//===- DeclFriend.h - Classes for C++ friend declarations -------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file defines the section of the AST representing C++ friend

// declarations.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_AST_DECLFRIEND_H

#define LLVM_CLANG_AST_DECLFRIEND_H

#include "clang/AST/Decl.h"

#include "clang/AST/DeclBase.h"

#include "clang/AST/DeclCXX.h"

#include "clang/AST/DeclTemplate.h"

#include "clang/AST/ExternalASTSource.h"

#include "clang/AST/TypeLoc.h"

#include "clang/Basic/LLVM.h"

#include "clang/Basic/SourceLocation.h"

#include "llvm/ADT/ArrayRef.h"

#include "llvm/ADT/PointerUnion.h"

#include "llvm/Support/Casting.h"

#include "llvm/Support/Compiler.h"

#include "llvm/Support/TrailingObjects.h"

#include <cassert>

#include <iterator>

namespace clang {

class ASTContext;

/// FriendDecl - Represents the declaration of a friend entity,

/// which can be a function, a type, or a templated function or type.

/// For example:

///

/// @code

/// template <typename T> class A {

///   friend int foo(T);

///   friend class B;

///   friend T; // only in C++0x

///   template <typename U> friend class C;

///   template <typename U> friend A& operator+=(A&, const U&) { ... }

/// };

/// @endcode

///

/// The semantic context of a friend decl is its declaring class.

class FriendDecl final

    : public Decl,

      private llvm::TrailingObjects<FriendDecl, TemplateParameterList *> {

  virtual void anchor();

public:

  using FriendUnion = llvm::PointerUnion<NamedDecl *, TypeSourceInfo *>;

private:

  friend class CXXRecordDecl;

  friend class CXXRecordDecl::friend_iterator;

  // The declaration that's a friend of this class.

  FriendUnion Friend;

  // A pointer to the next friend in the sequence.

  LazyDeclPtr NextFriend;

  // Location of the 'friend' specifier.

  SourceLocation FriendLoc;

  /// True if this 'friend' declaration is unsupported.  Eventually we

  /// will support every possible friend declaration, but for now we

  /// silently ignore some and set this flag to authorize all access.

  LLVM_PREFERRED_TYPE(bool)

  unsigned UnsupportedFriend : 1;

  // The number of "outer" template parameter lists in non-templatic

  // (currently unsupported) friend type declarations, such as

  //     template <class T> friend class A<T>::B;

  unsigned NumTPLists : 31;

  FriendDecl(DeclContext *DC, SourceLocation L, FriendUnion Friend,

             SourceLocation FriendL,

             ArrayRef<TemplateParameterList *> FriendTypeTPLists)

      : Decl(Decl::Friend, DC, L), Friend(Friend), FriendLoc(FriendL),

        UnsupportedFriend(false), NumTPLists(FriendTypeTPLists.size()) {

    for (unsigned i = 0; i < NumTPLists; ++i)

      getTrailingObjects<TemplateParameterList *>()[i] = FriendTypeTPLists[i];

  }

  FriendDecl(EmptyShell Empty, unsigned NumFriendTypeTPLists)

      : Decl(Decl::Friend, Empty), UnsupportedFriend(false),

        NumTPLists(NumFriendTypeTPLists) {}

  FriendDecl *getNextFriend() {

    if (!NextFriend.isOffset())

      return cast_or_null<FriendDecl>(NextFriend.get(nullptr));

    return getNextFriendSlowCase();

  }

  FriendDecl *getNextFriendSlowCase();

public:

  friend class ASTDeclReader;

  friend class ASTDeclWriter;

  friend class ASTNodeImporter;

  friend TrailingObjects;

  static FriendDecl *

  Create(ASTContext &C, DeclContext *DC, SourceLocation L, FriendUnion Friend_,

         SourceLocation FriendL,

         ArrayRef<TemplateParameterList *> FriendTypeTPLists = std::nullopt);

  static FriendDecl *CreateDeserialized(ASTContext &C, unsigned ID,

                                        unsigned FriendTypeNumTPLists);

  /// If this friend declaration names an (untemplated but possibly

  /// dependent) type, return the type; otherwise return null.  This

  /// is used for elaborated-type-specifiers and, in C++0x, for

  /// arbitrary friend type declarations.

