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|
use crate::deriving::{self, pathvec_std, path_std};
use crate::deriving::generic::*;
use crate::deriving::generic::ty::*;
use syntax::ast::{Expr, MetaItem, Mutability};
use syntax_expand::base::{Annotatable, ExtCtxt};
use syntax::ptr::P;
use syntax::symbol::sym;
use syntax_pos::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!(cx, hash::Hash), None, vec![], PathKind::Std);
let typaram = "__H";
let arg = Path::new_local(typaram);
let hash_trait_def = TraitDef {
span,
attributes: Vec::new(),
path,
additional_bounds: Vec::new(),
generics: LifetimeBounds::empty(),
is_unsafe: false,
supports_unions: false,
methods: vec![MethodDef {
name: "hash",
generics: LifetimeBounds {
lifetimes: Vec::new(),
bounds: vec![(typaram, vec![path_std!(cx, hash::Hasher)])],
},
explicit_self: borrowed_explicit_self(),
args: vec![(Ptr(Box::new(Literal(arg)),
Borrowed(None, Mutability::Mutable)), "state")],
ret_ty: nil_ty(),
attributes: vec![],
is_unsafe: false,
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<'_>) -> P<Expr> {
let state_expr = match &substr.nonself_args {
&[o_f] => o_f,
_ => {
cx.span_bug(trait_span,
"incorrect number of arguments in `derive(Hash)`")
}
};
let call_hash = |span, thing_expr| {
let hash_path = {
let strs = cx.std_path(&[sym::hash, sym::Hash, sym::hash]);
cx.expr_path(cx.path_global(span, strs))
};
let ref_thing = cx.expr_addr_of(span, thing_expr);
let expr = cx.expr_call(span, hash_path, vec![ref_thing, state_expr.clone()]);
cx.stmt_expr(expr)
};
let mut stmts = Vec::new();
let fields = match *substr.fields {
Struct(_, ref fs) | EnumMatching(_, 1, .., ref fs) => fs,
EnumMatching(.., ref fs) => {
let variant_value = deriving::call_intrinsic(cx,
trait_span,
"discriminant_value",
vec![cx.expr_self(trait_span)]);
stmts.push(call_hash(trait_span, variant_value));
fs
}
_ => cx.span_bug(trait_span, "impossible substructure in `derive(Hash)`"),
};
stmts.extend(fields.iter().map(|FieldInfo { ref self_, span, .. }|
call_hash(*span, self_.clone())));
cx.expr_block(cx.block(trait_span, stmts))
}
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