Allow merge to produce union #224
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TylorS
approved these changes
Apr 12, 2018
davidchase
approved these changes
Apr 12, 2018
Frikki
reviewed
Apr 12, 2018
| const s2 = now('a') | ||
| const s = merge(s1, s2) | ||
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| runEffects(s, newDefaultScheduler()) |
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Strange test, but I guess it’s a type assertion test in the IDE. I’m not sure 🤔 it is okay, or do the node tests also check types?
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Yeah, see the readme in test/flow. It'd probably be better to try to get typechecking working in merge's regular unit tests. I tried briefly, but something must not be right in our flow config, since I couldn't get type checking to fail when it should :/
Frikki
approved these changes
Apr 12, 2018
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As per recent discussion, this loosens the type of the 2-stream
mergeto accept streams of different types and produce a stream of the union.At first, this might seem unsafe because you might accidentally call merge with different types, say
AandBwhen you didn't mean to. However, since the resulting stream has a union type,A | B, when you try to use it, for example by mapping it with a functionA => C, the type checker will prevent it. Thus, I believe this is entirely safe, while adding some flexibility for situations where you might actually want to construct a union.