1 //! Some code that abstracts away much of the boilerplate of writing
2 //! `derive` instances for traits. Among other things it manages getting
3 //! access to the fields of the 4 different sorts of structs and enum
4 //! variants, as well as creating the method and impl ast instances.
6 //! Supported features (fairly exhaustive):
8 //! - Methods taking any number of parameters of any type, and returning
9 //! any type, other than vectors, bottom and closures.
10 //! - Generating `impl`s for types with type parameters and lifetimes
11 //! (e.g., `Option<T>`), the parameters are automatically given the
12 //! current trait as a bound. (This includes separate type parameters
13 //! and lifetimes for methods.)
14 //! - Additional bounds on the type parameters (`TraitDef.additional_bounds`)
16 //! The most important thing for implementors is the `Substructure` and
17 //! `SubstructureFields` objects. The latter groups 5 possibilities of the
20 //! - `Struct`, when `Self` is a struct (including tuple structs, e.g
21 //! `struct T(i32, char)`).
22 //! - `EnumMatching`, when `Self` is an enum and all the arguments are the
23 //! same variant of the enum (e.g., `Some(1)`, `Some(3)` and `Some(4)`)
24 //! - `EnumNonMatchingCollapsed` when `Self` is an enum and the arguments
25 //! are not the same variant (e.g., `None`, `Some(1)` and `None`).
26 //! - `StaticEnum` and `StaticStruct` for static methods, where the type
27 //! being derived upon is either an enum or struct respectively. (Any
28 //! argument with type Self is just grouped among the non-self
31 //! In the first two cases, the values from the corresponding fields in
32 //! all the arguments are grouped together. For `EnumNonMatchingCollapsed`
33 //! this isn't possible (different variants have different fields), so the
34 //! fields are inaccessible. (Previous versions of the deriving infrastructure
35 //! had a way to expand into code that could access them, at the cost of
36 //! generating exponential amounts of code; see issue #15375). There are no
37 //! fields with values in the static cases, so these are treated entirely
40 //! The non-static cases have `Option<ident>` in several places associated
41 //! with field `expr`s. This represents the name of the field it is
42 //! associated with. It is only not `None` when the associated field has
43 //! an identifier in the source code. For example, the `x`s in the
47 //! # #![allow(dead_code)]
48 //! struct A { x : i32 }
58 //! The `i32`s in `B` and `C0` don't have an identifier, so the
59 //! `Option<ident>`s would be `None` for them.
61 //! In the static cases, the structure is summarized, either into the just
62 //! spans of the fields or a list of spans and the field idents (for tuple
63 //! structs and record structs, respectively), or a list of these, for
64 //! enums (one for each variant). For empty struct and empty enum
65 //! variants, it is represented as a count of 0.
67 //! # "`cs`" functions
69 //! The `cs_...` functions ("combine substructure) are designed to
70 //! make life easier by providing some pre-made recipes for common
71 //! threads; mostly calling the function being derived on all the
72 //! arguments and then combining them back together in some way (or
73 //! letting the user chose that). They are not meant to be the only
74 //! way to handle the structures that this code creates.
78 //! The following simplified `PartialEq` is used for in-code examples:
82 //! fn eq(&self, other: &Self) -> bool;
84 //! impl PartialEq for i32 {
85 //! fn eq(&self, other: &i32) -> bool {
91 //! Some examples of the values of `SubstructureFields` follow, using the
92 //! above `PartialEq`, `A`, `B` and `C`.
96 //! When generating the `expr` for the `A` impl, the `SubstructureFields` is
99 //! Struct(vec![FieldInfo {
100 //! span: <span of x>
101 //! name: Some(<ident of x>),
102 //! self_: <expr for &self.x>,
103 //! other: vec![<expr for &other.x]
107 //! For the `B` impl, called with `B(a)` and `B(b)`,
110 //! Struct(vec![FieldInfo {
111 //! span: <span of `i32`>,
113 //! self_: <expr for &a>
114 //! other: vec![<expr for &b>]
120 //! When generating the `expr` for a call with `self == C0(a)` and `other
121 //! == C0(b)`, the SubstructureFields is
124 //! EnumMatching(0, <ast::Variant for C0>,
126 //! span: <span of i32>
128 //! self_: <expr for &a>,
129 //! other: vec![<expr for &b>]
133 //! For `C1 {x}` and `C1 {x}`,
136 //! EnumMatching(1, <ast::Variant for C1>,
138 //! span: <span of x>
139 //! name: Some(<ident of x>),
140 //! self_: <expr for &self.x>,
141 //! other: vec![<expr for &other.x>]
145 //! For `C0(a)` and `C1 {x}` ,
148 //! EnumNonMatchingCollapsed(
149 //! vec![<ident of self>, <ident of __arg_1>],
150 //! &[<ast::Variant for C0>, <ast::Variant for C1>],
151 //! &[<ident for self index value>, <ident of __arg_1 index value>])
154 //! It is the same for when the arguments are flipped to `C1 {x}` and
155 //! `C0(a)`; the only difference is what the values of the identifiers
156 //! <ident for self index value> and <ident of __arg_1 index value> will
157 //! be in the generated code.
159 //! `EnumNonMatchingCollapsed` deliberately provides far less information
160 //! than is generally available for a given pair of variants; see #15375
165 //! A static method on the types above would result in,
168 //! StaticStruct(<ast::VariantData of A>, Named(vec![(<ident of x>, <span of x>)]))
170 //! StaticStruct(<ast::VariantData of B>, Unnamed(vec![<span of x>]))
172 //! StaticEnum(<ast::EnumDef of C>,
173 //! vec![(<ident of C0>, <span of C0>, Unnamed(vec![<span of i32>])),
174 //! (<ident of C1>, <span of C1>, Named(vec![(<ident of x>, <span of x>)]))])
177 pub use StaticFields::*;
178 pub use SubstructureFields::*;
180 use std::cell::RefCell;
184 use rustc_ast::ptr::P;
185 use rustc_ast::{self as ast, BinOpKind, EnumDef, Expr, Generics, PatKind};
186 use rustc_ast::{GenericArg, GenericParamKind, VariantData};
187 use rustc_attr as attr;
188 use rustc_data_structures::map_in_place::MapInPlace;
189 use rustc_expand::base::{Annotatable, ExtCtxt};
190 use rustc_span::symbol::{kw, sym, Ident, Symbol};
191 use rustc_span::Span;
193 use ty::{Bounds, Path, Ptr, PtrTy, Self_, Ty};
199 pub struct TraitDef<'a> {
200 /// The span for the current #[derive(Foo)] header.
