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_attr as attr;
185 use rustc_expand::base::{Annotatable, ExtCtxt};
186 use rustc_session::parse::ParseSess;
187 use rustc_span::source_map::respan;
188 use rustc_span::symbol::{kw, sym, Symbol};
189 use rustc_span::Span;
190 use syntax::ast::{self, BinOpKind, EnumDef, Expr, Generics, Ident, PatKind};
191 use syntax::ast::{GenericArg, GenericParamKind, VariantData};
193 use syntax::util::map_in_place::MapInPlace;
195 use ty::{LifetimeBounds, Path, Ptr, PtrTy, Self_, Ty};
201 pub struct TraitDef<'a> {
202 /// The span for the current #[derive(Foo)] header.
205 pub attributes: Vec<ast::Attribute>,
207 /// Path of the trait, including any type parameters
210 /// Additional bounds required of any type parameters of the type,
211 /// other than the current trait
212 pub additional_bounds: Vec<Ty<'a>>,
214 /// Any extra lifetimes and/or bounds, e.g., `D: serialize::Decoder`
215 pub generics: LifetimeBounds<'a>,
217 /// Is it an `unsafe` trait?
220 /// Can this trait be derived for unions?
221 pub supports_unions: bool,
223 pub methods: Vec<MethodDef<'a>>,
225 pub associated_types: Vec<(ast::Ident, Ty<'a>)>,
228 pub struct MethodDef<'a> {
229 /// name of the method
231 /// List of generics, e.g., `R: rand::Rng`
232 pub generics: LifetimeBounds<'a>,
234 /// Whether there is a self argument (outer Option) i.e., whether
235 /// this is a static function, and whether it is a pointer (inner
237 pub explicit_self: Option<Option<PtrTy>>,
239 /// Arguments other than the self argument
240 pub args: Vec<(Ty<'a>, &'a str)>,
245 pub attributes: Vec<ast::Attribute>,
247 // Is it an `unsafe fn`?
250 /// Can we combine fieldless variants for enums into a single match arm?
251 pub unify_fieldless_variants: bool,
253 pub combine_substructure: RefCell<CombineSubstructureFunc<'a>>,
256 /// All the data about the data structure/method being derived upon.
257 pub struct Substructure<'a> {
259 pub type_ident: Ident,
260 /// ident of the method
261 pub method_ident: Ident,
262 /// dereferenced access to any `Self_` or `Ptr(Self_, _)` arguments
263 pub self_args: &'a [P<Expr>],
264 /// verbatim access to any other arguments
265 pub nonself_args: &'a [P<Expr>],
266 pub fields: &'a SubstructureFields<'a>,
269 /// Summary of the relevant parts of a struct/enum field.
270 pub struct FieldInfo<'a> {
272 /// None for tuple structs/normal enum variants, Some for normal
273 /// structs/struct enum variants.
274 pub name: Option<Ident>,
275 /// The expression corresponding to this field of `self`
276 /// (specifically, a reference to it).
278 /// The expressions corresponding to references to this field in
279 /// the other `Self` arguments.
280 pub other: Vec<P<Expr>>,
281 /// The attributes on the field
282 pub attrs: &'a [ast::Attribute],
285 /// Fields for a static method
286 pub enum StaticFields {
287 /// Tuple and unit structs/enum variants like this.
288 Unnamed(Vec<Span>, bool /*is tuple*/),
289 /// Normal structs/struct variants.
290 Named(Vec<(Ident, Span)>),
293 /// A summary of the possible sets of fields.
294 pub enum SubstructureFields<'a> {
295 Struct(&'a ast::VariantData, Vec<FieldInfo<'a>>),
296 /// Matching variants of the enum: variant index, variant count, ast::Variant,
297 /// fields: the field name is only non-`None` in the case of a struct
299 EnumMatching(usize, usize, &'a ast::Variant, Vec<FieldInfo<'a>>),
301 /// Non-matching variants of the enum, but with all state hidden from
302 /// the consequent code. The first component holds `Ident`s for all of
303 /// the `Self` arguments; the second component is a slice of all of the
304 /// variants for the enum itself, and the third component is a list of
305 /// `Ident`s bound to the variant index values for each of the actual
306 /// input `Self` arguments.
307 EnumNonMatchingCollapsed(Vec<Ident>, &'a [ast::Variant], &'a [Ident]),
309 /// A static method where `Self` is a struct.
310 StaticStruct(&'a ast::VariantData, StaticFields),
311 /// A static method where `Self` is an enum.
312 StaticEnum(&'a ast::EnumDef, Vec<(Ident, Span, StaticFields)>),
315 /// Combine the values of all the fields together. The last argument is
316 /// all the fields of all the structures.
317 pub type CombineSubstructureFunc<'a> =
318 Box<dyn FnMut(&mut ExtCtxt<'_>, Span, &Substructure<'_>) -> P<Expr> + 'a>;
320 /// Deal with non-matching enum variants. The tuple is a list of
321 /// identifiers (one for each `Self` argument, which could be any of the
322 /// variants since they have been collapsed together) and the identifiers
323 /// holding the variant index value for each of the `Self` arguments. The
324 /// last argument is all the non-`Self` args of the method being derived.
325 pub type EnumNonMatchCollapsedFunc<'a> =
326 Box<dyn FnMut(&mut ExtCtxt<'_>, Span, (&[Ident], &[Ident]), &[P<Expr>]) -> P<Expr> + 'a>;
328 pub fn combine_substructure(
329 f: CombineSubstructureFunc<'_>,
330 ) -> RefCell<CombineSubstructureFunc<'_>> {
334 /// This method helps to extract all the type parameters referenced from a
335 /// type. For a type parameter `<T>`, it looks for either a `TyPath` that
336 /// is not global and starts with `T`, or a `TyQPath`.
