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 //! - `EnumTag` when `Self` is an enum, for comparing the enum tags.
25 //! - `StaticEnum` and `StaticStruct` for static methods, where the type
26 //! being derived upon is either an enum or struct respectively. (Any
27 //! argument with type Self is just grouped among the non-self
30 //! In the first two cases, the values from the corresponding fields in
31 //! all the arguments are grouped together.
33 //! The non-static cases have `Option<ident>` in several places associated
34 //! with field `expr`s. This represents the name of the field it is
35 //! associated with. It is only not `None` when the associated field has
36 //! an identifier in the source code. For example, the `x`s in the
40 //! # #![allow(dead_code)]
41 //! struct A { x : i32 }
51 //! The `i32`s in `B` and `C0` don't have an identifier, so the
52 //! `Option<ident>`s would be `None` for them.
54 //! In the static cases, the structure is summarized, either into the just
55 //! spans of the fields or a list of spans and the field idents (for tuple
56 //! structs and record structs, respectively), or a list of these, for
57 //! enums (one for each variant). For empty struct and empty enum
58 //! variants, it is represented as a count of 0.
60 //! # "`cs`" functions
62 //! The `cs_...` functions ("combine substructure") are designed to
63 //! make life easier by providing some pre-made recipes for common
64 //! threads; mostly calling the function being derived on all the
65 //! arguments and then combining them back together in some way (or
66 //! letting the user chose that). They are not meant to be the only
67 //! way to handle the structures that this code creates.
71 //! The following simplified `PartialEq` is used for in-code examples:
75 //! fn eq(&self, other: &Self) -> bool;
77 //! impl PartialEq for i32 {
78 //! fn eq(&self, other: &i32) -> bool {
84 //! Some examples of the values of `SubstructureFields` follow, using the
85 //! above `PartialEq`, `A`, `B` and `C`.
89 //! When generating the `expr` for the `A` impl, the `SubstructureFields` is
92 //! Struct(vec![FieldInfo {
94 //! name: Some(<ident of x>),
95 //! self_: <expr for &self.x>,
96 //! other: vec![<expr for &other.x]
100 //! For the `B` impl, called with `B(a)` and `B(b)`,
103 //! Struct(vec![FieldInfo {
104 //! span: <span of `i32`>,
106 //! self_: <expr for &a>
107 //! other: vec![<expr for &b>]
113 //! When generating the `expr` for a call with `self == C0(a)` and `other
114 //! == C0(b)`, the SubstructureFields is
117 //! EnumMatching(0, <ast::Variant for C0>,
119 //! span: <span of i32>
121 //! self_: <expr for &a>,
122 //! other: vec![<expr for &b>]
126 //! For `C1 {x}` and `C1 {x}`,
129 //! EnumMatching(1, <ast::Variant for C1>,
131 //! span: <span of x>
132 //! name: Some(<ident of x>),
133 //! self_: <expr for &self.x>,
134 //! other: vec![<expr for &other.x>]
142 //! &[<ident of self tag>, <ident of other tag>], <expr to combine with>)
144 //! Note that this setup doesn't allow for the brute-force "match every variant
145 //! against every other variant" approach, which is bad because it produces a
146 //! quadratic amount of code (see #15375).
150 //! A static method on the types above would result in,
153 //! StaticStruct(<ast::VariantData of A>, Named(vec![(<ident of x>, <span of x>)]))
155 //! StaticStruct(<ast::VariantData of B>, Unnamed(vec![<span of x>]))
157 //! StaticEnum(<ast::EnumDef of C>,
158 //! vec![(<ident of C0>, <span of C0>, Unnamed(vec![<span of i32>])),
159 //! (<ident of C1>, <span of C1>, Named(vec![(<ident of x>, <span of x>)]))])
162 pub use StaticFields::*;
163 pub use SubstructureFields::*;
166 use rustc_ast::ptr::P;
168 self as ast, BindingAnnotation, ByRef, EnumDef, Expr, Generics, Mutability, PatKind,
170 use rustc_ast::{GenericArg, GenericParamKind, VariantData};
171 use rustc_attr as attr;
172 use rustc_expand::base::{Annotatable, ExtCtxt};
173 use rustc_span::symbol::{kw, sym, Ident, Symbol};
174 use rustc_span::{Span, DUMMY_SP};
175 use std::cell::RefCell;
179 use thin_vec::thin_vec;
180 use ty::{Bounds, Path, Ref, Self_, Ty};
184 pub struct TraitDef<'a> {
185 /// The span for the current #[derive(Foo)] header.
188 /// Path of the trait, including any type parameters
191 /// Whether to skip adding the current trait as a bound to the type parameters of the type.
192 pub skip_path_as_bound: bool,
194 /// Additional bounds required of any type parameters of the type,
195 /// other than the current trait
196 pub additional_bounds: Vec<Ty>,
198 /// Can this trait be derived for unions?
199 pub supports_unions: bool,
201 pub methods: Vec<MethodDef<'a>>,
203 pub associated_types: Vec<(Ident, Ty)>,
208 pub struct MethodDef<'a> {
209 /// name of the method
211 /// List of generics, e.g., `R: rand::Rng`
212 pub generics: Bounds,
214 /// Is there is a `&self` argument? If not, it is a static function.
215 pub explicit_self: bool,
217 /// Arguments other than the self argument.
218 pub nonself_args: Vec<(Ty, Symbol)>,
223 pub attributes: ast::AttrVec,
225 /// Can we combine fieldless variants for enums into a single match arm?
