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// 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::*;
pub fn expand_deriving_default(cx: &mut ExtCtxt,
span: Span,
mitem: @MetaItem,
item: @Item,
push: |@Item|) {
let trait_def = TraitDef {
span: span,
attributes: Vec::new(),
path: Path::new(vec!("std", "default", "Default")),
additional_bounds: Vec::new(),
generics: LifetimeBounds::empty(),
methods: vec!(
MethodDef {
name: "default",
generics: LifetimeBounds::empty(),
explicit_self: None,
args: Vec::new(),
ret_ty: Self,
inline: true,
const_nonmatching: false,
combine_substructure: default_substructure
})
};
trait_def.expand(cx, mitem, item, push)
}
fn default_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> @Expr {
let default_ident = vec!(
cx.ident_of("std"),
cx.ident_of("default"),
cx.ident_of("Default"),
cx.ident_of("default")
);
let default_call = |span| cx.expr_call_global(span, default_ident.clone(), Vec::new());
return match *substr.fields {
StaticStruct(_, ref summary) => {
match *summary {
Unnamed(ref fields) => {
if fields.is_empty() {
cx.expr_ident(trait_span, substr.type_ident)
} else {
let exprs = fields.iter().map(|sp| default_call(*sp)).collect();
cx.expr_call_ident(trait_span, substr.type_ident, exprs)
}
}
Named(ref fields) => {
let default_fields = fields.iter().map(|&(ident, span)| {
cx.field_imm(span, ident, default_call(span))
}).collect();
cx.expr_struct_ident(trait_span, substr.type_ident, default_fields)
}
}
}
StaticEnum(..) => {
cx.span_err(trait_span, "`Default` cannot be derived for enums, only structs");
// let compilation continue
cx.expr_uint(trait_span, 0)
}
_ => cx.span_bug(trait_span, "Non-static method in `deriving(Default)`")
};
}
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