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Commit | Line | Data |
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60c5eb7d XL |
1 | //! Error reporting machinery for lifetime errors. |
2 | ||
064997fb | 3 | use rustc_data_structures::fx::FxHashSet; |
923072b8 FG |
4 | use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan}; |
5 | use rustc_hir::def_id::DefId; | |
6 | use rustc_hir::intravisit::Visitor; | |
7 | use rustc_hir::{self as hir, Item, ItemKind, Node}; | |
74b04a01 | 8 | use rustc_infer::infer::{ |
04454e1e FG |
9 | error_reporting::nice_region_error::{ |
10 | self, find_anon_type, find_param_with_region, suggest_adding_lifetime_params, | |
923072b8 | 11 | HirTraitObjectVisitor, NiceRegionError, TraitObjectVisitor, |
04454e1e FG |
12 | }, |
13 | error_reporting::unexpected_hidden_region_diagnostic, | |
14 | NllRegionVariableOrigin, RelateParamBound, | |
74b04a01 | 15 | }; |
5099ac24 | 16 | use rustc_middle::hir::place::PlaceBase; |
f035d41b | 17 | use rustc_middle::mir::{ConstraintCategory, ReturnConstraint}; |
04454e1e | 18 | use rustc_middle::ty::subst::InternalSubsts; |
923072b8 FG |
19 | use rustc_middle::ty::Region; |
20 | use rustc_middle::ty::TypeVisitor; | |
ba9703b0 | 21 | use rustc_middle::ty::{self, RegionVid, Ty}; |
064997fb | 22 | use rustc_span::symbol::{kw, sym, Ident}; |
04454e1e | 23 | use rustc_span::Span; |
60c5eb7d | 24 | |
c295e0f8 | 25 | use crate::borrowck_errors; |
064997fb | 26 | use crate::session_diagnostics::GenericDoesNotLiveLongEnough; |
8faf50e0 | 27 | |
c295e0f8 XL |
28 | use super::{OutlivesSuggestionBuilder, RegionName}; |
29 | use crate::region_infer::BlameConstraint; | |
30 | use crate::{ | |
60c5eb7d | 31 | nll::ConstraintDescription, |
dfeec247 XL |
32 | region_infer::{values::RegionElement, TypeTest}, |
33 | universal_regions::DefiningTy, | |
34 | MirBorrowckCtxt, | |
60c5eb7d | 35 | }; |
8faf50e0 | 36 | |
923072b8 | 37 | impl<'tcx> ConstraintDescription for ConstraintCategory<'tcx> { |
0bf4aa26 | 38 | fn description(&self) -> &'static str { |
8faf50e0 XL |
39 | // Must end with a space. Allows for empty names to be provided. |
40 | match self { | |
0bf4aa26 | 41 | ConstraintCategory::Assignment => "assignment ", |
f035d41b | 42 | ConstraintCategory::Return(_) => "returning this value ", |
0731742a | 43 | ConstraintCategory::Yield => "yielding this value ", |
0bf4aa26 XL |
44 | ConstraintCategory::UseAsConst => "using this value as a constant ", |
45 | ConstraintCategory::UseAsStatic => "using this value as a static ", | |
46 | ConstraintCategory::Cast => "cast ", | |
923072b8 | 47 | ConstraintCategory::CallArgument(_) => "argument ", |
0bf4aa26 XL |
48 | ConstraintCategory::TypeAnnotation => "type annotation ", |
49 | ConstraintCategory::ClosureBounds => "closure body ", | |
50 | ConstraintCategory::SizedBound => "proving this value is `Sized` ", | |
51 | ConstraintCategory::CopyBound => "copying this value ", | |
52 | ConstraintCategory::OpaqueType => "opaque type ", | |
f035d41b | 53 | ConstraintCategory::ClosureUpvar(_) => "closure capture ", |
c295e0f8 XL |
54 | ConstraintCategory::Usage => "this usage ", |
55 | ConstraintCategory::Predicate(_) | |
56 | | ConstraintCategory::Boring | |
0bf4aa26 XL |
57 | | ConstraintCategory::BoringNoLocation |
58 | | ConstraintCategory::Internal => "", | |
8faf50e0 XL |
59 | } |
60 | } | |
61 | } | |
62 | ||
dfeec247 XL |
63 | /// A collection of errors encountered during region inference. This is needed to efficiently |
64 | /// report errors after borrow checking. | |
65 | /// | |
66 | /// Usually we expect this to either be empty or contain a small number of items, so we can avoid | |
67 | /// allocation most of the time. | |
923072b8 | 68 | pub(crate) type RegionErrors<'tcx> = Vec<RegionErrorKind<'tcx>>; |
60c5eb7d | 69 | |
dfeec247 | 70 | #[derive(Clone, Debug)] |
923072b8 | 71 | pub(crate) enum RegionErrorKind<'tcx> { |
dfeec247 XL |
72 | /// A generic bound failure for a type test (`T: 'a`). |
73 | TypeTestError { type_test: TypeTest<'tcx> }, | |
74 | ||
75 | /// An unexpected hidden region for an opaque type. | |
76 | UnexpectedHiddenRegion { | |
74b04a01 XL |
77 | /// The span for the member constraint. |
78 | span: Span, | |
dfeec247 XL |
79 | /// The hidden type. |
80 | hidden_ty: Ty<'tcx>, | |
064997fb FG |
81 | /// The opaque type. |
82 | key: ty::OpaqueTypeKey<'tcx>, | |
dfeec247 XL |
83 | /// The unexpected region. |
84 | member_region: ty::Region<'tcx>, | |
85 | }, | |
86 | ||
87 | /// Higher-ranked subtyping error. | |
88 | BoundUniversalRegionError { | |
89 | /// The placeholder free region. | |
90 | longer_fr: RegionVid, | |
91 | /// The region element that erroneously must be outlived by `longer_fr`. | |
92 | error_element: RegionElement, | |
94222f64 XL |
93 | /// The placeholder region. |
94 | placeholder: ty::PlaceholderRegion, | |
