C compilation fails if '__init__' has no return type

[JukkaL]

This program doesn't compile:

class C:
    def __init__(self):
        pass

Here's the output:

...
x86_64-linux-gnu-gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -g -fwrapv -O2 -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -I/home/jukka/src/mypy/mypyc/lib-rt -I/home/jukka/venv/mypy/include -I/usr/include/python3.8 -c build/__native.c -o build/temp.linux-x86_64-3.8/build/__native.o -O3 -Werror -Wno-unused-function -Wno-unused-label -Wno-unreachable-code -Wno-unused-variable -Wno-unused-command-line-argument -Wno-unknown-warning-option -Wno-unused-but-set-variable
build/__native.c: In function ‘CPyDef_C’:
build/__native.c:111:16: error: initialization of ‘char’ from ‘PyObject *’ {aka ‘struct _object *’} makes integer from pointer without a cast [-Werror=int-conversion]
  111 |     char res = CPyDef_C_____init__(self);
      |                ^~~~~~~~~~~~~~~~~~~
...

Maybe we should always give __init__ an implicit None return type.

[thomasjohns]

I'd like to give this one a try. I think a special case for __init__ in mypyc.irbuild.mapper.py could be a way to solve this.