1 mod ambiguity;
2 pub mod on_unimplemented;
3 pub mod suggestions;
4
5 use super::{
6 FulfillmentError, FulfillmentErrorCode, MismatchedProjectionTypes, Obligation, ObligationCause,
7 ObligationCauseCode, ObligationCtxt, OutputTypeParameterMismatch, Overflow,
8 PredicateObligation, SelectionError, TraitNotObjectSafe,
9 };
10 use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
11 use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
12 use crate::infer::{self, InferCtxt};
13 use crate::solve::{GenerateProofTree, InferCtxtEvalExt, UseGlobalCache};
14 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
15 use crate::traits::specialize::to_pretty_impl_header;
16 use crate::traits::NormalizeExt;
17 use on_unimplemented::{AppendConstMessage, OnUnimplementedNote, TypeErrCtxtExt as _};
18 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
19 use rustc_errors::{
20 pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
21 MultiSpan, Style,
22 };
23 use rustc_hir as hir;
24 use rustc_hir::def::Namespace;
25 use rustc_hir::def_id::{DefId, LocalDefId};
26 use rustc_hir::intravisit::Visitor;
27 use rustc_hir::{GenericParam, Item, Node};
28 use rustc_infer::infer::error_reporting::TypeErrCtxt;
29 use rustc_infer::infer::{InferOk, TypeTrace};
30 use rustc_middle::traits::select::OverflowError;
31 use rustc_middle::traits::solve::Goal;
32 use rustc_middle::traits::{DefiningAnchor, SelectionOutputTypeParameterMismatch};
33 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
34 use rustc_middle::ty::error::{ExpectedFound, TypeError};
35 use rustc_middle::ty::fold::{BottomUpFolder, TypeFolder, TypeSuperFoldable};
36 use rustc_middle::ty::print::{with_forced_trimmed_paths, FmtPrinter, Print};
37 use rustc_middle::ty::{
38 self, SubtypePredicate, ToPolyTraitRef, ToPredicate, TraitRef, Ty, TyCtxt, TypeFoldable,
39 TypeVisitable, TypeVisitableExt,
40 };
41 use rustc_session::config::{DumpSolverProofTree, TraitSolver};
42 use rustc_session::Limit;
43 use rustc_span::def_id::LOCAL_CRATE;
44 use rustc_span::symbol::sym;
45 use rustc_span::{ExpnKind, Span, DUMMY_SP};
46 use std::borrow::Cow;
47 use std::fmt;
48 use std::io::Write;
49 use std::iter;
50 use std::ops::ControlFlow;
51 use suggestions::TypeErrCtxtExt as _;
52
53 pub use rustc_infer::traits::error_reporting::*;
54
55 // When outputting impl candidates, prefer showing those that are more similar.
56 //
57 // We also compare candidates after skipping lifetimes, which has a lower
58 // priority than exact matches.
59 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
60 pub enum CandidateSimilarity {
61 Exact { ignoring_lifetimes: bool },
62 Fuzzy { ignoring_lifetimes: bool },
63 }
64
65 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
66 pub struct ImplCandidate<'tcx> {
67 pub trait_ref: ty::TraitRef<'tcx>,
68 pub similarity: CandidateSimilarity,
69 }
70
71 enum GetSafeTransmuteErrorAndReason {
72 Silent,
73 Error { err_msg: String, safe_transmute_explanation: String },
74 }
75
76 pub trait InferCtxtExt<'tcx> {
77 /// Given some node representing a fn-like thing in the HIR map,
78 /// returns a span and `ArgKind` information that describes the
79 /// arguments it expects. This can be supplied to
80 /// `report_arg_count_mismatch`.
get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Option<Span>, Vec<ArgKind>)>81 fn get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Option<Span>, Vec<ArgKind>)>;
82
83 /// Reports an error when the number of arguments needed by a
84 /// trait match doesn't match the number that the expression
85 /// provides.
report_arg_count_mismatch( &self, span: Span, found_span: Option<Span>, expected_args: Vec<ArgKind>, found_args: Vec<ArgKind>, is_closure: bool, closure_pipe_span: Option<Span>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>86 fn report_arg_count_mismatch(
87 &self,
88 span: Span,
89 found_span: Option<Span>,
90 expected_args: Vec<ArgKind>,
91 found_args: Vec<ArgKind>,
92 is_closure: bool,
93 closure_pipe_span: Option<Span>,
94 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
95
96 /// Checks if the type implements one of `Fn`, `FnMut`, or `FnOnce`
97 /// in that order, and returns the generic type corresponding to the
98 /// argument of that trait (corresponding to the closure arguments).
type_implements_fn_trait( &self, param_env: ty::ParamEnv<'tcx>, ty: ty::Binder<'tcx, Ty<'tcx>>, constness: ty::BoundConstness, polarity: ty::ImplPolarity, ) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()>99 fn type_implements_fn_trait(
100 &self,
101 param_env: ty::ParamEnv<'tcx>,
102 ty: ty::Binder<'tcx, Ty<'tcx>>,
103 constness: ty::BoundConstness,
104 polarity: ty::ImplPolarity,
105 ) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()>;
106 }
107
108 pub trait TypeErrCtxtExt<'tcx> {
build_overflow_error<T>( &self, predicate: &T, span: Span, suggest_increasing_limit: bool, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> where T: fmt::Display + TypeFoldable<TyCtxt<'tcx>> + Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>, <T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug109 fn build_overflow_error<T>(
110 &self,
111 predicate: &T,
112 span: Span,
113 suggest_increasing_limit: bool,
114 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>
115 where
116 T: fmt::Display
117 + TypeFoldable<TyCtxt<'tcx>>
118 + Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>,
119 <T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug;
120
report_overflow_error<T>( &self, predicate: &T, span: Span, suggest_increasing_limit: bool, mutate: impl FnOnce(&mut Diagnostic), ) -> ! where T: fmt::Display + TypeFoldable<TyCtxt<'tcx>> + Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>, <T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug121 fn report_overflow_error<T>(
122 &self,
123 predicate: &T,
124 span: Span,
125 suggest_increasing_limit: bool,
126 mutate: impl FnOnce(&mut Diagnostic),
127 ) -> !
128 where
129 T: fmt::Display
130 + TypeFoldable<TyCtxt<'tcx>>
131 + Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>,
132 <T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug;
133
report_overflow_no_abort(&self, obligation: PredicateObligation<'tcx>) -> ErrorGuaranteed134 fn report_overflow_no_abort(&self, obligation: PredicateObligation<'tcx>) -> ErrorGuaranteed;
135
report_fulfillment_errors(&self, errors: &[FulfillmentError<'tcx>]) -> ErrorGuaranteed136 fn report_fulfillment_errors(&self, errors: &[FulfillmentError<'tcx>]) -> ErrorGuaranteed;
137
report_overflow_obligation<T>( &self, obligation: &Obligation<'tcx, T>, suggest_increasing_limit: bool, ) -> ! where T: ToPredicate<'tcx> + Clone138 fn report_overflow_obligation<T>(
139 &self,
140 obligation: &Obligation<'tcx, T>,
141 suggest_increasing_limit: bool,
142 ) -> !
143 where
144 T: ToPredicate<'tcx> + Clone;
145
suggest_new_overflow_limit(&self, err: &mut Diagnostic)146 fn suggest_new_overflow_limit(&self, err: &mut Diagnostic);
147
report_overflow_obligation_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> !148 fn report_overflow_obligation_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> !;
149
150 /// The `root_obligation` parameter should be the `root_obligation` field
151 /// from a `FulfillmentError`. If no `FulfillmentError` is available,
152 /// then it should be the same as `obligation`.
report_selection_error( &self, obligation: PredicateObligation<'tcx>, root_obligation: &PredicateObligation<'tcx>, error: &SelectionError<'tcx>, )153 fn report_selection_error(
154 &self,
155 obligation: PredicateObligation<'tcx>,
156 root_obligation: &PredicateObligation<'tcx>,
157 error: &SelectionError<'tcx>,
158 );
159
report_const_param_not_wf( &self, ty: Ty<'tcx>, obligation: &PredicateObligation<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>160 fn report_const_param_not_wf(
161 &self,
162 ty: Ty<'tcx>,
163 obligation: &PredicateObligation<'tcx>,
164 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
165 }
166
167 impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
168 /// Given some node representing a fn-like thing in the HIR map,
169 /// returns a span and `ArgKind` information that describes the
170 /// arguments it expects. This can be supplied to
171 /// `report_arg_count_mismatch`.
get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Option<Span>, Vec<ArgKind>)>172 fn get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Option<Span>, Vec<ArgKind>)> {
173 let sm = self.tcx.sess.source_map();
174 let hir = self.tcx.hir();
175 Some(match node {
176 Node::Expr(&hir::Expr {
177 kind: hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, fn_arg_span, .. }),
178 ..
179 }) => (
180 fn_decl_span,
181 fn_arg_span,
182 hir.body(body)
183 .params
184 .iter()
185 .map(|arg| {
186 if let hir::Pat { kind: hir::PatKind::Tuple(ref args, _), span, .. } =
187 *arg.pat
188 {
189 Some(ArgKind::Tuple(
190 Some(span),
191 args.iter()
192 .map(|pat| {
193 sm.span_to_snippet(pat.span)
194 .ok()
195 .map(|snippet| (snippet, "_".to_owned()))
196 })
197 .collect::<Option<Vec<_>>>()?,
198 ))
199 } else {
200 let name = sm.span_to_snippet(arg.pat.span).ok()?;
201 Some(ArgKind::Arg(name, "_".to_owned()))
202 }
203 })
204 .collect::<Option<Vec<ArgKind>>>()?,
205 ),
206 Node::Item(&hir::Item { kind: hir::ItemKind::Fn(ref sig, ..), .. })
207 | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(ref sig, _), .. })
208 | Node::TraitItem(&hir::TraitItem {
209 kind: hir::TraitItemKind::Fn(ref sig, _), ..
210 }) => (
211 sig.span,
212 None,
213 sig.decl
214 .inputs
215 .iter()
216 .map(|arg| match arg.kind {
217 hir::TyKind::Tup(ref tys) => ArgKind::Tuple(
218 Some(arg.span),
219 vec![("_".to_owned(), "_".to_owned()); tys.len()],
220 ),
221 _ => ArgKind::empty(),
222 })
223 .collect::<Vec<ArgKind>>(),
224 ),
225 Node::Ctor(ref variant_data) => {
226 let span = variant_data.ctor_hir_id().map_or(DUMMY_SP, |id| hir.span(id));
227 (span, None, vec![ArgKind::empty(); variant_data.fields().len()])
228 }
229 _ => panic!("non-FnLike node found: {:?}", node),
230 })
231 }
232
233 /// Reports an error when the number of arguments needed by a
234 /// trait match doesn't match the number that the expression
235 /// provides.
report_arg_count_mismatch( &self, span: Span, found_span: Option<Span>, expected_args: Vec<ArgKind>, found_args: Vec<ArgKind>, is_closure: bool, closure_arg_span: Option<Span>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>236 fn report_arg_count_mismatch(
237 &self,
238 span: Span,
239 found_span: Option<Span>,
240 expected_args: Vec<ArgKind>,
241 found_args: Vec<ArgKind>,
242 is_closure: bool,
243 closure_arg_span: Option<Span>,
244 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
245 let kind = if is_closure { "closure" } else { "function" };
246
247 let args_str = |arguments: &[ArgKind], other: &[ArgKind]| {
248 let arg_length = arguments.len();
249 let distinct = matches!(other, &[ArgKind::Tuple(..)]);
250 match (arg_length, arguments.get(0)) {
251 (1, Some(ArgKind::Tuple(_, fields))) => {
252 format!("a single {}-tuple as argument", fields.len())
253 }
254 _ => format!(
255 "{} {}argument{}",
256 arg_length,
257 if distinct && arg_length > 1 { "distinct " } else { "" },
258 pluralize!(arg_length)
259 ),
260 }
261 };
262
263 let expected_str = args_str(&expected_args, &found_args);
264 let found_str = args_str(&found_args, &expected_args);
265
266 let mut err = struct_span_err!(
267 self.tcx.sess,
268 span,
269 E0593,
270 "{} is expected to take {}, but it takes {}",
271 kind,
272 expected_str,
273 found_str,
274 );
275
276 err.span_label(span, format!("expected {} that takes {}", kind, expected_str));
277
278 if let Some(found_span) = found_span {
279 err.span_label(found_span, format!("takes {}", found_str));
280
281 // Suggest to take and ignore the arguments with expected_args_length `_`s if
282 // found arguments is empty (assume the user just wants to ignore args in this case).
283 // For example, if `expected_args_length` is 2, suggest `|_, _|`.
284 if found_args.is_empty() && is_closure {
285 let underscores = vec!["_"; expected_args.len()].join(", ");
286 err.span_suggestion_verbose(
287 closure_arg_span.unwrap_or(found_span),
288 format!(
289 "consider changing the closure to take and ignore the expected argument{}",
290 pluralize!(expected_args.len())
291 ),
292 format!("|{}|", underscores),
293 Applicability::MachineApplicable,
294 );
295 }
296
297 if let &[ArgKind::Tuple(_, ref fields)] = &found_args[..] {
298 if fields.len() == expected_args.len() {
299 let sugg = fields
300 .iter()
301 .map(|(name, _)| name.to_owned())
302 .collect::<Vec<String>>()
303 .join(", ");
304 err.span_suggestion_verbose(
305 found_span,
306 "change the closure to take multiple arguments instead of a single tuple",
307 format!("|{}|", sugg),
308 Applicability::MachineApplicable,
309 );
310 }
311 }
312 if let &[ArgKind::Tuple(_, ref fields)] = &expected_args[..]
313 && fields.len() == found_args.len()
314 && is_closure
315 {
316 let sugg = format!(
317 "|({}){}|",
318 found_args
319 .iter()
320 .map(|arg| match arg {
321 ArgKind::Arg(name, _) => name.to_owned(),
322 _ => "_".to_owned(),
323 })
324 .collect::<Vec<String>>()
325 .join(", "),
326 // add type annotations if available
327 if found_args.iter().any(|arg| match arg {
328 ArgKind::Arg(_, ty) => ty != "_",
329 _ => false,
330 }) {
331 format!(
332 ": ({})",
333 fields
334 .iter()
335 .map(|(_, ty)| ty.to_owned())
336 .collect::<Vec<String>>()
337 .join(", ")
338 )
339 } else {
340 String::new()
341 },
342 );
343 err.span_suggestion_verbose(
344 found_span,
345 "change the closure to accept a tuple instead of individual arguments",
346 sugg,
347 Applicability::MachineApplicable,
348 );
349 }
350 }
351
352 err
353 }
354
type_implements_fn_trait( &self, param_env: ty::ParamEnv<'tcx>, ty: ty::Binder<'tcx, Ty<'tcx>>, constness: ty::BoundConstness, polarity: ty::ImplPolarity, ) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()>355 fn type_implements_fn_trait(
356 &self,
357 param_env: ty::ParamEnv<'tcx>,
358 ty: ty::Binder<'tcx, Ty<'tcx>>,
359 constness: ty::BoundConstness,
360 polarity: ty::ImplPolarity,
361 ) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()> {
362 self.commit_if_ok(|_| {
363 for trait_def_id in [
364 self.tcx.lang_items().fn_trait(),
365 self.tcx.lang_items().fn_mut_trait(),
366 self.tcx.lang_items().fn_once_trait(),
367 ] {
368 let Some(trait_def_id) = trait_def_id else { continue };
369 // Make a fresh inference variable so we can determine what the substitutions
370 // of the trait are.
371 let var = self.next_ty_var(TypeVariableOrigin {
372 span: DUMMY_SP,
373 kind: TypeVariableOriginKind::MiscVariable,
374 });
375 let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, [ty.skip_binder(), var]);
376 let obligation = Obligation::new(
377 self.tcx,
378 ObligationCause::dummy(),
379 param_env,
380 ty.rebind(ty::TraitPredicate { trait_ref, constness, polarity }),
381 );
382 let ocx = ObligationCtxt::new(self);
383 ocx.register_obligation(obligation);
384 if ocx.select_all_or_error().is_empty() {
385 return Ok((
386 self.tcx
387 .fn_trait_kind_from_def_id(trait_def_id)
388 .expect("expected to map DefId to ClosureKind"),
389 ty.rebind(self.resolve_vars_if_possible(var)),
390 ));
391 }
392 }
393
394 Err(())
395 })
396 }
397 }
398
399 impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
report_fulfillment_errors(&self, errors: &[FulfillmentError<'tcx>]) -> ErrorGuaranteed400 fn report_fulfillment_errors(&self, errors: &[FulfillmentError<'tcx>]) -> ErrorGuaranteed {
401 #[derive(Debug)]
402 struct ErrorDescriptor<'tcx> {
403 predicate: ty::Predicate<'tcx>,
404 index: Option<usize>, // None if this is an old error
405 }
406
407 let mut error_map: FxIndexMap<_, Vec<_>> = self
408 .reported_trait_errors
409 .borrow()
410 .iter()
411 .map(|(&span, predicates)| {
412 (
413 span,
414 predicates
415 .iter()
416 .map(|&predicate| ErrorDescriptor { predicate, index: None })
417 .collect(),
418 )
419 })
420 .collect();
421
422 for (index, error) in errors.iter().enumerate() {
423 // We want to ignore desugarings here: spans are equivalent even
424 // if one is the result of a desugaring and the other is not.
425 let mut span = error.obligation.cause.span;
426 let expn_data = span.ctxt().outer_expn_data();
427 if let ExpnKind::Desugaring(_) = expn_data.kind {
428 span = expn_data.call_site;
429 }
430
431 error_map.entry(span).or_default().push(ErrorDescriptor {
432 predicate: error.obligation.predicate,
433 index: Some(index),
434 });
435
436 self.reported_trait_errors
437 .borrow_mut()
438 .entry(span)
439 .or_default()
440 .push(error.obligation.predicate);
441 }
442
443 // We do this in 2 passes because we want to display errors in order, though
444 // maybe it *is* better to sort errors by span or something.
445 let mut is_suppressed = vec![false; errors.len()];
446 for (_, error_set) in error_map.iter() {
447 // We want to suppress "duplicate" errors with the same span.
448 for error in error_set {
449 if let Some(index) = error.index {
450 // Suppress errors that are either:
451 // 1) strictly implied by another error.
