No crash when encountering weakly typed namedtuple

[flying-sheep]

No description provided.

[OJFord]

I just encountered this too, would be great if this could be merged @prechelt.

[OJFord]

Actually, it just hits an error further down the line.

I've found a workaround though:

import typecheck as tc
from collections import namedtuple

NT = namedtuple('NT', 'x')

@tc.typecheck
def foobar(nt: lambda x: isinstance(x, NT)):
    pass