More detailed debugging

Author: Blaisorblade

compiler/src/dotty/tools/dotc/transform/patmat/Space.scala

@@ -703,18 +703,31 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       parent.argInfos.nonEmpty && minTypeMap.apply(parent) <:< maxTypeMap.apply(tp2)
     }
 
-    if (protoTp1 <:< tp2) {
-      if (isFullyDefined(protoTp1, force)) protoTp1
-      else instUndetMap.apply(protoTp1)
+    val sub1 = isSubType(protoTp1, tp2)
+    debug.println(s"Space.instantiate: protoTp1($protoTp1 ${protoTp1.show}) <:< tp2($tp2 ${tp2.show}) = $sub1")
+    def determine(comparer: Type, protoTp1: Type): Type = {
+      debug.println(i"Space.instantiate: isFullyDefined($comparer) = ...")
+      val determined = isFullyDefined(comparer, force)
+      debug.println(i"Space.instantiate: isFullyDefined($comparer) = $determined")
+      if (determined) protoTp1
+      else {
+        val res = instUndetMap.apply(protoTp1)
+        debug.println(i"Space.instantiate: instUndetMap.apply(protoTp1($protoTp1)) -> $res")
+        res
+      }
+    }
+
+    if (sub1) {
+      determine(protoTp1, protoTp1)
     }
     else {
       val protoTp2 = maxTypeMap.apply(tp2)
-      if (protoTp1 <:< protoTp2 || parentQualify) {
-        if (isFullyDefined(AndType(protoTp1, protoTp2), force)) protoTp1
-        else instUndetMap.apply(protoTp1)
+      val sub2 = protoTp1 <:< protoTp2
+      debug.println(s"Space.instantiate: protoTp1($protoTp1 ${protoTp1.show}) <:< protoTp2($protoTp2 ${protoTp2.show}) = $sub2")
+      if (sub2 || parentQualify) {
+        determine(AndType(protoTp1, protoTp2), protoTp1)
       }
       else {
-        debug.println(s"$protoTp1 <:< $protoTp2 = false")
         NoType
       }
     }