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use crate::internals::ast::{Container, Data};
use crate::internals::{attr, ungroup};
use proc_macro2::Span;
use std::collections::HashSet;
use syn::punctuated::{Pair, Punctuated};
use syn::Token;
// Remove the default from every type parameter because in the generated impls
// they look like associated types: "error: associated type bindings are not
// allowed here".
pub fn without_defaults(generics: &syn::Generics) -> syn::Generics {
syn::Generics {
params: generics
.params
.iter()
.map(|param| match param {
syn::GenericParam::Type(param) => syn::GenericParam::Type(syn::TypeParam {
eq_token: None,
default: None,
..param.clone()
}),
_ => param.clone(),
})
.collect(),
..generics.clone()
}
}
pub fn with_where_predicates(
generics: &syn::Generics,
predicates: &[syn::WherePredicate],
) -> syn::Generics {
let mut generics = generics.clone();
generics
.make_where_clause()
.predicates
.extend(predicates.iter().cloned());
generics
}
pub fn with_where_predicates_from_fields(
cont: &Container,
generics: &syn::Generics,
from_field: fn(&attr::Field) -> Option<&[syn::WherePredicate]>,
) -> syn::Generics {
let predicates = cont
.data
.all_fields()
.filter_map(|field| from_field(&field.attrs))
.flat_map(<[syn::WherePredicate]>::to_vec);
let mut generics = generics.clone();
generics.make_where_clause().predicates.extend(predicates);
generics
}
pub fn with_where_predicates_from_variants(
cont: &Container,
generics: &syn::Generics,
from_variant: fn(&attr::Variant) -> Option<&[syn::WherePredicate]>,
) -> syn::Generics {
let variants = match &cont.data {
Data::Enum(variants) => variants,
Data::Struct(_, _) => {
return generics.clone();
}
};
let predicates = variants
.iter()
.filter_map(|variant| from_variant(&variant.attrs))
.flat_map(<[syn::WherePredicate]>::to_vec);
let mut generics = generics.clone();
generics.make_where_clause().predicates.extend(predicates);
generics
}
// Puts the given bound on any generic type parameters that are used in fields
// for which filter returns true.
//
// For example, the following struct needs the bound `A: Serialize, B:
// Serialize`.
//
// struct S<'b, A, B: 'b, C> {
// a: A,
// b: Option<&'b B>
// #[serde(skip_serializing)]
// c: C,
// }
pub fn with_bound(
cont: &Container,
generics: &syn::Generics,
filter: fn(&attr::Field, Option<&attr::Variant>) -> bool,
bound: &syn::Path,
) -> syn::Generics {
struct FindTyParams<'ast> {
// Set of all generic type parameters on the current struct (A, B, C in
// the example). Initialized up front.
all_type_params: HashSet<syn::Ident>,
// Set of generic type parameters used in fields for which filter
// returns true (A and B in the example). Filled in as the visitor sees
// them.
relevant_type_params: HashSet<syn::Ident>,
// Fields whose type is an associated type of one of the generic type
// parameters.
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" {
// Hardcoded exception, because PhantomData<T> implements
// Serialize and Deserialize whether or not T implements it.
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);
}
}
// Everything below is simply traversing the syntax tree.
fn visit_type(&mut self, ty: &'ast syn::Type) {
match ty {
#![cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
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 {
#![cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
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 {
#![cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
syn::TypeParamBound::Trait(bound) => self.visit_path(&bound.path),
syn::TypeParamBound::Lifetime(_) | syn::TypeParamBound::Verbatim(_) => {}
_ => {}
}
}
// Type parameter should not be considered used by a macro path.
//
// struct TypeMacro<T> {
// mac: T!(),
// marker: PhantomData<T>,
// }
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(),
};
match &cont.data {
Data::Enum(variants) => {
for variant in variants {
let relevant_fields = variant
.fields
.iter()
.filter(|field| filter(&field.attrs, Some(&variant.attrs)));
for field in relevant_fields {
visitor.visit_field(field.original);
}
}
}
Data::Struct(_, fields) => {
for field in fields.iter().filter(|field| filter(&field.attrs, None)) {
visitor.visit_field(field.original);
}
}
}
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(|bounded_ty| {
syn::WherePredicate::Type(syn::PredicateType {
lifetimes: None,
// the type parameter that is being bounded e.g. T
bounded_ty: syn::Type::Path(bounded_ty),
colon_token: <Token![:]>::default(),
// the bound e.g. Serialize
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
}
pub fn with_self_bound(
cont: &Container,
generics: &syn::Generics,
bound: &syn::Path,
) -> syn::Generics {
let mut generics = generics.clone();
generics
.make_where_clause()
.predicates
.push(syn::WherePredicate::Type(syn::PredicateType {
lifetimes: None,
// the type that is being bounded e.g. MyStruct<'a, T>
bounded_ty: type_of_item(cont),
colon_token: <Token![:]>::default(),
// the bound e.g. Default
bounds: vec![syn::TypeParamBound::Trait(syn::TraitBound {
paren_token: None,
modifier: syn::TraitBoundModifier::None,
lifetimes: None,
path: bound.clone(),
})]
.into_iter()
.collect(),
}));
generics
}
pub fn with_lifetime_bound(generics: &syn::Generics, lifetime: &str) -> syn::Generics {
let bound = syn::Lifetime::new(lifetime, Span::call_site());
let def = syn::LifetimeParam {
attrs: Vec::new(),
lifetime: bound.clone(),
colon_token: None,
bounds: Punctuated::new(),
};
let params = Some(syn::GenericParam::Lifetime(def))
.into_iter()
.chain(generics.params.iter().cloned().map(|mut param| {
match &mut param {
syn::GenericParam::Lifetime(param) => {
param.bounds.push(bound.clone());
}
syn::GenericParam::Type(param) => {
param
.bounds
.push(syn::TypeParamBound::Lifetime(bound.clone()));
}
syn::GenericParam::Const(_) => {}
}
param
}))
.collect();
syn::Generics {
params,
..generics.clone()
}
}
fn type_of_item(cont: &Container) -> syn::Type {
syn::Type::Path(syn::TypePath {
qself: None,
path: syn::Path {
leading_colon: None,
segments: vec![syn::PathSegment {
ident: cont.ident.clone(),
arguments: syn::PathArguments::AngleBracketed(
syn::AngleBracketedGenericArguments {
colon2_token: None,
lt_token: <Token![<]>::default(),
args: cont
.generics
.params
.iter()
.map(|param| match param {
syn::GenericParam::Type(param) => {
syn::GenericArgument::Type(syn::Type::Path(syn::TypePath {
qself: None,
path: param.ident.clone().into(),
}))
}
syn::GenericParam::Lifetime(param) => {
syn::GenericArgument::Lifetime(param.lifetime.clone())
}
syn::GenericParam::Const(_) => {
panic!("Serde does not support const generics yet");
}
})
.collect(),
gt_token: <Token![>]>::default(),
},
),
}]
.into_iter()
.collect(),
},
})
}