swiftlang/swift

[SR-1715] NSProxy can not be subclassed

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#44,324 创建于 2016年6月9日

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bugcompilerdiagnostics qualitygood first issue

描述
Previous ID SR-1715
Radar None
Original Reporter manuyavuz (JIRA User)
Type Bug

Xcode 7.3.1 default toolchain
Votes 0
Component/s Compiler
Labels Bug, DiagnosticsQoI, StarterBug
Assignee step (JIRA)
Priority Medium

md5: 6ce9ad56a254833eb119945d8b995454

Issue Description:

Hi,

The following simple code

class MyProxy: NSProxy {
  init(value : Int) {
  } // Compiler error here
}

gives

Super.init isn't called on all paths before  returning from initializer

compiler error.

I can't call super.init() because NSProxy class does not have one.

This means a Swift type can not be subclasses from NSProxy class.

Is this intentional? If so, I think this class should be unavailable while writing Swift code, or at least have a warning in documentation or code reference.

贡献者指南

技术栈
swift
领域
tooling
议题类型
bug
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
2
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
1-3 hours
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
stale
清晰度议题是否清楚说明期望改动、验收标准和下一步。
mostly clear
前置要求
Swift basicsCompiler architecture overview
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
60
研究方向
Investigate the Swift compiler's diagnostic for missing super.init in initializers. The issue indicates that NSProxy lacks a super.init method, so the compiler should either allow subclassing without calling super.init or provide a specialized error. Look for relevant code in the compiler's semantic analysis (e.g., lib/Sema/TypeCheckInitializers.cpp) where the super.init call is enforced, and consider adding an exception for NSProxy. Check the existing comments for any hints or proposed approaches.