]>
Commit | Line | Data |
---|---|---|
f9f354fc | 1 | use either::Either; |
dc9dc135 | 2 | use rustc_data_structures::fx::FxHashSet; |
dc9dc135 | 3 | use rustc_errors::{Applicability, DiagnosticBuilder}; |
dfeec247 XL |
4 | use rustc_hir as hir; |
5 | use rustc_hir::def_id::DefId; | |
6 | use rustc_hir::{AsyncGeneratorKind, GeneratorKind}; | |
7 | use rustc_index::vec::Idx; | |
ba9703b0 XL |
8 | use rustc_middle::mir::{ |
9 | self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory, | |
10 | FakeReadCause, Local, LocalDecl, LocalInfo, LocalKind, Location, Operand, Place, PlaceRef, | |
11 | ProjectionElem, Rvalue, Statement, StatementKind, TerminatorKind, VarBindingForm, | |
12 | }; | |
f9f354fc | 13 | use rustc_middle::ty::{self, suggest_constraining_type_param, Ty}; |
dfeec247 XL |
14 | use rustc_span::source_map::DesugaringKind; |
15 | use rustc_span::Span; | |
dc9dc135 | 16 | |
dc9dc135 | 17 | use crate::dataflow::drop_flag_effects; |
dfeec247 | 18 | use crate::dataflow::indexes::{MoveOutIndex, MovePathIndex}; |
416331ca | 19 | use crate::util::borrowck_errors; |
dc9dc135 | 20 | |
60c5eb7d | 21 | use crate::borrow_check::{ |
dfeec247 XL |
22 | borrow_set::BorrowData, prefixes::IsPrefixOf, InitializationRequiringAction, MirBorrowckCtxt, |
23 | PrefixSet, WriteKind, | |
60c5eb7d XL |
24 | }; |
25 | ||
26 | use super::{ | |
dfeec247 | 27 | explain_borrow::BorrowExplanation, IncludingDowncast, RegionName, RegionNameSource, UseSpans, |
60c5eb7d XL |
28 | }; |
29 | ||
dc9dc135 XL |
30 | #[derive(Debug)] |
31 | struct MoveSite { | |
32 | /// Index of the "move out" that we found. The `MoveData` can | |
33 | /// then tell us where the move occurred. | |
34 | moi: MoveOutIndex, | |
35 | ||
36 | /// `true` if we traversed a back edge while walking from the point | |
37 | /// of error to the move site. | |
dfeec247 | 38 | traversed_back_edge: bool, |
dc9dc135 XL |
39 | } |
40 | ||
41 | /// Which case a StorageDeadOrDrop is for. | |
42 | #[derive(Copy, Clone, PartialEq, Eq, Debug)] | |
43 | enum StorageDeadOrDrop<'tcx> { | |
44 | LocalStorageDead, | |
45 | BoxedStorageDead, | |
46 | Destructor(Ty<'tcx>), | |
47 | } | |
48 | ||
49 | impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { | |
60c5eb7d | 50 | pub(in crate::borrow_check) fn report_use_of_moved_or_uninitialized( |
dc9dc135 XL |
51 | &mut self, |
52 | location: Location, | |
53 | desired_action: InitializationRequiringAction, | |
74b04a01 | 54 | (moved_place, used_place, span): (PlaceRef<'tcx>, PlaceRef<'tcx>, Span), |
dc9dc135 XL |
55 | mpi: MovePathIndex, |
56 | ) { | |
57 | debug!( | |
58 | "report_use_of_moved_or_uninitialized: location={:?} desired_action={:?} \ | |
59 | moved_place={:?} used_place={:?} span={:?} mpi={:?}", | |
60 | location, desired_action, moved_place, used_place, span, mpi | |
61 | ); | |
62 | ||
dfeec247 XL |
63 | let use_spans = |
64 | self.move_spans(moved_place, location).or_else(|| self.borrow_spans(span, location)); | |
dc9dc135 XL |
65 | let span = use_spans.args_or_use(); |
66 | ||
67 | let move_site_vec = self.get_moved_indexes(location, mpi); | |
dfeec247 XL |
68 | debug!("report_use_of_moved_or_uninitialized: move_site_vec={:?}", move_site_vec); |
69 | let move_out_indices: Vec<_> = | |
70 | move_site_vec.iter().map(|move_site| move_site.moi).collect(); | |
dc9dc135 XL |
71 | |
72 | if move_out_indices.is_empty() { | |
60c5eb7d | 73 | let root_place = PlaceRef { projection: &[], ..used_place }; |
dc9dc135 | 74 | |
e74abb32 | 75 | if !self.uninitialized_error_reported.insert(root_place) { |
dc9dc135 XL |
76 | debug!( |
77 | "report_use_of_moved_or_uninitialized place: error about {:?} suppressed", | |
78 | root_place | |
79 | ); | |
80 | return; | |
81 | } | |
82 | ||
dfeec247 XL |
83 | let item_msg = |
84 | match self.describe_place_with_options(used_place, IncludingDowncast(true)) { | |
85 | Some(name) => format!("`{}`", name), | |
86 | None => "value".to_owned(), | |
87 | }; | |
416331ca | 88 | let mut err = self.cannot_act_on_uninitialized_variable( |
dc9dc135 XL |
89 | span, |
90 | desired_action.as_noun(), | |
dfeec247 XL |
91 | &self |
92 | .describe_place_with_options(moved_place, IncludingDowncast(true)) | |
dc9dc135 | 93 | .unwrap_or_else(|| "_".to_owned()), |
dc9dc135 | 94 | ); |
e1599b0c | 95 | err.span_label(span, format!("use of possibly-uninitialized {}", item_msg)); |
dc9dc135 XL |
96 | |
97 | use_spans.var_span_label( | |
98 | &mut err, | |
99 | format!("{} occurs due to use{}", desired_action.as_noun(), use_spans.describe()), | |
100 | ); | |
101 | ||
102 | err.buffer(&mut self.errors_buffer); | |
103 | } else { | |
104 | if let Some((reported_place, _)) = self.move_error_reported.get(&move_out_indices) { | |
dfeec247 | 105 | if self.prefixes(*reported_place, PrefixSet::All).any(|p| p == used_place) { |
dc9dc135 XL |
106 | debug!( |
107 | "report_use_of_moved_or_uninitialized place: error suppressed \ | |
108 | mois={:?}", | |
109 | move_out_indices | |
110 | ); | |
111 | return; | |
112 | } | |
113 | } | |
114 | ||
115 | let msg = ""; //FIXME: add "partially " or "collaterally " | |
116 | ||
416331ca | 117 | let mut err = self.cannot_act_on_moved_value( |
dc9dc135 XL |
118 | span, |
119 | desired_action.as_noun(), | |
120 | msg, | |
416331ca | 121 | self.describe_place_with_options(moved_place, IncludingDowncast(true)), |
dc9dc135 XL |
122 | ); |
123 | ||
dfeec247 | 124 | self.add_moved_or_invoked_closure_note(location, used_place, &mut err); |
dc9dc135 XL |
125 | |
126 | let mut is_loop_move = false; | |
127 | let is_partial_move = move_site_vec.iter().any(|move_site| { | |
128 | let move_out = self.move_data.moves[(*move_site).moi]; | |
129 | let moved_place = &self.move_data.move_paths[move_out.path].place; | |
dfeec247 | 130 | used_place != moved_place.as_ref() && used_place.is_prefix_of(moved_place.as_ref()) |
dc9dc135 XL |
131 | }); |
132 | for move_site in &move_site_vec { | |
133 | let move_out = self.move_data.moves[(*move_site).moi]; | |
134 | let moved_place = &self.move_data.move_paths[move_out.path].place; | |
135 | ||
416331ca | 136 | let move_spans = self.move_spans(moved_place.as_ref(), move_out.source); |
dc9dc135 XL |
137 | let move_span = move_spans.args_or_use(); |
138 | ||
dfeec247 | 139 | let move_msg = if move_spans.for_closure() { " into closure" } else { "" }; |
dc9dc135 XL |
140 | |
141 | if span == move_span { | |
142 | err.span_label( | |
143 | span, | |
144 | format!("value moved{} here, in previous iteration of loop", move_msg), | |
145 | ); | |
146 | is_loop_move = true; | |
147 | } else if move_site.traversed_back_edge { | |
148 | err.span_label( | |
149 | move_span, | |
dfeec247 | 150 | format!("value moved{} here, in previous iteration of loop", move_msg), |
dc9dc135 XL |
151 | ); |
152 | } else { | |
153 | err.span_label(move_span, format!("value moved{} here", move_msg)); | |
154 | move_spans.var_span_label( | |
155 | &mut err, | |
156 | format!("variable moved due to use{}", move_spans.describe()), | |
157 | ); | |
158 | } | |
416331ca | 159 | if Some(DesugaringKind::ForLoop) == move_span.desugaring_kind() { |
e1599b0c XL |
160 | let sess = self.infcx.tcx.sess; |
161 | if let Ok(snippet) = sess.source_map().span_to_snippet(move_span) { | |
dc9dc135 XL |
162 | err.span_suggestion( |
163 | move_span, | |
164 | "consider borrowing to avoid moving into the for loop", | |
165 | format!("&{}", snippet), | |
166 | Applicability::MaybeIncorrect, | |
167 | ); | |
168 | } | |
169 | } | |
170 | } | |
171 | ||
172 | use_spans.var_span_label( | |
173 | &mut err, | |
174 | format!("{} occurs due to use{}", desired_action.as_noun(), use_spans.describe()), | |
175 | ); | |
176 | ||
177 | if !is_loop_move { | |
178 | err.span_label( | |
179 | span, | |
180 | format!( | |
181 | "value {} here {}", | |
182 | desired_action.as_verb_in_past_tense(), | |
183 | if is_partial_move { "after partial move" } else { "after move" }, | |
184 | ), | |
185 | ); | |
186 | } | |
187 | ||
dfeec247 | 188 | let ty = |
f9f354fc | 189 | Place::ty_from(used_place.local, used_place.projection, self.body, self.infcx.tcx) |
dfeec247 | 190 | .ty; |
e74abb32 | 191 | let needs_note = match ty.kind { |
dc9dc135 | 192 | ty::Closure(id, _) => { |
f9f354fc XL |
193 | let tables = self.infcx.tcx.typeck_tables_of(id.expect_local()); |
194 | let hir_id = self.infcx.tcx.hir().as_local_hir_id(id.expect_local()); | |
dc9dc135 XL |
195 | |
196 | tables.closure_kind_origins().get(hir_id).is_none() | |
197 | } | |
198 | _ => true, | |
199 | }; | |
200 | ||
201 | if needs_note { | |
202 | let mpi = self.move_data.moves[move_out_indices[0]].path; | |
203 | let place = &self.move_data.move_paths[mpi].place; | |
204 | ||
f9f354fc | 205 | let ty = place.ty(self.body, self.infcx.tcx).ty; |
416331ca XL |
206 | let opt_name = |
207 | self.describe_place_with_options(place.as_ref(), IncludingDowncast(true)); | |
dc9dc135 XL |
208 | let note_msg = match opt_name { |
209 | Some(ref name) => format!("`{}`", name), | |
210 | None => "value".to_owned(), | |
211 | }; | |
e74abb32 | 212 | if let ty::Param(param_ty) = ty.kind { |
dc9dc135 XL |
213 | let tcx = self.infcx.tcx; |
214 | let generics = tcx.generics_of(self.mir_def_id); | |
60c5eb7d XL |
215 | let param = generics.type_param(¶m_ty, tcx); |
216 | if let Some(generics) = | |
f9f354fc | 217 | tcx.hir().get_generics(tcx.closure_base_def_id(self.mir_def_id.to_def_id())) |
dfeec247 | 218 | { |
60c5eb7d | 219 | suggest_constraining_type_param( |
74b04a01 | 220 | tcx, |
60c5eb7d XL |
221 | generics, |
222 | &mut err, | |
223 | ¶m.name.as_str(), | |
224 | "Copy", | |
74b04a01 | 225 | None, |
dc9dc135 XL |
226 | ); |
227 | } | |
228 | } | |
e74abb32 XL |
229 | let span = if let Some(local) = place.as_local() { |
230 | let decl = &self.body.local_decls[local]; | |
dc9dc135 XL |
231 | Some(decl.source_info.span) |
232 | } else { | |
233 | None | |
234 | }; | |
