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+//! Some code that abstracts away much of the boilerplate of writing
+//! `derive` instances for traits. Among other things it manages getting
+//! access to the fields of the 4 different sorts of structs and enum
+//! variants, as well as creating the method and impl ast instances.
+//!
+//! Supported features (fairly exhaustive):
+//!
+//! - Methods taking any number of parameters of any type, and returning
+//! any type, other than vectors, bottom and closures.
+//! - Generating `impl`s for types with type parameters and lifetimes
+//! (e.g., `Option<T>`), the parameters are automatically given the
+//! current trait as a bound. (This includes separate type parameters
+//! and lifetimes for methods.)
+//! - Additional bounds on the type parameters (`TraitDef.additional_bounds`)
+//!
+//! The most important thing for implementors is the `Substructure` and
+//! `SubstructureFields` objects. The latter groups 5 possibilities of the
+//! arguments:
+//!
+//! - `Struct`, when `Self` is a struct (including tuple structs, e.g
+//! `struct T(i32, char)`).
+//! - `EnumMatching`, when `Self` is an enum and all the arguments are the
+//! same variant of the enum (e.g., `Some(1)`, `Some(3)` and `Some(4)`)
+//! - `EnumTag` when `Self` is an enum, for comparing the enum tags.
+//! - `StaticEnum` and `StaticStruct` for static methods, where the type
+//! being derived upon is either an enum or struct respectively. (Any
+//! argument with type Self is just grouped among the non-self
+//! arguments.)
+//!
+//! In the first two cases, the values from the corresponding fields in
+//! all the arguments are grouped together.
+//!
+//! The non-static cases have `Option<ident>` in several places associated
+//! with field `expr`s. This represents the name of the field it is
+//! associated with. It is only not `None` when the associated field has
+//! an identifier in the source code. For example, the `x`s in the
+//! following snippet
+//!
+//! ```rust
+//! # #![allow(dead_code)]
+//! struct A { x : i32 }
+//!
+//! struct B(i32);
+//!
+//! enum C {
+//! C0(i32),
+//! C1 { x: i32 }
+//! }
+//! ```
+//!
+//! The `i32`s in `B` and `C0` don't have an identifier, so the
+//! `Option<ident>`s would be `None` for them.
+//!
+//! In the static cases, the structure is summarized, either into the just
+//! spans of the fields or a list of spans and the field idents (for tuple
+//! structs and record structs, respectively), or a list of these, for
+//! enums (one for each variant). For empty struct and empty enum
+//! variants, it is represented as a count of 0.
+//!
+//! # "`cs`" functions
+//!
+//! The `cs_...` functions ("combine substructure") are designed to
+//! make life easier by providing some pre-made recipes for common
+//! threads; mostly calling the function being derived on all the
+//! arguments and then combining them back together in some way (or
+//! letting the user chose that). They are not meant to be the only
+//! way to handle the structures that this code creates.
+//!
+//! # Examples
+//!
+//! The following simplified `PartialEq` is used for in-code examples:
+//!
+//! ```rust
+//! trait PartialEq {
+//! fn eq(&self, other: &Self) -> bool;
+//! }
+//! impl PartialEq for i32 {
+//! fn eq(&self, other: &i32) -> bool {
+//! *self == *other
+//! }
+//! }
+//! ```
+//!
+//! Some examples of the values of `SubstructureFields` follow, using the
+//! above `PartialEq`, `A`, `B` and `C`.
+//!
+//! ## Structs
+//!
+//! When generating the `expr` for the `A` impl, the `SubstructureFields` is
+//!
+//! ```{.text}
+//! Struct(vec![FieldInfo {
+//! span: <span of x>
+//! name: Some(<ident of x>),
+//! self_: <expr for &self.x>,
+//! other: vec![<expr for &other.x]
+//! }])
+//! ```
+//!
+//! For the `B` impl, called with `B(a)` and `B(b)`,
+//!
+//! ```{.text}
+//! Struct(vec![FieldInfo {
+//! span: <span of `i32`>,
+//! name: None,
+//! self_: <expr for &a>
+//! other: vec![<expr for &b>]
+//! }])
+//! ```
+//!
+//! ## Enums
+//!
+//! When generating the `expr` for a call with `self == C0(a)` and `other
+//! == C0(b)`, the SubstructureFields is
+//!
+//! ```{.text}
+//! EnumMatching(0, <ast::Variant for C0>,
+//! vec![FieldInfo {
+//! span: <span of i32>
+//! name: None,
+//! self_: <expr for &a>,
+//! other: vec![<expr for &b>]
+//! }])
+//! ```
+//!
+//! For `C1 {x}` and `C1 {x}`,
+//!
+//! ```{.text}
+//! EnumMatching(1, <ast::Variant for C1>,
+//! vec![FieldInfo {
+//! span: <span of x>
+//! name: Some(<ident of x>),
+//! self_: <expr for &self.x>,
+//! other: vec![<expr for &other.x>]
+//! }])
+//! ```
+//!
+//! For the tags,
+//!
+//! ```{.text}
+//! EnumTag(
+//! &[<ident of self tag>, <ident of other tag>], <expr to combine with>)
+//! ```
+//! Note that this setup doesn't allow for the brute-force "match every variant
+//! against every other variant" approach, which is bad because it produces a
+//! quadratic amount of code (see #15375).
+//!
+//! ## Static
+//!
+//! A static method on the types above would result in,
+//!
+//! ```{.text}
+//! StaticStruct(<ast::VariantData of A>, Named(vec![(<ident of x>, <span of x>)]))
+//!
+//! StaticStruct(<ast::VariantData of B>, Unnamed(vec![<span of x>]))
+//!
+//! StaticEnum(<ast::EnumDef of C>,
+//! vec![(<ident of C0>, <span of C0>, Unnamed(vec![<span of i32>])),
+//! (<ident of C1>, <span of C1>, Named(vec![(<ident of x>, <span of x>)]))])
+//! ```
+
+pub use StaticFields::*;
+pub use SubstructureFields::*;
+
+use std::cell::RefCell;
+use std::iter;
+use std::vec;
+
+use rustc_ast::ptr::P;
+use rustc_ast::{self as ast, EnumDef, Expr, Generics, PatKind};
+use rustc_ast::{GenericArg, GenericParamKind, VariantData};
+use rustc_attr as attr;
+use rustc_expand::base::{Annotatable, ExtCtxt};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_span::Span;
+
+use ty::{Bounds, Path, Ref, Self_, Ty};
+
+use crate::deriving;
+
+pub mod ty;
+
+pub struct TraitDef<'a> {
+ /// The span for the current #[derive(Foo)] header.
+ pub span: Span,
+
+ pub attributes: Vec<ast::Attribute>,
+
+ /// Path of the trait, including any type parameters
+ pub path: Path,
+
+ /// Additional bounds required of any type parameters of the type,
+ /// other than the current trait
+ pub additional_bounds: Vec<Ty>,
+
+ /// Any extra lifetimes and/or bounds, e.g., `D: serialize::Decoder`
+ pub generics: Bounds,
+
+ /// Can this trait be derived for unions?
