src/vs/editor/contrib/snippet/snippetSession.ts/OneSnippet/getEnclosingRange
class OneSnippet:	getEnclosingRange(): Range | undefined {
		let result: Range | undefined;
		const model = this._editor.getModel();
		for (const decorationId of this._placeholderDecorations!.values()) {
			const placeholderRange = withNullAsUndefined(model.getDecorationRange(decorationId));
			if (!result) {
				result = placeholderRange;
			} else {
				result = result.plusRange(placeholderRange!);
			}
		}
		return result;
	}