rustc_hir_typeck/
cast.rs

1//! Code for type-checking cast expressions.
2//!
3//! A cast `e as U` is valid if one of the following holds:
4//! * `e` has type `T` and `T` coerces to `U`; *coercion-cast*
5//! * `e` has type `*T`, `U` is `*U_0`, and either `U_0: Sized` or
6//!    pointer_kind(`T`) = pointer_kind(`U_0`); *ptr-ptr-cast*
7//! * `e` has type `*T` and `U` is a numeric type, while `T: Sized`; *ptr-addr-cast*
8//! * `e` is an integer and `U` is `*U_0`, while `U_0: Sized`; *addr-ptr-cast*
9//! * `e` has type `T` and `T` and `U` are any numeric types; *numeric-cast*
10//! * `e` is a C-like enum and `U` is an integer type; *enum-cast*
11//! * `e` has type `bool` or `char` and `U` is an integer; *prim-int-cast*
12//! * `e` has type `u8` and `U` is `char`; *u8-char-cast*
13//! * `e` has type `&[T; n]` and `U` is `*const T`; *array-ptr-cast*
14//! * `e` is a function pointer type and `U` has type `*T`,
15//!   while `T: Sized`; *fptr-ptr-cast*
16//! * `e` is a function pointer type and `U` is an integer; *fptr-addr-cast*
17//!
18//! where `&.T` and `*T` are references of either mutability,
19//! and where pointer_kind(`T`) is the kind of the unsize info
20//! in `T` - the vtable for a trait definition (e.g., `fmt::Display` or
21//! `Iterator`, not `Iterator<Item=u8>`) or a length (or `()` if `T: Sized`).
22//!
23//! Note that lengths are not adjusted when casting raw slices -
24//! `T: *const [u16] as *const [u8]` creates a slice that only includes
25//! half of the original memory.
26//!
27//! Casting is not transitive, that is, even if `e as U1 as U2` is a valid
28//! expression, `e as U2` is not necessarily so (in fact it will only be valid if
29//! `U1` coerces to `U2`).
30
31use rustc_ast::util::parser::ExprPrecedence;
32use rustc_data_structures::fx::FxHashSet;
33use rustc_errors::codes::*;
34use rustc_errors::{Applicability, Diag, ErrorGuaranteed};
35use rustc_hir::def_id::DefId;
36use rustc_hir::{self as hir, ExprKind};
37use rustc_infer::infer::DefineOpaqueTypes;
38use rustc_macros::{TypeFoldable, TypeVisitable};
39use rustc_middle::mir::Mutability;
40use rustc_middle::ty::adjustment::AllowTwoPhase;
41use rustc_middle::ty::cast::{CastKind, CastTy};
42use rustc_middle::ty::error::TypeError;
43use rustc_middle::ty::{self, Ty, TyCtxt, TypeAndMut, TypeVisitableExt, VariantDef, elaborate};
44use rustc_middle::{bug, span_bug};
45use rustc_session::lint;
46use rustc_span::{DUMMY_SP, Span, sym};
47use rustc_trait_selection::infer::InferCtxtExt;
48use tracing::{debug, instrument};
49
50use super::FnCtxt;
51use crate::{errors, type_error_struct};
52
53/// Reifies a cast check to be checked once we have full type information for
54/// a function context.
55#[derive(Debug)]
56pub(crate) struct CastCheck<'tcx> {
57    /// The expression whose value is being casted
58    expr: &'tcx hir::Expr<'tcx>,
59    /// The source type for the cast expression
60    expr_ty: Ty<'tcx>,
61    expr_span: Span,
62    /// The target type. That is, the type we are casting to.
63    cast_ty: Ty<'tcx>,
64    cast_span: Span,
65    span: Span,
66}
67
68/// The kind of pointer and associated metadata (thin, length or vtable) - we
69/// only allow casts between wide pointers if their metadata have the same
70/// kind.
71#[derive(Debug, Copy, Clone, PartialEq, Eq, TypeVisitable, TypeFoldable)]
72enum PointerKind<'tcx> {
73    /// No metadata attached, ie pointer to sized type or foreign type
74    Thin,
75    /// A trait object
76    VTable(&'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>),
77    /// Slice
78    Length,
79    /// The unsize info of this projection or opaque type
80    OfAlias(ty::AliasTy<'tcx>),
81    /// The unsize info of this parameter
82    OfParam(ty::ParamTy),
83}
84
85impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
86    /// Returns the kind of unsize information of t, or None
87    /// if t is unknown.
