rustc_trait_selection/error_reporting/traits/
on_unimplemented.rs

1use std::iter;
2use std::path::PathBuf;
3
4use rustc_ast::{LitKind, MetaItem, MetaItemInner, MetaItemKind, MetaItemLit};
5use rustc_errors::codes::*;
6use rustc_errors::{ErrorGuaranteed, struct_span_code_err};
7use rustc_hir as hir;
8use rustc_hir::def_id::{DefId, LocalDefId};
9use rustc_hir::{AttrArgs, Attribute};
10use rustc_macros::LintDiagnostic;
11use rustc_middle::bug;
12use rustc_middle::ty::print::PrintTraitRefExt;
13use rustc_middle::ty::{self, GenericArgsRef, GenericParamDef, GenericParamDefKind, TyCtxt};
14use rustc_session::lint::builtin::UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES;
15use rustc_span::{Span, Symbol, sym};
16use tracing::{debug, info};
17
18use super::{ObligationCauseCode, PredicateObligation};
19use crate::error_reporting::TypeErrCtxt;
20use crate::error_reporting::traits::on_unimplemented_condition::{
21    ConditionOptions, OnUnimplementedCondition,
22};
23use crate::error_reporting::traits::on_unimplemented_format::{
24    Ctx, FormatArgs, FormatString, FormatWarning,
25};
26use crate::errors::{InvalidOnClause, NoValueInOnUnimplemented};
27use crate::infer::InferCtxtExt;
28
29impl<'tcx> TypeErrCtxt<'_, 'tcx> {
30    fn impl_similar_to(
31        &self,
32        trait_pred: ty::PolyTraitPredicate<'tcx>,
33        obligation: &PredicateObligation<'tcx>,
34    ) -> Option<(DefId, GenericArgsRef<'tcx>)> {
35        let tcx = self.tcx;
36        let param_env = obligation.param_env;
37        self.enter_forall(trait_pred, |trait_pred| {
38            let trait_self_ty = trait_pred.self_ty();
39
40            let mut self_match_impls = vec![];
41            let mut fuzzy_match_impls = vec![];
42
43            self.tcx.for_each_relevant_impl(trait_pred.def_id(), trait_self_ty, |def_id| {
44                let impl_args = self.fresh_args_for_item(obligation.cause.span, def_id);
45                let impl_trait_ref =
46                    tcx.impl_trait_ref(def_id).unwrap().instantiate(tcx, impl_args);
47
48                let impl_self_ty = impl_trait_ref.self_ty();
49
50                if self.can_eq(param_env, trait_self_ty, impl_self_ty) {
51                    self_match_impls.push((def_id, impl_args));
52
53                    if iter::zip(
54                        trait_pred.trait_ref.args.types().skip(1),
55                        impl_trait_ref.args.types().skip(1),
56                    )
57                    .all(|(u, v)| self.fuzzy_match_tys(u, v, false).is_some())
58                    {
59                        fuzzy_match_impls.push((def_id, impl_args));
60                    }
61                }
62            });
63
64            let impl_def_id_and_args = if let [impl_] = self_match_impls[..] {
65                impl_
66            } else if let [impl_] = fuzzy_match_impls[..] {
67                impl_
68            } else {
69                return None;
70            };
71
72            tcx.has_attr(impl_def_id_and_args.0, sym::rustc_on_unimplemented)
73                .then_some(impl_def_id_and_args)
74        })
75    }
76
77    /// Used to set on_unimplemented's `ItemContext`
78    /// to be the enclosing (async) block/function/closure
79    fn describe_enclosure(&self, def_id: LocalDefId) -> Option<&'static str> {
80        match self.tcx.hir_node_by_def_id(def_id) {
81            hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn { .. }, .. }) => Some("a function"),
82            hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. }) => {
83                Some("a trait method")
84            }
85            hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) => {
86                Some("a method")
87            }
88            hir::Node::Expr(hir::Expr {
89                kind: hir::ExprKind::Closure(hir::Closure { kind, .. }),
90                ..
