rustc_attr_parsing/attributes/diagnostic/
on_const.rs

1use rustc_feature::AttributeStability;
2use rustc_hir::attrs::diagnostic::Directive;
3use rustc_session::lint::builtin::MISPLACED_DIAGNOSTIC_ATTRIBUTES;
4
5use crate::attributes::diagnostic::*;
6use crate::attributes::prelude::*;
7use crate::errors::DiagnosticOnConstOnlyForTraitImpls;
8#[derive(#[automatically_derived]
impl ::core::default::Default for OnConstParser {
    #[inline]
    fn default() -> OnConstParser {
        OnConstParser {
            span: ::core::default::Default::default(),
            directive: ::core::default::Default::default(),
        }
    }
}Default)]
9pub(crate) struct OnConstParser {
10    span: Option<Span>,
11    directive: Option<(Span, Directive)>,
12}
13
14impl AttributeParser for OnConstParser {
15    const ATTRIBUTES: AcceptMapping<Self> = &[(
16        &[sym::diagnostic, sym::on_const],
17        ::rustc_feature::AttributeTemplate {
    word: false,
    list: Some(&[r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#]),
    one_of: &[],
    name_value_str: None,
    docs: None,
}template!(List: &[r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#]),
18        AttributeStability::Stable, // Unstable, stability checked manually in the parser
19        |this, cx, args| {
20            if !cx.features().diagnostic_on_const() {
21                // `UnknownDiagnosticAttribute` is emitted in rustc_resolve/macros.rs
22                args.ignore_args();
23                return;
24            }
25
26            let span = cx.attr_span;
27            this.span = Some(span);
28
29            // FIXME(mejrs) no constness field on `Target`,
30            // so non-constness is still checked in check_attr.rs
31            if !#[allow(non_exhaustive_omitted_patterns)] match cx.target {
    Target::Impl { of_trait: true } => true,
    _ => false,
}matches!(cx.target, Target::Impl { of_trait: true }) {
32                let target_span = cx.target_span;
33                cx.emit_lint(
34                    MISPLACED_DIAGNOSTIC_ATTRIBUTES,
35                    DiagnosticOnConstOnlyForTraitImpls { target_span },
36                    span,
37                );
38                return;
39            }
40
41            let mode = Mode::DiagnosticOnConst;
42
43            let Some(items) = parse_list(cx, args, mode) else { return };
44
45            let Some(directive) = parse_directive_items(cx, mode, items.mixed(), true) else {
46                return;
47            };
48            merge_directives(cx, &mut this.directive, (span, directive));
49        },
50    )];
51
52    // "Allowed" on all targets; noop on anything but non-const trait impls;
53    // this linted on in parser.
54    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
55
56    fn finalize(self, _cx: &FinalizeContext<'_, '_>) -> Option<AttributeKind> {
57        if let Some(span) = self.span {
58            Some(AttributeKind::OnConst { span, directive: self.directive.map(|d| Box::new(d.1)) })
59        } else {
60            None
61        }
62    }
63}
rustc_attr_parsing/attributes/diagnostic/on_const.rs

rustc_attr_parsing/attributes/diagnostic/
on_const.rs
