[swift-evolution] [Review] SE-0084: Allow trailing commas in parameter lists and tuples

[Chris Lattner]

On May 12, 2016, at 4:50 PM, Joe Groff <jgroff at apple.com> wrote:
>>> 	--- a.swift
>>> 	+++ a.swift
>>> 	 foo(
>>> 	   x: 0,
>>> 	-  y: 1
>>> 	+  y: 1,
>>> 	+  z: 2
>>> 	 )
>>> 
>>> Trailing commas avoid this:
>>> 
>>> 	--- a.swift
>>> 	+++ a.swift
>>> 	 foo(
>>> 	   x: 0,
>>> 	   y: 1,
>>> 	+  z: 2,
>>> 	 )
>> 
>> You’re arguing that you want to read Swift code written like this?
> 
> I wouldn't mind it.

I personally find that style repulsive :-) and I haven’t seen swift code commonly doing it.  I’m not sure that we want to encourage it either.

> The standard library already uses this style for function parameters, modulo the trailing comma, and I certainly prefer it to:
> 	
>> 	--- a.swift
>> 	+++ a.swift
>> 	 foo( x: 0
>> 	    , y: 1
>> 	+   , z: 2
>> 	    )

I agree that this is even worse, but I also haven’t seen this used in Swift code.  Have you?   Swift’s strictness with argument labels makes any of this pretty unappealing to use.

If we were really concerned about this, a narrower way to solve the same problem would be to allow a comma before the ), but *only* when there is a newline between them.  I still don’t see why we’d want to encourage this though.

-Chris