Macro lockbook_core::error_enum

macro_rules! error_enum {
    {enum $enum_name:ident {} } => { ... };
    {enum $enum_name:ident { $( $variant:ident ($type:ty) ),* }} => { ... };
    {enum $enum_name:ident { $( $variant:ident ($type:ty) ),*, }} => { ... };
}