91            }) => Some(self.describe_closure(*kind)),
92            _ => None,
93        }
94    }
95
96    pub fn on_unimplemented_note(
97        &self,
98        trait_pred: ty::PolyTraitPredicate<'tcx>,
99        obligation: &PredicateObligation<'tcx>,
100        long_ty_file: &mut Option<PathBuf>,
101    ) -> OnUnimplementedNote {
102        if trait_pred.polarity() != ty::PredicatePolarity::Positive {
103            return OnUnimplementedNote::default();
104        }
105
106        let (def_id, args) = self
107            .impl_similar_to(trait_pred, obligation)
108            .unwrap_or_else(|| (trait_pred.def_id(), trait_pred.skip_binder().trait_ref.args));
109        let trait_pred = trait_pred.skip_binder();
110
111        let mut self_types = vec![];
112        let mut generic_args: Vec<(Symbol, String)> = vec![];
113        let mut crate_local = false;
114        // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): HIR is not present for RPITITs,
115        // but I guess we could synthesize one here. We don't see any errors that rely on
116        // that yet, though.
117        let item_context = self.describe_enclosure(obligation.cause.body_id).unwrap_or("");
118
119        let direct = match obligation.cause.code() {
120            ObligationCauseCode::BuiltinDerived(..)
121            | ObligationCauseCode::ImplDerived(..)
122            | ObligationCauseCode::WellFormedDerived(..) => false,
123            _ => {
124                // this is a "direct", user-specified, rather than derived,
125                // obligation.
126                true
127            }
128        };
129
130        let from_desugaring = obligation.cause.span.desugaring_kind();
131
132        let cause = if let ObligationCauseCode::MainFunctionType = obligation.cause.code() {
133            Some("MainFunctionType".to_string())
134        } else {
135            None
136        };
137
138        // Add all types without trimmed paths or visible paths, ensuring they end up with
139        // their "canonical" def path.
140        ty::print::with_no_trimmed_paths!(ty::print::with_no_visible_paths!({
141            let generics = self.tcx.generics_of(def_id);
142            let self_ty = trait_pred.self_ty();
143            self_types.push(self_ty.to_string());
144            if let Some(def) = self_ty.ty_adt_def() {
145                // We also want to be able to select self's original
146                // signature with no type arguments resolved
147                self_types.push(self.tcx.type_of(def.did()).instantiate_identity().to_string());
148            }
149
150            for GenericParamDef { name, kind, index, .. } in generics.own_params.iter() {
151                let value = match kind {
152                    GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
153                        args[*index as usize].to_string()
154                    }
155                    GenericParamDefKind::Lifetime => continue,
156                };
157                generic_args.push((*name, value));
158
159                if let GenericParamDefKind::Type { .. } = kind {
160                    let param_ty = args[*index as usize].expect_ty();
161                    if let Some(def) = param_ty.ty_adt_def() {
162                        // We also want to be able to select the parameter's
163                        // original signature with no type arguments resolved
164                        generic_args.push((
165                            *name,
166                            self.tcx.type_of(def.did()).instantiate_identity().to_string(),
167                        ));
168                    }
169                }
170            }
171
172            if let Some(true) = self_ty.ty_adt_def().map(|def| def.did().is_local()) {
173                crate_local = true;
174            }
175
176            // Allow targeting all integers using `{integral}`, even if the exact type was resolved
177            if self_ty.is_integral() {
178                self_types.push("{integral}".to_owned());
179            }
180
181            if self_ty.is_array_slice() {
182                self_types.push("&[]".to_owned());
183            }
184
185            if self_ty.is_fn() {
186                let fn_sig = self_ty.fn_sig(self.tcx);
187                let shortname = if let ty::FnDef(def_id, _) = self_ty.kind()
188                    && self.tcx.codegen_fn_attrs(def_id).safe_target_features
189                {
190                    "#[target_feature] fn"
191                } else {
192                    match fn_sig.safety() {
193                        hir::Safety::Safe => "fn",
194                        hir::Safety::Unsafe => "unsafe fn",
195                    }
196                };
197                self_types.push(shortname.to_owned());
198            }
199
200            // Slices give us `[]`, `[{ty}]`
201            if let ty::Slice(aty) = self_ty.kind() {
202                self_types.push("[]".to_owned());
203                if let Some(def) = aty.ty_adt_def() {
204                    // We also want to be able to select the slice's type's original
205                    // signature with no type arguments resolved
206                    self_types
207                        .push(format!("[{}]", self.tcx.type_of(def.did()).instantiate_identity()));
208                }
209                if aty.is_integral() {
