lib/Sema/SemaTemplateInstantiateExpr.cpp

//===--- SemaTemplateInstantiateExpr.cpp - C++ Template Expr Instantiation ===/
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//===----------------------------------------------------------------------===/
//
//  This file implements C++ template instantiation for expressions.
//
//===----------------------------------------------------------------------===/
#include "Sema.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/Parse/DeclSpec.h"
#include "clang/Lex/Preprocessor.h" // for the identifier table
#include "llvm/Support/Compiler.h"
using namespace clang;

namespace {
  class VISIBILITY_HIDDEN TemplateExprInstantiator 
    : public StmtVisitor<TemplateExprInstantiator, Sema::OwningExprResult> {
    Sema &SemaRef;
    const TemplateArgumentList &TemplateArgs;

  public:
    typedef Sema::OwningExprResult OwningExprResult;

    TemplateExprInstantiator(Sema &SemaRef, 
                             const TemplateArgumentList &TemplateArgs)
      : SemaRef(SemaRef), TemplateArgs(TemplateArgs) { }

    // FIXME: Once we get closer to completion, replace these manually-written
    // declarations with automatically-generated ones from
    // clang/AST/StmtNodes.def.
    OwningExprResult VisitPredefinedExpr(PredefinedExpr *E);
    OwningExprResult VisitIntegerLiteral(IntegerLiteral *E);
    OwningExprResult VisitFloatingLiteral(FloatingLiteral *E);
    OwningExprResult VisitStringLiteral(StringLiteral *E);
    OwningExprResult VisitCharacterLiteral(CharacterLiteral *E);
    OwningExprResult VisitImaginaryLiteral(ImaginaryLiteral *E);
    OwningExprResult VisitDeclRefExpr(DeclRefExpr *E);
    OwningExprResult VisitParenExpr(ParenExpr *E);
    OwningExprResult VisitUnaryOperator(UnaryOperator *E);
    OwningExprResult VisitArraySubscriptExpr(ArraySubscriptExpr *E);
    OwningExprResult VisitCallExpr(CallExpr *E);
    // FIXME: VisitMemberExpr
    // FIXME: CompoundLiteralExpr
    OwningExprResult VisitBinaryOperator(BinaryOperator *E);
    OwningExprResult VisitCompoundAssignOperator(CompoundAssignOperator *E);
    OwningExprResult VisitCXXOperatorCallExpr(CXXOperatorCallExpr *E);
    OwningExprResult VisitCXXConditionDeclExpr(CXXConditionDeclExpr *E);
    OwningExprResult VisitConditionalOperator(ConditionalOperator *E);
    // FIXME: AddrLabelExpr
    OwningExprResult VisitStmtExpr(StmtExpr *E);
    OwningExprResult VisitTypesCompatibleExpr(TypesCompatibleExpr *E);
    OwningExprResult VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E);
    OwningExprResult VisitUnresolvedDeclRefExpr(UnresolvedDeclRefExpr *E);
    OwningExprResult VisitCXXTemporaryObjectExpr(CXXTemporaryObjectExpr *E);
    OwningExprResult VisitCastExpr(CastExpr *E);
    OwningExprResult VisitImplicitCastExpr(ImplicitCastExpr *E);
    OwningExprResult VisitExplicitCastExpr(ExplicitCastExpr *E);
    OwningExprResult VisitCStyleCastExpr(CStyleCastExpr *E);
    OwningExprResult VisitCXXNamedCastExpr(CXXNamedCastExpr *E);
    OwningExprResult VisitCXXStaticCastExpr(CXXStaticCastExpr *E);
    OwningExprResult VisitCXXDynamicCastExpr(CXXDynamicCastExpr *E);
    OwningExprResult VisitCXXReinterpretCastExpr(CXXReinterpretCastExpr *E);
    OwningExprResult VisitCXXConstCastExpr(CXXConstCastExpr *E);
    OwningExprResult VisitCXXThisExpr(CXXThisExpr *E);
    OwningExprResult VisitCXXBoolLiteralExpr(CXXBoolLiteralExpr *E);
    OwningExprResult VisitCXXNullPtrLiteralExpr(CXXNullPtrLiteralExpr *E);
    OwningExprResult VisitGNUNullExpr(GNUNullExpr *E);
    OwningExprResult VisitUnresolvedFunctionNameExpr(
                                              UnresolvedFunctionNameExpr *E);

