Type Alias ServerMutator 

pub type ServerMutator = Box<dyn Fn(&mut dyn MutationSql, &Value) -> Result<(), MutationReject>>;

A server-side mutator: authoritative, run once, against the open write transaction. May read its own transaction’s uncommitted writes via MutationSql::query (read- dependent mutators see the current base, §4.1). An Err rejects the mutation.

Aliased Type

pub struct ServerMutator(/* private fields */);