dfeec247 | 235 | self.note_type_does_not_implement_copy(&mut err, ¬e_msg, ty, span); |
dc9dc135 XL |
236 | } |
237 | ||
dfeec247 XL |
238 | if let Some((_, mut old_err)) = |
239 | self.move_error_reported.insert(move_out_indices, (used_place, err)) | |
dc9dc135 XL |
240 | { |
241 | // Cancel the old error so it doesn't ICE. | |
242 | old_err.cancel(); | |
243 | } | |
244 | } | |
245 | } | |
246 | ||
60c5eb7d | 247 | pub(in crate::borrow_check) fn report_move_out_while_borrowed( |
dc9dc135 XL |
248 | &mut self, |
249 | location: Location, | |
ba9703b0 | 250 | (place, span): (Place<'tcx>, Span), |
dc9dc135 XL |
251 | borrow: &BorrowData<'tcx>, |
252 | ) { | |
253 | debug!( | |
254 | "report_move_out_while_borrowed: location={:?} place={:?} span={:?} borrow={:?}", | |
255 | location, place, span, borrow | |
256 | ); | |
ba9703b0 XL |
257 | let value_msg = self.describe_any_place(place.as_ref()); |
258 | let borrow_msg = self.describe_any_place(borrow.borrowed_place.as_ref()); | |
dc9dc135 XL |
259 | |
260 | let borrow_spans = self.retrieve_borrow_spans(borrow); | |
261 | let borrow_span = borrow_spans.args_or_use(); | |
262 | ||
416331ca | 263 | let move_spans = self.move_spans(place.as_ref(), location); |
dc9dc135 XL |
264 | let span = move_spans.args_or_use(); |
265 | ||
ba9703b0 XL |
266 | let mut err = |
267 | self.cannot_move_when_borrowed(span, &self.describe_any_place(place.as_ref())); | |
dc9dc135 XL |
268 | err.span_label(borrow_span, format!("borrow of {} occurs here", borrow_msg)); |
269 | err.span_label(span, format!("move out of {} occurs here", value_msg)); | |
270 | ||
271 | borrow_spans.var_span_label( | |
272 | &mut err, | |
dfeec247 | 273 | format!("borrow occurs due to use{}", borrow_spans.describe()), |
dc9dc135 XL |
274 | ); |
275 | ||
dfeec247 XL |
276 | move_spans |
277 | .var_span_label(&mut err, format!("move occurs due to use{}", move_spans.describe())); | |
dc9dc135 | 278 | |
dfeec247 XL |
279 | self.explain_why_borrow_contains_point(location, borrow, None) |
280 | .add_explanation_to_diagnostic( | |
281 | self.infcx.tcx, | |
282 | &self.body, | |
283 | &self.local_names, | |
284 | &mut err, | |
285 | "", | |
286 | Some(borrow_span), | |
287 | ); | |
dc9dc135 XL |
288 | err.buffer(&mut self.errors_buffer); |
289 | } | |
290 | ||
60c5eb7d | 291 | pub(in crate::borrow_check) fn report_use_while_mutably_borrowed( |
dc9dc135 XL |
292 | &mut self, |
293 | location: Location, | |
ba9703b0 | 294 | (place, _span): (Place<'tcx>, Span), |
dc9dc135 XL |
295 | borrow: &BorrowData<'tcx>, |
296 | ) -> DiagnosticBuilder<'cx> { | |
dc9dc135 XL |
297 | let borrow_spans = self.retrieve_borrow_spans(borrow); |
298 | let borrow_span = borrow_spans.args_or_use(); | |
299 | ||
300 | // Conflicting borrows are reported separately, so only check for move | |
301 | // captures. | |
416331ca | 302 | let use_spans = self.move_spans(place.as_ref(), location); |
dc9dc135 XL |
303 | let span = use_spans.var_or_use(); |
304 | ||
416331ca | 305 | let mut err = self.cannot_use_when_mutably_borrowed( |
dc9dc135 | 306 | span, |
ba9703b0 | 307 | &self.describe_any_place(place.as_ref()), |
dc9dc135 | 308 | borrow_span, |
ba9703b0 | 309 | &self.describe_any_place(borrow.borrowed_place.as_ref()), |
dc9dc135 XL |
310 | ); |
311 | ||
312 | borrow_spans.var_span_label(&mut err, { | |
313 | let place = &borrow.borrowed_place; | |
ba9703b0 XL |
314 | let desc_place = self.describe_any_place(place.as_ref()); |
315 | format!("borrow occurs due to use of {}{}", desc_place, borrow_spans.describe()) | |
dc9dc135 XL |
316 | }); |
317 | ||
318 | self.explain_why_borrow_contains_point(location, borrow, None) | |
60c5eb7d XL |
319 | .add_explanation_to_diagnostic( |
320 | self.infcx.tcx, | |
321 | &self.body, | |
322 | &self.local_names, | |
323 | &mut err, | |
324 | "", | |
325 | None, | |
326 | ); | |
dc9dc135 XL |
327 | err |
328 | } | |
329 | ||
60c5eb7d | 330 | pub(in crate::borrow_check) fn report_conflicting_borrow( |
dc9dc135 XL |
331 | &mut self, |
332 | location: Location, | |
ba9703b0 | 333 | (place, span): (Place<'tcx>, Span), |
dc9dc135 XL |
334 | gen_borrow_kind: BorrowKind, |
335 | issued_borrow: &BorrowData<'tcx>, | |
336 | ) -> DiagnosticBuilder<'cx> { | |
337 | let issued_spans = self.retrieve_borrow_spans(issued_borrow); | |
338 | let issued_span = issued_spans.args_or_use(); | |
339 | ||
340 | let borrow_spans = self.borrow_spans(span, location); | |
341 | let span = borrow_spans.args_or_use(); | |
342 | ||
343 | let container_name = if issued_spans.for_generator() || borrow_spans.for_generator() { | |
344 | "generator" | |
345 | } else { | |
346 | "closure" | |
347 | }; | |
348 | ||
349 | let (desc_place, msg_place, msg_borrow, union_type_name) = | |
ba9703b0 | 350 | self.describe_place_for_conflicting_borrow(place, issued_borrow.borrowed_place); |
dc9dc135 XL |
351 | |
352 | let explanation = self.explain_why_borrow_contains_point(location, issued_borrow, None); | |
dfeec247 | 353 | let second_borrow_desc = if explanation.is_explained() { "second " } else { "" }; |
dc9dc135 XL |
354 | |
355 | // FIXME: supply non-"" `opt_via` when appropriate | |
dc9dc135 | 356 | let first_borrow_desc; |
dfeec247 | 357 | let mut err = match (gen_borrow_kind, issued_borrow.kind) { |
60c5eb7d | 358 | (BorrowKind::Shared, BorrowKind::Mut { .. }) => { |
dc9dc135 | 359 | first_borrow_desc = "mutable "; |
416331ca | 360 | self.cannot_reborrow_already_borrowed( |
dc9dc135 XL |
361 | span, |
362 | &desc_place, | |
363 | &msg_place, | |
60c5eb7d | 364 | "immutable", |
dc9dc135 XL |
365 | issued_span, |
366 | "it", | |
60c5eb7d | 367 | "mutable", |
dc9dc135 XL |
368 | &msg_borrow, |
369 | None, | |
dc9dc135 XL |
370 | ) |
371 | } | |
60c5eb7d | 372 | (BorrowKind::Mut { .. }, BorrowKind::Shared) => { |
dc9dc135 | 373 | first_borrow_desc = "immutable "; |
416331ca | 374 | self.cannot_reborrow_already_borrowed( |
dc9dc135 XL |
375 | span, |
376 | &desc_place, | |
377 | &msg_place, | |
60c5eb7d | 378 | "mutable", |
dc9dc135 XL |
379 | issued_span, |
380 | "it", | |
60c5eb7d | 381 | "immutable", |
dc9dc135 XL |
382 | &msg_borrow, |
383 | None, | |
dc9dc135 XL |
384 | ) |
385 | } | |
386 | ||
60c5eb7d | 387 | (BorrowKind::Mut { .. }, BorrowKind::Mut { .. }) => { |
dc9dc135 | 388 | first_borrow_desc = "first "; |
74b04a01 | 389 | let mut err = self.cannot_mutably_borrow_multiply( |
dc9dc135 XL |
390 | span, |
391 | &desc_place, | |
392 | &msg_place, | |
393 | issued_span, | |
394 | &msg_borrow, | |
395 | None, | |
74b04a01 XL |
396 | ); |
397 | self.suggest_split_at_mut_if_applicable( | |
398 | &mut err, | |
ba9703b0 XL |
399 | place, |
400 | issued_borrow.borrowed_place, | |
74b04a01 XL |
401 | ); |
402 | err | |
dc9dc135 XL |
403 | } |
404 | ||
60c5eb7d | 405 | (BorrowKind::Unique, BorrowKind::Unique) => { |
dc9dc135 | 406 | first_borrow_desc = "first "; |
dfeec247 | 407 | self.cannot_uniquely_borrow_by_two_closures(span, &desc_place, issued_span, None) |
dc9dc135 XL |
408 | } |
409 | ||
ba9703b0 | 410 | (BorrowKind::Mut { .. } | BorrowKind::Unique, BorrowKind::Shallow) => { |
dfeec247 | 411 | if let Some(immutable_section_description) = |
ba9703b0 | 412 | self.classify_immutable_section(issued_borrow.assigned_place) |
dfeec247 | 413 | { |
60c5eb7d XL |
414 | let mut err = self.cannot_mutate_in_immutable_section( |
415 | span, | |
416 | issued_span, | |
417 | &desc_place, | |
418 | immutable_section_description, | |
419 | "mutably borrow", | |
420 | ); | |
421 | borrow_spans.var_span_label( | |
422 | &mut err, | |
423 | format!( | |
ba9703b0 | 424 | "borrow occurs due to use of {}{}", |
60c5eb7d XL |
425 | desc_place, |
426 | borrow_spans.describe(), | |
427 | ), | |
428 | ); | |
dc9dc135 | 429 | |
60c5eb7d XL |
430 | return err; |
431 | } else { | |
432 | first_borrow_desc = "immutable "; | |
433 | self.cannot_reborrow_already_borrowed( | |
434 | span, | |
435 | &desc_place, | |
436 | &msg_place, | |
437 | "mutable", | |
438 | issued_span, | |
439 | "it", | |
440 | "immutable", | |
441 | &msg_borrow, | |
442 | None, | |
443 | ) | |
444 | } | |
dc9dc135 XL |
445 | } |
446 | ||
60c5eb7d | 447 | (BorrowKind::Unique, _) => { |
dc9dc135 | 448 | first_borrow_desc = "first "; |
416331ca | 449 | self.cannot_uniquely_borrow_by_one_closure( |
dc9dc135 XL |
450 | span, |
451 | container_name, | |
452 | &desc_place, | |
453 | "", | |
454 | issued_span, | |
455 | "it", | |
456 | "", | |
457 | None, | |
dc9dc135 | 458 | ) |
dfeec247 | 459 | } |
dc9dc135 | 460 | |
60c5eb7d | 461 | (BorrowKind::Shared, BorrowKind::Unique) => { |
dc9dc135 | 462 | first_borrow_desc = "first "; |
416331ca | 463 | self.cannot_reborrow_already_uniquely_borrowed( |
dc9dc135 XL |
464 | span, |
465 | container_name, | |
466 | &desc_place, | |
467 | "", | |
60c5eb7d | 468 | "immutable", |
dc9dc135 XL |
469 | issued_span, |
470 | "", | |
471 | None, | |
472 | second_borrow_desc, | |
dc9dc135 XL |
473 | ) |
474 | } | |
475 | ||
60c5eb7d | 476 | (BorrowKind::Mut { .. }, BorrowKind::Unique) => { |
dc9dc135 | 477 | first_borrow_desc = "first "; |
416331ca | 478 | self.cannot_reborrow_already_uniquely_borrowed( |
dc9dc135 XL |
479 | span, |
480 | container_name, | |
481 | &desc_place, | |
482 | "", | |
60c5eb7d | 483 | "mutable", |
dc9dc135 XL |
484 | issued_span, |
485 | "", | |
486 | None, | |
487 | second_borrow_desc, | |
dc9dc135 XL |
488 | ) |
489 | } | |
490 | ||
ba9703b0 XL |
491 | (BorrowKind::Shared, BorrowKind::Shared | BorrowKind::Shallow) |
492 | | ( | |
493 | BorrowKind::Shallow, | |
494 | BorrowKind::Mut { .. } | |
495 | | BorrowKind::Unique | |
496 | | BorrowKind::Shared | |
497 | | BorrowKind::Shallow, | |
498 | ) => unreachable!(), | |
dc9dc135 XL |
499 | }; |
500 | ||
501 | if issued_spans == borrow_spans { | |
502 | borrow_spans.var_span_label( | |
503 | &mut err, | |
ba9703b0 | 504 | format!("borrows occur due to use of {}{}", desc_place, borrow_spans.describe()), |
