Making statements generic

[varanauskas]

Currently some statement methods support generics for type hinting the result of the query, for example:

class Statement {
  all<T extends object = Record<string, any>>(...args: RestBindParameters): T[]
  get<T extends object>(...params: RestBindParameters): T | undefined
}

In a lot of cases the generic used is the same between these two methods because the same query was used to prepare the statement.

I propose adding a generic type to statement itself that would allow to both of these methods to be typed automatically:

interface UserTable {
  name: string;
  email: string;
}
const statement: Statement<UserTable> = new Database().prepare<UserTable>("SELECT name, email FROM users");

const singleUser: UserTable | undefined = statement.get();
const allUsers: UserTable[] = statement.all();

This would lay the groundwork for typing the iterator in the future so it could be used like so:

for (const row of statement) {
  const user: UserTable = row;
}

What remains unsolved is typing of value and values methods, I propose leaving them as is for simplifying the API/proposal