[clang] Distinguish unresolved templates in UnresolvedLookupExpr

Author: zyn0217

clang/include/clang/AST/ASTContext.h

@@ -1116,7 +1116,8 @@ class ASTContext : public RefCountedBase<ASTContext> {
   CanQualType BFloat16Ty;
   CanQualType Float16Ty; // C11 extension ISO/IEC TS 18661-3
   CanQualType VoidPtrTy, NullPtrTy;
-  CanQualType DependentTy, OverloadTy, BoundMemberTy, UnknownAnyTy;
+  CanQualType DependentTy, OverloadTy, BoundMemberTy, UnresolvedTemplateTy,
+      UnknownAnyTy;
   CanQualType BuiltinFnTy;
   CanQualType PseudoObjectTy, ARCUnbridgedCastTy;
   CanQualType ObjCBuiltinIdTy, ObjCBuiltinClassTy, ObjCBuiltinSelTy;

clang/include/clang/AST/BuiltinTypes.def

@@ -285,6 +285,8 @@ PLACEHOLDER_TYPE(Overload, OverloadTy)
 //   x->foo       # if only contains non-static members
 PLACEHOLDER_TYPE(BoundMember, BoundMemberTy)
 
+PLACEHOLDER_TYPE(UnresolvedTemplate, UnresolvedTemplateTy)
+
 // The type of an expression which refers to a pseudo-object,
 // such as those introduced by Objective C's @property or
 // VS.NET's __property declarations.  A placeholder type.  The

clang/include/clang/Serialization/ASTBitCodes.h

@@ -1099,6 +1099,8 @@ enum PredefinedTypeIDs {
 // \brief WebAssembly reference types with auto numeration
 #define WASM_TYPE(Name, Id, SingletonId) PREDEF_TYPE_##Id##_ID,
 #include "clang/Basic/WebAssemblyReferenceTypes.def"
+
+  PREDEF_TYPE_UNRESOLVED_TEMPLATE,
   // Sentinel value. Considered a predefined type but not useable as one.
   PREDEF_TYPE_LAST_ID
 };
@@ -1108,7 +1110,7 @@ enum PredefinedTypeIDs {
 ///
 /// Type IDs for non-predefined types will start at
 /// NUM_PREDEF_TYPE_IDs.
-const unsigned NUM_PREDEF_TYPE_IDS = 502;
+const unsigned NUM_PREDEF_TYPE_IDS = 503;
 
 // Ensure we do not overrun the predefined types we reserved
 // in the enum PredefinedTypeIDs above.

clang/lib/AST/ASTContext.cpp

@@ -1306,6 +1306,9 @@ void ASTContext::InitBuiltinTypes(const TargetInfo &Target,
   // Placeholder type for bound members.
   InitBuiltinType(BoundMemberTy,       BuiltinType::BoundMember);
 
+  // Placeholder type for unresolved templates.
+  InitBuiltinType(UnresolvedTemplateTy, BuiltinType::UnresolvedTemplate);
+
   // Placeholder type for pseudo-objects.
   InitBuiltinType(PseudoObjectTy,      BuiltinType::PseudoObject);
 

clang/lib/AST/NSAPI.cpp

@@ -454,6 +454,7 @@ NSAPI::getNSNumberFactoryMethodKind(QualType T) const {
 #define WASM_TYPE(Name, Id, SingletonId) case BuiltinType::Id:
 #include "clang/Basic/WebAssemblyReferenceTypes.def"
   case BuiltinType::BoundMember:
+  case BuiltinType::UnresolvedTemplate:
   case BuiltinType::Dependent:
   case BuiltinType::Overload:
   case BuiltinType::UnknownAny:

clang/lib/AST/Type.cpp

@@ -3381,6 +3381,8 @@ StringRef BuiltinType::getName(const PrintingPolicy &Policy) const {
     return "<overloaded function type>";
   case BoundMember:
     return "<bound member function type>";
+  case UnresolvedTemplate:
+    return "<unresolved template type>";
   case PseudoObject:
     return "<pseudo-object type>";
   case Dependent:
@@ -4673,6 +4675,7 @@ bool Type::canHaveNullability(bool ResultIfUnknown) const {
 #include "clang/AST/BuiltinTypes.def"
       return false;
 
