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'}}
+    }
+
+}

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

@@ -13,6 +13,18 @@
 //   basic_string(InputIterator begin, InputIterator end,
 //   const Allocator& a = Allocator());
 
+// 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>
@@ -116,4 +128,48 @@ int main()
     test(input_iterator<const char*>(s), input_iterator<const char*>(s+50), A());
     }
 #endif
+
+//  Test deduction guides
+#if TEST_STD_VER > 14
+    {
+    const char* s = "12345678901234";
+    std::basic_string s1{s, s+10, std::allocator<char>{}};
+    using S = decltype(s1); // what type did we get?
+    static_assert(std::is_same_v<S::value_type,                      char>,  "");
+    static_assert(std::is_same_v<S::traits_type,    std::char_traits<char>>, "");
+    static_assert(std::is_same_v<S::allocator_type,   std::allocator<char>>, "");
+    assert(s1.size() == 10);
+    assert(s1.compare(0, s1.size(), s, s1.size()) == 0);
+    }
+    {
+    const wchar_t* s = L"12345678901234";
+    std::basic_string s1{s, s+10, test_allocator<wchar_t>{}};
+    using S = decltype(s1); // what type did we get?
+    static_assert(std::is_same_v<S::value_type,                      wchar_t>,  "");
+    static_assert(std::is_same_v<S::traits_type,    std::char_traits<wchar_t>>, "");
+    static_assert(std::is_same_v<S::allocator_type,   test_allocator<wchar_t>>, "");
+    assert(s1.size() == 10);
+    assert(s1.compare(0, s1.size(), s, s1.size()) == 0);
+    }
+    {
+    const char16_t* s = u"12345678901234";
+    std::basic_string s1{s, s+10, min_allocator<char16_t>{}};
+    using S = decltype(s1); // what type did we get?
+    static_assert(std::is_same_v<S::value_type,                      char16_t>,  "");
+    static_assert(std::is_same_v<S::traits_type,    std::char_traits<char16_t>>, "");
+    static_assert(std::is_same_v<S::allocator_type,    min_allocator<char16_t>>, "");
+    assert(s1.size() == 10);
+    assert(s1.compare(0, s1.size(), s, s1.size()) == 0);
+    }
+    {
+    const char32_t* s = U"12345678901234";
+    std::basic_string s1{s, s+10, explicit_allocator<char32_t>{}};
+    using S = decltype(s1); // what type did we get?
+    static_assert(std::is_same_v<S::value_type,                        char32_t>,  "");
+    static_assert(std::is_same_v<S::traits_type,      std::char_traits<char32_t>>, "");
+    static_assert(std::is_same_v<S::allocator_type, explicit_allocator<char32_t>>, "");
+    assert(s1.size() == 10);
+    assert(s1.compare(0, s1.size(), s, s1.size()) == 0);
+    }
+#endif
 }