452 // 2) implied by an error with a smaller index.
453 for error2 in error_set {
454 if error2.index.is_some_and(|index2| is_suppressed[index2]) {
455 // Avoid errors being suppressed by already-suppressed
456 // errors, to prevent all errors from being suppressed
457 // at once.
458 continue;
459 }
460
461 if self.error_implies(error2.predicate, error.predicate)
462 && !(error2.index >= error.index
463 && self.error_implies(error.predicate, error2.predicate))
464 {
465 info!("skipping {:?} (implied by {:?})", error, error2);
466 is_suppressed[index] = true;
467 break;
468 }
469 }
470 }
471 }
472 }
473
474 for from_expansion in [false, true] {
475 for (error, suppressed) in iter::zip(errors, &is_suppressed) {
476 if !suppressed && error.obligation.cause.span.from_expansion() == from_expansion {
477 self.report_fulfillment_error(error);
478 }
479 }
480 }
481
482 self.tcx.sess.delay_span_bug(DUMMY_SP, "expected fulfillment errors")
483 }
484
485 /// Reports that an overflow has occurred and halts compilation. We
486 /// halt compilation unconditionally because it is important that
487 /// overflows never be masked -- they basically represent computations
488 /// whose result could not be truly determined and thus we can't say
489 /// if the program type checks or not -- and they are unusual
490 /// occurrences in any case.
report_overflow_error<T>( &self, predicate: &T, span: Span, suggest_increasing_limit: bool, mutate: impl FnOnce(&mut Diagnostic), ) -> ! where T: fmt::Display + TypeFoldable<TyCtxt<'tcx>> + Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>, <T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug,491 fn report_overflow_error<T>(
492 &self,
493 predicate: &T,
494 span: Span,
495 suggest_increasing_limit: bool,
496 mutate: impl FnOnce(&mut Diagnostic),
497 ) -> !
498 where
499 T: fmt::Display
500 + TypeFoldable<TyCtxt<'tcx>>
501 + Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>,
502 <T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug,
503 {
504 let mut err = self.build_overflow_error(predicate, span, suggest_increasing_limit);
505 mutate(&mut err);
506 err.emit();
507
508 self.tcx.sess.abort_if_errors();
509 bug!();
510 }
511
build_overflow_error<T>( &self, predicate: &T, span: Span, suggest_increasing_limit: bool, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> where T: fmt::Display + TypeFoldable<TyCtxt<'tcx>> + Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>, <T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug,512 fn build_overflow_error<T>(
513 &self,
514 predicate: &T,
515 span: Span,
516 suggest_increasing_limit: bool,
517 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>
518 where
519 T: fmt::Display
520 + TypeFoldable<TyCtxt<'tcx>>
521 + Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>,
522 <T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug,
523 {
524 let predicate = self.resolve_vars_if_possible(predicate.clone());
525 let mut pred_str = predicate.to_string();
526
527 if pred_str.len() > 50 {
528 // We don't need to save the type to a file, we will be talking about this type already
529 // in a separate note when we explain the obligation, so it will be available that way.
530 pred_str = predicate
531 .print(FmtPrinter::new_with_limit(
532 self.tcx,
533 Namespace::TypeNS,
534 rustc_session::Limit(6),
535 ))
536 .unwrap()
537 .into_buffer();
538 }
539 let mut err = struct_span_err!(
540 self.tcx.sess,
541 span,
542 E0275,
543 "overflow evaluating the requirement `{}`",
544 pred_str,
545 );
546
547 if suggest_increasing_limit {
548 self.suggest_new_overflow_limit(&mut err);
549 }
550
551 err
552 }
553
554 /// Reports that an overflow has occurred and halts compilation. We
555 /// halt compilation unconditionally because it is important that
556 /// overflows never be masked -- they basically represent computations
557 /// whose result could not be truly determined and thus we can't say
558 /// if the program type checks or not -- and they are unusual
559 /// occurrences in any case.
report_overflow_obligation<T>( &self, obligation: &Obligation<'tcx, T>, suggest_increasing_limit: bool, ) -> ! where T: ToPredicate<'tcx> + Clone,560 fn report_overflow_obligation<T>(
561 &self,
562 obligation: &Obligation<'tcx, T>,
563 suggest_increasing_limit: bool,
564 ) -> !
565 where
566 T: ToPredicate<'tcx> + Clone,
567 {
568 let predicate = obligation.predicate.clone().to_predicate(self.tcx);
569 let predicate = self.resolve_vars_if_possible(predicate);
570 self.report_overflow_error(
571 &predicate,
572 obligation.cause.span,
573 suggest_increasing_limit,
574 |err| {
575 self.note_obligation_cause_code(
576 obligation.cause.body_id,
577 err,
578 predicate,
579 obligation.param_env,
580 obligation.cause.code(),
581 &mut vec![],
582 &mut Default::default(),
583 );
584 },
585 );
586 }
587
suggest_new_overflow_limit(&self, err: &mut Diagnostic)588 fn suggest_new_overflow_limit(&self, err: &mut Diagnostic) {
589 let suggested_limit = match self.tcx.recursion_limit() {
590 Limit(0) => Limit(2),
591 limit => limit * 2,
592 };
593 err.help(format!(
594 "consider increasing the recursion limit by adding a \
595 `#![recursion_limit = \"{}\"]` attribute to your crate (`{}`)",
596 suggested_limit,
597 self.tcx.crate_name(LOCAL_CRATE),
598 ));
599 }
600
601 /// Reports that a cycle was detected which led to overflow and halts
602 /// compilation. This is equivalent to `report_overflow_obligation` except
603 /// that we can give a more helpful error message (and, in particular,
604 /// we do not suggest increasing the overflow limit, which is not
605 /// going to help).
report_overflow_obligation_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> !606 fn report_overflow_obligation_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> ! {
607 let cycle = self.resolve_vars_if_possible(cycle.to_owned());
608 assert!(!cycle.is_empty());
609
610 debug!(?cycle, "report_overflow_error_cycle");
611
612 // The 'deepest' obligation is most likely to have a useful
613 // cause 'backtrace'
614 self.report_overflow_obligation(
615 cycle.iter().max_by_key(|p| p.recursion_depth).unwrap(),
616 false,
617 );
618 }
619
report_overflow_no_abort(&self, obligation: PredicateObligation<'tcx>) -> ErrorGuaranteed620 fn report_overflow_no_abort(&self, obligation: PredicateObligation<'tcx>) -> ErrorGuaranteed {
621 let obligation = self.resolve_vars_if_possible(obligation);
622 let mut err = self.build_overflow_error(&obligation.predicate, obligation.cause.span, true);
623 self.note_obligation_cause(&mut err, &obligation);
624 self.point_at_returns_when_relevant(&mut err, &obligation);
625 err.emit()
626 }
627
report_selection_error( &self, mut obligation: PredicateObligation<'tcx>, root_obligation: &PredicateObligation<'tcx>, error: &SelectionError<'tcx>, )628 fn report_selection_error(
629 &self,
630 mut obligation: PredicateObligation<'tcx>,
631 root_obligation: &PredicateObligation<'tcx>,
632 error: &SelectionError<'tcx>,
633 ) {
634 let tcx = self.tcx;
635
636 if tcx.sess.opts.unstable_opts.dump_solver_proof_tree == DumpSolverProofTree::OnError {
637 dump_proof_tree(root_obligation, self.infcx);
638 }
639
640 let mut span = obligation.cause.span;
641 // FIXME: statically guarantee this by tainting after the diagnostic is emitted
642 self.set_tainted_by_errors(
643 tcx.sess.delay_span_bug(span, "`report_selection_error` did not emit an error"),
644 );
645
646 let mut err = match *error {
647 SelectionError::Unimplemented => {
648 // If this obligation was generated as a result of well-formedness checking, see if we
649 // can get a better error message by performing HIR-based well-formedness checking.
650 if let ObligationCauseCode::WellFormed(Some(wf_loc)) =
651 root_obligation.cause.code().peel_derives()
652 && !obligation.predicate.has_non_region_infer()
653 {
654 if let Some(cause) = self
655 .tcx
656 .diagnostic_hir_wf_check((tcx.erase_regions(obligation.predicate), *wf_loc))
657 {
658 obligation.cause = cause.clone();
659 span = obligation.cause.span;
660 }
661 }
662
663 if let ObligationCauseCode::CompareImplItemObligation {
664 impl_item_def_id,
665 trait_item_def_id,
666 kind: _,
667 } = *obligation.cause.code()
668 {
669 self.report_extra_impl_obligation(
670 span,
671 impl_item_def_id,
672 trait_item_def_id,
673 &format!("`{}`", obligation.predicate),
674 )
675 .emit();
676 return;
677 }
678
679 // Report a const-param specific error
680 if let ObligationCauseCode::ConstParam(ty) = *obligation.cause.code().peel_derives()
681 {
682 self.report_const_param_not_wf(ty, &obligation).emit();
683 return;
684 }
685
686 let bound_predicate = obligation.predicate.kind();
687 match bound_predicate.skip_binder() {
688 ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_predicate)) => {
689 let trait_predicate = bound_predicate.rebind(trait_predicate);
690 let mut trait_predicate = self.resolve_vars_if_possible(trait_predicate);
691
692 trait_predicate.remap_constness_diag(obligation.param_env);
693 let predicate_is_const = ty::BoundConstness::ConstIfConst
694 == trait_predicate.skip_binder().constness;
695
696 if self.tcx.sess.has_errors().is_some()
697 && trait_predicate.references_error()
698 {
699 return;
700 }
701 let trait_ref = trait_predicate.to_poly_trait_ref();
702
703 let (post_message, pre_message, type_def) = self
704 .get_parent_trait_ref(obligation.cause.code())
705 .map(|(t, s)| {
706 (
707 format!(" in `{}`", t),
708 format!("within `{}`, ", t),
709 s.map(|s| (format!("within this `{}`", t), s)),
710 )
711 })
712 .unwrap_or_default();
713
714 let OnUnimplementedNote {
715 message,
716 label,
717 note,
718 parent_label,
719 append_const_msg,
720 } = self.on_unimplemented_note(trait_ref, &obligation);
721 let have_alt_message = message.is_some() || label.is_some();
722 let is_try_conversion = self.is_try_conversion(span, trait_ref.def_id());
723 let is_unsize =
724 Some(trait_ref.def_id()) == self.tcx.lang_items().unsize_trait();
725 let (message, note, append_const_msg) = if is_try_conversion {
726 (
727 Some(format!(
728 "`?` couldn't convert the error to `{}`",
729 trait_ref.skip_binder().self_ty(),
730 )),
731 Some(
732 "the question mark operation (`?`) implicitly performs a \
733 conversion on the error value using the `From` trait"
734 .to_owned(),
735 ),
736 Some(AppendConstMessage::Default),
737 )
738 } else {
739 (message, note, append_const_msg)
740 };
741
742 let err_msg = self.get_standard_error_message(
743 &trait_predicate,
744 message,
745 predicate_is_const,
746 append_const_msg,
747 post_message,
748 );
749
750 let (err_msg, safe_transmute_explanation) = if Some(trait_ref.def_id())
751 == self.tcx.lang_items().transmute_trait()
752 {
753 // Recompute the safe transmute reason and use that for the error reporting
754 match self.get_safe_transmute_error_and_reason(
755 obligation.clone(),
756 trait_ref,
757 span,
758 ) {
759 GetSafeTransmuteErrorAndReason::Silent => return,
760 GetSafeTransmuteErrorAndReason::Error {
761 err_msg,
762 safe_transmute_explanation,
763 } => (err_msg, Some(safe_transmute_explanation)),
764 }
765 } else {
766 (err_msg, None)
767 };
768
769 let mut err = struct_span_err!(self.tcx.sess, span, E0277, "{}", err_msg);
770
771 if is_try_conversion && let Some(ret_span) = self.return_type_span(&obligation) {
772 err.span_label(
773 ret_span,
774 format!(
775 "expected `{}` because of this",
776 trait_ref.skip_binder().self_ty()
777 ),
778 );
779 }
780
781 if Some(trait_ref.def_id()) == tcx.lang_items().tuple_trait() {
782 self.add_tuple_trait_message(
783 &obligation.cause.code().peel_derives(),
784 &mut err,
785 );
786 }
787
788 if Some(trait_ref.def_id()) == tcx.lang_items().drop_trait()
789 && predicate_is_const
790 {
791 err.note("`~const Drop` was renamed to `~const Destruct`");
792 err.note("See <https://github.com/rust-lang/rust/pull/94901> for more details");
793 }
794
795 let explanation = get_explanation_based_on_obligation(
796 &obligation,
797 trait_ref,
798 &trait_predicate,
799 pre_message,
800 );
801
802 self.check_for_binding_assigned_block_without_tail_expression(
803 &obligation,
804 &mut err,
805 trait_predicate,
806 );
807 if self.suggest_add_reference_to_arg(
808 &obligation,
809 &mut err,
810 trait_predicate,
811 have_alt_message,
812 ) {
813 self.note_obligation_cause(&mut err, &obligation);
814 err.emit();
815 return;
816 }
817 if let Some(s) = label {
818 // If it has a custom `#[rustc_on_unimplemented]`
819 // error message, let's display it as the label!
820 err.span_label(span, s);
821 if !matches!(trait_ref.skip_binder().self_ty().kind(), ty::Param(_)) {
822 // When the self type is a type param We don't need to "the trait
823 // `std::marker::Sized` is not implemented for `T`" as we will point
824 // at the type param with a label to suggest constraining it.
825 err.help(explanation);
826 }
827 } else if let Some(custom_explanation) = safe_transmute_explanation {
828 err.span_label(span, custom_explanation);
829 } else {
830 err.span_label(span, explanation);
831 }
832
833 if let ObligationCauseCode::Coercion { source, target } =
834 *obligation.cause.code().peel_derives()
835 {
836 if Some(trait_ref.def_id()) == self.tcx.lang_items().sized_trait() {
837 self.suggest_borrowing_for_object_cast(
838 &mut err,
839 &root_obligation,
840 source,
841 target,
842 );
843 }
844 }
845
846 let UnsatisfiedConst(unsatisfied_const) = self
847 .maybe_add_note_for_unsatisfied_const(
848 &obligation,
849 trait_ref,
850 &trait_predicate,
851 &mut err,
852 span,
853 );
854
855 if let Some((msg, span)) = type_def {
856 err.span_label(span, msg);
857 }
858 if let Some(s) = note {
859 // If it has a custom `#[rustc_on_unimplemented]` note, let's display it
860 err.note(s);
861 }
862 if let Some(s) = parent_label {
863 let body = obligation.cause.body_id;
864 err.span_label(tcx.def_span(body), s);
865 }
866
867 self.suggest_floating_point_literal(&obligation, &mut err, &trait_ref);
868 self.suggest_dereferencing_index(&obligation, &mut err, trait_predicate);
869 let mut suggested =
870 self.suggest_dereferences(&obligation, &mut err, trait_predicate);
871 suggested |= self.suggest_fn_call(&obligation, &mut err, trait_predicate);
872 let impl_candidates = self.find_similar_impl_candidates(trait_predicate);
873 suggested = if let &[cand] = &impl_candidates[..] {
874 let cand = cand.trait_ref;
875 if let (ty::FnPtr(_), ty::FnDef(..)) =
876 (cand.self_ty().kind(), trait_ref.self_ty().skip_binder().kind())
877 {
878 err.span_suggestion(
879 span.shrink_to_hi(),
880 format!(
881 "the trait `{}` is implemented for fn pointer `{}`, try casting using `as`",
882 cand.print_only_trait_path(),
883 cand.self_ty(),
884 ),
885 format!(" as {}", cand.self_ty()),
886 Applicability::MaybeIncorrect,
887 );
888 true
889 } else {
890 false
891 }
892 } else {
893 false
894 } || suggested;
895 suggested |=
896 self.suggest_remove_reference(&obligation, &mut err, trait_predicate);
897 suggested |= self.suggest_semicolon_removal(
898 &obligation,
899 &mut err,
900 span,
901 trait_predicate,
902 );
903 self.note_version_mismatch(&mut err, &trait_ref);
904 self.suggest_remove_await(&obligation, &mut err);
905 self.suggest_derive(&obligation, &mut err, trait_predicate);
906
907 if Some(trait_ref.def_id()) == tcx.lang_items().try_trait() {
908 self.suggest_await_before_try(
909 &mut err,
910 &obligation,
911 trait_predicate,
912 span,
913 );
914 }
915
916 if self.suggest_add_clone_to_arg(&obligation, &mut err, trait_predicate) {
917 err.emit();
918 return;
919 }
920
921 if self.suggest_impl_trait(&mut err, &obligation, trait_predicate) {
922 err.emit();
923 return;
924 }
925
926 if is_unsize {
927 // If the obligation failed due to a missing implementation of the
928 // `Unsize` trait, give a pointer to why that might be the case
929 err.note(
930 "all implementations of `Unsize` are provided \
931 automatically by the compiler, see \
932 <https://doc.rust-lang.org/stable/std/marker/trait.Unsize.html> \
933 for more information",
934 );
935 }
936
937 let is_fn_trait = tcx.is_fn_trait(trait_ref.def_id());
938 let is_target_feature_fn = if let ty::FnDef(def_id, _) =
939 *trait_ref.skip_binder().self_ty().kind()
940 {
941 !self.tcx.codegen_fn_attrs(def_id).target_features.is_empty()
942 } else {
943 false
944 };
945 if is_fn_trait && is_target_feature_fn {
946 err.note(
947 "`#[target_feature]` functions do not implement the `Fn` traits",
948 );
949 }
950
951 self.try_to_add_help_message(
952 &obligation,
953 trait_ref,
954 &trait_predicate,
955 &mut err,
956 span,
957 is_fn_trait,
958 suggested,
959 unsatisfied_const,
960 );
961
962 // Changing mutability doesn't make a difference to whether we have
963 // an `Unsize` impl (Fixes ICE in #71036)
964 if !is_unsize {
965 self.suggest_change_mut(&obligation, &mut err, trait_predicate);
966 }
967
968 // If this error is due to `!: Trait` not implemented but `(): Trait` is
969 // implemented, and fallback has occurred, then it could be due to a
970 // variable that used to fallback to `()` now falling back to `!`. Issue a
971 // note informing about the change in behaviour.
