When computing Objective-C pointer conversions in C++, retain

the qualifiers (e.g., GC qualifiers) on the type we're converting
from, rather than just blindly adopting the qualifiers of the type
we're converting to or dropping qualifiers altogether. 

As an added bonus, properly diagnose GC qualifier mismatches to
eliminate a crash in the overload resolution failure diagnostics.

llvm-svn: 130255

1 files changed, 39 insertions, 5 deletions

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 6e6bf22be0b..7eb89787f99 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -1205,6 +1205,7 @@ static bool IsStandardConversion(Sema &S, Expr* From, QualType ToType,
     // Pointer conversions (C++ 4.10).
     SCS.Second = ICK_Pointer_Conversion;
     SCS.IncompatibleObjC = IncompatibleObjC;
+    FromType = FromType.getUnqualifiedType();
   } else if (S.IsMemberPointerConversion(From, FromType, ToType,
                                          InOverloadResolution, FromType)) {
     // Pointer to member conversions (4.11).
@@ -1671,6 +1672,20 @@ bool Sema::IsPointerConversion(Expr *From, QualType FromType, QualType ToType,
   
   return false;
 }
+ 
+/// \brief Adopt the given qualifiers for the given type.
+static QualType AdoptQualifiers(ASTContext &Context, QualType T, Qualifiers Qs){
+  Qualifiers TQs = T.getQualifiers();
+  
+  // Check whether qualifiers already match.
+  if (TQs == Qs)
+    return T;
+  
+  if (Qs.compatiblyIncludes(TQs))
+    return Context.getQualifiedType(T, Qs);
+  
+  return Context.getQualifiedType(T.getUnqualifiedType(), Qs);
+}
 
 /// isObjCPointerConversion - Determines whether this is an
 /// Objective-C pointer conversion. Subroutine of IsPointerConversion,
@@ -1681,6 +1696,9 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
   if (!getLangOptions().ObjC1)
     return false;
 
+  // The set of qualifiers on the type we're converting from.
+  Qualifiers FromQualifiers = FromType.getQualifiers();
+  
   // First, we handle all conversions on ObjC object pointer types.
   const ObjCObjectPointerType* ToObjCPtr =
     ToType->getAs<ObjCObjectPointerType>();
@@ -1694,10 +1712,11 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
                                        FromObjCPtr->getPointeeType()))
       return false;
 
+    // Check for compatible 
     // Objective C++: We're able to convert between "id" or "Class" and a
     // pointer to any interface (in both directions).
     if (ToObjCPtr->isObjCBuiltinType() && FromObjCPtr->isObjCBuiltinType()) {
-      ConvertedType = ToType;
+      ConvertedType = AdoptQualifiers(Context, ToType, FromQualifiers);
       return true;
     }
     // Conversions with Objective-C's id<...>.
@@ -1705,7 +1724,7 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
          ToObjCPtr->isObjCQualifiedIdType()) &&
         Context.ObjCQualifiedIdTypesAreCompatible(ToType, FromType,
                                                   /*compare=*/false)) {
-      ConvertedType = ToType;
+      ConvertedType = AdoptQualifiers(Context, ToType, FromQualifiers);
       return true;
     }
     // Objective C++: We're able to convert from a pointer to an
@@ -1720,6 +1739,7 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
       ConvertedType = BuildSimilarlyQualifiedPointerType(FromObjCPtr,
                                                    ToObjCPtr->getPointeeType(),
                                                          ToType, Context);
+      ConvertedType = AdoptQualifiers(Context, ConvertedType, FromQualifiers);
       return true;
     }
 
@@ -1731,6 +1751,7 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
       ConvertedType = BuildSimilarlyQualifiedPointerType(FromObjCPtr,
                                                    ToObjCPtr->getPointeeType(),
                                                          ToType, Context);
+      ConvertedType = AdoptQualifiers(Context, ConvertedType, FromQualifiers);
       return true;
     }
   }
@@ -1743,7 +1764,7 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
     // Objective C++: We're able to convert from a pointer to any object
     // to a block pointer type.
     if (FromObjCPtr && FromObjCPtr->isObjCBuiltinType()) {
-      ConvertedType = ToType;
+      ConvertedType = AdoptQualifiers(Context, ToType, FromQualifiers);
       return true;
     }
     ToPointeeType = ToBlockPtr->getPointeeType();
@@ -1752,7 +1773,7 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
            ToObjCPtr && ToObjCPtr->isObjCBuiltinType()) {
     // Objective C++: We're able to convert from a block pointer type to a
     // pointer to any object.
-    ConvertedType = ToType;
+    ConvertedType = AdoptQualifiers(Context, ToType, FromQualifiers);
     return true;
   }
   else
@@ -1775,6 +1796,7 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
     // We always complain about this conversion.
     IncompatibleObjC = true;
     ConvertedType = Context.getPointerType(ConvertedType);
+    ConvertedType = AdoptQualifiers(Context, ConvertedType, FromQualifiers);
     return true;
   }
   // Allow conversion of pointee being objective-c pointer to another one;
@@ -1784,6 +1806,7 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
       isObjCPointerConversion(FromPointeeType, ToPointeeType, ConvertedType,
                               IncompatibleObjC)) {
     ConvertedType = Context.getPointerType(ConvertedType);
+    ConvertedType = AdoptQualifiers(Context, ConvertedType, FromQualifiers);
     return true;
   }
 
@@ -1844,7 +1867,7 @@ bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType,
     if (HasObjCConversion) {
       // We had an Objective-C conversion. Allow this pointer
       // conversion, but complain about it.
-      ConvertedType = ToType;
+      ConvertedType = AdoptQualifiers(Context, ToType, FromQualifiers);
       IncompatibleObjC = true;
       return true;
     }
@@ -6541,6 +6564,17 @@ void DiagnoseBadConversion(Sema &S, OverloadCandidate *Cand, unsigned I) {
       return;
     }
 
+    if (FromQs.getObjCGCAttr() != ToQs.getObjCGCAttr()) {
+      S.Diag(Fn->getLocation(), diag::note_ovl_candidate_bad_gc)
+      << (unsigned) FnKind << FnDesc
+      << (FromExpr ? FromExpr->getSourceRange() : SourceRange())
+      << FromTy
+      << FromQs.getObjCGCAttr() << ToQs.getObjCGCAttr()
+      << (unsigned) isObjectArgument << I+1;
+      MaybeEmitInheritedConstructorNote(S, Fn);
+      return;
+    }
+
     unsigned CVR = FromQs.getCVRQualifiers() & ~ToQs.getCVRQualifiers();
     assert(CVR && "unexpected qualifiers mismatch");