Move named cast sema functions to their own file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@58769 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 677 insertions, 0 deletions

diff --git a/lib/Sema/SemaNamedCast.cpp b/lib/Sema/SemaNamedCast.cpp
new file mode 100644
index 0000000000..f6c8cb4a3c
--- /dev/null
+++ b/lib/Sema/SemaNamedCast.cpp
@@ -0,0 +1,677 @@
+//===--- SemaNamedCast.cpp - Semantic Analysis for Named Casts ------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements semantic analysis for C++ named casts.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Sema.h"
+#include "SemaInherit.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/Basic/Diagnostic.h"
+#include "llvm/ADT/SmallVector.h"
+using namespace clang;
+
+/// ActOnCXXNamedCast - Parse {dynamic,static,reinterpret,const}_cast's.
+Action::ExprResult
+Sema::ActOnCXXNamedCast(SourceLocation OpLoc, tok::TokenKind Kind,
+                        SourceLocation LAngleBracketLoc, TypeTy *Ty,
+                        SourceLocation RAngleBracketLoc,
+                        SourceLocation LParenLoc, ExprTy *E,
+                        SourceLocation RParenLoc) {
+  Expr *Ex = (Expr*)E;
+  QualType DestType = QualType::getFromOpaquePtr(Ty);
+  SourceRange OpRange(OpLoc, RParenLoc);
+  SourceRange DestRange(LAngleBracketLoc, RAngleBracketLoc);
+
+  switch (Kind) {
+  default: assert(0 && "Unknown C++ cast!");
+
+  case tok::kw_const_cast:
+    CheckConstCast(Ex, DestType, OpRange, DestRange);
+    return new CXXConstCastExpr(DestType.getNonReferenceType(), Ex, 
+                                DestType, OpLoc);
+
+  case tok::kw_dynamic_cast:
+    CheckDynamicCast(Ex, DestType, OpRange, DestRange);
+    return new CXXDynamicCastExpr(DestType.getNonReferenceType(), Ex, 
+                                  DestType, OpLoc);
+
+  case tok::kw_reinterpret_cast:
+    CheckReinterpretCast(Ex, DestType, OpRange, DestRange);
+    return new CXXReinterpretCastExpr(DestType.getNonReferenceType(), Ex, 
+                                      DestType, OpLoc);
+
+  case tok::kw_static_cast:
+    CheckStaticCast(Ex, DestType, OpRange);
+    return new CXXStaticCastExpr(DestType.getNonReferenceType(), Ex, 
+                                 DestType, OpLoc);
+  }
+
+  return true;
+}
+
+/// CheckConstCast - Check that a const_cast\<DestType\>(SrcExpr) is valid.
+/// Refer to C++ 5.2.11 for details. const_cast is typically used in code
+/// like this:
+/// const char *str = "literal";
+/// legacy_function(const_cast\<char*\>(str));
+void
+Sema::CheckConstCast(Expr *&SrcExpr, QualType DestType,
+                     const SourceRange &OpRange, const SourceRange &DestRange)
+{
+  QualType OrigDestType = DestType, OrigSrcType = SrcExpr->getType();
+
+  DestType = Context.getCanonicalType(DestType);
+  QualType SrcType = SrcExpr->getType();
+  if (const ReferenceType *DestTypeTmp = DestType->getAsReferenceType()) {
+    if (SrcExpr->isLvalue(Context) != Expr::LV_Valid) {
+      // Cannot cast non-lvalue to reference type.
+      Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue,
+        "const_cast", OrigDestType.getAsString(), SrcExpr->getSourceRange());
+      return;
+    }
+
+    // C++ 5.2.11p4: An lvalue of type T1 can be [cast] to an lvalue of type T2
+    //   [...] if a pointer to T1 can be [cast] to the type pointer to T2.
+    DestType = Context.getPointerType(DestTypeTmp->getPointeeType());
+    SrcType = Context.getPointerType(SrcType);
+  } else {
+    // C++ 5.2.11p1: Otherwise, the result is an rvalue and the
+    //   lvalue-to-rvalue, array-to-pointer, and function-to-pointer standard
+    //   conversions are performed on the expression.