226 /// If true, indicates that the trait operation uses the enum tag in some
228 pub unify_fieldless_variants: bool,
230 pub combine_substructure: RefCell<CombineSubstructureFunc<'a>>,
233 /// All the data about the data structure/method being derived upon.
234 pub struct Substructure<'a> {
236 pub type_ident: Ident,
237 /// Verbatim access to any non-selflike arguments, i.e. arguments that
238 /// don't have type `&Self`.
239 pub nonselflike_args: &'a [P<Expr>],
240 pub fields: &'a SubstructureFields<'a>,
243 /// Summary of the relevant parts of a struct/enum field.
244 pub struct FieldInfo {
246 /// None for tuple structs/normal enum variants, Some for normal
247 /// structs/struct enum variants.
248 pub name: Option<Ident>,
249 /// The expression corresponding to this field of `self`
250 /// (specifically, a reference to it).
251 pub self_expr: P<Expr>,
252 /// The expressions corresponding to references to this field in
253 /// the other selflike arguments.
254 pub other_selflike_exprs: Vec<P<Expr>>,
257 /// Fields for a static method
258 pub enum StaticFields {
259 /// Tuple and unit structs/enum variants like this.
260 Unnamed(Vec<Span>, bool /*is tuple*/),
261 /// Normal structs/struct variants.
262 Named(Vec<(Ident, Span)>),
265 /// A summary of the possible sets of fields.
266 pub enum SubstructureFields<'a> {
267 /// A non-static method with `Self` is a struct.
268 Struct(&'a ast::VariantData, Vec<FieldInfo>),
270 /// Matching variants of the enum: variant index, variant count, ast::Variant,
271 /// fields: the field name is only non-`None` in the case of a struct
273 EnumMatching(usize, usize, &'a ast::Variant, Vec<FieldInfo>),
275 /// The tag of an enum. The first field is a `FieldInfo` for the tags, as
276 /// if they were fields. The second field is the expression to combine the
277 /// tag expression with; it will be `None` if no match is necessary.
278 EnumTag(FieldInfo, Option<P<Expr>>),
280 /// A static method where `Self` is a struct.
281 StaticStruct(&'a ast::VariantData, StaticFields),
283 /// A static method where `Self` is an enum.
284 StaticEnum(&'a ast::EnumDef, Vec<(Ident, Span, StaticFields)>),
287 /// Combine the values of all the fields together. The last argument is
288 /// all the fields of all the structures.
289 pub type CombineSubstructureFunc<'a> =
290 Box<dyn FnMut(&mut ExtCtxt<'_>, Span, &Substructure<'_>) -> BlockOrExpr + 'a>;
292 pub fn combine_substructure(
293 f: CombineSubstructureFunc<'_>,
294 ) -> RefCell<CombineSubstructureFunc<'_>> {
298 struct TypeParameter {
299 bound_generic_params: Vec<ast::GenericParam>,
303 /// The code snippets built up for derived code are sometimes used as blocks
304 /// (e.g. in a function body) and sometimes used as expressions (e.g. in a match
305 /// arm). This structure avoids committing to either form until necessary,
306 /// avoiding the insertion of any unnecessary blocks.
308 /// The statements come before the expression.
309 pub struct BlockOrExpr(Vec<ast::Stmt>, Option<P<Expr>>);
312 pub fn new_stmts(stmts: Vec<ast::Stmt>) -> BlockOrExpr {
313 BlockOrExpr(stmts, None)
316 pub fn new_expr(expr: P<Expr>) -> BlockOrExpr {
317 BlockOrExpr(vec![], Some(expr))
320 pub fn new_mixed(stmts: Vec<ast::Stmt>, expr: Option<P<Expr>>) -> BlockOrExpr {
321 BlockOrExpr(stmts, expr)
324 // Converts it into a block.
325 fn into_block(mut self, cx: &ExtCtxt<'_>, span: Span) -> P<ast::Block> {
326 if let Some(expr) = self.1 {
327 self.0.push(cx.stmt_expr(expr));
329 cx.block(span, self.0)
332 // Converts it into an expression.
333 fn into_expr(self, cx: &ExtCtxt<'_>, span: Span) -> P<Expr> {
334 if self.0.is_empty() {
336 None => cx.expr_block(cx.block(span, vec![])),
339 } else if self.0.len() == 1
340 && let ast::StmtKind::Expr(expr) = &self.0[0].kind
343 // There's only a single statement expression. Pull it out.
346 // Multiple statements and/or expressions.
347 cx.expr_block(self.into_block(cx, span))
352 /// This method helps to extract all the type parameters referenced from a
353 /// type. For a type parameter `<T>`, it looks for either a `TyPath` that
354 /// is not global and starts with `T`, or a `TyQPath`.
355 /// Also include bound generic params from the input type.
356 fn find_type_parameters(
358 ty_param_names: &[Symbol],
360 ) -> Vec<TypeParameter> {
361 use rustc_ast::visit;
363 struct Visitor<'a, 'b> {
365 ty_param_names: &'a [Symbol],
366 bound_generic_params_stack: Vec<ast::GenericParam>,
367 type_params: Vec<TypeParameter>,
370 impl<'a, 'b> visit::Visitor<'a> for Visitor<'a, 'b> {
371 fn visit_ty(&mut self, ty: &'a ast::Ty) {
372 if let ast::TyKind::Path(_, path) = &ty.kind
373 && let Some(segment) = path.segments.first()
374 && self.ty_param_names.contains(&segment.ident.name)
376 self.type_params.push(TypeParameter {
377 bound_generic_params: self.bound_generic_params_stack.clone(),
382 visit::walk_ty(self, ty)
385 // Place bound generic params on a stack, to extract them when a type is encountered.
