PR9546, DR1268: A prvalue cannot be reinterpret_cast to an rvalue reference

type. But a glvalue can be reinterpret_cast to either flavor of reference.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@155789 91177308-0d34-0410-b5e6-96231b3b80d8

Author: zygoloid

lib/Sema/SemaCast.cpp

@@ -1504,10 +1504,9 @@ static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
   }
 
   if (const ReferenceType *DestTypeTmp = DestType->getAs<ReferenceType>()) {
-    bool LValue = DestTypeTmp->isLValueReferenceType();
-    if (LValue && !SrcExpr.get()->isLValue()) {
-      // Cannot cast non-lvalue to lvalue reference type. See the similar 
-      // comment in const_cast.
+    if (!SrcExpr.get()->isGLValue()) {
+      // Cannot cast non-glvalue to (lvalue or rvalue) reference type. See the
+      // similar comment in const_cast.
       msg = diag::err_bad_cxx_cast_rvalue;
       return TC_NotApplicable;
     }

test/CXX/expr/expr.post/expr.reinterpret.cast/p1-0x.cpp

@@ -10,7 +10,10 @@ template<typename T> T&& xvalue();
 void test_classification(char *ptr) {
   int (&fr0)(int) = reinterpret_cast<int (&&)(int)>(f);
   int &&ir0 = reinterpret_cast<int &&>(*ptr);
-  int &&ir1 = reinterpret_cast<int &&>(0);
-  int &&ir2 = reinterpret_cast<int &&>('a');
+  int &&ir1 = reinterpret_cast<int &&>(0); // expected-error {{rvalue to reference type}}
+  int &&ir2 = reinterpret_cast<int &&>('a'); // expected-error {{rvalue to reference type}}
   int &&ir3 = reinterpret_cast<int &&>(xvalue<char>());
+  // Per DR1268, reinterpret_cast can convert between lvalues and xvalues.
+  int &ir4 = reinterpret_cast<int &>(xvalue<char>());
+  int &&ir5 = reinterpret_cast<int &&>(*ptr);
 }