337 fn find_type_parameters(
339 ty_param_names: &[ast::Name],
341 ) -> Vec<P<ast::Ty>> {
344 struct Visitor<'a, 'b> {
346 ty_param_names: &'a [ast::Name],
347 types: Vec<P<ast::Ty>>,
350 impl<'a, 'b> visit::Visitor<'a> for Visitor<'a, 'b> {
351 fn visit_ty(&mut self, ty: &'a ast::Ty) {
352 if let ast::TyKind::Path(_, ref path) = ty.kind {
353 if let Some(segment) = path.segments.first() {
354 if self.ty_param_names.contains(&segment.ident.name) {
355 self.types.push(P(ty.clone()));
360 visit::walk_ty(self, ty)
363 fn visit_mac(&mut self, mac: &ast::Mac) {
364 self.cx.span_err(mac.span(), "`derive` cannot be used on items with type macros");
368 let mut visitor = Visitor { cx, ty_param_names, types: Vec::new() };
369 visit::Visitor::visit_ty(&mut visitor, ty);
374 impl<'a> TraitDef<'a> {
377 cx: &mut ExtCtxt<'_>,
378 mitem: &ast::MetaItem,
379 item: &'a Annotatable,
380 push: &mut dyn FnMut(Annotatable),
382 self.expand_ext(cx, mitem, item, push, false);
387 cx: &mut ExtCtxt<'_>,
388 mitem: &ast::MetaItem,
389 item: &'a Annotatable,
390 push: &mut dyn FnMut(Annotatable),
394 Annotatable::Item(ref item) => {
395 let is_packed = item.attrs.iter().any(|attr| {
396 for r in attr::find_repr_attrs(&cx.parse_sess, attr) {
397 if let attr::ReprPacked(_) = r {
403 let has_no_type_params = match item.kind {
404 ast::ItemKind::Struct(_, ref generics)
405 | ast::ItemKind::Enum(_, ref generics)
406 | ast::ItemKind::Union(_, ref generics) => {
407 !generics.params.iter().any(|param| match param.kind {
408 ast::GenericParamKind::Type { .. } => true,
413 // Non-ADT derive is an error, but it should have been
415 // librustc_expand/expand.rs:MacroExpander::fully_expand_fragment()
416 // librustc_expand/base.rs:Annotatable::derive_allowed()
420 let container_id = cx.current_expansion.id.expn_data().parent;
421 let always_copy = has_no_type_params && cx.resolver.has_derive_copy(container_id);
422 let use_temporaries = is_packed && always_copy;
424 let newitem = match item.kind {
425 ast::ItemKind::Struct(ref struct_def, ref generics) => self.expand_struct_def(
433 ast::ItemKind::Enum(ref enum_def, ref generics) => {
434 // We ignore `use_temporaries` here, because
435 // `repr(packed)` enums cause an error later on.
437 // This can only cause further compilation errors
438 // downstream in blatantly illegal code, so it
440 self.expand_enum_def(
449 ast::ItemKind::Union(ref struct_def, ref generics) => {
450 if self.supports_unions {
451 self.expand_struct_def(
460 cx.span_err(mitem.span, "this trait cannot be derived for unions");
466 // Keep the lint attributes of the previous item to control how the
467 // generated implementations are linted
468 let mut attrs = newitem.attrs.clone();
481 .contains(&a.name_or_empty())
485 push(Annotatable::Item(P(ast::Item { attrs: attrs, ..(*newitem).clone() })))
488 // Non-Item derive is an error, but it should have been
490 // librustc_expand/expand.rs:MacroExpander::fully_expand_fragment()
491 // librustc_expand/base.rs:Annotatable::derive_allowed()
497 /// Given that we are deriving a trait `DerivedTrait` for a type like:
499 /// ```ignore (only-for-syntax-highlight)
500 /// struct Struct<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z> where C: WhereTrait {
503 /// b1: <B as DeclaredTrait>::Item,
504 /// c1: <C as WhereTrait>::Item,
505 /// c2: Option<<C as WhereTrait>::Item>,
510 /// create an impl like:
512 /// ```ignore (only-for-syntax-highlight)
513 /// impl<'a, ..., 'z, A, B: DeclaredTrait, C, ... Z> where
515 /// A: DerivedTrait + B1 + ... + BN,
516 /// B: DerivedTrait + B1 + ... + BN,
517 /// C: DerivedTrait + B1 + ... + BN,
518 /// B::Item: DerivedTrait + B1 + ... + BN,
519 /// <C as WhereTrait>::Item: DerivedTrait + B1 + ... + BN,
526 /// where B1, ..., BN are the bounds given by `bounds_paths`.'. Z is a phantom type, and
527 /// therefore does not get bound by the derived trait.
528 fn create_derived_impl(
530 cx: &mut ExtCtxt<'_>,
533 field_tys: Vec<P<ast::Ty>>,
534 methods: Vec<P<ast::AssocItem>>,
536 let trait_path = self.path.to_path(cx, self.span, type_ident, generics);
538 // Transform associated types from `deriving::ty::Ty` into `ast::AssocItem`
539 let associated_types = self.associated_types.iter().map(|&(ident, ref type_def)| {
541 id: ast::DUMMY_NODE_ID,
544 vis: respan(self.span.shrink_to_lo(), ast::VisibilityKind::Inherited),
545 defaultness: ast::Defaultness::Final,
547 kind: ast::AssocItemKind::TyAlias(
550 Some(type_def.to_ty(cx, self.span, type_ident, generics)),
556 let Generics { mut params, mut where_clause, span } =
557 self.generics.to_generics(cx, self.span, type_ident, generics);
559 // Create the generic parameters
560 params.extend(generics.params.iter().map(|param| match param.kind {
561 GenericParamKind::Lifetime { .. } => param.clone(),
562 GenericParamKind::Type { .. } => {
563 // I don't think this can be moved out of the loop, since
564 // a GenericBound requires an ast id
566 // extra restrictions on the generics parameters to the
567 // type being derived upon
568 self.additional_bounds.iter().map(|p| {
569 cx.trait_bound(p.to_path(cx, self.span, type_ident, generics))
571 // require the current trait
572 iter::once(cx.trait_bound(trait_path.clone()))
574 // also add in any bounds from the declaration
575 param.bounds.iter().cloned()
578 cx.typaram(self.span, param.ident, vec![], bounds, None)
580 GenericParamKind::Const { .. } => param.clone(),
583 // and similarly for where clauses
584 where_clause.predicates.extend(generics.where_clause.predicates.iter().map(|clause| {
586 ast::WherePredicate::BoundPredicate(ref wb) => {
587 ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
589 bound_generic_params: wb.bound_generic_params.clone(),
590 bounded_ty: wb.bounded_ty.clone(),
591 bounds: wb.bounds.iter().cloned().collect(),
594 ast::WherePredicate::RegionPredicate(ref rb) => {
595 ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
597 lifetime: rb.lifetime,
598 bounds: rb.bounds.iter().cloned().collect(),
601 ast::WherePredicate::EqPredicate(ref we) => {
602 ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
603 id: ast::DUMMY_NODE_ID,
605 lhs_ty: we.lhs_ty.clone(),
606 rhs_ty: we.rhs_ty.clone(),
613 // Extra scope required here so ty_params goes out of scope before params is moved
615 let mut ty_params = params
617 .filter_map(|param| match param.kind {
618 ast::GenericParamKind::Type { .. } => Some(param),
623 if ty_params.peek().is_some() {
624 let ty_param_names: Vec<ast::Name> =
625 ty_params.map(|ty_param| ty_param.ident.name).collect();
627 for field_ty in field_tys {
628 let tys = find_type_parameters(&field_ty, &ty_param_names, cx);
631 // if we have already handled this type, skip it
632 if let ast::TyKind::Path(_, ref p) = ty.kind {
633 if p.segments.len() == 1
634 && ty_param_names.contains(&p.segments[0].ident.name)
639 let mut bounds: Vec<_> = self
642 .map(|p| cx.trait_bound(p.to_path(cx, self.span, type_ident, generics)))
645 // require the current trait
646 bounds.push(cx.trait_bound(trait_path.clone()));
648 let predicate = ast::WhereBoundPredicate {
650 bound_generic_params: Vec::new(),
655 let predicate = ast::WherePredicate::BoundPredicate(predicate);
656 where_clause.predicates.push(predicate);
662 let trait_generics = Generics { params, where_clause, span };
664 // Create the reference to the trait.
