "an `i16`.", I16Deserializer, visit_i16);
+primitive_deserializer!(i32, "an `i32`.", I32Deserializer, visit_i32);
+primitive_deserializer!(i64, "an `i64`.", I64Deserializer, visit_i64);
+primitive_deserializer!(i128, "an `i128`.", I128Deserializer, visit_i128);
+primitive_deserializer!(isize, "an `isize`.", IsizeDeserializer, visit_i64 as i64);
+primitive_deserializer!(u8, "a `u8`.", U8Deserializer, visit_u8);
+primitive_deserializer!(u16, "a `u16`.", U16Deserializer, visit_u16);
+primitive_deserializer!(u64, "a `u64`.", U64Deserializer, visit_u64);
+primitive_deserializer!(u128, "a `u128`.", U128Deserializer, visit_u128);
+primitive_deserializer!(usize, "a `usize`.", UsizeDeserializer, visit_u64 as u64);
+primitive_deserializer!(f32, "an `f32`.", F32Deserializer, visit_f32);
+primitive_deserializer!(f64, "an `f64`.", F64Deserializer, visit_f64);
+primitive_deserializer!(char, "a `char`.", CharDeserializer, visit_char);
+
+/// A deserializer holding a `u32`.
+pub struct U32Deserializer<E> {
+    value: u32,
+    marker: PhantomData<E>,
+}
+
+impl_copy_clone!(U32Deserializer);
+
+impl<'de, E> IntoDeserializer<'de, E> for u32
+where
+    E: de::Error,
+{
+    type Deserializer = U32Deserializer<E>;
+
+    fn into_deserializer(self) -> U32Deserializer<E> {
+        U32Deserializer::new(self)
+    }
+}
+
+impl<E> U32Deserializer<E> {
+    #[allow(missing_docs)]
+    pub fn new(value: u32) -> Self {
+        U32Deserializer {
+            value,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<'de, E> de::Deserializer<'de> for U32Deserializer<E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
+    }
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_u32(self.value)
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        name: &str,
+        variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let _ = name;
+        let _ = variants;
+        visitor.visit_enum(self)
+    }
+}
+
+impl<'de, E> de::EnumAccess<'de> for U32Deserializer<E>
+where
+    E: de::Error,
+{
+    type Error = E;
+    type Variant = private::UnitOnly<E>;
+
+    fn variant_seed<T>(self, seed: T) -> Result<(T::Value, Self::Variant), Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        seed.deserialize(self).map(private::unit_only)
+    }
+}
+
+impl<E> Debug for U32Deserializer<E> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("U32Deserializer")
+            .field("value", &self.value)
+            .finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer holding a `&str`.
+pub struct StrDeserializer<'a, E> {
+    value: &'a str,
+    marker: PhantomData<E>,
+}
+
+impl_copy_clone!(StrDeserializer<'de>);
+
+impl<'de, 'a, E> IntoDeserializer<'de, E> for &'a str
+where
+    E: de::Error,
+{
+    type Deserializer = StrDeserializer<'a, E>;
+
+    fn into_deserializer(self) -> StrDeserializer<'a, E> {
+        StrDeserializer::new(self)
+    }
+}
+
+impl<'a, E> StrDeserializer<'a, E> {
+    #[allow(missing_docs)]
+    pub fn new(value: &'a str) -> Self {
+        StrDeserializer {
+            value,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<'de, 'a, E> de::Deserializer<'de> for StrDeserializer<'a, E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_str(self.value)
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        name: &str,
+        variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let _ = name;
+        let _ = variants;
+        visitor.visit_enum(self)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
+    }
+}
+
+impl<'de, 'a, E> de::EnumAccess<'de> for StrDeserializer<'a, E>
+where
+    E: de::Error,
+{
+    type Error = E;
+    type Variant = private::UnitOnly<E>;
+
+    fn variant_seed<T>(self, seed: T) -> Result<(T::Value, Self::Variant), Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        seed.deserialize(self).map(private::unit_only)
+    }
+}
+
+impl<'a, E> Debug for StrDeserializer<'a, E> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("StrDeserializer")
+            .field("value", &self.value)
+            .finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer holding a `&str` with a lifetime tied to another
+/// deserializer.
