Misindent imports produces a confusing error

[mlachkar]

Minimized code

  import scala.concurrent._

@main def main(): Unit =
  def test = ()
  test

Output

[error] -- [E018] Syntax Error: /Users/meriamlachkar/perso/dotty/src/main/scala/Show.scala:3:24 
[error] 3 |@main def main(): Unit =
[error]   |                        ^
[error]   |                        expression expected but def found
[error] -- [E080] Syntax Error: /Users/meriamlachkar/perso/dotty/src/main/scala/Show.scala:5:2 
[error] 5 |  test
[error]   |  ^^^^
[error]   |  Expected a toplevel definition
[warn] -- [E129] Potential Issue Warning: /Users/meriamlachkar/perso/dotty/src/main/scala/Show.scala:3:22 
[warn] 3 |@main def main(): Unit =
[warn]   |                      ^
[warn]   |A pure expression does nothing in statement position; you may be omitting necessary parentheses
[warn] one warning found
[error] two errors found
[error] (Compile / compileIncremental) Compilation failed

Expectation

Fixing the import indentation fixes this error.
From reading the error message, it's not clear what causes the error.

[som-snytt]

Similar to #9515 where the error does not indicate where indentation was established.