665 let trait_ref = cx.trait_ref(trait_path);
667 let self_params: Vec<_> = generics
670 .map(|param| match param.kind {
671 GenericParamKind::Lifetime { .. } => {
672 GenericArg::Lifetime(cx.lifetime(self.span, param.ident))
674 GenericParamKind::Type { .. } => {
675 GenericArg::Type(cx.ty_ident(self.span, param.ident))
677 GenericParamKind::Const { .. } => {
678 GenericArg::Const(cx.const_ident(self.span, param.ident))
683 // Create the type of `self`.
684 let path = cx.path_all(self.span, false, vec![type_ident], self_params);
685 let self_type = cx.ty_path(path);
687 let attr = cx.attribute(cx.meta_word(self.span, sym::automatically_derived));
688 // Just mark it now since we know that it'll end up used downstream
689 attr::mark_used(&attr);
690 let opt_trait_ref = Some(trait_ref);
692 let word = syntax::attr::mk_nested_word_item(Ident::new(
693 Symbol::intern("unused_qualifications"),
696 let list = syntax::attr::mk_list_item(Ident::new(sym::allow, self.span), vec![word]);
700 let mut a = vec![attr, unused_qual];
701 a.extend(self.attributes.iter().cloned());
703 let unsafety = if self.is_unsafe { ast::Unsafe::Yes(self.span) } else { ast::Unsafe::No };
709 ast::ItemKind::Impl {
711 polarity: ast::ImplPolarity::Positive,
712 defaultness: ast::Defaultness::Final,
713 constness: ast::Const::No,
714 generics: trait_generics,
715 of_trait: opt_trait_ref,
717 items: methods.into_iter().chain(associated_types).collect(),
722 fn expand_struct_def(
724 cx: &mut ExtCtxt<'_>,
725 struct_def: &'a VariantData,
729 use_temporaries: bool,
731 let field_tys: Vec<P<ast::Ty>> =
732 struct_def.fields().iter().map(|field| field.ty.clone()).collect();
738 let (explicit_self, self_args, nonself_args, tys) =
739 method_def.split_self_nonself_args(cx, self, type_ident, generics);
741 let body = if from_scratch || method_def.is_static() {
742 method_def.expand_static_struct_method_body(
751 method_def.expand_struct_method_body(
762 method_def.create_method(cx, self, type_ident, generics, explicit_self, tys, body)
766 self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
771 cx: &mut ExtCtxt<'_>,
772 enum_def: &'a EnumDef,
773 type_attrs: &[ast::Attribute],
778 let mut field_tys = Vec::new();
780 for variant in &enum_def.variants {
781 field_tys.extend(variant.data.fields().iter().map(|field| field.ty.clone()));
788 let (explicit_self, self_args, nonself_args, tys) =
789 method_def.split_self_nonself_args(cx, self, type_ident, generics);
791 let body = if from_scratch || method_def.is_static() {
792 method_def.expand_static_enum_method_body(
801 method_def.expand_enum_method_body(
812 method_def.create_method(cx, self, type_ident, generics, explicit_self, tys, body)
816 self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
820 fn find_repr_type_name(sess: &ParseSess, type_attrs: &[ast::Attribute]) -> &'static str {
821 let mut repr_type_name = "isize";
822 for a in type_attrs {
823 for r in &attr::find_repr_attrs(sess, a) {
824 repr_type_name = match *r {
828 | attr::ReprTransparent
829 | attr::ReprNoNiche => continue,
831 attr::ReprC => "i32",
833 attr::ReprInt(attr::SignedInt(ast::IntTy::Isize)) => "isize",
834 attr::ReprInt(attr::SignedInt(ast::IntTy::I8)) => "i8",
835 attr::ReprInt(attr::SignedInt(ast::IntTy::I16)) => "i16",
836 attr::ReprInt(attr::SignedInt(ast::IntTy::I32)) => "i32",
837 attr::ReprInt(attr::SignedInt(ast::IntTy::I64)) => "i64",
838 attr::ReprInt(attr::SignedInt(ast::IntTy::I128)) => "i128",
840 attr::ReprInt(attr::UnsignedInt(ast::UintTy::Usize)) => "usize",
841 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U8)) => "u8",
842 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U16)) => "u16",
843 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U32)) => "u32",
844 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U64)) => "u64",
845 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U128)) => "u128",
852 impl<'a> MethodDef<'a> {
853 fn call_substructure_method(
855 cx: &mut ExtCtxt<'_>,
856 trait_: &TraitDef<'_>,
858 self_args: &[P<Expr>],
859 nonself_args: &[P<Expr>],
860 fields: &SubstructureFields<'_>,
862 let substructure = Substructure {
864 method_ident: cx.ident_of(self.name, trait_.span),
869 let mut f = self.combine_substructure.borrow_mut();
870 let f: &mut CombineSubstructureFunc<'_> = &mut *f;
871 f(cx, trait_.span, &substructure)
876 cx: &mut ExtCtxt<'_>,
877 trait_: &TraitDef<'_>,
881 self.ret_ty.to_ty(cx, trait_.span, type_ident, generics)
884 fn is_static(&self) -> bool {
885 self.explicit_self.is_none()
888 fn split_self_nonself_args(
890 cx: &mut ExtCtxt<'_>,
891 trait_: &TraitDef<'_>,
894 ) -> (Option<ast::ExplicitSelf>, Vec<P<Expr>>, Vec<P<Expr>>, Vec<(Ident, P<ast::Ty>)>) {
895 let mut self_args = Vec::new();
896 let mut nonself_args = Vec::new();
897 let mut arg_tys = Vec::new();
898 let mut nonstatic = false;
900 let ast_explicit_self = self.explicit_self.as_ref().map(|self_ptr| {
901 let (self_expr, explicit_self) = ty::get_explicit_self(cx, trait_.span, self_ptr);
903 self_args.push(self_expr);
909 for (ty, name) in self.args.iter() {
