1 //===--- MisplacedConstCheck.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 "MisplacedConstCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace misc {
19 
20 void MisplacedConstCheck::registerMatchers(MatchFinder *Finder) {
21   Finder->addMatcher(
22       valueDecl(hasType(isConstQualified()),
23                 hasType(typedefType(hasDeclaration(
24                     typedefDecl(hasType(pointerType(unless(pointee(
25                                     anyOf(isConstQualified(),
26                                           ignoringParens(functionType())))))))
27                         .bind("typedef")))))
28           .bind("decl"),
29       this);
30 }
31 
32 static QualType guessAlternateQualification(ASTContext &Context, QualType QT) {
33   // We're given a QualType from a typedef where the qualifiers apply to the
34   // pointer instead of the pointee. Strip the const qualifier from the pointer
35   // type and add it to the pointee instead.
36   if (!QT->isPointerType())
37     return QT;
38 
39   Qualifiers Quals = QT.getLocalQualifiers();
40   Quals.removeConst();
41 
42   QualType NewQT = Context.getPointerType(
43       QualType(QT->getPointeeType().getTypePtr(), Qualifiers::Const));
44   return NewQT.withCVRQualifiers(Quals.getCVRQualifiers());
45 }
46 
47 void MisplacedConstCheck::check(const MatchFinder::MatchResult &Result) {
48   const auto *Var = Result.Nodes.getNodeAs<ValueDecl>("decl");
49   const auto *Typedef = Result.Nodes.getNodeAs<TypedefDecl>("typedef");
50   ASTContext &Ctx = *Result.Context;
51   QualType CanQT = Var->getType().getCanonicalType();
52 
53   diag(Var->getLocation(), "%0 declared with a const-qualified typedef type; "
54                            "results in the type being '%1' instead of '%2'")
55       << Var << CanQT.getAsString(Ctx.getPrintingPolicy())
56       << guessAlternateQualification(Ctx, CanQT)
57              .getAsString(Ctx.getPrintingPolicy());
58   diag(Typedef->getLocation(), "typedef declared here", DiagnosticIDs::Note);
59 }
60 
61 } // namespace misc
62 } // namespace tidy
63 } // namespace clang
64