Microsoft/TypeScript

type.isLiteral() returns false for boolean literals

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#26,075 创建于 2018年7月31日

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 (7 评论) (2 反应) (0 负责人)TypeScript (48,455 star) (6,726 fork)batch import
BugDomain: APIDomain: Literal TypesHelp Wanted

描述

TypeScript Version: 3.1.0-dev.20180728 (new in 3.0.1)

Search Terms: isLiteral()

Code

  1. Create a boolean literal in the compiler api.
  2. Call isLiteral() on it.

Change seems to be done here:

https://github.com/Microsoft/TypeScript/commit/e46d214fceb72cc76145779543bf871ce9ff66b0#diff-233e1126c0abc811c4098757f9e4516eR428

Expected behavior: true for a boolean literal type (true or false)

Actual behavior: false

I have a few tests for assumptions about the compiler api in ts-simple-ast and this one started failing. Maybe it's not a bug, but I thought I would log it anyway to find out why this behaviour changed.

Is it because it doesn't have the Unit flag while string and number literals do? For what it's worth, in checker.ts it will internally return true for boolean literals in isLiteralType.

贡献者指南

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typescript
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developer experiencetooling
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bug
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前置要求
TypeScript compiler API basicsunderstanding of literal types
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
Look at the commit e46d214fceb72cc76145779543bf871ce9ff66b0, specifically the change in checker.ts around line 428 where isLiteralType is defined. The issue is that boolean literals (true/false) are not recognized as literals because they lack the Unit flag. Investigate if adding the Unit flag for boolean literals or adjusting the condition in isLiteralType to include boolean literals would fix the behavior. Check the linked commit and read the current implementation of isLiteralType in the checker.ts file.