88    fn pointer_kind(
89        &self,
90        t: Ty<'tcx>,
91        span: Span,
92    ) -> Result<Option<PointerKind<'tcx>>, ErrorGuaranteed> {
93        debug!("pointer_kind({:?}, {:?})", t, span);
94
95        let t = self.resolve_vars_if_possible(t);
96        t.error_reported()?;
97
98        if self.type_is_sized_modulo_regions(self.param_env, t) {
99            return Ok(Some(PointerKind::Thin));
100        }
101
102        let t = self.try_structurally_resolve_type(span, t);
103
104        Ok(match *t.kind() {
105            ty::Slice(_) | ty::Str => Some(PointerKind::Length),
106            ty::Dynamic(tty, _) => Some(PointerKind::VTable(tty)),
107            ty::Adt(def, args) if def.is_struct() => match def.non_enum_variant().tail_opt() {
108                None => Some(PointerKind::Thin),
109                Some(f) => {
110                    let field_ty = self.field_ty(span, f, args);
111                    self.pointer_kind(field_ty, span)?
112                }
113            },
114            ty::Tuple(fields) => match fields.last() {
115                None => Some(PointerKind::Thin),
116                Some(&f) => self.pointer_kind(f, span)?,
117            },
118
119            ty::UnsafeBinder(_) => todo!("FIXME(unsafe_binder)"),
120
121            // Pointers to foreign types are thin, despite being unsized
122            ty::Foreign(..) => Some(PointerKind::Thin),
123            // We should really try to normalize here.
124            ty::Alias(_, pi) => Some(PointerKind::OfAlias(pi)),
125            ty::Param(p) => Some(PointerKind::OfParam(p)),
126            // Insufficient type information.
127            ty::Placeholder(..) | ty::Bound(..) | ty::Infer(_) => None,
128
129            ty::Bool
130            | ty::Char
131            | ty::Int(..)
132            | ty::Uint(..)
133            | ty::Float(_)
134            | ty::Array(..)
135            | ty::CoroutineWitness(..)
136            | ty::RawPtr(_, _)
137            | ty::Ref(..)
138            | ty::Pat(..)
139            | ty::FnDef(..)
140            | ty::FnPtr(..)
141            | ty::Closure(..)
142            | ty::CoroutineClosure(..)
143            | ty::Coroutine(..)
144            | ty::Adt(..)
145            | ty::Never
146            | ty::Error(_) => {
147                let guar = self
148                    .dcx()
149                    .span_delayed_bug(span, format!("`{t:?}` should be sized but is not?"));
150                return Err(guar);
151            }
152        })
153    }
154}
155
156#[derive(Debug)]
157enum CastError<'tcx> {
158    ErrorGuaranteed(ErrorGuaranteed),
159
160    CastToBool,
161    CastToChar,
162    DifferingKinds {
163        src_kind: PointerKind<'tcx>,
164        dst_kind: PointerKind<'tcx>,
165    },
166    /// Cast of thin to wide raw ptr (e.g., `*const () as *const [u8]`).
167    SizedUnsizedCast,
168    IllegalCast,
169    NeedDeref,
170    NeedViaPtr,
171    NeedViaThinPtr,
172    NeedViaInt,
173    NonScalar,
174    UnknownExprPtrKind,
175    UnknownCastPtrKind,
176    /// Cast of int to (possibly) wide raw pointer.
177    ///
178    /// Argument is the specific name of the metadata in plain words, such as "a vtable"
179    /// or "a length". If this argument is None, then the metadata is unknown, for example,
180    /// when we're typechecking a type parameter with a ?Sized bound.
181    IntToWideCast(Option<&'static str>),
182    ForeignNonExhaustiveAdt,
183    PtrPtrAddingAutoTrait(Vec<DefId>),
184}
185
186impl From<ErrorGuaranteed> for CastError<'_> {
187    fn from(err: ErrorGuaranteed) -> Self {
188        CastError::ErrorGuaranteed(err)
189    }
190}
191
192fn make_invalid_casting_error<'a, 'tcx>(
193    span: Span,
194    expr_ty: Ty<'tcx>,
195    cast_ty: Ty<'tcx>,
196    fcx: &FnCtxt<'a, 'tcx>,
197) -> Diag<'a> {
198    type_error_struct!(
199        fcx.dcx(),
200        span,
201        expr_ty,
202        E0606,
203        "casting `{}` as `{}` is invalid",
204        fcx.ty_to_string(expr_ty),
205        fcx.ty_to_string(cast_ty)
206    )
207}
208
209/// If a cast from `from_ty` to `to_ty` is valid, returns a `Some` containing the kind
210/// of the cast.
