Misc 3 @WaffleLapkin @BoxyUwU

Warning: this quiz is still "work-in-progress", some questions might not have good explanations (or any at all), formatting/structure/titles/etc are not final, and so on. You might want to return here on a later date.

struct Foo {
    func: fn(),
}

fn print_heheh() {
    println!("ferrisUwu")
}

fn bar(foo: Foo) {
    foo.func();
}

fn main() {
    bar(Foo { func: print_heheh });
}
Solution 
error[E0599]: no method named `func` found for struct `Foo` in the current scope
  --> examples/misc_3.rs:10:9
   |
1  | struct Foo {
   | ---------- method `func` not found for this struct
...
10 |     foo.func();
   |         ^^^^ field, not a method
   |
help: to call the function stored in `func`, surround the field access with parentheses
   |
10 |     (foo.func)();
   |     +        +

For more information about this error, try `rustc --explain E0599`.
error: could not compile `code` (example "misc_3") due to 1 previous error

There is a syntactic difference between a method call and a normal call. expr.identifier() is always a method call and Foo does not have a method called func. To call the function stored in a field you need to add parenthesis:

fn bar(foo: Foo) {
    (foo.func)();
}

Note that the same problem does not apply to tuples and tuple structs, because you can't name a method with an integer identifier. i.e. the following would compile:

struct Foo(fn());

fn print_heheh() {
    println!("ferrisUwu")
}

fn main() {
    let foo = Foo(print_heheh);
    foo.0();
}