I have a constant object (const pronouns = {...} as const) that models pronouns in some languages. Its shape is basically { [L in Language]: Record, PronounInfo> }, with Language being a simple string literal union, PersonalForm being a language-specific subset of the template literal type TheoreticalPersonalForm, and PronounInfo holding the actual pronoun info. Instead of listing the allowed/needed personal forms per language explicitly, I define it through the shape of pronouns itself, like this:

type PersonalForm = keyof ((typeof pronouns)[L])

The problem is, when I then try to access the PronounInfos for a particular PersonalForm elsewhere (in a function), TypeScript says Property 'direct' does not exist on type ("blabla" standing in for a huge type expression):

function mysteriously_failing(lang: L, pronoun_p_f: PersonalForm) {
    let pronoun = pronouns[lang][pronoun_p_f].direct
                                               // ^ error here
}

Playground (note the type names I use are slightly different than in the example).

Why doesn't this work, what I can do apart from casting as PronounInfo?