rustc_attr_parsing/
interface.rs

1use std::convert::identity;
2
3use rustc_ast as ast;
4use rustc_ast::token::DocFragmentKind;
5use rustc_ast::{AttrItemKind, AttrStyle, CRATE_NODE_ID, NodeId, Safety};
6use rustc_data_structures::sync::{DynSend, DynSync};
7use rustc_errors::{Diag, DiagCtxtHandle, Diagnostic, Level, MultiSpan};
8use rustc_feature::{AttributeTemplate, Features};
9use rustc_hir::attrs::AttributeKind;
10use rustc_hir::{AttrArgs, AttrItem, AttrPath, Attribute, HashIgnoredAttrId, Target};
11use rustc_lint_defs::RegisteredTools;
12use rustc_session::Session;
13use rustc_session::lint::LintId;
14use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
15
16use crate::attributes::AttributeSafety;
17use crate::context::{
18    ATTRIBUTE_PARSERS, AcceptContext, FinalizeContext, FinalizeFn, SharedContext,
19};
20use crate::early_parsed::{EARLY_PARSED_ATTRIBUTES, EarlyParsedState};
21use crate::parser::{AllowExprMetavar, ArgParser, PathParser, RefPathParser};
22use crate::session_diagnostics::ParsedDescription;
23use crate::{OmitDoc, ShouldEmit};
24
25pub struct EmitAttribute(
26    pub  Box<
27        dyn for<'a> FnOnce(DiagCtxtHandle<'a>, Level, &Session) -> Diag<'a, ()>
28            + DynSend
29            + DynSync
30            + 'static,
31    >,
32);
33
34/// Context created once, for example as part of the ast lowering
35/// context, through which all attributes can be lowered.
36pub struct AttributeParser<'sess> {
37    pub(crate) tools: Option<&'sess RegisteredTools>,
38    pub(crate) features: Option<&'sess Features>,
39    pub(crate) sess: &'sess Session,
40    pub(crate) should_emit: ShouldEmit,
41
42    /// *Only* parse attributes with this symbol.
43    ///
44    /// Used in cases where we want the lowering infrastructure for parse just a single attribute.
45    parse_only: Option<&'static [Symbol]>,
46}
47
48impl<'sess> AttributeParser<'sess> {
49    /// This method allows you to parse attributes *before* you have access to features or tools.
50    /// One example where this is necessary, is to parse `feature` attributes themselves for
51    /// example.
52    ///
53    /// Try to use this as little as possible. Attributes *should* be lowered during
54    /// `rustc_ast_lowering`. Some attributes require access to features to parse, which would
55    /// crash if you tried to do so through [`parse_limited`](Self::parse_limited).
56    ///
57    /// To make sure use is limited, supply a `Symbol` you'd like to parse. Only attributes with
58    /// that symbol are picked out of the list of instructions and parsed. Those are returned.
59    ///
60    /// No diagnostics will be emitted when parsing limited. Lints are not emitted at all, while
61    /// errors will be emitted as a delayed bugs. in other words, we *expect* attributes parsed
62    /// with `parse_limited` to be reparsed later during ast lowering where we *do* emit the errors
63    ///
64    /// Due to this function not taking in RegisteredTools, *do not* use this for parsing any lint attributes
65    pub fn parse_limited(
66        sess: &'sess Session,
67        attrs: &[ast::Attribute],
68        sym: &'static [Symbol],
69    ) -> Option<Attribute> {
70        Self::parse_limited_should_emit(
71            sess,
72            attrs,
73            sym,
74            // Because we're not emitting warnings/errors, the target should not matter
75            DUMMY_SP,
76            CRATE_NODE_ID,
77            Target::Crate,
78            None,
79            ShouldEmit::Nothing,
80        )
81    }
82
83    /// This does the same as `parse_limited`, except it has a `should_emit` parameter which allows it to emit errors.
84    /// Usually you want `parse_limited`, which emits no errors.
