he/him 
Optimising for…of based on flow types and some basic type inference.pic.twitter.com/dsh59HrQj6
@sebmck More type resolution! See https://github.com/babel/babel/issues/653#issuecomment-78478787 … for more info.pic.twitter.com/1BWyu4FIvn
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@sebmck can babel put out code that checks of it's an array at runtime and does a regular for loop. So you can get speed even w/o inference -
@tikotzky I guess it could, although in those scenarios whether it's an array or not would be constant so the benefits would be tangible. - 2 more replies
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@sebmck can this lead to compile time errors? (Like when assigning to const) or perhaps runtime type checks? -
@ncreen_same Possibly, although it'd be pretty limited and the cases it wouldn't pick up would fail silently and it'd be pretty dangerous. - 1 more reply
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@sebmck That's pretty neat!Thanks. Twitter will use this to make your timeline better. UndoUndo
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