rust/tests/ui/fallible_impl_from.rs

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// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution.
//
// 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.
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#![deny(clippy::fallible_impl_from)]
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// docs example
struct Foo(i32);
impl From<String> for Foo {
fn from(s: String) -> Self {
Foo(s.parse().unwrap())
}
}
struct Valid(Vec<u8>);
impl<'a> From<&'a str> for Valid {
fn from(s: &'a str) -> Valid {
Valid(s.to_owned().into_bytes())
}
}
impl From<usize> for Valid {
fn from(i: usize) -> Valid {
Valid(Vec::with_capacity(i))
}
}
struct Invalid;
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impl From<usize> for Invalid {
fn from(i: usize) -> Invalid {
if i != 42 {
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panic!();
}
Invalid
}
}
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impl From<Option<String>> for Invalid {
fn from(s: Option<String>) -> Invalid {
let s = s.unwrap();
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if !s.is_empty() {
panic!(42);
} else if s.parse::<u32>().unwrap() != 42 {
panic!("{:?}", s);
}
Invalid
}
}
trait ProjStrTrait {
type ProjString;
}
impl<T> ProjStrTrait for Box<T> {
type ProjString = String;
}
impl<'a> From<&'a mut <Box<u32> as ProjStrTrait>::ProjString> for Invalid {
fn from(s: &'a mut <Box<u32> as ProjStrTrait>::ProjString) -> Invalid {
if s.parse::<u32>().ok().unwrap() != 42 {
panic!("{:?}", s);
}
Invalid
}
}
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struct Unreachable;
impl From<String> for Unreachable {
fn from(s: String) -> Unreachable {
if s.is_empty() {
return Unreachable;
}
match s.chars().next() {
Some(_) => Unreachable,
None => unreachable!(), // do not lint the unreachable macro
}
}
}
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fn main() {}