error[E0308]: mismatched types
  --> $DIR/issue-6458-4.rs:11:40
   |
LL |   fn foo(b: bool) -> Result<bool,String> { //~ ERROR mismatched types
   |  ________________________________________^
LL | |     Err("bar".to_string());
   | |                           - help: consider removing this semicolon
LL | | }
   | |_^ expected enum `std::result::Result`, found ()
   |
   = note: expected type `std::result::Result<bool, std::string::String>`
              found type `()`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.