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use crate::deriving::path_std;
use crate::deriving::generic::*;
use crate::deriving::generic::ty::*;
use syntax::ast::{self, Ident, Expr, MetaItem, GenericArg};
use syntax::expand::SpecialDerives;
use syntax::ptr::P;
use syntax::symbol::{sym, Symbol};
use syntax_expand::base::{Annotatable, ExtCtxt};
use syntax_pos::Span;
pub fn expand_deriving_eq(cx: &mut ExtCtxt<'_>,
span: Span,
mitem: &MetaItem,
item: &Annotatable,
push: &mut dyn FnMut(Annotatable)) {
cx.resolver.add_derives(cx.current_expansion.id.expn_data().parent, SpecialDerives::EQ);
let inline = cx.meta_word(span, sym::inline);
let hidden = syntax::attr::mk_nested_word_item(Ident::new(sym::hidden, span));
let doc = syntax::attr::mk_list_item(Ident::new(sym::doc, span), vec![hidden]);
let attrs = vec![cx.attribute(inline), cx.attribute(doc)];
let trait_def = TraitDef {
span,
attributes: Vec::new(),
path: path_std!(cx, cmp::Eq),
additional_bounds: Vec::new(),
generics: LifetimeBounds::empty(),
is_unsafe: false,
supports_unions: true,
methods: vec![MethodDef {
name: "assert_receiver_is_total_eq",
generics: LifetimeBounds::empty(),
explicit_self: borrowed_explicit_self(),
args: vec![],
ret_ty: nil_ty(),
attributes: attrs,
is_unsafe: false,
unify_fieldless_variants: true,
combine_substructure: combine_substructure(Box::new(|a, b, c| {
cs_total_eq_assert(a, b, c)
})),
}],
associated_types: Vec::new(),
};
super::inject_impl_of_structural_trait(
cx, span, item,
path_std!(cx, marker::StructuralEq),
push);
trait_def.expand_ext(cx, mitem, item, push, true)
}
fn cs_total_eq_assert(cx: &mut ExtCtxt<'_>,
trait_span: Span,
substr: &Substructure<'_>)
-> P<Expr> {
fn assert_ty_bounds(cx: &mut ExtCtxt<'_>, stmts: &mut Vec<ast::Stmt>,
ty: P<ast::Ty>, span: Span, helper_name: &str) {
// Generate statement `let _: helper_name<ty>;`,
// set the expn ID so we can use the unstable struct.
let span = cx.with_def_site_ctxt(span);
let assert_path = cx.path_all(span, true,
cx.std_path(&[sym::cmp, Symbol::intern(helper_name)]),
vec![GenericArg::Type(ty)]);
stmts.push(cx.stmt_let_type_only(span, cx.ty_path(assert_path)));
}
fn process_variant(cx: &mut ExtCtxt<'_>,
stmts: &mut Vec<ast::Stmt>,
variant: &ast::VariantData) {
for field in variant.fields() {
// let _: AssertParamIsEq<FieldTy>;
assert_ty_bounds(cx, stmts, field.ty.clone(), field.span, "AssertParamIsEq");
}
}
let mut stmts = Vec::new();
match *substr.fields {
StaticStruct(vdata, ..) => {
process_variant(cx, &mut stmts, vdata);
}
StaticEnum(enum_def, ..) => {
for variant in &enum_def.variants {
process_variant(cx, &mut stmts, &variant.data);
}
}
_ => cx.span_bug(trait_span, "unexpected substructure in `derive(Eq)`")
}
cx.expr_block(cx.block(trait_span, stmts))
}
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