[clang][bytecode] Fix two-pointer-style std::initializer_lists (#107682)

The first pointer needs to point to the first element of the underlying
array. This requires some changes to how we handle array expansion

1 files changed, 55 insertions, 0 deletions

diff --git a/clang/test/AST/ByteCode/initializer_list.cpp b/clang/test/AST/ByteCode/initializer_list.cpp
new file mode 100644
index 0000000..4e3b8dc
--- /dev/null
+++ b/clang/test/AST/ByteCode/initializer_list.cpp
@@ -0,0 +1,55 @@
+// RUN: %clang_cc1 -fexperimental-new-constant-interpreter -fms-extensions -std=c++20 -verify=expected,both %s
+// RUN: %clang_cc1 -std=c++20 -fms-extensions -verify=ref,both %s
+
+// both-no-diagnostics
+
+namespace std {
+  typedef decltype(sizeof(int)) size_t;
+  template <class _E>
+  class initializer_list
+  {
+    const _E* __begin_;
+    size_t    __size_;
+
+    initializer_list(const _E* __b, size_t __s)
+      : __begin_(__b),
+        __size_(__s)
+    {}
+
+  public:
+    typedef _E        value_type;
+    typedef const _E& reference;
+    typedef const _E& const_reference;
+    typedef size_t    size_type;
+
+    typedef const _E* iterator;
+    typedef const _E* const_iterator;
+
+    constexpr initializer_list() : __begin_(nullptr), __size_(0) {}
+
+    constexpr size_t    size()  const {return __size_;}
+    constexpr const _E* begin() const {return __begin_;}
+    constexpr const _E* end()   const {return __begin_ + __size_;}
+  };
+}
+
+class Thing {
+public:
+  int m = 12;
+  constexpr Thing(int m) : m(m) {}
+  constexpr bool operator==(const Thing& that) const {
+    return this->m == that.m;
+  }
+};
+
+constexpr bool is_contained(std::initializer_list<Thing> Set, const Thing &Element) {
+   return (*Set.begin() == Element);
+}
+
+constexpr int foo() {
+  const Thing a{12};
+  const Thing b{14};
+  return is_contained({a}, b);
+}
+
+static_assert(foo() == 0);