rust/tests/ui/format.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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#![allow(clippy::print_literal)]
#![warn(clippy::useless_format)]
struct Foo(pub String);
macro_rules! foo {
($($t:tt)*) => (Foo(format!($($t)*)))
}
fn main() {
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format!("foo");
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format!("{}", "foo");
format!("{:?}", "foo"); // don't warn about debug
format!("{:8}", "foo");
format!("{:width$}", "foo", width = 8);
format!("{:+}", "foo"); // warn when the format makes no difference
format!("{:<}", "foo"); // warn when the format makes no difference
format!("foo {}", "bar");
format!("{} bar", "foo");
let arg: String = "".to_owned();
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format!("{}", arg);
format!("{:?}", arg); // don't warn about debug
format!("{:8}", arg);
format!("{:width$}", arg, width = 8);
format!("{:+}", arg); // warn when the format makes no difference
format!("{:<}", arg); // warn when the format makes no difference
format!("foo {}", arg);
format!("{} bar", arg);
// we dont want to warn for non-string args, see #697
format!("{}", 42);
format!("{:?}", 42);
format!("{:+}", 42);
format!("foo {}", 42);
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format!("{} bar", 42);
// we only want to warn about `format!` itself
println!("foo");
println!("{}", "foo");
println!("foo {}", "foo");
println!("{}", 42);
println!("foo {}", 42);
// A format! inside a macro should not trigger a warning
foo!("should not warn");
// precision on string means slicing without panicking on size:
format!("{:.1}", "foo"); // could be "foo"[..1]
format!("{:.10}", "foo"); // could not be "foo"[..10]
format!("{:.prec$}", "foo", prec = 1);
format!("{:.prec$}", "foo", prec = 10);
format!("{}", 42.to_string());
let x = std::path::PathBuf::from("/bar/foo/qux");
format!("{}", x.display().to_string());
}