Add TypeTraits template for checking safe bitfields (WIP)

third_party/WebKit/Tools/Scripts/webkitpy/style/checkers/cpp.py

 # -*- coding: utf-8 -*-
 #
 # Copyright (C) 2009, 2010, 2012 Google Inc. All rights reserved.
 # Copyright (C) 2009 Torch Mobile Inc.
 # Copyright (C) 2009 Apple Inc. All rights reserved.
 # Copyright (C) 2010 Chris Jerdonek (cjerdonek@webkit.org)
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
@@ skipping 1475 matching lines @@
     if args:
         classinfo.unsigned_bitfields.append('%d: %s' % (line_number, args.group(1)))
         well_typed_bitfield = True
 
     # Look for other bitfield declarations. We don't care about those in
     # size-matching structs.
     if not (well_typed_bitfield or classinfo.name.startswith('SameSizeAs') or
             classinfo.name.startswith('Expected')):
         args = match(r'\s*(\S+)\s+(\S+)\s*:\s*\d+\s*;', line)
         if args:
-            error(line_number, 'runtime/bitfields', 4,
-                  'Member %s of class %s defined as a bitfield of type %s. '
-                  'Please declare all bitfields as unsigned.'
-                  % (args.group(2), classinfo.name, args.group(1)))
+            field_type = args.group(1)
+            field_name = args.group(2)
+
+            # Look for an unsigned assert for this type in this file.
+            has_assert = False
+            for other_line in clean_lines.lines:
+                if match(r'\bstatic_assert(\s*IsEnumSafeToStoreInBitfield\s*<\s*(\S+)?' + field_type + r'>::value\s*);', other_line):
+                    has_assert = True
+                    break
+
+            if not has_assert:
+                error(line_number, 'runtime/bitfields', 4,
+                      'Member %s of class %s defined as a bitfield of type %s. '
+                      'Please declare all bitfields as unsigned, or add '
+                      'static_assert(IsEnumSafeToStoreInBitfield<%s>::value).'
+                      % (field_name, classinfo.name, field_type, field_type))
 
 
 def check_spacing_for_function_call(line, line_number, error):
     """Checks for the correctness of various spacing around function calls.
 
     Args:
       line: The text of the line to check.
       line_number: The number of the line to check.
       error: The function to call with any errors found.
     """
@@ skipping 2698 matching lines @@
 
     def check(self, lines):
         _process_lines(self.file_path, self.file_extension, lines,
                        self.handle_style_error, self.min_confidence)
 
 
 # FIXME: Remove this function (requires refactoring unit tests).
 def process_file_data(filename, file_extension, lines, error, min_confidence, fs=None):
     checker = CppChecker(filename, file_extension, error, min_confidence, fs)
     checker.check(lines)