Fix regression in large string interpolations with non-String typed splices

[retronym]

Fixes scala/bug#11665

[som-snytt]

If scalacenter ran an annual "christmas tree of code" contest, it might help guard against regressions like this.

Crowdsource the test!

[retronym]

        test(1, s"$a")//  ~~~          | WHEEEE | 
        test(2, s"$a$a") //   ~~  #    /
        test(3, s"$a$a$a") //      @ /
        test(4, s"$a$a$a$a") //   _/\\
        test(5, s"$a$a$a$a$a") //    \\
        test(6, s"$a$a$a$a$a$a") //  ~~~~
        test(7, s"$a$a$a$a$a$a$a")
        test(8, s"$a$a$a$a$a$a$a$a")
        test(9, s"$a$a$a$a$a$a$a$a$a")
        test(10, s"$a$a$a$a$a$a$a$a$a$a")
        test(11, s"$a$a$a$a$a$a$a$a$a$a$a")
        test(12, s"$a$a$a$a$a$a$a$a$a$a$a$a")
        test(13, s"$a$a$a$a$a$a$a$a$a$a$a$a$a")
        test(14, s"$a$a$a$a$a$a$a$a$a$a$a$a$a$a")
        test(15, s"$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a")
        test(16, s"$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a")
        test(17, s"$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a")

?

[adriaanm]

1 test failure: https://scala-ci.typesafe.com/job/scala-2.12.x-validate-main/2177/testReport/junit/test.files/presentation/doc/

[ShaneDelmore]

This issue breaks a number of projects in the Twitter code base preventing us from upgrading to 2.12.9. Will this PR merit a hotfix release?

[SethTisue]

1 test failure

went away on /rebuild

[som-snytt]

The test doesn't compile under 2.13.

error: Error while emitting t11665/Test$
Method too large: t11665/Test$.main ([Ljava/lang/String;)V

[Ichoran]

Why is the test file indented with four-space indents?

Also, making each interpolation its own def would fix the method size problem.

def mkDef(n: Int) = "  def mk" + n.toString + " = \"" + "$a"*n + "\""
def mkTest(n: Int) = s"    test($n, mk$n)"

[retronym]

I've tweaked the test to fix indentation and avoid the large method size.

[som-snytt]

I was curious why 2.13 switches to fallback mode after 64. I'm too tired to think about that, but I did just do the Scalafix tutorial:

class String32 extends SemanticRule("String32") {

  override def fix(implicit doc: SemanticDocument): Patch = {
    doc.tree
      .collect { 
        case t @ Term.Interpolate(prefix @ Term.Name("s"), parts @ _, args) if args.length > 32 =>
          args.zipWithIndex.collect {
            case (arg, i) if i % 32 == 0 => Patch.addLeft(arg, "{") + Patch.addRight(arg, ".toString()}")
          }
      }
      .flatten
      .asPatch
  }
}

[SethTisue]

Will this PR merit a hotfix release?

Seems likely, depending on how hot “hot” is. We'll discuss at the next Scala team meeting. (for further discussion on 2.12.10 timing and contents, better to open a https://contributors.scala-lang.org thread)

[som-snytt]

If only folks running sbz, which would be sbt married to sbaz, could auto-download a hot scalafix that would run during their next build.