TTreeReader fails to read T<Double_32> as T<double>

[eguiraud]

First reported on the forum at https://root-forum.cern.ch/t/problem-with-type-conversion-for-lorentz-vector/53639 .

Minimal reproducer:

#include <Math/Vector4D.h>
#include <ROOT/RDataFrame.hxx>

float TakeMVector(ROOT::Math::PtEtaPhiMVector &) { return 4.2; }

int main() {
  ROOT::RDataFrame df("Tree", "example_file.root");

  df.Define("unused", "L"); // the failure disappears if this is commented out, even if "unused" is never used.

  auto dff4 = df.Define("x", TakeMVector, {"L"});
  dff4.Max<float>("x").GetValue();
}

with the input file at https://root-forum.cern.ch/t/problem-with-type-conversion-for-lorentz-vector/53639/3?u=eguiraud .

The program errors out with:

The branch L contains data of type ROOT::Math::LorentzVector<ROOT::Math::PtEtaPhiM4D<Double32_t> >. It cannot be accessed by a TTreeReaderValue<ROOT::Math::LorentzVector<ROOT::Math::PtEtaPhiM4D<double> >>

(so TTreeReaderValue cannot read a LorentzVector<PtEtaPhiM4D<Double32_t>> as a LorentzVector<PtEtaPhiM4D<double>>).

The following patch by @Axel-Naumann seems to fix the problem:

diff --git a/tree/treeplayer/src/TTreeReaderValue.cxx b/tree/treeplayer/src/TTreeReaderValue.cxx
index 2323cffee4..6d938f1b14 100644
--- a/tree/treeplayer/src/TTreeReaderValue.cxx
+++ b/tree/treeplayer/src/TTreeReaderValue.cxx
@@ -554,7 +554,8 @@ void ROOT::Internal::TTreeReaderValueBase::CreateProxy() {
       auto branchActualTypeAsClass = dynamic_cast<TClass*>(branchActualType);
       auto inheritance = dictAsClass && branchActualTypeAsClass && branchActualTypeAsClass->InheritsFrom(dictAsClass);

-      if (fDict != branchActualType && !inheritance) {
+      if (fDict != branchActualType && !inheritance
+          && dictAsClass->GetTypeInfo() != branchActualTypeAsClass->GetTypeInfo()) {
          TDataType *dictdt = dynamic_cast<TDataType*>(fDict);
          TDataType *actualdt = dynamic_cast<TDataType*>(branchActualType);
          bool complainAboutMismatch = true;

[eguiraud]

P.S.

adding ROOT.TClass.GetClass("ROOT::Math::LorentzVector<ROOT::Math::PtEtaPhiM4D<double>>") at the beginning of the program works around the issue.