210                    self_types.push("[{integral}]".to_string());
211                }
212            }
213
214            // Arrays give us `[]`, `[{ty}; _]` and `[{ty}; N]`
215            if let ty::Array(aty, len) = self_ty.kind() {
216                self_types.push("[]".to_string());
217                let len = len.try_to_target_usize(self.tcx);
218                self_types.push(format!("[{aty}; _]"));
219                if let Some(n) = len {
220                    self_types.push(format!("[{aty}; {n}]"));
221                }
222                if let Some(def) = aty.ty_adt_def() {
223                    // We also want to be able to select the array's type's original
224                    // signature with no type arguments resolved
225                    let def_ty = self.tcx.type_of(def.did()).instantiate_identity();
226                    self_types.push(format!("[{def_ty}; _]"));
227                    if let Some(n) = len {
228                        self_types.push(format!("[{def_ty}; {n}]"));
229                    }
230                }
231                if aty.is_integral() {
232                    self_types.push("[{integral}; _]".to_string());
233                    if let Some(n) = len {
234                        self_types.push(format!("[{{integral}}; {n}]"));
235                    }
236                }
237            }
238            if let ty::Dynamic(traits, _, _) = self_ty.kind() {
239                for t in traits.iter() {
240                    if let ty::ExistentialPredicate::Trait(trait_ref) = t.skip_binder() {
241                        self_types.push(self.tcx.def_path_str(trait_ref.def_id));
242                    }
243                }
244            }
245
246            // `&[{integral}]` - `FromIterator` needs that.
247            if let ty::Ref(_, ref_ty, rustc_ast::Mutability::Not) = self_ty.kind()
248                && let ty::Slice(sty) = ref_ty.kind()
249                && sty.is_integral()
250            {
251                self_types.push("&[{integral}]".to_owned());
252            }
253        }));
254
255        let this = self.tcx.def_path_str(trait_pred.trait_ref.def_id);
256        let trait_sugared = trait_pred.trait_ref.print_trait_sugared();
257
258        let condition_options = ConditionOptions {
259            self_types,
260            from_desugaring,
261            cause,
262            crate_local,
263            direct,
264            generic_args,
265        };
266
267        // Unlike the generic_args earlier,
268        // this one is *not* collected under `with_no_trimmed_paths!`
269        // for printing the type to the user
270        //
271        // This includes `Self`, as it is the first parameter in `own_params`.
272        let generic_args = self
273            .tcx
274            .generics_of(trait_pred.trait_ref.def_id)
275            .own_params
276            .iter()
277            .filter_map(|param| {
278                let value = match param.kind {
279                    GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
280                        if let Some(ty) = trait_pred.trait_ref.args[param.index as usize].as_type()
281                        {
282                            self.tcx.short_string(ty, long_ty_file)
283                        } else {
284                            trait_pred.trait_ref.args[param.index as usize].to_string()
285                        }
286                    }
287                    GenericParamDefKind::Lifetime => return None,
288                };
289                let name = param.name;
290                Some((name, value))
291            })
292            .collect();
293
294        let format_args = FormatArgs { this, trait_sugared, generic_args, item_context };
295
296        if let Ok(Some(command)) = OnUnimplementedDirective::of_item(self.tcx, def_id) {
297            command.evaluate(self.tcx, trait_pred.trait_ref, &condition_options, &format_args)
298        } else {
299            OnUnimplementedNote::default()
300        }
301    }
302}
303
304/// Represents a format string in a on_unimplemented attribute,
305/// like the "content" in `#[diagnostic::on_unimplemented(message = "content")]`
306#[derive(Clone, Debug)]
307pub struct OnUnimplementedFormatString {
308    /// Symbol of the format string, i.e. `"content"`
309    symbol: Symbol,
310    ///The span of the format string, i.e. `"content"`
311    span: Span,
312    is_diagnostic_namespace_variant: bool,
313}
314
315#[derive(Debug)]
316pub struct OnUnimplementedDirective {
317    condition: Option<OnUnimplementedCondition>,
318    subcommands: Vec<OnUnimplementedDirective>,
319    message: Option<(Span, OnUnimplementedFormatString)>,
320    label: Option<(Span, OnUnimplementedFormatString)>,
321    notes: Vec<OnUnimplementedFormatString>,
322    parent_label: Option<OnUnimplementedFormatString>,
323    append_const_msg: Option<AppendConstMessage>,
324}
325
326/// For the `#[rustc_on_unimplemented]` attribute
327#[derive(Default)]
328pub struct OnUnimplementedNote {
329    pub message: Option<String>,
330    pub label: Option<String>,
331    pub notes: Vec<String>,
332    pub parent_label: Option<String>,
333    // If none, should fall back to a generic message
334    pub append_const_msg: Option<AppendConstMessage>,
335}
336
337/// Append a message for `~const Trait` errors.