dc9dc135 XL |
505 | ); |
506 | } else { | |
507 | let borrow_place = &issued_borrow.borrowed_place; | |
ba9703b0 | 508 | let borrow_place_desc = self.describe_any_place(borrow_place.as_ref()); |
dc9dc135 XL |
509 | issued_spans.var_span_label( |
510 | &mut err, | |
511 | format!( | |
ba9703b0 | 512 | "first borrow occurs due to use of {}{}", |
dc9dc135 XL |
513 | borrow_place_desc, |
514 | issued_spans.describe(), | |
515 | ), | |
516 | ); | |
517 | ||
518 | borrow_spans.var_span_label( | |
519 | &mut err, | |
520 | format!( | |
ba9703b0 | 521 | "second borrow occurs due to use of {}{}", |
dc9dc135 XL |
522 | desc_place, |
523 | borrow_spans.describe(), | |
524 | ), | |
525 | ); | |
526 | } | |
527 | ||
528 | if union_type_name != "" { | |
529 | err.note(&format!( | |
ba9703b0 | 530 | "{} is a field of the union `{}`, so it overlaps the field {}", |
dc9dc135 XL |
531 | msg_place, union_type_name, msg_borrow, |
532 | )); | |
533 | } | |
534 | ||
535 | explanation.add_explanation_to_diagnostic( | |
536 | self.infcx.tcx, | |
60c5eb7d XL |
537 | &self.body, |
538 | &self.local_names, | |
dc9dc135 XL |
539 | &mut err, |
540 | first_borrow_desc, | |
541 | None, | |
542 | ); | |
543 | ||
544 | err | |
545 | } | |
546 | ||
74b04a01 XL |
547 | fn suggest_split_at_mut_if_applicable( |
548 | &self, | |
549 | err: &mut DiagnosticBuilder<'_>, | |
ba9703b0 XL |
550 | place: Place<'tcx>, |
551 | borrowed_place: Place<'tcx>, | |
74b04a01 | 552 | ) { |
ba9703b0 XL |
553 | if let ([ProjectionElem::Index(_)], [ProjectionElem::Index(_)]) = |
554 | (&place.projection[..], &borrowed_place.projection[..]) | |
555 | { | |
556 | err.help( | |
557 | "consider using `.split_at_mut(position)` or similar method to obtain \ | |
74b04a01 | 558 | two mutable non-overlapping sub-slices", |
ba9703b0 | 559 | ); |
74b04a01 XL |
560 | } |
561 | } | |
562 | ||
dc9dc135 XL |
563 | /// Returns the description of the root place for a conflicting borrow and the full |
564 | /// descriptions of the places that caused the conflict. | |
565 | /// | |
566 | /// In the simplest case, where there are no unions involved, if a mutable borrow of `x` is | |
567 | /// attempted while a shared borrow is live, then this function will return: | |
568 | /// | |
569 | /// ("x", "", "") | |
570 | /// | |
571 | /// In the simple union case, if a mutable borrow of a union field `x.z` is attempted while | |
572 | /// a shared borrow of another field `x.y`, then this function will return: | |
573 | /// | |
574 | /// ("x", "x.z", "x.y") | |
575 | /// | |
576 | /// In the more complex union case, where the union is a field of a struct, then if a mutable | |
577 | /// borrow of a union field in a struct `x.u.z` is attempted while a shared borrow of | |
578 | /// another field `x.u.y`, then this function will return: | |
579 | /// | |
580 | /// ("x.u", "x.u.z", "x.u.y") | |
581 | /// | |
582 | /// This is used when creating error messages like below: | |
583 | /// | |
f9f354fc XL |
584 | /// ```text |
585 | /// cannot borrow `a.u` (via `a.u.z.c`) as immutable because it is also borrowed as | |
586 | /// mutable (via `a.u.s.b`) [E0502] | |
587 | /// ``` | |
60c5eb7d | 588 | pub(in crate::borrow_check) fn describe_place_for_conflicting_borrow( |
dc9dc135 | 589 | &self, |
ba9703b0 XL |
590 | first_borrowed_place: Place<'tcx>, |
591 | second_borrowed_place: Place<'tcx>, | |
dc9dc135 XL |
592 | ) -> (String, String, String, String) { |
593 | // Define a small closure that we can use to check if the type of a place | |
594 | // is a union. | |
416331ca | 595 | let union_ty = |place_base, place_projection| { |
f9f354fc | 596 | let ty = Place::ty_from(place_base, place_projection, self.body, self.infcx.tcx).ty; |
dc9dc135 XL |
597 | ty.ty_adt_def().filter(|adt| adt.is_union()).map(|_| ty) |
598 | }; | |
dc9dc135 XL |
599 | |
600 | // Start with an empty tuple, so we can use the functions on `Option` to reduce some | |
601 | // code duplication (particularly around returning an empty description in the failure | |
602 | // case). | |
603 | Some(()) | |
604 | .filter(|_| { | |
605 | // If we have a conflicting borrow of the same place, then we don't want to add | |
606 | // an extraneous "via x.y" to our diagnostics, so filter out this case. | |
607 | first_borrowed_place != second_borrowed_place | |
608 | }) | |
609 | .and_then(|_| { | |
610 | // We're going to want to traverse the first borrowed place to see if we can find | |
611 | // field access to a union. If we find that, then we will keep the place of the | |
612 | // union being accessed and the field that was being accessed so we can check the | |
613 | // second borrowed place for the same union and a access to a different field. | |
dfeec247 | 614 | let Place { local, projection } = first_borrowed_place; |
416331ca | 615 | |
e74abb32 | 616 | let mut cursor = projection.as_ref(); |
e1599b0c XL |
617 | while let [proj_base @ .., elem] = cursor { |
618 | cursor = proj_base; | |
416331ca | 619 | |
dc9dc135 | 620 | match elem { |
ba9703b0 XL |
621 | ProjectionElem::Field(field, _) if union_ty(local, proj_base).is_some() => { |
622 | return Some((PlaceRef { local, projection: proj_base }, field)); | |
dfeec247 XL |
623 | } |
624 | _ => {} | |
dc9dc135 XL |
625 | } |
626 | } | |
627 | None | |
628 | }) | |
629 | .and_then(|(target_base, target_field)| { | |
630 | // With the place of a union and a field access into it, we traverse the second | |
631 | // borrowed place and look for a access to a different field of the same union. | |
ba9703b0 | 632 | let Place { local, ref projection } = second_borrowed_place; |
416331ca | 633 | |
74b04a01 | 634 | let mut cursor = &projection[..]; |
e1599b0c XL |
635 | while let [proj_base @ .., elem] = cursor { |
636 | cursor = proj_base; | |
416331ca | 637 | |
dc9dc135 | 638 | if let ProjectionElem::Field(field, _) = elem { |
ba9703b0 | 639 | if let Some(union_ty) = union_ty(local, proj_base) { |
416331ca | 640 | if field != target_field |
ba9703b0 | 641 | && local == target_base.local |
dfeec247 XL |
642 | && proj_base == target_base.projection |
643 | { | |
dc9dc135 | 644 | return Some(( |
ba9703b0 XL |
645 | self.describe_any_place(PlaceRef { |
646 | local, | |
647 | projection: proj_base, | |
648 | }), | |
649 | self.describe_any_place(first_borrowed_place.as_ref()), | |
650 | self.describe_any_place(second_borrowed_place.as_ref()), | |
dc9dc135 XL |
651 | union_ty.to_string(), |
652 | )); | |
653 | } | |
654 | } | |
655 | } | |
dc9dc135 XL |
656 | } |
657 | None | |
658 | }) | |
659 | .unwrap_or_else(|| { | |
660 | // If we didn't find a field access into a union, or both places match, then | |
661 | // only return the description of the first place. | |
662 | ( | |
ba9703b0 | 663 | self.describe_any_place(first_borrowed_place.as_ref()), |
dc9dc135 XL |
664 | "".to_string(), |
665 | "".to_string(), | |
666 | "".to_string(), | |
667 | ) | |
668 | }) | |
669 | } | |
670 | ||
671 | /// Reports StorageDeadOrDrop of `place` conflicts with `borrow`. | |
672 | /// | |
673 | /// This means that some data referenced by `borrow` needs to live | |
674 | /// past the point where the StorageDeadOrDrop of `place` occurs. | |
675 | /// This is usually interpreted as meaning that `place` has too | |
676 | /// short a lifetime. (But sometimes it is more useful to report | |
677 | /// it as a more direct conflict between the execution of a | |
678 | /// `Drop::drop` with an aliasing borrow.) | |
60c5eb7d | 679 | pub(in crate::borrow_check) fn report_borrowed_value_does_not_live_long_enough( |
dc9dc135 XL |
680 | &mut self, |
681 | location: Location, | |
682 | borrow: &BorrowData<'tcx>, | |
ba9703b0 | 683 | place_span: (Place<'tcx>, Span), |
dc9dc135 XL |
684 | kind: Option<WriteKind>, |
685 | ) { | |
686 | debug!( | |
687 | "report_borrowed_value_does_not_live_long_enough(\ | |
688 | {:?}, {:?}, {:?}, {:?}\ | |
689 | )", | |
690 | location, borrow, place_span, kind | |
691 | ); | |
692 | ||
693 | let drop_span = place_span.1; | |
dfeec247 XL |
694 | let root_place = |
695 | self.prefixes(borrow.borrowed_place.as_ref(), PrefixSet::All).last().unwrap(); | |
dc9dc135 XL |
696 | |
697 | let borrow_spans = self.retrieve_borrow_spans(borrow); | |
698 | let borrow_span = borrow_spans.var_or_use(); | |
699 | ||
e1599b0c | 700 | assert!(root_place.projection.is_empty()); |
74b04a01 | 701 | let proper_span = self.body.local_decls[root_place.local].source_info.span; |
dc9dc135 | 702 | |
e74abb32 XL |
703 | let root_place_projection = self.infcx.tcx.intern_place_elems(root_place.projection); |
704 | ||
dfeec247 | 705 | if self.access_place_error_reported.contains(&( |
74b04a01 | 706 | Place { local: root_place.local, projection: root_place_projection }, |
dfeec247 XL |
707 | borrow_span, |
708 | )) { | |
dc9dc135 XL |
709 | debug!( |
710 | "suppressing access_place error when borrow doesn't live long enough for {:?}", | |
711 | borrow_span | |
712 | ); | |
713 | return; | |
714 | } | |
715 | ||
dfeec247 | 716 | self.access_place_error_reported.insert(( |
74b04a01 | 717 | Place { local: root_place.local, projection: root_place_projection }, |
dfeec247 XL |
718 | borrow_span, |
719 | )); | |
dc9dc135 | 720 | |
dfeec247 XL |
721 | let borrowed_local = borrow.borrowed_place.local; |
722 | if self.body.local_decls[borrowed_local].is_ref_to_thread_local() { | |
723 | let err = | |
724 | self.report_thread_local_value_does_not_live_long_enough(drop_span, borrow_span); | |
725 | err.buffer(&mut self.errors_buffer); | |
726 | return; | |
727 | } | |
60c5eb7d | 728 | |
dc9dc135 | 729 | if let StorageDeadOrDrop::Destructor(dropped_ty) = |
416331ca | 730 | self.classify_drop_access_kind(borrow.borrowed_place.as_ref()) |
dc9dc135 XL |
731 | { |
732 | // If a borrow of path `B` conflicts with drop of `D` (and | |
733 | // we're not in the uninteresting case where `B` is a | |
