diff --git a/SyntaxTree/tree/TreeHelper.cs b/SyntaxTree/tree/TreeHelper.cs
index 1b618420c..dff8e7c7d 100644
--- a/SyntaxTree/tree/TreeHelper.cs
+++ b/SyntaxTree/tree/TreeHelper.cs
@@ -33,6 +33,8 @@ namespace PascalABCCompiler.SyntaxTree
         DirectDescendants
     }
 
+    public enum SugaredExpressionType { MatchedExpression }
+
     public partial class syntax_tree_node
     {
 
diff --git a/SyntaxVisitors/SugarVisitors/PatternsDesugaringVisitor.cs b/SyntaxVisitors/SugarVisitors/PatternsDesugaringVisitor.cs
index 25c5a1dd7..21d797a21 100644
--- a/SyntaxVisitors/SugarVisitors/PatternsDesugaringVisitor.cs
+++ b/SyntaxVisitors/SugarVisitors/PatternsDesugaringVisitor.cs
@@ -111,8 +111,9 @@ namespace SyntaxVisitors.SugarVisitors
 
         public override void visit(is_pattern_expr isPatternExpr)
         {
-            // TODO Patterns: convert to compilation error
-            Debug.Assert(GetLocation(isPatternExpr) != PatternLocation.Unknown, "Is-pattern expression is in an unknown context");
+            if (GetLocation(isPatternExpr) == PatternLocation.Unknown)
+                throw new SyntaxVisitorError("PATTERN_MATHING_IS_NOT_SUPPORTED_IN_THIS_CONTEXT", isPatternExpr.source_context);
+
             Debug.Assert(GetAscendant<statement_list>(isPatternExpr) != null, "Couldn't find statement list in upper nodes");
             
             DesugarIsExpression(isPatternExpr);
@@ -235,6 +236,7 @@ namespace SyntaxVisitors.SugarVisitors
             ReplaceUsingParent(isExpression, desugaringResult.SuccessVariable);
 
             var statementsToAdd = desugaringResult.GetDeconstructionDefinitions(pattern.source_context);
+            statementsToAdd.Add(GetMatchedExpressionCheck(isExpression.left));
             statementsToAdd.Add(desugaringResult.GetPatternCheckWithDeconstrunctorCall());
 
             AddDefinitionsInUpperStatementList(isExpression, statementsToAdd);
@@ -247,11 +249,12 @@ namespace SyntaxVisitors.SugarVisitors
             ReplaceUsingParent(isExpression, desugaringResult.SuccessVariable);
 
             var statementsToAdd = desugaringResult.GetDeconstructionDefinitions(pattern.source_context);
+            statementsToAdd.Add(GetMatchedExpressionCheck(isExpression.left));
             statementsToAdd.Add(desugaringResult.GetPatternCheckWithDeconstrunctorCall());
 
             var enclosingIf = GetAscendant<if_node>(isExpression);
             // Если уже обрабатывался ранее (второй встретившийся в том же условии is), то не изменяем if
-            if (processedIfNodes.Contains(enclosingIf))
+            if (processedIfNodes.Contains(enclosingIf)) 
                 AddDefinitionsInUpperStatementList(isExpression, statementsToAdd);
             // Иначе помещаем определения и if-then в отдельный блок, а else после этого блока
             else
@@ -267,6 +270,9 @@ namespace SyntaxVisitors.SugarVisitors
             }
         }
 
+        private semantic_check_sugared_statement_node GetMatchedExpressionCheck(expression matchedExpression)
+        => new semantic_check_sugared_statement_node(SugaredExpressionType.MatchedExpression, new List<syntax_tree_node>() { matchedExpression });
+
         private statement_list ConvertIfNode(if_node ifNode, List<statement> statementsBeforeIf, out statement elseBody)
         {
             // if e then <then> else <else>
diff --git a/TreeConverter/TreeConversion/SyntaxTreeVisitorNodes/Patterns.cs b/TreeConverter/TreeConversion/SyntaxTreeVisitorNodes/Patterns.cs
index 484aa216e..859349bbe 100644
--- a/TreeConverter/TreeConversion/SyntaxTreeVisitorNodes/Patterns.cs
+++ b/TreeConverter/TreeConversion/SyntaxTreeVisitorNodes/Patterns.cs
@@ -211,5 +211,16 @@ namespace PascalABCCompiler.TreeConverter
                 if (parameter.parameter_type != SemanticTree.parameter_type.var && parameter is common_parameter p)
                     AddError(p.loc, "DECONSTRUCTION_PARAMETERS_SHOULD_HAVE_VAR_MODIFIER");
         }
+
+        /// <summary>
+        /// Проверяет выражение, сопоставляемое с образцом
+        /// </summary>
+        /// <param name="matchedExpression"></param>
+        private void CheckMatchedExpression(expression matchedExpression)
+        {
+            var convertedExpression = convert_strong(matchedExpression);
+            if (convertedExpression.type.IsPointer)
+                AddError(get_location(matchedExpression), "PATTERN_MATCHING_DOESNT_SUPPORT_POINTERS");
+        }
     }
 }
diff --git a/TreeConverter/TreeConversion/syntax_tree_visitor.cs b/TreeConverter/TreeConversion/syntax_tree_visitor.cs
index 8cb4005b3..279e172e8 100644
--- a/TreeConverter/TreeConversion/syntax_tree_visitor.cs
+++ b/TreeConverter/TreeConversion/syntax_tree_visitor.cs
@@ -12276,8 +12276,7 @@ namespace PascalABCCompiler.TreeConverter
                 commonNode.name.ToLower() == compiler_string_consts.deconstruct_method_name)
             {
                 var deconstructor = commonNode;
-
-                // TODO Patterns: add warning for non-extension deconstruct
+                
                 if (!deconstructor.is_extension_method)
                 {
                     //AddWarning();
@@ -19413,6 +19412,13 @@ namespace PascalABCCompiler.TreeConverter
                 var expr = st.lst[0] as SyntaxTree.expression;
                 semantic_check_loop_stmt(expr);
             }
+            // Patterns
+            else if (st.typ is SugaredExpressionType.MatchedExpression)
+            {
+                var expr = st.lst[0] as expression;
+                CheckMatchedExpression(expr);
+            }
+            // !Patterns
             else
             {
                 AddError(get_location(st), "MISSED_SEMANTIC_CHECK_FOR_SUGARED_NODE_{0}", (st.typ as System.Type)?.Name??"Unknown");