+ pub supports_unions: bool,
+
+ pub methods: Vec<MethodDef<'a>>,
+
+ pub associated_types: Vec<(Ident, Ty)>,
+}
+
+pub struct MethodDef<'a> {
+ /// name of the method
+ pub name: Symbol,
+ /// List of generics, e.g., `R: rand::Rng`
+ pub generics: Bounds,
+
+ /// Is there is a `&self` argument? If not, it is a static function.
+ pub explicit_self: bool,
+
+ /// Arguments other than the self argument.
+ pub nonself_args: Vec<(Ty, Symbol)>,
+
+ /// Returns type
+ pub ret_ty: Ty,
+
+ pub attributes: Vec<ast::Attribute>,
+
+ /// Can we combine fieldless variants for enums into a single match arm?
+ /// If true, indicates that the trait operation uses the enum tag in some
+ /// way.
+ pub unify_fieldless_variants: bool,
+
+ pub combine_substructure: RefCell<CombineSubstructureFunc<'a>>,
+}
+
+/// All the data about the data structure/method being derived upon.
+pub struct Substructure<'a> {
+ /// ident of self
+ pub type_ident: Ident,
+ /// Verbatim access to any non-selflike arguments, i.e. arguments that
+ /// don't have type `&Self`.
+ pub nonselflike_args: &'a [P<Expr>],
+ pub fields: &'a SubstructureFields<'a>,
+}
+
+/// Summary of the relevant parts of a struct/enum field.
+pub struct FieldInfo {
+ pub span: Span,
+ /// None for tuple structs/normal enum variants, Some for normal
+ /// structs/struct enum variants.
+ pub name: Option<Ident>,
+ /// The expression corresponding to this field of `self`
+ /// (specifically, a reference to it).
+ pub self_expr: P<Expr>,
+ /// The expressions corresponding to references to this field in
+ /// the other selflike arguments.
+ pub other_selflike_exprs: Vec<P<Expr>>,
+}
+
+/// Fields for a static method
+pub enum StaticFields {
+ /// Tuple and unit structs/enum variants like this.
+ Unnamed(Vec<Span>, bool /*is tuple*/),
+ /// Normal structs/struct variants.
+ Named(Vec<(Ident, Span)>),
+}
+
+/// A summary of the possible sets of fields.
+pub enum SubstructureFields<'a> {
+ /// A non-static method with `Self` is a struct.
+ Struct(&'a ast::VariantData, Vec<FieldInfo>),
+
+ /// Matching variants of the enum: variant index, variant count, ast::Variant,
+ /// fields: the field name is only non-`None` in the case of a struct
+ /// variant.
+ EnumMatching(usize, usize, &'a ast::Variant, Vec<FieldInfo>),
+
+ /// The tag of an enum. The first field is a `FieldInfo` for the tags, as
+ /// if they were fields. The second field is the expression to combine the
+ /// tag expression with; it will be `None` if no match is necessary.
+ EnumTag(FieldInfo, Option<P<Expr>>),
+
+ /// A static method where `Self` is a struct.
+ StaticStruct(&'a ast::VariantData, StaticFields),
+
+ /// A static method where `Self` is an enum.
+ StaticEnum(&'a ast::EnumDef, Vec<(Ident, Span, StaticFields)>),
+}
+
+/// Combine the values of all the fields together. The last argument is
+/// all the fields of all the structures.
+pub type CombineSubstructureFunc<'a> =
+ Box<dyn FnMut(&mut ExtCtxt<'_>, Span, &Substructure<'_>) -> BlockOrExpr + 'a>;
+
+pub fn combine_substructure(
+ f: CombineSubstructureFunc<'_>,
+) -> RefCell<CombineSubstructureFunc<'_>> {
+ RefCell::new(f)
+}
+
+struct TypeParameter {
+ bound_generic_params: Vec<ast::GenericParam>,
+ ty: P<ast::Ty>,
+}
+
+// The code snippets built up for derived code are sometimes used as blocks
+// (e.g. in a function body) and sometimes used as expressions (e.g. in a match
+// arm). This structure avoids committing to either form until necessary,
+// avoiding the insertion of any unnecessary blocks.
+//
+// The statements come before the expression.
+pub struct BlockOrExpr(Vec<ast::Stmt>, Option<P<Expr>>);
+
+impl BlockOrExpr {
+ pub fn new_stmts(stmts: Vec<ast::Stmt>) -> BlockOrExpr {
+ BlockOrExpr(stmts, None)
+ }
+
+ pub fn new_expr(expr: P<Expr>) -> BlockOrExpr {
+ BlockOrExpr(vec![], Some(expr))
+ }
+
+ pub fn new_mixed(stmts: Vec<ast::Stmt>, expr: Option<P<Expr>>) -> BlockOrExpr {
+ BlockOrExpr(stmts, expr)
+ }
+
+ // Converts it into a block.
+ fn into_block(mut self, cx: &ExtCtxt<'_>, span: Span) -> P<ast::Block> {
+ if let Some(expr) = self.1 {
+ self.0.push(cx.stmt_expr(expr));
+ }
+ cx.block(span, self.0)
+ }
+
+ // Converts it into an expression.
+ fn into_expr(self, cx: &ExtCtxt<'_>, span: Span) -> P<Expr> {
+ if self.0.is_empty() {
+ match self.1 {
+ None => cx.expr_block(cx.block(span, vec![])),
+ Some(expr) => expr,
+ }
+ } else if self.0.len() == 1
+ && let ast::StmtKind::Expr(expr) = &self.0[0].kind
+ && self.1.is_none()
+ {
+ // There's only a single statement expression. Pull it out.
+ expr.clone()
+ } else {
+ // Multiple statements and/or expressions.
+ cx.expr_block(self.into_block(cx, span))
+ }
+ }
+}
+
+/// This method helps to extract all the type parameters referenced from a
+/// type. For a type parameter `<T>`, it looks for either a `TyPath` that
+/// is not global and starts with `T`, or a `TyQPath`.
+/// Also include bound generic params from the input type.
+fn find_type_parameters(
+ ty: &ast::Ty,
+ ty_param_names: &[Symbol],
+ cx: &ExtCtxt<'_>,
+) -> Vec<TypeParameter> {
+ use rustc_ast::visit;
+
+ struct Visitor<'a, 'b> {
+ cx: &'a ExtCtxt<'b>,
+ ty_param_names: &'a [Symbol],
+ bound_generic_params_stack: Vec<ast::GenericParam>,
+ type_params: Vec<TypeParameter>,
+ }
+
+ impl<'a, 'b> visit::Visitor<'a> for Visitor<'a, 'b> {
+ fn visit_ty(&mut self, ty: &'a ast::Ty) {
+ if let ast::TyKind::Path(_, ref path) = ty.kind {
+ if let Some(segment) = path.segments.first() {
+ if self.ty_param_names.contains(&segment.ident.name) {
+ self.type_params.push(TypeParameter {
+ bound_generic_params: self.bound_generic_params_stack.clone(),
+ ty: P(ty.clone()),
+ });
+ }
+ }
+ }
+
+ visit::walk_ty(self, ty)
+ }
+
+ // Place bound generic params on a stack, to extract them when a type is encountered.
