Sept 2017

> Bocoup, Boston, MA (Sept 26-28)
> https://github.com/tc39/agendas/blob/master/2017/09.md

> Checkbox means we completed it (some Stage 1 we may want to wait to start given instability of the proposal)
> https://tc39.github.io/process-document/ for a primer what each Stage means

### New Proposals
- [x] ✍️ [Pipeline Operator](https://github.com/babel/proposals/issues/29) Stage 1 (next: need a solution for method extraction, possibly just `::a`)
- [ ] [Extensible Numeric Literals](https://github.com/babel/proposals/issues/30) Stage 1 (also had objections, will probably wait)
- [ ] [First Class Protocols](https://github.com/babel/proposals/issues/31) Stage 1
- [ ] Subsume JSON to Stage 1
- [ ] [Partial application](https://github.com/babel/proposals/issues/32) to Stage 1 (but has strong objections on syntax/semantics, will probably wait)
- [ ] [Nullary Coalescing](https://github.com/babel/proposals/issues/14) to Stage 1 (need explainer for checking "nully" or "undefined"

### Moving Foward
- [x] ✍️ [Throw Expressions](https://github.com/babel/proposals/issues/23) from Stage 1 to Stage 2
- [ ] ✍️ [Private Methods (and accessors)](https://github.com/babel/proposals/issues/22) from Stage 2 to Stage 3
- [ ] ✍️ [`import.meta`](https://github.com/babel/proposals/issues/10) from Stage 2 to Stage 3

### Needs Consensus (Stage 4)
- [ ] [Early errors for RegExp literals](https://github.com/tc39/ecma262/pull/984)
- [ ] ✍️ [export-ns-from](https://github.com/babel/proposals/issues/16) from Stage 2 (needs tests)

### Needs Spec Work
- [Optional Chaining](https://github.com/babel/proposals/issues/18) stays at Stage 1 again (issues with short-circuiting only for `?.` and use of `?.[` and `?.(` in general, `?.` syntax is desired but may not align with `?.[` and `?.(` but `?&.` and other syntax changes are not preferred)
- [Object Shorthand Improvements](https://github.com/rbuckton/proposal-shorthand-improvements) stays at Stage 0
- [`Builtins.typeOf()` and `Builtins.is()`](https://github.com/jasnell/proposal-istypes) stays at Stage 0
- Numeric Separator stays at Stage 2

### Other (Builtins, etc)

- Template literal memory leak fix (needs consensus PR)
- [`Intl.NumberFormat.prototype.formatToParts`](https://github.com/tc39/proposal-intl-formatToParts) to Stage 4
- [`Intl.Segmenter`](https://github.com/tc39/proposal-intl-segmenter) to Stage 3
- [`Intl.RelativeTimeFormat`](https://github.com/tc39/proposal-intl-relative-time) to Stage 3
- [`Atomics.waitAsync`](https://github.com/tc39/proposal-atomics-wait-async) to Stage 2
- [`Intl.PluralRules`](https://github.com/tc39/proposal-intl-plural-rules) to Stage 4
- [`Array.prototype.flatMap` and `Array.prototype.flatten`](https://github.com/tc39/proposal-flatMap) from Stage 1 to Stage 2
- [`Intl.Locale`](https://github.com/zbraniecki/proposal-intl-locale) to Stage 1
- [`String.prototype.matchAll`](https://github.com/tc39/proposal-string-matchall) to Stage 2
- Needs consensus: https://github.com/tc39/ecma262/pull/778, https://github.com/tc39/ecma262/pull/888, https://github.com/tc39/ecma262/pull/988

Begin by reading the TC39 process primer and the linked proposal and specification issues in the checklist. The issue does not identify a single entry point, test, or completion criterion; determine which September 2017 status item is still intended before any work can be considered done.

Written by the indexing model from the issue text.