Introduce a new expression type, UnresolvedDeclRefExpr, that describes

dependent qualified-ids such as

  Fibonacci<N - 1>::value

where N is a template parameter. These references are "unresolved"
because the name is dependent and, therefore, cannot be resolved to a
declaration node (as we would do for a DeclRefExpr or
QualifiedDeclRefExpr). UnresolvedDeclRefExprs instantiate to
DeclRefExprs, QualifiedDeclRefExprs, etc.

Also, be a bit more careful about keeping only a single set of
specializations for a class template, and instantiating from the
definition of that template rather than a previous declaration. In
general, we need a better solution for this for all TagDecls, because
it's too easy to accidentally look at a declaration that isn't the
definition.

We can now process a simple Fibonacci computation described as a
template metaprogram.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@67308 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 107 insertions, 3 deletions

diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index 3755744126..df1e7c38a5 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -1455,6 +1455,7 @@ public:
   bool RequireCompleteDeclContext(const CXXScopeSpec &SS);
   
   DeclContext *computeDeclContext(const CXXScopeSpec &SS);
+  bool isDependentScopeSpecifier(const CXXScopeSpec &SS);
 
   /// ActOnCXXGlobalScopeSpecifier - Return the object that represents the
   /// global scope ('::').
@@ -1880,6 +1881,12 @@ public:
                            ClassTemplateSpecializationDecl *ClassTemplateSpec,
                            bool ExplicitInstantiation);
 
+  CXXScopeSpec InstantiateScopeSpecifier(const NestedNameSpecifier *Components,
+                                         unsigned NumComponents,
+                                         SourceRange Range,
+                                         const TemplateArgument *TemplateArgs,
+                                         unsigned NumTemplateArgs);
+
   // Simple function for cloning expressions.
   template<typename T> 
   OwningExprResult Clone(T *E) {
diff --git a/lib/Sema/SemaCXXScopeSpec.cpp b/lib/Sema/SemaCXXScopeSpec.cpp
index 156f3a12fb..9e1196143b 100644
--- a/lib/Sema/SemaCXXScopeSpec.cpp
+++ b/lib/Sema/SemaCXXScopeSpec.cpp
@@ -29,6 +29,21 @@ DeclContext *Sema::computeDeclContext(const CXXScopeSpec &SS) {
   return NNS.computeDeclContext(Context);
 }
 
+bool Sema::isDependentScopeSpecifier(const CXXScopeSpec &SS) {
+  if (!SS.isSet() || SS.isInvalid())
+    return false;
+
+  NestedNameSpecifier NNS
+    = NestedNameSpecifier::getFromOpaquePtr(SS.getCurrentScopeRep());
+
+  if (Type *T = NNS.getAsType())
+    return T->isDependentType();
+
+  // FIXME: What about the injected-class-name of a class template? It
+  // is dependent, but we represent it as a declaration.
+  return false;
+}
+
 /// \brief Require that the context specified by SS be complete.
 ///
 /// If SS refers to a type, this routine checks whether the type is
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 483b79a098..18d55d92f4 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -52,6 +52,20 @@ std::string Sema::getDeclName(DeclTy *d) {
 /// and then return NULL.
 Sema::TypeTy *Sema::getTypeName(IdentifierInfo &II, SourceLocation NameLoc,
                                 Scope *S, const CXXScopeSpec *SS) {
+  // C++ [temp.res]p3:
+  //   A qualified-id that refers to a type and in which the
+  //   nested-name-specifier depends on a template-parameter (14.6.2)
+  //   shall be prefixed by the keyword typename to indicate that the
+  //   qualified-id denotes a type, forming an
+  //   elaborated-type-specifier (7.1.5.3).
+  //
+  // We therefore do not perform any name lookup up SS is a dependent
+  // scope name. FIXME: we will need to perform a special kind of
+  // lookup if the scope specifier names a member of the current
+  // instantiation.
+  if (SS && isDependentScopeSpecifier(*SS))
+    return 0;
+
   NamedDecl *IIDecl = 0;
   LookupResult Result = LookupParsedName(S, SS, &II, LookupOrdinaryName, 
                                          false, false);
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index b15f6ab984..e43d4b8027 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -613,6 +613,21 @@ Sema::ActOnDeclarationNameExpr(Scope *S, SourceLocation Loc,
   // Could be enum-constant, value decl, instance variable, etc.
   if (SS && SS->isInvalid())
     return ExprError();
+
+  // C++ [temp.dep.expr]p3:
+  //   An id-expression is type-dependent if it contains:
+  //     -- a nested-name-specifier that contains a class-name that
+  //        names a dependent type.
+  if (SS && isDependentScopeSpecifier(*SS)) {
+    llvm::SmallVector<NestedNameSpecifier, 16> Specs;
+    for (CXXScopeSpec::iterator Spec = SS->begin(), SpecEnd = SS->end();
+         Spec != SpecEnd; ++Spec)
+      Specs.push_back(NestedNameSpecifier::getFromOpaquePtr(*Spec));
+    return Owned(UnresolvedDeclRefExpr::Create(Context, Name, Loc,
+                                               SS->getRange(), &Specs[0],
+                                               Specs.size()));
+  }
+
   LookupResult Lookup = LookupParsedName(S, SS, Name, LookupOrdinaryName,
                                          false, true, Loc);
 
diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index b4e505e7c2..fd39a9150f 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -477,7 +477,7 @@ Sema::ActOnClassTemplate(Scope *S, unsigned TagSpec, TagKind TK,
   ClassTemplateDecl *NewTemplate
     = ClassTemplateDecl::Create(Context, SemanticContext, NameLoc,
                                 DeclarationName(Name), TemplateParams,
-                                NewClass);
+                                NewClass, PrevClassTemplate);
   
