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Fix #8096: Change syntax of single-case try #8121

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Merged
merged 1 commit into from
Jan 30, 2020

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odersky
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@odersky odersky commented Jan 29, 2020

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@odersky odersky requested a review from bishabosha January 29, 2020 15:07
@odersky odersky added this to the 0.22 Tech Preview milestone Jan 30, 2020
@smarter
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smarter commented Jan 30, 2020

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)

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@bishabosha bishabosha left a comment

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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

@bishabosha bishabosha merged commit 7724627 into scala:master Jan 30, 2020
@bishabosha bishabosha deleted the fix-#8096 branch January 30, 2020 19:57
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3 participants