+pub struct BorrowedStrDeserializer<'de, E> {
+    value: &'de str,
+    marker: PhantomData<E>,
+}
+
+impl_copy_clone!(BorrowedStrDeserializer<'de>);
+
+impl<'de, E> BorrowedStrDeserializer<'de, E> {
+    /// Create a new borrowed deserializer from the given string.
+    pub fn new(value: &'de str) -> BorrowedStrDeserializer<'de, E> {
+        BorrowedStrDeserializer {
+            value,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<'de, E> de::Deserializer<'de> for BorrowedStrDeserializer<'de, E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_borrowed_str(self.value)
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        name: &str,
+        variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let _ = name;
+        let _ = variants;
+        visitor.visit_enum(self)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
+    }
+}
+
+impl<'de, E> de::EnumAccess<'de> for BorrowedStrDeserializer<'de, E>
+where
+    E: de::Error,
+{
+    type Error = E;
+    type Variant = private::UnitOnly<E>;
+
+    fn variant_seed<T>(self, seed: T) -> Result<(T::Value, Self::Variant), Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        seed.deserialize(self).map(private::unit_only)
+    }
+}
+
+impl<'de, E> Debug for BorrowedStrDeserializer<'de, E> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("BorrowedStrDeserializer")
+            .field("value", &self.value)
+            .finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer holding a `String`.
+#[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(doc_cfg, doc(cfg(any(feature = "std", feature = "alloc"))))]
+pub struct StringDeserializer<E> {
+    value: String,
+    marker: PhantomData<E>,
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<E> Clone for StringDeserializer<E> {
+    fn clone(&self) -> Self {
+        StringDeserializer {
+            value: self.value.clone(),
+            marker: PhantomData,
+        }
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(doc_cfg, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl<'de, E> IntoDeserializer<'de, E> for String
+where
+    E: de::Error,
+{
+    type Deserializer = StringDeserializer<E>;
+
+    fn into_deserializer(self) -> StringDeserializer<E> {
+        StringDeserializer::new(self)
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<E> StringDeserializer<E> {
+    #[allow(missing_docs)]
+    pub fn new(value: String) -> Self {
+        StringDeserializer {
+            value,
+            marker: PhantomData,
+        }
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<'de, E> de::Deserializer<'de> for StringDeserializer<E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_string(self.value)
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        name: &str,
+        variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let _ = name;
+        let _ = variants;
+        visitor.visit_enum(self)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<'de, E> de::EnumAccess<'de> for StringDeserializer<E>
+where
+    E: de::Error,
+{
+    type Error = E;
+    type Variant = private::UnitOnly<E>;
+
+    fn variant_seed<T>(self, seed: T) -> Result<(T::Value, Self::Variant), Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        seed.deserialize(self).map(private::unit_only)
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<E> Debug for StringDeserializer<E> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("StringDeserializer")
+            .field("value", &self.value)
+            .finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer holding a `Cow<str>`.