910 let ast_ty = ty.to_ty(cx, trait_.span, type_ident, generics);
911 let ident = cx.ident_of(name, trait_.span);
912 arg_tys.push((ident, ast_ty));
914 let arg_expr = cx.expr_ident(trait_.span, ident);
917 // for static methods, just treat any Self
918 // arguments as a normal arg
919 Self_ if nonstatic => {
920 self_args.push(arg_expr);
922 Ptr(ref ty, _) if (if let Self_ = **ty { true } else { false }) && nonstatic => {
923 self_args.push(cx.expr_deref(trait_.span, arg_expr))
926 nonself_args.push(arg_expr);
931 (ast_explicit_self, self_args, nonself_args, arg_tys)
936 cx: &mut ExtCtxt<'_>,
937 trait_: &TraitDef<'_>,
940 explicit_self: Option<ast::ExplicitSelf>,
941 arg_types: Vec<(Ident, P<ast::Ty>)>,
943 ) -> P<ast::AssocItem> {
944 // Create the generics that aren't for `Self`.
945 let fn_generics = self.generics.to_generics(cx, trait_.span, type_ident, generics);
948 let self_args = explicit_self.map(|explicit_self| {
949 let ident = Ident::with_dummy_span(kw::SelfLower).with_span_pos(trait_.span);
950 ast::Param::from_self(ast::AttrVec::default(), explicit_self, ident)
953 arg_types.into_iter().map(|(name, ty)| cx.param(trait_.span, name, ty));
954 self_args.into_iter().chain(nonself_args).collect()
957 let ret_type = self.get_ret_ty(cx, trait_, generics, type_ident);
959 let method_ident = cx.ident_of(self.name, trait_.span);
960 let fn_decl = cx.fn_decl(args, ast::FunctionRetTy::Ty(ret_type));
961 let body_block = cx.block_expr(body);
963 let unsafety = if self.is_unsafe { ast::Unsafe::Yes(trait_.span) } else { ast::Unsafe::No };
965 let trait_lo_sp = trait_.span.shrink_to_lo();
967 let sig = ast::FnSig {
968 header: ast::FnHeader { unsafety, ext: ast::Extern::None, ..ast::FnHeader::default() },
972 // Create the method.
974 id: ast::DUMMY_NODE_ID,
975 attrs: self.attributes.clone(),
977 vis: respan(trait_lo_sp, ast::VisibilityKind::Inherited),
978 defaultness: ast::Defaultness::Final,
980 kind: ast::AssocItemKind::Fn(sig, fn_generics, Some(body_block)),
986 /// #[derive(PartialEq)]
988 /// struct A { x: i32, y: i32 }
990 /// // equivalent to:
991 /// impl PartialEq for A {
992 /// fn eq(&self, other: &A) -> bool {
994 /// A {x: ref __self_0_0, y: ref __self_0_1} => {
996 /// A {x: ref __self_1_0, y: ref __self_1_1} => {
997 /// __self_0_0.eq(__self_1_0) && __self_0_1.eq(__self_1_1)
1005 /// // or if A is repr(packed) - note fields are matched by-value
1006 /// // instead of by-reference.
1007 /// impl PartialEq for A {
1008 /// fn eq(&self, other: &A) -> bool {
1010 /// A {x: __self_0_0, y: __self_0_1} => {
1012 /// A {x: __self_1_0, y: __self_1_1} => {
1013 /// __self_0_0.eq(&__self_1_0) && __self_0_1.eq(&__self_1_1)
1021 fn expand_struct_method_body<'b>(
1023 cx: &mut ExtCtxt<'_>,
1024 trait_: &TraitDef<'b>,
1025 struct_def: &'b VariantData,
1027 self_args: &[P<Expr>],
1028 nonself_args: &[P<Expr>],
1029 use_temporaries: bool,
1031 let mut raw_fields = Vec::new(); // Vec<[fields of self],
1032 // [fields of next Self arg], [etc]>
1033 let mut patterns = Vec::new();
1034 for i in 0..self_args.len() {
1035 let struct_path = cx.path(trait_.span, vec![type_ident]);
1036 let (pat, ident_expr) = trait_.create_struct_pattern(
1040 &format!("__self_{}", i),
1041 ast::Mutability::Not,
1045 raw_fields.push(ident_expr);
1048 // transpose raw_fields
1049 let fields = if !raw_fields.is_empty() {
1050 let mut raw_fields = raw_fields.into_iter().map(|v| v.into_iter());
1051 let first_field = raw_fields.next().unwrap();
1052 let mut other_fields: Vec<vec::IntoIter<_>> = raw_fields.collect();
1054 .map(|(span, opt_id, field, attrs)| FieldInfo {
1060 .map(|l| match l.next().unwrap() {
1068 cx.span_bug(trait_.span, "no `self` parameter for method in generic `derive`")
1071 // body of the inner most destructuring match
1072 let mut body = self.call_substructure_method(
1078 &Struct(struct_def, fields),
1081 // make a series of nested matches, to destructure the
1082 // structs. This is actually right-to-left, but it shouldn't
1084 for (arg_expr, pat) in self_args.iter().zip(patterns) {
1085 body = cx.expr_match(
1088 vec![cx.arm(trait_.span, pat.clone(), body)],
1095 fn expand_static_struct_method_body(
1097 cx: &mut ExtCtxt<'_>,
1098 trait_: &TraitDef<'_>,
1099 struct_def: &VariantData,
1101 self_args: &[P<Expr>],
1102 nonself_args: &[P<Expr>],
1104 let summary = trait_.summarise_struct(cx, struct_def);
1106 self.call_substructure_method(
1112 &StaticStruct(struct_def, summary),
1117 /// #[derive(PartialEq)]
1124 /// // is equivalent to
1126 /// impl PartialEq for A {
1127 /// fn eq(&self, other: &A) -> ::bool {
1128 /// match (&*self, &*other) {
1129 /// (&A1, &A1) => true,
1130 /// (&A2(ref self_0),
1131 /// &A2(ref __arg_1_0)) => (*self_0).eq(&(*__arg_1_0)),
1133 /// let __self_vi = match *self { A1(..) => 0, A2(..) => 1 };
1134 /// let __arg_1_vi = match *other { A1(..) => 0, A2(..) => 1 };
1142 /// (Of course `__self_vi` and `__arg_1_vi` are unused for
1143 /// `PartialEq`, and those subcomputations will hopefully be removed
1144 /// as their results are unused. The point of `__self_vi` and
1145 /// `__arg_1_vi` is for `PartialOrd`; see #15503.)
