src/libsyntax/ext/deriving/zero.rs

   1 // Copyright 2012-2013 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 ast::{MetaItem, Item, Expr};
  12 use codemap::Span;
  13 use ext::base::ExtCtxt;
  14 use ext::build::AstBuilder;
  15 use ext::deriving::generic::*;
  16 use ext::deriving::generic::ty::*;
  17 use parse::token::InternedString;
  18 use ptr::P;
  19
  20 pub fn expand_deriving_zero<F>(cx: &mut ExtCtxt,
  21                                span: Span,
  22                                mitem: &MetaItem,
  23                                item: &Item,
  24                                push: F) where
  25     F: FnOnce(P<Item>),
  26 {
  27     let inline = cx.meta_word(span, InternedString::new("inline"));
  28     let attrs = vec!(cx.attribute(span, inline));
  29     let trait_def = TraitDef {
  30         span: span,
  31         attributes: Vec::new(),
  32         path: Path::new(vec!("std", "num", "Zero")),
  33         additional_bounds: Vec::new(),
  34         generics: LifetimeBounds::empty(),
  35         methods: vec!(
  36             MethodDef {
  37                 name: "zero",
  38                 generics: LifetimeBounds::empty(),
  39                 explicit_self: None,
  40                 args: Vec::new(),
  41                 ret_ty: Self,
  42                 attributes: attrs.clone(),
  43                 combine_substructure: combine_substructure(|a, b, c| {
  44                     zero_substructure(a, b, c)
  45                 })
  46             },
  47             MethodDef {
  48                 name: "is_zero",
  49                 generics: LifetimeBounds::empty(),
  50                 explicit_self: borrowed_explicit_self(),
  51                 args: Vec::new(),
  52                 ret_ty: Literal(Path::new(vec!("bool"))),
  53                 attributes: attrs,
  54                 combine_substructure: combine_substructure(|cx, span, substr| {
  55                     cs_and(|cx, span, _, _| cx.span_bug(span,
  56                                                         "Non-matching enum \
  57                                                          variant in \
  58                                                          deriving(Zero)"),
  59                            cx, span, substr)
  60                 })
  61             }
  62         )
  63     };
  64     trait_def.expand(cx, mitem, item, push)
  65 }
  66
  67 fn zero_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
  68     let zero_ident = vec!(
  69         cx.ident_of("std"),
  70         cx.ident_of("num"),
  71         cx.ident_of("Zero"),
  72         cx.ident_of("zero")
  73     );
  74     let zero_call = |&: span| cx.expr_call_global(span, zero_ident.clone(), Vec::new());
  75
  76     return match *substr.fields {
  77         StaticStruct(_, ref summary) => {
  78             match *summary {
  79                 Unnamed(ref fields) => {
  80                     if fields.is_empty() {
  81                         cx.expr_ident(trait_span, substr.type_ident)
  82                     } else {
  83                         let exprs = fields.iter().map(|sp| zero_call(*sp)).collect();
  84                         cx.expr_call_ident(trait_span, substr.type_ident, exprs)
  85                     }
  86                 }
  87                 Named(ref fields) => {
  88                     let zero_fields = fields.iter().map(|&(ident, span)| {
  89                         cx.field_imm(span, ident, zero_call(span))
  90                     }).collect();
  91                     cx.expr_struct_ident(trait_span, substr.type_ident, zero_fields)
  92                 }
  93             }
  94         }
  95         StaticEnum(..) => {
  96             cx.span_err(trait_span, "`Zero` cannot be derived for enums, only structs");
  97             // let compilation continue
  98             cx.expr_uint(trait_span, 0)
  99         }
 100         _ => cx.bug("Non-static method in `deriving(Zero)`")
 101     };
 102 }