Add support for arrays in performance-implicit-conversion-in-loop

[pilki]

Summary

Add support for arrays (and structure that use naked pointers for their iterator, like std::array) in performance-implicit-conversion-in-loop

[alexfh]

LG

[pilki]

Thanks Alex!

I do not have the submit right, can you take care of it?

Thanks

clang-tidy/performance/ImplicitConversionInLoopCheck.h

 public:
   ImplicitConversionInLoopCheck(StringRef Name, ClangTidyContext *Context)
       : ClangTidyCheck(Name, Context) {}
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 
 private:
   void ReportAndFix(const ASTContext *Context, const VarDecl *VD,
-                    const CXXOperatorCallExpr *OperatorCall);
+                    const Expr *OperatorCall);
 };
 
 } // namespace performance
 } // namespace tidy
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_IMPLICIT_CONVERSION_IN_LOOP_CHECK_H_

clang-tidy/performance/ImplicitConversionInLoopCheck.cpp

 
 // Checks if the stmt is a ImplicitCastExpr with a CastKind that is not a NoOp.
 // The subtelty is that in some cases (user defined conversions), we can
 // get to ImplicitCastExpr inside each other, with the outer one a NoOp. In this
 // case we skip the first cast expr.
 static bool IsNonTrivialImplicitCast(const Stmt *ST) {
   if (const auto *ICE = dyn_cast<ImplicitCastExpr>(ST)) {
     return (ICE->getCastKind() != CK_NoOp) ||
             IsNonTrivialImplicitCast(ICE->getSubExpr());
   }
   return false;
 }
 
 void ImplicitConversionInLoopCheck::registerMatchers(MatchFinder *Finder) {
   // We look for const ref loop variables that (optionally inside an
   // ExprWithCleanup) materialize a temporary, and contain a implicit
   // conversion. The check on the implicit conversion is done in check() because
   // we can't access implicit conversion subnode via matchers: has() skips casts
   // and materialize! We also bind on the call to operator* to get the proper
-  // type in the diagnostic message.
+  // type in the diagnostic message. We use both cxxOperatorCallExpr for user
+  // defined operator and unaryOperator when the iterator is a pointer, like
+  // for arrays or std::array.
   //
   // Note that when the implicit conversion is done through a user defined
   // conversion operator, the node is a CXXMemberCallExpr, not a
   // CXXOperatorCallExpr, so it should not get caught by the
   // cxxOperatorCallExpr() matcher.
   Finder->addMatcher(
       cxxForRangeStmt(hasLoopVariable(
-          varDecl(hasType(qualType(references(qualType(isConstQualified())))),
-                  hasInitializer(expr(hasDescendant(cxxOperatorCallExpr().bind(
-                                          "operator-call")))
-                                     .bind("init")))
+          varDecl(
+              hasType(qualType(references(qualType(isConstQualified())))),
+              hasInitializer(
+                  expr(anyOf(hasDescendant(
+                                 cxxOperatorCallExpr().bind("operator-call")),
+                             hasDescendant(unaryOperator(hasOperatorName("*"))
+                                               .bind("operator-call"))))
               .bind("faulty-var"))),
       this);
 }
 
 void ImplicitConversionInLoopCheck::check(
     const MatchFinder::MatchResult &Result) {
   const auto *VD = Result.Nodes.getNodeAs<VarDecl>("faulty-var");
   const auto *Init = Result.Nodes.getNodeAs<Expr>("init");
   const auto *OperatorCall =
-      Result.Nodes.getNodeAs<CXXOperatorCallExpr>("operator-call");
+      Result.Nodes.getNodeAs<Expr>("operator-call");
 
   if (const auto *Cleanup = dyn_cast<ExprWithCleanups>(Init))
     Init = Cleanup->getSubExpr();
 
   const auto *Materialized = dyn_cast<MaterializeTemporaryExpr>(Init);
   if (!Materialized)
     return;
 
