Class fields status update

Daniel Ehrenberg

Igalia

In partnership with Bloomberg

TC39 September 2017

Small spec changes

• Public fields are configurable (reflecting consensus)
• Private field/CallExpression grammar production
• Throw on undeclared private fields from new Function
• Various small fixes (thanks anba!)
• TODO: plumbing for private scopes

ASI?

• Keeps coming up in the bug tracker
• Should we use normal ASI rules?
• Proposition: ASI is bad
• Proposition: ASI is weirder than normal in class bodies because they have different things:
• Need ; after field named get, set, static
• Need ; after field with initializer before generator, computed property key
• New class contextual keywords need [no LineTerminator here]
• Different from statement ASI!

Implementation status

• Spec
• V8 implementation in progress PR
• JSC implementation in progress PR
• Babel supports public fields with new current semantics; private fields in progress PR
• Test262 tests in progress PR