marshal.load() regression?

[simonkrauter]

Example program:

import marshal
import streams
type MyType = ref object
  field*: string
var list: seq[MyType]
let stream = newFileStream("input_file.json", fmRead)
marshal.load(stream, list)

Gives compilation error:
Error: for a 'var' type a variable needs to be passed; but 'seq[MyType](list)' is immutable

Nim Compiler Version 0.18.1 [Linux: amd64]
Compiled at 2018-05-20
git hash: dedf0f3
active boot switches: -d:release

Works with Nim 0.18.0.

[sinkingsugar]

I'm having the same issue after pulling devel.

[Vindaar]

Since I was curious what the issue is, I tried to remove everything that's not needed from the example in the OP. It seems to come down to a generic var argument at the second argument + an inherited type.
To summarize:

type
  Stream* = ref StreamObj
  StreamObj* = object of RootObj

  InhStream* = ref InhStreamObj
  InhStreamObj* = object of Stream
    f: string

proc newInhStream*(f: string): InhStream =
  new(result)
  result.f = f

var val: int
let str = newInhStream("input_file.json")

block:
  # works:
  proc load[T](data: var T, s: Stream) =
    discard
  load(val, str)

block:
  # works
  proc load[T](s: Stream, data: T) =
    discard
  load(str, val)

block:
  # broken
  proc load[T](s: Stream, data: var T) =
    discard
  load(str, val)

edit: specifying T further in the broken case, makes it also work. I just don't quite understand which type breaks it. I allowed all types I could think and concat them via | and it still works. :S