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, 14 insertions, 2 deletions

diff --git a/src/dotty/tools/dotc/typer/Namer.scala b/src/dotty/tools/dotc/typer/Namer.scala
index 7a2348cd3..a0862ee38 100644
--- a/src/dotty/tools/dotc/typer/Namer.scala
+++ b/src/dotty/tools/dotc/typer/Namer.scala
@@ -273,6 +273,18 @@ class Namer { typer: Typer =>
     }
 
     val inSuperCall = if (ctx.mode is Mode.InSuperCall) InSuperCall else EmptyFlags
+
+    /** The position of the name defined by `tree`
+     *  This is a point position if tree is synthetic, a range position if it comes from source.
+     *  It might also be that tree does not have a position (for instance when synthesized by
+     *  a calling chain from `viewExists`), in that case the return position is NoPosition.
+     */
+    def namePos(tree: MemberDef) =
+      if (tree.pos.exists)
+        if (tree.mods.is(Synthetic)) Position(tree.pos.point, tree.pos.point)
+        else Position(tree.pos.point, tree.pos.point + tree.name.length, tree.pos.point)
+      else tree.pos
+
     tree match {
       case tree: TypeDef if tree.isClassDef =>
         val name = checkNoConflict(tree.name.encode).asTypeName
@@ -280,7 +292,7 @@ class Namer { typer: Typer =>
         val cls = recordSym(ctx.newClassSymbol(
           ctx.owner, name, flags | inSuperCall,
           cls => adjustIfModule(new ClassCompleter(cls, tree)(ctx), tree),
-          privateWithinClass(tree.mods), tree.pos, ctx.source.file), tree)
+          privateWithinClass(tree.mods), namePos(tree), ctx.source.file), tree)
         cls.completer.asInstanceOf[ClassCompleter].init()
         cls
       case tree: MemberDef =>
@@ -315,7 +327,7 @@ class Namer { typer: Typer =>
         recordSym(ctx.newSymbol(
           ctx.owner, name, flags | deferred | method | higherKinded | inSuperCall1,
           adjustIfModule(completer, tree),
-          privateWithinClass(tree.mods), tree.pos), tree)
+          privateWithinClass(tree.mods), namePos(tree)), tree)
       case tree: Import =>
         recordSym(ctx.newSymbol(
           ctx.owner, nme.IMPORT, Synthetic, new Completer(tree), NoSymbol, tree.pos), tree)