Avoid creating BindDefinedType symbols

Author: odersky

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

@@ -443,9 +443,16 @@ class TreePickler(pickler: TastyPickler) {
           bindings.foreach(preRegister)
           withLength { pickleTree(call); pickleTree(expansion); bindings.foreach(pickleTree) }
         case Bind(name, body) =>
-          registerDef(tree.symbol)
+          val sym = tree.symbol
+          // If name is a type wildcard, symbol was removed by Typer#indexPattern.
+          // Use the type(-bounds) of the body instead as type of the Bind
+          if (sym.exists) registerDef(sym) else assert(name == tpnme.WILDCARD)
           writeByte(BIND)
-          withLength { pickleName(name); pickleType(tree.symbol.info); pickleTree(body) }
+          withLength {
+            pickleName(name)
+            pickleType(if (sym.exists) sym.info else body.tpe)
+            pickleTree(body)
+          }
         case Alternative(alts) =>
           writeByte(ALTERNATIVE)
           withLength { alts.foreach(pickleTree) }

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

@@ -1032,7 +1032,9 @@ class TreeUnpickler(reader: TastyReader,
               val sym = symAtAddr.getOrElse(start, forkAt(start).createSymbol())
               readName()
               readType()
-              Bind(sym, readTerm())
+              val body = readTerm()
+              if (sym.name == tpnme.WILDCARD) untpd.Bind(sym.name, body).withType(body.tpe)
+              else Bind(sym, body)
             case ALTERNATIVE =>
               Alternative(until(end)(readTerm()))
             case UNAPPLY =>
@@ -1187,7 +1189,7 @@ class TreeUnpickler(reader: TastyReader,
   class OwnerTree(val addr: Addr, tag: Int, reader: TreeReader, val end: Addr) {
 
     private var myChildren: List[OwnerTree] = null
-    
+
     /** All definitions that have the definition at `addr` as closest enclosing definition */
     def children: List[OwnerTree] = {
       if (myChildren == null) myChildren = {

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

@@ -1252,7 +1252,7 @@ class Typer extends Namer
     assignType(cpy.ByNameTypeTree(tree)(result1), result1)
   }
 
-  def typedTypeBoundsTree(tree: untpd.TypeBoundsTree)(implicit ctx: Context): TypeBoundsTree = track("typedTypeBoundsTree") {
+  def typedTypeBoundsTree(tree: untpd.TypeBoundsTree)(implicit ctx: Context): Tree = track("typedTypeBoundsTree") {
     val TypeBoundsTree(lo, hi) = tree
     val lo1 = typed(lo)
     val hi1 = typed(hi)
@@ -1267,8 +1267,7 @@ class Typer extends Namer
       // with an expected type in typedTyped. The type symbol is eliminated once
       // the enclosing pattern has been typechecked; see `indexPattern` in `typedCase`.
       val wildcardSym = ctx.newPatternBoundSymbol(tpnme.WILDCARD, tree1.tpe, tree.pos)
-      wildcardSym.setFlag(BindDefinedType) // can we get rid of this?
-      tree1.withType(wildcardSym.typeRef)
+      untpd.Bind(name, tree1).withType(wildcardSym.typeRef)
     }
     else tree1
   }