dfeec247 | 95 | }, |
e1599b0c | 96 | |
dfeec247 XL |
97 | /// Any other lifetime error. |
98 | RegionError { | |
99 | /// The origin of the region. | |
5869c6ff | 100 | fr_origin: NllRegionVariableOrigin, |
dfeec247 XL |
101 | /// The region that should outlive `shorter_fr`. |
102 | longer_fr: RegionVid, | |
103 | /// The region that should be shorter, but we can't prove it. | |
104 | shorter_fr: RegionVid, | |
105 | /// Indicates whether this is a reported error. We currently only report the first error | |
106 | /// encountered and leave the rest unreported so as not to overwhelm the user. | |
107 | is_reported: bool, | |
108 | }, | |
e1599b0c XL |
109 | } |
110 | ||
111 | /// Information about the various region constraints involved in a borrow checker error. | |
112 | #[derive(Clone, Debug)] | |
923072b8 | 113 | pub struct ErrorConstraintInfo<'tcx> { |
e1599b0c | 114 | // fr: outlived_fr |
60c5eb7d XL |
115 | pub(super) fr: RegionVid, |
116 | pub(super) fr_is_local: bool, | |
117 | pub(super) outlived_fr: RegionVid, | |
118 | pub(super) outlived_fr_is_local: bool, | |
e1599b0c XL |
119 | |
120 | // Category and span for best blame constraint | |
923072b8 | 121 | pub(super) category: ConstraintCategory<'tcx>, |
60c5eb7d | 122 | pub(super) span: Span, |
e1599b0c XL |
123 | } |
124 | ||
dfeec247 XL |
125 | impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> { |
126 | /// Converts a region inference variable into a `ty::Region` that | |
127 | /// we can use for error reporting. If `r` is universally bound, | |
128 | /// then we use the name that we have on record for it. If `r` is | |
129 | /// existentially bound, then we check its inferred value and try | |
130 | /// to find a good name from that. Returns `None` if we can't find | |
131 | /// one (e.g., this is just some random part of the CFG). | |
132 | pub(super) fn to_error_region(&self, r: RegionVid) -> Option<ty::Region<'tcx>> { | |
133 | self.to_error_region_vid(r).and_then(|r| self.regioncx.region_definition(r).external_name) | |
134 | } | |
8faf50e0 | 135 | |
dfeec247 XL |
136 | /// Returns the `RegionVid` corresponding to the region returned by |
137 | /// `to_error_region`. | |
138 | pub(super) fn to_error_region_vid(&self, r: RegionVid) -> Option<RegionVid> { | |
139 | if self.regioncx.universal_regions().is_universal_region(r) { | |
140 | Some(r) | |
141 | } else { | |
f035d41b XL |
142 | // We just want something nameable, even if it's not |
143 | // actually an upper bound. | |
144 | let upper_bound = self.regioncx.approx_universal_upper_bound(r); | |
8faf50e0 | 145 | |
dfeec247 XL |
146 | if self.regioncx.upper_bound_in_region_scc(r, upper_bound) { |
147 | self.to_error_region_vid(upper_bound) | |
e74abb32 | 148 | } else { |
dfeec247 | 149 | None |
8faf50e0 | 150 | } |
dfeec247 XL |
151 | } |
152 | } | |
e74abb32 | 153 | |
dfeec247 XL |
154 | /// Returns `true` if a closure is inferred to be an `FnMut` closure. |
155 | fn is_closure_fn_mut(&self, fr: RegionVid) -> bool { | |
5e7ed085 FG |
156 | if let Some(ty::ReFree(free_region)) = self.to_error_region(fr).as_deref() |
157 | && let ty::BoundRegionKind::BrEnv = free_region.bound_region | |
158 | && let DefiningTy::Closure(_, substs) = self.regioncx.universal_regions().defining_ty | |
159 | { | |
160 | return substs.as_closure().kind() == ty::ClosureKind::FnMut; | |
8faf50e0 XL |
161 | } |
162 | ||
dfeec247 | 163 | false |
8faf50e0 XL |
164 | } |
165 | ||
dfeec247 | 166 | /// Produces nice borrowck error diagnostics for all the errors collected in `nll_errors`. |
c295e0f8 | 167 | pub(crate) fn report_region_errors(&mut self, nll_errors: RegionErrors<'tcx>) { |
dfeec247 XL |
168 | // Iterate through all the errors, producing a diagnostic for each one. The diagnostics are |
169 | // buffered in the `MirBorrowckCtxt`. | |
170 | ||
171 | let mut outlives_suggestion = OutlivesSuggestionBuilder::default(); | |
172 | ||
173 | for nll_error in nll_errors.into_iter() { | |
174 | match nll_error { | |
175 | RegionErrorKind::TypeTestError { type_test } => { | |
176 | // Try to convert the lower-bound region into something named we can print for the user. | |
177 | let lower_bound_region = self.to_error_region(type_test.lower_bound); | |
178 | ||
179 | let type_test_span = type_test.locations.span(&self.body); | |
180 | ||
181 | if let Some(lower_bound_region) = lower_bound_region { | |
04454e1e FG |
182 | let generic_ty = type_test.generic_kind.to_ty(self.infcx.tcx); |
183 | let origin = RelateParamBound(type_test_span, generic_ty, None); | |
5099ac24 | 184 | self.buffer_error(self.infcx.construct_generic_bound_failure( |
064997fb | 185 | self.body.source.def_id().expect_local(), |
5099ac24 | 186 | type_test_span, |
04454e1e | 187 | Some(origin), |
5099ac24 FG |
188 | type_test.generic_kind, |
189 | lower_bound_region, | |
190 | )); | |
dfeec247 XL |
191 | } else { |
192 | // FIXME. We should handle this case better. It | |
193 | // indicates that we have e.g., some region variable | |
194 | // whose value is like `'a+'b` where `'a` and `'b` are | |
5e7ed085 | 195 | // distinct unrelated universal regions that are not |
dfeec247 XL |
196 | // known to outlive one another. It'd be nice to have |
197 | // some examples where this arises to decide how best | |
198 | // to report it; we could probably handle it by | |
199 | // iterating over the universal regions and reporting | |
200 | // an error that multiple bounds are required. | |
064997fb FG |
201 | self.buffer_error(self.infcx.tcx.sess.create_err( |
202 | GenericDoesNotLiveLongEnough { | |
203 | kind: type_test.generic_kind.to_string(), | |
204 | span: type_test_span, | |
205 | }, | |
5099ac24 | 206 | )); |
8faf50e0 XL |
207 | } |
208 | } | |
8faf50e0 | 209 | |
064997fb | 210 | RegionErrorKind::UnexpectedHiddenRegion { span, hidden_ty, key, member_region } => { |
74b04a01 | 211 | let named_ty = self.regioncx.name_regions(self.infcx.tcx, hidden_ty); |
064997fb | 212 | let named_key = self.regioncx.name_regions(self.infcx.tcx, key); |
74b04a01 | 213 | let named_region = self.regioncx.name_regions(self.infcx.tcx, member_region); |
5099ac24 | 214 | self.buffer_error(unexpected_hidden_region_diagnostic( |
dfeec247 | 215 | self.infcx.tcx, |
74b04a01 XL |
216 | span, |
217 | named_ty, | |
218 | named_region, | |
064997fb | 219 | named_key, |
5099ac24 | 220 | )); |
8faf50e0 | 221 | } |
e74abb32 | 222 | |
dfeec247 XL |
223 | RegionErrorKind::BoundUniversalRegionError { |
224 | longer_fr, | |
94222f64 | 225 | placeholder, |
dfeec247 XL |
226 | error_element, |
227 | } => { | |
94222f64 | 228 | let error_vid = self.regioncx.region_from_element(longer_fr, &error_element); |
dfeec247 XL |
229 | |
230 | // Find the code to blame for the fact that `longer_fr` outlives `error_fr`. | |
c295e0f8 | 231 | let (_, cause) = self.regioncx.find_outlives_blame_span( |
dfeec247 XL |
232 | &self.body, |
233 | longer_fr, | |
94222f64 XL |
234 | NllRegionVariableOrigin::Placeholder(placeholder), |
235 | error_vid, | |
dfeec247 XL |
236 | ); |
237 | ||
94222f64 XL |
238 | let universe = placeholder.universe; |
239 | let universe_info = self.regioncx.universe_info(universe); | |
240 | ||
c295e0f8 | 241 | universe_info.report_error(self, placeholder, error_element, cause); |
dfeec247 | 242 | } |
e74abb32 | 243 | |
dfeec247 XL |
244 | RegionErrorKind::RegionError { fr_origin, longer_fr, shorter_fr, is_reported } => { |
245 | if is_reported { | |
246 | self.report_region_error( | |
247 | longer_fr, | |
248 | fr_origin, | |
249 | shorter_fr, | |
250 | &mut outlives_suggestion, | |
251 | ); | |
252 | } else { | |
253 | // We only report the first error, so as not to overwhelm the user. See | |
254 | // `RegRegionErrorKind` docs. | |
255 | // | |
256 | // FIXME: currently we do nothing with these, but perhaps we can do better? | |
257 | // FIXME: try collecting these constraints on the outlives suggestion | |
258 | // builder. Does it make the suggestions any better? | |
259 | debug!( | |
260 | "Unreported region error: can't prove that {:?}: {:?}", | |
261 | longer_fr, shorter_fr | |
262 | ); | |
263 | } | |
264 | } | |
8faf50e0 XL |
265 | } |
266 | } | |
267 | ||
dfeec247 XL |
268 | // Emit one outlives suggestions for each MIR def we borrowck |
269 | outlives_suggestion.add_suggestion(self); | |
8faf50e0 XL |
270 | } |
271 | ||
923072b8 FG |
272 | fn get_impl_ident_and_self_ty_from_trait( |
273 | &self, | |
274 | def_id: DefId, | |
275 | trait_objects: &FxHashSet<DefId>, | |
276 | ) -> Option<(Ident, &'tcx hir::Ty<'tcx>)> { | |
277 | let tcx = self.infcx.tcx; | |
278 | match tcx.hir().get_if_local(def_id) { | |
279 | Some(Node::ImplItem(impl_item)) => { | |
280 | match tcx.hir().find_by_def_id(tcx.hir().get_parent_item(impl_item.hir_id())) { | |
281 | Some(Node::Item(Item { | |
282 | kind: ItemKind::Impl(hir::Impl { self_ty, .. }), | |
283 | .. | |
284 | })) => Some((impl_item.ident, self_ty)), | |
285 | _ => None, | |
286 | } | |
287 | } | |
288 | Some(Node::TraitItem(trait_item)) => { | |
289 | let trait_did = tcx.hir().get_parent_item(trait_item.hir_id()); | |
290 | match tcx.hir().find_by_def_id(trait_did) { | |
291 | Some(Node::Item(Item { kind: ItemKind::Trait(..), .. })) => { | |
292 | // The method being called is defined in the `trait`, but the `'static` | |
293 | // obligation comes from the `impl`. Find that `impl` so that we can point | |
294 | // at it in the suggestion. | |
295 | let trait_did = trait_did.to_def_id(); | |
296 | match tcx | |
297 | .hir() | |
298 | .trait_impls(trait_did) | |
299 | .iter() | |
300 | .filter_map(|&impl_did| { | |
301 | match tcx.hir().get_if_local(impl_did.to_def_id()) { | |
302 | Some(Node::Item(Item { | |
303 | kind: ItemKind::Impl(hir::Impl { self_ty, .. }), | |