203 pub attributes: Vec<ast::Attribute>,
205 /// Path of the trait, including any type parameters
208 /// Additional bounds required of any type parameters of the type,
209 /// other than the current trait
210 pub additional_bounds: Vec<Ty>,
212 /// Any extra lifetimes and/or bounds, e.g., `D: serialize::Decoder`
213 pub generics: Bounds,
215 /// Is it an `unsafe` trait?
218 /// Can this trait be derived for unions?
219 pub supports_unions: bool,
221 pub methods: Vec<MethodDef<'a>>,
223 pub associated_types: Vec<(Ident, Ty)>,
226 pub struct MethodDef<'a> {
227 /// name of the method
229 /// List of generics, e.g., `R: rand::Rng`
230 pub generics: Bounds,
232 /// Whether there is a self argument (outer Option) i.e., whether
233 /// this is a static function, and whether it is a pointer (inner
235 pub explicit_self: Option<Option<PtrTy>>,
237 /// Arguments other than the self argument
238 pub args: Vec<(Ty, Symbol)>,
243 pub attributes: Vec<ast::Attribute>,
245 // Is it an `unsafe fn`?
248 /// Can we combine fieldless variants for enums into a single match arm?
249 pub unify_fieldless_variants: bool,
251 pub combine_substructure: RefCell<CombineSubstructureFunc<'a>>,
254 /// All the data about the data structure/method being derived upon.
255 pub struct Substructure<'a> {
257 pub type_ident: Ident,
258 /// ident of the method
259 pub method_ident: Ident,
260 /// dereferenced access to any `Self_` or `Ptr(Self_, _)` arguments
261 pub self_args: &'a [P<Expr>],
262 /// verbatim access to any other arguments
263 pub nonself_args: &'a [P<Expr>],
264 pub fields: &'a SubstructureFields<'a>,
267 /// Summary of the relevant parts of a struct/enum field.
268 pub struct FieldInfo<'a> {
270 /// None for tuple structs/normal enum variants, Some for normal
271 /// structs/struct enum variants.
272 pub name: Option<Ident>,
273 /// The expression corresponding to this field of `self`
274 /// (specifically, a reference to it).
276 /// The expressions corresponding to references to this field in
277 /// the other `Self` arguments.
278 pub other: Vec<P<Expr>>,
279 /// The attributes on the field
280 pub attrs: &'a [ast::Attribute],
283 /// Fields for a static method
284 pub enum StaticFields {
285 /// Tuple and unit structs/enum variants like this.
286 Unnamed(Vec<Span>, bool /*is tuple*/),
287 /// Normal structs/struct variants.
288 Named(Vec<(Ident, Span)>),
291 /// A summary of the possible sets of fields.
292 pub enum SubstructureFields<'a> {
293 Struct(&'a ast::VariantData, Vec<FieldInfo<'a>>),
294 /// Matching variants of the enum: variant index, variant count, ast::Variant,
295 /// fields: the field name is only non-`None` in the case of a struct
297 EnumMatching(usize, usize, &'a ast::Variant, Vec<FieldInfo<'a>>),
299 /// Non-matching variants of the enum, but with all state hidden from
300 /// the consequent code. The first component holds `Ident`s for all of
301 /// the `Self` arguments; the second component is a slice of all of the
302 /// variants for the enum itself, and the third component is a list of
303 /// `Ident`s bound to the variant index values for each of the actual
304 /// input `Self` arguments.
305 EnumNonMatchingCollapsed(Vec<Ident>, &'a [ast::Variant], &'a [Ident]),
307 /// A static method where `Self` is a struct.
308 StaticStruct(&'a ast::VariantData, StaticFields),
309 /// A static method where `Self` is an enum.
310 StaticEnum(&'a ast::EnumDef, Vec<(Ident, Span, StaticFields)>),
313 /// Combine the values of all the fields together. The last argument is
314 /// all the fields of all the structures.
315 pub type CombineSubstructureFunc<'a> =
316 Box<dyn FnMut(&mut ExtCtxt<'_>, Span, &Substructure<'_>) -> P<Expr> + 'a>;
318 /// Deal with non-matching enum variants. The tuple is a list of
319 /// identifiers (one for each `Self` argument, which could be any of the
320 /// variants since they have been collapsed together) and the identifiers
321 /// holding the variant index value for each of the `Self` arguments. The
322 /// last argument is all the non-`Self` args of the method being derived.
323 pub type EnumNonMatchCollapsedFunc<'a> =
324 Box<dyn FnMut(&mut ExtCtxt<'_>, Span, (&[Ident], &[Ident]), &[P<Expr>]) -> P<Expr> + 'a>;
326 pub fn combine_substructure(
327 f: CombineSubstructureFunc<'_>,
328 ) -> RefCell<CombineSubstructureFunc<'_>> {
332 /// This method helps to extract all the type parameters referenced from a
333 /// type. For a type parameter `<T>`, it looks for either a `TyPath` that
334 /// is not global and starts with `T`, or a `TyQPath`.
335 fn find_type_parameters(
337 ty_param_names: &[Symbol],
339 ) -> Vec<P<ast::Ty>> {
340 use rustc_ast::visit;
342 struct Visitor<'a, 'b> {
344 ty_param_names: &'a [Symbol],
345 types: Vec<P<ast::Ty>>,
348 impl<'a, 'b> visit::Visitor<'a> for Visitor<'a, 'b> {
349 fn visit_ty(&mut self, ty: &'a ast::Ty) {
350 if let ast::TyKind::Path(_, ref path) = ty.kind {
351 if let Some(segment) = path.segments.first() {
352 if self.ty_param_names.contains(&segment.ident.name) {
353 self.types.push(P(ty.clone()));
358 visit::walk_ty(self, ty)
361 fn visit_mac(&mut self, mac: &ast::MacCall) {
362 self.cx.span_err(mac.span(), "`derive` cannot be used on items with type macros");
366 let mut visitor = Visitor { cx, ty_param_names, types: Vec::new() };
367 visit::Visitor::visit_ty(&mut visitor, ty);
372 impl<'a> TraitDef<'a> {
375 cx: &mut ExtCtxt<'_>,
376 mitem: &ast::MetaItem,
377 item: &'a Annotatable,
378 push: &mut dyn FnMut(Annotatable),
380 self.expand_ext(cx, mitem, item, push, false);
385 cx: &mut ExtCtxt<'_>,
386 mitem: &ast::MetaItem,
387 item: &'a Annotatable,
388 push: &mut dyn FnMut(Annotatable),
392 Annotatable::Item(ref item) => {
393 let is_packed = item.attrs.iter().any(|attr| {
394 for r in attr::find_repr_attrs(&cx.sess, attr) {
395 if let attr::ReprPacked(_) = r {
401 let has_no_type_params = match item.kind {
402 ast::ItemKind::Struct(_, ref generics)
403 | ast::ItemKind::Enum(_, ref generics)
404 | ast::ItemKind::Union(_, ref generics) => {
405 !generics.params.iter().any(|param| match param.kind {
406 ast::GenericParamKind::Type { .. } => true,
411 // Non-ADT derive is an error, but it should have been
413 // librustc_expand/expand.rs:MacroExpander::fully_expand_fragment()
414 // librustc_expand/base.rs:Annotatable::derive_allowed()
418 let container_id = cx.current_expansion.id.expn_data().parent;
419 let always_copy = has_no_type_params && cx.resolver.has_derive_copy(container_id);
420 let use_temporaries = is_packed && always_copy;
422 let newitem = match item.kind {
423 ast::ItemKind::Struct(ref struct_def, ref generics) => self.expand_struct_def(
431 ast::ItemKind::Enum(ref enum_def, ref generics) => {
432 // We ignore `use_temporaries` here, because
433 // `repr(packed)` enums cause an error later on.