972 if trait_predicate.skip_binder().self_ty().is_never()
973 && self.fallback_has_occurred
974 {
975 let predicate = trait_predicate.map_bound(|trait_pred| {
976 trait_pred.with_self_ty(self.tcx, Ty::new_unit(self.tcx))
977 });
978 let unit_obligation = obligation.with(tcx, predicate);
979 if self.predicate_may_hold(&unit_obligation) {
980 err.note(
981 "this error might have been caused by changes to \
982 Rust's type-inference algorithm (see issue #48950 \
983 <https://github.com/rust-lang/rust/issues/48950> \
984 for more information)",
985 );
986 err.help("did you intend to use the type `()` here instead?");
987 }
988 }
989
990 // Return early if the trait is Debug or Display and the invocation
991 // originates within a standard library macro, because the output
992 // is otherwise overwhelming and unhelpful (see #85844 for an
993 // example).
994
995 let in_std_macro =
996 match obligation.cause.span.ctxt().outer_expn_data().macro_def_id {
997 Some(macro_def_id) => {
998 let crate_name = tcx.crate_name(macro_def_id.krate);
999 crate_name == sym::std || crate_name == sym::core
1000 }
1001 None => false,
1002 };
1003
1004 if in_std_macro
1005 && matches!(
1006 self.tcx.get_diagnostic_name(trait_ref.def_id()),
1007 Some(sym::Debug | sym::Display)
1008 )
1009 {
1010 err.emit();
1011 return;
1012 }
1013
1014 err
1015 }
1016
1017 ty::PredicateKind::Subtype(predicate) => {
1018 // Errors for Subtype predicates show up as
1019 // `FulfillmentErrorCode::CodeSubtypeError`,
1020 // not selection error.
1021 span_bug!(span, "subtype requirement gave wrong error: `{:?}`", predicate)
1022 }
1023
1024 ty::PredicateKind::Coerce(predicate) => {
1025 // Errors for Coerce predicates show up as
1026 // `FulfillmentErrorCode::CodeSubtypeError`,
1027 // not selection error.
1028 span_bug!(span, "coerce requirement gave wrong error: `{:?}`", predicate)
1029 }
1030
1031 ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(..))
1032 | ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(..)) => {
1033 span_bug!(
1034 span,
1035 "outlives clauses should not error outside borrowck. obligation: `{:?}`",
1036 obligation
1037 )
1038 }
1039
1040 ty::PredicateKind::Clause(ty::ClauseKind::Projection(..)) => {
1041 span_bug!(
1042 span,
1043 "projection clauses should be implied from elsewhere. obligation: `{:?}`",
1044 obligation
1045 )
1046 }
1047
1048 ty::PredicateKind::ObjectSafe(trait_def_id) => {
1049 let violations = self.tcx.object_safety_violations(trait_def_id);
1050 report_object_safety_error(self.tcx, span, trait_def_id, violations)
1051 }
1052
1053 ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
1054 let found_kind = self.closure_kind(closure_substs).unwrap();
1055 self.report_closure_error(&obligation, closure_def_id, found_kind, kind)
1056 }
1057
1058 ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(ty)) => {
1059 let ty = self.resolve_vars_if_possible(ty);
1060 match self.tcx.sess.opts.unstable_opts.trait_solver {
1061 TraitSolver::Classic => {
1062 // WF predicates cannot themselves make
1063 // errors. They can only block due to
1064 // ambiguity; otherwise, they always
1065 // degenerate into other obligations
1066 // (which may fail).
1067 span_bug!(span, "WF predicate not satisfied for {:?}", ty);
1068 }
1069 TraitSolver::Next | TraitSolver::NextCoherence => {
1070 // FIXME: we'll need a better message which takes into account
1071 // which bounds actually failed to hold.
1072 self.tcx.sess.struct_span_err(
1073 span,
1074 format!("the type `{}` is not well-formed", ty),
1075 )
1076 }
1077 }
1078 }
1079
1080 ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(..)) => {
1081 // Errors for `ConstEvaluatable` predicates show up as
1082 // `SelectionError::ConstEvalFailure`,
1083 // not `Unimplemented`.
1084 span_bug!(
1085 span,
1086 "const-evaluatable requirement gave wrong error: `{:?}`",
1087 obligation
1088 )
1089 }
1090
1091 ty::PredicateKind::ConstEquate(..) => {
1092 // Errors for `ConstEquate` predicates show up as
1093 // `SelectionError::ConstEvalFailure`,
1094 // not `Unimplemented`.
1095 span_bug!(
1096 span,
1097 "const-equate requirement gave wrong error: `{:?}`",
1098 obligation
1099 )
1100 }
1101
1102 ty::PredicateKind::Ambiguous => span_bug!(span, "ambiguous"),
1103
1104 ty::PredicateKind::AliasRelate(..) => span_bug!(
1105 span,
1106 "AliasRelate predicate should never be the predicate cause of a SelectionError"
1107 ),
1108
1109 ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
1110 let mut diag = self.tcx.sess.struct_span_err(
1111 span,
1112 format!("the constant `{}` is not of type `{}`", ct, ty),
1113 );
1114 self.note_type_err(
1115 &mut diag,
1116 &obligation.cause,
1117 None,
1118 None,
1119 TypeError::Sorts(ty::error::ExpectedFound::new(true, ty, ct.ty())),
1120 false,
1121 false,
1122 );
1123 diag
1124 }
1125 }
1126 }
1127
1128 OutputTypeParameterMismatch(box SelectionOutputTypeParameterMismatch {
1129 found_trait_ref,
1130 expected_trait_ref,
1131 terr: terr @ TypeError::CyclicTy(_),
1132 }) => self.report_type_parameter_mismatch_cyclic_type_error(
1133 &obligation,
1134 found_trait_ref,
1135 expected_trait_ref,
1136 terr,
1137 ),
1138 OutputTypeParameterMismatch(box SelectionOutputTypeParameterMismatch {
1139 found_trait_ref,
1140 expected_trait_ref,
1141 terr: _,
1142 }) => {
1143 match self.report_type_parameter_mismatch_error(
1144 &obligation,
1145 span,
1146 found_trait_ref,
1147 expected_trait_ref,
1148 ) {
1149 Some(err) => err,
1150 None => return,
1151 }
1152 }
1153
1154 SelectionError::OpaqueTypeAutoTraitLeakageUnknown(def_id) => self.report_opaque_type_auto_trait_leakage(
1155 &obligation,
1156 def_id,
1157 ),
1158
1159 TraitNotObjectSafe(did) => {
1160 let violations = self.tcx.object_safety_violations(did);
1161 report_object_safety_error(self.tcx, span, did, violations)
1162 }
1163
1164 SelectionError::NotConstEvaluatable(NotConstEvaluatable::MentionsInfer) => {
1165 bug!(
1166 "MentionsInfer should have been handled in `traits/fulfill.rs` or `traits/select/mod.rs`"
1167 )
1168 }
1169 SelectionError::NotConstEvaluatable(NotConstEvaluatable::MentionsParam) => {
1170 match self.report_not_const_evaluatable_error(&obligation, span) {
1171 Some(err) => err,
1172 None => return,
1173 }
1174 }
1175
1176 // Already reported in the query.
1177 SelectionError::NotConstEvaluatable(NotConstEvaluatable::Error(_)) |
1178 // Already reported.
1179 Overflow(OverflowError::Error(_)) => return,
1180
1181 Overflow(_) => {
1182 bug!("overflow should be handled before the `report_selection_error` path");
1183 }
1184 SelectionError::ErrorReporting => {
1185 bug!("ErrorReporting Overflow should not reach `report_selection_err` call")
1186 }
1187 };
1188
1189 self.note_obligation_cause(&mut err, &obligation);
1190 self.point_at_returns_when_relevant(&mut err, &obligation);
1191 err.emit();
1192 }
1193
report_const_param_not_wf( &self, ty: Ty<'tcx>, obligation: &PredicateObligation<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>1194 fn report_const_param_not_wf(
1195 &self,
1196 ty: Ty<'tcx>,
1197 obligation: &PredicateObligation<'tcx>,
1198 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1199 let span = obligation.cause.span;
1200
1201 let mut diag = match ty.kind() {
1202 _ if ty.has_param() => {
1203 span_bug!(span, "const param tys cannot mention other generic parameters");
1204 }
1205 ty::Float(_) => {
1206 struct_span_err!(
1207 self.tcx.sess,
1208 span,
1209 E0741,
1210 "`{ty}` is forbidden as the type of a const generic parameter",
1211 )
1212 }
1213 ty::FnPtr(_) => {
1214 struct_span_err!(
1215 self.tcx.sess,
1216 span,
1217 E0741,
1218 "using function pointers as const generic parameters is forbidden",
1219 )
1220 }
1221 ty::RawPtr(_) => {
1222 struct_span_err!(
1223 self.tcx.sess,
1224 span,
1225 E0741,
1226 "using raw pointers as const generic parameters is forbidden",
1227 )
1228 }
1229 ty::Adt(def, _) => {
1230 // We should probably see if we're *allowed* to derive `ConstParamTy` on the type...
1231 let mut diag = struct_span_err!(
1232 self.tcx.sess,
1233 span,
1234 E0741,
1235 "`{ty}` must implement `ConstParamTy` to be used as the type of a const generic parameter",
1236 );
1237 // Only suggest derive if this isn't a derived obligation,
1238 // and the struct is local.
1239 if let Some(span) = self.tcx.hir().span_if_local(def.did())
1240 && obligation.cause.code().parent().is_none()
1241 {
1242 if ty.is_structural_eq_shallow(self.tcx) {
1243 diag.span_suggestion(
1244 span,
1245 "add `#[derive(ConstParamTy)]` to the struct",
1246 "#[derive(ConstParamTy)]\n",
1247 Applicability::MachineApplicable,
1248 );
1249 } else {
1250 // FIXME(adt_const_params): We should check there's not already an
1251 // overlapping `Eq`/`PartialEq` impl.
1252 diag.span_suggestion(
1253 span,
1254 "add `#[derive(ConstParamTy, PartialEq, Eq)]` to the struct",
1255 "#[derive(ConstParamTy, PartialEq, Eq)]\n",
1256 Applicability::MachineApplicable,
1257 );
1258 }
1259 }
1260 diag
1261 }
1262 _ => {
1263 struct_span_err!(
1264 self.tcx.sess,
1265 span,
1266 E0741,
1267 "`{ty}` can't be used as a const parameter type",
1268 )
1269 }
1270 };
1271
1272 let mut code = obligation.cause.code();
1273 let mut pred = obligation.predicate.to_opt_poly_trait_pred();
1274 while let Some((next_code, next_pred)) = code.parent() {
1275 if let Some(pred) = pred {
1276 let pred = self.instantiate_binder_with_placeholders(pred);
1277 diag.note(format!(
1278 "`{}` must implement `{}`, but it does not",
1279 pred.self_ty(),
1280 pred.print_modifiers_and_trait_path()
1281 ));
1282 }
1283 code = next_code;
1284 pred = next_pred;
1285 }
1286
1287 diag
1288 }
1289 }
1290
1291 trait InferCtxtPrivExt<'tcx> {
1292 // returns if `cond` not occurring implies that `error` does not occur - i.e., that
1293 // `error` occurring implies that `cond` occurs.
error_implies(&self, cond: ty::Predicate<'tcx>, error: ty::Predicate<'tcx>) -> bool1294 fn error_implies(&self, cond: ty::Predicate<'tcx>, error: ty::Predicate<'tcx>) -> bool;
1295
report_fulfillment_error(&self, error: &FulfillmentError<'tcx>)1296 fn report_fulfillment_error(&self, error: &FulfillmentError<'tcx>);
1297
report_projection_error( &self, obligation: &PredicateObligation<'tcx>, error: &MismatchedProjectionTypes<'tcx>, )1298 fn report_projection_error(
1299 &self,
1300 obligation: &PredicateObligation<'tcx>,
1301 error: &MismatchedProjectionTypes<'tcx>,
1302 );
1303
maybe_detailed_projection_msg( &self, pred: ty::ProjectionPredicate<'tcx>, normalized_ty: ty::Term<'tcx>, expected_ty: ty::Term<'tcx>, ) -> Option<String>1304 fn maybe_detailed_projection_msg(
1305 &self,
1306 pred: ty::ProjectionPredicate<'tcx>,
1307 normalized_ty: ty::Term<'tcx>,
1308 expected_ty: ty::Term<'tcx>,
1309 ) -> Option<String>;
1310
fuzzy_match_tys( &self, a: Ty<'tcx>, b: Ty<'tcx>, ignoring_lifetimes: bool, ) -> Option<CandidateSimilarity>1311 fn fuzzy_match_tys(
1312 &self,
1313 a: Ty<'tcx>,
1314 b: Ty<'tcx>,
1315 ignoring_lifetimes: bool,
1316 ) -> Option<CandidateSimilarity>;
1317
describe_generator(&self, body_id: hir::BodyId) -> Option<&'static str>1318 fn describe_generator(&self, body_id: hir::BodyId) -> Option<&'static str>;
1319
find_similar_impl_candidates( &self, trait_pred: ty::PolyTraitPredicate<'tcx>, ) -> Vec<ImplCandidate<'tcx>>1320 fn find_similar_impl_candidates(
1321 &self,
1322 trait_pred: ty::PolyTraitPredicate<'tcx>,
1323 ) -> Vec<ImplCandidate<'tcx>>;
1324
report_similar_impl_candidates( &self, impl_candidates: &[ImplCandidate<'tcx>], trait_ref: ty::PolyTraitRef<'tcx>, body_def_id: LocalDefId, err: &mut Diagnostic, other: bool, ) -> bool1325 fn report_similar_impl_candidates(
1326 &self,
1327 impl_candidates: &[ImplCandidate<'tcx>],
1328 trait_ref: ty::PolyTraitRef<'tcx>,
1329 body_def_id: LocalDefId,
1330 err: &mut Diagnostic,
1331 other: bool,
1332 ) -> bool;
1333
report_similar_impl_candidates_for_root_obligation( &self, obligation: &PredicateObligation<'tcx>, trait_predicate: ty::Binder<'tcx, ty::TraitPredicate<'tcx>>, body_def_id: LocalDefId, err: &mut Diagnostic, )1334 fn report_similar_impl_candidates_for_root_obligation(
1335 &self,
1336 obligation: &PredicateObligation<'tcx>,
1337 trait_predicate: ty::Binder<'tcx, ty::TraitPredicate<'tcx>>,
1338 body_def_id: LocalDefId,
1339 err: &mut Diagnostic,
1340 );
1341
1342 /// Gets the parent trait chain start
get_parent_trait_ref( &self, code: &ObligationCauseCode<'tcx>, ) -> Option<(String, Option<Span>)>1343 fn get_parent_trait_ref(
1344 &self,
1345 code: &ObligationCauseCode<'tcx>,
1346 ) -> Option<(String, Option<Span>)>;
1347
1348 /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
1349 /// with the same path as `trait_ref`, a help message about
1350 /// a probable version mismatch is added to `err`
note_version_mismatch( &self, err: &mut Diagnostic, trait_ref: &ty::PolyTraitRef<'tcx>, ) -> bool1351 fn note_version_mismatch(
1352 &self,
1353 err: &mut Diagnostic,
1354 trait_ref: &ty::PolyTraitRef<'tcx>,
1355 ) -> bool;
1356
1357 /// Creates a `PredicateObligation` with `new_self_ty` replacing the existing type in the
1358 /// `trait_ref`.
1359 ///
1360 /// For this to work, `new_self_ty` must have no escaping bound variables.
