Give position to symbols when unpickling

Previously, unpickled symbols always had position NoCoord, now their
position is set based on the corresponding tree position. This does not
always match the position used when they were pickled so `testPickling`
currently fails, this is fixed in the subsequent commits of this PR.

Symbol#isDefinedInCurrentRun is broken by this commit and fixed in a
latter commit in this PR.

Author: smarter

compiler/src/dotty/tools/dotc/core/Symbols.scala

@@ -131,8 +131,8 @@ trait Symbols { this: Context =>
     newClassSymbol(owner, name, flags, completer, privateWithin, coord, assocFile)
   }
 
-  def newRefinedClassSymbol = newCompleteClassSymbol(
-    ctx.owner, tpnme.REFINE_CLASS, NonMember, parents = Nil)
+  def newRefinedClassSymbol(coord: Coord = NoCoord) =
+    newCompleteClassSymbol(ctx.owner, tpnme.REFINE_CLASS, NonMember, parents = Nil, coord = coord)
 
   /** Create a module symbol with associated module class
    *  from its non-info fields and a function producing the info
@@ -441,6 +441,7 @@ object Symbols {
 
     /** Does this symbol come from a currently compiled source file? */
     final def isDefinedInCurrentRun(implicit ctx: Context): Boolean = {
+      // FIXME: broken now now that symbols unpickled from TASTY have a position
       pos.exists && defRunId == ctx.runId
     }
 
@@ -563,8 +564,12 @@ object Symbols {
       }
     }
 
-    /** The position of this symbol, or NoPosition is symbol was not loaded
-     *  from source.
+    /** The position of this symbol, or NoPosition if the symbol was not loaded
+     *  from source or from TASTY. This is always a zero-extent position.
+     *
+     *  NOTE: If the symbol was not loaded from the current compilation unit,
+     *  the implicit conversion `sourcePos` will return the wrong result, careful!
+     *  TODO: Consider changing this method return type to `SourcePosition`.
      */
     def pos: Position = if (coord.isPosition) coord.toPosition else NoPosition
 

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -254,7 +254,8 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
             case TYPEARGtype =>
               TypeArgRef(readType(), readType().asInstanceOf[TypeRef], readNat())
             case BIND =>
-              val sym = ctx.newSymbol(ctx.owner, readName().toTypeName, BindDefinedType, readType())
+              val sym = ctx.newSymbol(ctx.owner, readName().toTypeName, BindDefinedType, readType(),
+                coord = coordAt(start))
               registerSym(start, sym)
               if (currentAddr != end) readType()
               TypeRef(NoPrefix, sym)
@@ -453,11 +454,14 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
             rootd.symbol
           case _ =>
             val completer = adjustIfModule(new Completer(ctx.owner, subReader(start, end)))
+
+            val coord = coordAt(start)
+
             if (isClass)
-              ctx.newClassSymbol(ctx.owner, name.asTypeName, flags, completer, privateWithin, coord = start.index)
+              ctx.newClassSymbol(ctx.owner, name.asTypeName, flags, completer, privateWithin, coord)
             else
-              ctx.newSymbol(ctx.owner, name, flags, completer, privateWithin, coord = start.index)
-        } // TODO set position somehow (but take care not to upset Symbol#isDefinedInCurrentRun)
+              ctx.newSymbol(ctx.owner, name, flags, completer, privateWithin, coord)
+        }
       sym.annotations = annots
       ctx.enter(sym)
       registerSym(start, sym)
@@ -985,7 +989,7 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
             case BIND =>
               val name = readName()
               val info = readType()
-              val sym = ctx.newSymbol(ctx.owner, name, EmptyFlags, info)
+              val sym = ctx.newSymbol(ctx.owner, name, EmptyFlags, info, coord = coordAt(start))
               registerSym(start, sym)
               Bind(sym, readTerm())
             case ALTERNATIVE =>
@@ -1001,7 +1005,7 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
               val argPats = until(end)(readTerm())
               UnApply(fn, implicitArgs, argPats, patType)
             case REFINEDtpt =>
-              val refineCls = ctx.newRefinedClassSymbol
+              val refineCls = ctx.newRefinedClassSymbol(coordAt(start))
               typeAtAddr(start) = refineCls.typeRef
               val parent = readTpt()
               val refinements = readStats(refineCls, end)(localContext(refineCls))
@@ -1077,21 +1081,32 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
 
 // ------ Setting positions ------------------------------------------------
 
-    /** Set position of `tree` at given `addr`. */
-    def setPos[T <: untpd.Tree](addr: Addr, tree: T)(implicit ctx: Context): tree.type =
+    /** Pickled position for `addr`. */
+    def posAt(addr: Addr)(implicit ctx: Context): Position =
       if (ctx.mode.is(Mode.ReadPositions)) {
         posUnpicklerOpt match {
           case Some(posUnpickler) =>
-            //println(i"setPos $tree / ${tree.getClass} at $addr to ${posUnpickler.posAt(addr)}")
-            val pos = posUnpickler.posAt(addr)
-            if (pos.exists) tree.setPosUnchecked(pos)
-            tree
+            posUnpickler.posAt(addr)
           case _  =>
-            //println(i"no pos $tree")
-            tree
+            NoPosition
         }
-      }
-      else tree
+      } else NoPosition
+
+    /** Coordinate for the symbol at `addr`. */
+    def coordAt(addr: Addr)(implicit ctx: Context): Coord = {
+      val pos = posAt(addr)
+      if (pos.exists)
+        positionCoord(pos)
+      else
+        indexCoord(addr.index)
+    }
+
+    /** Set position of `tree` at given `addr`. */
+    def setPos[T <: untpd.Tree](addr: Addr, tree: T)(implicit ctx: Context): tree.type = {
+      val pos = posAt(addr)
+      if (pos.exists) tree.setPosUnchecked(pos)
+      tree
+    }
   }
 
   class LazyReader[T <: AnyRef](reader: TreeReader, op: TreeReader => Context => T) extends Trees.Lazy[T] {

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -759,7 +759,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     args match {
       case ValDef(_, _, _) :: _ =>
         typedDependent(args.asInstanceOf[List[ValDef]])(
-          ctx.fresh.setOwner(ctx.newRefinedClassSymbol).setNewScope)
+          ctx.fresh.setOwner(ctx.newRefinedClassSymbol(tree.pos)).setNewScope)
       case _ =>
         typed(cpy.AppliedTypeTree(tree)(untpd.TypeTree(funCls.typeRef), args :+ body), pt)
     }