Change assignability to account for type parameters extending unions #2778
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JsonFreeman
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Apr 15, 2015
Change assignability to account for type parameters extending unions
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Fixes #2576.
Right now, there are only three ways that a type parameter S can be assignable to a type T:
What is missing is a case that handles the base constraint of S being a union type. My proposal in this case is that S should be assignable to T if the base constraint of S is assignable to T.
This necessitates an accompanying change to the spec.