rustc_macros/
type_visitable.rs

1use quote::quote;
2use syn::parse_quote;
3
4pub(super) fn type_visitable_derive(
5    mut s: synstructure::Structure<'_>,
6) -> proc_macro2::TokenStream {
7    if let syn::Data::Union(_) = s.ast().data {
8        panic!("cannot derive on union")
9    }
10
11    // ignore fields with #[type_visitable(ignore)]
12    s.filter(|bi| {
13        let mut ignored = false;
14
15        bi.ast().attrs.iter().for_each(|attr| {
16            if !attr.path().is_ident("type_visitable") {
17                return;
18            }
19            let _ = attr.parse_nested_meta(|nested| {
20                if nested.path.is_ident("ignore") {
21                    ignored = true;
22                }
23                Ok(())
24            });
25        });
26
27        !ignored
28    });
29
30    if !s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
31        s.add_impl_generic(parse_quote! { 'tcx });
32    }
33
34    s.add_bounds(synstructure::AddBounds::Generics);
35    let body_visit = s.each(|bind| {
36        quote! {
37            match ::rustc_middle::ty::VisitorResult::branch(
38                ::rustc_middle::ty::TypeVisitable::visit_with(#bind, __visitor)
39            ) {
40                ::core::ops::ControlFlow::Continue(()) => {},
41                ::core::ops::ControlFlow::Break(r) => {
42                    return ::rustc_middle::ty::VisitorResult::from_residual(r);
43                },
44            }
45        }
46    });
47    s.bind_with(|_| synstructure::BindStyle::Move);
48
49    s.bound_impl(
50        quote!(::rustc_middle::ty::TypeVisitable<::rustc_middle::ty::TyCtxt<'tcx>>),
51        quote! {
52            fn visit_with<__V: ::rustc_middle::ty::TypeVisitor<::rustc_middle::ty::TyCtxt<'tcx>>>(
53                &self,
54                __visitor: &mut __V
55            ) -> __V::Result {
56                match *self { #body_visit }
57                <__V::Result as ::rustc_middle::ty::VisitorResult>::output()
58            }
59        },
60    )
61}
rustc_macros/type_visitable.rs

rustc_macros/
type_visitable.rs
