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
175
176
177
178
179
180
181
182
183
184
//! Represents the output of numeric operators in SQL
//!
//! Apps should not need to concern themselves with this module.
//! If you are looking for where the actual implementation of `std::ops::Add`
//! and friends are generated for columns, see
//! [`numeric_expr!`](../../macro.numeric_expr.html).
//!
//! Crates which add new types which allow numeric operators should implement
//! these traits to specify what the output is for a given right hand side.
//!
//! Unlike the traits in `std::ops`, the right hand side is an associated type
//! rather than a type parameter. The biggest drawback of this is that any type
//! can only have one right hand type which can be added/subtracted, etc. The
//! most immediately noticeable effect of this is that you cannot add a nullable
//! number to one that is not nullable.
//!
//! The reason for this is because of the impl of `std::ops::Add` that we need
//! to be able to write. We want the right hand side to allow Rust values which
//! should be sent as bind parameters, not just other Diesel expressions. That
//! means the impl would look like this:
//!
//! ```ignore
//! impl<ST, T> std::ops::Add<T> for my_column
//! where
//!     T: AsExpression<ST>,
//!     my_column::SqlType: diesel::ops::Add<ST>,
//! ```
//!
//! This impl is not valid in Rust, as `ST` is not constrained by the trait or
//! the implementing type. If there were two valid types for `ST` which
//! satisfied all constraints, Rust would not know which one to use, and there
//! would be no way for the user to specify which one should be used.

use super::*;

/// Represents SQL types which can be added.
pub trait Add {
    /// The SQL type which can be added to this one
    type Rhs: SqlType;
    /// The SQL type of the result of adding `Rhs` to `Self`
    type Output: SqlType;
}

/// Represents SQL types which can be subtracted.
pub trait Sub {
    /// The SQL type which can be subtracted from this one
    type Rhs: SqlType;
    /// The SQL type of the result of subtracting `Rhs` from `Self`
    type Output: SqlType;
}

/// Represents SQL types which can be multiplied.
pub trait Mul {
    /// The SQL type which this can be multiplied by
    type Rhs: SqlType;
    /// The SQL type of the result of multiplying `Self` by `Rhs`
    type Output: SqlType;
}

/// Represents SQL types which can be divided.
pub trait Div {
    /// The SQL type which this one can be divided by
    type Rhs: SqlType;
    /// The SQL type of the result of dividing `Self` by `Rhs`
    type Output: SqlType;
}

macro_rules! numeric_type {
    ($($tpe: ident),*) => {
        $(
        impl Add for $tpe {
            type Rhs = $tpe;
            type Output = $tpe;
        }

        impl Sub for $tpe {
            type Rhs = $tpe;
            type Output = $tpe;
        }

        impl Mul for $tpe {
            type Rhs = $tpe;
            type Output = $tpe;
        }

        impl Div for $tpe {
            type Rhs = $tpe;
            type Output = $tpe;
        }
        )*
    }
}

numeric_type!(SmallInt, Integer, BigInt, Float, Double, Numeric);

impl Add for Time {
    type Rhs = Interval;
    type Output = Time;
}

impl Sub for Time {
    type Rhs = Interval;
    type Output = Time;
}

impl Add for Date {
    type Rhs = Interval;
    type Output = Timestamp;
}

impl Sub for Date {
    type Rhs = Interval;
    type Output = Timestamp;
}

impl Add for Timestamp {
    type Rhs = Interval;
    type Output = Timestamp;
}

impl Sub for Timestamp {
    type Rhs = Interval;
    type Output = Timestamp;
}

impl Add for Interval {
    type Rhs = Interval;
    type Output = Interval;
}

impl Sub for Interval {
    type Rhs = Interval;
    type Output = Interval;
}

impl Mul for Interval {
    type Rhs = Integer;
    type Output = Interval;
}

impl Div for Interval {
    type Rhs = Integer;
    type Output = Interval;
}

impl<T> Add for Nullable<T>
where
    T: Add + SqlType<IsNull = is_nullable::NotNull>,
    T::Rhs: SqlType<IsNull = is_nullable::NotNull>,
    T::Output: SqlType<IsNull = is_nullable::NotNull>,
{
    type Rhs = Nullable<T::Rhs>;
    type Output = Nullable<T::Output>;
}

impl<T> Sub for Nullable<T>
where
    T: Sub + SqlType<IsNull = is_nullable::NotNull>,
    T::Rhs: SqlType<IsNull = is_nullable::NotNull>,
    T::Output: SqlType<IsNull = is_nullable::NotNull>,
{
    type Rhs = Nullable<T::Rhs>;
    type Output = Nullable<T::Output>;
}

impl<T> Mul for Nullable<T>
where
    T: Mul + SqlType<IsNull = is_nullable::NotNull>,
    T::Rhs: SqlType<IsNull = is_nullable::NotNull>,
    T::Output: SqlType<IsNull = is_nullable::NotNull>,
{
    type Rhs = Nullable<T::Rhs>;
    type Output = Nullable<T::Output>;
}

impl<T> Div for Nullable<T>
where
    T: Div + SqlType<IsNull = is_nullable::NotNull>,
    T::Rhs: SqlType<IsNull = is_nullable::NotNull>,
    T::Output: SqlType<IsNull = is_nullable::NotNull>,
{
    type Rhs = Nullable<T::Rhs>;
    type Output = Nullable<T::Output>;
}