85    ///
86    /// Due to this function not taking in RegisteredTools, *do not* use this for parsing any lint attributes
87    pub fn parse_limited_should_emit(
88        sess: &'sess Session,
89        attrs: &[ast::Attribute],
90        sym: &'static [Symbol],
91        target_span: Span,
92        target_node_id: NodeId,
93        target: Target,
94        features: Option<&'sess Features>,
95        should_emit: ShouldEmit,
96    ) -> Option<Attribute> {
97        let mut parsed = Self::parse_limited_all(
98            sess,
99            attrs,
100            Some(sym),
101            target,
102            target_span,
103            target_node_id,
104            features,
105            should_emit,
106            None,
107        );
108        if !(parsed.len() <= 1) {
    ::core::panicking::panic("assertion failed: parsed.len() <= 1")
};assert!(parsed.len() <= 1);
109        parsed.pop()
110    }
111
112    /// This method allows you to parse a list of attributes *before* `rustc_ast_lowering`.
113    /// This can be used for attributes that would be removed before `rustc_ast_lowering`, such as attributes on macro calls.
114    ///
115    /// Try to use this as little as possible. Attributes *should* be lowered during
116    /// `rustc_ast_lowering`. Some attributes require access to features to parse, which would
117    /// crash if you tried to do so through [`parse_limited_all`](Self::parse_limited_all).
118    /// Therefore, if `parse_only` is None, then features *must* be provided.
119    pub fn parse_limited_all(
120        sess: &'sess Session,
121        attrs: &[ast::Attribute],
122        parse_only: Option<&'static [Symbol]>,
123        target: Target,
124        target_span: Span,
125        target_node_id: NodeId,
126        features: Option<&'sess Features>,
127        should_emit: ShouldEmit,
128        tools: Option<&'sess RegisteredTools>,
129    ) -> Vec<Attribute> {
130        let mut p = Self { features, tools, parse_only, sess, should_emit };
131        p.parse_attribute_list(
132            attrs,
133            target_span,
134            target,
135            OmitDoc::Skip,
136            std::convert::identity,
137            |lint_id, span, kind| {
138                sess.psess.dyn_buffer_lint_sess(lint_id.lint, span, target_node_id, kind.0)
139            },
140        )
141    }
142
143    /// This method parses a single attribute, using `parse_fn`.
144    /// This is useful if you already know what exact attribute this is, and want to parse it.
145    pub fn parse_single<T>(
146        sess: &'sess Session,
147        attr: &ast::Attribute,
148        target_span: Span,
149        target_node_id: NodeId,
150        target: Target,
151        features: Option<&'sess Features>,
152        emit_errors: ShouldEmit,
153        parse_fn: fn(cx: &mut AcceptContext<'_, '_>, item: &ArgParser) -> Option<T>,
154        template: &AttributeTemplate,
155        allow_expr_metavar: AllowExprMetavar,
156        expected_safety: AttributeSafety,
157    ) -> Option<T> {
158        let ast::AttrKind::Normal(normal_attr) = &attr.kind else {
159            {
    ::core::panicking::panic_fmt(format_args!("parse_single called on a doc attr"));
}panic!("parse_single called on a doc attr")
160        };
161        let parts =
162            normal_attr.item.path.segments.iter().map(|seg| seg.ident.name).collect::<Vec<_>>();
163
164        let path = AttrPath::from_ast(&normal_attr.item.path, identity);
165        let args = ArgParser::from_attr_args(
166            &normal_attr.item.args.unparsed_ref().unwrap(),
167            &parts,
168            &sess.psess,
169            emit_errors,
170            allow_expr_metavar,
171        )?;
172        Self::parse_single_args(
173            sess,
174            attr.span,
175            normal_attr.item.span(),
176            attr.style,
177            path,
178            Some(normal_attr.item.unsafety),
179            expected_safety,
180            ParsedDescription::Attribute,
181            target_span,
182            target_node_id,
183            target,
184            features,
185            emit_errors,
186            &args,
187            parse_fn,
188            template,
189        )
190    }
191
192    /// This method is equivalent to `parse_single`, but parses arguments using `parse_fn` using manually created `args`.
193    /// This is useful when you want to parse other things than attributes using attribute parsers.
