Make positions fit for meta

In particular:

 - get rid of envelope, it's too complicated and hides too many errors
 - check that everywhere in parsed trees the position range of a parent
   node contains the position ranges of its children.
 - check that all non-empty trees coming from parser have positions.

The commit contains lots of fixes to make these checks pass.
In particular, it changes the scheme how definitions are positioned.
Previously the position of a definition was the token range of the
name defined by it. That does obviously not work with the parent/children
invariant. Now, the position is the whole definition range, with the
point at the defined name (care is taken to not count backticks).
Namer is changed to still use the token range of defined name as the
position of the symbol.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/dotty/tools/dotc/typer/FrontEnd.scala b/src/dotty/tools/dotc/typer/FrontEnd.scala
index 6ca69ea45..e008430a7 100644
--- a/src/dotty/tools/dotc/typer/FrontEnd.scala
+++ b/src/dotty/tools/dotc/typer/FrontEnd.scala
@@ -7,6 +7,7 @@ import Contexts._
 import Symbols._
 import dotty.tools.dotc.parsing.JavaParsers.JavaParser
 import parsing.Parsers.Parser
+import config.Config
 import config.Printers.{typr, default}
 import util.Stats._
 import scala.util.control.NonFatal
@@ -34,6 +35,7 @@ class FrontEnd extends Phase {
       else new Parser(unit.source).parse()
     val printer = if (ctx.settings.Xprint.value.contains("parser")) default else typr
     printer.println("parsed:\n" + unit.untpdTree.show)
+    if (Config.checkPositions) unit.untpdTree.checkPos(complete = true)
   }
 
   def enterSyms(implicit ctx: Context) = monitor("indexing") {