+ fn visit_poly_trait_ref(
+ &mut self,
+ trait_ref: &'a ast::PolyTraitRef,
+ modifier: &'a ast::TraitBoundModifier,
+ ) {
+ let stack_len = self.bound_generic_params_stack.len();
+ self.bound_generic_params_stack
+ .extend(trait_ref.bound_generic_params.clone().into_iter());
+
+ visit::walk_poly_trait_ref(self, trait_ref, modifier);
+
+ self.bound_generic_params_stack.truncate(stack_len);
+ }
+
+ fn visit_mac_call(&mut self, mac: &ast::MacCall) {
+ self.cx.span_err(mac.span(), "`derive` cannot be used on items with type macros");
+ }
+ }
+
+ let mut visitor = Visitor {
+ cx,
+ ty_param_names,
+ bound_generic_params_stack: Vec::new(),
+ type_params: Vec::new(),
+ };
+ visit::Visitor::visit_ty(&mut visitor, ty);
+
+ visitor.type_params
+}
+
+impl<'a> TraitDef<'a> {
+ pub fn expand(
+ self,
+ cx: &mut ExtCtxt<'_>,
+ mitem: &ast::MetaItem,
+ item: &'a Annotatable,
+ push: &mut dyn FnMut(Annotatable),
+ ) {
+ self.expand_ext(cx, mitem, item, push, false);
+ }
+
+ pub fn expand_ext(
+ self,
+ cx: &mut ExtCtxt<'_>,
+ mitem: &ast::MetaItem,
+ item: &'a Annotatable,
+ push: &mut dyn FnMut(Annotatable),
+ from_scratch: bool,
+ ) {
+ match *item {
+ Annotatable::Item(ref item) => {
+ let is_packed = item.attrs.iter().any(|attr| {
+ for r in attr::find_repr_attrs(&cx.sess, attr) {
+ if let attr::ReprPacked(_) = r {
+ return true;
+ }
+ }
+ false
+ });
+ let has_no_type_params = match item.kind {
+ ast::ItemKind::Struct(_, ref generics)
+ | ast::ItemKind::Enum(_, ref generics)
+ | ast::ItemKind::Union(_, ref generics) => !generics
+ .params
+ .iter()
+ .any(|param| matches!(param.kind, ast::GenericParamKind::Type { .. })),
+ _ => unreachable!(),
+ };
+ let container_id = cx.current_expansion.id.expn_data().parent.expect_local();
+ let always_copy = has_no_type_params && cx.resolver.has_derive_copy(container_id);
+
+ let newitem = match item.kind {
+ ast::ItemKind::Struct(ref struct_def, ref generics) => self.expand_struct_def(
+ cx,
+ &struct_def,
+ item.ident,
+ generics,
+ from_scratch,
+ is_packed,
+ always_copy,
+ ),
+ ast::ItemKind::Enum(ref enum_def, ref generics) => {
+ // We ignore `is_packed`/`always_copy` here, because
+ // `repr(packed)` enums cause an error later on.
+ //
+ // This can only cause further compilation errors
+ // downstream in blatantly illegal code, so it
+ // is fine.
+ self.expand_enum_def(cx, enum_def, item.ident, generics, from_scratch)
+ }
+ ast::ItemKind::Union(ref struct_def, ref generics) => {
+ if self.supports_unions {
+ self.expand_struct_def(
+ cx,
+ &struct_def,
+ item.ident,
+ generics,
+ from_scratch,
+ is_packed,
+ always_copy,
+ )
+ } else {
+ cx.span_err(mitem.span, "this trait cannot be derived for unions");
+ return;
+ }
+ }
+ _ => unreachable!(),
+ };
+ // Keep the lint attributes of the previous item to control how the
+ // generated implementations are linted
+ let mut attrs = newitem.attrs.clone();
+ attrs.extend(
+ item.attrs
+ .iter()
+ .filter(|a| {
+ [
+ sym::allow,
+ sym::warn,
+ sym::deny,
+ sym::forbid,
+ sym::stable,
+ sym::unstable,
+ ]
+ .contains(&a.name_or_empty())
+ })
+ .cloned(),
+ );
+ push(Annotatable::Item(P(ast::Item { attrs, ..(*newitem).clone() })))
+ }
+ _ => unreachable!(),
+ }
+ }
+
+ /// Given that we are deriving a trait `DerivedTrait` for a type like:
+ ///
+ /// ```ignore (only-for-syntax-highlight)
+ /// struct Struct<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z> where C: WhereTrait {
+ /// a: A,
+ /// b: B::Item,
+ /// b1: <B as DeclaredTrait>::Item,
+ /// c1: <C as WhereTrait>::Item,
+ /// c2: Option<<C as WhereTrait>::Item>,
+ /// ...
+ /// }
+ /// ```
+ ///
+ /// create an impl like:
+ ///
+ /// ```ignore (only-for-syntax-highlight)
+ /// impl<'a, ..., 'z, A, B: DeclaredTrait, C, ... Z> where
+ /// C: WhereTrait,
+ /// A: DerivedTrait + B1 + ... + BN,
+ /// B: DerivedTrait + B1 + ... + BN,
+ /// C: DerivedTrait + B1 + ... + BN,
+ /// B::Item: DerivedTrait + B1 + ... + BN,
+ /// <C as WhereTrait>::Item: DerivedTrait + B1 + ... + BN,
+ /// ...
+ /// {
+ /// ...
+ /// }
+ /// ```
+ ///
+ /// where B1, ..., BN are the bounds given by `bounds_paths`.'. Z is a phantom type, and
+ /// therefore does not get bound by the derived trait.
