LiteralPropertyName should allow BigInt

[JLHwung]

TypeScript Version: 3.8.0-dev.20200101

Search Terms: bigint, property name

Code

({1n: 123});

Expected behavior:
No error

Actual behavior:
Property Assignment Expected

Playground Link: https://www.typescriptlang.org/play/?ts=3.8.0-dev.20200101&ssl=1&ssc=1&pln=1&pc=15#code/BQbwBAjAdgXJBMBmMBfAlAbiA
Related Issues:

tc39/test262#2457
https://bugs.chromium.org/p/v8/issues/detail?id=10083

ecd1245 should be partially reverted.

[calebsander]

This was discussed quite a bit when support for bigint was added to TypeScript. We decided that there weren't many good use cases for bigint keys and it made more sense to require an explicit conversion to string instead. For example, see #15096 (comment).
Can you explain why you think this behavior should be changed?

[lucacasonato]

This currently forbids valid JS syntax in TS files (with a very confusing error message). https://www.typescriptlang.org/play/?#code/KYDwDg9gTgLgBDAnmYcCCcC8cDeAoOQuARgDsAuOAMwEMAbAZ2DwF8BuIA - even if not allowed in the checker, it should at least be allowed in the parser.