adds more test cases

tests/generics/t21601.nim

@@ -0,0 +1,12 @@
+discard """
+  errormsg: "'typedesc' is not a concrete type"
+  line: 10
+"""
+
+# issue #21601
+type Person = object
+
+type Builder* = ref object of RootObj
+  class*: typedesc
+
+echo Builder(class: Person).repr

tests/generics/t24848.nim

@@ -1,8 +1,9 @@
 discard """
   errormsg: "'array[0..0, typedesc[R[system.int]]]' is not a concrete type"
-  line: 7
+  line: 8
 """
 
+# issue #24848
 type R[C] = ref object
   b: C