101 lines
3.5 KiB
Rust
101 lines
3.5 KiB
Rust
use proc_macro::{TokenStream, TokenTree};
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use quote::{quote, quote_spanned};
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use rustc_hash::FxHashSet;
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use syn::{spanned::Spanned, Ident};
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/// Finds an identifier that will not conflict with the specified set of tokens.
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/// If the identifier is present in `haystack`, extra characters will be added
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/// to it until it no longer conflicts with anything.
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///
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/// Note that the returned identifier can still conflict in niche cases,
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/// such as if an identifier in `haystack` is hidden behind an un-expanded macro.
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pub fn ensure_no_collision(value: Ident, haystack: TokenStream) -> Ident {
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// Collect all the identifiers in `haystack` into a set.
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let idents = {
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// List of token streams that will be visited in future loop iterations.
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let mut unvisited = vec![haystack];
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// Identifiers we have found while searching tokens.
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let mut found = FxHashSet::default();
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while let Some(tokens) = unvisited.pop() {
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for t in tokens {
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match t {
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// Collect any identifiers we encounter.
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TokenTree::Ident(ident) => {
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found.insert(ident.to_string());
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}
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// Queue up nested token streams to be visited in a future loop iteration.
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TokenTree::Group(g) => unvisited.push(g.stream()),
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TokenTree::Punct(_) | TokenTree::Literal(_) => {}
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}
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}
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}
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found
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};
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let span = value.span();
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// If there's a collision, add more characters to the identifier
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// until it doesn't collide with anything anymore.
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let mut value = value.to_string();
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while idents.contains(&value) {
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value.push('X');
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}
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Ident::new(&value, span)
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}
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/// Derive a label trait
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///
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/// # Args
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///
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/// - `input`: The [`syn::DeriveInput`] for struct that is deriving the label trait
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/// - `trait_name`: Name of the label trait
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/// - `trait_path`: The [path](`syn::Path`) to the label trait
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/// - `dyn_eq_path`: The [path](`syn::Path`) to the `DynEq` trait
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pub fn derive_label(
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input: syn::DeriveInput,
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trait_name: &str,
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trait_path: &syn::Path,
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dyn_eq_path: &syn::Path,
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) -> TokenStream {
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if let syn::Data::Union(_) = &input.data {
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let message = format!("Cannot derive {trait_name} for unions.");
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return quote_spanned! {
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input.span() => compile_error!(#message);
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}
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.into();
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}
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let ident = input.ident.clone();
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let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
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let mut where_clause = where_clause.cloned().unwrap_or_else(|| syn::WhereClause {
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where_token: Default::default(),
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predicates: Default::default(),
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});
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where_clause.predicates.push(
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syn::parse2(quote! {
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Self: 'static + Send + Sync + Clone + Eq + ::std::fmt::Debug + ::std::hash::Hash
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})
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.unwrap(),
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);
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quote! {
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impl #impl_generics #trait_path for #ident #ty_generics #where_clause {
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fn dyn_clone(&self) -> ::std::boxed::Box<dyn #trait_path> {
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::std::boxed::Box::new(::std::clone::Clone::clone(self))
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}
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fn as_dyn_eq(&self) -> &dyn #dyn_eq_path {
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self
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}
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fn dyn_hash(&self, mut state: &mut dyn ::std::hash::Hasher) {
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let ty_id = ::std::any::TypeId::of::<Self>();
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::std::hash::Hash::hash(&ty_id, &mut state);
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::std::hash::Hash::hash(self, &mut state);
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}
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}
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}
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.into()
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}
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