Skip to content

Instantly share code, notes, and snippets.

What would you like to do?
Example of how to get source locations using scala macros
package slickdemo
import scala.reflect.macros.Context
import scala.language.experimental.macros
object Macros {
// scala.reflect.runtime.currentMirror
// universe.reify
/** Given a Tree, extracts the source code in its range. Assumes -Yrangepos scalac argument. */
def extractRange(t:Context#Tree):Option[String] = {
val pos = t.pos
val source = pos.source.content
if(pos.isRange) Option(new String(source.drop(pos.start).take(pos.end-pos.start))) else None
/** Gives the source code of an expression and the result of the expr in a tuple */
def sourceExpr[A](a: A): (String, A) = macro sourceExprImpl[A]
// previously based on log and logImpl
// from
def sourceExprImpl[A: c.WeakTypeTag](c: Context)(a: c.Expr[A]): c.Expr[(String, A)] = {
import c.universe._
val portion = extractRange(a.tree) getOrElse ""
val t2 = Select(Select(Ident(newTermName("scala")), newTermName("Tuple2")), newTermName("apply"))
// following advice from
//clone to avoid "Synthetic tree contains nonsynthetic tree" error under -Yrangepos
val adup: Tree = a.tree.duplicate
val tree = treeBuild.mkMethodCall(t2, List(Literal(Constant(portion)), adup))
val expr = c.Expr[(String, A)](tree)
def debugExpr[A](a: A): A = macro debugExprImpl[A]
def debugExprImpl[A: c.WeakTypeTag](c: Context)(a: c.Expr[A]): c.Expr[A] = {
import c.universe._
val portion = extractRange(a.tree) getOrElse ""
val adup: Tree = a.tree.duplicate
val expr = c.Expr[A](adup)
val t = Block(
ValDef(Modifiers(), newTermName("x"), TypeTree(), adup),
Apply(Select(Ident(newTermName("scala.Predef")), newTermName("println")), List(Ident(newTermName("x")))),
val const=c.Expr[String](Literal(Constant(portion)))
reify {
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment