[MSVC Compat] Implement __is_destructible, __is_nothrow_destructible

Our implementations of these type trait intrinsics simply mapped them to
__has_trivial_destructor.  Instead, flesh these intrinsics out with a
full implementation which matches the standard's description.

llvm-svn: 244564

1 files changed, 41 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 9dce8176006..f7103c885ad 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -3814,8 +3814,47 @@ static bool EvaluateUnaryTypeTrait(Sema &Self, TypeTrait UTT,
     return false;
   case UTT_IsDestructible:
   case UTT_IsNothrowDestructible:
-    // FIXME: Implement UTT_IsDestructible and UTT_IsNothrowDestructible.
-    // For now, let's fall through.
+    // C++14 [meta.unary.prop]:
+    //   For reference types, is_destructible<T>::value is true.
+    if (T->isReferenceType())
+      return true;
+
+    // Objective-C++ ARC: autorelease types don't require destruction.
+    if (T->isObjCLifetimeType() &&
+        T.getObjCLifetime() == Qualifiers::OCL_Autoreleasing)
+      return true;
+
+    // C++14 [meta.unary.prop]:
+    //   For incomplete types and function types, is_destructible<T>::value is
+    //   false.
+    if (T->isIncompleteType() || T->isFunctionType())
+      return false;
+
+    // C++14 [meta.unary.prop]:
+    //   For object types and given U equal to remove_all_extents_t<T>, if the
+    //   expression std::declval<U&>().~U() is well-formed when treated as an
+    //   unevaluated operand (Clause 5), then is_destructible<T>::value is true
+    if (auto *RD = C.getBaseElementType(T)->getAsCXXRecordDecl()) {
+      CXXDestructorDecl *Destructor = Self.LookupDestructor(RD);
+      if (!Destructor)
+        return false;
+      //  C++14 [dcl.fct.def.delete]p2:
+      //    A program that refers to a deleted function implicitly or
+      //    explicitly, other than to declare it, is ill-formed.
+      if (Destructor->isDeleted())
+        return false;
+      if (C.getLangOpts().AccessControl && Destructor->getAccess() != AS_public)
+        return false;
+      if (UTT == UTT_IsNothrowDestructible) {
+        const FunctionProtoType *CPT =
+            Destructor->getType()->getAs<FunctionProtoType>();
+        CPT = Self.ResolveExceptionSpec(KeyLoc, CPT);
+        if (!CPT || !CPT->isNothrow(C))
+          return false;
+      }
+    }
+    return true;
+
   case UTT_HasTrivialDestructor:
     // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html
     //   If __is_pod (type) is true or type is a reference type