1146 fn expand_enum_method_body<'b>(
1148 cx: &mut ExtCtxt<'_>,
1149 trait_: &TraitDef<'b>,
1150 enum_def: &'b EnumDef,
1151 type_attrs: &[ast::Attribute],
1153 self_args: Vec<P<Expr>>,
1154 nonself_args: &[P<Expr>],
1156 self.build_enum_match_tuple(
1167 /// Creates a match for a tuple of all `self_args`, where either all
1168 /// variants match, or it falls into a catch-all for when one variant
1171 /// There are N + 1 cases because is a case for each of the N
1172 /// variants where all of the variants match, and one catch-all for
1173 /// when one does not match.
1175 /// As an optimization we generate code which checks whether all variants
1176 /// match first which makes llvm see that C-like enums can be compiled into
1177 /// a simple equality check (for PartialEq).
1179 /// The catch-all handler is provided access the variant index values
1180 /// for each of the self-args, carried in precomputed variables.
1183 /// let __self0_vi = unsafe {
1184 /// std::intrinsics::discriminant_value(&self) } as i32;
1185 /// let __self1_vi = unsafe {
1186 /// std::intrinsics::discriminant_value(&arg1) } as i32;
1187 /// let __self2_vi = unsafe {
1188 /// std::intrinsics::discriminant_value(&arg2) } as i32;
1190 /// if __self0_vi == __self1_vi && __self0_vi == __self2_vi && ... {
1192 /// (Variant1, Variant1, ...) => Body1
1193 /// (Variant2, Variant2, ...) => Body2,
1195 /// _ => ::core::intrinsics::unreachable()
1199 /// ... // catch-all remainder can inspect above variant index values.
1202 fn build_enum_match_tuple<'b>(
1204 cx: &mut ExtCtxt<'_>,
1205 trait_: &TraitDef<'b>,
1206 enum_def: &'b EnumDef,
1207 type_attrs: &[ast::Attribute],
1209 mut self_args: Vec<P<Expr>>,
1210 nonself_args: &[P<Expr>],
1212 let sp = trait_.span;
1213 let variants = &enum_def.variants;
1215 let self_arg_names = iter::once("__self".to_string())
1221 .map(|(arg_count, _self_arg)| format!("__arg_{}", arg_count)),
1223 .collect::<Vec<String>>();
1225 let self_arg_idents =
1226 self_arg_names.iter().map(|name| cx.ident_of(name, sp)).collect::<Vec<ast::Ident>>();
1228 // The `vi_idents` will be bound, solely in the catch-all, to
1229 // a series of let statements mapping each self_arg to an int
1230 // value corresponding to its discriminant.
1231 let vi_idents = self_arg_names
1234 let vi_suffix = format!("{}_vi", &name[..]);
1235 cx.ident_of(&vi_suffix[..], trait_.span)
1237 .collect::<Vec<ast::Ident>>();
1239 // Builds, via callback to call_substructure_method, the
1240 // delegated expression that handles the catch-all case,
1241 // using `__variants_tuple` to drive logic if necessary.
1242 let catch_all_substructure =
1243 EnumNonMatchingCollapsed(self_arg_idents, &variants[..], &vi_idents[..]);
1245 let first_fieldless = variants.iter().find(|v| v.data.fields().is_empty());
1247 // These arms are of the form:
1248 // (Variant1, Variant1, ...) => Body1
1249 // (Variant2, Variant2, ...) => Body2
1251 // where each tuple has length = self_args.len()
1252 let mut match_arms: Vec<ast::Arm> = variants
1255 .filter(|&(_, v)| !(self.unify_fieldless_variants && v.data.fields().is_empty()))
1256 .map(|(index, variant)| {
1257 let mk_self_pat = |cx: &mut ExtCtxt<'_>, self_arg_name: &str| {
1258 let (p, idents) = trait_.create_enum_variant_pattern(
1263 ast::Mutability::Not,
1265 (cx.pat(sp, PatKind::Ref(p, ast::Mutability::Not)), idents)
1268 // A single arm has form (&VariantK, &VariantK, ...) => BodyK
1269 // (see "Final wrinkle" note below for why.)
1270 let mut subpats = Vec::with_capacity(self_arg_names.len());
1271 let mut self_pats_idents = Vec::with_capacity(self_arg_names.len() - 1);
1272 let first_self_pat_idents = {
1273 let (p, idents) = mk_self_pat(cx, &self_arg_names[0]);
1277 for self_arg_name in &self_arg_names[1..] {
1278 let (p, idents) = mk_self_pat(cx, &self_arg_name[..]);
1280 self_pats_idents.push(idents);
1283 // Here is the pat = `(&VariantK, &VariantK, ...)`
1284 let single_pat = cx.pat_tuple(sp, subpats);
1286 // For the BodyK, we need to delegate to our caller,
1287 // passing it an EnumMatching to indicate which case
1290 // All of the Self args have the same variant in these
1291 // cases. So we transpose the info in self_pats_idents
1292 // to gather the getter expressions together, in the
1293 // form that EnumMatching expects.