+    case BuiltinType::UnresolvedTemplate:
     // Dependent types that could instantiate to a pointer type.
     case BuiltinType::Dependent:
     case BuiltinType::Overload:

clang/lib/AST/TypeLoc.cpp

@@ -399,6 +399,7 @@ TypeSpecifierType BuiltinTypeLoc::getWrittenTypeSpec() const {
   case BuiltinType::NullPtr:
   case BuiltinType::Overload:
   case BuiltinType::Dependent:
+  case BuiltinType::UnresolvedTemplate:
   case BuiltinType::BoundMember:
   case BuiltinType::UnknownAny:
   case BuiltinType::ARCUnbridgedCast:

clang/lib/Sema/SemaExpr.cpp

@@ -6349,6 +6349,7 @@ static bool isPlaceholderToRemoveAsArg(QualType type) {
 #include "clang/AST/BuiltinTypes.def"
     return false;
 
+  case BuiltinType::UnresolvedTemplate:
   // We cannot lower out overload sets; they might validly be resolved
   // by the call machinery.
   case BuiltinType::Overload:
@@ -21234,6 +21235,24 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
   if (!placeholderType) return E;
 
   switch (placeholderType->getKind()) {
+  case BuiltinType::UnresolvedTemplate: {
+    auto *ULE = cast<UnresolvedLookupExpr>(E);
+    const DeclarationNameInfo &NameInfo = ULE->getNameInfo();
+    NestedNameSpecifierLoc Loc = ULE->getQualifierLoc();
+    NamedDecl *Temp = *ULE->decls_begin();
+    bool IsTypeAliasTemplateDecl = isa<TypeAliasTemplateDecl>(Temp);
+    if (NestedNameSpecifier *NNS = Loc.getNestedNameSpecifier())
+      Diag(NameInfo.getLoc(), diag::err_template_kw_refers_to_type_template)
+          << NNS << NameInfo.getName().getAsString() << Loc.getSourceRange()
+          << IsTypeAliasTemplateDecl;
+    else
+      Diag(NameInfo.getLoc(), diag::err_template_kw_refers_to_type_template)
+          << "" << NameInfo.getName().getAsString() << Loc.getSourceRange()
+          << IsTypeAliasTemplateDecl;
+    Diag(Temp->getLocation(), diag::note_referenced_type_template)
+        << IsTypeAliasTemplateDecl;
+    return CreateRecoveryExpr(NameInfo.getBeginLoc(), NameInfo.getEndLoc(), {});
+  }
 
   // Overloaded expressions.
   case BuiltinType::Overload: {

clang/lib/Sema/SemaTemplate.cpp

@@ -5553,7 +5553,7 @@ ExprResult Sema::BuildTemplateIdExpr(const CXXScopeSpec &SS,
         R.getRepresentativeDecl(), TemplateKWLoc, TemplateArgs);
     if (Res.isInvalid() || Res.isUsable())
       return Res;
-    // Result is dependent. Carry on to build an UnresolvedLookupEpxr.
+    // Result is dependent. Carry on to build an UnresolvedLookupExpr.
     KnownDependent = true;
   }
 
@@ -5571,6 +5571,10 @@ ExprResult Sema::BuildTemplateIdExpr(const CXXScopeSpec &SS,
       TemplateKWLoc, R.getLookupNameInfo(), RequiresADL, TemplateArgs,
       R.begin(), R.end(), KnownDependent);
 
+  if (ULE->getType() == Context.OverloadTy && R.isSingleResult() &&
+      !R.getFoundDecl()->getAsFunction())
+    ULE->setType(Context.UnresolvedTemplateTy);
+
   return ULE;
 }
 
