extensions/typescript-language-features/src/languageFeatures/diagnostics.ts/DiagnosticSettings/update
class DiagnosticSettings:	private update(language: DiagnosticLanguage, f: (x: LanguageDiagnosticSettings) => LanguageDiagnosticSettings): boolean {
		const currentSettings = this.get(language);
		const newSettings = f(currentSettings);
		this._languageSettings.set(language, newSettings);
		return !areLanguageDiagnosticSettingsEqual(currentSettings, newSettings);
	}