211///
212/// This is a helper used from clippy.
213pub fn check_cast<'tcx>(
214    tcx: TyCtxt<'tcx>,
215    param_env: ty::ParamEnv<'tcx>,
216    e: &'tcx hir::Expr<'tcx>,
217    from_ty: Ty<'tcx>,
218    to_ty: Ty<'tcx>,
219) -> Option<CastKind> {
220    let hir_id = e.hir_id;
221    let local_def_id = hir_id.owner.def_id;
222
223    let root_ctxt = crate::TypeckRootCtxt::new(tcx, local_def_id);
224    let fn_ctxt = FnCtxt::new(&root_ctxt, param_env, local_def_id);
225
226    if let Ok(check) = CastCheck::new(
227        &fn_ctxt, e, from_ty, to_ty,
228        // We won't show any errors to the user, so the span is irrelevant here.
229        DUMMY_SP, DUMMY_SP,
230    ) {
231        check.do_check(&fn_ctxt).ok()
232    } else {
233        None
234    }
235}
236
237impl<'a, 'tcx> CastCheck<'tcx> {
238    pub(crate) fn new(
239        fcx: &FnCtxt<'a, 'tcx>,
240        expr: &'tcx hir::Expr<'tcx>,
241        expr_ty: Ty<'tcx>,
242        cast_ty: Ty<'tcx>,
243        cast_span: Span,
244        span: Span,
245    ) -> Result<CastCheck<'tcx>, ErrorGuaranteed> {
246        let expr_span = expr.span.find_ancestor_inside(span).unwrap_or(expr.span);
247        let check = CastCheck { expr, expr_ty, expr_span, cast_ty, cast_span, span };
248
249        // For better error messages, check for some obviously unsized
250        // cases now. We do a more thorough check at the end, once
251        // inference is more completely known.
252        match cast_ty.kind() {
253            ty::Dynamic(_, _) | ty::Slice(..) => Err(check.report_cast_to_unsized_type(fcx)),
254            _ => Ok(check),
255        }
256    }
257
258    fn report_cast_error(&self, fcx: &FnCtxt<'a, 'tcx>, e: CastError<'tcx>) {
259        match e {
260            CastError::ErrorGuaranteed(_) => {
261                // an error has already been reported
262            }
263            CastError::NeedDeref => {
264                let mut err =
265                    make_invalid_casting_error(self.span, self.expr_ty, self.cast_ty, fcx);
266
267                if matches!(self.expr.kind, ExprKind::AddrOf(..)) {
268                    // get just the borrow part of the expression
269                    let span = self.expr_span.with_hi(self.expr.peel_borrows().span.lo());
270                    err.span_suggestion_verbose(
271                        span,
272                        "remove the unneeded borrow",
273                        "",
274                        Applicability::MachineApplicable,
275                    );
276                } else {
277                    err.span_suggestion_verbose(
278                        self.expr_span.shrink_to_lo(),
279                        "dereference the expression",
280                        "*",
281                        Applicability::MachineApplicable,
282                    );
283                }
284
285                err.emit();
286            }
287            CastError::NeedViaThinPtr | CastError::NeedViaPtr => {
288                let mut err =
289                    make_invalid_casting_error(self.span, self.expr_ty, self.cast_ty, fcx);
290                if self.cast_ty.is_integral() {
291                    err.help(format!("cast through {} first", match e {
292                        CastError::NeedViaPtr => "a raw pointer",
293                        CastError::NeedViaThinPtr => "a thin pointer",
294                        e => unreachable!("control flow means we should never encounter a {e:?}"),
295                    }));
296                }
297
298                self.try_suggest_collection_to_bool(fcx, &mut err);
299
300                err.emit();
301            }
302            CastError::NeedViaInt => {
303                make_invalid_casting_error(self.span, self.expr_ty, self.cast_ty, fcx)
304                    .with_help("cast through an integer first")
305                    .emit();
306            }
307            CastError::IllegalCast => {
308                make_invalid_casting_error(self.span, self.expr_ty, self.cast_ty, fcx).emit();
309            }
310            CastError::DifferingKinds { src_kind, dst_kind } => {
311                let mut err =
312                    make_invalid_casting_error(self.span, self.expr_ty, self.cast_ty, fcx);
313
314                match (src_kind, dst_kind) {
315                    (PointerKind::VTable(_), PointerKind::VTable(_)) => {
316                        err.note("the trait objects may have different vtables");
