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//===--- LexicallyOrderedRecursiveASTVisitor.h - ----------------*- 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 LexicallyOrderedRecursiveASTVisitor interface, which

//  recursively traverses the entire AST in a lexical order.

//

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

#ifndef LLVM_CLANG_AST_LEXICALLYORDEREDRECURSIVEASTVISITOR_H

#define LLVM_CLANG_AST_LEXICALLYORDEREDRECURSIVEASTVISITOR_H

#include "clang/AST/RecursiveASTVisitor.h"

#include "clang/Basic/LLVM.h"

#include "clang/Basic/SourceManager.h"

#include "llvm/Support/SaveAndRestore.h"

namespace clang {

/// A RecursiveASTVisitor subclass that guarantees that AST traversal is

/// performed in a lexical order (i.e. the order in which declarations are

/// written in the source).

///

/// RecursiveASTVisitor doesn't guarantee lexical ordering because there are

/// some declarations, like Objective-C @implementation declarations

/// that might be represented in the AST differently to how they were written

/// in the source.

/// In particular, Objective-C @implementation declarations may contain

/// non-Objective-C declarations, like functions:

///

///   @implementation MyClass

///

///   - (void) method { }

///   void normalFunction() { }

///

///   @end

///

/// Clang's AST stores these declarations outside of the @implementation

/// declaration, so the example above would be represented using the following

/// AST:

///   |-ObjCImplementationDecl ... MyClass

///   | `-ObjCMethodDecl ... method

///   |    ...

///   `-FunctionDecl ... normalFunction

///       ...

///

/// This class ensures that these declarations are traversed before the

/// corresponding TraverseDecl for the @implementation returns. This ensures

/// that the lexical parent relationship between these declarations and the

/// @implementation is preserved while traversing the AST. Note that the

/// current implementation doesn't mix these declarations with the declarations

/// contained in the @implementation, so the traversal of all of the

/// declarations in the @implementation still doesn't follow the lexical order.

template <typename Derived>

class LexicallyOrderedRecursiveASTVisitor

    : public RecursiveASTVisitor<Derived> {

  using BaseType = RecursiveASTVisitor<Derived>;

public:

  LexicallyOrderedRecursiveASTVisitor(const SourceManager &SM) : SM(SM) {}

  bool TraverseObjCImplementationDecl(ObjCImplementationDecl *D) {

    // Objective-C @implementation declarations should not trigger early exit

    // until the additional decls are traversed as their children are not

    // lexically ordered.

    bool Result = BaseType::TraverseObjCImplementationDecl(D);

    return TraverseAdditionalLexicallyNestedDeclarations() ? Result : false;

  }

  bool TraverseObjCCategoryImplDecl(ObjCCategoryImplDecl *D) {

    bool Result = BaseType::TraverseObjCCategoryImplDecl(D);

    return TraverseAdditionalLexicallyNestedDeclarations() ? Result : false;

  }

  bool TraverseDeclContextHelper(DeclContext *DC) {

    if (!DC)

      return true;

    for (auto I = DC->decls_begin(), E = DC->decls_end(); I != E;) {

      Decl *Child = *I;

      if (BaseType::canIgnoreChildDeclWhileTraversingDeclContext(Child)) {

        ++I;

        continue;

      }

      if (!isa<ObjCImplementationDecl>(Child) &&

          !isa<ObjCCategoryImplDecl>(Child)) {

        if (!BaseType::getDerived().TraverseDecl(Child))

          return false;

        ++I;

        continue;

      }

      // Gather declarations that follow the Objective-C implementation

      // declarations but are lexically contained in the implementation.

      LexicallyNestedDeclarations.clear();

      for (++I; I != E; ++I) {

        Decl *Sibling = *I;

        if (!SM.isBeforeInTranslationUnit(Sibling->getBeginLoc(),

                                          Child->getEndLoc()))

          break;

        if (!BaseType::canIgnoreChildDeclWhileTraversingDeclContext(Sibling))

          LexicallyNestedDeclarations.push_back(Sibling);

      }

      if (!BaseType::getDerived().TraverseDecl(Child))

        return false;

    }

    return true;

  }

  Stmt::child_range getStmtChildren(Stmt *S) { return S->children(); }

  SmallVector<Stmt *, 8> getStmtChildren(CXXOperatorCallExpr *CE) {

    SmallVector<Stmt *, 8> Children(CE->children());

    bool Swap;

    // Switch the operator and the first operand for all infix and postfix

    // operations.

    switch (CE->getOperator()) {

    case OO_Arrow:

    case OO_Call:

    case OO_Subscript:

      Swap = true;

      break;

    case OO_PlusPlus:

    case OO_MinusMinus:

      // These are postfix unless there is exactly one argument.

      Swap = Children.size() != 2;

      break;

    default:

      Swap = CE->isInfixBinaryOp();

      break;

    }

    if (Swap && Children.size() > 1)

      std::swap(Children[0], Children[1]);

    return Children;

  }

private:

  bool TraverseAdditionalLexicallyNestedDeclarations() {

    // FIXME: Ideally the gathered declarations and the declarations in the

    // @implementation should be mixed and sorted to get a true lexical order,

    // but right now we only care about getting the correct lexical parent, so

    // we can traverse the gathered nested declarations after the declarations

    // in the decl context.

    assert(!BaseType::getDerived().shouldTraversePostOrder() &&

           "post-order traversal is not supported for lexically ordered "

           "recursive ast visitor");

    for (Decl *D : LexicallyNestedDeclarations) {

      if (!BaseType::getDerived().TraverseDecl(D))

        return false;

    }

    return true;

  }

  const SourceManager &SM;

  llvm::SmallVector<Decl *, 8> LexicallyNestedDeclarations;

};

} // end namespace clang

#endif // LLVM_CLANG_AST_LEXICALLYORDEREDRECURSIVEASTVISITOR_H