386 fn visit_poly_trait_ref(&mut self, trait_ref: &'a ast::PolyTraitRef) {
387 let stack_len = self.bound_generic_params_stack.len();
388 self.bound_generic_params_stack.extend(trait_ref.bound_generic_params.iter().cloned());
390 visit::walk_poly_trait_ref(self, trait_ref);
392 self.bound_generic_params_stack.truncate(stack_len);
395 fn visit_mac_call(&mut self, mac: &ast::MacCall) {
396 self.cx.span_err(mac.span(), "`derive` cannot be used on items with type macros");
400 let mut visitor = Visitor {
403 bound_generic_params_stack: Vec::new(),
404 type_params: Vec::new(),
406 visit::Visitor::visit_ty(&mut visitor, ty);
411 impl<'a> TraitDef<'a> {
414 cx: &mut ExtCtxt<'_>,
415 mitem: &ast::MetaItem,
416 item: &'a Annotatable,
417 push: &mut dyn FnMut(Annotatable),
419 self.expand_ext(cx, mitem, item, push, false);
424 cx: &mut ExtCtxt<'_>,
425 mitem: &ast::MetaItem,
426 item: &'a Annotatable,
427 push: &mut dyn FnMut(Annotatable),
431 Annotatable::Item(item) => {
432 let is_packed = item.attrs.iter().any(|attr| {
433 for r in attr::find_repr_attrs(&cx.sess, attr) {
434 if let attr::ReprPacked(_) = r {
440 let has_no_type_params = match &item.kind {
441 ast::ItemKind::Struct(_, generics)
442 | ast::ItemKind::Enum(_, generics)
443 | ast::ItemKind::Union(_, generics) => !generics
446 .any(|param| matches!(param.kind, ast::GenericParamKind::Type { .. })),
449 let container_id = cx.current_expansion.id.expn_data().parent.expect_local();
451 is_packed && has_no_type_params && cx.resolver.has_derive_copy(container_id);
453 let newitem = match &item.kind {
454 ast::ItemKind::Struct(struct_def, generics) => self.expand_struct_def(
462 ast::ItemKind::Enum(enum_def, generics) => {
463 // We ignore `is_packed` here, because `repr(packed)`
464 // enums cause an error later on.
466 // This can only cause further compilation errors
467 // downstream in blatantly illegal code, so it is fine.
468 self.expand_enum_def(cx, enum_def, item.ident, generics, from_scratch)
470 ast::ItemKind::Union(struct_def, generics) => {
471 if self.supports_unions {
472 self.expand_struct_def(
481 cx.span_err(mitem.span, "this trait cannot be derived for unions");
487 // Keep the lint attributes of the previous item to control how the
488 // generated implementations are linted
489 let mut attrs = newitem.attrs.clone();
502 .contains(&a.name_or_empty())
506 push(Annotatable::Item(P(ast::Item { attrs, ..(*newitem).clone() })))
512 /// Given that we are deriving a trait `DerivedTrait` for a type like:
514 /// ```ignore (only-for-syntax-highlight)
515 /// struct Struct<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z> where C: WhereTrait {
518 /// b1: <B as DeclaredTrait>::Item,
519 /// c1: <C as WhereTrait>::Item,
520 /// c2: Option<<C as WhereTrait>::Item>,
525 /// create an impl like:
527 /// ```ignore (only-for-syntax-highlight)
528 /// impl<'a, ..., 'z, A, B: DeclaredTrait, C, ... Z> where
530 /// A: DerivedTrait + B1 + ... + BN,
531 /// B: DerivedTrait + B1 + ... + BN,
532 /// C: DerivedTrait + B1 + ... + BN,
533 /// B::Item: DerivedTrait + B1 + ... + BN,
534 /// <C as WhereTrait>::Item: DerivedTrait + B1 + ... + BN,
541 /// where B1, ..., BN are the bounds given by `bounds_paths`.'. Z is a phantom type, and
542 /// therefore does not get bound by the derived trait.