mk_trait_obligation_with_new_self_ty( &self, param_env: ty::ParamEnv<'tcx>, trait_ref_and_ty: ty::Binder<'tcx, (ty::TraitPredicate<'tcx>, Ty<'tcx>)>, ) -> PredicateObligation<'tcx>1361 fn mk_trait_obligation_with_new_self_ty(
1362 &self,
1363 param_env: ty::ParamEnv<'tcx>,
1364 trait_ref_and_ty: ty::Binder<'tcx, (ty::TraitPredicate<'tcx>, Ty<'tcx>)>,
1365 ) -> PredicateObligation<'tcx>;
1366
maybe_report_ambiguity(&self, obligation: &PredicateObligation<'tcx>)1367 fn maybe_report_ambiguity(&self, obligation: &PredicateObligation<'tcx>);
1368
predicate_can_apply( &self, param_env: ty::ParamEnv<'tcx>, pred: ty::PolyTraitPredicate<'tcx>, ) -> bool1369 fn predicate_can_apply(
1370 &self,
1371 param_env: ty::ParamEnv<'tcx>,
1372 pred: ty::PolyTraitPredicate<'tcx>,
1373 ) -> bool;
1374
note_obligation_cause(&self, err: &mut Diagnostic, obligation: &PredicateObligation<'tcx>)1375 fn note_obligation_cause(&self, err: &mut Diagnostic, obligation: &PredicateObligation<'tcx>);
1376
suggest_unsized_bound_if_applicable( &self, err: &mut Diagnostic, obligation: &PredicateObligation<'tcx>, )1377 fn suggest_unsized_bound_if_applicable(
1378 &self,
1379 err: &mut Diagnostic,
1380 obligation: &PredicateObligation<'tcx>,
1381 );
1382
annotate_source_of_ambiguity( &self, err: &mut Diagnostic, impls: &[ambiguity::Ambiguity], predicate: ty::Predicate<'tcx>, )1383 fn annotate_source_of_ambiguity(
1384 &self,
1385 err: &mut Diagnostic,
1386 impls: &[ambiguity::Ambiguity],
1387 predicate: ty::Predicate<'tcx>,
1388 );
1389
maybe_suggest_unsized_generics(&self, err: &mut Diagnostic, span: Span, node: Node<'tcx>)1390 fn maybe_suggest_unsized_generics(&self, err: &mut Diagnostic, span: Span, node: Node<'tcx>);
1391
maybe_indirection_for_unsized( &self, err: &mut Diagnostic, item: &'tcx Item<'tcx>, param: &'tcx GenericParam<'tcx>, ) -> bool1392 fn maybe_indirection_for_unsized(
1393 &self,
1394 err: &mut Diagnostic,
1395 item: &'tcx Item<'tcx>,
1396 param: &'tcx GenericParam<'tcx>,
1397 ) -> bool;
1398
is_recursive_obligation( &self, obligated_types: &mut Vec<Ty<'tcx>>, cause_code: &ObligationCauseCode<'tcx>, ) -> bool1399 fn is_recursive_obligation(
1400 &self,
1401 obligated_types: &mut Vec<Ty<'tcx>>,
1402 cause_code: &ObligationCauseCode<'tcx>,
1403 ) -> bool;
1404
get_standard_error_message( &self, trait_predicate: &ty::PolyTraitPredicate<'tcx>, message: Option<String>, predicate_is_const: bool, append_const_msg: Option<AppendConstMessage>, post_message: String, ) -> String1405 fn get_standard_error_message(
1406 &self,
1407 trait_predicate: &ty::PolyTraitPredicate<'tcx>,
1408 message: Option<String>,
1409 predicate_is_const: bool,
1410 append_const_msg: Option<AppendConstMessage>,
1411 post_message: String,
1412 ) -> String;
1413
get_safe_transmute_error_and_reason( &self, obligation: PredicateObligation<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>, span: Span, ) -> GetSafeTransmuteErrorAndReason1414 fn get_safe_transmute_error_and_reason(
1415 &self,
1416 obligation: PredicateObligation<'tcx>,
1417 trait_ref: ty::PolyTraitRef<'tcx>,
1418 span: Span,
1419 ) -> GetSafeTransmuteErrorAndReason;
1420
add_tuple_trait_message( &self, obligation_cause_code: &ObligationCauseCode<'tcx>, err: &mut Diagnostic, )1421 fn add_tuple_trait_message(
1422 &self,
1423 obligation_cause_code: &ObligationCauseCode<'tcx>,
1424 err: &mut Diagnostic,
1425 );
1426
try_to_add_help_message( &self, obligation: &PredicateObligation<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>, trait_predicate: &ty::PolyTraitPredicate<'tcx>, err: &mut Diagnostic, span: Span, is_fn_trait: bool, suggested: bool, unsatisfied_const: bool, )1427 fn try_to_add_help_message(
1428 &self,
1429 obligation: &PredicateObligation<'tcx>,
1430 trait_ref: ty::PolyTraitRef<'tcx>,
1431 trait_predicate: &ty::PolyTraitPredicate<'tcx>,
1432 err: &mut Diagnostic,
1433 span: Span,
1434 is_fn_trait: bool,
1435 suggested: bool,
1436 unsatisfied_const: bool,
1437 );
1438
add_help_message_for_fn_trait( &self, trait_ref: ty::PolyTraitRef<'tcx>, err: &mut Diagnostic, implemented_kind: ty::ClosureKind, params: ty::Binder<'tcx, Ty<'tcx>>, )1439 fn add_help_message_for_fn_trait(
1440 &self,
1441 trait_ref: ty::PolyTraitRef<'tcx>,
1442 err: &mut Diagnostic,
1443 implemented_kind: ty::ClosureKind,
1444 params: ty::Binder<'tcx, Ty<'tcx>>,
1445 );
1446
maybe_add_note_for_unsatisfied_const( &self, obligation: &PredicateObligation<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>, trait_predicate: &ty::PolyTraitPredicate<'tcx>, err: &mut Diagnostic, span: Span, ) -> UnsatisfiedConst1447 fn maybe_add_note_for_unsatisfied_const(
1448 &self,
1449 obligation: &PredicateObligation<'tcx>,
1450 trait_ref: ty::PolyTraitRef<'tcx>,
1451 trait_predicate: &ty::PolyTraitPredicate<'tcx>,
1452 err: &mut Diagnostic,
1453 span: Span,
1454 ) -> UnsatisfiedConst;
1455
report_closure_error( &self, obligation: &PredicateObligation<'tcx>, closure_def_id: DefId, found_kind: ty::ClosureKind, kind: ty::ClosureKind, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>1456 fn report_closure_error(
1457 &self,
1458 obligation: &PredicateObligation<'tcx>,
1459 closure_def_id: DefId,
1460 found_kind: ty::ClosureKind,
1461 kind: ty::ClosureKind,
1462 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
1463
report_type_parameter_mismatch_cyclic_type_error( &self, obligation: &PredicateObligation<'tcx>, found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>, expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>, terr: TypeError<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>1464 fn report_type_parameter_mismatch_cyclic_type_error(
1465 &self,
1466 obligation: &PredicateObligation<'tcx>,
1467 found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
1468 expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
1469 terr: TypeError<'tcx>,
1470 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
1471
report_opaque_type_auto_trait_leakage( &self, obligation: &PredicateObligation<'tcx>, def_id: DefId, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>1472 fn report_opaque_type_auto_trait_leakage(
1473 &self,
1474 obligation: &PredicateObligation<'tcx>,
1475 def_id: DefId,
1476 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
1477
report_type_parameter_mismatch_error( &self, obligation: &PredicateObligation<'tcx>, span: Span, found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>, expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>, ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>1478 fn report_type_parameter_mismatch_error(
1479 &self,
1480 obligation: &PredicateObligation<'tcx>,
1481 span: Span,
1482 found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
1483 expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
1484 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>;
1485
report_not_const_evaluatable_error( &self, obligation: &PredicateObligation<'tcx>, span: Span, ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>1486 fn report_not_const_evaluatable_error(
1487 &self,
1488 obligation: &PredicateObligation<'tcx>,
1489 span: Span,
1490 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>;
1491 }
1492
1493 impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
1494 // returns if `cond` not occurring implies that `error` does not occur - i.e., that
1495 // `error` occurring implies that `cond` occurs.
error_implies(&self, cond: ty::Predicate<'tcx>, error: ty::Predicate<'tcx>) -> bool1496 fn error_implies(&self, cond: ty::Predicate<'tcx>, error: ty::Predicate<'tcx>) -> bool {
1497 if cond == error {
1498 return true;
1499 }
1500
1501 // FIXME: It should be possible to deal with `ForAll` in a cleaner way.
1502 let bound_error = error.kind();
1503 let (cond, error) = match (cond.kind().skip_binder(), bound_error.skip_binder()) {
1504 (
1505 ty::PredicateKind::Clause(ty::ClauseKind::Trait(..)),
1506 ty::PredicateKind::Clause(ty::ClauseKind::Trait(error)),
1507 ) => (cond, bound_error.rebind(error)),
1508 _ => {
1509 // FIXME: make this work in other cases too.
1510 return false;
1511 }
1512 };
1513
1514 for pred in super::elaborate(self.tcx, std::iter::once(cond)) {
1515 let bound_predicate = pred.kind();
1516 if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(implication)) =
1517 bound_predicate.skip_binder()
1518 {
1519 let error = error.to_poly_trait_ref();
1520 let implication = bound_predicate.rebind(implication.trait_ref);
1521 // FIXME: I'm just not taking associated types at all here.
1522 // Eventually I'll need to implement param-env-aware
1523 // `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic.
1524 let param_env = ty::ParamEnv::empty();
1525 if self.can_sub(param_env, error, implication) {
1526 debug!("error_implies: {:?} -> {:?} -> {:?}", cond, error, implication);
1527 return true;
1528 }
1529 }
1530 }
1531
1532 false
1533 }
1534
1535 #[instrument(skip(self), level = "debug")]
report_fulfillment_error(&self, error: &FulfillmentError<'tcx>)1536 fn report_fulfillment_error(&self, error: &FulfillmentError<'tcx>) {
1537 if self.tcx.sess.opts.unstable_opts.dump_solver_proof_tree == DumpSolverProofTree::OnError {
1538 dump_proof_tree(&error.root_obligation, self.infcx);
1539 }
1540
1541 match error.code {
1542 FulfillmentErrorCode::CodeSelectionError(ref selection_error) => {
1543 self.report_selection_error(
1544 error.obligation.clone(),
1545 &error.root_obligation,
1546 selection_error,
1547 );
1548 }
1549 FulfillmentErrorCode::CodeProjectionError(ref e) => {
1550 self.report_projection_error(&error.obligation, e);
1551 }
1552 FulfillmentErrorCode::CodeAmbiguity { overflow: false } => {
1553 self.maybe_report_ambiguity(&error.obligation);
1554 }
1555 FulfillmentErrorCode::CodeAmbiguity { overflow: true } => {
1556 self.report_overflow_no_abort(error.obligation.clone());
1557 }
1558 FulfillmentErrorCode::CodeSubtypeError(ref expected_found, ref err) => {
1559 self.report_mismatched_types(
1560 &error.obligation.cause,
1561 expected_found.expected,
1562 expected_found.found,
1563 *err,
1564 )
1565 .emit();
1566 }
1567 FulfillmentErrorCode::CodeConstEquateError(ref expected_found, ref err) => {
1568 let mut diag = self.report_mismatched_consts(
1569 &error.obligation.cause,
1570 expected_found.expected,
1571 expected_found.found,
1572 *err,
1573 );
1574 let code = error.obligation.cause.code().peel_derives().peel_match_impls();
1575 if let ObligationCauseCode::BindingObligation(..)
1576 | ObligationCauseCode::ItemObligation(..)
1577 | ObligationCauseCode::ExprBindingObligation(..)
1578 | ObligationCauseCode::ExprItemObligation(..) = code
1579 {
1580 self.note_obligation_cause_code(
1581 error.obligation.cause.body_id,
1582 &mut diag,
1583 error.obligation.predicate,
1584 error.obligation.param_env,
1585 code,
1586 &mut vec![],
1587 &mut Default::default(),
1588 );
1589 }
1590 diag.emit();
1591 }
1592 FulfillmentErrorCode::CodeCycle(ref cycle) => {
1593 self.report_overflow_obligation_cycle(cycle);
1594 }
1595 }
1596 }
1597
1598 #[instrument(level = "debug", skip_all)]
report_projection_error( &self, obligation: &PredicateObligation<'tcx>, error: &MismatchedProjectionTypes<'tcx>, )1599 fn report_projection_error(
1600 &self,
1601 obligation: &PredicateObligation<'tcx>,
1602 error: &MismatchedProjectionTypes<'tcx>,
1603 ) {
1604 let predicate = self.resolve_vars_if_possible(obligation.predicate);
1605
1606 if predicate.references_error() {
1607 return;
1608 }
1609
1610 self.probe(|_| {
1611 let ocx = ObligationCtxt::new(self);
1612
1613 // try to find the mismatched types to report the error with.
1614 //
1615 // this can fail if the problem was higher-ranked, in which
1616 // cause I have no idea for a good error message.
1617 let bound_predicate = predicate.kind();
1618 let (values, err) = if let ty::PredicateKind::Clause(ty::ClauseKind::Projection(data)) =
1619 bound_predicate.skip_binder()
1620 {
1621 let data = self.instantiate_binder_with_fresh_vars(
1622 obligation.cause.span,
1623 infer::LateBoundRegionConversionTime::HigherRankedType,
1624 bound_predicate.rebind(data),
1625 );
1626 let unnormalized_term = match data.term.unpack() {
1627 ty::TermKind::Ty(_) => Ty::new_projection(
1628 self.tcx,
1629 data.projection_ty.def_id,
1630 data.projection_ty.substs,
1631 )
1632 .into(),
1633 ty::TermKind::Const(ct) => ty::Const::new_unevaluated(
1634 self.tcx,
1635 ty::UnevaluatedConst {
1636 def: data.projection_ty.def_id,
1637 substs: data.projection_ty.substs,
1638 },
1639 ct.ty(),
1640 )
1641 .into(),
1642 };
1643 let normalized_term =
1644 ocx.normalize(&obligation.cause, obligation.param_env, unnormalized_term);
1645
1646 debug!(?obligation.cause, ?obligation.param_env);
1647
1648 debug!(?normalized_term, data.ty = ?data.term);
1649
1650 let is_normalized_term_expected = !matches!(
1651 obligation.cause.code().peel_derives(),
1652 ObligationCauseCode::ItemObligation(_)
1653 | ObligationCauseCode::BindingObligation(_, _)
1654 | ObligationCauseCode::ExprItemObligation(..)
1655 | ObligationCauseCode::ExprBindingObligation(..)
1656 | ObligationCauseCode::Coercion { .. }
1657 | ObligationCauseCode::OpaqueType
1658 );
1659
1660 // constrain inference variables a bit more to nested obligations from normalize so
1661 // we can have more helpful errors.
1662 //
1663 // we intentionally drop errors from normalization here,
1664 // since the normalization is just done to improve the error message.
1665 let _ = ocx.select_where_possible();
1666
1667 if let Err(new_err) = ocx.eq_exp(
1668 &obligation.cause,
1669 obligation.param_env,
1670 is_normalized_term_expected,
1671 normalized_term,
1672 data.term,
1673 ) {
1674 (Some((data, is_normalized_term_expected, normalized_term, data.term)), new_err)
1675 } else {
1676 (None, error.err)
1677 }
1678 } else {
1679 (None, error.err)
1680 };
1681
1682 let msg = values
1683 .and_then(|(predicate, _, normalized_term, expected_term)| {
1684 self.maybe_detailed_projection_msg(predicate, normalized_term, expected_term)
1685 })
1686 .unwrap_or_else(|| {
1687 with_forced_trimmed_paths!(format!(
1688 "type mismatch resolving `{}`",
1689 self.resolve_vars_if_possible(predicate)
1690 .print(FmtPrinter::new_with_limit(
1691 self.tcx,
1692 Namespace::TypeNS,
1693 rustc_session::Limit(10),
1694 ))
1695 .unwrap()
1696 .into_buffer()
1697 ))
1698 });
1699 let mut diag = struct_span_err!(self.tcx.sess, obligation.cause.span, E0271, "{msg}");
1700
1701 let secondary_span = (|| {
1702 let ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj)) =
1703 predicate.kind().skip_binder()
1704 else {
1705 return None;
1706 };
1707
1708 let trait_assoc_item = self.tcx.opt_associated_item(proj.projection_ty.def_id)?;
1709 let trait_assoc_ident = trait_assoc_item.ident(self.tcx);
1710
1711 let mut associated_items = vec![];
1712 self.tcx.for_each_relevant_impl(
1713 self.tcx.trait_of_item(proj.projection_ty.def_id)?,
1714 proj.projection_ty.self_ty(),
1715 |impl_def_id| {
1716 associated_items.extend(
1717 self.tcx
1718 .associated_items(impl_def_id)
1719 .in_definition_order()
1720 .find(|assoc| assoc.ident(self.tcx) == trait_assoc_ident),
1721 );
1722 },
1723 );
1724
1725 let [associated_item]: &[ty::AssocItem] = &associated_items[..] else {
1726 return None;
1727 };
1728 match self.tcx.hir().get_if_local(associated_item.def_id) {
1729 Some(
1730 hir::Node::TraitItem(hir::TraitItem {
1731 kind: hir::TraitItemKind::Type(_, Some(ty)),
1732 ..
1733 })
1734 | hir::Node::ImplItem(hir::ImplItem {
1735 kind: hir::ImplItemKind::Type(ty),
1736 ..
1737 }),
1738 ) => Some((
1739 ty.span,
1740 with_forced_trimmed_paths!(Cow::from(format!(
1741 "type mismatch resolving `{}`",
1742 self.resolve_vars_if_possible(predicate)
1743 .print(FmtPrinter::new_with_limit(
1744 self.tcx,
1745 Namespace::TypeNS,
1746 rustc_session::Limit(5),
1747 ))
1748 .unwrap()
1749 .into_buffer()
1750 ))),
1751 )),
1752 _ => None,
1753 }
1754 })();
1755
1756 self.note_type_err(
1757 &mut diag,
1758 &obligation.cause,
1759 secondary_span,
1760 values.map(|(_, is_normalized_ty_expected, normalized_ty, expected_ty)| {
1761 infer::ValuePairs::Terms(ExpectedFound::new(
1762 is_normalized_ty_expected,
1763 normalized_ty,
1764 expected_ty,
1765 ))
1766 }),
1767 err,
1768 true,
1769 false,
1770 );
1771 self.note_obligation_cause(&mut diag, obligation);
1772 diag.emit();
1773 });
1774 }
1775
maybe_detailed_projection_msg( &self, pred: ty::ProjectionPredicate<'tcx>, normalized_ty: ty::Term<'tcx>, expected_ty: ty::Term<'tcx>, ) -> Option<String>1776 fn maybe_detailed_projection_msg(
1777 &self,
1778 pred: ty::ProjectionPredicate<'tcx>,
1779 normalized_ty: ty::Term<'tcx>,
1780 expected_ty: ty::Term<'tcx>,
1781 ) -> Option<String> {
1782 let trait_def_id = pred.projection_ty.trait_def_id(self.tcx);
1783 let self_ty = pred.projection_ty.self_ty();
1784
1785 with_forced_trimmed_paths! {
1786 if Some(pred.projection_ty.def_id) == self.tcx.lang_items().fn_once_output() {
1787 let fn_kind = self_ty.prefix_string(self.tcx);
1788 let item = match self_ty.kind() {
1789 ty::FnDef(def, _) => self.tcx.item_name(*def).to_string(),
1790 _ => self_ty.to_string(),
1791 };
1792 Some(format!(
1793 "expected `{item}` to be a {fn_kind} that returns `{expected_ty}`, but it \
1794 returns `{normalized_ty}`",
1795 ))
1796 } else if Some(trait_def_id) == self.tcx.lang_items().future_trait() {
1797 Some(format!(
1798 "expected `{self_ty}` to be a future that resolves to `{expected_ty}`, but it \
1799 resolves to `{normalized_ty}`"
1800 ))
1801 } else if Some(trait_def_id) == self.tcx.get_diagnostic_item(sym::Iterator) {
1802 Some(format!(
1803 "expected `{self_ty}` to be an iterator that yields `{expected_ty}`, but it \
1804 yields `{normalized_ty}`"
1805 ))
1806 } else {
1807 None
1808 }
1809 }
1810 }
1811
fuzzy_match_tys( &self, mut a: Ty<'tcx>, mut b: Ty<'tcx>, ignoring_lifetimes: bool, ) -> Option<CandidateSimilarity>1812 fn fuzzy_match_tys(
1813 &self,
1814 mut a: Ty<'tcx>,
1815 mut b: Ty<'tcx>,
1816 ignoring_lifetimes: bool,
1817 ) -> Option<CandidateSimilarity> {
1818 /// returns the fuzzy category of a given type, or None
1819 /// if the type can be equated to any type.
1820 fn type_category(tcx: TyCtxt<'_>, t: Ty<'_>) -> Option<u32> {
1821 match t.kind() {
1822 ty::Bool => Some(0),
1823 ty::Char => Some(1),
1824 ty::Str => Some(2),
1825 ty::Adt(def, _) if Some(def.did()) == tcx.lang_items().string() => Some(2),
1826 ty::Int(..)
