On Fri, Aug 14, 2020, 7:45 PM David Mertz <mertz@gnosis.cx> wrote:
On Fri, Aug 14, 2020, 7:39 PM Caleb Donovick 
class T(Protocol):
    x: int
    y: str

# with some abuse of notation obviously these would generate unique types
assert T == Struct[x=int, y=str]
I don't see what that can possible get you that `Struct(x=int, y=str)` doesn't.

I'm +0 on the idea, but I don't think "square brackets look nicer" is sufficient reason for a change.

One problem is type hint creation has been extended to built-ins in python 3.9, so that you do not have to import Dict, List, et al anymore.

Without kwd args inside [ ], you would not be able to do this:

Vector = dict[i=float, j=float]

...but for obvious reasons, call syntax using built ins to create custom type hints isn't an option :

dict(i=float, j=float)  # this syntax isn't available

So the improvement allowing usage of built ins for typing is somewhat negated.

Instead you would have to import Dict from typing:

Vector = typing.Dict(i=str, j=float)

To me it is instructive that the line of code above currently causes a TypeError. For some reason, the mpy team decided not to go this direction, and instead in Python 3.8 introduced typing.TypedDict:

class Vector(TypedDict):
    i = float
    j = float

I suppose type hint creation could be extended to allow syntax you are proposing, like Dict(i=float, j=float). But it certainly appears to me that it was rejected for a reason, though I can't say what that reason is (I'm sure someone else could).