//===- IdentifierResolver.cpp - Lexical Scope Name lookup -----------------===//

//

// 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 implements the IdentifierResolver class, which is used for lexical

// scoped lookup, based on declaration names.

//

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

#include "clang/Sema/IdentifierResolver.h"

#include "clang/AST/Decl.h"

#include "clang/AST/DeclBase.h"

#include "clang/AST/DeclarationName.h"

#include "clang/Basic/IdentifierTable.h"

#include "clang/Basic/LangOptions.h"

#include "clang/Lex/ExternalPreprocessorSource.h"

#include "clang/Lex/Preprocessor.h"

#include "clang/Sema/Scope.h"

#include "llvm/Support/ErrorHandling.h"

#include <cassert>

#include <cstdint>

using namespace clang;

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

// IdDeclInfoMap class

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

/// IdDeclInfoMap - Associates IdDeclInfos with declaration names.

/// Allocates 'pools' (vectors of IdDeclInfos) to avoid allocating each

/// individual IdDeclInfo to heap.

class IdentifierResolver::IdDeclInfoMap {

  static const unsigned int POOL_SIZE = 512;

  /// We use our own linked-list implementation because it is sadly

  /// impossible to add something to a pre-C++0x STL container without

  /// a completely unnecessary copy.

  struct IdDeclInfoPool {

    IdDeclInfoPool *Next;

    IdDeclInfo Pool[POOL_SIZE];

    IdDeclInfoPool(IdDeclInfoPool *Next) : Next(Next) {}

  };

  IdDeclInfoPool *CurPool = nullptr;

  unsigned int CurIndex = POOL_SIZE;

public:

  IdDeclInfoMap() = default;

  ~IdDeclInfoMap() {

    IdDeclInfoPool *Cur = CurPool;

    while (IdDeclInfoPool *P = Cur) {

      Cur = Cur->Next;

      delete P;

    }

  }

  IdDeclInfoMap(const IdDeclInfoMap &) = delete;

  IdDeclInfoMap &operator=(const IdDeclInfoMap &) = delete;

  /// Returns the IdDeclInfo associated to the DeclarationName.

  /// It creates a new IdDeclInfo if one was not created before for this id.

  IdDeclInfo &operator[](DeclarationName Name);

};

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

// IdDeclInfo Implementation

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

/// RemoveDecl - Remove the decl from the scope chain.

/// The decl must already be part of the decl chain.

void IdentifierResolver::IdDeclInfo::RemoveDecl(NamedDecl *D) {

  for (DeclsTy::iterator I = Decls.end(); I != Decls.begin(); --I) {

    if (D == *(I-1)) {

      Decls.erase(I-1);

      return;

    }

  }

  llvm_unreachable("Didn't find this decl on its identifier's chain!");

}

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

// IdentifierResolver Implementation

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

IdentifierResolver::IdentifierResolver(Preprocessor &PP)

    : LangOpt(PP.getLangOpts()), PP(PP), IdDeclInfos(new IdDeclInfoMap) {}

IdentifierResolver::~IdentifierResolver() {

  delete IdDeclInfos;

}

/// isDeclInScope - If 'Ctx' is a function/method, isDeclInScope returns true

/// if 'D' is in Scope 'S', otherwise 'S' is ignored and isDeclInScope returns

/// true if 'D' belongs to the given declaration context.

bool IdentifierResolver::isDeclInScope(Decl *D, DeclContext *Ctx, Scope *S,

                                       bool AllowInlineNamespace) const {

  Ctx = Ctx->getRedeclContext();

  // The names for HLSL cbuffer/tbuffers only used by the CPU-side

  // reflection API which supports querying bindings. It will not have name

  // conflict with other Decls.

  if (LangOpt.HLSL && isa<HLSLBufferDecl>(D))

    return false;

  if (Ctx->isFunctionOrMethod() || (S && S->isFunctionPrototypeScope())) {

    // Ignore the scopes associated within transparent declaration contexts.

    while (S->getEntity() &&

           (S->getEntity()->isTransparentContext() ||

            (!LangOpt.CPlusPlus && isa<RecordDecl>(S->getEntity()))))

      S = S->getParent();

    if (S->isDeclScope(D))

      return true;

    if (LangOpt.CPlusPlus) {

      // C++ 3.3.2p3:

      // The name declared in a catch exception-declaration is local to the

      // handler and shall not be redeclared in the outermost block of the

      // handler.

      // C++ 3.3.2p4:

      // Names declared in the for-init-statement, and in the condition of if,

      // while, for, and switch statements are local to the if, while, for, or

      // switch statement (including the controlled statement), and shall not be

      // redeclared in a subsequent condition of that statement nor in the

      // outermost block (or, for the if statement, any of the outermost blocks)

      // of the controlled statement.