+    DefaultFunctionArrayConversion(SrcExpr);
+    SrcType = SrcExpr->getType();
+  }
+
+  if (!DestType->isPointerType()) {
+    // Cannot cast to non-pointer, non-reference type. Note that, if DestType
+    // was a reference type, we converted it to a pointer above.
+    // C++ 5.2.11p3: For two pointer types [...]
+    Diag(OpRange.getBegin(), diag::err_bad_const_cast_dest,
+      OrigDestType.getAsString(), DestRange);
+    return;
+  }
+  if (DestType->isFunctionPointerType()) {
+    // Cannot cast direct function pointers.
+    // C++ 5.2.11p2: [...] where T is any object type or the void type [...]
+    // T is the ultimate pointee of source and target type.
+    Diag(OpRange.getBegin(), diag::err_bad_const_cast_dest,
+      OrigDestType.getAsString(), DestRange);
+    return;
+  }
+  SrcType = Context.getCanonicalType(SrcType);
+
+  // Unwrap the pointers. Ignore qualifiers. Terminate early if the types are
+  // completely equal.
+  // FIXME: const_cast should probably not be able to convert between pointers
+  // to different address spaces.
+  // C++ 5.2.11p3 describes the core semantics of const_cast. All cv specifiers
+  // in multi-level pointers may change, but the level count must be the same,
+  // as must be the final pointee type.
+  while (SrcType != DestType && UnwrapSimilarPointerTypes(SrcType, DestType)) {
+    SrcType = SrcType.getUnqualifiedType();
+    DestType = DestType.getUnqualifiedType();
+  }
+
+  // Doug Gregor said to disallow this until users complain.
+#if 0
+  // If we end up with constant arrays of equal size, unwrap those too. A cast
+  // from const int [N] to int (&)[N] is invalid by my reading of the
+  // standard, but g++ accepts it even with -ansi -pedantic.
+  // No more than one level, though, so don't embed this in the unwrap loop
+  // above.
+  const ConstantArrayType *SrcTypeArr, *DestTypeArr;
+  if ((SrcTypeArr = Context.getAsConstantArrayType(SrcType)) &&
+     (DestTypeArr = Context.getAsConstantArrayType(DestType)))
+  {
+    if (SrcTypeArr->getSize() != DestTypeArr->getSize()) {
+      // Different array sizes.
+      Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic, "const_cast",
+        OrigDestType.getAsString(), OrigSrcType.getAsString(), OpRange);
+      return;
+    }
+    SrcType = SrcTypeArr->getElementType().getUnqualifiedType();
+    DestType = DestTypeArr->getElementType().getUnqualifiedType();
+  }
+#endif
+
+  // Since we're dealing in canonical types, the remainder must be the same.
+  if (SrcType != DestType) {
+    // Cast between unrelated types.
+    Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic, "const_cast",
+      OrigDestType.getAsString(), OrigSrcType.getAsString(), OpRange);
+    return;
+  }
+}
+
+/// CheckReinterpretCast - Check that a reinterpret_cast\<DestType\>(SrcExpr) is
+/// valid.
+/// Refer to C++ 5.2.10 for details. reinterpret_cast is typically used in code
+/// like this:
+/// char *bytes = reinterpret_cast\<char*\>(int_ptr);
+void
+Sema::CheckReinterpretCast(Expr *&SrcExpr, QualType DestType,
+                           const SourceRange &OpRange,
+                           const SourceRange &DestRange)
+{
+  QualType OrigDestType = DestType, OrigSrcType = SrcExpr->getType();
+
+  DestType = Context.getCanonicalType(DestType);
+  QualType SrcType = SrcExpr->getType();
+  if (const ReferenceType *DestTypeTmp = DestType->getAsReferenceType()) {
+    if (SrcExpr->isLvalue(Context) != Expr::LV_Valid) {
+      // Cannot cast non-lvalue to reference type.
+      Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue,
+        "reinterpret_cast", OrigDestType.getAsString(),
+        SrcExpr->getSourceRange());
+      return;
+    }
+
+    // C++ 5.2.10p10: [...] a reference cast reinterpret_cast<T&>(x) has the
+    //   same effect as the conversion *reinterpret_cast<T*>(&x) with the
+    //   built-in & and * operators.
