[NFC][TEST] Add testcase for std::unordered_map

Author: flovent

clang-tools-extra/test/clang-tidy/checkers/modernize/Inputs/use-structured-binding/fake_std_pair_tuple.h

@@ -20,6 +20,24 @@ namespace std {
   tuple<Args...> tie(Args&... args) {
     return tuple<Args...>(args...);
   }
+
+  template <typename Key, typename Value>
+  class unordered_map {
+  public:
+    using value_type = pair<Key, Value>;
+
+    class iterator {
+    public:
+      iterator& operator++();
+      bool operator!=(const iterator &other);
+      const value_type &operator*() const;
+      value_type operator*();
+      const value_type* operator->() const;
+    };
+
+    iterator begin() const;
+    iterator end() const;
+  };
 }
 
 template<typename T1, typename T2>

clang-tools-extra/test/clang-tidy/checkers/modernize/use-structured-binding.cpp

@@ -651,3 +651,15 @@ void IgnoreDirectInit() {
     int y = P.second;
   }
 }
+
+void StdMapTestCases() {
+  for (auto p : std::unordered_map<int, int>()) {
+    // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES: for (auto [x, y] : std::unordered_map<int, int>()) {
+    // CHECK-NEXT: // REMOVE
+    int x = p.first;
+    int y = p.second; // REMOVE
+    // CHECK-FIXES: // REMOVE
+  }
+}
+