Suggest using the enum when a variant is used as a type

[Wilfred]

Consider the code:

enum Fruit {
    Apple(i64),
    Orange(i64),
}

fn should_return_fruit() -> Apple {
    Apple(5)
}

The current error wording is:

error[E0412]: type name `Apple` is undefined or not in scope
 --> <anon>:7:29
  |
7 | fn should_return_fruit() -> Apple {
  |                             ^^^^^ undefined or not in scope
  |
  = help: no candidates by the name of `Apple` found in your project; maybe you misspelled the name or forgot to import an external crate?

I periodically make this exact mistake. It would be really nice if rustc could spot this error and say did you mean Fruit?

[Aatch]

I'm not sure about your exact case, but I think such a suggestion for this:

enum Fruit {
    Apple(i64),
    Orange(i64),
}

fn should_return_fruit() -> Fruit::Apple {
    Fruit::Apple(5)
}

Or, more likely, this:

use Fruit::*;
enum Fruit {
    Apple(i64),
    Orange(i64),
}

fn should_return_fruit() -> Apple {
    Apple(5)
}

Makes sense, and likely isn't too hard to implement.

[retep998]

Or, more likely, this:

use Fruit::*;
enum Fruit {
    Apple(i64),
    Orange(i64),
}

fn should_return_fruit() -> Apple {
    Apple(5)
}

@Aatch I'm pretty sure that is invalid because Apple isn't a type and cannot be specified as the return type for should_return_fruit.

[Aatch]

@retep998 that's the point. I meant that suggestion should work in those cases, but not the original example, as Apple isn't in scope.

By "more likely", I meant that it's more likely to come up than the first example.

[sanxiyn]

@Aatch's example gives this error, which seems good to me:

error[E0248]: found value `Fruit::Apple` used as a type
 --> 35675.rs:8:29
  |
8 | fn should_return_fruit() -> Apple {
  |                             ^^^^^ value used as a type

That is, different errors are given depending on whether name is in scope.