Move TyperState.instType

Author: Aleksander Boruch-Gruszecki

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

@@ -53,6 +53,19 @@ trait ConstraintHandling {
    */
   protected var comparedTypeLambdas: Set[TypeLambda] = Set.empty
 
+  /** Gives for each instantiated type var that does not yet have its `inst` field
+    *  set, the instance value stored in the constraint. Storing instances in constraints
+    *  is done only in a temporary way for contexts that may be retracted
+    *  without also retracting the type var as a whole.
+    */
+  def instType(tvar: TypeVar): Type = constraint.entry(tvar.origin) match {
+    case _: TypeBounds => NoType
+    case tp: TypeParamRef =>
+      var tvar1 = constraint.typeVarOfParam(tp)
+      if (tvar1.exists) tvar1 else tp
+    case tp => tp
+  }
+
   protected def addOneBound(param: TypeParamRef, bound: Type, isUpper: Boolean): Boolean =
     !constraint.contains(param) || {
       def occursIn(bound: Type): Boolean = {
@@ -140,6 +153,7 @@ trait ConstraintHandling {
         val lo1 = constraint.nonParamBounds(p1).lo
         val hi2 = constraint.nonParamBounds(p2).hi
         constr_println(i"adding $description down1 = $down1, up2 = $up2$location")
+        assert(constraint.contains(p2))
         constraint = constraint.addLess(p1, p2)
         down1.forall(addOneBound(_, hi2, isUpper = true)) &&
         up2.forall(addOneBound(_, lo1, isUpper = false))

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

@@ -79,19 +79,6 @@ class TyperState(previous: TyperState /* | Null */) {
   def ownedVars: TypeVars = myOwnedVars
   def ownedVars_=(vs: TypeVars): Unit = myOwnedVars = vs
 
-  /** Gives for each instantiated type var that does not yet have its `inst` field
-   *  set, the instance value stored in the constraint. Storing instances in constraints
-   *  is done only in a temporary way for contexts that may be retracted
-   *  without also retracting the type var as a whole.
-   */
-  def instType(tvar: TypeVar)(implicit ctx: Context): Type = constraint.entry(tvar.origin) match {
-    case _: TypeBounds => NoType
-    case tp: TypeParamRef =>
-      var tvar1 = constraint.typeVarOfParam(tp)
-      if (tvar1.exists) tvar1 else tp
-    case tp => tp
-  }
-
   /** The closest ancestor of this typer state (including possibly this typer state itself)
    *  which is not yet committed, or which does not have a parent.
    */
@@ -173,7 +160,7 @@ class TyperState(previous: TyperState /* | Null */) {
     val toCollect = new mutable.ListBuffer[TypeLambda]
     constraint foreachTypeVar { tvar =>
       if (!tvar.inst.exists) {
-        val inst = instType(tvar)
+        val inst = ctx.typeComparer.instType(tvar)
         if (inst.exists && (tvar.owningState.get eq this)) {
           tvar.inst = inst
           val lam = tvar.origin.binder