fixes #7601, array construction of ptr generics (#7671)

* fixes #7601, array construction of ptr generics

* add more test

tests/array/tarraycons_ptr_generic2.nim

@@ -0,0 +1,17 @@
+discard """
+  file: "tarraycons_ptr_generic2.nim"
+  line: 17
+  errormsg: "type mismatch: got <ptr Hard[system.string]> but expected 'Book[system.string]'"
+"""
+
+type
+  Book[T] = ref object of RootObj
+    cover: T
+  Hard[T] = ref object of Book[T]
+  Soft[T] = ref object of Book[T]
+
+var bn = Book[string](cover: "none")
+var hs = Hard[string](cover: "skin")
+var bp = Soft[string](cover: "paper")
+
+let z = [bn, hs.addr, bp]