Swift在从Objective C桥接到Swift时没有显示返回类型。如何获得返回值？

Question

当从Objective C桥接到Swift时，Swift没有显示函数的返回类型。这里有什么问题以及如何获得返回值？

// Objective C

#import <Foundation/Foundation.h>

@interface Test: NSObject

+(BOOL)testName :(NSString*)name challenge:(NSString**)challenge error:(NSError**)error;

@end

// Swift
import Foundation

open class Test : NSObject {

    open class func testName(_ name: String!, challenge: AutoreleasingUnsafeMutablePointer<NSString?>!) throws
}

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