src/vs/workbench/services/textmodelResolver/common/textModelResolverService.ts/ResourceModelCollection/ensureResolvedModel
class ResourceModelCollection:	private ensureResolvedModel(model: ITextEditorModel, key: string): model is IResolvedTextEditorModel {
		if (isResolvedTextEditorModel(model)) {
			return true;
		}

		throw new Error(`Unable to resolve resource ${key}`);
	}