304 | .. | |
305 | })) if trait_objects.iter().all(|did| { | |
306 | // FIXME: we should check `self_ty` against the receiver | |
307 | // type in the `UnifyReceiver` context, but for now, use | |
308 | // this imperfect proxy. This will fail if there are | |
309 | // multiple `impl`s for the same trait like | |
310 | // `impl Foo for Box<dyn Bar>` and `impl Foo for dyn Bar`. | |
311 | // In that case, only the first one will get suggestions. | |
312 | let mut traits = vec![]; | |
313 | let mut hir_v = HirTraitObjectVisitor(&mut traits, *did); | |
314 | hir_v.visit_ty(self_ty); | |
315 | !traits.is_empty() | |
316 | }) => | |
317 | { | |
318 | Some(self_ty) | |
319 | } | |
320 | _ => None, | |
321 | } | |
322 | }) | |
323 | .next() | |
324 | { | |
325 | Some(self_ty) => Some((trait_item.ident, self_ty)), | |
326 | _ => None, | |
327 | } | |
328 | } | |
329 | _ => None, | |
330 | } | |
331 | } | |
332 | _ => None, | |
333 | } | |
334 | } | |
335 | ||
8faf50e0 XL |
336 | /// Report an error because the universal region `fr` was required to outlive |
337 | /// `outlived_fr` but it is not known to do so. For example: | |
338 | /// | |
04454e1e | 339 | /// ```compile_fail,E0312 |
8faf50e0 XL |
340 | /// fn foo<'a, 'b>(x: &'a u32) -> &'b u32 { x } |
341 | /// ``` | |
342 | /// | |
343 | /// Here we would be invoked with `fr = 'a` and `outlived_fr = `'b`. | |
c295e0f8 | 344 | pub(crate) fn report_region_error( |
dfeec247 | 345 | &mut self, |
8faf50e0 | 346 | fr: RegionVid, |
5869c6ff | 347 | fr_origin: NllRegionVariableOrigin, |
8faf50e0 | 348 | outlived_fr: RegionVid, |
dfeec247 XL |
349 | outlives_suggestion: &mut OutlivesSuggestionBuilder, |
350 | ) { | |
351 | debug!("report_region_error(fr={:?}, outlived_fr={:?})", fr, outlived_fr); | |
8faf50e0 | 352 | |
c295e0f8 | 353 | let BlameConstraint { category, cause, variance_info, from_closure: _ } = |
dfeec247 XL |
354 | self.regioncx.best_blame_constraint(&self.body, fr, fr_origin, |r| { |
355 | self.regioncx.provides_universal_region(r, fr, outlived_fr) | |
356 | }); | |
8faf50e0 | 357 | |
c295e0f8 | 358 | debug!("report_region_error: category={:?} {:?} {:?}", category, cause, variance_info); |
923072b8 | 359 | |
8faf50e0 XL |
360 | // Check if we can use one of the "nice region errors". |
361 | if let (Some(f), Some(o)) = (self.to_error_region(fr), self.to_error_region(outlived_fr)) { | |
c295e0f8 | 362 | let nice = NiceRegionError::new_from_span(self.infcx, cause.span, o, f); |
9fa01778 | 363 | if let Some(diag) = nice.try_report_from_nll() { |
5099ac24 | 364 | self.buffer_error(diag); |
dfeec247 | 365 | return; |
8faf50e0 XL |
366 | } |
367 | } | |
368 | ||
369 | let (fr_is_local, outlived_fr_is_local): (bool, bool) = ( | |
dfeec247 XL |
370 | self.regioncx.universal_regions().is_local_free_region(fr), |
371 | self.regioncx.universal_regions().is_local_free_region(outlived_fr), | |
8faf50e0 | 372 | ); |
0bf4aa26 | 373 | |
a1dfa0c6 | 374 | debug!( |
dfeec247 | 375 | "report_region_error: fr_is_local={:?} outlived_fr_is_local={:?} category={:?}", |
a1dfa0c6 XL |
376 | fr_is_local, outlived_fr_is_local, category |
377 | ); | |
e1599b0c | 378 | |
e1599b0c | 379 | let errci = ErrorConstraintInfo { |
dfeec247 XL |
380 | fr, |
381 | outlived_fr, | |
382 | fr_is_local, | |
383 | outlived_fr_is_local, | |
384 | category, | |
c295e0f8 | 385 | span: cause.span, |
e1599b0c XL |
386 | }; |
387 | ||
17df50a5 | 388 | let mut diag = match (category, fr_is_local, outlived_fr_is_local) { |
f035d41b XL |
389 | (ConstraintCategory::Return(kind), true, false) if self.is_closure_fn_mut(fr) => { |
390 | self.report_fnmut_error(&errci, kind) | |
a1dfa0c6 XL |
391 | } |
392 | (ConstraintCategory::Assignment, true, false) | |
923072b8 | 393 | | (ConstraintCategory::CallArgument(_), true, false) => { |
dfeec247 | 394 | let mut db = self.report_escaping_data_error(&errci); |
60c5eb7d | 395 | |
dfeec247 | 396 | outlives_suggestion.intermediate_suggestion(self, &errci, &mut db); |
60c5eb7d XL |
397 | outlives_suggestion.collect_constraint(fr, outlived_fr); |
398 | ||
399 | db | |
400 | } | |
401 | _ => { | |
dfeec247 | 402 | let mut db = self.report_general_error(&errci); |
60c5eb7d | 403 | |
dfeec247 | 404 | outlives_suggestion.intermediate_suggestion(self, &errci, &mut db); |
60c5eb7d XL |
405 | outlives_suggestion.collect_constraint(fr, outlived_fr); |
406 | ||
407 | db | |
408 | } | |
a1dfa0c6 | 409 | }; |
dfeec247 | 410 | |
17df50a5 XL |
411 | match variance_info { |
412 | ty::VarianceDiagInfo::None => {} | |
a2a8927a XL |
413 | ty::VarianceDiagInfo::Invariant { ty, param_index } => { |
414 | let (desc, note) = match ty.kind() { | |
415 | ty::RawPtr(ty_mut) => { | |
416 | assert_eq!(ty_mut.mutbl, rustc_hir::Mutability::Mut); | |
417 | ( | |
04454e1e | 418 | format!("a mutable pointer to `{}`", ty_mut.ty), |
a2a8927a XL |
