src/librustc_mir/util/borrowck_errors.rs

   1 use rustc::ty::{self, Ty, TyCtxt};
   2 use rustc_errors::{DiagnosticBuilder, DiagnosticId};
   3 use syntax_pos::{MultiSpan, Span};
   4
   5 impl<'cx, 'tcx> crate::borrow_check::MirBorrowckCtxt<'cx, 'tcx> {
   6     crate fn cannot_move_when_borrowed(
   7         &self,
   8         span: Span,
   9         desc: &str,
  10     ) -> DiagnosticBuilder<'cx> {
  11         struct_span_err!(
  12             self,
  13             span,
  14             E0505,
  15             "cannot move out of `{}` because it is borrowed",
  16             desc,
  17         )
  18     }
  19
  20     crate fn cannot_use_when_mutably_borrowed(
  21         &self,
  22         span: Span,
  23         desc: &str,
  24         borrow_span: Span,
  25         borrow_desc: &str,
  26     ) -> DiagnosticBuilder<'cx> {
  27         let mut err = struct_span_err!(
  28             self,
  29             span,
  30             E0503,
  31             "cannot use `{}` because it was mutably borrowed",
  32             desc,
  33         );
  34
  35         err.span_label(
  36             borrow_span,
  37             format!("borrow of `{}` occurs here", borrow_desc),
  38         );
  39         err.span_label(span, format!("use of borrowed `{}`", borrow_desc));
  40         err
  41     }
  42
  43     crate fn cannot_act_on_uninitialized_variable(
  44         &self,
  45         span: Span,
  46         verb: &str,
  47         desc: &str,
  48     ) -> DiagnosticBuilder<'cx> {
  49         struct_span_err!(
  50             self,
  51             span,
  52             E0381,
  53             "{} of possibly-uninitialized variable: `{}`",
  54             verb,
  55             desc,
  56         )
  57     }
  58
  59     crate fn cannot_mutably_borrow_multiply(
  60         &self,
  61         new_loan_span: Span,
  62         desc: &str,
  63         opt_via: &str,
  64         old_loan_span: Span,
  65         old_opt_via: &str,
  66         old_load_end_span: Option<Span>,
  67     ) -> DiagnosticBuilder<'cx> {
  68         let via = |msg: &str|
  69             if msg.is_empty() { msg.to_string() } else { format!(" (via `{}`)", msg) };
  70         let mut err = struct_span_err!(
  71             self,
  72             new_loan_span,
  73             E0499,
  74             "cannot borrow `{}`{} as mutable more than once at a time",
  75             desc,
  76             via(opt_via),
  77         );
  78         if old_loan_span == new_loan_span {
  79             // Both borrows are happening in the same place
  80             // Meaning the borrow is occurring in a loop
  81             err.span_label(
  82                 new_loan_span,
  83                 format!(
  84                     "mutable borrow starts here in previous \
  85                      iteration of loop{}",
  86                     opt_via
  87                 ),
  88             );
  89             if let Some(old_load_end_span) = old_load_end_span {
  90                 err.span_label(old_load_end_span, "mutable borrow ends here");
  91             }
  92         } else {
  93             err.span_label(
  94                 old_loan_span,
  95                 format!("first mutable borrow occurs here{}", via(old_opt_via)),
  96             );
  97             err.span_label(
  98                 new_loan_span,
  99                 format!("second mutable borrow occurs here{}", via(opt_via)),
 100             );
 101             if let Some(old_load_end_span) = old_load_end_span {
 102                 err.span_label(old_load_end_span, "first borrow ends here");
 103             }
 104         }
 105         err
 106     }
 107
 108     crate fn cannot_uniquely_borrow_by_two_closures(
 109         &self,
 110         new_loan_span: Span,
 111         desc: &str,
 112         old_loan_span: Span,
 113         old_load_end_span: Option<Span>,
 114     ) -> DiagnosticBuilder<'cx> {
 115         let mut err = struct_span_err!(
 116             self,
 117             new_loan_span,
 118             E0524,
 119             "two closures require unique access to `{}` at the same time",
 120             desc,
 121         );
 122         if old_loan_span == new_loan_span {
 123             err.span_label(
