rustc_attr_parsing/attributes/
cfg.rs

1use std::convert::identity;
2
3use rustc_ast::token::Delimiter;
4use rustc_ast::tokenstream::DelimSpan;
5use rustc_ast::{AttrItem, Attribute, LitKind, ast, token};
6use rustc_errors::{Applicability, Diagnostic, PResult, msg};
7use rustc_feature::{
8    AttrSuggestionStyle, AttributeTemplate, Features, GatedCfg, find_gated_cfg, template,
9};
10use rustc_hir::attrs::CfgEntry;
11use rustc_hir::{AttrPath, RustcVersion, Target};
12use rustc_parse::parser::{ForceCollect, Parser, Recovery};
13use rustc_parse::{exp, parse_in};
14use rustc_session::Session;
15use rustc_session::config::ExpectedValues;
16use rustc_session::lint::builtin::UNEXPECTED_CFGS;
17use rustc_session::parse::{ParseSess, feature_err};
18use rustc_span::{ErrorGuaranteed, Span, Symbol, sym};
19use thin_vec::ThinVec;
20
21use crate::attributes::AttributeSafety;
22use crate::attributes::diagnostic::check_cfg;
23use crate::context::{AcceptContext, ShouldEmit};
24use crate::parser::{
25    AllowExprMetavar, ArgParser, MetaItemListParser, MetaItemOrLitParser, NameValueParser,
26};
27use crate::session_diagnostics::{
28    AttributeParseError, AttributeParseErrorReason, CfgAttrBadDelim, MetaBadDelimSugg,
29    ParsedDescription,
30};
31use crate::{AttributeParser, parse_version, session_diagnostics};
32
33pub const CFG_TEMPLATE: AttributeTemplate = ::rustc_feature::AttributeTemplate {
    word: false,
    list: Some(&["predicate"]),
    one_of: &[],
    name_value_str: None,
    docs: Some("https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute"),
}template!(
34    List: &["predicate"],
35    "https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute"
36);
37
38const CFG_ATTR_TEMPLATE: AttributeTemplate = ::rustc_feature::AttributeTemplate {
    word: false,
    list: Some(&["predicate, attr1, attr2, ..."]),
    one_of: &[],
    name_value_str: None,
    docs: Some("https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg_attr-attribute"),
}template!(
39    List: &["predicate, attr1, attr2, ..."],
40    "https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg_attr-attribute"
41);
42
43pub fn parse_cfg(cx: &mut AcceptContext<'_, '_>, args: &ArgParser) -> Option<CfgEntry> {
44    let list = cx.expect_list(args, cx.attr_span)?;
45
46    let Some(single) = list.as_single() else {
47        let target = cx.target;
48        let mut adcx = cx.adcx();
49        if list.is_empty() {
50            // `#[cfg()]`
51            let message = ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("if the {0} should be disabled, use `#[cfg(false)]`",
                target))
    })format!("if the {target} should be disabled, use `#[cfg(false)]`");
52            adcx.push_suggestion(message, list.span, "(false)".to_string());
53        } else {
54            // `#[cfg(foo, bar)]`
55            if let Ok(args) = adcx
56                .sess()
57                .source_map()
58                .span_to_source(list.span, |src, start, end| Ok(src[start..end].to_string()))
59            {
60                let all = ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("(all{0})", args))
    })format!("(all{args})");
61                let any = ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("(any{0})", args))
    })format!("(any{args})");
62
63                let all_msg = ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("if the {0} should be enabled when all these predicates are, wrap them in `all`",
                target))
    })format!(
64                    "if the {target} should be enabled when all these predicates are, wrap them in `all`"
65                );
66                let any_msg = ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("alternately, if the {0} should be enabled when any of these predicates are, wrap them in `any`",
                target))
    })format!(
67                    "alternately, if the {target} should be enabled when any of these predicates are, wrap them in `any`"
68                );
69
70                adcx.push_suggestion(all_msg, list.span, all);
71                adcx.push_suggestion(any_msg, list.span, any);
72            }
73        }
74
75        adcx.expected_single_argument(list.span, list.len());
76        return None;
77    };
78    parse_cfg_entry(cx, single).ok()
79}
80
81pub fn parse_cfg_entry(
82    cx: &mut AcceptContext<'_, '_>,
83    item: &MetaItemOrLitParser,
84) -> Result<CfgEntry, ErrorGuaranteed> {
85    Ok(match item {
86        MetaItemOrLitParser::MetaItemParser(meta) => match meta.args() {
87            ArgParser::List(list) => match meta.path().word_sym() {
88                Some(sym::not) => {
89                    let Some(single) = list.as_single() else {
90                        return Err(cx.adcx().expected_single_argument(list.span, list.len()));
91                    };
92                    CfgEntry::Not(Box::new(parse_cfg_entry(cx, single)?), list.span)
93                }
94                Some(sym::any) => CfgEntry::Any(
95                    list.mixed().flat_map(|sub_item| parse_cfg_entry(cx, sub_item)).collect(),
96                    list.span,
97                ),
98                Some(sym::all) => CfgEntry::All(
99                    list.mixed().flat_map(|sub_item| parse_cfg_entry(cx, sub_item)).collect(),
100                    list.span,
101                ),
102                Some(sym::target) => parse_cfg_entry_target(cx, list, meta.span())?,
103                Some(sym::version) => parse_cfg_entry_version(cx, list, meta.span())?,
104                _ => {
105                    return Err(cx.emit_err(session_diagnostics::InvalidPredicate {
106                        span: meta.span(),
107                        predicate: meta.path().to_string(),
108                    }));
109                }
110            },
111            a @ (ArgParser::NoArgs | ArgParser::NameValue(_)) => {
112                let Some(name) = meta.path().word_sym().filter(|s| !s.is_path_segment_keyword())
113                else {
114                    return Err(cx.adcx().expected_identifier(meta.path().span()));
115                };
116                parse_name_value(name, meta.path().span(), a.as_name_value(), meta.span(), cx)?
