QUERY · ISSUE

Minor Viper Flaw: Misleading error message

openby RaulKompassopened 2021-09-16updated 2021-09-20

Accessing an undefined variable in Python and Micropython:

def quot(a:int, b:int) -> int:
    return c//b

results in NameError: name 'c' isn't defined during execution.

Above function with @micropython.viper results in ViperTypeError: return expected 'int' but got 'object'during compilation.
Just now I realize that viper has to assume that c is some global python object. Which means the error message is correct. But it is misleading.
An addition like name 'c' isn't defined while compiling would be helpful imho.

CANDIDATE · ISSUE

Type Inference issue when using struct in viper

openby GuillaumeLeclercopened 2023-05-28updated 2023-05-28

bug

MY_TYPE = {
    "var": 0 | uctypes.UINT32
}
storage = bytearray(uctypes.sizeof(MY_TYPE))

@micropython.viper
def bugreport():
    data = uctypes.struct(ptr32(storage), MY_TYPE)
    data.var += int(1)

bugreport()

For some reason data.var is an object even though it's type is clearly defined from the struct. the following error occurs:

ViperTypeError: can\'t do binary op between \'object\' and \'int\'

Assessment

Q Qwen · high

Both issues involve ViperTypeError exceptions in MicroPython's viper compiler, but they address different root causes. Issue #7808 is about misleading error messages when accessing undefined variables (the variable is treated as a Python object during compilation). Issue #11638 is about type inference failures with uctypes.struct fields, where defined struct fields are incorrectly treated as objects. While both result in ViperTypeError, the underlying problems are distinct: one is about error message clarity for undefined variables, the other is about type inference for struct fields.

Suggested action

Keep both issues open as they address different bugs. The maintainer may want to review if there's a common underlying issue in the type checking system, but they should be tracked separately.

Minor Viper Flaw: Misleading error message

Type Inference issue when using struct in viper

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