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_data_structures
::thin_vec
::ThinVec
;
185 use rustc_target
::spec
::abi
::Abi
;
186 use syntax
::ast
::{self, BinOpKind, EnumDef, Expr, Generics, Ident, PatKind}
;
187 use syntax
::ast
::{VariantData, GenericParamKind, GenericArg}
;
189 use syntax
::ext
::base
::{Annotatable, ExtCtxt}
;
190 use syntax
::ext
::build
::AstBuilder
;
191 use syntax
::source_map
::{self, respan}
;
192 use syntax
::util
::map_in_place
::MapInPlace
;
194 use syntax
::symbol
::{Symbol, keywords, sym}
;
195 use syntax
::parse
::ParseSess
;
196 use syntax_pos
::{DUMMY_SP, Span}
;
198 use ty
::{LifetimeBounds, Path, Ptr, PtrTy, Self_, Ty}
;
204 pub struct TraitDef
<'a
> {
205 /// The span for the current #[derive(Foo)] header.
208 pub attributes
: Vec
<ast
::Attribute
>,
210 /// Path of the trait, including any type parameters
213 /// Additional bounds required of any type parameters of the type,
214 /// other than the current trait
215 pub additional_bounds
: Vec
<Ty
<'a
>>,
217 /// Any extra lifetimes and/or bounds, e.g., `D: serialize::Decoder`
218 pub generics
: LifetimeBounds
<'a
>,
220 /// Is it an `unsafe` trait?
223 /// Can this trait be derived for unions?
224 pub supports_unions
: bool
,
226 pub methods
: Vec
<MethodDef
<'a
>>,
228 pub associated_types
: Vec
<(ast
::Ident
, Ty
<'a
>)>,
232 pub struct MethodDef
<'a
> {
233 /// name of the method
235 /// List of generics, e.g., `R: rand::Rng`
236 pub generics
: LifetimeBounds
<'a
>,
238 /// Whether there is a self argument (outer Option) i.e., whether
239 /// this is a static function, and whether it is a pointer (inner
241 pub explicit_self
: Option
<Option
<PtrTy
<'a
>>>,
243 /// Arguments other than the self argument
244 pub args
: Vec
<(Ty
<'a
>, &'a
str)>,
249 pub attributes
: Vec
<ast
::Attribute
>,
251 // Is it an `unsafe fn`?
254 /// Can we combine fieldless variants for enums into a single match arm?
255 pub unify_fieldless_variants
: bool
,
257 pub combine_substructure
: RefCell
<CombineSubstructureFunc
<'a
>>,
260 /// All the data about the data structure/method being derived upon.
261 pub struct Substructure
<'a
> {
263 pub type_ident
: Ident
,
264 /// ident of the method
265 pub method_ident
: Ident
,
266 /// dereferenced access to any `Self_` or `Ptr(Self_, _)` arguments
267 pub self_args
: &'a
[P
<Expr
>],
268 /// verbatim access to any other arguments
269 pub nonself_args
: &'a
[P
<Expr
>],
270 pub fields
: &'a SubstructureFields
<'a
>,
273 /// Summary of the relevant parts of a struct/enum field.
274 pub struct FieldInfo
<'a
> {
276 /// None for tuple structs/normal enum variants, Some for normal
277 /// structs/struct enum variants.
278 pub name
: Option
<Ident
>,
279 /// The expression corresponding to this field of `self`
280 /// (specifically, a reference to it).
282 /// The expressions corresponding to references to this field in
283 /// the other `Self` arguments.
284 pub other
: Vec
<P
<Expr
>>,
285 /// The attributes on the field
286 pub attrs
: &'a
[ast
::Attribute
],
289 /// Fields for a static method
290 pub enum StaticFields
{
291 /// Tuple and unit structs/enum variants like this.
292 Unnamed(Vec
<Span
>, bool
/*is tuple*/),
293 /// Normal structs/struct variants.
294 Named(Vec
<(Ident
, Span
)>),
297 /// A summary of the possible sets of fields.
298 pub enum SubstructureFields
<'a
> {
299 Struct(&'a ast
::VariantData
, Vec
<FieldInfo
<'a
>>),
300 /// Matching variants of the enum: variant index, variant count, ast::Variant,
301 /// fields: the field name is only non-`None` in the case of a struct
303 EnumMatching(usize, usize, &'a ast
::Variant
, Vec
<FieldInfo
<'a
>>),
305 /// Non-matching variants of the enum, but with all state hidden from
306 /// the consequent code. The first component holds `Ident`s for all of
307 /// the `Self` arguments; the second component is a slice of all of the
308 /// variants for the enum itself, and the third component is a list of
309 /// `Ident`s bound to the variant index values for each of the actual
310 /// input `Self` arguments.
311 EnumNonMatchingCollapsed(Vec
<Ident
>, &'a
[ast
::Variant
], &'a
[Ident
]),
313 /// A static method where `Self` is a struct.
314 StaticStruct(&'a ast
::VariantData
, StaticFields
),
315 /// A static method where `Self` is an enum.
316 StaticEnum(&'a ast
::EnumDef
, Vec
<(Ident
, Span
, StaticFields
)>),
321 /// Combine the values of all the fields together. The last argument is
322 /// all the fields of all the structures.
323 pub type CombineSubstructureFunc
<'a
> =
324 Box
<dyn FnMut(&mut ExtCtxt
<'_
>, Span
, &Substructure
<'_
>) -> P
<Expr
> + 'a
>;
326 /// Deal with non-matching enum variants. The tuple is a list of
327 /// identifiers (one for each `Self` argument, which could be any of the
328 /// variants since they have been collapsed together) and the identifiers
329 /// holding the variant index value for each of the `Self` arguments. The
330 /// last argument is all the non-`Self` args of the method being derived.
331 pub type EnumNonMatchCollapsedFunc
<'a
> =
332 Box
<dyn FnMut(&mut ExtCtxt
<'_
>, Span
, (&[Ident
], &[Ident
]), &[P
<Expr
>]) -> P
<Expr
> + 'a
>;
334 pub fn combine_substructure
<'a
>(f
: CombineSubstructureFunc
<'a
>)
335 -> RefCell
<CombineSubstructureFunc
<'a
>> {
339 /// This method helps to extract all the type parameters referenced from a
340 /// type. For a type parameter `<T>`, it looks for either a `TyPath` that
341 /// is not global and starts with `T`, or a `TyQPath`.