734 | // prefix of `D`), then report this as a more interesting | |
735 | // destructor conflict. | |
416331ca | 736 | if !borrow.borrowed_place.as_ref().is_prefix_of(place_span.0.as_ref()) { |
dc9dc135 XL |
737 | self.report_borrow_conflicts_with_destructor( |
738 | location, borrow, place_span, kind, dropped_ty, | |
739 | ); | |
740 | return; | |
741 | } | |
742 | } | |
743 | ||
416331ca | 744 | let place_desc = self.describe_place(borrow.borrowed_place.as_ref()); |
dc9dc135 XL |
745 | |
746 | let kind_place = kind.filter(|_| place_desc.is_some()).map(|k| (k, place_span.0)); | |
747 | let explanation = self.explain_why_borrow_contains_point(location, &borrow, kind_place); | |
748 | ||
e74abb32 XL |
749 | debug!( |
750 | "report_borrowed_value_does_not_live_long_enough(place_desc: {:?}, explanation: {:?})", | |
dfeec247 | 751 | place_desc, explanation |
e74abb32 | 752 | ); |
dc9dc135 | 753 | let err = match (place_desc, explanation) { |
dc9dc135 XL |
754 | // If the outlives constraint comes from inside the closure, |
755 | // for example: | |
756 | // | |
757 | // let x = 0; | |
758 | // let y = &x; | |
759 | // Box::new(|| y) as Box<Fn() -> &'static i32> | |
760 | // | |
761 | // then just use the normal error. The closure isn't escaping | |
762 | // and `move` will not help here. | |
763 | ( | |
764 | Some(ref name), | |
765 | BorrowExplanation::MustBeValidFor { | |
ba9703b0 XL |
766 | category: |
767 | category | |
768 | @ | |
769 | (ConstraintCategory::Return | |
770 | | ConstraintCategory::CallArgument | |
771 | | ConstraintCategory::OpaqueType), | |
dc9dc135 XL |
772 | from_closure: false, |
773 | ref region_name, | |
774 | span, | |
775 | .. | |
776 | }, | |
ba9703b0 XL |
777 | ) if borrow_spans.for_generator() | borrow_spans.for_closure() => self |
778 | .report_escaping_closure_capture( | |
779 | borrow_spans, | |
780 | borrow_span, | |
781 | region_name, | |
782 | category, | |
e74abb32 | 783 | span, |
ba9703b0 XL |
784 | &format!("`{}`", name), |
785 | ), | |
dc9dc135 XL |
786 | ( |
787 | ref name, | |
788 | BorrowExplanation::MustBeValidFor { | |
789 | category: ConstraintCategory::Assignment, | |
790 | from_closure: false, | |
dfeec247 XL |
791 | region_name: |
792 | RegionName { | |
793 | source: | |
794 | RegionNameSource::AnonRegionFromUpvar(upvar_span, ref upvar_name), | |
795 | .. | |
796 | }, | |
dc9dc135 XL |
797 | span, |
798 | .. | |
799 | }, | |
800 | ) => self.report_escaping_data(borrow_span, name, upvar_span, upvar_name, span), | |
801 | (Some(name), explanation) => self.report_local_value_does_not_live_long_enough( | |
802 | location, | |
803 | &name, | |
804 | &borrow, | |
805 | drop_span, | |
806 | borrow_spans, | |
807 | explanation, | |
808 | ), | |
809 | (None, explanation) => self.report_temporary_value_does_not_live_long_enough( | |
810 | location, | |
811 | &borrow, | |
812 | drop_span, | |
813 | borrow_spans, | |
814 | proper_span, | |
815 | explanation, | |
816 | ), | |
817 | }; | |
818 | ||
819 | err.buffer(&mut self.errors_buffer); | |
820 | } | |
821 | ||
822 | fn report_local_value_does_not_live_long_enough( | |
823 | &mut self, | |
824 | location: Location, | |
825 | name: &str, | |
826 | borrow: &BorrowData<'tcx>, | |
827 | drop_span: Span, | |
828 | borrow_spans: UseSpans, | |
829 | explanation: BorrowExplanation, | |
830 | ) -> DiagnosticBuilder<'cx> { | |
831 | debug!( | |
832 | "report_local_value_does_not_live_long_enough(\ | |
833 | {:?}, {:?}, {:?}, {:?}, {:?}\ | |
834 | )", | |
835 | location, name, borrow, drop_span, borrow_spans | |
836 | ); | |
837 | ||
838 | let borrow_span = borrow_spans.var_or_use(); | |
839 | if let BorrowExplanation::MustBeValidFor { | |
840 | category, | |
841 | span, | |
842 | ref opt_place_desc, | |
843 | from_closure: false, | |
844 | .. | |
dfeec247 XL |
845 | } = explanation |
846 | { | |
dc9dc135 XL |
847 | if let Some(diag) = self.try_report_cannot_return_reference_to_local( |
848 | borrow, | |
849 | borrow_span, | |
850 | span, | |
851 | category, | |
852 | opt_place_desc.as_ref(), | |
853 | ) { | |
854 | return diag; | |
855 | } | |
856 | } | |
857 | ||
dfeec247 | 858 | let mut err = self.path_does_not_live_long_enough(borrow_span, &format!("`{}`", name)); |
dc9dc135 XL |
859 | |
860 | if let Some(annotation) = self.annotate_argument_and_return_for_borrow(borrow) { | |
861 | let region_name = annotation.emit(self, &mut err); | |
862 | ||
863 | err.span_label( | |
864 | borrow_span, | |
865 | format!("`{}` would have to be valid for `{}`...", name, region_name), | |
866 | ); | |
867 | ||
f9f354fc XL |
868 | let fn_hir_id = self.infcx.tcx.hir().as_local_hir_id(self.mir_def_id); |
869 | err.span_label( | |
870 | drop_span, | |
871 | format!( | |
872 | "...but `{}` will be dropped here, when the {} returns", | |
873 | name, | |
874 | self.infcx | |
875 | .tcx | |
876 | .hir() | |
877 | .opt_name(fn_hir_id) | |
878 | .map(|name| format!("function `{}`", name)) | |
879 | .unwrap_or_else(|| { | |
880 | match &self | |
881 | .infcx | |
882 | .tcx | |
883 | .typeck_tables_of(self.mir_def_id) | |
884 | .node_type(fn_hir_id) | |
885 | .kind | |
886 | { | |
887 | ty::Closure(..) => "enclosing closure", | |
888 | ty::Generator(..) => "enclosing generator", | |
889 | kind => bug!("expected closure or generator, found {:?}", kind), | |
890 | } | |
891 | .to_string() | |
892 | }) | |
893 | ), | |
894 | ); | |
dc9dc135 | 895 | |
f9f354fc XL |
896 | err.note( |
897 | "functions cannot return a borrow to data owned within the function's scope, \ | |
898 | functions can only return borrows to data passed as arguments", | |
899 | ); | |
900 | err.note( | |
901 | "to learn more, visit <https://doc.rust-lang.org/book/ch04-02-\ | |
902 | references-and-borrowing.html#dangling-references>", | |
903 | ); | |
dc9dc135 XL |
904 | |
905 | if let BorrowExplanation::MustBeValidFor { .. } = explanation { | |
906 | } else { | |
907 | explanation.add_explanation_to_diagnostic( | |
908 | self.infcx.tcx, | |
60c5eb7d XL |
909 | &self.body, |
910 | &self.local_names, | |
dc9dc135 XL |
911 | &mut err, |
912 | "", | |
913 | None, | |
914 | ); | |
915 | } | |
916 | } else { | |
917 | err.span_label(borrow_span, "borrowed value does not live long enough"); | |
dfeec247 | 918 | err.span_label(drop_span, format!("`{}` dropped here while still borrowed", name)); |
dc9dc135 | 919 | |
dfeec247 | 920 | let within = if borrow_spans.for_generator() { " by generator" } else { "" }; |
dc9dc135 | 921 | |
dfeec247 | 922 | borrow_spans.args_span_label(&mut err, format!("value captured here{}", within)); |
dc9dc135 XL |
923 | |
924 | explanation.add_explanation_to_diagnostic( | |
dfeec247 XL |
925 | self.infcx.tcx, |
926 | &self.body, | |
927 | &self.local_names, | |
928 | &mut err, | |
929 | "", | |
930 | None, | |
931 | ); | |
dc9dc135 XL |
932 | } |
933 | ||
934 | err | |
935 | } | |
936 | ||
937 | fn report_borrow_conflicts_with_destructor( | |
938 | &mut self, | |
939 | location: Location, | |
940 | borrow: &BorrowData<'tcx>, | |
ba9703b0 | 941 | (place, drop_span): (Place<'tcx>, Span), |
dc9dc135 XL |
942 | kind: Option<WriteKind>, |
943 | dropped_ty: Ty<'tcx>, | |
944 | ) { | |
945 | debug!( | |
946 | "report_borrow_conflicts_with_destructor(\ | |
947 | {:?}, {:?}, ({:?}, {:?}), {:?}\ | |
948 | )", | |
949 | location, borrow, place, drop_span, kind, | |
950 | ); | |
951 | ||
952 | let borrow_spans = self.retrieve_borrow_spans(borrow); | |
953 | let borrow_span = borrow_spans.var_or_use(); | |
954 | ||
416331ca | 955 | let mut err = self.cannot_borrow_across_destructor(borrow_span); |
dc9dc135 | 956 | |
416331ca | 957 | let what_was_dropped = match self.describe_place(place.as_ref()) { |
60c5eb7d | 958 | Some(name) => format!("`{}`", name), |
dc9dc135 XL |
959 | None => String::from("temporary value"), |
960 | }; | |
961 | ||
416331ca | 962 | let label = match self.describe_place(borrow.borrowed_place.as_ref()) { |
dc9dc135 XL |
963 | Some(borrowed) => format!( |
964 | "here, drop of {D} needs exclusive access to `{B}`, \ | |
965 | because the type `{T}` implements the `Drop` trait", | |
966 | D = what_was_dropped, | |
967 | T = dropped_ty, | |
968 | B = borrowed | |
969 | ), | |
970 | None => format!( | |
971 | "here is drop of {D}; whose type `{T}` implements the `Drop` trait", | |
972 | D = what_was_dropped, | |
973 | T = dropped_ty | |
974 | ), | |
975 | }; | |
976 | err.span_label(drop_span, label); | |
977 | ||
978 | // Only give this note and suggestion if they could be relevant. | |
979 | let explanation = | |
980 | self.explain_why_borrow_contains_point(location, borrow, kind.map(|k| (k, place))); | |
981 | match explanation { | |
982 | BorrowExplanation::UsedLater { .. } | |
983 | | BorrowExplanation::UsedLaterWhenDropped { .. } => { | |
984 | err.note("consider using a `let` binding to create a longer lived value"); | |
985 | } | |
986 | _ => {} | |
987 | } | |
988 | ||
60c5eb7d XL |
989 | explanation.add_explanation_to_diagnostic( |
990 | self.infcx.tcx, | |
991 | &self.body, | |
992 | &self.local_names, | |
993 | &mut err, | |
994 | "", | |
995 | None, | |
996 | ); | |
dc9dc135 XL |
997 | |
998 | err.buffer(&mut self.errors_buffer); | |
999 | } | |
1000 | ||
1001 | fn report_thread_local_value_does_not_live_long_enough( | |
1002 | &mut self, | |
1003 | drop_span: Span, | |
1004 | borrow_span: Span, | |
1005 | ) -> DiagnosticBuilder<'cx> { | |
1006 | debug!( | |
1007 | "report_thread_local_value_does_not_live_long_enough(\ | |
1008 | {:?}, {:?}\ | |
1009 | )", | |
1010 | drop_span, borrow_span | |
1011 | ); | |
1012 | ||
416331ca | 1013 | let mut err = self.thread_local_value_does_not_live_long_enough(borrow_span); |
dc9dc135 XL |
1014 | |
1015 | err.span_label( | |
1016 | borrow_span, | |
1017 | "thread-local variables cannot be borrowed beyond the end of the function", | |
1018 | ); | |
1019 | err.span_label(drop_span, "end of enclosing function is here"); | |