+    // This code does this transformation for the checked types.
+    DestType = Context.getPointerType(DestTypeTmp->getPointeeType());
+    SrcType = Context.getPointerType(SrcType);
+  } else {
+    // C++ 5.2.10p1: [...] the lvalue-to-rvalue, array-to-pointer, and
+    //   function-to-pointer standard conversions are performed on the
+    //   expression v.
+    DefaultFunctionArrayConversion(SrcExpr);
+    SrcType = SrcExpr->getType();
+  }
+
+  // Canonicalize source for comparison.
+  SrcType = Context.getCanonicalType(SrcType);
+
+  bool destIsPtr = DestType->isPointerType();
+  bool srcIsPtr = SrcType->isPointerType();
+  if (!destIsPtr && !srcIsPtr) {
+    // Except for std::nullptr_t->integer, which is not supported yet, and
+    // lvalue->reference, which is handled above, at least one of the two
+    // arguments must be a pointer.
+    Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic, "reinterpret_cast",
+      OrigDestType.getAsString(), OrigSrcType.getAsString(), OpRange);
+    return;
+  }
+
+  if (SrcType == DestType) {
+    // C++ 5.2.10p2 has a note that mentions that, subject to all other
+    // restrictions, a cast to the same type is allowed. The intent is not
+    // entirely clear here, since all other paragraphs explicitly forbid casts
+    // to the same type. However, the behavior of compilers is pretty consistent
+    // on this point: allow same-type conversion if the involved are pointers,
+    // disallow otherwise.
+    return;
+  }
+
+  // Note: Clang treats enumeration types as integral types. If this is ever
+  // changed for C++, the additional check here will be redundant.
+  if (DestType->isIntegralType() && !DestType->isEnumeralType()) {
+    assert(srcIsPtr);
+    // C++ 5.2.10p4: A pointer can be explicitly converted to any integral
+    //   type large enough to hold it.
+    if (Context.getTypeSize(SrcType) > Context.getTypeSize(DestType)) {
+      Diag(OpRange.getBegin(), diag::err_bad_reinterpret_cast_small_int,
+        OrigDestType.getAsString(), DestRange);
+    }
+    return;
+  }
+
+  if (SrcType->isIntegralType() || SrcType->isEnumeralType()) {
+    assert(destIsPtr);
+    // C++ 5.2.10p5: A value of integral or enumeration type can be explicitly
+    //   converted to a pointer.
+    return;
+  }
+
+  if (!destIsPtr || !srcIsPtr) {
+    // With the valid non-pointer conversions out of the way, we can be even
+    // more stringent.
+    Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic, "reinterpret_cast",
+      OrigDestType.getAsString(), OrigSrcType.getAsString(), OpRange);
+    return;
+  }
+
+  // C++ 5.2.10p2: The reinterpret_cast operator shall not cast away constness.
+  if (CastsAwayConstness(SrcType, DestType)) {
+    Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away,
+      "reinterpret_cast", OrigDestType.getAsString(), OrigSrcType.getAsString(),
+      OpRange);
+    return;
+  }
+
+  // Not casting away constness, so the only remaining check is for compatible
+  // pointer categories.
+
+  if (SrcType->isFunctionPointerType()) {
+    if (DestType->isFunctionPointerType()) {
+      // C++ 5.2.10p6: A pointer to a function can be explicitly converted to
+      // a pointer to a function of a different type.
+      return;
+    }
+
+    // FIXME: Handle member pointers.
+
+    // C++0x 5.2.10p8: Converting a pointer to a function into a pointer to
+    //   an object type or vice versa is conditionally-supported.
+    // Compilers support it in C++03 too, though, because it's necessary for
+    // casting the return value of dlsym() and GetProcAddress().
+    // FIXME: Conditionally-supported behavior should be configurable in the
+    // TargetInfo or similar.
