In FIR, the source of FirFunctionCall is set to call's selector.
In practice, sometimes (e.g. for DEBUG_INFO_CALL)
we expect the selector as the source,
and sometimes (e.g. for DEBUG_INFO_EXPRESSION_TYPE)
we expect the whole qualified call as the source.
Also, some diagnostics, like REDUNDANT_CALL_OF_CONVERSION_METHOD,
are expected to be reported on a selector, not on a whole call.
At this moment we ignore the problem & just don't support
DEBUG_INFO_EXPRESSION_TYPE for qualified calls.
Mikhail Glukhikh
52a07e31c7