1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
use lib::*;
use ser::{Error, Impossible, Serialize, Serializer};

impl Error for fmt::Error {
    fn custom<T: Display>(_msg: T) -> Self {
        fmt::Error
    }
}

macro_rules! fmt_primitives {
    ($($f:ident: $t:ty,)*) => {
        $(
            fn $f(self, v: $t) -> fmt::Result {
                Display::fmt(&v, self)
            }
        )*
    };
}

/// ```edition2018
/// use serde::Serialize;
/// use std::fmt::{self, Display};
///
/// #[derive(Serialize)]
/// #[serde(rename_all = "kebab-case")]
/// pub enum MessageType {
///     StartRequest,
///     EndRequest,
/// }
///
/// impl Display for MessageType {
///     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
///         self.serialize(f)
///     }
/// }
/// ```
impl<'a, 'b> Serializer for &'a mut fmt::Formatter<'b> {
    type Ok = ();
    type Error = fmt::Error;
    type SerializeSeq = Impossible<(), fmt::Error>;
    type SerializeTuple = Impossible<(), fmt::Error>;
    type SerializeTupleStruct = Impossible<(), fmt::Error>;
    type SerializeTupleVariant = Impossible<(), fmt::Error>;
    type SerializeMap = Impossible<(), fmt::Error>;
    type SerializeStruct = Impossible<(), fmt::Error>;
    type SerializeStructVariant = Impossible<(), fmt::Error>;

    fmt_primitives! {
        serialize_bool: bool,
        serialize_i8: i8,
        serialize_i16: i16,
        serialize_i32: i32,
        serialize_i64: i64,
        serialize_u8: u8,
        serialize_u16: u16,
        serialize_u32: u32,
        serialize_u64: u64,
        serialize_f32: f32,
        serialize_f64: f64,
        serialize_char: char,
        serialize_str: &str,
        serialize_unit_struct: &'static str,
    }

    serde_if_integer128! {
        fmt_primitives! {
            serialize_i128: i128,
            serialize_u128: u128,
        }
    }

    fn serialize_unit_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
    ) -> fmt::Result {
        Display::fmt(variant, self)
    }

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

    fn serialize_bytes(self, _v: &[u8]) -> fmt::Result {
        Err(fmt::Error)
    }

    fn serialize_none(self) -> fmt::Result {
        Err(fmt::Error)
    }

    fn serialize_some<T: ?Sized>(self, _value: &T) -> fmt::Result
    where
        T: Serialize,
    {
        Err(fmt::Error)
    }

    fn serialize_unit(self) -> fmt::Result {
        Err(fmt::Error)
    }

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

    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq, fmt::Error> {
        Err(fmt::Error)
    }

    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple, fmt::Error> {
        Err(fmt::Error)
    }

    fn serialize_tuple_struct(
        self,
        _name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleStruct, fmt::Error> {
        Err(fmt::Error)
    }

    fn serialize_tuple_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        _variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleVariant, fmt::Error> {
        Err(fmt::Error)
    }

    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, fmt::Error> {
        Err(fmt::Error)
    }

    fn serialize_struct(
        self,
        _name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStruct, fmt::Error> {
        Err(fmt::Error)
    }

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

    fn collect_str<T: ?Sized>(self, value: &T) -> fmt::Result
    where
        T: Display,
    {
        Display::fmt(value, self)
    }
}