317                    }
318                    (
319                        PointerKind::OfParam(_) | PointerKind::OfAlias(_),
320                        PointerKind::OfParam(_)
321                        | PointerKind::OfAlias(_)
322                        | PointerKind::VTable(_)
323                        | PointerKind::Length,
324                    )
325                    | (
326                        PointerKind::VTable(_) | PointerKind::Length,
327                        PointerKind::OfParam(_) | PointerKind::OfAlias(_),
328                    ) => {
329                        err.note("the pointers may have different metadata");
330                    }
331                    (PointerKind::VTable(_), PointerKind::Length)
332                    | (PointerKind::Length, PointerKind::VTable(_)) => {
333                        err.note("the pointers have different metadata");
334                    }
335                    (
336                        PointerKind::Thin,
337                        PointerKind::Thin
338                        | PointerKind::VTable(_)
339                        | PointerKind::Length
340                        | PointerKind::OfParam(_)
341                        | PointerKind::OfAlias(_),
342                    )
343                    | (
344                        PointerKind::VTable(_)
345                        | PointerKind::Length
346                        | PointerKind::OfParam(_)
347                        | PointerKind::OfAlias(_),
348                        PointerKind::Thin,
349                    )
350                    | (PointerKind::Length, PointerKind::Length) => {
351                        span_bug!(self.span, "unexpected cast error: {e:?}")
352                    }
353                }
354
355                err.emit();
356            }
357            CastError::CastToBool => {
358                let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
359                let help = if self.expr_ty.is_numeric() {
360                    errors::CannotCastToBoolHelp::Numeric(
361                        self.expr_span.shrink_to_hi().with_hi(self.span.hi()),
362                    )
363                } else {
364                    errors::CannotCastToBoolHelp::Unsupported(self.span)
365                };
366                fcx.dcx().emit_err(errors::CannotCastToBool { span: self.span, expr_ty, help });
367            }
368            CastError::CastToChar => {
369                let mut err = type_error_struct!(
370                    fcx.dcx(),
371                    self.span,
372                    self.expr_ty,
373                    E0604,
374                    "only `u8` can be cast as `char`, not `{}`",
375                    self.expr_ty
376                );
377                err.span_label(self.span, "invalid cast");
378                if self.expr_ty.is_numeric() {
379                    if self.expr_ty == fcx.tcx.types.u32 {
380                        err.multipart_suggestion(
381                            "consider using `char::from_u32` instead",
382                            vec![
383                                (self.expr_span.shrink_to_lo(), "char::from_u32(".to_string()),
384                                (self.expr_span.shrink_to_hi().to(self.cast_span), ")".to_string()),
385                            ],
386                            Applicability::MachineApplicable,
387                        );
388                    } else if self.expr_ty == fcx.tcx.types.i8 {
389                        err.span_help(self.span, "consider casting from `u8` instead");
390                    } else {
391                        err.span_help(
392                            self.span,
393                            "consider using `char::from_u32` instead (via a `u32`)",
394                        );
395                    };
396                }
397                err.emit();
398            }
399            CastError::NonScalar => {
400                let mut err = type_error_struct!(
401                    fcx.dcx(),
402                    self.span,
403                    self.expr_ty,
404                    E0605,
405                    "non-primitive cast: `{}` as `{}`",
406                    self.expr_ty,
407                    fcx.ty_to_string(self.cast_ty)
408                );
409
410                if let Ok(snippet) = fcx.tcx.sess.source_map().span_to_snippet(self.expr_span)
411                    && matches!(self.expr.kind, ExprKind::AddrOf(..))
