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use crate::deriving::generic::ty::*;
use crate::deriving::generic::*;
use crate::deriving::{path_std, pathvec_std};
use rustc_ast::{MetaItem, Mutability};
use rustc_expand::base::{Annotatable, ExtCtxt};
use rustc_span::symbol::sym;
use rustc_span::Span;
pub fn expand_deriving_hash(
cx: &mut ExtCtxt<'_>,
span: Span,
mitem: &MetaItem,
item: &Annotatable,
push: &mut dyn FnMut(Annotatable),
) {
let path = Path::new_(pathvec_std!(hash::Hash), vec![], PathKind::Std);
let typaram = sym::__H;
let arg = Path::new_local(typaram);
let hash_trait_def = TraitDef {
span,
attributes: Vec::new(),
path,
additional_bounds: Vec::new(),
generics: Bounds::empty(),
supports_unions: false,
methods: vec![MethodDef {
name: sym::hash,
generics: Bounds { bounds: vec![(typaram, vec![path_std!(hash::Hasher)])] },
explicit_self: true,
nonself_args: vec![(Ref(Box::new(Path(arg)), Mutability::Mut), sym::state)],
ret_ty: Unit,
attributes: vec![],
unify_fieldless_variants: true,
combine_substructure: combine_substructure(Box::new(|a, b, c| {
hash_substructure(a, b, c)
})),
}],
associated_types: Vec::new(),
};
hash_trait_def.expand(cx, mitem, item, push);
}
fn hash_substructure(
cx: &mut ExtCtxt<'_>,
trait_span: Span,
substr: &Substructure<'_>,
) -> BlockOrExpr {
let [state_expr] = substr.nonselflike_args else {
cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`");
};
let call_hash = |span, expr| {
let hash_path = {
let strs = cx.std_path(&[sym::hash, sym::Hash, sym::hash]);
cx.expr_path(cx.path_global(span, strs))
};
let expr = cx.expr_call(span, hash_path, vec![expr, state_expr.clone()]);
cx.stmt_expr(expr)
};
let (stmts, match_expr) = match substr.fields {
Struct(_, fields) | EnumMatching(.., fields) => {
let stmts =
fields.iter().map(|field| call_hash(field.span, field.self_expr.clone())).collect();
(stmts, None)
}
EnumTag(tag_field, match_expr) => {
assert!(tag_field.other_selflike_exprs.is_empty());
let stmts = vec![call_hash(tag_field.span, tag_field.self_expr.clone())];
(stmts, match_expr.clone())
}
_ => cx.span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
};
BlockOrExpr::new_mixed(stmts, match_expr)
}
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