rust/tests/ui/write_literal.rs

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#![allow(unused_must_use)]
#![warn(write_literal)]
use std::io::Write;
fn main() {
let mut v = Vec::new();
// These should be fine
write!(&mut v, "Hello");
writeln!(&mut v, "Hello");
let world = "world";
writeln!(&mut v, "Hello {}", world);
writeln!(&mut v, "3 in hex is {:X}", 3);
// These should throw warnings
write!(&mut v, "Hello {}", "world");
writeln!(&mut v, "Hello {} {}", world, "world");
writeln!(&mut v, "Hello {}", "world");
writeln!(&mut v, "10 / 4 is {}", 2.5);
writeln!(&mut v, "2 + 1 = {}", 3);
writeln!(&mut v, "2 + 1 = {:.4}", 3);
writeln!(&mut v, "2 + 1 = {:5.4}", 3);
writeln!(&mut v, "Debug test {:?}", "hello, world");
// positional args don't change the fact
// that we're using a literal -- this should
// throw a warning
writeln!(&mut v, "{0} {1}", "hello", "world");
writeln!(&mut v, "{1} {0}", "hello", "world");
// named args shouldn't change anything either
writeln!(&mut v, "{foo} {bar}", foo = "hello", bar = "world");
writeln!(&mut v, "{bar} {foo}", foo = "hello", bar = "world");
}