Scala 3 Inspection Macro

This is an implementation of inspection macros in Scala 3, which rewrites the AST to insert logging statements.

There's already an implementation for Scala 2 but Scala 3 macros are different enough that they must be re-implemented from scratch.

Other macro example projects are mostly concerned with types rather than rewriting trees, so this is hopefully breaking new territory for Scala 3.

Decorate If

InspectionMacros.decorateIfs(dif => logger.debug(s"${dif.code} = ${dif.result}")) {
  if (System.currentTimeMillis() - 1 < 0) {
    println("decorateIfs: if block")
  } else if (System.getProperty("derp") != null) {
    println("decorateIfs: if else block")
  } else {
    println("decorateIfs: else block")
  }
}

will stick block of logger.debug into each branch, so the end result is:

if (java.lang.System.currentTimeMillis().-(1).<(0)) {
  output$proxy2.apply(example.BranchInspection.apply("java.lang.System.currentTimeMillis().-(1).<(0)", true))
  scala.Predef.println("decorateIfs: if block")
} else {
  output$proxy2.apply(example.BranchInspection.apply("java.lang.System.currentTimeMillis().-(1).<(0)", false))
  if (java.lang.System.getProperty("derp").!=(null)) {
    output$proxy2.apply(example.BranchInspection.apply("java.lang.System.getProperty(\"derp\").!=(null)", true))
    scala.Predef.println("decorateIfs: if else block")
  } else {
    output$proxy2.apply(example.BranchInspection.apply("java.lang.System.getProperty(\"derp\").!=(null)", false))
    scala.Predef.println("decorateIfs: else block")
  }
}

Decorate Match

decorateMatch inserts statements into each case, so that:

val string = java.time.Instant.now().toString
InspectionMacros.decorateMatch(dm => logger.debug(s"${dm.code} = ${dm.result}")) {
  string match {
    case s if s.startsWith("20") =>
      println("this example is still valid")
    case _ =>
      println("oh dear")
  }
}

produces the following code:

string match {
  case s if s.startsWith("20") =>
    {
      output$proxy2.apply(example.BranchInspection.apply("case s if s.startsWith(\"20\")", true))
      scala.Predef.println("this example is still valid")
    }
  case _ =>
    {
      output$proxy2.apply(example.BranchInspection.apply("case _", true))
      scala.Predef.println("oh dear")
    }
}

and the given output:

62   [run-main-5] DEBUG example.Main - case s if s.startsWith("20") = true

Dump Expression

val dr: ExprInspection[Int] = InspectionMacros.dumpExpression(1 + 1)
println(s"result: ${dr.code} = ${dr.value}")

produces:

result: 1 + 1 = 2