src/libsyntax_ext/deriving/cmp/ord.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::{self, 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_ord(cx: &mut ExtCtxt,
  22                            span: Span,
  23                            mitem: &MetaItem,
  24                            item: &Annotatable,
  25                            push: &mut FnMut(Annotatable)) {
  26     let inline = cx.meta_word(span, InternedString::new("inline"));
  27     let attrs = vec![cx.attribute(span, inline)];
  28     let trait_def = TraitDef {
  29         span: span,
  30         attributes: Vec::new(),
  31         path: path_std!(cx, core::cmp::Ord),
  32         additional_bounds: Vec::new(),
  33         generics: LifetimeBounds::empty(),
  34         is_unsafe: false,
  35         methods: vec![MethodDef {
  36                           name: "cmp",
  37                           generics: LifetimeBounds::empty(),
  38                           explicit_self: borrowed_explicit_self(),
  39                           args: vec![borrowed_self()],
  40                           ret_ty: Literal(path_std!(cx, core::cmp::Ordering)),
  41                           attributes: attrs,
  42                           is_unsafe: false,
  43                           unify_fieldless_variants: true,
  44                           combine_substructure: combine_substructure(Box::new(|a, b, c| {
  45                               cs_cmp(a, b, c)
  46                           })),
  47                       }],
  48         associated_types: Vec::new(),
  49     };
  50
  51     trait_def.expand(cx, mitem, item, push)
  52 }
  53
  54
  55 pub fn ordering_collapsed(cx: &mut ExtCtxt,
  56                           span: Span,
  57                           self_arg_tags: &[ast::Ident])
  58                           -> P<ast::Expr> {
  59     let lft = cx.expr_ident(span, self_arg_tags[0]);
  60     let rgt = cx.expr_addr_of(span, cx.expr_ident(span, self_arg_tags[1]));
  61     cx.expr_method_call(span, lft, cx.ident_of("cmp"), vec![rgt])
  62 }
  63
  64 pub fn cs_cmp(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<Expr> {
  65     let test_id = cx.ident_of("__cmp");
  66     let equals_path = cx.path_global(span, cx.std_path(&["cmp", "Ordering", "Equal"]));
  67
  68     let cmp_path = cx.std_path(&["cmp", "Ord", "cmp"]);
  69
  70     // Builds:
  71     //
  72     // match ::std::cmp::Ord::cmp(&self_field1, &other_field1) {
  73     // ::std::cmp::Ordering::Equal =>
  74     // match ::std::cmp::Ord::cmp(&self_field2, &other_field2) {
  75     // ::std::cmp::Ordering::Equal => {
  76     // ...
  77     // }
  78     // __cmp => __cmp
  79     // },
  80     // __cmp => __cmp
  81     // }
  82     //
  83     cs_fold(// foldr nests the if-elses correctly, leaving the first field
  84             // as the outermost one, and the last as the innermost.
  85             false,
  86             |cx, span, old, self_f, other_fs| {
  87         // match new {
  88         //     ::std::cmp::Ordering::Equal => old,
  89         //     __cmp => __cmp
  90         // }
  91
  92         let new = {
  93             let other_f = match (other_fs.len(), other_fs.get(0)) {
  94                 (1, Some(o_f)) => o_f,
  95                 _ => cx.span_bug(span, "not exactly 2 arguments in `derive(Ord)`"),
  96             };
  97
  98             let args = vec![
  99                     cx.expr_addr_of(span, self_f),
 100                     cx.expr_addr_of(span, other_f.clone()),
 101                 ];
 102
 103             cx.expr_call_global(span, cmp_path.clone(), args)
 104         };
 105
 106         let eq_arm = cx.arm(span,
 107                             vec![cx.pat_enum(span, equals_path.clone(), vec![])],
 108                             old);
 109         let neq_arm = cx.arm(span,
 110                              vec![cx.pat_ident(span, test_id)],
 111                              cx.expr_ident(span, test_id));
 112
 113         cx.expr_match(span, new, vec![eq_arm, neq_arm])
 114     },
 115             cx.expr_path(equals_path.clone()),
 116             Box::new(|cx, span, (self_args, tag_tuple), _non_self_args| {
 117         if self_args.len() != 2 {
 118             cx.span_bug(span, "not exactly 2 arguments in `derive(Ord)`")
 119         } else {
 120             ordering_collapsed(cx, span, tag_tuple)
 121         }
 122     }),
 123             cx,
 124             span,
 125             substr)
 126 }