1 //===--- UnusedUsingDeclsCheck.cpp - clang-tidy----------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "UnusedUsingDeclsCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/Lex/Lexer.h"
14 
15 using namespace clang::ast_matchers;
16 
17 namespace clang {
18 namespace tidy {
19 namespace misc {
20 
21 void UnusedUsingDeclsCheck::registerMatchers(MatchFinder *Finder) {
22   Finder->addMatcher(usingDecl(isExpansionInMainFile()).bind("using"), this);
23   auto DeclMatcher = hasDeclaration(namedDecl().bind("used"));
24   Finder->addMatcher(loc(recordType(DeclMatcher)), this);
25   Finder->addMatcher(loc(templateSpecializationType(DeclMatcher)), this);
26 }
27 
28 void UnusedUsingDeclsCheck::check(const MatchFinder::MatchResult &Result) {
29   if (const auto *Using = Result.Nodes.getNodeAs<UsingDecl>("using")) {
30     // FIXME: Implement the correct behavior for using declarations with more
31     // than one shadow.
32     if (Using->shadow_size() != 1)
33       return;
34     const auto *TargetDecl =
35         Using->shadow_begin()->getTargetDecl()->getCanonicalDecl();
36 
37     // FIXME: Handle other target types.
38     if (!isa<RecordDecl>(TargetDecl) && !isa<ClassTemplateDecl>(TargetDecl))
39       return;
40 
41     FoundDecls[TargetDecl] = Using;
42     FoundRanges[TargetDecl] = CharSourceRange::getCharRange(
43         Using->getLocStart(),
44         Lexer::findLocationAfterToken(
45             Using->getLocEnd(), tok::semi, *Result.SourceManager,
46             Result.Context->getLangOpts(),
47             /*SkipTrailingWhitespaceAndNewLine=*/true));
48     return;
49   }
50 
51   // Mark using declarations as used by setting FoundDecls' value to zero. As
52   // the AST is walked in order, usages are only marked after a the
53   // corresponding using declaration has been found.
54   // FIXME: This currently doesn't look at whether the type reference is
55   // actually found with the help of the using declaration.
56   if (const auto *Used = Result.Nodes.getNodeAs<NamedDecl>("used")) {
57     if (const auto *Specialization =
58             dyn_cast<ClassTemplateSpecializationDecl>(Used))
59       Used = Specialization->getSpecializedTemplate();
60     auto I = FoundDecls.find(Used->getCanonicalDecl());
61     if (I != FoundDecls.end())
62       I->second = nullptr;
63   }
64 }
65 
66 void UnusedUsingDeclsCheck::onEndOfTranslationUnit() {
67   for (const auto &FoundDecl : FoundDecls) {
68     if (FoundDecl.second == nullptr)
69       continue;
70     diag(FoundDecl.second->getLocation(), "using decl %0 is unused")
71         << FoundDecl.second
72         << FixItHint::CreateRemoval(FoundRanges[FoundDecl.first]);
73   }
74   FoundDecls.clear();
75 }
76 
77 } // namespace misc
78 } // namespace tidy
79 } // namespace clang
80