342 fn find_type_parameters(ty
: &ast
::Ty
,
343 ty_param_names
: &[ast
::Name
],
349 struct Visitor
<'a
, 'b
: 'a
> {
352 ty_param_names
: &'a
[ast
::Name
],
353 types
: Vec
<P
<ast
::Ty
>>,
356 impl<'a
, 'b
> visit
::Visitor
<'a
> for Visitor
<'a
, 'b
> {
357 fn visit_ty(&mut self, ty
: &'a ast
::Ty
) {
358 if let ast
::TyKind
::Path(_
, ref path
) = ty
.node
{
359 if let Some(segment
) = path
.segments
.first() {
360 if self.ty_param_names
.contains(&segment
.ident
.name
) {
361 self.types
.push(P(ty
.clone()));
366 visit
::walk_ty(self, ty
)
369 fn visit_mac(&mut self, mac
: &ast
::Mac
) {
370 let span
= mac
.span
.with_ctxt(self.span
.ctxt());
371 self.cx
.span_err(span
, "`derive` cannot be used on items with type macros");
375 let mut visitor
= Visitor
{
382 visit
::Visitor
::visit_ty(&mut visitor
, ty
);
387 impl<'a
> TraitDef
<'a
> {
389 cx
: &mut ExtCtxt
<'_
>,
390 mitem
: &ast
::MetaItem
,
391 item
: &'a Annotatable
,
392 push
: &mut dyn FnMut(Annotatable
)) {
393 self.expand_ext(cx
, mitem
, item
, push
, false);
396 pub fn expand_ext(self,
397 cx
: &mut ExtCtxt
<'_
>,
398 mitem
: &ast
::MetaItem
,
399 item
: &'a Annotatable
,
400 push
: &mut dyn FnMut(Annotatable
),
401 from_scratch
: bool
) {
403 Annotatable
::Item(ref item
) => {
404 let is_packed
= item
.attrs
.iter().any(|attr
| {
405 for r
in attr
::find_repr_attrs(&cx
.parse_sess
, attr
) {
406 if let attr
::ReprPacked(_
) = r
{
412 let has_no_type_params
= match item
.node
{
413 ast
::ItemKind
::Struct(_
, ref generics
) |
414 ast
::ItemKind
::Enum(_
, ref generics
) |
415 ast
::ItemKind
::Union(_
, ref generics
) => {
416 !generics
.params
.iter().any(|param
| match param
.kind
{
417 ast
::GenericParamKind
::Type { .. }
=> true,
422 // Non-ADT derive is an error, but it should have been
424 // libsyntax/ext/expand.rs:MacroExpander::expand()
429 attr
::contains_name(&item
.attrs
, sym
::rustc_copy_clone_marker
) &&
431 let use_temporaries
= is_packed
&& is_always_copy
;
433 let newitem
= match item
.node
{
434 ast
::ItemKind
::Struct(ref struct_def
, ref generics
) => {
435 self.expand_struct_def(cx
, &struct_def
, item
.ident
, generics
, from_scratch
,
438 ast
::ItemKind
::Enum(ref enum_def
, ref generics
) => {
439 // We ignore `use_temporaries` here, because
440 // `repr(packed)` enums cause an error later on.
442 // This can only cause further compilation errors
443 // downstream in blatantly illegal code, so it
445 self.expand_enum_def(cx
, enum_def
, &item
.attrs
,
446 item
.ident
, generics
, from_scratch
)
448 ast
::ItemKind
::Union(ref struct_def
, ref generics
) => {
449 if self.supports_unions
{
450 self.expand_struct_def(cx
, &struct_def
, item
.ident
,
451 generics
, from_scratch
,
454 cx
.span_err(mitem
.span
,
455 "this trait cannot be derived for unions");
461 // Keep the lint attributes of the previous item to control how the
462 // generated implementations are linted
463 let mut attrs
= newitem
.attrs
.clone();
464 attrs
.extend(item
.attrs
467 [sym
::allow
, sym
::warn
, sym
::deny
, sym
::forbid
, sym
::stable
, sym
::unstable
]
468 .contains(&a
.name_or_empty())
471 push(Annotatable
::Item(P(ast
::Item { attrs: attrs, ..(*newitem).clone() }
)))
474 // Non-Item derive is an error, but it should have been
476 // libsyntax/ext/expand.rs:MacroExpander::expand()
482 /// Given that we are deriving a trait `DerivedTrait` for a type like:
484 /// ```ignore (only-for-syntax-highlight)
485 /// struct Struct<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z> where C: WhereTrait {
488 /// b1: <B as DeclaredTrait>::Item,
489 /// c1: <C as WhereTrait>::Item,
490 /// c2: Option<<C as WhereTrait>::Item>,
495 /// create an impl like:
497 /// ```ignore (only-for-syntax-highlight)
498 /// impl<'a, ..., 'z, A, B: DeclaredTrait, C, ... Z> where
500 /// A: DerivedTrait + B1 + ... + BN,
501 /// B: DerivedTrait + B1 + ... + BN,
502 /// C: DerivedTrait + B1 + ... + BN,
503 /// B::Item: DerivedTrait + B1 + ... + BN,
504 /// <C as WhereTrait>::Item: DerivedTrait + B1 + ... + BN,
511 /// where B1, ..., BN are the bounds given by `bounds_paths`.'. Z is a phantom type, and
512 /// therefore does not get bound by the derived trait.
513 fn create_derived_impl(&self,
514 cx
: &mut ExtCtxt
<'_
>,
517 field_tys
: Vec
<P
<ast
::Ty
>>,
518 methods
: Vec
<ast
::ImplItem
>)
520 let trait_path
= self.path
.to_path(cx
, self.span
, type_ident
, generics
);
522 // Transform associated types from `deriving::ty::Ty` into `ast::ImplItem`
523 let associated_types
= self.associated_types
.iter().map(|&(ident
, ref type_def
)| {
525 id
: ast
::DUMMY_NODE_ID
,
528 vis
: respan(self.span
.shrink_to_lo(), ast
::VisibilityKind
::Inherited
),
529 defaultness
: ast
::Defaultness
::Final
,
531 generics
: Generics
::default(),
532 node
: ast
::ImplItemKind
::Type(type_def
.to_ty(cx
, self.span
, type_ident
, generics
)),
537 let Generics { mut params, mut where_clause, span }
= self.generics
538 .to_generics(cx
, self.span
, type_ident
, generics
);
540 // Create the generic parameters
541 params
.extend(generics
.params
.iter().map(|param
| match param
.kind
{
542 GenericParamKind
::Lifetime { .. }
=> param
.clone(),
543 GenericParamKind
::Type { .. }
=> {
544 // I don't think this can be moved out of the loop, since
545 // a GenericBound requires an ast id
547 // extra restrictions on the generics parameters to the
548 // type being derived upon
549 self.additional_bounds
.iter().map(|p
| {
550 cx
.trait_bound(p
.to_path(cx
, self.span
, type_ident
, generics
))
552 // require the current trait
553 iter
::once(cx
.trait_bound(trait_path
.clone()))
555 // also add in any bounds from the declaration
556 param
.bounds
.iter().cloned()
559 cx
.typaram(self.span
, param
.ident
, vec
![], bounds
, None
)
561 GenericParamKind
::Const { .. }
=> param
.clone(),
564 // and similarly for where clauses
565 where_clause
.predicates
.extend(generics
.where_clause
.predicates
.iter().map(|clause
| {
567 ast
::WherePredicate
::BoundPredicate(ref wb
) => {
568 ast
::WherePredicate
::BoundPredicate(ast
::WhereBoundPredicate
{
570 bound_generic_params
: wb
.bound_generic_params
.clone(),
571 bounded_ty
: wb
.bounded_ty
.clone(),
572 bounds
: wb
.bounds
.iter().cloned().collect(),
575 ast
::WherePredicate
::RegionPredicate(ref rb
) => {
576 ast
::WherePredicate
::RegionPredicate(ast
::WhereRegionPredicate
{
578 lifetime
: rb
.lifetime
,
579 bounds
: rb
.bounds
.iter().cloned().collect(),
582 ast
::WherePredicate
::EqPredicate(ref we
) => {
583 ast
::WherePredicate
::EqPredicate(ast
::WhereEqPredicate
{
584 id
: ast
::DUMMY_NODE_ID
,
586 lhs_ty
: we
.lhs_ty
.clone(),
587 rhs_ty
: we
.rhs_ty
.clone(),
594 // Extra scope required here so ty_params goes out of scope before params is moved
596 let mut ty_params
= params
.iter()
597 .filter_map(|param
| match param
.kind
{
598 ast
::GenericParamKind
::Type { .. }
=> Some(param
),
603 if ty_params
.peek().is_some() {
604 let ty_param_names
: Vec
<ast
::Name
> = ty_params
605 .map(|ty_param
| ty_param
.ident
.name
)
608 for field_ty
in field_tys
{
609 let tys
= find_type_parameters(&field_ty
, &ty_param_names
, self.span
, cx
);
612 // if we have already handled this type, skip it
613 if let ast
::TyKind
::Path(_
, ref p
) = ty
.node
{
614 if p
.segments
.len() == 1 &&
615 ty_param_names
.contains(&p
.segments
[0].ident
.name
) {
619 let mut bounds
: Vec
<_
> = self.additional_bounds
622 cx
.trait_bound(p
.to_path(cx
, self.span
, type_ident
, generics
))
626 // require the current trait
627 bounds
.push(cx
.trait_bound(trait_path
.clone()));
629 let predicate
= ast
::WhereBoundPredicate
{
631 bound_generic_params
: Vec
::new(),
636 let predicate
= ast
::WherePredicate
::BoundPredicate(predicate
);
637 where_clause
.predicates
.push(predicate
);
643 let trait_generics
= Generics
{
649 // Create the reference to the trait.