1827 | ty::Uint(..)
1828 | ty::Float(..)
1829 | ty::Infer(ty::IntVar(..) | ty::FloatVar(..)) => Some(4),
1830 ty::Ref(..) | ty::RawPtr(..) => Some(5),
1831 ty::Array(..) | ty::Slice(..) => Some(6),
1832 ty::FnDef(..) | ty::FnPtr(..) => Some(7),
1833 ty::Dynamic(..) => Some(8),
1834 ty::Closure(..) => Some(9),
1835 ty::Tuple(..) => Some(10),
1836 ty::Param(..) => Some(11),
1837 ty::Alias(ty::Projection, ..) => Some(12),
1838 ty::Alias(ty::Inherent, ..) => Some(13),
1839 ty::Alias(ty::Opaque, ..) => Some(14),
1840 ty::Alias(ty::Weak, ..) => Some(15),
1841 ty::Never => Some(16),
1842 ty::Adt(..) => Some(17),
1843 ty::Generator(..) => Some(18),
1844 ty::Foreign(..) => Some(19),
1845 ty::GeneratorWitness(..) => Some(20),
1846 ty::GeneratorWitnessMIR(..) => Some(21),
1847 ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) | ty::Error(_) => None,
1848 }
1849 }
1850
1851 let strip_references = |mut t: Ty<'tcx>| -> Ty<'tcx> {
1852 loop {
1853 match t.kind() {
1854 ty::Ref(_, inner, _) | ty::RawPtr(ty::TypeAndMut { ty: inner, .. }) => {
1855 t = *inner
1856 }
1857 _ => break t,
1858 }
1859 }
1860 };
1861
1862 if !ignoring_lifetimes {
1863 a = strip_references(a);
1864 b = strip_references(b);
1865 }
1866
1867 let cat_a = type_category(self.tcx, a)?;
1868 let cat_b = type_category(self.tcx, b)?;
1869 if a == b {
1870 Some(CandidateSimilarity::Exact { ignoring_lifetimes })
1871 } else if cat_a == cat_b {
1872 match (a.kind(), b.kind()) {
1873 (ty::Adt(def_a, _), ty::Adt(def_b, _)) => def_a == def_b,
1874 (ty::Foreign(def_a), ty::Foreign(def_b)) => def_a == def_b,
1875 // Matching on references results in a lot of unhelpful
1876 // suggestions, so let's just not do that for now.
1877 //
1878 // We still upgrade successful matches to `ignoring_lifetimes: true`
1879 // to prioritize that impl.
1880 (ty::Ref(..) | ty::RawPtr(..), ty::Ref(..) | ty::RawPtr(..)) => {
1881 self.fuzzy_match_tys(a, b, true).is_some()
1882 }
1883 _ => true,
1884 }
1885 .then_some(CandidateSimilarity::Fuzzy { ignoring_lifetimes })
1886 } else if ignoring_lifetimes {
1887 None
1888 } else {
1889 self.fuzzy_match_tys(a, b, true)
1890 }
1891 }
1892
describe_generator(&self, body_id: hir::BodyId) -> Option<&'static str>1893 fn describe_generator(&self, body_id: hir::BodyId) -> Option<&'static str> {
1894 self.tcx.hir().body(body_id).generator_kind.map(|gen_kind| match gen_kind {
1895 hir::GeneratorKind::Gen => "a generator",
1896 hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Block) => "an async block",
1897 hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Fn) => "an async function",
1898 hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Closure) => "an async closure",
1899 })
1900 }
1901
find_similar_impl_candidates( &self, trait_pred: ty::PolyTraitPredicate<'tcx>, ) -> Vec<ImplCandidate<'tcx>>1902 fn find_similar_impl_candidates(
1903 &self,
1904 trait_pred: ty::PolyTraitPredicate<'tcx>,
1905 ) -> Vec<ImplCandidate<'tcx>> {
1906 let mut candidates: Vec<_> = self
1907 .tcx
1908 .all_impls(trait_pred.def_id())
1909 .filter_map(|def_id| {
1910 if self.tcx.impl_polarity(def_id) == ty::ImplPolarity::Negative
1911 || !trait_pred
1912 .skip_binder()
1913 .is_constness_satisfied_by(self.tcx.constness(def_id))
1914 || !self.tcx.is_user_visible_dep(def_id.krate)
1915 {
1916 return None;
1917 }
1918
1919 let imp = self.tcx.impl_trait_ref(def_id).unwrap().skip_binder();
1920
1921 self.fuzzy_match_tys(trait_pred.skip_binder().self_ty(), imp.self_ty(), false)
1922 .map(|similarity| ImplCandidate { trait_ref: imp, similarity })
1923 })
1924 .collect();
1925 if candidates.iter().any(|c| matches!(c.similarity, CandidateSimilarity::Exact { .. })) {
1926 // If any of the candidates is a perfect match, we don't want to show all of them.
1927 // This is particularly relevant for the case of numeric types (as they all have the
1928 // same category).
1929 candidates.retain(|c| matches!(c.similarity, CandidateSimilarity::Exact { .. }));
1930 }
1931 candidates
1932 }
1933
report_similar_impl_candidates( &self, impl_candidates: &[ImplCandidate<'tcx>], trait_ref: ty::PolyTraitRef<'tcx>, body_def_id: LocalDefId, err: &mut Diagnostic, other: bool, ) -> bool1934 fn report_similar_impl_candidates(
1935 &self,
1936 impl_candidates: &[ImplCandidate<'tcx>],
1937 trait_ref: ty::PolyTraitRef<'tcx>,
1938 body_def_id: LocalDefId,
1939 err: &mut Diagnostic,
1940 other: bool,
1941 ) -> bool {
1942 let other = if other { "other " } else { "" };
1943 let report = |candidates: Vec<TraitRef<'tcx>>, err: &mut Diagnostic| {
1944 if candidates.is_empty() {
1945 return false;
1946 }
1947 if let &[cand] = &candidates[..] {
1948 let (desc, mention_castable) =
1949 match (cand.self_ty().kind(), trait_ref.self_ty().skip_binder().kind()) {
1950 (ty::FnPtr(_), ty::FnDef(..)) => {
1951 (" implemented for fn pointer `", ", cast using `as`")
1952 }
1953 (ty::FnPtr(_), _) => (" implemented for fn pointer `", ""),
1954 _ => (" implemented for `", ""),
1955 };
1956 err.highlighted_help(vec![
1957 (format!("the trait `{}` ", cand.print_only_trait_path()), Style::NoStyle),
1958 ("is".to_string(), Style::Highlight),
1959 (desc.to_string(), Style::NoStyle),
1960 (cand.self_ty().to_string(), Style::Highlight),
1961 ("`".to_string(), Style::NoStyle),
1962 (mention_castable.to_string(), Style::NoStyle),
1963 ]);
1964 return true;
1965 }
1966 let trait_ref = TraitRef::identity(self.tcx, candidates[0].def_id);
1967 // Check if the trait is the same in all cases. If so, we'll only show the type.
1968 let mut traits: Vec<_> =
1969 candidates.iter().map(|c| c.print_only_trait_path().to_string()).collect();
1970 traits.sort();
1971 traits.dedup();
1972 // FIXME: this could use a better heuristic, like just checking
1973 // that substs[1..] is the same.
1974 let all_traits_equal = traits.len() == 1;
1975
1976 let candidates: Vec<String> = candidates
1977 .into_iter()
1978 .map(|c| {
1979 if all_traits_equal {
1980 format!("\n {}", c.self_ty())
1981 } else {
1982 format!("\n {}", c)
1983 }
1984 })
1985 .collect();
1986
1987 let end = if candidates.len() <= 9 { candidates.len() } else { 8 };
1988 err.help(format!(
1989 "the following {other}types implement trait `{}`:{}{}",
1990 trait_ref.print_only_trait_path(),
1991 candidates[..end].join(""),
1992 if candidates.len() > 9 {
1993 format!("\nand {} others", candidates.len() - 8)
1994 } else {
1995 String::new()
1996 }
1997 ));
1998 true
1999 };
2000
2001 let def_id = trait_ref.def_id();
2002 if impl_candidates.is_empty() {
2003 if self.tcx.trait_is_auto(def_id)
2004 || self.tcx.lang_items().iter().any(|(_, id)| id == def_id)
2005 || self.tcx.get_diagnostic_name(def_id).is_some()
2006 {
2007 // Mentioning implementers of `Copy`, `Debug` and friends is not useful.
2008 return false;
2009 }
2010 let mut impl_candidates: Vec<_> = self
2011 .tcx
2012 .all_impls(def_id)
2013 // Ignore automatically derived impls and `!Trait` impls.
2014 .filter(|&def_id| {
2015 self.tcx.impl_polarity(def_id) != ty::ImplPolarity::Negative
2016 || self.tcx.is_automatically_derived(def_id)
2017 })
2018 .filter_map(|def_id| self.tcx.impl_trait_ref(def_id))
2019 .map(ty::EarlyBinder::subst_identity)
2020 .filter(|trait_ref| {
2021 let self_ty = trait_ref.self_ty();
2022 // Avoid mentioning type parameters.
2023 if let ty::Param(_) = self_ty.kind() {
2024 false
2025 }
2026 // Avoid mentioning types that are private to another crate
2027 else if let ty::Adt(def, _) = self_ty.peel_refs().kind() {
2028 // FIXME(compiler-errors): This could be generalized, both to
2029 // be more granular, and probably look past other `#[fundamental]`
2030 // types, too.
2031 self.tcx.visibility(def.did()).is_accessible_from(body_def_id, self.tcx)
2032 } else {
2033 true
2034 }
2035 })
2036 .collect();
2037
2038 impl_candidates.sort();
2039 impl_candidates.dedup();
2040 return report(impl_candidates, err);
2041 }
2042
2043 // Sort impl candidates so that ordering is consistent for UI tests.
2044 // because the ordering of `impl_candidates` may not be deterministic:
2045 // https://github.com/rust-lang/rust/pull/57475#issuecomment-455519507
2046 //
2047 // Prefer more similar candidates first, then sort lexicographically
2048 // by their normalized string representation.
2049 let mut impl_candidates: Vec<_> = impl_candidates
2050 .iter()
2051 .cloned()
2052 .map(|mut cand| {
2053 // Fold the consts so that they shows up as, e.g., `10`
2054 // instead of `core::::array::{impl#30}::{constant#0}`.
2055 cand.trait_ref = cand.trait_ref.fold_with(&mut BottomUpFolder {
2056 tcx: self.tcx,
2057 ty_op: |ty| ty,
2058 lt_op: |lt| lt,
2059 ct_op: |ct| ct.eval(self.tcx, ty::ParamEnv::empty()),
2060 });
2061 cand
2062 })
2063 .collect();
2064 impl_candidates.sort_by_key(|cand| (cand.similarity, cand.trait_ref));
2065 impl_candidates.dedup();
2066
2067 report(impl_candidates.into_iter().map(|cand| cand.trait_ref).collect(), err)
2068 }
2069
report_similar_impl_candidates_for_root_obligation( &self, obligation: &PredicateObligation<'tcx>, trait_predicate: ty::Binder<'tcx, ty::TraitPredicate<'tcx>>, body_def_id: LocalDefId, err: &mut Diagnostic, )2070 fn report_similar_impl_candidates_for_root_obligation(
2071 &self,
2072 obligation: &PredicateObligation<'tcx>,
2073 trait_predicate: ty::Binder<'tcx, ty::TraitPredicate<'tcx>>,
2074 body_def_id: LocalDefId,
2075 err: &mut Diagnostic,
2076 ) {
2077 // This is *almost* equivalent to
2078 // `obligation.cause.code().peel_derives()`, but it gives us the
2079 // trait predicate for that corresponding root obligation. This
2080 // lets us get a derived obligation from a type parameter, like
2081 // when calling `string.strip_suffix(p)` where `p` is *not* an
2082 // implementer of `Pattern<'_>`.
2083 let mut code = obligation.cause.code();
2084 let mut trait_pred = trait_predicate;
2085 let mut peeled = false;
2086 while let Some((parent_code, parent_trait_pred)) = code.parent() {
2087 code = parent_code;
2088 if let Some(parent_trait_pred) = parent_trait_pred {
2089 trait_pred = parent_trait_pred;
2090 peeled = true;
2091 }
2092 }
2093 let def_id = trait_pred.def_id();
2094 // Mention *all* the `impl`s for the *top most* obligation, the
2095 // user might have meant to use one of them, if any found. We skip
2096 // auto-traits or fundamental traits that might not be exactly what
2097 // the user might expect to be presented with. Instead this is
2098 // useful for less general traits.
2099 if peeled
2100 && !self.tcx.trait_is_auto(def_id)
2101 && !self.tcx.lang_items().iter().any(|(_, id)| id == def_id)
2102 {
2103 let trait_ref = trait_pred.to_poly_trait_ref();
2104 let impl_candidates = self.find_similar_impl_candidates(trait_pred);
2105 self.report_similar_impl_candidates(
2106 &impl_candidates,
2107 trait_ref,
2108 body_def_id,
2109 err,
2110 true,
2111 );
2112 }
2113 }
2114
2115 /// Gets the parent trait chain start
get_parent_trait_ref( &self, code: &ObligationCauseCode<'tcx>, ) -> Option<(String, Option<Span>)>2116 fn get_parent_trait_ref(
2117 &self,
2118 code: &ObligationCauseCode<'tcx>,
2119 ) -> Option<(String, Option<Span>)> {
2120 match code {
2121 ObligationCauseCode::BuiltinDerivedObligation(data) => {
2122 let parent_trait_ref = self.resolve_vars_if_possible(data.parent_trait_pred);
2123 match self.get_parent_trait_ref(&data.parent_code) {
2124 Some(t) => Some(t),
2125 None => {
2126 let ty = parent_trait_ref.skip_binder().self_ty();
2127 let span = TyCategory::from_ty(self.tcx, ty)
2128 .map(|(_, def_id)| self.tcx.def_span(def_id));
2129 Some((ty.to_string(), span))
2130 }
2131 }
2132 }
2133 ObligationCauseCode::FunctionArgumentObligation { parent_code, .. } => {
2134 self.get_parent_trait_ref(&parent_code)
2135 }
2136 _ => None,
2137 }
2138 }
2139
2140 /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
2141 /// with the same path as `trait_ref`, a help message about
2142 /// a probable version mismatch is added to `err`
note_version_mismatch( &self, err: &mut Diagnostic, trait_ref: &ty::PolyTraitRef<'tcx>, ) -> bool2143 fn note_version_mismatch(
2144 &self,
2145 err: &mut Diagnostic,
2146 trait_ref: &ty::PolyTraitRef<'tcx>,
2147 ) -> bool {
2148 let get_trait_impls = |trait_def_id| {
2149 let mut trait_impls = vec![];
2150 self.tcx.for_each_relevant_impl(
2151 trait_def_id,
2152 trait_ref.skip_binder().self_ty(),
2153 |impl_def_id| {
2154 trait_impls.push(impl_def_id);
2155 },
2156 );
2157 trait_impls
2158 };
2159
2160 let required_trait_path = self.tcx.def_path_str(trait_ref.def_id());
2161 let traits_with_same_path: std::collections::BTreeSet<_> = self
2162 .tcx
2163 .all_traits()
2164 .filter(|trait_def_id| *trait_def_id != trait_ref.def_id())
2165 .filter(|trait_def_id| self.tcx.def_path_str(*trait_def_id) == required_trait_path)
2166 .collect();
2167 let mut suggested = false;
2168 for trait_with_same_path in traits_with_same_path {
2169 let trait_impls = get_trait_impls(trait_with_same_path);
2170 if trait_impls.is_empty() {
2171 continue;
2172 }
2173 let impl_spans: Vec<_> =
2174 trait_impls.iter().map(|impl_def_id| self.tcx.def_span(*impl_def_id)).collect();
2175 err.span_help(
2176 impl_spans,
2177 format!("trait impl{} with same name found", pluralize!(trait_impls.len())),
2178 );
2179 let trait_crate = self.tcx.crate_name(trait_with_same_path.krate);
2180 let crate_msg = format!(
2181 "perhaps two different versions of crate `{}` are being used?",
2182 trait_crate
2183 );
2184 err.note(crate_msg);
2185 suggested = true;
2186 }
2187 suggested
2188 }
2189
mk_trait_obligation_with_new_self_ty( &self, param_env: ty::ParamEnv<'tcx>, trait_ref_and_ty: ty::Binder<'tcx, (ty::TraitPredicate<'tcx>, Ty<'tcx>)>, ) -> PredicateObligation<'tcx>2190 fn mk_trait_obligation_with_new_self_ty(
2191 &self,
2192 param_env: ty::ParamEnv<'tcx>,
2193 trait_ref_and_ty: ty::Binder<'tcx, (ty::TraitPredicate<'tcx>, Ty<'tcx>)>,
2194 ) -> PredicateObligation<'tcx> {
2195 let trait_pred =
2196 trait_ref_and_ty.map_bound(|(tr, new_self_ty)| tr.with_self_ty(self.tcx, new_self_ty));
2197
2198 Obligation::new(self.tcx, ObligationCause::dummy(), param_env, trait_pred)
2199 }
2200
2201 #[instrument(skip(self), level = "debug")]
maybe_report_ambiguity(&self, obligation: &PredicateObligation<'tcx>)2202 fn maybe_report_ambiguity(&self, obligation: &PredicateObligation<'tcx>) {
2203 // Unable to successfully determine, probably means
2204 // insufficient type information, but could mean
2205 // ambiguous impls. The latter *ought* to be a
2206 // coherence violation, so we don't report it here.
2207
2208 let predicate = self.resolve_vars_if_possible(obligation.predicate);
2209 let span = obligation.cause.span;
2210
2211 debug!(?predicate, obligation.cause.code = ?obligation.cause.code());
2212
2213 // Ambiguity errors are often caused as fallout from earlier errors.
2214 // We ignore them if this `infcx` is tainted in some cases below.