+    if (!getLangOptions().CPlusPlus0x) {
+      Diag(OpRange.getBegin(), diag::ext_reinterpret_cast_fn_obj, OpRange);
+    }
+    return;
+  }
+
+  // FIXME: Handle member pointers.
+
+  if (DestType->isFunctionPointerType()) {
+    // See above.
+    if (!getLangOptions().CPlusPlus0x) {
+      Diag(OpRange.getBegin(), diag::ext_reinterpret_cast_fn_obj, OpRange);
+    }
+    return;
+  }
+
+  // C++ 5.2.10p7: A pointer to an object can be explicitly converted to
+  //   a pointer to an object of different type.
+  // Void pointers are not specified, but supported by every compiler out there.
+  // So we finish by allowing everything that remains - it's got to be two
+  // object pointers.
+}
+
+/// CastsAwayConstness - Check if the pointer conversion from SrcType
+/// to DestType casts away constness as defined in C++
+/// 5.2.11p8ff. This is used by the cast checkers.  Both arguments
+/// must denote pointer types.
+bool
+Sema::CastsAwayConstness(QualType SrcType, QualType DestType)
+{
+ // Casting away constness is defined in C++ 5.2.11p8 with reference to
+  // C++ 4.4.
+  // We piggyback on Sema::IsQualificationConversion for this, since the rules
+  // are non-trivial. So first we construct Tcv *...cv* as described in
+  // C++ 5.2.11p8.
+
+  QualType UnwrappedSrcType = SrcType, UnwrappedDestType = DestType;
+  llvm::SmallVector<unsigned, 8> cv1, cv2;
+
+  // Find the qualifications.
+  while (UnwrapSimilarPointerTypes(UnwrappedSrcType, UnwrappedDestType)) {
+    cv1.push_back(UnwrappedSrcType.getCVRQualifiers());
+    cv2.push_back(UnwrappedDestType.getCVRQualifiers());
+  }
+  assert(cv1.size() > 0 && "Must have at least one pointer level.");
+
+  // Construct void pointers with those qualifiers (in reverse order of
+  // unwrapping, of course).
+  QualType SrcConstruct = Context.VoidTy;
+  QualType DestConstruct = Context.VoidTy;
+  for (llvm::SmallVector<unsigned, 8>::reverse_iterator i1 = cv1.rbegin(),
+                                                        i2 = cv2.rbegin();
+       i1 != cv1.rend(); ++i1, ++i2)
+  {
+    SrcConstruct = Context.getPointerType(SrcConstruct.getQualifiedType(*i1));
+    DestConstruct = Context.getPointerType(DestConstruct.getQualifiedType(*i2));
+  }
+
+  // Test if they're compatible.
+  return SrcConstruct != DestConstruct &&
+    !IsQualificationConversion(SrcConstruct, DestConstruct);
+}
+
+/// CheckStaticCast - Check that a static_cast\<DestType\>(SrcExpr) is valid.
+/// Refer to C++ 5.2.9 for details. Static casts are mostly used for making
+/// implicit conversions explicit and getting rid of data loss warnings.
+void
+Sema::CheckStaticCast(Expr *&SrcExpr, QualType DestType,
+                      const SourceRange &OpRange)
+{
+  // The order the tests is not entirely arbitrary. There is one conversion
+  // that can be handled in two different ways. Given:
+  // struct A {};
+  // struct B : public A {
+  //   B(); B(const A&);
+  // };
+  // const A &a = B();
+  // the cast static_cast<const B&>(a) could be seen as either a static
+  // reference downcast, or an explicit invocation of the user-defined
+  // conversion using B's conversion constructor.
+  // DR 427 specifies that the downcast is to be applied here.
+
+  // C++ 5.2.9p4: Any expression can be explicitly converted to type "cv void".
+  if (DestType->isVoidType()) {
+    return;
+  }
+
+  // C++ 5.2.9p5, reference downcast.
+  // See the function for details.
+  // DR 427 specifies that this is to be applied before paragraph 2.
+  if (IsStaticReferenceDowncast(SrcExpr, DestType)) {
+    return;
+  }
+
+  // C++ 5.2.9p2: An expression e can be explicitly converted to a type T
+  //   [...] if the declaration "T t(e);" is well-formed, [...].
