Sema: Implement DR477

[majnemer]

Summary

Friend declarations shouldn't mention explicit or virtual.

[rsmith]

LGTM, thanks!

[majnemer]

Closed by commit rL207682 (authored by @majnemer).

include/clang/Basic/DiagnosticParseKinds.td

def ext_keyword_as_ident : ExtWarn<
   InGroup<KeywordCompat>;
 
 def error_empty_enum : Error<"use of empty enum">;
 def err_invalid_sign_spec : Error<"'%0' cannot be signed or unsigned">;
 def err_invalid_short_spec : Error<"'short %0' is invalid">;
 def err_invalid_long_spec : Error<"'long %0' is invalid">;
 def err_invalid_longlong_spec : Error<"'long long %0' is invalid">;
 def err_invalid_complex_spec : Error<"'_Complex %0' is invalid">;
-def err_friend_storage_spec : Error<"'%0' is invalid in friend declarations">;
+def err_friend_decl_spec : Error<"'%0' is invalid in friend declarations">;
 
 def ext_ident_list_in_param : Extension<
   "type-less parameter names in function declaration">;
 def ext_c99_variable_decl_in_for_loop : Extension<
   "variable declaration in for loop is a C99-specific feature">, InGroup<C99>;
 def ext_c99_compound_literal : Extension<
   "compound literals are a C99-specific feature">, InGroup<C99>;
 def ext_enumerator_list_comma_c : Extension<

lib/Sema/DeclSpec.cpp

if (isFriendSpecified() &&
 
     if (DeclSpec::TSCS TSC = getThreadStorageClassSpec()) {
       if (!SpecName.empty()) SpecName += " ";
       SpecName += getSpecifierName(TSC);
       SCLoc = getThreadStorageClassSpecLoc();
       ThreadHint = FixItHint::CreateRemoval(SCLoc);
     }
 
-    Diag(D, SCLoc, diag::err_friend_storage_spec)
+    Diag(D, SCLoc, diag::err_friend_decl_spec)
       << SpecName << StorageHint << ThreadHint;
 
     ClearStorageClassSpecs();
   }
 
+  // C++11 [dcl.fct.spec]p5:
+  //   The virtual specifier shall be used only in the initial
+  //   declaration of a non-static class member function;
+  // C++11 [dcl.fct.spec]p6:
+  //   The explicit specifier shall be used only in the declaration of
+  //   a constructor or conversion function within its class
+  //   definition;
+  if (isFriendSpecified() && (isVirtualSpecified() || isExplicitSpecified())) {
+    StringRef Keyword;
+    SourceLocation SCLoc;
+
+    if (isVirtualSpecified()) {
+      Keyword = "virtual";
+      SCLoc = getVirtualSpecLoc();
+    } else {
+      Keyword = "explicit";
+      SCLoc = getExplicitSpecLoc();
+    }
+
+    FixItHint Hint = FixItHint::CreateRemoval(SCLoc);
+    Diag(D, SCLoc, diag::err_friend_decl_spec)
+      << Keyword << Hint;
+
+    FS_virtual_specified = FS_explicit_specified = false;
+    FS_virtualLoc = FS_explicitLoc = SourceLocation();
+  }
+
   assert(!TypeSpecOwned || isDeclRep((TST) TypeSpecType));
- 
   // Okay, now we can infer the real type.
 
   // TODO: return "auto function" and other bad things based on the real type.
 
   // 'data definition has no type or storage class'?
 }
 
 bool DeclSpec::isMissingDeclaratorOk() {

test/CXX/dcl.dcl/dcl.spec/dcl.fct.spec/p6.cpp

 // RUN: %clang_cc1 -verify %s
 
 class A {
 public:
   explicit A();
   
   explicit operator int(); // expected-warning {{explicit conversion functions are a C++11 extension}}
 
   explicit void f0(); // expected-error {{'explicit' can only be applied to a constructor or conversion function}}
   
   operator bool();
 };
 
 explicit A::A() { } // expected-error {{'explicit' can only be specified inside the class definition}}
 explicit A::operator bool() { return false; }  // expected-warning {{explicit conversion functions are a C++11 extension}}\
                                                // expected-error {{'explicit' can only be specified inside the class definition}}
+
+class B {
+  friend explicit A::A(); // expected-error {{'explicit' is invalid in friend declarations}}
+};

test/CXX/drs/dr4xx.cpp

namespace dr474 { // dr474: yes
   int g();
   namespace N {
     int g(); // expected-error {{cannot be overloaded}}
   }
 }
 
 // dr475 FIXME write a codegen test
 
-namespace dr477 { // dr477: no
+namespace dr477 { // dr477: 3.5
   struct A {
     explicit A();
     virtual void f();
   };
   struct B {
-    friend explicit A::A(); // FIXME: reject this
-    friend virtual void A::f(); // FIXME: reject this
+    friend explicit A::A(); // expected-error {{'explicit' is invalid in friend declarations}}
+    friend virtual void A::f(); // expected-error {{'virtual' is invalid in friend declarations}}
   };
   explicit A::A() {} // expected-error {{can only be specified inside the class definition}}
   virtual void A::f() {} // expected-error {{can only be specified inside the class definition}}
 }
 
 namespace dr478 { // dr478: yes
   struct A { virtual void f() = 0; }; // expected-note {{unimplemented}}
   void f(A *a);

www/cxx_dr_status.html

<tr class="open" id="476">
     <td>extension</td>
     <td>Determining the buffer size for placement new</td>
     <td align="center">Not resolved</td>
   </tr>
   <tr id="477">
     <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#477">477</a></td>
     <td>CD1</td>
     <td>Can <TT>virtual</TT> appear in a <TT>friend</TT> declaration?</td>
-    <td class="none" align="center">No</td>
+    <td class="svn" align="center">SVN</td>
   </tr>
   <tr id="478">
     <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_closed.html#478">478</a></td>
     <td>NAD</td>
     <td>May a function parameter be an array of an abstract class type?</td>
     <td class="full" align="center">Yes</td>
   </tr>
   <tr id="479">