1020 | ||
1021 | err | |
1022 | } | |
1023 | ||
1024 | fn report_temporary_value_does_not_live_long_enough( | |
1025 | &mut self, | |
1026 | location: Location, | |
1027 | borrow: &BorrowData<'tcx>, | |
1028 | drop_span: Span, | |
1029 | borrow_spans: UseSpans, | |
1030 | proper_span: Span, | |
1031 | explanation: BorrowExplanation, | |
1032 | ) -> DiagnosticBuilder<'cx> { | |
1033 | debug!( | |
1034 | "report_temporary_value_does_not_live_long_enough(\ | |
1035 | {:?}, {:?}, {:?}, {:?}\ | |
1036 | )", | |
1037 | location, borrow, drop_span, proper_span | |
1038 | ); | |
1039 | ||
dfeec247 XL |
1040 | if let BorrowExplanation::MustBeValidFor { category, span, from_closure: false, .. } = |
1041 | explanation | |
1042 | { | |
dc9dc135 XL |
1043 | if let Some(diag) = self.try_report_cannot_return_reference_to_local( |
1044 | borrow, | |
1045 | proper_span, | |
1046 | span, | |
1047 | category, | |
1048 | None, | |
1049 | ) { | |
1050 | return diag; | |
1051 | } | |
1052 | } | |
1053 | ||
416331ca | 1054 | let mut err = self.temporary_value_borrowed_for_too_long(proper_span); |
dfeec247 XL |
1055 | err.span_label(proper_span, "creates a temporary which is freed while still in use"); |
1056 | err.span_label(drop_span, "temporary value is freed at the end of this statement"); | |
dc9dc135 XL |
1057 | |
1058 | match explanation { | |
1059 | BorrowExplanation::UsedLater(..) | |
1060 | | BorrowExplanation::UsedLaterInLoop(..) | |
1061 | | BorrowExplanation::UsedLaterWhenDropped { .. } => { | |
1062 | // Only give this note and suggestion if it could be relevant. | |
1063 | err.note("consider using a `let` binding to create a longer lived value"); | |
1064 | } | |
1065 | _ => {} | |
1066 | } | |
60c5eb7d XL |
1067 | explanation.add_explanation_to_diagnostic( |
1068 | self.infcx.tcx, | |
1069 | &self.body, | |
1070 | &self.local_names, | |
1071 | &mut err, | |
1072 | "", | |
1073 | None, | |
1074 | ); | |
dc9dc135 | 1075 | |
dfeec247 | 1076 | let within = if borrow_spans.for_generator() { " by generator" } else { "" }; |
dc9dc135 | 1077 | |
dfeec247 | 1078 | borrow_spans.args_span_label(&mut err, format!("value captured here{}", within)); |
dc9dc135 XL |
1079 | |
1080 | err | |
1081 | } | |
1082 | ||
1083 | fn try_report_cannot_return_reference_to_local( | |
1084 | &self, | |
1085 | borrow: &BorrowData<'tcx>, | |
1086 | borrow_span: Span, | |
1087 | return_span: Span, | |
1088 | category: ConstraintCategory, | |
1089 | opt_place_desc: Option<&String>, | |
1090 | ) -> Option<DiagnosticBuilder<'cx>> { | |
dc9dc135 XL |
1091 | let return_kind = match category { |
1092 | ConstraintCategory::Return => "return", | |
1093 | ConstraintCategory::Yield => "yield", | |
1094 | _ => return None, | |
1095 | }; | |
1096 | ||
1097 | // FIXME use a better heuristic than Spans | |
dfeec247 XL |
1098 | let reference_desc = if return_span == self.body.source_info(borrow.reserve_location).span { |
1099 | "reference to" | |
1100 | } else { | |
1101 | "value referencing" | |
1102 | }; | |
dc9dc135 XL |
1103 | |
1104 | let (place_desc, note) = if let Some(place_desc) = opt_place_desc { | |
e74abb32 XL |
1105 | let local_kind = if let Some(local) = borrow.borrowed_place.as_local() { |
1106 | match self.body.local_kind(local) { | |
dfeec247 XL |
1107 | LocalKind::ReturnPointer | LocalKind::Temp => { |
1108 | bug!("temporary or return pointer with a name") | |
1109 | } | |
e74abb32 | 1110 | LocalKind::Var => "local variable ", |
dfeec247 | 1111 | LocalKind::Arg if !self.upvars.is_empty() && local == Local::new(1) => { |
e74abb32 XL |
1112 | "variable captured by `move` " |
1113 | } | |
dfeec247 | 1114 | LocalKind::Arg => "function parameter ", |
dc9dc135 | 1115 | } |
e74abb32 XL |
1116 | } else { |
1117 | "local data " | |
dc9dc135 XL |
1118 | }; |
1119 | ( | |
1120 | format!("{}`{}`", local_kind, place_desc), | |
1121 | format!("`{}` is borrowed here", place_desc), | |
1122 | ) | |
1123 | } else { | |
dfeec247 XL |
1124 | let root_place = |
1125 | self.prefixes(borrow.borrowed_place.as_ref(), PrefixSet::All).last().unwrap(); | |
1126 | let local = root_place.local; | |
74b04a01 | 1127 | match self.body.local_kind(local) { |
dfeec247 XL |
1128 | LocalKind::ReturnPointer | LocalKind::Temp => { |
1129 | ("temporary value".to_string(), "temporary value created here".to_string()) | |
1130 | } | |
dc9dc135 XL |
1131 | LocalKind::Arg => ( |
1132 | "function parameter".to_string(), | |
1133 | "function parameter borrowed here".to_string(), | |
1134 | ), | |
dfeec247 XL |
1135 | LocalKind::Var => { |
1136 | ("local binding".to_string(), "local binding introduced here".to_string()) | |
1137 | } | |
dc9dc135 XL |
1138 | } |
1139 | }; | |
1140 | ||
416331ca | 1141 | let mut err = self.cannot_return_reference_to_local( |
dc9dc135 XL |
1142 | return_span, |
1143 | return_kind, | |
1144 | reference_desc, | |
1145 | &place_desc, | |
dc9dc135 XL |
1146 | ); |
1147 | ||
1148 | if return_span != borrow_span { | |
1149 | err.span_label(borrow_span, note); | |
1150 | } | |
1151 | ||
1152 | Some(err) | |
1153 | } | |
1154 | ||
1155 | fn report_escaping_closure_capture( | |
1156 | &mut self, | |
e74abb32 | 1157 | use_span: UseSpans, |
dc9dc135 XL |
1158 | var_span: Span, |
1159 | fr_name: &RegionName, | |
1160 | category: ConstraintCategory, | |
1161 | constraint_span: Span, | |
1162 | captured_var: &str, | |
1163 | ) -> DiagnosticBuilder<'cx> { | |
1164 | let tcx = self.infcx.tcx; | |
e74abb32 | 1165 | let args_span = use_span.args_or_use(); |
dc9dc135 XL |
1166 | |
1167 | let suggestion = match tcx.sess.source_map().span_to_snippet(args_span) { | |
e1599b0c XL |
1168 | Ok(mut string) => { |
1169 | if string.starts_with("async ") { | |
1170 | string.insert_str(6, "move "); | |
1171 | } else if string.starts_with("async|") { | |
1172 | string.insert_str(5, " move"); | |
1173 | } else { | |
1174 | string.insert_str(0, "move "); | |
1175 | }; | |
1176 | string | |
dfeec247 XL |
1177 | } |
1178 | Err(_) => "move |<args>| <body>".to_string(), | |
dc9dc135 | 1179 | }; |
e74abb32 XL |
1180 | let kind = match use_span.generator_kind() { |
1181 | Some(generator_kind) => match generator_kind { | |
1182 | GeneratorKind::Async(async_kind) => match async_kind { | |
1183 | AsyncGeneratorKind::Block => "async block", | |
1184 | AsyncGeneratorKind::Closure => "async closure", | |
74b04a01 | 1185 | _ => bug!("async block/closure expected, but async function found."), |
e74abb32 XL |
1186 | }, |
1187 | GeneratorKind::Gen => "generator", | |
dfeec247 | 1188 | }, |
e74abb32 XL |
1189 | None => "closure", |
1190 | }; | |
ba9703b0 XL |
1191 | |
1192 | let mut err = | |
1193 | self.cannot_capture_in_long_lived_closure(args_span, kind, captured_var, var_span); | |
dc9dc135 XL |
1194 | err.span_suggestion( |
1195 | args_span, | |
e74abb32 XL |
1196 | &format!( |
1197 | "to force the {} to take ownership of {} (and any \ | |
1198 | other referenced variables), use the `move` keyword", | |
dfeec247 | 1199 | kind, captured_var |
e74abb32 | 1200 | ), |
dc9dc135 XL |
1201 | suggestion, |
1202 | Applicability::MachineApplicable, | |
1203 | ); | |
1204 | ||
60c5eb7d | 1205 | let msg = match category { |
ba9703b0 XL |
1206 | ConstraintCategory::Return | ConstraintCategory::OpaqueType => { |
1207 | format!("{} is returned here", kind) | |
1208 | } | |
dc9dc135 XL |
1209 | ConstraintCategory::CallArgument => { |
1210 | fr_name.highlight_region_name(&mut err); | |
60c5eb7d | 1211 | format!("function requires argument type to outlive `{}`", fr_name) |
dc9dc135 | 1212 | } |
dfeec247 XL |
1213 | _ => bug!( |
1214 | "report_escaping_closure_capture called with unexpected constraint \ | |
74b04a01 | 1215 | category: `{:?}`", |
dfeec247 XL |
1216 | category |
1217 | ), | |
60c5eb7d XL |
1218 | }; |
1219 | err.span_note(constraint_span, &msg); | |
dc9dc135 XL |
1220 | err |
1221 | } | |
1222 | ||
1223 | fn report_escaping_data( | |
1224 | &mut self, | |
1225 | borrow_span: Span, | |
1226 | name: &Option<String>, | |
1227 | upvar_span: Span, | |
1228 | upvar_name: &str, | |
1229 | escape_span: Span, | |
1230 | ) -> DiagnosticBuilder<'cx> { | |
1231 | let tcx = self.infcx.tcx; | |
1232 | ||
f9f354fc | 1233 | let (_, escapes_from) = tcx.article_and_description(self.mir_def_id.to_def_id()); |
dc9dc135 | 1234 | |
dfeec247 XL |
1235 | let mut err = |
1236 | borrowck_errors::borrowed_data_escapes_closure(tcx, escape_span, escapes_from); | |
dc9dc135 XL |
1237 | |
1238 | err.span_label( | |
1239 | upvar_span, | |
74b04a01 | 1240 | format!("`{}` declared here, outside of the {} body", upvar_name, escapes_from), |
dc9dc135 XL |
1241 | ); |
1242 | ||
dfeec247 | 1243 | err.span_label(borrow_span, format!("borrow is only valid in the {} body", escapes_from)); |
dc9dc135 XL |
1244 | |
1245 | if let Some(name) = name { | |
1246 | err.span_label( | |
1247 | escape_span, | |
1248 | format!("reference to `{}` escapes the {} body here", name, escapes_from), | |
1249 | ); | |
1250 | } else { | |
1251 | err.span_label( | |
1252 | escape_span, | |
1253 | format!("reference escapes the {} body here", escapes_from), | |
1254 | ); | |
1255 | } | |
1256 | ||
1257 | err | |
1258 | } | |
1259 | ||
1260 | fn get_moved_indexes(&mut self, location: Location, mpi: MovePathIndex) -> Vec<MoveSite> { | |
f9f354fc XL |
1261 | fn predecessor_locations( |
1262 | body: &'a mir::Body<'tcx>, | |
1263 | location: Location, | |
1264 | ) -> impl Iterator<Item = Location> + 'a { | |
1265 | if location.statement_index == 0 { | |
1266 | let predecessors = body.predecessors()[location.block].to_vec(); | |
1267 | Either::Left(predecessors.into_iter().map(move |bb| body.terminator_loc(bb))) | |
1268 | } else { | |
1269 | Either::Right(std::iter::once(Location { | |
1270 | statement_index: location.statement_index - 1, | |
1271 | ..location | |
1272 | })) | |
1273 | } | |
1274 | } | |
1275 | ||
dc9dc135 | 1276 | let mut stack = Vec::new(); |
