Add more complete testing for operator new

This replaces builtins_new_included.cc with operator_new.cc, and covers
all variants of operator new that do _not_ require <new> to be
included:

- Raw explicit ::operator new/::operator delete calls
- New expressions, both of builtin and user-defined types
- Aligned allocation (currently disabled, as we misdiagnose it,
  see PR include-what-you-use#777).

run_iwyu_tests.py

@@ -113,6 +113,7 @@ def setUp(self):
           self.Include('macro_defined_by_includer-prefix.h')],
       'macro_location.cc': ['-Wno-sizeof-pointer-div'],
       'ms_inline_asm.cc': ['-fms-extensions'],
+      'operator_new.cc': ['-std=c++17'],
       'placement_new.cc': ['-std=c++17'],
       'prefix_header_attribution.cc': [self.Include('prefix_header_attribution-d1.h')],
       'prefix_header_includes_add.cc': prefix_headers,
@@ -181,6 +182,7 @@ def setUp(self):
       'no_fwd_decls.cc': ['.'],
       'no_h_includes_cc.cc': ['.'],
       'non_transitive_include.cc': ['.'],
+      'operator_new.cc': ['.'],
       'overloaded_class.cc': ['.'],
       'pch_in_code.cc': ['.'],
       'pointer_arith.cc': ['.'],

tests/cxx/operator_new.cc

@@ -0,0 +1,85 @@
+//===--- operator_new.cc - test input file for iwyu -----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// Test that iwyu suggests the include for <new> be removed if only
+// built-in functions are used.
+
+#include <new>
+#include "tests/cxx/direct.h"
+
+// The most primitive ::operator new/delete are builtins, and are basically
+// wrappers around malloc.
+void ExplicitOperators() {
+  // IWYU: IndirectClass needs a declaration
+  // IWYU: IndirectClass is...*indirect.h
+  IndirectClass* elem = (IndirectClass*)::operator new(sizeof(IndirectClass));
+  ::operator delete(elem);
+
+  // IWYU: IndirectClass needs a declaration
+  // IWYU: IndirectClass is...*indirect.h
+  IndirectClass* arr = (IndirectClass*)::operator new[](4 * sizeof(IndirectClass));
+  ::operator delete[](arr);
+}
+
+// New- and delete-expressions, unless using placement syntax, only use builtin
+// operators. They're equivalent with the above, but also run ctors/dtors.
+// For placement syntax, see tests/cxx/placement_new.cc
+void ExpressionsBuiltinTypes() {
+  char* elem = new char;
+  delete elem;
+
+  int* arr = new int[4];
+  delete[] arr;
+}
+
+// New- and delete-expressions with user-defined types.
+void ExpressionsUserTypes() {
+  // IWYU: IndirectClass needs a declaration
+  // IWYU: IndirectClass is...*indirect.h
+  IndirectClass* elem = new IndirectClass;
+  // IWYU: IndirectClass is...*indirect.h
+  delete elem;
+
+  // IWYU: IndirectClass needs a declaration
+  // IWYU: IndirectClass is...*indirect.h
+  IndirectClass* arr = new IndirectClass[4];
+  // IWYU: IndirectClass is...*indirect.h
+  delete[] arr;
+}
+
+#if 0
+// Aligned allocation uses operator new(size_t, std::align_val_t) under the
+// hood in C++17, but does not require <new> to be included for it. Pre-C++17,
+// the alignment is just ignored.
+void ImplicitAlignedAllocation() {
+  struct alignas(32) Aligned {
+    float value[8];
+  };
+
+  Aligned* elem = new Aligned;
+  delete elem;
+
+  Aligned* arr = new Aligned[10];
+  delete[] arr;
+}
+#endif
+
+/**** IWYU_SUMMARY
+
+tests/cxx/operator_new.cc should add these lines:
+#include "tests/cxx/indirect.h"
+
+tests/cxx/operator_new.cc should remove these lines:
+- #include <new>  // lines XX-XX
+- #include "tests/cxx/direct.h"  // lines XX-XX
+
+The full include-list for tests/cxx/operator_new.cc:
+#include "tests/cxx/indirect.h"  // for IndirectClass
+
+***** IWYU_SUMMARY */