419 | "mutable pointers are invariant over their type parameter".to_string(), |
420 | ) | |
421 | } | |
422 | ty::Ref(_, inner_ty, mutbl) => { | |
423 | assert_eq!(*mutbl, rustc_hir::Mutability::Mut); | |
424 | ( | |
04454e1e | 425 | format!("a mutable reference to `{inner_ty}`"), |
a2a8927a XL |
426 | "mutable references are invariant over their type parameter" |
427 | .to_string(), | |
428 | ) | |
429 | } | |
430 | ty::Adt(adt, substs) => { | |
431 | let generic_arg = substs[param_index as usize]; | |
432 | let identity_substs = | |
5e7ed085 FG |
433 | InternalSubsts::identity_for_item(self.infcx.tcx, adt.did()); |
434 | let base_ty = self.infcx.tcx.mk_adt(*adt, identity_substs); | |
a2a8927a XL |
435 | let base_generic_arg = identity_substs[param_index as usize]; |
436 | let adt_desc = adt.descr(); | |
437 | ||
438 | let desc = format!( | |
04454e1e | 439 | "the type `{ty}`, which makes the generic argument `{generic_arg}` invariant" |
a2a8927a XL |
440 | ); |
441 | let note = format!( | |
04454e1e FG |
442 | "the {adt_desc} `{base_ty}` is invariant over the parameter `{base_generic_arg}`" |
443 | ); | |
444 | (desc, note) | |
445 | } | |
446 | ty::FnDef(def_id, _) => { | |
447 | let name = self.infcx.tcx.item_name(*def_id); | |
448 | let identity_substs = | |
449 | InternalSubsts::identity_for_item(self.infcx.tcx, *def_id); | |
450 | let desc = format!("a function pointer to `{name}`"); | |
451 | let note = format!( | |
452 | "the function `{name}` is invariant over the parameter `{}`", | |
453 | identity_substs[param_index as usize] | |
a2a8927a XL |
454 | ); |
455 | (desc, note) | |
456 | } | |
457 | _ => panic!("Unexpected type {:?}", ty), | |
17df50a5 | 458 | }; |
a2a8927a XL |
459 | diag.note(&format!("requirement occurs because of {desc}",)); |
460 | diag.note(¬e); | |
17df50a5 XL |
461 | diag.help("see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance"); |
462 | } | |
463 | } | |
464 | ||
5099ac24 | 465 | self.buffer_error(diag); |
a1dfa0c6 XL |
466 | } |
467 | ||
0bf4aa26 XL |
468 | /// Report a specialized error when `FnMut` closures return a reference to a captured variable. |
469 | /// This function expects `fr` to be local and `outlived_fr` to not be local. | |
470 | /// | |
471 | /// ```text | |
472 | /// error: captured variable cannot escape `FnMut` closure body | |
473 | /// --> $DIR/issue-53040.rs:15:8 | |
474 | /// | | |
475 | /// LL | || &mut v; | |
476 | /// | -- ^^^^^^ creates a reference to a captured variable which escapes the closure body | |
477 | /// | | | |
478 | /// | inferred to be a `FnMut` closure | |
479 | /// | | |
480 | /// = note: `FnMut` closures only have access to their captured variables while they are | |
481 | /// executing... | |
482 | /// = note: ...therefore, returned references to captured variables will escape the closure | |
483 | /// ``` | |
f035d41b XL |
484 | fn report_fnmut_error( |
485 | &self, | |
923072b8 | 486 | errci: &ErrorConstraintInfo<'tcx>, |
f035d41b | 487 | kind: ReturnConstraint, |
5e7ed085 | 488 | ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { |
dfeec247 | 489 | let ErrorConstraintInfo { outlived_fr, span, .. } = errci; |
e1599b0c | 490 | |
dfeec247 | 491 | let mut diag = self |
e1599b0c | 492 | .infcx |
a1dfa0c6 XL |
493 | .tcx |
494 | .sess | |
e1599b0c | 495 | .struct_span_err(*span, "captured variable cannot escape `FnMut` closure body"); |
0bf4aa26 | 496 | |
f035d41b | 497 | let mut output_ty = self.regioncx.universal_regions().unnormalized_output_ty; |
1b1a35ee | 498 | if let ty::Opaque(def_id, _) = *output_ty.kind() { |
f035d41b XL |
499 | output_ty = self.infcx.tcx.type_of(def_id) |
500 | }; | |
501 | ||
502 | debug!("report_fnmut_error: output_ty={:?}", output_ty); | |
503 | ||
1b1a35ee | 504 | let message = match output_ty.kind() { |
f035d41b XL |
505 | ty::Closure(_, _) => { |
506 | "returns a closure that contains a reference to a captured variable, which then \ | |
507 | escapes the closure body" | |
508 | } | |
5e7ed085 | 509 | ty::Adt(def, _) if self.infcx.tcx.is_diagnostic_item(sym::gen_future, def.did()) => { |
f035d41b XL |
510 | "returns an `async` block that contains a reference to a captured variable, which then \ |
511 | escapes the closure body" | |
512 | } | |
513 | _ => "returns a reference to a captured variable which escapes the closure body", | |
0bf4aa26 XL |
514 | }; |
515 | ||
e1599b0c | 516 | diag.span_label(*span, message); |
0bf4aa26 | 517 | |
5099ac24 | 518 | if let ReturnConstraint::ClosureUpvar(upvar_field) = kind { |
f035d41b XL |
519 | let def_id = match self.regioncx.universal_regions().defining_ty { |
520 | DefiningTy::Closure(def_id, _) => def_id, | |
1b1a35ee | 521 | ty => bug!("unexpected DefiningTy {:?}", ty), |
f035d41b XL |
522 | }; |
523 | ||
5099ac24 FG |
524 | let captured_place = &self.upvars[upvar_field.index()].place; |
525 | let defined_hir = match captured_place.place.base { | |