543 fn create_derived_impl(
545 cx: &mut ExtCtxt<'_>,
548 field_tys: Vec<P<ast::Ty>>,
549 methods: Vec<P<ast::AssocItem>>,
551 let trait_path = self.path.to_path(cx, self.span, type_ident, generics);
553 // Transform associated types from `deriving::ty::Ty` into `ast::AssocItem`
554 let associated_types = self.associated_types.iter().map(|&(ident, ref type_def)| {
556 id: ast::DUMMY_NODE_ID,
559 vis: ast::Visibility {
560 span: self.span.shrink_to_lo(),
561 kind: ast::VisibilityKind::Inherited,
564 attrs: ast::AttrVec::new(),
565 kind: ast::AssocItemKind::Type(Box::new(ast::TyAlias {
566 defaultness: ast::Defaultness::Final,
567 generics: Generics::default(),
569 ast::TyAliasWhereClause::default(),
570 ast::TyAliasWhereClause::default(),
572 where_predicates_split: 0,
574 ty: Some(type_def.to_ty(cx, self.span, type_ident, generics)),
580 let mut where_clause = ast::WhereClause::default();
581 where_clause.span = generics.where_clause.span;
582 let ctxt = self.span.ctxt();
583 let span = generics.span.with_ctxt(ctxt);
585 // Create the generic parameters
586 let params: Vec<_> = generics
589 .map(|param| match ¶m.kind {
590 GenericParamKind::Lifetime { .. } => param.clone(),
591 GenericParamKind::Type { .. } => {
592 // I don't think this can be moved out of the loop, since
593 // a GenericBound requires an ast id
595 // extra restrictions on the generics parameters to the
596 // type being derived upon
597 self.additional_bounds.iter().map(|p| {
598 cx.trait_bound(p.to_path(cx, self.span, type_ident, generics))
600 // require the current trait
601 self.skip_path_as_bound.not().then(|| cx.trait_bound(trait_path.clone()))
603 // also add in any bounds from the declaration
604 param.bounds.iter().cloned()
607 cx.typaram(param.ident.span.with_ctxt(ctxt), param.ident, bounds, None)
609 GenericParamKind::Const { ty, kw_span, .. } => {
610 let const_nodefault_kind = GenericParamKind::Const {
612 kw_span: kw_span.with_ctxt(ctxt),
614 // We can't have default values inside impl block
617 let mut param_clone = param.clone();
618 param_clone.kind = const_nodefault_kind;
624 // and similarly for where clauses
625 where_clause.predicates.extend(generics.where_clause.predicates.iter().map(|clause| {
627 ast::WherePredicate::BoundPredicate(wb) => {
628 let span = wb.span.with_ctxt(ctxt);
629 ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
634 ast::WherePredicate::RegionPredicate(wr) => {
635 let span = wr.span.with_ctxt(ctxt);
636 ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
641 ast::WherePredicate::EqPredicate(we) => {
642 let span = we.span.with_ctxt(ctxt);
643 ast::WherePredicate::EqPredicate(ast::WhereEqPredicate { span, ..we.clone() })
649 // Extra scope required here so ty_params goes out of scope before params is moved
651 let mut ty_params = params
653 .filter(|param| matches!(param.kind, ast::GenericParamKind::Type { .. }))
656 if ty_params.peek().is_some() {
657 let ty_param_names: Vec<Symbol> =
658 ty_params.map(|ty_param| ty_param.ident.name).collect();
660 for field_ty in field_tys {
661 let field_ty_params = find_type_parameters(&field_ty, &ty_param_names, cx);
663 for field_ty_param in field_ty_params {
664 // if we have already handled this type, skip it
665 if let ast::TyKind::Path(_, p) = &field_ty_param.ty.kind
666 && let [sole_segment] = &*p.segments
667 && ty_param_names.contains(&sole_segment.ident.name)
671 let mut bounds: Vec<_> = self
674 .map(|p| cx.trait_bound(p.to_path(cx, self.span, type_ident, generics)))
677 // require the current trait
678 bounds.push(cx.trait_bound(trait_path.clone()));
680 let predicate = ast::WhereBoundPredicate {
682 bound_generic_params: field_ty_param.bound_generic_params,
683 bounded_ty: field_ty_param.ty,
687 let predicate = ast::WherePredicate::BoundPredicate(predicate);
688 where_clause.predicates.push(predicate);
694 let trait_generics = Generics { params, where_clause, span };
696 // Create the reference to the trait.
697 let trait_ref = cx.trait_ref(trait_path);
699 let self_params: Vec<_> = generics
702 .map(|param| match param.kind {
703 GenericParamKind::Lifetime { .. } => {
704 GenericArg::Lifetime(cx.lifetime(param.ident.span.with_ctxt(ctxt), param.ident))
706 GenericParamKind::Type { .. } => {
707 GenericArg::Type(cx.ty_ident(param.ident.span.with_ctxt(ctxt), param.ident))
709 GenericParamKind::Const { .. } => {
710 GenericArg::Const(cx.const_ident(param.ident.span.with_ctxt(ctxt), param.ident))
715 // Create the type of `self`.
716 let path = cx.path_all(self.span, false, vec![type_ident], self_params);
717 let self_type = cx.ty_path(path);
719 let attr = cx.attr_word(sym::automatically_derived, self.span);
720 let attrs = thin_vec![attr];
721 let opt_trait_ref = Some(trait_ref);
727 ast::ItemKind::Impl(Box::new(ast::Impl {
728 unsafety: ast::Unsafe::No,
729 polarity: ast::ImplPolarity::Positive,
730 defaultness: ast::Defaultness::Final,
731 constness: if self.is_const { ast::Const::Yes(DUMMY_SP) } else { ast::Const::No },
732 generics: trait_generics,
733 of_trait: opt_trait_ref,
735 items: methods.into_iter().chain(associated_types).collect(),
740 fn expand_struct_def(
742 cx: &mut ExtCtxt<'_>,
743 struct_def: &'a VariantData,
749 let field_tys: Vec<P<ast::Ty>> =
750 struct_def.fields().iter().map(|field| field.ty.clone()).collect();
756 let (explicit_self, selflike_args, nonselflike_args, nonself_arg_tys) =
757 method_def.extract_arg_details(cx, self, type_ident, generics);
759 let body = if from_scratch || method_def.is_static() {
760 method_def.expand_static_struct_method_body(
768 method_def.expand_struct_method_body(
779 method_def.create_method(
791 self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
796 cx: &mut ExtCtxt<'_>,
797 enum_def: &'a EnumDef,
802 let mut field_tys = Vec::new();
804 for variant in &enum_def.variants {
805 field_tys.extend(variant.data.fields().iter().map(|field| field.ty.clone()));
812 let (explicit_self, selflike_args, nonselflike_args, nonself_arg_tys) =
813 method_def.extract_arg_details(cx, self, type_ident, generics);
815 let body = if from_scratch || method_def.is_static() {
816 method_def.expand_static_enum_method_body(
824 method_def.expand_enum_method_body(
834 method_def.create_method(
846 self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
850 impl<'a> MethodDef<'a> {
851 fn call_substructure_method(
853 cx: &mut ExtCtxt<'_>,
854 trait_: &TraitDef<'_>,
856 nonselflike_args: &[P<Expr>],
857 fields: &SubstructureFields<'_>,
859 let span = trait_.span;
860 let substructure = Substructure { type_ident, nonselflike_args, fields };
861 let mut f = self.combine_substructure.borrow_mut();
862 let f: &mut CombineSubstructureFunc<'_> = &mut *f;
863 f(cx, span, &substructure)
868 cx: &mut ExtCtxt<'_>,
869 trait_: &TraitDef<'_>,
873 self.ret_ty.to_ty(cx, trait_.span, type_ident, generics)
876 fn is_static(&self) -> bool {
880 // The return value includes:
881 // - explicit_self: The `&self` arg, if present.