117            }
118        },
119        MetaItemOrLitParser::Lit(lit) => match lit.kind {
120            LitKind::Bool(b) => CfgEntry::Bool(b, lit.span),
121            _ => return Err(cx.adcx().expected_identifier(lit.span)),
122        },
123    })
124}
125
126fn parse_cfg_entry_version(
127    cx: &mut AcceptContext<'_, '_>,
128    list: &MetaItemListParser,
129    meta_span: Span,
130) -> Result<CfgEntry, ErrorGuaranteed> {
131    try_gate_cfg(sym::version, meta_span, cx.sess(), cx.features_option());
132    let Some(version) = list.as_single() else {
133        return Err(
134            cx.emit_err(session_diagnostics::ExpectedSingleVersionLiteral { span: list.span })
135        );
136    };
137    let Some(version_lit) = version.lit() else {
138        return Err(
139            cx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: version.span() })
140        );
141    };
142    let Some(version_str) = version_lit.value_str() else {
143        return Err(
144            cx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: version_lit.span })
145        );
146    };
147
148    let min_version = parse_version(version_str).or_else(|| {
149        cx.sess()
150            .dcx()
151            .emit_warn(session_diagnostics::UnknownVersionLiteral { span: version_lit.span });
152        None
153    });
154
155    Ok(CfgEntry::Version(min_version, list.span))
156}
157
158fn parse_cfg_entry_target(
159    cx: &mut AcceptContext<'_, '_>,
160    list: &MetaItemListParser,
161    meta_span: Span,
162) -> Result<CfgEntry, ErrorGuaranteed> {
163    if let Some(features) = cx.features_option()
164        && !features.cfg_target_compact()
165    {
166        feature_err(
167            cx.sess(),
168            sym::cfg_target_compact,
169            meta_span,
170            rustc_errors::DiagMessage::Inline(std::borrow::Cow::Borrowed("compact `cfg(target(..))` is experimental and subject to change"))msg!("compact `cfg(target(..))` is experimental and subject to change"),
171        )
172        .emit();
173    }
174
175    let mut result = ThinVec::new();
176    for sub_item in list.mixed() {
177        // First, validate that this is a NameValue item
178        let Some((name, value)) = cx.expect_name_value(sub_item, sub_item.span(), None) else {
179            continue;
180        };
181
182        // Then, parse it as a name-value item
183        if name.is_path_segment_keyword() {
184            return Err(cx.adcx().expected_identifier(name.span));
185        }
186        let name = Symbol::intern(&::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("target_{0}", name))
    })format!("target_{name}"));
187        if let Ok(cfg) = parse_name_value(name, sub_item.span(), Some(value), sub_item.span(), cx) {
188            result.push(cfg);
189        }
190    }
191    Ok(CfgEntry::All(result, list.span))
192}
193
194pub(crate) fn parse_name_value(
195    name: Symbol,
196    name_span: Span,
197    value: Option<&NameValueParser>,
198    span: Span,
199    cx: &mut AcceptContext<'_, '_>,
200) -> Result<CfgEntry, ErrorGuaranteed> {
201    try_gate_cfg(name, span, cx.sess(), cx.features_option());
202
203    let value = match value {
204        None => None,
205        Some(value) => {
206            let Some(value_str) = value.value_as_str() else {
207                return Err(cx
208                    .adcx()
209                    .expected_string_literal(value.value_span, Some(value.value_as_lit())));
210            };
211            Some((value_str, value.value_span))
212        }
213    };
214
215    match cx.sess.check_config.expecteds.get(&name) {
216        Some(ExpectedValues::Some(values)) if !values.contains(&value.map(|(v, _)| v)) => cx
217            .emit_lint_with_sess(
218                UNEXPECTED_CFGS,
219                move |dcx, level, sess| {
220                    check_cfg::unexpected_cfg_value(sess, (name, name_span), value)
221                        .into_diag(dcx, level)
222                },
223                span,
224            ),
225        None if cx.sess.check_config.exhaustive_names => cx.emit_lint_with_sess(
226            UNEXPECTED_CFGS,
227            move |dcx, level, sess| {
228                check_cfg::unexpected_cfg_name(sess, (name, name_span), value).into_diag(dcx, level)
229            },
230            span,
231        ),
232        _ => { /* not unexpected */ }
233    }
234
235    Ok(CfgEntry::NameValue { name, value: value.map(|(v, _)| v), span })
236}
237
