Generic types wrapped with Partial cannot be assigned to empty objects

[JustASquid]

TypeScript Version: 2.1.4

Code

interface I {
	a: string;
}

function f1<T extends Partial<I>>() {
	// Error TS2322
	let i: T = {};
}

function f2<T extends I>() {
	// Error TS2322
	let i: Partial<T> = {};
}

Expected behavior:
No errors

Actual behavior:
Error TS2322: Type '{}' is not assignable to type 'T' / 'Partial'

Forgive me if this is simply a limitation of the Typescript engine and the implementation of Partial, but I don't know enough about the internals to make a judgement there.

[RyanCavanaugh]

The first example is not a bug. Being constrained by a partial type does not mean that you don't have additional required properties. Remember that a constraint is an upper bound on a type, not a lower bound - the concrete type of T at any call site may have additional properties and those properties may be required; the Partial<I> constraint only means that any properties in T which match those of I must have types which are assignable to the corresponding types in I

The second example is fixed in master.

[JustASquid]

Thanks Ryan, you're totally right about the first case.