specialisation error 502 is misleading

[nrc]

error[E0520]: `Foo` specializes an item from a parent `impl`, but neither that item nor the `impl` are marked `default`

Because the impl itself cannot be marked default, only the individual item.

[giannicic]

Hi, I'm very new to rust and I'm trying to learn more about this language.
I would like to make the change. Seems that I have to change the error text (e.g. ..., but the item of the parent impl is not marked default), Is it right?
However searching about specialization documents I found this issue rust/issues/31844 where seems that a default implwill be possible.
Am i missing something?

[nrc]

The text should suggest that the item could be default, but not that the parent impl could be, because it can't. It might be in the future (as suggested by #31844) but that is not certain.

[giannicic]

Hi @nrc ,
I'm seeing a bit more deep the specialization feature. I'm wondering if I can try to implement the default impl.
I have in mind to do what is described in the following quotes taken from the RFC

we could easily add a shorthand later on in which default impl Trait for Type is sugar for adding default to all items in the impl.

For the moment, with this implementation, the default impl must define all items of the trait (not a part of them) and, therefore, they will be all treated as default items.
Would you accept a PR for this?

[nrc]

@giannicic there is some debate at the moment about some of the details of specialisation. It would probably be best to open a thread on internals.rust-lang.org before starting to work on this.

[kyrias]

PR #36652 was merged, so this can be closed now.