clang-tools 6.0.0

ImplicitConversionInLoopCheck.cpp
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1 //===--- ImplicitConversionInLoopCheck.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 "ImplicitConversionInLoopCheck.h"
11
12 #include "clang/AST/ASTContext.h"
13 #include "clang/AST/Decl.h"
14 #include "clang/ASTMatchers/ASTMatchFinder.h"
15 #include "clang/ASTMatchers/ASTMatchers.h"
16 #include "clang/Lex/Lexer.h"
17
18 using namespace clang::ast_matchers;
19
20 namespace clang {
21 namespace tidy {
22 namespace performance {
23
24 // Checks if the stmt is a ImplicitCastExpr with a CastKind that is not a NoOp.
25 // The subtelty is that in some cases (user defined conversions), we can
26 // get to ImplicitCastExpr inside each other, with the outer one a NoOp. In this
27 // case we skip the first cast expr.
28 static bool IsNonTrivialImplicitCast(const Stmt *ST) {
29 if (const auto *ICE = dyn_cast<ImplicitCastExpr>(ST)) {
30 return (ICE->getCastKind() != CK_NoOp) ||
31 IsNonTrivialImplicitCast(ICE->getSubExpr());
32 }
33 return false;
34 }
35
36 void ImplicitConversionInLoopCheck::registerMatchers(MatchFinder *Finder) {
37 // We look for const ref loop variables that (optionally inside an
38 // ExprWithCleanup) materialize a temporary, and contain a implicit
39 // conversion. The check on the implicit conversion is done in check() because
40 // we can't access implicit conversion subnode via matchers: has() skips casts
41 // and materialize! We also bind on the call to operator* to get the proper
42 // type in the diagnostic message.
43 //
44 // Note that when the implicit conversion is done through a user defined
45 // conversion operator, the node is a CXXMemberCallExpr, not a
46 // CXXOperatorCallExpr, so it should not get caught by the
47 // cxxOperatorCallExpr() matcher.
48 Finder->addMatcher(
49 cxxForRangeStmt(hasLoopVariable(
50 varDecl(hasType(qualType(references(qualType(isConstQualified())))),
51 hasInitializer(expr(hasDescendant(cxxOperatorCallExpr().bind(
52 "operator-call")))
53 .bind("init")))
54 .bind("faulty-var"))),
55 this);
56 }
57
58 void ImplicitConversionInLoopCheck::check(
59 const MatchFinder::MatchResult &Result) {
60 const auto *VD = Result.Nodes.getNodeAs<VarDecl>("faulty-var");
61 const auto *Init = Result.Nodes.getNodeAs<Expr>("init");
62 const auto *OperatorCall =
63 Result.Nodes.getNodeAs<CXXOperatorCallExpr>("operator-call");
64
65 if (const auto *Cleanup = dyn_cast<ExprWithCleanups>(Init))
66 Init = Cleanup->getSubExpr();
67
68 const auto *Materialized = dyn_cast<MaterializeTemporaryExpr>(Init);
69 if (!Materialized)
70 return;
71
72 // We ignore NoOp casts. Those are generated if the * operator on the
73 // iterator returns a value instead of a reference, and the loop variable
74 // is a reference. This situation is fine (it probably produces the same
75 // code at the end).
76 if (IsNonTrivialImplicitCast(Materialized->getTemporary()))
77 ReportAndFix(Result.Context, VD, OperatorCall);
78 }
79
80 void ImplicitConversionInLoopCheck::ReportAndFix(
81 const ASTContext *Context, const VarDecl *VD,
82 const CXXOperatorCallExpr *OperatorCall) {
83 // We only match on const ref, so we should print a const ref version of the
84 // type.
85 QualType ConstType = OperatorCall->getType().withConst();
86 QualType ConstRefType = Context->getLValueReferenceType(ConstType);
87 const char Message[] =
88 "the type of the loop variable %0 is different from the one returned "
89 "by the iterator and generates an implicit conversion; you can either "
90 "change the type to the matching one (%1 but 'const auto&' is always a "
91 "valid option) or remove the reference to make it explicit that you are "
92 "creating a new value";
93 diag(VD->getLocStart(), Message) << VD << ConstRefType;
94 }
95
96 } // namespace performance
97 } // namespace tidy
98 } // namespace clang
clang::ast_matchers
Definition: ClangTidyDiagnosticConsumer.h:27
clang::tidy::modernize::Message
static const StringRef Message
Definition: UseTransparentFunctorsCheck.cpp:71
ImplicitConversionInLoopCheck.h
clang::tidy::performance::IsNonTrivialImplicitCast
static bool IsNonTrivialImplicitCast(const Stmt *ST)
Definition: ImplicitConversionInLoopCheck.cpp:28
clang
Definition: AndroidTidyModule.cpp:28