Implement name hiding for names found through virtual base subobjects

that are hidden by other derived base subobjects reached along a
lookup path that does *not* pass through the hiding subobject (C++
[class.member.lookup]p6). Fixes PR6462.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@97640 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 83 insertions, 1 deletions

diff --git a/lib/AST/CXXInheritance.cpp b/lib/AST/CXXInheritance.cpp
index 8615df4e79..70f8ee4bca 100644
--- a/lib/AST/CXXInheritance.cpp
+++ b/lib/AST/CXXInheritance.cpp
@@ -90,6 +90,17 @@ bool CXXRecordDecl::isDerivedFrom(CXXRecordDecl *Base, CXXBasePaths &Paths) cons
   return lookupInBases(&FindBaseClass, Base->getCanonicalDecl(), Paths);
 }
 
+bool CXXRecordDecl::isVirtuallyDerivedFrom(CXXRecordDecl *Base) const {
+  CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/false,
+                     /*DetectVirtual=*/false);
+
+  if (getCanonicalDecl() == Base->getCanonicalDecl())
+    return false;
+  
+  Paths.setOrigin(const_cast<CXXRecordDecl*>(this));  
+  return lookupInBases(&FindVirtualBaseClass, Base->getCanonicalDecl(), Paths);
+}
+
 static bool BaseIsNot(const CXXRecordDecl *Base, void *OpaqueTarget) {
   // OpaqueTarget is a CXXRecordDecl*.
   return Base->getCanonicalDecl() != (const CXXRecordDecl*) OpaqueTarget;
@@ -271,7 +282,68 @@ bool CXXBasePaths::lookupInBases(ASTContext &Context,
 bool CXXRecordDecl::lookupInBases(BaseMatchesCallback *BaseMatches,
                                   void *UserData,
                                   CXXBasePaths &Paths) const {
-  return Paths.lookupInBases(getASTContext(), this, BaseMatches, UserData);
+  // If we didn't find anything, report that.
+  if (!Paths.lookupInBases(getASTContext(), this, BaseMatches, UserData))
+    return false;
+
+  // If we're not recording paths or we won't ever find ambiguities,
+  // we're done.
+  if (!Paths.isRecordingPaths() || !Paths.isFindingAmbiguities())
+    return true;
+  
+  // C++ [class.member.lookup]p6:
+  //   When virtual base classes are used, a hidden declaration can be
+  //   reached along a path through the sub-object lattice that does
+  //   not pass through the hiding declaration. This is not an
+  //   ambiguity. The identical use with nonvirtual base classes is an
+  //   ambiguity; in that case there is no unique instance of the name
+  //   that hides all the others.
+  //
+  // FIXME: This is an O(N^2) algorithm, but DPG doesn't see an easy
+  // way to make it any faster.
+  for (CXXBasePaths::paths_iterator P = Paths.begin(), PEnd = Paths.end();
+       P != PEnd; /* increment in loop */) {
+    bool Hidden = false;
+
+    for (CXXBasePath::iterator PE = P->begin(), PEEnd = P->end();
+         PE != PEEnd && !Hidden; ++PE) {
+      if (PE->Base->isVirtual()) {
+        CXXRecordDecl *VBase = 0;
+        if (const RecordType *Record = PE->Base->getType()->getAs<RecordType>())
+          VBase = cast<CXXRecordDecl>(Record->getDecl());
+        if (!VBase)
+          break;
+
+        // The declaration(s) we found along this path were found in a
+        // subobject of a virtual base. Check whether this virtual
+        // base is a subobject of any other path; if so, then the
+        // declaration in this path are hidden by that patch.
+        for (CXXBasePaths::paths_iterator HidingP = Paths.begin(),
+                                       HidingPEnd = Paths.end();
+             HidingP != HidingPEnd;
+             ++HidingP) {
+          CXXRecordDecl *HidingClass = 0;
+          if (const RecordType *Record
+                       = HidingP->back().Base->getType()->getAs<RecordType>())
+            HidingClass = cast<CXXRecordDecl>(Record->getDecl());
+          if (!HidingClass)
+            break;
+
+          if (HidingClass->isVirtuallyDerivedFrom(VBase)) {
+            Hidden = true;
+            break;
+          }
+        }
+      }
+    }
+
+    if (Hidden)
+      P = Paths.Paths.erase(P);
+    else
+      ++P;
+  }
+  
+  return true;
 }
 
 bool CXXRecordDecl::FindBaseClass(const CXXBaseSpecifier *Specifier, 
@@ -283,6 +355,16 @@ bool CXXRecordDecl::FindBaseClass(const CXXBaseSpecifier *Specifier,
            ->getCanonicalDecl() == BaseRecord;
 }
 
+bool CXXRecordDecl::FindVirtualBaseClass(const CXXBaseSpecifier *Specifier, 
+                                         CXXBasePath &Path,
+                                         void *BaseRecord) {
+  assert(((Decl *)BaseRecord)->getCanonicalDecl() == BaseRecord &&
+         "User data for FindBaseClass is not canonical!");
+  return Specifier->isVirtual() &&
+         Specifier->getType()->getAs<RecordType>()->getDecl()
+           ->getCanonicalDecl() == BaseRecord;
+}
+
 bool CXXRecordDecl::FindTagMember(const CXXBaseSpecifier *Specifier, 
                                   CXXBasePath &Path,
                                   void *Name) {