Codegen error for base type pointer access; missing pointer dereference

[haxscramper]

Following code

type
  Base = ref object of RootObj
    fld1: int

  Derived = ref object of Base
    fld2: string


block:
  proc newBase(val: var Base) =
    if val == nil: new(val)
    val.fld1 = 12

  proc newBase(): Base = newBase(result)

  proc newDerived(val: var Derived) =
    if val == nil: new(val)
    val.fld2 = "somefield"
    newBase Base(val)

  proc newDerived(): Derived = newDerived(result)

  echo newDerived()[]
  echo newBase()[]

Current Output

Results in C codegen error (type hashes removed for redability).

error: member reference base type 'tyObject_DerivedcolonObjectType *' (aka 'struct tyObject_DerivedcolonObjectType *') is not a structure or union
        T5_ = &val->Sup;

In particular, error is generated for the line T5_ = &val->Sup; and can be fixed by manually editing it to T5_ = &((*val)->Sup);.

Issue persists for all nim versions that I tried (via playground), my particular version is

$ nim -v
Nim Compiler Version 1.4.0 [Linux: amd64]
Compiled at 2020-10-16
Copyright (c) 2006-2020 by Andreas Rumpf

git hash: bdcd87afca238a0a7b2c70971827cf9172817b12
active boot switches: -d:release -d:danger

[timotheecour]

Can you edit the title to something less generic?