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) => {
25                    let Some(value_str) = name_value.value_as_str() else {
26                        cx.expected_string_literal(
27                            name_value.value_span,
28                            Some(&name_value.value_as_lit()),
29                        );
30                        return None;
31                    };
32                    Some(value_str)
33                }
34                ArgParser::List(_) => {
35                    let suggestions =
36                        <Self as SingleAttributeParser<S>>::TEMPLATE.suggestions(false, "must_use");
37                    cx.emit_err(session_diagnostics::MustUseIllFormedAttributeInput {
38                        num_suggestions: suggestions.len(),
39                        suggestions: DiagArgValue::StrListSepByAnd(
40                            suggestions.into_iter().map(|s| format!("`{s}`").into()).collect(),
41                        ),
42                        span: cx.attr_span,
43                    });
44                    return None;
45                }
46            },
47        })
48    }
49}
rustc_attr_parsing/attributes/must_use.rs

rustc_attr_parsing/attributes/
must_use.rs
