Improve the Objective-C common-type computation used by the ternary operator.

The Objective-C common-type computation had a few problems that
required a significant rework, including:
  - Quadradic behavior when finding the common base type; now it's
  linear.
  - Keeping around type arguments when computing the common type
  between a specialized and an unspecialized type
  - Introducing redundant protocol qualifiers.

Part of rdar://problem/6294649. Also fixes rdar://problem/19572837 by
addressing a longstanding bug in
ASTContext::CollectInheritedProtocols().

llvm-svn: 241544

1 files changed, 5 insertions, 5 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index afc9279cba1..a4911c20c68 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -6273,7 +6273,10 @@ QualType Sema::FindCompositeObjCPointerType(ExprResult &LHS, ExprResult &RHS,
 
     // FIXME: Consider unifying with 'areComparableObjCPointerTypes'.
     // It could return the composite type.
-    if (Context.canAssignObjCInterfaces(LHSOPT, RHSOPT)) {
+    if (!(compositeType =
+          Context.areCommonBaseCompatible(LHSOPT, RHSOPT)).isNull()) {
+      // Nothing more to do.
+    } else if (Context.canAssignObjCInterfaces(LHSOPT, RHSOPT)) {
       compositeType = RHSOPT->isObjCBuiltinType() ? RHSTy : LHSTy;
     } else if (Context.canAssignObjCInterfaces(RHSOPT, LHSOPT)) {
       compositeType = LHSOPT->isObjCBuiltinType() ? LHSTy : RHSTy;
@@ -6287,10 +6290,7 @@ QualType Sema::FindCompositeObjCPointerType(ExprResult &LHS, ExprResult &RHS,
       compositeType = Context.getObjCIdType();
     } else if (LHSTy->isObjCIdType() || RHSTy->isObjCIdType()) {
       compositeType = Context.getObjCIdType();
-    } else if (!(compositeType =
-                 Context.areCommonBaseCompatible(LHSOPT, RHSOPT)).isNull())
-      ;
-    else {
+    } else {
       Diag(QuestionLoc, diag::ext_typecheck_cond_incompatible_operands)
       << LHSTy << RHSTy
       << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();