Microsoft/TypeScript

Precedence in parsing types

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#7,094 创建于 2016年2月16日

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 (5 评论) (0 反应) (0 负责人)TypeScript (48,455 star) (6,726 fork)batch import
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描述

It looks to me like this should parse, but it doesn't:

var x: number | (string)=>void;

It works with added parens:

var x: number | ((string)=>void);

But if the parser is not too hacky, then maybe it's easy to make the first work?

(FWIW, I ran into this in a rest argument, where it would be nice to avoid the extra parens in

function foo(...xs: (number | ()=>void)[]): void { }

)

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typescript
领域
tooling
议题类型
bug
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前置要求
TypeScript syntaxparsing concepts
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。
30
研究方向
The TypeScript parser is in `src/compiler/parser.ts`. Look for how union types are parsed (likely in `parseUnionType` or similar) and how function types are parsed. The issue is that when a union type contains a function type on the right side, the parser incorrectly interprets the arrow without parentheses. Add logic to handle this precedence correctly without requiring extra parentheses.