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      1 //===--- TransUnusedInitDelegate.cpp - Transformations to ARC mode --------===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 // Transformations:
      9 //===----------------------------------------------------------------------===//
     10 //
     11 // rewriteUnusedInitDelegate:
     12 //
     13 // Rewrites an unused result of calling a delegate initialization, to assigning
     14 // the result to self.
     15 // e.g
     16 //  [self init];
     17 // ---->
     18 //  self = [self init];
     19 //
     20 //===----------------------------------------------------------------------===//
     21 
     22 #include "Transforms.h"
     23 #include "Internals.h"
     24 #include "clang/AST/ASTContext.h"
     25 #include "clang/Sema/SemaDiagnostic.h"
     26 
     27 using namespace clang;
     28 using namespace arcmt;
     29 using namespace trans;
     30 
     31 namespace {
     32 
     33 class UnusedInitRewriter : public RecursiveASTVisitor<UnusedInitRewriter> {
     34   Stmt *Body;
     35   MigrationPass &Pass;
     36 
     37   ExprSet Removables;
     38 
     39 public:
     40   UnusedInitRewriter(MigrationPass &pass)
     41     : Body(nullptr), Pass(pass) { }
     42 
     43   void transformBody(Stmt *body, Decl *ParentD) {
     44     Body = body;
     45     collectRemovables(body, Removables);
     46     TraverseStmt(body);
     47   }
     48 
     49   bool VisitObjCMessageExpr(ObjCMessageExpr *ME) {
     50     if (ME->isDelegateInitCall() &&
     51         isRemovable(ME) &&
     52         Pass.TA.hasDiagnostic(diag::err_arc_unused_init_message,
     53                               ME->getExprLoc())) {
     54       Transaction Trans(Pass.TA);
     55       Pass.TA.clearDiagnostic(diag::err_arc_unused_init_message,
     56                               ME->getExprLoc());
     57       SourceRange ExprRange = ME->getSourceRange();
     58       Pass.TA.insert(ExprRange.getBegin(), "if (!(self = ");
     59       std::string retStr = ")) return ";
     60       retStr += getNilString(Pass);
     61       Pass.TA.insertAfterToken(ExprRange.getEnd(), retStr);
     62     }
     63     return true;
     64   }
     65 
     66 private:
     67   bool isRemovable(Expr *E) const {
     68     return Removables.count(E);
     69   }
     70 };
     71 
     72 } // anonymous namespace
     73 
     74 void trans::rewriteUnusedInitDelegate(MigrationPass &pass) {
     75   BodyTransform<UnusedInitRewriter> trans(pass);
     76   trans.TraverseDecl(pass.Ctx.getTranslationUnitDecl());
     77 }
     78