dry-python/classes

Internal error

ArneBachmannDLR opened this issue · 3 comments

ArneBachmannDLR commented

Bug report

As mentioned on Twitter, I got disappointing results when trying classes on my code for the first time, leading to me going back to singledispatch.

What's wrong

I run latest mypy and get:

test.py:8: error: Internal error: attempted lookup of unknown name
test.py:12: error: Internal error: attempted lookup of unknown name

Here is the code:

from classes import typeclass

@typeclass
def listContents(value, path:str, wfile) -> None: pass

@listContents.instance(dict)
def _listContentsDict(value:dict, path:str, wfile) -> None: pass

@listContents.instance(list)
def _listContentsList(value:list, path:str, wfile) -> None: pass

How is that should be

Mypy running successfully.

System information

  • python version: Miniforge3 python 3.8.8 environment (same for 3.9)
  • classes version: 0.3.0
  • mypy version: 0.902 (0.910 for 3.9)
sobolevn commented

Hi, @ArneBachmannDLR! I have checked that now it works with the current master.
Version 0.4.0 will be released soon!

reveal_type(listContents)
# Revealed type is "classes._typeclass._TypeClass[Union[builtins.list[Any], builtins.dict[Any, Any]], def (value: Any, path: builtins.str, wfile: Any), <nothing>, Literal['ex.listContents']]"
ArneBachmannDLR commented

Happy to test it soon!

As a sidenode, pulling in external dependencies is usually something I tend to avoid. To commit to a new library there has to be a lot of benefits. I think for classes it would be something like better type safety in mypy and during runtime, right?

Also I think users may be confused by the mention of dry-python vs. classes. What is it?

sobolevn commented

I think for classes it would be something like better type safety in mypy and during runtime, right?

Yes, we have both new runtime features and type-safety features.

Also I think users may be confused by the mention of dry-python vs. classes. What is it?

dry-python is a family of libraries: https://github.com/dry-python
It also includes returns and lambdas at the moment.

I am going to close this issue, since it is solved. But, feel free to ask any questions 🙂