    // Base case. I'm supposed to ignore this.
    Sema::OwningExprResult VisitStmt(Stmt *S) { 
      S->dump();
      assert(false && "Cannot instantiate this kind of expression");
      return SemaRef.ExprError(); 
    }
  };
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitPredefinedExpr(PredefinedExpr *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitIntegerLiteral(IntegerLiteral *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitFloatingLiteral(FloatingLiteral *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitStringLiteral(StringLiteral *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitCharacterLiteral(CharacterLiteral *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitImaginaryLiteral(ImaginaryLiteral *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitCXXBoolLiteralExpr(CXXBoolLiteralExpr *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitCXXNullPtrLiteralExpr(CXXNullPtrLiteralExpr *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitGNUNullExpr(GNUNullExpr *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitUnresolvedFunctionNameExpr(
                                              UnresolvedFunctionNameExpr *E) {
  return SemaRef.Clone(E);
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitDeclRefExpr(DeclRefExpr *E) {
  Decl *D = E->getDecl();
  ValueDecl *NewD = 0;
  if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D)) {
    assert(NTTP->getDepth() == 0 && "No nested templates yet");
    const TemplateArgument &Arg = TemplateArgs[NTTP->getPosition()]; 
    QualType T = Arg.getIntegralType();
    if (T->isCharType() || T->isWideCharType())
      return SemaRef.Owned(new (SemaRef.Context) CharacterLiteral(
                                          Arg.getAsIntegral()->getZExtValue(),
                                          T->isWideCharType(),
                                          T, 
                                       E->getSourceRange().getBegin()));
    else if (T->isBooleanType())
      return SemaRef.Owned(new (SemaRef.Context) CXXBoolLiteralExpr(
                                          Arg.getAsIntegral()->getBoolValue(),
                                                 T, 
                                       E->getSourceRange().getBegin()));

    return SemaRef.Owned(new (SemaRef.Context) IntegerLiteral(
                                                 *Arg.getAsIntegral(),
                                                 T, 
                                       E->getSourceRange().getBegin()));
  } else if (ParmVarDecl *Parm = dyn_cast<ParmVarDecl>(D))
    NewD = SemaRef.CurrentInstantiationScope->getInstantiationOf(Parm);
  else if (isa<FunctionDecl>(D) || isa<OverloadedFunctionDecl>(D))
    // FIXME: Instantiate decl!
    NewD = cast<ValueDecl>(D);
  else
    assert(false && "Unhandled declaratrion reference kind");

  if (!NewD)
    return SemaRef.ExprError();

  QualType T = NewD->getType();
  return SemaRef.Owned(new (SemaRef.Context) DeclRefExpr(NewD,
                                                      T.getNonReferenceType(),
                                                           E->getLocation(),
                                                        T->isDependentType(),
                                                        T->isDependentType()));
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitParenExpr(ParenExpr *E) {
  Sema::OwningExprResult SubExpr = Visit(E->getSubExpr());
  if (SubExpr.isInvalid())
    return SemaRef.ExprError();

  return SemaRef.Owned(new (SemaRef.Context) ParenExpr(
                                               E->getLParen(), E->getRParen(), 
                                               (Expr *)SubExpr.release()));
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitUnaryOperator(UnaryOperator *E) {
  Sema::OwningExprResult Arg = Visit(E->getSubExpr());
  if (Arg.isInvalid())
    return SemaRef.ExprError();

  return SemaRef.CreateBuiltinUnaryOp(E->getOperatorLoc(),
                                      E->getOpcode(),
                                      move(Arg));
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
  Sema::OwningExprResult LHS = Visit(E->getLHS());
  if (LHS.isInvalid())
    return SemaRef.ExprError();

  Sema::OwningExprResult RHS = Visit(E->getRHS());
  if (RHS.isInvalid())
    return SemaRef.ExprError();

