src/libsyntax_ext/deriving/cmp/partial_eq.rs

   1 // Copyright 2013 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 use deriving::generic::*;
  12 use deriving::generic::ty::*;
  13
  14 use syntax::ast::{BinOpKind, Expr, MetaItem};
  15 use syntax::ext::base::{Annotatable, ExtCtxt};
  16 use syntax::ext::build::AstBuilder;
  17 use syntax::parse::token::InternedString;
  18 use syntax::ptr::P;
  19 use syntax_pos::Span;
  20
  21 pub fn expand_deriving_partial_eq(cx: &mut ExtCtxt,
  22                                   span: Span,
  23                                   mitem: &MetaItem,
  24                                   item: &Annotatable,
  25                                   push: &mut FnMut(Annotatable)) {
  26     // structures are equal if all fields are equal, and non equal, if
  27     // any fields are not equal or if the enum variants are different
  28     fn cs_eq(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<Expr> {
  29         cs_fold(true, // use foldl
  30                 |cx, span, subexpr, self_f, other_fs| {
  31             let other_f = match (other_fs.len(), other_fs.get(0)) {
  32                 (1, Some(o_f)) => o_f,
  33                 _ => cx.span_bug(span, "not exactly 2 arguments in `derive(PartialEq)`"),
  34             };
  35
  36             let eq = cx.expr_binary(span, BinOpKind::Eq, self_f, other_f.clone());
  37
  38             cx.expr_binary(span, BinOpKind::And, subexpr, eq)
  39         },
  40                 cx.expr_bool(span, true),
  41                 Box::new(|cx, span, _, _| cx.expr_bool(span, false)),
  42                 cx,
  43                 span,
  44                 substr)
  45     }
  46     fn cs_ne(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<Expr> {
  47         cs_fold(true, // use foldl
  48                 |cx, span, subexpr, self_f, other_fs| {
  49             let other_f = match (other_fs.len(), other_fs.get(0)) {
  50                 (1, Some(o_f)) => o_f,
  51                 _ => cx.span_bug(span, "not exactly 2 arguments in `derive(PartialEq)`"),
  52             };
  53
  54             let eq = cx.expr_binary(span, BinOpKind::Ne, self_f, other_f.clone());
  55
  56             cx.expr_binary(span, BinOpKind::Or, subexpr, eq)
  57         },
  58                 cx.expr_bool(span, false),
  59                 Box::new(|cx, span, _, _| cx.expr_bool(span, true)),
  60                 cx,
  61                 span,
  62                 substr)
  63     }
  64
  65     macro_rules! md {
  66         ($name:expr, $f:ident) => { {
  67             let inline = cx.meta_word(span, InternedString::new("inline"));
  68             let attrs = vec!(cx.attribute(span, inline));
  69             MethodDef {
  70                 name: $name,
  71                 generics: LifetimeBounds::empty(),
  72                 explicit_self: borrowed_explicit_self(),
  73                 args: vec!(borrowed_self()),
  74                 ret_ty: Literal(path_local!(bool)),
  75                 attributes: attrs,
  76                 is_unsafe: false,
  77                 unify_fieldless_variants: true,
  78                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
  79                     $f(a, b, c)
  80                 }))
  81             }
  82         } }
  83     }
  84
  85     // avoid defining `ne` if we can
  86     // c-like enums, enums without any fields and structs without fields
  87     // can safely define only `eq`.
  88     let mut methods = vec![md!("eq", cs_eq)];
  89     if !is_type_without_fields(item) {
  90         methods.push(md!("ne", cs_ne));
  91     }
  92
  93     let trait_def = TraitDef {
  94         span: span,
  95         attributes: Vec::new(),
  96         path: path_std!(cx, core::cmp::PartialEq),
  97         additional_bounds: Vec::new(),
  98         generics: LifetimeBounds::empty(),
  99         is_unsafe: false,
 100         supports_unions: false,
 101         methods: methods,
 102         associated_types: Vec::new(),
 103     };
 104     trait_def.expand(cx, mitem, item, push)
 105 }