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Type constraint lost in conditional type #43578
Description
Bug Report
🔎 Search Terms
- extends
- contain
- constraint
🕗 Version & Regression Information
4.3.0-dev.20210407
This was working in the TS 4.3 beta
⏯ Playground Link
💻 Code
export type AddFirstParameterToFunctions<Target> = {
[K in keyof Target]: Target[K] extends (...args: any[]) => void
? (...args: Parameters<Target[K]>) => void
: void
};🙁 Actual behavior
Parameters<Target[K]> has the error:
Type 'Target[K]' does not satisfy the constraint '(...args: any) => any'.
Type 'Target[keyof Target]' is not assignable to type '(...args: any) => any'.
Type 'Target[string] | Target[number] | Target[symbol]' is not assignable to type '(...args: any) => any'.
Type 'Target[string]' is not assignable to type '(...args: any) => any'
🙂 Expected behavior
This code previously compiled without errors in the TS 4.3-beta
Activity
Update to daily TS and workaround TS 4.3 issue
Build with latest TS nightly (#120690)
DanielRosenwasser commentedon Apr 7, 2021
It's likely that #43439 changed something up if it's a difference since the beta. Anders Hejlsberg (@ahejlsberg) and Wesley Wigham (@weswigham) might want to take a look at this.
[-]Type constrain lost in conditional type[/-][+]Type constraint lost in conditional type[/+]weswigham commentedon Apr 7, 2021
That PR had a carve out for TypeParameters for compat - it can probably be relatively safely expanded to all TypeVariables to cover this case.