  // Since the overloaded array-subscript operator (operator[]) can
  // only be a member function, we can make several simplifying
  // assumptions here:
  //   1) Normal name lookup (from the current scope) will not ever
  //   find any declarations of operator[] that won't also be found be
  //   member operator lookup, so it is safe to pass a NULL Scope
  //   during the instantiation to avoid the lookup entirely.
  //
  //   2) Neither normal name lookup nor argument-dependent lookup at
  //   template definition time will find any operators that won't be
  //   found at template instantiation time, so we do not need to
  //   cache the results of name lookup as we do for the binary
  //   operators.
  SourceLocation LLocFake = ((Expr*)LHS.get())->getSourceRange().getBegin();
  return SemaRef.ActOnArraySubscriptExpr(/*Scope=*/0, move(LHS),
                                         /*FIXME:*/LLocFake,
                                         move(RHS),
                                         E->getRBracketLoc());
}

Sema::OwningExprResult TemplateExprInstantiator::VisitCallExpr(CallExpr *E) {
  // Instantiate callee
  OwningExprResult Callee = Visit(E->getCallee());
  if (Callee.isInvalid())
    return SemaRef.ExprError();

  // Instantiate arguments
  llvm::SmallVector<Expr*, 8> Args;
  llvm::SmallVector<SourceLocation, 4> FakeCommaLocs;
  for (unsigned I = 0, N = E->getNumArgs(); I != N; ++I) {
    OwningExprResult Arg = Visit(E->getArg(I));
    if (Arg.isInvalid()) {
      for (unsigned Victim = 0; Victim != I; ++Victim)
        Args[Victim]->Destroy(SemaRef.Context);
      return SemaRef.ExprError();
    }

    FakeCommaLocs.push_back(
     SemaRef.PP.getLocForEndOfToken(E->getArg(I)->getSourceRange().getEnd()));
    Args.push_back(Arg.takeAs<Expr>());
  }

  SourceLocation FakeLParenLoc 
    = ((Expr *)Callee.get())->getSourceRange().getBegin();
  return SemaRef.ActOnCallExpr(/*Scope=*/0, move(Callee), 
                               /*FIXME:*/FakeLParenLoc,
                               Sema::MultiExprArg(SemaRef,
                                                  (void **)&Args.front(),
                                                  Args.size()),
                               /*FIXME:*/&FakeCommaLocs.front(), 
                               E->getRParenLoc());
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitBinaryOperator(BinaryOperator *E) {
  Sema::OwningExprResult LHS = Visit(E->getLHS());
  if (LHS.isInvalid())
    return SemaRef.ExprError();

  Sema::OwningExprResult RHS = Visit(E->getRHS());
  if (RHS.isInvalid())
    return SemaRef.ExprError();

  Sema::OwningExprResult Result
    = SemaRef.CreateBuiltinBinOp(E->getOperatorLoc(), 
                                 E->getOpcode(),
                                 (Expr *)LHS.get(),
                                 (Expr *)RHS.get());
  if (Result.isInvalid())
    return SemaRef.ExprError();

  LHS.release();
  RHS.release();
  return move(Result);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCompoundAssignOperator(
                                                 CompoundAssignOperator *E) {
  return VisitBinaryOperator(E);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCXXOperatorCallExpr(CXXOperatorCallExpr *E) {
  Sema::OwningExprResult First = Visit(E->getArg(0));
  if (First.isInvalid())
    return SemaRef.ExprError();

  Expr *Args[2] = { (Expr *)First.get(), 0 };

  Sema::OwningExprResult Second(SemaRef);
  if (E->getNumArgs() == 2) {
    Second = Visit(E->getArg(1));

    if (Second.isInvalid())
      return SemaRef.ExprError();

