[Sema][ObjC++] Objective-C++ support for __is_base_of(B, D)

[erik.pilkington]

Summary

This patch adds Objective-C interfaces support for the type trait is_base_of, so that __is_base_of(NSString, NSMutableString) is true.

rdar://24308607

Thanks for taking a look!
Erik

[arphaman]

LGTM! A couple of comments below:

lib/Sema/SemaExprCXX.cpp

4725 ↗

(On Diff #97905)

Please capitalize lhsObjTy and rhsObjTy.

test/SemaObjCXX/is-base-of.mm

14 ↗

(On Diff #97905)

I'd also add a test that verifies that id isn't a valid base, e.g:

static_assert(!__is_base_of(id, NSObj), "");

cfe/trunk/lib/Sema/SemaExprCXX.cpp

static bool EvaluateBinaryTypeTrait(Sema &Self, TypeTrait BTT, QualType LhsT,
   switch(BTT) {
   case BTT_IsBaseOf: {
     // C++0x [meta.rel]p2
     // Base is a base class of Derived without regard to cv-qualifiers or
     // Base and Derived are not unions and name the same class type without
     // regard to cv-qualifiers.
 
     const RecordType *lhsRecord = LhsT->getAs<RecordType>();
-    if (!lhsRecord) return false;
-
     const RecordType *rhsRecord = RhsT->getAs<RecordType>();
-    if (!rhsRecord) return false;
+    if (!rhsRecord || !lhsRecord) {
+      const ObjCObjectType *LHSObjTy = LhsT->getAs<ObjCObjectType>();
+      const ObjCObjectType *RHSObjTy = RhsT->getAs<ObjCObjectType>();
+      if (!LHSObjTy || !RHSObjTy)
+        return false;
+
+      ObjCInterfaceDecl *BaseInterface = LHSObjTy->getInterface();
+      ObjCInterfaceDecl *DerivedInterface = RHSObjTy->getInterface();
+      if (!BaseInterface || !DerivedInterface)
+        return false;
+
+      if (Self.RequireCompleteType(
+              KeyLoc, RhsT, diag::err_incomplete_type_used_in_type_trait_expr))
+        return false;
+
+      return BaseInterface->isSuperClassOf(DerivedInterface);
+    }
 
     assert(Self.Context.hasSameUnqualifiedType(LhsT, RhsT)
              == (lhsRecord == rhsRecord));
 
     if (lhsRecord == rhsRecord)
       return !lhsRecord->getDecl()->isUnion();
 
     // C++0x [meta.rel]p2:

cfe/trunk/test/SemaObjCXX/is-base-of.mm

+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+
+@interface NSObj
+@end
+
+@interface NSChild : NSObj
+@end
+
+static_assert(__is_base_of(NSObj, NSChild), "");
+static_assert(!__is_base_of(NSChild, NSObj), "");
+
+static_assert(__is_base_of(NSObj, NSObj), "");
+
+static_assert(!__is_base_of(NSObj *, NSChild *), "");
+static_assert(!__is_base_of(NSChild *, NSObj *), "");
+
+static_assert(__is_base_of(const volatile NSObj, NSChild), "");
+static_assert(__is_base_of(NSObj, const volatile NSChild), "");
+
+@class NSForward; // expected-note{{forward declaration of class}}
+
+static_assert(!__is_base_of(NSForward, NSObj), "");
+static_assert(!__is_base_of(NSObj, NSForward), ""); // expected-error{{incomplete type 'NSForward'}}
+
+static_assert(!__is_base_of(id, NSObj), "");