c++: constexpr trivial -fno-elide-ctors [PR104646]

The constexpr constructor checking code got confused by the expansion of a
trivial copy constructor; we don't need to do that checking for defaulted
ctors, anyway.

	PR c++/104646

gcc/cp/ChangeLog:

	* constexpr.cc (maybe_save_constexpr_fundef): Don't do extra
	checks for defaulted ctors.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/constexpr-fno-elide-ctors1.C: New test.

gcc/cp/constexpr.cc

@@ -920,7 +920,8 @@ maybe_save_constexpr_fundef (tree fun)
   if (!potential && complain)
     require_potential_rvalue_constant_expression (massaged);
 
-  if (DECL_CONSTRUCTOR_P (fun) && potential)
+  if (DECL_CONSTRUCTOR_P (fun) && potential
+      && !DECL_DEFAULTED_FN (fun))
     {
       if (cx_check_missing_mem_inits (DECL_CONTEXT (fun),
 				      massaged, complain))

gcc/testsuite/g++.dg/cpp0x/constexpr-fno-elide-ctors1.C

@@ -0,0 +1,89 @@
+// PR c++/104646
+// { dg-do compile { target c++11 } }
+// { dg-additional-options -fno-elide-constructors }
+
+template <typename _T1> struct pair {
+  _T1 first;
+  int second;
+};
+template <typename _Iterator> class __normal_iterator {
+  _Iterator __traits_type;
+
+public:
+  constexpr __normal_iterator() {}
+};
+template <typename> class allocator;
+template <typename> struct allocator_traits;
+template <typename _Tp> struct allocator_traits<allocator<_Tp>> {
+  using value_type = _Tp;
+  template <typename _Up> using rebind_alloc = allocator<_Up>;
+};
+template <typename _Alloc> struct __alloc_traits {
+  typedef allocator_traits<_Alloc> _Base_type;
+  typedef typename _Base_type::value_type &const_reference;
+  template <typename _Tp> struct rebind {
+    typedef typename _Base_type::template rebind_alloc<_Tp> other;
+  };
+};
+template <typename _Tp, typename _Alloc> struct _Vector_base {
+  typedef typename __alloc_traits<_Alloc>::template rebind<_Tp>::other _Tp_alloc_type;
+};
+template <typename _Tp, typename _Alloc = allocator<_Tp>> class vector {
+public:
+  typename __alloc_traits<
+      typename _Vector_base<_Tp, _Alloc>::_Tp_alloc_type>::const_reference
+  operator[](long);
+};
+enum match_flag_type {};
+template <typename, typename> class Trans_NS___cxx11_basic_regex;
+class Trans_NS___cxx11_match_results;
+enum _RegexExecutorPolicy { _S_auto };
+template <typename, typename, typename _CharT, typename _TraitsT,
+          _RegexExecutorPolicy, bool>
+bool __regex_algo_impl(Trans_NS___cxx11_match_results &,
+                       const Trans_NS___cxx11_basic_regex<_CharT, _TraitsT> &);
+template <typename, typename, typename, bool> class _Executor;
+template <typename _Ch_type, typename = _Ch_type>
+class Trans_NS___cxx11_basic_regex {};
+class Trans_NS___cxx11_match_results : vector<int> {
+  template <typename, typename, typename _Cp, typename _Rp,
+            _RegexExecutorPolicy, bool>
+  friend bool __regex_algo_impl(Trans_NS___cxx11_match_results &,
+                                const Trans_NS___cxx11_basic_regex<_Cp, _Rp> &);
+};
+template <typename _Bi_iter, typename _Alloc, typename _Ch_type,
+          typename _Rx_traits>
+void regex_search(_Bi_iter, _Alloc,
+                  Trans_NS___cxx11_basic_regex<_Ch_type, _Rx_traits>) {
+  __regex_algo_impl<_Bi_iter, _Alloc, _Ch_type, _Rx_traits, _S_auto, false>;
+}
+match_flag_type __regex_algo_impl___flags;
+template <typename, typename, typename _CharT, typename _TraitsT,
+          _RegexExecutorPolicy, bool>
+bool __regex_algo_impl(
+    Trans_NS___cxx11_match_results &__m,
+    const Trans_NS___cxx11_basic_regex<_CharT, _TraitsT> &__re) {
+  __normal_iterator<const char *> __e, __s;
+  _Executor<int, int, _TraitsT, false> __executor(__s, __e, __m, __re,
+                                                  __regex_algo_impl___flags);
+  __executor._M_match();
+  return false;
+}
+template <typename, typename, typename, bool> class _Executor {
+public:
+  _Executor(__normal_iterator<const char *>, __normal_iterator<const char *>,
+            vector<int>, Trans_NS___cxx11_basic_regex<char>, match_flag_type);
+  void _M_match() { _M_dfs(); }
+  void _M_dfs();
+  vector<pair<__normal_iterator<char *>>> _M_rep_count;
+};
+long _M_rep_once_more___i;
+template <typename _BiIter, typename _Alloc, typename _TraitsT, bool __dfs_mode>
+void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::_M_dfs() {
+  auto __rep_count = _M_rep_count[_M_rep_once_more___i];
+}
+char main___trans_tmp_1;
+void main___trans_tmp_2() {
+  Trans_NS___cxx11_basic_regex<char> re;
+  regex_search(main___trans_tmp_1, main___trans_tmp_2, re);
+}