'Name already defined' error when importing function from module with the same name

mypy shows an unexpected error, when I import all attributes from a module using * and a function has the same name as the module.

Example:
I have a package named foo, that contains the files __init__.pyi, a.pyi, b.pyi and c.pyi.

# a.pyi
def a() -> None: ...

# b.pyi
def not_b() -> None: ...

# c.pyi
def c() -> None: ...

# __init__.pyi
from .a import *
from .b import *
from .c import c

mypy foo shows the following error:
foo/__init__.pyi:1: error: Name 'a' already defined (by an import).

I have used mypy 0.620.

Start with the reported foo package and its init.pyi, a.pyi, b.pyi, and c.pyi files, then run mypy foo to reproduce the duplicate-name error. Trace handling of star imports and the explicit from .c import c import, and add coverage showing that the valid imports produce no erroneous redefinition diagnostic.