rustc_attr_parsing/attributes/
must_use.rs

1use rustc_attr_data_structures::AttributeKind;
2use rustc_errors::DiagArgValue;
3use rustc_feature::{AttributeTemplate, template};
4use rustc_span::{Symbol, sym};
5
6use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
7use crate::context::{AcceptContext, Stage};
8use crate::parser::ArgParser;
9use crate::session_diagnostics;
10
11pub(crate) struct MustUseParser;
12
13impl<S: Stage> SingleAttributeParser<S> for MustUseParser {
14    const PATH: &[Symbol] = &[sym::must_use];
15    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepLast;
16    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
17    const TEMPLATE: AttributeTemplate = template!(Word, NameValueStr: "reason");
18
19    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
20        Some(AttributeKind::MustUse {
21            span: cx.attr_span,
22            reason: match args {
23                ArgParser::NoArgs => None,
24                ArgParser::NameValue(name_value) => name_value.value_as_str(),
25                ArgParser::List(_) => {
26                    let suggestions =
27                        <Self as SingleAttributeParser<S>>::TEMPLATE.suggestions(false, "must_use");
28                    cx.emit_err(session_diagnostics::MustUseIllFormedAttributeInput {
29                        num_suggestions: suggestions.len(),
30                        suggestions: DiagArgValue::StrListSepByAnd(
31                            suggestions.into_iter().map(|s| format!("`{s}`").into()).collect(),
32                        ),
33                        span: cx.attr_span,
34                    });
35                    return None;
36                }
37            },
38        })
39    }
40}
rustc_attr_parsing/attributes/must_use.rs

rustc_attr_parsing/attributes/
must_use.rs
