clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.cpp

   1 //===--- RedundantControlFlowCheck.cpp - clang-tidy------------------------===//
   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
   9 #include "RedundantControlFlowCheck.h"
  10 #include "clang/AST/ASTContext.h"
  11 #include "clang/ASTMatchers/ASTMatchFinder.h"
  12 #include "clang/Lex/Lexer.h"
  13
  14 using namespace clang::ast_matchers;
  15
  16 namespace clang::tidy::readability {
  17
  18 namespace {
  19
  20 const char *const RedundantReturnDiag = "redundant return statement at the end "
  21                                         "of a function with a void return type";
  22 const char *const RedundantContinueDiag = "redundant continue statement at the "
  23                                           "end of loop statement";
  24
  25 bool isLocationInMacroExpansion(const SourceManager &SM, SourceLocation Loc) {
  26   return SM.isMacroBodyExpansion(Loc) || SM.isMacroArgExpansion(Loc);
  27 }
  28
  29 } // namespace
  30
  31 void RedundantControlFlowCheck::registerMatchers(MatchFinder *Finder) {
  32   Finder->addMatcher(
  33       functionDecl(isDefinition(), returns(voidType()),
  34                    hasBody(compoundStmt(hasAnySubstatement(
  35                                             returnStmt(unless(has(expr())))))
  36                                .bind("return"))),
  37       this);
  38   Finder->addMatcher(
  39       mapAnyOf(forStmt, cxxForRangeStmt, whileStmt, doStmt)
  40           .with(hasBody(compoundStmt(hasAnySubstatement(continueStmt()))
  41                             .bind("continue"))),
  42       this);
  43 }
  44
  45 void RedundantControlFlowCheck::check(const MatchFinder::MatchResult &Result) {
  46   if (const auto *Return = Result.Nodes.getNodeAs<CompoundStmt>("return"))
  47     checkRedundantReturn(Result, Return);
  48   else if (const auto *Continue =
  49                Result.Nodes.getNodeAs<CompoundStmt>("continue"))
  50     checkRedundantContinue(Result, Continue);
  51 }
  52
  53 void RedundantControlFlowCheck::checkRedundantReturn(
  54     const MatchFinder::MatchResult &Result, const CompoundStmt *Block) {
  55   CompoundStmt::const_reverse_body_iterator Last = Block->body_rbegin();
  56   if (const auto *Return = dyn_cast<ReturnStmt>(*Last))
  57     issueDiagnostic(Result, Block, Return->getSourceRange(),
  58                     RedundantReturnDiag);
  59 }
  60
  61 void RedundantControlFlowCheck::checkRedundantContinue(
  62     const MatchFinder::MatchResult &Result, const CompoundStmt *Block) {
  63   CompoundStmt::const_reverse_body_iterator Last = Block->body_rbegin();
  64   if (const auto *Continue = dyn_cast<ContinueStmt>(*Last))
  65     issueDiagnostic(Result, Block, Continue->getSourceRange(),
  66                     RedundantContinueDiag);
  67 }
  68
  69 void RedundantControlFlowCheck::issueDiagnostic(
  70     const MatchFinder::MatchResult &Result, const CompoundStmt *const Block,
  71     const SourceRange &StmtRange, const char *const Diag) {
  72   SourceManager &SM = *Result.SourceManager;
  73   if (isLocationInMacroExpansion(SM, StmtRange.getBegin()))
  74     return;
  75
  76   CompoundStmt::const_reverse_body_iterator Previous = ++Block->body_rbegin();
  77   SourceLocation Start;
  78   if (Previous != Block->body_rend())
  79     Start = Lexer::findLocationAfterToken(
  80         cast<Stmt>(*Previous)->getEndLoc(), tok::semi, SM, getLangOpts(),
  81         /*SkipTrailingWhitespaceAndNewLine=*/true);
  82   if (!Start.isValid())
  83     Start = StmtRange.getBegin();
  84   auto RemovedRange = CharSourceRange::getCharRange(
  85       Start, Lexer::findLocationAfterToken(
  86                  StmtRange.getEnd(), tok::semi, SM, getLangOpts(),
  87                  /*SkipTrailingWhitespaceAndNewLine=*/true));
  88
  89   diag(StmtRange.getBegin(), Diag) << FixItHint::CreateRemoval(RemovedRange);
  90 }
  91
  92 } // namespace clang::tidy::readability