rust/tests/ui/format.rs
Philipp Hansch ff98e3f9f5
Fix useless_format false positive with macros
Clippy was issuing a warning when `format!` was used inside a macro.
That's a problem because macros have different syntax and can be outside
the control of the user.

This skips the `useless_format` check if the `format!` call is inside a
macro.
2018-04-05 07:52:26 +02:00

44 lines
1.0 KiB
Rust
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#![warn(useless_format)]
struct Foo(pub String);
macro_rules! foo {
($($t:tt)*) => (Foo(format!($($t)*)))
}
fn main() {
format!("foo");
format!("{}", "foo");
format!("{:?}", "foo"); // we only want to warn about `{}`
format!("{:+}", "foo"); // we only want to warn about `{}`
format!("foo {}", "bar");
format!("{} bar", "foo");
let arg: String = "".to_owned();
format!("{}", arg);
format!("{:?}", arg); // we only want to warn about `{}`
format!("{:+}", arg); // we only want to warn about `{}`
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);
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");
}