f9f354fc | 1277 | stack.extend(predecessor_locations(self.body, location).map(|predecessor| { |
dc9dc135 XL |
1278 | let is_back_edge = location.dominates(predecessor, &self.dominators); |
1279 | (predecessor, is_back_edge) | |
1280 | })); | |
1281 | ||
1282 | let mut visited = FxHashSet::default(); | |
1283 | let mut result = vec![]; | |
1284 | ||
1285 | 'dfs: while let Some((location, is_back_edge)) = stack.pop() { | |
1286 | debug!( | |
1287 | "report_use_of_moved_or_uninitialized: (current_location={:?}, back_edge={})", | |
1288 | location, is_back_edge | |
1289 | ); | |
1290 | ||
1291 | if !visited.insert(location) { | |
1292 | continue; | |
1293 | } | |
1294 | ||
1295 | // check for moves | |
dfeec247 XL |
1296 | let stmt_kind = |
1297 | self.body[location.block].statements.get(location.statement_index).map(|s| &s.kind); | |
dc9dc135 XL |
1298 | if let Some(StatementKind::StorageDead(..)) = stmt_kind { |
1299 | // this analysis only tries to find moves explicitly | |
1300 | // written by the user, so we ignore the move-outs | |
1301 | // created by `StorageDead` and at the beginning | |
1302 | // of a function. | |
1303 | } else { | |
1304 | // If we are found a use of a.b.c which was in error, then we want to look for | |
1305 | // moves not only of a.b.c but also a.b and a. | |
1306 | // | |
1307 | // Note that the moves data already includes "parent" paths, so we don't have to | |
1308 | // worry about the other case: that is, if there is a move of a.b.c, it is already | |
1309 | // marked as a move of a.b and a as well, so we will generate the correct errors | |
1310 | // there. | |
1311 | let mut mpis = vec![mpi]; | |
1312 | let move_paths = &self.move_data.move_paths; | |
74b04a01 | 1313 | mpis.extend(move_paths[mpi].parents(move_paths).map(|(mpi, _)| mpi)); |
dc9dc135 XL |
1314 | |
1315 | for moi in &self.move_data.loc_map[location] { | |
1316 | debug!("report_use_of_moved_or_uninitialized: moi={:?}", moi); | |
1317 | if mpis.contains(&self.move_data.moves[*moi].path) { | |
1318 | debug!("report_use_of_moved_or_uninitialized: found"); | |
dfeec247 | 1319 | result.push(MoveSite { moi: *moi, traversed_back_edge: is_back_edge }); |
dc9dc135 XL |
1320 | |
1321 | // Strictly speaking, we could continue our DFS here. There may be | |
1322 | // other moves that can reach the point of error. But it is kind of | |
1323 | // confusing to highlight them. | |
1324 | // | |
1325 | // Example: | |
1326 | // | |
1327 | // ``` | |
1328 | // let a = vec![]; | |
1329 | // let b = a; | |
1330 | // let c = a; | |
1331 | // drop(a); // <-- current point of error | |
1332 | // ``` | |
1333 | // | |
1334 | // Because we stop the DFS here, we only highlight `let c = a`, | |
1335 | // and not `let b = a`. We will of course also report an error at | |
1336 | // `let c = a` which highlights `let b = a` as the move. | |
1337 | continue 'dfs; | |
1338 | } | |
1339 | } | |
1340 | } | |
1341 | ||
1342 | // check for inits | |
1343 | let mut any_match = false; | |
1344 | drop_flag_effects::for_location_inits( | |
1345 | self.infcx.tcx, | |
60c5eb7d | 1346 | &self.body, |
dc9dc135 XL |
1347 | self.move_data, |
1348 | location, | |
1349 | |m| { | |
1350 | if m == mpi { | |
1351 | any_match = true; | |
1352 | } | |
1353 | }, | |
1354 | ); | |
1355 | if any_match { | |
1356 | continue 'dfs; | |
1357 | } | |
1358 | ||
f9f354fc | 1359 | stack.extend(predecessor_locations(self.body, location).map(|predecessor| { |
dc9dc135 XL |
1360 | let back_edge = location.dominates(predecessor, &self.dominators); |
1361 | (predecessor, is_back_edge || back_edge) | |
1362 | })); | |
1363 | } | |
1364 | ||
1365 | result | |
1366 | } | |
1367 | ||
60c5eb7d | 1368 | pub(in crate::borrow_check) fn report_illegal_mutation_of_borrowed( |
dc9dc135 XL |
1369 | &mut self, |
1370 | location: Location, | |
ba9703b0 | 1371 | (place, span): (Place<'tcx>, Span), |
dc9dc135 XL |
1372 | loan: &BorrowData<'tcx>, |
1373 | ) { | |
1374 | let loan_spans = self.retrieve_borrow_spans(loan); | |
1375 | let loan_span = loan_spans.args_or_use(); | |
1376 | ||
ba9703b0 | 1377 | let descr_place = self.describe_any_place(place.as_ref()); |
dc9dc135 | 1378 | if loan.kind == BorrowKind::Shallow { |
ba9703b0 | 1379 | if let Some(section) = self.classify_immutable_section(loan.assigned_place) { |
60c5eb7d XL |
1380 | let mut err = self.cannot_mutate_in_immutable_section( |
1381 | span, | |
1382 | loan_span, | |
ba9703b0 | 1383 | &descr_place, |
60c5eb7d XL |
1384 | section, |
1385 | "assign", | |
1386 | ); | |
1387 | loan_spans.var_span_label( | |
1388 | &mut err, | |
1389 | format!("borrow occurs due to use{}", loan_spans.describe()), | |
1390 | ); | |
dc9dc135 | 1391 | |
60c5eb7d | 1392 | err.buffer(&mut self.errors_buffer); |
dc9dc135 | 1393 | |
60c5eb7d XL |
1394 | return; |
1395 | } | |
dc9dc135 XL |
1396 | } |
1397 | ||
ba9703b0 | 1398 | let mut err = self.cannot_assign_to_borrowed(span, loan_span, &descr_place); |
dc9dc135 | 1399 | |
dfeec247 XL |
1400 | loan_spans |
1401 | .var_span_label(&mut err, format!("borrow occurs due to use{}", loan_spans.describe())); | |
1402 | ||
1403 | self.explain_why_borrow_contains_point(location, loan, None).add_explanation_to_diagnostic( | |
1404 | self.infcx.tcx, | |
1405 | &self.body, | |
1406 | &self.local_names, | |
dc9dc135 | 1407 | &mut err, |
dfeec247 XL |
1408 | "", |
1409 | None, | |
dc9dc135 XL |
1410 | ); |
1411 | ||
dc9dc135 XL |
1412 | err.buffer(&mut self.errors_buffer); |
1413 | } | |
1414 | ||
1415 | /// Reports an illegal reassignment; for example, an assignment to | |
1416 | /// (part of) a non-`mut` local that occurs potentially after that | |
1417 | /// local has already been initialized. `place` is the path being | |
1418 | /// assigned; `err_place` is a place providing a reason why | |
1419 | /// `place` is not mutable (e.g., the non-`mut` local `x` in an | |
1420 | /// assignment to `x.f`). | |
60c5eb7d | 1421 | pub(in crate::borrow_check) fn report_illegal_reassignment( |
dc9dc135 XL |
1422 | &mut self, |
1423 | _location: Location, | |
ba9703b0 | 1424 | (place, span): (Place<'tcx>, Span), |
dc9dc135 | 1425 | assigned_span: Span, |
ba9703b0 | 1426 | err_place: Place<'tcx>, |
dc9dc135 | 1427 | ) { |
60c5eb7d XL |
1428 | let (from_arg, local_decl, local_name) = match err_place.as_local() { |
1429 | Some(local) => ( | |
1430 | self.body.local_kind(local) == LocalKind::Arg, | |
1431 | Some(&self.body.local_decls[local]), | |
1432 | self.local_names[local], | |
1433 | ), | |
1434 | None => (false, None, None), | |
dc9dc135 XL |
1435 | }; |
1436 | ||
1437 | // If root local is initialized immediately (everything apart from let | |
1438 | // PATTERN;) then make the error refer to that local, rather than the | |
1439 | // place being assigned later. | |
1440 | let (place_description, assigned_span) = match local_decl { | |
ba9703b0 | 1441 | Some(LocalDecl { |
dfeec247 | 1442 | local_info: |
f9f354fc | 1443 | Some(box LocalInfo::User( |
ba9703b0 XL |
1444 | ClearCrossCrate::Clear |
1445 | | ClearCrossCrate::Set(BindingForm::Var(VarBindingForm { | |
1446 | opt_match_place: None, | |
1447 | .. | |
1448 | })), | |
f9f354fc XL |
1449 | )) |
1450 | | Some(box LocalInfo::StaticRef { .. }) | |
1451 | | None, | |
dc9dc135 XL |
1452 | .. |
1453 | }) | |
ba9703b0 XL |
1454 | | None => (self.describe_any_place(place.as_ref()), assigned_span), |
1455 | Some(decl) => (self.describe_any_place(err_place.as_ref()), decl.source_info.span), | |
dc9dc135 XL |
1456 | }; |
1457 | ||
ba9703b0 | 1458 | let mut err = self.cannot_reassign_immutable(span, &place_description, from_arg); |
dc9dc135 XL |
1459 | let msg = if from_arg { |
1460 | "cannot assign to immutable argument" | |
1461 | } else { | |
1462 | "cannot assign twice to immutable variable" | |
1463 | }; | |
1464 | if span != assigned_span { | |
1465 | if !from_arg { | |
ba9703b0 | 1466 | err.span_label(assigned_span, format!("first assignment to {}", place_description)); |
dc9dc135 XL |
1467 | } |
1468 | } | |
1469 | if let Some(decl) = local_decl { | |
60c5eb7d | 1470 | if let Some(name) = local_name { |
dc9dc135 XL |
1471 | if decl.can_be_made_mutable() { |
1472 | err.span_suggestion( | |
1473 | decl.source_info.span, | |
1474 | "make this binding mutable", | |
1475 | format!("mut {}", name), | |
1476 | Applicability::MachineApplicable, | |
1477 | ); | |
1478 | } | |
1479 | } | |
1480 | } | |
1481 | err.span_label(span, msg); | |
1482 | err.buffer(&mut self.errors_buffer); | |
1483 | } | |
1484 | ||
74b04a01 | 1485 | fn classify_drop_access_kind(&self, place: PlaceRef<'tcx>) -> StorageDeadOrDrop<'tcx> { |
dc9dc135 | 1486 | let tcx = self.infcx.tcx; |
416331ca | 1487 | match place.projection { |
dfeec247 | 1488 | [] => StorageDeadOrDrop::LocalStorageDead, |
e1599b0c XL |
1489 | [proj_base @ .., elem] => { |
1490 | // FIXME(spastorino) make this iterate | |
416331ca | 1491 | let base_access = self.classify_drop_access_kind(PlaceRef { |
dfeec247 | 1492 | local: place.local, |
e1599b0c | 1493 | projection: proj_base, |
416331ca | 1494 | }); |
dc9dc135 XL |
1495 | match elem { |
1496 | ProjectionElem::Deref => match base_access { | |
1497 | StorageDeadOrDrop::LocalStorageDead | |
1498 | | StorageDeadOrDrop::BoxedStorageDead => { | |
1499 | assert!( | |
f9f354fc | 1500 | Place::ty_from(place.local, proj_base, self.body, tcx).ty.is_box(), |
dc9dc135 XL |
1501 | "Drop of value behind a reference or raw pointer" |
1502 | ); | |
1503 | StorageDeadOrDrop::BoxedStorageDead | |
1504 | } | |
1505 | StorageDeadOrDrop::Destructor(_) => base_access, | |
1506 | }, | |
1507 | ProjectionElem::Field(..) | ProjectionElem::Downcast(..) => { | |
f9f354fc | 1508 | let base_ty = Place::ty_from(place.local, proj_base, self.body, tcx).ty; |
e74abb32 | 1509 | match base_ty.kind { |
dc9dc135 XL |
1510 | ty::Adt(def, _) if def.has_dtor(tcx) => { |
