proc formatValue(result: var string; x: Any; spec: string) {.
    ...raises: [ValueError, Exception], tags: [RootEffect], forbids: [].}

proc formatValue(result: var string; x: bool; spec: string) {.
    ...raises: [ValueError], tags: [], forbids: [].}

proc formatValue(result: var string; x: char; spec: string) {.
    ...raises: [ValueError], tags: [], forbids: [].}

proc formatValue(result: var string; x: cstring; spec: string) {.
    ...raises: [ValueError], tags: [], forbids: [].}