Add small reproducer for type mismatch issue

test/k4FWCoreTest/CMakeLists.txt

@@ -204,3 +204,5 @@ add_test_with_env(GaudiFunctional options/ExampleGaudiFunctional.py PROPERTIES F
 add_custom_command(TARGET k4FWCoreTestPlugins POST_BUILD
                    COMMAND ${CMAKE_COMMAND} -E copy_directory
                    ${PROJECT_SOURCE_DIR}/python/k4FWCore/ ${PROJECT_BINARY_DIR}/k4FWCore/genConfDir/k4FWCore)
+
+add_test_with_env(TypeMisMatchDemo options/TypeMisMatchDemo.py)

test/k4FWCoreTest/options/TypeMisMatchDemo.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+
+from Gaudi.Configuration import INFO, DEBUG
+from Configurables import ExampleFunctionalProducer, TypeMisMatchDemo, EventDataSvc
+
+from k4FWCore import ApplicationMgr
+
+producer = ExampleFunctionalProducer("Producer", OutputCollection=["MCParticles"])
+
+mismatch = TypeMisMatchDemo(InputCollection=["MCParticles"], OutputLevel=DEBUG)
+
+ApplicationMgr(
+    TopAlg=[producer, mismatch],
+    EvtSel="NONE",
+    EvtMax=1,
+    ExtSvc=[EventDataSvc("EventDataSvc")],
+    OutputLevel=INFO,
+)

test/k4FWCoreTest/src/components/TypeMisMatchDemo.cpp

@@ -0,0 +1,26 @@
+#include "edm4hep/MCParticleCollection.h"
+#include "edm4hep/TrackCollection.h"
+
+#include "k4FWCore/Transformer.h"
+
+#include <Gaudi/Property.h>
+#include <GaudiKernel/ISvcLocator.h>
+
+#include <string>
+
+struct TypeMisMatchDemo final : k4FWCore::Transformer<edm4hep::MCParticleCollection(const edm4hep::TrackCollection&)> {
+  TypeMisMatchDemo(const std::string& name, ISvcLocator* svcLoc)
+      : Transformer(name, svcLoc, {KeyValues("InputCollection", {"MCParticles"})},
+                    {KeyValues("OutputCollection", {"MCParticles2"})}) {}
+
+  edm4hep::MCParticleCollection operator()(const edm4hep::TrackCollection& inputs) const final {
+    debug() << inputs.size() << " type = " << inputs.getTypeName() << endmsg;
+    auto track = inputs[0];
+    // The next line goes boom
+    debug() << track.getTrackerHits().size() << endmsg;
+
+    return edm4hep::MCParticleCollection{};
+  }
+};
+
+DECLARE_COMPONENT(TypeMisMatchDemo)