[clang-tools-extra] [clang-tidy][NFC] Add missing Option tests in cppcoreguidelines and performance [3/N] (PR #185210)

[Baranov Victor via cfe-commits]

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@@ -0,0 +1,27 @@
+// RUN: %check_clang_tidy %s performance-inefficient-string-concatenation %t -- \
+// RUN:   -config="{CheckOptions: {performance-inefficient-string-concatenation.StrictMode: true}}"
+
+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;
+}
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vbvictor wrote:

`#include <string>` instead?

https://github.com/llvm/llvm-project/pull/185210