error[E0596]: cannot borrow data in a `&` reference as mutable
  --> $DIR/index-mut-help.rs:21:5
   |
LL |     map["peter"].clear();           //~ ERROR
   |     ^^^^^^^^^^^^ cannot borrow as mutable
   |
   = help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `std::collections::HashMap<&str, std::string::String>`

error[E0594]: cannot assign to data in a `&` reference
  --> $DIR/index-mut-help.rs:22:5
   |
LL |     map["peter"] = "0".to_string(); //~ ERROR
   |     ^^^^^^^^^^^^ cannot assign

error[E0596]: cannot borrow data in a `&` reference as mutable
  --> $DIR/index-mut-help.rs:23:13
   |
LL |     let _ = &mut map["peter"];      //~ ERROR
   |             ^^^^^^^^^^^^^^^^^ cannot borrow as mutable
   |
   = help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `std::collections::HashMap<&str, std::string::String>`

error: aborting due to 3 previous errors

Some errors occurred: E0594, E0596.
For more information about an error, try `rustc --explain E0594`.