1295 // The transposition is driven by walking across the
1296 // arg fields of the variant for the first self pat.
1297 let field_tuples = first_self_pat_idents
1300 // For each arg field of self, pull out its getter expr ...
1301 .map(|(field_index, (sp, opt_ident, self_getter_expr, attrs))| {
1302 // ... but FieldInfo also wants getter expr
1303 // for matching other arguments of Self type;
1304 // so walk across the *other* self_pats_idents
1305 // and pull out getter for same field in each
1306 // of them (using `field_index` tracked above).
1307 // That is the heart of the transposition.
1308 let others = self_pats_idents
1311 let (_, _opt_ident, ref other_getter_expr, _) = fields[field_index];
1313 // All Self args have same variant, so
1314 // opt_idents are the same. (Assert
1315 // here to make it self-evident that
1316 // it is okay to ignore `_opt_ident`.)
1317 assert!(opt_ident == _opt_ident);
1319 other_getter_expr.clone()
1321 .collect::<Vec<P<Expr>>>();
1326 self_: self_getter_expr,
1331 .collect::<Vec<FieldInfo<'_>>>();
1333 // Now, for some given VariantK, we have built up
1334 // expressions for referencing every field of every
1335 // Self arg, assuming all are instances of VariantK.
1336 // Build up code associated with such a case.
1337 let substructure = EnumMatching(index, variants.len(), variant, field_tuples);
1338 let arm_expr = self.call_substructure_method(
1347 cx.arm(sp, single_pat, arm_expr)
1351 let default = match first_fieldless {
1352 Some(v) if self.unify_fieldless_variants => {
1353 // We need a default case that handles the fieldless variants.
1354 // The index and actual variant aren't meaningful in this case,
1355 // so just use whatever
1356 let substructure = EnumMatching(0, variants.len(), v, Vec::new());
1357 Some(self.call_substructure_method(
1366 _ if variants.len() > 1 && self_args.len() > 1 => {
1367 // Since we know that all the arguments will match if we reach
1368 // the match expression we add the unreachable intrinsics as the
1369 // result of the catch all which should help llvm in optimizing it
1370 Some(deriving::call_intrinsic(cx, sp, "unreachable", vec![]))
1374 if let Some(arm) = default {
1375 match_arms.push(cx.arm(sp, cx.pat_wild(sp), arm));
1378 // We will usually need the catch-all after matching the
1379 // tuples `(VariantK, VariantK, ...)` for each VariantK of the
1382 // * when there is only one Self arg, the arms above suffice
1383 // (and the deriving we call back into may not be prepared to
1384 // handle EnumNonMatchCollapsed), and,
1386 // * when the enum has only one variant, the single arm that
1387 // is already present always suffices.
1389 // * In either of the two cases above, if we *did* add a
1390 // catch-all `_` match, it would trigger the
1391 // unreachable-pattern error.
1393 if variants.len() > 1 && self_args.len() > 1 {
1394 // Build a series of let statements mapping each self_arg
1395 // to its discriminant value. If this is a C-style enum
1396 // with a specific repr type, then casts the values to
1397 // that type. Otherwise casts to `i32` (the default repr
1400 // i.e., for `enum E<T> { A, B(1), C(T, T) }`, and a deriving
1401 // with three Self args, builds three statements:
1404 // let __self0_vi = unsafe {
1405 // std::intrinsics::discriminant_value(&self) } as i32;
1406 // let __self1_vi = unsafe {
1407 // std::intrinsics::discriminant_value(&arg1) } as i32;
1408 // let __self2_vi = unsafe {
1409 // std::intrinsics::discriminant_value(&arg2) } as i32;
1411 let mut index_let_stmts: Vec<ast::Stmt> = Vec::with_capacity(vi_idents.len() + 1);
1413 // We also build an expression which checks whether all discriminants are equal
1414 // discriminant_test = __self0_vi == __self1_vi && __self0_vi == __self2_vi && ...
1415 let mut discriminant_test = cx.expr_bool(sp, true);
1417 let target_type_name = find_repr_type_name(&cx.parse_sess, type_attrs);
1419 let mut first_ident = None;
1420 for (&ident, self_arg) in vi_idents.iter().zip(&self_args) {
1421 let self_addr = cx.expr_addr_of(sp, self_arg.clone());
1423 deriving::call_intrinsic(cx, sp, "discriminant_value", vec![self_addr]);
1425 let target_ty = cx.ty_ident(sp, cx.ident_of(target_type_name, sp));
1426 let variant_disr = cx.expr_cast(sp, variant_value, target_ty);
1427 let let_stmt = cx.stmt_let(sp, false, ident, variant_disr);
1428 index_let_stmts.push(let_stmt);
1432 let first_expr = cx.expr_ident(sp, first);
1433 let id = cx.expr_ident(sp, ident);
1434 let test = cx.expr_binary(sp, BinOpKind::Eq, first_expr, id);
1436 cx.expr_binary(sp, BinOpKind::And, discriminant_test, test)
1439 first_ident = Some(ident);
1444 let arm_expr = self.call_substructure_method(
1450 &catch_all_substructure,
1453 // Final wrinkle: the self_args are expressions that deref
1454 // down to desired places, but we cannot actually deref
1455 // them when they are fed as r-values into a tuple
1456 // expression; here add a layer of borrowing, turning
1457 // `(*self, *__arg_0, ...)` into `(&*self, &*__arg_0, ...)`.
