src/libsyntax_ext/deriving/generic/mod.rs

   1 // Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Some code that abstracts away much of the boilerplate of writing
  12 //! `derive` instances for traits. Among other things it manages getting
  13 //! access to the fields of the 4 different sorts of structs and enum
  14 //! variants, as well as creating the method and impl ast instances.
  15 //!
  16 //! Supported features (fairly exhaustive):
  17 //!
  18 //! - Methods taking any number of parameters of any type, and returning
  19 //!   any type, other than vectors, bottom and closures.
  20 //! - Generating `impl`s for types with type parameters and lifetimes
  21 //!   (e.g. `Option<T>`), the parameters are automatically given the
  22 //!   current trait as a bound. (This includes separate type parameters
  23 //!   and lifetimes for methods.)
  24 //! - Additional bounds on the type parameters (`TraitDef.additional_bounds`)
  25 //!
  26 //! The most important thing for implementors is the `Substructure` and
  27 //! `SubstructureFields` objects. The latter groups 5 possibilities of the
  28 //! arguments:
  29 //!
  30 //! - `Struct`, when `Self` is a struct (including tuple structs, e.g
  31 //!   `struct T(i32, char)`).
  32 //! - `EnumMatching`, when `Self` is an enum and all the arguments are the
  33 //!   same variant of the enum (e.g. `Some(1)`, `Some(3)` and `Some(4)`)
  34 //! - `EnumNonMatchingCollapsed` when `Self` is an enum and the arguments
  35 //!   are not the same variant (e.g. `None`, `Some(1)` and `None`).
  36 //! - `StaticEnum` and `StaticStruct` for static methods, where the type
  37 //!   being derived upon is either an enum or struct respectively. (Any
  38 //!   argument with type Self is just grouped among the non-self
  39 //!   arguments.)
  40 //!
  41 //! In the first two cases, the values from the corresponding fields in
  42 //! all the arguments are grouped together. For `EnumNonMatchingCollapsed`
  43 //! this isn't possible (different variants have different fields), so the
  44 //! fields are inaccessible. (Previous versions of the deriving infrastructure
  45 //! had a way to expand into code that could access them, at the cost of
  46 //! generating exponential amounts of code; see issue #15375). There are no
  47 //! fields with values in the static cases, so these are treated entirely
  48 //! differently.
  49 //!
  50 //! The non-static cases have `Option<ident>` in several places associated
  51 //! with field `expr`s. This represents the name of the field it is
  52 //! associated with. It is only not `None` when the associated field has
  53 //! an identifier in the source code. For example, the `x`s in the
  54 //! following snippet
  55 //!
  56 //! ```rust
  57 //! # #![allow(dead_code)]
  58 //! struct A { x : i32 }
  59 //!
  60 //! struct B(i32);
  61 //!
  62 //! enum C {
  63 //!     C0(i32),
  64 //!     C1 { x: i32 }
  65 //! }
  66 //! ```
  67 //!
  68 //! The `i32`s in `B` and `C0` don't have an identifier, so the
  69 //! `Option<ident>`s would be `None` for them.
  70 //!
  71 //! In the static cases, the structure is summarized, either into the just
  72 //! spans of the fields or a list of spans and the field idents (for tuple
  73 //! structs and record structs, respectively), or a list of these, for
  74 //! enums (one for each variant). For empty struct and empty enum
  75 //! variants, it is represented as a count of 0.
  76 //!
  77 //! # "`cs`" functions
  78 //!
  79 //! The `cs_...` functions ("combine substructure) are designed to
  80 //! make life easier by providing some pre-made recipes for common
  81 //! threads; mostly calling the function being derived on all the
  82 //! arguments and then combining them back together in some way (or
  83 //! letting the user chose that). They are not meant to be the only
  84 //! way to handle the structures that this code creates.
  85 //!
  86 //! # Examples
  87 //!
  88 //! The following simplified `PartialEq` is used for in-code examples:
  89 //!
  90 //! ```rust
  91 //! trait PartialEq {
  92 //!     fn eq(&self, other: &Self) -> bool;
  93 //! }
  94 //! impl PartialEq for i32 {
  95 //!     fn eq(&self, other: &i32) -> bool {
  96 //!         *self == *other
  97 //!     }
  98 //! }
  99 //! ```
 100 //!
 101 //! Some examples of the values of `SubstructureFields` follow, using the
 102 //! above `PartialEq`, `A`, `B` and `C`.
 103 //!
 104 //! ## Structs
 105 //!
 106 //! When generating the `expr` for the `A` impl, the `SubstructureFields` is
 107 //!
 108 //! ```{.text}
 109 //! Struct(vec![FieldInfo {
 110 //!            span: <span of x>
 111 //!            name: Some(<ident of x>),
 112 //!            self_: <expr for &self.x>,
 113 //!            other: vec![<expr for &other.x]
 114 //!          }])
 115 //! ```
 116 //!
 117 //! For the `B` impl, called with `B(a)` and `B(b)`,
 118 //!
 119 //! ```{.text}
 120 //! Struct(vec![FieldInfo {
 121 //!           span: <span of `i32`>,
 122 //!           name: None,
 123 //!           self_: <expr for &a>
 124 //!           other: vec![<expr for &b>]
 125 //!          }])
 126 //! ```
 127 //!
 128 //! ## Enums
 129 //!
 130 //! When generating the `expr` for a call with `self == C0(a)` and `other
 131 //! == C0(b)`, the SubstructureFields is
 132 //!
 133 //! ```{.text}
 134 //! EnumMatching(0, <ast::Variant for C0>,
 135 //!              vec![FieldInfo {
 136 //!                 span: <span of i32>
 137 //!                 name: None,
 138 //!                 self_: <expr for &a>,
 139 //!                 other: vec![<expr for &b>]
 140 //!               }])
 141 //! ```
 142 //!
 143 //! For `C1 {x}` and `C1 {x}`,
 144 //!
 145 //! ```{.text}
 146 //! EnumMatching(1, <ast::Variant for C1>,
 147 //!              vec![FieldInfo {
 148 //!                 span: <span of x>
 149 //!                 name: Some(<ident of x>),
 150 //!                 self_: <expr for &self.x>,
 151 //!                 other: vec![<expr for &other.x>]
 152 //!                }])
 153 //! ```
 154 //!
 155 //! For `C0(a)` and `C1 {x}` ,
 156 //!
 157 //! ```{.text}
 158 //! EnumNonMatchingCollapsed(
 159 //!     vec![<ident of self>, <ident of __arg_1>],
 160 //!     &[<ast::Variant for C0>, <ast::Variant for C1>],
 161 //!     &[<ident for self index value>, <ident of __arg_1 index value>])
 162 //! ```
 163 //!
 164 //! It is the same for when the arguments are flipped to `C1 {x}` and
 165 //! `C0(a)`; the only difference is what the values of the identifiers
 166 //! <ident for self index value> and <ident of __arg_1 index value> will
 167 //! be in the generated code.
 168 //!
 169 //! `EnumNonMatchingCollapsed` deliberately provides far less information
 170 //! than is generally available for a given pair of variants; see #15375
 171 //! for discussion.
 172 //!
 173 //! ## Static
 174 //!
 175 //! A static method on the types above would result in,
 176 //!
 177 //! ```{.text}
 178 //! StaticStruct(<ast::VariantData of A>, Named(vec![(<ident of x>, <span of x>)]))
 179 //!
 180 //! StaticStruct(<ast::VariantData of B>, Unnamed(vec![<span of x>]))
 181 //!
 182 //! StaticEnum(<ast::EnumDef of C>,
 183 //!            vec![(<ident of C0>, <span of C0>, Unnamed(vec![<span of i32>])),
 184 //!                 (<ident of C1>, <span of C1>, Named(vec![(<ident of x>, <span of x>)]))])
 185 //! ```
 186
 187 pub use self::StaticFields::*;
 188 pub use self::SubstructureFields::*;
 189
 190 use std::cell::RefCell;
 191 use std::iter;
 192 use std::vec;
 193
 194 use rustc_data_structures::thin_vec::ThinVec;
 195 use rustc_target::spec::abi::Abi;
 196 use syntax::ast::{self, BinOpKind, EnumDef, Expr, Generics, Ident, PatKind};
 197 use syntax::ast::{VariantData, GenericParamKind, GenericArg};
 198 use syntax::attr;
 199 use syntax::ext::base::{Annotatable, ExtCtxt};
 200 use syntax::ext::build::AstBuilder;
 201 use syntax::source_map::{self, respan};
 202 use syntax::util::move_map::MoveMap;
 203 use syntax::ptr::P;
 204 use syntax::symbol::{Symbol, keywords};
 205 use syntax::parse::ParseSess;
 206 use syntax_pos::{DUMMY_SP, Span};
 207
 208 use self::ty::{LifetimeBounds, Path, Ptr, PtrTy, Self_, Ty};
 209
 210 use deriving;
 211
 212 pub mod ty;
 213
 214 pub struct TraitDef<'a> {
 215     /// The span for the current #[derive(Foo)] header.
 216     pub span: Span,
 217
 218     pub attributes: Vec<ast::Attribute>,
 219
 220     /// Path of the trait, including any type parameters
 221     pub path: Path<'a>,
 222
 223     /// Additional bounds required of any type parameters of the type,
 224     /// other than the current trait
 225     pub additional_bounds: Vec<Ty<'a>>,
 226
 227     /// Any extra lifetimes and/or bounds, e.g. `D: serialize::Decoder`
 228     pub generics: LifetimeBounds<'a>,
 229
 230     /// Is it an `unsafe` trait?
