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    1081

    //! Definition of a TOML value

    use std::collections::{BTreeMap, HashMap};
    use std::fmt;
    use std::hash::Hash;
    use std::mem::discriminant;
    use std::ops;
    use std::str::FromStr;
    use std::vec;

    use serde::de;
    use serde::de::IntoDeserializer;
    use serde::ser;

    use crate::datetime::{self, DatetimeFromString};
    pub use crate::datetime::{Date, Datetime, DatetimeParseError, Offset, Time};

    pub use crate::map::{Entry, Map};

    /// Representation of a TOML value.
    #[derive(PartialEq, Clone, Debug)]
    pub enum Value {
        /// Represents a TOML string
        String(String),
        /// Represents a TOML integer
        Integer(i64),
        /// Represents a TOML float
        Float(f64),
        /// Represents a TOML boolean
        Boolean(bool),
        /// Represents a TOML datetime
        Datetime(Datetime),
        /// Represents a TOML array
        Array(Array),
        /// Represents a TOML table
        Table(Table),
    }

    /// Type representing a TOML array, payload of the `Value::Array` variant
    pub type Array = Vec<Value>;

    /// Type representing a TOML table, payload of the `Value::Table` variant.
    /// By default it is backed by a BTreeMap, enable the `preserve_order` feature
    /// to use a LinkedHashMap instead.
    pub type Table = Map<String, Value>;

    impl Value {
        /// Convert a `T` into `toml::Value` which is an enum that can represent
        /// any valid TOML data.
        ///
        /// This conversion can fail if `T`'s implementation of `Serialize` decides to
        /// fail, or if `T` contains a map with non-string keys.
        pub fn try_from<T>(value: T) -> Result<Value, crate::ser::Error>
        where
            T: ser::Serialize,
        {
            value.serialize(Serializer)
        }

        /// Interpret a `toml::Value` as an instance of type `T`.
        ///
        /// This conversion can fail if the structure of the `Value` does not match the
        /// structure expected by `T`, for example if `T` is a struct type but the
        /// `Value` contains something other than a TOML table. It can also fail if the
        /// structure is correct but `T`'s implementation of `Deserialize` decides that
        /// something is wrong with the data, for example required struct fields are
        /// missing from the TOML map or some number is too big to fit in the expected
        /// primitive type.
        pub fn try_into<'de, T>(self) -> Result<T, crate::de::Error>
        where
            T: de::Deserialize<'de>,
        {
            de::Deserialize::deserialize(self)
        }

        /// Index into a TOML array or map. A string index can be used to access a
        /// value in a map, and a usize index can be used to access an element of an
        /// array.
        ///
        /// Returns `None` if the type of `self` does not match the type of the
        /// index, for example if the index is a string and `self` is an array or a
        /// number. Also returns `None` if the given key does not exist in the map
        /// or the given index is not within the bounds of the array.
        pub fn get<I: Index>(&self, index: I) -> Option<&Value> {
            index.index(self)
        }

        /// Mutably index into a TOML array or map. A string index can be used to
        /// access a value in a map, and a usize index can be used to access an
        /// element of an array.
        ///
        /// Returns `None` if the type of `self` does not match the type of the
        /// index, for example if the index is a string and `self` is an array or a
        /// number. Also returns `None` if the given key does not exist in the map
        /// or the given index is not within the bounds of the array.
        pub fn get_mut<I: Index>(&mut self, index: I) -> Option<&mut Value> {
            index.index_mut(self)
        }

        /// Extracts the integer value if it is an integer.
        pub fn as_integer(&self) -> Option<i64> {
            match *self {
                Value::Integer(i) => Some(i),
                _ => None,
            }
        }

        /// Tests whether this value is an integer.
        pub fn is_integer(&self) -> bool {
            self.as_integer().is_some()
        }

        /// Extracts the float value if it is a float.
        pub fn as_float(&self) -> Option<f64> {
            match *self {
                Value::Float(f) => Some(f),
                _ => None,
            }
        }

