Add assert for 'bad' code path in GetUniqueNamespaceDeclaration

[teemperor]

Summary

If we call this function with a non-namespace as a second argument (and a nullptr name), we currently
only get a nullptr as a return when we hit the "Bad!!!" code path. This patch just adds an assert as this
seems to be a programming error in the calling code.

[teemperor]

Friendly ping @shafik

[teemperor]

• rebase patch to monorepo

[shafik]

lldb/trunk/source/Symbol/ClangASTContext.cpp

1957

We don't have a way to trigger this branch?

[davide]

lldb/trunk/source/Symbol/ClangASTContext.cpp

1957

I guess this is the whole point of the assertion. It can't be hit. BTW, you can replace it with llvm_unreachable()

[davide]

lldb/trunk/source/Symbol/ClangASTContext.cpp

1957

"can't" in this context is a very strong word. It shouldn't. If it gets hit, we should remove the assertion.

lldb/trunk/source/Symbol/ClangASTContext.cpp

if (decl_ctx == translation_unit_decl) {
         namespace_decl =
             NamespaceDecl::Create(*ast, decl_ctx, false, SourceLocation(),
                                   SourceLocation(), nullptr, nullptr);
         parent_namespace_decl->setAnonymousNamespace(namespace_decl);
         parent_namespace_decl->addDecl(namespace_decl);
         assert(namespace_decl ==
                parent_namespace_decl->getAnonymousNamespace());
       } else {
-        // BAD!!!
+        assert(false && "GetUniqueNamespaceDeclaration called with no name and "
+                        "no namespace as decl_ctx");
       }
     }
   }
 #ifdef LLDB_CONFIGURATION_DEBUG
   VerifyDecl(namespace_decl);
 #endif
   return namespace_decl;
 }