435 // This can only cause further compilation errors
436 // downstream in blatantly illegal code, so it
438 self.expand_enum_def(cx, enum_def, item.ident, generics, from_scratch)
440 ast::ItemKind::Union(ref struct_def, ref generics) => {
441 if self.supports_unions {
442 self.expand_struct_def(
451 cx.span_err(mitem.span, "this trait cannot be derived for unions");
457 // Keep the lint attributes of the previous item to control how the
458 // generated implementations are linted
459 let mut attrs = newitem.attrs.clone();
472 .contains(&a.name_or_empty())
476 push(Annotatable::Item(P(ast::Item { attrs, ..(*newitem).clone() })))
479 // Non-Item derive is an error, but it should have been
481 // librustc_expand/expand.rs:MacroExpander::fully_expand_fragment()
482 // librustc_expand/base.rs:Annotatable::derive_allowed()
487 /// Given that we are deriving a trait `DerivedTrait` for a type like:
489 /// ```ignore (only-for-syntax-highlight)
490 /// struct Struct<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z> where C: WhereTrait {
493 /// b1: <B as DeclaredTrait>::Item,
494 /// c1: <C as WhereTrait>::Item,
495 /// c2: Option<<C as WhereTrait>::Item>,
500 /// create an impl like:
502 /// ```ignore (only-for-syntax-highlight)
503 /// impl<'a, ..., 'z, A, B: DeclaredTrait, C, ... Z> where
505 /// A: DerivedTrait + B1 + ... + BN,
506 /// B: DerivedTrait + B1 + ... + BN,
507 /// C: DerivedTrait + B1 + ... + BN,
508 /// B::Item: DerivedTrait + B1 + ... + BN,
509 /// <C as WhereTrait>::Item: DerivedTrait + B1 + ... + BN,
516 /// where B1, ..., BN are the bounds given by `bounds_paths`.'. Z is a phantom type, and
517 /// therefore does not get bound by the derived trait.
518 fn create_derived_impl(
520 cx: &mut ExtCtxt<'_>,
523 field_tys: Vec<P<ast::Ty>>,
524 methods: Vec<P<ast::AssocItem>>,
526 let trait_path = self.path.to_path(cx, self.span, type_ident, generics);
528 // Transform associated types from `deriving::ty::Ty` into `ast::AssocItem`
529 let associated_types = self.associated_types.iter().map(|&(ident, ref type_def)| {
531 id: ast::DUMMY_NODE_ID,
534 vis: ast::Visibility {
535 span: self.span.shrink_to_lo(),
536 kind: ast::VisibilityKind::Inherited,
540 kind: ast::AssocItemKind::TyAlias(
541 ast::Defaultness::Final,
544 Some(type_def.to_ty(cx, self.span, type_ident, generics)),
550 let Generics { mut params, mut where_clause, span } =
551 self.generics.to_generics(cx, self.span, type_ident, generics);
553 // Create the generic parameters
554 params.extend(generics.params.iter().map(|param| match param.kind {
555 GenericParamKind::Lifetime { .. } => param.clone(),
556 GenericParamKind::Type { .. } => {
557 // I don't think this can be moved out of the loop, since
558 // a GenericBound requires an ast id
560 // extra restrictions on the generics parameters to the
561 // type being derived upon
562 self.additional_bounds.iter().map(|p| {
563 cx.trait_bound(p.to_path(cx, self.span, type_ident, generics))
565 // require the current trait
566 iter::once(cx.trait_bound(trait_path.clone()))
568 // also add in any bounds from the declaration
569 param.bounds.iter().cloned()
572 cx.typaram(self.span, param.ident, vec![], bounds, None)
574 GenericParamKind::Const { .. } => param.clone(),
577 // and similarly for where clauses
578 where_clause.predicates.extend(generics.where_clause.predicates.iter().map(|clause| {
580 ast::WherePredicate::BoundPredicate(ref wb) => {
581 ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
583 bound_generic_params: wb.bound_generic_params.clone(),
584 bounded_ty: wb.bounded_ty.clone(),
585 bounds: wb.bounds.to_vec(),
588 ast::WherePredicate::RegionPredicate(ref rb) => {
589 ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
591 lifetime: rb.lifetime,
592 bounds: rb.bounds.to_vec(),
595 ast::WherePredicate::EqPredicate(ref we) => {
596 ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
597 id: ast::DUMMY_NODE_ID,
599 lhs_ty: we.lhs_ty.clone(),
600 rhs_ty: we.rhs_ty.clone(),
607 // Extra scope required here so ty_params goes out of scope before params is moved
609 let mut ty_params = params
611 .filter_map(|param| match param.kind {
612 ast::GenericParamKind::Type { .. } => Some(param),
617 if ty_params.peek().is_some() {
618 let ty_param_names: Vec<Symbol> =
619 ty_params.map(|ty_param| ty_param.ident.name).collect();
621 for field_ty in field_tys {
622 let tys = find_type_parameters(&field_ty, &ty_param_names, cx);
625 // if we have already handled this type, skip it
626 if let ast::TyKind::Path(_, ref p) = ty.kind {
627 if p.segments.len() == 1
628 && ty_param_names.contains(&p.segments[0].ident.name)
633 let mut bounds: Vec<_> = self
636 .map(|p| cx.trait_bound(p.to_path(cx, self.span, type_ident, generics)))
639 // require the current trait
640 bounds.push(cx.trait_bound(trait_path.clone()));
642 let predicate = ast::WhereBoundPredicate {
644 bound_generic_params: Vec::new(),
649 let predicate = ast::WherePredicate::BoundPredicate(predicate);
650 where_clause.predicates.push(predicate);
656 let trait_generics = Generics { params, where_clause, span };
658 // Create the reference to the trait.