+  ImplicitConversionSequence ICS = TryDirectInitialization(SrcExpr, DestType);
+  if (ICS.ConversionKind != ImplicitConversionSequence::BadConversion) {
+    assert(ICS.ConversionKind != ImplicitConversionSequence::EllipsisConversion
+      && "Direct initialization cannot result in ellipsis conversion");
+    // UserDefinedConversionSequence has a StandardConversionSequence as a
+    // prefix. Accessing Standard is therefore safe.
+    // FIXME: Of course, this is definitely not enough.
+    if(ICS.Standard.First != ICK_Identity) {
+      DefaultFunctionArrayConversion(SrcExpr);
+    }
+    // FIXME: Test the details, such as accessible base.
+    return;
+  }
+
+  // C++ 5.2.9p6: May apply the reverse of any standard conversion, except
+  // lvalue-to-rvalue, array-to-pointer, function-to-pointer, and boolean
+  // conversions, subject to further restrictions.
+  // Also, C++ 5.2.9p1 forbids casting away constness, which makes reversal
+  // of qualification conversions impossible.
+
+  // The lvalue-to-rvalue, array-to-pointer and function-to-pointer conversions
+  // are applied to the expression.
+  QualType OrigSrcType = SrcExpr->getType();
+  DefaultFunctionArrayConversion(SrcExpr);
+
+  QualType SrcType = Context.getCanonicalType(SrcExpr->getType());
+
+  // Reverse integral promotion/conversion. All such conversions are themselves
+  // again integral promotions or conversions and are thus already handled by
+  // p2 (TryDirectInitialization above).
+  // (Note: any data loss warnings should be suppressed.)
+  // The exception is the reverse of enum->integer, i.e. integer->enum (and
+  // enum->enum). See also C++ 5.2.9p7.
+  // The same goes for reverse floating point promotion/conversion and
+  // floating-integral conversions. Again, only floating->enum is relevant.
+  if (DestType->isEnumeralType()) {
+    if (SrcType->isComplexType() || SrcType->isVectorType()) {
+      // Fall through - these cannot be converted.
+    } else if (SrcType->isArithmeticType() || SrcType->isEnumeralType()) {
+      return;
+    }
+  }
+
+  // Reverse pointer upcast. C++ 4.10p3 specifies pointer upcast.
+  // C++ 5.2.9p8 additionally disallows a cast path through virtual inheritance.
+  if (IsStaticPointerDowncast(SrcType, DestType)) {
+    return;
+  }
+
+  // Reverse member pointer conversion. C++ 5.11 specifies member pointer
+  // conversion. C++ 5.2.9p9 has additional information.
+  // DR54's access restrictions apply here also.
+  // FIXME: Don't have member pointers yet.
+
+  // Reverse pointer conversion to void*. C++ 4.10.p2 specifies conversion to
+  // void*. C++ 5.2.9p10 specifies additional restrictions, which really is
+  // just the usual constness stuff.
+  if (const PointerType *SrcPointer = SrcType->getAsPointerType()) {
+    QualType SrcPointee = SrcPointer->getPointeeType();
+    if (SrcPointee->isVoidType()) {
+      if (const PointerType *DestPointer = DestType->getAsPointerType()) {
+        QualType DestPointee = DestPointer->getPointeeType();
+        if (DestPointee->isObjectType()) {
+          // This is definitely the intended conversion, but it might fail due
+          // to a const violation.
+          if (!DestPointee.isAtLeastAsQualifiedAs(SrcPointee)) {
+            Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away,
+              "static_cast", DestType.getAsString(),
+              OrigSrcType.getAsString(), OpRange);
+          }
+          return;
+        }
+      }
+    }
+  }
+
+  // We tried everything. Everything! Nothing works! :-(
+  // FIXME: Error reporting could be a lot better. Should store the reason
+  // why every substep failed and, at the end, select the most specific and
+  // report that.
+  Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_generic, "static_cast",
+    DestType.getAsString(), OrigSrcType.getAsString(), OpRange);
+}
+
+/// Tests whether a conversion according to C++ 5.2.9p5 is valid.
