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//! Procedural macro support crate for the `topo` crate.

#![deny(missing_docs)]

extern crate proc_macro;
use proc_macro::TokenStream;

/// Transforms a function declaration into a topologically-nested function which, when called,
/// attaches its call subtopology to that of its caller's (parent's).
#[proc_macro_attribute]
pub fn nested(_attrs: TokenStream, input: TokenStream) -> TokenStream {
    let mut input_fn: syn::ItemFn = syn::parse_macro_input!(input);
    let inner_block = input_fn.block;

    input_fn.block = syn::parse_quote! {{ topo::call(|| #inner_block) }};

    quote::quote!(#[track_caller] #input_fn).into()
}