clang-tools-extra/clangd/refactor/tweaks/RemoveUsingNamespace.cpp

   1 //===--- RemoveUsingNamespace.cpp --------------------------------*- C++-*-===//
   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 #include "AST.h"
   9 #include "FindTarget.h"
  10 #include "Selection.h"
  11 #include "refactor/Tweak.h"
  12 #include "support/Logger.h"
  13 #include "clang/AST/Decl.h"
  14 #include "clang/AST/DeclBase.h"
  15 #include "clang/AST/DeclCXX.h"
  16 #include "clang/AST/RecursiveASTVisitor.h"
  17 #include "clang/Basic/SourceLocation.h"
  18 #include "clang/Tooling/Core/Replacement.h"
  19
  20 namespace clang {
  21 namespace clangd {
  22 namespace {
  23 /// Removes the 'using namespace' under the cursor and qualifies all accesses in
  24 /// the current file. E.g.,
  25 ///   using namespace std;
  26 ///   vector<int> foo(std::map<int, int>);
  27 /// Would become:
  28 ///   std::vector<int> foo(std::map<int, int>);
  29 /// Currently limited to using namespace directives inside global namespace to
  30 /// simplify implementation. Also the namespace must not contain using
  31 /// directives.
  32 class RemoveUsingNamespace : public Tweak {
  33 public:
  34   const char *id() const override;
  35
  36   bool prepare(const Selection &Inputs) override;
  37   Expected<Effect> apply(const Selection &Inputs) override;
  38   std::string title() const override {
  39     return "Remove using namespace, re-qualify names instead";
  40   }
  41   llvm::StringLiteral kind() const override {
  42     return CodeAction::REFACTOR_KIND;
  43   }
  44
  45 private:
  46   const UsingDirectiveDecl *TargetDirective = nullptr;
  47 };
  48 REGISTER_TWEAK(RemoveUsingNamespace)
  49
  50 class FindSameUsings : public RecursiveASTVisitor<FindSameUsings> {
  51 public:
  52   FindSameUsings(const UsingDirectiveDecl &Target,
  53                  std::vector<const UsingDirectiveDecl *> &Results)
  54       : TargetNS(Target.getNominatedNamespace()),
  55         TargetCtx(Target.getDeclContext()), Results(Results) {}
  56
  57   bool VisitUsingDirectiveDecl(UsingDirectiveDecl *D) {
  58     if (D->getNominatedNamespace() != TargetNS ||
  59         D->getDeclContext() != TargetCtx)
  60       return true;
  61     Results.push_back(D);
  62     return true;
  63   }
  64
  65 private:
  66   const NamespaceDecl *TargetNS;
  67   const DeclContext *TargetCtx;
  68   std::vector<const UsingDirectiveDecl *> &Results;
  69 };
  70
  71 /// Produce edit removing 'using namespace xxx::yyy' and the trailing semicolon.
  72 llvm::Expected<tooling::Replacement>
  73 removeUsingDirective(ASTContext &Ctx, const UsingDirectiveDecl *D) {
  74   auto &SM = Ctx.getSourceManager();
  75   llvm::Optional<Token> NextTok =
  76       Lexer::findNextToken(D->getEndLoc(), SM, Ctx.getLangOpts());
  77   if (!NextTok || NextTok->isNot(tok::semi))
  78     return error("no semicolon after using-directive");
  79   // FIXME: removing the semicolon may be invalid in some obscure cases, e.g.
  80   //        if (x) using namespace std; else using namespace bar;
  81   return tooling::Replacement(
  82       SM,
  83       CharSourceRange::getTokenRange(D->getBeginLoc(), NextTok->getLocation()),
  84       "", Ctx.getLangOpts());
  85 }
  86
  87 // Returns true iff the parent of the Node is a TUDecl.
  88 bool isTopLevelDecl(const SelectionTree::Node *Node) {
  89   return Node->Parent && Node->Parent->ASTNode.get<TranslationUnitDecl>();
  90 }
  91
  92 // Returns the first visible context that contains this DeclContext.
  93 // For example: Returns ns1 for S1 and a.
  94 // namespace ns1 {
  95 // inline namespace ns2 { struct S1 {}; }
  96 // enum E { a, b, c, d };
  97 // }
  98 const DeclContext *visibleContext(const DeclContext *D) {
  99   while (D->isInlineNamespace() || D->isTransparentContext())
 100     D = D->getParent();
 101   return D;
 102 }
 103
 104 bool RemoveUsingNamespace::prepare(const Selection &Inputs) {
 105   // Find the 'using namespace' directive under the cursor.