238pub fn eval_config_entry(sess: &Session, cfg_entry: &CfgEntry) -> EvalConfigResult {
239    match cfg_entry {
240        CfgEntry::All(subs, ..) => {
241            for sub in subs {
242                let res = eval_config_entry(sess, sub);
243                if !res.as_bool() {
244                    return res;
245                }
246            }
247            EvalConfigResult::True
248        }
249        CfgEntry::Any(subs, span) => {
250            for sub in subs {
251                let res = eval_config_entry(sess, sub);
252                if res.as_bool() {
253                    return res;
254                }
255            }
256            EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *span }
257        }
258        CfgEntry::Not(sub, span) => {
259            if eval_config_entry(sess, sub).as_bool() {
260                EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *span }
261            } else {
262                EvalConfigResult::True
263            }
264        }
265        CfgEntry::Bool(b, span) => {
266            if *b {
267                EvalConfigResult::True
268            } else {
269                EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *span }
270            }
271        }
272        CfgEntry::NameValue { name, value, span } => {
273            if sess.config.contains(&(*name, *value)) {
274                EvalConfigResult::True
275            } else {
276                EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *span }
277            }
278        }
279        CfgEntry::Version(min_version, version_span) => {
280            let Some(min_version) = min_version else {
281                return EvalConfigResult::False {
282                    reason: cfg_entry.clone(),
283                    reason_span: *version_span,
284                };
285            };
286            // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
287            let min_version_ok = if sess.opts.unstable_opts.assume_incomplete_release {
288                RustcVersion::current_overridable() > *min_version
289            } else {
290                RustcVersion::current_overridable() >= *min_version
291            };
292            if min_version_ok {
293                EvalConfigResult::True
294            } else {
295                EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *version_span }
296            }
297        }
298    }
299}
300
301pub enum EvalConfigResult {
302    True,
303    False { reason: CfgEntry, reason_span: Span },
304}
305
306impl EvalConfigResult {
307    pub fn as_bool(&self) -> bool {
308        match self {
309            EvalConfigResult::True => true,
310            EvalConfigResult::False { .. } => false,
311        }
312    }
313}
314
315pub fn parse_cfg_attr(
316    cfg_attr: &Attribute,
317    sess: &Session,
318    features: Option<&Features>,
319    lint_node_id: ast::NodeId,
320) -> Option<(CfgEntry, Vec<(AttrItem, Span)>)> {
321    match cfg_attr.get_normal_item().args.unparsed_ref().unwrap() {
322        ast::AttrArgs::Delimited(ast::DelimArgs { dspan, delim, tokens }) if !tokens.is_empty() => {
323            check_cfg_attr_bad_delim(&sess.psess, *dspan, *delim);
324            match parse_in(&sess.psess, tokens.clone(), "`cfg_attr` input", |p| {
325                parse_cfg_attr_internal(p, sess, features, lint_node_id, cfg_attr)
326            }) {
327                Ok(r) => return Some(r),
328                Err(e) => {
329                    let suggestions = CFG_ATTR_TEMPLATE
330                        .suggestions(AttrSuggestionStyle::Attribute(cfg_attr.style), sym::cfg_attr);
331                    e.with_span_suggestions(
332                        cfg_attr.span,
333                        "must be of the form",
334                        suggestions,
335                        Applicability::HasPlaceholders,
336                    )
337                    .with_note(::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("for more information, visit <{0}>",
                CFG_ATTR_TEMPLATE.docs.expect("cfg_attr has docs")))
    })format!(
338                        "for more information, visit <{}>",
339                        CFG_ATTR_TEMPLATE.docs.expect("cfg_attr has docs")
340                    ))
341                    .emit();
342                }
343            }
344        }
345        _ => {
346            let (span, reason) = if let ast::AttrArgs::Delimited(ast::DelimArgs { dspan, .. }) =
347                cfg_attr.get_normal_item().args.unparsed_ref()?
