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//! Implementation of the `#[cfg_accessible(path)]` attribute macro.
use rustc_ast as ast;
use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier};
use rustc_feature::AttributeTemplate;
use rustc_parse::validate_attr;
use rustc_span::symbol::sym;
use rustc_span::Span;
pub(crate) struct Expander;
fn validate_input<'a>(ecx: &mut ExtCtxt<'_>, mi: &'a ast::MetaItem) -> Option<&'a ast::Path> {
match mi.meta_item_list() {
None => {}
Some([]) => ecx.span_err(mi.span, "`cfg_accessible` path is not specified"),
Some([_, .., l]) => ecx.span_err(l.span(), "multiple `cfg_accessible` paths are specified"),
Some([nmi]) => match nmi.meta_item() {
None => ecx.span_err(nmi.span(), "`cfg_accessible` path cannot be a literal"),
Some(mi) => {
if !mi.is_word() {
ecx.span_err(mi.span, "`cfg_accessible` path cannot accept arguments");
}
return Some(&mi.path);
}
},
}
None
}
impl MultiItemModifier for Expander {
fn expand(
&self,
ecx: &mut ExtCtxt<'_>,
span: Span,
meta_item: &ast::MetaItem,
item: Annotatable,
_is_derive_const: bool,
) -> ExpandResult<Vec<Annotatable>, Annotatable> {
let template = AttributeTemplate { list: Some("path"), ..Default::default() };
validate_attr::check_builtin_meta_item(
&ecx.sess.parse_sess,
&meta_item,
ast::AttrStyle::Outer,
sym::cfg_accessible,
template,
);
let Some(path) = validate_input(ecx, meta_item) else {
return ExpandResult::Ready(Vec::new());
};
match ecx.resolver.cfg_accessible(ecx.current_expansion.id, path) {
Ok(true) => ExpandResult::Ready(vec![item]),
Ok(false) => ExpandResult::Ready(Vec::new()),
Err(Indeterminate) if ecx.force_mode => {
ecx.span_err(span, "cannot determine whether the path is accessible or not");
ExpandResult::Ready(vec![item])
}
Err(Indeterminate) => ExpandResult::Retry(item),
}
}
}
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