526 | PlaceBase::Local(hirid) => Some(hirid), | |
527 | PlaceBase::Upvar(upvar) => Some(upvar.var_path.hir_id), | |
528 | _ => None, | |
529 | }; | |
530 | ||
923072b8 | 531 | if let Some(def_hir) = defined_hir { |
5099ac24 | 532 | let upvars_map = self.infcx.tcx.upvars_mentioned(def_id).unwrap(); |
923072b8 FG |
533 | let upvar_def_span = self.infcx.tcx.hir().span(def_hir); |
534 | let upvar_span = upvars_map.get(&def_hir).unwrap().span; | |
5099ac24 FG |
535 | diag.span_label(upvar_def_span, "variable defined here"); |
536 | diag.span_label(upvar_span, "variable captured here"); | |
537 | } | |
f035d41b XL |
538 | } |
539 | ||
3dfed10e XL |
540 | if let Some(fr_span) = self.give_region_a_name(*outlived_fr).unwrap().span() { |
541 | diag.span_label(fr_span, "inferred to be a `FnMut` closure"); | |
0bf4aa26 XL |
542 | } |
543 | ||
a1dfa0c6 XL |
544 | diag.note( |
545 | "`FnMut` closures only have access to their captured variables while they are \ | |
546 | executing...", | |
547 | ); | |
0bf4aa26 XL |
548 | diag.note("...therefore, they cannot allow references to captured variables to escape"); |
549 | ||
e1599b0c | 550 | diag |
0bf4aa26 XL |
551 | } |
552 | ||
94222f64 | 553 | /// Reports an error specifically for when data is escaping a closure. |
0bf4aa26 XL |
554 | /// |
555 | /// ```text | |
556 | /// error: borrowed data escapes outside of function | |
557 | /// --> $DIR/lifetime-bound-will-change-warning.rs:44:5 | |
558 | /// | | |
559 | /// LL | fn test2<'a>(x: &'a Box<Fn()+'a>) { | |
560 | /// | - `x` is a reference that is only valid in the function body | |
561 | /// LL | // but ref_obj will not, so warn. | |
562 | /// LL | ref_obj(x) | |
563 | /// | ^^^^^^^^^^ `x` escapes the function body here | |
564 | /// ``` | |
5e7ed085 FG |
565 | fn report_escaping_data_error( |
566 | &self, | |
923072b8 | 567 | errci: &ErrorConstraintInfo<'tcx>, |
5e7ed085 | 568 | ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { |
dfeec247 XL |
569 | let ErrorConstraintInfo { span, category, .. } = errci; |
570 | ||
571 | let fr_name_and_span = self.regioncx.get_var_name_and_span_for_region( | |
572 | self.infcx.tcx, | |
573 | &self.body, | |
574 | &self.local_names, | |
575 | &self.upvars, | |
576 | errci.fr, | |
577 | ); | |
578 | let outlived_fr_name_and_span = self.regioncx.get_var_name_and_span_for_region( | |
579 | self.infcx.tcx, | |
580 | &self.body, | |
581 | &self.local_names, | |
582 | &self.upvars, | |
60c5eb7d XL |
583 | errci.outlived_fr, |
584 | ); | |
8faf50e0 | 585 | |
74b04a01 XL |
586 | let (_, escapes_from) = self |
587 | .infcx | |
588 | .tcx | |
589 | .article_and_description(self.regioncx.universal_regions().defining_ty.def_id()); | |
8faf50e0 | 590 | |
0bf4aa26 XL |
591 | // Revert to the normal error in these cases. |
592 | // Assignments aren't "escapes" in function items. | |
593 | if (fr_name_and_span.is_none() && outlived_fr_name_and_span.is_none()) | |
74b04a01 XL |
594 | || (*category == ConstraintCategory::Assignment |
595 | && self.regioncx.universal_regions().defining_ty.is_fn_def()) | |
596 | || self.regioncx.universal_regions().defining_ty.is_const() | |
0bf4aa26 | 597 | { |
dfeec247 XL |
598 | return self.report_general_error(&ErrorConstraintInfo { |
599 | fr_is_local: true, | |
600 | outlived_fr_is_local: false, | |
601 | ..*errci | |
602 | }); | |
8faf50e0 XL |
603 | } |
604 | ||
dfeec247 XL |
605 | let mut diag = |
606 | borrowck_errors::borrowed_data_escapes_closure(self.infcx.tcx, *span, escapes_from); | |
8faf50e0 | 607 | |
0bf4aa26 XL |
608 | if let Some((Some(outlived_fr_name), outlived_fr_span)) = outlived_fr_name_and_span { |
609 | diag.span_label( | |
610 | outlived_fr_span, | |
04454e1e | 611 | format!("`{outlived_fr_name}` declared here, outside of the {escapes_from} body",), |
0bf4aa26 | 612 | ); |
8faf50e0 XL |
613 | } |
614 | ||
0bf4aa26 XL |
615 | if let Some((Some(fr_name), fr_span)) = fr_name_and_span { |
616 | diag.span_label( | |
617 | fr_span, | |
618 | format!( | |
04454e1e | 619 | "`{fr_name}` is a reference that is only valid in the {escapes_from} body", |
0bf4aa26 XL |
620 | ), |
621 | ); | |
8faf50e0 | 622 | |
04454e1e | 623 | diag.span_label(*span, format!("`{fr_name}` escapes the {escapes_from} body here")); |
8faf50e0 XL |
624 | } |
625 | ||
c295e0f8 XL |
626 | // Only show an extra note if we can find an 'error region' for both of the region |
627 | // variables. This avoids showing a noisy note that just mentions 'synthetic' regions | |
628 | // that don't help the user understand the error. | |
923072b8 FG |
629 | match (self.to_error_region(errci.fr), self.to_error_region(errci.outlived_fr)) { |
630 | (Some(f), Some(o)) => { | |
631 | self.maybe_suggest_constrain_dyn_trait_impl(&mut diag, f, o, category); | |
c295e0f8 | 632 | |
923072b8 FG |
633 | let fr_region_name = self.give_region_a_name(errci.fr).unwrap(); |
