[clang-tidy] Update fuchsia-multiple-inheritance to check for templates

[juliehockett]

Summary

Updating fuchsia-multiple-inheritance to not crash when a record inherits a template.

Fixes PR36052.

[hokein]

LGTM

clang-tools-extra/trunk/clang-tidy/fuchsia/MultipleInheritanceCheck.cpp

 bool MultipleInheritanceCheck::isInterface(const CXXRecordDecl *Node) {
   // Short circuit the lookup if we have analyzed this record before.
   bool PreviousIsInterfaceResult;
   if (getInterfaceStatus(Node, PreviousIsInterfaceResult))
     return PreviousIsInterfaceResult;
 
   // To be an interface, all base classes must be interfaces as well.
   for (const auto &I : Node->bases()) {
-    if (I.isVirtual()) continue;  
+    if (I.isVirtual()) continue;
     const auto *Ty = I.getType()->getAs<RecordType>();
     assert(Ty && "RecordType of base class is unknown");
     const RecordDecl *D = Ty->getDecl()->getDefinition();
     if (!D) continue;
     const auto *Base = cast<CXXRecordDecl>(D);
     if (!isInterface(Base)) {
       addNodeToInterfaceMap(Node, false);
       return false;

 }
 
 void MultipleInheritanceCheck::check(const MatchFinder::MatchResult &Result) {
   if (const auto *D = Result.Nodes.getNodeAs<CXXRecordDecl>("decl")) {
     // Check against map to see if if the class inherits from multiple
     // concrete classes
     unsigned NumConcrete = 0;
     for (const auto &I : D->bases()) {
-      if (I.isVirtual()) continue;
+      if (I.isVirtual() || I.getType()->getAs<TemplateTypeParmType>()) continue;
       const auto *Ty = I.getType()->getAs<RecordType>();
       assert(Ty && "RecordType of base class is unknown");
       const auto *Base = cast<CXXRecordDecl>(Ty->getDecl()->getDefinition());
       if (!isInterface(Base)) NumConcrete++;
     }
     
     // Check virtual bases to see if there is more than one concrete 
     // non-virtual base.

clang-tools-extra/trunk/test/clang-tidy/fuchsia-multiple-inheritance.cpp

 struct V12 : virtual Static_Base {};
 struct D7 : V11, V12 {};
 
 struct Static_Base_2 {};
 struct V13 : virtual Static_Base_2 { static void f(); };
 struct V14 : virtual Static_Base_2 { static void g(); };
 struct D8 : V13, V14 {};
 
+template<typename T> struct A : T {};
+template<typename T> struct B : virtual T {};