+bool
+Sema::IsStaticReferenceDowncast(Expr *SrcExpr, QualType DestType)
+{
+  // C++ 5.2.9p5: An lvalue of type "cv1 B", where B is a class type, can be
+  //   cast to type "reference to cv2 D", where D is a class derived from B,
+  //   if a valid standard conversion from "pointer to D" to "pointer to B"
+  //   exists, cv2 >= cv1, and B is not a virtual base class of D.
+  // In addition, DR54 clarifies that the base must be accessible in the
+  // current context. Although the wording of DR54 only applies to the pointer
+  // variant of this rule, the intent is clearly for it to apply to the this
+  // conversion as well.
+
+  if (SrcExpr->isLvalue(Context) != Expr::LV_Valid) {
+    return false;
+  }
+
+  const ReferenceType *DestReference = DestType->getAsReferenceType();
+  if (!DestReference) {
+    return false;
+  }
+  QualType DestPointee = DestReference->getPointeeType();
+
+  return IsStaticDowncast(SrcExpr->getType(), DestPointee);
+}
+
+/// Tests whether a conversion according to C++ 5.2.9p8 is valid.
+bool
+Sema::IsStaticPointerDowncast(QualType SrcType, QualType DestType)
+{
+  // C++ 5.2.9p8: An rvalue of type "pointer to cv1 B", where B is a class
+  //   type, can be converted to an rvalue of type "pointer to cv2 D", where D
+  //   is a class derived from B, if a valid standard conversion from "pointer
+  //   to D" to "pointer to B" exists, cv2 >= cv1, and B is not a virtual base
+  //   class of D.
+  // In addition, DR54 clarifies that the base must be accessible in the
+  // current context.
+
+  const PointerType *SrcPointer = SrcType->getAsPointerType();
+  if (!SrcPointer) {
+    return false;
+  }
+
+  const PointerType *DestPointer = DestType->getAsPointerType();
+  if (!DestPointer) {
+    return false;
+  }
+
+  return IsStaticDowncast(SrcPointer->getPointeeType(),
+                          DestPointer->getPointeeType());
+}
+
+/// IsStaticDowncast - Common functionality of IsStaticReferenceDowncast and
+/// IsStaticPointerDowncast. Tests whether a static downcast from SrcType to
+/// DestType, both of which must be canonical, is possible and allowed.
+bool
+Sema::IsStaticDowncast(QualType SrcType, QualType DestType)
+{
+  // Downcast can only happen in class hierarchies, so we need classes.
+  if (!DestType->isRecordType() || !SrcType->isRecordType()) {
+    return false;
+  }
+
+  // Comparing cv is cheaper, so do it first.
+  if (!DestType.isAtLeastAsQualifiedAs(SrcType)) {
+    return false;
+  }
+
+  BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/false,
+                  /*DetectVirtual=*/true);
+  if (!IsDerivedFrom(DestType, SrcType, Paths)) {
+    return false;
+  }
+
+  if (Paths.isAmbiguous(SrcType.getUnqualifiedType())) {
+    return false;
+  }
+
+  if (Paths.getDetectedVirtual() != 0) {
+    return false;
+  }
+
+  // FIXME: Test accessibility.
+
+  return true;
+}
+
+/// TryDirectInitialization - Attempt to direct-initialize a value of the
+/// given type (DestType) from the given expression (SrcExpr), as one would
+/// do when creating an object with new with parameters. This function returns
+/// an implicit conversion sequence that can be used to perform the
+/// initialization.
+/// This routine is very similar to TryCopyInitialization; the differences
+/// between the two (C++ 8.5p12 and C++ 8.5p14) are:
+/// 1) In direct-initialization, all constructors of the target type are
+///    considered, including those marked as explicit.
+/// 2) In direct-initialization, overload resolution is performed over the
+///    constructors of the target type. In copy-initialization, overload
+///    resolution is performed over all conversion functions that result in
+///    the target type. This can lead to different functions used.
+ImplicitConversionSequence
+Sema::TryDirectInitialization(Expr *SrcExpr, QualType DestType)
+{
+  if (!DestType->isRecordType()) {
+    // For non-class types, copy and direct initialization are identical.
