C++ Sema::IsDerivedFrom方法代码示例

/// TryStaticMemberPointerUpcast - Tests whether a conversion according to
/// C++ 5.2.9p9 is valid:
///
///   An rvalue of type "pointer to member of D of type cv1 T" can be
///   converted to an rvalue of type "pointer to member of B of type cv2 T",
///   where B is a base class of D [...].
///
TryCastResult
TryStaticMemberPointerUpcast(Sema &Self, QualType SrcType, QualType DestType,
                             bool CStyle, const SourceRange &OpRange,
                             unsigned &msg)
{
  const MemberPointerType *DestMemPtr = DestType->getAs<MemberPointerType>();
  if (!DestMemPtr)
    return TC_NotApplicable;
  const MemberPointerType *SrcMemPtr = SrcType->getAs<MemberPointerType>();
  if (!SrcMemPtr) {
    msg = diag::err_bad_static_cast_member_pointer_nonmp;
    return TC_NotApplicable;
  }

  // T == T, modulo cv
  if (Self.Context.getCanonicalType(
        SrcMemPtr->getPointeeType().getUnqualifiedType()) !=
      Self.Context.getCanonicalType(DestMemPtr->getPointeeType().
                                    getUnqualifiedType()))
    return TC_NotApplicable;

  // B base of D
  QualType SrcClass(SrcMemPtr->getClass(), 0);
  QualType DestClass(DestMemPtr->getClass(), 0);
  BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/!CStyle,
                  /*DetectVirtual=*/true);
  if (!Self.IsDerivedFrom(SrcClass, DestClass, Paths)) {
    return TC_NotApplicable;
  }

  // B is a base of D. But is it an allowed base? If not, it's a hard error.
  if (Paths.isAmbiguous(DestClass)) {
    Paths.clear();
    Paths.setRecordingPaths(true);
    bool StillOkay = Self.IsDerivedFrom(SrcClass, DestClass, Paths);
    assert(StillOkay);
    StillOkay = StillOkay;
    std::string PathDisplayStr = Self.getAmbiguousPathsDisplayString(Paths);
    Self.Diag(OpRange.getBegin(), diag::err_ambiguous_memptr_conv)
      << 1 << SrcClass << DestClass << PathDisplayStr << OpRange;
    msg = 0;
    return TC_Failed;
  }

  if (const RecordType *VBase = Paths.getDetectedVirtual()) {
    Self.Diag(OpRange.getBegin(), diag::err_memptr_conv_via_virtual)
      << SrcClass << DestClass << QualType(VBase, 0) << OpRange;
    msg = 0;
    return TC_Failed;
  }

  if (!CStyle && Self.CheckBaseClassAccess(DestType, SrcType,
                          diag::err_downcast_from_inaccessible_base, Paths,
                          OpRange.getBegin(), DeclarationName())) {
    msg = 0;
    return TC_Failed;
  }

  return TC_Success;
}

/// TryStaticMemberPointerUpcast - Tests whether a conversion according to
/// C++ 5.2.9p9 is valid:
///
///   An rvalue of type "pointer to member of D of type cv1 T" can be
///   converted to an rvalue of type "pointer to member of B of type cv2 T",
///   where B is a base class of D [...].
///
TryStaticCastResult
TryStaticMemberPointerUpcast(Sema &Self, QualType SrcType, QualType DestType,
                             const SourceRange &OpRange)
{
  const MemberPointerType *SrcMemPtr = SrcType->getAsMemberPointerType();
  if (!SrcMemPtr)
    return TSC_NotApplicable;
  const MemberPointerType *DestMemPtr = DestType->getAsMemberPointerType();
  if (!DestMemPtr)
    return TSC_NotApplicable;

  // T == T, modulo cv
  if (Self.Context.getCanonicalType(
        SrcMemPtr->getPointeeType().getUnqualifiedType()) !=
      Self.Context.getCanonicalType(DestMemPtr->getPointeeType().
                                    getUnqualifiedType()))
    return TSC_NotApplicable;

  // B base of D
  QualType SrcClass(SrcMemPtr->getClass(), 0);
  QualType DestClass(DestMemPtr->getClass(), 0);
  BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/false,
                  /*DetectVirtual=*/true);
  if (!Self.IsDerivedFrom(SrcClass, DestClass, Paths)) {
    return TSC_NotApplicable;
  }

