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

[via cfe-commits]

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@@ -0,0 +1,622 @@
+// 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
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flovent wrote:

Added in [8d3054c](https://github.com/llvm/llvm-project/pull/158462/commits/8d3054c482a758adccb73487b3dd43806294b2a8)

Because of refatoring job of `matchTwoVarDecl`, right now we remove continuous `DeclStmt`s, so i only check for `// REMOVE` in next line here. 

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