fix a regrsesion in signature matching of derived ptr types

compiler/sigmatch.nim

@@ -1240,13 +1240,15 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
         if prev == nil: put(c, f, a)
         result = isGeneric
       else:
-        var aAsObject = roota.lastSon
-        if rootf.lastSon.kind in {tyAnd, tyOr}:
+        let fKind = rootf.lastSon.kind
+        if fKind in {tyAnd, tyOr}:
           result = typeRel(c, lastSon(f), a)
           if result != isNone: put(c, f, a)
           return
 
-        if rootf.lastSon.kind == tyRef and aAsObject.kind == tyRef:
+        var aAsObject = roota.lastSon
+
+        if fKind in {tyRef, tyPtr} and aAsObject.kind == fKind:
           aAsObject = aAsObject.base
 
         if aAsObject.kind == tyObject:

tests/generics/tptrinheritance.nim

@@ -0,0 +1,20 @@
+type NSPasteboardItem* = ptr object
+type NSPasteboard* = ptr object
+type NSArrayAbstract = ptr object {.inheritable.}
+type NSMutableArrayAbstract = ptr object of NSArrayAbstract
+type NSArray*[T] = ptr object of NSArrayAbstract
+type NSMutableArray*[T] = ptr object of NSArray[T]
+
+proc newMutableArrayAbstract*(): NSMutableArrayAbstract = discard
+
+template newMutableArray*(T: typedesc): NSMutableArray[T] =
+  cast[NSMutableArray[T]](newMutableArrayAbstract())
+
+proc writeObjects*(p: NSPasteboard, o: ptr NSArray[NSPasteboardItem]) = discard
+
+let a = newMutableArray NSPasteboardItem
+var x: NSMutableArray[NSPasteboardItem]
+var y: NSArray[NSPasteboardItem] = x
+
+writeObjects(nil, a)
+