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|
use heck::ToKebabCase;
use proc_macro2::TokenStream;
use quote::quote;
use syn::{parse_quote, Result};
use crate::util::{foundations, BareType};
/// Expand the `#[scope]` macro.
pub fn scope(_: TokenStream, item: syn::Item) -> Result<TokenStream> {
let syn::Item::Impl(mut item) = item else {
bail!(item, "expected module or impl item");
};
let self_ty = &item.self_ty;
let mut primitive_ident_ext = None;
if let syn::Type::Path(syn::TypePath { path, .. }) = self_ty.as_ref() {
if let Some(ident) = path.get_ident() {
if is_primitive(ident) {
let ident_ext = quote::format_ident!("{ident}Ext");
primitive_ident_ext = Some(ident_ext);
}
}
}
let self_ty_expr = match &primitive_ident_ext {
None => quote! { #self_ty },
Some(ident_ext) => quote! { <#self_ty as #ident_ext> },
};
let mut definitions = vec![];
let mut constructor = quote! { None };
for child in &mut item.items {
let def = match child {
syn::ImplItem::Const(item) => handle_const(&self_ty_expr, item)?,
syn::ImplItem::Fn(item) => match handle_fn(self_ty, item)? {
FnKind::Member(tokens) => tokens,
FnKind::Constructor(tokens) => {
constructor = tokens;
continue;
}
},
syn::ImplItem::Verbatim(item) => handle_type_or_elem(item)?,
_ => bail!(child, "unexpected item in scope"),
};
definitions.push(def);
}
item.items.retain(|item| !matches!(item, syn::ImplItem::Verbatim(_)));
let base = match &primitive_ident_ext {
None => quote! { #item },
Some(ident_ext) => rewrite_primitive_base(&item, ident_ext),
};
Ok(quote! {
#base
impl #foundations::NativeScope for #self_ty {
fn constructor() -> ::std::option::Option<&'static #foundations::NativeFuncData> {
#constructor
}
fn scope() -> #foundations::Scope {
let mut scope = #foundations::Scope::deduplicating();
#(#definitions;)*
scope
}
}
})
}
/// Process a const item and returns its definition.
fn handle_const(self_ty: &TokenStream, item: &syn::ImplItemConst) -> Result<TokenStream> {
let ident = &item.ident;
let name = ident.to_string().to_kebab_case();
Ok(quote! { scope.define(#name, #self_ty::#ident) })
}
/// Process a type item.
fn handle_type_or_elem(item: &TokenStream) -> Result<TokenStream> {
let item: BareType = syn::parse2(item.clone())?;
let ident = &item.ident;
let define = if item.attrs.iter().any(|attr| attr.path().is_ident("elem")) {
quote! { define_elem }
} else {
quote! { define_type }
};
Ok(quote! { scope.#define::<#ident>() })
}
/// Process a function, return its definition, and register it as a constructor
/// if applicable.
fn handle_fn(self_ty: &syn::Type, item: &mut syn::ImplItemFn) -> Result<FnKind> {
let Some(attr) = item.attrs.iter_mut().find(|attr| attr.meta.path().is_ident("func"))
else {
bail!(item, "scope function is missing #[func] attribute");
};
let ident_data = quote::format_ident!("{}_data", item.sig.ident);
match &mut attr.meta {
syn::Meta::Path(_) => {
*attr = parse_quote! { #[func(parent = #self_ty)] };
}
syn::Meta::List(list) => {
let tokens = &list.tokens;
let meta: crate::func::Meta = syn::parse2(tokens.clone())?;
list.tokens = quote! { #tokens, parent = #self_ty };
if meta.constructor {
return Ok(FnKind::Constructor(quote! { Some(#self_ty::#ident_data()) }));
}
}
syn::Meta::NameValue(_) => bail!(attr.meta, "invalid func attribute"),
}
Ok(FnKind::Member(quote! { scope.define_func_with_data(#self_ty::#ident_data()) }))
}
enum FnKind {
Constructor(TokenStream),
Member(TokenStream),
}
/// Whether the identifier describes a primitive type.
fn is_primitive(ident: &syn::Ident) -> bool {
ident == "bool" || ident == "i64" || ident == "f64"
}
/// Rewrite an impl block for a primitive into a trait + trait impl.
fn rewrite_primitive_base(item: &syn::ItemImpl, ident_ext: &syn::Ident) -> TokenStream {
let mut sigs = vec![];
let mut items = vec![];
for sub in &item.items {
match sub.clone() {
syn::ImplItem::Fn(mut func) => {
func.vis = syn::Visibility::Inherited;
items.push(func.clone());
let mut sig = func.sig;
let inputs = sig.inputs.iter().cloned().map(|mut input| {
if let syn::FnArg::Typed(typed) = &mut input {
typed.attrs.clear();
}
input
});
sig.inputs = parse_quote! { #(#inputs),* };
let ident_data = quote::format_ident!("{}_data", sig.ident);
sigs.push(quote! { #sig; });
sigs.push(quote! {
fn #ident_data() -> &'static #foundations::NativeFuncData;
});
}
syn::ImplItem::Const(cons) => {
sigs.push(quote! { #cons });
}
_ => {}
}
}
let self_ty = &item.self_ty;
quote! {
#[allow(non_camel_case_types)]
trait #ident_ext {
#(#sigs)*
}
impl #ident_ext for #self_ty {
#(#items)*
}
}
}
|