  TypeSourceInfo *getFriendType() const {

    return Friend.dyn_cast<TypeSourceInfo*>();

  }

  unsigned getFriendTypeNumTemplateParameterLists() const {

    return NumTPLists;

  }

  TemplateParameterList *getFriendTypeTemplateParameterList(unsigned N) const {

    assert(N < NumTPLists);

    return getTrailingObjects<TemplateParameterList *>()[N];

  }

  /// If this friend declaration doesn't name a type, return the inner

  /// declaration.

  NamedDecl *getFriendDecl() const {

    return Friend.dyn_cast<NamedDecl *>();

  }

  /// Retrieves the location of the 'friend' keyword.

  SourceLocation getFriendLoc() const {

    return FriendLoc;

  }

  /// Retrieves the source range for the friend declaration.

  SourceRange getSourceRange() const override LLVM_READONLY {

    if (NamedDecl *ND = getFriendDecl()) {

      if (const auto *FD = dyn_cast<FunctionDecl>(ND))

        return FD->getSourceRange();

      if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(ND))

        return FTD->getSourceRange();

      if (const auto *CTD = dyn_cast<ClassTemplateDecl>(ND))

        return CTD->getSourceRange();

      if (const auto *DD = dyn_cast<DeclaratorDecl>(ND)) {

        if (DD->getOuterLocStart() != DD->getInnerLocStart())

          return DD->getSourceRange();

      }

      return SourceRange(getFriendLoc(), ND->getEndLoc());

    }

    else if (TypeSourceInfo *TInfo = getFriendType()) {

      SourceLocation StartL =

          (NumTPLists == 0) ? getFriendLoc()

                            : getTrailingObjects<TemplateParameterList *>()[0]

                                  ->getTemplateLoc();

      return SourceRange(StartL, TInfo->getTypeLoc().getEndLoc());

    }

    else

      return SourceRange(getFriendLoc(), getLocation());

  }

  /// Determines if this friend kind is unsupported.

  bool isUnsupportedFriend() const {

    return UnsupportedFriend;

  }

  void setUnsupportedFriend(bool Unsupported) {

    UnsupportedFriend = Unsupported;

  }

  // Implement isa/cast/dyncast/etc.

  static bool classof(const Decl *D) { return classofKind(D->getKind()); }

  static bool classofKind(Kind K) { return K == Decl::Friend; }

};

/// An iterator over the friend declarations of a class.

class CXXRecordDecl::friend_iterator {

  friend class CXXRecordDecl;

  FriendDecl *Ptr;

  explicit friend_iterator(FriendDecl *Ptr) : Ptr(Ptr) {}

public:

  friend_iterator() = default;

  using value_type = FriendDecl *;

  using reference = FriendDecl *;

  using pointer = FriendDecl *;

  using difference_type = int;

  using iterator_category = std::forward_iterator_tag;

  reference operator*() const { return Ptr; }

  friend_iterator &operator++() {

    assert(Ptr && "attempt to increment past end of friend list");

    Ptr = Ptr->getNextFriend();

    return *this;

  }

  friend_iterator operator++(int) {

    friend_iterator tmp = *this;

    ++*this;

    return tmp;

  }

  bool operator==(const friend_iterator &Other) const {

    return Ptr == Other.Ptr;

  }

  bool operator!=(const friend_iterator &Other) const {

    return Ptr != Other.Ptr;

  }

  friend_iterator &operator+=(difference_type N) {

    assert(N >= 0 && "cannot rewind a CXXRecordDecl::friend_iterator");

    while (N--)

      ++*this;

    return *this;

  }

  friend_iterator operator+(difference_type N) const {

    friend_iterator tmp = *this;

    tmp += N;

    return tmp;

  }

};

inline CXXRecordDecl::friend_iterator CXXRecordDecl::friend_begin() const {

  return friend_iterator(getFirstFriend());

}

inline CXXRecordDecl::friend_iterator CXXRecordDecl::friend_end() const {

  return friend_iterator(nullptr);

}

inline CXXRecordDecl::friend_range CXXRecordDecl::friends() const {

  return friend_range(friend_begin(), friend_end());

}

inline void CXXRecordDecl::pushFriendDecl(FriendDecl *FD) {

  assert(!FD->NextFriend && "friend already has next friend?");

  FD->NextFriend = data().FirstFriend;

  data().FirstFriend = FD;

}

} // namespace clang

#endif // LLVM_CLANG_AST_DECLFRIEND_H