650 let trait_ref
= cx
.trait_ref(trait_path
);
652 let self_params
: Vec
<_
> = generics
.params
.iter().map(|param
| match param
.kind
{
653 GenericParamKind
::Lifetime { .. }
=> {
654 GenericArg
::Lifetime(cx
.lifetime(self.span
, param
.ident
))
656 GenericParamKind
::Type { .. }
=> {
657 GenericArg
::Type(cx
.ty_ident(self.span
, param
.ident
))
659 GenericParamKind
::Const { .. }
=> {
660 GenericArg
::Const(cx
.const_ident(self.span
, param
.ident
))
664 // Create the type of `self`.
665 let path
= cx
.path_all(self.span
, false, vec
![type_ident
], self_params
, vec
![]);
666 let self_type
= cx
.ty_path(path
);
668 let attr
= cx
.attribute(self.span
,
669 cx
.meta_word(self.span
,
670 Symbol
::intern("automatically_derived")));
671 // Just mark it now since we know that it'll end up used downstream
672 attr
::mark_used(&attr
);
673 let opt_trait_ref
= Some(trait_ref
);
675 let word
= cx
.meta_list_item_word(self.span
, Symbol
::intern("unused_qualifications"));
676 cx
.attribute(self.span
, cx
.meta_list(self.span
, Symbol
::intern("allow"), vec
![word
]))
679 let mut a
= vec
![attr
, unused_qual
];
680 a
.extend(self.attributes
.iter().cloned());
682 let unsafety
= if self.is_unsafe
{
683 ast
::Unsafety
::Unsafe
685 ast
::Unsafety
::Normal
689 keywords
::Invalid
.ident(),
691 ast
::ItemKind
::Impl(unsafety
,
692 ast
::ImplPolarity
::Positive
,
693 ast
::Defaultness
::Final
,
697 methods
.into_iter().chain(associated_types
).collect()))
700 fn expand_struct_def(&self,
701 cx
: &mut ExtCtxt
<'_
>,
702 struct_def
: &'a VariantData
,
706 use_temporaries
: bool
)
708 let field_tys
: Vec
<P
<ast
::Ty
>> = struct_def
.fields()
710 .map(|field
| field
.ty
.clone())
713 let methods
= self.methods
716 let (explicit_self
, self_args
, nonself_args
, tys
) =
717 method_def
.split_self_nonself_args(cx
, self, type_ident
, generics
);
719 let body
= if from_scratch
|| method_def
.is_static() {
720 method_def
.expand_static_struct_method_body(cx
,
727 method_def
.expand_struct_method_body(cx
,
736 method_def
.create_method(cx
,
747 self.create_derived_impl(cx
, type_ident
, generics
, field_tys
, methods
)
750 fn expand_enum_def(&self,
751 cx
: &mut ExtCtxt
<'_
>,
752 enum_def
: &'a EnumDef
,
753 type_attrs
: &[ast
::Attribute
],
758 let mut field_tys
= Vec
::new();
760 for variant
in &enum_def
.variants
{
761 field_tys
.extend(variant
.node
765 .map(|field
| field
.ty
.clone()));
768 let methods
= self.methods
771 let (explicit_self
, self_args
, nonself_args
, tys
) =
772 method_def
.split_self_nonself_args(cx
, self, type_ident
, generics
);
774 let body
= if from_scratch
|| method_def
.is_static() {
775 method_def
.expand_static_enum_method_body(cx
,
782 method_def
.expand_enum_method_body(cx
,
791 method_def
.create_method(cx
,
802 self.create_derived_impl(cx
, type_ident
, generics
, field_tys
, methods
)
806 fn find_repr_type_name(sess
: &ParseSess
, type_attrs
: &[ast
::Attribute
]) -> &'
static str {
807 let mut repr_type_name
= "isize";
808 for a
in type_attrs
{
809 for r
in &attr
::find_repr_attrs(sess
, a
) {
810 repr_type_name
= match *r
{
811 attr
::ReprPacked(_
) | attr
::ReprSimd
| attr
::ReprAlign(_
) | attr
::ReprTransparent
=>
814 attr
::ReprC
=> "i32",
816 attr
::ReprInt(attr
::SignedInt(ast
::IntTy
::Isize
)) => "isize",
817 attr
::ReprInt(attr
::SignedInt(ast
::IntTy
::I8
)) => "i8",
818 attr
::ReprInt(attr
::SignedInt(ast
::IntTy
::I16
)) => "i16",
819 attr
::ReprInt(attr
::SignedInt(ast
::IntTy
::I32
)) => "i32",
820 attr
::ReprInt(attr
::SignedInt(ast
::IntTy
::I64
)) => "i64",
821 attr
::ReprInt(attr
::SignedInt(ast
::IntTy
::I128
)) => "i128",
823 attr
::ReprInt(attr
::UnsignedInt(ast
::UintTy
::Usize
)) => "usize",
824 attr
::ReprInt(attr
::UnsignedInt(ast
::UintTy
::U8
)) => "u8",
825 attr
::ReprInt(attr
::UnsignedInt(ast
::UintTy
::U16
)) => "u16",
826 attr
::ReprInt(attr
::UnsignedInt(ast
::UintTy
::U32
)) => "u32",
827 attr
::ReprInt(attr
::UnsignedInt(ast
::UintTy
::U64
)) => "u64",
828 attr
::ReprInt(attr
::UnsignedInt(ast
::UintTy
::U128
)) => "u128",
835 impl<'a
> MethodDef
<'a
> {
836 fn call_substructure_method(&self,
837 cx
: &mut ExtCtxt
<'_
>,
838 trait_
: &TraitDef
<'_
>,
840 self_args
: &[P
<Expr
>],
841 nonself_args
: &[P
<Expr
>],
842 fields
: &SubstructureFields
<'_
>)
844 let substructure
= Substructure
{
846 method_ident
: cx
.ident_of(self.name
),
851 let mut f
= self.combine_substructure
.borrow_mut();
852 let f
: &mut CombineSubstructureFunc
<'_
> = &mut *f
;
853 f(cx
, trait_
.span
, &substructure
)
857 cx
: &mut ExtCtxt
<'_
>,
858 trait_
: &TraitDef
<'_
>,
862 self.ret_ty
.to_ty(cx
, trait_
.span
, type_ident
, generics
)
865 fn is_static(&self) -> bool
{
866 self.explicit_self
.is_none()
869 fn split_self_nonself_args
871 cx
: &mut ExtCtxt
<'_
>,
872 trait_
: &TraitDef
<'_
>,
875 -> (Option
<ast
::ExplicitSelf
>, Vec
<P
<Expr
>>, Vec
<P
<Expr
>>, Vec
<(Ident
, P
<ast
::Ty
>)>) {
877 let mut self_args
= Vec
::new();
878 let mut nonself_args
= Vec
::new();
879 let mut arg_tys
= Vec
::new();
880 let mut nonstatic
= false;
882 let ast_explicit_self
= self.explicit_self
.as_ref().map(|self_ptr
| {
883 let (self_expr
, explicit_self
) = ty
::get_explicit_self(cx
, trait_
.span
, self_ptr
);
885 self_args
.push(self_expr
);
891 for (ty
, name
) in self.args
