TransUnusedInitDelegate.cpp

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//===--- TransUnusedInitDelegate.cpp - Transformations to ARC mode --------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// Transformations:
//===----------------------------------------------------------------------===//
//
// rewriteUnusedInitDelegate:
//
// Rewrites an unused result of calling a delegate initialization, to assigning
// the result to self.
// e.g
//  [self init];
// ---->
//  self = [self init];
//
//===----------------------------------------------------------------------===//
 
#include "Transforms.h"
#include "Internals.h"
#include "clang/AST/ASTContext.h"
#include "clang/Sema/SemaDiagnostic.h"
 
using namespace clang;
using namespace arcmt;
using namespace trans;
 
namespace {
 
class UnusedInitRewriter : public RecursiveASTVisitor<UnusedInitRewriter> {
  Stmt *Body;
  MigrationPass &Pass;
 
  ExprSet Removables;
 
public:
  UnusedInitRewriter(MigrationPass &pass)
    : Body(nullptr), Pass(pass) { }
 
  void transformBody(Stmt *body, Decl *ParentD) {
    Body = body;
    collectRemovables(body, Removables);
    TraverseStmt(body);
  }
 
  bool VisitObjCMessageExpr(ObjCMessageExpr *ME) {
    if (ME->isDelegateInitCall() &&
        isRemovable(ME) &&
        Pass.TA.hasDiagnostic(diag::err_arc_unused_init_message,
                              ME->getExprLoc())) {
      Transaction Trans(Pass.TA);
      Pass.TA.clearDiagnostic(diag::err_arc_unused_init_message,
                              ME->getExprLoc());
      SourceRange ExprRange = ME->getSourceRange();
      Pass.TA.insert(ExprRange.getBegin(), "if (!(self = ");
      std::string retStr = ")) return ";
      retStr += getNilString(Pass);
      Pass.TA.insertAfterToken(ExprRange.getEnd(), retStr);
    }
    return true;
  }
 
private:
  bool isRemovable(Expr *E) const {
    return Removables.count(E);
  }
};
 
} // anonymous namespace
 
void trans::rewriteUnusedInitDelegate(MigrationPass &pass) {
  BodyTransform<UnusedInitRewriter> trans(pass);
  trans.TraverseDecl(pass.Ctx.getTranslationUnitDecl());
}