882 // - selflike_args: Expressions for `&self` (if present) and also any other
883 // args with the same type (e.g. the `other` arg in `PartialEq::eq`).
884 // - nonselflike_args: Expressions for all the remaining args.
885 // - nonself_arg_tys: Additional information about all the args other than
887 fn extract_arg_details(
889 cx: &mut ExtCtxt<'_>,
890 trait_: &TraitDef<'_>,
893 ) -> (Option<ast::ExplicitSelf>, Vec<P<Expr>>, Vec<P<Expr>>, Vec<(Ident, P<ast::Ty>)>) {
894 let mut selflike_args = Vec::new();
895 let mut nonselflike_args = Vec::new();
896 let mut nonself_arg_tys = Vec::new();
897 let span = trait_.span;
899 let explicit_self = if self.explicit_self {
900 let (self_expr, explicit_self) = ty::get_explicit_self(cx, span);
901 selflike_args.push(self_expr);
907 for (ty, name) in self.nonself_args.iter() {
908 let ast_ty = ty.to_ty(cx, span, type_ident, generics);
909 let ident = Ident::new(*name, span);
910 nonself_arg_tys.push((ident, ast_ty));
912 let arg_expr = cx.expr_ident(span, ident);
915 // Selflike (`&Self`) arguments only occur in non-static methods.
916 Ref(box Self_, _) if !self.is_static() => selflike_args.push(arg_expr),
917 Self_ => cx.span_bug(span, "`Self` in non-return position"),
918 _ => nonselflike_args.push(arg_expr),
922 (explicit_self, selflike_args, nonselflike_args, nonself_arg_tys)
927 cx: &mut ExtCtxt<'_>,
928 trait_: &TraitDef<'_>,
931 explicit_self: Option<ast::ExplicitSelf>,
932 nonself_arg_tys: Vec<(Ident, P<ast::Ty>)>,
934 ) -> P<ast::AssocItem> {
935 let span = trait_.span;
936 // Create the generics that aren't for `Self`.
937 let fn_generics = self.generics.to_generics(cx, span, type_ident, generics);
940 let self_arg = explicit_self.map(|explicit_self| {
941 let ident = Ident::with_dummy_span(kw::SelfLower).with_span_pos(span);
942 ast::Param::from_self(ast::AttrVec::default(), explicit_self, ident)
945 nonself_arg_tys.into_iter().map(|(name, ty)| cx.param(span, name, ty));
946 self_arg.into_iter().chain(nonself_args).collect()
949 let ret_type = self.get_ret_ty(cx, trait_, generics, type_ident);
951 let method_ident = Ident::new(self.name, span);
952 let fn_decl = cx.fn_decl(args, ast::FnRetTy::Ty(ret_type));
953 let body_block = body.into_block(cx, span);
955 let trait_lo_sp = span.shrink_to_lo();
957 let sig = ast::FnSig { header: ast::FnHeader::default(), decl: fn_decl, span };
958 let defaultness = ast::Defaultness::Final;
960 // Create the method.
962 id: ast::DUMMY_NODE_ID,
963 attrs: self.attributes.clone(),
965 vis: ast::Visibility {
967 kind: ast::VisibilityKind::Inherited,
971 kind: ast::AssocItemKind::Fn(Box::new(ast::Fn {
974 generics: fn_generics,
975 body: Some(body_block),
981 /// The normal case uses field access.
983 /// #[derive(PartialEq)]
985 /// struct A { x: u8, y: u8 }
987 /// // equivalent to:
988 /// impl PartialEq for A {
989 /// fn eq(&self, other: &A) -> bool {
990 /// self.x == other.x && self.y == other.y
994 /// But if the struct is `repr(packed)`, we can't use something like
995 /// `&self.x` because that might cause an unaligned ref. So for any trait
996 /// method that takes a reference, if the struct impls `Copy` then we use a
997 /// local block to force a copy:
999 /// # struct A { x: u8, y: u8 }
1000 /// impl PartialEq for A {
1001 /// fn eq(&self, other: &A) -> bool {
1002 /// // Desugars to `{ self.x }.eq(&{ other.y }) && ...`
1003 /// { self.x } == { other.y } && { self.y } == { other.y }
1006 /// impl Hash for A {
1007 /// fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
1008 /// ::core::hash::Hash::hash(&{ self.x }, state);
1009 /// ::core::hash::Hash::hash(&{ self.y }, state)
1013 /// If the struct doesn't impl `Copy`, we use the normal `&self.x`. This
1014 /// only works if the fields match the alignment required by the
1015 /// `packed(N)` attribute. (We'll get errors later on if not.)
