1 use deriving::path_std;
2 use deriving::generic::*;
3 use deriving::generic::ty::*;
5 use syntax::ast::{Expr, MetaItem};
6 use syntax::ext::base::{Annotatable, DummyResult, ExtCtxt};
7 use syntax::ext::build::AstBuilder;
9 use syntax::symbol::Symbol;
12 pub fn expand_deriving_default(cx: &mut ExtCtxt,
16 push: &mut dyn FnMut(Annotatable)) {
17 let inline = cx.meta_word(span, Symbol::intern("inline"));
18 let attrs = vec![cx.attribute(span, inline)];
19 let trait_def = TraitDef {
21 attributes: Vec::new(),
22 path: path_std!(cx, default::Default),
23 additional_bounds: Vec::new(),
24 generics: LifetimeBounds::empty(),
26 supports_unions: false,
27 methods: vec![MethodDef {
29 generics: LifetimeBounds::empty(),
35 unify_fieldless_variants: false,
36 combine_substructure: combine_substructure(Box::new(|a, b, c| {
37 default_substructure(a, b, c)
40 associated_types: Vec::new(),
42 trait_def.expand(cx, mitem, item, push)
45 fn default_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
46 let default_ident = cx.std_path(&["default", "Default", "default"]);
47 let default_call = |span| cx.expr_call_global(span, default_ident.clone(), Vec::new());
49 return match *substr.fields {
50 StaticStruct(_, ref summary) => {
52 Unnamed(ref fields, is_tuple) => {
54 cx.expr_ident(trait_span, substr.type_ident)
56 let exprs = fields.iter().map(|sp| default_call(*sp)).collect();
57 cx.expr_call_ident(trait_span, substr.type_ident, exprs)
60 Named(ref fields) => {
61 let default_fields = fields.iter()
62 .map(|&(ident, span)| cx.field_imm(span, ident, default_call(span)))
64 cx.expr_struct_ident(trait_span, substr.type_ident, default_fields)
69 span_err!(cx, trait_span, E0665,
70 "`Default` cannot be derived for enums, only structs");
71 // let compilation continue
72 DummyResult::raw_expr(trait_span)
74 _ => cx.span_bug(trait_span, "Non-static method in `derive(Default)`"),