swiftlang/swift

[SR-5337] Improve diagnostic for 'var' in parameter position

Open

#47,911 创建于 2017年6月29日

在 GitHub 查看
 (2 评论) (0 反应) (0 负责人)Swift (69,989 star) (10,719 fork)batch import
compilerdiagnostics qualitygood first issueimprovement

描述
Previous ID SR-5337
Radar None
Original Reporter @CodaFi
Type Improvement
Votes 1
Component/s Compiler
Labels Improvement, DiagnosticsQoI, StarterBug
Assignee None
Priority Medium

md5: df452a4dc52959caff3a154681f76513

Issue Description:

For code that looks like this

func foo(inout x : Int) {}

or

func foo(_ f : (Int) -> Void) {}

foo { (var x) in
  
}

We used to offer to remove the errant 'var' specifier and extract it into a variable in the body of the function/closure. This diagnostic necessitated a compromise in our modeling of parameter declarations that I have removed. In its place, it would be nice to have a diagnostic of similar quality.

Some ideas would be to redo the old diagnostic, but by first "enqueueing" it then emitting the variable into the body of the function/closure after we parse the opening brace/'in' after a parameter list. Or we could simply do what we do for 'inout' and remove the 'var' specifier then assume the user actually wanted 'inout', etc.

贡献者指南

技术栈
swiftcpp
领域
developer experiencetooling
议题类型
feature
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。
4
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。
over 1 week
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。
clear
前置要求
Swift programmingCompiler internalsDiagnostic engineering
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。
25
研究方向
First, study the Swift compiler's parsing of parameter declarations and the current diagnostic handling for 'var' in that position. Look at the git history for recent changes to the diagnostic system that removed the old compromise. Then, design a new diagnostic that removes the 'var' specifier and introduces a variable declaration in the function/closure body. The implementation should likely modify the parser or the diagnostic emitter to enqueue a fix it after parsing the opening brace. Review related files in the 'lib/Parse' and 'lib/Sema' directories.
[SR-5337] Improve diagnostic for 'var' in parameter position · swiftlang/swift#47911 | Good First Issue