1016 fn expand_struct_method_body<'b>(
1018 cx: &mut ExtCtxt<'_>,
1019 trait_: &TraitDef<'b>,
1020 struct_def: &'b VariantData,
1022 selflike_args: &[P<Expr>],
1023 nonselflike_args: &[P<Expr>],
1026 assert!(selflike_args.len() == 1 || selflike_args.len() == 2);
1028 let selflike_fields =
1029 trait_.create_struct_field_access_fields(cx, selflike_args, struct_def, copy_fields);
1030 self.call_substructure_method(
1035 &Struct(struct_def, selflike_fields),
1039 fn expand_static_struct_method_body(
1041 cx: &mut ExtCtxt<'_>,
1042 trait_: &TraitDef<'_>,
1043 struct_def: &VariantData,
1045 nonselflike_args: &[P<Expr>],
1047 let summary = trait_.summarise_struct(cx, struct_def);
1049 self.call_substructure_method(
1054 &StaticStruct(struct_def, summary),
1059 /// #[derive(PartialEq)]
1066 /// is equivalent to:
1068 /// #![feature(core_intrinsics)]
1073 /// impl ::core::cmp::PartialEq for A {
1075 /// fn eq(&self, other: &A) -> bool {
1076 /// let __self_tag = ::core::intrinsics::discriminant_value(self);
1077 /// let __arg1_tag = ::core::intrinsics::discriminant_value(other);
1078 /// __self_tag == __arg1_tag &&
1079 /// match (self, other) {
1080 /// (A::A2(__self_0), A::A2(__arg1_0)) =>
1081 /// *__self_0 == *__arg1_0,
1087 /// Creates a tag check combined with a match for a tuple of all
1088 /// `selflike_args`, with an arm for each variant with fields, possibly an
1089 /// arm for each fieldless variant (if `!unify_fieldless_variants` is not
1090 /// true), and possibly a default arm.
1091 fn expand_enum_method_body<'b>(
1093 cx: &mut ExtCtxt<'_>,
1094 trait_: &TraitDef<'b>,
1095 enum_def: &'b EnumDef,
1097 selflike_args: Vec<P<Expr>>,
1098 nonselflike_args: &[P<Expr>],
1100 let span = trait_.span;
1101 let variants = &enum_def.variants;
1103 // Traits that unify fieldless variants always use the tag(s).
1104 let uses_tags = self.unify_fieldless_variants;
1106 // There is no sensible code to be generated for *any* deriving on a
1107 // zero-variant enum. So we just generate a failing expression.
1108 if variants.is_empty() {
1109 return BlockOrExpr(vec![], Some(deriving::call_unreachable(cx, span)));
1112 let prefixes = iter::once("__self".to_string())
1118 .map(|(arg_count, _selflike_arg)| format!("__arg{}", arg_count)),
1120 .collect::<Vec<String>>();
1122 // Build a series of let statements mapping each selflike_arg
1123 // to its discriminant value.
1125 // e.g. for `PartialEq::eq` builds two statements:
1127 // let __self_tag = ::core::intrinsics::discriminant_value(self);
1128 // let __arg1_tag = ::core::intrinsics::discriminant_value(other);
1130 let get_tag_pieces = |cx: &ExtCtxt<'_>| {
1131 let tag_idents: Vec<_> = prefixes
1133 .map(|name| Ident::from_str_and_span(&format!("{}_tag", name), span))
1136 let mut tag_exprs: Vec<_> = tag_idents
1138 .map(|&ident| cx.expr_addr_of(span, cx.expr_ident(span, ident)))
1141 let self_expr = tag_exprs.remove(0);
1142 let other_selflike_exprs = tag_exprs;
1143 let tag_field = FieldInfo { span, name: None, self_expr, other_selflike_exprs };
1145 let tag_let_stmts: Vec<_> = iter::zip(&tag_idents, &selflike_args)
1146 .map(|(&ident, selflike_arg)| {
1147 let variant_value = deriving::call_intrinsic(
1150 sym::discriminant_value,
1151 vec![selflike_arg.clone()],
1153 cx.stmt_let(span, false, ident, variant_value)
1157 (tag_field, tag_let_stmts)
1160 // There are some special cases involving fieldless enums where no
1161 // match is necessary.
1162 let all_fieldless = variants.iter().all(|v| v.data.fields().is_empty());
1164 if uses_tags && variants.len() > 1 {
1165 // If the type is fieldless and the trait uses the tag and
1166 // there are multiple variants, we need just an operation on
1168 let (tag_field, mut tag_let_stmts) = get_tag_pieces(cx);
1169 let mut tag_check = self.call_substructure_method(
1174 &EnumTag(tag_field, None),
1176 tag_let_stmts.append(&mut tag_check.0);
1177 return BlockOrExpr(tag_let_stmts, tag_check.1);
1180 if variants.len() == 1 {
1181 // If there is a single variant, we don't need an operation on
1182 // the tag(s). Just use the most degenerate result.
1183 return self.call_substructure_method(
1188 &EnumMatching(0, 1, &variants[0], Vec::new()),
1193 // These arms are of the form:
1194 // (Variant1, Variant1, ...) => Body1
1195 // (Variant2, Variant2, ...) => Body2
1197 // where each tuple has length = selflike_args.len()
1198 let mut match_arms: Vec<ast::Arm> = variants
1201 .filter(|&(_, v)| !(self.unify_fieldless_variants && v.data.fields().is_empty()))
1202 .map(|(index, variant)| {
1203 // A single arm has form (&VariantK, &VariantK, ...) => BodyK
1204 // (see "Final wrinkle" note below for why.)
