feat(corelib): Iterator::collect (draft)

[julio4]

Implementing collect on Iterator.
Currently a draft PR because I'm having some issues.

fn collect<B, +FromIterator<B, Self::Item>, +Drop<T>>(
    self: T,
) -> B {
    FromIterator::from_iter(self)
}

error: Trait has no implementation in context: Iterator::<T>

Not sure why it's not doing the bound correctly as we're in the default implementation of trait Iterator<T>, so we're sure T is implementing Iterator.

I tried to force trait bound:

fn collect<B, +Iterator<T>, +FromIterator<B, Self::Item>, +Drop<T>>(
    self: T,
) -> B {
    FromIterator::from_iter(self)
}

warning: In a trait, paths of the same trait are not allowed. Did you mean to use Self::?
error: Type mismatch: Iterator::Item and _::Item.

Then tried to enforce bounds on Items:

fn collect<B, impl TIter: Iterator<T>, +FromIterator<B, TIter::Item>, +Drop<T>>(
    self: T,
) -> B {
    FromIterator::from_iter(self)
}

warning: In a trait, paths of the same trait are not allowed. Did you mean to use Self::?
Error: Compilation failed.

The compilation fails without any specific error.

If I replace +Iterator<T> with impl TIter: Self it always fails with error: Trait has no implementation in context: core::iter::traits::iterator::Iterator::<T>.

[reviewable-StarkWare]

This change is 

[orizi]

the first one is definitely the correct one - but some inference is probably missing.
added some specific suggestions.

Reviewed 1 of 3 files at r1, all commit messages.
Reviewable status: 1 of 3 files reviewed, 4 unresolved discussions (waiting on @julio4)

---

corelib/src/test/iter_test.cairo line 17 at r1 (raw file):

    assert_eq!(*arr[0], 0);
    assert_eq!(*arr[1], 1);
    assert_eq!(*arr[2], 2);

Suggestion:

    assert_eq!((0..3_u32).into_iter().collect(), array![0, 1, 2]);

---

corelib/src/iter/traits/iterator.cairo line 99 at r1 (raw file):

    #[inline]
    #[must_use]
    fn collect<B, +FromIterator<B, Self::Item>, +Drop<T>>(

Suggestion:

    fn collect<B, +FromIterator<B, Self::Item>, +Destruct<T>>(

---

corelib/src/iter/traits/iterator.cairo line 99 at r1 (raw file):

    #[inline]
    #[must_use]
    fn collect<B, +FromIterator<B, Self::Item>, +Drop<T>>(

doc

---

corelib/src/iter/traits/iterator.cairo line 102 at r1 (raw file):

        self: T,
    ) -> B {
        FromIterator::from_iter(self)

Suggestion:

        FromIterator::<B, Self::Item>::from_iter::<T, Self>(self)