Partial does not work inside a method that uses the class generic parameter type

[asfernandes]

TypeScript Version: 2.1.6

The subject is a bit difficult to write, but look in the code inside method.

{ id: 1 } should be implicit convertible to Partial<T> as T extends { id: number }.

interface Intf<T extends { id: number }>
{
	find: (obj: Partial<T>) => T;
}

interface Obj
{
	id: number;
	name: string;
}

const intf: Intf<Obj> = {
	find(obj: Obj)
	{
		return obj;
	}
}

intf.find({ id: 1, name: '' });	// ok
intf.find({ id: 1 });	// ok

class Component<T extends { id: number }>
{
	constructor (public intf: Intf<T>)
	{
	}

	method()
	{
		this.intf.find({ id: 1 } as T);	// ok
		this.intf.find({ id: 1 });	// error! why?
	}
}

const component = new Component<Obj>(intf);
component.intf.find({ id: 1, name: '' });	// ok
component.intf.find({ id: 1 });	// ok

[mhegazy]

The error is correct since T can be more specialized than its constraint {id: number}. consider:

const component = new Component<{id: 2}>(intf);
component.intf.find({ id: 1 });	// Error

[asfernandes]

Then what about this?

class Component<T extends { id: number }>
{
	constructor (obj: T)
	{
		obj.id = 10;
	}
}

new Component<{id: 2}>({ id: 2 });

It works and violates the type system as well the behavior I intended does.

[mhegazy]

That is a duplicate of #14150