refactored SearchExpression

ParadoxSaveParser.Lib/SearchExpression/NoMatchExpression.cs

@@ -0,0 +1,23 @@
+namespace ParadoxSaveParser.Lib;
+
+/// <summary>"~" — matches nothing, so the branch is skipped.</summary>
+internal sealed class NoMatchExpression : ISearchExpression
+{
+    // stateless, so one instance serves every "~" in every query
+    public static readonly NoMatchExpression Instance = new();
+
+    private NoMatchExpression()
+    {
+    }
+
+    public bool DoesMatch(MatchCandidate candidate, out ISearchExpression? nextSearchExpression)
+    {
+        nextSearchExpression = null;
+        return false;
+    }
+
+    // no keys and no children, and shared between queries, so nothing may be stored here
+    public void ReEncode(Encoding encoding)
+    {
+    }
+}