Fix #10709: Add missing level check before inlining

[nicolasstucki]

If an a call to an inline method is within a quote, this call must not be inlined.

• Delay inlining within quotes.
• Disallow inline def within quotes. Same as inline def in inline def.
• Disable tests/run-staging/i3876-{d,e}.scala. This test requires inlining after Pickler to be able to inline the missing expression. This will be fixed by Expand non-transparent macros after Typer #9984 and it only affects scala.quoted.staging.run.

[liufengyun]

LGTM

[nicolasstucki]

Just to double-check. @liufengyun did you see the second commit while reviewing?

[liufengyun]

Just to double-check. @liufengyun did you see the second commit while reviewing?

Thanks. For tests/run-staging/i3876-e.scala, it is not obvious to me why inlineLambda is inlined after Pickler:

import scala.quoted._
import scala.quoted.staging._
object Test {
  def main(args: Array[String]): Unit = {
    given Toolbox = Toolbox.make(getClass.getClassLoader)

    def x(using Quotes): Expr[Int] = '{ println(); 3 }

    def f4(using Quotes): Expr[Int => Int] = '{
      inlineLambda
    }
    println(run(Expr.betaReduce('{$f4($x)})))
    println(withQuotes(Expr.betaReduce('{$f4($x)}).show))
  }

  transparent inline def inlineLambda: Int => Int = x => x + x
}

[nicolasstucki]

Indeed, it is not obvious.

why inlineLambda is inlined after Pickler

The issue is that it is not, but it should. This is only needed in scala.quoted.staging as it has a special compiler that starts after Pickler.

Previously we would evaluate '{$f4($x)} to '{ (x => x + x).apply({println(); 3}) }.

Now we evaluate '{$f4($x)} to '{ inlineLambda({println(); 3}) }. In this particular case the betaReduce operation would be a no-opp, but BetaReduce phase would reduce it later. If we were to use this value in a macro then the code inlineLambda({println(); 3}) would be inserted somewhere and then inline calls from it would be inlined by Typer. In i3876-e we do not pass again in typer after generating '{ inlineLambda({println(); 3}) } and therefore we do not get a chance to inline this call. #9984 will make it possible to inline after pickler. This phase can also be used in the special instance of the compiler used for scala.quoted.staging.run.

[liufengyun]

Thanks for the detailed explanation, it makes sense 👍

[nicolasstucki]

The downside of this PR is that it will temporarily break scala.quoted.staging.run that runs code with calls to inline methods.

[liufengyun]

The downside of this PR is that it will temporarily break scala.quoted.staging.run that runs code with calls to inline methods.

I don't think it matters much, as it's not as commonly used as macros and the fix is coming in RC1.

[nicolasstucki]

#10803 will fix scala.quoted.staging.run