TokRepr

Turn an instance into a Rust [TokenStream] that represents the instance.

This crate provides the [TokRepr] trait which turns an instance into Rust code that when called, produce an expression that evaluates to the same instance. This can be useful for code generation in procedural macros.

Use-Case

This trait is primarily meant to assist with the creation of procedural macros. It can be useful if the macro needs to output an instance of a complex data structure. Without if, writing the token stream manually, or with the quote! trait can be a burden.

How it works

The trait is implemented for Rust primitives and most data types from the standard library. It uses proc_macro2 and quote.

For user-defined types, the trait can be implemented manually or automatically with the derive macro. See the macro documentation for configuration options.

Limitations

This trait generates code. Like all procedural macros, the generated code is unhygienic. Implementers of TokRepr need to pay attention to the scope of identifiers. The derive macro assumes that the struct or enum is in scope at the macro call site.

See also

The uneval crate provides a similar feature but leverages serde for serialization, which has the advantage of being widely implemented for data structure types. It does not provide a way to customize the codegen of a type.