 124                 old_loan_span,
 125                 "closures are constructed here in different iterations of loop"
 126             );
 127         } else {
 128             err.span_label(old_loan_span, "first closure is constructed here");
 129             err.span_label(new_loan_span, "second closure is constructed here");
 130         }
 131         if let Some(old_load_end_span) = old_load_end_span {
 132             err.span_label(old_load_end_span, "borrow from first closure ends here");
 133         }
 134         err
 135     }
 136
 137     crate fn cannot_uniquely_borrow_by_one_closure(
 138         &self,
 139         new_loan_span: Span,
 140         container_name: &str,
 141         desc_new: &str,
 142         opt_via: &str,
 143         old_loan_span: Span,
 144         noun_old: &str,
 145         old_opt_via: &str,
 146         previous_end_span: Option<Span>,
 147     ) -> DiagnosticBuilder<'cx> {
 148         let mut err = struct_span_err!(
 149             self,
 150             new_loan_span,
 151             E0500,
 152             "closure requires unique access to `{}` but {} is already borrowed{}",
 153             desc_new,
 154             noun_old,
 155             old_opt_via,
 156         );
 157         err.span_label(
 158             new_loan_span,
 159             format!("{} construction occurs here{}", container_name, opt_via),
 160         );
 161         err.span_label(old_loan_span, format!("borrow occurs here{}", old_opt_via));
 162         if let Some(previous_end_span) = previous_end_span {
 163             err.span_label(previous_end_span, "borrow ends here");
 164         }
 165         err
 166     }
 167
 168     crate fn cannot_reborrow_already_uniquely_borrowed(
 169         &self,
 170         new_loan_span: Span,
 171         container_name: &str,
 172         desc_new: &str,
 173         opt_via: &str,
 174         kind_new: &str,
 175         old_loan_span: Span,
 176         old_opt_via: &str,
 177         previous_end_span: Option<Span>,
 178         second_borrow_desc: &str,
 179     ) -> DiagnosticBuilder<'cx> {
 180         let mut err = struct_span_err!(
 181             self,
 182             new_loan_span,
 183             E0501,
 184             "cannot borrow `{}`{} as {} because previous closure \
 185              requires unique access",
 186             desc_new,
 187             opt_via,
 188             kind_new,
 189         );
 190         err.span_label(
 191             new_loan_span,
 192             format!("{}borrow occurs here{}", second_borrow_desc, opt_via),
 193         );
 194         err.span_label(
 195             old_loan_span,
 196             format!("{} construction occurs here{}", container_name, old_opt_via),
 197         );
 198         if let Some(previous_end_span) = previous_end_span {
 199             err.span_label(previous_end_span, "borrow from closure ends here");
 200         }
 201         err
 202     }
 203
 204     crate fn cannot_reborrow_already_borrowed(
 205         &self,
 206         span: Span,
 207         desc_new: &str,
 208         msg_new: &str,
 209         kind_new: &str,
 210         old_span: Span,
 211         noun_old: &str,
 212         kind_old: &str,
 213         msg_old: &str,
 214         old_load_end_span: Option<Span>,
 215     ) -> DiagnosticBuilder<'cx> {
 216         let via = |msg: &str|
 217             if msg.is_empty() { msg.to_string() } else { format!(" (via `{}`)", msg) };
 218         let mut err = struct_span_err!(
 219             self,
 220             span,
 221             E0502,
 222             "cannot borrow `{}`{} as {} because {} is also borrowed \
 223              as {}{}",
 224             desc_new,
 225             via(msg_new),
 226             kind_new,
 227             noun_old,
 228             kind_old,
 229             via(msg_old),
 230         );
 231
 232         if msg_new == "" {
 233             // If `msg_new` is empty, then this isn't a borrow of a union field.
 234             err.span_label(span, format!("{} borrow occurs here", kind_new));
 235             err.span_label(old_span, format!("{} borrow occurs here", kind_old));
 236         } else {
 237             // If `msg_new` isn't empty, then this a borrow of a union field.
