[cppyy] fix: instantiation of templated functions

bindings/pyroot/cppyy/CPyCppyy/src/TemplateProxy.cxx

@@ -142,6 +142,12 @@ PyObject* TemplateProxy::Instantiate(const std::string& fname,
             } else
                 PyErr_Clear();
 
+            if (!bArgSet && (Py_TYPE(itemi) == &TemplateProxy_Type)) {
+                TemplateProxy *tp = (TemplateProxy*)itemi;
+                PyObject *tmpl_name = CPyCppyy_PyText_FromFormat("decltype(%s%s)", tp->fTI->fCppName.c_str(), tp->fTemplateArgs ? CPyCppyy_PyText_AsString(tp->fTemplateArgs) : "");
+                PyTuple_SET_ITEM(tpArgs, i, tmpl_name);
+                bArgSet = true;
+            }
             if (!bArgSet) {
             // normal case (may well fail)
                 PyErr_Clear();

bindings/pyroot/cppyy/cppyy/test/test_templates.py

@@ -1,4 +1,4 @@
 import py, pytest, os
 from pytest import mark, raises
 from support import setup_make, pylong
 
@@ -29,8 +29,8 @@
     def test01_template_member_functions(self):
         """Template member functions lookup and calls"""
 
         import cppyy
         import sys
 
         m = cppyy.gbl.MyTemplatedMethodClass()
 
@@ -46,7 +46,7 @@
         if sys.hexversion >= 0x3000000:
             targ = 'long'
         else:
             targ = long
         assert m.get_size[targ]()     == m.get_long_size()
 
         import ctypes
@@ -110,19 +110,19 @@
         from cppyy.gbl.std import vector
         # float in, float out
         ggsr = cppyy.gbl.global_get_some_result['std::vector<float>']
         assert type(ggsr(vector['float']([0.5])).m_retval) == float
         assert ggsr(vector['float']([0.5])).m_retval == 0.5
         # int in, float out
         ggsr = cppyy.gbl.global_get_some_result['std::vector<int>']
         assert type(ggsr(vector['int']([5])).m_retval) == float
         assert ggsr(vector['int']([5])).m_retval == 5.
         # float in, int out
         ggsr = cppyy.gbl.global_get_some_result['std::vector<float>, int']
         assert type(ggsr(vector['float']([0.3])).m_retval) == int
         assert ggsr(vector['float']([0.3])).m_retval == 0
         # int in, int out
         ggsr = cppyy.gbl.global_get_some_result['std::vector<int>, int']
         assert type(ggsr(vector['int']([5])).m_retval) == int
         assert ggsr(vector['int']([5])).m_retval == 5
 
     def test04_variadic_function(self):
@@ -1341,5 +1341,41 @@
         assert type(e1+e2) == cppyy.gbl.TypeReduction.Expr[int]
 
 
+class TestTEMPLATED_CALLBACK:
+    def setup_class(cls):
+        cls.test_dct = test_dct
+        import cppyy
+        cls.templates = cppyy.load_reflection_info(cls.test_dct)
+
+    def test01_templated_callbacks(self):
+        import cppyy
+        from cppyy.gbl import std
+
+        cppyy.cppdef(r"""
+        bool foo() { return true; }
+
+        int bar(int a, int b) { return a + b; }
+
+        template <typename T, typename U>
+        T baz(T a, U b, std::string c) {
+            return (T)(a + b) + std::stoi(c);
+        }
+
+        template <typename F, typename R, typename... Args>
+        R returned_callback(F callable, R r, Args... args) {
+            return callable(r, std::forward<Args>(args)...);
+        }
+
+        template <typename F, typename... Args>
+        bool callback(F callable, Args&&... args) {
+            return callable(std::forward<Args>(args)...);
+        }
+        """)
+
+        assert cppyy.gbl.callback(cppyy.gbl.foo)
+        assert cppyy.gbl.returned_callback(cppyy.gbl.bar, 1, 1) == 2
+        assert cppyy.gbl.returned_callback(cppyy.gbl.baz[int, int], 1, 1, std.string("1")) == 3
+
+
 if __name__ == "__main__":
     exit(pytest.main(args=['-sv', '-ra', __file__]))

interpreter/cling/lib/Interpreter/LookupHelper.cpp

@@ -1691,7 +1691,9 @@ namespace cling {
         clang::QualType QT = clang::Sema::GetTypeFromParser(Res.get(), &TSI);
         QT = QT.getCanonicalType();
         {
-          ExprValueKind VK = VK_PRValue;
+          // XValue is an object that can be "moved" whereas PRValue is temporary value
+          // This enables overloads that require the object to be moved
+          ExprValueKind VK = VK_XValue;
           if (QT->getAs<LValueReferenceType>()) {
             VK = VK_LValue;
           }