|  | warning: `#[must_use]` attribute cannot be used on trait methods in impl blocks | 
|  | --> $DIR/fn_must_use.rs:41:5 | 
|  | | | 
|  | LL |     #[must_use] | 
|  | |     ^^^^^^^^^^^ | 
|  | | | 
|  | = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! | 
|  | = help: `#[must_use]` can be applied to data types, foreign functions, functions, inherent methods, provided trait methods, required trait methods, traits, and unions | 
|  | = note: requested on the command line with `-W unused-attributes` | 
|  |  | 
|  | warning: unused return value of `need_to_use_this_value` that must be used | 
|  | --> $DIR/fn_must_use.rs:57:5 | 
|  | | | 
|  | LL |     need_to_use_this_value(); | 
|  | |     ^^^^^^^^^^^^^^^^^^^^^^^^ | 
|  | | | 
|  | = note: it's important | 
|  | note: the lint level is defined here | 
|  | --> $DIR/fn_must_use.rs:3:9 | 
|  | | | 
|  | LL | #![warn(unused_must_use)] | 
|  | |         ^^^^^^^^^^^^^^^ | 
|  | help: use `let _ = ...` to ignore the resulting value | 
|  | | | 
|  | LL |     let _ = need_to_use_this_value(); | 
|  | |     +++++++ | 
|  |  | 
|  | warning: unused return value of `MyStruct::need_to_use_this_method_value` that must be used | 
|  | --> $DIR/fn_must_use.rs:62:5 | 
|  | | | 
|  | LL |     m.need_to_use_this_method_value(); | 
|  | |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | 
|  | | | 
|  | help: use `let _ = ...` to ignore the resulting value | 
|  | | | 
|  | LL |     let _ = m.need_to_use_this_method_value(); | 
|  | |     +++++++ | 
|  |  | 
|  | warning: unused return value of `EvenNature::is_even` that must be used | 
|  | --> $DIR/fn_must_use.rs:63:5 | 
|  | | | 
|  | LL |     m.is_even(); // trait method! | 
|  | |     ^^^^^^^^^^^ | 
|  | | | 
|  | = note: no side effects | 
|  | help: use `let _ = ...` to ignore the resulting value | 
|  | | | 
|  | LL |     let _ = m.is_even(); // trait method! | 
|  | |     +++++++ | 
|  |  | 
|  | warning: unused return value of `MyStruct::need_to_use_this_associated_function_value` that must be used | 
|  | --> $DIR/fn_must_use.rs:66:5 | 
|  | | | 
|  | LL |     MyStruct::need_to_use_this_associated_function_value(); | 
|  | |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | 
|  | | | 
|  | help: use `let _ = ...` to ignore the resulting value | 
|  | | | 
|  | LL |     let _ = MyStruct::need_to_use_this_associated_function_value(); | 
|  | |     +++++++ | 
|  |  | 
|  | warning: unused return value of `std::cmp::PartialEq::eq` that must be used | 
|  | --> $DIR/fn_must_use.rs:72:5 | 
|  | | | 
|  | LL |     2.eq(&3); | 
|  | |     ^^^^^^^^ | 
|  | | | 
|  | help: use `let _ = ...` to ignore the resulting value | 
|  | | | 
|  | LL |     let _ = 2.eq(&3); | 
|  | |     +++++++ | 
|  |  | 
|  | warning: unused return value of `std::cmp::PartialEq::eq` that must be used | 
|  | --> $DIR/fn_must_use.rs:73:5 | 
|  | | | 
|  | LL |     m.eq(&n); | 
|  | |     ^^^^^^^^ | 
|  | | | 
|  | help: use `let _ = ...` to ignore the resulting value | 
|  | | | 
|  | LL |     let _ = m.eq(&n); | 
|  | |     +++++++ | 
|  |  | 
|  | warning: unused comparison that must be used | 
|  | --> $DIR/fn_must_use.rs:76:5 | 
|  | | | 
|  | LL |     2 == 3; | 
|  | |     ^^^^^^ the comparison produces a value | 
|  | | | 
|  | help: use `let _ = ...` to ignore the resulting value | 
|  | | | 
|  | LL |     let _ = 2 == 3; | 
|  | |     +++++++ | 
|  |  | 
|  | warning: unused comparison that must be used | 
|  | --> $DIR/fn_must_use.rs:77:5 | 
|  | | | 
|  | LL |     m == n; | 
|  | |     ^^^^^^ the comparison produces a value | 
|  | | | 
|  | help: use `let _ = ...` to ignore the resulting value | 
|  | | | 
|  | LL |     let _ = m == n; | 
|  | |     +++++++ | 
|  |  | 
|  | warning: 9 warnings emitted | 
|  |  |