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Tangerino opened this issue May 6, 2025 · 2 comments
Closed

mpy-cross compiles bad code #17255

Tangerino opened this issue May 6, 2025 · 2 comments
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@Tangerino
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Port, board and/or hardware

ESP32

MicroPython version

MicroPython v1.23.0-preview.332.g49ce7a607.dirty on 2024-04-22; mpy-cross emitting mpy v6.3

Reproduction

This code

from typing import List

my_list: List = []

print(mylist)

Fails to run, as expected

>>> import typing
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: no module named 'typing'
>>> import typing_test
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "typing_test.py", line 1, in <module>
ImportError: no module named 'typing'

But can be compiled as in:

Image

Expected behaviour

Expected compilation error since the module does not exists

Observed behaviour

I expected an output error since the module typing does not exists and I discovered this only in runtime

Additional Information

No, I've provided everything above.

Code of Conduct

Yes, I agree
@Tangerino Tangerino added the bug label May 6, 2025
@Josverl
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Josverl commented May 6, 2025 •
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I do not consider this a bug,
Whether or not a typing module is available at runtime, does not, and should not matter to producing byte-code.

There is another issue in your example my_list: List = [] is an Annotated Assign (annassign), where the type annotation : List is ignored by the MicroPython lexer/parser , essentially downgrading it to just an Assign.

if (kind == PN_annassign) {

The documentation is somewhat confusing on this this, as PEP 562 is documented as completed.

One could say that the documentation should read : Partially implemented. The syntax is accepted , but the annotations are not parsed / compiled.

also see the PR that introduced this: #6126

@peterhinch
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Closing. This is not a bug for the reason stated

Whether or not a typing module is available at runtime, does not, and should not matter to producing byte-code.

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@Josverl @Tangerino @peterhinch