Mixins with "block", when nested, result in invalid generated Go code

[servernoj]

My mixin is defined as

mixin parent
  block

and then I use them as

+parent
  +parent
    .content

I expect the generated function to produce (in Pug/Jade sense)

.content

but CLI tool produces Go source that cannot compile (only the function shown for brevity):

func Jade_l(wr io.Writer) {
  buffer := &WriterAsBuffer{wr}
  {
    {
      buffer := new(bytes.Buffer)
      {
        var block []byte
        {
          buffer := new(bytes.Buffer)
          buffer.WriteString(l__0)

          block = buffer.Bytes()
        }

        buffer.Write(block)
      }

      block = buffer.Bytes()
    }

    buffer.Write(block)
  }
}

specifically, it needs one more declaration of block, like this

func Jade_l(wr io.Writer) {
  buffer := &WriterAsBuffer{wr}
  {
    var block []byte // <-- THIS ONE
    {
      buffer := new(bytes.Buffer)
      {
...

My actual code doesn't nest the mixin in itself, but the case above illustrates the problem with a minimal level of unnecessary details.

[servernoj]

After some more digging, it looks like the generated code is OK up to the point when it is optimized, and one of the needed declarations of the block variable is removed. I believe it is happening here:

jade/cmd/jade/go_ast_unbk.go

Line 21 in 2a11849

dsSl = append(dsSl, xds)

I don't understand the entirety of the logic, but commenting out that statement fixes the problem.