BigInt estree value is always null

[mroch]

Flow version: 0.179.0

Expected behavior

The value prop of a BigIntLiteral in ESTree should be a BigInt when using flow_parser.js in an environment that supports BigInt.

Actual behavior

we always return null:

flow/src/parser/estree_translator.ml

Line 1324 in c005082

node ?comments "BigIntLiteral" loc [("value", null); ("bigint", string raw)]

Fix

Translator_intf needs a method similar to regexp that returns null in most implementations, but JsTranslator tries to instantiate a BigInt in flow_parser_js.ml, wrapped in a try/with so it returns null if the JS runtime doesn't support it.

[fisker]

Should we change its type to Literal and add raw?