      //

      assert(S->getParent() && "No TUScope?");

      // If the current decl is in a lambda, we shouldn't consider this is a

      // redefinition as lambda has its own scope.

      if (S->getParent()->isControlScope() && !S->isFunctionScope()) {

        S = S->getParent();

        if (S->isDeclScope(D))

          return true;

      }

      if (S->isFnTryCatchScope())

        return S->getParent()->isDeclScope(D);

    }

    return false;

  }

  // FIXME: If D is a local extern declaration, this check doesn't make sense;

  // we should be checking its lexical context instead in that case, because

  // that is its scope.

  DeclContext *DCtx = D->getDeclContext()->getRedeclContext();

  return AllowInlineNamespace ? Ctx->InEnclosingNamespaceSetOf(DCtx)

                              : Ctx->Equals(DCtx);

}

/// AddDecl - Link the decl to its shadowed decl chain.

void IdentifierResolver::AddDecl(NamedDecl *D) {

  DeclarationName Name = D->getDeclName();

  if (IdentifierInfo *II = Name.getAsIdentifierInfo())

    updatingIdentifier(*II);

  void *Ptr = Name.getFETokenInfo();

  if (!Ptr) {

    Name.setFETokenInfo(D);

    return;

  }

  IdDeclInfo *IDI;

  if (isDeclPtr(Ptr)) {

    Name.setFETokenInfo(nullptr);

    IDI = &(*IdDeclInfos)[Name];

    NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);

    IDI->AddDecl(PrevD);

  } else

    IDI = toIdDeclInfo(Ptr);

  IDI->AddDecl(D);

}

void IdentifierResolver::InsertDeclAfter(iterator Pos, NamedDecl *D) {

  DeclarationName Name = D->getDeclName();

  if (IdentifierInfo *II = Name.getAsIdentifierInfo())

    updatingIdentifier(*II);

  void *Ptr = Name.getFETokenInfo();

  if (!Ptr) {

    AddDecl(D);

    return;

  }

  if (isDeclPtr(Ptr)) {

    // We only have a single declaration: insert before or after it,

    // as appropriate.

    if (Pos == iterator()) {

      // Add the new declaration before the existing declaration.

      NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);

      RemoveDecl(PrevD);

      AddDecl(D);

      AddDecl(PrevD);

    } else {

      // Add new declaration after the existing declaration.

      AddDecl(D);

    }

    return;

  }

  // General case: insert the declaration at the appropriate point in the

  // list, which already has at least two elements.

  IdDeclInfo *IDI = toIdDeclInfo(Ptr);

  if (Pos.isIterator()) {

    IDI->InsertDecl(Pos.getIterator() + 1, D);

  } else

    IDI->InsertDecl(IDI->decls_begin(), D);

}

/// RemoveDecl - Unlink the decl from its shadowed decl chain.

/// The decl must already be part of the decl chain.

void IdentifierResolver::RemoveDecl(NamedDecl *D) {

  assert(D && "null param passed");

  DeclarationName Name = D->getDeclName();

  if (IdentifierInfo *II = Name.getAsIdentifierInfo())

    updatingIdentifier(*II);

  void *Ptr = Name.getFETokenInfo();

  assert(Ptr && "Didn't find this decl on its identifier's chain!");

  if (isDeclPtr(Ptr)) {

    assert(D == Ptr && "Didn't find this decl on its identifier's chain!");

    Name.setFETokenInfo(nullptr);

    return;

  }

  return toIdDeclInfo(Ptr)->RemoveDecl(D);

}

llvm::iterator_range<IdentifierResolver::iterator>

IdentifierResolver::decls(DeclarationName Name) {

  return {begin(Name), end()};

}

IdentifierResolver::iterator IdentifierResolver::begin(DeclarationName Name) {

  if (IdentifierInfo *II = Name.getAsIdentifierInfo())

    readingIdentifier(*II);

  void *Ptr = Name.getFETokenInfo();

  if (!Ptr) return end();

  if (isDeclPtr(Ptr))

    return iterator(static_cast<NamedDecl*>(Ptr));

  IdDeclInfo *IDI = toIdDeclInfo(Ptr);

  IdDeclInfo::DeclsTy::iterator I = IDI->decls_end();

  if (I != IDI->decls_begin())

    return iterator(I-1);

  // No decls found.

  return end();

}

namespace {

enum DeclMatchKind {

  DMK_Different,

  DMK_Replace,

  DMK_Ignore

};

} // namespace

/// Compare two declarations to see whether they are different or,

/// if they are the same, whether the new declaration should replace the

/// existing declaration.

static DeclMatchKind compareDeclarations(NamedDecl *Existing, NamedDecl *New) {

  // If the declarations are identical, ignore the new one.

  if (Existing == New)

    return DMK_Ignore;

  // If the declarations have different kinds, they're obviously different.

  if (Existing->getKind() != New->getKind())

    return DMK_Different;

  // If the declarations are redeclarations of each other, keep the newest one.

  if (Existing->getCanonicalDecl() == New->getCanonicalDecl()) {

    // If we're adding an imported declaration, don't replace another imported

    // declaration.

    if (Existing->isFromASTFile() && New->isFromASTFile())

      return DMK_Different;

    // If either of these is the most recent declaration, use it.