338#[derive(Clone, Copy, PartialEq, Eq, Debug, Default)]
339pub enum AppendConstMessage {
340    #[default]
341    Default,
342    Custom(Symbol, Span),
343}
344
345#[derive(LintDiagnostic)]
346#[diag(trait_selection_malformed_on_unimplemented_attr)]
347#[help]
348pub struct MalformedOnUnimplementedAttrLint {
349    #[label]
350    pub span: Span,
351}
352
353impl MalformedOnUnimplementedAttrLint {
354    pub fn new(span: Span) -> Self {
355        Self { span }
356    }
357}
358
359#[derive(LintDiagnostic)]
360#[diag(trait_selection_missing_options_for_on_unimplemented_attr)]
361#[help]
362pub struct MissingOptionsForOnUnimplementedAttr;
363
364#[derive(LintDiagnostic)]
365#[diag(trait_selection_ignored_diagnostic_option)]
366pub struct IgnoredDiagnosticOption {
367    pub option_name: &'static str,
368    #[label]
369    pub span: Span,
370    #[label(trait_selection_other_label)]
371    pub prev_span: Span,
372}
373
374impl IgnoredDiagnosticOption {
375    pub fn maybe_emit_warning<'tcx>(
376        tcx: TyCtxt<'tcx>,
377        item_def_id: DefId,
378        new: Option<Span>,
379        old: Option<Span>,
380        option_name: &'static str,
381    ) {
382        if let (Some(new_item), Some(old_item)) = (new, old) {
383            if let Some(item_def_id) = item_def_id.as_local() {
384                tcx.emit_node_span_lint(
385                    UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
386                    tcx.local_def_id_to_hir_id(item_def_id),
387                    new_item,
388                    IgnoredDiagnosticOption { span: new_item, prev_span: old_item, option_name },
389                );
390            }
391        }
392    }
393}
394
395#[derive(LintDiagnostic)]
396#[diag(trait_selection_wrapped_parser_error)]
397pub struct WrappedParserError {
398    pub description: String,
399    pub label: String,
400}
401
402impl<'tcx> OnUnimplementedDirective {
403    fn parse(
404        tcx: TyCtxt<'tcx>,
405        item_def_id: DefId,
406        items: &[MetaItemInner],
407        span: Span,
408        is_root: bool,
409        is_diagnostic_namespace_variant: bool,
410    ) -> Result<Option<Self>, ErrorGuaranteed> {
411        let mut errored = None;
412        let mut item_iter = items.iter();
413
414        let parse_value = |value_str, span| {
415            OnUnimplementedFormatString::try_parse(
416                tcx,
417                item_def_id,
418                value_str,
419                span,
420                is_diagnostic_namespace_variant,
421            )
422            .map(Some)
423        };
424
425        let condition = if is_root {
426            None
427        } else {
428            let cond = item_iter
429                .next()
430                .ok_or_else(|| tcx.dcx().emit_err(InvalidOnClause::Empty { span }))?;
431
432            match OnUnimplementedCondition::parse(cond) {
433                Ok(condition) => Some(condition),
434                Err(e) => return Err(tcx.dcx().emit_err(e)),
435            }
436        };
437
438        let mut message = None;
439        let mut label = None;
440        let mut notes = Vec::new();
441        let mut parent_label = None;
442        let mut subcommands = vec![];
443        let mut append_const_msg = None;
444
445        let get_value_and_span = |item: &_, key| {
446            if let MetaItemInner::MetaItem(MetaItem {
447                path,
448                kind: MetaItemKind::NameValue(MetaItemLit { span, kind: LitKind::Str(s, _), .. }),
449                ..
