Refactor CompareReferenceRelationship and its callers in preparation for

implementing the resolution of CWG2352.

No functionality change, except that we now convert the referent of a
reference binding to the underlying type of the reference in more cases;
we used to happen to preserve the type sugar from the referent if the
only type change was in the cv-qualifiers.

This exposed a bug in how we generate code for trivial assignment
operators: if the type sugar (particularly the may_alias attribute)
got lost during reference binding, we'd use the "wrong" TBAA information
for the load during the assignment.

1 files changed, 3 insertions, 7 deletions

diff --git a/clang/lib/Sema/SemaCast.cpp b/clang/lib/Sema/SemaCast.cpp
index d0b9fe12289..6216206690b 100644
--- a/clang/lib/Sema/SemaCast.cpp
+++ b/clang/lib/Sema/SemaCast.cpp
@@ -1306,10 +1306,6 @@ TryCastResult TryLValueToRValueCast(Sema &Self, Expr *SrcExpr,
   // Because we try the reference downcast before this function, from now on
   // this is the only cast possibility, so we issue an error if we fail now.
   // FIXME: Should allow casting away constness if CStyle.
-  bool DerivedToBase;
-  bool ObjCConversion;
-  bool ObjCLifetimeConversion;
-  bool FunctionConversion;
   QualType FromType = SrcExpr->getType();
   QualType ToType = R->getPointeeType();
   if (CStyle) {
@@ -1317,9 +1313,9 @@ TryCastResult TryLValueToRValueCast(Sema &Self, Expr *SrcExpr,
     ToType = ToType.getUnqualifiedType();
   }
 
+  Sema::ReferenceConversions RefConv;
   Sema::ReferenceCompareResult RefResult = Self.CompareReferenceRelationship(
-      SrcExpr->getBeginLoc(), ToType, FromType, DerivedToBase, ObjCConversion,
-      ObjCLifetimeConversion, FunctionConversion);
+      SrcExpr->getBeginLoc(), ToType, FromType, &RefConv);
   if (RefResult != Sema::Ref_Compatible) {
     if (CStyle || RefResult == Sema::Ref_Incompatible)
       return TC_NotApplicable;
@@ -1331,7 +1327,7 @@ TryCastResult TryLValueToRValueCast(Sema &Self, Expr *SrcExpr,
     return TC_Failed;
   }
 
-  if (DerivedToBase) {
+  if (RefConv & Sema::ReferenceConversions::DerivedToBase) {
     Kind = CK_DerivedToBase;
     CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
                        /*DetectVirtual=*/true);