+ fn create_derived_impl(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ type_ident: Ident,
+ generics: &Generics,
+ field_tys: Vec<P<ast::Ty>>,
+ methods: Vec<P<ast::AssocItem>>,
+ ) -> P<ast::Item> {
+ let trait_path = self.path.to_path(cx, self.span, type_ident, generics);
+
+ // Transform associated types from `deriving::ty::Ty` into `ast::AssocItem`
+ let associated_types = self.associated_types.iter().map(|&(ident, ref type_def)| {
+ P(ast::AssocItem {
+ id: ast::DUMMY_NODE_ID,
+ span: self.span,
+ ident,
+ vis: ast::Visibility {
+ span: self.span.shrink_to_lo(),
+ kind: ast::VisibilityKind::Inherited,
+ tokens: None,
+ },
+ attrs: Vec::new(),
+ kind: ast::AssocItemKind::TyAlias(Box::new(ast::TyAlias {
+ defaultness: ast::Defaultness::Final,
+ generics: Generics::default(),
+ where_clauses: (
+ ast::TyAliasWhereClause::default(),
+ ast::TyAliasWhereClause::default(),
+ ),
+ where_predicates_split: 0,
+ bounds: Vec::new(),
+ ty: Some(type_def.to_ty(cx, self.span, type_ident, generics)),
+ })),
+ tokens: None,
+ })
+ });
+
+ let Generics { mut params, mut where_clause, .. } =
+ self.generics.to_generics(cx, self.span, type_ident, generics);
+ where_clause.span = generics.where_clause.span;
+ let ctxt = self.span.ctxt();
+ let span = generics.span.with_ctxt(ctxt);
+
+ // Create the generic parameters
+ params.extend(generics.params.iter().map(|param| match &param.kind {
+ GenericParamKind::Lifetime { .. } => param.clone(),
+ GenericParamKind::Type { .. } => {
+ // I don't think this can be moved out of the loop, since
+ // a GenericBound requires an ast id
+ let bounds: Vec<_> =
+ // extra restrictions on the generics parameters to the
+ // type being derived upon
+ self.additional_bounds.iter().map(|p| {
+ cx.trait_bound(p.to_path(cx, self.span, type_ident, generics))
+ }).chain(
+ // require the current trait
+ iter::once(cx.trait_bound(trait_path.clone()))
+ ).chain(
+ // also add in any bounds from the declaration
+ param.bounds.iter().cloned()
+ ).collect();
+
+ cx.typaram(param.ident.span.with_ctxt(ctxt), param.ident, vec![], bounds, None)
+ }
+ GenericParamKind::Const { ty, kw_span, .. } => {
+ let const_nodefault_kind = GenericParamKind::Const {
+ ty: ty.clone(),
+ kw_span: kw_span.with_ctxt(ctxt),
+
+ // We can't have default values inside impl block
+ default: None,
+ };
+ let mut param_clone = param.clone();
+ param_clone.kind = const_nodefault_kind;
+ param_clone
+ }
+ }));
+
+ // and similarly for where clauses
+ where_clause.predicates.extend(generics.where_clause.predicates.iter().map(|clause| {
+ match clause {
+ ast::WherePredicate::BoundPredicate(wb) => {
+ let span = wb.span.with_ctxt(ctxt);
+ ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
+ span,
+ ..wb.clone()
+ })
+ }
+ ast::WherePredicate::RegionPredicate(wr) => {
+ let span = wr.span.with_ctxt(ctxt);
+ ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
+ span,
+ ..wr.clone()
+ })
+ }
+ ast::WherePredicate::EqPredicate(we) => {
+ let span = we.span.with_ctxt(ctxt);
+ ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
+ id: ast::DUMMY_NODE_ID,
+ span,
+ ..we.clone()
+ })
+ }
+ }
+ }));
+
+ {
+ // Extra scope required here so ty_params goes out of scope before params is moved
+
+ let mut ty_params = params
+ .iter()
+ .filter(|param| matches!(param.kind, ast::GenericParamKind::Type { .. }))
+ .peekable();
+
+ if ty_params.peek().is_some() {
+ let ty_param_names: Vec<Symbol> =
+ ty_params.map(|ty_param| ty_param.ident.name).collect();
+
+ for field_ty in field_tys {
+ let field_ty_params = find_type_parameters(&field_ty, &ty_param_names, cx);
+
+ for field_ty_param in field_ty_params {
+ // if we have already handled this type, skip it
+ if let ast::TyKind::Path(_, ref p) = field_ty_param.ty.kind {
+ if p.segments.len() == 1
+ && ty_param_names.contains(&p.segments[0].ident.name)
+ {
+ continue;
+ };
+ }
+ let mut bounds: Vec<_> = self
+ .additional_bounds
+ .iter()
+ .map(|p| cx.trait_bound(p.to_path(cx, self.span, type_ident, generics)))
+ .collect();
+
+ // require the current trait
+ bounds.push(cx.trait_bound(trait_path.clone()));
+
+ let predicate = ast::WhereBoundPredicate {
+ span: self.span,
+ bound_generic_params: field_ty_param.bound_generic_params,
+ bounded_ty: field_ty_param.ty,
+ bounds,
+ };
+
+ let predicate = ast::WherePredicate::BoundPredicate(predicate);
+ where_clause.predicates.push(predicate);
+ }
+ }
+ }
+ }
+
+ let trait_generics = Generics { params, where_clause, span };
+
+ // Create the reference to the trait.
+ let trait_ref = cx.trait_ref(trait_path);
+
+ let self_params: Vec<_> = generics
+ .params
+ .iter()
+ .map(|param| match param.kind {
+ GenericParamKind::Lifetime { .. } => {
+ GenericArg::Lifetime(cx.lifetime(param.ident.span.with_ctxt(ctxt), param.ident))
+ }
+ GenericParamKind::Type { .. } => {
+ GenericArg::Type(cx.ty_ident(param.ident.span.with_ctxt(ctxt), param.ident))
+ }
+ GenericParamKind::Const { .. } => {
+ GenericArg::Const(cx.const_ident(param.ident.span.with_ctxt(ctxt), param.ident))
+ }
+ })
+ .collect();
+
+ // Create the type of `self`.
+ let path = cx.path_all(self.span, false, vec![type_ident], self_params);
+ let self_type = cx.ty_path(path);
+
+ let attr = cx.attribute(cx.meta_word(self.span, sym::automatically_derived));
+ let opt_trait_ref = Some(trait_ref);
+
+ let mut a = vec![attr];
+ a.extend(self.attributes.iter().cloned());
+
+ cx.item(
+ self.span,
+ Ident::empty(),
+ a,
+ ast::ItemKind::Impl(Box::new(ast::Impl {
+ unsafety: ast::Unsafe::No,
+ polarity: ast::ImplPolarity::Positive,
+ defaultness: ast::Defaultness::Final,
+ constness: ast::Const::No,
+ generics: trait_generics,
+ of_trait: opt_trait_ref,
+ self_ty: self_type,
+ items: methods.into_iter().chain(associated_types).collect(),
+ })),
+ )
+ }
+
+ fn expand_struct_def(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ struct_def: &'a VariantData,
+ type_ident: Ident,
+ generics: &Generics,
+ from_scratch: bool,
+ is_packed: bool,
+ always_copy: bool,
+ ) -> P<ast::Item> {
+ let field_tys: Vec<P<ast::Ty>> =
+ struct_def.fields().iter().map(|field| field.ty.clone()).collect();
+
+ let methods = self
+ .methods
+ .iter()
+ .map(|method_def| {
+ let (explicit_self, selflike_args, nonselflike_args, nonself_arg_tys) =
+ method_def.extract_arg_details(cx, self, type_ident, generics);
+
+ let body = if from_scratch || method_def.is_static() {
+ method_def.expand_static_struct_method_body(
+ cx,
+ self,
+ struct_def,
+ type_ident,
+ &nonselflike_args,
+ )
+ } else {
+ method_def.expand_struct_method_body(
+ cx,
+ self,
+ struct_def,
+ type_ident,
+ &selflike_args,
+ &nonselflike_args,
+ is_packed,
+ always_copy,
+ )
+ };
+
+ method_def.create_method(
+ cx,
+ self,
+ type_ident,
+ generics,
+ explicit_self,
+ nonself_arg_tys,
+ body,
+ )
+ })
+ .collect();
+
+ self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
+ }
+
+ fn expand_enum_def(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ enum_def: &'a EnumDef,
+ type_ident: Ident,
+ generics: &Generics,
+ from_scratch: bool,
+ ) -> P<ast::Item> {
+ let mut field_tys = Vec::new();
+
+ for variant in &enum_def.variants {
+ field_tys.extend(variant.data.fields().iter().map(|field| field.ty.clone()));
+ }
+
+ let methods = self
+ .methods
+ .iter()
+ .map(|method_def| {
+ let (explicit_self, selflike_args, nonselflike_args, nonself_arg_tys) =
+ method_def.extract_arg_details(cx, self, type_ident, generics);
+
+ let body = if from_scratch || method_def.is_static() {
+ method_def.expand_static_enum_method_body(
+ cx,
+ self,
+ enum_def,
+ type_ident,
+ &nonselflike_args,
+ )
+ } else {
+ method_def.expand_enum_method_body(
+ cx,
+ self,
+ enum_def,
+ type_ident,
+ selflike_args,
+ &nonselflike_args,
+ )
+ };
+
+ method_def.create_method(
+ cx,
+ self,
+ type_ident,
+ generics,
+ explicit_self,
+ nonself_arg_tys,
+ body,
+ )
+ })
+ .collect();
+
+ self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
+ }
+}
+
+impl<'a> MethodDef<'a> {
+ fn call_substructure_method(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ trait_: &TraitDef<'_>,
+ type_ident: Ident,
+ nonselflike_args: &[P<Expr>],
+ fields: &SubstructureFields<'_>,
+ ) -> BlockOrExpr {
+ let span = trait_.span;
+ let substructure = Substructure { type_ident, nonselflike_args, fields };
+ let mut f = self.combine_substructure.borrow_mut();
+ let f: &mut CombineSubstructureFunc<'_> = &mut *f;
+ f(cx, span, &substructure)
+ }
+
+ fn get_ret_ty(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ trait_: &TraitDef<'_>,
+ generics: &Generics,
+ type_ident: Ident,
+ ) -> P<ast::Ty> {
+ self.ret_ty.to_ty(cx, trait_.span, type_ident, generics)
+ }
+
+ fn is_static(&self) -> bool {
+ !self.explicit_self
+ }
+
+ // The return value includes:
+ // - explicit_self: The `&self` arg, if present.
