quote generates Rust code inside procedural macros using syntax-like interpolation. It offers a higher-level alternative to building generated code directly from raw token streams. section 8.3
Listing 8.9 Implementing the PrintName derive macro
#[proc_macro_derive(PrintName)]
pub fn print_name(input: TokenStream) -> TokenStream { #1
let input = parse_macro_input!(input as DeriveInput); #1
let generics = add_trait_bounds(input.generics); #2
let (impl_generics, type_generics, where_clause) = #3
generics.split_for_impl(); #3
let name = input.ident;
let expanded = quote! { #4
impl #impl_generics print_name::PrintName for #name #type_generics
#where_clause {
fn name() -> &'static str {
stringify!(#name) #5
}
}
};
TokenStream::from(expanded) #6
}
fn add_trait_bounds(mut generics: Generics) -> Generics {
for param in &mut generics.params {
if let GenericParam::Type(ref mut type_param) = *param {
type_param.bounds.push( #7
parse_quote!(print_name::PrintName) #7
); #7
}
}
generics
}
The PrintName derive macro interpolates generics and a type name into an implementation, then converts the generated code into a token stream. section 8.3