        /// Tests whether this value is a float.
        pub fn is_float(&self) -> bool {
            self.as_float().is_some()
        }

        /// Extracts the boolean value if it is a boolean.
        pub fn as_bool(&self) -> Option<bool> {
            match *self {
                Value::Boolean(b) => Some(b),
                _ => None,
            }
        }

        /// Tests whether this value is a boolean.
        pub fn is_bool(&self) -> bool {
            self.as_bool().is_some()
        }

        /// Extracts the string of this value if it is a string.
        pub fn as_str(&self) -> Option<&str> {
            match *self {
                Value::String(ref s) => Some(&**s),
                _ => None,
            }
        }

        /// Tests if this value is a string.
        pub fn is_str(&self) -> bool {
            self.as_str().is_some()
        }

        /// Extracts the datetime value if it is a datetime.
        ///
        /// Note that a parsed TOML value will only contain ISO 8601 dates. An
        /// example date is:
        ///
        /// ```notrust
        /// 1979-05-27T07:32:00Z
        /// ```
        pub fn as_datetime(&self) -> Option<&Datetime> {
            match *self {
                Value::Datetime(ref s) => Some(s),
                _ => None,
            }
        }

        /// Tests whether this value is a datetime.
        pub fn is_datetime(&self) -> bool {
            self.as_datetime().is_some()
        }

        /// Extracts the array value if it is an array.
        pub fn as_array(&self) -> Option<&Vec<Value>> {
            match *self {
                Value::Array(ref s) => Some(s),
                _ => None,
            }
        }

        /// Extracts the array value if it is an array.
        pub fn as_array_mut(&mut self) -> Option<&mut Vec<Value>> {
            match *self {
                Value::Array(ref mut s) => Some(s),
                _ => None,
            }
        }

        /// Tests whether this value is an array.
        pub fn is_array(&self) -> bool {
            self.as_array().is_some()
        }

        /// Extracts the table value if it is a table.
        pub fn as_table(&self) -> Option<&Table> {
            match *self {
                Value::Table(ref s) => Some(s),
                _ => None,
            }
        }

        /// Extracts the table value if it is a table.
        pub fn as_table_mut(&mut self) -> Option<&mut Table> {
            match *self {
                Value::Table(ref mut s) => Some(s),
                _ => None,
            }
        }

        /// Tests whether this value is a table.
        pub fn is_table(&self) -> bool {
            self.as_table().is_some()
        }

        /// Tests whether this and another value have the same type.
        pub fn same_type(&self, other: &Value) -> bool {
            discriminant(self) == discriminant(other)
        }

        /// Returns a human-readable representation of the type of this value.
        pub fn type_str(&self) -> &'static str {
            match *self {
                Value::String(..) => "string",
                Value::Integer(..) => "integer",
                Value::Float(..) => "float",
                Value::Boolean(..) => "boolean",
                Value::Datetime(..) => "datetime",
                Value::Array(..) => "array",
                Value::Table(..) => "table",
            }
        }
    }

    impl<I> ops::Index<I> for Value
    where
        I: Index,
    {
        type Output = Value;

        fn index(&self, index: I) -> &Value {
            self.get(index).expect("index not found")
        }
    }

    impl<I> ops::IndexMut<I> for Value
    where
        I: Index,
    {
        fn index_mut(&mut self, index: I) -> &mut Value {
            self.get_mut(index).expect("index not found")
        }
    }

    impl<'a> From<&'a str> for Value {
        #[inline]
        fn from(val: &'a str) -> Value {
            Value::String(val.to_string())
        }
    }

    impl<V: Into<Value>> From<Vec<V>> for Value {
        fn from(val: Vec<V>) -> Value {
            Value::Array(val.into_iter().map(|v| v.into()).collect())
        }
    }

    impl<S: Into<String>, V: Into<Value>> From<BTreeMap<S, V>> for Value {
        fn from(val: BTreeMap<S, V>) -> Value {
            let table = val.into_iter().map(|(s, v)| (s.into(), v.into())).collect();

