Rust playground illustrating the issue

I have a struct (call it Collection) which implements IntoIterator. I'd like to be able to instantiate this struct using from, passing in another IntoIterator:

let collection = Collection::from([1, 2, 3]);

So, I believe I need to implement From<impl IntoIterator> for Collection. However, this results in conflicting implementations of From with the default blanket implementation From<T> for T.

• Collection implements From<I> where I: IntoIterator
• Collection implements IntoIterator
• Collection could be I
• This gives From<Collection> for Collection
• Which has the same signature as the blanket From<T> for T, resulting in the conflict

I haven't been able to find any way around this... I was thinking I could exclude Collection from I, but this requires negative_impls, which is unstable.

This feels like a fairly common pattern? Looking at the docs for Vec<> I can see it implements From<> with brute force for the common iterable types, but I was hoping to be able to write something more generic.

I have of course already implemented FromIterator for Collection, so I can construct it with from_iter() – I just want to make the shorter from() work too.

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