Issue Description:

Enum cases can conform to protocol static func requirements. However, when the static func involves closures, the error messages produced by the compiler can seem confusing. Take this case:

enum MyEnum: MyProtocol { // Error: Type `MyEnum` does not conform to protocol `MyProtocol`
  case one(value: (Bool) -> Void) 
}
 
protocol MyProtocol { 
  static func one(value: (Bool) -> Void) -> Self 
}

For this, the compiler will show an error on `enum MyEnum` as seen above. If you apply Xcode's "fix it", you would get the following code generated, which leads to another error:

enum MyEnum: MyProtocol {
  static func one(value: (Bool) -> Void) -> MyEnum { // Error: Invalid redeclaration of one(value:)
    code...   
  }
  case one(value: (Bool) -> Void) 

However, the reason that `MyEnum` did not conform to `MyProtocol` was because the closure was not marked `@escaping` in the protocol requirements. Perhaps, the error message for this instance can be improved to notify the programmer of this condition.