194    pub fn parse_single_args<T, I>(
195        sess: &'sess Session,
196        attr_span: Span,
197        inner_span: Span,
198        attr_style: AttrStyle,
199        attr_path: AttrPath,
200        attr_safety: Option<Safety>,
201        expected_safety: AttributeSafety,
202        parsed_description: ParsedDescription,
203        target_span: Span,
204        target_node_id: NodeId,
205        target: Target,
206        features: Option<&'sess Features>,
207        should_emit: ShouldEmit,
208        args: &I,
209        parse_fn: fn(cx: &mut AcceptContext<'_, '_>, item: &I) -> T,
210        template: &AttributeTemplate,
211    ) -> T {
212        let mut parser = Self { features, tools: None, parse_only: None, sess, should_emit };
213        let mut emit_lint = |lint_id: LintId, span: MultiSpan, kind: EmitAttribute| {
214            sess.psess.dyn_buffer_lint_sess(lint_id.lint, span, target_node_id, kind.0)
215        };
216        if let Some(safety) = attr_safety {
217            parser.check_attribute_safety(
218                &attr_path,
219                inner_span,
220                safety,
221                expected_safety,
222                &mut emit_lint,
223            );
224        }
225        let mut cx: AcceptContext<'_, 'sess> = AcceptContext {
226            shared: SharedContext {
227                cx: &mut parser,
228                target_span,
229                target,
230                emit_lint: &mut emit_lint,
231            },
232            attr_span,
233            inner_span,
234            attr_style,
235            parsed_description,
236            template,
237            attr_path,
238        };
239        parse_fn(&mut cx, args)
240    }
241}
242
243impl<'sess> AttributeParser<'sess> {
244    pub fn new(
245        sess: &'sess Session,
246        features: &'sess Features,
247        tools: &'sess RegisteredTools,
248        should_emit: ShouldEmit,
249    ) -> Self {
250        Self { features: Some(features), tools: Some(tools), parse_only: None, sess, should_emit }
251    }
252
253    pub(crate) fn sess(&self) -> &'sess Session {
254        &self.sess
255    }
256
257    pub(crate) fn features(&self) -> &'sess Features {
258        self.features.expect("features not available at this point in the compiler")
259    }
260
261    pub(crate) fn features_option(&self) -> Option<&'sess Features> {
262        self.features
263    }
264
265    pub(crate) fn dcx(&self) -> DiagCtxtHandle<'sess> {
266        self.sess().dcx()
267    }
268
269    pub(crate) fn emit_err(&self, diag: impl for<'x> Diagnostic<'x>) -> ErrorGuaranteed {
270        self.should_emit.emit_err(self.sess.dcx().create_err(diag))
271    }
272
273    /// Parse a list of attributes.
274    ///
275    /// `target_span` is the span of the thing this list of attributes is applied to,
276    /// and when `omit_doc` is set, doc attributes are filtered out.
277    pub fn parse_attribute_list(
278        &mut self,
279        attrs: &[ast::Attribute],
280        target_span: Span,
281        target: Target,
282        omit_doc: OmitDoc,
283        lower_span: impl Copy + Fn(Span) -> Span,
284        mut emit_lint: impl FnMut(LintId, MultiSpan, EmitAttribute),
285    ) -> Vec<Attribute> {
286        let mut attributes = Vec::new();
287        // We store the attributes we intend to discard at the end of this function in order to
288        // check they are applied to the right target and error out if necessary. In practice, we
289        // end up dropping only derive attributes and derive helpers, both being fully processed
290        // at macro expansion.
291        let mut dropped_attributes = Vec::new();
292        let mut attr_paths: Vec<RefPathParser<'_>> = Vec::new();
293        let mut early_parsed_state = EarlyParsedState::default();
294
295        let mut finalizers: Vec<FinalizeFn> = Vec::with_capacity(attrs.len());
296
297        for attr in attrs {
298            // If we're only looking for a single attribute, skip all the ones we don't care about.
299            if let Some(expected) = self.parse_only {
300                if !attr.path_matches(expected) {
301                    continue;
302                }
303            }
304
305            // Sometimes, for example for `#![doc = include_str!("readme.md")]`,
306            // doc still contains a non-literal. You might say, when we're lowering attributes
307            // that's expanded right? But no, sometimes, when parsing attributes on macros,
308            // we already use the lowering logic and these are still there. So, when `omit_doc`
309            // is set we *also* want to ignore these.