+ // - selflike_args: Expressions for `&self` (if present) and also any other
+ // args with the same type (e.g. the `other` arg in `PartialEq::eq`).
+ // - nonselflike_args: Expressions for all the remaining args.
+ // - nonself_arg_tys: Additional information about all the args other than
+ // `&self`.
+ fn extract_arg_details(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ trait_: &TraitDef<'_>,
+ type_ident: Ident,
+ generics: &Generics,
+ ) -> (Option<ast::ExplicitSelf>, Vec<P<Expr>>, Vec<P<Expr>>, Vec<(Ident, P<ast::Ty>)>) {
+ let mut selflike_args = Vec::new();
+ let mut nonselflike_args = Vec::new();
+ let mut nonself_arg_tys = Vec::new();
+ let span = trait_.span;
+
+ let explicit_self = if self.explicit_self {
+ let (self_expr, explicit_self) = ty::get_explicit_self(cx, span);
+ selflike_args.push(self_expr);
+ Some(explicit_self)
+ } else {
+ None
+ };
+
+ for (ty, name) in self.nonself_args.iter() {
+ let ast_ty = ty.to_ty(cx, span, type_ident, generics);
+ let ident = Ident::new(*name, span);
+ nonself_arg_tys.push((ident, ast_ty));
+
+ let arg_expr = cx.expr_ident(span, ident);
+
+ match ty {
+ // Selflike (`&Self`) arguments only occur in non-static methods.
+ Ref(box Self_, _) if !self.is_static() => selflike_args.push(arg_expr),
+ Self_ => cx.span_bug(span, "`Self` in non-return position"),
+ _ => nonselflike_args.push(arg_expr),
+ }
+ }
+
+ (explicit_self, selflike_args, nonselflike_args, nonself_arg_tys)
+ }
+
+ fn create_method(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ trait_: &TraitDef<'_>,
+ type_ident: Ident,
+ generics: &Generics,
+ explicit_self: Option<ast::ExplicitSelf>,
+ nonself_arg_tys: Vec<(Ident, P<ast::Ty>)>,
+ body: BlockOrExpr,
+ ) -> P<ast::AssocItem> {
+ let span = trait_.span;
+ // Create the generics that aren't for `Self`.
+ let fn_generics = self.generics.to_generics(cx, span, type_ident, generics);
+
+ let args = {
+ let self_arg = explicit_self.map(|explicit_self| {
+ let ident = Ident::with_dummy_span(kw::SelfLower).with_span_pos(span);
+ ast::Param::from_self(ast::AttrVec::default(), explicit_self, ident)
+ });
+ let nonself_args =
+ nonself_arg_tys.into_iter().map(|(name, ty)| cx.param(span, name, ty));
+ self_arg.into_iter().chain(nonself_args).collect()
+ };
+
+ let ret_type = self.get_ret_ty(cx, trait_, generics, type_ident);
+
+ let method_ident = Ident::new(self.name, span);
+ let fn_decl = cx.fn_decl(args, ast::FnRetTy::Ty(ret_type));
+ let body_block = body.into_block(cx, span);
+
+ let trait_lo_sp = span.shrink_to_lo();
+
+ let sig = ast::FnSig { header: ast::FnHeader::default(), decl: fn_decl, span };
+ let defaultness = ast::Defaultness::Final;
+
+ // Create the method.
+ P(ast::AssocItem {
+ id: ast::DUMMY_NODE_ID,
+ attrs: self.attributes.clone(),
+ span,
+ vis: ast::Visibility {
+ span: trait_lo_sp,
+ kind: ast::VisibilityKind::Inherited,
+ tokens: None,
+ },
+ ident: method_ident,
+ kind: ast::AssocItemKind::Fn(Box::new(ast::Fn {
+ defaultness,
+ sig,
+ generics: fn_generics,
+ body: Some(body_block),
+ })),
+ tokens: None,
+ })
+ }
+
+ /// The normal case uses field access.
+ /// ```
+ /// #[derive(PartialEq)]
+ /// # struct Dummy;
+ /// struct A { x: u8, y: u8 }
+ ///
+ /// // equivalent to:
+ /// impl PartialEq for A {
+ /// fn eq(&self, other: &A) -> bool {
+ /// self.x == other.x && self.y == other.y
+ /// }
+ /// }
+ /// ```
+ /// But if the struct is `repr(packed)`, we can't use something like
+ /// `&self.x` because that might cause an unaligned ref. So for any trait
+ /// method that takes a reference, if the struct impls `Copy` then we use a
+ /// local block to force a copy:
+ /// ```
+ /// # struct A { x: u8, y: u8 }
+ /// impl PartialEq for A {
+ /// fn eq(&self, other: &A) -> bool {
+ /// // Desugars to `{ self.x }.eq(&{ other.y }) && ...`
+ /// { self.x } == { other.y } && { self.y } == { other.y }
+ /// }
+ /// }
+ /// impl Hash for A {
+ /// fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
+ /// ::core::hash::Hash::hash(&{ self.x }, state);
+ /// ::core::hash::Hash::hash(&{ self.y }, state)
+ /// }
+ /// }
+ /// ```
+ /// If the struct doesn't impl `Copy`, we use let-destructuring with `ref`:
+ /// ```
+ /// # struct A { x: u8, y: u8 }
+ /// impl PartialEq for A {
+ /// fn eq(&self, other: &A) -> bool {
+ /// let Self { x: ref __self_0_0, y: ref __self_0_1 } = *self;
+ /// let Self { x: ref __self_1_0, y: ref __self_1_1 } = *other;
+ /// *__self_0_0 == *__self_1_0 && *__self_0_1 == *__self_1_1
+ /// }
+ /// }
+ /// ```
+ /// This latter case only works if the fields match the alignment required
+ /// by the `packed(N)` attribute. (We'll get errors later on if not.)