659 let trait_ref = cx.trait_ref(trait_path);
661 let self_params: Vec<_> = generics
664 .map(|param| match param.kind {
665 GenericParamKind::Lifetime { .. } => {
666 GenericArg::Lifetime(cx.lifetime(self.span, param.ident))
668 GenericParamKind::Type { .. } => {
669 GenericArg::Type(cx.ty_ident(self.span, param.ident))
671 GenericParamKind::Const { .. } => {
672 GenericArg::Const(cx.const_ident(self.span, param.ident))
677 // Create the type of `self`.
678 let path = cx.path_all(self.span, false, vec![type_ident], self_params);
679 let self_type = cx.ty_path(path);
681 let attr = cx.attribute(cx.meta_word(self.span, sym::automatically_derived));
682 // Just mark it now since we know that it'll end up used downstream
683 cx.sess.mark_attr_used(&attr);
684 let opt_trait_ref = Some(trait_ref);
686 let word = rustc_ast::attr::mk_nested_word_item(Ident::new(
687 sym::unused_qualifications,
690 let list = rustc_ast::attr::mk_list_item(Ident::new(sym::allow, self.span), vec![word]);
694 let mut a = vec![attr, unused_qual];
695 a.extend(self.attributes.iter().cloned());
697 let unsafety = if self.is_unsafe { ast::Unsafe::Yes(self.span) } else { ast::Unsafe::No };
703 ast::ItemKind::Impl {
705 polarity: ast::ImplPolarity::Positive,
706 defaultness: ast::Defaultness::Final,
707 constness: ast::Const::No,
708 generics: trait_generics,
709 of_trait: opt_trait_ref,
711 items: methods.into_iter().chain(associated_types).collect(),
716 fn expand_struct_def(
718 cx: &mut ExtCtxt<'_>,
719 struct_def: &'a VariantData,
723 use_temporaries: bool,
725 let field_tys: Vec<P<ast::Ty>> =
726 struct_def.fields().iter().map(|field| field.ty.clone()).collect();
732 let (explicit_self, self_args, nonself_args, tys) =
733 method_def.split_self_nonself_args(cx, self, type_ident, generics);
735 let body = if from_scratch || method_def.is_static() {
736 method_def.expand_static_struct_method_body(
745 method_def.expand_struct_method_body(
756 method_def.create_method(cx, self, type_ident, generics, explicit_self, tys, body)
760 self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
765 cx: &mut ExtCtxt<'_>,
766 enum_def: &'a EnumDef,
771 let mut field_tys = Vec::new();
773 for variant in &enum_def.variants {
774 field_tys.extend(variant.data.fields().iter().map(|field| field.ty.clone()));
781 let (explicit_self, self_args, nonself_args, tys) =
782 method_def.split_self_nonself_args(cx, self, type_ident, generics);
784 let body = if from_scratch || method_def.is_static() {
785 method_def.expand_static_enum_method_body(
794 method_def.expand_enum_method_body(
804 method_def.create_method(cx, self, type_ident, generics, explicit_self, tys, body)
808 self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
812 impl<'a> MethodDef<'a> {
813 fn call_substructure_method(
815 cx: &mut ExtCtxt<'_>,
816 trait_: &TraitDef<'_>,
818 self_args: &[P<Expr>],
819 nonself_args: &[P<Expr>],
820 fields: &SubstructureFields<'_>,
822 let substructure = Substructure {
824 method_ident: Ident::new(self.name, trait_.span),
829 let mut f = self.combine_substructure.borrow_mut();
830 let f: &mut CombineSubstructureFunc<'_> = &mut *f;
831 f(cx, trait_.span, &substructure)
836 cx: &mut ExtCtxt<'_>,
837 trait_: &TraitDef<'_>,
841 self.ret_ty.to_ty(cx, trait_.span, type_ident, generics)
844 fn is_static(&self) -> bool {
845 self.explicit_self.is_none()
848 fn split_self_nonself_args(
850 cx: &mut ExtCtxt<'_>,
851 trait_: &TraitDef<'_>,
854 ) -> (Option<ast::ExplicitSelf>, Vec<P<Expr>>, Vec<P<Expr>>, Vec<(Ident, P<ast::Ty>)>) {
855 let mut self_args = Vec::new();
856 let mut nonself_args = Vec::new();
857 let mut arg_tys = Vec::new();
858 let mut nonstatic = false;
860 let ast_explicit_self = self.explicit_self.as_ref().map(|self_ptr| {
861 let (self_expr, explicit_self) = ty::get_explicit_self(cx, trait_.span, self_ptr);
863 self_args.push(self_expr);
869 for (ty, name) in self.args.iter() {
870 let ast_ty = ty.to_ty(cx, trait_.span, type_ident, generics);
871 let ident = Ident::new(*name, trait_.span);
872 arg_tys.push((ident, ast_ty));
874 let arg_expr = cx.expr_ident(trait_.span, ident);
877 // for static methods, just treat any Self
878 // arguments as a normal arg
879 Self_ if nonstatic => {
880 self_args.push(arg_expr);
882 Ptr(ref ty, _) if (if let Self_ = **ty { true } else { false }) && nonstatic => {
883 self_args.push(cx.expr_deref(trait_.span, arg_expr))
886 nonself_args.push(arg_expr);
891 (ast_explicit_self, self_args, nonself_args, arg_tys)
896 cx: &mut ExtCtxt<'_>,
897 trait_: &TraitDef<'_>,
900 explicit_self: Option<ast::ExplicitSelf>,
901 arg_types: Vec<(Ident, P<ast::Ty>)>,
903 ) -> P<ast::AssocItem> {
904 // Create the generics that aren't for `Self`.
905 let fn_generics = self.generics.to_generics(cx, trait_.span, type_ident, generics);
908 let self_args = explicit_self.map(|explicit_self| {
909 let ident = Ident::with_dummy_span(kw::SelfLower).with_span_pos(trait_.span);
910 ast::Param::from_self(ast::AttrVec::default(), explicit_self, ident)
913 arg_types.into_iter().map(|(name, ty)| cx.param(trait_.span, name, ty));
914 self_args.into_iter().chain(nonself_args).collect()
917 let ret_type = self.get_ret_ty(cx, trait_, generics, type_ident);
919 let method_ident = Ident::new(self.name, trait_.span);
920 let fn_decl = cx.fn_decl(args, ast::FnRetTy::Ty(ret_type));
921 let body_block = cx.block_expr(body);
923 let unsafety = if self.is_unsafe { ast::Unsafe::Yes(trait_.span) } else { ast::Unsafe::No };
925 let trait_lo_sp = trait_.span.shrink_to_lo();
927 let sig = ast::FnSig {
928 header: ast::FnHeader { unsafety, ext: ast::Extern::None, ..ast::FnHeader::default() },
932 let def = ast::Defaultness::Final;
934 // Create the method.
