Can't figure out where goes wrong with this snippet... Any hint?

[LintaoAmons]

local append2 = postfix({
  trig = ".append2",
}, {
  d(1, function(_, parent)
    local matched = parent.snippet.env.POSTFIX_MATCH
    return sn(nil, {
      fmt("{} = append({}, {})", { t({ matched }), rep(1), i(1) }),
    })
  end),
})

[L3MON4D3]

Aaaah, fmt shouldn't be wrapped in a table, just fmt(...) instead of {fmt(...),} should do it

[LintaoAmons]

Thanks!