.iter() {
892 let ast_ty
= ty
.to_ty(cx
, trait_
.span
, type_ident
, generics
);
893 let ident
= cx
.ident_of(name
).gensym();
894 arg_tys
.push((ident
, ast_ty
));
896 let arg_expr
= cx
.expr_ident(trait_
.span
, ident
);
899 // for static methods, just treat any Self
900 // arguments as a normal arg
901 Self_
if nonstatic
=> {
902 self_args
.push(arg_expr
);
904 Ptr(ref ty
, _
) if (if let Self_
= **ty { true }
else { false }
) && nonstatic
=> {
905 self_args
.push(cx
.expr_deref(trait_
.span
, arg_expr
))
908 nonself_args
.push(arg_expr
);
913 (ast_explicit_self
, self_args
, nonself_args
, arg_tys
)
916 fn create_method(&self,
917 cx
: &mut ExtCtxt
<'_
>,
918 trait_
: &TraitDef
<'_
>,
922 explicit_self
: Option
<ast
::ExplicitSelf
>,
923 arg_types
: Vec
<(Ident
, P
<ast
::Ty
>)>,
927 // create the generics that aren't for Self
928 let fn_generics
= self.generics
.to_generics(cx
, trait_
.span
, type_ident
, generics
);
931 let self_args
= explicit_self
.map(|explicit_self
| {
932 ast
::Arg
::from_self(explicit_self
,
933 keywords
::SelfLower
.ident().with_span_pos(trait_
.span
))
935 let nonself_args
= arg_types
.into_iter()
936 .map(|(name
, ty
)| cx
.arg(trait_
.span
, name
, ty
));
937 self_args
.into_iter().chain(nonself_args
).collect()
940 let ret_type
= self.get_ret_ty(cx
, trait_
, generics
, type_ident
);
942 let method_ident
= cx
.ident_of(self.name
);
943 let fn_decl
= cx
.fn_decl(args
, ast
::FunctionRetTy
::Ty(ret_type
));
944 let body_block
= cx
.block_expr(body
);
946 let unsafety
= if self.is_unsafe
{
947 ast
::Unsafety
::Unsafe
949 ast
::Unsafety
::Normal
952 // Create the method.
954 id
: ast
::DUMMY_NODE_ID
,
955 attrs
: self.attributes
.clone(),
956 generics
: fn_generics
,
958 vis
: respan(trait_
.span
.shrink_to_lo(), ast
::VisibilityKind
::Inherited
),
959 defaultness
: ast
::Defaultness
::Final
,
961 node
: ast
::ImplItemKind
::Method(ast
::MethodSig
{
962 header
: ast
::FnHeader
{
964 ..ast
::FnHeader
::default()
974 /// #[derive(PartialEq)]
976 /// struct A { x: i32, y: i32 }
978 /// // equivalent to:
979 /// impl PartialEq for A {
980 /// fn eq(&self, other: &A) -> bool {
982 /// A {x: ref __self_0_0, y: ref __self_0_1} => {
984 /// A {x: ref __self_1_0, y: ref __self_1_1} => {
985 /// __self_0_0.eq(__self_1_0) && __self_0_1.eq(__self_1_1)
993 /// // or if A is repr(packed) - note fields are matched by-value
994 /// // instead of by-reference.
995 /// impl PartialEq for A {
996 /// fn eq(&self, other: &A) -> bool {
998 /// A {x: __self_0_0, y: __self_0_1} => {
1000 /// A {x: __self_1_0, y: __self_1_1} => {
1001 /// __self_0_0.eq(&__self_1_0) && __self_0_1.eq(&__self_1_1)
1009 fn expand_struct_method_body
<'b
>(&self,
1010 cx
: &mut ExtCtxt
<'_
>,
1011 trait_
: &TraitDef
<'b
>,
1012 struct_def
: &'b VariantData
,
1014 self_args
: &[P
<Expr
>],
1015 nonself_args
: &[P
<Expr
>],
1016 use_temporaries
: bool
)
1019 let mut raw_fields
= Vec
::new(); // Vec<[fields of self],
1020 // [fields of next Self arg], [etc]>
1021 let mut patterns
= Vec
::new();
1022 for i
in 0..self_args
.len() {
1023 let struct_path
= cx
.path(DUMMY_SP
, vec
![type_ident
]);
1024 let (pat
, ident_expr
) = trait_
.create_struct_pattern(cx
,
1027 &format
!("__self_{}", i
),
1028 ast
::Mutability
::Immutable
,
1031 raw_fields
.push(ident_expr
);
1034 // transpose raw_fields
1035 let fields
= if !raw_fields
.is_empty() {
1036 let mut raw_fields
= raw_fields
.into_iter().map(|v
| v
.into_iter());
1037 let first_field
= raw_fields
.next().unwrap();
1038 let mut other_fields
: Vec
<vec
::IntoIter
<_
>> = raw_fields
.collect();
1039 first_field
.map(|(span
, opt_id
, field
, attrs
)| {
1044 other
: other_fields
.iter_mut()
1046 match l
.next().unwrap() {
1056 cx
.span_bug(trait_
.span
,
1057 "no self arguments to non-static method in generic \
1061 // body of the inner most destructuring match
1062 let mut body
= self.call_substructure_method(cx
,
1067 &Struct(struct_def
, fields
));
1069 // make a series of nested matches, to destructure the
1070 // structs. This is actually right-to-left, but it shouldn't
1072 for (arg_expr
, pat
) in self_args
.iter().zip(patterns
) {
1073 body
= cx
.expr_match(trait_
.span
,
1075 vec
![cx
.arm(trait_
.span
, vec
![pat
.clone()], body
)])
1081 fn expand_static_struct_method_body(&self,
1082 cx
: &mut ExtCtxt
<'_
>,
1083 trait_
: &TraitDef
<'_
>,
1084 struct_def
: &VariantData
,
1086 self_args
: &[P
<Expr
>],
1087 nonself_args
: &[P
<Expr
>])
1089 let summary
= trait_
.summarise_struct(cx
, struct_def
);
1091 self.call_substructure_method(cx
,
1096 &StaticStruct(struct_def
, summary
))
1100 /// #[derive(PartialEq)]
1107 /// // is equivalent to
1109 /// impl PartialEq for A {
1110 /// fn eq(&self, other: &A) -> ::bool {
1111 /// match (&*self, &*other) {
1112 /// (&A1, &A1) => true,
1113 /// (&A2(ref self_0),
1114 /// &A2(ref __arg_1_0)) => (*self_0).eq(&(*__arg_1_0)),
1116 /// let __self_vi = match *self { A1(..) => 0, A2(..) => 1 };
1117 /// let __arg_1_vi = match *other { A1(..) => 0, A2(..) => 1 };
1125 /// (Of course `__self_vi` and `__arg_1_vi` are unused for
1126 /// `PartialEq`, and those subcomputations will hopefully be removed
1127 /// as their results are unused. The point of `__self_vi` and
1128 /// `__arg_1_vi` is for `PartialOrd`; see #15503.)
