Ambiguous assignment operator in Geant4Output2EDM4hep.cpp on LCG macOS platforms

[dkonst13]

Hello,

Building master of DD4Hep we encountered a compilation error related to an ambiguous assignment operator on LCG macOS platforms. The error occurs in the following code snippet:

/Users/sftnight/build/workspace/lcg_nightly_pipeline/build/frameworks/DD4hep-master/src/DD4hep/master/DDG4/edm4hep/Geant4Output2EDM4hep.cpp:476:45: error: use of overloaded operator '=' is ambiguous (with operand types 'std::map<std::string, std::pair<edm4hep::SimCalorimeterHitCollection, edm4hep::CaloHitContributionCollection>>::mapped_type' (aka 'std::pair<edm4hep::SimCalorimeterHitCollection, edm4hep::CaloHitContributionCollection>') and 'void')
    auto& hits = m_calorimeterHits[colName] = {};
                 ~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~
/Library/Developer/CommandLineTools/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/__utility/pair.h:262:11: note: candidate function
    pair& operator=(typename conditional<
          ^
/Library/Developer/CommandLineTools/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/__utility/pair.h:275:11: note: candidate function
    pair& operator=(typename conditional<
          ^
/Library/Developer/CommandLineTools/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/__utility/pair.h:40:29: note: candidate function (the implicit copy assignment operator) has been implicitly deleted
struct _LIBCPP_TEMPLATE_VIS pair
                            ^

DD4hep/DDG4/edm4hep/Geant4Output2EDM4hep.cpp

Line 476 in 3347996

auto& hits = m_calorimeterHits[colName] = {};

[MarkusFrankATcernch]

Aaarghh! Always the bloody macs. I will take care.

[MarkusFrankATcernch]

@dkonst13 Does PR #1131 solve the compilation problem?

[MarkusFrankATcernch]

@dkonst13 Can this issue be closed ?

[veprbl]

Fix in 1131 looks sufficient to me.