throw null

src/ast_utils.js

@@ -170,7 +170,18 @@ export const find_node = (node, pred) => {
 export const find_error_origin_node = node =>
   find_node(
     node, 
-    n => n.result != null && !n.result.ok && n.result.error != null
+    n => n.result != null && !n.result.ok && (
+      n.result.error != null
+      ||
+      // In case if throw null or throw undefined
+      n.type == 'throw'
+      ||
+      // await can also throw null
+      n.type == 'unary' && n.operator == 'await'
+      // or function call throwing null or undefined
+      || 
+      n.type == 'function_call'
+    )
   )
 
 /* Maps tree nodes, discarding mapped children, so maps only node contents, not

src/calltree.js

@@ -36,10 +36,10 @@ export const set_location = (state, location) => set_cursor_position(
 
 const is_stackoverflow = node =>
   // Chrome
-  node.error.message == 'Maximum call stack size exceeded'
+  node.error?.message == 'Maximum call stack size exceeded'
   ||
   // Firefox
-  node.error.message == "too much recursion"
+  node.error?.message == "too much recursion"
 
 export const calltree_node_loc = node => node.toplevel  
     ? {module: node.module}

src/editor/calltree.js

@@ -115,7 +115,7 @@ export class CallTree {
             el('i', '', 
               'toplevel: ' + (n.module == '' ? '*scratch*' : n.module),
             ),
-            n.ok ? '' : el('span', 'call_header error', '\xa0', n.error.toString()),
+            n.ok ? '' : el('span', 'call_header error', '\xa0', stringify_for_header(n.error)),
           )
         : el('span', 
               'call_header ' 
@@ -135,7 +135,7 @@ export class CallTree {
              ),
             ')' ,
             // TODO: show error message only where it was thrown, not every frame?
-            ': ', (n.ok ? stringify_for_header(n.value) : n.error.toString()) 
+            ': ', (n.ok ? stringify_for_header(n.value) : stringify_for_header(n.error)) 
           ),
       ),
       (n.children == null || !is_expanded)

src/editor/editor.js

@@ -1,5 +1,5 @@
 import {exec, get_state} from '../index.js'
-import {ValueExplorer} from './value_explorer.js'
+import {ValueExplorer, stringify_for_header} from './value_explorer.js'
 import {el, stringify, fn_link} from './domutils.js'
 import {FLAGS} from '../feature_flags.js'
 
@@ -244,7 +244,7 @@ export class Editor {
 
       exp.render(value)
     } else {
-      content.appendChild(el('span', 'eval_error', error.toString()))
+      content.appendChild(el('span', 'eval_error', stringify_for_header(error)))
     }
 
     this.widget = {