1 files changed, 44 insertions, 0 deletions
diff --git a/clang-tools-extra/test/clang-tidy/performance-inefficient-string-concatenation.cpp b/clang-tools-extra/test/clang-tidy/performance-inefficient-string-concatenation.cpp
new file mode 100644
index 00000000000..f4b293a04bf
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/performance-inefficient-string-concatenation.cpp
@@ -0,0 +1,44 @@
+// RUN: %check_clang_tidy %s performance-inefficient-string-concatenation %t
+
+namespace std {
+template <typename T>
+class basic_string {
+public:
+  basic_string() {}
+  ~basic_string() {}
+  basic_string<T> *operator+=(const basic_string<T> &) {}
+  friend basic_string<T> operator+(const basic_string<T> &, const basic_string<T> &) {}
+};
+typedef basic_string<char> string;
+typedef basic_string<wchar_t> wstring;
+}
+
+void f(std::string) {}
+std::string g(std::string) {}
+
+int main() {
+  std::string mystr1, mystr2;
+  std::wstring mywstr1, mywstr2;
+
+  for (int i = 0; i < 10; ++i) {
+    f(mystr1 + mystr2 + mystr1);
+    // CHECK-MESSAGES: :[[@LINE-1]]:23: warning: string concatenation results in allocation of unnecessary temporary strings; consider using 'operator+=' or 'string::append()' instead
+    mystr1 = mystr1 + mystr2;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: string concatenation
+    mystr1 = mystr2 + mystr2 + mystr2;
+    // CHECK-MESSAGES: :[[@LINE-1]]:30: warning: string concatenation
+    mystr1 = mystr2 + mystr1;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: string concatenation
+    mywstr1 = mywstr2 + mywstr1;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: string concatenation
+    mywstr1 = mywstr2 + mywstr2 + mywstr2;
+    // CHECK-MESSAGES: :[[@LINE-1]]:33: warning: string concatenation
+
+    mywstr1 = mywstr2 + mywstr2;
+    mystr1 = mystr2 + mystr2;
+    mystr1 += mystr2;
+    f(mystr2 + mystr1);
+    mystr1 = g(mystr1);
+  }
+  return 0;
+}