450            }) = item
451                && *path == key
452            {
453                Some((*s, *span))
454            } else {
455                None
456            }
457        };
458
459        for item in item_iter {
460            if let Some((message_, span)) = get_value_and_span(item, sym::message)
461                && message.is_none()
462            {
463                message = parse_value(message_, span)?.map(|l| (item.span(), l));
464                continue;
465            } else if let Some((label_, span)) = get_value_and_span(item, sym::label)
466                && label.is_none()
467            {
468                label = parse_value(label_, span)?.map(|l| (item.span(), l));
469                continue;
470            } else if let Some((note_, span)) = get_value_and_span(item, sym::note) {
471                if let Some(note) = parse_value(note_, span)? {
472                    notes.push(note);
473                    continue;
474                }
475            } else if item.has_name(sym::parent_label)
476                && parent_label.is_none()
477                && !is_diagnostic_namespace_variant
478            {
479                if let Some(parent_label_) = item.value_str() {
480                    parent_label = parse_value(parent_label_, item.span())?;
481                    continue;
482                }
483            } else if item.has_name(sym::on)
484                && is_root
485                && message.is_none()
486                && label.is_none()
487                && notes.is_empty()
488                && !is_diagnostic_namespace_variant
489            // FIXME(diagnostic_namespace): disallow filters for now
490            {
491                if let Some(items) = item.meta_item_list() {
492                    match Self::parse(
493                        tcx,
494                        item_def_id,
495                        items,
496                        item.span(),
497                        false,
498                        is_diagnostic_namespace_variant,
499                    ) {
500                        Ok(Some(subcommand)) => subcommands.push(subcommand),
501                        Ok(None) => bug!(
502                            "This cannot happen for now as we only reach that if `is_diagnostic_namespace_variant` is false"
503                        ),
504                        Err(reported) => errored = Some(reported),
505                    };
506                    continue;
507                }
508            } else if item.has_name(sym::append_const_msg)
509                && append_const_msg.is_none()
510                && !is_diagnostic_namespace_variant
511            {
512                if let Some(msg) = item.value_str() {
513                    append_const_msg = Some(AppendConstMessage::Custom(msg, item.span()));
514                    continue;
515                } else if item.is_word() {
516                    append_const_msg = Some(AppendConstMessage::Default);
517                    continue;
518                }
519            }
520
521            if is_diagnostic_namespace_variant {
522                if let Some(def_id) = item_def_id.as_local() {
523                    tcx.emit_node_span_lint(
524                        UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
525                        tcx.local_def_id_to_hir_id(def_id),
526                        vec![item.span()],
527                        MalformedOnUnimplementedAttrLint::new(item.span()),
528                    );
529                }
530            } else {
531                // nothing found
532                tcx.dcx().emit_err(NoValueInOnUnimplemented { span: item.span() });
533            }
534        }
535
536        if let Some(reported) = errored {
537            if is_diagnostic_namespace_variant { Ok(None) } else { Err(reported) }
538        } else {
539            Ok(Some(OnUnimplementedDirective {
540                condition,
541                subcommands,
542                message,
543                label,
544                notes,
545                parent_label,
546                append_const_msg,
547            }))
548        }
549    }
550
551    pub fn of_item(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> Result<Option<Self>, ErrorGuaranteed> {
552        if !tcx.is_trait(item_def_id) {
553            // It could be a trait_alias (`trait MyTrait = SomeOtherTrait`)
554            // or an implementation (`impl MyTrait for Foo {}`)
555            //
556            // We don't support those.