+#[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(doc_cfg, doc(cfg(any(feature = "std", feature = "alloc"))))]
+pub struct CowStrDeserializer<'a, E> {
+    value: Cow<'a, str>,
+    marker: PhantomData<E>,
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<'a, E> Clone for CowStrDeserializer<'a, E> {
+    fn clone(&self) -> Self {
+        CowStrDeserializer {
+            value: self.value.clone(),
+            marker: PhantomData,
+        }
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(doc_cfg, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl<'de, 'a, E> IntoDeserializer<'de, E> for Cow<'a, str>
+where
+    E: de::Error,
+{
+    type Deserializer = CowStrDeserializer<'a, E>;
+
+    fn into_deserializer(self) -> CowStrDeserializer<'a, E> {
+        CowStrDeserializer::new(self)
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<'a, E> CowStrDeserializer<'a, E> {
+    #[allow(missing_docs)]
+    pub fn new(value: Cow<'a, str>) -> Self {
+        CowStrDeserializer {
+            value,
+            marker: PhantomData,
+        }
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<'de, 'a, E> de::Deserializer<'de> for CowStrDeserializer<'a, E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.value {
+            Cow::Borrowed(string) => visitor.visit_str(string),
+            Cow::Owned(string) => visitor.visit_string(string),
+        }
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        name: &str,
+        variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let _ = name;
+        let _ = variants;
+        visitor.visit_enum(self)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<'de, 'a, E> de::EnumAccess<'de> for CowStrDeserializer<'a, E>
+where
+    E: de::Error,
+{
+    type Error = E;
+    type Variant = private::UnitOnly<E>;
+
+    fn variant_seed<T>(self, seed: T) -> Result<(T::Value, Self::Variant), Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        seed.deserialize(self).map(private::unit_only)
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+impl<'a, E> Debug for CowStrDeserializer<'a, E> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("CowStrDeserializer")
+            .field("value", &self.value)
+            .finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer holding a `&[u8]`. Always calls [`Visitor::visit_bytes`].
+pub struct BytesDeserializer<'a, E> {
+    value: &'a [u8],
+    marker: PhantomData<E>,
+}
+
+impl<'a, E> BytesDeserializer<'a, E> {
+    /// Create a new deserializer from the given bytes.
+    pub fn new(value: &'a [u8]) -> Self {
+        BytesDeserializer {
+            value,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl_copy_clone!(BytesDeserializer<'a>);
+
+impl<'de, 'a, E> IntoDeserializer<'de, E> for &'a [u8]
+where
+    E: de::Error,
+{
+    type Deserializer = BytesDeserializer<'a, E>;
+
+    fn into_deserializer(self) -> BytesDeserializer<'a, E> {
+        BytesDeserializer::new(self)
+    }
+}
+
+impl<'de, 'a, E> Deserializer<'de> for BytesDeserializer<'a, E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_bytes(self.value)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+}
+
+impl<'a, E> Debug for BytesDeserializer<'a, E> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("BytesDeserializer")
+            .field("value", &self.value)
+            .finish()
+    }
+}
+
+/// A deserializer holding a `&[u8]` with a lifetime tied to another
+/// deserializer. Always calls [`Visitor::visit_borrowed_bytes`].
+pub struct BorrowedBytesDeserializer<'de, E> {
+    value: &'de [u8],
+    marker: PhantomData<E>,
+}
+
+impl<'de, E> BorrowedBytesDeserializer<'de, E> {
+    /// Create a new borrowed deserializer from the given borrowed bytes.
+    pub fn new(value: &'de [u8]) -> Self {
+        BorrowedBytesDeserializer {
+            value,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl_copy_clone!(BorrowedBytesDeserializer<'de>);
+
+impl<'de, E> Deserializer<'de> for BorrowedBytesDeserializer<'de, E>
+where
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_borrowed_bytes(self.value)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+}
+
+impl<'de, E> Debug for BorrowedBytesDeserializer<'de, E> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("BorrowedBytesDeserializer")
+            .field("value", &self.value)
+            .finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer that iterates over a sequence.
+#[derive(Clone)]
+pub struct SeqDeserializer<I, E> {
+    iter: iter::Fuse<I>,
+    count: usize,
+    marker: PhantomData<E>,
+}
+
+impl<I, E> SeqDeserializer<I, E>
+where
+    I: Iterator,
+{
+    /// Construct a new `SeqDeserializer<I, E>`.
+    pub fn new(iter: I) -> Self {
+        SeqDeserializer {
+            iter: iter.fuse(),
+            count: 0,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<I, E> SeqDeserializer<I, E>
+where
+    I: Iterator,
+    E: de::Error,
+{
+    /// Check for remaining elements after passing a `SeqDeserializer` to
+    /// `Visitor::visit_seq`.
