Fewer braces and lambda: incorrect indentation region detection

[kitbellew]

Compiler version

• 3.3.3
• 3.3.4 LTS
• 3.5.2 Next

Minimized code

  def fn2(arg: String, arg2: String)(f: String => Unit): Unit =
    f(arg)

  // doesn't compile
  fn2(
      arg = "blue sleeps faster than tuesday",
      arg2 = "the quick brown fox jumped over the lazy dog"): env =>
      val x = env
      println(x)

  // does compile
  fn2(
      arg = "blue sleeps faster than tuesday",
      arg2 = "the quick brown fox jumped over the lazy dog"):
    env =>
      val x = env
      println(x)

  // does compile
  fn2(
      arg = "blue sleeps faster than tuesday",
      arg2 = "the quick brown fox jumped over the lazy dog"
  ): env =>
      val x = env
      println(x)

Output

scastie marks two errors:

• fn2 line with not a legal formal parameter for a function literal
• val x = env line with Not found: env

Expectation

According to the documentation, the first argument clause (with arg and arg2) does not start an indentation region, hence as long as the lambda body is indented relative to fn2 invocation, it should work.

• https://dotty.epfl.ch/docs/reference/other-new-features/indentation.html#optional-braces-3
• https://dotty.epfl.ch/docs/reference/other-new-features/indentation.html#indentation-and-braces-1

P.S. The problem was first reported in scalameta/scalafmt#4569.