Collect collections gotchas.

[adriaanm]

Let's build a collection of collection usage patterns that surprised users, to inform the renovations in 2.13.

[adriaanm]

https://news.ycombinator.com/item?id=12730239

[dwijnand]

I believe the partial methods are a gotcha that would be nice to improve: eg. Option.get, Seq.head, Seq.reduce.

A good naming convention to alert the reader might be sufficient (in Ruby it's a ! suffix, in Scala I've generally seen the methods prefixed with unsafe, so perhaps unsafeGet, unsafeHead, etc)

[lrytz]

A related concern: apply vs get is often confusing in maps, also because get is the partial method in Option. But it would be a loss if Map[A, B] was no longer an A => B.

[SethTisue]

this ship has sailed

[dwijnand]

How do we avoid that in the future? I tend to avoid nudging tickets if I see they're in the intended milestone, but maybe it's better to?