+    pub fn end(self) -> Result<(), E> {
+        let remaining = self.iter.count();
+        if remaining == 0 {
+            Ok(())
+        } else {
+            // First argument is the number of elements in the data, second
+            // argument is the number of elements expected by the Deserialize.
+            Err(de::Error::invalid_length(
+                self.count + remaining,
+                &ExpectedInSeq(self.count),
+            ))
+        }
+    }
+}
+
+impl<'de, I, T, E> de::Deserializer<'de> for SeqDeserializer<I, E>
+where
+    I: Iterator<Item = T>,
+    T: IntoDeserializer<'de, E>,
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(mut self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let v = tri!(visitor.visit_seq(&mut self));
+        tri!(self.end());
+        Ok(v)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+}
+
+impl<'de, I, T, E> de::SeqAccess<'de> for SeqDeserializer<I, E>
+where
+    I: Iterator<Item = T>,
+    T: IntoDeserializer<'de, E>,
+    E: de::Error,
+{
+    type Error = E;
+
+    fn next_element_seed<V>(&mut self, seed: V) -> Result<Option<V::Value>, Self::Error>
+    where
+        V: de::DeserializeSeed<'de>,
+    {
+        match self.iter.next() {
+            Some(value) => {
+                self.count += 1;
+                seed.deserialize(value.into_deserializer()).map(Some)
+            }
+            None => Ok(None),
+        }
+    }
+
+    fn size_hint(&self) -> Option<usize> {
+        size_hint::from_bounds(&self.iter)
+    }
+}
+
+struct ExpectedInSeq(usize);
+
+impl Expected for ExpectedInSeq {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        if self.0 == 1 {
+            write!(formatter, "1 element in sequence")
+        } else {
+            write!(formatter, "{} elements in sequence", self.0)
+        }
+    }
+}
+
+impl<I, E> Debug for SeqDeserializer<I, E>
+where
+    I: Debug,
+{
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("SeqDeserializer")
+            .field("iter", &self.iter)
+            .field("count", &self.count)
+            .finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(doc_cfg, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl<'de, T, E> IntoDeserializer<'de, E> for Vec<T>
+where
+    T: IntoDeserializer<'de, E>,
+    E: de::Error,
+{
+    type Deserializer = SeqDeserializer<<Self as IntoIterator>::IntoIter, E>;
+
+    fn into_deserializer(self) -> Self::Deserializer {
+        SeqDeserializer::new(self.into_iter())
+    }
+}
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(doc_cfg, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl<'de, T, E> IntoDeserializer<'de, E> for BTreeSet<T>
+where
+    T: IntoDeserializer<'de, E> + Eq + Ord,
+    E: de::Error,
+{
+    type Deserializer = SeqDeserializer<<Self as IntoIterator>::IntoIter, E>;
+
+    fn into_deserializer(self) -> Self::Deserializer {
+        SeqDeserializer::new(self.into_iter())
+    }
+}
+
+#[cfg(feature = "std")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
+impl<'de, T, S, E> IntoDeserializer<'de, E> for HashSet<T, S>
+where
+    T: IntoDeserializer<'de, E> + Eq + Hash,
+    S: BuildHasher,
+    E: de::Error,
+{
+    type Deserializer = SeqDeserializer<<Self as IntoIterator>::IntoIter, E>;
+
+    fn into_deserializer(self) -> Self::Deserializer {
+        SeqDeserializer::new(self.into_iter())
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer holding a `SeqAccess`.
+#[derive(Clone, Debug)]
+pub struct SeqAccessDeserializer<A> {
+    seq: A,
+}
+
+impl<A> SeqAccessDeserializer<A> {
+    /// Construct a new `SeqAccessDeserializer<A>`.
+    pub fn new(seq: A) -> Self {
+        SeqAccessDeserializer { seq }
+    }
+}
+
+impl<'de, A> de::Deserializer<'de> for SeqAccessDeserializer<A>
+where
+    A: de::SeqAccess<'de>,
+{
+    type Error = A::Error;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_seq(self.seq)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer that iterates over a map.