    Decl *MostRecent = Existing->getMostRecentDecl();

    if (Existing == MostRecent)

      return DMK_Ignore;

    if (New == MostRecent)

      return DMK_Replace;

    // If the existing declaration is somewhere in the previous declaration

    // chain of the new declaration, then prefer the new declaration.

    for (auto *RD : New->redecls()) {

      if (RD == Existing)

        return DMK_Replace;

      if (RD->isCanonicalDecl())

        break;

    }

    return DMK_Ignore;

  }

  return DMK_Different;

}

bool IdentifierResolver::tryAddTopLevelDecl(NamedDecl *D, DeclarationName Name){

  if (IdentifierInfo *II = Name.getAsIdentifierInfo())

    readingIdentifier(*II);

  void *Ptr = Name.getFETokenInfo();

  if (!Ptr) {

    Name.setFETokenInfo(D);

    return true;

  }

  IdDeclInfo *IDI;

  if (isDeclPtr(Ptr)) {

    NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);

    switch (compareDeclarations(PrevD, D)) {

    case DMK_Different:

      break;

    case DMK_Ignore:

      return false;

    case DMK_Replace:

      Name.setFETokenInfo(D);

      return true;

    }

    Name.setFETokenInfo(nullptr);

    IDI = &(*IdDeclInfos)[Name];

    // If the existing declaration is not visible in translation unit scope,

    // then add the new top-level declaration first.

    if (!PrevD->getDeclContext()->getRedeclContext()->isTranslationUnit()) {

      IDI->AddDecl(D);

      IDI->AddDecl(PrevD);

    } else {

      IDI->AddDecl(PrevD);

      IDI->AddDecl(D);

    }

    return true;

  }

  IDI = toIdDeclInfo(Ptr);

  // See whether this declaration is identical to any existing declarations.

  // If not, find the right place to insert it.

  for (IdDeclInfo::DeclsTy::iterator I = IDI->decls_begin(),

                                  IEnd = IDI->decls_end();

       I != IEnd; ++I) {

    switch (compareDeclarations(*I, D)) {

    case DMK_Different:

      break;

    case DMK_Ignore:

      return false;

    case DMK_Replace:

      *I = D;

      return true;

    }

    if (!(*I)->getDeclContext()->getRedeclContext()->isTranslationUnit()) {

      // We've found a declaration that is not visible from the translation

      // unit (it's in an inner scope). Insert our declaration here.

      IDI->InsertDecl(I, D);

      return true;

    }

  }

  // Add the declaration to the end.

  IDI->AddDecl(D);

  return true;

}

void IdentifierResolver::readingIdentifier(IdentifierInfo &II) {

  if (II.isOutOfDate())

    PP.getExternalSource()->updateOutOfDateIdentifier(II);

}

void IdentifierResolver::updatingIdentifier(IdentifierInfo &II) {

  if (II.isOutOfDate())

    PP.getExternalSource()->updateOutOfDateIdentifier(II);

  if (II.isFromAST())

    II.setFETokenInfoChangedSinceDeserialization();

}

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

// IdDeclInfoMap Implementation

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

/// Returns the IdDeclInfo associated to the DeclarationName.

/// It creates a new IdDeclInfo if one was not created before for this id.

IdentifierResolver::IdDeclInfo &

IdentifierResolver::IdDeclInfoMap::operator[](DeclarationName Name) {

  void *Ptr = Name.getFETokenInfo();

  if (Ptr) return *toIdDeclInfo(Ptr);

  if (CurIndex == POOL_SIZE) {

    CurPool = new IdDeclInfoPool(CurPool);

    CurIndex = 0;

  }

  IdDeclInfo *IDI = &CurPool->Pool[CurIndex];

  Name.setFETokenInfo(reinterpret_cast<void*>(

                              reinterpret_cast<uintptr_t>(IDI) | 0x1)

                                                                     );

  ++CurIndex;

  return *IDI;

}

void IdentifierResolver::iterator::incrementSlowCase() {

  NamedDecl *D = **this;

  void *InfoPtr = D->getDeclName().getFETokenInfo();

  assert(!isDeclPtr(InfoPtr) && "Decl with wrong id ?");

  IdDeclInfo *Info = toIdDeclInfo(InfoPtr);

  BaseIter I = getIterator();

  if (I != Info->decls_begin())

    *this = iterator(I-1);

  else // No more decls.

    *this = iterator();

}