   // Set the lexical context of these templates
   NewClass->setLexicalDeclContext(CurContext);
diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index 7df9941aa5..10f9926b3e 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -625,6 +625,7 @@ namespace {
     OwningExprResult VisitCXXOperatorCallExpr(CXXOperatorCallExpr *E);
     OwningExprResult VisitConditionalOperator(ConditionalOperator *E);
     OwningExprResult VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E);
+    OwningExprResult VisitUnresolvedDeclRefExpr(UnresolvedDeclRefExpr *E);
     OwningExprResult VisitCXXTemporaryObjectExpr(CXXTemporaryObjectExpr *E);
     OwningExprResult VisitImplicitCastExpr(ImplicitCastExpr *E);
       
@@ -897,6 +898,26 @@ TemplateExprInstantiator::VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E) {
 }
 
 Sema::OwningExprResult 
+TemplateExprInstantiator::VisitUnresolvedDeclRefExpr(UnresolvedDeclRefExpr *E) {
+  CXXScopeSpec SS = SemaRef.InstantiateScopeSpecifier(E->begin(), E->size(),
+                                                      E->getQualifierRange(),
+                                                      TemplateArgs,
+                                                      NumTemplateArgs);
+  if (SS.isInvalid() || SS.isEmpty())
+    return SemaRef.ExprError();
+
+  // FIXME: We're passing in a NULL scope, because
+  // ActOnDeclarationNameExpr doesn't actually use the scope when we
+  // give it a non-empty scope specifier. Investigate whether it would
+  // be better to refactor ActOnDeclarationNameExpr.
+  return SemaRef.ActOnDeclarationNameExpr(/*Scope=*/0, E->getLocation(), 
+                                          E->getDeclName(), 
+                                          /*HasTrailingLParen=*/false,
+                                          &SS,
+                                          /*FIXME:isAddressOfOperand=*/false);
+}
+
+Sema::OwningExprResult 
 TemplateExprInstantiator::VisitCXXTemporaryObjectExpr(
                                                   CXXTemporaryObjectExpr *E) {
   QualType T = E->getType();
@@ -1047,7 +1068,9 @@ Sema::InstantiateClassTemplateSpecialization(
   // the best template.
   ClassTemplateDecl *Template = ClassTemplateSpec->getSpecializedTemplate();
 
-  if (!Template->getTemplatedDecl()->getDefinition(Context)) {
+  RecordDecl *Pattern = cast_or_null<RecordDecl>(
+                          Template->getTemplatedDecl()->getDefinition(Context));
+  if (!Pattern) {
     Diag(ClassTemplateSpec->getLocation(), 
          diag::err_template_implicit_instantiate_undefined)
       << Context.getTypeDeclType(ClassTemplateSpec);
@@ -1084,7 +1107,6 @@ Sema::InstantiateClassTemplateSpecialization(
   // FIXME: Create the injected-class-name for the
   // instantiation. Should this be a typedef or something like it?
 
-  RecordDecl *Pattern = Template->getTemplatedDecl();
   llvm::SmallVector<DeclTy *, 32> Fields;
   for (RecordDecl::decl_iterator Member = Pattern->decls_begin(),
                               MemberEnd = Pattern->decls_end();
@@ -1118,3 +1140,34 @@ Sema::InstantiateClassTemplateSpecialization(
 
   return Invalid;
 }
+
+/// \brief Instantiate a sequence of nested-name-specifiers into a
+/// scope specifier.
+CXXScopeSpec 
+Sema::InstantiateScopeSpecifier(const NestedNameSpecifier *Components,
+                                unsigned NumComponents,
+                                SourceRange Range,
+                                const TemplateArgument *TemplateArgs,
+                                unsigned NumTemplateArgs) {
+  CXXScopeSpec SS;
+  for (unsigned Comp = 0; Comp < NumComponents; ++Comp) {
+    if (Type *T = Components[Comp].getAsType()) {
+      QualType NewT = InstantiateType(QualType(T, 0), TemplateArgs, 
+                                      NumTemplateArgs, Range.getBegin(),
+                                      DeclarationName());
+      if (NewT.isNull())
+        return SS;
+      NestedNameSpecifier NNS(NewT.getTypePtr());
+      SS.addScopeRep(NNS.getAsOpaquePtr());
+    } else {
+      DeclContext *DC = Components[Comp].getAsDeclContext();
+      // FIXME: injected-class-name might be dependent, and therefore
+      // would need instantiation.
+      NestedNameSpecifier NNS(DC);
+      SS.addScopeRep(NNS.getAsOpaquePtr());
+    }
+  }
+
+  SS.setRange(Range);
+  return SS;
+}