1129 fn expand_enum_method_body
<'b
>(&self,
1130 cx
: &mut ExtCtxt
<'_
>,
1131 trait_
: &TraitDef
<'b
>,
1132 enum_def
: &'b EnumDef
,
1133 type_attrs
: &[ast
::Attribute
],
1135 self_args
: Vec
<P
<Expr
>>,
1136 nonself_args
: &[P
<Expr
>])
1138 self.build_enum_match_tuple(cx
,
1148 /// Creates a match for a tuple of all `self_args`, where either all
1149 /// variants match, or it falls into a catch-all for when one variant
1152 /// There are N + 1 cases because is a case for each of the N
1153 /// variants where all of the variants match, and one catch-all for
1154 /// when one does not match.
1156 /// As an optimization we generate code which checks whether all variants
1157 /// match first which makes llvm see that C-like enums can be compiled into
1158 /// a simple equality check (for PartialEq).
1160 /// The catch-all handler is provided access the variant index values
1161 /// for each of the self-args, carried in precomputed variables.
1164 /// let __self0_vi = unsafe {
1165 /// std::intrinsics::discriminant_value(&self) } as i32;
1166 /// let __self1_vi = unsafe {
1167 /// std::intrinsics::discriminant_value(&arg1) } as i32;
1168 /// let __self2_vi = unsafe {
1169 /// std::intrinsics::discriminant_value(&arg2) } as i32;
1171 /// if __self0_vi == __self1_vi && __self0_vi == __self2_vi && ... {
1173 /// (Variant1, Variant1, ...) => Body1
1174 /// (Variant2, Variant2, ...) => Body2,
1176 /// _ => ::core::intrinsics::unreachable()
1180 /// ... // catch-all remainder can inspect above variant index values.
1183 fn build_enum_match_tuple
<'b
>(&self,
1184 cx
: &mut ExtCtxt
<'_
>,
1185 trait_
: &TraitDef
<'b
>,
1186 enum_def
: &'b EnumDef
,
1187 type_attrs
: &[ast
::Attribute
],
1189 mut self_args
: Vec
<P
<Expr
>>,
1190 nonself_args
: &[P
<Expr
>])
1192 let sp
= trait_
.span
;
1193 let variants
= &enum_def
.variants
;
1195 let self_arg_names
= iter
::once("__self".to_string()).chain(
1199 .map(|(arg_count
, _self_arg
)|
1200 format
!("__arg_{}", arg_count
)
1202 ).collect
::<Vec
<String
>>();
1204 let self_arg_idents
= self_arg_names
.iter()
1205 .map(|name
| cx
.ident_of(&name
[..]))
1206 .collect
::<Vec
<ast
::Ident
>>();
1208 // The `vi_idents` will be bound, solely in the catch-all, to
1209 // a series of let statements mapping each self_arg to an int
1210 // value corresponding to its discriminant.
1211 let vi_idents
= self_arg_names
.iter()
1213 let vi_suffix
= format
!("{}_vi", &name
[..]);
1214 cx
.ident_of(&vi_suffix
[..]).gensym()
1216 .collect
::<Vec
<ast
::Ident
>>();
1218 // Builds, via callback to call_substructure_method, the
1219 // delegated expression that handles the catch-all case,
1220 // using `__variants_tuple` to drive logic if necessary.
1221 let catch_all_substructure
=
1222 EnumNonMatchingCollapsed(self_arg_idents
, &variants
[..], &vi_idents
[..]);
1224 let first_fieldless
= variants
.iter().find(|v
| v
.node
.data
.fields().is_empty());
1226 // These arms are of the form:
1227 // (Variant1, Variant1, ...) => Body1
1228 // (Variant2, Variant2, ...) => Body2
1230 // where each tuple has length = self_args.len()
1231 let mut match_arms
: Vec
<ast
::Arm
> = variants
.iter()
1233 .filter(|&(_
, v
)| !(self.unify_fieldless_variants
&& v
.node
.data
.fields().is_empty()))
1234 .map(|(index
, variant
)| {
1235 let mk_self_pat
= |cx
: &mut ExtCtxt
<'_
>, self_arg_name
: &str| {
1236 let (p
, idents
) = trait_
.create_enum_variant_pattern(cx
,
1240 ast
::Mutability
::Immutable
);
1241 (cx
.pat(sp
, PatKind
::Ref(p
, ast
::Mutability
::Immutable
)), idents
)
1244 // A single arm has form (&VariantK, &VariantK, ...) => BodyK
1245 // (see "Final wrinkle" note below for why.)
1246 let mut subpats
= Vec
::with_capacity(self_arg_names
.len());
1247 let mut self_pats_idents
= Vec
::with_capacity(self_arg_names
.len() - 1);
1248 let first_self_pat_idents
= {
1249 let (p
, idents
) = mk_self_pat(cx
, &self_arg_names
[0]);
1253 for self_arg_name
in &self_arg_names
[1..] {
1254 let (p
, idents
) = mk_self_pat(cx
, &self_arg_name
[..]);
1256 self_pats_idents
.push(idents
);
1259 // Here is the pat = `(&VariantK, &VariantK, ...)`
1260 let single_pat
= cx
.pat_tuple(sp
, subpats
);
1262 // For the BodyK, we need to delegate to our caller,
1263 // passing it an EnumMatching to indicate which case
1266 // All of the Self args have the same variant in these
1267 // cases. So we transpose the info in self_pats_idents
1268 // to gather the getter expressions together, in the
1269 // form that EnumMatching expects.
1271 // The transposition is driven by walking across the
1272 // arg fields of the variant for the first self pat.
1273 let field_tuples
= first_self_pat_idents
.into_iter().enumerate()
1274 // For each arg field of self, pull out its getter expr ...
1275 .map(|(field_index
, (sp
, opt_ident
, self_getter_expr
, attrs
))| {
1276 // ... but FieldInfo also wants getter expr
1277 // for matching other arguments of Self type;
1278 // so walk across the *other* self_pats_idents
1279 // and pull out getter for same field in each
1280 // of them (using `field_index` tracked above).