            Value::Table(table)
        }
    }

    impl<S: Into<String> + Hash + Eq, V: Into<Value>> From<HashMap<S, V>> for Value {
        fn from(val: HashMap<S, V>) -> Value {
            let table = val.into_iter().map(|(s, v)| (s.into(), v.into())).collect();

            Value::Table(table)
        }
    }

    macro_rules! impl_into_value {
        ($variant:ident : $T:ty) => {
            impl From<$T> for Value {
                #[inline]
                fn from(val: $T) -> Value {
                    Value::$variant(val.into())
                }
            }
        };
    }

    impl_into_value!(String: String);
    impl_into_value!(Integer: i64);
    impl_into_value!(Integer: i32);
    impl_into_value!(Integer: i8);
    impl_into_value!(Integer: u8);
    impl_into_value!(Integer: u32);
    impl_into_value!(Float: f64);
    impl_into_value!(Float: f32);
    impl_into_value!(Boolean: bool);
    impl_into_value!(Datetime: Datetime);
    impl_into_value!(Table: Table);

    /// Types that can be used to index a `toml::Value`
    ///
    /// Currently this is implemented for `usize` to index arrays and `str` to index
    /// tables.
    ///
    /// This trait is sealed and not intended for implementation outside of the
    /// `toml` crate.
    pub trait Index: Sealed {
        #[doc(hidden)]
        fn index<'a>(&self, val: &'a Value) -> Option<&'a Value>;
        #[doc(hidden)]
        fn index_mut<'a>(&self, val: &'a mut Value) -> Option<&'a mut Value>;
    }

    /// An implementation detail that should not be implemented, this will change in
    /// the future and break code otherwise.
    #[doc(hidden)]
    pub trait Sealed {}
    impl Sealed for usize {}
    impl Sealed for str {}
    impl Sealed for String {}
    impl<'a, T: Sealed + ?Sized> Sealed for &'a T {}

    impl Index for usize {
        fn index<'a>(&self, val: &'a Value) -> Option<&'a Value> {
            match *val {
                Value::Array(ref a) => a.get(*self),
                _ => None,
            }
        }

        fn index_mut<'a>(&self, val: &'a mut Value) -> Option<&'a mut Value> {
            match *val {
                Value::Array(ref mut a) => a.get_mut(*self),
                _ => None,
            }
        }
    }

    impl Index for str {
        fn index<'a>(&self, val: &'a Value) -> Option<&'a Value> {
            match *val {
                Value::Table(ref a) => a.get(self),
                _ => None,
            }
        }

        fn index_mut<'a>(&self, val: &'a mut Value) -> Option<&'a mut Value> {
            match *val {
                Value::Table(ref mut a) => a.get_mut(self),
                _ => None,
            }
        }
    }

    impl Index for String {
        fn index<'a>(&self, val: &'a Value) -> Option<&'a Value> {
            self[..].index(val)
        }

        fn index_mut<'a>(&self, val: &'a mut Value) -> Option<&'a mut Value> {
            self[..].index_mut(val)
        }
    }

    impl<'s, T: ?Sized> Index for &'s T
    where
        T: Index,
    {
        fn index<'a>(&self, val: &'a Value) -> Option<&'a Value> {
            (**self).index(val)
        }

        fn index_mut<'a>(&self, val: &'a mut Value) -> Option<&'a mut Value> {
            (**self).index_mut(val)
        }
    }

    impl fmt::Display for Value {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            crate::ser::to_string(self)
                .expect("Unable to represent value as string")
                .fmt(f)
        }
    }

    impl FromStr for Value {
        type Err = crate::de::Error;
        fn from_str(s: &str) -> Result<Value, Self::Err> {
            crate::from_str(s)
        }
    }

