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Cannot define an arrow function with a single generic type parameter that has a default value with JSXΒ #47062

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@giladgo

Description

@giladgo

Bug Report

πŸ”Ž Search Terms

typescript
jsx
tsx
generic
arrow function
default value

πŸ•— Version & Regression Information

  • This is the behavior in every version I tried, and I reviewed the FAQ for entries about generics.

⏯ Playground Link

Playground link with relevant code

πŸ’» Code

import React from 'react'

const myFunc = <T = string,>() => {

}

πŸ™ Actual behavior

The typescript compiler throws multiple errors

πŸ™‚ Expected behavior

I would be allowed to create an arrow function with a single type parameter that has a default value.

Note:

  • This happens only on with JSX enabled
  • Removing the default value (= string) doesn't throw errors
  • Adding a second type parameter before T, ie <K, T=string> doesn't throw errors

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