348            {
349                (dspan.entire(), AttributeParseErrorReason::ExpectedAtLeastOneArgument)
350            } else {
351                (cfg_attr.span, AttributeParseErrorReason::ExpectedList)
352            };
353
354            sess.dcx().emit_err(AttributeParseError {
355                span,
356                attr_span: cfg_attr.span,
357                template: CFG_ATTR_TEMPLATE,
358                path: AttrPath::from_ast(&cfg_attr.get_normal_item().path, identity),
359                description: ParsedDescription::Attribute,
360                reason,
361                suggestions: session_diagnostics::AttributeParseErrorSuggestions::CreatedByTemplate(
362                    CFG_ATTR_TEMPLATE
363                        .suggestions(AttrSuggestionStyle::Attribute(cfg_attr.style), sym::cfg_attr),
364                ),
365            });
366        }
367    }
368    None
369}
370
371fn check_cfg_attr_bad_delim(psess: &ParseSess, span: DelimSpan, delim: Delimiter) {
372    if let Delimiter::Parenthesis = delim {
373        return;
374    }
375    psess.dcx().emit_err(CfgAttrBadDelim {
376        span: span.entire(),
377        sugg: MetaBadDelimSugg { open: span.open, close: span.close },
378    });
379}
380
381/// Parses `cfg_attr(pred, attr_item_list)` where `attr_item_list` is comma-delimited.
382fn parse_cfg_attr_internal<'a>(
383    parser: &mut Parser<'a>,
384    sess: &'a Session,
385    features: Option<&Features>,
386    lint_node_id: ast::NodeId,
387    attribute: &Attribute,
388) -> PResult<'a, (CfgEntry, Vec<(ast::AttrItem, Span)>)> {
389    // Parse cfg predicate
390    let pred_start = parser.token.span;
391    let meta = MetaItemOrLitParser::parse_single(
392        parser,
393        ShouldEmit::ErrorsAndLints { recovery: Recovery::Allowed },
394        AllowExprMetavar::Yes,
395    )?;
396    let pred_span = pred_start.with_hi(parser.token.span.hi());
397
398    let cfg_predicate = AttributeParser::parse_single_args(
399        sess,
400        attribute.span,
401        attribute.get_normal_item().span(),
402        attribute.style,
403        AttrPath { segments: attribute.path().into_boxed_slice(), span: attribute.span },
404        Some(attribute.get_normal_item().unsafety),
405        AttributeSafety::Normal,
406        ParsedDescription::Attribute,
407        pred_span,
408        lint_node_id,
409        Target::Crate,
410        features,
411        ShouldEmit::ErrorsAndLints { recovery: Recovery::Allowed },
412        &meta,
413        parse_cfg_entry,
414        &CFG_ATTR_TEMPLATE,
415    )
416    .map_err(|_err: ErrorGuaranteed| {
417        // We have an `ErrorGuaranteed` so this delayed bug cannot fail, but we need a `Diag` for the `PResult` so we make one anyways
418        let mut diag = sess.dcx().struct_err(
419            "cfg_entry parsing failing with `ShouldEmit::ErrorsAndLints` should emit a error.",
420        );
421        diag.downgrade_to_delayed_bug();
422        diag
423    })?;
424
425    parser.expect(::rustc_parse::parser::token_type::ExpTokenPair {
    tok: rustc_ast::token::Comma,
    token_type: ::rustc_parse::parser::token_type::TokenType::Comma,
}exp!(Comma))?;
426
427    // Presumably, the majority of the time there will only be one attr.
428    let mut expanded_attrs = Vec::with_capacity(1);
429    while parser.token != token::Eof {
430        let lo = parser.token.span;
431        let item = parser.parse_attr_item(ForceCollect::Yes)?;
432        expanded_attrs.push((item, lo.to(parser.prev_token.span)));
433        if !parser.eat(::rustc_parse::parser::token_type::ExpTokenPair {
    tok: rustc_ast::token::Comma,
    token_type: ::rustc_parse::parser::token_type::TokenType::Comma,
}exp!(Comma)) {
434            break;
435        }
436    }
437
438    Ok((cfg_predicate, expanded_attrs))
439}
440
441fn try_gate_cfg(name: Symbol, span: Span, sess: &Session, features: Option<&Features>) {
442    let gate = find_gated_cfg(|sym| sym == name);
443    if let (Some(feats), Some(gated_cfg)) = (features, gate) {
444        gate_cfg(gated_cfg, span, sess, feats);
445    }
446}
447
448fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &Session, features: &Features) {
449    let (cfg, feature, has_feature) = gated_cfg;
450    if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
451        let explain = ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("`cfg({0})` is experimental and subject to change",
                cfg))
    })format!("`cfg({cfg})` is experimental and subject to change");
452        feature_err(sess, *feature, cfg_span, explain).emit();
453    }
454}
rustc_attr_parsing/attributes/cfg.rs

rustc_attr_parsing/attributes/
cfg.rs