    impl ser::Serialize for Value {
        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
        where
            S: ser::Serializer,
        {
            use serde::ser::SerializeMap;

            match *self {
                Value::String(ref s) => serializer.serialize_str(s),
                Value::Integer(i) => serializer.serialize_i64(i),
                Value::Float(f) => serializer.serialize_f64(f),
                Value::Boolean(b) => serializer.serialize_bool(b),
                Value::Datetime(ref s) => s.serialize(serializer),
                Value::Array(ref a) => a.serialize(serializer),
                Value::Table(ref t) => {
                    let mut map = serializer.serialize_map(Some(t.len()))?;
                    // Be sure to visit non-tables first (and also non
                    // array-of-tables) as all keys must be emitted first.
                    for (k, v) in t {
                        if !v.is_table() && !v.is_array()
                            || (v
                                .as_array()
                                .map(|a| !a.iter().any(|v| v.is_table()))
                                .unwrap_or(false))
                        {
                            map.serialize_entry(k, v)?;
                        }
                    }
                    for (k, v) in t {
                        if v.as_array()
                            .map(|a| a.iter().any(|v| v.is_table()))
                            .unwrap_or(false)
                        {
                            map.serialize_entry(k, v)?;
                        }
                    }
                    for (k, v) in t {
                        if v.is_table() {
                            map.serialize_entry(k, v)?;
                        }
                    }
                    map.end()
                }
            }
        }
    }

    impl<'de> de::Deserialize<'de> for Value {
        fn deserialize<D>(deserializer: D) -> Result<Value, D::Error>
        where
            D: de::Deserializer<'de>,
        {
            struct ValueVisitor;

            impl<'de> de::Visitor<'de> for ValueVisitor {
                type Value = Value;

                fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
                    formatter.write_str("any valid TOML value")
                }

                fn visit_bool<E>(self, value: bool) -> Result<Value, E> {
                    Ok(Value::Boolean(value))
                }

                fn visit_i64<E>(self, value: i64) -> Result<Value, E> {
                    Ok(Value::Integer(value))
                }

                fn visit_u64<E: de::Error>(self, value: u64) -> Result<Value, E> {
                    if value <= i64::max_value() as u64 {
                        Ok(Value::Integer(value as i64))
                    } else {
                        Err(de::Error::custom("u64 value was too large"))
                    }
                }

                fn visit_u32<E>(self, value: u32) -> Result<Value, E> {
                    Ok(Value::Integer(value.into()))
                }

                fn visit_i32<E>(self, value: i32) -> Result<Value, E> {
                    Ok(Value::Integer(value.into()))
                }

                fn visit_f64<E>(self, value: f64) -> Result<Value, E> {
                    Ok(Value::Float(value))
                }

                fn visit_str<E>(self, value: &str) -> Result<Value, E> {
                    Ok(Value::String(value.into()))
                }

                fn visit_string<E>(self, value: String) -> Result<Value, E> {
                    Ok(Value::String(value))
                }

                fn visit_some<D>(self, deserializer: D) -> Result<Value, D::Error>
                where
                    D: de::Deserializer<'de>,
                {
                    de::Deserialize::deserialize(deserializer)
                }

                fn visit_seq<V>(self, mut visitor: V) -> Result<Value, V::Error>
                where
                    V: de::SeqAccess<'de>,
                {
                    let mut vec = Vec::new();
                    while let Some(elem) = visitor.next_element()? {
                        vec.push(elem);
                    }
                    Ok(Value::Array(vec))
                }

