All logging functions in `scala.reflect.macros.FrontEnds` don't work in implicit macros pattern

[tribbloid]

reproduction steps

Main example:

https://stackoverflow.com/questions/67328769/in-scala-2-13-how-to-log-information-warning-error-reliably-in-macro

using Scala 2.13.5, if you use any macro logging function in a macro, e.g.

class EmitMsg[T] {}

object EmitMsg {

  implicit def emit[A]: EmitMsg[A] = macro Macros.emit[A]

  final class Macros(val c: whitebox.Context) {

    def emit[A: c.WeakTypeTag]: c.Tree = {
      c.abort(c.enclosingPosition, "ERROR!")
    }
  }
}

The logging will only be triggered if the macro function (in this case EmitMsg.emit) was called directly, if it is called as part of an implicit macros pattern (https://docs.scala-lang.org/overviews/macros/implicits.html), it will be ignored. Namely, all error message degrades to "implicit not found" message, and all info & warning message won't be logged or displayed anywhere.

problem

Give the ubiquity of implicit macros pattern, this issue may seriously degrade the capability of macro system.

This issue is also blocking my PR for singleton-ops:

fthomas/singleton-ops#186

[som-snytt]

I think this duplicates #10946 where the feature request is for a dynamic error message customized by the macro.

This would hook into the standard implicitNotFound machinery. Per the linked overview:

A nice thing about implicit macros is that they seamlessly meld into the pre-existing infrastructure of implicit search.

[tribbloid]

@som-snytt Thanks a lot, I can't find in the post which mentioned macro anywhere (or compilet-time context warning/info). It may be possible to merge these 2 issues into one, as the "shading" of error message could happen twice in a row:

• type-mismatch error shading implicit not found error
• implicit not found error shading macro context error

[SethTisue]

It appears that (especially when considered in combination with #10946) some design thinking would be required to address this.

I wonder what Scala 3 does.