[clang-tools-extra] [clang-tidy] Add new check `modernize-use-structured-binding` (PR #158462)

[Baranov Victor via cfe-commits]

================
@@ -0,0 +1,433 @@
+// RUN: %check_clang_tidy -check-suffix=ALL,CPP20ORLATER -std=c++20-or-later %s modernize-use-structured-binding %t -- -- -I %S/Inputs/use-structured-binding/
+// RUN: %check_clang_tidy -check-suffix=ALL -std=c++17 %s modernize-use-structured-binding %t -- -- -I %S/Inputs/use-structured-binding/
+#include "fake_std_pair_tuple.h"
+
+template<typename T>
+void MarkUsed(T x);
+
+struct TestClass {
+  int a;
+  int b;
+  TestClass() : a(0), b(0) {}
+  TestClass& operator++();
+  TestClass(int x, int y) : a(x), b(y) {}
+};
+
+void DecomposeByAssignWarnCases() {
+  {
+    auto P = getPair<int, int>();
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:5: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: auto [x, y] = getPair<int, int>();
+    int x = P.first;
+    int y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  {
+    auto P = getPair<int, int>();
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:5: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: auto [x, y] = getPair<int, int>();
+    int x = P.first, y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  {
+    auto P = getPair<int, int>();
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:5: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: auto [x, y] = getPair<int, int>();
+    int x = P.first, y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+    int z;
+  }
+
+  {
+    auto P = getPair<int, int>();
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:5: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: auto [x, y] = getPair<int, int>();
+    int x = P.first;
+    auto y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  {
+    const auto P = getPair<int, int>();
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:5: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: const auto [x, y] = getPair<int, int>();
+    const int x = P.first;
+    const auto y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  {
+    std::pair<int, int> otherP;
+    auto& P = otherP;
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:5: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: auto& [x, y] = otherP;
+    int& x = P.first;
+    auto& y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  {
+    std::pair<int, int> otherP;
+    const auto& P = otherP;
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:5: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: const auto& [x, y] = otherP;
+    const int& x = P.first;
+    const auto& y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+}
+
+void forRangeWarnCases() {
+  std::pair<int, int> Pairs[10];
+  for (auto P : Pairs) {
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: for (auto [x, y] : Pairs) {
+    int x = P.first;
+    int y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  for (auto P : Pairs) {
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: for (auto [x, y] : Pairs) {
+    int x = P.first, y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  for (auto P : Pairs) {
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: for (auto [x, y] : Pairs) {
+    int x = P.first, y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+    int z;
+  }
+
+  for (const auto P : Pairs) {
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: for (const auto [x, y] : Pairs) {
+    const int x = P.first;
+    const int y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  for (auto& P : Pairs) {
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: for (auto& [x, y] : Pairs) {
+    int& x = P.first;