                fn visit_map<V>(self, mut visitor: V) -> Result<Value, V::Error>
                where
                    V: de::MapAccess<'de>,
                {
                    let mut key = String::new();
                    let datetime = visitor.next_key_seed(DatetimeOrTable { key: &mut key })?;
                    match datetime {
                        Some(true) => {
                            let date: DatetimeFromString = visitor.next_value()?;
                            return Ok(Value::Datetime(date.value));
                        }
                        None => return Ok(Value::Table(Map::new())),
                        Some(false) => {}
                    }
                    let mut map = Map::new();
                    map.insert(key, visitor.next_value()?);
                    while let Some(key) = visitor.next_key::<String>()? {
                        if let Entry::Vacant(vacant) = map.entry(&key) {
                            vacant.insert(visitor.next_value()?);
                        } else {
                            let msg = format!("duplicate key: `{}`", key);
                            return Err(de::Error::custom(msg));
                        }
                    }
                    Ok(Value::Table(map))
                }
            }

            deserializer.deserialize_any(ValueVisitor)
        }
    }

    impl<'de> de::Deserializer<'de> for Value {
        type Error = crate::de::Error;

        fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, crate::de::Error>
        where
            V: de::Visitor<'de>,
        {
            match self {
                Value::Boolean(v) => visitor.visit_bool(v),
                Value::Integer(n) => visitor.visit_i64(n),
                Value::Float(n) => visitor.visit_f64(n),
                Value::String(v) => visitor.visit_string(v),
                Value::Datetime(v) => visitor.visit_string(v.to_string()),
                Value::Array(v) => {
                    let len = v.len();
                    let mut deserializer = SeqDeserializer::new(v);
                    let seq = visitor.visit_seq(&mut deserializer)?;
                    let remaining = deserializer.iter.len();
                    if remaining == 0 {
                        Ok(seq)
                    } else {
                        Err(de::Error::invalid_length(len, &"fewer elements in array"))
                    }
                }
                Value::Table(v) => {
                    let len = v.len();
                    let mut deserializer = MapDeserializer::new(v);
                    let map = visitor.visit_map(&mut deserializer)?;
                    let remaining = deserializer.iter.len();
                    if remaining == 0 {
                        Ok(map)
                    } else {
                        Err(de::Error::invalid_length(len, &"fewer elements in map"))
                    }
                }
            }
        }

        #[inline]
        fn deserialize_enum<V>(
            self,
            _name: &str,
            _variants: &'static [&'static str],
            visitor: V,
        ) -> Result<V::Value, crate::de::Error>
        where
            V: de::Visitor<'de>,
        {
            match self {
                Value::String(variant) => visitor.visit_enum(variant.into_deserializer()),
                _ => Err(de::Error::invalid_type(
                    de::Unexpected::UnitVariant,
                    &"string only",
                )),
            }
        }

        // `None` is interpreted as a missing field so be sure to implement `Some`
        // as a present field.
        fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, crate::de::Error>
        where
            V: de::Visitor<'de>,
        {
            visitor.visit_some(self)
        }

        fn deserialize_newtype_struct<V>(
            self,
            _name: &'static str,
            visitor: V,
        ) -> Result<V::Value, crate::de::Error>
        where
            V: de::Visitor<'de>,
        {
            visitor.visit_newtype_struct(self)
        }

        serde::forward_to_deserialize_any! {
            bool u8 u16 u32 u64 i8 i16 i32 i64 f32 f64 char str string unit seq
            bytes byte_buf map unit_struct tuple_struct struct
            tuple ignored_any identifier
        }
    }

    struct SeqDeserializer {
        iter: vec::IntoIter<Value>,
    }

    impl SeqDeserializer {
        fn new(vec: Vec<Value>) -> Self {
            SeqDeserializer {
                iter: vec.into_iter(),
            }
        }
    }

    impl<'de> de::SeqAccess<'de> for SeqDeserializer {
        type Error = crate::de::Error;

        fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, crate::de::Error>
        where
            T: de::DeserializeSeed<'de>,
        {
            match self.iter.next() {
                Some(value) => seed.deserialize(value).map(Some),
                None => Ok(None),
            }
        }

        fn size_hint(&self) -> Option<usize> {
            match self.iter.size_hint() {
                (lower, Some(upper)) if lower == upper => Some(upper),
                _ => None,
            }
        }
    }

