fixes #3338

compiler/seminst.nim

@@ -239,14 +239,20 @@ proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
   pushInfoContext(info)
   var entry = TInstantiation.new
   entry.sym = result
-  newSeq(entry.concreteTypes, gp.len)
+  # we need to compare both the generic types and the concrete types:
+  # generic[void](), generic[int]()
+  # see ttypeor.nim test.
   var i = 0
+  newSeq(entry.concreteTypes, fn.typ.len+gp.len)
   for s in instantiateGenericParamList(c, gp, pt):
     addDecl(c, s)
     entry.concreteTypes[i] = s.typ
     inc i
   pushProcCon(c, result)
   instantiateProcType(c, pt, result, info)
+  for j in 0 .. result.typ.len-1:
+    entry.concreteTypes[i] = result.typ.sons[j]
+    inc i
   if tfTriggersCompileTime in result.typ.flags:
     incl(result.flags, sfCompileTime)
   n.sons[genericParamsPos] = ast.emptyNode