src/vs/workbench/services/themes/common/themeCompatibility.ts/convertSettings
export function convertSettings(oldSettings: ITextMateThemingRule[], result: { textMateRules: ITextMateThemingRule[]; colors: IColorMap }): void {
	for (const rule of oldSettings) {
		result.textMateRules.push(rule);
		if (!rule.scope) {
			const settings = rule.settings;
			if (!settings) {
				rule.settings = {};
			} else {
				for (const settingKey in settings) {
					const key = <keyof typeof settings>settingKey;
					const mappings = settingToColorIdMapping[key];
					if (mappings) {
						const colorHex = settings[key];
						if (typeof colorHex === 'string') {
							const color = Color.fromHex(colorHex);
							for (const colorId of mappings) {
								result.colors[colorId] = color;
							}
						}
					}
					if (key !== 'foreground' && key !== 'background' && key !== 'fontStyle') {
						delete settings[key];
					}
				}
			}
		}
	}
}