 231     pub is_unsafe: bool,
 232
 233     /// Can this trait be derived for unions?
 234     pub supports_unions: bool,
 235
 236     pub methods: Vec<MethodDef<'a>>,
 237
 238     pub associated_types: Vec<(ast::Ident, Ty<'a>)>,
 239 }
 240
 241
 242 pub struct MethodDef<'a> {
 243     /// name of the method
 244     pub name: &'a str,
 245     /// List of generics, e.g. `R: rand::Rng`
 246     pub generics: LifetimeBounds<'a>,
 247
 248     /// Whether there is a self argument (outer Option) i.e. whether
 249     /// this is a static function, and whether it is a pointer (inner
 250     /// Option)
 251     pub explicit_self: Option<Option<PtrTy<'a>>>,
 252
 253     /// Arguments other than the self argument
 254     pub args: Vec<(Ty<'a>, &'a str)>,
 255
 256     /// Return type
 257     pub ret_ty: Ty<'a>,
 258
 259     pub attributes: Vec<ast::Attribute>,
 260
 261     // Is it an `unsafe fn`?
 262     pub is_unsafe: bool,
 263
 264     /// Can we combine fieldless variants for enums into a single match arm?
 265     pub unify_fieldless_variants: bool,
 266
 267     pub combine_substructure: RefCell<CombineSubstructureFunc<'a>>,
 268 }
 269
 270 /// All the data about the data structure/method being derived upon.
 271 pub struct Substructure<'a> {
 272     /// ident of self
 273     pub type_ident: Ident,
 274     /// ident of the method
 275     pub method_ident: Ident,
 276     /// dereferenced access to any `Self_` or `Ptr(Self_, _)` arguments
 277     pub self_args: &'a [P<Expr>],
 278     /// verbatim access to any other arguments
 279     pub nonself_args: &'a [P<Expr>],
 280     pub fields: &'a SubstructureFields<'a>,
 281 }
 282
 283 /// Summary of the relevant parts of a struct/enum field.
 284 pub struct FieldInfo<'a> {
 285     pub span: Span,
 286     /// None for tuple structs/normal enum variants, Some for normal
 287     /// structs/struct enum variants.
 288     pub name: Option<Ident>,
 289     /// The expression corresponding to this field of `self`
 290     /// (specifically, a reference to it).
 291     pub self_: P<Expr>,
 292     /// The expressions corresponding to references to this field in
 293     /// the other `Self` arguments.
 294     pub other: Vec<P<Expr>>,
 295     /// The attributes on the field
 296     pub attrs: &'a [ast::Attribute],
 297 }
 298
 299 /// Fields for a static method
 300 pub enum StaticFields {
 301     /// Tuple and unit structs/enum variants like this.
 302     Unnamed(Vec<Span>, bool /*is tuple*/),
 303     /// Normal structs/struct variants.
 304     Named(Vec<(Ident, Span)>),
 305 }
 306
 307 /// A summary of the possible sets of fields.
 308 pub enum SubstructureFields<'a> {
 309     Struct(&'a ast::VariantData, Vec<FieldInfo<'a>>),
 310     /// Matching variants of the enum: variant index, variant count, ast::Variant,
 311     /// fields: the field name is only non-`None` in the case of a struct
 312     /// variant.
 313     EnumMatching(usize, usize, &'a ast::Variant, Vec<FieldInfo<'a>>),
 314
 315     /// Non-matching variants of the enum, but with all state hidden from
 316     /// the consequent code.  The first component holds `Ident`s for all of
 317     /// the `Self` arguments; the second component is a slice of all of the
 318     /// variants for the enum itself, and the third component is a list of
 319     /// `Ident`s bound to the variant index values for each of the actual
 320     /// input `Self` arguments.
 321     EnumNonMatchingCollapsed(Vec<Ident>, &'a [ast::Variant], &'a [Ident]),
 322
 323     /// A static method where `Self` is a struct.
 324     StaticStruct(&'a ast::VariantData, StaticFields),
 325     /// A static method where `Self` is an enum.
 326     StaticEnum(&'a ast::EnumDef, Vec<(Ident, Span, StaticFields)>),
 327 }
 328
 329
 330
 331 /// Combine the values of all the fields together. The last argument is
 332 /// all the fields of all the structures.
 333 pub type CombineSubstructureFunc<'a> =
 334     Box<dyn FnMut(&mut ExtCtxt, Span, &Substructure) -> P<Expr> + 'a>;
 335
 336 /// Deal with non-matching enum variants.  The tuple is a list of
 337 /// identifiers (one for each `Self` argument, which could be any of the
 338 /// variants since they have been collapsed together) and the identifiers
 339 /// holding the variant index value for each of the `Self` arguments.  The
 340 /// last argument is all the non-`Self` args of the method being derived.
 341 pub type EnumNonMatchCollapsedFunc<'a> =
 342     Box<dyn FnMut(&mut ExtCtxt, Span, (&[Ident], &[Ident]), &[P<Expr>]) -> P<Expr> + 'a>;
 343
 344 pub fn combine_substructure<'a>(f: CombineSubstructureFunc<'a>)
 345                                 -> RefCell<CombineSubstructureFunc<'a>> {
 346     RefCell::new(f)
 347 }
 348
 349 /// This method helps to extract all the type parameters referenced from a
 350 /// type. For a type parameter `<T>`, it looks for either a `TyPath` that
 351 /// is not global and starts with `T`, or a `TyQPath`.
 352 fn find_type_parameters(ty: &ast::Ty,
 353                         ty_param_names: &[ast::Name],
 354                         span: Span,
 355                         cx: &ExtCtxt)
 356                         -> Vec<P<ast::Ty>> {
 357     use syntax::visit;
 358
 359     struct Visitor<'a, 'b: 'a> {
 360         cx: &'a ExtCtxt<'b>,
 361         span: Span,
 362         ty_param_names: &'a [ast::Name],
 363         types: Vec<P<ast::Ty>>,
 364     }
 365
 366     impl<'a, 'b> visit::Visitor<'a> for Visitor<'a, 'b> {
 367         fn visit_ty(&mut self, ty: &'a ast::Ty) {
 368             if let ast::TyKind::Path(_, ref path) = ty.node {
 369                 if let Some(segment) = path.segments.first() {
 370                     if self.ty_param_names.contains(&segment.ident.name) {
 371                         self.types.push(P(ty.clone()));
 372                     }
 373                 }
 374             }
 375
 376             visit::walk_ty(self, ty)
 377         }
 378
 379         fn visit_mac(&mut self, mac: &ast::Mac) {
 380             let span = mac.span.with_ctxt(self.span.ctxt());
 381             self.cx.span_err(span, "`derive` cannot be used on items with type macros");
 382         }
 383     }
 384
 385     let mut visitor = Visitor {
 386         ty_param_names,
 387         types: Vec::new(),
 388         span,
 389         cx,
 390     };
 391
 392     visit::Visitor::visit_ty(&mut visitor, ty);
 393
 394     visitor.types
 395 }
 396
 397 impl<'a> TraitDef<'a> {
 398     pub fn expand(self,
 399                   cx: &mut ExtCtxt,
 400                   mitem: &ast::MetaItem,
 401                   item: &'a Annotatable,
 402                   push: &mut dyn FnMut(Annotatable)) {
 403         self.expand_ext(cx, mitem, item, push, false);
 404     }
 405
 406     pub fn expand_ext(self,
 407                       cx: &mut ExtCtxt,
 408                       mitem: &ast::MetaItem,
 409                       item: &'a Annotatable,
 410                       push: &mut dyn FnMut(Annotatable),
 411                       from_scratch: bool) {
 412         match *item {
 413             Annotatable::Item(ref item) => {
 414                 let is_packed = item.attrs.iter().any(|attr| {
 415                     for r in attr::find_repr_attrs(&cx.parse_sess, attr) {
 416                         if let attr::ReprPacked(_) = r {
 417                             return true;
 418                         }
 419                     }
 420                     false
 421                 });
 422                 let has_no_type_params = match item.node {
 423                     ast::ItemKind::Struct(_, ref generics) |
 424                     ast::ItemKind::Enum(_, ref generics) |
 425                     ast::ItemKind::Union(_, ref generics) => {
 426                         !generics.params.iter().any(|param| match param.kind {
 427                             ast::GenericParamKind::Type { .. } => true,
 428                             _ => false,
 429                         })
 430                     }
 431                     _ => {
 432                         // Non-ADT derive is an error, but it should have been
 433                         // set earlier; see
 434                         // libsyntax/ext/expand.rs:MacroExpander::expand()
 435                         return;
 436                     }
 437                 };
 438                 let is_always_copy =
 439                     attr::contains_name(&item.attrs, "rustc_copy_clone_marker") &&
 440                     has_no_type_params;
 441                 let use_temporaries = is_packed && is_always_copy;
 442
 443                 let newitem = match item.node {
 444                     ast::ItemKind::Struct(ref struct_def, ref generics) => {
 445                         self.expand_struct_def(cx, &struct_def, item.ident, generics, from_scratch,
 446                                                use_temporaries)
 447                     }
 448                     ast::ItemKind::Enum(ref enum_def, ref generics) => {
 449                         // We ignore `use_temporaries` here, because
 450                         // `repr(packed)` enums cause an error later on.
 451                         //
 452                         // This can only cause further compilation errors
 453                         // downstream in blatantly illegal code, so it
 454                         // is fine.