 106   auto *CA = Inputs.ASTSelection.commonAncestor();
 107   if (!CA)
 108     return false;
 109   TargetDirective = CA->ASTNode.get<UsingDirectiveDecl>();
 110   if (!TargetDirective)
 111     return false;
 112   if (!isa<Decl>(TargetDirective->getDeclContext()))
 113     return false;
 114   // FIXME: Unavailable for namespaces containing using-namespace decl.
 115   // It is non-trivial to deal with cases where identifiers come from the inner
 116   // namespace. For example map has to be changed to aa::map.
 117   // namespace aa {
 118   //   namespace bb { struct map {}; }
 119   //   using namespace bb;
 120   // }
 121   // using namespace a^a;
 122   // int main() { map m; }
 123   // We need to make this aware of the transitive using-namespace decls.
 124   if (!TargetDirective->getNominatedNamespace()->using_directives().empty())
 125     return false;
 126   return isTopLevelDecl(CA);
 127 }
 128
 129 Expected<Tweak::Effect> RemoveUsingNamespace::apply(const Selection &Inputs) {
 130   auto &Ctx = Inputs.AST->getASTContext();
 131   auto &SM = Ctx.getSourceManager();
 132   // First, collect *all* using namespace directives that redeclare the same
 133   // namespace.
 134   std::vector<const UsingDirectiveDecl *> AllDirectives;
 135   FindSameUsings(*TargetDirective, AllDirectives).TraverseAST(Ctx);
 136
 137   SourceLocation FirstUsingDirectiveLoc;
 138   for (auto *D : AllDirectives) {
 139     if (FirstUsingDirectiveLoc.isInvalid() ||
 140         SM.isBeforeInTranslationUnit(D->getBeginLoc(), FirstUsingDirectiveLoc))
 141       FirstUsingDirectiveLoc = D->getBeginLoc();
 142   }
 143
 144   // Collect all references to symbols from the namespace for which we're
 145   // removing the directive.
 146   std::vector<SourceLocation> IdentsToQualify;
 147   for (auto &D : Inputs.AST->getLocalTopLevelDecls()) {
 148     findExplicitReferences(
 149         D,
 150         [&](ReferenceLoc Ref) {
 151           if (Ref.Qualifier)
 152             return; // This reference is already qualified.
 153
 154           for (auto *T : Ref.Targets) {
 155             if (!visibleContext(T->getDeclContext())
 156                      ->Equals(TargetDirective->getNominatedNamespace()))
 157               return;
 158           }
 159           SourceLocation Loc = Ref.NameLoc;
 160           if (Loc.isMacroID()) {
 161             // Avoid adding qualifiers before macro expansions, it's probably
 162             // incorrect, e.g.
 163             //   namespace std { int foo(); }
 164             //   #define FOO 1 + foo()
 165             //   using namespace foo; // provides matrix
 166             //   auto x = FOO; // Must not changed to auto x = std::FOO
 167             if (!SM.isMacroArgExpansion(Loc))
 168               return; // FIXME: report a warning to the users.
 169             Loc = SM.getFileLoc(Ref.NameLoc);
 170           }
 171           assert(Loc.isFileID());
 172           if (SM.getFileID(Loc) != SM.getMainFileID())
 173             return; // FIXME: report these to the user as warnings?
 174           if (SM.isBeforeInTranslationUnit(Loc, FirstUsingDirectiveLoc))
 175             return; // Directive was not visible before this point.
 176           IdentsToQualify.push_back(Loc);
 177         },
 178         Inputs.AST->getHeuristicResolver());
 179   }
 180   // Remove duplicates.
 181   llvm::sort(IdentsToQualify);
 182   IdentsToQualify.erase(
 183       std::unique(IdentsToQualify.begin(), IdentsToQualify.end()),
 184       IdentsToQualify.end());
 185
 186   // Produce replacements to remove the using directives.
 187   tooling::Replacements R;
 188   for (auto *D : AllDirectives) {
 189     auto RemoveUsing = removeUsingDirective(Ctx, D);
 190     if (!RemoveUsing)
 191       return RemoveUsing.takeError();
 192     if (auto Err = R.add(*RemoveUsing))
 193       return std::move(Err);
 194   }
 195   // Produce replacements to add the qualifiers.
 196   std::string Qualifier = printUsingNamespaceName(Ctx, *TargetDirective) + "::";
 197   for (auto Loc : IdentsToQualify) {
 198     if (auto Err = R.add(tooling::Replacement(Ctx.getSourceManager(), Loc,
 199                                               /*Length=*/0, Qualifier)))
 200       return std::move(Err);
 201   }
 202   return Effect::mainFileEdit(SM, std::move(R));
 203 }
 204
 205 } // namespace
 206 } // namespace clangd
 207 } // namespace clang