[libc++] Replace a few .compile.fail.cpp tests by proper clang-verify tests (#167346)

We want to eliminate all .compile.fail.cpp tests since they are brittle:
these tests pass regardless of the specific compilation error, which
means that e.g. a mising include will render the test null.

This is not an exhaustive pass, just a few tests I stumbled upon.

Author: ldionne

libcxx/test/std/input.output/file.streams/c.files/gets.compile.fail.cpp renamed to libcxx/test/std/input.output/file.streams/c.files/gets-removed.verify.cpp

@@ -7,15 +7,11 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11
-// test <cstdio>
 
-// gets
+// Verify that std::gets has been removed in C++14 and later
 
 #include <cstdio>
 
-int main(int, char**)
-{
-    (void) std::gets((char *) NULL);
-
-  return 0;
+void f(char const* str) {
+  (void)std::gets(str); // expected-error {{no member named 'gets' in namespace 'std'}}
 }

libcxx/test/std/re/re.iter/re.tokiter/re.tokiter.cnstr/array.compile.fail.cpp

@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11
+
+// Ensure that we don't allow iterators into temporary std::regex objects.
+
+// <regex>
+//
+// class regex_iterator<BidirectionalIterator, charT, traits>
+//
+// regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
+//                      const regex_type&& re, int submatch = 0,
+//                      regex_constants::match_flag_type m =
+//                                              regex_constants::match_default);
+//
+// template <size_t N>
+// regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
+//                      const regex_type&& re,
+//                      const int (&submatches)[N],
+//                      regex_constants::match_flag_type m =
+//                                              regex_constants::match_default);
+//
+// regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
+//                      const regex_type&& re,
+//                      initializer_list<int> submatches,
+//                      regex_constants::match_flag_type m =
+//                                              regex_constants::match_default);
+//
+// template <std::size_t N>
+// regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
+//                      const regex_type&& re,
+//                      const std::vector<int>& submatches,
+//                      regex_constants::match_flag_type m =
+//                                              regex_constants::match_default);
+
+#include <iterator>
+#include <regex>
+#include <vector>
+
+void f() {
+  std::regex phone_numbers("\\d{3}-\\d{4}");
+  const char phone_book[] = "start 555-1234, 555-2345, 555-3456 end";
+
+  { // int submatch
+    std::cregex_token_iterator i(std::begin(phone_book), std::end(phone_book) - 1, std::regex("\\d{3}-\\d{4}"), -1);
+    // expected-error@-1 {{call to deleted constructor of 'std::cregex_token_iterator'}}
+  }
+  { // const int (&submatches)[N]
+    const int indices[] = {-1, 0, 1};
+    std::cregex_token_iterator i(
+        std::begin(phone_book), std::end(phone_book) - 1, std::regex("\\d{3}-\\d{4}"), indices);
+    // expected-error@-2 {{call to deleted constructor of 'std::cregex_token_iterator'}}
+  }
+  { // initializer_list<int> submatches
+    std::cregex_token_iterator i(
+        std::begin(phone_book), std::end(phone_book) - 1, std::regex("\\d{3}-\\d{4}"), {-1, 0, 1});
+    // expected-error@-2 {{call to deleted constructor of 'std::cregex_token_iterator'}}
+  }
+  { // const std::vector<int>& submatches
+    std::vector<int> v;
+    v.push_back(-1);
+    v.push_back(-1);
+    std::cregex_token_iterator i(std::begin(phone_book), std::end(phone_book) - 1, std::regex("\\d{3}-\\d{4}"), v);
+    // expected-error@-1 {{call to deleted constructor of 'std::cregex_token_iterator'}}
+  }
+}