2 let a: String = &String::from("a");
3 //~^ ERROR mismatched types
4 let b: String = &format!("b");
5 //~^ ERROR mismatched types
6 let c: String = &mut format!("c");
7 //~^ ERROR mismatched types
8 let d: String = &mut (format!("d"));
9 //~^ ERROR mismatched types