936 id: ast::DUMMY_NODE_ID,
937 attrs: self.attributes.clone(),
939 vis: ast::Visibility {
941 kind: ast::VisibilityKind::Inherited,
945 kind: ast::AssocItemKind::Fn(def, sig, fn_generics, Some(body_block)),
951 /// #[derive(PartialEq)]
953 /// struct A { x: i32, y: i32 }
955 /// // equivalent to:
956 /// impl PartialEq for A {
957 /// fn eq(&self, other: &A) -> bool {
959 /// A {x: ref __self_0_0, y: ref __self_0_1} => {
961 /// A {x: ref __self_1_0, y: ref __self_1_1} => {
962 /// __self_0_0.eq(__self_1_0) && __self_0_1.eq(__self_1_1)
970 /// // or if A is repr(packed) - note fields are matched by-value
971 /// // instead of by-reference.
972 /// impl PartialEq for A {
973 /// fn eq(&self, other: &A) -> bool {
975 /// A {x: __self_0_0, y: __self_0_1} => {
977 /// A {x: __self_1_0, y: __self_1_1} => {
978 /// __self_0_0.eq(&__self_1_0) && __self_0_1.eq(&__self_1_1)
986 fn expand_struct_method_body<'b>(
988 cx: &mut ExtCtxt<'_>,
989 trait_: &TraitDef<'b>,
990 struct_def: &'b VariantData,
992 self_args: &[P<Expr>],
993 nonself_args: &[P<Expr>],
994 use_temporaries: bool,
996 let mut raw_fields = Vec::new(); // Vec<[fields of self],
997 // [fields of next Self arg], [etc]>
998 let mut patterns = Vec::new();
999 for i in 0..self_args.len() {
1000 let struct_path = cx.path(trait_.span, vec![type_ident]);
1001 let (pat, ident_expr) = trait_.create_struct_pattern(
1005 &format!("__self_{}", i),
1006 ast::Mutability::Not,
1010 raw_fields.push(ident_expr);
1013 // transpose raw_fields
1014 let fields = if !raw_fields.is_empty() {
1015 let mut raw_fields = raw_fields.into_iter().map(|v| v.into_iter());
1016 let first_field = raw_fields.next().unwrap();
1017 let mut other_fields: Vec<vec::IntoIter<_>> = raw_fields.collect();
1019 .map(|(span, opt_id, field, attrs)| FieldInfo {
1026 let (.., ex, _) = l.next().unwrap();
1034 cx.span_bug(trait_.span, "no `self` parameter for method in generic `derive`")
1037 // body of the inner most destructuring match
1038 let mut body = self.call_substructure_method(
1044 &Struct(struct_def, fields),
1047 // make a series of nested matches, to destructure the
1048 // structs. This is actually right-to-left, but it shouldn't
1050 for (arg_expr, pat) in self_args.iter().zip(patterns) {
1051 body = cx.expr_match(
1054 vec![cx.arm(trait_.span, pat.clone(), body)],
1061 fn expand_static_struct_method_body(
1063 cx: &mut ExtCtxt<'_>,
1064 trait_: &TraitDef<'_>,
1065 struct_def: &VariantData,
1067 self_args: &[P<Expr>],
1068 nonself_args: &[P<Expr>],
1070 let summary = trait_.summarise_struct(cx, struct_def);
1072 self.call_substructure_method(
1078 &StaticStruct(struct_def, summary),
1083 /// #[derive(PartialEq)]
1090 /// // is equivalent to
1092 /// impl PartialEq for A {
1093 /// fn eq(&self, other: &A) -> ::bool {
1094 /// match (&*self, &*other) {
1095 /// (&A1, &A1) => true,
1096 /// (&A2(ref self_0),
1097 /// &A2(ref __arg_1_0)) => (*self_0).eq(&(*__arg_1_0)),
1099 /// let __self_vi = match *self { A1(..) => 0, A2(..) => 1 };
1100 /// let __arg_1_vi = match *other { A1(..) => 0, A2(..) => 1 };
1108 /// (Of course `__self_vi` and `__arg_1_vi` are unused for
1109 /// `PartialEq`, and those subcomputations will hopefully be removed
1110 /// as their results are unused. The point of `__self_vi` and
1111 /// `__arg_1_vi` is for `PartialOrd`; see #15503.)
1112 fn expand_enum_method_body<'b>(
1114 cx: &mut ExtCtxt<'_>,
1115 trait_: &TraitDef<'b>,
1116 enum_def: &'b EnumDef,
1118 self_args: Vec<P<Expr>>,
1119 nonself_args: &[P<Expr>],
1121 self.build_enum_match_tuple(cx, trait_, enum_def, type_ident, self_args, nonself_args)
1124 /// Creates a match for a tuple of all `self_args`, where either all
1125 /// variants match, or it falls into a catch-all for when one variant
1128 /// There are N + 1 cases because is a case for each of the N
1129 /// variants where all of the variants match, and one catch-all for
1130 /// when one does not match.
1132 /// As an optimization we generate code which checks whether all variants
1133 /// match first which makes llvm see that C-like enums can be compiled into
1134 /// a simple equality check (for PartialEq).
1136 /// The catch-all handler is provided access the variant index values
1137 /// for each of the self-args, carried in precomputed variables.
1140 /// let __self0_vi = unsafe {
1141 /// std::intrinsics::discriminant_value(&self) };
1142 /// let __self1_vi = unsafe {
1143 /// std::intrinsics::discriminant_value(&arg1) };
1144 /// let __self2_vi = unsafe {
1145 /// std::intrinsics::discriminant_value(&arg2) };
1147 /// if __self0_vi == __self1_vi && __self0_vi == __self2_vi && ... {
1149 /// (Variant1, Variant1, ...) => Body1
1150 /// (Variant2, Variant2, ...) => Body2,
1152 /// _ => ::core::intrinsics::unreachable()
1156 /// ... // catch-all remainder can inspect above variant index values.
1159 fn build_enum_match_tuple<'b>(
1161 cx: &mut ExtCtxt<'_>,
1162 trait_: &TraitDef<'b>,
1163 enum_def: &'b EnumDef,
1165 mut self_args: Vec<P<Expr>>,
1166 nonself_args: &[P<Expr>],
1168 let sp = trait_.span;
1169 let variants = &enum_def.variants;
1171 let self_arg_names = iter::once("__self".to_string())
1177 .map(|(arg_count, _self_arg)| format!("__arg_{}", arg_count)),
1179 .collect::<Vec<String>>();
1181 let self_arg_idents = self_arg_names
1183 .map(|name| Ident::from_str_and_span(name, sp))
1184 .collect::<Vec<Ident>>();
1186 // The `vi_idents` will be bound, solely in the catch-all, to
1187 // a series of let statements mapping each self_arg to an int
1188 // value corresponding to its discriminant.