1281 // That is the heart of the transposition.
1282 let others
= self_pats_idents
.iter().map(|fields
| {
1283 let (_
, _opt_ident
, ref other_getter_expr
, _
) =
1284 fields
[field_index
];
1286 // All Self args have same variant, so
1287 // opt_idents are the same. (Assert
1288 // here to make it self-evident that
1289 // it is okay to ignore `_opt_ident`.)
1290 assert
!(opt_ident
== _opt_ident
);
1292 other_getter_expr
.clone()
1293 }).collect
::<Vec
<P
<Expr
>>>();
1295 FieldInfo
{ span
: sp
,
1297 self_
: self_getter_expr
,
1301 }).collect
::<Vec
<FieldInfo
<'_
>>>();
1303 // Now, for some given VariantK, we have built up
1304 // expressions for referencing every field of every
1305 // Self arg, assuming all are instances of VariantK.
1306 // Build up code associated with such a case.
1307 let substructure
= EnumMatching(index
, variants
.len(), variant
, field_tuples
);
1308 let arm_expr
= self.call_substructure_method(cx
,
1315 cx
.arm(sp
, vec
![single_pat
], arm_expr
)
1319 let default = match first_fieldless
{
1320 Some(v
) if self.unify_fieldless_variants
=> {
1321 // We need a default case that handles the fieldless variants.
1322 // The index and actual variant aren't meaningful in this case,
1323 // so just use whatever
1324 let substructure
= EnumMatching(0, variants
.len(), v
, Vec
::new());
1325 Some(self.call_substructure_method(cx
,
1332 _
if variants
.len() > 1 && self_args
.len() > 1 => {
1333 // Since we know that all the arguments will match if we reach
1334 // the match expression we add the unreachable intrinsics as the
1335 // result of the catch all which should help llvm in optimizing it
1336 Some(deriving
::call_intrinsic(cx
, sp
, "unreachable", vec
![]))
1340 if let Some(arm
) = default {
1341 match_arms
.push(cx
.arm(sp
, vec
![cx
.pat_wild(sp
)], arm
));
1344 // We will usually need the catch-all after matching the
1345 // tuples `(VariantK, VariantK, ...)` for each VariantK of the
1348 // * when there is only one Self arg, the arms above suffice
1349 // (and the deriving we call back into may not be prepared to
1350 // handle EnumNonMatchCollapsed), and,
1352 // * when the enum has only one variant, the single arm that
1353 // is already present always suffices.
1355 // * In either of the two cases above, if we *did* add a
1356 // catch-all `_` match, it would trigger the
1357 // unreachable-pattern error.
1359 if variants
.len() > 1 && self_args
.len() > 1 {
1360 // Build a series of let statements mapping each self_arg
1361 // to its discriminant value. If this is a C-style enum
1362 // with a specific repr type, then casts the values to
1363 // that type. Otherwise casts to `i32` (the default repr
1366 // i.e., for `enum E<T> { A, B(1), C(T, T) }`, and a deriving
1367 // with three Self args, builds three statements:
1370 // let __self0_vi = unsafe {
1371 // std::intrinsics::discriminant_value(&self) } as i32;
1372 // let __self1_vi = unsafe {
1373 // std::intrinsics::discriminant_value(&arg1) } as i32;
1374 // let __self2_vi = unsafe {
1375 // std::intrinsics::discriminant_value(&arg2) } as i32;
1377 let mut index_let_stmts
: Vec
<ast
::Stmt
> = Vec
::with_capacity(vi_idents
.len() + 1);
1379 // We also build an expression which checks whether all discriminants are equal
1380 // discriminant_test = __self0_vi == __self1_vi && __self0_vi == __self2_vi && ...
1381 let mut discriminant_test
= cx
.expr_bool(sp
, true);
1383 let target_type_name
= find_repr_type_name(&cx
.parse_sess
, type_attrs
);
1385 let mut first_ident
= None
;
1386 for (&ident
, self_arg
) in vi_idents
.iter().zip(&self_args
) {
1387 let self_addr
= cx
.expr_addr_of(sp
, self_arg
.clone());
1389 deriving
::call_intrinsic(cx
, sp
, "discriminant_value", vec
![self_addr
]);
1391 let target_ty
= cx
.ty_ident(sp
, cx
.ident_of(target_type_name
));
1392 let variant_disr
= cx
.expr_cast(sp
, variant_value
, target_ty
);
1393 let let_stmt
= cx
.stmt_let(sp
, false, ident
, variant_disr
);
1394 index_let_stmts
.push(let_stmt
);
1398 let first_expr
= cx
.expr_ident(sp
, first
);
1399 let id
= cx
.expr_ident(sp
, ident
);
1400 let test
= cx
.expr_binary(sp
, BinOpKind
::Eq
, first_expr
, id
);
1402 cx
.expr_binary(sp
, BinOpKind
::And
, discriminant_test
, test
)
1405 first_ident
= Some(ident
);
1410 let arm_expr
= self.call_substructure_method(cx
,
1415 &catch_all_substructure
);
1417 // Final wrinkle: the self_args are expressions that deref
1418 // down to desired places, but we cannot actually deref
1419 // them when they are fed as r-values into a tuple
1420 // expression; here add a layer of borrowing, turning
1421 // `(*self, *__arg_0, ...)` into `(&*self, &*__arg_0, ...)`.
1422 self_args
.map_in_place(|self_arg
| cx
.expr_addr_of(sp
, self_arg
));
1423 let match_arg
= cx
.expr(sp
, ast
::ExprKind
::Tup(self_args
));
1425 // Lastly we create an expression which branches on all discriminants being equal
1426 // if discriminant_test {
1428 // (Variant1, Variant1, ...) => Body1
1429 // (Variant2, Variant2, ...) => Body2,
1431 // _ => ::core::intrinsics::unreachable()
1435 // <delegated expression referring to __self0_vi, et al.>
1437 let all_match
= cx
.expr_match(sp
, match_arg
, match_arms
);
1438 let arm_expr
= cx
.expr_if(sp
, discriminant_test
, all_match
, Some(arm_expr
));
1439 index_let_stmts
.push(cx
.stmt_expr(arm_expr
));
1440 cx
.expr_block(cx
.block(sp
, index_let_stmts
))
1441 } else if variants
.is_empty() {
1442 // As an additional wrinkle, For a zero-variant enum A,
1443 // currently the compiler
1444 // will accept `fn (a: &Self) { match *a { } }`
1445 // but rejects `fn (a: &Self) { match (&*a,) { } }`
1446 // as well as `fn (a: &Self) { match ( *a,) { } }`
1448 // This means that the strategy of building up a tuple of
1449 // all Self arguments fails when Self is a zero variant
1450 // enum: rustc rejects the expanded program, even though
1451 // the actual code tends to be impossible to execute (at
1452 // least safely), according to the type system.
1454 // The most expedient fix for this is to just let the
1455 // code fall through to the catch-all. But even this is
1456 // error-prone, since the catch-all as defined above would
1457 // generate code like this:
1459 // _ => { let __self0 = match *self { };
1460 // let __self1 = match *__arg_0 { };
1461 // <catch-all-expr> }
1463 // Which is yields bindings for variables which type
1464 // inference cannot resolve to unique types.
