Fix for Crash in nested name specifier decltype

[bviyer]

Summary

There was a crash when qualtype is null in the function Sema::ActOnCXXNestedNameSpecifierDecltype. If it is null then just return without processing it further.

[bviyer]

Ping!

[erik.pilkington]

Hi Balaji, thanks for working on this!

lib/Sema/SemaCXXScopeSpec.cpp

849–850

T.isNull()? Also, we use 2 space indentation in LLVM.

test/SemaCXX/qualtype-null-check.cpp

1

I can't reproduce this failure with TOT clang, are you sure you copied in the testcase right?

[erik.pilkington]

Looks like @rtrieu beat you to the punch in r336475! Presumably thats why the test case wasn't failing on TOT. Since this is already fixed, you should mark this revision as abandoned.

[bviyer]

Thank you Eric. I abandoned the revision as you suggested.

lib/Sema/SemaCXXScopeSpec.cpp

bool Sema::ActOnCXXNestedNameSpecifierDecltype(CXXScopeSpec &SS,
                                                const DeclSpec &DS,
                                                SourceLocation ColonColonLoc) {
   if (SS.isInvalid() || DS.getTypeSpecType() == DeclSpec::TST_error)
     return true;
 
   assert(DS.getTypeSpecType() == DeclSpec::TST_decltype);
 
   QualType T = BuildDecltypeType(DS.getRepAsExpr(), DS.getTypeSpecTypeLoc());
+  if (T.getTypePtrOrNull() == nullptr)
+      return true;
   if (!T->isDependentType() && !T->getAs<TagType>()) {
     Diag(DS.getTypeSpecTypeLoc(), diag::err_expected_class_or_namespace) 
       << T << getLangOpts().CPlusPlus;
     return true;
   }
 
   TypeLocBuilder TLB;
   DecltypeTypeLoc DecltypeTL = TLB.push<DecltypeTypeLoc>(T);

test/SemaCXX/qualtype-null-check.cpp

+// RUN: %clang_cc1 -fsyntax-only -std=c++14 -verify %s
+struct A
+{
+    bool x{&decltype(foo)::foo}; // expected-error {{reference to non-static member function must be called}}
+    void foo(int);
+};