   // We ignore NoOp casts. Those are generated if the * operator on the
   // iterator returns a value instead of a reference, and the loop variable
   // is a reference. This situation is fine (it probably produces the same
   // code at the end).
   if (IsNonTrivialImplicitCast(Materialized->getTemporary()))
     ReportAndFix(Result.Context, VD, OperatorCall);
 }
 
 void ImplicitConversionInLoopCheck::ReportAndFix(
     const ASTContext *Context, const VarDecl *VD,
-    const CXXOperatorCallExpr *OperatorCall) {
+    const Expr *OperatorCall) {
   // We only match on const ref, so we should print a const ref version of the
   // type.
   QualType ConstType = OperatorCall->getType().withConst();
   QualType ConstRefType = Context->getLValueReferenceType(ConstType);
   const char Message[] =
       "the type of the loop variable %0 is different from the one returned "
       "by the iterator and generates an implicit conversion; you can either "
       "change the type to the matching one (%1 but 'const auto&' is always a "
       "valid option) or remove the reference to make it explicit that you are "
       "creating a new value";
   diag(VD->getLocStart(), Message) << VD << ConstRefType;
 }
 
 } // namespace performance
 } // namespace tidy
 } // namespace clang

test/clang-tidy/performance-implicit-conversion-in-loop.cpp

public:
   ImplicitWrapper(const T& t);
 };
 
 // With this class, the implicit conversion is a call to the conversion
 // operators of SimpleClass and ComplexClass.
 template <typename T>
 class OperatorWrapper {
  public:
-  explicit OperatorWrapper(const T& t);
+  OperatorWrapper() = delete;
 };
 
 struct SimpleClass {
   int foo;
   operator OperatorWrapper<SimpleClass>();
 };
 
 // The materialize expression is not the same when the class has a destructor,
void ComplexClassRefIterator() {
   for (ComplexClass foo : ComplexRefView()) {}
 }
 
 void ImplicitSimpleClassIterator() {
   for (const ImplicitWrapper<SimpleClass>& foo : SimpleView()) {}
   // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the loop variable 'foo' is different from the one returned by the iterator and generates an implicit conversion; you can either change the type to the matching one ('const SimpleClass &' but 'const auto&' is always a valid option) or remove the reference to make it explicit that you are creating a new value [performance-implicit-conversion-in-loop]
   // for (ImplicitWrapper<SimpleClass>& foo : SimpleView()) {}
   for (const ImplicitWrapper<SimpleClass> foo : SimpleView()) {}
-  for (ImplicitWrapper<SimpleClass>foo : SimpleView()) {}
+  for (ImplicitWrapper<SimpleClass> foo : SimpleView()) {}
 }
 
 void ImplicitSimpleClassRefIterator() {
   for (const ImplicitWrapper<SimpleClass>& foo : SimpleRefView()) {}
   // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const SimpleClass &'.*}}
   // for (ImplicitWrapper<SimpleClass>& foo : SimpleRefView()) {}
   for (const ImplicitWrapper<SimpleClass> foo : SimpleRefView()) {}
-  for (ImplicitWrapper<SimpleClass>foo : SimpleRefView()) {}
+  for (ImplicitWrapper<SimpleClass> foo : SimpleRefView()) {}
 }
 
+void ImplicitSimpleClassArray() {
+  SimpleClass array[5];
+  for (const ImplicitWrapper<SimpleClass>& foo : array) {}
+  // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const SimpleClass &'.*}}
+  // for (ImplicitWrapper<SimpleClass>& foo : array) {}
+  for (const ImplicitWrapper<SimpleClass> foo : array) {}
+  for (ImplicitWrapper<SimpleClass> foo : array) {}
+}
+
 void ImplicitComplexClassIterator() {
   for (const ImplicitWrapper<ComplexClass>& foo : ComplexView()) {}
   // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const ComplexClass &'.*}}
   // for (ImplicitWrapper<ComplexClass>& foo : ComplexView()) {}
   for (const ImplicitWrapper<ComplexClass> foo : ComplexView()) {}
-  for (ImplicitWrapper<ComplexClass>foo : ComplexView()) {}
+  for (ImplicitWrapper<ComplexClass> foo : ComplexView()) {}
 }
 
