Generics aren't working as expected when using them with Partial

Bug Report

🔎 Search Terms

generic partial

🕗 Version & Regression Information

4.2.2

⏯ Playground Link

Playground Link

💻 Code

type FunctionType<T> = {
  func(arg: Partial<T>): any;
};

type StringType = {
  str: string;
};

function example<T extends StringType>(ft: FunctionType<T>) {
  ft.func({ str: "" });
}

🙁 Actual behavior

The code doesn't compile because ft.func({ str: "" }) gives the following error

Argument of type '{ str: ""; }' is not assignable to parameter of type 'Partial<T>'.

🙂 Expected behavior

I would expect the code to compile

[MartinJohns]

The type "abc" extends the type string.
The type { str: "abc" } extends the type { str: string }.
"" is not a valid value for the type "abc".

This is unrelated to Partial<T>. It's due to your misunderstanding of generics.

Here's a simplified example of the problem at hand:

function example<T extends string>(): T { return ""; }

example<"abc">();

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.