I don't know how JSC handles it, but in SM `eval` has significant negative effects on surrounding code. (We also decline to optimize functions containing `with` statements, but that's less because it's impossible and more because nobody uses them.)

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cogman10 8 hours ago | parent | next [-]

Last I saw (and I admit this is pretty dated) V8 was doing the same thing. try/catch at one point in V8 would cause the surrounding method to be deoptimized.

	▲	IainIreland 8 hours ago \| parent [-]
		Yeah, SM will compile functions with try/catch/finally, but we don't support unwinding directly into optimized code, so the catch block itself will not be optimized.

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pizlonator 7 hours ago | parent | prev [-]

JSC will still JIT optimize functions that use eval.

It’s true that there are some necessary pessimizations but nothing as severe as failing to optimize the code at all