[hist] Move RAxisVariant declaration

Needed in the public interface of the histogram classes, so it should
not be in the Internal namespace.

Author: hahnjo

hist/histv7/inc/ROOT/RAxes.hxx

@@ -22,29 +22,29 @@ class TBuffer;
 
 namespace ROOT {
 namespace Experimental {
+
+/// Variant of all supported axis types.
+using RAxisVariant = std::variant<RRegularAxis, RVariableBinAxis>;
+
 namespace Internal {
 
 /**
 Bin configurations for all dimensions of a histogram.
 */
 class RAxes final {
-public:
-   using AxisVariant = std::variant<RRegularAxis, RVariableBinAxis>;
-
-private:
-   std::vector<AxisVariant> fAxes;
+   std::vector<RAxisVariant> fAxes;
 
 public:
    /// \param[in] axes the axis objects, must have size > 0
-   explicit RAxes(std::vector<AxisVariant> axes) : fAxes(std::move(axes))
+   explicit RAxes(std::vector<RAxisVariant> axes) : fAxes(std::move(axes))
    {
       if (fAxes.empty()) {
          throw std::invalid_argument("must have at least 1 axis object");
       }
    }
 
    std::size_t GetNDimensions() const { return fAxes.size(); }
-   const std::vector<AxisVariant> &Get() const { return fAxes; }
+   const std::vector<RAxisVariant> &Get() const { return fAxes; }
 
    friend bool operator==(const RAxes &lhs, const RAxes &rhs) { return lhs.fAxes == rhs.fAxes; }
 

hist/histv7/test/hist_axes.cxx

@@ -27,7 +27,7 @@ TEST(RAxes, Constructor)
    EXPECT_TRUE(std::get_if<RRegularAxis>(&v[0]) != nullptr);
    EXPECT_TRUE(std::get_if<RVariableBinAxis>(&v[1]) != nullptr);
 
-   std::vector<RAxes::AxisVariant> newAxes{variableBinAxis, regularAxis};
+   std::vector<RAxisVariant> newAxes{variableBinAxis, regularAxis};
    axes = RAxes(newAxes);
    EXPECT_EQ(axes.GetNDimensions(), 2);
 

hist/histv7/test/hist_test.hxx

@@ -9,6 +9,7 @@
 
 #include "gtest/gtest.h"
 
+using ROOT::Experimental::RAxisVariant;
 using ROOT::Experimental::RBinIndex;
 using ROOT::Experimental::RBinIndexRange;
 using ROOT::Experimental::RRegularAxis;