#291 causes drastic performance drop in DetectIdentifiers

[cpiber]

We have around 115 equations on which we call DetectIdentifiers. Before (v2.16.1), this took around 50ms. After the change, it takes 17.1 seconds, all of which is spent in evaluating the regex (of which 50% is spent in Match.AddMatch).

Interestingly, #323 improves this somewhat to 16.7 seconds. In any case, a 330 times slowdown seems a bit excessive.

[cpiber]

Turns out the \b is responsible, just adding that in the front drops us back down to 50ms

		private static readonly Regex RootIdentifierDetectionRegex =
-			new Regex(@"(?<id>@?[\p{L}\p{Nl}_][\p{L}\p{Nl}\p{Nd}\p{Mn}\p{Mc}\p{Pc}\p{Cf}_]*)", RegexOptions.Compiled);
+			new Regex(@"\b(?<id>@?[\p{L}\p{Nl}_][\p{L}\p{Nl}\p{Nd}\p{Mn}\p{Mc}\p{Pc}\p{Cf}_]*)", RegexOptions.Compiled);

		private static readonly Regex ChildIdentifierDetectionRegex = new Regex(
-			@"(?<id>@?[\p{L}\p{Nl}_][\p{L}\p{Nl}\p{Nd}\p{Mn}\p{Mc}\p{Pc}\p{Cf}_]*(\.[\p{L}\p{Nl}_][\p{L}\p{Nl}\p{Nd}\p{Mn}\p{Mc}\p{Pc}\p{Cf}_]*)*)",
+			@"\b(?<id>@?[\p{L}\p{Nl}_][\p{L}\p{Nl}\p{Nd}\p{Mn}\p{Mc}\p{Pc}\p{Cf}_]*(\.[\p{L}\p{Nl}_][\p{L}\p{Nl}\p{Nd}\p{Mn}\p{Mc}\p{Pc}\p{Cf}_]*)*)",
			RegexOptions.Compiled);

@metoule can you please comment in more detail why you removed it?

[metoule]

@cpiber based on my comment on #291, it was to support identifiers starting with a @ (e.g. @this). I'll check if it can be reintroduced

[cpiber]

@metoule I have something added in #332, please check it, seems I understood your comment right

[davideicardi]

Closed by #332