Mark type ascriptions added in ensureNoLocalRefs as inferred

# Conflicts:
#	compiler/src/dotty/tools/dotc/typer/RefineTypes.scala

Author: odersky

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -981,11 +981,13 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     }
 
     /** cast tree to `tp`, assuming no exception is raised, i.e the operation is pure */
-    def cast(tp: Type)(using Context): Tree = {
-      assert(tp.isValueType, i"bad cast: $tree.asInstanceOf[$tp]")
+    def cast(tp: Type)(using Context): Tree = cast(TypeTree(tp))
+
+    /** cast tree to `tp`, assuming no exception is raised, i.e the operation is pure */
+    def cast(tpt: TypeTree)(using Context): Tree =
+      assert(tpt.tpe.isValueType, i"bad cast: $tree.asInstanceOf[$tpt]")
       tree.select(if (ctx.erasedTypes) defn.Any_asInstanceOf else defn.Any_typeCast)
-        .appliedToType(tp)
-    }
+        .appliedToTypeTree(tpt)
 
     /** cast `tree` to `tp` (or its box/unbox/cast equivalent when after
      *  erasure and value and non-value types are mixed),

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

@@ -1058,13 +1058,14 @@ class Typer extends Namer
         cpy.Block(block)(stats, expr1) withType expr1.tpe // no assignType here because avoid is redundant
       case _ =>
         val target = pt.simplified
-        if tree.tpe <:< target then Typed(tree, TypeTree(pt.simplified))
+        val targetTpt = InferredTypeTree().withType(target)
+        if tree.tpe <:< target then Typed(tree, targetTpt)
         else
           // This case should not normally arise. It currently does arise in test cases
           // pos/t4080b.scala and pos/i7067.scala. In that case, a type ascription is wrong
           // and would not pass Ycheck. We have to use a cast instead. TODO: follow-up why
           // the cases arise and eliminate them, if possible.
-          tree.cast(target)
+          tree.cast(targetTpt)
     }
     def noLeaks(t: Tree): Boolean = escapingRefs(t, localSyms).isEmpty
     if (noLeaks(tree)) tree