not iterable error

test/test.js

@@ -837,6 +837,23 @@ export const tests = [
     )
   }),
 
+  test('array spread not iterable', () => {
+    assert_code_error(
+      `[...null]`,
+      new Error('null is not iterable'),
+    )
+  }),
+
+  test('args spread not iterable', () => {
+    assert_code_error(
+      `
+        function x() {} 
+        x(...null)
+      `,
+      new Error('null is not iterable'),
+    )
+  }),
+
   test('module not found', () => {
     const parsed = parse_modules(
       'a',
@@ -2336,6 +2353,20 @@ const y = x()`
     assert_equal(s2.value_explorer.result.error.message, 'boom')
   }),
 
+  test('move_cursor error in fn args bug', () => {
+    const code = `
+    function x() {} 
+    x(null.foo)
+    `
+    const i = test_initial_state(code)
+    
+    const m = COMMANDS.move_cursor(i, code.indexOf('x(null'))
+    assert_equal(
+      m.value_explorer.result.error, 
+      new Error("Cannot read properties of null (reading 'foo')")
+    )
+  }),
+
   test('frame follows cursor toplevel', () => {
     const code = `
       const x = () => {

test/utils.js

@@ -1,3 +1,4 @@
+import {find_error_origin_node} from '../src/ast_utils.js'
 import {parse, print_debug_node, load_modules} from '../src/parse_js.js'
 import {eval_modules} from '../src/eval.js'
 import {active_frame, pp_calltree} from '../src/calltree.js'
@@ -81,9 +82,8 @@ export const assert_code_evals_to = (codestring, expected) => {
 export const assert_code_error = (codestring, error) => {
   const state = test_initial_state(codestring)
   const frame = active_frame(state)
-  const result = frame.children.at(-1).result
-  assert_equal(result.ok, false)
-  assert_equal(result.error, error)
+  assert_equal(frame.result.ok, false)
+  assert_equal(find_error_origin_node(frame).result.error, error)
 }
 
 export const assert_code_evals_to_async = async (codestring, expected) => {
@@ -168,9 +168,10 @@ export const test_deferred_calls_state = code => {
 
 export const stringify = val => 
   JSON.stringify(val, (key, value) => {
-    // TODO do not use instanceof because currently not implemented in parser
-    if(value?.constructor == Set){
+    if(value instanceof Set){
       return [...value]
+    } else if(value instanceof Error) {
+      return {message: value.message}
     } else {
       return value
     }