SpreadElement and Cannot read property 'start' of undefined

[ainthek]

Problem of Flex or Grasp ? Seems like Grasp problem to me:
Can anyone test standalone Flex please ?

This fails:
echo "x={};y={...x}" | grasp -s 'program'
Cannot read property 'start' of undefined

echo "x={};y={...x}" | grasp -s 'program' --parser '(acorn, {locations: true, ecmaVersion: 2018, sourceType: 'script', allowHashBang: true})'
Cannot read property 'start' of undefined

Acorn can parse this and the result is:
$ echo "x={};y={...x}" | acorn --ecma2018
{
"type": "Program",
"start": 0,
"end": 14,
"body": [
{
"type": "ExpressionStatement",
"start": 0,
"end": 5,
"expression": {
"type": "AssignmentExpression",
"start": 0,
"end": 4,
"operator": "=",
"left": {
"type": "Identifier",
"start": 0,
"end": 1,
"name": "x"
},
"right": {
"type": "ObjectExpression",
"start": 2,
"end": 4,
"properties": []
}
}
},
{
"type": "ExpressionStatement",
"start": 5,
"end": 13,
"expression": {
"type": "AssignmentExpression",
"start": 5,
"end": 13,
"operator": "=",
"left": {
"type": "Identifier",
"start": 5,
"end": 6,
"name": "y"
},
"right": {
"type": "ObjectExpression",
"start": 7,
"end": 13,
"properties": [
{
"type": "SpreadElement",
"start": 8,
"end": 12,
"argument": {
"type": "Identifier",
"start": 11,
"end": 12,
"name": "x"
}
}
]
}
}
}
],
"sourceType": "script"
}

[adros]

Flow parser is OK. Error occures in grasp-squery/lib/common.js#17 (property.key is undefined)

See screenshot from debugger

[ainthek]

Please any fix for this ?