1466 // One option to the above might be to add explicit type
1467 // annotations. But the *only* reason to go down that path
1468 // would be to try to make the expanded output consistent
1469 // with the case when the number of enum variants >= 1.
1471 // That just isn't worth it. In fact, trying to generate
1472 // sensible code for *any* deriving on a zero-variant enum
1473 // does not make sense. But at the same time, for now, we
1474 // do not want to cause a compile failure just because the
1475 // user happened to attach a deriving to their
1476 // zero-variant enum.
1478 // Instead, just generate a failing expression for the
1479 // zero variant case, skipping matches and also skipping
1480 // delegating back to the end user code entirely.
1482 // (See also #4499 and #12609; note that some of the
1483 // discussions there influence what choice we make here;
1484 // e.g., if we feature-gate `match x { ... }` when x refers
1485 // to an uninhabited type (e.g., a zero-variant enum or a
1486 // type holding such an enum), but do not feature-gate
1487 // zero-variant enums themselves, then attempting to
1488 // derive Debug on such a type could here generate code
1489 // that needs the feature gate enabled.)
1491 deriving
::call_intrinsic(cx
, sp
, "unreachable", vec
![])
1494 // Final wrinkle: the self_args are expressions that deref
1495 // down to desired places, but we cannot actually deref
1496 // them when they are fed as r-values into a tuple
1497 // expression; here add a layer of borrowing, turning
1498 // `(*self, *__arg_0, ...)` into `(&*self, &*__arg_0, ...)`.
1499 self_args
.map_in_place(|self_arg
| cx
.expr_addr_of(sp
, self_arg
));
1500 let match_arg
= cx
.expr(sp
, ast
::ExprKind
::Tup(self_args
));
1501 cx
.expr_match(sp
, match_arg
, match_arms
)
1505 fn expand_static_enum_method_body(&self,
1506 cx
: &mut ExtCtxt
<'_
>,
1507 trait_
: &TraitDef
<'_
>,
1510 self_args
: &[P
<Expr
>],
1511 nonself_args
: &[P
<Expr
>])
1513 let summary
= enum_def
.variants
1516 let sp
= v
.span
.with_ctxt(trait_
.span
.ctxt());
1517 let summary
= trait_
.summarise_struct(cx
, &v
.node
.data
);
1518 (v
.node
.ident
, sp
, summary
)
1521 self.call_substructure_method(cx
,
1526 &StaticEnum(enum_def
, summary
))
1530 // general helper methods.
1531 impl<'a
> TraitDef
<'a
> {
1532 fn summarise_struct(&self, cx
: &mut ExtCtxt
<'_
>, struct_def
: &VariantData
) -> StaticFields
{
1533 let mut named_idents
= Vec
::new();
1534 let mut just_spans
= Vec
::new();
1535 for field
in struct_def
.fields() {
1536 let sp
= field
.span
.with_ctxt(self.span
.ctxt());
1538 Some(ident
) => named_idents
.push((ident
, sp
)),
1539 _
=> just_spans
.push(sp
),
1543 let is_tuple
= if let ast
::VariantData
::Tuple(..) = struct_def { true }
else { false }
;
1544 match (just_spans
.is_empty(), named_idents
.is_empty()) {
1546 cx
.span_bug(self.span
,
1547 "a struct with named and unnamed \
1548 fields in generic `derive`")
1551 (_
, false) => Named(named_idents
),
1553 (false, _
) => Unnamed(just_spans
, is_tuple
),
1555 _
=> Named(Vec
::new()),
1559 fn create_subpatterns(&self,
1560 cx
: &mut ExtCtxt
<'_
>,
1561 field_paths
: Vec
<ast
::Ident
>,
1562 mutbl
: ast
::Mutability
,
1563 use_temporaries
: bool
)
1564 -> Vec
<P
<ast
::Pat
>> {
1567 let binding_mode
= if use_temporaries
{
1568 ast
::BindingMode
::ByValue(ast
::Mutability
::Immutable
)
1570 ast
::BindingMode
::ByRef(mutbl
)
1573 PatKind
::Ident(binding_mode
, (*path
).clone(), None
))
1578 fn create_struct_pattern
1580 cx
: &mut ExtCtxt
<'_
>,
1581 struct_path
: ast
::Path
,
1582 struct_def
: &'a VariantData
,
1584 mutbl
: ast
::Mutability
,
1585 use_temporaries
: bool
)
1586 -> (P
<ast
::Pat
>, Vec
<(Span
, Option
<Ident
>, P
<Expr
>, &'a
[ast
::Attribute
])>)
1588 let mut paths
= Vec
::new();
1589 let mut ident_exprs
= Vec
::new();
1590 for (i
, struct_field
) in struct_def
.fields().iter().enumerate() {
1591 let sp
= struct_field
.span
.with_ctxt(self.span
.ctxt());
1592 let ident
= cx
.ident_of(&format
!("{}_{}", prefix
, i
)).gensym();
1593 paths
.push(ident
.with_span_pos(sp
));
1594 let val
= cx
.expr_path(cx
.path_ident(sp
, ident
));
1595 let val
= if use_temporaries
{
1598 cx
.expr_deref(sp
, val
)
1600 let val
= cx
.expr(sp
, ast
::ExprKind
::Paren(val
));
1602 ident_exprs
.push((sp
, struct_field
.ident
, val
, &struct_field
.attrs
[..]));
1605 let subpats
= self.create_subpatterns(cx
, paths
, mutbl
, use_temporaries
);
1606 let pattern
= match *struct_def
{
1607 VariantData
::Struct(..) => {
1608 let field_pats
= subpats
.into_iter()
1610 .map(|(pat
, &(sp
, ident
, ..))| {
1611 if ident
.is_none() {
1612 cx
.span_bug(sp
, "a braced struct with unnamed fields in `derive`");
1614 source_map
::Spanned
{
1615 span
: pat
.span
.with_ctxt(self.span
.ctxt()),
1616 node
: ast
::FieldPat
{
1617 ident
: ident
.unwrap(),
1619 is_shorthand
: false,
1620 attrs
: ThinVec
::new(),
1625 cx
.pat_struct(self.span
, struct_path
, field_pats
)
1627 VariantData
::Tuple(..) => {
1628 cx
.pat_tuple_struct(self.span
, struct_path
, subpats
)
1630 VariantData
::Unit(..) => {
1631 cx
.pat_path(self.span
, struct_path
)
1635 (pattern
, ident_exprs
)
1638 fn create_enum_variant_pattern
1640 cx
: &mut ExtCtxt
<'_
>,
1641 enum_ident
: ast
::Ident
,
1642 variant
: &'a ast
::Variant
,
1644 mutbl
: ast
::Mutability
)
1645 -> (P
<ast
::Pat
>, Vec
<(Span
, Option
<Ident
>, P
<Expr
>, &'a
[ast
::Attribute
])>) {
1646 let sp
= variant
.span
.with_ctxt(self.span
.ctxt());
1647 let variant_path
= cx
.path(sp
, vec
![enum_ident
, variant
.node
.ident
]);
1648 let use_temporaries
= false; // enums can't be repr(packed)
1649 self.create_struct_pattern(cx
, variant_path
, &variant
.node
.data
, prefix
, mutbl
,
1654 // helpful premade recipes
1656 pub fn cs_fold_fields
<'a
, F
>(use_foldl
: bool
,
1659 cx
: &mut ExtCtxt
<'_
>,
1660 all_fields
: &[FieldInfo
<'a
>])
1662 where F
: FnMut(&mut ExtCtxt
<'_
>, Span
, P
<Expr
>, P
<Expr
>, &[P
<Expr
>]) -> P
<Expr
>
1665 all_fields
.iter().fold(base
, |old
, field
| {
1666 f(cx
, field
.span
, old
, field
.self_
.clone(), &field
.other
)
1669 all_fields
.iter().rev().fold(base
, |old
, field
| {
1670 f(cx
, field
.span
, old
, field
.self_
.clone(), &field
.other
)
1675 pub fn cs_fold_enumnonmatch(mut enum_nonmatch_f
: EnumNonMatchCollapsedFunc
<'_
>,
1676 cx
: &mut ExtCtxt
<'_
>,
1678 substructure
: &Substructure
<'_
>)
1681 match *substructure
.fields
{
1682 EnumNonMatchingCollapsed(ref all_args
, _
, tuple
) => {
1685 (&all_args
[..], tuple
),
1686 substructure
.nonself_args
)
1688 _
=> cx
.span_bug(trait_span
, "cs_fold_enumnonmatch expected an EnumNonMatchingCollapsed")
1692 pub fn cs_fold_static(cx
: &mut ExtCtxt
<'_
>,
1696 cx
.span_bug(trait_span
, "static function in `derive`")
1699 /// Fold the fields. `use_foldl` controls whether this is done
1700 /// left-to-right (`true`) or right-to-left (`false`).
