Syn-Helpers

Framework for building derive proc macros over structures (struct and enum).

Handles: - Getting expressions referencing fields - Building patterns for enums - Using the same logic for deriving over a enum or struct - Error handling and generating compile_error output - Generics on trait and structure (including conflict rectification)

This crate extends (and re-exports) the excellent syn and quote

Example

Evaluate do_thing function on every field (expect those with the #[ignore] attribute)

```rust use synhelpers::{ syn::{parsequote, DeriveInput, GenericParam, Ident, Stmt}, procmacro2::Span, quote, derivetrait, FieldMut, HasAttributes, Trait, TraitItem, TypeOfSelf, Constructable, };

let mytrait = Trait { name: parsequote!(::mycrate::MyTrait), genericparameters: None, items: vec![TraitItem::newmethod( Ident::new("methodone", Span::callsite()), None, TypeOfSelf::Reference, Vec::default(), None, |mut item| { item.mapconstructable(|mut constructable| { Ok(constructable .getfieldsmut() .fieldsiteratormut() .flatmap(|mut field| -> Option { if field .getattributes() .iter() .any(|attr| attr.path.isident("ignore")) { None } else { let reference = field.getreference(); Some(parsequote!(dothing(#reference);)) } }) .collect()) }) }, )], };

let r#struct: DeriveInput = parse_quote! { struct X { a: String, b: i32 } };

let stream = derivetrait(r#struct, mytrait);

asserteq!( stream.tostring(), quote! { #[automaticallyderived] impl ::mycrate::MyTrait for X { fn methodone(&self) { let X { a: ref _0, b: ref _1 } = self; dothing(0); dothing(1); } } }.tostring() ) ```

Used in:

• derive-partial-eq-extras
• derive-debug-extras

Design work in progress