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extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro2::{Span, TokenStream as TokenStream2};
use quote::quote;
use syn;
use syn::spanned::Spanned;
use syn::{parse_macro_input, DeriveInput, Ident, Lifetime, Type};
use synstructure::Structure;
#[proc_macro_derive(Yokeable)]
pub fn yokeable_derive(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
TokenStream::from(yokeable_derive_impl(&input))
}
fn yokeable_derive_impl(input: &DeriveInput) -> TokenStream2 {
let typarams = input.generics.type_params().count();
if typarams != 0 {
return syn::Error::new(
input.generics.span(),
"derive(Yokeable) does not support type parameters",
)
.to_compile_error();
}
let lts = input.generics.lifetimes().count();
if lts == 0 {
let name = &input.ident;
quote! {
unsafe impl<'a> yoke::Yokeable<'a> for #name {
type Output = Self;
fn transform(&self) -> &Self::Output {
self
}
fn transform_owned(self) -> Self::Output {
self
}
unsafe fn make(this: Self::Output) -> Self {
this
}
fn transform_mut<F>(&'a mut self, f: F)
where
F: 'static + for<'b> FnOnce(&'b mut Self::Output) {
f(self)
}
}
}
} else {
if lts != 1 {
return syn::Error::new(
input.generics.span(),
"derive(Yokeable) cannot have multiple lifetime parameters",
)
.to_compile_error();
}
let name = &input.ident;
quote! {
unsafe impl<'a> yoke::Yokeable<'a> for #name<'static> {
type Output = #name<'a>;
fn transform(&'a self) -> &'a Self::Output {
self
}
fn transform_owned(self) -> Self::Output {
self
}
unsafe fn make(this: Self::Output) -> Self {
use std::{mem, ptr};
debug_assert!(mem::size_of::<Self::Output>() == mem::size_of::<Self>());
let ptr: *const Self = (&this as *const Self::Output).cast();
mem::forget(this);
ptr::read(ptr)
}
fn transform_mut<F>(&'a mut self, f: F)
where
F: 'static + for<'b> FnOnce(&'b mut Self::Output) {
unsafe { f(std::mem::transmute::<&'a mut Self, &'a mut Self::Output>(self)) }
}
}
}
}
}
#[proc_macro_derive(ZeroCopyFrom)]
pub fn zcf_derive(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
TokenStream::from(zcf_derive_impl(&input))
}
fn zcf_derive_impl(input: &DeriveInput) -> TokenStream2 {
let typarams = input.generics.type_params().count();
if typarams != 0 {
return syn::Error::new(
input.generics.span(),
"derive(ZeroCopyFrom) does not support type parameters",
)
.to_compile_error();
}
let lts = input.generics.lifetimes().count();
let name = &input.ident;
if lts == 0 {
quote! {
impl ZeroCopyFrom<#name> for #name {
fn zero_copy_from(this: &Self) -> Self {
*this
}
}
}
} else {
if lts != 1 {
return syn::Error::new(
input.generics.span(),
"derive(ZeroCopyFrom) cannot have multiple lifetime parameters",
)
.to_compile_error();
}
let lt_name = &input.generics.lifetimes().next().unwrap().lifetime;
let structure = Structure::new(&input);
let body = structure.each_variant(|vi| {
vi.construct(|f, i| {
let binding = format!("__binding_{}", i);
let field = Ident::new(&binding, Span::call_site());
let fty = replace_lifetime(&f.ty, static_lt());
quote! {
<#fty as yoke::ZeroCopyFrom<_>>::zero_copy_from(#field)
}
})
});
quote! {
impl<'s> yoke::ZeroCopyFrom<#name<'s>> for #name<'static> {
fn zero_copy_from<#lt_name>(this: &#lt_name #name<'s>) -> #name<#lt_name> {
match *this { #body }
}
}
}
}
}
fn static_lt() -> Lifetime {
Lifetime::new("'static", Span::call_site())
}
fn replace_lifetime(x: &Type, lt: Lifetime) -> Type {
match *x {
Type::Group(ref inner) => {
let mut inner = inner.clone();
inner.elem = Box::new(replace_lifetime(&inner.elem, lt.clone()));
Type::Group(inner)
}
Type::Array(ref inner) => {
let mut inner = inner.clone();
inner.elem = Box::new(replace_lifetime(&inner.elem, lt.clone()));
Type::Array(inner)
}
Type::Paren(ref inner) => {
let mut inner = inner.clone();
inner.elem = Box::new(replace_lifetime(&inner.elem, lt.clone()));
Type::Paren(inner)
}
Type::Reference(ref inner) => {
let mut inner = inner.clone();
inner.elem = Box::new(replace_lifetime(&inner.elem, lt.clone()));
inner.lifetime = inner.lifetime.as_ref().map(|_| lt.clone());
Type::Reference(inner)
}
Type::Path(ref path) => {
let mut path = path.clone();
for segment in path.path.segments.iter_mut() {
match segment.arguments {
syn::PathArguments::AngleBracketed(ref mut a) => {
for arg in a.args.iter_mut() {
match arg {
syn::GenericArgument::Lifetime(ref mut l) => *l = lt.clone(),
_ => (),
}
}
}
_ => (),
}
}
Type::Path(path)
}
ref other => other.clone(),
}
}