fix #1897

SyntaxTree/tree/TreeHelper.cs

@@ -1836,5 +1836,10 @@ namespace PascalABCCompiler.SyntaxTree
         }
     }
 
+    public partial class semantic_check_sugared_statement_node
+    {
+        public bool visited = false;
+    }
+
     }
 

TestSuite/errors/err0317.pas

@@ -0,0 +1,3 @@
+begin
+  Writeln(1 mod 0);
+end.

TestSuite/loopn.pas

@@ -0,0 +1,10 @@
+begin
+  var n := 10;
+  loop n do
+    Print(1);
+  var p: procedure;
+  p := ()->begin
+    Print(n);
+  end;
+  Assert(1=1);
+end.

TreeConverter/TreeConversion/syntax_tree_visitor.cs

@@ -20111,6 +20111,9 @@ namespace PascalABCCompiler.TreeConverter
 
         public override void visit(SyntaxTree.semantic_check_sugared_statement_node st)
         {
+            if (st.visited)
+                return;
+            st.visited = true;
             if (st.typ as System.Type == typeof(SyntaxTree.assign_tuple))
             {
                 var vars = st.lst[0] as SyntaxTree.addressed_value_list;