lib/Sema/SemaTemplateVariadic.cpp

//===------- SemaTemplateVariadic.cpp - C++ Variadic Templates ------------===/
//
//                     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++0x variadic templates.
//===----------------------------------------------------------------------===/

#include "clang/Sema/Sema.h"
#include "clang/Sema/SemaInternal.h"
#include "clang/AST/Expr.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/TypeLoc.h"

using namespace clang;

//----------------------------------------------------------------------------
// Visitor that collects unexpanded parameter packs
//----------------------------------------------------------------------------

// FIXME: No way to easily map from TemplateTypeParmTypes to
// TemplateTypeParmDecls, so we have this horrible PointerUnion.
typedef std::pair<llvm::PointerUnion<const TemplateTypeParmType*, NamedDecl*>,
                  SourceLocation> UnexpandedParameterPack;

namespace {
  /// \brief A class that collects unexpanded parameter packs.
  class CollectUnexpandedParameterPacksVisitor :
    public RecursiveASTVisitor<CollectUnexpandedParameterPacksVisitor> 
  {
    typedef RecursiveASTVisitor<CollectUnexpandedParameterPacksVisitor>
      inherited;

    llvm::SmallVectorImpl<UnexpandedParameterPack> &Unexpanded;

  public:
    explicit CollectUnexpandedParameterPacksVisitor(
                  llvm::SmallVectorImpl<UnexpandedParameterPack> &Unexpanded)
      : Unexpanded(Unexpanded) { }

    //------------------------------------------------------------------------
    // Recording occurrences of (unexpanded) parameter packs.
    //------------------------------------------------------------------------

    /// \brief Record occurrences of template type parameter packs.
    bool VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TL) {
      if (TL.getTypePtr()->isParameterPack())
        Unexpanded.push_back(std::make_pair(TL.getTypePtr(), TL.getNameLoc()));
      return true;
    }

    /// \brief Record occurrences of template type parameter packs
    /// when we don't have proper source-location information for
    /// them.
    ///
    /// Ideally, this routine would never be used.
    bool VisitTemplateTypeParmType(TemplateTypeParmType *T) {
      if (T->isParameterPack())
        Unexpanded.push_back(std::make_pair(T, SourceLocation()));

      return true;
    }

    // FIXME: Record occurrences of non-type and template template
    // parameter packs.

    // FIXME: Once we have pack expansions in the AST, block their
    // traversal.

    //------------------------------------------------------------------------
    // Pruning the search for unexpanded parameter packs.
    //------------------------------------------------------------------------

    /// \brief Suppress traversal into statements and expressions that
    /// do not contain unexpanded parameter packs.
    bool TraverseStmt(Stmt *S) { 
      if (Expr *E = dyn_cast_or_null<Expr>(S))
        if (E->containsUnexpandedParameterPack())
          return inherited::TraverseStmt(E);

      return true; 
    }

    /// \brief Suppress traversal into types that do not contain
    /// unexpanded parameter packs.
    bool TraverseType(QualType T) {
      if (!T.isNull() && T->containsUnexpandedParameterPack())
        return inherited::TraverseType(T);

      return true;
    }

    /// \brief Suppress traversel into types with location information
    /// that do not contain unexpanded parameter packs.
    bool TraverseTypeLoc(TypeLoc TL) {
      if (!TL.getType().isNull() && TL.
          getType()->containsUnexpandedParameterPack())
        return inherited::TraverseTypeLoc(TL);

      return true;
    }

    /// \brief Suppress traversal of declarations, since they cannot
    /// contain unexpanded parameter packs.
    bool TraverseDecl(Decl *D) { return true; }
  };
}

/// \brief Diagnose all of the unexpanded parameter packs in the given
/// vector.
static void 
DiagnoseUnexpandedParameterPacks(Sema &S, SourceLocation Loc,
                                 Sema::UnexpandedParameterPackContext UPPC,
             const llvm::SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
  llvm::SmallVector<SourceLocation, 4> Locations;
  llvm::SmallVector<IdentifierInfo *, 4> Names;
  llvm::SmallPtrSet<IdentifierInfo *, 4> NamesKnown;

  for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
    IdentifierInfo *Name = 0;
    if (const TemplateTypeParmType *TTP
          = Unexpanded[I].first.dyn_cast<const TemplateTypeParmType *>())
      Name = TTP->getName();
    else
      Name = Unexpanded[I].first.get<NamedDecl *>()->getIdentifier();

    if (Name && NamesKnown.insert(Name))
      Names.push_back(Name);

    if (Unexpanded[I].second.isValid())
      Locations.push_back(Unexpanded[I].second);
  }

  DiagnosticBuilder DB
    = Names.size() == 0? S.Diag(Loc, diag::err_unexpanded_parameter_pack_0)
                           << (int)UPPC
    : Names.size() == 1? S.Diag(Loc, diag::err_unexpanded_parameter_pack_1)
                           << (int)UPPC << Names[0]
    : Names.size() == 2? S.Diag(Loc, diag::err_unexpanded_parameter_pack_2)
                           << (int)UPPC << Names[0] << Names[1]
    : S.Diag(Loc, diag::err_unexpanded_parameter_pack_3_or_more)
        << (int)UPPC << Names[0] << Names[1];

  for (unsigned I = 0, N = Locations.size(); I != N; ++I)
    DB << SourceRange(Locations[I]);
}

bool Sema::DiagnoseUnexpandedParameterPack(SourceLocation Loc, 
                                           TypeSourceInfo *T,
                                         UnexpandedParameterPackContext UPPC) {
  // C++0x [temp.variadic]p5:
  //   An appearance of a name of a parameter pack that is not expanded is 
  //   ill-formed.
  if (!T->getType()->containsUnexpandedParameterPack())
    return false;

  llvm::SmallVector<UnexpandedParameterPack, 2> Unexpanded;
  CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseTypeLoc(
                                                              T->getTypeLoc());
  assert(!Unexpanded.empty() && "Unable to find unexpanded parameter packs");
  DiagnoseUnexpandedParameterPacks(*this, Loc, UPPC, Unexpanded);
  return true;
}

bool Sema::DiagnoseUnexpandedParameterPack(Expr *E,
                                           UnexpandedParameterPackContext UPPC) {
  // C++0x [temp.variadic]p5:
  //   An appearance of a name of a parameter pack that is not expanded is 
  //   ill-formed.
  if (!E->containsUnexpandedParameterPack())
    return false;

  llvm::SmallVector<UnexpandedParameterPack, 2> Unexpanded;
  CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseStmt(E);
  assert(!Unexpanded.empty() && "Unable to find unexpanded parameter packs");
  DiagnoseUnexpandedParameterPacks(*this, E->getLocStart(), UPPC, Unexpanded);
  return true;
}