+pub struct MapDeserializer<'de, I, E>
+where
+    I: Iterator,
+    I::Item: private::Pair,
+{
+    iter: iter::Fuse<I>,
+    value: Option<Second<I::Item>>,
+    count: usize,
+    lifetime: PhantomData<&'de ()>,
+    error: PhantomData<E>,
+}
+
+impl<'de, I, E> MapDeserializer<'de, I, E>
+where
+    I: Iterator,
+    I::Item: private::Pair,
+{
+    /// Construct a new `MapDeserializer<I, E>`.
+    pub fn new(iter: I) -> Self {
+        MapDeserializer {
+            iter: iter.fuse(),
+            value: None,
+            count: 0,
+            lifetime: PhantomData,
+            error: PhantomData,
+        }
+    }
+}
+
+impl<'de, I, E> MapDeserializer<'de, I, E>
+where
+    I: Iterator,
+    I::Item: private::Pair,
+    E: de::Error,
+{
+    /// Check for remaining elements after passing a `MapDeserializer` to
+    /// `Visitor::visit_map`.
+    pub fn end(self) -> Result<(), E> {
+        let remaining = self.iter.count();
+        if remaining == 0 {
+            Ok(())
+        } else {
+            // First argument is the number of elements in the data, second
+            // argument is the number of elements expected by the Deserialize.
+            Err(de::Error::invalid_length(
+                self.count + remaining,
+                &ExpectedInMap(self.count),
+            ))
+        }
+    }
+}
+
+impl<'de, I, E> MapDeserializer<'de, I, E>
+where
+    I: Iterator,
+    I::Item: private::Pair,
+{
+    fn next_pair(&mut self) -> Option<(First<I::Item>, Second<I::Item>)> {
+        match self.iter.next() {
+            Some(kv) => {
+                self.count += 1;
+                Some(private::Pair::split(kv))
+            }
+            None => None,
+        }
+    }
+}
+
+impl<'de, I, E> de::Deserializer<'de> for MapDeserializer<'de, I, E>
+where
+    I: Iterator,
+    I::Item: private::Pair,
+    First<I::Item>: IntoDeserializer<'de, E>,
+    Second<I::Item>: IntoDeserializer<'de, E>,
+    E: de::Error,
+{
+    type Error = E;
+
+    fn deserialize_any<V>(mut self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let value = tri!(visitor.visit_map(&mut self));
+        tri!(self.end());
+        Ok(value)
+    }
+
+    fn deserialize_seq<V>(mut self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let value = tri!(visitor.visit_seq(&mut self));
+        tri!(self.end());
+        Ok(value)
+    }
+
+    fn deserialize_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let _ = len;
+        self.deserialize_seq(visitor)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct tuple_struct map
+        struct enum identifier ignored_any
+    }
+}
+
+impl<'de, I, E> de::MapAccess<'de> for MapDeserializer<'de, I, E>
+where
+    I: Iterator,
+    I::Item: private::Pair,
+    First<I::Item>: IntoDeserializer<'de, E>,
+    Second<I::Item>: IntoDeserializer<'de, E>,
+    E: de::Error,
+{
+    type Error = E;
+
+    fn next_key_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        match self.next_pair() {
+            Some((key, value)) => {
+                self.value = Some(value);
+                seed.deserialize(key.into_deserializer()).map(Some)
+            }
+            None => Ok(None),
+        }
+    }
+
+    fn next_value_seed<T>(&mut self, seed: T) -> Result<T::Value, Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        let value = self.value.take();
+        // Panic because this indicates a bug in the program rather than an
+        // expected failure.