    Args[1] = (Expr *)Second.get();
  }

  if (!E->isTypeDependent()) { 
    // Since our original expression was not type-dependent, we do not
    // perform lookup again at instantiation time (C++ [temp.dep]p1).
    // Instead, we just build the new overloaded operator call
    // expression.
    First.release();
    Second.release();
    // FIXME: Don't reuse the callee here. We need to instantiate it.
    return SemaRef.Owned(new (SemaRef.Context) CXXOperatorCallExpr(
                                                       SemaRef.Context, 
                                                       E->getOperator(),
                                                       E->getCallee(), 
                                                       Args, E->getNumArgs(),
                                                       E->getType(), 
                                                       E->getOperatorLoc()));
  }

  bool isPostIncDec = E->getNumArgs() == 2 && 
    (E->getOperator() == OO_PlusPlus || E->getOperator() == OO_MinusMinus);
  if (E->getNumArgs() == 1 || isPostIncDec) {
    if (!Args[0]->getType()->isOverloadableType()) {
      // The argument is not of overloadable type, so try to create a
      // built-in unary operation.
      UnaryOperator::Opcode Opc 
        = UnaryOperator::getOverloadedOpcode(E->getOperator(), isPostIncDec);

      return SemaRef.CreateBuiltinUnaryOp(E->getOperatorLoc(), Opc,
                                          move(First));
    }

    // Fall through to perform overload resolution
  } else {
    assert(E->getNumArgs() == 2 && "Expected binary operation");

    Sema::OwningExprResult Result(SemaRef);
    if (!Args[0]->getType()->isOverloadableType() && 
        !Args[1]->getType()->isOverloadableType()) {
      // Neither of the arguments is an overloadable type, so try to
      // create a built-in binary operation.
      BinaryOperator::Opcode Opc = 
        BinaryOperator::getOverloadedOpcode(E->getOperator());
      Result = SemaRef.CreateBuiltinBinOp(E->getOperatorLoc(), Opc, 
                                          Args[0], Args[1]);
      if (Result.isInvalid())
        return SemaRef.ExprError();

      First.release();
      Second.release();
      return move(Result);
    }

    // Fall through to perform overload resolution.
  }

  // Compute the set of functions that were found at template
  // definition time.
  Sema::FunctionSet Functions;
  DeclRefExpr *DRE = cast<DeclRefExpr>(E->getCallee());
  OverloadedFunctionDecl *Overloads 
    = cast<OverloadedFunctionDecl>(DRE->getDecl());
  
  // FIXME: Do we have to check
  // IsAcceptableNonMemberOperatorCandidate for each of these?
  for (OverloadedFunctionDecl::function_iterator 
         F = Overloads->function_begin(),
         FEnd = Overloads->function_end();
       F != FEnd; ++F)
    Functions.insert(*F);
  
  // Add any functions found via argument-dependent lookup.
  DeclarationName OpName 
    = SemaRef.Context.DeclarationNames.getCXXOperatorName(E->getOperator());
  SemaRef.ArgumentDependentLookup(OpName, Args, E->getNumArgs(), Functions);

  // Create the overloaded operator invocation.
  if (E->getNumArgs() == 1 || isPostIncDec) {
    UnaryOperator::Opcode Opc 
      = UnaryOperator::getOverloadedOpcode(E->getOperator(), isPostIncDec);
    return SemaRef.CreateOverloadedUnaryOp(E->getOperatorLoc(), Opc,
                                           Functions, move(First));
  }

  // FIXME: This would be far less ugly if CreateOverloadedBinOp took in ExprArg
  // arguments!
  BinaryOperator::Opcode Opc = 
    BinaryOperator::getOverloadedOpcode(E->getOperator());
  OwningExprResult Result 
    = SemaRef.CreateOverloadedBinOp(E->getOperatorLoc(), Opc, 
                                    Functions, Args[0], Args[1]);

  if (Result.isInvalid())
    return SemaRef.ExprError();

  First.release();
  Second.release();
  return move(Result);  
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCXXConditionDeclExpr(CXXConditionDeclExpr *E) {
  VarDecl *Var 
    = cast_or_null<VarDecl>(SemaRef.InstantiateDecl(E->getVarDecl(),
                                                    SemaRef.CurContext,
                                                    TemplateArgs));
  if (!Var)
    return SemaRef.ExprError();

  return SemaRef.Owned(new (SemaRef.Context) CXXConditionDeclExpr(
                                                    E->getStartLoc(), 
                                                    SourceLocation(),
                                                    Var));
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitConditionalOperator(ConditionalOperator *E) {
  Sema::OwningExprResult Cond = Visit(E->getCond());
  if (Cond.isInvalid())
    return SemaRef.ExprError();

