src/vs/editor/common/services/unicodeTextModelHighlighter.ts/CodePointHighlighter/getCandidateCodePoints
class CodePointHighlighter:	public getCandidateCodePoints(): Set<number> | 'allNonBasicAscii' {
		if (this.options.nonBasicASCII) {
			return 'allNonBasicAscii';
		}

		const set = new Set<number>();

		if (this.options.invisibleCharacters) {
			for (const cp of strings.InvisibleCharacters.codePoints) {
				if (!isAllowedInvisibleCharacter(String.fromCodePoint(cp))) {
					set.add(cp);
				}
			}
		}

		if (this.options.ambiguousCharacters) {
			for (const cp of this.ambiguousCharacters.getConfusableCodePoints()) {
				set.add(cp);
			}
		}

		for (const cp of this.allowedCodePoints) {
			set.delete(cp);
		}

		return set;
	}