1189 let vi_idents = self_arg_names
1192 let vi_suffix = format!("{}_vi", &name[..]);
1193 Ident::from_str_and_span(&vi_suffix, trait_.span)
1195 .collect::<Vec<Ident>>();
1197 // Builds, via callback to call_substructure_method, the
1198 // delegated expression that handles the catch-all case,
1199 // using `__variants_tuple` to drive logic if necessary.
1200 let catch_all_substructure =
1201 EnumNonMatchingCollapsed(self_arg_idents, &variants[..], &vi_idents[..]);
1203 let first_fieldless = variants.iter().find(|v| v.data.fields().is_empty());
1205 // These arms are of the form:
1206 // (Variant1, Variant1, ...) => Body1
1207 // (Variant2, Variant2, ...) => Body2
1209 // where each tuple has length = self_args.len()
1210 let mut match_arms: Vec<ast::Arm> = variants
1213 .filter(|&(_, v)| !(self.unify_fieldless_variants && v.data.fields().is_empty()))
1214 .map(|(index, variant)| {
1215 let mk_self_pat = |cx: &mut ExtCtxt<'_>, self_arg_name: &str| {
1216 let (p, idents) = trait_.create_enum_variant_pattern(
1221 ast::Mutability::Not,
1223 (cx.pat(sp, PatKind::Ref(p, ast::Mutability::Not)), idents)
1226 // A single arm has form (&VariantK, &VariantK, ...) => BodyK
1227 // (see "Final wrinkle" note below for why.)
1228 let mut subpats = Vec::with_capacity(self_arg_names.len());
1229 let mut self_pats_idents = Vec::with_capacity(self_arg_names.len() - 1);
1230 let first_self_pat_idents = {
1231 let (p, idents) = mk_self_pat(cx, &self_arg_names[0]);
1235 for self_arg_name in &self_arg_names[1..] {
1236 let (p, idents) = mk_self_pat(cx, &self_arg_name[..]);
1238 self_pats_idents.push(idents);
1241 // Here is the pat = `(&VariantK, &VariantK, ...)`
1242 let single_pat = cx.pat_tuple(sp, subpats);
1244 // For the BodyK, we need to delegate to our caller,
1245 // passing it an EnumMatching to indicate which case
1248 // All of the Self args have the same variant in these
1249 // cases. So we transpose the info in self_pats_idents
1250 // to gather the getter expressions together, in the
1251 // form that EnumMatching expects.
1253 // The transposition is driven by walking across the
1254 // arg fields of the variant for the first self pat.
1255 let field_tuples = first_self_pat_idents
1258 // For each arg field of self, pull out its getter expr ...
1259 .map(|(field_index, (sp, opt_ident, self_getter_expr, attrs))| {
1260 // ... but FieldInfo also wants getter expr
1261 // for matching other arguments of Self type;
1262 // so walk across the *other* self_pats_idents
1263 // and pull out getter for same field in each
1264 // of them (using `field_index` tracked above).
1265 // That is the heart of the transposition.
1266 let others = self_pats_idents
1269 let (_, _opt_ident, ref other_getter_expr, _) = fields[field_index];
1271 // All Self args have same variant, so
1272 // opt_idents are the same. (Assert
1273 // here to make it self-evident that
1274 // it is okay to ignore `_opt_ident`.)
1275 assert!(opt_ident == _opt_ident);
1277 other_getter_expr.clone()
1279 .collect::<Vec<P<Expr>>>();
1284 self_: self_getter_expr,
1289 .collect::<Vec<FieldInfo<'_>>>();
1291 // Now, for some given VariantK, we have built up
1292 // expressions for referencing every field of every
1293 // Self arg, assuming all are instances of VariantK.
1294 // Build up code associated with such a case.
1295 let substructure = EnumMatching(index, variants.len(), variant, field_tuples);
1296 let arm_expr = self.call_substructure_method(
1305 cx.arm(sp, single_pat, arm_expr)
1309 let default = match first_fieldless {
1310 Some(v) if self.unify_fieldless_variants => {
1311 // We need a default case that handles the fieldless variants.
1312 // The index and actual variant aren't meaningful in this case,
1313 // so just use whatever
1314 let substructure = EnumMatching(0, variants.len(), v, Vec::new());
1315 Some(self.call_substructure_method(
1324 _ if variants.len() > 1 && self_args.len() > 1 => {
1325 // Since we know that all the arguments will match if we reach
1326 // the match expression we add the unreachable intrinsics as the
1327 // result of the catch all which should help llvm in optimizing it
1328 Some(deriving::call_intrinsic(cx, sp, sym::unreachable, vec![]))
1332 if let Some(arm) = default {
1333 match_arms.push(cx.arm(sp, cx.pat_wild(sp), arm));
1336 // We will usually need the catch-all after matching the
1337 // tuples `(VariantK, VariantK, ...)` for each VariantK of the
1340 // * when there is only one Self arg, the arms above suffice
1341 // (and the deriving we call back into may not be prepared to
1342 // handle EnumNonMatchCollapsed), and,
1344 // * when the enum has only one variant, the single arm that
1345 // is already present always suffices.
1347 // * In either of the two cases above, if we *did* add a
1348 // catch-all `_` match, it would trigger the
1349 // unreachable-pattern error.
1351 if variants.len() > 1 && self_args.len() > 1 {
1352 // Build a series of let statements mapping each self_arg
1353 // to its discriminant value.
1355 // i.e., for `enum E<T> { A, B(1), C(T, T) }`, and a deriving
1356 // with three Self args, builds three statements:
1359 // let __self0_vi = unsafe {
1360 // std::intrinsics::discriminant_value(&self) };
1361 // let __self1_vi = unsafe {
1362 // std::intrinsics::discriminant_value(&arg1) };
1363 // let __self2_vi = unsafe {
1364 // std::intrinsics::discriminant_value(&arg2) };
1366 let mut index_let_stmts: Vec<ast::Stmt> = Vec::with_capacity(vi_idents.len() + 1);
1368 // We also build an expression which checks whether all discriminants are equal
1369 // discriminant_test = __self0_vi == __self1_vi && __self0_vi == __self2_vi && ...
1370 let mut discriminant_test = cx.expr_bool(sp, true);
1372 let mut first_ident = None;
1373 for (&ident, self_arg) in vi_idents.iter().zip(&self_args) {
1374 let self_addr = cx.expr_addr_of(sp, self_arg.clone());
1376 deriving::call_intrinsic(cx, sp, sym::discriminant_value, vec![self_addr]);
1377 let let_stmt = cx.stmt_let(sp, false, ident, variant_value);
1378 index_let_stmts.push(let_stmt);
1382 let first_expr = cx.expr_ident(sp, first);
1383 let id = cx.expr_ident(sp, ident);
1384 let test = cx.expr_binary(sp, BinOpKind::Eq, first_expr, id);
1386 cx.expr_binary(sp, BinOpKind::And, discriminant_test, test)
1389 first_ident = Some(ident);
1394 let arm_expr = self.call_substructure_method(
1400 &catch_all_substructure,
1403 // Final wrinkle: the self_args are expressions that deref
1404 // down to desired places, but we cannot actually deref
1405 // them when they are fed as r-values into a tuple
1406 // expression; here add a layer of borrowing, turning
1407 // `(*self, *__arg_0, ...)` into `(&*self, &*__arg_0, ...)`.