1701 pub fn cs_fold
<F
>(use_foldl
: bool
,
1704 enum_nonmatch_f
: EnumNonMatchCollapsedFunc
<'_
>,
1705 cx
: &mut ExtCtxt
<'_
>,
1707 substructure
: &Substructure
<'_
>)
1709 where F
: FnMut(&mut ExtCtxt
<'_
>, Span
, P
<Expr
>, P
<Expr
>, &[P
<Expr
>]) -> P
<Expr
>
1711 match *substructure
.fields
{
1712 EnumMatching(.., ref all_fields
) |
1713 Struct(_
, ref all_fields
) => {
1714 cs_fold_fields(use_foldl
, f
, base
, cx
, all_fields
)
1716 EnumNonMatchingCollapsed(..) => {
1717 cs_fold_enumnonmatch(enum_nonmatch_f
, cx
, trait_span
, substructure
)
1719 StaticEnum(..) | StaticStruct(..) => {
1720 cs_fold_static(cx
, trait_span
)
1725 /// Function to fold over fields, with three cases, to generate more efficient and concise code.
1726 /// When the `substructure` has grouped fields, there are two cases:
1727 /// Zero fields: call the base case function with `None` (like the usual base case of `cs_fold`).
1728 /// One or more fields: call the base case function on the first value (which depends on
1729 /// `use_fold`), and use that as the base case. Then perform `cs_fold` on the remainder of the
1731 /// When the `substructure` is a `EnumNonMatchingCollapsed`, the result of `enum_nonmatch_f`
1732 /// is returned. Statics may not be folded over.
1733 /// See `cs_op` in `partial_ord.rs` for a model example.
1734 pub fn cs_fold1
<F
, B
>(use_foldl
: bool
,
1737 enum_nonmatch_f
: EnumNonMatchCollapsedFunc
<'_
>,
1738 cx
: &mut ExtCtxt
<'_
>,
1740 substructure
: &Substructure
<'_
>)
1742 where F
: FnMut(&mut ExtCtxt
<'_
>, Span
, P
<Expr
>, P
<Expr
>, &[P
<Expr
>]) -> P
<Expr
>,
1743 B
: FnMut(&mut ExtCtxt
<'_
>, Option
<(Span
, P
<Expr
>, &[P
<Expr
>])>) -> P
<Expr
>
1745 match *substructure
.fields
{
1746 EnumMatching(.., ref all_fields
) |
1747 Struct(_
, ref all_fields
) => {
1748 let (base
, all_fields
) = match (all_fields
.is_empty(), use_foldl
) {
1750 let field
= &all_fields
[0];
1751 let args
= (field
.span
, field
.self_
.clone(), &field
.other
[..]);
1752 (b(cx
, Some(args
)), &all_fields
[1..])
1755 let idx
= all_fields
.len() - 1;
1756 let field
= &all_fields
[idx
];
1757 let args
= (field
.span
, field
.self_
.clone(), &field
.other
[..]);
1758 (b(cx
, Some(args
)), &all_fields
[..idx
])
1760 (true, _
) => (b(cx
, None
), &all_fields
[..])
1763 cs_fold_fields(use_foldl
, f
, base
, cx
, all_fields
)
1765 EnumNonMatchingCollapsed(..) => {
1766 cs_fold_enumnonmatch(enum_nonmatch_f
, cx
, trait_span
, substructure
)
1768 StaticEnum(..) | StaticStruct(..) => {
1769 cs_fold_static(cx
, trait_span
)
1774 /// Call the method that is being derived on all the fields, and then
1775 /// process the collected results. i.e.
1777 /// ```ignore (only-for-syntax-highlight)
1778 /// f(cx, span, vec![self_1.method(__arg_1_1, __arg_2_1),
1779 /// self_2.method(__arg_1_2, __arg_2_2)])
1782 pub fn cs_same_method
<F
>(f
: F
,
1783 mut enum_nonmatch_f
: EnumNonMatchCollapsedFunc
<'_
>,
1784 cx
: &mut ExtCtxt
<'_
>,
1786 substructure
: &Substructure
<'_
>)
1788 where F
: FnOnce(&mut ExtCtxt
<'_
>, Span
, Vec
<P
<Expr
>>) -> P
<Expr
>
1790 match *substructure
.fields
{
1791 EnumMatching(.., ref all_fields
) |
1792 Struct(_
, ref all_fields
) => {
1793 // call self_n.method(other_1_n, other_2_n, ...)
1794 let called
= all_fields
.iter()
1796 cx
.expr_method_call(field
.span
,
1797 field
.self_
.clone(),
1798 substructure
.method_ident
,
1801 .map(|e
| cx
.expr_addr_of(field
.span
, e
.clone()))
1806 f(cx
, trait_span
, called
)
1808 EnumNonMatchingCollapsed(ref all_self_args
, _
, tuple
) => {
1811 (&all_self_args
[..], tuple
),
1812 substructure
.nonself_args
)
1814 StaticEnum(..) | StaticStruct(..) => cx
.span_bug(trait_span
, "static function in `derive`"),
1818 /// Returns `true` if the type has no value fields
1819 /// (for an enum, no variant has any fields)
1820 pub fn is_type_without_fields(item
: &Annotatable
) -> bool
{
1821 if let Annotatable
::Item(ref item
) = *item
{
1823 ast
::ItemKind
::Enum(ref enum_def
, _
) => {
1824 enum_def
.variants
.iter().all(|v
| v
.node
.data
.fields().is_empty())
1826 ast
::ItemKind
::Struct(ref variant_data
, _
) => variant_data
.fields().is_empty(),