557            return Ok(None);
558        }
559        if let Some(attr) = tcx.get_attr(item_def_id, sym::rustc_on_unimplemented) {
560            return Self::parse_attribute(attr, false, tcx, item_def_id);
561        } else {
562            tcx.get_attrs_by_path(item_def_id, &[sym::diagnostic, sym::on_unimplemented])
563                .filter_map(|attr| Self::parse_attribute(attr, true, tcx, item_def_id).transpose())
564                .try_fold(None, |aggr: Option<Self>, directive| {
565                    let directive = directive?;
566                    if let Some(aggr) = aggr {
567                        let mut subcommands = aggr.subcommands;
568                        subcommands.extend(directive.subcommands);
569                        let mut notes = aggr.notes;
570                        notes.extend(directive.notes);
571                        IgnoredDiagnosticOption::maybe_emit_warning(
572                            tcx,
573                            item_def_id,
574                            directive.message.as_ref().map(|f| f.0),
575                            aggr.message.as_ref().map(|f| f.0),
576                            "message",
577                        );
578                        IgnoredDiagnosticOption::maybe_emit_warning(
579                            tcx,
580                            item_def_id,
581                            directive.label.as_ref().map(|f| f.0),
582                            aggr.label.as_ref().map(|f| f.0),
583                            "label",
584                        );
585                        IgnoredDiagnosticOption::maybe_emit_warning(
586                            tcx,
587                            item_def_id,
588                            directive.condition.as_ref().map(|i| i.span()),
589                            aggr.condition.as_ref().map(|i| i.span()),
590                            "condition",
591                        );
592                        IgnoredDiagnosticOption::maybe_emit_warning(
593                            tcx,
594                            item_def_id,
595                            directive.parent_label.as_ref().map(|f| f.span),
596                            aggr.parent_label.as_ref().map(|f| f.span),
597                            "parent_label",
598                        );
599                        IgnoredDiagnosticOption::maybe_emit_warning(
600                            tcx,
601                            item_def_id,
602                            directive.append_const_msg.as_ref().and_then(|c| {
603                                if let AppendConstMessage::Custom(_, s) = c {
604                                    Some(*s)
605                                } else {
606                                    None
607                                }
608                            }),
609                            aggr.append_const_msg.as_ref().and_then(|c| {
610                                if let AppendConstMessage::Custom(_, s) = c {
611                                    Some(*s)
612                                } else {
613                                    None
614                                }
615                            }),
616                            "append_const_msg",
617                        );
618
619                        Ok(Some(Self {
620                            condition: aggr.condition.or(directive.condition),
621                            subcommands,
622                            message: aggr.message.or(directive.message),
623                            label: aggr.label.or(directive.label),
624                            notes,
625                            parent_label: aggr.parent_label.or(directive.parent_label),
626                            append_const_msg: aggr.append_const_msg.or(directive.append_const_msg),
627                        }))
628                    } else {
629                        Ok(Some(directive))
630                    }
631                })
632        }
633    }
634
635    fn parse_attribute(
636        attr: &Attribute,
637        is_diagnostic_namespace_variant: bool,
638        tcx: TyCtxt<'tcx>,
639        item_def_id: DefId,
640    ) -> Result<Option<Self>, ErrorGuaranteed> {
641        let result = if let Some(items) = attr.meta_item_list() {
642            Self::parse(
643                tcx,
644                item_def_id,
645                &items,
646                attr.span(),
647                true,
648                is_diagnostic_namespace_variant,
649            )
650        } else if let Some(value) = attr.value_str() {
651            if !is_diagnostic_namespace_variant {
652                Ok(Some(OnUnimplementedDirective {
653                    condition: None,
654                    message: None,
655                    subcommands: vec![],
656                    label: Some((
657                        attr.span(),
658                        OnUnimplementedFormatString::try_parse(
659                            tcx,
660                            item_def_id,
661                            value,
662                            attr.value_span().unwrap_or(attr.span()),
663                            is_diagnostic_namespace_variant,
664                        )?,
665                    )),
666                    notes: Vec::new(),
667                    parent_label: None,
668                    append_const_msg: None,