+        let value = value.expect("MapAccess::next_value called before next_key");
+        seed.deserialize(value.into_deserializer())
+    }
+
+    fn next_entry_seed<TK, TV>(
+        &mut self,
+        kseed: TK,
+        vseed: TV,
+    ) -> Result<Option<(TK::Value, TV::Value)>, Self::Error>
+    where
+        TK: de::DeserializeSeed<'de>,
+        TV: de::DeserializeSeed<'de>,
+    {
+        match self.next_pair() {
+            Some((key, value)) => {
+                let key = tri!(kseed.deserialize(key.into_deserializer()));
+                let value = tri!(vseed.deserialize(value.into_deserializer()));
+                Ok(Some((key, value)))
+            }
+            None => Ok(None),
+        }
+    }
+
+    fn size_hint(&self) -> Option<usize> {
+        size_hint::from_bounds(&self.iter)
+    }
+}
+
+impl<'de, I, E> de::SeqAccess<'de> for MapDeserializer<'de, I, E>
+where
+    I: Iterator,
+    I::Item: private::Pair,
+    First<I::Item>: IntoDeserializer<'de, E>,
+    Second<I::Item>: IntoDeserializer<'de, E>,
+    E: de::Error,
+{
+    type Error = E;
+
+    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        match self.next_pair() {
+            Some((k, v)) => {
+                let de = PairDeserializer(k, v, PhantomData);
+                seed.deserialize(de).map(Some)
+            }
+            None => Ok(None),
+        }
+    }
+
+    fn size_hint(&self) -> Option<usize> {
+        size_hint::from_bounds(&self.iter)
+    }
+}
+
+// Cannot #[derive(Clone)] because of the bound `Second<I::Item>: Clone`.
+impl<'de, I, E> Clone for MapDeserializer<'de, I, E>
+where
+    I: Iterator + Clone,
+    I::Item: private::Pair,
+    Second<I::Item>: Clone,
+{
+    fn clone(&self) -> Self {
+        MapDeserializer {
+            iter: self.iter.clone(),
+            value: self.value.clone(),
+            count: self.count,
+            lifetime: self.lifetime,
+            error: self.error,
+        }
+    }
+}
+
+impl<'de, I, E> Debug for MapDeserializer<'de, I, E>
+where
+    I: Iterator + Debug,
+    I::Item: private::Pair,
+    Second<I::Item>: Debug,
+{
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("MapDeserializer")
+            .field("iter", &self.iter)
+            .field("value", &self.value)
+            .field("count", &self.count)
+            .finish()
+    }
+}
+
+// Used in the `impl SeqAccess for MapDeserializer` to visit the map as a
+// sequence of pairs.
+struct PairDeserializer<A, B, E>(A, B, PhantomData<E>);
+
+impl<'de, A, B, E> de::Deserializer<'de> for PairDeserializer<A, B, E>
+where
+    A: IntoDeserializer<'de, E>,
+    B: IntoDeserializer<'de, E>,
+    E: de::Error,
+{
+    type Error = E;
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct tuple_struct map
+        struct enum identifier ignored_any
+    }
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        self.deserialize_seq(visitor)
+    }
+
+    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let mut pair_visitor = PairVisitor(Some(self.0), Some(self.1), PhantomData);
+        let pair = tri!(visitor.visit_seq(&mut pair_visitor));
+        if pair_visitor.1.is_none() {
+            Ok(pair)
+        } else {
+            let remaining = pair_visitor.size_hint().unwrap();
+            // First argument is the number of elements in the data, second
+            // argument is the number of elements expected by the Deserialize.
+            Err(de::Error::invalid_length(2, &ExpectedInSeq(2 - remaining)))
+        }
+    }
+
+    fn deserialize_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        if len == 2 {
+            self.deserialize_seq(visitor)
+        } else {
+            // First argument is the number of elements in the data, second
+            // argument is the number of elements expected by the Deserialize.
