Implement deduction guide for basic_string as described in P0433

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@324569 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/strings/basic.string/string.cons/iter_alloc.fail.cpp

@@ -0,0 +1,54 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <string>
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// template<class InputIterator,
+//      class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
+//  basic_string(InputIterator, InputIterator, Allocator = Allocator())
+//    -> basic_string<typename iterator_traits<InputIterator>::value_type,
+//                 char_traits<typename iterator_traits<InputIterator>::value_type>,
+//                 Allocator>;
+//
+//  The deduction guide shall not participate in overload resolution if InputIterator
+//  is a type that does not qualify as an input iterator, or if Allocator is a type
+//  that does not qualify as an allocator.
+
+
+#include <string>
+#include <iterator>
+#include <cassert>
+#include <cstddef>
+
+#include "test_macros.h"
+
+class NotAnItertor {};
+
+template <typename T>
+struct NotAnAllocator { typedef T value_type; };
+
+int main()
+{
+    { // Not an iterator at all
+    std::basic_string s1{NotAnItertor{}, NotAnItertor{}, std::allocator<char>{}}; // expected-error {{no viable constructor or deduction guide for deduction of template arguments of 'basic_string'}}
+    }
+    { // Not an input iterator
+    const char16_t* s = u"12345678901234";
+    std::basic_string<char16_t> s0;
+    std::basic_string s1{std::back_insert_iterator(s0), //  expected-error {{no viable constructor or deduction guide for deduction of template arguments of 'basic_string'}}
+                         std::back_insert_iterator(s0),
+                         std::allocator<char16_t>{}};
+    }
+    { // Not an allocator
+    const wchar_t* s = L"12345678901234";
+    std::basic_string s1{s, s+10, NotAnAllocator<wchar_t>{}}; // expected-error {{no viable constructor or deduction guide for deduction of template arguments of 'basic_string'}}
+    }
+
+}