Macro op 

macro_rules! op {
    (@count) => { ... };
    (@count $head:tt $(, $tail:tt)*) => { ... };
    (@maybe $x:expr) => { ... };
    (@maybe) => { ... };
    (@name $Op:ident, $name:literal) => { ... };
    (@name $Op:ident) => { ... };
    (@infix $v:expr) => { ... };
    (@infix) => { ... };
    (@commutative $v:expr) => { ... };
    (@commutative) => { ... };
    (@associative $v:expr) => { ... };
    (@associative) => { ... };
    (@complexity $v:expr) => { ... };
    (@complexity) => { ... };
    (
        $(#[$meta:meta])*
        $Op:ident for<$T:ident> { $($body:tt)* }
    ) => { ... };
    (
        $(#[$meta:meta])*
        $vis:vis $Op:ident for<$T:ident> {
            $(name: $name:literal,)?
            $(display: $display:expr,)?
            $(infix: $infix:expr,)?
            $(aliases: [$($alias:expr),* $(,)?],)?
            $(commutative: $commutative:expr,)?
            $(associative: $associative:expr,)?
            $(complexity: $complexity:expr,)?
            eval: |[$($eval_arg:pat_param),+ $(,)?]| $eval_body:block,
            partial: |[$($partial_arg:pat_param),+ $(,)?], $idx:pat_param| $partial_body:block $(,)?
        }
    ) => { ... };
    (
        $(#[$meta:meta])*
        $Op:ident for $t:ty { $($body:tt)* }
    ) => { ... };
    (
        $(#[$meta:meta])*
        $vis:vis $Op:ident for $t:ty {
            $(name: $name:literal,)?
            $(display: $display:expr,)?
            $(infix: $infix:expr,)?
            $(aliases: [$($alias:expr),* $(,)?],)?
            $(commutative: $commutative:expr,)?
            $(associative: $associative:expr,)?
            $(complexity: $complexity:expr,)?
            eval: |[$($eval_arg:pat_param),+ $(,)?]| $eval_body:block,
            partial: |[$($partial_arg:pat_param),+ $(,)?], $idx:pat_param| $partial_body:block $(,)?
        }
    ) => { ... };
}

Define an operator marker type implementing crate::traits::Operator + crate::traits::OpTag.

This is the same DSL used for builtins in operator_enum::builtin, but exported so downstream crates can define their own operators with identical syntax.