2215
2216 let bound_predicate = predicate.kind();
2217 let mut err = match bound_predicate.skip_binder() {
2218 ty::PredicateKind::Clause(ty::ClauseKind::Trait(data)) => {
2219 let trait_ref = bound_predicate.rebind(data.trait_ref);
2220 debug!(?trait_ref);
2221
2222 if predicate.references_error() {
2223 return;
2224 }
2225
2226 // This is kind of a hack: it frequently happens that some earlier
2227 // error prevents types from being fully inferred, and then we get
2228 // a bunch of uninteresting errors saying something like "<generic
2229 // #0> doesn't implement Sized". It may even be true that we
2230 // could just skip over all checks where the self-ty is an
2231 // inference variable, but I was afraid that there might be an
2232 // inference variable created, registered as an obligation, and
2233 // then never forced by writeback, and hence by skipping here we'd
2234 // be ignoring the fact that we don't KNOW the type works
2235 // out. Though even that would probably be harmless, given that
2236 // we're only talking about builtin traits, which are known to be
2237 // inhabited. We used to check for `self.tcx.sess.has_errors()` to
2238 // avoid inundating the user with unnecessary errors, but we now
2239 // check upstream for type errors and don't add the obligations to
2240 // begin with in those cases.
2241 if self.tcx.lang_items().sized_trait() == Some(trait_ref.def_id()) {
2242 if let None = self.tainted_by_errors() {
2243 self.emit_inference_failure_err(
2244 obligation.cause.body_id,
2245 span,
2246 trait_ref.self_ty().skip_binder().into(),
2247 ErrorCode::E0282,
2248 false,
2249 )
2250 .emit();
2251 }
2252 return;
2253 }
2254
2255 // Typically, this ambiguity should only happen if
2256 // there are unresolved type inference variables
2257 // (otherwise it would suggest a coherence
2258 // failure). But given #21974 that is not necessarily
2259 // the case -- we can have multiple where clauses that
2260 // are only distinguished by a region, which results
2261 // in an ambiguity even when all types are fully
2262 // known, since we don't dispatch based on region
2263 // relationships.
2264
2265 // Pick the first substitution that still contains inference variables as the one
2266 // we're going to emit an error for. If there are none (see above), fall back to
2267 // a more general error.
2268 let subst = data.trait_ref.substs.iter().find(|s| s.has_non_region_infer());
2269
2270 let mut err = if let Some(subst) = subst {
2271 self.emit_inference_failure_err(
2272 obligation.cause.body_id,
2273 span,
2274 subst,
2275 ErrorCode::E0283,
2276 true,
2277 )
2278 } else {
2279 struct_span_err!(
2280 self.tcx.sess,
2281 span,
2282 E0283,
2283 "type annotations needed: cannot satisfy `{}`",
2284 predicate,
2285 )
2286 };
2287
2288 let ambiguities = ambiguity::recompute_applicable_impls(
2289 self.infcx,
2290 &obligation.with(self.tcx, trait_ref),
2291 );
2292 let has_non_region_infer =
2293 trait_ref.skip_binder().substs.types().any(|t| !t.is_ty_or_numeric_infer());
2294 // It doesn't make sense to talk about applicable impls if there are more
2295 // than a handful of them.
2296 if ambiguities.len() > 1 && ambiguities.len() < 10 && has_non_region_infer {
2297 if self.tainted_by_errors().is_some() && subst.is_none() {
2298 // If `subst.is_none()`, then this is probably two param-env
2299 // candidates or impl candidates that are equal modulo lifetimes.
2300 // Therefore, if we've already emitted an error, just skip this
2301 // one, since it's not particularly actionable.
2302 err.cancel();
2303 return;
2304 }
2305 self.annotate_source_of_ambiguity(&mut err, &ambiguities, predicate);
2306 } else {
2307 if self.tainted_by_errors().is_some() {
2308 err.cancel();
2309 return;
2310 }
2311 err.note(format!("cannot satisfy `{}`", predicate));
2312 let impl_candidates = self
2313 .find_similar_impl_candidates(predicate.to_opt_poly_trait_pred().unwrap());
2314 if impl_candidates.len() < 10 {
2315 self.report_similar_impl_candidates(
2316 impl_candidates.as_slice(),
2317 trait_ref,
2318 obligation.cause.body_id,
2319 &mut err,
2320 false,
2321 );
2322 }
2323 }
2324
2325 if let ObligationCauseCode::ItemObligation(def_id)
2326 | ObligationCauseCode::ExprItemObligation(def_id, ..) = *obligation.cause.code()
2327 {
2328 self.suggest_fully_qualified_path(&mut err, def_id, span, trait_ref.def_id());
2329 }
2330
2331 if let Some(ty::subst::GenericArgKind::Type(_)) = subst.map(|subst| subst.unpack())
2332 && let Some(body_id) = self.tcx.hir().maybe_body_owned_by(obligation.cause.body_id)
2333 {
2334 let mut expr_finder = FindExprBySpan::new(span);
2335 expr_finder.visit_expr(&self.tcx.hir().body(body_id).value);
2336
2337 if let Some(hir::Expr {
2338 kind: hir::ExprKind::Path(hir::QPath::Resolved(None, path)), .. }
2339 ) = expr_finder.result
2340 && let [
2341 ..,
2342 trait_path_segment @ hir::PathSegment {
2343 res: rustc_hir::def::Res::Def(rustc_hir::def::DefKind::Trait, trait_id),
2344 ..
2345 },
2346 hir::PathSegment {
2347 ident: assoc_item_name,
2348 res: rustc_hir::def::Res::Def(_, item_id),
2349 ..
2350 }
2351 ] = path.segments
2352 && data.trait_ref.def_id == *trait_id
2353 && self.tcx.trait_of_item(*item_id) == Some(*trait_id)
2354 && let None = self.tainted_by_errors()
2355 {
2356 let (verb, noun) = match self.tcx.associated_item(item_id).kind {
2357 ty::AssocKind::Const => ("refer to the", "constant"),
2358 ty::AssocKind::Fn => ("call", "function"),
2359 ty::AssocKind::Type => ("refer to the", "type"), // this is already covered by E0223, but this single match arm doesn't hurt here
2360 };
2361
2362 // Replace the more general E0283 with a more specific error
2363 err.cancel();
2364 err = self.tcx.sess.struct_span_err_with_code(
2365 span,
2366 format!(
2367 "cannot {verb} associated {noun} on trait without specifying the corresponding `impl` type",
2368 ),
2369 rustc_errors::error_code!(E0790),
2370 );
2371
2372 if let Some(local_def_id) = data.trait_ref.def_id.as_local()
2373 && let Some(hir::Node::Item(hir::Item { ident: trait_name, kind: hir::ItemKind::Trait(_, _, _, _, trait_item_refs), .. })) = self.tcx.hir().find_by_def_id(local_def_id)
2374 && let Some(method_ref) = trait_item_refs.iter().find(|item_ref| item_ref.ident == *assoc_item_name) {
2375 err.span_label(method_ref.span, format!("`{}::{}` defined here", trait_name, assoc_item_name));
2376 }
2377
2378 err.span_label(span, format!("cannot {verb} associated {noun} of trait"));
2379
2380 let trait_impls = self.tcx.trait_impls_of(data.trait_ref.def_id);
2381
2382 if trait_impls.blanket_impls().is_empty()
2383 && let Some(impl_def_id) = trait_impls.non_blanket_impls().values().flatten().next()
2384 {
2385 let non_blanket_impl_count = trait_impls.non_blanket_impls().values().flatten().count();
2386 // If there is only one implementation of the trait, suggest using it.
2387 // Otherwise, use a placeholder comment for the implementation.
2388 let (message, impl_suggestion) = if non_blanket_impl_count == 1 {(
2389 "use the fully-qualified path to the only available implementation".to_string(),
2390 format!("<{} as ", self.tcx.type_of(impl_def_id).subst_identity())
2391 )} else {(
2392 format!(
2393 "use a fully-qualified path to a specific available implementation ({} found)",
2394 non_blanket_impl_count
2395 ),
2396 "</* self type */ as ".to_string()
2397 )};
2398 let mut suggestions = vec![(
2399 path.span.shrink_to_lo(),
2400 impl_suggestion
2401 )];
2402 if let Some(generic_arg) = trait_path_segment.args {
2403 let between_span = trait_path_segment.ident.span.between(generic_arg.span_ext);
2404 // get rid of :: between Trait and <type>
2405 // must be '::' between them, otherwise the parser won't accept the code
2406 suggestions.push((between_span, "".to_string(),));
2407 suggestions.push((generic_arg.span_ext.shrink_to_hi(), ">".to_string()));
2408 } else {
2409 suggestions.push((trait_path_segment.ident.span.shrink_to_hi(), ">".to_string()));
2410 }
2411 err.multipart_suggestion(
2412 message,
2413 suggestions,
2414 Applicability::MaybeIncorrect
2415 );
2416 }
2417 }
2418 };
2419
2420 err
2421 }
2422
2423 ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg)) => {
2424 // Same hacky approach as above to avoid deluging user
2425 // with error messages.
2426 if arg.references_error()
2427 || self.tcx.sess.has_errors().is_some()
2428 || self.tainted_by_errors().is_some()
2429 {
2430 return;
2431 }
2432
2433 self.emit_inference_failure_err(
2434 obligation.cause.body_id,
2435 span,
2436 arg,
2437 ErrorCode::E0282,
2438 false,
2439 )
2440 }
2441
2442 ty::PredicateKind::Subtype(data) => {
2443 if data.references_error()
2444 || self.tcx.sess.has_errors().is_some()
2445 || self.tainted_by_errors().is_some()
2446 {
2447 // no need to overload user in such cases
2448 return;
2449 }
2450 let SubtypePredicate { a_is_expected: _, a, b } = data;
2451 // both must be type variables, or the other would've been instantiated
2452 assert!(a.is_ty_var() && b.is_ty_var());
2453 self.emit_inference_failure_err(
2454 obligation.cause.body_id,
2455 span,
2456 a.into(),
2457 ErrorCode::E0282,
2458 true,
2459 )
2460 }
2461 ty::PredicateKind::Clause(ty::ClauseKind::Projection(data)) => {
2462 if predicate.references_error() || self.tainted_by_errors().is_some() {
2463 return;
2464 }
2465 let subst = data
2466 .projection_ty
2467 .substs
2468 .iter()
2469 .chain(Some(data.term.into_arg()))
2470 .find(|g| g.has_non_region_infer());
2471 if let Some(subst) = subst {
2472 let mut err = self.emit_inference_failure_err(
2473 obligation.cause.body_id,
2474 span,
2475 subst,
2476 ErrorCode::E0284,
2477 true,
2478 );
2479 err.note(format!("cannot satisfy `{}`", predicate));
2480 err
2481 } else {
2482 // If we can't find a substitution, just print a generic error
2483 let mut err = struct_span_err!(
2484 self.tcx.sess,
2485 span,
2486 E0284,
2487 "type annotations needed: cannot satisfy `{}`",
2488 predicate,
2489 );
2490 err.span_label(span, format!("cannot satisfy `{}`", predicate));
2491 err
2492 }
2493 }
2494
2495 ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(data)) => {
2496 if predicate.references_error() || self.tainted_by_errors().is_some() {
2497 return;
2498 }
2499 let subst = data.walk().find(|g| g.is_non_region_infer());
2500 if let Some(subst) = subst {
2501 let err = self.emit_inference_failure_err(
2502 obligation.cause.body_id,
2503 span,
2504 subst,
2505 ErrorCode::E0284,
2506 true,
2507 );
2508 err
2509 } else {
2510 // If we can't find a substitution, just print a generic error
2511 let mut err = struct_span_err!(
2512 self.tcx.sess,
2513 span,
2514 E0284,
2515 "type annotations needed: cannot satisfy `{}`",
2516 predicate,
2517 );
2518 err.span_label(span, format!("cannot satisfy `{}`", predicate));
2519 err
2520 }
2521 }
2522 _ => {
2523 if self.tcx.sess.has_errors().is_some() || self.tainted_by_errors().is_some() {
2524 return;
2525 }
2526 let mut err = struct_span_err!(
2527 self.tcx.sess,
2528 span,
2529 E0284,
2530 "type annotations needed: cannot satisfy `{}`",
2531 predicate,
2532 );
2533 err.span_label(span, format!("cannot satisfy `{}`", predicate));
2534 err
2535 }
2536 };
2537 self.note_obligation_cause(&mut err, obligation);
2538 err.emit();
2539 }
2540
annotate_source_of_ambiguity( &self, err: &mut Diagnostic, ambiguities: &[ambiguity::Ambiguity], predicate: ty::Predicate<'tcx>, )2541 fn annotate_source_of_ambiguity(
2542 &self,
2543 err: &mut Diagnostic,
2544 ambiguities: &[ambiguity::Ambiguity],
2545 predicate: ty::Predicate<'tcx>,
2546 ) {
2547 let mut spans = vec![];
2548 let mut crates = vec![];
2549 let mut post = vec![];
2550 let mut has_param_env = false;
2551 for ambiguity in ambiguities {
2552 match ambiguity {
2553 ambiguity::Ambiguity::DefId(impl_def_id) => {
2554 match self.tcx.span_of_impl(*impl_def_id) {
2555 Ok(span) => spans.push(span),
2556 Err(name) => {
2557 crates.push(name);
2558 if let Some(header) = to_pretty_impl_header(self.tcx, *impl_def_id) {
2559 post.push(header);
2560 }
2561 }
2562 }
2563 }
2564 ambiguity::Ambiguity::ParamEnv(span) => {
2565 has_param_env = true;
2566 spans.push(*span);
2567 }
2568 }
2569 }
2570 let mut crate_names: Vec<_> = crates.iter().map(|n| format!("`{}`", n)).collect();
2571 crate_names.sort();
2572 crate_names.dedup();
2573 post.sort();
2574 post.dedup();
2575
2576 if self.tainted_by_errors().is_some()
2577 && (crate_names.len() == 1
2578 && spans.len() == 0
2579 && ["`core`", "`alloc`", "`std`"].contains(&crate_names[0].as_str())
2580 || predicate.visit_with(&mut HasNumericInferVisitor).is_break())
2581 {
2582 // Avoid complaining about other inference issues for expressions like
2583 // `42 >> 1`, where the types are still `{integer}`, but we want to
2584 // Do we need `trait_ref.skip_binder().self_ty().is_numeric() &&` too?
2585 // NOTE(eddyb) this was `.cancel()`, but `err`
2586 // is borrowed, so we can't fully defuse it.
2587 err.downgrade_to_delayed_bug();
2588 return;
2589 }
2590
2591 let msg = format!(
2592 "multiple `impl`s{} satisfying `{}` found",
2593 if has_param_env { " or `where` clauses" } else { "" },
2594 predicate
2595 );
2596 let post = if post.len() > 1 || (post.len() == 1 && post[0].contains('\n')) {
2597 format!(":\n{}", post.iter().map(|p| format!("- {}", p)).collect::<Vec<_>>().join("\n"),)
2598 } else if post.len() == 1 {
2599 format!(": `{}`", post[0])
2600 } else {
2601 String::new()
2602 };
2603
2604 match (spans.len(), crates.len(), crate_names.len()) {
2605 (0, 0, 0) => {
2606 err.note(format!("cannot satisfy `{}`", predicate));
2607 }
2608 (0, _, 1) => {
2609 err.note(format!("{} in the `{}` crate{}", msg, crates[0], post,));
2610 }
2611 (0, _, _) => {
2612 err.note(format!(
2613 "{} in the following crates: {}{}",
2614 msg,
2615 crate_names.join(", "),
2616 post,
2617 ));
2618 }
2619 (_, 0, 0) => {
2620 let span: MultiSpan = spans.into();
2621 err.span_note(span, msg);
2622 }
2623 (_, 1, 1) => {
2624 let span: MultiSpan = spans.into();
2625 err.span_note(span, msg);
2626 err.note(format!("and another `impl` found in the `{}` crate{}", crates[0], post,));
2627 }
2628 _ => {
2629 let span: MultiSpan = spans.into();
2630 err.span_note(span, msg);
2631 err.note(format!(
2632 "and more `impl`s found in the following crates: {}{}",
2633 crate_names.join(", "),
2634 post,
2635 ));
2636 }
2637 }
2638 }
2639
2640 /// Returns `true` if the trait predicate may apply for *some* assignment
2641 /// to the type parameters.
predicate_can_apply( &self, param_env: ty::ParamEnv<'tcx>, pred: ty::PolyTraitPredicate<'tcx>, ) -> bool2642 fn predicate_can_apply(
2643 &self,
2644 param_env: ty::ParamEnv<'tcx>,
2645 pred: ty::PolyTraitPredicate<'tcx>,
2646 ) -> bool {
2647 struct ParamToVarFolder<'a, 'tcx> {
2648 infcx: &'a InferCtxt<'tcx>,
2649 var_map: FxHashMap<Ty<'tcx>, Ty<'tcx>>,
2650 }
2651
2652 impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for ParamToVarFolder<'a, 'tcx> {
2653 fn interner(&self) -> TyCtxt<'tcx> {
2654 self.infcx.tcx
2655 }
2656
2657 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
2658 if let ty::Param(_) = *ty.kind() {
2659 let infcx = self.infcx;
2660 *self.var_map.entry(ty).or_insert_with(|| {
2661 infcx.next_ty_var(TypeVariableOrigin {
2662 kind: TypeVariableOriginKind::MiscVariable,
2663 span: DUMMY_SP,
2664 })
2665 })
2666 } else {
2667 ty.super_fold_with(self)
2668 }
2669 }
2670 }
2671
2672 self.probe(|_| {
2673 let cleaned_pred =
2674 pred.fold_with(&mut ParamToVarFolder { infcx: self, var_map: Default::default() });
2675
2676 let InferOk { value: cleaned_pred, .. } =
2677 self.infcx.at(&ObligationCause::dummy(), param_env).normalize(cleaned_pred);
2678
2679 let obligation =
2680 Obligation::new(self.tcx, ObligationCause::dummy(), param_env, cleaned_pred);
2681
2682 self.predicate_may_hold(&obligation)
2683 })
2684 }
2685
note_obligation_cause(&self, err: &mut Diagnostic, obligation: &PredicateObligation<'tcx>)2686 fn note_obligation_cause(&self, err: &mut Diagnostic, obligation: &PredicateObligation<'tcx>) {
2687 // First, attempt to add note to this error with an async-await-specific
2688 // message, and fall back to regular note otherwise.