  // B is a base of D. But is it an allowed base? If not, it's a hard error.
  if (Paths.isAmbiguous(DestClass)) {
    Paths.clear();
    Paths.setRecordingPaths(true);
    bool StillOkay = Self.IsDerivedFrom(SrcClass, DestClass, Paths);
    assert(StillOkay);
    StillOkay = StillOkay;
    std::string PathDisplayStr = Self.getAmbiguousPathsDisplayString(Paths);
    Self.Diag(OpRange.getBegin(), diag::err_ambiguous_memptr_conv)
      << 1 << SrcClass << DestClass << PathDisplayStr << OpRange;
    return TSC_Failed;
  }

  if (const RecordType *VBase = Paths.getDetectedVirtual()) {
    Self.Diag(OpRange.getBegin(), diag::err_memptr_conv_via_virtual)
      << SrcClass << DestClass << QualType(VBase, 0) << OpRange;
    return TSC_Failed;
  }

  // FIXME: Test accessibility.

  return TSC_Success;
}

//.........这里部分代码省略.........
  if (DestPointer) {
    DestPointee = DestPointer->getPointeeType();
  } else if (DestReference) {
    DestPointee = DestReference->getPointeeType();
  } else {
    Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ref_or_ptr)
      << OrigDestType << DestRange;
    return;
  }

  const RecordType *DestRecord = DestPointee->getAsRecordType();
  if (DestPointee->isVoidType()) {
    assert(DestPointer && "Reference to void is not possible");
  } else if (DestRecord) {
    if (Self.RequireCompleteType(OpRange.getBegin(), DestPointee, 
                                    diag::err_bad_dynamic_cast_incomplete,
                                    DestRange))
      return;
  } else {
    Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
      << DestPointee.getUnqualifiedType() << DestRange;
    return;
  }

  // C++0x 5.2.7p2: If T is a pointer type, v shall be an rvalue of a pointer to
  //   complete class type, [...]. If T is an lvalue reference type, v shall be
  //   an lvalue of a complete class type, [...]. If T is an rvalue reference
  //   type, v shall be an expression having a complete effective class type,
  //   [...]

  QualType SrcType = Self.Context.getCanonicalType(OrigSrcType);
  QualType SrcPointee;
  if (DestPointer) {
    if (const PointerType *SrcPointer = SrcType->getAsPointerType()) {
      SrcPointee = SrcPointer->getPointeeType();
    } else {
      Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ptr)
        << OrigSrcType << SrcExpr->getSourceRange();
      return;
    }
  } else if (DestReference->isLValueReferenceType()) {
    if (SrcExpr->isLvalue(Self.Context) != Expr::LV_Valid) {
      Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue)
        << "dynamic_cast" << OrigDestType << OpRange;
    }
    SrcPointee = SrcType;
  } else {
    SrcPointee = SrcType;
  }

  const RecordType *SrcRecord = SrcPointee->getAsRecordType();
  if (SrcRecord) {
    if (Self.RequireCompleteType(OpRange.getBegin(), SrcPointee,
                                    diag::err_bad_dynamic_cast_incomplete,
                                    SrcExpr->getSourceRange()))
      return;
  } else {
    Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
      << SrcPointee.getUnqualifiedType() << SrcExpr->getSourceRange();
    return;
  }

  assert((DestPointer || DestReference) &&
    "Bad destination non-ptr/ref slipped through.");
  assert((DestRecord || DestPointee->isVoidType()) &&
    "Bad destination pointee slipped through.");
  assert(SrcRecord && "Bad source pointee slipped through.");

  // C++ 5.2.7p1: The dynamic_cast operator shall not cast away constness.
  if (!DestPointee.isAtLeastAsQualifiedAs(SrcPointee)) {
    Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away)
      << "dynamic_cast" << OrigDestType << OrigSrcType << OpRange;
    return;
  }

  // C++ 5.2.7p3: If the type of v is the same as the required result type,
  //   [except for cv].
  if (DestRecord == SrcRecord) {
    return;
  }

