> > > 1. This information can be used by typecheckers, and also by users, to >> > reason about programs. If isinstance(x, ImmutableArray), then x is an >> > instantiation of ImmutableArray. >> >> That's how type-checkers work. The class doesn't need to be in the std >> lib for a type-checker to reason about it. >> > No, it's not how they work, since it's not true. I meant the actual type, > not a subtype. > I now see my error - I meant isinstance(x, SealedArray)... sorry. Similarly the reasoning about ImmutableStruct with constant propagation.
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~Elazar >
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