// ModuleA public extension Array { public var first: Element? { return nil } } // ModuleB public extension Array { public var first: Element? { return self[0] } } // main import ModuleA import ModuleB let a = [1,2,3].first さすがにこれはambigous (edited)// ModuleA public extension Array { public var first: Element? { return nil } } // ModuleB public extension Array { public var first: Element? { return self[0] } } // main import ModuleA import ModuleB let a = [1,2,3].first さすがにこれはambigous (edited)