+    // C++ 8.5p11
+    // FIXME: Those parts should be in a common function, actually.
+    return TryCopyInitialization(SrcExpr, DestType);
+  }
+
+  // FIXME: Not enough support for the rest yet, actually.
+  ImplicitConversionSequence ICS;
+  ICS.ConversionKind = ImplicitConversionSequence::BadConversion;
+  return ICS;
+}
+
+/// CheckDynamicCast - Check that a dynamic_cast\<DestType\>(SrcExpr) is valid.
+/// Refer to C++ 5.2.7 for details. Dynamic casts are used mostly for runtime-
+/// checked downcasts in class hierarchies.
+void
+Sema::CheckDynamicCast(Expr *&SrcExpr, QualType DestType,
+                       const SourceRange &OpRange,
+                       const SourceRange &DestRange)
+{
+  QualType OrigDestType = DestType, OrigSrcType = SrcExpr->getType();
+  DestType = Context.getCanonicalType(DestType);
+
+  // C++ 5.2.7p1: T shall be a pointer or reference to a complete class type,
+  //   or "pointer to cv void".
+
+  QualType DestPointee;
+  const PointerType *DestPointer = DestType->getAsPointerType();
+  const ReferenceType *DestReference = DestType->getAsReferenceType();
+  if (DestPointer) {
+    DestPointee = DestPointer->getPointeeType();
+  } else if (DestReference) {
+    DestPointee = DestReference->getPointeeType();
+  } else {
+    Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ref_or_ptr,
+      OrigDestType.getAsString(), DestRange);
+    return;
+  }
+
+  const RecordType *DestRecord = DestPointee->getAsRecordType();
+  if (DestPointee->isVoidType()) {
+    assert(DestPointer && "Reference to void is not possible");
+  } else if (DestRecord) {
+    if (!DestRecord->getDecl()->isDefinition()) {
+      Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_incomplete,
+        DestPointee.getUnqualifiedType().getAsString(), DestRange);
+      return;
+    }
+  } else {
+    Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class,
+      DestPointee.getUnqualifiedType().getAsString(), DestRange);
+    return;
+  }
+
+  // C++ 5.2.7p2: If T is a pointer type, v shall be an rvalue of a pointer to
+  //   complete class type, [...]. If T is a reference type, v shall be an
+  //   lvalue of a complete class type, [...].
+
+  QualType SrcType = Context.getCanonicalType(OrigSrcType);
+  QualType SrcPointee;
+  if (DestPointer) {
+    if (const PointerType *SrcPointer = SrcType->getAsPointerType()) {
+      SrcPointee = SrcPointer->getPointeeType();
+    } else {
+      Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ptr,
+        OrigSrcType.getAsString(), SrcExpr->getSourceRange());
+      return;
+    }
+  } else {
+    if (SrcExpr->isLvalue(Context) != Expr::LV_Valid) {
+      Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_rvalue, "dynamic_cast",
+        OrigDestType.getAsString(), OpRange);
+    }
+    SrcPointee = SrcType;
+  }
+
+  const RecordType *SrcRecord = SrcPointee->getAsRecordType();
+  if (SrcRecord) {
+    if (!SrcRecord->getDecl()->isDefinition()) {
+      Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_incomplete,
+        SrcPointee.getUnqualifiedType().getAsString(),
+        SrcExpr->getSourceRange());
+      return;
+    }
+  } else {
+    Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class,
+      SrcPointee.getUnqualifiedType().getAsString(),
+      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)) {
+    Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_const_away, "dynamic_cast",
+      OrigDestType.getAsString(), OrigSrcType.getAsString(), 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 && IsDerivedFrom(SrcPointee, DestPointee)) {
+    CheckDerivedToBaseConversion(SrcPointee, DestPointee, OpRange.getBegin(),
+      OpRange);
+    // Diagnostic already emitted on error.
+    return;
+  }
+
+  // C++ 5.2.7p6: Otherwise, v shall be [polymorphic].
+  // FIXME: Information not yet available.
+
+  // Done. Everything else is run-time checks.
+}