src/vs/editor/common/cursor/cursorTypeOperations.ts/TypeOperations/_findAutoClosingPairOpen
class TypeOperations:	private static _findAutoClosingPairOpen(config: CursorConfiguration, model: ITextModel, positions: Position[], ch: string): StandardAutoClosingPairConditional | null {
		const candidates = config.autoClosingPairs.autoClosingPairsOpenByEnd.get(ch);
		if (!candidates) {
			return null;
		}

		// Determine which auto-closing pair it is
		let result: StandardAutoClosingPairConditional | null = null;
		for (const candidate of candidates) {
			if (result === null || candidate.open.length > result.open.length) {
				let candidateIsMatch = true;
				for (const position of positions) {
					const relevantText = model.getValueInRange(new Range(position.lineNumber, position.column - candidate.open.length + 1, position.lineNumber, position.column));
					if (relevantText + ch !== candidate.open) {
						candidateIsMatch = false;
						break;
					}
				}

				if (candidateIsMatch) {
					result = candidate;
				}
			}
		}
		return result;
	}