bitcode_derive/
bound.rs
use crate::attribute::BitcodeAttrs;
use std::collections::{HashMap, HashSet};
use syn::punctuated::Pair;
use syn::Token;
#[derive(Default)]
pub struct FieldBounds {
bounds: HashMap<syn::Path, (Vec<syn::Field>, Vec<syn::Type>)>,
}
impl FieldBounds {
pub fn add_bound_type(
&mut self,
field: syn::Field,
field_attrs: &BitcodeAttrs,
bound: syn::Path,
) {
let bounds = self.bounds.entry(bound).or_default();
if let Some(bound_type) = field_attrs.bound_type() {
bounds.1.push(bound_type);
} else {
bounds.0.push(field);
}
}
pub fn added_to(self, mut generics: syn::Generics) -> syn::Generics {
for (bound, (fields, extra_bound_types)) in self.bounds {
generics = with_bound(&fields, extra_bound_types, &generics, &bound);
}
generics
}
}
fn with_bound(
fields: &[syn::Field],
extra_bound_types: Vec<syn::Type>,
generics: &syn::Generics,
bound: &syn::Path,
) -> syn::Generics {
struct FindTyParams<'ast> {
all_type_params: HashSet<syn::Ident>,
relevant_type_params: HashSet<syn::Ident>,
associated_type_usage: Vec<&'ast syn::TypePath>,
}
impl<'ast> FindTyParams<'ast> {
fn visit_field(&mut self, field: &'ast syn::Field) {
if let syn::Type::Path(ty) = ungroup(&field.ty) {
if let Some(Pair::Punctuated(t, _)) = ty.path.segments.pairs().next() {
if self.all_type_params.contains(&t.ident) {
self.associated_type_usage.push(ty);
}
}
}
self.visit_type(&field.ty);
}
fn visit_path(&mut self, path: &'ast syn::Path) {
if let Some(seg) = path.segments.last() {
if seg.ident == "PhantomData" {
return;
}
}
if path.leading_colon.is_none() && path.segments.len() == 1 {
let id = &path.segments[0].ident;
if self.all_type_params.contains(id) {
self.relevant_type_params.insert(id.clone());
}
}
for segment in &path.segments {
self.visit_path_segment(segment);
}
}
fn visit_type(&mut self, ty: &'ast syn::Type) {
match ty {
syn::Type::Array(ty) => self.visit_type(&ty.elem),
syn::Type::BareFn(ty) => {
for arg in &ty.inputs {
self.visit_type(&arg.ty);
}
self.visit_return_type(&ty.output);
}
syn::Type::Group(ty) => self.visit_type(&ty.elem),
syn::Type::ImplTrait(ty) => {
for bound in &ty.bounds {
self.visit_type_param_bound(bound);
}
}
syn::Type::Macro(ty) => self.visit_macro(&ty.mac),
syn::Type::Paren(ty) => self.visit_type(&ty.elem),
syn::Type::Path(ty) => {
if let Some(qself) = &ty.qself {
self.visit_type(&qself.ty);
}
self.visit_path(&ty.path);
}
syn::Type::Ptr(ty) => self.visit_type(&ty.elem),
syn::Type::Reference(ty) => self.visit_type(&ty.elem),
syn::Type::Slice(ty) => self.visit_type(&ty.elem),
syn::Type::TraitObject(ty) => {
for bound in &ty.bounds {
self.visit_type_param_bound(bound);
}
}
syn::Type::Tuple(ty) => {
for elem in &ty.elems {
self.visit_type(elem);
}
}
syn::Type::Infer(_) | syn::Type::Never(_) | syn::Type::Verbatim(_) => {}
_ => {}
}
}
fn visit_path_segment(&mut self, segment: &'ast syn::PathSegment) {
self.visit_path_arguments(&segment.arguments);
}
fn visit_path_arguments(&mut self, arguments: &'ast syn::PathArguments) {
match arguments {
syn::PathArguments::None => {}
syn::PathArguments::AngleBracketed(arguments) => {
for arg in &arguments.args {
match arg {
syn::GenericArgument::Type(arg) => self.visit_type(arg),
syn::GenericArgument::AssocType(arg) => self.visit_type(&arg.ty),
syn::GenericArgument::Lifetime(_)
| syn::GenericArgument::Const(_)
| syn::GenericArgument::AssocConst(_)
| syn::GenericArgument::Constraint(_) => {}
_ => {}
}
}
}
syn::PathArguments::Parenthesized(arguments) => {
for argument in &arguments.inputs {
self.visit_type(argument);
}
self.visit_return_type(&arguments.output);
}
}
}
fn visit_return_type(&mut self, return_type: &'ast syn::ReturnType) {
match return_type {
syn::ReturnType::Default => {}
syn::ReturnType::Type(_, output) => self.visit_type(output),
}
}
fn visit_type_param_bound(&mut self, bound: &'ast syn::TypeParamBound) {
match bound {
syn::TypeParamBound::Trait(bound) => self.visit_path(&bound.path),
syn::TypeParamBound::Lifetime(_) | syn::TypeParamBound::Verbatim(_) => {}
_ => {}
}
}
fn visit_macro(&mut self, _mac: &'ast syn::Macro) {}
}
let all_type_params = generics
.type_params()
.map(|param| param.ident.clone())
.collect();
let mut visitor = FindTyParams {
all_type_params,
relevant_type_params: HashSet::new(),
associated_type_usage: Vec::new(),
};
for field in fields {
visitor.visit_field(field)
}
let relevant_type_params = visitor.relevant_type_params;
let associated_type_usage = visitor.associated_type_usage;
let new_predicates = generics
.type_params()
.map(|param| param.ident.clone())
.filter(|id| relevant_type_params.contains(id))
.map(|id| syn::TypePath {
qself: None,
path: id.into(),
})
.chain(associated_type_usage.into_iter().cloned())
.map(syn::Type::Path)
.chain(extra_bound_types)
.map(|bounded_ty| {
syn::WherePredicate::Type(syn::PredicateType {
lifetimes: None,
bounded_ty,
colon_token: <Token![:]>::default(),
bounds: vec![syn::TypeParamBound::Trait(syn::TraitBound {
paren_token: None,
modifier: syn::TraitBoundModifier::None,
lifetimes: None,
path: bound.clone(),
})]
.into_iter()
.collect(),
})
});
let mut generics = generics.clone();
generics
.make_where_clause()
.predicates
.extend(new_predicates);
generics
}
fn ungroup(mut ty: &syn::Type) -> &syn::Type {
while let syn::Type::Group(group) = ty {
ty = &group.elem;
}
ty
}