 void ImplicitComplexClassRefIterator() {
+  ComplexClass array[5];
+  for (const ImplicitWrapper<ComplexClass>& foo : array) {}
+  // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const ComplexClass &'.*}}
+  // for (ImplicitWrapper<ComplexClass>& foo : array) {}
+  for (const ImplicitWrapper<ComplexClass> foo : array) {}
+  for (ImplicitWrapper<ComplexClass> foo : array) {}
+}
+
+void ImplicitComplexClassArray() {
   for (const ImplicitWrapper<ComplexClass>& foo : ComplexRefView()) {}
   // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const ComplexClass &'.*}}
   // for (ImplicitWrapper<ComplexClass>& foo : ComplexRefView()) {}
   for (const ImplicitWrapper<ComplexClass> foo : ComplexRefView()) {}
-  for (ImplicitWrapper<ComplexClass>foo : ComplexRefView()) {}
+  for (ImplicitWrapper<ComplexClass> foo : ComplexRefView()) {}
 }
 
 void OperatorSimpleClassIterator() {
   for (const OperatorWrapper<SimpleClass>& foo : SimpleView()) {}
   // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const SimpleClass &'.*}}
   // for (OperatorWrapper<SimpleClass>& foo : SimpleView()) {}
   for (const OperatorWrapper<SimpleClass> foo : SimpleView()) {}
-  for (OperatorWrapper<SimpleClass>foo : SimpleView()) {}
+  for (OperatorWrapper<SimpleClass> foo : SimpleView()) {}
 }
 
 void OperatorSimpleClassRefIterator() {
   for (const OperatorWrapper<SimpleClass>& foo : SimpleRefView()) {}
   // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const SimpleClass &'.*}}
   // for (OperatorWrapper<SimpleClass>& foo : SimpleRefView()) {}
   for (const OperatorWrapper<SimpleClass> foo : SimpleRefView()) {}
-  for (OperatorWrapper<SimpleClass>foo : SimpleRefView()) {}
+  for (OperatorWrapper<SimpleClass> foo : SimpleRefView()) {}
 }
 
+void OperatorSimpleClassArray() {
+  SimpleClass array[5];
+  for (const OperatorWrapper<SimpleClass>& foo : array) {}
+  // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const SimpleClass &'.*}}
+  // for (OperatorWrapper<SimpleClass>& foo : array) {}
+  for (const OperatorWrapper<SimpleClass> foo : array) {}
+  for (OperatorWrapper<SimpleClass> foo : array) {}
+}
+
 void OperatorComplexClassIterator() {
   for (const OperatorWrapper<ComplexClass>& foo : ComplexView()) {}
   // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const ComplexClass &'.*}}
   // for (OperatorWrapper<ComplexClass>& foo : ComplexView()) {}
   for (const OperatorWrapper<ComplexClass> foo : ComplexView()) {}
-  for (OperatorWrapper<ComplexClass>foo : ComplexView()) {}
+  for (OperatorWrapper<ComplexClass> foo : ComplexView()) {}
 }
 
 void OperatorComplexClassRefIterator() {
   for (const OperatorWrapper<ComplexClass>& foo : ComplexRefView()) {}
   // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const ComplexClass &'.*}}
   // for (OperatorWrapper<ComplexClass>& foo : ComplexRefView()) {}
   for (const OperatorWrapper<ComplexClass> foo : ComplexRefView()) {}
-  for (OperatorWrapper<ComplexClass>foo : ComplexRefView()) {}
+  for (OperatorWrapper<ComplexClass> foo : ComplexRefView()) {}
 }
+
+void OperatorComplexClassArray() {
+  ComplexClass array[5];
+  for (const OperatorWrapper<ComplexClass>& foo : array) {}
+  // CHECK-MESSAGES: [[@LINE-1]]:{{[0-9]*}}: warning: the type of the{{.*'const ComplexClass &'.*}}
+  // for (OperatorWrapper<ComplexClass>& foo : array) {}
+  for (const OperatorWrapper<ComplexClass> foo : array) {}
+  for (OperatorWrapper<ComplexClass> foo : array) {}
+}