[clang] [Clang][P1061] Add stuctured binding packs (PR #121417)

[Jason Rice via cfe-commits]

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@@ -0,0 +1,82 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++2b %s -verify
+// expected-no-diagnostics
+
+template <typename T>
+struct type_ { };
+
+template <typename ...T>
+auto sum(T... t) { return (t + ...); }
+
+struct my_struct {
+	int a;
+	int b;
+	int c;
+  int d;
+};
+
+struct fake_tuple {
+  int arr[4] = {1, 2, 3, 6};
+
+  template <unsigned i>
+  int get() {
+    return arr[i];
+  }
+};
+
+namespace std {
+  template <typename T>
+  struct tuple_size;
+  template <unsigned i, typename T>
+  struct tuple_element;
+
+  template <>
+  struct tuple_size<fake_tuple> {
+    static constexpr unsigned value = 4;
+  };
+
+  template <unsigned i>
+  struct tuple_element<i, fake_tuple> {
+    using type = int;
+  };
+}
+
+
+template <typename T>
+void decompose_tuple() {
+  auto tup = T{{1, 2, 3, 6}};
+  auto&& [x, ...rest, y] = tup;
+
+  ((void)type_<int>(type_<decltype(rest)>{}), ...);
+
+  T arrtup[2] = {T{{1, 2, 3, 6}},
+                 T{{7, 9, 10, 11}}};
+  int sum = 0;
+  for (auto [...xs] : arrtup) {
+    sum += (xs + ...);
+  }
+}
+
+template <typename T>
+void decompose_struct() {
+  T obj{1, 2, 3, 6};
+  auto [x, ...rest, y] = obj;
+}
+
+template <typename T>
+void decompose_array() {
+  // previously unable to use non-dependent array here
+  // Fixes https://bugs.llvm.org/show_bug.cgi?id=45964
----------------
ricejasonf wrote:

It was me that submitted that fix which I broke out from this. I can remove the comment if you want.

https://github.com/llvm/llvm-project/pull/121417