type for empty elements

src/SimpleStateMachine.StructuralSearch/FindParser.cs

@@ -8,7 +8,7 @@ namespace SimpleStateMachine.StructuralSearch
 {
     public class FindParser : IFindParser
     {
-        public static readonly IFindParser Empty = new EmptyFindParser();
+        public static readonly EmptyFindParser Empty = new ();
 
         private SeriesParser Parser { get; }
         public FindParser(SeriesParser parser)    

src/SimpleStateMachine.StructuralSearch/Input/Input.cs

@@ -4,8 +4,8 @@ namespace SimpleStateMachine.StructuralSearch
 {
     public static class Input
     {
-        public static readonly IInput Empty = new EmptyInput();
-        public static IInput String(string input) => new StringInput(input);
-        public static IInput File(FileInfo fileInfo) => new FileInput(fileInfo);
+        public static readonly EmptyInput Empty = new ();
+        public static StringInput String(string input) => new (input);
+        public static FileInput File(FileInfo fileInfo) => new (fileInfo);
     }
 }

src/SimpleStateMachine.StructuralSearch/ParsingContext.cs

@@ -5,7 +5,7 @@ namespace SimpleStateMachine.StructuralSearch
 {
     public class ParsingContext : IParsingContext
     {
-        public static IParsingContext Empty = new EmptyParsingContext(SimpleStateMachine.StructuralSearch.Input.Empty);
+        public static readonly EmptyParsingContext Empty = new (SimpleStateMachine.StructuralSearch.Input.Empty);
 
         public ParsingContext(IInput input)
         {

src/SimpleStateMachine.StructuralSearch/Rules/FindRule/EmptyRule.cs

@@ -14,5 +14,5 @@ public void SetContext(ref IParsingContext context)
 
 public static class Rule
 {
-    public static readonly IRule Empty = new EmptyRule();
+    public static readonly EmptyRule Empty = new();
 }

src/SimpleStateMachine.StructuralSearch/Rules/ReplaceRule/ReplaceRule.cs

@@ -5,7 +5,7 @@ namespace SimpleStateMachine.StructuralSearch
 {
     public class ReplaceRule : IReplaceRule
     {
-        public static readonly IReplaceRule Empty = new EmptyReplaceRule();
+        public static readonly EmptyReplaceRule Empty = new ();
 
         public IEnumerable<ReplaceSubRule> Rules { get; }
         public IRule ConditionRule { get; }

src/SimpleStateMachine.StructuralSearch/Templates/ReplaceTemplate/ReplaceBuilder.cs

@@ -6,7 +6,7 @@ namespace SimpleStateMachine.StructuralSearch.ReplaceTemplate
 {
     public class ReplaceBuilder : IReplaceBuilder
     {
-        public static readonly IReplaceBuilder Empty = new EmptyReplaceBuilder();
+        public static readonly EmptyReplaceBuilder Empty = new ();
 
         public IEnumerable<IRuleParameter> Steps { get; }