  // C++ 5.2.7p5
  // Upcasts are resolved statically.
  if (DestRecord && Self.IsDerivedFrom(SrcPointee, DestPointee)) {
    Self.CheckDerivedToBaseConversion(SrcPointee, DestPointee,
                                      OpRange.getBegin(), OpRange);
    // Diagnostic already emitted on error.
    return;
  }

  // C++ 5.2.7p6: Otherwise, v shall be [polymorphic].
  const RecordDecl *SrcDecl = SrcRecord->getDecl()->getDefinition(Self.Context);
  assert(SrcDecl && "Definition missing");
  if (!cast<CXXRecordDecl>(SrcDecl)->isPolymorphic()) {
    Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_polymorphic)
      << SrcPointee.getUnqualifiedType() << SrcExpr->getSourceRange();
  }

  // Done. Everything else is run-time checks.
}

/// TryStaticDowncast - Common functionality of TryStaticReferenceDowncast and
/// TryStaticPointerDowncast. Tests whether a static downcast from SrcType to
/// DestType, both of which must be canonical, is possible and allowed.
TryStaticCastResult
TryStaticDowncast(Sema &Self, QualType SrcType, QualType DestType,
                  const SourceRange &OpRange, QualType OrigSrcType,
                  QualType OrigDestType)
{
  // Downcast can only happen in class hierarchies, so we need classes.
  if (!DestType->isRecordType() || !SrcType->isRecordType()) {
    return TSC_NotApplicable;
  }

  BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/false,
                  /*DetectVirtual=*/true);
  if (!Self.IsDerivedFrom(DestType, SrcType, Paths)) {
    return TSC_NotApplicable;
  }

  // Target type does derive from source type. Now we're serious. If an error
  // appears now, it's not ignored.
  // This may not be entirely in line with the standard. Take for example:
  // struct A {};
  // struct B : virtual A {
  //   B(A&);
  // };
  // 
  // void f()
  // {
  //   (void)static_cast<const B&>(*((A*)0));
  // }
  // As far as the standard is concerned, p5 does not apply (A is virtual), so
  // p2 should be used instead - "const B& t(*((A*)0));" is perfectly valid.
  // However, both GCC and Comeau reject this example, and accepting it would
  // mean more complex code if we're to preserve the nice error message.
  // FIXME: Being 100% compliant here would be nice to have.

  // Must preserve cv, as always.
  if (!DestType.isAtLeastAsQualifiedAs(SrcType)) {
    Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away)
      << "static_cast" << OrigDestType << OrigSrcType << OpRange;
    return TSC_Failed;
  }

  if (Paths.isAmbiguous(SrcType.getUnqualifiedType())) {
    // This code is analoguous to that in CheckDerivedToBaseConversion, except
    // that it builds the paths in reverse order.
    // To sum up: record all paths to the base and build a nice string from
    // them. Use it to spice up the error message.
    Paths.clear();
    Paths.setRecordingPaths(true);
    Self.IsDerivedFrom(DestType, SrcType, Paths);
    std::string PathDisplayStr;
    std::set<unsigned> DisplayedPaths;
    for (BasePaths::paths_iterator Path = Paths.begin();
         Path != Paths.end(); ++Path) {
      if (DisplayedPaths.insert(Path->back().SubobjectNumber).second) {
        // We haven't displayed a path to this particular base
        // class subobject yet.
        PathDisplayStr += "\n    ";
        for (BasePath::const_reverse_iterator Element = Path->rbegin();
             Element != Path->rend(); ++Element)
          PathDisplayStr += Element->Base->getType().getAsString() + " -> ";
        PathDisplayStr += DestType.getAsString();
      }
    }

    Self.Diag(OpRange.getBegin(), diag::err_ambiguous_base_to_derived_cast)
      << SrcType.getUnqualifiedType() << DestType.getUnqualifiedType()
      << PathDisplayStr << OpRange;
    return TSC_Failed;
  }

  if (Paths.getDetectedVirtual() != 0) {
    QualType VirtualBase(Paths.getDetectedVirtual(), 0);
    Self.Diag(OpRange.getBegin(), diag::err_static_downcast_via_virtual)
      << OrigSrcType << OrigDestType << VirtualBase << OpRange;
    return TSC_Failed;
  }

  // FIXME: Test accessibility.

  return TSC_Success;
}