43 lines
1.1 KiB
Rust
43 lines
1.1 KiB
Rust
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
|
|
// file at the top-level directory of this distribution and at
|
|
// http://rust-lang.org/COPYRIGHT.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
|
// option. This file may not be copied, modified, or distributed
|
|
// except according to those terms.
|
|
|
|
pub struct Nullable<T: NotNull>(T);
|
|
|
|
pub trait NotNull {}
|
|
|
|
pub trait IntoNullable {
|
|
type Nullable;
|
|
}
|
|
|
|
impl<T: NotNull> IntoNullable for T {
|
|
type Nullable = Nullable<T>;
|
|
}
|
|
|
|
impl<T: NotNull> IntoNullable for Nullable<T> {
|
|
type Nullable = Nullable<T>;
|
|
}
|
|
|
|
pub trait Expression {
|
|
type SqlType;
|
|
}
|
|
|
|
pub trait Column: Expression {}
|
|
|
|
#[derive(Debug, Copy, Clone)]
|
|
//~^ ERROR the trait bound `<Col as Expression>::SqlType: NotNull` is not satisfied
|
|
pub enum ColumnInsertValue<Col, Expr> where
|
|
Col: Column,
|
|
Expr: Expression<SqlType=<Col::SqlType as IntoNullable>::Nullable>,
|
|
{
|
|
Expression(Col, Expr),
|
|
Default(Col),
|
|
}
|
|
|
|
fn main() {}
|