How do you test functions and closures for equality?

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Chris Lattner wrote on the developer forums:

This is a feature we intentionally do not want to support. There are
a variety of things that will cause pointer equality of functions (in
the swift type system sense, which includes several kinds of closures)
to fail or change depending on optimization. If “===” were defined on
functions, the compiler would not be allowed to merge identical method
bodies, share thunks, and perform certain capture optimizations in
closures. Further, equality of this sort would be extremely
surprising in some generics contexts, where you can get reabstraction
thunks that adjust the actual signature of a function to the one the
function type expects.

https://devforums.apple.com/message/1035180#1035180

This means that you should not even try to compare closures for equality because optimizations may affect the outcome.

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