Microsoft/TypeScript

Parser does not reject `await a as any ** 1`

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#41,755 创建于 2020年12月1日

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 (8 评论) (0 反应) (0 负责人)TypeScript (48,455 star) (6,726 fork)batch import
BugDomain: API: TransformsEffort: ModerateHelp Wanted

描述

TypeScript Version: 4.2.0-dev.20201201

Search Terms: exponentiation, await

Code

await a as any ** 1

Expected behavior: Parser should throw

An unary expression with the 'await' operator is not allowed in the left-hand side of an exponentiation expression. Consider enclosing the expression in parentheses.

Actual behavior: Does not throw

Playground Link: https://www.typescriptlang.org/play?ts=4.2.0-dev.20201201#code/G4QwTgBCELwQCmA9gWwJYGcCmA6MWMkAbYLACgEYBKAbgCgQMBPAOwGMIyrYA+KAdxBoALlCgYoLJhABUMiBSA

Related Issues: https://github.com/microsoft/TypeScript/issues/40916, since in November meeting we have reached consensus that await x ** 1 is illegal and the parser already throws on await a! ** 1, I think it should either throw for await a as any ** 1, or add parenthesis in the output for await a if as any serves as an implicit parenthesis.

贡献者指南

技术栈
typescript
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。
3
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。
clear
前置要求
TypeScript parser basicsExponentiation operator precedence
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。
70
研究方向
The issue is that the parser currently does not reject `await a as any ** 1`. The fix likely involves adding a check in the parser (src/compiler/parser.ts) similar to the existing check for `await a! ** 1`. Review the related issue #40916 and the discussion in the comments. The expected behavior is to throw an error about unary expression with await not allowed on left hand side of exponentiation.