 455                         self.expand_enum_def(cx, enum_def, &item.attrs,
 456                                              item.ident, generics, from_scratch)
 457                     }
 458                     ast::ItemKind::Union(ref struct_def, ref generics) => {
 459                         if self.supports_unions {
 460                             self.expand_struct_def(cx, &struct_def, item.ident,
 461                                                    generics, from_scratch,
 462                                                    use_temporaries)
 463                         } else {
 464                             cx.span_err(mitem.span,
 465                                         "this trait cannot be derived for unions");
 466                             return;
 467                         }
 468                     }
 469                     _ => unreachable!(),
 470                 };
 471                 // Keep the lint attributes of the previous item to control how the
 472                 // generated implementations are linted
 473                 let mut attrs = newitem.attrs.clone();
 474                 attrs.extend(item.attrs
 475                     .iter()
 476                     .filter(|a| {
 477                         match &*a.name().as_str() {
 478                             "allow" | "warn" | "deny" | "forbid" | "stable" | "unstable" => true,
 479                             _ => false,
 480                         }
 481                     })
 482                     .cloned());
 483                 push(Annotatable::Item(P(ast::Item { attrs: attrs, ..(*newitem).clone() })))
 484             }
 485             _ => {
 486                 // Non-Item derive is an error, but it should have been
 487                 // set earlier; see
 488                 // libsyntax/ext/expand.rs:MacroExpander::expand()
 489                 return;
 490             }
 491         }
 492     }
 493
 494     /// Given that we are deriving a trait `DerivedTrait` for a type like:
 495     ///
 496     /// ```ignore (only-for-syntax-highlight)
 497     /// struct Struct<'a, ..., 'z, A, B: DeclaredTrait, C, ..., Z> where C: WhereTrait {
 498     ///     a: A,
 499     ///     b: B::Item,
 500     ///     b1: <B as DeclaredTrait>::Item,
 501     ///     c1: <C as WhereTrait>::Item,
 502     ///     c2: Option<<C as WhereTrait>::Item>,
 503     ///     ...
 504     /// }
 505     /// ```
 506     ///
 507     /// create an impl like:
 508     ///
 509     /// ```ignore (only-for-syntax-highlight)
 510     /// impl<'a, ..., 'z, A, B: DeclaredTrait, C, ...  Z> where
 511     ///     C:                       WhereTrait,
 512     ///     A: DerivedTrait + B1 + ... + BN,
 513     ///     B: DerivedTrait + B1 + ... + BN,
 514     ///     C: DerivedTrait + B1 + ... + BN,
 515     ///     B::Item:                 DerivedTrait + B1 + ... + BN,
 516     ///     <C as WhereTrait>::Item: DerivedTrait + B1 + ... + BN,
 517     ///     ...
 518     /// {
 519     ///     ...
 520     /// }
 521     /// ```
 522     ///
 523     /// where B1, ..., BN are the bounds given by `bounds_paths`.'. Z is a phantom type, and
 524     /// therefore does not get bound by the derived trait.
 525     fn create_derived_impl(&self,
 526                            cx: &mut ExtCtxt,
 527                            type_ident: Ident,
 528                            generics: &Generics,
 529                            field_tys: Vec<P<ast::Ty>>,
 530                            methods: Vec<ast::ImplItem>)
 531                            -> P<ast::Item> {
 532         let trait_path = self.path.to_path(cx, self.span, type_ident, generics);
 533
 534         // Transform associated types from `deriving::ty::Ty` into `ast::ImplItem`
 535         let associated_types = self.associated_types.iter().map(|&(ident, ref type_def)| {
 536             ast::ImplItem {
 537                 id: ast::DUMMY_NODE_ID,
 538                 span: self.span,
 539                 ident,
 540                 vis: respan(self.span.shrink_to_lo(), ast::VisibilityKind::Inherited),
 541                 defaultness: ast::Defaultness::Final,
 542                 attrs: Vec::new(),
 543                 generics: Generics::default(),
 544                 node: ast::ImplItemKind::Type(type_def.to_ty(cx, self.span, type_ident, generics)),
 545                 tokens: None,
 546             }
 547         });
 548
 549         let Generics { mut params, mut where_clause, span } = self.generics
 550             .to_generics(cx, self.span, type_ident, generics);
 551
 552         // Create the generic parameters
 553         params.extend(generics.params.iter().map(|param| match param.kind {
 554             GenericParamKind::Lifetime { .. } => param.clone(),
 555             GenericParamKind::Type { .. } => {
 556                 // I don't think this can be moved out of the loop, since
 557                 // a GenericBound requires an ast id
 558                 let bounds: Vec<_> =
 559                     // extra restrictions on the generics parameters to the
 560                     // type being derived upon
 561                     self.additional_bounds.iter().map(|p| {
 562                         cx.trait_bound(p.to_path(cx, self.span, type_ident, generics))
 563                     }).chain(
 564                         // require the current trait
 565                         iter::once(cx.trait_bound(trait_path.clone()))
 566                     ).chain(
 567                         // also add in any bounds from the declaration
 568                         param.bounds.iter().cloned()
 569                     ).collect();
 570
 571                 cx.typaram(self.span, param.ident, vec![], bounds, None)
 572             }
 573         }));
 574
 575         // and similarly for where clauses
 576         where_clause.predicates.extend(generics.where_clause.predicates.iter().map(|clause| {
 577             match *clause {
 578                 ast::WherePredicate::BoundPredicate(ref wb) => {
 579                     ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate {
 580                         span: self.span,
 581                         bound_generic_params: wb.bound_generic_params.clone(),
 582                         bounded_ty: wb.bounded_ty.clone(),
 583                         bounds: wb.bounds.iter().cloned().collect(),
 584                     })
 585                 }
 586                 ast::WherePredicate::RegionPredicate(ref rb) => {
 587                     ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate {
 588                         span: self.span,
 589                         lifetime: rb.lifetime,
 590                         bounds: rb.bounds.iter().cloned().collect(),
 591                     })
 592                 }
 593                 ast::WherePredicate::EqPredicate(ref we) => {
 594                     ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
 595                         id: ast::DUMMY_NODE_ID,
 596                         span: self.span,
 597                         lhs_ty: we.lhs_ty.clone(),
 598                         rhs_ty: we.rhs_ty.clone(),
 599                     })
 600                 }
 601             }
 602         }));
 603
 604         {
 605             // Extra scope required here so ty_params goes out of scope before params is moved
 606
 607             let mut ty_params = params.iter()
 608                 .filter_map(|param| match param.kind {
 609                     ast::GenericParamKind::Type { .. } => Some(param),
 610                     _ => None,
 611                 })
 612                 .peekable();
 613
 614             if ty_params.peek().is_some() {
 615                 let ty_param_names: Vec<ast::Name> = ty_params
 616                     .map(|ty_param| ty_param.ident.name)
 617                     .collect();
 618
 619                 for field_ty in field_tys {
 620                     let tys = find_type_parameters(&field_ty, &ty_param_names, self.span, cx);
 621
 622                     for ty in tys {
 623                         // if we have already handled this type, skip it
 624                         if let ast::TyKind::Path(_, ref p) = ty.node {
 625                             if p.segments.len() == 1 &&
 626                                ty_param_names.contains(&p.segments[0].ident.name) {
 627                                 continue;
 628                             };
 629                         }
 630                         let mut bounds: Vec<_> = self.additional_bounds
 631                             .iter()
 632                             .map(|p| {
 633                                 cx.trait_bound(p.to_path(cx, self.span, type_ident, generics))
 634                             })
 635                             .collect();
 636
 637                         // require the current trait
 638                         bounds.push(cx.trait_bound(trait_path.clone()));
 639
 640                         let predicate = ast::WhereBoundPredicate {
 641                             span: self.span,
 642                             bound_generic_params: Vec::new(),
 643                             bounded_ty: ty,
 644                             bounds,
 645                         };
 646
 647                         let predicate = ast::WherePredicate::BoundPredicate(predicate);
 648                         where_clause.predicates.push(predicate);
 649                     }
 650                 }
 651             }
 652         }
 653
 654         let trait_generics = Generics {
 655             params,
 656             where_clause,
 657             span,
 658         };
 659
 660         // Create the reference to the trait.
 661         let trait_ref = cx.trait_ref(trait_path);
 662
 663         let self_params: Vec<_> = generics.params.iter().map(|param| match param.kind {
 664             GenericParamKind::Lifetime { .. } => {
 665                 GenericArg::Lifetime(cx.lifetime(self.span, param.ident))
 666             }
 667             GenericParamKind::Type { .. } => {
 668                 GenericArg::Type(cx.ty_ident(self.span, param.ident))
 669             }
 670         }).collect();
 671
 672         // Create the type of `self`.