1408 self_args.map_in_place(|self_arg| cx.expr_addr_of(sp, self_arg));
1409 let match_arg = cx.expr(sp, ast::ExprKind::Tup(self_args));
1411 // Lastly we create an expression which branches on all discriminants being equal
1412 // if discriminant_test {
1414 // (Variant1, Variant1, ...) => Body1
1415 // (Variant2, Variant2, ...) => Body2,
1417 // _ => ::core::intrinsics::unreachable()
1421 // <delegated expression referring to __self0_vi, et al.>
1423 let all_match = cx.expr_match(sp, match_arg, match_arms);
1424 let arm_expr = cx.expr_if(sp, discriminant_test, all_match, Some(arm_expr));
1425 index_let_stmts.push(cx.stmt_expr(arm_expr));
1426 cx.expr_block(cx.block(sp, index_let_stmts))
1427 } else if variants.is_empty() {
1428 // As an additional wrinkle, For a zero-variant enum A,
1429 // currently the compiler
1430 // will accept `fn (a: &Self) { match *a { } }`
1431 // but rejects `fn (a: &Self) { match (&*a,) { } }`
1432 // as well as `fn (a: &Self) { match ( *a,) { } }`
1434 // This means that the strategy of building up a tuple of
1435 // all Self arguments fails when Self is a zero variant
1436 // enum: rustc rejects the expanded program, even though
1437 // the actual code tends to be impossible to execute (at
1438 // least safely), according to the type system.
1440 // The most expedient fix for this is to just let the
1441 // code fall through to the catch-all. But even this is
1442 // error-prone, since the catch-all as defined above would
1443 // generate code like this:
1445 // _ => { let __self0 = match *self { };
1446 // let __self1 = match *__arg_0 { };
1447 // <catch-all-expr> }
1449 // Which is yields bindings for variables which type
1450 // inference cannot resolve to unique types.
1452 // One option to the above might be to add explicit type
1453 // annotations. But the *only* reason to go down that path
1454 // would be to try to make the expanded output consistent
1455 // with the case when the number of enum variants >= 1.
1457 // That just isn't worth it. In fact, trying to generate
1458 // sensible code for *any* deriving on a zero-variant enum
1459 // does not make sense. But at the same time, for now, we
1460 // do not want to cause a compile failure just because the
1461 // user happened to attach a deriving to their
1462 // zero-variant enum.
1464 // Instead, just generate a failing expression for the
1465 // zero variant case, skipping matches and also skipping
1466 // delegating back to the end user code entirely.
1468 // (See also #4499 and #12609; note that some of the
1469 // discussions there influence what choice we make here;
1470 // e.g., if we feature-gate `match x { ... }` when x refers
1471 // to an uninhabited type (e.g., a zero-variant enum or a
1472 // type holding such an enum), but do not feature-gate
1473 // zero-variant enums themselves, then attempting to
1474 // derive Debug on such a type could here generate code
1475 // that needs the feature gate enabled.)
1477 deriving::call_intrinsic(cx, sp, sym::unreachable, vec![])
1479 // Final wrinkle: the self_args are expressions that deref
1480 // down to desired places, but we cannot actually deref
1481 // them when they are fed as r-values into a tuple
1482 // expression; here add a layer of borrowing, turning
1483 // `(*self, *__arg_0, ...)` into `(&*self, &*__arg_0, ...)`.
1484 self_args.map_in_place(|self_arg| cx.expr_addr_of(sp, self_arg));
1485 let match_arg = cx.expr(sp, ast::ExprKind::Tup(self_args));
1486 cx.expr_match(sp, match_arg, match_arms)
1490 fn expand_static_enum_method_body(
1492 cx: &mut ExtCtxt<'_>,
1493 trait_: &TraitDef<'_>,
1496 self_args: &[P<Expr>],
1497 nonself_args: &[P<Expr>],
1499 let summary = enum_def
1503 let sp = v.span.with_ctxt(trait_.span.ctxt());
1504 let summary = trait_.summarise_struct(cx, &v.data);
1505 (v.ident, sp, summary)
1508 self.call_substructure_method(
1514 &StaticEnum(enum_def, summary),
1519 // general helper methods.
1520 impl<'a> TraitDef<'a> {
1521 fn summarise_struct(&self, cx: &mut ExtCtxt<'_>, struct_def: &VariantData) -> StaticFields {
1522 let mut named_idents = Vec::new();
1523 let mut just_spans = Vec::new();
1524 for field in struct_def.fields() {
1525 let sp = field.span.with_ctxt(self.span.ctxt());
1527 Some(ident) => named_idents.push((ident, sp)),
1528 _ => just_spans.push(sp),
1532 let is_tuple = if let ast::VariantData::Tuple(..) = struct_def { true } else { false };
1533 match (just_spans.is_empty(), named_idents.is_empty()) {
1534 (false, false) => cx.span_bug(
1536 "a struct with named and unnamed \
1537 fields in generic `derive`",
1540 (_, false) => Named(named_idents),
1542 (false, _) => Unnamed(just_spans, is_tuple),
1544 _ => Named(Vec::new()),
1548 fn create_subpatterns(
1550 cx: &mut ExtCtxt<'_>,
1551 field_paths: Vec<Ident>,
1552 mutbl: ast::Mutability,
1553 use_temporaries: bool,
1554 ) -> Vec<P<ast::Pat>> {
1558 let binding_mode = if use_temporaries {
1559 ast::BindingMode::ByValue(ast::Mutability::Not)
1561 ast::BindingMode::ByRef(mutbl)
1563 cx.pat(path.span, PatKind::Ident(binding_mode, *path, None))
1568 fn create_struct_pattern(
1570 cx: &mut ExtCtxt<'_>,
1571 struct_path: ast::Path,
1572 struct_def: &'a VariantData,
1574 mutbl: ast::Mutability,
1575 use_temporaries: bool,
1576 ) -> (P<ast::Pat>, Vec<(Span, Option<Ident>, P<Expr>, &'a [ast::Attribute])>) {
1577 let mut paths = Vec::new();
1578 let mut ident_exprs = Vec::new();
1579 for (i, struct_field) in struct_def.fields().iter().enumerate() {
1580 let sp = struct_field.span.with_ctxt(self.span.ctxt());
