[clang] Exclude invalid destructors from lookups.

[adamcz]

Summary

This fixes a crash when declaring a destructor with a wrong name, then
writing result to pch file and loading it again. The PCH storage uses
DeclarationNameKey as key and it is the same key for both the invalid
destructor and the implicit one that was created because the other one
was invalid. When querying for the Foo::~Foo we end up getting
Foo::~Bar, which is then rejected and we end up with nullptr in
CXXRecordDecl::GetDestructor().

Fixes https://bugs.llvm.org/show_bug.cgi?id=47270

[sammccall]

clang/lib/AST/DeclBase.cpp

1489

split into separate block, add a comment why

clang/test/PCH/cxx-invalid-destructor.cpp

3

nit: -fno-validate-pch shouldn't be needed IIUC

clang/test/PCH/cxx-invalid-destructor.h

7

nit: we can eliminate Bar I think?

[adamcz]

addressed review comments

clang/test/PCH/cxx-invalid-destructor.cpp

3

We need this, otherwise the PCH file is rejected for containing errors.

clang/lib/AST/DeclBase.cpp

static bool shouldBeHidden(NamedDecl *D) {
   // FIXME: This feels like a hack. Should DeclarationName support
   // template-ids, or is there a better way to keep specializations
   // from being visible?
   if (isa<ClassTemplateSpecializationDecl>(D))
     return true;
   if (auto *FD = dyn_cast<FunctionDecl>(D))
     if (FD->isFunctionTemplateSpecialization())
       return true;
 
+  // Hide destructors that are invalid. There should always be one destructor,
+  // but if it is an invalid decl, another one is created. We need to hide the
+  // invalid one from places that expect exactly one destructor, like the
+  // serialization code.
+  if (isa<CXXDestructorDecl>(D) && D->isInvalidDecl())
+    return true;
+
   return false;
 }
 
 void DeclContext::removeDecl(Decl *D) {
   assert(D->getLexicalDeclContext() == this &&
          "decl being removed from non-lexical context");
   assert((D->NextInContextAndBits.getPointer() || D == LastDecl) &&
          "decl is not in decls list");

clang/test/PCH/cxx-invalid-destructor.h

+struct Base {
+  ~Base();
+};
+
+struct Foo : public Base {
+  ~Base();
+};

clang/test/PCH/cxx-invalid-destructor.cpp

+// RUN: %clang_cc1 -x c++ -std=c++11 -emit-pch -o %t %S/cxx-invalid-destructor.h -fallow-pch-with-compiler-errors
+// RUN: %clang_cc1 -x c++ -std=c++11 -include-pch %t %S/cxx-invalid-destructor.cpp -fsyntax-only -fno-validate-pch
+
+Foo f;