 673         let path = cx.path_all(self.span, false, vec![type_ident], self_params, vec![]);
 674         let self_type = cx.ty_path(path);
 675
 676         let attr = cx.attribute(self.span,
 677                                 cx.meta_word(self.span,
 678                                              Symbol::intern("automatically_derived")));
 679         // Just mark it now since we know that it'll end up used downstream
 680         attr::mark_used(&attr);
 681         let opt_trait_ref = Some(trait_ref);
 682         let unused_qual = {
 683             let word = cx.meta_list_item_word(self.span, Symbol::intern("unused_qualifications"));
 684             cx.attribute(self.span, cx.meta_list(self.span, Symbol::intern("allow"), vec![word]))
 685         };
 686
 687         let mut a = vec![attr, unused_qual];
 688         a.extend(self.attributes.iter().cloned());
 689
 690         let unsafety = if self.is_unsafe {
 691             ast::Unsafety::Unsafe
 692         } else {
 693             ast::Unsafety::Normal
 694         };
 695
 696         cx.item(self.span,
 697                 keywords::Invalid.ident(),
 698                 a,
 699                 ast::ItemKind::Impl(unsafety,
 700                                     ast::ImplPolarity::Positive,
 701                                     ast::Defaultness::Final,
 702                                     trait_generics,
 703                                     opt_trait_ref,
 704                                     self_type,
 705                                     methods.into_iter().chain(associated_types).collect()))
 706     }
 707
 708     fn expand_struct_def(&self,
 709                          cx: &mut ExtCtxt,
 710                          struct_def: &'a VariantData,
 711                          type_ident: Ident,
 712                          generics: &Generics,
 713                          from_scratch: bool,
 714                          use_temporaries: bool)
 715                          -> P<ast::Item> {
 716         let field_tys: Vec<P<ast::Ty>> = struct_def.fields()
 717             .iter()
 718             .map(|field| field.ty.clone())
 719             .collect();
 720
 721         let methods = self.methods
 722             .iter()
 723             .map(|method_def| {
 724                 let (explicit_self, self_args, nonself_args, tys) =
 725                     method_def.split_self_nonself_args(cx, self, type_ident, generics);
 726
 727                 let body = if from_scratch || method_def.is_static() {
 728                     method_def.expand_static_struct_method_body(cx,
 729                                                                 self,
 730                                                                 struct_def,
 731                                                                 type_ident,
 732                                                                 &self_args[..],
 733                                                                 &nonself_args[..])
 734                 } else {
 735                     method_def.expand_struct_method_body(cx,
 736                                                          self,
 737                                                          struct_def,
 738                                                          type_ident,
 739                                                          &self_args[..],
 740                                                          &nonself_args[..],
 741                                                          use_temporaries)
 742                 };
 743
 744                 method_def.create_method(cx,
 745                                          self,
 746                                          type_ident,
 747                                          generics,
 748                                          Abi::Rust,
 749                                          explicit_self,
 750                                          tys,
 751                                          body)
 752             })
 753             .collect();
 754
 755         self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
 756     }
 757
 758     fn expand_enum_def(&self,
 759                        cx: &mut ExtCtxt,
 760                        enum_def: &'a EnumDef,
 761                        type_attrs: &[ast::Attribute],
 762                        type_ident: Ident,
 763                        generics: &Generics,
 764                        from_scratch: bool)
 765                        -> P<ast::Item> {
 766         let mut field_tys = Vec::new();
 767
 768         for variant in &enum_def.variants {
 769             field_tys.extend(variant.node
 770                 .data
 771                 .fields()
 772                 .iter()
 773                 .map(|field| field.ty.clone()));
 774         }
 775
 776         let methods = self.methods
 777             .iter()
 778             .map(|method_def| {
 779                 let (explicit_self, self_args, nonself_args, tys) =
 780                     method_def.split_self_nonself_args(cx, self, type_ident, generics);
 781
 782                 let body = if from_scratch || method_def.is_static() {
 783                     method_def.expand_static_enum_method_body(cx,
 784                                                               self,
 785                                                               enum_def,
 786                                                               type_ident,
 787                                                               &self_args[..],
 788                                                               &nonself_args[..])
 789                 } else {
 790                     method_def.expand_enum_method_body(cx,
 791                                                        self,
 792                                                        enum_def,
 793                                                        type_attrs,
 794                                                        type_ident,
 795                                                        self_args,
 796                                                        &nonself_args[..])
 797                 };
 798
 799                 method_def.create_method(cx,
 800                                          self,
 801                                          type_ident,
 802                                          generics,
 803                                          Abi::Rust,
 804                                          explicit_self,
 805                                          tys,
 806                                          body)
 807             })
 808             .collect();
 809
 810         self.create_derived_impl(cx, type_ident, generics, field_tys, methods)
 811     }
 812 }
 813
 814 fn find_repr_type_name(sess: &ParseSess, type_attrs: &[ast::Attribute]) -> &'static str {
 815     let mut repr_type_name = "isize";
 816     for a in type_attrs {
 817         for r in &attr::find_repr_attrs(sess, a) {
 818             repr_type_name = match *r {
 819                 attr::ReprPacked(_) | attr::ReprSimd | attr::ReprAlign(_) | attr::ReprTransparent =>
 820                     continue,
 821
 822                 attr::ReprC => "i32",
 823
 824                 attr::ReprInt(attr::SignedInt(ast::IntTy::Isize)) => "isize",
 825                 attr::ReprInt(attr::SignedInt(ast::IntTy::I8)) => "i8",
 826                 attr::ReprInt(attr::SignedInt(ast::IntTy::I16)) => "i16",
 827                 attr::ReprInt(attr::SignedInt(ast::IntTy::I32)) => "i32",
 828                 attr::ReprInt(attr::SignedInt(ast::IntTy::I64)) => "i64",
 829                 attr::ReprInt(attr::SignedInt(ast::IntTy::I128)) => "i128",
 830
 831                 attr::ReprInt(attr::UnsignedInt(ast::UintTy::Usize)) => "usize",
 832                 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U8)) => "u8",
 833                 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U16)) => "u16",
 834                 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U32)) => "u32",
 835                 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U64)) => "u64",
 836                 attr::ReprInt(attr::UnsignedInt(ast::UintTy::U128)) => "u128",
 837             }
 838         }
 839     }
 840     repr_type_name
 841 }
 842
 843 impl<'a> MethodDef<'a> {
 844     fn call_substructure_method(&self,
 845                                 cx: &mut ExtCtxt,
 846                                 trait_: &TraitDef,
 847                                 type_ident: Ident,
 848                                 self_args: &[P<Expr>],
 849                                 nonself_args: &[P<Expr>],
 850                                 fields: &SubstructureFields)
 851                                 -> P<Expr> {
 852         let substructure = Substructure {
 853             type_ident,
 854             method_ident: cx.ident_of(self.name),
 855             self_args,
 856             nonself_args,
 857             fields,
 858         };
 859         let mut f = self.combine_substructure.borrow_mut();
 860         let f: &mut CombineSubstructureFunc = &mut *f;
 861         f(cx, trait_.span, &substructure)
 862     }
 863
 864     fn get_ret_ty(&self,
 865                   cx: &mut ExtCtxt,
 866                   trait_: &TraitDef,
 867                   generics: &Generics,
 868                   type_ident: Ident)
 869                   -> P<ast::Ty> {
 870         self.ret_ty.to_ty(cx, trait_.span, type_ident, generics)
 871     }
 872
 873     fn is_static(&self) -> bool {
 874         self.explicit_self.is_none()
 875     }
 876
 877     fn split_self_nonself_args
 878         (&self,
 879          cx: &mut ExtCtxt,
 880          trait_: &TraitDef,
 881          type_ident: Ident,
 882          generics: &Generics)
 883          -> (Option<ast::ExplicitSelf>, Vec<P<Expr>>, Vec<P<Expr>>, Vec<(Ident, P<ast::Ty>)>) {
 884
 885         let mut self_args = Vec::new();
 886         let mut nonself_args = Vec::new();
 887         let mut arg_tys = Vec::new();
 888         let mut nonstatic = false;
 889
 890         let ast_explicit_self = self.explicit_self.as_ref().map(|self_ptr| {
 891             let (self_expr, explicit_self) = ty::get_explicit_self(cx, trait_.span, self_ptr);
 892
 893             self_args.push(self_expr);
 894             nonstatic = true;
 895
 896             explicit_self
 897         });
 898
 899         for (ty, name) in self.args.iter() {
 900             let ast_ty = ty.to_ty(cx, trait_.span, type_ident, generics);
 901             let ident = cx.ident_of(name).gensym();
 902             arg_tys.push((ident, ast_ty));
 903
 904             let arg_expr = cx.expr_ident(trait_.span, ident);
 905
 906             match *ty {
 907                 // for static methods, just treat any Self
 908                 // arguments as a normal arg
 909                 Self_ if nonstatic => {
 910                     self_args.push(arg_expr);
 911                 }
 912                 Ptr(ref ty, _) if (if let Self_ = **ty { true } else { false }) && nonstatic => {
 913                     self_args.push(cx.expr_deref(trait_.span, arg_expr))
 914                 }
 915                 _ => {
 916                     nonself_args.push(arg_expr);
 917                 }
 918             }
 919         }
 920
 921         (ast_explicit_self, self_args, nonself_args, arg_tys)
 922     }
 923
 924     fn create_method(&self,
 925                      cx: &mut ExtCtxt,
 926                      trait_: &TraitDef,
 927                      type_ident: Ident,
 928                      generics: &Generics,
 929                      abi: Abi,
 930                      explicit_self: Option<ast::ExplicitSelf>,
 931                      arg_types: Vec<(Ident, P<ast::Ty>)>,
 932                      body: P<Expr>)
 933                      -> ast::ImplItem {
 934
 935         // create the generics that aren't for Self
 936         let fn_generics = self.generics.to_generics(cx, trait_.span, type_ident, generics);
 937
 938         let args = {
 939             let self_args = explicit_self.map(|explicit_self| {
 940                 ast::Arg::from_self(explicit_self,
 941                                     keywords::SelfLower.ident().with_span_pos(trait_.span))
 942             });
 943             let nonself_args = arg_types.into_iter()
 944                 .map(|(name, ty)| cx.arg(trait_.span, name, ty));
 945             self_args.into_iter().chain(nonself_args).collect()
 946         };
 947
 948         let ret_type = self.get_ret_ty(cx, trait_, generics, type_ident);
 949
 950         let method_ident = cx.ident_of(self.name);
 951         let fn_decl = cx.fn_decl(args, ast::FunctionRetTy::Ty(ret_type));
 952         let body_block = cx.block_expr(body);
 953
 954         let unsafety = if self.is_unsafe {
 955             ast::Unsafety::Unsafe
 956         } else {
 957             ast::Unsafety::Normal
 958         };
 959
 960         // Create the method.
