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

   1 //===--- RedundantDeclarationCheck.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 "RedundantDeclarationCheck.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 AST_MATCHER(FunctionDecl, doesDeclarationForceExternallyVisibleDefinition) {
  19   return Node.doesDeclarationForceExternallyVisibleDefinition();
  20 }
  21
  22 RedundantDeclarationCheck::RedundantDeclarationCheck(StringRef Name,
  23                                                      ClangTidyContext *Context)
  24     : ClangTidyCheck(Name, Context),
  25       IgnoreMacros(Options.getLocalOrGlobal("IgnoreMacros", true)) {}
  26
  27 void RedundantDeclarationCheck::storeOptions(
  28     ClangTidyOptions::OptionMap &Opts) {
  29   Options.store(Opts, "IgnoreMacros", IgnoreMacros);
  30 }
  31
  32 void RedundantDeclarationCheck::registerMatchers(MatchFinder *Finder) {
  33   Finder->addMatcher(
  34       namedDecl(anyOf(varDecl(unless(isDefinition())),
  35                       functionDecl(unless(anyOf(
  36                           isDefinition(), isDefaulted(),
  37                           doesDeclarationForceExternallyVisibleDefinition(),
  38                           hasAncestor(friendDecl()))))),
  39                 optionally(hasParent(linkageSpecDecl().bind("extern"))))
  40           .bind("Decl"),
  41       this);
  42 }
  43
  44 void RedundantDeclarationCheck::check(const MatchFinder::MatchResult &Result) {
  45   const auto *D = Result.Nodes.getNodeAs<NamedDecl>("Decl");
  46   const auto *Prev = D->getPreviousDecl();
  47   if (!Prev)
  48     return;
  49   if (!Prev->getLocation().isValid())
  50     return;
  51   if (Prev->getLocation() == D->getLocation())
  52     return;
  53   if (IgnoreMacros &&
  54       (D->getLocation().isMacroID() || Prev->getLocation().isMacroID()))
  55     return;
  56   // Don't complain when the previous declaration is a friend declaration.
  57   for (const auto &Parent : Result.Context->getParents(*Prev))
  58     if (Parent.get<FriendDecl>())
  59       return;
  60
  61   const SourceManager &SM = *Result.SourceManager;
  62
  63   const bool DifferentHeaders =
  64       !SM.isInMainFile(D->getLocation()) &&
  65       !SM.isWrittenInSameFile(Prev->getLocation(), D->getLocation());
  66
  67   bool MultiVar = false;
  68   if (const auto *VD = dyn_cast<VarDecl>(D)) {
  69     // Is this a multivariable declaration?
  70     for (const auto *Other : VD->getDeclContext()->decls()) {
  71       if (Other != D && Other->getBeginLoc() == VD->getBeginLoc()) {
  72         MultiVar = true;
  73         break;
  74       }
  75     }
  76   }
  77
  78   SourceLocation EndLoc = Lexer::getLocForEndOfToken(
  79       D->getSourceRange().getEnd(), 0, SM, Result.Context->getLangOpts());
  80   {
  81     auto Diag = diag(D->getLocation(), "redundant %0 declaration") << D;
  82     if (!MultiVar && !DifferentHeaders) {
  83       SourceLocation BeginLoc;
  84       if (const auto *Extern =
  85               Result.Nodes.getNodeAs<LinkageSpecDecl>("extern");
  86           Extern && !Extern->hasBraces())
  87         BeginLoc = Extern->getExternLoc();
  88       else
  89         BeginLoc = D->getSourceRange().getBegin();
  90
  91       Diag << FixItHint::CreateRemoval(SourceRange(BeginLoc, EndLoc));
  92     }
  93   }
  94   diag(Prev->getLocation(), "previously declared here", DiagnosticIDs::Note);
  95 }
  96 } // namespace clang::tidy::readability