    struct MapDeserializer {
        iter: <Map<String, Value> as IntoIterator>::IntoIter,
        value: Option<(String, Value)>,
    }

    impl MapDeserializer {
        fn new(map: Map<String, Value>) -> Self {
            MapDeserializer {
                iter: map.into_iter(),
                value: None,
            }
        }
    }

    impl<'de> de::MapAccess<'de> for MapDeserializer {
        type Error = crate::de::Error;

        fn next_key_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, crate::de::Error>
        where
            T: de::DeserializeSeed<'de>,
        {
            match self.iter.next() {
                Some((key, value)) => {
                    self.value = Some((key.clone(), value));
                    seed.deserialize(Value::String(key)).map(Some)
                }
                None => Ok(None),
            }
        }

        fn next_value_seed<T>(&mut self, seed: T) -> Result<T::Value, crate::de::Error>
        where
            T: de::DeserializeSeed<'de>,
        {
            let (key, res) = match self.value.take() {
                Some((key, value)) => (key, seed.deserialize(value)),
                None => return Err(de::Error::custom("value is missing")),
            };
            res.map_err(|mut error| {
                error.add_key_context(&key);
                error
            })
        }

        fn size_hint(&self) -> Option<usize> {
            match self.iter.size_hint() {
                (lower, Some(upper)) if lower == upper => Some(upper),
                _ => None,
            }
        }
    }

    impl<'de> de::IntoDeserializer<'de, crate::de::Error> for Value {
        type Deserializer = Self;

        fn into_deserializer(self) -> Self {
            self
        }
    }

    struct Serializer;

    impl ser::Serializer for Serializer {
        type Ok = Value;
        type Error = crate::ser::Error;

        type SerializeSeq = SerializeVec;
        type SerializeTuple = SerializeVec;
        type SerializeTupleStruct = SerializeVec;
        type SerializeTupleVariant = SerializeVec;
        type SerializeMap = SerializeMap;
        type SerializeStruct = SerializeMap;
        type SerializeStructVariant = ser::Impossible<Value, crate::ser::Error>;

        fn serialize_bool(self, value: bool) -> Result<Value, crate::ser::Error> {
            Ok(Value::Boolean(value))
        }

        fn serialize_i8(self, value: i8) -> Result<Value, crate::ser::Error> {
            self.serialize_i64(value.into())
        }

        fn serialize_i16(self, value: i16) -> Result<Value, crate::ser::Error> {
            self.serialize_i64(value.into())
        }

        fn serialize_i32(self, value: i32) -> Result<Value, crate::ser::Error> {
            self.serialize_i64(value.into())
        }

        fn serialize_i64(self, value: i64) -> Result<Value, crate::ser::Error> {
            Ok(Value::Integer(value))
        }

        fn serialize_u8(self, value: u8) -> Result<Value, crate::ser::Error> {
            self.serialize_i64(value.into())
        }

        fn serialize_u16(self, value: u16) -> Result<Value, crate::ser::Error> {
            self.serialize_i64(value.into())
        }

        fn serialize_u32(self, value: u32) -> Result<Value, crate::ser::Error> {
            self.serialize_i64(value.into())
        }

        fn serialize_u64(self, value: u64) -> Result<Value, crate::ser::Error> {
            if value <= i64::max_value() as u64 {
                self.serialize_i64(value as i64)
            } else {
                Err(ser::Error::custom("u64 value was too large"))
            }
        }

        fn serialize_f32(self, value: f32) -> Result<Value, crate::ser::Error> {
            self.serialize_f64(value.into())
        }

        fn serialize_f64(self, value: f64) -> Result<Value, crate::ser::Error> {
            Ok(Value::Float(value))
        }

        fn serialize_char(self, value: char) -> Result<Value, crate::ser::Error> {
            let mut s = String::new();
            s.push(value);
            self.serialize_str(&s)
        }