+            Err(de::Error::invalid_length(2, &ExpectedInSeq(len)))
+        }
+    }
+}
+
+struct PairVisitor<A, B, E>(Option<A>, Option<B>, PhantomData<E>);
+
+impl<'de, A, B, E> de::SeqAccess<'de> for PairVisitor<A, B, E>
+where
+    A: IntoDeserializer<'de, E>,
+    B: IntoDeserializer<'de, E>,
+    E: de::Error,
+{
+    type Error = E;
+
+    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        if let Some(k) = self.0.take() {
+            seed.deserialize(k.into_deserializer()).map(Some)
+        } else if let Some(v) = self.1.take() {
+            seed.deserialize(v.into_deserializer()).map(Some)
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn size_hint(&self) -> Option<usize> {
+        if self.0.is_some() {
+            Some(2)
+        } else if self.1.is_some() {
+            Some(1)
+        } else {
+            Some(0)
+        }
+    }
+}
+
+struct ExpectedInMap(usize);
+
+impl Expected for ExpectedInMap {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        if self.0 == 1 {
+            write!(formatter, "1 element in map")
+        } else {
+            write!(formatter, "{} elements in map", self.0)
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+#[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg_attr(doc_cfg, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl<'de, K, V, E> IntoDeserializer<'de, E> for BTreeMap<K, V>
+where
+    K: IntoDeserializer<'de, E> + Eq + Ord,
+    V: IntoDeserializer<'de, E>,
+    E: de::Error,
+{
+    type Deserializer = MapDeserializer<'de, <Self as IntoIterator>::IntoIter, E>;
+
+    fn into_deserializer(self) -> Self::Deserializer {
+        MapDeserializer::new(self.into_iter())
+    }
+}
+
+#[cfg(feature = "std")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
+impl<'de, K, V, S, E> IntoDeserializer<'de, E> for HashMap<K, V, S>
+where
+    K: IntoDeserializer<'de, E> + Eq + Hash,
+    V: IntoDeserializer<'de, E>,
+    S: BuildHasher,
+    E: de::Error,
+{
+    type Deserializer = MapDeserializer<'de, <Self as IntoIterator>::IntoIter, E>;
+
+    fn into_deserializer(self) -> Self::Deserializer {
+        MapDeserializer::new(self.into_iter())
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer holding a `MapAccess`.
+#[derive(Clone, Debug)]
+pub struct MapAccessDeserializer<A> {
+    map: A,
+}
+
+impl<A> MapAccessDeserializer<A> {
+    /// Construct a new `MapAccessDeserializer<A>`.
+    pub fn new(map: A) -> Self {
+        MapAccessDeserializer { map }
+    }
+}
+
+impl<'de, A> de::Deserializer<'de> for MapAccessDeserializer<A>
+where
+    A: de::MapAccess<'de>,
+{
+    type Error = A::Error;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_map(self.map)
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        _name: &str,
+        _variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_enum(self)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
+    }
+}
+
+impl<'de, A> de::EnumAccess<'de> for MapAccessDeserializer<A>
+where
+    A: de::MapAccess<'de>,
+{
+    type Error = A::Error;
+    type Variant = private::MapAsEnum<A>;
+
+    fn variant_seed<T>(mut self, seed: T) -> Result<(T::Value, Self::Variant), Self::Error>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        match tri!(self.map.next_key_seed(seed)) {
+            Some(key) => Ok((key, private::map_as_enum(self.map))),
+            None => Err(de::Error::invalid_type(de::Unexpected::Map, &"enum")),
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+/// A deserializer holding an `EnumAccess`.
+#[derive(Clone, Debug)]
+pub struct EnumAccessDeserializer<A> {
+    access: A,
+}
+
+impl<A> EnumAccessDeserializer<A> {
+    /// Construct a new `EnumAccessDeserializer<A>`.
