impl TrustedLen for all RangeFrom<A>, IterRangeFrom<A>

[Dan54]

Remove the A: TrustedStep requirement for std::ops::RangeFrom<A> and std::range::IterRangeFrom<A> to implement TrustedLen.

These iterators cannot return None, so returning (usize::MAX, None) from size_hint() is always correct

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[hanna-kruppe]

Does this actually make a difference? From a quick glance at the docs, seems like all types that implement Step (required for RangeFrom to be an iterator) also implement TrustedStep.

[Dan54]

Does this actually make a difference? From a quick glance at the docs, seems like all types that implement Step (required for RangeFrom to be an iterator) also implement TrustedStep.

This is true in std, but Step is public, so it may not be true for other crates.

[hanna-kruppe]

It's an unstable trait, though, and judging by the tracking issue it's one that probably won't be stabilized without major changes. So I'd be surprised if other crates are seriously implementing it. Do you have an example in mind?

[Dan54]

I mainly did this as it was low hanging fruit, I don't have a specific example where this happens.