rustc_builtin_macros/
define_opaque.rs

1use rustc_ast::{DUMMY_NODE_ID, ast};
2use rustc_expand::base::{Annotatable, ExtCtxt};
3use rustc_span::Span;
4
5pub(crate) fn expand(
6    ecx: &mut ExtCtxt<'_>,
7    _expand_span: Span,
8    meta_item: &ast::MetaItem,
9    mut item: Annotatable,
10) -> Vec<Annotatable> {
11    let define_opaque = match &mut item {
12        Annotatable::Item(p) => match &mut p.kind {
13            ast::ItemKind::Fn(f) => Some(&mut f.define_opaque),
14            _ => None,
15        },
16        Annotatable::AssocItem(i, _assoc_ctxt) => match &mut i.kind {
17            ast::AssocItemKind::Fn(func) => Some(&mut func.define_opaque),
18            _ => None,
19        },
20        Annotatable::Stmt(s) => match &mut s.kind {
21            ast::StmtKind::Item(p) => match &mut p.kind {
22                ast::ItemKind::Fn(f) => Some(&mut f.define_opaque),
23                _ => None,
24            },
25            _ => None,
26        },
27        _ => None,
28    };
29
30    let Some(list) = meta_item.meta_item_list() else {
31        ecx.dcx().span_err(meta_item.span, "expected list of type aliases");
32        return vec![item];
33    };
34
35    if let Some(define_opaque) = define_opaque {
36        *define_opaque = Some(
37            list.iter()
38                .filter_map(|entry| match entry {
39                    ast::MetaItemInner::MetaItem(meta_item) if meta_item.is_word() => {
40                        Some((DUMMY_NODE_ID, meta_item.path.clone()))
41                    }
42                    _ => {
43                        ecx.dcx().span_err(entry.span(), "expected path to type alias");
44                        None
45                    }
46                })
47                .collect(),
48        );
49    } else {
50        ecx.dcx().span_err(meta_item.span, "only functions and methods can define opaque types");
51    }
52
53    vec![item]
54}
rustc_builtin_macros/define_opaque.rs

rustc_builtin_macros/
define_opaque.rs
