Extended unicode escapes in identifiers are not parsed

[weswigham]

TypeScript Version: 3.4.0-dev.201xxxxx

Search Terms:

Code

const x\u{0061} = 12;

Expected behavior:
No error

Actual behavior:
Many errors.

Playground Link:

IdentifierPart is defined to accept \UnicodeEscapeSequence which is defined as both normal and extended unicode escapes - right now we only handle normal (\u0061) and not extended (\u{0061}) escapes.

[weswigham]

cc @rbuckton is this just an oversight in our scanIdentifierParts function? Or perhaps a more recent change to ecma262?

[ajafff]

duplicate of #5291?

[weswigham]

So it is.