An experiment of generating expression structures/enums in macros so they can be used directly in programs. If the properties of the struct are const-compatible the result from the macro can be used in a const context.

A trait ToExpr is defined in crates/core with implementation for std types. The signaure includes a function to_expr to print itself as tokens.

trait ToExpr {
    fn to_expr(&self) -> TokenStream;
}

There is a helper derive macro ToExpr defined in crates/macro that auto-implements the trait on structs and enums when defined.

1. Define a library of structs/enums you will create and use (see crates/example_lib)
2. Define a macro that creats object instances and returns their expressions (see crates/example_macro)
3. Use the macro and the library in your rust code (see crates/example_bin)

Run the demo via cargo run -p to-expr-example-bin.

This may prove useful where you want to use const expressions but generate the values for these in macros. Possible other usage would involve parsing config/json files via serde at compile-time.