src/vs/editor/common/core/characterClassifier.ts/CharacterClassifier/set
class CharacterClassifier:	public set(charCode: number, _value: T): void {
		const value = toUint8(_value);

		if (charCode >= 0 && charCode < 256) {
			this._asciiMap[charCode] = value;
		} else {
			this._map.set(charCode, value);
		}
	}