44440e5c18
fmt::Show is for debugging, and can and should be implemented for
all public types. This trait is used with `{:?}` syntax. There still
exists #[derive(Show)].
fmt::String is for types that faithfully be represented as a String.
Because of this, there is no way to derive fmt::String, all
implementations must be purposeful. It is used by the default format
syntax, `{}`.
This will break most instances of `{}`, since that now requires the type
to impl fmt::String. In most cases, replacing `{}` with `{:?}` is the
correct fix. Types that were being printed specifically for users should
receive a fmt::String implementation to fix this.
Part of #20013
[breaking-change]
61 lines
1.5 KiB
Rust
61 lines
1.5 KiB
Rust
// Copyright 2012 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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pub mod kitty {
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use std::fmt;
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pub struct cat {
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meows : uint,
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pub how_hungry : int,
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pub name : String,
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}
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impl fmt::String for cat {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "{}", self.name)
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}
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}
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impl cat {
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fn meow(&mut self) {
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println!("Meow");
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self.meows += 1u;
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if self.meows % 5u == 0u {
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self.how_hungry += 1;
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}
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}
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}
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impl cat {
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pub fn speak(&mut self) { self.meow(); }
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pub fn eat(&mut self) -> bool {
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if self.how_hungry > 0 {
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println!("OM NOM NOM");
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self.how_hungry -= 2;
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return true;
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}
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else {
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println!("Not hungry!");
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return false;
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}
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}
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}
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pub fn cat(in_x : uint, in_y : int, in_name: String) -> cat {
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cat {
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meows: in_x,
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how_hungry: in_y,
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name: in_name
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}
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}
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}
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