Input

Input Enum

Input is the unified proc macro input context — it wraps either a syn::DeriveInput or syn::Item and provides common accessors:

pub enum Input {
    Derive(syn::DeriveInput),
    Item(syn::Item),
}

impl Input {
    pub fn attrs(&self) -> &[syn::Attribute];
    pub fn ident(&self) -> &syn::Ident;
    pub fn generics(&self) -> &syn::Generics;
    pub fn vis(&self) -> &syn::Visibility;
}

Convert from standard syn types:

// From a derive macro input:
let input: zyn::Input = zyn::parse_input!(ts as syn::DeriveInput).into();

// From an attribute macro input:
let input: zyn::Input = zyn::parse_input!(ts as syn::Item).into();

// Parse directly:
let input: zyn::Input = zyn::parse!(token_stream)?;

Input implements Default, Parse, ToTokens, and syn::spanned::Spanned.

FromInput Trait

pub trait FromInput: Sized {
    fn from_input(input: &Input) -> zyn::Result<Self>;
}

Returns zyn::Result<Self> — an alias for Result<Self, Diagnostics>. Errors are accumulated as Diagnostics instead of short-circuiting.

Implemented by:

Threading Input Through zyn!

Inside zyn!, an input variable of type &zyn::Input is always in scope (defaults to a sentinel value). Shadow it before calling zyn! to pass real proc macro context:

#[proc_macro_derive(MyDerive)]
pub fn my_derive(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input: zyn::Input = zyn::parse_input!(ts as syn::DeriveInput).into();

    zyn::zyn! {
        @my_element(name = some_ident)
    }.into()
}

Every element’s render(&self, input: &Input) body also has input available directly — no need to pass it as a prop.