From db07b3f7cdcb505329c1280d7cf70791739a7cad Mon Sep 17 00:00:00 2001
From: Fariborz Jahanian <fjahanian@apple.com>
Date: Tue, 27 Oct 2009 23:02:38 +0000
Subject: [PATCH] Type of a conditional expression with two distinct
 objective-c class pointer is the most derived common class of the two. This
 is <rdar://problem/7334235>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@85337 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/AST/ASTContext.h     |  4 +++-
 lib/AST/ASTContext.cpp             | 22 ++++++++++++++++++++++
 lib/Sema/SemaExpr.cpp              |  5 ++++-
 test/SemaObjC/conditional-expr-6.m | 26 ++++++++++++++++++++++++++
 4 files changed, 55 insertions(+), 2 deletions(-)
 create mode 100644 test/SemaObjC/conditional-expr-6.m

diff --git a/include/clang/AST/ASTContext.h b/include/clang/AST/ASTContext.h
index 3acddab4b2..c4017d3e37 100644
--- a/include/clang/AST/ASTContext.h
+++ b/include/clang/AST/ASTContext.h
@@ -1019,7 +1019,9 @@ public:
   bool canAssignObjCInterfaces(const ObjCInterfaceType *LHS,
                                const ObjCInterfaceType *RHS);
   bool areComparableObjCPointerTypes(QualType LHS, QualType RHS);
-
+  QualType areCommonBaseCompatible(const ObjCObjectPointerType *LHSOPT,
+                                   const ObjCObjectPointerType *RHSOPT);
+  
   // Functions for calculating composite types
   QualType mergeTypes(QualType, QualType);
   QualType mergeFunctionTypes(QualType, QualType);
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 6c63c524b4..eb6d39225b 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -3846,6 +3846,28 @@ bool ASTContext::canAssignObjCInterfaces(const ObjCObjectPointerType *LHSOPT,
   return false;
 }
 
+/// areCommonBaseCompatible - Returns common base class of the two classes if
+/// one found. Note that this is O'2 algorithm. But it will be called as the
+/// last type comparison in a ?-exp of ObjC pointer types before a 
+/// warning is issued. So, its invokation is extremely rare.
+QualType ASTContext::areCommonBaseCompatible(
+                                          const ObjCObjectPointerType *LHSOPT,
+                                          const ObjCObjectPointerType *RHSOPT) {
+  const ObjCInterfaceType* LHS = LHSOPT->getInterfaceType();
+  const ObjCInterfaceType* RHS = RHSOPT->getInterfaceType();
+  if (!LHS || !RHS)
+    return QualType();
+  
+  while (const ObjCInterfaceDecl *LHSIDecl = LHS->getDecl()->getSuperClass()) {
+    QualType LHSTy = getObjCInterfaceType(LHSIDecl);
+    LHS = LHSTy->getAs<ObjCInterfaceType>();
+    if (canAssignObjCInterfaces(LHS, RHS))
+      return getObjCObjectPointerType(LHSTy);
+  }
+    
+  return QualType();
+}
+
 bool ASTContext::canAssignObjCInterfaces(const ObjCInterfaceType *LHS,
                                          const ObjCInterfaceType *RHS) {
   // Verify that the base decls are compatible: the RHS must be a subclass of
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index f4e58f07f8..12f1f513d4 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -3525,7 +3525,10 @@ QualType Sema::CheckConditionalOperands(Expr *&Cond, Expr *&LHS, Expr *&RHS,
       compositeType = Context.getObjCIdType();
     } else if (LHSTy->isObjCIdType() || RHSTy->isObjCIdType()) {
       compositeType = Context.getObjCIdType();
-    } else {
+    } else if (!(compositeType = 
+                 Context.areCommonBaseCompatible(LHSOPT, RHSOPT)).isNull())
+      ;
+    else {
       Diag(QuestionLoc, diag::ext_typecheck_cond_incompatible_operands)
         << LHSTy << RHSTy
         << LHS->getSourceRange() << RHS->getSourceRange();
diff --git a/test/SemaObjC/conditional-expr-6.m b/test/SemaObjC/conditional-expr-6.m
new file mode 100644
index 0000000000..88e943f3c6
--- /dev/null
+++ b/test/SemaObjC/conditional-expr-6.m
@@ -0,0 +1,26 @@
+// RUN: clang-cc -fsyntax-only -verify %s
+
+@interface NSObject @end
+
+@interface NSInterm : NSObject
+@end
+
+@interface NSArray : NSInterm 
+@end
+
+@interface NSSet : NSObject
+@end
+
+
+NSObject* test (int argc) {
+    NSArray *array = ((void*)0);
+    NSSet *set = ((void*)0);
+    return (argc) ? set : array ;
+}
+
+
+NSObject* test1 (int argc) {
+    NSArray *array = ((void*)0);
+    NSSet *set = ((void*)0);
+    return (argc) ? array : set;
+}