clang/test/SemaCXX/single-element-init-list.cpp

   1 // RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify %s
   2
   3 // This is heavily affected by the speculative resolution applied to CWG2311
   4 // So behaviour shown here is subject to change.
   5
   6 // expected-no-diagnostics
   7
   8 namespace std {
   9   typedef decltype(sizeof(int)) size_t;
  10
  11   // libc++'s implementation
  12   template <class _E>
  13   class initializer_list
  14   {
  15     const _E* __begin_;
  16     size_t    __size_;
  17
  18     initializer_list(const _E* __b, size_t __s)
  19       : __begin_(__b),
  20         __size_(__s)
  21     {}
  22
  23   public:
  24     typedef _E        value_type;
  25     typedef const _E& reference;
  26     typedef const _E& const_reference;
  27     typedef size_t    size_type;
  28
  29     typedef const _E* iterator;
  30     typedef const _E* const_iterator;
  31
  32     constexpr initializer_list() : __begin_(nullptr), __size_(0) {}
  33
  34     constexpr size_t    size()  const {return __size_;}
  35     const _E* begin() const {return __begin_;}
  36     const _E* end()   const {return __begin_ + __size_;}
  37   };
  38
  39   template<typename T>
  40   struct vector {
  41     size_t sz;
  42     constexpr vector() : sz(0) {}
  43     constexpr vector(initializer_list<T> ilist) : sz(ilist.size()) {}
  44     constexpr vector(const vector& other) : sz(other.sz) {}
  45     constexpr std::size_t size() const { return sz; }
  46   };
  47 }
  48
  49 // https://github.com/llvm/llvm-project/pull/77768#issuecomment-1908062472
  50 namespace Issue1 {
  51   struct A {
  52     constexpr A() {}
  53   };
  54
  55   struct B {
  56     int called_ctor;
  57     constexpr explicit B(A) : called_ctor(0) {}
  58     constexpr explicit B(std::vector<A>) : called_ctor(1) {}
  59   };
  60
  61   struct C {
  62     B b;
  63     constexpr C() : b({A()}) {}
  64   };
  65
  66   static_assert(C().b.called_ctor == 0);
  67 }
  68
  69 // https://github.com/llvm/llvm-project/pull/77768#issuecomment-1957171805
  70 namespace Issue2 {
  71   struct A {
  72     constexpr A(int x_) {}
  73     constexpr A(const std::vector<A>& a) {}
  74   };
  75
  76   void f() {
  77     constexpr std::vector<A> a{1,2};
  78     constexpr std::vector<A> b{a};
  79     // -> constexpr std::vector<A> b(std::initializer_list<A>{ A(a) });
  80     static_assert(b.size() == 1);
  81   }
  82 }