Fix expression evaluation after clang r232793

[labath]

Summary

I do not entirely understand what is going on here, but it seems lldb has used
setHasExternalLexicalStorage on a TagDecl to trigger some kind of lazy loading of class contents.
However, r232793 in clang removed this possibility, which broke expression evaluation in lldb.
This CL fixes this by calling CompleteTagDecl manually.

I do not know if this is the correct fix for this issue, so I am mostly just drawing attention to
it. Feel free to commit a more correct solution.

[labath]

abandoning as this is fixed already

[labath]

Un-abandoning, since the offending commit was reverted. This can still serve as a starting point when it is re-committed.

[clayborg]

We really do not want this change. This means anytime we play with a class it will complete it right away, regardless of needing a full definition or not. This fix should be done in clang so that clang naturally knows how to say "I need a full definition and I need to know to complete a class when required".

source/Symbol/ClangASTImporter.cpp

ClangASTImporter::Minion::Imported (clang::Decl *from, clang::Decl *to)
     }
 
     if (TagDecl *from_tag_decl = dyn_cast<TagDecl>(from))
     {
         TagDecl *to_tag_decl = dyn_cast<TagDecl>(to);
 
         to_tag_decl->setHasExternalLexicalStorage();
         to_tag_decl->setMustBuildLookupTable();
+        m_master.CompleteTagDecl(to_tag_decl);
 
         if (log)
             log->Printf("    [ClangASTImporter] To is a TagDecl - attributes %s%s [%s->%s]",
                         (to_tag_decl->hasExternalLexicalStorage() ? " Lexical" : ""),
                         (to_tag_decl->hasExternalVisibleStorage() ? " Visible" : ""),
                         (from_tag_decl->isCompleteDefinition() ? "complete" : "incomplete"),
                         (to_tag_decl->isCompleteDefinition() ? "complete" : "incomplete"));
     }
 
     if (isa<NamespaceDecl>(from))
     {
         NamespaceDecl *to_namespace_decl = dyn_cast<NamespaceDecl>(to);
 
         m_master.BuildNamespaceMap(to_namespace_decl);
 
         to_namespace_decl->setHasExternalVisibleStorage();
     }
 
     if (isa<ObjCInterfaceDecl>(from))
     {
         ObjCInterfaceDecl *to_interface_decl = dyn_cast<ObjCInterfaceDecl>(to);
 
         to_interface_decl->setHasExternalLexicalStorage();
         to_interface_decl->setHasExternalVisibleStorage();
+        m_master.CompleteObjCInterfaceDecl(to_interface_decl);
 
         /*to_interface_decl->setExternallyCompleted();*/
 
         if (log)
             log->Printf("    [ClangASTImporter] To is an ObjCInterfaceDecl - attributes %s%s%s",
                         (to_interface_decl->hasExternalLexicalStorage() ? " Lexical" : ""),
                         (to_interface_decl->hasExternalVisibleStorage() ? " Visible" : ""),
                         (to_interface_decl->hasDefinition() ? " HasDefinition" : ""));