1511 | // Report the outermost adt with a destructor | |
1512 | match base_access { | |
1513 | StorageDeadOrDrop::Destructor(_) => base_access, | |
1514 | StorageDeadOrDrop::LocalStorageDead | |
1515 | | StorageDeadOrDrop::BoxedStorageDead => { | |
1516 | StorageDeadOrDrop::Destructor(base_ty) | |
1517 | } | |
1518 | } | |
1519 | } | |
1520 | _ => base_access, | |
1521 | } | |
1522 | } | |
1523 | ||
1524 | ProjectionElem::ConstantIndex { .. } | |
1525 | | ProjectionElem::Subslice { .. } | |
1526 | | ProjectionElem::Index(_) => base_access, | |
1527 | } | |
1528 | } | |
1529 | } | |
1530 | } | |
1531 | ||
60c5eb7d | 1532 | /// Describe the reason for the fake borrow that was assigned to `place`. |
ba9703b0 XL |
1533 | fn classify_immutable_section(&self, place: Place<'tcx>) -> Option<&'static str> { |
1534 | use rustc_middle::mir::visit::Visitor; | |
1535 | struct FakeReadCauseFinder<'tcx> { | |
1536 | place: Place<'tcx>, | |
60c5eb7d XL |
1537 | cause: Option<FakeReadCause>, |
1538 | } | |
ba9703b0 | 1539 | impl<'tcx> Visitor<'tcx> for FakeReadCauseFinder<'tcx> { |
60c5eb7d XL |
1540 | fn visit_statement(&mut self, statement: &Statement<'tcx>, _: Location) { |
1541 | match statement { | |
ba9703b0 XL |
1542 | Statement { kind: StatementKind::FakeRead(cause, box place), .. } |
1543 | if *place == self.place => | |
dfeec247 | 1544 | { |
60c5eb7d XL |
1545 | self.cause = Some(*cause); |
1546 | } | |
1547 | _ => (), | |
1548 | } | |
1549 | } | |
1550 | } | |
1551 | let mut visitor = FakeReadCauseFinder { place, cause: None }; | |
ba9703b0 | 1552 | visitor.visit_body(&self.body); |
60c5eb7d XL |
1553 | match visitor.cause { |
1554 | Some(FakeReadCause::ForMatchGuard) => Some("match guard"), | |
1555 | Some(FakeReadCause::ForIndex) => Some("indexing expression"), | |
1556 | _ => None, | |
1557 | } | |
1558 | } | |
1559 | ||
dc9dc135 XL |
1560 | /// Annotate argument and return type of function and closure with (synthesized) lifetime for |
1561 | /// borrow of local value that does not live long enough. | |
1562 | fn annotate_argument_and_return_for_borrow( | |
1563 | &self, | |
1564 | borrow: &BorrowData<'tcx>, | |
1565 | ) -> Option<AnnotatedBorrowFnSignature<'tcx>> { | |
1566 | // Define a fallback for when we can't match a closure. | |
1567 | let fallback = || { | |
f9f354fc | 1568 | let is_closure = self.infcx.tcx.is_closure(self.mir_def_id.to_def_id()); |
dc9dc135 XL |
1569 | if is_closure { |
1570 | None | |
1571 | } else { | |
1572 | let ty = self.infcx.tcx.type_of(self.mir_def_id); | |
e74abb32 | 1573 | match ty.kind { |
f9f354fc XL |
1574 | ty::FnDef(_, _) | ty::FnPtr(_) => self.annotate_fn_sig( |
1575 | self.mir_def_id.to_def_id(), | |
1576 | self.infcx.tcx.fn_sig(self.mir_def_id), | |
1577 | ), | |
dc9dc135 XL |
1578 | _ => None, |
1579 | } | |
1580 | } | |
1581 | }; | |
1582 | ||
1583 | // In order to determine whether we need to annotate, we need to check whether the reserve | |
1584 | // place was an assignment into a temporary. | |
1585 | // | |
1586 | // If it was, we check whether or not that temporary is eventually assigned into the return | |
1587 | // place. If it was, we can add annotations about the function's return type and arguments | |
1588 | // and it'll make sense. | |
1589 | let location = borrow.reserve_location; | |
dfeec247 XL |
1590 | debug!("annotate_argument_and_return_for_borrow: location={:?}", location); |
1591 | if let Some(&Statement { kind: StatementKind::Assign(box (ref reservation, _)), .. }) = | |
1592 | &self.body[location.block].statements.get(location.statement_index) | |
dc9dc135 | 1593 | { |
dfeec247 | 1594 | debug!("annotate_argument_and_return_for_borrow: reservation={:?}", reservation); |
dc9dc135 | 1595 | // Check that the initial assignment of the reserve location is into a temporary. |
e74abb32 XL |
1596 | let mut target = match reservation.as_local() { |
1597 | Some(local) if self.body.local_kind(local) == LocalKind::Temp => local, | |
dc9dc135 XL |
1598 | _ => return None, |
1599 | }; | |
1600 | ||
1601 | // Next, look through the rest of the block, checking if we are assigning the | |
1602 | // `target` (that is, the place that contains our borrow) to anything. | |
1603 | let mut annotated_closure = None; | |
dfeec247 | 1604 | for stmt in &self.body[location.block].statements[location.statement_index + 1..] { |
dc9dc135 XL |
1605 | debug!( |
1606 | "annotate_argument_and_return_for_borrow: target={:?} stmt={:?}", | |
1607 | target, stmt | |
1608 | ); | |
dfeec247 | 1609 | if let StatementKind::Assign(box (place, rvalue)) = &stmt.kind { |
e74abb32 XL |
1610 | if let Some(assigned_to) = place.as_local() { |
1611 | debug!( | |
1612 | "annotate_argument_and_return_for_borrow: assigned_to={:?} \ | |
1613 | rvalue={:?}", | |
1614 | assigned_to, rvalue | |
1615 | ); | |
1616 | // Check if our `target` was captured by a closure. | |
1617 | if let Rvalue::Aggregate( | |
1618 | box AggregateKind::Closure(def_id, substs), | |
1619 | operands, | |
1620 | ) = rvalue | |
1621 | { | |
1622 | for operand in operands { | |
1623 | let assigned_from = match operand { | |
1624 | Operand::Copy(assigned_from) | Operand::Move(assigned_from) => { | |
1625 | assigned_from | |
1626 | } | |
1627 | _ => continue, | |
1628 | }; | |
1629 | debug!( | |
1630 | "annotate_argument_and_return_for_borrow: assigned_from={:?}", | |
dc9dc135 | 1631 | assigned_from |
e74abb32 | 1632 | ); |
dc9dc135 | 1633 | |
e74abb32 XL |
1634 | // Find the local from the operand. |
1635 | let assigned_from_local = match assigned_from.local_or_deref_local() | |
1636 | { | |
1637 | Some(local) => local, | |
1638 | None => continue, | |
1639 | }; | |
dc9dc135 | 1640 | |
e74abb32 XL |
1641 | if assigned_from_local != target { |
1642 | continue; | |
1643 | } | |
dc9dc135 | 1644 | |
e74abb32 XL |
1645 | // If a closure captured our `target` and then assigned |
1646 | // into a place then we should annotate the closure in | |
1647 | // case it ends up being assigned into the return place. | |
ba9703b0 XL |
1648 | annotated_closure = |
1649 | self.annotate_fn_sig(*def_id, substs.as_closure().sig()); | |
e74abb32 XL |
1650 | debug!( |
1651 | "annotate_argument_and_return_for_borrow: \ | |
1652 | annotated_closure={:?} assigned_from_local={:?} \ | |
1653 | assigned_to={:?}", | |
1654 | annotated_closure, assigned_from_local, assigned_to | |
1655 | ); | |
1656 | ||
1657 | if assigned_to == mir::RETURN_PLACE { | |
1658 | // If it was assigned directly into the return place, then | |
1659 | // return now. | |
1660 | return annotated_closure; | |
1661 | } else { | |
1662 | // Otherwise, update the target. | |
1663 | target = assigned_to; | |
1664 | } | |
dc9dc135 | 1665 | } |
dc9dc135 | 1666 | |
e74abb32 XL |
1667 | // If none of our closure's operands matched, then skip to the next |
1668 | // statement. | |
1669 | continue; | |
1670 | } | |
dc9dc135 | 1671 | |
e74abb32 XL |
1672 | // Otherwise, look at other types of assignment. |
1673 | let assigned_from = match rvalue { | |
1674 | Rvalue::Ref(_, _, assigned_from) => assigned_from, | |
1675 | Rvalue::Use(operand) => match operand { | |
1676 | Operand::Copy(assigned_from) | Operand::Move(assigned_from) => { | |
1677 | assigned_from | |
1678 | } | |
1679 | _ => continue, | |
1680 | }, | |
dc9dc135 | 1681 | _ => continue, |
e74abb32 XL |
1682 | }; |
1683 | debug!( | |
1684 | "annotate_argument_and_return_for_borrow: \ | |
1685 | assigned_from={:?}", | |
1686 | assigned_from, | |
1687 | ); | |
dc9dc135 | 1688 | |
e74abb32 XL |
1689 | // Find the local from the rvalue. |
1690 | let assigned_from_local = match assigned_from.local_or_deref_local() { | |
1691 | Some(local) => local, | |
1692 | None => continue, | |
1693 | }; | |
1694 | debug!( | |
1695 | "annotate_argument_and_return_for_borrow: \ | |
1696 | assigned_from_local={:?}", | |
1697 | assigned_from_local, | |
1698 | ); | |
dc9dc135 | 1699 | |
e74abb32 XL |
1700 | // Check if our local matches the target - if so, we've assigned our |
1701 | // borrow to a new place. | |
1702 | if assigned_from_local != target { | |
1703 | continue; | |
1704 | } | |
dc9dc135 | 1705 | |
e74abb32 XL |
1706 | // If we assigned our `target` into a new place, then we should |
1707 | // check if it was the return place. | |
1708 | debug!( | |
1709 | "annotate_argument_and_return_for_borrow: \ | |
1710 | assigned_from_local={:?} assigned_to={:?}", | |
1711 | assigned_from_local, assigned_to | |
1712 | ); | |
1713 | if assigned_to == mir::RETURN_PLACE { | |
1714 | // If it was then return the annotated closure if there was one, | |
1715 | // else, annotate this function. | |
1716 | return annotated_closure.or_else(fallback); | |
1717 | } | |
dc9dc135 | 1718 | |
e74abb32 XL |
1719 | // If we didn't assign into the return place, then we just update |
1720 | // the target. | |
1721 | target = assigned_to; | |
1722 | } | |
dc9dc135 XL |
1723 | } |
1724 | } | |
1725 | ||
1726 | // Check the terminator if we didn't find anything in the statements. | |
1727 | let terminator = &self.body[location.block].terminator(); | |
1728 | debug!( | |
1729 | "annotate_argument_and_return_for_borrow: target={:?} terminator={:?}", | |
1730 | target, terminator | |
1731 | ); | |
dfeec247 XL |
1732 | if let TerminatorKind::Call { destination: Some((place, _)), args, .. } = |
1733 | &terminator.kind | |
dc9dc135 | 1734 | { |
e74abb32 | 1735 | if let Some(assigned_to) = place.as_local() { |
dc9dc135 | 1736 | debug!( |
e74abb32 XL |
1737 | "annotate_argument_and_return_for_borrow: assigned_to={:?} args={:?}", |
1738 | assigned_to, args | |
dc9dc135 | 1739 | ); |
e74abb32 XL |
1740 | for operand in args { |
1741 | let assigned_from = match operand { | |
1742 | Operand::Copy(assigned_from) | Operand::Move(assigned_from) => { | |
1743 | assigned_from | |
1744 | } | |
1745 | _ => continue, | |
1746 | }; | |
dc9dc135 | 1747 | debug!( |
e74abb32 XL |