 961         ast::ImplItem {
 962             id: ast::DUMMY_NODE_ID,
 963             attrs: self.attributes.clone(),
 964             generics: fn_generics,
 965             span: trait_.span,
 966             vis: respan(trait_.span.shrink_to_lo(), ast::VisibilityKind::Inherited),
 967             defaultness: ast::Defaultness::Final,
 968             ident: method_ident,
 969             node: ast::ImplItemKind::Method(ast::MethodSig {
 970                                                 header: ast::FnHeader {
 971                                                     unsafety, abi,
 972                                                     ..ast::FnHeader::default()
 973                                                 },
 974                                                 decl: fn_decl,
 975                                             },
 976                                             body_block),
 977             tokens: None,
 978         }
 979     }
 980
 981     /// ```
 982     /// #[derive(PartialEq)]
 983     /// # struct Dummy;
 984     /// struct A { x: i32, y: i32 }
 985     ///
 986     /// // equivalent to:
 987     /// impl PartialEq for A {
 988     ///     fn eq(&self, other: &A) -> bool {
 989     ///         match *self {
 990     ///             A {x: ref __self_0_0, y: ref __self_0_1} => {
 991     ///                 match *other {
 992     ///                     A {x: ref __self_1_0, y: ref __self_1_1} => {
 993     ///                         __self_0_0.eq(__self_1_0) && __self_0_1.eq(__self_1_1)
 994     ///                     }
 995     ///                 }
 996     ///             }
 997     ///         }
 998     ///     }
 999     /// }
1000     ///
1001     /// // or if A is repr(packed) - note fields are matched by-value
1002     /// // instead of by-reference.
1003     /// impl PartialEq for A {
1004     ///     fn eq(&self, other: &A) -> bool {
1005     ///         match *self {
1006     ///             A {x: __self_0_0, y: __self_0_1} => {
1007     ///                 match other {
1008     ///                     A {x: __self_1_0, y: __self_1_1} => {
1009     ///                         __self_0_0.eq(&__self_1_0) && __self_0_1.eq(&__self_1_1)
1010     ///                     }
1011     ///                 }
1012     ///             }
1013     ///         }
1014     ///     }
1015     /// }
1016     /// ```
1017     fn expand_struct_method_body<'b>(&self,
1018                                      cx: &mut ExtCtxt,
1019                                      trait_: &TraitDef<'b>,
1020                                      struct_def: &'b VariantData,
1021                                      type_ident: Ident,
1022                                      self_args: &[P<Expr>],
1023                                      nonself_args: &[P<Expr>],
1024                                      use_temporaries: bool)
1025                                      -> P<Expr> {
1026
1027         let mut raw_fields = Vec::new(); // Vec<[fields of self],
1028                                  // [fields of next Self arg], [etc]>
1029         let mut patterns = Vec::new();
1030         for i in 0..self_args.len() {
1031             let struct_path = cx.path(DUMMY_SP, vec![type_ident]);
1032             let (pat, ident_expr) = trait_.create_struct_pattern(cx,
1033                                                                  struct_path,
1034                                                                  struct_def,
1035                                                                  &format!("__self_{}", i),
1036                                                                  ast::Mutability::Immutable,
1037                                                                  use_temporaries);
1038             patterns.push(pat);
1039             raw_fields.push(ident_expr);
1040         }
1041
1042         // transpose raw_fields
1043         let fields = if !raw_fields.is_empty() {
1044             let mut raw_fields = raw_fields.into_iter().map(|v| v.into_iter());
1045             let first_field = raw_fields.next().unwrap();
1046             let mut other_fields: Vec<vec::IntoIter<_>> = raw_fields.collect();
1047             first_field.map(|(span, opt_id, field, attrs)| {
1048                     FieldInfo {
1049                         span,
1050                         name: opt_id,
1051                         self_: field,
1052                         other: other_fields.iter_mut()
1053                             .map(|l| {
1054                                 match l.next().unwrap() {
1055                                     (.., ex, _) => ex,
1056                                 }
1057                             })
1058                             .collect(),
1059                         attrs,
1060                     }
1061                 })
1062                 .collect()
1063         } else {
1064             cx.span_bug(trait_.span,
1065                         "no self arguments to non-static method in generic \
1066                          `derive`")
1067         };
1068
1069         // body of the inner most destructuring match
1070         let mut body = self.call_substructure_method(cx,
1071                                                      trait_,
1072                                                      type_ident,
1073                                                      self_args,
1074                                                      nonself_args,
1075                                                      &Struct(struct_def, fields));
1076
1077         // make a series of nested matches, to destructure the
1078         // structs. This is actually right-to-left, but it shouldn't
1079         // matter.
1080         for (arg_expr, pat) in self_args.iter().zip(patterns) {
1081             body = cx.expr_match(trait_.span,
1082                                  arg_expr.clone(),
1083                                  vec![cx.arm(trait_.span, vec![pat.clone()], body)])
1084         }
1085
1086         body
1087     }
1088
1089     fn expand_static_struct_method_body(&self,
1090                                         cx: &mut ExtCtxt,
1091                                         trait_: &TraitDef,
1092                                         struct_def: &VariantData,
1093                                         type_ident: Ident,
1094                                         self_args: &[P<Expr>],
1095                                         nonself_args: &[P<Expr>])
1096                                         -> P<Expr> {
1097         let summary = trait_.summarise_struct(cx, struct_def);
1098
1099         self.call_substructure_method(cx,
1100                                       trait_,
1101                                       type_ident,
1102                                       self_args,
1103                                       nonself_args,
1104                                       &StaticStruct(struct_def, summary))
1105     }
1106
1107     /// ```
1108     /// #[derive(PartialEq)]
1109     /// # struct Dummy;
1110     /// enum A {
1111     ///     A1,
1112     ///     A2(i32)
1113     /// }
1114     ///
1115     /// // is equivalent to
1116     ///
1117     /// impl PartialEq for A {
1118     ///     fn eq(&self, other: &A) -> ::bool {
1119     ///         match (&*self, &*other) {
1120     ///             (&A1, &A1) => true,
1121     ///             (&A2(ref self_0),
1122     ///              &A2(ref __arg_1_0)) => (*self_0).eq(&(*__arg_1_0)),
1123     ///             _ => {
1124     ///                 let __self_vi = match *self { A1(..) => 0, A2(..) => 1 };
1125     ///                 let __arg_1_vi = match *other { A1(..) => 0, A2(..) => 1 };
1126     ///                 false
1127     ///             }
1128     ///         }
1129     ///     }
1130     /// }
1131     /// ```
1132     ///
1133     /// (Of course `__self_vi` and `__arg_1_vi` are unused for
1134     /// `PartialEq`, and those subcomputations will hopefully be removed
1135     /// as their results are unused.  The point of `__self_vi` and
1136     /// `__arg_1_vi` is for `PartialOrd`; see #15503.)
1137     fn expand_enum_method_body<'b>(&self,
1138                                    cx: &mut ExtCtxt,
1139                                    trait_: &TraitDef<'b>,
1140                                    enum_def: &'b EnumDef,
1141                                    type_attrs: &[ast::Attribute],
1142                                    type_ident: Ident,
1143                                    self_args: Vec<P<Expr>>,
1144                                    nonself_args: &[P<Expr>])
1145                                    -> P<Expr> {
1146         self.build_enum_match_tuple(cx,
1147                                     trait_,
1148                                     enum_def,
1149                                     type_attrs,
1150                                     type_ident,
1151                                     self_args,
1152                                     nonself_args)
1153     }
1154
1155
1156     /// Creates a match for a tuple of all `self_args`, where either all
1157     /// variants match, or it falls into a catch-all for when one variant
1158     /// does not match.
1159
1160     /// There are N + 1 cases because is a case for each of the N
1161     /// variants where all of the variants match, and one catch-all for
1162     /// when one does not match.
1163
1164     /// As an optimization we generate code which checks whether all variants
1165     /// match first which makes llvm see that C-like enums can be compiled into
1166     /// a simple equality check (for PartialEq).
1167
1168     /// The catch-all handler is provided access the variant index values
1169     /// for each of the self-args, carried in precomputed variables.
1170
1171     /// ```{.text}
1172     /// let __self0_vi = unsafe {
1173     ///     std::intrinsics::discriminant_value(&self) } as i32;
1174     /// let __self1_vi = unsafe {
1175     ///     std::intrinsics::discriminant_value(&arg1) } as i32;
1176     /// let __self2_vi = unsafe {
1177     ///     std::intrinsics::discriminant_value(&arg2) } as i32;
1178     ///
1179     /// if __self0_vi == __self1_vi && __self0_vi == __self2_vi && ... {
1180     ///     match (...) {
1181     ///         (Variant1, Variant1, ...) => Body1
1182     ///         (Variant2, Variant2, ...) => Body2,
1183     ///         ...
