Unexpected behavior when validate typing.Tuple[str, int]

[xbanke]

• typical version: 2.0.33
• Python version: 3.7
• Operating System: CentOS

Description

Hey, @seandstewart
As title said, when transmute a tuple type with typed elements.

import typing, typic


@typic.al
def foo(a: typing.Tuple[str, int]):
    print(a)

    
foo(('abc', 123))  # ('abc', '123')

The second element type int is transmuted to str type.

[seandstewart]

Thanks for submitting. Looks like there a few things not quite right with our tuple implementation.

Tuple validation doesn't respect argument order either:

import typic
from typing import Tuple

proto = typic.protocol(Tuple[str, int])
proto.transmute((1, 1))  # ('1', '1')  <-- should be ('1', 1)
proto.validate(("foo", 1))  # ("foo", 1)  <-- okay
proto.validate((1, "foo"))  # (1, 'foo') <-- should raise a validation error
proto.validate((1, "foo", "bar"))  # (1, 'foo', 'bar') <-- should raise a validation error

I think this is inherent in the implementation, which treats tuple like just another iterable, when in fact the shape of a tuple is quite meaningful. If the tuple is unbounded in size (e.g., notated with an ellipsis), then yes, that is correct, but if the tuple is constrained in size, we should treat it more like we treat a class, TypedDict, or NamedTuple.