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Differentiate todo! and unimplemented!
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llogiq committed Dec 24, 2019
1 parent 99b8953 commit f4d0a04
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Showing 5 changed files with 29 additions and 24 deletions.
45 changes: 25 additions & 20 deletions src/libcore/macros/mod.rs
Expand Up @@ -556,13 +556,15 @@ macro_rules! unreachable {
});
}

/// Indicates unfinished code by panicking with a message of "not yet implemented".
/// Indicates unimplemented code by panicking with a message of "not implemented".
///
/// This allows the your code to type-check, which is useful if you are prototyping or
/// implementing a trait that requires multiple methods which you don't plan of using all of.
///
/// There is no difference between `unimplemented!` and `todo!` apart from the
/// name.
/// The difference between `unimplemented!` and [`todo!`](macro.todo.html) is that while `todo!`
/// conveys an intent of implementing the functionality later and the message is "not yet
/// implemented", `unimplemented!` makes no such claims. Its message is "not implemented".
/// Also some IDEs will mark `todo!`s.
///
/// # Panics
///
Expand All @@ -573,7 +575,7 @@ macro_rules! unreachable {
///
/// # Examples
///
/// Here's an example of some in-progress code. We have a trait `Foo`:
/// Say we have a trait `Foo`:
///
/// ```
/// trait Foo {
Expand All @@ -583,13 +585,13 @@ macro_rules! unreachable {
/// }
/// ```
///
/// We want to implement `Foo` for 'MyStruct', but so far we only know how to
/// implement the `bar()` function. `baz()` and `qux()` will still need to be defined
/// We want to implement `Foo` for 'MyStruct', but for some reason it only makes sense
/// to implement the `bar()` function. `baz()` and `qux()` will still need to be defined
/// in our implementation of `Foo`, but we can use `unimplemented!` in their definitions
/// to allow our code to compile.
///
/// In the meantime, we want to have our program stop running once these
/// unimplemented functions are reached.
/// We still want to have our program stop running if the unimplemented methods are
/// reached.
///
/// ```
/// # trait Foo {
Expand All @@ -605,19 +607,18 @@ macro_rules! unreachable {
/// }
///
/// fn baz(&self) {
/// // We aren't sure how to even start writing baz yet,
/// // so we have no logic here at all.
/// // This will display "thread 'main' panicked at 'not yet implemented'".
/// // It makes no sense to `baz` a `MyStruct`, so we have no logic here
/// // at all.
/// // This will display "thread 'main' panicked at 'not implemented'".
/// unimplemented!();
/// }
///
/// fn qux(&self) -> Result<u64, ()> {
/// let n = self.bar();
/// // We have some logic here,
/// // so we can use unimplemented! to display what we have so far.
/// // We can add a message to unimplemented! to display our omission.
/// // This will display:
/// // "thread 'main' panicked at 'not yet implemented: we need to divide by 2'".
/// unimplemented!("we need to divide by {}", n);
/// // "thread 'main' panicked at 'not implemented: MyStruct isn't quxable'".
/// unimplemented!("MyStruct isn't quxable");
/// }
/// }
///
Expand All @@ -629,17 +630,21 @@ macro_rules! unreachable {
#[macro_export]
#[stable(feature = "rust1", since = "1.0.0")]
macro_rules! unimplemented {
() => (panic!("not yet implemented"));
($($arg:tt)+) => (panic!("not yet implemented: {}", $crate::format_args!($($arg)+)));
() => (panic!("not implemented"));
($($arg:tt)+) => (panic!("not implemented: {}", $crate::format_args!($($arg)+)));
}

/// Indicates unfinished code.
///
/// This can be useful if you are prototyping and are just looking to have your
/// code typecheck.
///
/// There is no difference between `unimplemented!` and `todo!` apart from the
/// name.
/// The difference between [`unimplemented!`] and `todo!` is that while `todo!` conveys
/// an intent of implementing the functionality later and the message is "not yet
/// implemented", `unimplemented!` makes no such claims. Its message is "not implemented".
/// Also some IDEs will mark `todo!`s.
///
/// [`unimplemented!`]: macro.unimplemented.html
///
/// # Panics
///
Expand Down Expand Up @@ -682,7 +687,7 @@ macro_rules! unimplemented {
/// let s = MyStruct;
/// s.bar();
///
/// // we aren't even using baz() yet, so this is fine.
/// // we aren't even using baz(), so this is fine.
/// }
/// ```
#[macro_export]
Expand Down
2 changes: 1 addition & 1 deletion src/test/run-fail/unimplemented-macro-panic.rs
@@ -1,4 +1,4 @@
// error-pattern:not yet implemented
// error-pattern:not implemented
fn main() {
unimplemented!()
}
2 changes: 1 addition & 1 deletion src/test/ui/consts/const-eval/const_panic.stderr
Expand Up @@ -25,7 +25,7 @@ error: any use of this value will cause an error
LL | pub const X: () = unimplemented!();
| ------------------^^^^^^^^^^^^^^^^-
| |
| the evaluated program panicked at 'not yet implemented', $DIR/const_panic.rs:10:19
| the evaluated program panicked at 'not implemented', $DIR/const_panic.rs:10:19
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

Expand Down
2 changes: 1 addition & 1 deletion src/test/ui/consts/const-eval/const_panic_libcore.stderr
Expand Up @@ -25,7 +25,7 @@ error: any use of this value will cause an error
LL | const X: () = unimplemented!();
| --------------^^^^^^^^^^^^^^^^-
| |
| the evaluated program panicked at 'not yet implemented', $DIR/const_panic_libcore.rs:11:15
| the evaluated program panicked at 'not implemented', $DIR/const_panic_libcore.rs:11:15
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

Expand Down
Expand Up @@ -25,7 +25,7 @@ error: any use of this value will cause an error
LL | const X: () = unimplemented!();
| --------------^^^^^^^^^^^^^^^^-
| |
| the evaluated program panicked at 'not yet implemented', $DIR/const_panic_libcore_main.rs:15:15
| the evaluated program panicked at 'not implemented', $DIR/const_panic_libcore_main.rs:15:15
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

Expand Down

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