Add pattern examples & fix desugaring

Patterns/patterns-switch.pas

@@ -0,0 +1,8 @@
+begin
+  var a := new List<integer>(arr(1, 2));
+  match a with
+    integer(var c): write(1);
+    boolean(var s): write(2);
+    List<integer>(var l):write(3)
+  end;
+end.

Patterns/patterns.pas

@@ -0,0 +1,26 @@
+type
+  Person = auto class
+    name: string;
+    age: integer;
+  end;
+
+type
+  Student = class(Person);
+
+begin
+  var b1 := new Student('asd', 30) is Person(var c);
+  writeln(c);
+  
+  var b2 := 1 is integer(var d);
+  writeln(d);
+  
+  var arr := Arr(1, 3, 5, 7, 9);
+  
+  var l := new List<integer>(arr);
+  var b4 := l is List<integer>(var f);
+  writeln(f);
+  
+  var delegate: Func<word, char> := PABCSystem.ChrUnicode;
+  var b5 := delegate is Func<word, char>(var g);
+  writeln(g);
+end.

SyntaxTreeConverters/StandardSyntaxConverter.cs

@@ -42,6 +42,9 @@ namespace PascalABCCompiler.SyntaxTreeConverters
             // double_question_desugar_visitor
             DoubleQuestionDesugarVisitor.New.ProcessNode(root);
 
+            // pattern matching
+            MatchWithVisitor.New.ProcessNode(root);
+            IsPatternVisitor.New.ProcessNode(root);
 
             // Всё, связанное с yield
             MarkMethodHasYieldAndCheckSomeErrorsVisitor.New.ProcessNode(root);