@@ -5609,8 +5613,9 @@ Sema::BuildQualifiedTemplateIdExpr(CXXScopeSpec &SS,
     Diag(NameInfo.getLoc(), diag::err_template_kw_refers_to_type_template)
         << SS.getScopeRep() << NameInfo.getName().getAsString() << SS.getRange()
         << isTypeAliasTemplateDecl;
-    Diag(Temp->getLocation(), diag::note_referenced_type_template) << 0;
-    return ExprError();
+    Diag(Temp->getLocation(), diag::note_referenced_type_template)
+        << isTypeAliasTemplateDecl;
+    return CreateRecoveryExpr(NameInfo.getBeginLoc(), NameInfo.getEndLoc(), {});
   };
 
   if (ClassTemplateDecl *Temp = R.getAsSingle<ClassTemplateDecl>())

clang/lib/Serialization/ASTCommon.cpp

@@ -186,6 +186,9 @@ serialization::TypeIdxFromBuiltin(const BuiltinType *BT) {
   case BuiltinType::Overload:
     ID = PREDEF_TYPE_OVERLOAD_ID;
     break;
+  case BuiltinType::UnresolvedTemplate:
+    ID = PREDEF_TYPE_UNRESOLVED_TEMPLATE;
+    break;
   case BuiltinType::BoundMember:
     ID = PREDEF_TYPE_BOUND_MEMBER;
     break;

clang/lib/Serialization/ASTReader.cpp

@@ -7311,6 +7311,9 @@ QualType ASTReader::GetType(TypeID ID) {
     case PREDEF_TYPE_OVERLOAD_ID:
       T = Context.OverloadTy;
       break;
+    case PREDEF_TYPE_UNRESOLVED_TEMPLATE:
+      T = Context.UnresolvedTemplateTy;
+      break;
     case PREDEF_TYPE_BOUND_MEMBER:
       T = Context.BoundMemberTy;
       break;

clang/test/SemaCXX/PR62533.cpp

@@ -2,7 +2,7 @@
 
 template<typename T>
 struct test {
-  template<typename> using fun_diff = char; // expected-note 2{{class template declared here}}
+  template<typename> using fun_diff = char; // expected-note 2{{type alias template declared here}}
 };
 
 template<typename T, typename V>

clang/test/SemaTemplate/template-id-expr.cpp

@@ -186,3 +186,74 @@ class E {
 #endif
 template<typename T> using D = int; // expected-note {{declared here}} 
 E<D> ed; // expected-note {{instantiation of}}
+
+namespace non_functions {
+
+#if __cplusplus >= 201103L
+namespace PR88832 {
+template <typename T> struct O {
+  static const T v = 0;
+};
+
+struct P {
+  template <typename T> using I = typename O<T>::v; // #TypeAlias
+};
+
+struct Q {
+  template <typename T> int foo() {
+    return T::template I<int>; // expected-error {{'P::I' is expected to be a non-type template, but instantiated to a type alias template}}
+    // expected-note@#TypeAlias {{type alias template declared here}}
+  }
+};
+
+int bar() {
+  return Q().foo<P>(); // expected-note-re {{function template specialization {{.*}} requested here}}
+}
+
+} // namespace PR88832
+#endif
+
+namespace PR63243 {
+
+namespace std {
+template <class T> struct add_pointer { // #add_pointer
+};
+} // namespace std
+
+class A {};
+
+int main() {
+  std::__add_pointer<A>::type ptr; // #ill-formed-decl
+  // expected-error@#ill-formed-decl {{no template named '__add_pointer'}}
+  // expected-note@#add_pointer {{'add_pointer' declared here}}
+  // expected-error@#ill-formed-decl {{expected ';' after expression}}
+  // expected-error@#ill-formed-decl {{no type named 'type' in the global namespace}}
+  // expected-error@#ill-formed-decl {{'std::add_pointer' is expected to be a non-type template, but instantiated to a class template}}
+  // expected-note@#add_pointer {{class template declared here}}
+
+  // expected-warning@#ill-formed-decl {{keyword '__add_pointer' will be made available as an identifier here}}
+}
+
+} // namespace PR63243
+
+namespace PR48673 {
+
+template <typename T> struct C {
+  template <int TT> class Type {}; // #ClassTemplate
+};
+
+template <typename T1> struct A {
+  void foo() {
+    C<T1>::template Type<2>;  // #templated-decl-as-expression
+    // expected-error@#templated-decl-as-expression {{'C<float>::Type' is expected to be a non-type template, but instantiated to a class template}}}
+    // expected-note@#ClassTemplate {{class template declared here}}
+  }
+};
+
+void test() {
+  A<float>().foo(); // expected-note-re {{instantiation of member function {{.*}} requested here}}
+}
+
+} // namespace PR48673
+
+}