1206 let fields = trait_.create_struct_pattern_fields(cx, &variant.data, &prefixes);
1208 let sp = variant.span.with_ctxt(trait_.span.ctxt());
1209 let variant_path = cx.path(sp, vec![type_ident, variant.ident]);
1210 let by_ref = ByRef::No; // because enums can't be repr(packed)
1211 let mut subpats: Vec<_> = trait_.create_struct_patterns(
1219 // `(VariantK, VariantK, ...)` or just `VariantK`.
1220 let single_pat = if subpats.len() == 1 {
1221 subpats.pop().unwrap()
1223 cx.pat_tuple(span, subpats)
1226 // For the BodyK, we need to delegate to our caller,
1227 // passing it an EnumMatching to indicate which case
1230 // Now, for some given VariantK, we have built up
1231 // expressions for referencing every field of every
1232 // Self arg, assuming all are instances of VariantK.
1233 // Build up code associated with such a case.
1234 let substructure = EnumMatching(index, variants.len(), variant, fields);
1236 .call_substructure_method(
1243 .into_expr(cx, span);
1245 cx.arm(span, single_pat, arm_expr)
1249 // Add a default arm to the match, if necessary.
1250 let first_fieldless = variants.iter().find(|v| v.data.fields().is_empty());
1251 let default = match first_fieldless {
1252 Some(v) if self.unify_fieldless_variants => {
1253 // We need a default case that handles all the fieldless
1254 // variants. The index and actual variant aren't meaningful in
1255 // this case, so just use dummy values.
1257 self.call_substructure_method(
1262 &EnumMatching(0, variants.len(), v, Vec::new()),
1264 .into_expr(cx, span),
1267 _ if variants.len() > 1 && selflike_args.len() > 1 => {
1268 // Because we know that all the arguments will match if we reach
1269 // the match expression we add the unreachable intrinsics as the
1270 // result of the default which should help llvm in optimizing it.
1271 Some(deriving::call_unreachable(cx, span))
1275 if let Some(arm) = default {
1276 match_arms.push(cx.arm(span, cx.pat_wild(span), arm));
1279 // Create a match expression with one arm per discriminant plus
1280 // possibly a default arm, e.g.:
1281 // match (self, other) {
1282 // (Variant1, Variant1, ...) => Body1
1283 // (Variant2, Variant2, ...) => Body2,
1285 // _ => ::core::intrinsics::unreachable()
1287 let get_match_expr = |mut selflike_args: Vec<P<Expr>>| {
1288 let match_arg = if selflike_args.len() == 1 {
1289 selflike_args.pop().unwrap()
1291 cx.expr(span, ast::ExprKind::Tup(selflike_args))
1293 cx.expr_match(span, match_arg, match_arms)
1296 // If the trait uses the tag and there are multiple variants, we need
1297 // to add a tag check operation before the match. Otherwise, the match
1299 if uses_tags && variants.len() > 1 {
1300 let (tag_field, mut tag_let_stmts) = get_tag_pieces(cx);
1302 // Combine a tag check with the match.
1303 let mut tag_check_plus_match = self.call_substructure_method(
1308 &EnumTag(tag_field, Some(get_match_expr(selflike_args))),
1310 tag_let_stmts.append(&mut tag_check_plus_match.0);
1311 BlockOrExpr(tag_let_stmts, tag_check_plus_match.1)
1313 BlockOrExpr(vec![], Some(get_match_expr(selflike_args)))
1317 fn expand_static_enum_method_body(
1319 cx: &mut ExtCtxt<'_>,
1320 trait_: &TraitDef<'_>,
1323 nonselflike_args: &[P<Expr>],
1325 let summary = enum_def
1329 let sp = v.span.with_ctxt(trait_.span.ctxt());
1330 let summary = trait_.summarise_struct(cx, &v.data);
1331 (v.ident, sp, summary)
1334 self.call_substructure_method(
1339 &StaticEnum(enum_def, summary),
1344 // general helper methods.
1345 impl<'a> TraitDef<'a> {
1346 fn summarise_struct(&self, cx: &mut ExtCtxt<'_>, struct_def: &VariantData) -> StaticFields {
1347 let mut named_idents = Vec::new();
1348 let mut just_spans = Vec::new();
1349 for field in struct_def.fields() {
1350 let sp = field.span.with_ctxt(self.span.ctxt());
1352 Some(ident) => named_idents.push((ident, sp)),
1353 _ => just_spans.push(sp),
1357 let is_tuple = matches!(struct_def, ast::VariantData::Tuple(..));
1358 match (just_spans.is_empty(), named_idents.is_empty()) {
1360 cx.span_bug(self.span, "a struct with named and unnamed fields in generic `derive`")
1363 (_, false) => Named(named_idents),
1365 (false, _) => Unnamed(just_spans, is_tuple),
1367 _ => Named(Vec::new()),
1371 fn create_struct_patterns(
1373 cx: &mut ExtCtxt<'_>,
1374 struct_path: ast::Path,
1375 struct_def: &'a VariantData,
1376 prefixes: &[String],
1378 ) -> Vec<P<ast::Pat>> {
1383 struct_def.fields().iter().enumerate().map(|(i, struct_field)| {
1384 let sp = struct_field.span.with_ctxt(self.span.ctxt());
1385 let ident = self.mk_pattern_ident(prefix, i);
1386 let path = ident.with_span_pos(sp);
1393 BindingAnnotation(by_ref, Mutability::Not),
1401 let struct_path = struct_path.clone();
1403 VariantData::Struct(..) => {
1404 let field_pats = pieces_iter
1405 .map(|(sp, ident, pat)| {
1406 if ident.is_none() {
1409 "a braced struct with unnamed fields in `derive`",
1413 ident: ident.unwrap(),
1414 is_shorthand: false,
1415 attrs: ast::AttrVec::new(),
1416 id: ast::DUMMY_NODE_ID,
1417 span: pat.span.with_ctxt(self.span.ctxt()),
1419 is_placeholder: false,
1423 cx.pat_struct(self.span, struct_path, field_pats)
1425 VariantData::Tuple(..) => {
1426 let subpats = pieces_iter.map(|(_, _, subpat)| subpat).collect();
1427 cx.pat_tuple_struct(self.span, struct_path, subpats)
1429 VariantData::Unit(..) => cx.pat_path(self.span, struct_path),
1435 fn create_fields<F>(&self, struct_def: &'a VariantData, mk_exprs: F) -> Vec<FieldInfo>
1437 F: Fn(usize, &ast::FieldDef, Span) -> Vec<P<ast::Expr>>,
1443 .map(|(i, struct_field)| {
1444 // For this field, get an expr for each selflike_arg. E.g. for
1445 // `PartialEq::eq`, one for each of `&self` and `other`.
