No way to get GIArgInfo or GITypeInfo for the instance parameter of a method
There doesn't seem to be a way to get a GIArgInfo or GITypeInfo for the instance parameter of a method. Normally one would get the type information from the parent of the method's GICallableInfo:
g_base_info_get_container(callable_info). However, I'm working on a refactor in GJS where I'd like to store the GITypeInfo for each parameter, regardless of whether it's the instance parameter or not, and without such an API there will need to be a certain amount of duplicated code paths.