2689 if !self.maybe_note_obligation_cause_for_async_await(err, obligation) {
2690 self.note_obligation_cause_code(
2691 obligation.cause.body_id,
2692 err,
2693 obligation.predicate,
2694 obligation.param_env,
2695 obligation.cause.code(),
2696 &mut vec![],
2697 &mut Default::default(),
2698 );
2699 self.suggest_unsized_bound_if_applicable(err, obligation);
2700 }
2701 }
2702
2703 #[instrument(level = "debug", skip_all)]
suggest_unsized_bound_if_applicable( &self, err: &mut Diagnostic, obligation: &PredicateObligation<'tcx>, )2704 fn suggest_unsized_bound_if_applicable(
2705 &self,
2706 err: &mut Diagnostic,
2707 obligation: &PredicateObligation<'tcx>,
2708 ) {
2709 let ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) = obligation.predicate.kind().skip_binder() else { return; };
2710 let (ObligationCauseCode::BindingObligation(item_def_id, span)
2711 | ObligationCauseCode::ExprBindingObligation(item_def_id, span, ..))
2712 = *obligation.cause.code().peel_derives() else { return; };
2713 debug!(?pred, ?item_def_id, ?span);
2714
2715 let (Some(node), true) = (
2716 self.tcx.hir().get_if_local(item_def_id),
2717 Some(pred.def_id()) == self.tcx.lang_items().sized_trait(),
2718 ) else {
2719 return;
2720 };
2721 self.maybe_suggest_unsized_generics(err, span, node);
2722 }
2723
2724 #[instrument(level = "debug", skip_all)]
maybe_suggest_unsized_generics(&self, err: &mut Diagnostic, span: Span, node: Node<'tcx>)2725 fn maybe_suggest_unsized_generics(&self, err: &mut Diagnostic, span: Span, node: Node<'tcx>) {
2726 let Some(generics) = node.generics() else {
2727 return;
2728 };
2729 let sized_trait = self.tcx.lang_items().sized_trait();
2730 debug!(?generics.params);
2731 debug!(?generics.predicates);
2732 let Some(param) = generics.params.iter().find(|param| param.span == span) else {
2733 return;
2734 };
2735 // Check that none of the explicit trait bounds is `Sized`. Assume that an explicit
2736 // `Sized` bound is there intentionally and we don't need to suggest relaxing it.
2737 let explicitly_sized = generics
2738 .bounds_for_param(param.def_id)
2739 .flat_map(|bp| bp.bounds)
2740 .any(|bound| bound.trait_ref().and_then(|tr| tr.trait_def_id()) == sized_trait);
2741 if explicitly_sized {
2742 return;
2743 }
2744 debug!(?param);
2745 match node {
2746 hir::Node::Item(
2747 item @ hir::Item {
2748 // Only suggest indirection for uses of type parameters in ADTs.
2749 kind:
2750 hir::ItemKind::Enum(..) | hir::ItemKind::Struct(..) | hir::ItemKind::Union(..),
2751 ..
2752 },
2753 ) => {
2754 if self.maybe_indirection_for_unsized(err, item, param) {
2755 return;
2756 }
2757 }
2758 _ => {}
2759 };
2760 // Didn't add an indirection suggestion, so add a general suggestion to relax `Sized`.
2761 let (span, separator) = if let Some(s) = generics.bounds_span_for_suggestions(param.def_id)
2762 {
2763 (s, " +")
2764 } else {
2765 (span.shrink_to_hi(), ":")
2766 };
2767 err.span_suggestion_verbose(
2768 span,
2769 "consider relaxing the implicit `Sized` restriction",
2770 format!("{} ?Sized", separator),
2771 Applicability::MachineApplicable,
2772 );
2773 }
2774
maybe_indirection_for_unsized( &self, err: &mut Diagnostic, item: &Item<'tcx>, param: &GenericParam<'tcx>, ) -> bool2775 fn maybe_indirection_for_unsized(
2776 &self,
2777 err: &mut Diagnostic,
2778 item: &Item<'tcx>,
2779 param: &GenericParam<'tcx>,
2780 ) -> bool {
2781 // Suggesting `T: ?Sized` is only valid in an ADT if `T` is only used in a
2782 // borrow. `struct S<'a, T: ?Sized>(&'a T);` is valid, `struct S<T: ?Sized>(T);`
2783 // is not. Look for invalid "bare" parameter uses, and suggest using indirection.
2784 let mut visitor =
2785 FindTypeParam { param: param.name.ident().name, invalid_spans: vec![], nested: false };
2786 visitor.visit_item(item);
2787 if visitor.invalid_spans.is_empty() {
2788 return false;
2789 }
2790 let mut multispan: MultiSpan = param.span.into();
2791 multispan.push_span_label(
2792 param.span,
2793 format!("this could be changed to `{}: ?Sized`...", param.name.ident()),
2794 );
2795 for sp in visitor.invalid_spans {
2796 multispan.push_span_label(
2797 sp,
2798 format!("...if indirection were used here: `Box<{}>`", param.name.ident()),
2799 );
2800 }
2801 err.span_help(
2802 multispan,
2803 format!(
2804 "you could relax the implicit `Sized` bound on `{T}` if it were \
2805 used through indirection like `&{T}` or `Box<{T}>`",
2806 T = param.name.ident(),
2807 ),
2808 );
2809 true
2810 }
2811
is_recursive_obligation( &self, obligated_types: &mut Vec<Ty<'tcx>>, cause_code: &ObligationCauseCode<'tcx>, ) -> bool2812 fn is_recursive_obligation(
2813 &self,
2814 obligated_types: &mut Vec<Ty<'tcx>>,
2815 cause_code: &ObligationCauseCode<'tcx>,
2816 ) -> bool {
2817 if let ObligationCauseCode::BuiltinDerivedObligation(ref data) = cause_code {
2818 let parent_trait_ref = self.resolve_vars_if_possible(data.parent_trait_pred);
2819 let self_ty = parent_trait_ref.skip_binder().self_ty();
2820 if obligated_types.iter().any(|ot| ot == &self_ty) {
2821 return true;
2822 }
2823 if let ty::Adt(def, substs) = self_ty.kind()
2824 && let [arg] = &substs[..]
2825 && let ty::subst::GenericArgKind::Type(ty) = arg.unpack()
2826 && let ty::Adt(inner_def, _) = ty.kind()
2827 && inner_def == def
2828 {
2829 return true;
2830 }
2831 }
2832 false
2833 }
2834
get_standard_error_message( &self, trait_predicate: &ty::PolyTraitPredicate<'tcx>, message: Option<String>, predicate_is_const: bool, append_const_msg: Option<AppendConstMessage>, post_message: String, ) -> String2835 fn get_standard_error_message(
2836 &self,
2837 trait_predicate: &ty::PolyTraitPredicate<'tcx>,
2838 message: Option<String>,
2839 predicate_is_const: bool,
2840 append_const_msg: Option<AppendConstMessage>,
2841 post_message: String,
2842 ) -> String {
2843 message
2844 .and_then(|cannot_do_this| {
2845 match (predicate_is_const, append_const_msg) {
2846 // do nothing if predicate is not const
2847 (false, _) => Some(cannot_do_this),
2848 // suggested using default post message
2849 (true, Some(AppendConstMessage::Default)) => {
2850 Some(format!("{cannot_do_this} in const contexts"))
2851 }
2852 // overridden post message
2853 (true, Some(AppendConstMessage::Custom(custom_msg))) => {
2854 Some(format!("{cannot_do_this}{custom_msg}"))
2855 }
2856 // fallback to generic message
2857 (true, None) => None,
2858 }
2859 })
2860 .unwrap_or_else(|| {
2861 format!("the trait bound `{}` is not satisfied{}", trait_predicate, post_message)
2862 })
2863 }
2864
get_safe_transmute_error_and_reason( &self, obligation: PredicateObligation<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>, span: Span, ) -> GetSafeTransmuteErrorAndReason2865 fn get_safe_transmute_error_and_reason(
2866 &self,
2867 obligation: PredicateObligation<'tcx>,
2868 trait_ref: ty::PolyTraitRef<'tcx>,
2869 span: Span,
2870 ) -> GetSafeTransmuteErrorAndReason {
2871 use rustc_transmute::Answer;
2872
2873 // Erase regions because layout code doesn't particularly care about regions.
2874 let trait_ref = self.tcx.erase_regions(self.tcx.erase_late_bound_regions(trait_ref));
2875
2876 let src_and_dst = rustc_transmute::Types {
2877 dst: trait_ref.substs.type_at(0),
2878 src: trait_ref.substs.type_at(1),
2879 };
2880 let scope = trait_ref.substs.type_at(2);
2881 let Some(assume) =
2882 rustc_transmute::Assume::from_const(self.infcx.tcx, obligation.param_env, trait_ref.substs.const_at(3)) else {
2883 span_bug!(span, "Unable to construct rustc_transmute::Assume where it was previously possible");
2884 };
2885
2886 match rustc_transmute::TransmuteTypeEnv::new(self.infcx).is_transmutable(
2887 obligation.cause,
2888 src_and_dst,
2889 scope,
2890 assume,
2891 ) {
2892 Answer::No(reason) => {
2893 let dst = trait_ref.substs.type_at(0);
2894 let src = trait_ref.substs.type_at(1);
2895 let err_msg = format!(
2896 "`{src}` cannot be safely transmuted into `{dst}` in the defining scope of `{scope}`"
2897 );
2898 let safe_transmute_explanation = match reason {
2899 rustc_transmute::Reason::SrcIsUnspecified => {
2900 format!("`{src}` does not have a well-specified layout")
2901 }
2902
2903 rustc_transmute::Reason::DstIsUnspecified => {
2904 format!("`{dst}` does not have a well-specified layout")
2905 }
2906
2907 rustc_transmute::Reason::DstIsBitIncompatible => {
2908 format!("At least one value of `{src}` isn't a bit-valid value of `{dst}`")
2909 }
2910
2911 rustc_transmute::Reason::DstIsPrivate => format!(
2912 "`{dst}` is or contains a type or field that is not visible in that scope"
2913 ),
2914 rustc_transmute::Reason::DstIsTooBig => {
2915 format!("The size of `{src}` is smaller than the size of `{dst}`")
2916 }
2917 rustc_transmute::Reason::DstHasStricterAlignment {
2918 src_min_align,
2919 dst_min_align,
2920 } => {
2921 format!(
2922 "The minimum alignment of `{src}` ({src_min_align}) should be greater than that of `{dst}` ({dst_min_align})"
2923 )
2924 }
2925 rustc_transmute::Reason::DstIsMoreUnique => {
2926 format!("`{src}` is a shared reference, but `{dst}` is a unique reference")
2927 }
2928 // Already reported by rustc
2929 rustc_transmute::Reason::TypeError => {
2930 return GetSafeTransmuteErrorAndReason::Silent;
2931 }
2932 rustc_transmute::Reason::SrcLayoutUnknown => {
2933 format!("`{src}` has an unknown layout")
2934 }
2935 rustc_transmute::Reason::DstLayoutUnknown => {
2936 format!("`{dst}` has an unknown layout")
2937 }
2938 };
2939 GetSafeTransmuteErrorAndReason::Error { err_msg, safe_transmute_explanation }
2940 }
2941 // Should never get a Yes at this point! We already ran it before, and did not get a Yes.
2942 Answer::Yes => span_bug!(
2943 span,
2944 "Inconsistent rustc_transmute::is_transmutable(...) result, got Yes",
2945 ),
2946 other => span_bug!(span, "Unsupported rustc_transmute::Answer variant: `{other:?}`"),
2947 }
2948 }
2949
add_tuple_trait_message( &self, obligation_cause_code: &ObligationCauseCode<'tcx>, err: &mut Diagnostic, )2950 fn add_tuple_trait_message(
2951 &self,
2952 obligation_cause_code: &ObligationCauseCode<'tcx>,
2953 err: &mut Diagnostic,
2954 ) {
2955 match obligation_cause_code {
2956 ObligationCauseCode::RustCall => {
2957 err.set_primary_message("functions with the \"rust-call\" ABI must take a single non-self tuple argument");
2958 }
2959 ObligationCauseCode::BindingObligation(def_id, _)
2960 | ObligationCauseCode::ItemObligation(def_id)
2961 if self.tcx.is_fn_trait(*def_id) =>
2962 {
2963 err.code(rustc_errors::error_code!(E0059));
2964 err.set_primary_message(format!(
2965 "type parameter to bare `{}` trait must be a tuple",
2966 self.tcx.def_path_str(*def_id)
2967 ));
2968 }
2969 _ => {}
2970 }
2971 }
2972
try_to_add_help_message( &self, obligation: &PredicateObligation<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>, trait_predicate: &ty::PolyTraitPredicate<'tcx>, err: &mut Diagnostic, span: Span, is_fn_trait: bool, suggested: bool, unsatisfied_const: bool, )2973 fn try_to_add_help_message(
2974 &self,
2975 obligation: &PredicateObligation<'tcx>,
2976 trait_ref: ty::PolyTraitRef<'tcx>,
2977 trait_predicate: &ty::PolyTraitPredicate<'tcx>,
2978 err: &mut Diagnostic,
2979 span: Span,
2980 is_fn_trait: bool,
2981 suggested: bool,
2982 unsatisfied_const: bool,
2983 ) {
2984 let body_def_id = obligation.cause.body_id;
2985 // Try to report a help message
2986 if is_fn_trait
2987 && let Ok((implemented_kind, params)) = self.type_implements_fn_trait(
2988 obligation.param_env,
2989 trait_ref.self_ty(),
2990 trait_predicate.skip_binder().constness,
2991 trait_predicate.skip_binder().polarity,
2992 )
2993 {
2994 self.add_help_message_for_fn_trait(trait_ref, err, implemented_kind, params);
2995 } else if !trait_ref.has_non_region_infer()
2996 && self.predicate_can_apply(obligation.param_env, *trait_predicate)
2997 {
2998 // If a where-clause may be useful, remind the
2999 // user that they can add it.
3000 //
3001 // don't display an on-unimplemented note, as
3002 // these notes will often be of the form
3003 // "the type `T` can't be frobnicated"
3004 // which is somewhat confusing.
3005 self.suggest_restricting_param_bound(
3006 err,
3007 *trait_predicate,
3008 None,
3009 obligation.cause.body_id,
3010 );
3011 } else if !suggested && !unsatisfied_const {
3012 // Can't show anything else useful, try to find similar impls.
3013 let impl_candidates = self.find_similar_impl_candidates(*trait_predicate);
3014 if !self.report_similar_impl_candidates(
3015 &impl_candidates,
3016 trait_ref,
3017 body_def_id,
3018 err,
3019 true,
3020 ) {
3021 self.report_similar_impl_candidates_for_root_obligation(&obligation, *trait_predicate, body_def_id, err);
3022 }
3023
3024 self.maybe_suggest_convert_to_slice(
3025 err,
3026 trait_ref,
3027 impl_candidates.as_slice(),
3028 span,
3029 );
3030 }
3031 }
3032
add_help_message_for_fn_trait( &self, trait_ref: ty::PolyTraitRef<'tcx>, err: &mut Diagnostic, implemented_kind: ty::ClosureKind, params: ty::Binder<'tcx, Ty<'tcx>>, )3033 fn add_help_message_for_fn_trait(
3034 &self,
3035 trait_ref: ty::PolyTraitRef<'tcx>,
3036 err: &mut Diagnostic,
3037 implemented_kind: ty::ClosureKind,
3038 params: ty::Binder<'tcx, Ty<'tcx>>,
3039 ) {
3040 // If the type implements `Fn`, `FnMut`, or `FnOnce`, suppress the following
3041 // suggestion to add trait bounds for the type, since we only typically implement
3042 // these traits once.
3043
3044 // Note if the `FnMut` or `FnOnce` is less general than the trait we're trying
3045 // to implement.
3046 let selected_kind = self
3047 .tcx
3048 .fn_trait_kind_from_def_id(trait_ref.def_id())
3049 .expect("expected to map DefId to ClosureKind");
3050 if !implemented_kind.extends(selected_kind) {
3051 err.note(format!(
3052 "`{}` implements `{}`, but it must implement `{}`, which is more general",
3053 trait_ref.skip_binder().self_ty(),
3054 implemented_kind,
3055 selected_kind
3056 ));
3057 }
3058
3059 // Note any argument mismatches
3060 let given_ty = params.skip_binder();
3061 let expected_ty = trait_ref.skip_binder().substs.type_at(1);
3062 if let ty::Tuple(given) = given_ty.kind()
3063 && let ty::Tuple(expected) = expected_ty.kind()
3064 {
3065 if expected.len() != given.len() {
3066 // Note number of types that were expected and given
3067 err.note(
3068 format!(
3069 "expected a closure taking {} argument{}, but one taking {} argument{} was given",
3070 given.len(),
3071 pluralize!(given.len()),
3072 expected.len(),
3073 pluralize!(expected.len()),
3074 )
3075 );
3076 } else if !self.same_type_modulo_infer(given_ty, expected_ty) {
3077 // Print type mismatch
3078 let (expected_args, given_args) =
3079 self.cmp(given_ty, expected_ty);
3080 err.note_expected_found(
3081 &"a closure with arguments",
3082 expected_args,
3083 &"a closure with arguments",
3084 given_args,
3085 );
3086 }
3087 }
3088 }
3089
maybe_add_note_for_unsatisfied_const( &self, obligation: &PredicateObligation<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>, trait_predicate: &ty::PolyTraitPredicate<'tcx>, err: &mut Diagnostic, span: Span, ) -> UnsatisfiedConst3090 fn maybe_add_note_for_unsatisfied_const(
3091 &self,
3092 obligation: &PredicateObligation<'tcx>,
3093 trait_ref: ty::PolyTraitRef<'tcx>,
3094 trait_predicate: &ty::PolyTraitPredicate<'tcx>,
3095 err: &mut Diagnostic,
3096 span: Span,
3097 ) -> UnsatisfiedConst {
3098 let mut unsatisfied_const = UnsatisfiedConst(false);
3099 if trait_predicate.is_const_if_const() && obligation.param_env.is_const() {
3100 let non_const_predicate = trait_ref.without_const();
3101 let non_const_obligation = Obligation {
3102 cause: obligation.cause.clone(),
3103 param_env: obligation.param_env.without_const(),
3104 predicate: non_const_predicate.to_predicate(self.tcx),
3105 recursion_depth: obligation.recursion_depth,
3106 };
3107 if self.predicate_may_hold(&non_const_obligation) {
3108 unsatisfied_const = UnsatisfiedConst(true);
3109 err.span_note(
3110 span,
3111 format!(
3112 "the trait `{}` is implemented for `{}`, \
3113 but that implementation is not `const`",
3114 non_const_predicate.print_modifiers_and_trait_path(),
3115 trait_ref.skip_binder().self_ty(),
3116 ),
3117 );
3118 }
3119 }
3120 unsatisfied_const
3121 }
3122
report_closure_error( &self, obligation: &PredicateObligation<'tcx>, closure_def_id: DefId, found_kind: ty::ClosureKind, kind: ty::ClosureKind, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>3123 fn report_closure_error(
3124 &self,
3125 obligation: &PredicateObligation<'tcx>,
3126 closure_def_id: DefId,
3127 found_kind: ty::ClosureKind,
3128 kind: ty::ClosureKind,
3129 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
3130 let closure_span = self.tcx.def_span(closure_def_id);
3131 let mut err = struct_span_err!(
3132 self.tcx.sess,
3133 closure_span,
3134 E0525,
3135 "expected a closure that implements the `{}` trait, \
3136 but this closure only implements `{}`",
3137 kind,
3138 found_kind
3139 );
3140
3141 err.span_label(
3142 closure_span,
3143 format!("this closure implements `{}`, not `{}`", found_kind, kind),
3144 );
3145 err.span_label(
3146 obligation.cause.span,
3147 format!("the requirement to implement `{}` derives from here", kind),
3148 );
3149
3150 // Additional context information explaining why the closure only implements
3151 // a particular trait.
