Support friend function declarations in local classes correctly.

Fixes a crash and diagnoses the error condition of an unqualified
friend which doesn't resolve to something.  I'm still not certain how
this is useful.

llvm-svn: 116393

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -444,6 +444,8 @@ def err_introducing_special_friend : Error<
   "destructor|conversion operator}0 as a friend">;
 def err_tagless_friend_type_template : Error<
   "friend type templates must use an elaborated type">;
+def err_no_matching_local_friend : Error<
+  "no matching function found in local scope">;
 
 def err_abstract_type_in_decl : Error<
   "%select{return|parameter|variable|field}0 type %1 is an abstract class">;

clang/lib/Sema/SemaDecl.cpp

@@ -3153,6 +3153,20 @@ void Sema::AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD) {
   }
 }
 
+static void DiagnoseInvalidRedeclaration(Sema &S, FunctionDecl *NewFD) {
+  LookupResult Prev(S, NewFD->getDeclName(), NewFD->getLocation(),
+                    Sema::LookupOrdinaryName, Sema::ForRedeclaration);
+  S.LookupQualifiedName(Prev, NewFD->getDeclContext());
+  assert(!Prev.isAmbiguous() &&
+         "Cannot have an ambiguity in previous-declaration lookup");
+  for (LookupResult::iterator Func = Prev.begin(), FuncEnd = Prev.end();
+       Func != FuncEnd; ++Func) {
+    if (isa<FunctionDecl>(*Func) &&
+        isNearlyMatchingFunction(S.Context, cast<FunctionDecl>(*Func), NewFD))
+      S.Diag((*Func)->getLocation(), diag::note_member_def_close_match);
+  }
+}
+
 NamedDecl*
 Sema::ActOnFunctionDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                               QualType R, TypeSourceInfo *TInfo,
@@ -3470,13 +3484,6 @@ Sema::ActOnFunctionDeclarator(Scope* S, Declarator& D, DeclContext* DC,
   FilterLookupForScope(*this, Previous, DC, S, NewFD->hasLinkage());
 
   if (isFriend) {
-    // DC is the namespace in which the function is being declared.
-    assert((DC->isFileContext() || !Previous.empty() ||
-            (D.getCXXScopeSpec().isSet() &&
-             D.getCXXScopeSpec().getScopeRep()->isDependent())) &&
-           "previously-undeclared friend function being created "
-           "in a non-namespace context");
-
     // For now, claim that the objects have no previous declaration.
     if (FunctionTemplate) {
       FunctionTemplate->setObjectOfFriendDecl(false);
@@ -3675,24 +3682,36 @@ Sema::ActOnFunctionDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                                                 : TPC_FunctionTemplate);
   }
 
-  if (D.getCXXScopeSpec().isSet() && !NewFD->isInvalidDecl()) {
-    if (isFriend || !CurContext->isRecord()) {
-      // Fake up an access specifier if it's supposed to be a class member.
-      if (!Redeclaration && isa<CXXRecordDecl>(NewFD->getDeclContext()))
-        NewFD->setAccess(AS_public);
+  if (NewFD->isInvalidDecl()) {
+    // Ignore all the rest of this.
 
-      // An out-of-line member function declaration must also be a
-      // definition (C++ [dcl.meaning]p1).
-      // Note that this is not the case for explicit specializations of
-      // function templates or member functions of class templates, per
-      // C++ [temp.expl.spec]p2. We also allow these declarations as an extension
-      // for compatibility with old SWIG code which likes to generate them.
-      if (!IsFunctionDefinition && !isFriend &&
-          !isFunctionTemplateSpecialization && !isExplicitSpecialization) {
-        Diag(NewFD->getLocation(), diag::ext_out_of_line_declaration)
-          << D.getCXXScopeSpec().getRange();
-      }
-      if (!Redeclaration && !(isFriend && CurContext->isDependentContext())) {
+  } else if (CurContext->isRecord() && D.getCXXScopeSpec().isSet() &&
+             !isFriend) {
+    // The user provided a superfluous scope specifier inside a class
+    // definition:
+    //
+    // class X {
+    //   void X::f();
+    // };
+    Diag(NewFD->getLocation(), diag::warn_member_extra_qualification)
+      << Name << FixItHint::CreateRemoval(D.getCXXScopeSpec().getRange());
+
+  } else if (!Redeclaration) {
+    // Fake up an access specifier if it's supposed to be a class member.
+    if (isa<CXXRecordDecl>(NewFD->getDeclContext()))
+      NewFD->setAccess(AS_public);
+
+    // Qualified decls generally require a previous declaration.
+    if (D.getCXXScopeSpec().isSet()) {
+      // ...with the major exception of dependent friend declarations.
+      // In theory, this condition could be whether the qualifier
+      // is dependent;  in practice, the way we nest template parameters
+      // prevents this sort of matching from working, so we have to base it
+      // on the general dependence of the context.
+      if (isFriend && CurContext->isDependentContext()) {
+        // ignore these
+
+      } else {
         // The user tried to provide an out-of-line definition for a
         // function that is a member of a class or namespace, but there
         // was no such member function declared (C++ [class.mfct]p2,
@@ -3711,27 +3730,28 @@ Sema::ActOnFunctionDeclarator(Scope* S, Declarator& D, DeclContext* DC,
           << Name << DC << D.getCXXScopeSpec().getRange();
         NewFD->setInvalidDecl();
 
