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• Would you like to work on a fix?

How are you using Babel?

Programmatic API (babel.transform, babel.parse)

Input code

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Configuration file name

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Configuration

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Current and expected behavior

I noticed that in Babel 8 the node definitions for LHS positions are defined incorrectly, e.g.:

and

and

and some more places, worth combing through all definitions.

For example, OptionalMemberExpression is not valid assignment target - you can't do foo?.bar = 42;. Same for TSAsExpression - foo as number = 42; is not legal either. Some other TS node types I'm not sure about, worth checking.

It's also not clear why those places use manual lists instead of the old LVal alias, although that alias currently also includes problematic node types like:

• RestElement:

  babel/packages/babel-types/src/definitions/core.ts

  Line 1005 in f68ac51

  aliases: ["LVal", "PatternLike"],

• AssignmentPattern:

  babel/packages/babel-types/src/definitions/core.ts

  Line 1295 in f68ac51

  aliases: ["Pattern", "PatternLike", "LVal"],

These nodes can't be LVal by themselves, they are just pattern-like nodes that can appear inside other patterns but not by themselves.

Environment

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Possible solution

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Additional context

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