seq.map does not type check correctly

[evanlouie]

Describe the bug

The functional pipe examples where seq.map is the first function in the pipe causes a type error.

To Reproduce Steps to reproduce the behavior:

Expected behavior

pyright type checks correctly

Code or Screenshots

This causes type error:

from expression.collections import seq, Seq

xs = Seq.of(9, 10, 11)
ys = xs.pipe(
    seq.map(lambda x: x * 10),
    seq.filter(lambda x: x > 100),
    seq.fold(lambda s, x: s + x, 0)
)

This passes:

from expression.collections import seq, Seq

xs = Seq.of(9, 10, 11)
ys = xs.pipe(
    seq.filter(lambda x: x > 100),
    seq.map(lambda x: x * 10),
    seq.fold(lambda s, x: s + x, 0)
)

Additional context Add any other context about the problem here.

• MacOS
• Expression version 4.2.4
• Tested on Python 3.11.4 and 3.10.12

[dbrattli]

Hi Pyright is unfortunately not good at inferring the types of lambda functions. The problem here is not seq.map nor the pipe method. To fix this (until pyright can infer the types better) you need to assign the lambdas to variables and give them types e.g:

mapper: Callable[[int], int] = lambda x: x * 10
predicate: Callable[[int], bool] = lambda x: x > 100
folder: Callable[[int, int], int] = lambda s, x: s + x

ys = xs.pipe(
    seq.map(mapper),
    seq.filter(predicate),
    seq.fold(folder, 0),
)

I'll update the examples