Teach the evaluation of the __is_convertible_to trait to translate

access control errors into SFINAE errors, so that the trait provides
enough support to implement the C++0x std::is_convertible type trait.

To get there, the SFINAETrap now knows how to set up a SFINAE context
independent of any template instantiations or template argument
deduction steps, and (separately) can set a Sema flag to translate
access control errors into SFINAE errors. The latter can also be
useful if we decide that access control errors during template argument
deduction should cause substitution failure (rather than a hard error)
as has been proposed for C++0x.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@124446 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 4 deletions

diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index ca104ef581..cf2e10d531 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -2537,13 +2537,14 @@ static bool EvaluateBinaryTypeTrait(Sema &Self, BinaryTypeTrait BTT,
     InitializationKind Kind(InitializationKind::CreateCopy(KeyLoc, 
                                                            SourceLocation()));
     
-    // Perform the initialization within a SFINAE trap.
-    // FIXME: We don't implement the access-checking bits yet, because we don't
-    // handle access control as part of SFINAE.
-    Sema::SFINAETrap SFINAE(Self);
+    // Perform the initialization within a SFINAE trap at translation unit 
+    // scope.
+    Sema::SFINAETrap SFINAE(Self, /*AccessCheckingSFINAE=*/true);
+    Sema::ContextRAII TUContext(Self, Self.Context.getTranslationUnitDecl());
     InitializationSequence Init(Self, To, Kind, &FromPtr, 1);
     if (Init.getKind() == InitializationSequence::FailedSequence)
       return false;
+
     ExprResult Result = Init.Perform(Self, To, Kind, MultiExprArg(&FromPtr, 1));
     return !Result.isInvalid() && !SFINAE.hasErrorOccurred();
   }