Argument of type 'string | String' is not assignable to parameter of type 'string'.

[kkmuffme]

🔎 Search Terms

"string|String" primitive object collapse

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/FDBmFcDsGMBcEsD2kAEpGIBQoLYFMBnAgQwHM8AuFKAa0kQHdUBKFAb2AEhP5QVMunbAEJ+uQiXIp4kArGIw8iPgGVYAJxmkUrAGS6UsAJ4AHJX3xEyeFMIC8dlAHI5myKSc6UAH2+DRAPTEAEbQACYBAHSwhLDYlpI2zFysHFwAvsCZIMBAA

💻 Code

function foo( message: unknown ) {
		if (
		( ! ( message instanceof String ) && typeof message !== 'string' ) ||
		! /abcd/.test( message )
	) {

	}
}

🙁 Actual behavior

Argument of type 'string | String' is not assignable to parameter of type 'string'.
Type 'String' is not assignable to type 'string'.
'string' is a primitive, but 'String' is a wrapper object. Prefer using 'string' when possible.

🙂 Expected behavior

No error, should be collapsed, since String can be used as string in .test()

Additional information about the issue

Maybe related to #22617 ?

[RyanCavanaugh]

This is basically #2361

[RyanCavanaugh]

No error, should be collapsed, since String can be used as string in .test()

BTW the problem with this argument is that you have to come up with some reasonable way to describe why String is valid here but not Boolean. They both undergo identical conversion inside the test method but it's obviously very suspect to call /blah/.test(SomeBoolean) the same way it is to write /blah/.test(true)