1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
|
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use ast::{MetaItem, item, Expr};
use codemap::Span;
use ext::base::ExtCtxt;
use ext::build::AstBuilder;
use ext::deriving::generic::*;
use std::vec;
pub fn expand_deriving_zero(cx: @ExtCtxt,
span: Span,
mitem: @MetaItem,
in_items: ~[@item])
-> ~[@item] {
let trait_def = TraitDef {
path: Path::new(~["std", "num", "Zero"]),
additional_bounds: ~[],
generics: LifetimeBounds::empty(),
methods: ~[
MethodDef {
name: "zero",
generics: LifetimeBounds::empty(),
explicit_self: None,
args: ~[],
ret_ty: Self,
const_nonmatching: false,
combine_substructure: zero_substructure
},
MethodDef {
name: "is_zero",
generics: LifetimeBounds::empty(),
explicit_self: borrowed_explicit_self(),
args: ~[],
ret_ty: Literal(Path::new(~["bool"])),
const_nonmatching: false,
combine_substructure: |cx, span, substr| {
cs_and(|cx, span, _, _| cx.span_bug(span,
"Non-matching enum \
variant in \
deriving(Zero)"),
cx, span, substr)
}
}
]
};
trait_def.expand(cx, span, mitem, in_items)
}
fn zero_substructure(cx: @ExtCtxt, span: Span, substr: &Substructure) -> @Expr {
let zero_ident = ~[
cx.ident_of("std"),
cx.ident_of("num"),
cx.ident_of("Zero"),
cx.ident_of("zero")
];
let zero_call = cx.expr_call_global(span, zero_ident.clone(), ~[]);
return match *substr.fields {
StaticStruct(_, ref summary) => {
match *summary {
Left(count) => {
if count == 0 {
cx.expr_ident(span, substr.type_ident)
} else {
let exprs = vec::from_elem(count, zero_call);
cx.expr_call_ident(span, substr.type_ident, exprs)
}
}
Right(ref fields) => {
let zero_fields = do fields.map |ident| {
cx.field_imm(span, *ident, zero_call)
};
cx.expr_struct_ident(span, substr.type_ident, zero_fields)
}
}
}
StaticEnum(*) => {
cx.span_fatal(span, "`Zero` cannot be derived for enums, \
only structs")
}
_ => cx.bug("Non-static method in `deriving(Zero)`")
};
}
|
