Extended Description

Running clang-tidy with -checks='-*,bugprone-virtual-near-miss' on the following valid source code triggers an assertion:

========================================================
template <template class T> struct A : T<0>
{
void foo();
};

This is a recent regression between revision 9f58181 and ba1d954.

clang-tidy: /llvm-project/llvm/include/llvm/Support/Casting.h:104: static bool llvm::isa_impl_cl<To, const From*>::doit(const From*) [with To = clang::CXXRecordDecl; From = clang::NamedDecl]: Assertion `Val && "isa<> used on a null pointer"' failed.
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0. Program arguments: /LLVM-trunk/bin/clang-tidy -checks=-*,bugprone-virtual-near-miss CTbug.cc --

1. parser at end of file
   #​0 0x000000000273143c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/LLVM-trunk/bin/clang-tidy+0x273143c)
   #​1 0x000000000272f294 llvm::sys::RunSignalHandlers() (/LLVM-trunk/bin/clang-tidy+0x272f294)
   #​2 0x000000000272f3f3 SignalHandler(int) Signals.cpp:0:0
   #​3 0x00007f990aa7c680 __restore_rt sigaction.c:0:0
   #​4 0x00007f9909817207 raise (/lib64/libc.so.6+0x36207)
   #​5 0x00007f99098188f8 abort (/lib64/libc.so.6+0x378f8)
   #​6 0x00007f9909810026 __assert_fail_base (/lib64/libc.so.6+0x2f026)
   #​7 0x00007f99098100d2 (/lib64/libc.so.6+0x2f0d2)
   #​8 0x000000000059e5cd clang::tidy::bugprone::VirtualNearMissCheck::check(clang::ast_matchers::MatchFinder::MatchResult const&) (/LLVM-trunk/bin/clang-tidy+0x59e5cd)
   #​9 0x0000000002040de1 clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor::MatchVisitor::visitMatch(clang::ast_matchers::BoundNodes const&) ASTMatchFinder.cpp:0:0
   #​10 0x00000000020804e7 clang::ast_matchers::internal::BoundNodesTreeBuilder::visitMatches(clang::ast_matchers::internal::BoundNodesTreeBuilder::Visitor*) (/LLVM-trunk/bin/clang-tidy+0x20804e7)
   #​11 0x0000000002042adb clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor::matchWithFilter(clang::DynTypedNode const&) ASTMatchFinder.cpp:0:0
   #​12 0x0000000002063b7b clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor::TraverseDecl(clang::Decl*) ASTMatchFinder.cpp:0:0
   #​13 0x00000000020642aa clang::RecursiveASTVisitor<clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor>::TraverseDeclContextHelper(clang::DeclContext*) (.part.7214) ASTMatchFinder.cpp:0:0
   #​14 0x0000000002062b5c clang::RecursiveASTVisitor<clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor>::TraverseDecl(clang::Decl*) ASTMatchFinder.cpp:0:0
   #​15 0x0000000002063b86 clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor::TraverseDecl(clang::Decl*) ASTMatchFinder.cpp:0:0
   #​16 0x0000000002079c3d clang::RecursiveASTVisitor<clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor>::TraverseClassTemplateDecl(clang::ClassTemplateDecl*) ASTMatchFinder.cpp:0:0
   #​17 0x0000000002063b86 clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor::TraverseDecl(clang::Decl*) ASTMatchFinder.cpp:0:0
   #​18 0x00000000020642aa clang::RecursiveASTVisitor<clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor>::TraverseDeclContextHelper(clang::DeclContext*) (.part.7214) ASTMatchFinder.cpp:0:0
   #​19 0x0000000002062ce4 clang::RecursiveASTVisitor<clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor>::TraverseDecl(clang::Decl*) ASTMatchFinder.cpp:0:0
   #​20 0x0000000002063b86 clang::ast_matchers::internal::(anonymous namespace)::MatchASTVisitor::TraverseDecl(clang::Decl*) ASTMatchFinder.cpp:0:0
   #​21 0x0000000002063e45 clang::ast_matchers::MatchFinder::matchAST(clang::ASTContext&) (/LLVM-trunk/bin/clang-tidy+0x2063e45)
   #​22 0x00000000013f1428 clang::MultiplexConsumer::HandleTranslationUnit(clang::ASTContext&) (/LLVM-trunk/bin/clang-tidy+0x13f1428)
   #​23 0x0000000001589849 clang::ParseAST(clang::Sema&, bool, bool) (/LLVM-trunk/bin/clang-tidy+0x1589849)
   #​24 0x00000000013d5c41 clang::FrontendAction::Execute() (/LLVM-trunk/bin/clang-tidy+0x13d5c41)
   #​25 0x0000000001367dd1 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/LLVM-trunk/bin/clang-tidy+0x1367dd1)
   #​26 0x0000000000d362be clang::tooling::FrontendActionFactory::runInvocation(std::shared_ptrclang::CompilerInvocation, clang::FileManager*, std::shared_ptrclang::PCHContainerOperations, clang::DiagnosticConsumer*) (/LLVM-trunk/bin/clang-tidy+0xd362be)
   #​27 0x0000000000cea630 clang::tidy::runClangTidy(clang::tidy::ClangTidyContext&, clang::tooling::CompilationDatabase const&, llvm::ArrayRef<std::__cxx11::basic_string<char, std::char_traits, std::allocator > >, llvm::IntrusiveRefCntPtrllvm::vfs::OverlayFileSystem, bool, llvm::StringRef)::ActionFactory::runInvocation(std::shared_ptrclang::CompilerInvocation, clang::FileManager*, std::shared_ptrclang::PCHContainerOperations, clang::DiagnosticConsumer*) ClangTidy.cpp:0:0
   #​28 0x0000000000d2e444 clang::tooling::ToolInvocation::runInvocation(char const*, clang::driver::Compilation*, std::shared_ptrclang::CompilerInvocation, std::shared_ptrclang::PCHContainerOperations) (/LLVM-trunk/bin/clang-tidy+0xd2e444)
   #​29 0x0000000000d32d4d clang::tooling::ToolInvocation::run() (/LLVM-trunk/bin/clang-tidy+0xd32d4d)
   #​30 0x0000000000d35488 clang::tooling::ClangTool::run(clang::tooling::ToolAction*) (/LLVM-trunk/bin/clang-tidy+0xd35488)
   #​31 0x0000000000cf1a2e clang::tidy::runClangTidy(clang::tidy::ClangTidyContext&, clang::tooling::CompilationDatabase const&, llvm::ArrayRef<std::__cxx11::basic_string<char, std::char_traits, std::allocator > >, llvm::IntrusiveRefCntPtrllvm::vfs::OverlayFileSystem, bool, llvm::StringRef) (/LLVM-trunk/bin/clang-tidy+0xcf1a2e)