  Sema::OwningExprResult LHS = SemaRef.InstantiateExpr(E->getLHS(), 
                                                       TemplateArgs);
  if (LHS.isInvalid())
    return SemaRef.ExprError();

  Sema::OwningExprResult RHS = Visit(E->getRHS());
  if (RHS.isInvalid())
    return SemaRef.ExprError();

  if (!E->isTypeDependent()) { 
    // Since our original expression was not type-dependent, we do not
    // perform lookup again at instantiation time (C++ [temp.dep]p1).
    // Instead, we just build the new conditional operator call expression.
    return SemaRef.Owned(new (SemaRef.Context) ConditionalOperator(
                                                           Cond.takeAs<Expr>(),
                                                           LHS.takeAs<Expr>(), 
                                                           RHS.takeAs<Expr>(),
                                                           E->getType()));
  }


  return SemaRef.ActOnConditionalOp(/*FIXME*/E->getCond()->getLocEnd(),
                                    /*FIXME*/E->getFalseExpr()->getLocStart(),
                                    move(Cond), move(LHS), move(RHS));
}

Sema::OwningExprResult TemplateExprInstantiator::VisitStmtExpr(StmtExpr *E) {
  Sema::OwningStmtResult SubStmt = SemaRef.InstantiateStmt(E->getSubStmt(),
                                                           TemplateArgs);
  if (SubStmt.isInvalid())
    return SemaRef.ExprError();
  
  return SemaRef.ActOnStmtExpr(E->getLParenLoc(), move(SubStmt),
                               E->getRParenLoc());
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitTypesCompatibleExpr(TypesCompatibleExpr *E) {
  QualType Type1 = SemaRef.InstantiateType(E->getArgType1(), TemplateArgs,
                                           /*FIXME:*/ E->getBuiltinLoc(),
                                           DeclarationName());
  if (Type1.isNull())
    return SemaRef.ExprError();

  QualType Type2 = SemaRef.InstantiateType(E->getArgType2(), TemplateArgs,
                                           /*FIXME:*/ E->getBuiltinLoc(),
                                           DeclarationName());
  if (Type2.isNull())
    return SemaRef.ExprError();

  return SemaRef.ActOnTypesCompatibleExpr(E->getBuiltinLoc(),
                                          Type1.getAsOpaquePtr(),
                                          Type2.getAsOpaquePtr(),
                                          E->getRParenLoc());
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E) {
  bool isSizeOf = E->isSizeOf();

  if (E->isArgumentType()) {
    QualType T = E->getArgumentType();
    if (T->isDependentType()) {
      T = SemaRef.InstantiateType(T, TemplateArgs, 
                                  /*FIXME*/E->getOperatorLoc(),
                                &SemaRef.PP.getIdentifierTable().get("sizeof"));
      if (T.isNull())
        return SemaRef.ExprError();
    }

    return SemaRef.CreateSizeOfAlignOfExpr(T, E->getOperatorLoc(), isSizeOf,
                                           E->getSourceRange());
  } 

  Sema::OwningExprResult Arg = Visit(E->getArgumentExpr());
  if (Arg.isInvalid())
    return SemaRef.ExprError();

  Sema::OwningExprResult Result
    = SemaRef.CreateSizeOfAlignOfExpr((Expr *)Arg.get(), E->getOperatorLoc(),
                                      isSizeOf, E->getSourceRange());
  if (Result.isInvalid())
    return SemaRef.ExprError();

  Arg.release();
  return move(Result);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitUnresolvedDeclRefExpr(UnresolvedDeclRefExpr *E) {
  NestedNameSpecifier *NNS 
    = SemaRef.InstantiateNestedNameSpecifier(E->getQualifier(), 
                                             E->getQualifierRange(),
                                             TemplateArgs);
  if (!NNS)
    return SemaRef.ExprError();

