Problem with templates in type definitions

[vegansk]

The code:

template seqType(t: typedesc): typedesc =
  when t is int:
    seq[int]
  else:
    seq[string]

proc mkSeq[T: int|string](v: T): seqType(T) =
  result = newSeq[T](1)
  result[0] = v

echo mkSeq("a")
# Fails here
echo mkSeq(1)

fails to compile with the message:

typetest.nim(13, 11) template/generic instantiation from here
typetest.nim(8, 21) Error: type mismatch: got (seq[int]) but expected 'seq[string]'

[vegansk]

The problem is that t is tyTypeDesc(tyGenericParam T) here: https://github.com/nim-lang/Nim/blob/devel/compiler/vm.nim#L1083. That's why VM chooses else branch