+ fn expand_struct_method_body<'b>(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ trait_: &TraitDef<'b>,
+ struct_def: &'b VariantData,
+ type_ident: Ident,
+ selflike_args: &[P<Expr>],
+ nonselflike_args: &[P<Expr>],
+ is_packed: bool,
+ always_copy: bool,
+ ) -> BlockOrExpr {
+ let span = trait_.span;
+ assert!(selflike_args.len() == 1 || selflike_args.len() == 2);
+
+ let mk_body = |cx, selflike_fields| {
+ self.call_substructure_method(
+ cx,
+ trait_,
+ type_ident,
+ nonselflike_args,
+ &Struct(struct_def, selflike_fields),
+ )
+ };
+
+ if !is_packed {
+ let selflike_fields =
+ trait_.create_struct_field_access_fields(cx, selflike_args, struct_def, false);
+ mk_body(cx, selflike_fields)
+ } else if always_copy {
+ let selflike_fields =
+ trait_.create_struct_field_access_fields(cx, selflike_args, struct_def, true);
+ mk_body(cx, selflike_fields)
+ } else {
+ // Neither packed nor copy. Need to use ref patterns.
+ let prefixes: Vec<_> =
+ (0..selflike_args.len()).map(|i| format!("__self_{}", i)).collect();
+ let addr_of = always_copy;
+ let selflike_fields =
+ trait_.create_struct_pattern_fields(cx, struct_def, &prefixes, addr_of);
+ let mut body = mk_body(cx, selflike_fields);
+
+ let struct_path = cx.path(span, vec![Ident::new(kw::SelfUpper, type_ident.span)]);
+ let use_ref_pat = is_packed && !always_copy;
+ let patterns =
+ trait_.create_struct_patterns(cx, struct_path, struct_def, &prefixes, use_ref_pat);
+
+ // Do the let-destructuring.
+ let mut stmts: Vec<_> = iter::zip(selflike_args, patterns)
+ .map(|(selflike_arg_expr, pat)| {
+ let selflike_arg_expr = cx.expr_deref(span, selflike_arg_expr.clone());
+ cx.stmt_let_pat(span, pat, selflike_arg_expr)
+ })
+ .collect();
+ stmts.extend(std::mem::take(&mut body.0));
+ BlockOrExpr(stmts, body.1)
+ }
+ }
+
+ fn expand_static_struct_method_body(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ trait_: &TraitDef<'_>,
+ struct_def: &VariantData,
+ type_ident: Ident,
+ nonselflike_args: &[P<Expr>],
+ ) -> BlockOrExpr {
+ let summary = trait_.summarise_struct(cx, struct_def);
+
+ self.call_substructure_method(
+ cx,
+ trait_,
+ type_ident,
+ nonselflike_args,
+ &StaticStruct(struct_def, summary),
+ )
+ }
+
+ /// ```
+ /// #[derive(PartialEq)]
+ /// # struct Dummy;
+ /// enum A {
+ /// A1,
+ /// A2(i32)
+ /// }
+ /// ```
+ /// is equivalent to:
+ /// ```
+ /// impl ::core::cmp::PartialEq for A {
+ /// #[inline]
+ /// fn eq(&self, other: &A) -> bool {
+ /// let __self_tag = ::core::intrinsics::discriminant_value(self);
+ /// let __arg1_tag = ::core::intrinsics::discriminant_value(other);
+ /// __self_tag == __arg1_tag &&
+ /// match (self, other) {
+ /// (A::A2(__self_0), A::A2(__arg1_0)) =>
+ /// *__self_0 == *__arg1_0,
+ /// _ => true,
+ /// }
+ /// }
+ /// }
+ /// ```
+ /// Creates a tag check combined with a match for a tuple of all
+ /// `selflike_args`, with an arm for each variant with fields, possibly an
+ /// arm for each fieldless variant (if `!unify_fieldless_variants` is not
+ /// true), and possibly a default arm.
+ fn expand_enum_method_body<'b>(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ trait_: &TraitDef<'b>,
+ enum_def: &'b EnumDef,
+ type_ident: Ident,
+ selflike_args: Vec<P<Expr>>,
+ nonselflike_args: &[P<Expr>],
+ ) -> BlockOrExpr {
+ let span = trait_.span;
+ let variants = &enum_def.variants;
+
+ // Traits that unify fieldless variants always use the tag(s).
+ let uses_tags = self.unify_fieldless_variants;
+
+ // There is no sensible code to be generated for *any* deriving on a
+ // zero-variant enum. So we just generate a failing expression.
+ if variants.is_empty() {
+ return BlockOrExpr(vec![], Some(deriving::call_unreachable(cx, span)));
+ }
+
+ let prefixes = iter::once("__self".to_string())
+ .chain(
+ selflike_args
+ .iter()
+ .enumerate()
+ .skip(1)
+ .map(|(arg_count, _selflike_arg)| format!("__arg{}", arg_count)),
+ )
+ .collect::<Vec<String>>();
+
+ // Build a series of let statements mapping each selflike_arg
+ // to its discriminant value.
+ //
+ // e.g. for `PartialEq::eq` builds two statements:
+ // ```
+ // let __self_tag = ::core::intrinsics::discriminant_value(self);
+ // let __arg1_tag = ::core::intrinsics::discriminant_value(other);
+ // ```
+ let get_tag_pieces = |cx: &ExtCtxt<'_>| {
+ let tag_idents: Vec<_> = prefixes
+ .iter()
+ .map(|name| Ident::from_str_and_span(&format!("{}_tag", name), span))
+ .collect();
+
+ let mut tag_exprs: Vec<_> = tag_idents
+ .iter()
+ .map(|&ident| cx.expr_addr_of(span, cx.expr_ident(span, ident)))
+ .collect();
+
+ let self_expr = tag_exprs.remove(0);
+ let other_selflike_exprs = tag_exprs;
+ let tag_field = FieldInfo { span, name: None, self_expr, other_selflike_exprs };
+
+ let tag_let_stmts: Vec<_> = iter::zip(&tag_idents, &selflike_args)
+ .map(|(&ident, selflike_arg)| {
+ let variant_value = deriving::call_intrinsic(
+ cx,
+ span,
+ sym::discriminant_value,
+ vec![selflike_arg.clone()],
+ );
+ cx.stmt_let(span, false, ident, variant_value)
+ })
+ .collect();
+
+ (tag_field, tag_let_stmts)
+ };
+
+ // There are some special cases involving fieldless enums where no
+ // match is necessary.
+ let all_fieldless = variants.iter().all(|v| v.data.fields().is_empty());
+ if all_fieldless {
+ if uses_tags && variants.len() > 1 {
+ // If the type is fieldless and the trait uses the tag and
+ // there are multiple variants, we need just an operation on
+ // the tag(s).
+ let (tag_field, mut tag_let_stmts) = get_tag_pieces(cx);
+ let mut tag_check = self.call_substructure_method(
+ cx,
+ trait_,
+ type_ident,
+ nonselflike_args,
+ &EnumTag(tag_field, None),
+ );
+ tag_let_stmts.append(&mut tag_check.0);
+ return BlockOrExpr(tag_let_stmts, tag_check.1);
+ }
+
+ if variants.len() == 1 {
+ // If there is a single variant, we don't need an operation on
+ // the tag(s). Just use the most degenerate result.
