78 lines
2.9 KiB
Rust
78 lines
2.9 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use ast::{MetaItem, Item, Expr};
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use codemap::Span;
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use ext::base::ExtCtxt;
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use ext::build::AstBuilder;
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use ext::deriving::generic::*;
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pub fn expand_deriving_default(cx: &mut ExtCtxt,
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span: Span,
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mitem: @MetaItem,
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item: @Item,
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push: |@Item|) {
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let trait_def = TraitDef {
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span: span,
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attributes: Vec::new(),
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path: Path::new(vec!("std", "default", "Default")),
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additional_bounds: Vec::new(),
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generics: LifetimeBounds::empty(),
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methods: vec!(
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MethodDef {
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name: "default",
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generics: LifetimeBounds::empty(),
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explicit_self: None,
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args: Vec::new(),
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ret_ty: Self,
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inline: true,
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const_nonmatching: false,
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combine_substructure: default_substructure
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})
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};
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trait_def.expand(cx, mitem, item, push)
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}
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fn default_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> @Expr {
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let default_ident = vec!(
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cx.ident_of("std"),
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cx.ident_of("default"),
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cx.ident_of("Default"),
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cx.ident_of("default")
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);
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let default_call = |span| cx.expr_call_global(span, default_ident.clone(), Vec::new());
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return match *substr.fields {
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StaticStruct(_, ref summary) => {
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match *summary {
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Unnamed(ref fields) => {
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if fields.is_empty() {
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cx.expr_ident(trait_span, substr.type_ident)
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} else {
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let exprs = fields.iter().map(|sp| default_call(*sp)).collect();
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cx.expr_call_ident(trait_span, substr.type_ident, exprs)
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}
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}
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Named(ref fields) => {
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let default_fields = fields.iter().map(|&(ident, span)| {
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cx.field_imm(span, ident, default_call(span))
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}).collect();
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cx.expr_struct_ident(trait_span, substr.type_ident, default_fields)
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}
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}
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}
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StaticEnum(..) => {
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cx.span_err(trait_span, "`Default` cannot be derived for enums, only structs");
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// let compilation continue
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cx.expr_uint(trait_span, 0)
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}
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_ => cx.span_bug(trait_span, "Non-static method in `deriving(Default)`")
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};
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}
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