669                }))
670            } else {
671                let item = attr.get_normal_item();
672                let report_span = match &item.args {
673                    AttrArgs::Empty => item.path.span,
674                    AttrArgs::Delimited(args) => args.dspan.entire(),
675                    AttrArgs::Eq { eq_span, expr } => eq_span.to(expr.span),
676                };
677
678                if let Some(item_def_id) = item_def_id.as_local() {
679                    tcx.emit_node_span_lint(
680                        UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
681                        tcx.local_def_id_to_hir_id(item_def_id),
682                        report_span,
683                        MalformedOnUnimplementedAttrLint::new(report_span),
684                    );
685                }
686                Ok(None)
687            }
688        } else if is_diagnostic_namespace_variant {
689            match attr {
690                Attribute::Unparsed(p) if !matches!(p.args, AttrArgs::Empty) => {
691                    if let Some(item_def_id) = item_def_id.as_local() {
692                        tcx.emit_node_span_lint(
693                            UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
694                            tcx.local_def_id_to_hir_id(item_def_id),
695                            attr.span(),
696                            MalformedOnUnimplementedAttrLint::new(attr.span()),
697                        );
698                    }
699                }
700                _ => {
701                    if let Some(item_def_id) = item_def_id.as_local() {
702                        tcx.emit_node_span_lint(
703                            UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
704                            tcx.local_def_id_to_hir_id(item_def_id),
705                            attr.span(),
706                            MissingOptionsForOnUnimplementedAttr,
707                        )
708                    }
709                }
710            };
711
712            Ok(None)
713        } else {
714            let reported = tcx.dcx().delayed_bug("of_item: neither meta_item_list nor value_str");
715            return Err(reported);
716        };
717        debug!("of_item({:?}) = {:?}", item_def_id, result);
718        result
719    }
720
721    pub(crate) fn evaluate(
722        &self,
723        tcx: TyCtxt<'tcx>,
724        trait_ref: ty::TraitRef<'tcx>,
725        condition_options: &ConditionOptions,
726        args: &FormatArgs<'tcx>,
727    ) -> OnUnimplementedNote {
728        let mut message = None;
729        let mut label = None;
730        let mut notes = Vec::new();
731        let mut parent_label = None;
732        let mut append_const_msg = None;
733        info!(
734            "evaluate({:?}, trait_ref={:?}, options={:?}, args ={:?})",
735            self, trait_ref, condition_options, args
736        );
737
738        for command in self.subcommands.iter().chain(Some(self)).rev() {
739            debug!(?command);
740            if let Some(ref condition) = command.condition
741                && !condition.matches_predicate(condition_options)
742            {
743                debug!("evaluate: skipping {:?} due to condition", command);
744                continue;
745            }
746            debug!("evaluate: {:?} succeeded", command);
747            if let Some(ref message_) = command.message {
748                message = Some(message_.clone());
749            }
750
751            if let Some(ref label_) = command.label {
752                label = Some(label_.clone());
753            }
754
755            notes.extend(command.notes.clone());
756
757            if let Some(ref parent_label_) = command.parent_label {
758                parent_label = Some(parent_label_.clone());
759            }
760
761            append_const_msg = command.append_const_msg;
762        }
763
764        OnUnimplementedNote {
765            label: label.map(|l| l.1.format(tcx, trait_ref, args)),
766            message: message.map(|m| m.1.format(tcx, trait_ref, args)),
767            notes: notes.into_iter().map(|n| n.format(tcx, trait_ref, args)).collect(),
768            parent_label: parent_label.map(|e_s| e_s.format(tcx, trait_ref, args)),
769            append_const_msg,
770        }
771    }
772}
773
774impl<'tcx> OnUnimplementedFormatString {
775    fn try_parse(
776        tcx: TyCtxt<'tcx>,
777        item_def_id: DefId,
778        from: Symbol,
779        span: Span,
780        is_diagnostic_namespace_variant: bool,
781    ) -> Result<Self, ErrorGuaranteed> {
782        let result =
783            OnUnimplementedFormatString { symbol: from, span, is_diagnostic_namespace_variant };
784        result.verify(tcx, item_def_id)?;
785        Ok(result)
786    }
787
788    fn verify(&self, tcx: TyCtxt<'tcx>, trait_def_id: DefId) -> Result<(), ErrorGuaranteed> {
789        if !tcx.is_trait(trait_def_id) {
790            return Ok(());
791        };
792
793        let ctx = if self.is_diagnostic_namespace_variant {
794            Ctx::DiagnosticOnUnimplemented { tcx, trait_def_id }
795        } else {
796            Ctx::RustcOnUnimplemented { tcx, trait_def_id }
797        };
798
799        let mut result = Ok(());
800
801        match FormatString::parse(self.symbol, self.span, &ctx) {
802            // Warnings about format specifiers, deprecated parameters, wrong parameters etc.
