Fix #8096: Change syntax of single-case try

[odersky]

No description provided.

[smarter]

I recently noticed this and I wonder if the same sort of fix could be applied:

object Test {
  def test: Unit = {
    println("1")

      (x: Int) => 0

    println("2")
  }
}

You might think the body of the lambda is just 0, and the warning would agree with you:

-- [E129] Potential Issue Warning: try/indentlambda.scala:5:18 -----------------
5 |      (x: Int) => 0
  |                  ^
  |A pure expression does nothing in statement position; you may be omitting necessary parentheses

but actually every line after that is also part of the body of the lambda:

result of try/indentlambda.scala after typer:
package <empty> {
  final lazy module val Test: Test$ = new Test$()
  final module class Test$() extends Object(), _root_.scala.Serializable {
    this: Test.type =>
    def test: Unit =
      {
        println("1")
        {
          {
            def $anonfun(x: Int): Unit =
              {
                0
                println("2")
              }
            closure($anonfun)
          }
          ()
        }
      }
  }
}

(scalac does the same)

[bishabosha]

The current run test indeed proves that "OK" is not swallowed by the catch, but perhaps this neg test should be added, which compiles on 0.21:

def k: Unit =
  val s: String = try
    "WUT"
  catch case t => println("caught something") // error: Type Mismatch Error

  "OK" // warning: A pure expression does nothing in statement position