diff options
Diffstat (limited to 'third_party/rust/serde_derive/src/bound.rs')
| -rw-r--r-- | third_party/rust/serde_derive/src/bound.rs | 406 |
1 files changed, 406 insertions, 0 deletions
diff --git a/third_party/rust/serde_derive/src/bound.rs b/third_party/rust/serde_derive/src/bound.rs new file mode 100644 index 0000000000..74c95069c3 --- /dev/null +++ b/third_party/rust/serde_derive/src/bound.rs @@ -0,0 +1,406 @@ +use std::collections::HashSet; + +use syn; +use syn::punctuated::{Pair, Punctuated}; + +use internals::ast::{Container, Data}; +use internals::{attr, ungroup}; + +use proc_macro2::Span; + +// 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 { + 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(_) => {} + + #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))] + _ => {} + } + } + + 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::Binding(arg) => self.visit_type(&arg.ty), + syn::GenericArgument::Lifetime(_) + | syn::GenericArgument::Constraint(_) + | syn::GenericArgument::Const(_) => {} + } + } + } + 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(_) => {} + } + } + + // 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.iter() { + 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::LifetimeDef { + 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(), + }, + }) +} |