  CXXScopeSpec SS;
  SS.setRange(E->getQualifierRange());
  SS.setScopeRep(NNS);

  // FIXME: We're passing in a NULL scope, because
  // ActOnDeclarationNameExpr doesn't actually use the scope when we
  // give it a non-empty scope specifier. Investigate whether it would
  // be better to refactor ActOnDeclarationNameExpr.
  return SemaRef.ActOnDeclarationNameExpr(/*Scope=*/0, E->getLocation(), 
                                          E->getDeclName(), 
                                          /*HasTrailingLParen=*/false,
                                          &SS,
                                          /*FIXME:isAddressOfOperand=*/false);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCXXTemporaryObjectExpr(
                                                  CXXTemporaryObjectExpr *E) {
  QualType T = E->getType();
  if (T->isDependentType()) {
    T = SemaRef.InstantiateType(T, TemplateArgs,
                                E->getTypeBeginLoc(), DeclarationName());
    if (T.isNull())
      return SemaRef.ExprError();
  }

  llvm::SmallVector<Expr *, 16> Args;
  Args.reserve(E->getNumArgs());
  bool Invalid = false;
  for (CXXTemporaryObjectExpr::arg_iterator Arg = E->arg_begin(), 
                                         ArgEnd = E->arg_end();
       Arg != ArgEnd; ++Arg) {
    OwningExprResult InstantiatedArg = Visit(*Arg);
    if (InstantiatedArg.isInvalid()) {
      Invalid = true;
      break;
    }

    Args.push_back((Expr *)InstantiatedArg.release());
  }

  if (!Invalid) {
    SourceLocation CommaLoc;
    // FIXME: HACK!
    if (Args.size() > 1)
      CommaLoc 
        = SemaRef.PP.getLocForEndOfToken(Args[0]->getSourceRange().getEnd());
    Sema::OwningExprResult Result(
      SemaRef.ActOnCXXTypeConstructExpr(SourceRange(E->getTypeBeginLoc()
                                                    /*, FIXME*/),
                                        T.getAsOpaquePtr(),
                                        /*FIXME*/E->getTypeBeginLoc(),
                                        Sema::MultiExprArg(SemaRef,
                                                           (void**)&Args[0],
                                                           Args.size()),
                                        /*HACK*/&CommaLoc,
                                        E->getSourceRange().getEnd()));
    // At this point, Args no longer owns the arguments, no matter what.
    return move(Result);
  }

  // Clean up the instantiated arguments.
  // FIXME: Would rather do this with RAII.
  for (unsigned Idx = 0; Idx < Args.size(); ++Idx)
    SemaRef.DeleteExpr(Args[Idx]);

  return SemaRef.ExprError();
}

Sema::OwningExprResult TemplateExprInstantiator::VisitCastExpr(CastExpr *E) {
  assert(false && "Cannot instantiate abstract CastExpr");
  return SemaRef.ExprError();
}

Sema::OwningExprResult TemplateExprInstantiator::VisitImplicitCastExpr(
                                                         ImplicitCastExpr *E) {
  assert(!E->isTypeDependent() && "Implicit casts must have known types");

  Sema::OwningExprResult SubExpr = Visit(E->getSubExpr());
  if (SubExpr.isInvalid())
    return SemaRef.ExprError();

  ImplicitCastExpr *ICE = 
    new (SemaRef.Context) ImplicitCastExpr(E->getType(),
                                           (Expr *)SubExpr.release(),
                                           E->isLvalueCast());
  return SemaRef.Owned(ICE);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitExplicitCastExpr(ExplicitCastExpr *E) {
  assert(false && "Cannot instantiate abstract ExplicitCastExpr");
  return SemaRef.ExprError();
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCStyleCastExpr(CStyleCastExpr *E) {
  // Instantiate the type that we're casting to.
  SourceLocation TypeStartLoc 
    = SemaRef.PP.getLocForEndOfToken(E->getLParenLoc());
  QualType ExplicitTy = SemaRef.InstantiateType(E->getTypeAsWritten(),
                                                TemplateArgs,
                                                TypeStartLoc,
                                                DeclarationName());
  if (ExplicitTy.isNull())
    return SemaRef.ExprError();

