Improve handling of friend types in several ways:

  - When instantiating a friend type template, perform semantic
  analysis on the resulting type.
  - Downgrade the errors concerning friend type declarations that do
  not refer to classes to ExtWarns in C++98/03. C++0x allows
  practically any type to be befriended, and ignores the friend
  declaration if the type is not a class.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@100635 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 63 insertions, 64 deletions

diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 75dbb46d42..60b6220227 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -5328,39 +5328,48 @@ FriendDecl *Sema::CheckFriendTypeDecl(SourceLocation FriendLoc,
   QualType T = TSInfo->getType();
   SourceRange TypeRange = TSInfo->getTypeLoc().getSourceRange();
   
-  // C++03 [class.friend]p2:
-  //   An elaborated-type-specifier shall be used in a friend declaration
-  //   for a class.*
-  //
-  //   * The class-key of the elaborated-type-specifier is required.
-  if (!getLangOptions().CPlusPlus0x && !T->isElaboratedTypeSpecifier()) {
-    // If we evaluated the type to a record type, suggest putting
-    // a tag in front.
-    if (const RecordType *RT = T->getAs<RecordType>()) {
-      RecordDecl *RD = RT->getDecl();
-      
-      std::string InsertionText = std::string(" ") + RD->getKindName();
-      
-      Diag(FriendLoc, diag::err_unelaborated_friend_type)
-        << (unsigned) RD->getTagKind()
+  if (!getLangOptions().CPlusPlus0x) {
+    // C++03 [class.friend]p2:
+    //   An elaborated-type-specifier shall be used in a friend declaration
+    //   for a class.*
+    //
+    //   * The class-key of the elaborated-type-specifier is required.
+    if (!ActiveTemplateInstantiations.empty()) {
+      // Do not complain about the form of friend template types during
+      // template instantiation; we will already have complained when the
+      // template was declared.
+    } else if (!T->isElaboratedTypeSpecifier()) {
+      // If we evaluated the type to a record type, suggest putting
+      // a tag in front.
+      if (const RecordType *RT = T->getAs<RecordType>()) {
+        RecordDecl *RD = RT->getDecl();
+        
+        std::string InsertionText = std::string(" ") + RD->getKindName();
+        
+        Diag(TypeRange.getBegin(), diag::ext_unelaborated_friend_type)
+          << (unsigned) RD->getTagKind()
+          << T
+          << FixItHint::CreateInsertion(PP.getLocForEndOfToken(FriendLoc),
+                                        InsertionText);
+      } else {
+        Diag(FriendLoc, diag::ext_nonclass_type_friend)
+          << T
+          << SourceRange(FriendLoc, TypeRange.getEnd());
+      }
+    } else if (T->getAs<EnumType>()) {
+      Diag(FriendLoc, diag::ext_enum_friend)
         << T
-        << SourceRange(FriendLoc)
-        << FixItHint::CreateInsertion(TypeRange.getBegin(),
-                                      InsertionText);
-      return 0; 
-    } else {
-      Diag(FriendLoc, diag::err_unexpected_friend)
         << SourceRange(FriendLoc, TypeRange.getEnd());
-      return 0;
     }
   }
   
-  // Enum types cannot be friends.
-  if (T->getAs<EnumType>()) {
-    Diag(FriendLoc, diag::err_enum_friend)
-      << SourceRange(FriendLoc, TypeRange.getEnd());
-    return 0;
-  }  
+  // C++0x [class.friend]p3:
+  //   If the type specifier in a friend declaration designates a (possibly
+  //   cv-qualified) class type, that class is declared as a friend; otherwise, 
+  //   the friend declaration is ignored.
+  
+  // FIXME: C++0x has some syntactic restrictions on friend type declarations
+  // in [class.friend]p3 that we do not implement.
   
   return FriendDecl::Create(Context, CurContext, FriendLoc, TSInfo, FriendLoc);
 }
@@ -5421,13 +5430,6 @@ Sema::DeclPtrTy Sema::ActOnFriendTypeDecl(Scope *S, const DeclSpec &DS,
     return DeclPtrTy();
   }
   
-  // Enum templates cannot be friends.
-  if (TempParams.size() && T->getAs<EnumType>()) {
-    Diag(DS.getTypeSpecTypeLoc(), diag::err_enum_friend)
-    << SourceRange(DS.getFriendSpecLoc());
-    return DeclPtrTy();
-  }
-
   // C++98 [class.friend]p1: A friend of a class is a function
   //   or class that is not a member of the class . . .
   // This is fixed in DR77, which just barely didn't make the C++03
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 3375ccc0eb..69f183c706 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -476,47 +476,44 @@ Decl *TemplateDeclInstantiator::VisitFieldDecl(FieldDecl *D) {
 }
 
 Decl *TemplateDeclInstantiator::VisitFriendDecl(FriendDecl *D) {
-  FriendDecl::FriendUnion FU;
-
   // Handle friend type expressions by simply substituting template
-  // parameters into the pattern type.
+  // parameters into the pattern type and checking the result.
   if (TypeSourceInfo *Ty = D->getFriendType()) {
     TypeSourceInfo *InstTy = 
       SemaRef.SubstType(Ty, TemplateArgs,
                         D->getLocation(), DeclarationName());
-    if (!InstTy) return 0;
+    if (!InstTy) 
+      return 0;
 
-    // This assertion is valid because the source type was necessarily
-    // an elaborated-type-specifier with a record tag.
-    assert(getLangOptions().CPlusPlus0x || InstTy->getType()->isRecordType());
+    FriendDecl *FD = SemaRef.CheckFriendTypeDecl(D->getFriendLoc(), InstTy);
+    if (!FD)
+      return 0;
+    
+    FD->setAccess(AS_public);
+    Owner->addDecl(FD);
+    return FD;
+  } 
+  
+  NamedDecl *ND = D->getFriendDecl();
+  assert(ND && "friend decl must be a decl or a type!");
 
-    FU = InstTy;
+  // FIXME: We have a problem here, because the nested call to Visit(ND)
+  // will inject the thing that the friend references into the current
+  // owner, which is wrong.
+  Decl *NewND;
 
-  // Handle everything else by appropriate substitution.
+  // Hack to make this work almost well pending a rewrite.
+  if (D->wasSpecialization()) {
+    // Totally egregious hack to work around PR5866
+    return 0;
   } else {
-    NamedDecl *ND = D->getFriendDecl();
-    assert(ND && "friend decl must be a decl or a type!");
-
-    // FIXME: We have a problem here, because the nested call to Visit(ND)
-    // will inject the thing that the friend references into the current
-    // owner, which is wrong.
-    Decl *NewND;
-
-    // Hack to make this work almost well pending a rewrite.
-    if (D->wasSpecialization()) {
-      // Totally egregious hack to work around PR5866
-      return 0;
-    } else {
-      NewND = Visit(ND);
-    }
-    if (!NewND) return 0;
-
-    FU = cast<NamedDecl>(NewND);
+    NewND = Visit(ND);
   }
+  if (!NewND) return 0;
 
   FriendDecl *FD =
-    FriendDecl::Create(SemaRef.Context, Owner, D->getLocation(), FU,
-                       D->getFriendLoc());
+    FriendDecl::Create(SemaRef.Context, Owner, D->getLocation(), 
+                       cast<NamedDecl>(NewND), D->getFriendLoc());
   FD->setAccess(AS_public);
   Owner->addDecl(FD);
   return FD;