412                {
413                    err.note(format!(
414                        "casting reference expression `{}` because `&` binds tighter than `as`",
415                        snippet
416                    ));
417                }
418
419                let mut sugg = None;
420                let mut sugg_mutref = false;
421                if let ty::Ref(reg, cast_ty, mutbl) = *self.cast_ty.kind() {
422                    if let ty::RawPtr(expr_ty, _) = *self.expr_ty.kind()
423                        && fcx.may_coerce(
424                            Ty::new_ref(fcx.tcx, fcx.tcx.lifetimes.re_erased, expr_ty, mutbl),
425                            self.cast_ty,
426                        )
427                    {
428                        sugg = Some((format!("&{}*", mutbl.prefix_str()), cast_ty == expr_ty));
429                    } else if let ty::Ref(expr_reg, expr_ty, expr_mutbl) = *self.expr_ty.kind()
430                        && expr_mutbl == Mutability::Not
431                        && mutbl == Mutability::Mut
432                        && fcx.may_coerce(Ty::new_mut_ref(fcx.tcx, expr_reg, expr_ty), self.cast_ty)
433                    {
434                        sugg_mutref = true;
435                    }
436
437                    if !sugg_mutref
438                        && sugg == None
439                        && fcx.may_coerce(
440                            Ty::new_ref(fcx.tcx, reg, self.expr_ty, mutbl),
441                            self.cast_ty,
442                        )
443                    {
444                        sugg = Some((format!("&{}", mutbl.prefix_str()), false));
445                    }
446                } else if let ty::RawPtr(_, mutbl) = *self.cast_ty.kind()
447                    && fcx.may_coerce(
448                        Ty::new_ref(fcx.tcx, fcx.tcx.lifetimes.re_erased, self.expr_ty, mutbl),
449                        self.cast_ty,
450                    )
451                {
452                    sugg = Some((format!("&{}", mutbl.prefix_str()), false));
453                }
454                if sugg_mutref {
455                    err.span_label(self.span, "invalid cast");
456                    err.span_note(self.expr_span, "this reference is immutable");
457                    err.span_note(self.cast_span, "trying to cast to a mutable reference type");
458                } else if let Some((sugg, remove_cast)) = sugg {
459                    err.span_label(self.span, "invalid cast");
460
461                    let has_parens = fcx
462                        .tcx
463                        .sess
464                        .source_map()
465                        .span_to_snippet(self.expr_span)
466                        .is_ok_and(|snip| snip.starts_with('('));
467
468                    // Very crude check to see whether the expression must be wrapped
469                    // in parentheses for the suggestion to work (issue #89497).
470                    // Can/should be extended in the future.
471                    let needs_parens =
472                        !has_parens && matches!(self.expr.kind, hir::ExprKind::Cast(..));
473
474                    let mut suggestion = vec![(self.expr_span.shrink_to_lo(), sugg)];
475                    if needs_parens {
476                        suggestion[0].1 += "(";
477                        suggestion.push((self.expr_span.shrink_to_hi(), ")".to_string()));
478                    }
479                    if remove_cast {
480                        suggestion.push((
481                            self.expr_span.shrink_to_hi().to(self.cast_span),
482                            String::new(),
483                        ));
484                    }
485
486                    err.multipart_suggestion_verbose(
487                        "consider borrowing the value",
488                        suggestion,
489                        Applicability::MachineApplicable,
490                    );
491                } else if !matches!(
492                    self.cast_ty.kind(),
493                    ty::FnDef(..) | ty::FnPtr(..) | ty::Closure(..)
494                ) {
495                    // Check `impl From<self.expr_ty> for self.cast_ty {}` for accurate suggestion:
496                    if let Some(from_trait) = fcx.tcx.get_diagnostic_item(sym::From) {
497                        let ty = fcx.resolve_vars_if_possible(self.cast_ty);
498                        let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
499                        if fcx
500                            .infcx
501                            .type_implements_trait(from_trait, [ty, expr_ty], fcx.param_env)
502                            .must_apply_modulo_regions()
503                        {
504                            let to_ty = if let ty::Adt(def, args) = self.cast_ty.kind() {
505                                fcx.tcx.value_path_str_with_args(def.did(), args)
506                            } else {
507                                self.cast_ty.to_string()
508                            };
509                            err.multipart_suggestion(
510                                "consider using the `From` trait instead",
511                                vec![
512                                    (self.expr_span.shrink_to_lo(), format!("{to_ty}::from(")),
513                                    (
514                                        self.expr_span.shrink_to_hi().to(self.cast_span),
515                                        ")".to_string(),
516                                    ),
517                                ],
518                                Applicability::MaybeIncorrect,
519                            );
520                        }
521                    }
522
523                    let (msg, note) = if let ty::Adt(adt, _) = self.expr_ty.kind()
