SI-7331 tb.parse returns unpositioned trees

This commit gets rid off code wrapping that was previously used by
toolbox to get into correct parsing mode. Instead combination of
templateStats/accept(EOF) is used. This is the same solution as the one
used in repl and built-in scriptRunner

This pull request doesn't attempt to generalize this approach in any
way and re-use it all over the place due to the caution of possible
accidental compatibility breakage. I plan to do it separately against
master.

Additionally there are a few more changes that make importers be aware
of positions and a test for that (via @jedesah).

src/compiler/scala/tools/reflect/ToolBoxFactory.scala

@@ -8,6 +8,7 @@ import scala.tools.nsc.typechecker.Modes
 import scala.tools.nsc.io.VirtualDirectory
 import scala.tools.nsc.interpreter.AbstractFileClassLoader
 import scala.tools.nsc.util.FreshNameCreator
+import scala.tools.nsc.ast.parser.Tokens.EOF
 import scala.reflect.internal.Flags._
 import scala.reflect.internal.util.{BatchSourceFile, NoSourceFile, NoFile}
 import java.lang.{Class => jClass}
@@ -273,14 +274,13 @@ abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>
       def parse(code: String): Tree = {
         val run = new Run
         reporter.reset()
-        val wrappedCode = "object wrapper {" + EOL + code + EOL + "}"
-        val file = new BatchSourceFile("<toolbox>", wrappedCode)
+        val file = new BatchSourceFile("<toolbox>", code)
         val unit = new CompilationUnit(file)
         phase = run.parserPhase
         val parser = new syntaxAnalyzer.UnitParser(unit)
-        val wrappedTree = parser.parse()
+        val parsed = parser.templateStats()
+        parser.accept(EOF)
         throwIfErrors()
-        val PackageDef(_, List(ModuleDef(_, _, Template(_, _, _ :: parsed)))) = wrappedTree
         parsed match {
           case expr :: Nil => expr
           case stats :+ expr => Block(stats, expr)
@@ -402,7 +402,7 @@ abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>
 
     def compile(tree: u.Tree): () => Any = {
       if (compiler.settings.verbose.value) println("importing "+tree)
-      var ctree: compiler.Tree = importer.importTree(tree)
+      val ctree: compiler.Tree = importer.importTree(tree)
 
       if (compiler.settings.verbose.value) println("compiling "+ctree)
       compiler.compile(ctree)

src/reflect/scala/reflect/internal/Importers.scala

@@ -443,7 +443,12 @@ trait Importers extends api.Importers { self: SymbolTable =>
         }
       })
       tryFixup()
-      mytree
+      // we have to be careful with position import as some shared trees
+      // like EmptyTree, emptyValDef don't support position assignment
+      if (tree.pos != NoPosition)
+        mytree.setPos(importPosition(tree.pos))
+      else
+        mytree
     }
 
     def importValDef(tree: from.ValDef): ValDef = importTree(tree).asInstanceOf[ValDef]

test/files/run/t7331a.check

@@ -0,0 +1,2 @@
+source-<toolbox>,line-1,offset=0
+2

test/files/run/t7331a.scala

@@ -0,0 +1,10 @@
+import scala.reflect.runtime.universe._
+import scala.reflect.runtime.{currentMirror => cm}
+import scala.tools.reflect.ToolBox
+
+object Test extends App {
+  val tb = cm.mkToolBox()
+  val tree = tb.parse("x")
+  println(tree.pos)
+  println(tree.pos.source.content.length)
+}

test/files/run/t7331b.check

@@ -0,0 +1,3 @@
+reflective compilation has failed: 
+
+')' expected but eof found.

test/files/run/t7331b.scala

@@ -0,0 +1,11 @@
+import scala.reflect.runtime.universe._
+import scala.reflect.runtime.{currentMirror => cm}
+import scala.tools.reflect.{ToolBox, ToolBoxError}
+
+object Test extends App {
+  val tb = cm.mkToolBox()
+  try tb.parse("f(x")
+  catch {
+    case ToolBoxError(msg, _) => println(msg)
+  }
+}

test/files/run/t7331c.check

@@ -0,0 +1,3 @@
+ClassDef(Modifiers(), newTypeName("C"), List(), Template(List(Select(Ident(scala), newTypeName("AnyRef"))), emptyValDef, List(DefDef(Modifiers(), nme.CONSTRUCTOR, List(), List(List()), TypeTree(), Block(List(Apply(Select(Super(This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR), List())), Literal(Constant(())))))))
+source-<toolbox>,line-1,offset=6
+NoPosition

test/files/run/t7331c.scala

@@ -0,0 +1,11 @@
+import scala.reflect.runtime.universe._
+import scala.reflect.runtime.{currentMirror => cm}
+import scala.tools.reflect.ToolBox
+
+object Test extends App {
+  val tb = cm.mkToolBox()
+  val tree = tb.parse("class C").asInstanceOf[ClassDef]
+  println(showRaw(tree))
+  println(tree.pos)
+  println(tree.impl.self.pos)
+}