+    int& y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  for (const auto& P : Pairs) {
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: for (const auto& [x, y] : Pairs) {
+    const int& x = P.first;
+    const int& y = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  std::pair<TestClass, TestClass> ClassPairs[10];
+  for (auto P : ClassPairs) {
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: for (auto [c1, c2] : ClassPairs) {
+    TestClass c1 = P.first;
+    TestClass c2 = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+
+  for (const auto P : ClassPairs) {
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: for (const auto [c1, c2] : ClassPairs) {
+    const TestClass c1 = P.first;
+    const TestClass c2 = P.second; // REMOVE
+    // CHECK-FIXES-ALL: // REMOVE
+  }
+}
+
+void forRangeNotWarnCases() {
+  std::pair<int, int> Pairs[10];
+  for (auto P : Pairs) {
+    int x = P.first;
+    MarkUsed(x);
+    int y = P.second;
+  }
+
+  for (auto P : Pairs) {
+    MarkUsed(P);
+    int x = P.first;
+    int y = P.second;
+  }
+
+  for (auto P : Pairs) {
+    int x = P.first;
+    int y = P.second;
+    MarkUsed(P);
+  }
+
+  std::pair<TestClass, TestClass> ClassPairs[10];
+  for (auto P : ClassPairs) {
+    TestClass c1 = P.first;
+    ++ c1 ;
+    TestClass c2 = P.second;
+  }
+
+  int c;
+  for (auto P : ClassPairs) {
+    TestClass c1 = P.first;
+    c ++ ;
+    TestClass c2 = P.second;
+  }
+}
+
+void stdTieWarnCases() {
+  int a = 0;
+  int b = 0; // REMOVE
+  // CHECK-FIXES-ALL: // REMOVE
+  std::tie(a, b) = getPair<int, int>();
+  // CHECK-MESSAGES-ALL: :[[@LINE-1]]:3: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-ALL: auto [a, b] = getPair<int, int>();
+
+  int x = 0, y = 0; // REMOVE
+  // CHECK-FIXES-ALL: // REMOVE
+  std::tie(x, y) = getPair<int, int>();
+  // CHECK-MESSAGES-ALL: :[[@LINE-1]]:3: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-ALL: auto [x, y] = getPair<int, int>();
+
+  int* pa = nullptr;
+  int* pb = nullptr; // REMOVE
+  // CHECK-FIXES-ALL: // REMOVE
+  std::tie(pa, pb) = getPair<int*, int*>();
+  // CHECK-MESSAGES-ALL: :[[@LINE-1]]:3: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-ALL: auto [pa, pb] = getPair<int*, int*>();
+
+  TestClass c1 (1, 2);
+  TestClass c2 = TestClass {3, 4}; // REMOVE
+  // CHECK-FIXES-ALL: // REMOVE
+  std::tie(c1, c2) = getPair<TestClass, TestClass>();
+  // CHECK-MESSAGES-ALL: :[[@LINE-1]]:3: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-ALL: auto [c1, c2] = getPair<TestClass, TestClass>();
+}
+
+void stdTieNotWarnCases() {
+  int a = 0;
+  int b = 0;
+  a = 4;
+  std::tie(a, b) = getPair<int, int>(); // no warning
+
+  int c = 0, d = 0;
+  int e = 0;
+  std::tie(a, b) = getPair<int, int>(); // no warning
+
+  int* pa = nullptr;
+  int* pb = nullptr;
+  MarkUsed(pa);
+  std::tie(pa, pb) = getPair<int*, int*>(); // no warning
+
+  TestClass c1 (1, 2);
+  TestClass c2 = TestClass {3, 4};
+  MarkUsed(c2);
+  std::tie(c1, c2) = getPair<TestClass, TestClass>();
+}
+
+void NotWarnForVarHasSpecifiers() {
+  {
+    auto P = getPair<int, int>();
+    const int x = P.first;
+    int y = P.second;
+  }
+
+  {
+    auto P = getPair<int, int>();
+    volatile int x = P.first;
+    int y = P.second;
+  }
+
+  {
+    auto P = getPair<int, int>();
+    int x = P.first;
+    [[maybe_unused]] int y = P.second;
+  }
+
+  {
+    static auto P = getPair<int, int>();
+    int x = P.first;
+    int y = P.second;
+  }
+}
+
+void NotWarnForMultiUsedPairVar() {
+  {
+    auto P = getPair<int, int>();
+    int x = P.first;
+    int y = P.second;
+    MarkUsed(P);
+  }
+
+  {
+    auto P = getPair<int, int>();
+    int x = P.first;
+    MarkUsed(P);
+    int y = P.second;
+  }
+
+  {
+    auto P = getPair<int, int>();
+    MarkUsed(P);
