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 "SourceCode.h"
12 #include "refactor/Tweak.h"
13 #include "support/Logger.h"
14 #include "clang/AST/Decl.h"
15 #include "clang/AST/DeclBase.h"
16 #include "clang/AST/DeclCXX.h"
17 #include "clang/AST/RecursiveASTVisitor.h"
18 #include "clang/Basic/SourceLocation.h"
19 #include "clang/Tooling/Core/Replacement.h"
20 #include "clang/Tooling/Refactoring/RecursiveSymbolVisitor.h"
21 #include "llvm/ADT/ScopeExit.h"
22 
23 namespace clang {
24 namespace clangd {
25 namespace {
26 /// Removes the 'using namespace' under the cursor and qualifies all accesses in
27 /// the current file. E.g.,
28 ///   using namespace std;
29 ///   vector<int> foo(std::map<int, int>);
30 /// Would become:
31 ///   std::vector<int> foo(std::map<int, int>);
32 /// Currently limited to using namespace directives inside global namespace to
33 /// simplify implementation. Also the namespace must not contain using
34 /// directives.
35 class RemoveUsingNamespace : public Tweak {
36 public:
37   const char *id() const override;
38 
39   bool prepare(const Selection &Inputs) override;
40   Expected<Effect> apply(const Selection &Inputs) override;
41   std::string title() const override {
42     return "Remove using namespace, re-qualify names instead";
43   }
44   llvm::StringLiteral kind() const override {
45     return CodeAction::REFACTOR_KIND;
46   }
47 
48 private:
49   const UsingDirectiveDecl *TargetDirective = nullptr;
50 };
51 REGISTER_TWEAK(RemoveUsingNamespace)
52 
53 class FindSameUsings : public RecursiveASTVisitor<FindSameUsings> {
54 public:
55   FindSameUsings(const UsingDirectiveDecl &Target,
56                  std::vector<const UsingDirectiveDecl *> &Results)
57       : TargetNS(Target.getNominatedNamespace()),
58         TargetCtx(Target.getDeclContext()), Results(Results) {}
59 
60   bool VisitUsingDirectiveDecl(UsingDirectiveDecl *D) {
61     if (D->getNominatedNamespace() != TargetNS ||
62         D->getDeclContext() != TargetCtx)
63       return true;
64     Results.push_back(D);
65     return true;
66   }
67 
68 private:
69   const NamespaceDecl *TargetNS;
70   const DeclContext *TargetCtx;
71   std::vector<const UsingDirectiveDecl *> &Results;
72 };
73 
74 /// Produce edit removing 'using namespace xxx::yyy' and the trailing semicolon.
75 llvm::Expected<tooling::Replacement>
76 removeUsingDirective(ASTContext &Ctx, const UsingDirectiveDecl *D) {
77   auto &SM = Ctx.getSourceManager();
78   llvm::Optional<Token> NextTok =
79       Lexer::findNextToken(D->getEndLoc(), SM, Ctx.getLangOpts());
80   if (!NextTok || NextTok->isNot(tok::semi))
81     return error("no semicolon after using-directive");
82   // FIXME: removing the semicolon may be invalid in some obscure cases, e.g.
83   //        if (x) using namespace std; else using namespace bar;
84   return tooling::Replacement(
85       SM,
86       CharSourceRange::getTokenRange(D->getBeginLoc(), NextTok->getLocation()),
87       "", Ctx.getLangOpts());
88 }
89 
90 // Returns true iff the parent of the Node is a TUDecl.
91 bool isTopLevelDecl(const SelectionTree::Node *Node) {
92   return Node->Parent && Node->Parent->ASTNode.get<TranslationUnitDecl>();
93 }
94 
95 // Returns the first visible context that contains this DeclContext.
96 // For example: Returns ns1 for S1 and a.
97 // namespace ns1 {
98 // inline namespace ns2 { struct S1 {}; }
99 // enum E { a, b, c, d };
100 // }
101 const DeclContext *visibleContext(const DeclContext *D) {
102   while (D->isInlineNamespace() || D->isTransparentContext())
103     D = D->getParent();
104   return D;
105 }
106 
107 bool RemoveUsingNamespace::prepare(const Selection &Inputs) {
108   // Find the 'using namespace' directive under the cursor.
