diff options
| -rw-r--r-- | src/libcore/macros.rs | 59 | ||||
| -rw-r--r-- | src/libstd/lib.rs | 3 |
2 files changed, 61 insertions, 1 deletions
diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs index b052f59b0f5..d77936c7ddd 100644 --- a/src/libcore/macros.rs +++ b/src/libcore/macros.rs @@ -559,6 +559,65 @@ macro_rules! unimplemented { ($($arg:tt)+) => (panic!("not yet implemented: {}", format_args!($($arg)*))); } +/// A standardized placeholder for marking unfinished code. +/// +/// This can be useful if you are prototyping and are just looking to have your +/// code typecheck. `todo!` works exactly like `unimplemented!`, there only +/// difference between the two macros is the name. +/// +/// # Panics +/// +/// This will always [panic!](macro.panic.html) +/// +/// # Examples +/// +/// Here's an example of some in-progress code. We have a trait `Foo`: +/// +/// ``` +/// trait Foo { +/// fn bar(&self); +/// fn baz(&self); +/// } +/// ``` +/// +/// 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)] +/// +/// # trait Foo { +/// # fn bar(&self); +/// # fn baz(&self); +/// # } +/// 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. +/// } +/// ``` +#[macro_export] +#[unstable(feature = "todo_macro", issue = "59277")] +macro_rules! todo { + () => (panic!("not yet implemented")); + ($($arg:tt)+) => (panic!("not yet implemented: {}", format_args!($($arg)*))); +} + /// A macro to create an array of [`MaybeUninit`] /// /// This macro constructs an uninitialized array of the type `[MaybeUninit<K>; N]`. diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs index fc8ac9a0b3e..296c4c88727 100644 --- a/src/libstd/lib.rs +++ b/src/libstd/lib.rs @@ -301,6 +301,7 @@ #![feature(stmt_expr_attributes)] #![feature(str_internals)] #![feature(thread_local)] +#![feature(todo_macro)] #![feature(toowned_clone_into)] #![feature(try_reserve)] #![feature(unboxed_closures)] @@ -323,7 +324,7 @@ use prelude::v1::*; #[stable(feature = "rust1", since = "1.0.0")] pub use core::{assert_eq, assert_ne, debug_assert, debug_assert_eq, debug_assert_ne}; #[stable(feature = "rust1", since = "1.0.0")] -pub use core::{unreachable, unimplemented, write, writeln, r#try}; +pub use core::{unreachable, unimplemented, write, writeln, r#try, todo}; #[allow(unused_imports)] // macros from `alloc` are not used on all platforms #[macro_use] |