        fn serialize_str(self, value: &str) -> Result<Value, crate::ser::Error> {
            Ok(Value::String(value.to_owned()))
        }

        fn serialize_bytes(self, value: &[u8]) -> Result<Value, crate::ser::Error> {
            let vec = value.iter().map(|&b| Value::Integer(b.into())).collect();
            Ok(Value::Array(vec))
        }

        fn serialize_unit(self) -> Result<Value, crate::ser::Error> {
            Err(crate::ser::Error::UnsupportedType)
        }

        fn serialize_unit_struct(self, _name: &'static str) -> Result<Value, crate::ser::Error> {
            Err(crate::ser::Error::UnsupportedType)
        }

        fn serialize_unit_variant(
            self,
            _name: &'static str,
            _variant_index: u32,
            _variant: &'static str,
        ) -> Result<Value, crate::ser::Error> {
            self.serialize_str(_variant)
        }

        fn serialize_newtype_struct<T: ?Sized>(
            self,
            _name: &'static str,
            value: &T,
        ) -> Result<Value, crate::ser::Error>
        where
            T: ser::Serialize,
        {
            value.serialize(self)
        }

        fn serialize_newtype_variant<T: ?Sized>(
            self,
            _name: &'static str,
            _variant_index: u32,
            _variant: &'static str,
            _value: &T,
        ) -> Result<Value, crate::ser::Error>
        where
            T: ser::Serialize,
        {
            Err(crate::ser::Error::UnsupportedType)
        }

        fn serialize_none(self) -> Result<Value, crate::ser::Error> {
            Err(crate::ser::Error::UnsupportedNone)
        }

        fn serialize_some<T: ?Sized>(self, value: &T) -> Result<Value, crate::ser::Error>
        where
            T: ser::Serialize,
        {
            value.serialize(self)
        }

        fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq, crate::ser::Error> {
            Ok(SerializeVec {
                vec: Vec::with_capacity(len.unwrap_or(0)),
            })
        }

        fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple, crate::ser::Error> {
            self.serialize_seq(Some(len))
        }

        fn serialize_tuple_struct(
            self,
            _name: &'static str,
            len: usize,
        ) -> Result<Self::SerializeTupleStruct, crate::ser::Error> {
            self.serialize_seq(Some(len))
        }

        fn serialize_tuple_variant(
            self,
            _name: &'static str,
            _variant_index: u32,
            _variant: &'static str,
            len: usize,
        ) -> Result<Self::SerializeTupleVariant, crate::ser::Error> {
            self.serialize_seq(Some(len))
        }

        fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, crate::ser::Error> {
            Ok(SerializeMap {
                map: Map::new(),
                next_key: None,
            })
        }

        fn serialize_struct(
            self,
            _name: &'static str,
            len: usize,
        ) -> Result<Self::SerializeStruct, crate::ser::Error> {
            self.serialize_map(Some(len))
        }

        fn serialize_struct_variant(
            self,
            _name: &'static str,
            _variant_index: u32,
            _variant: &'static str,
            _len: usize,
        ) -> Result<Self::SerializeStructVariant, crate::ser::Error> {
            Err(crate::ser::Error::UnsupportedType)
        }
    }

    struct SerializeVec {
        vec: Vec<Value>,
    }

    struct SerializeMap {
        map: Map<String, Value>,
        next_key: Option<String>,
    }

    impl ser::SerializeSeq for SerializeVec {
        type Ok = Value;
        type Error = crate::ser::Error;

        fn serialize_element<T: ?Sized>(&mut self, value: &T) -> Result<(), crate::ser::Error>
        where
            T: ser::Serialize,
        {
            self.vec.push(Value::try_from(value)?);
            Ok(())
        }

        fn end(self) -> Result<Value, crate::ser::Error> {
            Ok(Value::Array(self.vec))
        }
    }

    impl ser::SerializeTuple for SerializeVec {
        type Ok = Value;
        type Error = crate::ser::Error;