1458 self_args.map_in_place(|self_arg| cx.expr_addr_of(sp, self_arg));
1459 let match_arg = cx.expr(sp, ast::ExprKind::Tup(self_args));
1461 // Lastly we create an expression which branches on all discriminants being equal
1462 // if discriminant_test {
1464 // (Variant1, Variant1, ...) => Body1
1465 // (Variant2, Variant2, ...) => Body2,
1467 // _ => ::core::intrinsics::unreachable()
1471 // <delegated expression referring to __self0_vi, et al.>
1473 let all_match = cx.expr_match(sp, match_arg, match_arms);
1474 let arm_expr = cx.expr_if(sp, discriminant_test, all_match, Some(arm_expr));
1475 index_let_stmts.push(cx.stmt_expr(arm_expr));
1476 cx.expr_block(cx.block(sp, index_let_stmts))
1477 } else if variants.is_empty() {
1478 // As an additional wrinkle, For a zero-variant enum A,
1479 // currently the compiler
1480 // will accept `fn (a: &Self) { match *a { } }`
1481 // but rejects `fn (a: &Self) { match (&*a,) { } }`
1482 // as well as `fn (a: &Self) { match ( *a,) { } }`
1484 // This means that the strategy of building up a tuple of
1485 // all Self arguments fails when Self is a zero variant
1486 // enum: rustc rejects the expanded program, even though
1487 // the actual code tends to be impossible to execute (at
1488 // least safely), according to the type system.
1490 // The most expedient fix for this is to just let the
1491 // code fall through to the catch-all. But even this is
1492 // error-prone, since the catch-all as defined above would
1493 // generate code like this:
1495 // _ => { let __self0 = match *self { };
1496 // let __self1 = match *__arg_0 { };
1497 // <catch-all-expr> }
1499 // Which is yields bindings for variables which type
1500 // inference cannot resolve to unique types.
1502 // One option to the above might be to add explicit type
1503 // annotations. But the *only* reason to go down that path
1504 // would be to try to make the expanded output consistent
1505 // with the case when the number of enum variants >= 1.
1507 // That just isn't worth it. In fact, trying to generate
1508 // sensible code for *any* deriving on a zero-variant enum
1509 // does not make sense. But at the same time, for now, we
1510 // do not want to cause a compile failure just because the
1511 // user happened to attach a deriving to their
1512 // zero-variant enum.
1514 // Instead, just generate a failing expression for the
1515 // zero variant case, skipping matches and also skipping
1516 // delegating back to the end user code entirely.
1518 // (See also #4499 and #12609; note that some of the
1519 // discussions there influence what choice we make here;
1520 // e.g., if we feature-gate `match x { ... }` when x refers
1521 // to an uninhabited type (e.g., a zero-variant enum or a
1522 // type holding such an enum), but do not feature-gate
1523 // zero-variant enums themselves, then attempting to
1524 // derive Debug on such a type could here generate code
1525 // that needs the feature gate enabled.)
1527 deriving::call_intrinsic(cx, sp, "unreachable", vec![])
1529 // Final wrinkle: the self_args are expressions that deref
1530 // down to desired places, but we cannot actually deref
1531 // them when they are fed as r-values into a tuple
1532 // expression; here add a layer of borrowing, turning
1533 // `(*self, *__arg_0, ...)` into `(&*self, &*__arg_0, ...)`.
1534 self_args.map_in_place(|self_arg| cx.expr_addr_of(sp, self_arg));
1535 let match_arg = cx.expr(sp, ast::ExprKind::Tup(self_args));
1536 cx.expr_match(sp, match_arg, match_arms)
1540 fn expand_static_enum_method_body(
1542 cx: &mut ExtCtxt<'_>,
1543 trait_: &TraitDef<'_>,
1546 self_args: &[P<Expr>],
1547 nonself_args: &[P<Expr>],
1549 let summary = enum_def
1553 let sp = v.span.with_ctxt(trait_.span.ctxt());
1554 let summary = trait_.summarise_struct(cx, &v.data);
1555 (v.ident, sp, summary)
1558 self.call_substructure_method(
1564 &StaticEnum(enum_def, summary),
1569 // general helper methods.
1570 impl<'a> TraitDef<'a> {
1571 fn summarise_struct(&self, cx: &mut ExtCtxt<'_>, struct_def: &VariantData) -> StaticFields {
1572 let mut named_idents = Vec::new();
1573 let mut just_spans = Vec::new();
1574 for field in struct_def.fields() {
1575 let sp = field.span.with_ctxt(self.span.ctxt());
1577 Some(ident) => named_idents.push((ident, sp)),
1578 _ => just_spans.push(sp),
1582 let is_tuple = if let ast::VariantData::Tuple(..) = struct_def { true } else { false };
1583 match (just_spans.is_empty(), named_idents.is_empty()) {
1584 (false, false) => cx.span_bug(
1586 "a struct with named and unnamed \
1587 fields in generic `derive`",
1590 (_, false) => Named(named_idents),
1592 (false, _) => Unnamed(just_spans, is_tuple),
1594 _ => Named(Vec::new()),
1598 fn create_subpatterns(
1600 cx: &mut ExtCtxt<'_>,
1601 field_paths: Vec<ast::Ident>,
1602 mutbl: ast::Mutability,
1603 use_temporaries: bool,
1604 ) -> Vec<P<ast::Pat>> {
1608 let binding_mode = if use_temporaries {
1609 ast::BindingMode::ByValue(ast::Mutability::Not)
1611 ast::BindingMode::ByRef(mutbl)
1613 cx.pat(path.span, PatKind::Ident(binding_mode, *path, None))
1618 fn create_struct_pattern(
1620 cx: &mut ExtCtxt<'_>,
1621 struct_path: ast::Path,
1622 struct_def: &'a VariantData,
1624 mutbl: ast::Mutability,
1625 use_temporaries: bool,
1626 ) -> (P<ast::Pat>, Vec<(Span, Option<Ident>, P<Expr>, &'a [ast::Attribute])>) {
1627 let mut paths = Vec::new();
1628 let mut ident_exprs = Vec::new();
1629 for (i, struct_field) in struct_def.fields().iter().enumerate() {
1630 let sp = struct_field.span.with_ctxt(self.span.ctxt());