803            // In other words we'd like to let the author know, but we can still try to format the string later
804            Ok(FormatString { warnings, .. }) => {
805                if self.is_diagnostic_namespace_variant {
806                    for w in warnings {
807                        w.emit_warning(tcx, trait_def_id)
808                    }
809                } else {
810                    for w in warnings {
811                        match w {
812                            FormatWarning::UnknownParam { argument_name, span } => {
813                                let reported = struct_span_code_err!(
814                                    tcx.dcx(),
815                                    span,
816                                    E0230,
817                                    "cannot find parameter {} on this trait",
818                                    argument_name,
819                                )
820                                .emit();
821                                result = Err(reported);
822                            }
823                            FormatWarning::PositionalArgument { span, .. } => {
824                                let reported = struct_span_code_err!(
825                                    tcx.dcx(),
826                                    span,
827                                    E0231,
828                                    "positional format arguments are not allowed here"
829                                )
830                                .emit();
831                                result = Err(reported);
832                            }
833                            FormatWarning::InvalidSpecifier { .. }
834                            | FormatWarning::FutureIncompat { .. } => {}
835                        }
836                    }
837                }
838            }
839            // Errors from the underlying `rustc_parse_format::Parser`
840            Err(errors) => {
841                // we cannot return errors from processing the format string as hard error here
842                // as the diagnostic namespace guarantees that malformed input cannot cause an error
843                //
844                // if we encounter any error while processing we nevertheless want to show it as warning
845                // so that users are aware that something is not correct
846                for e in errors {
847                    if self.is_diagnostic_namespace_variant {
848                        if let Some(trait_def_id) = trait_def_id.as_local() {
849                            tcx.emit_node_span_lint(
850                                UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
851                                tcx.local_def_id_to_hir_id(trait_def_id),
852                                self.span,
853                                WrappedParserError { description: e.description, label: e.label },
854                            );
855                        }
856                    } else {
857                        let reported = struct_span_code_err!(
858                            tcx.dcx(),
859                            self.span,
860                            E0231,
861                            "{}",
862                            e.description,
863                        )
864                        .emit();
865                        result = Err(reported);
866                    }
867                }
868            }
869        }
870
871        result
872    }
873
874    pub fn format(
875        &self,
876        tcx: TyCtxt<'tcx>,
877        trait_ref: ty::TraitRef<'tcx>,
878        args: &FormatArgs<'tcx>,
879    ) -> String {
880        let trait_def_id = trait_ref.def_id;
881        let ctx = if self.is_diagnostic_namespace_variant {
882            Ctx::DiagnosticOnUnimplemented { tcx, trait_def_id }
883        } else {
884            Ctx::RustcOnUnimplemented { tcx, trait_def_id }
885        };
886
887        if let Ok(s) = FormatString::parse(self.symbol, self.span, &ctx) {
888            s.format(args)
889        } else {
890            // we cannot return errors from processing the format string as hard error here
891            // as the diagnostic namespace guarantees that malformed input cannot cause an error
892            //
893            // if we encounter any error while processing the format string
894            // we don't want to show the potentially half assembled formatted string,
895            // therefore we fall back to just showing the input string in this case
896            //
897            // The actual parser errors are emitted earlier
898            // as lint warnings in OnUnimplementedFormatString::verify
899            self.symbol.as_str().into()
900        }
901    }
902}
rustc_trait_selection/error_reporting/traits/on_unimplemented.rs

rustc_trait_selection/error_reporting/traits/
on_unimplemented.rs