+ return self.call_substructure_method(
+ cx,
+ trait_,
+ type_ident,
+ nonselflike_args,
+ &EnumMatching(0, 1, &variants[0], Vec::new()),
+ );
+ };
+ }
+
+ // These arms are of the form:
+ // (Variant1, Variant1, ...) => Body1
+ // (Variant2, Variant2, ...) => Body2
+ // ...
+ // where each tuple has length = selflike_args.len()
+ let mut match_arms: Vec<ast::Arm> = variants
+ .iter()
+ .enumerate()
+ .filter(|&(_, v)| !(self.unify_fieldless_variants && v.data.fields().is_empty()))
+ .map(|(index, variant)| {
+ // A single arm has form (&VariantK, &VariantK, ...) => BodyK
+ // (see "Final wrinkle" note below for why.)
+
+ let addr_of = false; // because enums can't be repr(packed)
+ let fields =
+ trait_.create_struct_pattern_fields(cx, &variant.data, &prefixes, addr_of);
+
+ let sp = variant.span.with_ctxt(trait_.span.ctxt());
+ let variant_path = cx.path(sp, vec![type_ident, variant.ident]);
+ let use_ref_pat = false; // because enums can't be repr(packed)
+ let mut subpats: Vec<_> = trait_.create_struct_patterns(
+ cx,
+ variant_path,
+ &variant.data,
+ &prefixes,
+ use_ref_pat,
+ );
+
+ // `(VariantK, VariantK, ...)` or just `VariantK`.
+ let single_pat = if subpats.len() == 1 {
+ subpats.pop().unwrap()
+ } else {
+ cx.pat_tuple(span, subpats)
+ };
+
+ // For the BodyK, we need to delegate to our caller,
+ // passing it an EnumMatching to indicate which case
+ // we are in.
+ //
+ // Now, for some given VariantK, we have built up
+ // expressions for referencing every field of every
+ // Self arg, assuming all are instances of VariantK.
+ // Build up code associated with such a case.
+ let substructure = EnumMatching(index, variants.len(), variant, fields);
+ let arm_expr = self
+ .call_substructure_method(
+ cx,
+ trait_,
+ type_ident,
+ nonselflike_args,
+ &substructure,
+ )
+ .into_expr(cx, span);
+
+ cx.arm(span, single_pat, arm_expr)
+ })
+ .collect();
+
+ // Add a default arm to the match, if necessary.
+ let first_fieldless = variants.iter().find(|v| v.data.fields().is_empty());
+ let default = match first_fieldless {
+ Some(v) if self.unify_fieldless_variants => {
+ // We need a default case that handles all the fieldless
+ // variants. The index and actual variant aren't meaningful in
+ // this case, so just use dummy values.
+ Some(
+ self.call_substructure_method(
+ cx,
+ trait_,
+ type_ident,
+ nonselflike_args,
+ &EnumMatching(0, variants.len(), v, Vec::new()),
+ )
+ .into_expr(cx, span),
+ )
+ }
+ _ if variants.len() > 1 && selflike_args.len() > 1 => {
+ // Because we know that all the arguments will match if we reach
+ // the match expression we add the unreachable intrinsics as the
+ // result of the default which should help llvm in optimizing it.
+ Some(deriving::call_unreachable(cx, span))
+ }
+ _ => None,
+ };
+ if let Some(arm) = default {
+ match_arms.push(cx.arm(span, cx.pat_wild(span), arm));
+ }
+
+ // Create a match expression with one arm per discriminant plus
+ // possibly a default arm, e.g.:
+ // match (self, other) {
+ // (Variant1, Variant1, ...) => Body1
+ // (Variant2, Variant2, ...) => Body2,
+ // ...
+ // _ => ::core::intrinsics::unreachable()
+ // }
+ let get_match_expr = |mut selflike_args: Vec<P<Expr>>| {
+ let match_arg = if selflike_args.len() == 1 {
+ selflike_args.pop().unwrap()
+ } else {
+ cx.expr(span, ast::ExprKind::Tup(selflike_args))
+ };
+ cx.expr_match(span, match_arg, match_arms)
+ };
+
+ // If the trait uses the tag and there are multiple variants, we need
+ // to add a tag check operation before the match. Otherwise, the match
+ // is enough.
+ if uses_tags && variants.len() > 1 {
+ let (tag_field, mut tag_let_stmts) = get_tag_pieces(cx);
+
+ // Combine a tag check with the match.
+ let mut tag_check_plus_match = self.call_substructure_method(
+ cx,
+ trait_,
+ type_ident,
+ nonselflike_args,
+ &EnumTag(tag_field, Some(get_match_expr(selflike_args))),
+ );
+ tag_let_stmts.append(&mut tag_check_plus_match.0);
+ BlockOrExpr(tag_let_stmts, tag_check_plus_match.1)
+ } else {
+ BlockOrExpr(vec![], Some(get_match_expr(selflike_args)))
+ }
+ }
+
+ fn expand_static_enum_method_body(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ trait_: &TraitDef<'_>,
+ enum_def: &EnumDef,
+ type_ident: Ident,
+ nonselflike_args: &[P<Expr>],
+ ) -> BlockOrExpr {
+ let summary = enum_def
+ .variants
+ .iter()
+ .map(|v| {
+ let sp = v.span.with_ctxt(trait_.span.ctxt());
+ let summary = trait_.summarise_struct(cx, &v.data);
+ (v.ident, sp, summary)
+ })
+ .collect();
+ self.call_substructure_method(
+ cx,
+ trait_,
+ type_ident,
+ nonselflike_args,
+ &StaticEnum(enum_def, summary),
+ )
+ }
+}
+
+// general helper methods.
+impl<'a> TraitDef<'a> {
+ fn summarise_struct(&self, cx: &mut ExtCtxt<'_>, struct_def: &VariantData) -> StaticFields {
+ let mut named_idents = Vec::new();
+ let mut just_spans = Vec::new();
+ for field in struct_def.fields() {
+ let sp = field.span.with_ctxt(self.span.ctxt());
+ match field.ident {
+ Some(ident) => named_idents.push((ident, sp)),
+ _ => just_spans.push(sp),
+ }
+ }
+
+ let is_tuple = matches!(struct_def, ast::VariantData::Tuple(..));
+ match (just_spans.is_empty(), named_idents.is_empty()) {
+ (false, false) => {
+ cx.span_bug(self.span, "a struct with named and unnamed fields in generic `derive`")
+ }
+ // named fields
+ (_, false) => Named(named_idents),
+ // unnamed fields
+ (false, _) => Unnamed(just_spans, is_tuple),
+ // empty
+ _ => Named(Vec::new()),
+ }
+ }
+
+ fn create_struct_patterns(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ struct_path: ast::Path,
+ struct_def: &'a VariantData,
+ prefixes: &[String],
+ use_ref_pat: bool,
+ ) -> Vec<P<ast::Pat>> {
+ prefixes
+ .iter()
+ .map(|prefix| {
+ let pieces_iter =
+ struct_def.fields().iter().enumerate().map(|(i, struct_field)| {
+ let sp = struct_field.span.with_ctxt(self.span.ctxt());
+ let binding_mode = if use_ref_pat {
+ ast::BindingMode::ByRef(ast::Mutability::Not)
+ } else {
+ ast::BindingMode::ByValue(ast::Mutability::Not)
+ };
+ let ident = self.mk_pattern_ident(prefix, i);
+ let path = ident.with_span_pos(sp);
+ (
+ sp,
+ struct_field.ident,
+ cx.pat(path.span, PatKind::Ident(binding_mode, path, None)),
+ )
+ });
+
+ let struct_path = struct_path.clone();
+ match *struct_def {
+ VariantData::Struct(..) => {
+ let field_pats = pieces_iter
+ .map(|(sp, ident, pat)| {
+ if ident.is_none() {
+ cx.span_bug(
+ sp,
+ "a braced struct with unnamed fields in `derive`",
+ );
+ }
+ ast::PatField {
+ ident: ident.unwrap(),
+ is_shorthand: false,
+ attrs: ast::AttrVec::new(),
+ id: ast::DUMMY_NODE_ID,
+ span: pat.span.with_ctxt(self.span.ctxt()),
+ pat,
+ is_placeholder: false,
+ }
+ })
+ .collect();
+ cx.pat_struct(self.span, struct_path, field_pats)
+ }
+ VariantData::Tuple(..) => {
+ let subpats = pieces_iter.map(|(_, _, subpat)| subpat).collect();
+ cx.pat_tuple_struct(self.span, struct_path, subpats)
+ }
+ VariantData::Unit(..) => cx.pat_path(self.span, struct_path),
+ }
+ })
+ .collect()
+ }
+
+ fn create_fields<F>(&self, struct_def: &'a VariantData, mk_exprs: F) -> Vec<FieldInfo>
+ where
+ F: Fn(usize, &ast::FieldDef, Span) -> Vec<P<ast::Expr>>,
+ {
+ struct_def
+ .fields()
+ .iter()
+ .enumerate()
+ .map(|(i, struct_field)| {
+ // For this field, get an expr for each selflike_arg. E.g. for
+ // `PartialEq::eq`, one for each of `&self` and `other`.