1748 | "annotate_argument_and_return_for_borrow: assigned_from={:?}", |
1749 | assigned_from, | |
dc9dc135 XL |
1750 | ); |
1751 | ||
e74abb32 XL |
1752 | if let Some(assigned_from_local) = assigned_from.local_or_deref_local() { |
1753 | debug!( | |
1754 | "annotate_argument_and_return_for_borrow: assigned_from_local={:?}", | |
1755 | assigned_from_local, | |
1756 | ); | |
1757 | ||
1758 | if assigned_to == mir::RETURN_PLACE && assigned_from_local == target { | |
1759 | return annotated_closure.or_else(fallback); | |
1760 | } | |
dc9dc135 XL |
1761 | } |
1762 | } | |
1763 | } | |
1764 | } | |
1765 | } | |
1766 | ||
1767 | // If we haven't found an assignment into the return place, then we need not add | |
1768 | // any annotations. | |
1769 | debug!("annotate_argument_and_return_for_borrow: none found"); | |
1770 | None | |
1771 | } | |
1772 | ||
1773 | /// Annotate the first argument and return type of a function signature if they are | |
1774 | /// references. | |
1775 | fn annotate_fn_sig( | |
1776 | &self, | |
1777 | did: DefId, | |
1778 | sig: ty::PolyFnSig<'tcx>, | |
1779 | ) -> Option<AnnotatedBorrowFnSignature<'tcx>> { | |
1780 | debug!("annotate_fn_sig: did={:?} sig={:?}", did, sig); | |
1781 | let is_closure = self.infcx.tcx.is_closure(did); | |
f9f354fc | 1782 | let fn_hir_id = self.infcx.tcx.hir().as_local_hir_id(did.as_local()?); |
dc9dc135 XL |
1783 | let fn_decl = self.infcx.tcx.hir().fn_decl_by_hir_id(fn_hir_id)?; |
1784 | ||
1785 | // We need to work out which arguments to highlight. We do this by looking | |
1786 | // at the return type, where there are three cases: | |
1787 | // | |
1788 | // 1. If there are named arguments, then we should highlight the return type and | |
1789 | // highlight any of the arguments that are also references with that lifetime. | |
1790 | // If there are no arguments that have the same lifetime as the return type, | |
1791 | // then don't highlight anything. | |
1792 | // 2. The return type is a reference with an anonymous lifetime. If this is | |
1793 | // the case, then we can take advantage of (and teach) the lifetime elision | |
1794 | // rules. | |
1795 | // | |
1796 | // We know that an error is being reported. So the arguments and return type | |
1797 | // must satisfy the elision rules. Therefore, if there is a single argument | |
1798 | // then that means the return type and first (and only) argument have the same | |
1799 | // lifetime and the borrow isn't meeting that, we can highlight the argument | |
1800 | // and return type. | |
1801 | // | |
1802 | // If there are multiple arguments then the first argument must be self (else | |
1803 | // it would not satisfy the elision rules), so we can highlight self and the | |
1804 | // return type. | |
1805 | // 3. The return type is not a reference. In this case, we don't highlight | |
1806 | // anything. | |
1807 | let return_ty = sig.output(); | |
e74abb32 | 1808 | match return_ty.skip_binder().kind { |
dc9dc135 XL |
1809 | ty::Ref(return_region, _, _) if return_region.has_name() && !is_closure => { |
1810 | // This is case 1 from above, return type is a named reference so we need to | |
1811 | // search for relevant arguments. | |
1812 | let mut arguments = Vec::new(); | |
1813 | for (index, argument) in sig.inputs().skip_binder().iter().enumerate() { | |
e74abb32 | 1814 | if let ty::Ref(argument_region, _, _) = argument.kind { |
dc9dc135 | 1815 | if argument_region == return_region { |
ba9703b0 | 1816 | // Need to use the `rustc_middle::ty` types to compare against the |
dfeec247 | 1817 | // `return_region`. Then use the `rustc_hir` type to get only |
dc9dc135 | 1818 | // the lifetime span. |
e74abb32 | 1819 | if let hir::TyKind::Rptr(lifetime, _) = &fn_decl.inputs[index].kind { |
dc9dc135 XL |
1820 | // With access to the lifetime, we can get |
1821 | // the span of it. | |
1822 | arguments.push((*argument, lifetime.span)); | |
1823 | } else { | |
1824 | bug!("ty type is a ref but hir type is not"); | |
1825 | } | |
1826 | } | |
1827 | } | |
1828 | } | |
1829 | ||
1830 | // We need to have arguments. This shouldn't happen, but it's worth checking. | |
1831 | if arguments.is_empty() { | |
1832 | return None; | |
1833 | } | |
1834 | ||
1835 | // We use a mix of the HIR and the Ty types to get information | |
1836 | // as the HIR doesn't have full types for closure arguments. | |
1837 | let return_ty = *sig.output().skip_binder(); | |
1838 | let mut return_span = fn_decl.output.span(); | |
74b04a01 | 1839 | if let hir::FnRetTy::Return(ty) = &fn_decl.output { |
e74abb32 | 1840 | if let hir::TyKind::Rptr(lifetime, _) = ty.kind { |
dc9dc135 XL |
1841 | return_span = lifetime.span; |
1842 | } | |
1843 | } | |
1844 | ||
1845 | Some(AnnotatedBorrowFnSignature::NamedFunction { | |
1846 | arguments, | |
1847 | return_ty, | |
1848 | return_span, | |
1849 | }) | |
1850 | } | |
1851 | ty::Ref(_, _, _) if is_closure => { | |
1852 | // This is case 2 from above but only for closures, return type is anonymous | |
1853 | // reference so we select | |
1854 | // the first argument. | |
1855 | let argument_span = fn_decl.inputs.first()?.span; | |
1856 | let argument_ty = sig.inputs().skip_binder().first()?; | |
1857 | ||
1858 | // Closure arguments are wrapped in a tuple, so we need to get the first | |
1859 | // from that. | |
e74abb32 | 1860 | if let ty::Tuple(elems) = argument_ty.kind { |
dc9dc135 | 1861 | let argument_ty = elems.first()?.expect_ty(); |
e74abb32 | 1862 | if let ty::Ref(_, _, _) = argument_ty.kind { |
dc9dc135 XL |
1863 | return Some(AnnotatedBorrowFnSignature::Closure { |
1864 | argument_ty, | |
1865 | argument_span, | |
1866 | }); | |
1867 | } | |
1868 | } | |
1869 | ||
1870 | None | |
1871 | } | |
1872 | ty::Ref(_, _, _) => { | |
1873 | // This is also case 2 from above but for functions, return type is still an | |
1874 | // anonymous reference so we select the first argument. | |
1875 | let argument_span = fn_decl.inputs.first()?.span; | |
1876 | let argument_ty = sig.inputs().skip_binder().first()?; | |
1877 | ||
1878 | let return_span = fn_decl.output.span(); | |
1879 | let return_ty = *sig.output().skip_binder(); | |
1880 | ||
1881 | // We expect the first argument to be a reference. | |
e74abb32 | 1882 | match argument_ty.kind { |
dc9dc135 XL |
1883 | ty::Ref(_, _, _) => {} |
1884 | _ => return None, | |
1885 | } | |
1886 | ||
1887 | Some(AnnotatedBorrowFnSignature::AnonymousFunction { | |
1888 | argument_ty, | |
1889 | argument_span, | |
1890 | return_ty, | |
1891 | return_span, | |
1892 | }) | |
1893 | } | |
1894 | _ => { | |
1895 | // This is case 3 from above, return type is not a reference so don't highlight | |
1896 | // anything. | |
1897 | None | |
1898 | } | |
1899 | } | |
1900 | } | |
1901 | } | |
1902 | ||
1903 | #[derive(Debug)] | |
1904 | enum AnnotatedBorrowFnSignature<'tcx> { | |
1905 | NamedFunction { | |
1906 | arguments: Vec<(Ty<'tcx>, Span)>, | |
1907 | return_ty: Ty<'tcx>, | |
1908 | return_span: Span, | |
1909 | }, | |
1910 | AnonymousFunction { | |
1911 | argument_ty: Ty<'tcx>, | |
1912 | argument_span: Span, | |
1913 | return_ty: Ty<'tcx>, | |
1914 | return_span: Span, | |
1915 | }, | |
1916 | Closure { | |
1917 | argument_ty: Ty<'tcx>, | |
1918 | argument_span: Span, | |
1919 | }, | |
1920 | } | |
1921 | ||
1922 | impl<'tcx> AnnotatedBorrowFnSignature<'tcx> { | |
1923 | /// Annotate the provided diagnostic with information about borrow from the fn signature that | |
1924 | /// helps explain. | |
60c5eb7d | 1925 | pub(in crate::borrow_check) fn emit( |
dc9dc135 XL |
1926 | &self, |
1927 | cx: &mut MirBorrowckCtxt<'_, 'tcx>, | |
1928 | diag: &mut DiagnosticBuilder<'_>, | |
1929 | ) -> String { | |
1930 | match self { | |
dfeec247 | 1931 | AnnotatedBorrowFnSignature::Closure { argument_ty, argument_span } => { |
dc9dc135 XL |
1932 | diag.span_label( |
1933 | *argument_span, | |
1934 | format!("has type `{}`", cx.get_name_for_ty(argument_ty, 0)), | |
1935 | ); | |
1936 | ||
1937 | cx.get_region_name_for_ty(argument_ty, 0) | |
1938 | } | |
1939 | AnnotatedBorrowFnSignature::AnonymousFunction { | |
1940 | argument_ty, | |
1941 | argument_span, | |
1942 | return_ty, | |
1943 | return_span, | |
1944 | } => { | |
1945 | let argument_ty_name = cx.get_name_for_ty(argument_ty, 0); | |
1946 | diag.span_label(*argument_span, format!("has type `{}`", argument_ty_name)); | |
1947 | ||
1948 | let return_ty_name = cx.get_name_for_ty(return_ty, 0); | |
1949 | let types_equal = return_ty_name == argument_ty_name; | |
1950 | diag.span_label( | |
1951 | *return_span, | |
1952 | format!( | |
1953 | "{}has type `{}`", | |
1954 | if types_equal { "also " } else { "" }, | |
1955 | return_ty_name, | |
1956 | ), | |
1957 | ); | |
1958 | ||
1959 | diag.note( | |
1960 | "argument and return type have the same lifetime due to lifetime elision rules", | |
1961 | ); | |
1962 | diag.note( | |
1963 | "to learn more, visit <https://doc.rust-lang.org/book/ch10-03-\ | |
1964 | lifetime-syntax.html#lifetime-elision>", | |
1965 | ); | |
1966 | ||
1967 | cx.get_region_name_for_ty(return_ty, 0) | |
1968 | } | |
dfeec247 | 1969 | AnnotatedBorrowFnSignature::NamedFunction { arguments, return_ty, return_span } => { |
dc9dc135 XL |
1970 | // Region of return type and arguments checked to be the same earlier. |
1971 | let region_name = cx.get_region_name_for_ty(return_ty, 0); | |
1972 | for (_, argument_span) in arguments { | |
1973 | diag.span_label(*argument_span, format!("has lifetime `{}`", region_name)); | |
1974 | } | |
1975 | ||
dfeec247 | 1976 | diag.span_label(*return_span, format!("also has lifetime `{}`", region_name,)); |
dc9dc135 XL |
1977 | |
1978 | diag.help(&format!( | |
1979 | "use data from the highlighted arguments which match the `{}` lifetime of \ | |
1980 | the return type", | |
1981 | region_name, | |
1982 | )); | |
1983 | ||
1984 | region_name | |
1985 | } | |
1986 | } | |
1987 | } | |
1988 | } |