Do not concatenate Strings with +

When concatenating something to a String, consider string interpolation rather than +.

Reason

Because of a little gem called any2stringadd, + is just not very sane in Scala.

It has, for example, wildly different behaviours for similar collections:

List("foo") + "bar"
// res0: String = "List(foo)bar"

Set("foo") + "bar"
// res1: Set[String] = Set("foo", "bar")

+ also causes this kind of absolutely nonsensical error message:

List(1) + 2
// error: type mismatch;
//  found   : Int(2)
//  required: String
// List(1) + 2
//           ^

This is because of my old nemesis, implicit conversions. What the compiler actually ends up trying is:

any2stringadd(List(1)).+(2)

It makes sense when you understand the underlying mechanisms, but good luck explaining that to a beginner.

String interpolation, on the other hand, is safe and coherent:

s"${List("foo")}bar"
// res4: String = "List(foo)bar"

s"${Set("foo")}bar"
// res5: String = "Set(foo)bar"

s"${List(1)}${2}"
// res6: String = "List(1)2"

Checked by