1631 let ident = cx.ident_of(&format!("{}_{}", prefix, i), self.span);
1632 paths.push(ident.with_span_pos(sp));
1633 let val = cx.expr_path(cx.path_ident(sp, ident));
1634 let val = if use_temporaries { val } else { cx.expr_deref(sp, val) };
1635 let val = cx.expr(sp, ast::ExprKind::Paren(val));
1637 ident_exprs.push((sp, struct_field.ident, val, &struct_field.attrs[..]));
1640 let subpats = self.create_subpatterns(cx, paths, mutbl, use_temporaries);
1641 let pattern = match *struct_def {
1642 VariantData::Struct(..) => {
1643 let field_pats = subpats
1646 .map(|(pat, &(sp, ident, ..))| {
1647 if ident.is_none() {
1648 cx.span_bug(sp, "a braced struct with unnamed fields in `derive`");
1651 ident: ident.unwrap(),
1652 is_shorthand: false,
1653 attrs: ast::AttrVec::new(),
1654 id: ast::DUMMY_NODE_ID,
1655 span: pat.span.with_ctxt(self.span.ctxt()),
1657 is_placeholder: false,
1661 cx.pat_struct(self.span, struct_path, field_pats)
1663 VariantData::Tuple(..) => cx.pat_tuple_struct(self.span, struct_path, subpats),
1664 VariantData::Unit(..) => cx.pat_path(self.span, struct_path),
1667 (pattern, ident_exprs)
1670 fn create_enum_variant_pattern(
1672 cx: &mut ExtCtxt<'_>,
1673 enum_ident: ast::Ident,
1674 variant: &'a ast::Variant,
1676 mutbl: ast::Mutability,
1677 ) -> (P<ast::Pat>, Vec<(Span, Option<Ident>, P<Expr>, &'a [ast::Attribute])>) {
1678 let sp = variant.span.with_ctxt(self.span.ctxt());
1679 let variant_path = cx.path(sp, vec![enum_ident, variant.ident]);
1680 let use_temporaries = false; // enums can't be repr(packed)
1681 self.create_struct_pattern(cx, variant_path, &variant.data, prefix, mutbl, use_temporaries)
1685 // helpful premade recipes
1687 pub fn cs_fold_fields<'a, F>(
1691 cx: &mut ExtCtxt<'_>,
1692 all_fields: &[FieldInfo<'a>],
1695 F: FnMut(&mut ExtCtxt<'_>, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>,
1700 .fold(base, |old, field| f(cx, field.span, old, field.self_.clone(), &field.other))
1705 .fold(base, |old, field| f(cx, field.span, old, field.self_.clone(), &field.other))
1709 pub fn cs_fold_enumnonmatch(
1710 mut enum_nonmatch_f: EnumNonMatchCollapsedFunc<'_>,
1711 cx: &mut ExtCtxt<'_>,
1713 substructure: &Substructure<'_>,
1715 match *substructure.fields {
1716 EnumNonMatchingCollapsed(ref all_args, _, tuple) => {
1717 enum_nonmatch_f(cx, trait_span, (&all_args[..], tuple), substructure.nonself_args)
1719 _ => cx.span_bug(trait_span, "cs_fold_enumnonmatch expected an EnumNonMatchingCollapsed"),
1723 pub fn cs_fold_static(cx: &mut ExtCtxt<'_>, trait_span: Span) -> P<Expr> {
1724 cx.span_bug(trait_span, "static function in `derive`")
1727 /// Fold the fields. `use_foldl` controls whether this is done
1728 /// left-to-right (`true`) or right-to-left (`false`).
1733 enum_nonmatch_f: EnumNonMatchCollapsedFunc<'_>,
1734 cx: &mut ExtCtxt<'_>,
1736 substructure: &Substructure<'_>,
1739 F: FnMut(&mut ExtCtxt<'_>, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>,
1741 match *substructure.fields {
1742 EnumMatching(.., ref all_fields) | Struct(_, ref all_fields) => {
1743 cs_fold_fields(use_foldl, f, base, cx, all_fields)
1745 EnumNonMatchingCollapsed(..) => {
1746 cs_fold_enumnonmatch(enum_nonmatch_f, cx, trait_span, substructure)
1748 StaticEnum(..) | StaticStruct(..) => cs_fold_static(cx, trait_span),
1752 /// Function to fold over fields, with three cases, to generate more efficient and concise code.
1753 /// When the `substructure` has grouped fields, there are two cases:
1754 /// Zero fields: call the base case function with `None` (like the usual base case of `cs_fold`).
1755 /// One or more fields: call the base case function on the first value (which depends on
1756 /// `use_fold`), and use that as the base case. Then perform `cs_fold` on the remainder of the
1758 /// When the `substructure` is a `EnumNonMatchingCollapsed`, the result of `enum_nonmatch_f`
1759 /// is returned. Statics may not be folded over.
1760 /// See `cs_op` in `partial_ord.rs` for a model example.
1761 pub fn cs_fold1<F, B>(
1765 enum_nonmatch_f: EnumNonMatchCollapsedFunc<'_>,
1766 cx: &mut ExtCtxt<'_>,
1768 substructure: &Substructure<'_>,
1771 F: FnMut(&mut ExtCtxt<'_>, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>,
1772 B: FnMut(&mut ExtCtxt<'_>, Option<(Span, P<Expr>, &[P<Expr>])>) -> P<Expr>,
1774 match *substructure.fields {
1775 EnumMatching(.., ref all_fields) | Struct(_, ref all_fields) => {
1776 let (base, all_fields) = match (all_fields.is_empty(), use_foldl) {
1778 let field = &all_fields[0];
1779 let args = (field.span, field.self_.clone(), &field.other[..]);
1780 (b(cx, Some(args)), &all_fields[1..])
1783 let idx = all_fields.len() - 1;
1784 let field = &all_fields[idx];
1785 let args = (field.span, field.self_.clone(), &field.other[..]);
1786 (b(cx, Some(args)), &all_fields[..idx])
1788 (true, _) => (b(cx, None), &all_fields[..]),
1791 cs_fold_fields(use_foldl, f, base, cx, all_fields)
1793 EnumNonMatchingCollapsed(..) => {
1794 cs_fold_enumnonmatch(enum_nonmatch_f, cx, trait_span, substructure)
1796 StaticEnum(..) | StaticStruct(..) => cs_fold_static(cx, trait_span),
1800 /// Returns `true` if the type has no value fields
1801 /// (for an enum, no variant has any fields)
1802 pub fn is_type_without_fields(item: &Annotatable) -> bool {
1803 if let Annotatable::Item(ref item) = *item {
1805 ast::ItemKind::Enum(ref enum_def, _) => {
1806 enum_def.variants.iter().all(|v| v.data.fields().is_empty())
1808 ast::ItemKind::Struct(ref variant_data, _) => variant_data.fields().is_empty(),