list [foo(bar=1)]
 key   6:6        ^             
 key   6:9         ^-^          foo
 key  10:13            ^-^      bar
 num  14:15                ^    1
 val  14:15                ^    1
pair  10:15            ^---^    bar=1
 grp  10:15            ^---^    bar=1
 val  10:15            ^---^    bar=1
pair   6:15        ^-------^    foo(bar=1
 grp   6:15        ^-------^    foo(bar=1
pair   6:15        ^-------^    foo(bar=1
msg         :list [foo(bar=1)]
format      :list [#)]
[
    {
        "foo": [
            {
                "bar": 1
            }
        ]
    }
]