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