src/vs/workbench/api/common/extHostLanguageFeatures.ts/EvaluatableExpressionAdapter/provideEvaluatableExpression
class EvaluatableExpressionAdapter:	public provideEvaluatableExpression(resource: URI, position: IPosition, token: CancellationToken): Promise<modes.EvaluatableExpression | undefined> {

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

		return asPromise(() => this._provider.provideEvaluatableExpression(doc, pos, token)).then(value => {
			if (value) {
				return typeConvert.EvaluatableExpression.from(value);
			}
			return undefined;
		});
	}