 238             err.span_label(
 239                 span,
 240                 format!(
 241                     "{} borrow of `{}` -- which overlaps with `{}` -- occurs here",
 242                     kind_new, msg_new, msg_old,
 243                 )
 244             );
 245             err.span_label(
 246                 old_span,
 247                 format!("{} borrow occurs here{}", kind_old, via(msg_old)),
 248             );
 249         }
 250
 251         if let Some(old_load_end_span) = old_load_end_span {
 252             err.span_label(old_load_end_span, format!("{} borrow ends here", kind_old));
 253         }
 254         err
 255     }
 256
 257     crate fn cannot_assign_to_borrowed(
 258         &self,
 259         span: Span,
 260         borrow_span: Span,
 261         desc: &str,
 262     ) -> DiagnosticBuilder<'cx> {
 263         let mut err = struct_span_err!(
 264             self,
 265             span,
 266             E0506,
 267             "cannot assign to `{}` because it is borrowed",
 268             desc,
 269         );
 270
 271         err.span_label(borrow_span, format!("borrow of `{}` occurs here", desc));
 272         err.span_label(
 273             span,
 274             format!("assignment to borrowed `{}` occurs here", desc),
 275         );
 276         err
 277     }
 278
 279     crate fn cannot_reassign_immutable(
 280         &self,
 281         span: Span,
 282         desc: &str,
 283         is_arg: bool,
 284     ) -> DiagnosticBuilder<'cx> {
 285         let msg = if is_arg {
 286             "to immutable argument"
 287         } else {
 288             "twice to immutable variable"
 289         };
 290         struct_span_err!(
 291             self,
 292             span,
 293             E0384,
 294             "cannot assign {} `{}`",
 295             msg,
 296             desc,
 297         )
 298     }
 299
 300     crate fn cannot_assign(&self, span: Span, desc: &str) -> DiagnosticBuilder<'cx> {
 301         struct_span_err!(self, span, E0594, "cannot assign to {}", desc)
 302     }
 303
 304     crate fn cannot_move_out_of(
 305         &self,
 306         move_from_span: Span,
 307         move_from_desc: &str,
 308     ) -> DiagnosticBuilder<'cx> {
 309         struct_span_err!(
 310             self,
 311             move_from_span,
 312             E0507,
 313             "cannot move out of {}",
 314             move_from_desc,
 315         )
 316     }
 317
 318     /// Signal an error due to an attempt to move out of the interior
 319     /// of an array or slice. `is_index` is None when error origin
 320     /// didn't capture whether there was an indexing operation or not.
 321     crate fn cannot_move_out_of_interior_noncopy(
 322         &self,
 323         move_from_span: Span,
 324         ty: Ty<'_>,
 325         is_index: Option<bool>,
 326     ) -> DiagnosticBuilder<'cx> {
 327         let type_name = match (&ty.kind, is_index) {
 328             (&ty::Array(_, _), Some(true)) | (&ty::Array(_, _), None) => "array",
 329             (&ty::Slice(_), _) => "slice",
 330             _ => span_bug!(move_from_span, "this path should not cause illegal move"),
 331         };
 332         let mut err = struct_span_err!(
 333             self,
 334             move_from_span,
 335             E0508,
 336             "cannot move out of type `{}`, a non-copy {}",
 337             ty,
 338             type_name,
 339         );
 340         err.span_label(move_from_span, "cannot move out of here");
 341         err
 342     }
 343
 344     crate fn cannot_move_out_of_interior_of_drop(
 345         &self,
 346         move_from_span: Span,
 347         container_ty: Ty<'_>,
 348     ) -> DiagnosticBuilder<'cx> {
 349         let mut err = struct_span_err!(
 350             self,
 351             move_from_span,
 352             E0509,
 353             "cannot move out of type `{}`, which implements the `Drop` trait",
 354             container_ty,
 355         );
 356         err.span_label(move_from_span, "cannot move out of here");
 357         err
 358     }
 359
 360     crate fn cannot_act_on_moved_value(
 361         &self,
 362         use_span: Span,
 363         verb: &str,
 364         optional_adverb_for_moved: &str,
 365         moved_path: Option<String>,
 366     ) -> DiagnosticBuilder<'cx> {
 367         let moved_path = moved_path
 368             .map(|mp| format!(": `{}`", mp))
 369             .unwrap_or_default();
 370
 371         struct_span_err!(
 372             self,
 373             use_span,
 374             E0382,
 375             "{} of {}moved value{}",
 376             verb,
 377             optional_adverb_for_moved,
 378             moved_path,
 379         )
 380     }
 381
 382     crate fn cannot_borrow_path_as_mutable_because(
 383         &self,
 384         span: Span,
 385         path: &str,
 386         reason: &str,
 387     ) -> DiagnosticBuilder<'cx> {
 388         struct_span_err!(