1184     ///         _ => ::core::intrinsics::unreachable()
1185     ///     }
1186     /// }
1187     /// else {
1188     ///     ... // catch-all remainder can inspect above variant index values.
1189     /// }
1190     /// ```
1191     fn build_enum_match_tuple<'b>(&self,
1192                                   cx: &mut ExtCtxt,
1193                                   trait_: &TraitDef<'b>,
1194                                   enum_def: &'b EnumDef,
1195                                   type_attrs: &[ast::Attribute],
1196                                   type_ident: Ident,
1197                                   self_args: Vec<P<Expr>>,
1198                                   nonself_args: &[P<Expr>])
1199                                   -> P<Expr> {
1200         let sp = trait_.span;
1201         let variants = &enum_def.variants;
1202
1203         let self_arg_names = iter::once("__self".to_string()).chain(
1204             self_args.iter()
1205                 .enumerate()
1206                 .skip(1)
1207                 .map(|(arg_count, _self_arg)|
1208                     format!("__arg_{}", arg_count)
1209                 )
1210             ).collect::<Vec<String>>();
1211
1212         let self_arg_idents = self_arg_names.iter()
1213             .map(|name| cx.ident_of(&name[..]))
1214             .collect::<Vec<ast::Ident>>();
1215
1216         // The `vi_idents` will be bound, solely in the catch-all, to
1217         // a series of let statements mapping each self_arg to an int
1218         // value corresponding to its discriminant.
1219         let vi_idents = self_arg_names.iter()
1220             .map(|name| {
1221                 let vi_suffix = format!("{}_vi", &name[..]);
1222                 cx.ident_of(&vi_suffix[..]).gensym()
1223             })
1224             .collect::<Vec<ast::Ident>>();
1225
1226         // Builds, via callback to call_substructure_method, the
1227         // delegated expression that handles the catch-all case,
1228         // using `__variants_tuple` to drive logic if necessary.
1229         let catch_all_substructure =
1230             EnumNonMatchingCollapsed(self_arg_idents, &variants[..], &vi_idents[..]);
1231
1232         let first_fieldless = variants.iter().find(|v| v.node.data.fields().is_empty());
1233
1234         // These arms are of the form:
1235         // (Variant1, Variant1, ...) => Body1
1236         // (Variant2, Variant2, ...) => Body2
1237         // ...
1238         // where each tuple has length = self_args.len()
1239         let mut match_arms: Vec<ast::Arm> = variants.iter()
1240             .enumerate()
1241             .filter(|&(_, v)| !(self.unify_fieldless_variants && v.node.data.fields().is_empty()))
1242             .map(|(index, variant)| {
1243                 let mk_self_pat = |cx: &mut ExtCtxt, self_arg_name: &str| {
1244                     let (p, idents) = trait_.create_enum_variant_pattern(cx,
1245                                                      type_ident,
1246                                                      variant,
1247                                                      self_arg_name,
1248                                                      ast::Mutability::Immutable);
1249                     (cx.pat(sp, PatKind::Ref(p, ast::Mutability::Immutable)), idents)
1250                 };
1251
1252                 // A single arm has form (&VariantK, &VariantK, ...) => BodyK
1253                 // (see "Final wrinkle" note below for why.)
1254                 let mut subpats = Vec::with_capacity(self_arg_names.len());
1255                 let mut self_pats_idents = Vec::with_capacity(self_arg_names.len() - 1);
1256                 let first_self_pat_idents = {
1257                     let (p, idents) = mk_self_pat(cx, &self_arg_names[0]);
1258                     subpats.push(p);
1259                     idents
1260                 };
1261                 for self_arg_name in &self_arg_names[1..] {
1262                     let (p, idents) = mk_self_pat(cx, &self_arg_name[..]);
1263                     subpats.push(p);
1264                     self_pats_idents.push(idents);
1265                 }
1266
1267                 // Here is the pat = `(&VariantK, &VariantK, ...)`
1268                 let single_pat = cx.pat_tuple(sp, subpats);
1269
1270                 // For the BodyK, we need to delegate to our caller,
1271                 // passing it an EnumMatching to indicate which case
1272                 // we are in.
1273
1274                 // All of the Self args have the same variant in these
1275                 // cases.  So we transpose the info in self_pats_idents
1276                 // to gather the getter expressions together, in the
1277                 // form that EnumMatching expects.
1278
1279                 // The transposition is driven by walking across the
1280                 // arg fields of the variant for the first self pat.
1281                 let field_tuples = first_self_pat_idents.into_iter().enumerate()
1282                     // For each arg field of self, pull out its getter expr ...
1283                     .map(|(field_index, (sp, opt_ident, self_getter_expr, attrs))| {
1284                         // ... but FieldInfo also wants getter expr
1285                         // for matching other arguments of Self type;
1286                         // so walk across the *other* self_pats_idents
1287                         // and pull out getter for same field in each
1288                         // of them (using `field_index` tracked above).
1289                         // That is the heart of the transposition.
1290                         let others = self_pats_idents.iter().map(|fields| {
1291                             let (_, _opt_ident, ref other_getter_expr, _) =
1292                                 fields[field_index];
1293
1294                             // All Self args have same variant, so
1295                             // opt_idents are the same.  (Assert
1296                             // here to make it self-evident that
1297                             // it is okay to ignore `_opt_ident`.)
1298                             assert!(opt_ident == _opt_ident);
1299
1300                             other_getter_expr.clone()
1301                         }).collect::<Vec<P<Expr>>>();
1302
1303                         FieldInfo { span: sp,
1304                                     name: opt_ident,
1305                                     self_: self_getter_expr,
1306                                     other: others,
1307                                     attrs,
1308                         }
1309                     }).collect::<Vec<FieldInfo>>();
1310
1311                 // Now, for some given VariantK, we have built up
1312                 // expressions for referencing every field of every
1313                 // Self arg, assuming all are instances of VariantK.
1314                 // Build up code associated with such a case.
1315                 let substructure = EnumMatching(index, variants.len(), variant, field_tuples);
1316                 let arm_expr = self.call_substructure_method(cx,
1317                                                              trait_,
1318                                                              type_ident,
1319                                                              &self_args[..],
1320                                                              nonself_args,
1321                                                              &substructure);
1322
1323                 cx.arm(sp, vec![single_pat], arm_expr)
1324             })
1325             .collect();
1326
1327         let default = match first_fieldless {
1328             Some(v) if self.unify_fieldless_variants => {
1329                 // We need a default case that handles the fieldless variants.
1330                 // The index and actual variant aren't meaningful in this case,
1331                 // so just use whatever
1332                 let substructure = EnumMatching(0, variants.len(), v, Vec::new());
1333                 Some(self.call_substructure_method(cx,
1334                                                    trait_,
1335                                                    type_ident,
1336                                                    &self_args[..],
1337                                                    nonself_args,
1338                                                    &substructure))
1339             }
1340             _ if variants.len() > 1 && self_args.len() > 1 => {
1341                 // Since we know that all the arguments will match if we reach
1342                 // the match expression we add the unreachable intrinsics as the
1343                 // result of the catch all which should help llvm in optimizing it
1344                 Some(deriving::call_intrinsic(cx, sp, "unreachable", vec![]))
1345             }
1346             _ => None,
1347         };
1348         if let Some(arm) = default {
1349             match_arms.push(cx.arm(sp, vec![cx.pat_wild(sp)], arm));
1350         }
1351
1352         // We will usually need the catch-all after matching the
1353         // tuples `(VariantK, VariantK, ...)` for each VariantK of the
1354         // enum.  But:
1355         //
1356         // * when there is only one Self arg, the arms above suffice
1357         // (and the deriving we call back into may not be prepared to
1358         // handle EnumNonMatchCollapsed), and,
1359         //
1360         // * when the enum has only one variant, the single arm that
1361         // is already present always suffices.
1362         //
1363         // * In either of the two cases above, if we *did* add a
1364         //   catch-all `_` match, it would trigger the
1365         //   unreachable-pattern error.
1366         //
1367         if variants.len() > 1 && self_args.len() > 1 {
1368             // Build a series of let statements mapping each self_arg
1369             // to its discriminant value. If this is a C-style enum
1370             // with a specific repr type, then casts the values to
1371             // that type.  Otherwise casts to `i32` (the default repr
1372             // type).
1373             //
1374             // i.e. for `enum E<T> { A, B(1), C(T, T) }`, and a deriving
1375             // with three Self args, builds three statements:
1376             //
1377             // ```
1378             // let __self0_vi = unsafe {
1379             //     std::intrinsics::discriminant_value(&self) } as i32;
1380             // let __self1_vi = unsafe {
1381             //     std::intrinsics::discriminant_value(&arg1) } as i32;
1382             // let __self2_vi = unsafe {
1383             //     std::intrinsics::discriminant_value(&arg2) } as i32;
1384             // ```
1385             let mut index_let_stmts: Vec<ast::Stmt> = Vec::with_capacity(vi_idents.len() + 1);
1386
1387             // We also build an expression which checks whether all discriminants are equal
1388             // discriminant_test = __self0_vi == __self1_vi && __self0_vi == __self2_vi && ...
