MaybeEquatable.swift

public typealias PartialApplySelfToIsEqual = (Any?) -> Bool
public protocol MaybeEquatable {
    func partialApplySelftoIsEqual() -> PartialApplySelfToIsEqual
}

extension MaybeEquatable {
    public func partialApplySelftoIsEqual() -> PartialApplySelfToIsEqual {
        { _ in false }
    }
}

extension MaybeEquatable where Self: Equatable {
    public func partialApplySelftoIsEqual() -> PartialApplySelfToIsEqual {
        { self == $0 as? Self }
    }
}

extension MaybeEquatable {
    public func isEqual(to other: Any?) -> Bool {
        self.partialApplySelftoIsEqual()(other)
    }
}

// end user interface
public func anyIsEqual(_ a: Any, _ b: Any) -> Bool {
    guard let a = a as? MaybeEquatable else { return false }
    return a.isEqual(to: b)
}

// you need to mark your type
extension String: MaybeEquatable {}

print(anyIsEqual("str", "str")) // => true
print(anyIsEqual({}, {})) // => false

Thanks @omochi https://gist.github.com/omochi/b68706b90134db8c3771195da170d4b5