 389             self,
 390             span,
 391             E0596,
 392             "cannot borrow {} as mutable{}",
 393             path,
 394             reason,
 395         )
 396     }
 397
 398     crate fn cannot_mutate_in_match_guard(
 399         &self,
 400         mutate_span: Span,
 401         match_span: Span,
 402         match_place: &str,
 403         action: &str,
 404     ) -> DiagnosticBuilder<'cx> {
 405         let mut err = struct_span_err!(
 406             self,
 407             mutate_span,
 408             E0510,
 409             "cannot {} `{}` in match guard",
 410             action,
 411             match_place,
 412         );
 413         err.span_label(mutate_span, format!("cannot {}", action));
 414         err.span_label(match_span, String::from("value is immutable in match guard"));
 415         err
 416     }
 417
 418     crate fn cannot_borrow_across_generator_yield(
 419         &self,
 420         span: Span,
 421         yield_span: Span,
 422     ) -> DiagnosticBuilder<'cx> {
 423         let mut err = struct_span_err!(
 424             self,
 425             span,
 426             E0626,
 427             "borrow may still be in use when generator yields",
 428         );
 429         err.span_label(yield_span, "possible yield occurs here");
 430         err
 431     }
 432
 433     crate fn cannot_borrow_across_destructor(
 434         &self,
 435         borrow_span: Span,
 436     ) -> DiagnosticBuilder<'cx> {
 437         struct_span_err!(
 438             self,
 439             borrow_span,
 440             E0713,
 441             "borrow may still be in use when destructor runs",
 442         )
 443     }
 444
 445     crate fn path_does_not_live_long_enough(
 446         &self,
 447         span: Span,
 448         path: &str,
 449     ) -> DiagnosticBuilder<'cx> {
 450         struct_span_err!(
 451             self,
 452             span,
 453             E0597,
 454             "{} does not live long enough",
 455             path,
 456         )
 457     }
 458
 459     crate fn cannot_return_reference_to_local(
 460         &self,
 461         span: Span,
 462         return_kind: &str,
 463         reference_desc: &str,
 464         path_desc: &str,
 465     ) -> DiagnosticBuilder<'cx> {
 466         let mut err = struct_span_err!(
 467             self,
 468             span,
 469             E0515,
 470             "cannot {RETURN} {REFERENCE} {LOCAL}",
 471             RETURN=return_kind,
 472             REFERENCE=reference_desc,
 473             LOCAL=path_desc,
 474         );
 475
 476         err.span_label(
 477             span,
 478             format!("{}s a {} data owned by the current function", return_kind, reference_desc),
 479         );
 480
 481         err
 482     }
 483
 484     crate fn cannot_capture_in_long_lived_closure(
 485         &self,
 486         closure_span: Span,
 487         borrowed_path: &str,
 488         capture_span: Span,
 489     ) -> DiagnosticBuilder<'cx> {
 490         let mut err = struct_span_err!(
 491             self,
 492             closure_span,
 493             E0373,
 494             "closure may outlive the current function, \
 495              but it borrows {}, \
 496              which is owned by the current function",
 497             borrowed_path,
 498         );
 499         err.span_label(capture_span, format!("{} is borrowed here", borrowed_path))
 500             .span_label(
 501                 closure_span,
 502                 format!("may outlive borrowed value {}", borrowed_path),
 503             );
 504         err
 505     }
 506
 507     crate fn thread_local_value_does_not_live_long_enough(
 508         &self,
 509         span: Span,
 510     ) -> DiagnosticBuilder<'cx> {
 511         struct_span_err!(
 512             self,
 513             span,
 514             E0712,
 515             "thread-local variable borrowed past end of function",
 516         )
 517     }
 518
 519     crate fn temporary_value_borrowed_for_too_long(
 520         &self,
 521         span: Span,
 522     ) -> DiagnosticBuilder<'cx> {
 523         struct_span_err!(
 524             self,
 525             span,
 526             E0716,
 527             "temporary value dropped while borrowed",
 528         )
 529     }
 530
 531     fn struct_span_err_with_code<S: Into<MultiSpan>>(
 532         &self,
 533         sp: S,
 534         msg: &str,
 535         code: DiagnosticId,
 536     ) -> DiagnosticBuilder<'tcx> {
 537         self.infcx.tcx.sess.struct_span_err_with_code(sp, msg, code)
 538     }
 539 }
 540
 541 crate fn borrowed_data_escapes_closure<'tcx>(
 542     tcx: TyCtxt<'tcx>,
 543     escape_span: Span,
 544     escapes_from: &str,
 545 ) -> DiagnosticBuilder<'tcx> {
 546     struct_span_err!(
 547         tcx.sess,
 548         escape_span,
 549         E0521,
 550         "borrowed data escapes outside of {}",
 551         escapes_from,
 552     )
 553 }