Creating a typed template variable from a generic directive

Issue

I would like to have names of parameters of a specific back end route available in my template when working with forms.
My idea is that by passing name of a route, e.g. GetReservations, to a custom directive, I would have access to parameter names of that route, e.g. date: string and time: string.

<form [backend-route]="'GetReservations'" #params>
  <label>Date</label>
  <input [name]="params.date" type="text"/>
  <label>Time</label>
  <input [name]="params.time" type="text"/>
</form>

Is it possible, using this or some other way, to have a template variable params with some desired type?
I haven't had much experience with Angular's template syntax, so I am not sure what is possible.

Solution

Answering my own question.
Instead of using an attribute directive, using a structural directive let's you declare template variables, and by using ngTemplateContextGuard, you can set their type.

<form *backendRoute="'GetReservations'; let params;">

@Directive({selector: '[backendRoute]'})
export class RouteDirective<TRouteName extends keyof Actions & keyof ActionResults> {

    @Input('backendRoute') typeToken: TRouteName | [TRouteName, (result: ActionResults[TRouteName]) => void];
    
    constructor(private tpl: TemplateRef<Context<Actions[TRouteName]>>,
                private vcr: ViewContainerRef) {
    }

    static ngTemplateContextGuard<TRouteName extends keyof Actions & keyof ActionResults>(dir: RouteDirective<TRouteName>,
                                     ctx: unknown): ctx is Context<Actions[TRouteName]> {
        return true
    };
}

// Not yet sure how this works
class Context<T> {
    $implicit!: T;
    subscribe!: T;

    constructor(value: T) {
        this.$implicit = value;
        this.subscribe = value;
    }
}

Answered By - Desperado