        fn serialize_element<T: ?Sized>(&mut self, value: &T) -> Result<(), crate::ser::Error>
        where
            T: ser::Serialize,
        {
            ser::SerializeSeq::serialize_element(self, value)
        }

        fn end(self) -> Result<Value, crate::ser::Error> {
            ser::SerializeSeq::end(self)
        }
    }

    impl ser::SerializeTupleStruct for SerializeVec {
        type Ok = Value;
        type Error = crate::ser::Error;

        fn serialize_field<T: ?Sized>(&mut self, value: &T) -> Result<(), crate::ser::Error>
        where
            T: ser::Serialize,
        {
            ser::SerializeSeq::serialize_element(self, value)
        }

        fn end(self) -> Result<Value, crate::ser::Error> {
            ser::SerializeSeq::end(self)
        }
    }

    impl ser::SerializeTupleVariant for SerializeVec {
        type Ok = Value;
        type Error = crate::ser::Error;

        fn serialize_field<T: ?Sized>(&mut self, value: &T) -> Result<(), crate::ser::Error>
        where
            T: ser::Serialize,
        {
            ser::SerializeSeq::serialize_element(self, value)
        }

        fn end(self) -> Result<Value, crate::ser::Error> {
            ser::SerializeSeq::end(self)
        }
    }

    impl ser::SerializeMap for SerializeMap {
        type Ok = Value;
        type Error = crate::ser::Error;

        fn serialize_key<T: ?Sized>(&mut self, key: &T) -> Result<(), crate::ser::Error>
        where
            T: ser::Serialize,
        {
            match Value::try_from(key)? {
                Value::String(s) => self.next_key = Some(s),
                _ => return Err(crate::ser::Error::KeyNotString),
            };
            Ok(())
        }

        fn serialize_value<T: ?Sized>(&mut self, value: &T) -> Result<(), crate::ser::Error>
        where
            T: ser::Serialize,
        {
            let key = self.next_key.take();
            let key = key.expect("serialize_value called before serialize_key");
            match Value::try_from(value) {
                Ok(value) => {
                    self.map.insert(key, value);
                }
                Err(crate::ser::Error::UnsupportedNone) => {}
                Err(e) => return Err(e),
            }
            Ok(())
        }

        fn end(self) -> Result<Value, crate::ser::Error> {
            Ok(Value::Table(self.map))
        }
    }

    impl ser::SerializeStruct for SerializeMap {
        type Ok = Value;
        type Error = crate::ser::Error;

        fn serialize_field<T: ?Sized>(
            &mut self,
            key: &'static str,
            value: &T,
        ) -> Result<(), crate::ser::Error>
        where
            T: ser::Serialize,
        {
            ser::SerializeMap::serialize_key(self, key)?;
            ser::SerializeMap::serialize_value(self, value)
        }

        fn end(self) -> Result<Value, crate::ser::Error> {
            ser::SerializeMap::end(self)
        }
    }

    struct DatetimeOrTable<'a> {
        key: &'a mut String,
    }

    impl<'a, 'de> de::DeserializeSeed<'de> for DatetimeOrTable<'a> {
        type Value = bool;

        fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
        where
            D: de::Deserializer<'de>,
        {
            deserializer.deserialize_any(self)
        }
    }

    impl<'a, 'de> de::Visitor<'de> for DatetimeOrTable<'a> {
        type Value = bool;

        fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
            formatter.write_str("a string key")
        }

        fn visit_str<E>(self, s: &str) -> Result<bool, E>
        where
            E: de::Error,
        {
            if s == datetime::FIELD {
                Ok(true)
            } else {
                self.key.push_str(s);
                Ok(false)
            }
        }

        fn visit_string<E>(self, s: String) -> Result<bool, E>
        where
            E: de::Error,
        {
            if s == datetime::FIELD {
                Ok(true)
            } else {
                *self.key = s;
                Ok(false)
            }
        }
    }