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use crate::deriving::generic::ty::*;
use crate::deriving::generic::*;
use crate::deriving::{path_std, pathvec_std};
use rustc_ast::MetaItem;
use rustc_expand::base::{Annotatable, ExtCtxt};
use rustc_span::symbol::{sym, Ident};
use rustc_span::Span;
use thin_vec::thin_vec;
pub fn expand_deriving_partial_ord(
cx: &mut ExtCtxt<'_>,
span: Span,
mitem: &MetaItem,
item: &Annotatable,
push: &mut dyn FnMut(Annotatable),
is_const: bool,
) {
let ordering_ty = Path(path_std!(cmp::Ordering));
let ret_ty =
Path(Path::new_(pathvec_std!(option::Option), vec![Box::new(ordering_ty)], PathKind::Std));
let attrs = thin_vec![cx.attr_word(sym::inline, span)];
let partial_cmp_def = MethodDef {
name: sym::partial_cmp,
generics: Bounds::empty(),
explicit_self: true,
nonself_args: vec![(self_ref(), sym::other)],
ret_ty,
attributes: attrs,
fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
combine_substructure: combine_substructure(Box::new(|cx, span, substr| {
cs_partial_cmp(cx, span, substr)
})),
};
let trait_def = TraitDef {
span,
path: path_std!(cmp::PartialOrd),
skip_path_as_bound: false,
additional_bounds: vec![],
supports_unions: false,
methods: vec![partial_cmp_def],
associated_types: Vec::new(),
is_const,
};
trait_def.expand(cx, mitem, item, push)
}
pub fn cs_partial_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
let test_id = Ident::new(sym::cmp, span);
let equal_path = cx.path_global(span, cx.std_path(&[sym::cmp, sym::Ordering, sym::Equal]));
let partial_cmp_path = cx.std_path(&[sym::cmp, sym::PartialOrd, sym::partial_cmp]);
// Builds:
//
// match ::core::cmp::PartialOrd::partial_cmp(&self.x, &other.x) {
// ::core::option::Option::Some(::core::cmp::Ordering::Equal) =>
// ::core::cmp::PartialOrd::partial_cmp(&self.y, &other.y),
// cmp => cmp,
// }
let expr = cs_fold(
// foldr nests the if-elses correctly, leaving the first field
// as the outermost one, and the last as the innermost.
false,
cx,
span,
substr,
|cx, fold| match fold {
CsFold::Single(field) => {
let [other_expr] = &field.other_selflike_exprs[..] else {
cx.span_bug(field.span, "not exactly 2 arguments in `derive(Ord)`");
};
let args = vec![field.self_expr.clone(), other_expr.clone()];
cx.expr_call_global(field.span, partial_cmp_path.clone(), args)
}
CsFold::Combine(span, expr1, expr2) => {
let eq_arm =
cx.arm(span, cx.pat_some(span, cx.pat_path(span, equal_path.clone())), expr1);
let neq_arm =
cx.arm(span, cx.pat_ident(span, test_id), cx.expr_ident(span, test_id));
cx.expr_match(span, expr2, vec![eq_arm, neq_arm])
}
CsFold::Fieldless => cx.expr_some(span, cx.expr_path(equal_path.clone())),
},
);
BlockOrExpr::new_expr(expr)
}
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