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#![recursion_limit="256"]
/*!
* Procedural macro to derive RTTI trait.
*
* See crate [`rtti`](https://crates.io/crates/rtti) for [documentation](https://docs.rs/rtti/).
*/
extern crate proc_macro;
extern crate proc_macro2;
extern crate syn;
#[macro_use]
extern crate quote;
use proc_macro::TokenStream;
use proc_macro2::Span;
use syn::Meta::{List, NameValue, Word};
use syn::NestedMeta::Meta;
#[proc_macro_derive(RTTI, attributes(rtti))]
pub fn macro_rtti(input: TokenStream) -> TokenStream {
let ast: syn::DeriveInput = syn::parse(input).unwrap();
let gen = impl_rtti(&ast);
gen.into()
}
fn impl_rtti(ast: &syn::DeriveInput) -> quote::Tokens {
let ident = ast.ident;
let name = ast.ident.to_string();
let visibility = translate_visibility(&ast.vis);
let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
let dummy_const = syn::Ident::new(&format!("_IMPL_RTTI_FOR_{}", ident), Span::def_site());
let dummy_type = dummy_type();
let body = if let syn::Data::Struct(ref data) = ast.data {
if let syn::Fields::Named(ref fields) = data.fields {
// handle structs with named members
let idents: Vec<_> = fields.named.iter().map(|field| field.ident.unwrap()).collect();
let names: Vec<_> = idents.iter().map(|ident| ident.to_string()).collect();
let visibilities: Vec<_> = fields.named.iter().map(|field| translate_visibility(&field.vis)).collect();
let types: Vec<_> = fields.named.iter().map(|field| {
if parse_attr_ignore(&field.attrs) {
&dummy_type
} else {
&field.ty
}
}).collect();
let hints: Vec<_> = fields.named.iter().map(|field| {
parse_attr_hint(&field.attrs)
}).collect();
quote! {
Type::Struct(Struct {
name: #name,
vis: Visibility::#visibility,
size: ::std::mem::size_of::<#ident #impl_generics>(),
fields: {
let mut fields = Vec::new();
let dummy: #ident #impl_generics = unsafe { ::std::mem::uninitialized() };
#(
fields.push((#names, Field {
vis: Visibility::#visibilities,
offset: {
let dummy_ref = &dummy;
let field_ref = &dummy.#idents;
(field_ref as *const _ as usize) - (dummy_ref as *const _ as usize)
},
ty: <#types>::ctti(),
hints: {
let mut hints = Vec::new();
#(
hints.push(#hints);
)*
hints
}
}));
)*
std::mem::forget(dummy);
fields
}
})
}
} else if let syn::Fields::Unnamed(ref fields) = data.fields {
// handle structs with unnamed members
let visibilities: Vec<_> = fields.unnamed.iter().map(|field| translate_visibility(&field.vis)).collect();
let indices: Vec<_> = (0..visibilities.len()).map(|x| syn::Index::from(x)).collect();
let types: Vec<_> = fields.unnamed.iter().map(|field| {
if parse_attr_ignore(&field.attrs) {
&dummy_type
} else {
&field.ty
}
}).collect();
let hints: Vec<_> = fields.unnamed.iter().map(|field| {
parse_attr_hint(&field.attrs)
}).collect();
quote! {
Type::Tuple(Tuple {
name: #name,
vis: Visibility::#visibility,
size: ::std::mem::size_of::<#ident #impl_generics>(),
fields: {
let mut fields = Vec::new();
let dummy: #ident #impl_generics = unsafe { ::std::mem::uninitialized() };
#(
fields.push(Field {
vis: Visibility::#visibilities,
offset: {
let dummy_ref = &dummy;
let field_ref = &(dummy.#indices);
(field_ref as *const _ as usize) - (dummy_ref as *const _ as usize)
},
ty: <#types>::ctti(),
hints: {
let mut hints = Vec::new();
#(
hints.push(#hints);
)*
hints
}
});
)*
std::mem::forget(dummy);
fields
}
})
}
} else {
panic!("#[derive(RTTI)] NYI unit struct.");
}
} else if let syn::Data::Enum(ref data) = ast.data {
let variants = &data.variants;
let idents: Vec<_> = variants.iter().map(|variant| variant.ident).collect();
