Implement core issue 5: a temporary created for copy-initialization has a

cv-unqualified type. This is essential in order to allow move-only objects of
const-qualified types to be copy-initialized via a converting constructor.

llvm-svn: 150309

clang/lib/Sema/SemaInit.cpp

@@ -3743,8 +3743,10 @@ static void TryUserDefinedConversion(Sema &S,
 
   if (isa<CXXConstructorDecl>(Function)) {
     // Add the user-defined conversion step. Any cv-qualification conversion is
-    // subsumed by the initialization.
-    Sequence.AddUserConversionStep(Function, Best->FoundDecl, DestType,
+    // subsumed by the initialization. Per DR5, the created temporary is of the
+    // cv-unqualified type of the destination.
+    Sequence.AddUserConversionStep(Function, Best->FoundDecl,
+                                   DestType.getUnqualifiedType(),
                                    HadMultipleCandidates);
     return;
   }
@@ -3752,7 +3754,7 @@ static void TryUserDefinedConversion(Sema &S,
   // Add the user-defined conversion step that calls the conversion function.
   QualType ConvType = Function->getCallResultType();
   if (ConvType->getAs<RecordType>()) {
-    // If we're converting to a class type, there may be an copy if
+    // If we're converting to a class type, there may be an copy of
     // the resulting temporary object (possible to create an object of
     // a base class type). That copy is not a separate conversion, so
     // we just make a note of the actual destination type (possibly a
@@ -4899,7 +4901,7 @@ InitializationSequence::Perform(Sema &S,
                                       Loc, ConstructorArgs))
           return ExprError();
 
-        // Build the an expression that constructs a temporary.
+        // Build an expression that constructs a temporary.
         CurInit = S.BuildCXXConstructExpr(Loc, Step->Type, Constructor,
                                           move_arg(ConstructorArgs),
                                           HadMultipleCandidates,

clang/test/SemaCXX/copy-initialization.cpp

@@ -42,3 +42,26 @@ namespace PR6757 {
     f(foo);
   }
 }
+
+namespace DR5 {
+  // Core issue 5: if a temporary is created in copy-initialization, it is of
+  // the cv-unqualified version of the destination type.
+  namespace Ex1 {
+    struct C { };
+    C c;
+    struct A {
+        A(const A&);
+        A(const C&);
+    };
+    const volatile A a = c; // ok
+  }
+
+  namespace Ex2 {
+    struct S {
+      S(S&&); // expected-warning {{C++11}}
+      S(int);
+    };
+    const S a(0);
+    const S b = 0;
+  }
+}