fixes ilegal recursion (#22105)

compiler/semobjconstr.nim

@@ -376,7 +376,9 @@ proc semConstructTypeAux(c: PContext,
     if status in {initPartial, initNone, initUnknown}:
       discard collectMissingFields(c, t.n, constrCtx, result.defaults)
     let base = t[0]
-    if base == nil: break
+    if base == nil or base.id == t.id or 
+      base.kind in { tyRef, tyPtr } and base[0].id == t.id: 
+        break
     t = skipTypes(base, skipPtrs)
     if t.kind != tyObject:
       # XXX: This is not supposed to happen, but apparently

tests/objects/tillegal_recursion2.nim

@@ -0,0 +1,6 @@
+discard """
+  errormsg: "Cannot inherit from: 'Foo'"
+  line: 6
+"""
+type
+  Foo = object of Foo

tests/objects/tillegal_recursion3.nim

@@ -0,0 +1,6 @@
+discard """
+  errormsg: "Cannot inherit from: 'Foo'"
+  line: 6
+"""
+type
+  Foo = object of ref Foo