-        LookupResult Prev(*this, Name, D.getIdentifierLoc(), LookupOrdinaryName,
-                          ForRedeclaration);
-        LookupQualifiedName(Prev, DC);
-        assert(!Prev.isAmbiguous() &&
-               "Cannot have an ambiguity in previous-declaration lookup");
-        for (LookupResult::iterator Func = Prev.begin(), FuncEnd = Prev.end();
-             Func != FuncEnd; ++Func) {
-          if (isa<FunctionDecl>(*Func) &&
-              isNearlyMatchingFunction(Context, cast<FunctionDecl>(*Func), NewFD))
-            Diag((*Func)->getLocation(), diag::note_member_def_close_match);
-        }
+        DiagnoseInvalidRedeclaration(*this, NewFD);
       }
-    } else {
-      // The user provided a superfluous scope specifier inside a class definition:
-      //
-      // class X {
-      //   void X::f();
-      // };
-      Diag(NewFD->getLocation(), diag::warn_member_extra_qualification)
-        << Name << FixItHint::CreateRemoval(D.getCXXScopeSpec().getRange());
+
+    // Unqualified local friend declarations are required to resolve
+    // to something.
+    } else if (isFriend && cast<CXXRecordDecl>(CurContext)->isLocalClass()) {
+      Diag(D.getIdentifierLoc(), diag::err_no_matching_local_friend);
+      NewFD->setInvalidDecl();
+      DiagnoseInvalidRedeclaration(*this, NewFD);
     }
+
+  } else if (!IsFunctionDefinition && D.getCXXScopeSpec().isSet() &&
+             !isFriend && !isFunctionTemplateSpecialization &&
+             !isExplicitSpecialization) {
+    // An out-of-line member function declaration must also be a
+    // definition (C++ [dcl.meaning]p1).
+    // Note that this is not the case for explicit specializations of
+    // function templates or member functions of class templates, per
+    // C++ [temp.expl.spec]p2. We also allow these declarations as an extension
+    // for compatibility with old SWIG code which likes to generate them.
+    Diag(NewFD->getLocation(), diag::ext_out_of_line_declaration)
+      << D.getCXXScopeSpec().getRange();
   }
 
   // Handle attributes. We need to have merged decls when handling attributes

clang/lib/Sema/SemaDeclCXX.cpp

@@ -6344,12 +6344,26 @@ Decl *Sema::ActOnFriendFunctionDecl(Scope *S, Declarator &D, bool IsDefinition,
 
   // There are four cases here.
   //   - There's no scope specifier, in which case we just go to the
-  //     appropriate namespace and create a function or function template
+  //     appropriate scope and look for a function or function template
   //     there as appropriate.
   // Recover from invalid scope qualifiers as if they just weren't there.
   if (SS.isInvalid() || !SS.isSet()) {
-    // Walk out to the nearest namespace scope looking for matches.
+    // C++0x [namespace.memdef]p3:
+    //   If the name in a friend declaration is neither qualified nor
+    //   a template-id and the declaration is a function or an
+    //   elaborated-type-specifier, the lookup to determine whether
+    //   the entity has been previously declared shall not consider
+    //   any scopes outside the innermost enclosing namespace.
+    // C++0x [class.friend]p11:
+    //   If a friend declaration appears in a local class and the name
+    //   specified is an unqualified name, a prior declaration is
+    //   looked up without considering scopes that are outside the
+    //   innermost enclosing non-class scope. For a friend function
+    //   declaration, if there is no prior declaration, the program is
+    //   ill-formed.
+    bool isLocal = cast<CXXRecordDecl>(CurContext)->isLocalClass();
 
+    // Find the appropriate context according to the above.
     DC = CurContext;
     while (true) {
       // Skip class contexts.  If someone can cite chapter and verse
@@ -6365,9 +6379,9 @@ Decl *Sema::ActOnFriendFunctionDecl(Scope *S, Declarator &D, bool IsDefinition,
       LookupQualifiedName(Previous, DC);
 
       // TODO: decide what we think about using declarations.
-      if (!Previous.empty())
+      if (isLocal || !Previous.empty())
         break;
-      
+
       if (DC->isFileContext()) break;
       DC = DC->getParent();
     }
@@ -6381,6 +6395,8 @@ Decl *Sema::ActOnFriendFunctionDecl(Scope *S, Declarator &D, bool IsDefinition,
         && !getLangOptions().CPlusPlus0x)
       Diag(DS.getFriendSpecLoc(), diag::err_friend_is_member);
 
+    S = getScopeForDeclContext(S, DC);
+
   //   - There's a non-dependent scope specifier, in which case we
   //     compute it and do a previous lookup there for a function
   //     or function template.
@@ -6425,7 +6441,7 @@ Decl *Sema::ActOnFriendFunctionDecl(Scope *S, Declarator &D, bool IsDefinition,
     assert(isa<CXXRecordDecl>(DC) && "friend declaration not in class?");
   }
 
-  if (DC->isFileContext()) {
+  if (!DC->isRecord()) {
     // This implies that it has to be an operator or function.
     if (D.getName().getKind() == UnqualifiedId::IK_ConstructorName ||
         D.getName().getKind() == UnqualifiedId::IK_DestructorName ||

clang/test/CXX/class.access/class.friend/p11.cpp

@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+// rdar://problem/8540720
+namespace test0 {
+  void foo() {
+    void bar();
+    class A {
+      friend void bar();
+    };
+  }
+}
+
+namespace test1 {
+  void foo() {
+    class A {
+      friend void bar(); // expected-error {{no matching function found in local scope}}
+    };
+  }
+}