[core] Fix improper name normalization in KeepNParams

The algorithm was not recording any default arguments into argsToKeep,
but it actually needs to keep them as long as they are followed by a
non-default argument.

This would cause issues such as this:

// std::less<int> is a default argument, but MyAlloc is not
using MyMap = std::map<int, int, std::less<int>, MyAlloc>;

TClass::GetClass("MyMap")->GetName() # prints "map<int,int,MyAlloc>" !

Author: silverweed

core/clingutils/src/TClingUtils.cxx

@@ -4047,6 +4047,7 @@ static void KeepNParams(clang::QualType& normalizedType,
    const int nNormArgs = normArgs.size();
 
    bool mightHaveChanged = false;
+   int latestNonDefaultArg = -1;
 
    // becomes true when a parameter has a value equal to its default
    for (int formal = 0, inst = 0; formal != nArgs; ++formal, ++inst) {
@@ -4085,10 +4086,12 @@ static void KeepNParams(clang::QualType& normalizedType,
                argsToKeep.push_back(normTArg);
             }
             // Done.
+            latestNonDefaultArg = -1;
             break;
          }
          mightHaveChanged |= RecurseKeepNParams(normTArg, tArg, interp, normCtxt, astCtxt);
          argsToKeep.push_back(normTArg);
+         latestNonDefaultArg = formal;
          continue;
       } else {
          if (!isStdDropDefault) {
@@ -4110,16 +4113,21 @@ static void KeepNParams(clang::QualType& normalizedType,
       } else if (argKind == clang::TemplateArgument::Integral){
          equal = areEqualValues(tArg, *tParPtr);
       }
+
+      argsToKeep.push_back(normTArg);
       if (!equal) {
+         latestNonDefaultArg = formal;
          mightHaveChanged |= RecurseKeepNParams(normTArg, tArg, interp, normCtxt, astCtxt);
-         argsToKeep.push_back(normTArg);
       } else {
          mightHaveChanged = true;
       }
 
 
    } // of loop over parameters and arguments
 
+   if (latestNonDefaultArg >= 0)
+      argsToKeep.resize(latestNonDefaultArg + 1);
+
    if (!prefix_changed && !mightHaveChanged) {
       normalizedType = originalNormalizedType;
       return;
@@ -4140,7 +4148,6 @@ static void KeepNParams(clang::QualType& normalizedType,
       normalizedType = astCtxt.getElaboratedType(clang::ElaboratedTypeKeyword::None, prefix, normalizedType);
       normalizedType = astCtxt.getQualifiedType(normalizedType,prefix_qualifiers);
    }
-
 }
 
 ////////////////////////////////////////////////////////////////////////////////

core/foundation/test/testClassEdit.cxx

@@ -310,7 +310,26 @@ TEST(TClassEdit, GetNormalizedName)
 
    n.clear();
    EXPECT_THROW(TClassEdit::GetNormalizedName(n, "_Atomic(map<string, TObjArray* >*"), std::runtime_error);
+}
+
+TEST(TClassEdit, GetNormalizedNameTypedef)
+{
+   std::string n;
+
+   gInterpreter->Declare(R"(
+      struct MyAlloc {};
+      using MyMap = std::map<int,int,std::less<int>,MyAlloc>;
+   )");
+
+   TClassEdit::GetNormalizedName(n, "MyMap");
+   EXPECT_STREQ("map<int,int,less<int>,MyAlloc>", n.c_str());
+
+   gInterpreter->Declare(R"(
+      using MyMapDefault = std::map<int,int,std::less<int>,std::allocator<std::pair<const int,int>>>;
+   )");
 
+   TClassEdit::GetNormalizedName(n, "MyMapDefault");
+   EXPECT_STREQ("std::map<int,int>", n.c_str());
 }
 
 // https://github.com/root-project/root/issues/18654