...

compiler/Parser.cs

@@ -195,7 +195,17 @@ public class Parser
 
         if (TryExpectKeyword(Keyword.Return))
         {
-            var value = ParseExpression();
+            NodeExpression? value = null;
+
+            if (Peek() is TokenIdent token && token.Ident == "void")
+            {
+                Next();
+            }
+            else
+            {
+                value = ParseExpression();
+            }
+
             return new NodeStatementReturn(TokensFrom(startIndex), value);
         }
 
@@ -792,9 +802,9 @@ public class NodeStatementExpression(List<Token> tokens, NodeExpression expressi
     public NodeExpression Expression { get; } = expression;
 }
 
-public class NodeStatementReturn(List<Token> tokens, NodeExpression value) : NodeStatement(tokens)
+public class NodeStatementReturn(List<Token> tokens, NodeExpression? value) : NodeStatement(tokens)
 {
-    public NodeExpression Value { get; } = value;
+    public NodeExpression? Value { get; } = value;
 }
 
 public class NodeStatementVariableDeclaration(List<Token> tokens, TokenIdent name, NodeType? type, NodeExpression value) : NodeStatement(tokens)