Pointer to structs

[certik]

After #606 is fixed, we need to support the following use case:

@dataclass
class A:
    x: i32
    y: f32

def f(pa: Pointer[A]):
    print(pa.x)
    print(pa.y)

def g():
    x: A = A()
    px: Pointer[A] = pointer(x)
    px.x = 5
    px.y = 5.5
    f(px)

g()

[czgdp1807]

Initialisation at declaration is not supported yet. So, instead of the following,

x: A = A()
px: Pointer[A] = pointer(x)

you should use the following,

x: A
x = A()
px: Pointer[A]
px = pointer(x)

Rest everything works. Should we prioritise supporting initialisation at declaration for structs?

[certik]

I think we can, I opened up #626 for the initialization, I've been hitting bugs in this a lot, and our users will as well, so we might as well sit down and fix it properly and robustly.