109   auto *CA = Inputs.ASTSelection.commonAncestor();
110   if (!CA)
111     return false;
112   TargetDirective = CA->ASTNode.get<UsingDirectiveDecl>();
113   if (!TargetDirective)
114     return false;
115   if (!isa<Decl>(TargetDirective->getDeclContext()))
116     return false;
117   // FIXME: Unavailable for namespaces containing using-namespace decl.
118   // It is non-trivial to deal with cases where identifiers come from the inner
119   // namespace. For example map has to be changed to aa::map.
120   // namespace aa {
121   //   namespace bb { struct map {}; }
122   //   using namespace bb;
123   // }
124   // using namespace a^a;
125   // int main() { map m; }
126   // We need to make this aware of the transitive using-namespace decls.
127   if (!TargetDirective->getNominatedNamespace()->using_directives().empty())
128     return false;
129   return isTopLevelDecl(CA);
130 }
131 
132 Expected<Tweak::Effect> RemoveUsingNamespace::apply(const Selection &Inputs) {
133   auto &Ctx = Inputs.AST->getASTContext();
134   auto &SM = Ctx.getSourceManager();
135   // First, collect *all* using namespace directives that redeclare the same
136   // namespace.
137   std::vector<const UsingDirectiveDecl *> AllDirectives;
138   FindSameUsings(*TargetDirective, AllDirectives).TraverseAST(Ctx);
139 
140   SourceLocation FirstUsingDirectiveLoc;
141   for (auto *D : AllDirectives) {
142     if (FirstUsingDirectiveLoc.isInvalid() ||
143         SM.isBeforeInTranslationUnit(D->getBeginLoc(), FirstUsingDirectiveLoc))
144       FirstUsingDirectiveLoc = D->getBeginLoc();
145   }
146 
147   // Collect all references to symbols from the namespace for which we're
148   // removing the directive.
149   std::vector<SourceLocation> IdentsToQualify;
150   for (auto &D : Inputs.AST->getLocalTopLevelDecls()) {
151     findExplicitReferences(
152         D,
153         [&](ReferenceLoc Ref) {
154           if (Ref.Qualifier)
155             return; // This reference is already qualified.
156 
157           for (auto *T : Ref.Targets) {
158             if (!visibleContext(T->getDeclContext())
159                      ->Equals(TargetDirective->getNominatedNamespace()))
160               return;
161           }
162           SourceLocation Loc = Ref.NameLoc;
163           if (Loc.isMacroID()) {
164             // Avoid adding qualifiers before macro expansions, it's probably
165             // incorrect, e.g.
166             //   namespace std { int foo(); }
167             //   #define FOO 1 + foo()
168             //   using namespace foo; // provides matrix
169             //   auto x = FOO; // Must not changed to auto x = std::FOO
170             if (!SM.isMacroArgExpansion(Loc))
171               return; // FIXME: report a warning to the users.
172             Loc = SM.getFileLoc(Ref.NameLoc);
173           }
174           assert(Loc.isFileID());
175           if (SM.getFileID(Loc) != SM.getMainFileID())
176             return; // FIXME: report these to the user as warnings?
177           if (SM.isBeforeInTranslationUnit(Loc, FirstUsingDirectiveLoc))
178             return; // Directive was not visible before this point.
179           IdentsToQualify.push_back(Loc);
180         },
181         Inputs.AST->getHeuristicResolver());
182   }
183   // Remove duplicates.
184   llvm::sort(IdentsToQualify);
185   IdentsToQualify.erase(
186       std::unique(IdentsToQualify.begin(), IdentsToQualify.end()),
187       IdentsToQualify.end());
188 
189   // Produce replacements to remove the using directives.
190   tooling::Replacements R;
191   for (auto *D : AllDirectives) {
192     auto RemoveUsing = removeUsingDirective(Ctx, D);
193     if (!RemoveUsing)
194       return RemoveUsing.takeError();
195     if (auto Err = R.add(*RemoveUsing))
196       return std::move(Err);
197   }
198   // Produce replacements to add the qualifiers.
199   std::string Qualifier = printUsingNamespaceName(Ctx, *TargetDirective) + "::";
200   for (auto Loc : IdentsToQualify) {
201     if (auto Err = R.add(tooling::Replacement(Ctx.getSourceManager(), Loc,
202                                               /*Length=*/0, Qualifier)))
203       return std::move(Err);
204   }
205   return Effect::mainFileEdit(SM, std::move(R));
206 }
207 
208 } // namespace
209 } // namespace clangd
210 } // namespace clang
211