3152 if let Some(typeck_results) = &self.typeck_results {
3153 let hir_id = self.tcx.hir().local_def_id_to_hir_id(closure_def_id.expect_local());
3154 match (found_kind, typeck_results.closure_kind_origins().get(hir_id)) {
3155 (ty::ClosureKind::FnOnce, Some((span, place))) => {
3156 err.span_label(
3157 *span,
3158 format!(
3159 "closure is `FnOnce` because it moves the \
3160 variable `{}` out of its environment",
3161 ty::place_to_string_for_capture(self.tcx, place)
3162 ),
3163 );
3164 }
3165 (ty::ClosureKind::FnMut, Some((span, place))) => {
3166 err.span_label(
3167 *span,
3168 format!(
3169 "closure is `FnMut` because it mutates the \
3170 variable `{}` here",
3171 ty::place_to_string_for_capture(self.tcx, place)
3172 ),
3173 );
3174 }
3175 _ => {}
3176 }
3177 }
3178
3179 err
3180 }
3181
report_type_parameter_mismatch_cyclic_type_error( &self, obligation: &PredicateObligation<'tcx>, found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>, expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>, terr: TypeError<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>3182 fn report_type_parameter_mismatch_cyclic_type_error(
3183 &self,
3184 obligation: &PredicateObligation<'tcx>,
3185 found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
3186 expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
3187 terr: TypeError<'tcx>,
3188 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
3189 let self_ty = found_trait_ref.self_ty().skip_binder();
3190 let (cause, terr) = if let ty::Closure(def_id, _) = self_ty.kind() {
3191 (
3192 ObligationCause::dummy_with_span(self.tcx.def_span(def_id)),
3193 TypeError::CyclicTy(self_ty),
3194 )
3195 } else {
3196 (obligation.cause.clone(), terr)
3197 };
3198 self.report_and_explain_type_error(
3199 TypeTrace::poly_trait_refs(&cause, true, expected_trait_ref, found_trait_ref),
3200 terr,
3201 )
3202 }
3203
report_opaque_type_auto_trait_leakage( &self, obligation: &PredicateObligation<'tcx>, def_id: DefId, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>3204 fn report_opaque_type_auto_trait_leakage(
3205 &self,
3206 obligation: &PredicateObligation<'tcx>,
3207 def_id: DefId,
3208 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
3209 let name = match self.tcx.opaque_type_origin(def_id.expect_local()) {
3210 hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_) => {
3211 format!("opaque type")
3212 }
3213 hir::OpaqueTyOrigin::TyAlias { .. } => {
3214 format!("`{}`", self.tcx.def_path_debug_str(def_id))
3215 }
3216 };
3217 let mut err = self.tcx.sess.struct_span_err(
3218 obligation.cause.span,
3219 format!("cannot check whether the hidden type of {name} satisfies auto traits"),
3220 );
3221 err.span_note(self.tcx.def_span(def_id), "opaque type is declared here");
3222 match self.defining_use_anchor {
3223 DefiningAnchor::Bubble | DefiningAnchor::Error => {}
3224 DefiningAnchor::Bind(bind) => {
3225 err.span_note(
3226 self.tcx.def_ident_span(bind).unwrap_or_else(|| self.tcx.def_span(bind)),
3227 "this item depends on auto traits of the hidden type, \
3228 but may also be registering the hidden type. \
3229 This is not supported right now. \
3230 You can try moving the opaque type and the item that actually registers a hidden type into a new submodule".to_string(),
3231 );
3232 }
3233 };
3234 err
3235 }
3236
report_type_parameter_mismatch_error( &self, obligation: &PredicateObligation<'tcx>, span: Span, found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>, expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>, ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>3237 fn report_type_parameter_mismatch_error(
3238 &self,
3239 obligation: &PredicateObligation<'tcx>,
3240 span: Span,
3241 found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
3242 expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
3243 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
3244 let found_trait_ref = self.resolve_vars_if_possible(found_trait_ref);
3245 let expected_trait_ref = self.resolve_vars_if_possible(expected_trait_ref);
3246
3247 if expected_trait_ref.self_ty().references_error() {
3248 return None;
3249 }
3250
3251 let Some(found_trait_ty) = found_trait_ref.self_ty().no_bound_vars() else {
3252 return None;
3253 };
3254
3255 let found_did = match *found_trait_ty.kind() {
3256 ty::Closure(did, _) | ty::Foreign(did) | ty::FnDef(did, _) | ty::Generator(did, ..) => {
3257 Some(did)
3258 }
3259 ty::Adt(def, _) => Some(def.did()),
3260 _ => None,
3261 };
3262
3263 let found_node = found_did.and_then(|did| self.tcx.hir().get_if_local(did));
3264 let found_span = found_did.and_then(|did| self.tcx.hir().span_if_local(did));
3265
3266 if self.reported_closure_mismatch.borrow().contains(&(span, found_span)) {
3267 // We check closures twice, with obligations flowing in different directions,
3268 // but we want to complain about them only once.
3269 return None;
3270 }
3271
3272 self.reported_closure_mismatch.borrow_mut().insert((span, found_span));
3273
3274 let mut not_tupled = false;
3275
3276 let found = match found_trait_ref.skip_binder().substs.type_at(1).kind() {
3277 ty::Tuple(ref tys) => vec![ArgKind::empty(); tys.len()],
3278 _ => {
3279 not_tupled = true;
3280 vec![ArgKind::empty()]
3281 }
3282 };
3283
3284 let expected_ty = expected_trait_ref.skip_binder().substs.type_at(1);
3285 let expected = match expected_ty.kind() {
3286 ty::Tuple(ref tys) => {
3287 tys.iter().map(|t| ArgKind::from_expected_ty(t, Some(span))).collect()
3288 }
3289 _ => {
3290 not_tupled = true;
3291 vec![ArgKind::Arg("_".to_owned(), expected_ty.to_string())]
3292 }
3293 };
3294
3295 // If this is a `Fn` family trait and either the expected or found
3296 // is not tupled, then fall back to just a regular mismatch error.
3297 // This shouldn't be common unless manually implementing one of the
3298 // traits manually, but don't make it more confusing when it does
3299 // happen.
3300 Some(
3301 if Some(expected_trait_ref.def_id()) != self.tcx.lang_items().gen_trait() && not_tupled
3302 {
3303 self.report_and_explain_type_error(
3304 TypeTrace::poly_trait_refs(
3305 &obligation.cause,
3306 true,
3307 expected_trait_ref,
3308 found_trait_ref,
3309 ),
3310 ty::error::TypeError::Mismatch,
3311 )
3312 } else if found.len() == expected.len() {
3313 self.report_closure_arg_mismatch(
3314 span,
3315 found_span,
3316 found_trait_ref,
3317 expected_trait_ref,
3318 obligation.cause.code(),
3319 found_node,
3320 obligation.param_env,
3321 )
3322 } else {
3323 let (closure_span, closure_arg_span, found) = found_did
3324 .and_then(|did| {
3325 let node = self.tcx.hir().get_if_local(did)?;
3326 let (found_span, closure_arg_span, found) =
3327 self.get_fn_like_arguments(node)?;
3328 Some((Some(found_span), closure_arg_span, found))
3329 })
3330 .unwrap_or((found_span, None, found));
3331
3332 self.report_arg_count_mismatch(
3333 span,
3334 closure_span,
3335 expected,
3336 found,
3337 found_trait_ty.is_closure(),
3338 closure_arg_span,
3339 )
3340 },
3341 )
3342 }
3343
report_not_const_evaluatable_error( &self, obligation: &PredicateObligation<'tcx>, span: Span, ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>3344 fn report_not_const_evaluatable_error(
3345 &self,
3346 obligation: &PredicateObligation<'tcx>,
3347 span: Span,
3348 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
3349 if !self.tcx.features().generic_const_exprs {
3350 let mut err = self
3351 .tcx
3352 .sess
3353 .struct_span_err(span, "constant expression depends on a generic parameter");
3354 // FIXME(const_generics): we should suggest to the user how they can resolve this
3355 // issue. However, this is currently not actually possible
3356 // (see https://github.com/rust-lang/rust/issues/66962#issuecomment-575907083).
3357 //
3358 // Note that with `feature(generic_const_exprs)` this case should not
3359 // be reachable.
3360 err.note("this may fail depending on what value the parameter takes");
3361 err.emit();
3362 return None;
3363 }
3364
3365 match obligation.predicate.kind().skip_binder() {
3366 ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(ct)) => {
3367 let ty::ConstKind::Unevaluated(uv) = ct.kind() else {
3368 bug!("const evaluatable failed for non-unevaluated const `{ct:?}`");
3369 };
3370 let mut err = self.tcx.sess.struct_span_err(span, "unconstrained generic constant");
3371 let const_span = self.tcx.def_span(uv.def);
3372 match self.tcx.sess.source_map().span_to_snippet(const_span) {
3373 Ok(snippet) => err.help(format!(
3374 "try adding a `where` bound using this expression: `where [(); {}]:`",
3375 snippet
3376 )),
3377 _ => err.help("consider adding a `where` bound using this expression"),
3378 };
3379 Some(err)
3380 }
3381 _ => {
3382 span_bug!(
3383 span,
3384 "unexpected non-ConstEvaluatable predicate, this should not be reachable"
3385 )
3386 }
3387 }
3388 }
3389 }
3390
3391 struct UnsatisfiedConst(pub bool);
3392
get_explanation_based_on_obligation<'tcx>( obligation: &PredicateObligation<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>, trait_predicate: &ty::PolyTraitPredicate<'tcx>, pre_message: String, ) -> String3393 fn get_explanation_based_on_obligation<'tcx>(
3394 obligation: &PredicateObligation<'tcx>,
3395 trait_ref: ty::PolyTraitRef<'tcx>,
3396 trait_predicate: &ty::PolyTraitPredicate<'tcx>,
3397 pre_message: String,
3398 ) -> String {
3399 if let ObligationCauseCode::MainFunctionType = obligation.cause.code() {
3400 "consider using `()`, or a `Result`".to_owned()
3401 } else {
3402 let ty_desc = match trait_ref.skip_binder().self_ty().kind() {
3403 ty::FnDef(_, _) => Some("fn item"),
3404 ty::Closure(_, _) => Some("closure"),
3405 _ => None,
3406 };
3407
3408 match ty_desc {
3409 Some(desc) => format!(
3410 "{}the trait `{}` is not implemented for {} `{}`",
3411 pre_message,
3412 trait_predicate.print_modifiers_and_trait_path(),
3413 desc,
3414 trait_ref.skip_binder().self_ty(),
3415 ),
3416 None => format!(
3417 "{}the trait `{}` is not implemented for `{}`",
3418 pre_message,
3419 trait_predicate.print_modifiers_and_trait_path(),
3420 trait_ref.skip_binder().self_ty(),
3421 ),
3422 }
3423 }
3424 }
3425 /// Crude way of getting back an `Expr` from a `Span`.
3426 pub struct FindExprBySpan<'hir> {
3427 pub span: Span,
3428 pub result: Option<&'hir hir::Expr<'hir>>,
3429 pub ty_result: Option<&'hir hir::Ty<'hir>>,
3430 }
3431
3432 impl<'hir> FindExprBySpan<'hir> {
new(span: Span) -> Self3433 pub fn new(span: Span) -> Self {
3434 Self { span, result: None, ty_result: None }
3435 }
3436 }
3437
3438 impl<'v> Visitor<'v> for FindExprBySpan<'v> {
visit_expr(&mut self, ex: &'v hir::Expr<'v>)3439 fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) {
3440 if self.span == ex.span {
3441 self.result = Some(ex);
3442 } else {
3443 hir::intravisit::walk_expr(self, ex);
3444 }
3445 }
visit_ty(&mut self, ty: &'v hir::Ty<'v>)3446 fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) {
3447 if self.span == ty.span {
3448 self.ty_result = Some(ty);
3449 } else {
3450 hir::intravisit::walk_ty(self, ty);
3451 }
3452 }
3453 }
3454
3455 /// Look for type `param` in an ADT being used only through a reference to confirm that suggesting
3456 /// `param: ?Sized` would be a valid constraint.
3457 struct FindTypeParam {
3458 param: rustc_span::Symbol,
3459 invalid_spans: Vec<Span>,
3460 nested: bool,
3461 }
3462
3463 impl<'v> Visitor<'v> for FindTypeParam {
visit_where_predicate(&mut self, _: &'v hir::WherePredicate<'v>)3464 fn visit_where_predicate(&mut self, _: &'v hir::WherePredicate<'v>) {
3465 // Skip where-clauses, to avoid suggesting indirection for type parameters found there.
3466 }
3467
visit_ty(&mut self, ty: &hir::Ty<'_>)3468 fn visit_ty(&mut self, ty: &hir::Ty<'_>) {
3469 // We collect the spans of all uses of the "bare" type param, like in `field: T` or
3470 // `field: (T, T)` where we could make `T: ?Sized` while skipping cases that are known to be
3471 // valid like `field: &'a T` or `field: *mut T` and cases that *might* have further `Sized`
3472 // obligations like `Box<T>` and `Vec<T>`, but we perform no extra analysis for those cases
3473 // and suggest `T: ?Sized` regardless of their obligations. This is fine because the errors
3474 // in that case should make what happened clear enough.
3475 match ty.kind {
3476 hir::TyKind::Ptr(_) | hir::TyKind::Ref(..) | hir::TyKind::TraitObject(..) => {}
3477 hir::TyKind::Path(hir::QPath::Resolved(None, path))
3478 if path.segments.len() == 1 && path.segments[0].ident.name == self.param =>
3479 {
3480 if !self.nested {
3481 debug!(?ty, "FindTypeParam::visit_ty");
3482 self.invalid_spans.push(ty.span);
3483 }
3484 }
3485 hir::TyKind::Path(_) => {
3486 let prev = self.nested;
3487 self.nested = true;
3488 hir::intravisit::walk_ty(self, ty);
3489 self.nested = prev;
3490 }
3491 _ => {
3492 hir::intravisit::walk_ty(self, ty);
3493 }
3494 }
3495 }
3496 }
3497
3498 /// Summarizes information
3499 #[derive(Clone)]
3500 pub enum ArgKind {
3501 /// An argument of non-tuple type. Parameters are (name, ty)
3502 Arg(String, String),
3503
3504 /// An argument of tuple type. For a "found" argument, the span is
3505 /// the location in the source of the pattern. For an "expected"
3506 /// argument, it will be None. The vector is a list of (name, ty)
3507 /// strings for the components of the tuple.
3508 Tuple(Option<Span>, Vec<(String, String)>),
3509 }
3510
3511 impl ArgKind {
empty() -> ArgKind3512 fn empty() -> ArgKind {
3513 ArgKind::Arg("_".to_owned(), "_".to_owned())
3514 }
3515
3516 /// Creates an `ArgKind` from the expected type of an
3517 /// argument. It has no name (`_`) and an optional source span.
from_expected_ty(t: Ty<'_>, span: Option<Span>) -> ArgKind3518 pub fn from_expected_ty(t: Ty<'_>, span: Option<Span>) -> ArgKind {
3519 match t.kind() {
3520 ty::Tuple(tys) => ArgKind::Tuple(
3521 span,
3522 tys.iter().map(|ty| ("_".to_owned(), ty.to_string())).collect::<Vec<_>>(),
3523 ),
3524 _ => ArgKind::Arg("_".to_owned(), t.to_string()),
3525 }
3526 }
3527 }
3528
3529 struct HasNumericInferVisitor;
3530
3531 impl<'tcx> ty::TypeVisitor<TyCtxt<'tcx>> for HasNumericInferVisitor {
3532 type BreakTy = ();
3533
visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy>3534 fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
3535 if matches!(ty.kind(), ty::Infer(ty::FloatVar(_) | ty::IntVar(_))) {
3536 ControlFlow::Break(())
3537 } else {
3538 ControlFlow::Continue(())
3539 }
3540 }
3541 }
3542
3543 #[derive(Copy, Clone)]
3544 pub enum DefIdOrName {
3545 DefId(DefId),
3546 Name(&'static str),
3547 }
3548
dump_proof_tree<'tcx>(o: &Obligation<'tcx, ty::Predicate<'tcx>>, infcx: &InferCtxt<'tcx>)3549 pub fn dump_proof_tree<'tcx>(o: &Obligation<'tcx, ty::Predicate<'tcx>>, infcx: &InferCtxt<'tcx>) {
3550 infcx.probe(|_| {
3551 let goal = Goal { predicate: o.predicate, param_env: o.param_env };
3552 let tree = infcx
3553 .evaluate_root_goal(goal, GenerateProofTree::Yes(UseGlobalCache::No))
3554 .1
3555 .expect("proof tree should have been generated");
3556 let mut lock = std::io::stdout().lock();
3557 let _ = lock.write_fmt(format_args!("{tree:?}"));
3558 let _ = lock.flush();
3559 });
3560 }
3561