Make -Xprompt work as desired under -Werror

[dwijnand]

Fixes #19713

[dwijnand]

Tested manually with bin/scalac -Werror -Xprompt tests/warn/i15661.scala.

[odersky]

I think I tried the same fix but it did not work. The problem is that the warning is emitted (sent to ConsoleReporter) only at the end of the compilation run.

Did you do an -Xprompt with abort and then check whether the stacktrace makes sense?

[odersky]

I think I tried the same fix but it did not work. The problem is that the warning is emitted (sent to ConsoleReporter) only at the end of the compilation run.

Did you do an -Xprompt with abort and then check whether the stacktrace makes sense?

[dwijnand]

I don't think I looked closely. I'll check again, sorry.

[dwijnand]

Yes, using the example, it makes sense:

-- [E092] Pattern Match Unchecked Warning: tests/warn/i15661.scala:5:19 --------
5 |    case Composite(l: List[Int], v: Int) => println(v) // warn: type test for List[Int] cannot be checked at runtime
  |                   ^
  |the type test for List[Int] cannot be checked at runtime because its type arguments can't be determined from List[T$1]
  |
  | longer explanation available when compiling with `-explain`

a)bort, s)tack, r)esume: s
java.lang.Throwable
	at dotty.tools.dotc.reporting.Reporter$.loop$1(Reporter.scala:48)
	at dotty.tools.dotc.reporting.Reporter$.displayPrompt(Reporter.scala:56)
	at dotty.tools.dotc.reporting.ConsoleReporter.doReport(ConsoleReporter.scala:24)
	at dotty.tools.dotc.reporting.Reporter.issueUnconfigured(Reporter.scala:171)
	at dotty.tools.dotc.reporting.Reporter.go$1(Reporter.scala:181)
	at dotty.tools.dotc.reporting.Reporter.issueIfNotSuppressed(Reporter.scala:195)
	at dotty.tools.dotc.reporting.Reporter.report(Reporter.scala:207)
	at dotty.tools.dotc.report$.issueWarning(report.scala:24)
	at dotty.tools.dotc.report$.uncheckedWarning(report.scala:33)
	at dotty.tools.dotc.transform.TypeTestsCasts$.checkTypePattern(TypeTestsCasts.scala:397)
	at dotty.tools.dotc.transform.TypeTestsCasts$.interceptWith$1(TypeTestsCasts.scala:367)
	at dotty.tools.dotc.transform.TypeTestsCasts$.interceptTypeApply(TypeTestsCasts.scala:383)
	at dotty.tools.dotc.transform.Erasure$Typer.typedTypeApply(Erasure.scala:811)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3137)

[odersky]

OK, not sure why I thought this did not work before. Let's try this!