[Sema] Call to deleted functions are supposed to be verboten

[davide]

Summary

I originally tried to fix this in SemaExpr (ActOnCallExpr), putting this check just before BuildCallToMemberFunction() call, but eventaully convinced myself SemaOverload should be the right place to fix.

Thanks,

Davide

[mclow.lists]

I don't spend a lot of time on the internals of clang; but this looks reasonable to me.

[davide]

Addressing comments.

[rsmith]

lib/Sema/SemaOverload.cpp

11608

This check should happen when we build the MemberExpr, not when we use it. It looks like the bug is in Sema::BuildMemberReferenceExpr, at around line 1050 of SemaExprMember.cpp:

bool ShouldCheckUse = true;
if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MemberDecl)) {
  // Don't diagnose the use of a virtual member function unless it's
  // explicitly qualified.
  if (MD->isVirtual() && !SS.isSet())
    ShouldCheckUse = false;
}

// Check the use of this member.
if (ShouldCheckUse && DiagnoseUseOfDecl(MemberDecl, MemberLoc))
  return ExprError();

This is wrong: we should DiagnoseUseOfDecl (including diagnosing the use of a deleted function) even for a virtual function. Which tests fail if we unconditionally DiagnoseUseOfDecl here?

lib/Sema/SemaOverload.cpp

   DeclAccessPair FoundDecl = DeclAccessPair::make(nullptr, AS_public);
   NestedNameSpecifier *Qualifier = nullptr;
   if (isa<MemberExpr>(NakedMemExpr)) {
     MemExpr = cast<MemberExpr>(NakedMemExpr);
     Method = cast<CXXMethodDecl>(MemExpr->getMemberDecl());
     FoundDecl = MemExpr->getFoundDecl();
     Qualifier = MemExpr->getQualifier();
     UnbridgedCasts.restore();
+
+    // Calls to deleted member functions are verboten.
+    if (Method && Method->isDeleted())
+      Diag(MemExpr->getLocStart(), diag::err_ovl_deleted_member_call)
+      << true /* isDeleted */
+      << Method
+      << getDeletedOrUnavailableSuffix(Method)
+      << MemExpr->getSourceRange();
   } else {
     UnresolvedMemberExpr *UnresExpr = cast<UnresolvedMemberExpr>(NakedMemExpr);
     Qualifier = UnresExpr->getQualifier();
 
     QualType ObjectType = UnresExpr->getBaseType();
     Expr::Classification ObjectClassification
       = UnresExpr->isArrow()? Expr::Classification::makeSimpleLValue()
                             : UnresExpr->getBase()->Classify(Context);

test/SemaCXX/deleted-function-access.cpp

+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
+
+struct S { virtual void f() = delete;
+            void g() { f(); } }; //expected-error{{call to deleted member function 'f'}}