src/vs/workbench/api/browser/mainThreadLanguageFeatures.ts/MainThreadLanguageFeatures/$registerDeclarationSupport
class MainThreadLanguageFeatures:	$registerDeclarationSupport(handle: number, selector: IDocumentFilterDto[]): void {
		this._registrations.set(handle, this._languageFeaturesService.declarationProvider.register(selector, <languages.DeclarationProvider>{
			provideDeclaration: (model, position, token) => {
				return this._proxy.$provideDeclaration(handle, model.uri, position, token).then(MainThreadLanguageFeatures._reviveLocationLinkDto);
			}
		}));
	}