  // Instantiate the subexpression.
  OwningExprResult SubExpr = Visit(E->getSubExpr());
  if (SubExpr.isInvalid())
    return SemaRef.ExprError();
  
  return SemaRef.ActOnCastExpr(E->getLParenLoc(), 
                               ExplicitTy.getAsOpaquePtr(),
                               E->getRParenLoc(),
                               move(SubExpr));
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCXXNamedCastExpr(CXXNamedCastExpr *E) {
  // Figure out which cast operator we're dealing with.
  tok::TokenKind Kind;
  switch (E->getStmtClass()) {
  case Stmt::CXXStaticCastExprClass:
    Kind = tok::kw_static_cast;
    break;

  case Stmt::CXXDynamicCastExprClass:
    Kind = tok::kw_dynamic_cast;
    break;

  case Stmt::CXXReinterpretCastExprClass:
    Kind = tok::kw_reinterpret_cast;
    break;

  case Stmt::CXXConstCastExprClass:
    Kind = tok::kw_const_cast;
    break;

  default:
    assert(false && "Invalid C++ named cast");
    return SemaRef.ExprError();
  }

  // Instantiate the type that we're casting to.
  SourceLocation TypeStartLoc 
    = SemaRef.PP.getLocForEndOfToken(E->getOperatorLoc());
  QualType ExplicitTy = SemaRef.InstantiateType(E->getTypeAsWritten(),
                                                TemplateArgs,
                                                TypeStartLoc,
                                                DeclarationName());
  if (ExplicitTy.isNull())
    return SemaRef.ExprError();

  // Instantiate the subexpression.
  OwningExprResult SubExpr = Visit(E->getSubExpr());
  if (SubExpr.isInvalid())
    return SemaRef.ExprError();
  
  SourceLocation FakeLAngleLoc 
    = SemaRef.PP.getLocForEndOfToken(E->getOperatorLoc());
  SourceLocation FakeRAngleLoc = E->getSubExpr()->getSourceRange().getBegin();
  SourceLocation FakeRParenLoc
    = SemaRef.PP.getLocForEndOfToken(
                                E->getSubExpr()->getSourceRange().getEnd());
  return SemaRef.ActOnCXXNamedCast(E->getOperatorLoc(), Kind,
                                   /*FIXME:*/FakeLAngleLoc,
                                   ExplicitTy.getAsOpaquePtr(),
                                   /*FIXME:*/FakeRAngleLoc,
                                   /*FIXME:*/FakeRAngleLoc,
                                   move(SubExpr),
                                   /*FIXME:*/FakeRParenLoc);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCXXStaticCastExpr(CXXStaticCastExpr *E) {
  return VisitCXXNamedCastExpr(E);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCXXDynamicCastExpr(CXXDynamicCastExpr *E) {
  return VisitCXXNamedCastExpr(E);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCXXReinterpretCastExpr(
                                                CXXReinterpretCastExpr *E) {
  return VisitCXXNamedCastExpr(E);
}

Sema::OwningExprResult 
TemplateExprInstantiator::VisitCXXConstCastExpr(CXXConstCastExpr *E) {
  return VisitCXXNamedCastExpr(E);
}

Sema::OwningExprResult
TemplateExprInstantiator::VisitCXXThisExpr(CXXThisExpr *E) {
  QualType ThisType = 
    cast<CXXMethodDecl>(SemaRef.CurContext)->getThisType(SemaRef.Context);
    
  CXXThisExpr *TE = 
    new (SemaRef.Context) CXXThisExpr(E->getLocStart(), ThisType);
  
  return SemaRef.Owned(TE);
}

Sema::OwningExprResult 
Sema::InstantiateExpr(Expr *E, const TemplateArgumentList &TemplateArgs) {
  if (!E)
    return Owned((Expr *)0);

  TemplateExprInstantiator Instantiator(*this, TemplateArgs);
  return Instantiator.Visit(E);
}