1389             let mut discriminant_test = cx.expr_bool(sp, true);
1390
1391             let target_type_name = find_repr_type_name(&cx.parse_sess, type_attrs);
1392
1393             let mut first_ident = None;
1394             for (&ident, self_arg) in vi_idents.iter().zip(&self_args) {
1395                 let self_addr = cx.expr_addr_of(sp, self_arg.clone());
1396                 let variant_value =
1397                     deriving::call_intrinsic(cx, sp, "discriminant_value", vec![self_addr]);
1398
1399                 let target_ty = cx.ty_ident(sp, cx.ident_of(target_type_name));
1400                 let variant_disr = cx.expr_cast(sp, variant_value, target_ty);
1401                 let let_stmt = cx.stmt_let(sp, false, ident, variant_disr);
1402                 index_let_stmts.push(let_stmt);
1403
1404                 match first_ident {
1405                     Some(first) => {
1406                         let first_expr = cx.expr_ident(sp, first);
1407                         let id = cx.expr_ident(sp, ident);
1408                         let test = cx.expr_binary(sp, BinOpKind::Eq, first_expr, id);
1409                         discriminant_test =
1410                             cx.expr_binary(sp, BinOpKind::And, discriminant_test, test)
1411                     }
1412                     None => {
1413                         first_ident = Some(ident);
1414                     }
1415                 }
1416             }
1417
1418             let arm_expr = self.call_substructure_method(cx,
1419                                                          trait_,
1420                                                          type_ident,
1421                                                          &self_args[..],
1422                                                          nonself_args,
1423                                                          &catch_all_substructure);
1424
1425             // Final wrinkle: the self_args are expressions that deref
1426             // down to desired places, but we cannot actually deref
1427             // them when they are fed as r-values into a tuple
1428             // expression; here add a layer of borrowing, turning
1429             // `(*self, *__arg_0, ...)` into `(&*self, &*__arg_0, ...)`.
1430             let borrowed_self_args = self_args.move_map(|self_arg| cx.expr_addr_of(sp, self_arg));
1431             let match_arg = cx.expr(sp, ast::ExprKind::Tup(borrowed_self_args));
1432
1433             // Lastly we create an expression which branches on all discriminants being equal
1434             //  if discriminant_test {
1435             //      match (...) {
1436             //          (Variant1, Variant1, ...) => Body1
1437             //          (Variant2, Variant2, ...) => Body2,
1438             //          ...
1439             //          _ => ::core::intrinsics::unreachable()
1440             //      }
1441             //  }
1442             //  else {
1443             //      <delegated expression referring to __self0_vi, et al.>
1444             //  }
1445             let all_match = cx.expr_match(sp, match_arg, match_arms);
1446             let arm_expr = cx.expr_if(sp, discriminant_test, all_match, Some(arm_expr));
1447             index_let_stmts.push(cx.stmt_expr(arm_expr));
1448             cx.expr_block(cx.block(sp, index_let_stmts))
1449         } else if variants.is_empty() {
1450             // As an additional wrinkle, For a zero-variant enum A,
1451             // currently the compiler
1452             // will accept `fn (a: &Self) { match   *a   { } }`
1453             // but rejects `fn (a: &Self) { match (&*a,) { } }`
1454             // as well as  `fn (a: &Self) { match ( *a,) { } }`
1455             //
1456             // This means that the strategy of building up a tuple of
1457             // all Self arguments fails when Self is a zero variant
1458             // enum: rustc rejects the expanded program, even though
1459             // the actual code tends to be impossible to execute (at
1460             // least safely), according to the type system.
1461             //
1462             // The most expedient fix for this is to just let the
1463             // code fall through to the catch-all.  But even this is
1464             // error-prone, since the catch-all as defined above would
1465             // generate code like this:
1466             //
1467             //     _ => { let __self0 = match *self { };
1468             //            let __self1 = match *__arg_0 { };
1469             //            <catch-all-expr> }
1470             //
1471             // Which is yields bindings for variables which type
1472             // inference cannot resolve to unique types.
1473             //
1474             // One option to the above might be to add explicit type
1475             // annotations.  But the *only* reason to go down that path
1476             // would be to try to make the expanded output consistent
1477             // with the case when the number of enum variants >= 1.
1478             //
1479             // That just isn't worth it.  In fact, trying to generate
1480             // sensible code for *any* deriving on a zero-variant enum
1481             // does not make sense.  But at the same time, for now, we
1482             // do not want to cause a compile failure just because the
1483             // user happened to attach a deriving to their
1484             // zero-variant enum.
1485             //
1486             // Instead, just generate a failing expression for the
1487             // zero variant case, skipping matches and also skipping
1488             // delegating back to the end user code entirely.
1489             //
1490             // (See also #4499 and #12609; note that some of the
1491             // discussions there influence what choice we make here;
1492             // e.g. if we feature-gate `match x { ... }` when x refers
1493             // to an uninhabited type (e.g. a zero-variant enum or a
1494             // type holding such an enum), but do not feature-gate
1495             // zero-variant enums themselves, then attempting to
1496             // derive Debug on such a type could here generate code
1497             // that needs the feature gate enabled.)
1498
1499             deriving::call_intrinsic(cx, sp, "unreachable", vec![])
1500         } else {
1501
1502             // Final wrinkle: the self_args are expressions that deref
1503             // down to desired places, but we cannot actually deref
1504             // them when they are fed as r-values into a tuple
1505             // expression; here add a layer of borrowing, turning
1506             // `(*self, *__arg_0, ...)` into `(&*self, &*__arg_0, ...)`.
1507             let borrowed_self_args = self_args.move_map(|self_arg| cx.expr_addr_of(sp, self_arg));
1508             let match_arg = cx.expr(sp, ast::ExprKind::Tup(borrowed_self_args));
1509             cx.expr_match(sp, match_arg, match_arms)
1510         }
1511     }
1512
1513     fn expand_static_enum_method_body(&self,
1514                                       cx: &mut ExtCtxt,
1515                                       trait_: &TraitDef,
1516                                       enum_def: &EnumDef,
1517                                       type_ident: Ident,
1518                                       self_args: &[P<Expr>],
1519                                       nonself_args: &[P<Expr>])
1520                                       -> P<Expr> {
1521         let summary = enum_def.variants
1522             .iter()
1523             .map(|v| {
1524                 let sp = v.span.with_ctxt(trait_.span.ctxt());
1525                 let summary = trait_.summarise_struct(cx, &v.node.data);
1526                 (v.node.ident, sp, summary)
1527             })
1528             .collect();
1529         self.call_substructure_method(cx,
1530                                       trait_,
1531                                       type_ident,
1532                                       self_args,
1533                                       nonself_args,
1534                                       &StaticEnum(enum_def, summary))
1535     }
1536 }
1537
1538 // general helper methods.
1539 impl<'a> TraitDef<'a> {
1540     fn summarise_struct(&self, cx: &mut ExtCtxt, struct_def: &VariantData) -> StaticFields {
1541         let mut named_idents = Vec::new();
1542         let mut just_spans = Vec::new();
1543         for field in struct_def.fields() {
1544             let sp = field.span.with_ctxt(self.span.ctxt());
1545             match field.ident {
1546                 Some(ident) => named_idents.push((ident, sp)),
1547                 _ => just_spans.push(sp),
1548             }
1549         }
1550
1551         match (just_spans.is_empty(), named_idents.is_empty()) {
1552             (false, false) => {
1553                 cx.span_bug(self.span,
1554                             "a struct with named and unnamed \
1555                                           fields in generic `derive`")
1556             }
1557             // named fields
1558             (_, false) => Named(named_idents),
1559             // empty structs
1560             _ if struct_def.is_struct() => Named(named_idents),
1561             _ => Unnamed(just_spans, struct_def.is_tuple()),
1562         }
1563     }
1564
1565     fn create_subpatterns(&self,
1566                           cx: &mut ExtCtxt,
1567                           field_paths: Vec<ast::Ident>,
1568                           mutbl: ast::Mutability,
1569                           use_temporaries: bool)
1570                           -> Vec<P<ast::Pat>> {
1571         field_paths.iter()
1572             .map(|path| {
1573                 let binding_mode = if use_temporaries {
1574                     ast::BindingMode::ByValue(ast::Mutability::Immutable)
1575                 } else {
1576                     ast::BindingMode::ByRef(mutbl)
1577                 };
1578                 cx.pat(path.span,
1579                        PatKind::Ident(binding_mode, (*path).clone(), None))
1580             })
1581             .collect()
1582     }
1583
1584     fn create_struct_pattern
1585         (&self,
1586          cx: &mut ExtCtxt,
1587          struct_path: ast::Path,
1588          struct_def: &'a VariantData,
1589          prefix: &str,
1590          mutbl: ast::Mutability,
1591          use_temporaries: bool)
1592          -> (P<ast::Pat>, Vec<(Span, Option<Ident>, P<Expr>, &'a [ast::Attribute])>)
1593     {
1594         let mut paths = Vec::new();
1595         let mut ident_exprs = Vec::new();
1596         for (i, struct_field) in struct_def.fields().iter().enumerate() {
