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Coherence constraints for Choose #2

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ebfull opened this issue Oct 23, 2015 · 0 comments
Open

Coherence constraints for Choose #2

ebfull opened this issue Oct 23, 2015 · 0 comments

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@ebfull
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ebfull commented Oct 23, 2015

None of these have safety implications, but there are a number of coherence constraints ideal for Choose:

  • We don't want types like Choose<A, Choose<B, Finally<A>>> to be expressible. That is, there exists no Chooser<A, B> such that Chooser<A, B>: Chooser<S> and B: Chooser<S>.
  • We should ensure that Choose<P, Q> only allows Choose and Finally to exist as Q.
  • Finally should not exist outside of Choose, if possible.

As a bonus, it may not be necessary to use Finally at all, but I am doubtful.
@ebfull ebfull changed the title Well-formedness for Choose Coherence constraints for Choose Oct 23, 2015
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