Warn when using take_random/2 with a stream

[Devon Estes]

I realized today that Enum.take_random/2 can enter an infinite loop if someone calls it with an unbounded Stream as the enum. I also see that there‘s a warning of sorts (although nothing expressly mentioning a Stream as an enum), but I‘m not sure this is going to address user confusion by this behavior.

Would it make sense to emit a warning when using a Stream as an argument to take_random/2? Clearly since it‘s possible for this to _not_ get stuck in an infinite loop when using a steam we shouldn’t error, but a warning might at least help folks call something that converts the stream to a list before calling take_random/2.

Thoughts?

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Devon Estes
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www.devonestes.com

[José Valim]

I don't think it makes sense to explicitly check on Stream because:

1. Not all streams are infinite

2. Not all infinite streams are %Stream{}

So we would have both false positives and false negatives. Also note this problem happens with reduce, sum, count, etc.

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