1597             let sp = struct_field.span.with_ctxt(self.span.ctxt());
1598             let ident = cx.ident_of(&format!("{}_{}", prefix, i)).gensym();
1599             paths.push(ident.with_span_pos(sp));
1600             let val = cx.expr_path(cx.path_ident(sp, ident));
1601             let val = if use_temporaries {
1602                 val
1603             } else {
1604                 cx.expr_deref(sp, val)
1605             };
1606             let val = cx.expr(sp, ast::ExprKind::Paren(val));
1607
1608             ident_exprs.push((sp, struct_field.ident, val, &struct_field.attrs[..]));
1609         }
1610
1611         let subpats = self.create_subpatterns(cx, paths, mutbl, use_temporaries);
1612         let pattern = match *struct_def {
1613             VariantData::Struct(..) => {
1614                 let field_pats = subpats.into_iter()
1615                     .zip(&ident_exprs)
1616                     .map(|(pat, &(sp, ident, ..))| {
1617                         if ident.is_none() {
1618                             cx.span_bug(sp, "a braced struct with unnamed fields in `derive`");
1619                         }
1620                         source_map::Spanned {
1621                             span: pat.span.with_ctxt(self.span.ctxt()),
1622                             node: ast::FieldPat {
1623                                 ident: ident.unwrap(),
1624                                 pat,
1625                                 is_shorthand: false,
1626                                 attrs: ThinVec::new(),
1627                             },
1628                         }
1629                     })
1630                     .collect();
1631                 cx.pat_struct(self.span, struct_path, field_pats)
1632             }
1633             VariantData::Tuple(..) => {
1634                 cx.pat_tuple_struct(self.span, struct_path, subpats)
1635             }
1636             VariantData::Unit(..) => {
1637                 cx.pat_path(self.span, struct_path)
1638             }
1639         };
1640
1641         (pattern, ident_exprs)
1642     }
1643
1644     fn create_enum_variant_pattern
1645         (&self,
1646          cx: &mut ExtCtxt,
1647          enum_ident: ast::Ident,
1648          variant: &'a ast::Variant,
1649          prefix: &str,
1650          mutbl: ast::Mutability)
1651          -> (P<ast::Pat>, Vec<(Span, Option<Ident>, P<Expr>, &'a [ast::Attribute])>) {
1652         let sp = variant.span.with_ctxt(self.span.ctxt());
1653         let variant_path = cx.path(sp, vec![enum_ident, variant.node.ident]);
1654         let use_temporaries = false; // enums can't be repr(packed)
1655         self.create_struct_pattern(cx, variant_path, &variant.node.data, prefix, mutbl,
1656                                    use_temporaries)
1657     }
1658 }
1659
1660 // helpful premade recipes
1661
1662 pub fn cs_fold_fields<'a, F>(use_foldl: bool,
1663                              mut f: F,
1664                              base: P<Expr>,
1665                              cx: &mut ExtCtxt,
1666                              all_fields: &[FieldInfo<'a>])
1667                              -> P<Expr>
1668     where F: FnMut(&mut ExtCtxt, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>
1669 {
1670     if use_foldl {
1671         all_fields.iter().fold(base, |old, field| {
1672             f(cx, field.span, old, field.self_.clone(), &field.other)
1673         })
1674     } else {
1675         all_fields.iter().rev().fold(base, |old, field| {
1676             f(cx, field.span, old, field.self_.clone(), &field.other)
1677         })
1678     }
1679 }
1680
1681 pub fn cs_fold_enumnonmatch(mut enum_nonmatch_f: EnumNonMatchCollapsedFunc,
1682                             cx: &mut ExtCtxt,
1683                             trait_span: Span,
1684                             substructure: &Substructure)
1685                             -> P<Expr>
1686 {
1687     match *substructure.fields {
1688         EnumNonMatchingCollapsed(ref all_args, _, tuple) => {
1689             enum_nonmatch_f(cx,
1690                             trait_span,
1691                             (&all_args[..], tuple),
1692                             substructure.nonself_args)
1693         }
1694         _ => cx.span_bug(trait_span, "cs_fold_enumnonmatch expected an EnumNonMatchingCollapsed")
1695     }
1696 }
1697
1698 pub fn cs_fold_static(cx: &mut ExtCtxt,
1699                       trait_span: Span)
1700                       -> P<Expr>
1701 {
1702     cx.span_bug(trait_span, "static function in `derive`")
1703 }
1704
1705 /// Fold the fields. `use_foldl` controls whether this is done
1706 /// left-to-right (`true`) or right-to-left (`false`).
1707 pub fn cs_fold<F>(use_foldl: bool,
1708                   f: F,
1709                   base: P<Expr>,
1710                   enum_nonmatch_f: EnumNonMatchCollapsedFunc,
1711                   cx: &mut ExtCtxt,
1712                   trait_span: Span,
1713                   substructure: &Substructure)
1714                   -> P<Expr>
1715     where F: FnMut(&mut ExtCtxt, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>
1716 {
1717     match *substructure.fields {
1718         EnumMatching(.., ref all_fields) |
1719         Struct(_, ref all_fields) => {
1720             cs_fold_fields(use_foldl, f, base, cx, all_fields)
1721         }
1722         EnumNonMatchingCollapsed(..) => {
1723             cs_fold_enumnonmatch(enum_nonmatch_f, cx, trait_span, substructure)
1724         }
1725         StaticEnum(..) | StaticStruct(..) => {
1726             cs_fold_static(cx, trait_span)
1727         }
1728     }
1729 }
1730
1731 /// Function to fold over fields, with three cases, to generate more efficient and concise code.
1732 /// When the `substructure` has grouped fields, there are two cases:
1733 /// Zero fields: call the base case function with None (like the usual base case of `cs_fold`).
1734 /// One or more fields: call the base case function on the first value (which depends on
1735 /// `use_fold`), and use that as the base case. Then perform `cs_fold` on the remainder of the
1736 /// fields.
1737 /// When the `substructure` is a `EnumNonMatchingCollapsed`, the result of `enum_nonmatch_f`
1738 /// is returned. Statics may not be folded over.
1739 /// See `cs_op` in `partial_ord.rs` for a model example.
1740 pub fn cs_fold1<F, B>(use_foldl: bool,
1741                       f: F,
1742                       mut b: B,
1743                       enum_nonmatch_f: EnumNonMatchCollapsedFunc,
1744                       cx: &mut ExtCtxt,
1745                       trait_span: Span,
1746                       substructure: &Substructure)
1747                       -> P<Expr>
1748     where F: FnMut(&mut ExtCtxt, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>,
1749           B: FnMut(&mut ExtCtxt, Option<(Span, P<Expr>, &[P<Expr>])>) -> P<Expr>
1750 {
1751     match *substructure.fields {
1752         EnumMatching(.., ref all_fields) |
1753         Struct(_, ref all_fields) => {
1754             let (base, all_fields) = match (all_fields.is_empty(), use_foldl) {
1755                 (false, true) => {
1756                     let field = &all_fields[0];
1757                     let args = (field.span, field.self_.clone(), &field.other[..]);
1758                     (b(cx, Some(args)), &all_fields[1..])
1759                 }
1760                 (false, false) => {
1761                     let idx = all_fields.len() - 1;
1762                     let field = &all_fields[idx];
1763                     let args = (field.span, field.self_.clone(), &field.other[..]);
1764                     (b(cx, Some(args)), &all_fields[..idx])
1765                 }
1766                 (true, _) => (b(cx, None), &all_fields[..])
1767             };
1768
1769             cs_fold_fields(use_foldl, f, base, cx, all_fields)
1770         }
1771         EnumNonMatchingCollapsed(..) => {
1772             cs_fold_enumnonmatch(enum_nonmatch_f, cx, trait_span, substructure)
1773         }
1774         StaticEnum(..) | StaticStruct(..) => {
1775             cs_fold_static(cx, trait_span)
1776         }
1777     }
1778 }
1779
1780 /// Call the method that is being derived on all the fields, and then
1781 /// process the collected results. i.e.
1782 ///
1783 /// ```ignore (only-for-syntax-highlight)
1784 /// f(cx, span, vec![self_1.method(__arg_1_1, __arg_2_1),
1785 ///                  self_2.method(__arg_1_2, __arg_2_2)])
1786 /// ```
1787 #[inline]
1788 pub fn cs_same_method<F>(f: F,
1789                          mut enum_nonmatch_f: EnumNonMatchCollapsedFunc,
1790                          cx: &mut ExtCtxt,
1791                          trait_span: Span,
1792                          substructure: &Substructure)
1793                          -> P<Expr>
1794     where F: FnOnce(&mut ExtCtxt, Span, Vec<P<Expr>>) -> P<Expr>
1795 {
1796     match *substructure.fields {
1797         EnumMatching(.., ref all_fields) |
1798         Struct(_, ref all_fields) => {
1799             // call self_n.method(other_1_n, other_2_n, ...)
1800             let called = all_fields.iter()
1801                 .map(|field| {
1802                     cx.expr_method_call(field.span,
1803                                         field.self_.clone(),
1804                                         substructure.method_ident,
1805                                         field.other
1806                                             .iter()
1807                                             .map(|e| cx.expr_addr_of(field.span, e.clone()))
1808                                             .collect())
1809                 })
1810                 .collect();
1811
1812             f(cx, trait_span, called)
1813         }
1814         EnumNonMatchingCollapsed(ref all_self_args, _, tuple) => {
1815             enum_nonmatch_f(cx,
1816                             trait_span,
1817                             (&all_self_args[..], tuple),
1818                             substructure.nonself_args)
1819         }
1820         StaticEnum(..) | StaticStruct(..) => cx.span_bug(trait_span, "static function in `derive`"),
1821     }
1822 }
1823
1824 /// Return true if the type has no value fields
1825 /// (for an enum, no variant has any fields)
1826 pub fn is_type_without_fields(item: &Annotatable) -> bool {
1827     if let Annotatable::Item(ref item) = *item {
1828         match item.node {
1829             ast::ItemKind::Enum(ref enum_def, _) => {
1830                 enum_def.variants.iter().all(|v| v.node.data.fields().is_empty())
1831             }
1832             ast::ItemKind::Struct(ref variant_data, _) => variant_data.fields().is_empty(),
1833             _ => false,
1834         }
1835     } else {
1836         false
1837     }
1838 }