Fix PR 33189: Clang assertion on template destructor declaration

Summary:
This patch aims to fix the bug reported at
https://bugs.llvm.org/show_bug.cgi?id=33189. Clang hits an assertion
when a template destructor declaration is present. This is caused by
later processing that does not expect to encounter a template when
looking at a destructor. The resolution is to treat the destructor as
being not declared when later processing is interested in the properties
of the destructor of a class.

Reviewers: rcraik, hubert.reinterpretcast, aaron.ballman, rsmith

Reviewed By: rsmith

Subscribers: rsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D33833

Patch by Kuang He!

llvm-svn: 306905

clang/lib/AST/DeclCXX.cpp

@@ -1417,11 +1417,8 @@ CXXDestructorDecl *CXXRecordDecl::getDestructor() const {
                                           Context.getCanonicalType(ClassType));
 
   DeclContext::lookup_result R = lookup(Name);
-  if (R.empty())
-    return nullptr;
 
-  CXXDestructorDecl *Dtor = cast<CXXDestructorDecl>(R.front());
-  return Dtor;
+  return R.empty() ? nullptr : dyn_cast<CXXDestructorDecl>(R.front());
 }
 
 bool CXXRecordDecl::isAnyDestructorNoReturn() const {

clang/test/SemaTemplate/destructor-template.cpp

@@ -86,3 +86,9 @@ namespace PR16852 {
   template<typename T> decltype(S<T>().~S()) f(); // expected-note {{candidate template ignored: couldn't infer template argument 'T'}}
   void g() { f(); } // expected-error {{no matching function for call to 'f'}}
 }
+
+class PR33189
+{
+  template <class T>
+  ~PR33189() { } // expected-error{{destructor cannot be declared as a template}}
+};