Theme.getUrls type annotation is misleading

[nex3]

The type annotation for Theme.getUrls() is:

typedoc/src/lib/output/theme.ts

Line 44 in d4098e8

abstract getUrls(project: ProjectReflection): UrlMapping[];

and UrlMapping is:

typedoc/src/lib/output/models/UrlMapping.ts

Line 4 in d4098e8

export class UrlMapping<Model = any> {

This implies that a theme can return a UrlContext with any model value. However, this condition:

typedoc/src/lib/output/renderer.ts

Lines 303 to 307 in d4098e8

	if (page.model instanceof Reflection) {
	page.contents = this.theme!.render(page, template);
	} else {
	throw new Error("Should be unreachable");
	}

throws an error if the model isn't specifically a Reflection. It seems like either getUrls() should specifically return a UrlMapping<Reflection>, or Theme should be made generic over the model type.

(My use-case here is adding a generated file to my theme that isn't based on a model at all, but rather on some side-loaded data, so I'd prefer the latter, but I can work around the former.)

[Gerrit0]

Eventually, I'd like to make the current return type of getUrls truly valid, IIRC it currently uses any due to some variance issues that make UrlMapping<Reflection> non-assignable to UrlMapping<DeclarationReflection>... I've been having too much fun at work lately to want to work much on code stuff on the weekend.

[Gerrit0]

Work on #247 will eventually enable that ^ for now, fixed