Implement CWG1170, which makes access-control errors into template

argument deduction failures. Only implemented in C++0x, since this is
a significant change in behavior from C++98/03.

llvm-svn: 131209

clang/docs/LanguageExtensions.html

@@ -32,6 +32,7 @@ td {
   </ul>
 <li><a href="#checking_upcoming_features">Checks for Upcoming Standard Language Features</a></li>
   <ul>
+  <li><a href="#cxx_access_control_sfinae">C++0x SFINAE includes access control</a></li>
   <li><a href="#cxx_alias_templates">C++0x alias templates</a></li>
   <li><a href="#cxx_attributes">C++0x attributes</a></li>
   <li><a href="#cxx_decltype">C++0x <tt>decltype()</tt></a></li>
@@ -379,6 +380,10 @@ not yet implemented will be noted.</p>
 <p>Use <tt>__has_feature(cxx_decltype)</tt> to determine if support for the
 <tt>decltype()</tt> specifier is enabled.</p>
 
+<h3 id="cxx_access_control_sfinae">C++0x SFINAE includes access control</h3>
+
+<p>Use <tt>__has_feature(cxx_access_control_sfinae)</tt> to determine whether access-control errors (e.g., calling a private constructor) are considered to be template argument deduction errors (aka SFINAE errors), per <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1170">C++ DR1170</a>.</p>
+
 <h3 id="cxx_alias_templates">C++0x alias templates</h3>
 
 <p>Use <tt>__has_feature(cxx_alias_templates)</tt> to determine if support for

clang/lib/Lex/PPMacroExpansion.cpp

@@ -557,6 +557,7 @@ static bool HasFeature(const Preprocessor &PP, const IdentifierInfo *II) {
            .Case("ownership_returns", true)
            .Case("ownership_takes", true)
            // C++0x features
+           .Case("cxx_access_control_sfinae", LangOpts.CPlusPlus0x)
            .Case("cxx_alias_templates", LangOpts.CPlusPlus0x)
            .Case("cxx_attributes", LangOpts.CPlusPlus0x)
            .Case("cxx_auto_type", LangOpts.CPlusPlus0x)

clang/lib/Sema/Sema.cpp

@@ -577,9 +577,12 @@ Sema::SemaDiagnosticBuilder::~SemaDiagnosticBuilder() {
       break;
       
     case DiagnosticIDs::SFINAE_AccessControl:
-      // Unless access checking is specifically called out as a SFINAE
-      // error, report this diagnostic.
-      if (!SemaRef.AccessCheckingSFINAE)
+      // Per C++ Core Issue 1170, access control is part of SFINAE.
+      // Additionally, the AccessCheckingSFINAE flag can be used to temporary
+      // make access control a part of SFINAE for the purposes of checking
+      // type traits.
+      if (!SemaRef.AccessCheckingSFINAE &&
+          !SemaRef.getLangOptions().CPlusPlus0x)
         break;
         
     case DiagnosticIDs::SFINAE_SubstitutionFailure:

clang/test/CXX/temp/temp.fct.spec/temp.deduct/cwg1170.cpp

@@ -0,0 +1,41 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++0x %s
+
+#if !__has_feature(cxx_access_control_sfinae)
+#  error No support for access control as part of SFINAE?
+#endif
+
+typedef char yes_type;
+typedef char (&no_type)[2];
+
+template<unsigned N> struct unsigned_c { };
+
+template<typename T>
+class has_copy_constructor {
+  static T t;
+
+  template<typename U> static yes_type check(unsigned_c<sizeof(U(t))> * = 0);
+  template<typename U> static no_type check(...);
+
+public:
+  static const bool value = (sizeof(check<T>(0)) == sizeof(yes_type));
+};
+
+struct HasCopy { };
+
+struct HasNonConstCopy {
+  HasNonConstCopy(HasNonConstCopy&);
+};
+
+struct HasDeletedCopy {
+  HasDeletedCopy(const HasDeletedCopy&) = delete;
+};
+
+struct HasPrivateCopy {
+private:
+  HasPrivateCopy(const HasPrivateCopy&);
+};
+
+int check0[has_copy_constructor<HasCopy>::value? 1 : -1];
+int check1[has_copy_constructor<HasNonConstCopy>::value? 1 : -1];
+int check2[has_copy_constructor<HasDeletedCopy>::value? -1 : 1];
+int check3[has_copy_constructor<HasPrivateCopy>::value? -1 : 1];