Inaccurate code is generated for a relative import statement inside an __init__.py module of a nested package (usually leading to an ImportError at program runtime).

Conditions:

• Relative import statement
• Module is the __init__.py module
• The package / directory of the __init__.py is not the top-level one (file not the highest __init__.py)

Outcome:
The statement tries to import from the parent package of the correct package, generally causing an ImportError.
E.g. (typed) from .module import foo -> (compiled) from ..module import foo

To reproduce:
Have mypy 1.12.0, and its mypyc extension, installed.
Create a file structure as follows:

.
└── a/
    ├── __init__.py
    └── b/
        ├── __init__.py
        └── bar.py

In a/b/__init__.py, add a valid relative import statement:

from . import bar

Compile with mypyc a in the terminal, successfully.
Execute the following statement to run a/b/__init__.py, in the python IDLE or a new ./main.py file:

import a.b

Result:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "a\b\__init__.py", line 1, in <module>
    from . import bar
ImportError: cannot import name 'bar' from 'a' (~\mypyc-test\a\__init__.cp312-win_amd64.pyd)

The statement tries to import a.bar instead of the intended a.b.bar

Expected behavior
The compiled program runs with no errors, the relative import statement is generated correctly.

Actual behavior
The generated relative import is off by one level, often causing an import error when running the compiled program.

Environment

• Mypy version used: 1.12.0 (compiled)
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.12.4
• Windows 11