634 | fr_region_name.highlight_region_name(&mut diag); | |
635 | let outlived_fr_region_name = self.give_region_a_name(errci.outlived_fr).unwrap(); | |
636 | outlived_fr_region_name.highlight_region_name(&mut diag); | |
637 | ||
638 | diag.span_label( | |
639 | *span, | |
640 | format!( | |
641 | "{}requires that `{}` must outlive `{}`", | |
642 | category.description(), | |
643 | fr_region_name, | |
644 | outlived_fr_region_name, | |
645 | ), | |
646 | ); | |
647 | } | |
648 | _ => {} | |
c295e0f8 | 649 | } |
923072b8 | 650 | |
e1599b0c | 651 | diag |
8faf50e0 XL |
652 | } |
653 | ||
0bf4aa26 XL |
654 | /// Reports a region inference error for the general case with named/synthesized lifetimes to |
655 | /// explain what is happening. | |
656 | /// | |
657 | /// ```text | |
658 | /// error: unsatisfied lifetime constraints | |
659 | /// --> $DIR/regions-creating-enums3.rs:17:5 | |
660 | /// | | |
661 | /// LL | fn mk_add_bad1<'a,'b>(x: &'a ast<'a>, y: &'b ast<'b>) -> ast<'a> { | |
662 | /// | -- -- lifetime `'b` defined here | |
663 | /// | | | |
664 | /// | lifetime `'a` defined here | |
665 | /// LL | ast::add(x, y) | |
666 | /// | ^^^^^^^^^^^^^^ function was supposed to return data with lifetime `'a` but it | |
667 | /// | is returning data with lifetime `'b` | |
668 | /// ``` | |
5e7ed085 FG |
669 | fn report_general_error( |
670 | &self, | |
923072b8 | 671 | errci: &ErrorConstraintInfo<'tcx>, |
5e7ed085 | 672 | ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { |
e1599b0c | 673 | let ErrorConstraintInfo { |
dfeec247 XL |
674 | fr, |
675 | fr_is_local, | |
676 | outlived_fr, | |
677 | outlived_fr_is_local, | |
678 | span, | |
679 | category, | |
680 | .. | |
e1599b0c XL |
681 | } = errci; |
682 | ||
dfeec247 XL |
683 | let mut diag = |
684 | self.infcx.tcx.sess.struct_span_err(*span, "lifetime may not live long enough"); | |
8faf50e0 | 685 | |
29967ef6 XL |
686 | let (_, mir_def_name) = |
687 | self.infcx.tcx.article_and_description(self.mir_def_id().to_def_id()); | |
8faf50e0 | 688 | |
dfeec247 | 689 | let fr_name = self.give_region_a_name(*fr).unwrap(); |
e1599b0c | 690 | fr_name.highlight_region_name(&mut diag); |
dfeec247 | 691 | let outlived_fr_name = self.give_region_a_name(*outlived_fr).unwrap(); |
e1599b0c XL |
692 | outlived_fr_name.highlight_region_name(&mut diag); |
693 | ||
8faf50e0 | 694 | match (category, outlived_fr_is_local, fr_is_local) { |
f035d41b | 695 | (ConstraintCategory::Return(_), true, _) => { |
a1dfa0c6 | 696 | diag.span_label( |
e1599b0c | 697 | *span, |
a1dfa0c6 | 698 | format!( |
04454e1e FG |
699 | "{mir_def_name} was supposed to return data with lifetime `{outlived_fr_name}` but it is returning \ |
700 | data with lifetime `{fr_name}`", | |
a1dfa0c6 XL |
701 | ), |
702 | ); | |
703 | } | |
8faf50e0 | 704 | _ => { |
a1dfa0c6 | 705 | diag.span_label( |
e1599b0c | 706 | *span, |
a1dfa0c6 XL |
707 | format!( |
708 | "{}requires that `{}` must outlive `{}`", | |
709 | category.description(), | |
710 | fr_name, | |
711 | outlived_fr_name, | |
712 | ), | |
713 | ); | |
714 | } | |
8faf50e0 XL |
715 | } |
716 | ||
dfeec247 | 717 | self.add_static_impl_trait_suggestion(&mut diag, *fr, fr_name, *outlived_fr); |
04454e1e | 718 | self.suggest_adding_lifetime_params(&mut diag, *fr, *outlived_fr); |
0bf4aa26 | 719 | |
e1599b0c | 720 | diag |
8faf50e0 XL |
721 | } |
722 | ||
94222f64 | 723 | /// Adds a suggestion to errors where an `impl Trait` is returned. |
0bf4aa26 XL |
724 | /// |
725 | /// ```text | |
dc9dc135 | 726 | /// help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as |
0bf4aa26 XL |
727 | /// a constraint |
728 | /// | | |
729 | /// LL | fn iter_values_anon(&self) -> impl Iterator<Item=u32> + 'a { | |
730 | /// | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | |
731 | /// ``` | |
732 | fn add_static_impl_trait_suggestion( | |
733 | &self, | |
5e7ed085 | 734 | diag: &mut Diagnostic, |
0bf4aa26 XL |
735 | fr: RegionVid, |
736 | // We need to pass `fr_name` - computing it again will label it twice. | |
737 | fr_name: RegionName, | |
738 | outlived_fr: RegionVid, | |
739 | ) { | |
04454e1e FG |
740 | if let (Some(f), Some(outlived_f)) = |
741 | (self.to_error_region(fr), self.to_error_region(outlived_fr)) | |
a1dfa0c6 | 742 | { |
04454e1e FG |
743 | if *outlived_f != ty::ReStatic { |
744 | return; | |
745 | } | |
746 | ||
747 | let fn_returns = self | |
dfeec247 | 748 | .infcx |
a1dfa0c6 XL |
749 | .tcx |
750 | .is_suitable_region(f) | |
04454e1e FG |
751 | .map(|r| self.infcx.tcx.return_type_impl_or_dyn_traits(r.def_id)) |
752 | .unwrap_or_default(); | |
0bf4aa26 | 753 | |
04454e1e FG |
754 | if fn_returns.is_empty() { |
755 | return; | |
0bf4aa26 | 756 | } |
04454e1e FG |
757 | |
758 | let param = if let Some(param) = find_param_with_region(self.infcx.tcx, f, outlived_f) { | |
759 | param | |
