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use proc_macro2::TokenStream;
use quote::ToTokens;
use std::collections::btree_map::Entry;
use std::collections::{BTreeMap as Map, BTreeSet as Set};
use syn::punctuated::Punctuated;
use syn::{parse_quote, GenericArgument, Generics, Ident, PathArguments, Token, Type, WhereClause};
pub struct ParamsInScope<'a> {
names: Set<&'a Ident>,
}
impl<'a> ParamsInScope<'a> {
pub fn new(generics: &'a Generics) -> Self {
ParamsInScope {
names: generics.type_params().map(|param| ¶m.ident).collect(),
}
}
pub fn intersects(&self, ty: &Type) -> bool {
let mut found = false;
crawl(self, ty, &mut found);
found
}
}
fn crawl(in_scope: &ParamsInScope, ty: &Type, found: &mut bool) {
if let Type::Path(ty) = ty {
if ty.qself.is_none() {
if let Some(ident) = ty.path.get_ident() {
if in_scope.names.contains(ident) {
*found = true;
}
}
}
for segment in &ty.path.segments {
if let PathArguments::AngleBracketed(arguments) = &segment.arguments {
for arg in &arguments.args {
if let GenericArgument::Type(ty) = arg {
crawl(in_scope, ty, found);
}
}
}
}
}
}
pub struct InferredBounds {
bounds: Map<String, (Set<String>, Punctuated<TokenStream, Token![+]>)>,
order: Vec<TokenStream>,
}
impl InferredBounds {
pub fn new() -> Self {
InferredBounds {
bounds: Map::new(),
order: Vec::new(),
}
}
#[allow(clippy::type_repetition_in_bounds, clippy::trait_duplication_in_bounds)] // clippy bug: https://github.com/rust-lang/rust-clippy/issues/8771
pub fn insert(&mut self, ty: impl ToTokens, bound: impl ToTokens) {
let ty = ty.to_token_stream();
let bound = bound.to_token_stream();
let entry = self.bounds.entry(ty.to_string());
if let Entry::Vacant(_) = entry {
self.order.push(ty);
}
let (set, tokens) = entry.or_default();
if set.insert(bound.to_string()) {
tokens.push(bound);
}
}
pub fn augment_where_clause(&self, generics: &Generics) -> WhereClause {
let mut generics = generics.clone();
let where_clause = generics.make_where_clause();
for ty in &self.order {
let (_set, bounds) = &self.bounds[&ty.to_string()];
where_clause.predicates.push(parse_quote!(#ty: #bounds));
}
generics.where_clause.unwrap()
}
}