improved scope struct access

[Wicpar]

This improves the scope struct acces, by adding an into_iter and a safe TryFrom<HashMap>;

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[HeroicKatora]

into_iter(self) looks quite good, sure.

That said, I'm not sure if TryFrom is the right trait here, necessarily. In that the parameter HashSet<String> is quite specific and that specificity is motivated by implementation details primarily.

On the other hand, why not special case the zero-allocation conversion.

I'd be eager to explore alternatives and hear more arguments either.

[Wicpar]

TryFrom can be implemented for any number of types on any given struct, there will never be any conflict unlike with impl x for T. Even if you wish to change the undelying structure you can always replace the implementation with .into_iter().collect() and implement a second TryFrom for the new underlying structure.