56290a0044
This commit is an implementation of [RFC 503][rfc] which is a stabilization story for the prelude. Most of the RFC was directly applied, removing reexports. Some reexports are kept around, however: * `range` remains until range syntax has landed to reduce churn. * `Path` and `GenericPath` remain until path reform lands. This is done to prevent many imports of `GenericPath` which will soon be removed. * All `io` traits remain until I/O reform lands so imports can be rewritten all at once to `std::io::prelude::*`. This is a breaking change because many prelude reexports have been removed, and the RFC can be consulted for the exact list of removed reexports, as well as to find the locations of where to import them. [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0503-prelude-stabilization.md [breaking-change] Closes #20068
55 lines
1.6 KiB
Rust
55 lines
1.6 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::ops::Mul;
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struct Vec2 {
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x: f64,
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y: f64
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}
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impl Copy for Vec2 {}
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// methods we want to export as methods as well as operators
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impl Vec2 {
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#[inline(always)]
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fn vmul(self, other: f64) -> Vec2 {
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Vec2 { x: self.x * other, y: self.y * other }
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}
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}
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// Right-hand-side operator visitor pattern
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trait RhsOfVec2Mul<Result> { fn mul_vec2_by(&self, lhs: &Vec2) -> Result; }
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// Vec2's implementation of Mul "from the other side" using the above trait
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impl<Res, Rhs: RhsOfVec2Mul<Res>> Mul<Rhs,Res> for Vec2 {
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fn mul(self, rhs: Rhs) -> Res { rhs.mul_vec2_by(&self) }
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}
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// Implementation of 'f64 as right-hand-side of Vec2::Mul'
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impl RhsOfVec2Mul<Vec2> for f64 {
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fn mul_vec2_by(&self, lhs: &Vec2) -> Vec2 { lhs.vmul(*self) }
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}
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// Usage with failing inference
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pub fn main() {
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let a = Vec2 { x: 3.0f64, y: 4.0f64 };
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// the following compiles and works properly
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let v1: Vec2 = a * 3.0f64;
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println!("{} {}", v1.x, v1.y);
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// the following compiles but v2 will not be Vec2 yet and
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// using it later will cause an error that the type of v2
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// must be known
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let v2 = a * 3.0f64;
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println!("{} {}", v2.x, v2.y); // error regarding v2's type
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}
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