Add rootPosition to Tasty reflect

Fixes the two existing source macros and allow the
implementation of Minitest fromContext macro.

Author: nicolasstucki

compiler/src/dotty/tools/dotc/quoted/QuoteDriver.scala

@@ -3,16 +3,14 @@ package dotty.tools.dotc.quoted
 import dotty.tools.dotc.ast.tpd
 import dotty.tools.dotc.Driver
 import dotty.tools.dotc.core.Contexts.{Context, ContextBase}
+import dotty.tools.dotc.tastyreflect.TastyImpl
 import dotty.tools.io.{AbstractFile, Directory, PlainDirectory, VirtualDirectory}
 import dotty.tools.repl.AbstractFileClassLoader
 
 import scala.quoted.{Expr, Type}
 import scala.quoted.Toolbox
-
 import java.net.URLClassLoader
 
-import dotty.tools.dotc.tastyreflect.TastyImpl
-
 class QuoteDriver extends Driver {
   import tpd._
 

compiler/src/dotty/tools/dotc/tastyreflect/TastyImpl.scala

@@ -9,7 +9,7 @@ import dotty.tools.dotc.core._
 import dotty.tools.dotc.core.quoted.PickledQuotes
 import dotty.tools.dotc.reporting.Reporter
 import dotty.tools.dotc.reporting.diagnostic.MessageContainer
-import dotty.tools.dotc.util.SourcePosition
+import dotty.tools.dotc.util.{Positions, SourcePosition}
 
 import scala.quoted
 import scala.reflect.ClassTag
@@ -45,6 +45,8 @@ class TastyImpl(val rootContext: Contexts.Context) extends scala.tasty.Tasty { s
     def source: java.nio.file.Path = ctx.compilationUnit.source.file.jpath
   }
 
+  def rootPosition: SourcePosition = SourcePosition(rootContext.source, Positions.NoPosition)
+
   // ===== Id =======================================================
 
   type Id = untpd.Ident

compiler/src/dotty/tools/dotc/transform/Splicer.scala

@@ -21,6 +21,7 @@ import dotty.tools.dotc.tastyreflect.TastyImpl
 
 import scala.util.control.NonFatal
 import dotty.tools.dotc.util.Positions.Position
+import dotty.tools.dotc.util.SourcePosition
 
 import scala.reflect.ClassTag
 
@@ -103,7 +104,9 @@ object Splicer {
       value.asInstanceOf[Object]
 
     protected def interpretTastyContext()(implicit env: Env): Object =
-      new TastyImpl(ctx)
+      new TastyImpl(ctx) {
+        override def rootPosition: SourcePosition = SourcePosition(ctx.source, pos)
+      }
 
     protected def interpretStaticMethodCall(fn: Tree, args: => List[Object])(implicit env: Env): Object = {
       val (clazz, instance) = loadModule(fn.symbol.owner)

library/src/scala/tasty/Tasty.scala

@@ -39,6 +39,9 @@ abstract class Tasty { tasty =>
 
   implicit def rootContext: Context
 
+  /** Root position of this tasty context. For macros it corresponds to the expansion site. */
+  def rootPosition: Position
+
   // ===== Id =======================================================
 
   type Id

tests/run-with-compiler/tasty-positioned.check

@@ -0,0 +1,4 @@
+foo 5
+foo 6
+foo 8
+foo 9

tests/run-with-compiler/tasty-positioned/quoted_1.scala

@@ -0,0 +1,19 @@
+import scala.quoted._
+
+import scala.tasty._
+
+class LineNumber(val value: Int) {
+  override def toString: String = value.toString
+}
+
+object LineNumber {
+
+  implicit transparent def line: LineNumber =
+    ~lineImpl(TopLevelSplice.tastyContext) // FIXME infer TopLevelSplice.tastyContext within top level ~
+
+  def lineImpl(implicit tasty: Tasty): Expr[LineNumber] = {
+    import tasty._
+    '(new LineNumber(~rootPosition.startLine.toExpr))
+  }
+
+}

tests/run/tasty-linenumber-2.check

@@ -13,8 +13,7 @@ object LineNumber {
 
   def lineImpl(x: Type[Unit])(implicit tasty: Tasty): Expr[LineNumber] = {
     import tasty._
-
-    '(new LineNumber(~x.toTasty.pos.startLine.toExpr))
+    '(new LineNumber(~rootPosition.startLine.toExpr))
   }
 
 }