Swift optional escaping closure parameter

from: swift-users mailing list

Basically, @escaping is valid only on closures in function parameter position. The noescape-by-default rule only applies to these closures at function parameter position, otherwise they are escaping. Aggregates, such as enums with associated values (e.g. Optional), tuples, structs, etc., if they have closures, follow the default rules for closures that are not at function parameter position, i.e. they are escaping.

So optional function parameter is @escaping by default.
@noeascape only apply to function parameter by default.

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