760 | } else { | |
761 | return; | |
762 | }; | |
763 | ||
064997fb | 764 | let lifetime = if f.has_name() { fr_name.name } else { kw::UnderscoreLifetime }; |
04454e1e FG |
765 | |
766 | let arg = match param.param.pat.simple_ident() { | |
767 | Some(simple_ident) => format!("argument `{}`", simple_ident), | |
768 | None => "the argument".to_string(), | |
769 | }; | |
770 | let captures = format!("captures data from {}", arg); | |
771 | ||
772 | return nice_region_error::suggest_new_region_bound( | |
773 | self.infcx.tcx, | |
774 | diag, | |
775 | fn_returns, | |
064997fb | 776 | lifetime.to_string(), |
04454e1e FG |
777 | Some(arg), |
778 | captures, | |
779 | Some((param.param_ty_span, param.param_ty.to_string())), | |
780 | ); | |
0bf4aa26 XL |
781 | } |
782 | } | |
04454e1e | 783 | |
923072b8 FG |
784 | fn maybe_suggest_constrain_dyn_trait_impl( |
785 | &self, | |
786 | diag: &mut DiagnosticBuilder<'tcx, ErrorGuaranteed>, | |
787 | f: Region<'tcx>, | |
788 | o: Region<'tcx>, | |
789 | category: &ConstraintCategory<'tcx>, | |
790 | ) { | |
791 | if !o.is_static() { | |
792 | return; | |
793 | } | |
794 | ||
795 | let tcx = self.infcx.tcx; | |
796 | ||
797 | let instance = if let ConstraintCategory::CallArgument(Some(func_ty)) = category { | |
798 | let (fn_did, substs) = match func_ty.kind() { | |
799 | ty::FnDef(fn_did, substs) => (fn_did, substs), | |
800 | _ => return, | |
801 | }; | |
802 | debug!(?fn_did, ?substs); | |
803 | ||
804 | // Only suggest this on function calls, not closures | |
805 | let ty = tcx.type_of(fn_did); | |
806 | debug!("ty: {:?}, ty.kind: {:?}", ty, ty.kind()); | |
807 | if let ty::Closure(_, _) = ty.kind() { | |
808 | return; | |
809 | } | |
810 | ||
811 | if let Ok(Some(instance)) = ty::Instance::resolve( | |
812 | tcx, | |
813 | self.param_env, | |
814 | *fn_did, | |
815 | self.infcx.resolve_vars_if_possible(substs), | |
816 | ) { | |
817 | instance | |
818 | } else { | |
819 | return; | |
820 | } | |
821 | } else { | |
822 | return; | |
823 | }; | |
824 | ||
825 | let param = match find_param_with_region(tcx, f, o) { | |
826 | Some(param) => param, | |
827 | None => return, | |
828 | }; | |
829 | debug!(?param); | |
830 | ||
831 | let mut visitor = TraitObjectVisitor(FxHashSet::default()); | |
832 | visitor.visit_ty(param.param_ty); | |
833 | ||
834 | let Some((ident, self_ty)) = | |
835 | self.get_impl_ident_and_self_ty_from_trait(instance.def_id(), &visitor.0) else {return}; | |
836 | ||
837 | self.suggest_constrain_dyn_trait_in_impl(diag, &visitor.0, ident, self_ty); | |
838 | } | |
839 | ||
840 | #[instrument(skip(self, err), level = "debug")] | |
841 | fn suggest_constrain_dyn_trait_in_impl( | |
842 | &self, | |
843 | err: &mut Diagnostic, | |
844 | found_dids: &FxHashSet<DefId>, | |
845 | ident: Ident, | |
846 | self_ty: &hir::Ty<'_>, | |
847 | ) -> bool { | |
848 | debug!("err: {:#?}", err); | |
849 | let mut suggested = false; | |
850 | for found_did in found_dids { | |
851 | let mut traits = vec![]; | |
852 | let mut hir_v = HirTraitObjectVisitor(&mut traits, *found_did); | |
853 | hir_v.visit_ty(&self_ty); | |
854 | debug!("trait spans found: {:?}", traits); | |
855 | for span in &traits { | |
856 | let mut multi_span: MultiSpan = vec![*span].into(); | |
064997fb FG |
857 | multi_span |
858 | .push_span_label(*span, "this has an implicit `'static` lifetime requirement"); | |
923072b8 FG |
859 | multi_span.push_span_label( |
860 | ident.span, | |
064997fb | 861 | "calling this method introduces the `impl`'s 'static` requirement", |
923072b8 FG |
862 | ); |
863 | err.span_note(multi_span, "the used `impl` has a `'static` requirement"); | |
864 | err.span_suggestion_verbose( | |
865 | span.shrink_to_hi(), | |
866 | "consider relaxing the implicit `'static` requirement", | |
867 | " + '_", | |
868 | Applicability::MaybeIncorrect, | |
869 | ); | |
870 | suggested = true; | |
871 | } | |
872 | } | |
873 | suggested | |
874 | } | |
875 | ||
04454e1e FG |
876 | fn suggest_adding_lifetime_params( |
877 | &self, | |
878 | diag: &mut Diagnostic, | |
879 | sub: RegionVid, | |
880 | sup: RegionVid, | |
881 | ) { | |
882 | let (Some(sub), Some(sup)) = (self.to_error_region(sub), self.to_error_region(sup)) else { | |
883 | return | |
884 | }; | |
885 | ||
886 | let Some((ty_sub, _)) = self | |
887 | .infcx | |
888 | .tcx | |
889 | .is_suitable_region(sub) | |
890 | .and_then(|anon_reg| find_anon_type(self.infcx.tcx, sub, &anon_reg.boundregion)) else { | |
891 | return | |
892 | }; | |
893 | ||
894 | let Some((ty_sup, _)) = self | |
895 | .infcx | |
896 | .tcx | |
897 | .is_suitable_region(sup) | |
898 | .and_then(|anon_reg| find_anon_type(self.infcx.tcx, sup, &anon_reg.boundregion)) else { | |
899 | return | |
900 | }; | |
901 | ||
902 | suggest_adding_lifetime_params(self.infcx.tcx, sub, ty_sup, ty_sub, diag); | |
903 | } | |
8faf50e0 | 904 | } |