# [−][src]Macro std::todo

    macro_rules! todo {
        () => { ... };
        ($ ($ arg : tt) +) => { ... };
    }

🔬 This is a nightly-only experimental API. (`todo_macro` #59277)

Indicates unfinished code.

This can be useful if you are prototyping and are just looking to have your code typecheck. `todo!` works exactly like `unimplemented!`. The only difference between the two macros is the name.

# Panics

This will always panic!

# Examples

Here's an example of some in-progress code. We have a trait `Foo`:

    trait Foo {
        fn bar(&self);
        fn baz(&self);
    }Run

We want to implement `Foo` on one of our types, but we also want to work on just `bar()` first. In order for our code to compile, we need to implement `baz()`, so we can use `todo!`:

    #![feature(todo_macro)]

    struct MyStruct;

    impl Foo for MyStruct {
        fn bar(&self) {
            // implementation goes here
        }

        fn baz(&self) {
            // let's not worry about implementing baz() for now
            todo!();
        }
    }

    fn main() {
        let s = MyStruct;
        s.bar();

        // we aren't even using baz() yet, so this is fine.
    }Run

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