310            let is_doc_attribute = attr.has_name(sym::doc);
311            if omit_doc == OmitDoc::Skip && is_doc_attribute {
312                continue;
313            }
314
315            let attr_span = lower_span(attr.span);
316            match &attr.kind {
317                ast::AttrKind::DocComment(comment_kind, symbol) => {
318                    if omit_doc == OmitDoc::Skip {
319                        continue;
320                    }
321
322                    attributes.push(Attribute::Parsed(AttributeKind::DocComment {
323                        style: attr.style,
324                        kind: DocFragmentKind::Sugared(*comment_kind),
325                        span: attr_span,
326                        comment: *symbol,
327                    }));
328                }
329                ast::AttrKind::Normal(n) => {
330                    attr_paths.push(PathParser(&n.item.path));
331                    let attr_path = AttrPath::from_ast(&n.item.path, lower_span);
332
333                    let args = match &n.item.args {
334                        AttrItemKind::Unparsed(args) => args,
335                        AttrItemKind::Parsed(parsed) => {
336                            early_parsed_state
337                                .accept_early_parsed_attribute(attr_span, lower_span, parsed);
338                            continue;
339                        }
340                    };
341
342                    let parts =
343                        n.item.path.segments.iter().map(|seg| seg.ident.name).collect::<Vec<_>>();
344
345                    if let Some(accept) = ATTRIBUTE_PARSERS.accepters.get(parts.as_slice()) {
346                        self.check_attribute_safety(
347                            &attr_path,
348                            lower_span(n.item.span()),
349                            n.item.unsafety,
350                            accept.safety,
351                            &mut emit_lint,
352                        );
353
354                        let Some(args) = ArgParser::from_attr_args(
355                            args,
356                            &parts,
357                            &self.sess.psess,
358                            self.should_emit,
359                            AllowExprMetavar::No,
360                        ) else {
361                            continue;
362                        };
363
364                        // Special-case handling for `#[doc = "..."]`: if we go through with
365                        // `DocParser`, the order of doc comments will be messed up because `///`
366                        // doc comments are added into `attributes` whereas attributes parsed with
367                        // `DocParser` are added into `parsed_attributes` which are then appended
368                        // to `attributes`. So if you have:
369                        //
370                        // /// bla
371                        // #[doc = "a"]
372                        // /// blob
373                        //
374                        // You would get:
375                        //
376                        // bla
377                        // blob
378                        // a
379                        if is_doc_attribute
380                            && let ArgParser::NameValue(nv) = &args
381                            // If not a string key/value, it should emit an error, but to make
382                            // things simpler, it's handled in `DocParser` because it's simpler to
383                            // emit an error with `AcceptContext`.
384                            && let Some(comment) = nv.value_as_str()
385                        {
386                            attributes.push(Attribute::Parsed(AttributeKind::DocComment {
387                                style: attr.style,
388                                kind: DocFragmentKind::Raw(nv.value_span),
389                                span: attr_span,
390                                comment,
391                            }));
392                            continue;
393                        }
394
395                        let mut cx: AcceptContext<'_, 'sess> = AcceptContext {
396                            shared: SharedContext {
397                                cx: self,
398                                target_span,
399                                target,
400                                emit_lint: &mut emit_lint,
401                            },
402                            attr_span,
403                            inner_span: lower_span(n.item.span()),
404                            attr_style: attr.style,
405                            parsed_description: ParsedDescription::Attribute,
406                            template: &accept.template,
407                            attr_path: attr_path.clone(),
408                        };
409
410                        (accept.accept_fn)(&mut cx, &args);
411                        finalizers.push(accept.finalizer);
412
413                        if !#[allow(non_exhaustive_omitted_patterns)] match cx.should_emit {
    ShouldEmit::Nothing => true,
    _ => false,
}matches!(cx.should_emit, ShouldEmit::Nothing) {
414                            Self::check_target(&accept.allowed_targets, target, &mut cx);
415                        }
416                    } else {
417                        let attr = AttrItem {
418                            path: attr_path.clone(),
419                            args: self
420                                .lower_attr_args(n.item.args.unparsed_ref().unwrap(), lower_span),
421                            id: HashIgnoredAttrId { attr_id: attr.id },
422                            style: attr.style,
423                            span: attr_span,
424                        };
425
426                        self.check_attribute_safety(
427                            &attr_path,
428                            lower_span(n.item.span()),
429                            n.item.unsafety,
430                            AttributeSafety::Normal,
431                            &mut emit_lint,
432                        );
433
434                        if !#[allow(non_exhaustive_omitted_patterns)] match self.should_emit {
    ShouldEmit::Nothing => true,
    _ => false,
}matches!(self.should_emit, ShouldEmit::Nothing)
435                            && target == Target::Crate
436                        {
437                            self.check_invalid_crate_level_attr_item(&attr, n.item.span());
438                        }
439
440                        let attr = Attribute::Unparsed(Box::new(attr));
441
442                        if self.tools.is_some_and(|tools| {
443                            tools.iter().any(|tool| tool.name == parts[0])
444                            // FIXME: this can be removed once #152369 has been merged.
