Inconsistent TS2345 error when using function generics

[moshest]

Bug Report

🔎 Search Terms

• Inconsistent 2345
• function generics
• extends 2345
• generics 2345

🕗 Version & Regression Information

• This changed from version 4.7.4+ and above

⏯ Playground Link

Playground link with relevant code

💻 Code

function func<T extends { foo: 1 }>(arg: T): void {}

func({ foo: 1, bar: 1 });

🙁 Actual behavior

bar property sometimes displayed as valid and sometimes produce an error:

Argument of type '{ foo: 1; bar: number; }' is not assignable to parameter of type '{ foo: 1; }'.
  Object literal may only specify known properties, and 'bar' does not exist in type '{ foo: 1; }'.(2345)

When playing with the code live and change bar to bar222 or ba sometimes the error shown and sometimes not.
Refreshing the playground link with the changes always remove the error.

Screen.Recording.2022-09-17.at.20.20.57.mov

🙂 Expected behavior

Always display as valid without any error.

{ foo: 1, bar: 1 } is a valid subtype of { foo: 1 } and so can legally be used to instantiate T.

---

Maybe related to #49490

[fatcerberus]

Expected behavior: Always display an error for unknown properties.

The correct behavior is for there to be no error here: excess property checks aren’t intended to apply to generic constraints. { foo: 1, bar: 1 } is a valid subtype of { foo: 1 } and so can legally be used to instantiate T.

[moshest]

@fatcerberus you are right, I've updated the issue description.

[RyanCavanaugh]

This looks similar to some other bugs we've seen reported where weird errors show up while typing

[JonathonChen]

I also encounter the similar situation when passing function paramter in different ways.(typescipt version 4.1.3)

interface AAA {
  hyYears: Array<any>;
}

function func(process: AAA) {
  console.log(process);
}

const unresolveParams = {
  hyYears: [],
  periodDataId: 1,
};


func(unresolveParams); // why this line can't detect the extra parameter

func({
  hyYears: [],
  periodDataId: 1, //  ts(2345) detect the extra parameter. Argument of type '{ hyYears: undefined[]; periodDataId: number; func(unresolveParams: any): any; }' is not assignable to parameter of type 'AAA'
});

[Andarist]

If only I bisected this correctly, the regression has been introduced by #36747

[Andarist]

@JonathonChen your case is not a bug, you can learn more about this here

[jakebailey]

@Andarist How did you happen to reproduce this? Just using the editor or did you manage to get a test working? (I so far have not...)

[Andarist]

I was using the editor with TS built from different commits. I was doing that within the TS repo itself so I could pretty easily jump between commits/builds

[jakebailey]

Darn 🙁

I haven't yet found the right fourslash calls to get this reproducing, so into the server RPC logs I go...

[jakebailey]

Got it:

////declare function func<T extends { foo: 1 }>(arg: T): void;
////
////func({ foo: 1, bar/*1*/: 1 });

goTo.marker("1");
edit.insert("2");
verify.completions({ exact: undefined });
verify.noErrors();

(I spent all that time figuring out how to assert in fourslash that there are no completions so I could perform the request.)