--- /dev/null
+// run-rustfix
+
+#![allow(clippy::print_literal, clippy::redundant_clone)]
+#![warn(clippy::useless_format)]
+
+struct Foo(pub String);
+
+macro_rules! foo {
+ ($($t:tt)*) => (Foo(format!($($t)*)))
+}
+
+fn main() {
+ "foo".to_string();
+ "{}".to_string();
+ "{} abc {}".to_string();
+ r##"foo {}
+" bar"##.to_string();
+
+ "foo".to_string();
+ format!("{:?}", "foo"); // Don't warn about `Debug`.
+ format!("{:8}", "foo");
+ format!("{:width$}", "foo", width = 8);
+ "foo".to_string(); // Warn when the format makes no difference.
+ "foo".to_string(); // Warn when the format makes no difference.
+ format!("foo {}", "bar");
+ format!("{} bar", "foo");
+
+ let arg: String = "".to_owned();
+ arg.to_string();
+ format!("{:?}", arg); // Don't warn about debug.
+ format!("{:8}", arg);
+ format!("{:width$}", arg, width = 8);
+ arg.to_string(); // Warn when the format makes no difference.
+ arg.to_string(); // Warn when the format makes no difference.
+ format!("foo {}", arg);
+ format!("{} bar", arg);
+
+ // We don’t want to warn for non-string args; see issue #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");
+
+ // 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);
+
+ 42.to_string();
+ let x = std::path::PathBuf::from("/bar/foo/qux");
+ x.display().to_string();
+
+ // False positive
+ let a = "foo".to_string();
+ let _ = Some(a + "bar");
+}