[clang-tidy] ForRangeCopyCheck that warns on and fixes unnecessary copies of loop variables.

Patch by Felix Berger!

Differential revision: http://reviews.llvm.org/D13849

llvm-svn: 259199

1 files changed, 223 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/performance-for-range-copy.cpp b/clang-tools-extra/test/clang-tidy/performance-for-range-copy.cpp
new file mode 100644
index 00000000000..c65160936a7
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/performance-for-range-copy.cpp
@@ -0,0 +1,223 @@
+// RUN: %check_clang_tidy %s performance-for-range-copy %t
+
+namespace std {
+
+template <typename _Tp>
+struct remove_reference { typedef _Tp type; };
+
+template <typename _Tp>
+constexpr typename std::remove_reference<_Tp>::type &&move(_Tp &&__t) {
+  return static_cast<typename std::remove_reference<_Tp>::type &&>(__t);
+}
+
+} // std
+
+template <typename T>
+struct Iterator {
+  void operator++() {}
+  const T& operator*() {
+    static T* TT = new T();
+    return *TT;
+  }
+  bool operator!=(const Iterator &) { return false; }
+  typedef const T& const_reference;
+};
+template <typename T>
+struct View {
+  T begin() { return T(); }
+  T begin() const { return T(); }
+  T end() { return T(); }
+  T end() const { return T(); }
+  typedef typename T::const_reference const_reference;
+};
+
+struct ConstructorConvertible {
+};
+
+struct S {
+  S();
+  S(const S &);
+  S(const ConstructorConvertible&) {}
+  ~S();
+  S &operator=(const S &);
+};
+
+struct Convertible {
+  operator S() const {
+    return S();
+  }
+};
+
+void negativeConstReference() {
+  for (const S &S1 : View<Iterator<S>>()) {
+  }
+}
+
+void negativeUserDefinedConversion() {
+  Convertible C[0];
+  for (const S &S1 : C) {
+  }
+}
+
+void negativeImplicitConstructorConversion() {
+  ConstructorConvertible C[0];
+  for (const S &S1 : C) {
+  }
+}
+
+template <typename T>
+void uninstantiated() {
+  for (const S S1 : View<Iterator<S>>()) {}
+  // CHECK-MESSAGES: [[@LINE-1]]:16: warning: the loop variable's type is not a reference type; this creates a copy in each iteration; consider making this a reference [performance-for-range-copy]
+  // CHECK-FIXES: {{^}}  for (const S& S1 : View<Iterator<S>>()) {}
+
+  // Don't warn on dependent types.
+  for (const T t1 : View<Iterator<T>>()) {
+  }
+}
+
+template <typename T>
+void instantiated() {
+  for (const S S2 : View<Iterator<S>>()) {}
+  // CHECK-MESSAGES: [[@LINE-1]]:16: warning: the loop variable's type is {{.*}}
+  // CHECK-FIXES: {{^}}  for (const S& S2 : View<Iterator<S>>()) {}
+
+  for (const T T2 : View<Iterator<T>>()) {}
+  // CHECK-MESSAGES: [[@LINE-1]]:16: warning: the loop variable's type is {{.*}}
+  // CHECK-FIXES: {{^}}  for (const T& T2 : View<Iterator<T>>()) {}
+}
+
+template <typename T>
+void instantiatedNegativeTypedefConstReference() {
+  for (typename T::const_reference T2 : T()) {
+    S S1 = T2;
+  }
+}
+
+void f() {
+  instantiated<int>();
+  instantiated<S>();
+  instantiatedNegativeTypedefConstReference<View<Iterator<S>>>();
+}
+
+struct Mutable {
+  Mutable() {}
+  Mutable(const Mutable &) = default;
+  Mutable(const Mutable &, const Mutable &) {}
+  void setBool(bool B) {}
+  bool constMethod() const {
+    return true;
+  }
+  Mutable& operator[](int I) {
+    return *this;
+  }
+  bool operator==(const Mutable &Other) const {
+    return true;
+  }
+  ~Mutable() {}
+};
+
+Mutable& operator<<(Mutable &Out, bool B) {
+  Out.setBool(B);
+  return Out;
+}
+
+bool operator!=(const Mutable& M1, const Mutable& M2) {
+  return false;
+}
+
