REPLだとimport Foundation前に評価すると、インポート前も後もfalse

$ swift Welcome to Apple Swift version 5.2 (swiftlang-1103.0.32.1 clang-1103.0.32.29). Type :help for assistance. 1> let a: Bool = nil as String? is AnyObject a: Bool = false 2> import Foundation 3> let b: Bool = nil as String? is AnyObject b: Bool = false 4> ^D

評価前にimport Foundationするとtrue

$ swift Welcome to Apple Swift version 5.2 (swiftlang-1103.0.32.1 clang-1103.0.32.29). Type :help for assistance. 1> import Foundation 2> let a: Bool = nil as String? is AnyObject a: Bool = true