src/vs/workbench/api/common/extHostLanguageFeatures.ts/DocumentHighlightAdapter/provideDocumentHighlights
class DocumentHighlightAdapter:	async provideDocumentHighlights(resource: URI, position: IPosition, token: CancellationToken): Promise<languages.DocumentHighlight[] | undefined> {

		const doc = this._documents.getDocument(resource);
		const pos = typeConvert.Position.to(position);

		const value = await this._provider.provideDocumentHighlights(doc, pos, token);
		if (Array.isArray(value)) {
			return value.map(typeConvert.DocumentHighlight.from);
		}
		return undefined;
	}