1 //===--- MisplacedConstCheck.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 "MisplacedConstCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12
13 using namespace clang::ast_matchers;
14
15 namespace clang {
16 namespace tidy {
17 namespace misc {
18
registerMatchers(MatchFinder * Finder)19 void MisplacedConstCheck::registerMatchers(MatchFinder *Finder) {
20 auto NonConstAndNonFunctionPointerType = hasType(pointerType(unless(
21 pointee(anyOf(isConstQualified(), ignoringParens(functionType()))))));
22
23 Finder->addMatcher(
24 valueDecl(
25 hasType(isConstQualified()),
26 hasType(typedefType(hasDeclaration(anyOf(
27 typedefDecl(NonConstAndNonFunctionPointerType).bind("typedef"),
28 typeAliasDecl(NonConstAndNonFunctionPointerType)
29 .bind("typeAlias"))))))
30 .bind("decl"),
31 this);
32 }
33
guessAlternateQualification(ASTContext & Context,QualType QT)34 static QualType guessAlternateQualification(ASTContext &Context, QualType QT) {
35 // We're given a QualType from a typedef where the qualifiers apply to the
36 // pointer instead of the pointee. Strip the const qualifier from the pointer
37 // type and add it to the pointee instead.
38 if (!QT->isPointerType())
39 return QT;
40
41 Qualifiers Quals = QT.getLocalQualifiers();
42 Quals.removeConst();
43
44 QualType NewQT = Context.getPointerType(
45 QualType(QT->getPointeeType().getTypePtr(), Qualifiers::Const));
46 return NewQT.withCVRQualifiers(Quals.getCVRQualifiers());
47 }
48
check(const MatchFinder::MatchResult & Result)49 void MisplacedConstCheck::check(const MatchFinder::MatchResult &Result) {
50 const auto *Var = Result.Nodes.getNodeAs<ValueDecl>("decl");
51 ASTContext &Ctx = *Result.Context;
52 QualType CanQT = Var->getType().getCanonicalType();
53
54 SourceLocation AliasLoc;
55 const char *AliasType;
56 if (const auto *Typedef = Result.Nodes.getNodeAs<TypedefDecl>("typedef")) {
57 AliasLoc = Typedef->getLocation();
58 AliasType = "typedef";
59 } else if (const auto *TypeAlias =
60 Result.Nodes.getNodeAs<TypeAliasDecl>("typeAlias")) {
61 AliasLoc = TypeAlias->getLocation();
62 AliasType = "type alias";
63 } else {
64 llvm_unreachable("registerMatchers has registered an unknown matcher,"
65 " code out of sync");
66 }
67
68 diag(Var->getLocation(), "%0 declared with a const-qualified %1; "
69 "results in the type being '%2' instead of '%3'")
70 << Var << AliasType << CanQT.getAsString(Ctx.getPrintingPolicy())
71 << guessAlternateQualification(Ctx, CanQT)
72 .getAsString(Ctx.getPrintingPolicy());
73 diag(AliasLoc, "%0 declared here", DiagnosticIDs::Note) << AliasType;
74 }
75
76 } // namespace misc
77 } // namespace tidy
78 } // namespace clang
79