+void use(const Mutable &M);
+void useTwice(const Mutable &M1, const Mutable &M2);
+void useByValue(Mutable M);
+void useByConstValue(const Mutable M);
+void mutate(Mutable *M);
+void mutate(Mutable &M);
+void onceConstOnceMutated(const Mutable &M1, Mutable &M2);
+
+void negativeVariableIsMutated() {
+  for (auto M : View<Iterator<Mutable>>()) {
+    mutate(M);
+  }
+  for (auto M : View<Iterator<Mutable>>()) {
+    mutate(&M);
+  }
+  for (auto M : View<Iterator<Mutable>>()) {
+    M.setBool(true);
+  }
+}
+
+void negativeOnceConstOnceMutated() {
+  for (auto M : View<Iterator<Mutable>>()) {
+    onceConstOnceMutated(M, M);
+  }
+}
+
+void negativeVarIsMoved() {
+  for (auto M : View<Iterator<Mutable>>()) {
+    auto Moved = std::move(M);
+  }
+}
+
+void negativeNonConstOperatorIsInvoked() {
+  for (auto NonConstOperatorInvokee : View<Iterator<Mutable>>()) {
+    auto& N = NonConstOperatorInvokee[0];
+  }
+}
+
+void negativeNonConstNonMemberOperatorInvoked() {
+  for (auto NonConstOperatorInvokee : View<Iterator<Mutable>>()) {
+    NonConstOperatorInvokee << true;
+  }
+}
+
+void positiveOnlyConstMethodInvoked() {
+  for (auto M : View<Iterator<Mutable>>()) {
+    // CHECK-MESSAGES: [[@LINE-1]]:13: warning: loop variable is copied but only used as const reference; consider making it a const reference [performance-for-range-copy]
+    // CHECK-FIXES: for (const auto& M : View<Iterator<Mutable>>()) {
+    M.constMethod();
+  }
+}
+
+void positiveOnlyUsedAsConstArguments() {
+  for (auto UsedAsConst : View<Iterator<Mutable>>()) {
+    // CHECK-MESSAGES: [[@LINE-1]]:13: warning: loop variable is copied but only used as const reference; consider making it a const reference [performance-for-range-copy]
+    // CHECK-FIXES: for (const auto& UsedAsConst : View<Iterator<Mutable>>()) {
+    use(UsedAsConst);
+    useTwice(UsedAsConst, UsedAsConst);
+    useByValue(UsedAsConst);
+    useByConstValue(UsedAsConst);
+  }
+}
+
+void positiveOnlyUsedInCopyConstructor() {
+  for (auto A : View<Iterator<Mutable>>()) {
+    // CHECK-MESSAGES: [[@LINE-1]]:13: warning: loop variable is copied but only used as const reference; consider making it a const reference [performance-for-range-copy]
+    // CHECK-FIXES: for (const auto& A : View<Iterator<Mutable>>()) {
+    Mutable Copy = A;
+    Mutable Copy2(A);
+  }
+}
+
+void positiveTwoConstConstructorArgs() {
+  for (auto A : View<Iterator<Mutable>>()) {
+    // CHECK-MESSAGES: [[@LINE-1]]:13: warning: loop variable is copied but only used as const reference; consider making it a const reference [performance-for-range-copy]
+    // CHECK-FIXES: for (const auto& A : View<Iterator<Mutable>>()) {
+    Mutable Copy(A, A);
+  }
+}
+
+void PositiveConstMemberOperatorInvoked() {
+  for (auto ConstOperatorInvokee : View<Iterator<Mutable>>()) {
+    // CHECK-MESSAGES: [[@LINE-1]]:13: warning: loop variable is copied but only used as const reference; consider making it a const reference [performance-for-range-copy]
+    // CHECK-FIXES: for (const auto& ConstOperatorInvokee : View<Iterator<Mutable>>()) {
+    bool result = ConstOperatorInvokee == Mutable();
+  }
+}
+
+void PositiveConstNonMemberOperatorInvoked() {
+  for (auto ConstOperatorInvokee : View<Iterator<Mutable>>()) {
+    // CHECK-MESSAGES: [[@LINE-1]]:13: warning: loop variable is copied but only used as const reference; consider making it a const reference [performance-for-range-copy]
+    // CHECK-FIXES: for (const auto& ConstOperatorInvokee : View<Iterator<Mutable>>()) {
+    bool result = ConstOperatorInvokee != Mutable();
+  }
+}