use quote::quote;
use proc_macro2::TokenStream;
use syn::{Data, DeriveInput, parse_quote};
pub fn debug_derive(ast: DeriveInput) -> proc_macro::TokenStream {
let name_str = ast.ident.to_string();
let implementation = implementation::derive(&name_str, &ast.data);
let name = &ast.ident;
let mut generics = ast.generics.clone();
let (impl_generics, ty_generics, where_clause) = {
let wh = generics.make_where_clause();
for t in ast.generics.type_params() {
let name = &t.ident;
wh.predicates.push(parse_quote!{ #name : core::fmt::Debug });
}
generics.split_for_impl()
};
let gen = quote!{
impl #impl_generics core::fmt::Debug for #name #ty_generics #where_clause {
fn fmt(&self, fmt: &mut core::fmt::Formatter) -> core::fmt::Result {
#implementation
}
}
};
gen.into()
}
#[cfg(not(feature = "std"))]
mod implementation {
use super::*;
pub fn derive(_name_str: &str, _data: &Data) -> TokenStream {
quote! {
fmt.write_str("<wasm:stripped>")
}
}
}
#[cfg(feature = "std")]
mod implementation {
use super::*;
use proc_macro2::Span;
use syn::{Ident, Index, token::SelfValue};
pub fn derive(name_str: &str, data: &Data) -> TokenStream {
match *data {
Data::Struct(ref s) => derive_struct(&name_str, &s.fields),
Data::Union(ref u) => derive_fields(&name_str, Fields::new(u.fields.named.iter(), None)),
Data::Enum(ref e) => derive_enum(&name_str, &e),
}
}
enum Fields {
Indexed {
indices: Vec<Index>,
},
Unnamed {
vars: Vec<Ident>,
},
Named {
names: Vec<Ident>,
this: Option<SelfValue>,
},
}
impl Fields {
fn new<'a>(fields: impl Iterator<Item=&'a syn::Field>, this: Option<SelfValue>) -> Self {
let mut indices = vec![];
let mut names = vec![];
for (i, f) in fields.enumerate() {
if let Some(ident) = f.ident.clone() {
names.push(ident);
} else {
indices.push(Index::from(i));
}
}
if names.is_empty() {
Self::Indexed {
indices,
}
} else {
Self::Named {
names,
this,
}
}
}
}
fn derive_fields<'a>(
name_str: &str,
fields: Fields,
) -> TokenStream {
match fields {
Fields::Named { names, this } => {
let names_str: Vec<_> = names.iter()
.map(|x| x.to_string())
.collect();
let fields = match this {
None => quote! { #( .field(#names_str, #names) )* },
Some(this) => quote! { #( .field(#names_str, &#this.#names) )* },
};
quote! {
fmt.debug_struct(#name_str)
#fields
.finish()
}
},
Fields::Indexed { indices } => {
quote! {
fmt.debug_tuple(#name_str)
#( .field(&self.#indices) )*
.finish()
}
},
Fields::Unnamed { vars } => {
quote! {
fmt.debug_tuple(#name_str)
#( .field(#vars) )*
.finish()
}
},
}
}
fn derive_enum(
name: &str,
e: &syn::DataEnum,
) -> TokenStream {
let v = e.variants
.iter()
.map(|v| {
let name = format!("{}::{}", name, v.ident);
let ident = &v.ident;
match v.fields {
syn::Fields::Named(ref f) => {
let names: Vec<_> = f.named.iter().flat_map(|f| f.ident.clone()).collect();
let fields_impl = derive_fields(&name, Fields::Named {
names: names.clone(),
this: None,
});
(ident, (quote!{ { #( ref #names ),* } }, fields_impl))
},
syn::Fields::Unnamed(ref f) => {
let names = f.unnamed.iter()
.enumerate()
.map(|(id, _)| Ident::new(&format!("a{}", id), Span::call_site()))
.collect::<Vec<_>>();
let fields_impl = derive_fields(&name, Fields::Unnamed { vars: names.clone() });
(ident, (quote! { ( #( ref #names ),* ) }, fields_impl))
},
syn::Fields::Unit => {
let fields_impl = derive_fields(&name, Fields::Indexed { indices: vec![] });
(ident, (quote! { }, fields_impl))
},
}
});
type Vecs<A, B> = (Vec<A>, Vec<B>);
let (variants, others): Vecs<_, _> = v.unzip();
let (match_fields, variants_impl): Vecs<_, _> = others.into_iter().unzip();
quote! {
match self {
#( Self::#variants #match_fields => #variants_impl, )*
_ => Ok(()),
}
}
}
fn derive_struct(
name_str: &str,
fields: &syn::Fields,
) -> TokenStream {
match *fields {
syn::Fields::Named(ref f) => derive_fields(
name_str,
Fields::new(f.named.iter(), Some(syn::Token!(self)(Span::call_site()))),
),
syn::Fields::Unnamed(ref f) => derive_fields(
name_str,
Fields::new(f.unnamed.iter(), None),
),
syn::Fields::Unit => derive_fields(
name_str,
Fields::Indexed { indices: vec![] },
),
}
}
}