Diagnose non-const-callable hash functions and comparators

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@291969 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/containers/associative/non_const_comparator.fail.cpp

@@ -24,7 +24,9 @@ struct BadCompare {
 };
 
 int main() {
-  static_assert(!std::__is_const_comparable<BadCompare, int>::value, "");
+  static_assert(!std::__invokable<BadCompare const&, int const&, int const&>::value, "");
+  static_assert(std::__invokable<BadCompare&, int const&, int const&>::value, "");
+
   // expected-warning@__tree:* 4 {{the specified comparator type does not provide a const call operator}}
   {
     using C = std::set<int, BadCompare>;

test/libcxx/containers/unord/non_const_comparator.fail.cpp

@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+// REQUIRES: diagnose-if-support, verify-support
+
+// Test that libc++ generates a warning diagnostic when the container is
+// provided a non-const callable comparator.
+
+#include <unordered_set>
+#include <unordered_map>
+
+struct BadHash {
+  template <class T>
+  size_t operator()(T const& t) {
+    return std::hash<T>{}(t);
+  }
+};
+
+struct BadEqual {
+  template <class T, class U>
+  bool operator()(T const& t, U const& u) {
+    return t == u;
+  }
+};
+
+int main() {
+  static_assert(!std::__invokable<BadEqual const&, int const&, int const&>::value, "");
+  static_assert(std::__invokable<BadEqual&, int const&, int const&>::value, "");
+
+  // expected-warning@__hash_table:* 4 {{the specified comparator type does not provide a const call operator}}
+  // expected-warning@__hash_table:* 4 {{the specified hash functor does not provide a const call operator}}
+
+  {
+    using C = std::unordered_set<int, BadHash, BadEqual>;
+    C s;
+  }
+  {
+    using C = std::unordered_multiset<long, BadHash, BadEqual>;
+    C s;
+  }
+  {
+    using C = std::unordered_map<int, int, BadHash, BadEqual>;
+    C s;
+  }
+  {
+    using C = std::unordered_multimap<long, int, BadHash, BadEqual>;
+    C s;
+  }
+}