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