Declaration emit is incorrect when type parameter names collide

[DanielRosenwasser]

function f<T>(p: T) {
    let g: <T>(x: T) => typeof p = null as any;
    return g;
}

Calling f(10) will produce something of type <T>(x: T) => number, however, the declaration emit is the following:

declare function f<T>(p: T): <T>(x: T) => T;

But calling that f produces the type <T>(x: T) => T.

[gcnew]

I'm looking forward for a solution to this issue. It would be a big problem when polymorphic unification gets implemented, because generic parameters must be instantiated with a copy of their type parameters for inference to properly work.

declare function id<X>(x: X): X;
declare function mapPair<A, B, C, D>(
    fx: (a: A) => B,
    fy: (c: C) => D
): (a: A, c: C) => [B, D];

mapPair(id, id) // = mapPair<X, X, X, X>, but should be mapPair<X1, X1, X2, X2>

My newest prototype from #9949 does the instantiation, however the variables remain with the same symbol name. They have different ids, but their textual representation is the same.