SE-0257: Eliding commas from multiline expression lists

[anandabits (Matthew Johnson)]

@allevato

Elision in one place doesn’t mean we should allow elision everywhere, because not all kinds of elision are the same. This may be a subjective statement, but IMO the rules around parenthesis elision (simple vs complete signatures) are far more consistent and understandable than the proposed ones around comma elision, which are based on whether the thing on the next line could potentially be parsed as part of the same expression and which precludes very obvious use cases like arrays of enum cases or other implicit static member references.

Let's not build strawmen. I am not making the claim that elision in one place implies we should allow it everywhere. I am drawing an analogy between one form of separator punctuation and another and using human experience with one form to consider how humans will react in the presence of the other form.

I'm not sure what you mean by simple vs complete signatures. I was referring to complex expressions that rely on operator precedence (potentially of user-defined operators and precedences). It is possible to write expressions that are quite difficult for humans to parse accurately due to parentheses elision and this is not a problem - humans are quite capable of exercising good judgement about when parentheses are necessary for readable code. We are quite capable of learning to apply the same kind of judgment with regard to comma elision.