Add expectations to lexer

libs/UIX.Asm/Lexer.cs

@@ -33,7 +33,7 @@ public static class Lexer
 
         var identifierResult = Parse.Letter.AtLeastOnce().Text().Invoke(input);
         if (!identifierResult.WasSuccessful)
-            return Result.Failure<Instruction>(input, "Invalid code", System.Array.Empty<string>());
+            return Result.Failure<Instruction>(input, "Invalid code", []);
 
         input = identifierResult.Remainder;
         var identifier = identifierResult.Value;
@@ -73,12 +73,12 @@ public static class Lexer
         var importDirectiveResult = Parse.String(".import-")(input);
         input = importDirectiveResult.Remainder;
         if (!importDirectiveResult.WasSuccessful)
-            return Result.Failure<IImport>(input, "Invalid import directive", null);
+            return Result.Failure<IImport>(input, "Invalid import directive", ["Expected '.import'"]);
 
         var importTypeResult = Parse.Letter.AtLeastOnce().Text()(input);
         input = importTypeResult.Remainder;
         if (!importTypeResult.WasSuccessful)
-            return Result.Failure<IImport>(input, "Invalid import type", null);
+            return Result.Failure<IImport>(input, "Invalid import type", ["Expected 'ns'"]);
 
         IImport import;
         switch (importTypeResult.Value.ToUpperInvariant())
@@ -87,20 +87,20 @@ public static class Lexer
                 var uriResult = Uri.Token()(input);
                 input = uriResult.Remainder;
                 if (!uriResult.WasSuccessful)
-                    return Result.Failure<IImport>(input, "Invalid URI", null);
+                    return Result.Failure<IImport>(input, "Invalid URI", ["Expected a valid URI"]);
 
                 input = Parse.String("as").Token()(input).Remainder;
 
                 var nameResult = AlphanumericText(input);
                 input = nameResult.Remainder;
                 if (!nameResult.WasSuccessful)
-                    return Result.Failure<IImport>(input, "Invalid namespace alias", null);
+                    return Result.Failure<IImport>(input, "Invalid namespace alias", ["Expected a valid namespace alias"]);
 
                 import = new NamespaceImport(uriResult.Value, nameResult.Value);
                 break;
 
             default:
-                return Result.Failure<IImport>(input, $"Unknown import type '{importTypeResult.Value}'", null);
+                return Result.Failure<IImport>(input, $"Unknown import type '{importTypeResult.Value}'", ["Expected 'ns'"]);
         }
 
         return Result.Success(import, input);