90 lines
2.9 KiB
Rust
90 lines
2.9 KiB
Rust
use crate::deriving::generic::ty::*;
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use crate::deriving::generic::*;
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use crate::deriving::path_std;
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use errors::struct_span_err;
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use rustc_expand::base::{Annotatable, DummyResult, ExtCtxt};
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use rustc_span::symbol::{kw, sym};
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use rustc_span::Span;
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use syntax::ast::{Expr, MetaItem};
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use syntax::ptr::P;
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use rustc_error_codes::*;
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pub fn expand_deriving_default(
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cx: &mut ExtCtxt<'_>,
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span: Span,
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mitem: &MetaItem,
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item: &Annotatable,
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push: &mut dyn FnMut(Annotatable),
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) {
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let inline = cx.meta_word(span, sym::inline);
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let attrs = vec![cx.attribute(inline)];
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let trait_def = TraitDef {
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span,
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attributes: Vec::new(),
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path: path_std!(cx, default::Default),
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additional_bounds: Vec::new(),
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generics: LifetimeBounds::empty(),
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is_unsafe: false,
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supports_unions: false,
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methods: vec![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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attributes: attrs,
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is_unsafe: false,
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unify_fieldless_variants: false,
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combine_substructure: combine_substructure(Box::new(|a, b, c| {
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default_substructure(a, b, c)
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})),
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}],
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associated_types: Vec::new(),
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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(
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cx: &mut ExtCtxt<'_>,
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trait_span: Span,
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substr: &Substructure<'_>,
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) -> P<Expr> {
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// Note that `kw::Default` is "default" and `sym::Default` is "Default"!
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let default_ident = cx.std_path(&[kw::Default, sym::Default, kw::Default]);
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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) => match *summary {
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Unnamed(ref fields, is_tuple) => {
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if !is_tuple {
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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
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.iter()
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.map(|&(ident, span)| 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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StaticEnum(..) => {
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struct_span_err!(
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cx.parse_sess.span_diagnostic,
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trait_span,
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E0665,
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"`Default` cannot be derived for enums, only structs"
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)
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.emit();
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// let compilation continue
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DummyResult::raw_expr(trait_span, true)
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}
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_ => cx.span_bug(trait_span, "method in `derive(Default)`"),
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};
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}
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