Macro settings_codec 

macro_rules! settings_codec {
    () => { ... };
}

SettingsSchema::from_settings_value and SettingsSchema::to_settings_value compiled where the impl is, never in the crates that read the setting: for a large settings type whose crate is in the shared runtime or an engine, every app or pane reading it otherwise carries its own copy of serde’s decoder. Use it inside the impl SettingsSchema.