let names: Vec<_> = idents.iter().map(|ident| ident.to_string()).collect();
let variant_hints: Vec<_> = variants.iter().map(|variant| {
parse_attr_hint(&variant.attrs)
}).collect();
let field_types: Vec<Vec<_>> = variants.iter().map(|variant| {
variant.fields.iter().map(|field| {
if parse_attr_ignore(&field.attrs) {
&dummy_type
} else {
&field.ty
}
}).collect()
}).collect();
let field_hints: Vec<Vec<_>> = variants.iter().map(|variant| {
variant.fields.iter().map(|field| parse_attr_hint(&field.attrs)).collect()
}).collect();
quote! {
Type::Enum(Enum {
name: #name,
vis: Visibility::#visibility,
size: ::std::mem::size_of::<#ident #impl_generics>(),
variants: {
let mut variants = Vec::new();
//let dummy: #ident #impl_generics = unsafe { ::std::mem::uninitialized() };
#(
variants.push((#names, Variant {
fields: {
let mut fields = Vec::new();
#(
fields.push(Field {
vis: Visibility::Public,
offset: 0, /*{
let dummy_ref = &dummy;
let field_ref = &dummy.#idents;
(field_ref as *const _ as usize) - (dummy_ref as *const _ as usize)
},*/
ty: <#field_types>::ctti(),
hints: {
let mut hints = Vec::new();
#(
hints.push(#field_hints);
)*
hints
}
});
)*
fields
},
hints: {
let mut hints = Vec::new();
#(
hints.push(#variant_hints);
)*
hints
}
}));
)*
//std::mem::forget(dummy);
variants
}
})
}
} else {
panic!("#[derive(RTTI)] NYI union");
};
quote! {
#[allow(non_upper_case_globals,unused_mut)]
const #dummy_const: () = {
extern crate rtti;
use rtti::*;
impl #impl_generics RTTI for #ident #ty_generics #where_clause {
fn ctti() -> Type {
#body
}
}
};
}
}
fn translate_visibility(vis: &syn::Visibility) -> syn::Ident {
#[allow(unreachable_patterns)]
match vis {
&syn::Visibility::Public(_) => syn::Ident::from("Public"),
&syn::Visibility::Crate(_) => syn::Ident::from("Crate"),
&syn::Visibility::Restricted(_) => syn::Ident::from("Restricted"),
&syn::Visibility::Inherited => syn::Ident::from("Inherited"),
_ => syn::Ident::from("Unknown"),
}
}
fn parse_attr_hint(attrs: &Vec<syn::Attribute>) -> Vec<String> {
let mut hints = Vec::new();
for meta_items in attrs.iter().filter_map(filter_attr_rtti) {
for meta_item in meta_items {
match meta_item {
// Parse `#[rtti(hint = "foo")]`
Meta(NameValue(ref m)) if m.ident == "hint" => {
if let Some(s) = parse_lit(&m.lit) {
hints.push(s.value().to_string());
}
},
_ => {}
}
}
}
hints
}
fn parse_attr_ignore(attrs: &Vec<syn::Attribute>) -> bool {
for meta_items in attrs.iter().filter_map(filter_attr_rtti) {
for meta_item in meta_items {
match meta_item {
// Parse `#[rtti(ignore)]`
Meta(Word(ref ident)) if ident == "ignore" => {
return true;
},
_ => {}
}
}
}
false
}
fn parse_lit(lit: &syn::Lit) -> Option<&syn::LitStr> {
if let syn::Lit::Str(ref lit) = *lit {
Some(lit)
} else {
None
}
}
fn filter_attr_rtti(attr: &syn::Attribute) -> Option<Vec<syn::NestedMeta>> {
if attr.path.segments.len() == 1 && attr.path.segments[0].ident == "rtti" {
match attr.interpret_meta() {
Some(List(ref meta)) => Some(meta.nested.iter().cloned().collect()),
_ => {
// TODO: produce an error
None
}
}
} else {
None
}
}
fn dummy_type() -> &'static syn::Type {
// TODO: pull in lazy_static instead?
static mut DUMMY: Option<syn::Type> = None;
unsafe {
if DUMMY.is_none() {
DUMMY = Some(syn::Type::Path(syn::TypePath {
qself: None,
path: {
// there must be a shorter way than this.
let p1: syn::PathSegment = "rtti".into();
let p2: syn::PathSegment = "Ignored".into();
syn::Path {
leading_colon: None,
segments: {
let mut punc = syn::punctuated::Punctuated::new();
punc.push(p1);
punc.push(p2);
punc // rain dance ceremony completed
}
}
}
}));
}
DUMMY.as_ref().unwrap()
}
}