+ let sp = struct_field.span.with_ctxt(self.span.ctxt());
+ let mut exprs: Vec<_> = mk_exprs(i, struct_field, sp);
+ let self_expr = exprs.remove(0);
+ let other_selflike_exprs = exprs;
+ FieldInfo {
+ span: sp.with_ctxt(self.span.ctxt()),
+ name: struct_field.ident,
+ self_expr,
+ other_selflike_exprs,
+ }
+ })
+ .collect()
+ }
+
+ fn mk_pattern_ident(&self, prefix: &str, i: usize) -> Ident {
+ Ident::from_str_and_span(&format!("{}_{}", prefix, i), self.span)
+ }
+
+ fn create_struct_pattern_fields(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ struct_def: &'a VariantData,
+ prefixes: &[String],
+ addr_of: bool,
+ ) -> Vec<FieldInfo> {
+ self.create_fields(struct_def, |i, _struct_field, sp| {
+ prefixes
+ .iter()
+ .map(|prefix| {
+ let ident = self.mk_pattern_ident(prefix, i);
+ let expr = cx.expr_path(cx.path_ident(sp, ident));
+ if addr_of { cx.expr_addr_of(sp, expr) } else { expr }
+ })
+ .collect()
+ })
+ }
+
+ fn create_struct_field_access_fields(
+ &self,
+ cx: &mut ExtCtxt<'_>,
+ selflike_args: &[P<Expr>],
+ struct_def: &'a VariantData,
+ copy: bool,
+ ) -> Vec<FieldInfo> {
+ self.create_fields(struct_def, |i, struct_field, sp| {
+ selflike_args
+ .iter()
+ .map(|selflike_arg| {
+ // Note: we must use `struct_field.span` rather than `sp` in the
+ // `unwrap_or_else` case otherwise the hygiene is wrong and we get
+ // "field `0` of struct `Point` is private" errors on tuple
+ // structs.
+ let mut field_expr = cx.expr(
+ sp,
+ ast::ExprKind::Field(
+ selflike_arg.clone(),
+ struct_field.ident.unwrap_or_else(|| {
+ Ident::from_str_and_span(&i.to_string(), struct_field.span)
+ }),
+ ),
+ );
+ if copy {
+ field_expr = cx.expr_block(
+ cx.block(struct_field.span, vec![cx.stmt_expr(field_expr)]),
+ );
+ }
+ cx.expr_addr_of(sp, field_expr)
+ })
+ .collect()
+ })
+ }
+}
+
+/// The function passed to `cs_fold` is called repeatedly with a value of this
+/// type. It describes one part of the code generation. The result is always an
+/// expression.
+pub enum CsFold<'a> {
+ /// The basic case: a field expression for one or more selflike args. E.g.
+ /// for `PartialEq::eq` this is something like `self.x == other.x`.
+ Single(&'a FieldInfo),
+
+ /// The combination of two field expressions. E.g. for `PartialEq::eq` this
+ /// is something like `<field1 equality> && <field2 equality>`.
+ Combine(Span, P<Expr>, P<Expr>),
+
+ // The fallback case for a struct or enum variant with no fields.
+ Fieldless,
+}
+
+/// Folds over fields, combining the expressions for each field in a sequence.
+/// Statics may not be folded over.
+pub fn cs_fold<F>(
+ use_foldl: bool,
+ cx: &mut ExtCtxt<'_>,
+ trait_span: Span,
+ substructure: &Substructure<'_>,
+ mut f: F,
+) -> P<Expr>
+where
+ F: FnMut(&mut ExtCtxt<'_>, CsFold<'_>) -> P<Expr>,
+{
+ match substructure.fields {
+ EnumMatching(.., all_fields) | Struct(_, all_fields) => {
+ if all_fields.is_empty() {
+ return f(cx, CsFold::Fieldless);
+ }
+
+ let (base_field, rest) = if use_foldl {
+ all_fields.split_first().unwrap()
+ } else {
+ all_fields.split_last().unwrap()
+ };
+
+ let base_expr = f(cx, CsFold::Single(base_field));
+
+ let op = |old, field: &FieldInfo| {
+ let new = f(cx, CsFold::Single(field));
+ f(cx, CsFold::Combine(field.span, old, new))
+ };
+
+ if use_foldl {
+ rest.iter().fold(base_expr, op)
+ } else {
+ rest.iter().rfold(base_expr, op)
+ }
+ }
+ EnumTag(tag_field, match_expr) => {
+ let tag_check_expr = f(cx, CsFold::Single(tag_field));
+ if let Some(match_expr) = match_expr {
+ if use_foldl {
+ f(cx, CsFold::Combine(trait_span, tag_check_expr, match_expr.clone()))
+ } else {
+ f(cx, CsFold::Combine(trait_span, match_expr.clone(), tag_check_expr))
+ }
+ } else {
+ tag_check_expr
+ }
+ }
+ StaticEnum(..) | StaticStruct(..) => cx.span_bug(trait_span, "static function in `derive`"),
+ }
+}
+
+/// Returns `true` if the type has no value fields
+/// (for an enum, no variant has any fields)
+pub fn is_type_without_fields(item: &Annotatable) -> bool {
+ if let Annotatable::Item(ref item) = *item {
+ match item.kind {
+ ast::ItemKind::Enum(ref enum_def, _) => {
+ enum_def.variants.iter().all(|v| v.data.fields().is_empty())
+ }
+ ast::ItemKind::Struct(ref variant_data, _) => variant_data.fields().is_empty(),
+ _ => false,
+ }
+ } else {
+ false
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-12 11:06:42 +0000