src/vs/workbench/services/themes/common/colorThemeData.ts/readSemanticTokenRule
function readSemanticTokenRule(selectorString: string, settings: ISemanticTokenColorizationSetting | string | boolean | undefined): SemanticTokenRule | undefined {
	const selector = tokenClassificationRegistry.parseTokenSelector(selectorString);
	let style: TokenStyle | undefined;
	if (typeof settings === 'string') {
		style = TokenStyle.fromSettings(settings, undefined);
	} else if (isSemanticTokenColorizationSetting(settings)) {
		style = TokenStyle.fromSettings(settings.foreground, settings.fontStyle, settings.bold, settings.underline, settings.italic);
	}
	if (style) {
		return { selector, style };
	}
	return undefined;
}