+    int x = P.first;
+    int y = P.second;
+  }
+
+  {
+    std::pair<int, int> Pairs[10];
+    for (auto P : Pairs) {
+      int x = P.first;
+      int y = P.second;
+
+      MarkUsed(P);
+    }
+  }
+}
+
+#define DECOMPOSE(P)                                                    \
+    int x = P.first;                                                    \
+    int y = P.second;                                                   \
+
+void NotWarnForMacro1() {
+  auto P = getPair<int, int>();
+  DECOMPOSE(P);
+}
+
+#define GETPAIR auto P = getPair<int, int>()
+
+void NotWarnForMacro2() {
+  GETPAIR;
+  int x = P.first;
+  int y = P.second;
+}
+
+void captureByVal() {
+  auto P = getPair<int, int>();
+  // CHECK-MESSAGES-CPP20ORLATER: :[[@LINE-1]]:3: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-CPP20ORLATER: auto [x, y] = getPair<int, int>();
+  int x = P.first;
+  int y = P.second; // REMOVE
+  // CHECK-FIXES-CPP20ORLATER: // REMOVE
+
+  auto lambda = [x]() {
+    int y = x;
+  };
+}
+
+void captureByRef() {
+  auto P = getPair<int, int>();
+  // CHECK-MESSAGES-CPP20ORLATER: :[[@LINE-1]]:3: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-CPP20ORLATER: auto [x, y] = getPair<int, int>();
+  int x = P.first;
+  int y = P.second; // REMOVE
+  // CHECK-FIXES-CPP20ORLATER: // REMOVE
+
+  auto lambda = [&x]() {
+    x = 1;
+  };
+}
+
+void captureByAllRef() {
+  auto P = getPair<int, int>();
+  // CHECK-MESSAGES-CPP20ORLATER: :[[@LINE-1]]:3: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-CPP20ORLATER: auto [x, y] = getPair<int, int>();
+  int x = P.first;
+  int y = P.second; // REMOVE
+  // CHECK-FIXES-CPP20ORLATER: // REMOVE
+
+  auto lambda = [&]() {
+    x = 1;
+  };
+}
+
+void deepLambda() {
+  auto P = getPair<int, int>();
+  // CHECK-MESSAGES-CPP20ORLATER: :[[@LINE-1]]:3: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-CPP20ORLATER: auto [x, y] = getPair<int, int>();
+  int x = P.first;
+  int y = P.second; // REMOVE
+  // CHECK-FIXES-CPP20ORLATER: // REMOVE
+
+  {
+    auto lambda = [x]() {
+      int y = x;
+    };
+  }
+}
+
+void forRangeNotWarn() {
+  std::pair<int, int> Pairs[10];
+  for (auto P : Pairs) {
+  // CHECK-MESSAGES-CPP20ORLATER: :[[@LINE-1]]:8: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-CPP20ORLATER: for (auto [x, y] : Pairs) {
+    int x = P.first;
+    int y = P.second; // REMOVE
+    // CHECK-FIXES-CPP20ORLATER: // REMOVE
+
+    auto lambda = [&]() {
+    x = 1;
+  };
+  }
+}
+
+void stdTieNotWarn() {
+  int x = 0;
+  int y = 0; // REMOVE
+  // CHECK-FIXES-CPP20ORLATER: // REMOVE
+  std::tie(x, y) = getPair<int, int>();
+  // CHECK-MESSAGES-CPP20ORLATER: :[[@LINE-1]]:3: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+  // CHECK-FIXES-CPP20ORLATER: auto [x, y] = getPair<int, int>();
+
+  auto lambda = [&x]() {
+    x = 1;
+  };
+}
+
+struct otherPair {
+  int first;
+  int second;
+};
+
+void OtherPairTest() {
+  {
+    auto P = otherPair();
+    // CHECK-MESSAGES-ALL: :[[@LINE-1]]:5: warning: use a structured binding to decompose a pair [modernize-use-structured-binding]
+    // CHECK-FIXES-ALL: auto [x, y] = otherPair();
+    int x = P.first;
+    int y = P.second;
+  }
+}
+
+struct otherNonPair1 {
+  int first;
+  int second;
+
+private:
+  int third;
+};
+
+struct otherNonPair2 {
+  int first;
+  int second;
+  int third;
+};
+
+void OtherNonPairTest() {
+  {
+    auto P = otherNonPair1();
+    int x = P.first;
+    int y = P.second;
+  }
+
+  {
+    auto P = otherNonPair2();
+    int x = P.first;
+    int y = P.second;
+  }
+}
----------------
vbvictor wrote:

Could we add tests with custom pair that have `const`, `&`, `*`, `static`, etc.. qualifiers on fields

https://github.com/llvm/llvm-project/pull/158462