+    pub fn new(access: A) -> Self {
+        EnumAccessDeserializer { access }
+    }
+}
+
+impl<'de, A> de::Deserializer<'de> for EnumAccessDeserializer<A>
+where
+    A: de::EnumAccess<'de>,
+{
+    type Error = A::Error;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        visitor.visit_enum(self.access)
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+mod private {
+    use crate::lib::*;
+
+    use crate::de::{
+        self, DeserializeSeed, Deserializer, MapAccess, Unexpected, VariantAccess, Visitor,
+    };
+
+    pub struct UnitOnly<E> {
+        marker: PhantomData<E>,
+    }
+
+    pub fn unit_only<T, E>(t: T) -> (T, UnitOnly<E>) {
+        (
+            t,
+            UnitOnly {
+                marker: PhantomData,
+            },
+        )
+    }
+
+    impl<'de, E> de::VariantAccess<'de> for UnitOnly<E>
+    where
+        E: de::Error,
+    {
+        type Error = E;
+
+        fn unit_variant(self) -> Result<(), Self::Error> {
+            Ok(())
+        }
+
+        fn newtype_variant_seed<T>(self, _seed: T) -> Result<T::Value, Self::Error>
+        where
+            T: de::DeserializeSeed<'de>,
+        {
+            Err(de::Error::invalid_type(
+                Unexpected::UnitVariant,
+                &"newtype variant",
+            ))
+        }
+
+        fn tuple_variant<V>(self, _len: usize, _visitor: V) -> Result<V::Value, Self::Error>
+        where
+            V: de::Visitor<'de>,
+        {
+            Err(de::Error::invalid_type(
+                Unexpected::UnitVariant,
+                &"tuple variant",
+            ))
+        }
+
+        fn struct_variant<V>(
+            self,
+            _fields: &'static [&'static str],
+            _visitor: V,
+        ) -> Result<V::Value, Self::Error>
+        where
+            V: de::Visitor<'de>,
+        {
+            Err(de::Error::invalid_type(
+                Unexpected::UnitVariant,
+                &"struct variant",
+            ))
+        }
+    }
+
+    pub struct MapAsEnum<A> {
+        map: A,
+    }
+
+    pub fn map_as_enum<A>(map: A) -> MapAsEnum<A> {
+        MapAsEnum { map }
+    }
+
+    impl<'de, A> VariantAccess<'de> for MapAsEnum<A>
+    where
+        A: MapAccess<'de>,
+    {
+        type Error = A::Error;
+
+        fn unit_variant(mut self) -> Result<(), Self::Error> {
+            self.map.next_value()
+        }
+
+        fn newtype_variant_seed<T>(mut self, seed: T) -> Result<T::Value, Self::Error>
+        where
+            T: DeserializeSeed<'de>,
+        {
+            self.map.next_value_seed(seed)
+        }
+
+        fn tuple_variant<V>(mut self, len: usize, visitor: V) -> Result<V::Value, Self::Error>
+        where
+            V: Visitor<'de>,
+        {
+            self.map.next_value_seed(SeedTupleVariant { len, visitor })
+        }
+
+        fn struct_variant<V>(
+            mut self,
+            _fields: &'static [&'static str],
+            visitor: V,
+        ) -> Result<V::Value, Self::Error>
+        where
+            V: Visitor<'de>,
+        {
+            self.map.next_value_seed(SeedStructVariant { visitor })
+        }
+    }
+
+    struct SeedTupleVariant<V> {
+        len: usize,
+        visitor: V,
+    }
+
+    impl<'de, V> DeserializeSeed<'de> for SeedTupleVariant<V>
+    where
+        V: Visitor<'de>,
+    {
+        type Value = V::Value;
+
+        fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+        where
+            D: Deserializer<'de>,
+        {
+            deserializer.deserialize_tuple(self.len, self.visitor)
+        }
+    }
+
+    struct SeedStructVariant<V> {
+        visitor: V,
+    }
+
+    impl<'de, V> DeserializeSeed<'de> for SeedStructVariant<V>
+    where
+        V: Visitor<'de>,
+    {
+        type Value = V::Value;
+
+        fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+        where
+            D: Deserializer<'de>,
+        {
+            deserializer.deserialize_map(self.visitor)
+        }
+    }
+
+    /// Avoid having to restate the generic types on `MapDeserializer`. The
+    /// `Iterator::Item` contains enough information to figure out K and V.
+    pub trait Pair {
+        type First;
+        type Second;
+        fn split(self) -> (Self::First, Self::Second);
+    }
+
+    impl<A, B> Pair for (A, B) {
+        type First = A;
+        type Second = B;
+        fn split(self) -> (A, B) {
+            self
+        }
+    }
+
+    pub type First<T> = <T as Pair>::First;
+    pub type Second<T> = <T as Pair>::Second;
+}