1446 let sp = struct_field.span.with_ctxt(self.span.ctxt());
1447 let mut exprs: Vec<_> = mk_exprs(i, struct_field, sp);
1448 let self_expr = exprs.remove(0);
1449 let other_selflike_exprs = exprs;
1451 span: sp.with_ctxt(self.span.ctxt()),
1452 name: struct_field.ident,
1454 other_selflike_exprs,
1460 fn mk_pattern_ident(&self, prefix: &str, i: usize) -> Ident {
1461 Ident::from_str_and_span(&format!("{}_{}", prefix, i), self.span)
1464 fn create_struct_pattern_fields(
1466 cx: &mut ExtCtxt<'_>,
1467 struct_def: &'a VariantData,
1468 prefixes: &[String],
1469 ) -> Vec<FieldInfo> {
1470 self.create_fields(struct_def, |i, _struct_field, sp| {
1474 let ident = self.mk_pattern_ident(prefix, i);
1475 cx.expr_path(cx.path_ident(sp, ident))
1481 fn create_struct_field_access_fields(
1483 cx: &mut ExtCtxt<'_>,
1484 selflike_args: &[P<Expr>],
1485 struct_def: &'a VariantData,
1487 ) -> Vec<FieldInfo> {
1488 self.create_fields(struct_def, |i, struct_field, sp| {
1491 .map(|selflike_arg| {
1492 // Note: we must use `struct_field.span` rather than `sp` in the
1493 // `unwrap_or_else` case otherwise the hygiene is wrong and we get
1494 // "field `0` of struct `Point` is private" errors on tuple
1496 let mut field_expr = cx.expr(
1498 ast::ExprKind::Field(
1499 selflike_arg.clone(),
1500 struct_field.ident.unwrap_or_else(|| {
1501 Ident::from_str_and_span(&i.to_string(), struct_field.span)
1506 field_expr = cx.expr_block(
1507 cx.block(struct_field.span, vec![cx.stmt_expr(field_expr)]),
1510 cx.expr_addr_of(sp, field_expr)
1517 /// The function passed to `cs_fold` is called repeatedly with a value of this
1518 /// type. It describes one part of the code generation. The result is always an
1520 pub enum CsFold<'a> {
1521 /// The basic case: a field expression for one or more selflike args. E.g.
1522 /// for `PartialEq::eq` this is something like `self.x == other.x`.
1523 Single(&'a FieldInfo),
1525 /// The combination of two field expressions. E.g. for `PartialEq::eq` this
1526 /// is something like `<field1 equality> && <field2 equality>`.
1527 Combine(Span, P<Expr>, P<Expr>),
1529 // The fallback case for a struct or enum variant with no fields.
1533 /// Folds over fields, combining the expressions for each field in a sequence.
1534 /// Statics may not be folded over.
1537 cx: &mut ExtCtxt<'_>,
1539 substructure: &Substructure<'_>,
1543 F: FnMut(&mut ExtCtxt<'_>, CsFold<'_>) -> P<Expr>,
1545 match substructure.fields {
1546 EnumMatching(.., all_fields) | Struct(_, all_fields) => {
1547 if all_fields.is_empty() {
1548 return f(cx, CsFold::Fieldless);
1551 let (base_field, rest) = if use_foldl {
1552 all_fields.split_first().unwrap()
1554 all_fields.split_last().unwrap()
1557 let base_expr = f(cx, CsFold::Single(base_field));
1559 let op = |old, field: &FieldInfo| {
1560 let new = f(cx, CsFold::Single(field));
1561 f(cx, CsFold::Combine(field.span, old, new))
1565 rest.iter().fold(base_expr, op)
1567 rest.iter().rfold(base_expr, op)
1570 EnumTag(tag_field, match_expr) => {
1571 let tag_check_expr = f(cx, CsFold::Single(tag_field));
1572 if let Some(match_expr) = match_expr {
1574 f(cx, CsFold::Combine(trait_span, tag_check_expr, match_expr.clone()))
1576 f(cx, CsFold::Combine(trait_span, match_expr.clone(), tag_check_expr))
1582 StaticEnum(..) | StaticStruct(..) => cx.span_bug(trait_span, "static function in `derive`"),