445                            // https://github.com/rust-lang/rust/pull/152369
446                            || [sym::allow, sym::deny, sym::expect, sym::forbid, sym::warn]
447                                .contains(&parts[0])
448                        }) {
449                            attributes.push(attr);
450                        } else {
451                            dropped_attributes.push(attr);
452                        }
453                    }
454                }
455            }
456        }
457
458        early_parsed_state.finalize_early_parsed_attributes(&mut attributes);
459        for f in &finalizers {
460            if let Some(attr) = f(&mut FinalizeContext {
461                shared: SharedContext { cx: self, target_span, target, emit_lint: &mut emit_lint },
462                all_attrs: &attr_paths,
463            }) {
464                attributes.push(Attribute::Parsed(attr));
465            }
466        }
467
468        if !#[allow(non_exhaustive_omitted_patterns)] match self.should_emit {
    ShouldEmit::Nothing => true,
    _ => false,
}matches!(self.should_emit, ShouldEmit::Nothing) && target == Target::WherePredicate {
469            self.check_invalid_where_predicate_attrs(attributes.iter().chain(&dropped_attributes));
470        }
471
472        attributes
473    }
474
475    /// Returns whether there is a parser for an attribute with this name
476    pub fn is_parsed_attribute(path: &[Symbol]) -> bool {
477        /// The list of attributes that are parsed attributes,
478        /// even though they don't have a parser in `Late::parsers()`
479        const SPECIAL_ATTRIBUTES: &[&[Symbol]] = &[
480            // Cfg attrs are removed after being early-parsed, so don't need to be in the parser list
481            &[sym::cfg],
482            &[sym::cfg_attr],
483        ];
484
485        ATTRIBUTE_PARSERS.accepters.contains_key(path)
486            || EARLY_PARSED_ATTRIBUTES.contains(&path)
487            || SPECIAL_ATTRIBUTES.contains(&path)
488    }
489
490    fn lower_attr_args(&self, args: &ast::AttrArgs, lower_span: impl Fn(Span) -> Span) -> AttrArgs {
491        match args {
492            ast::AttrArgs::Empty => AttrArgs::Empty,
493            ast::AttrArgs::Delimited(args) => AttrArgs::Delimited(args.clone()),
494            // This is an inert key-value attribute - it will never be visible to macros
495            // after it gets lowered to HIR. Therefore, we can extract literals to handle
496            // nonterminals in `#[doc]` (e.g. `#[doc = $e]`).
497            ast::AttrArgs::Eq { eq_span, expr } => {
498                // In valid code the value always ends up as a single literal. Otherwise, a dummy
499                // literal suffices because the error is handled elsewhere.
500                let lit = if let ast::ExprKind::Lit(token_lit) = expr.kind
501                    && let Ok(lit) =
502                        ast::MetaItemLit::from_token_lit(token_lit, lower_span(expr.span))
503                {
504                    lit
505                } else {
506                    let guar = self.dcx().span_delayed_bug(
507                        args.span().unwrap_or(DUMMY_SP),
508                        "expr in place where literal is expected (builtin attr parsing)",
509                    );
510                    ast::MetaItemLit {
511                        symbol: sym::dummy,
512                        suffix: None,
513                        kind: ast::LitKind::Err(guar),
514                        span: DUMMY_SP,
515                    }
516                };
517                AttrArgs::Eq { eq_span: lower_span(*eq_span), expr: lit }
518            }
519        }
520    }
521}
rustc_attr_parsing/interface.rs

rustc_attr_parsing/
interface.rs
