I have two TypeScript examples where I’m trying to ensure that a parameter type (Param) is inferred as string. In the first example, it works as expected, but in the second, it does not. Here are the details:

Working Case

class Chat<T> {
    constructor(private adapter: BaseChatAdapter<T>) {}

    send(message: T) {}
}

interface BaseChatAdapter<T> {
    send(message: T): void;
}

class StringAdapter<T = string> implements BaseChatAdapter<T> {
    send(message: T) {}
}

const c = new Chat(new StringAdapter());

type Param = Parameters<typeof c['send']>[0]; // Param is inferred as string

Non-working Case

class Chat<T> {
    constructor(private adapter: BaseChatAdapter<T>) {}

    send(message: T) {}
}

interface BaseChatAdapter<T> {
    // The 'send' method is removed
}

class StringAdapter<T = string> implements BaseChatAdapter<T> {
    send(message: T) {}
}

const c = new Chat(new StringAdapter());

type Param = Parameters<typeof c['send']>[0]; // Param is inferred as {}

In the second example, Param is inferred as {}, even though I expect it to be string. The only difference between the two cases is the commented-out send method in the BaseChatAdapter interface.

Questions:

1. Why does the absence of the send method in the BaseChatAdapter interface affect the type inference in the second example?

2. Is there a way to ensure Param is correctly inferred as string in the second case without explicitly defining the method in the interface?

Any insights or explanations would be greatly appreciated!