Swift:从接口类型数组转换为Object数组崩溃

我有一个符合接口的对象数组

interface SomeInterface{}

和一个符合该接口的类

class SomeClass : NSObject, SomeInterface{}

现在,我创建一个SomeInterface对象数组

var myInterfaceObjects : SomeInterface[] = SomeInterface[]()

然后我想将此数组转换为SomeClass对象数组

var someClassObjects : SomeClass[] = myInterfaceObjects as SomeClass[] //CRASH!

我如何在没有崩溃的情况下垂头丧气？

fatal error: can't reinterpretCast values of different sizes
(lldb) bt
* thread #1: tid = 0x935ef, 0x001986b8 libswift_stdlib_core.dylib`Swift.reinterpretCast (A) -> B + 220, queue = 'com.apple.main-thread', stop reason = EXC_BREAKPOINT (code=EXC_ARM_BREAKPOINT, subcode=0xe7ffdefe)
  * frame #0: 0x001986b8 libswift_stdlib_core.dylib`Swift.reinterpretCast (A) -> B + 220
    frame #1: 0x001bebdc libswift_stdlib_core.dylib`Swift.ContiguousArrayBuffer.storesOnlyElementsOfType (Swift.ContiguousArrayBuffer)(B.Type) -> Swift.Bool + 912
    frame #2: 0x001bde08 libswift_stdlib_core.dylib`Swift._arrayCheckedDownCast (Swift.Array) -> Swift.Optional> + 292
    frame #3: 0x00094c84 MyApp`MyApp.MyClass.(data=SomeInterface[]! at 0x27db0870, response=Foundation.NSHTTPURLResponse! at 0x27db086c, error=None, self=) -> (Swift.Bool) -> ()).(closure #1) + 428 at MyClass.swift:81

var someClassObjects : [SomeClass] = myInterfaceObjects.map { $0 as SomeClass }