fix GetNumBases to handle templated typedefs (#681)

* fix GetNumBases to handle templated typedefs

Co-authored-by: Vassil Vassilev <v.g.vassilev@gmail.com>

---------

Co-authored-by: Vassil Vassilev <v.g.vassilev@gmail.com>

Author: Vipul-Cariappa

lib/CppInterOp/Compatibility.h

@@ -5,9 +5,13 @@
 #ifndef CPPINTEROP_COMPATIBILITY_H
 #define CPPINTEROP_COMPATIBILITY_H
 
+#include "clang/AST/DeclTemplate.h"
 #include "clang/AST/GlobalDecl.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/Specifiers.h"
 #include "clang/Basic/Version.h"
 #include "clang/Config/config.h"
+#include "clang/Sema/Sema.h"
 
 #ifdef _MSC_VER
 #define dup _dup
@@ -413,6 +417,22 @@ template <typename T> inline T convertTo(clang::Value V) {
 }
 #endif // CPPINTEROP_USE_CLING
 
+inline void InstantiateClassTemplateSpecialization(
+    Interpreter& interp, clang::ClassTemplateSpecializationDecl* CTSD) {
+#ifdef CPPINTEROP_USE_CLING
+  cling::Interpreter::PushTransactionRAII RAII(&interp);
+#endif
+#if CLANG_VERSION_MAJOR < 20
+  interp.getSema().InstantiateClassTemplateSpecialization(
+      clang::SourceLocation::getFromRawEncoding(1), CTSD,
+      clang::TemplateSpecializationKind::TSK_Undeclared, /*Complain=*/true);
+#else
+  interp.getSema().InstantiateClassTemplateSpecialization(
+      clang::SourceLocation::getFromRawEncoding(1), CTSD,
+      clang::TemplateSpecializationKind::TSK_Undeclared, /*Complain=*/true,
+      /*PrimaryHasMatchedPackOnParmToNonPackOnArg=*/false);
+#endif
+}
 } // namespace compat
 
 #endif // CPPINTEROP_COMPATIBILITY_H

lib/CppInterOp/CppInterOp.cpp

@@ -718,6 +718,9 @@ TCppScope_t GetParentScope(TCppScope_t scope) {
 TCppIndex_t GetNumBases(TCppScope_t klass) {
   auto* D = (Decl*)klass;
 
+  if (auto* CTSD = llvm::dyn_cast_or_null<ClassTemplateSpecializationDecl>(D))
+    if (!CTSD->hasDefinition())
+      compat::InstantiateClassTemplateSpecialization(getInterp(), CTSD);
   if (auto* CXXRD = llvm::dyn_cast_or_null<CXXRecordDecl>(D)) {
     if (CXXRD->hasDefinition())
       return CXXRD->getNumBases();

unittests/CppInterOp/ScopeReflectionTest.cpp

@@ -641,6 +641,13 @@ TEST(ScopeReflectionTest, GetNumBases) {
     class D : public B, public C {};
     class E : public D {};
     class NoDef;
+
+    template<typename T, int N>
+    struct Klass : public A {
+        T t{N};
+    };
+
+    typedef Klass<int, 1> TKlass;
   )";
 
   GetAllTopLevelDecls(code, Decls);
@@ -653,6 +660,7 @@ TEST(ScopeReflectionTest, GetNumBases) {
   // FIXME: Perhaps we should have a special number or error out as this
   // operation is not well defined if a class has no definition.
   EXPECT_EQ(Cpp::GetNumBases(Decls[5]), 0);
+  EXPECT_EQ(Cpp::GetNumBases(Cpp::GetUnderlyingScope(Decls[7])), 1);
 }
 
 TEST(ScopeReflectionTest, GetBaseClass) {