1581 let ident = Ident::from_str_and_span(&format!("{}_{}", prefix, i), self.span);
1582 paths.push(ident.with_span_pos(sp));
1583 let val = cx.expr_path(cx.path_ident(sp, ident));
1584 let val = if use_temporaries { val } else { cx.expr_deref(sp, val) };
1585 let val = cx.expr(sp, ast::ExprKind::Paren(val));
1587 ident_exprs.push((sp, struct_field.ident, val, &struct_field.attrs[..]));
1590 let subpats = self.create_subpatterns(cx, paths, mutbl, use_temporaries);
1591 let pattern = match *struct_def {
1592 VariantData::Struct(..) => {
1593 let field_pats = subpats
1596 .map(|(pat, &(sp, ident, ..))| {
1597 if ident.is_none() {
1598 cx.span_bug(sp, "a braced struct with unnamed fields in `derive`");
1601 ident: ident.unwrap(),
1602 is_shorthand: false,
1603 attrs: ast::AttrVec::new(),
1604 id: ast::DUMMY_NODE_ID,
1605 span: pat.span.with_ctxt(self.span.ctxt()),
1607 is_placeholder: false,
1611 cx.pat_struct(self.span, struct_path, field_pats)
1613 VariantData::Tuple(..) => cx.pat_tuple_struct(self.span, struct_path, subpats),
1614 VariantData::Unit(..) => cx.pat_path(self.span, struct_path),
1617 (pattern, ident_exprs)
1620 fn create_enum_variant_pattern(
1622 cx: &mut ExtCtxt<'_>,
1624 variant: &'a ast::Variant,
1626 mutbl: ast::Mutability,
1627 ) -> (P<ast::Pat>, Vec<(Span, Option<Ident>, P<Expr>, &'a [ast::Attribute])>) {
1628 let sp = variant.span.with_ctxt(self.span.ctxt());
1629 let variant_path = cx.path(sp, vec![enum_ident, variant.ident]);
1630 let use_temporaries = false; // enums can't be repr(packed)
1631 self.create_struct_pattern(cx, variant_path, &variant.data, prefix, mutbl, use_temporaries)
1635 // helpful premade recipes
1637 pub fn cs_fold_fields<'a, F>(
1641 cx: &mut ExtCtxt<'_>,
1642 all_fields: &[FieldInfo<'a>],
1645 F: FnMut(&mut ExtCtxt<'_>, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>,
1650 .fold(base, |old, field| f(cx, field.span, old, field.self_.clone(), &field.other))
1655 .fold(base, |old, field| f(cx, field.span, old, field.self_.clone(), &field.other))
1659 pub fn cs_fold_enumnonmatch(
1660 mut enum_nonmatch_f: EnumNonMatchCollapsedFunc<'_>,
1661 cx: &mut ExtCtxt<'_>,
1663 substructure: &Substructure<'_>,
1665 match *substructure.fields {
1666 EnumNonMatchingCollapsed(ref all_args, _, tuple) => {
1667 enum_nonmatch_f(cx, trait_span, (&all_args[..], tuple), substructure.nonself_args)
1669 _ => cx.span_bug(trait_span, "cs_fold_enumnonmatch expected an EnumNonMatchingCollapsed"),
1673 pub fn cs_fold_static(cx: &mut ExtCtxt<'_>, trait_span: Span) -> P<Expr> {
1674 cx.span_bug(trait_span, "static function in `derive`")
1677 /// Fold the fields. `use_foldl` controls whether this is done
1678 /// left-to-right (`true`) or right-to-left (`false`).
1683 enum_nonmatch_f: EnumNonMatchCollapsedFunc<'_>,
1684 cx: &mut ExtCtxt<'_>,
1686 substructure: &Substructure<'_>,
1689 F: FnMut(&mut ExtCtxt<'_>, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>,
1691 match *substructure.fields {
1692 EnumMatching(.., ref all_fields) | Struct(_, ref all_fields) => {
1693 cs_fold_fields(use_foldl, f, base, cx, all_fields)
1695 EnumNonMatchingCollapsed(..) => {
1696 cs_fold_enumnonmatch(enum_nonmatch_f, cx, trait_span, substructure)
1698 StaticEnum(..) | StaticStruct(..) => cs_fold_static(cx, trait_span),
1702 /// Function to fold over fields, with three cases, to generate more efficient and concise code.
1703 /// When the `substructure` has grouped fields, there are two cases:
1704 /// Zero fields: call the base case function with `None` (like the usual base case of `cs_fold`).
1705 /// One or more fields: call the base case function on the first value (which depends on
1706 /// `use_fold`), and use that as the base case. Then perform `cs_fold` on the remainder of the
1708 /// When the `substructure` is a `EnumNonMatchingCollapsed`, the result of `enum_nonmatch_f`
1709 /// is returned. Statics may not be folded over.
1710 /// See `cs_op` in `partial_ord.rs` for a model example.
1711 pub fn cs_fold1<F, B>(
1715 enum_nonmatch_f: EnumNonMatchCollapsedFunc<'_>,
1716 cx: &mut ExtCtxt<'_>,
1718 substructure: &Substructure<'_>,
1721 F: FnMut(&mut ExtCtxt<'_>, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>,
1722 B: FnMut(&mut ExtCtxt<'_>, Option<(Span, P<Expr>, &[P<Expr>])>) -> P<Expr>,
1724 match *substructure.fields {
1725 EnumMatching(.., ref all_fields) | Struct(_, ref all_fields) => {
1726 let (base, all_fields) = match (all_fields.is_empty(), use_foldl) {
1728 let field = &all_fields[0];
1729 let args = (field.span, field.self_.clone(), &field.other[..]);
1730 (b(cx, Some(args)), &all_fields[1..])
1733 let idx = all_fields.len() - 1;
1734 let field = &all_fields[idx];
1735 let args = (field.span, field.self_.clone(), &field.other[..]);
1736 (b(cx, Some(args)), &all_fields[..idx])
1738 (true, _) => (b(cx, None), &all_fields[..]),
1741 cs_fold_fields(use_foldl, f, base, cx, all_fields)
1743 EnumNonMatchingCollapsed(..) => {
1744 cs_fold_enumnonmatch(enum_nonmatch_f, cx, trait_span, substructure)
1746 StaticEnum(..) | StaticStruct(..) => cs_fold_static(cx, trait_span),
1750 /// Returns `true` if the type has no value fields
1751 /// (for an enum, no variant has any fields)
1752 pub fn is_type_without_fields(item: &Annotatable) -> bool {
1753 if let Annotatable::Item(ref item) = *item {
1755 ast::ItemKind::Enum(ref enum_def, _) => {
1756 enum_def.variants.iter().all(|v| v.data.fields().is_empty())
1758 ast::ItemKind::Struct(ref variant_data, _) => variant_data.fields().is_empty(),