1 //===--- UseUsingCheck.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 "UseUsingCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/Lex/Lexer.h"
12 
13 using namespace clang::ast_matchers;
14 
15 namespace clang {
16 namespace tidy {
17 namespace modernize {
18 
19 static constexpr llvm::StringLiteral ParentDeclName = "parent-decl";
20 static constexpr llvm::StringLiteral TagDeclName = "tag-decl";
21 static constexpr llvm::StringLiteral TypedefName = "typedef";
22 
23 UseUsingCheck::UseUsingCheck(StringRef Name, ClangTidyContext *Context)
24     : ClangTidyCheck(Name, Context),
25       IgnoreMacros(Options.getLocalOrGlobal("IgnoreMacros", true)) {}
26 
27 void UseUsingCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
28   Options.store(Opts, "IgnoreMacros", IgnoreMacros);
29 }
30 
31 void UseUsingCheck::registerMatchers(MatchFinder *Finder) {
32   Finder->addMatcher(typedefDecl(unless(isInstantiated()),
33                                  hasParent(decl().bind(ParentDeclName)))
34                          .bind(TypedefName),
35                      this);
36 
37   // This matcher is used to find tag declarations in source code within
38   // typedefs. They appear in the AST just *prior* to the typedefs.
39   Finder->addMatcher(
40       tagDecl(
41           anyOf(allOf(unless(anyOf(isImplicit(),
42                                    classTemplateSpecializationDecl())),
43                       hasParent(decl().bind(ParentDeclName))),
44                 // We want the parent of the ClassTemplateDecl, not the parent
45                 // of the specialization.
46                 classTemplateSpecializationDecl(hasAncestor(classTemplateDecl(
47                     hasParent(decl().bind(ParentDeclName)))))))
48           .bind(TagDeclName),
49       this);
50 }
51 
52 void UseUsingCheck::check(const MatchFinder::MatchResult &Result) {
53   const auto *ParentDecl = Result.Nodes.getNodeAs<Decl>(ParentDeclName);
54   if (!ParentDecl)
55     return;
56 
57   // Match CXXRecordDecl only to store the range of the last non-implicit full
58   // declaration, to later check whether it's within the typdef itself.
59   const auto *MatchedTagDecl = Result.Nodes.getNodeAs<TagDecl>(TagDeclName);
60   if (MatchedTagDecl) {
61     // It is not sufficient to just track the last TagDecl that we've seen,
62     // because if one struct or union is nested inside another, the last TagDecl
63     // before the typedef will be the nested one (PR#50990). Therefore, we also
64     // keep track of the parent declaration, so that we can look up the last
65     // TagDecl that is a sibling of the typedef in the AST.
66     LastTagDeclRanges[ParentDecl] = MatchedTagDecl->getSourceRange();
67     return;
68   }
69 
70   const auto *MatchedDecl = Result.Nodes.getNodeAs<TypedefDecl>(TypedefName);
71   if (MatchedDecl->getLocation().isInvalid())
72     return;
73 
74   SourceLocation StartLoc = MatchedDecl->getBeginLoc();
75 
76   if (StartLoc.isMacroID() && IgnoreMacros)
77     return;
78 
79   static const char *UseUsingWarning = "use 'using' instead of 'typedef'";
80 
81   // Warn at StartLoc but do not fix if there is macro or array.
82   if (MatchedDecl->getUnderlyingType()->isArrayType() || StartLoc.isMacroID()) {
83     diag(StartLoc, UseUsingWarning);
84     return;
85   }
86 
87   PrintingPolicy PrintPolicy(getLangOpts());
88   PrintPolicy.SuppressScope = true;
89   PrintPolicy.ConstantArraySizeAsWritten = true;
90   PrintPolicy.UseVoidForZeroParams = false;
91   PrintPolicy.PrintInjectedClassNameWithArguments = false;
92 
93   std::string Type = MatchedDecl->getUnderlyingType().getAsString(PrintPolicy);
94   std::string Name = MatchedDecl->getNameAsString();
95   SourceRange ReplaceRange = MatchedDecl->getSourceRange();
96 
97   // typedefs with multiple comma-separated definitions produce multiple
98   // consecutive TypedefDecl nodes whose SourceRanges overlap. Each range starts
99   // at the "typedef" and then continues *across* previous definitions through
100   // the end of the current TypedefDecl definition.
101   // But also we need to check that the ranges belong to the same file because
102   // different files may contain overlapping ranges.
103   std::string Using = "using ";
104   if (ReplaceRange.getBegin().isMacroID() ||
105       (Result.SourceManager->getFileID(ReplaceRange.getBegin()) !=
106        Result.SourceManager->getFileID(LastReplacementEnd)) ||
107       (ReplaceRange.getBegin() >= LastReplacementEnd)) {
108     // This is the first (and possibly the only) TypedefDecl in a typedef. Save
109     // Type and Name in case we find subsequent TypedefDecl's in this typedef.
110     FirstTypedefType = Type;
111     FirstTypedefName = Name;
112   } else {
113     // This is additional TypedefDecl in a comma-separated typedef declaration.
114     // Start replacement *after* prior replacement and separate with semicolon.
115     ReplaceRange.setBegin(LastReplacementEnd);
116     Using = ";\nusing ";
117 
118     // If this additional TypedefDecl's Type starts with the first TypedefDecl's
119     // type, make this using statement refer back to the first type, e.g. make
120     // "typedef int Foo, *Foo_p;" -> "using Foo = int;\nusing Foo_p = Foo*;"
121     if (Type.size() > FirstTypedefType.size() &&
122         Type.substr(0, FirstTypedefType.size()) == FirstTypedefType)
123       Type = FirstTypedefName + Type.substr(FirstTypedefType.size() + 1);
124   }
125   if (!ReplaceRange.getEnd().isMacroID())
126     LastReplacementEnd = ReplaceRange.getEnd().getLocWithOffset(Name.size());
127 
128   auto Diag = diag(ReplaceRange.getBegin(), UseUsingWarning);
129 
130   // If typedef contains a full tag declaration, extract its full text.
131   auto LastTagDeclRange = LastTagDeclRanges.find(ParentDecl);
132   if (LastTagDeclRange != LastTagDeclRanges.end() &&
133       LastTagDeclRange->second.isValid() &&
134       ReplaceRange.fullyContains(LastTagDeclRange->second)) {
135     Type = std::string(Lexer::getSourceText(
136         CharSourceRange::getTokenRange(LastTagDeclRange->second),
137         *Result.SourceManager, getLangOpts()));
138     if (Type.empty())
139       return;
140   }
141 
142   std::string Replacement = Using + Name + " = " + Type;
143   Diag << FixItHint::CreateReplacement(ReplaceRange, Replacement);
144 }
145 } // namespace modernize
146 } // namespace tidy
147 } // namespace clang
148