524                        && adt.is_enum()
525                        && self.cast_ty.is_numeric()
526                    {
527                        (
528                            "an `as` expression can be used to convert enum types to numeric \
529                             types only if the enum type is unit-only or field-less",
530                            Some(
531                                "see https://doc.rust-lang.org/reference/items/enumerations.html#casting for more information",
532                            ),
533                        )
534                    } else {
535                        (
536                            "an `as` expression can only be used to convert between primitive \
537                             types or to coerce to a specific trait object",
538                            None,
539                        )
540                    };
541
542                    err.span_label(self.span, msg);
543
544                    if let Some(note) = note {
545                        err.note(note);
546                    }
547                } else {
548                    err.span_label(self.span, "invalid cast");
549                }
550
551                fcx.suggest_no_capture_closure(&mut err, self.cast_ty, self.expr_ty);
552                self.try_suggest_collection_to_bool(fcx, &mut err);
553
554                err.emit();
555            }
556            CastError::SizedUnsizedCast => {
557                let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
558                let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
559                fcx.dcx().emit_err(errors::CastThinPointerToWidePointer {
560                    span: self.span,
561                    expr_ty,
562                    cast_ty,
563                    teach: fcx.tcx.sess.teach(E0607),
564                });
565            }
566            CastError::IntToWideCast(known_metadata) => {
567                let expr_if_nightly = fcx.tcx.sess.is_nightly_build().then_some(self.expr_span);
568                let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
569                let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
570                let metadata = known_metadata.unwrap_or("type-specific metadata");
571                let known_wide = known_metadata.is_some();
572                let span = self.cast_span;
573                fcx.dcx().emit_err(errors::IntToWide {
574                    span,
575                    metadata,
576                    expr_ty,
577                    cast_ty,
578                    expr_if_nightly,
579                    known_wide,
580                });
581            }
582            CastError::UnknownCastPtrKind | CastError::UnknownExprPtrKind => {
583                let unknown_cast_to = match e {
584                    CastError::UnknownCastPtrKind => true,
585                    CastError::UnknownExprPtrKind => false,
586                    e => unreachable!("control flow means we should never encounter a {e:?}"),
587                };
588                let (span, sub) = if unknown_cast_to {
589                    (self.cast_span, errors::CastUnknownPointerSub::To(self.cast_span))
590                } else {
591                    (self.cast_span, errors::CastUnknownPointerSub::From(self.span))
592                };
593                fcx.dcx().emit_err(errors::CastUnknownPointer { span, to: unknown_cast_to, sub });
594            }
595            CastError::ForeignNonExhaustiveAdt => {
596                make_invalid_casting_error(
597                    self.span,
598                    self.expr_ty,
599                    self.cast_ty,
600                    fcx,
601                )
602                .with_note("cannot cast an enum with a non-exhaustive variant when it's defined in another crate")
603                .emit();
604            }
605            CastError::PtrPtrAddingAutoTrait(added) => {
606                fcx.dcx().emit_err(errors::PtrCastAddAutoToObject {
607                    span: self.span,
608                    traits_len: added.len(),
609                    traits: {
610                        let mut traits: Vec<_> = added
611                            .into_iter()
612                            .map(|trait_did| fcx.tcx.def_path_str(trait_did))
613                            .collect();
614
615                        traits.sort();
616                        traits.into()
617                    },
618                });
619            }
620        }
621    }
622
623    fn report_cast_to_unsized_type(&self, fcx: &FnCtxt<'a, 'tcx>) -> ErrorGuaranteed {
624        if let Err(err) = self.cast_ty.error_reported() {
625            return err;
626        }
627        if let Err(err) = self.expr_ty.error_reported() {
628            return err;
629        }
630
631        let tstr = fcx.ty_to_string(self.cast_ty);
632        let mut err = type_error_struct!(
633            fcx.dcx(),
634            self.span,
635            self.expr_ty,
636            E0620,
637            "cast to unsized type: `{}` as `{}`",
638            fcx.resolve_vars_if_possible(self.expr_ty),
639            tstr
640        );
641        match self.expr_ty.kind() {
642            ty::Ref(_, _, mt) => {
643                let mtstr = mt.prefix_str();
644                err.span_suggestion_verbose(
645                    self.cast_span.shrink_to_lo(),
646                    "consider casting to a reference instead",
647                    format!("&{mtstr}"),
648                    Applicability::MachineApplicable,
649                );
650            }
651            ty::Adt(def, ..) if def.is_box() => {
652                err.multipart_suggestion(
653                    "you can cast to a `Box` instead",
654                    vec![
655                        (self.cast_span.shrink_to_lo(), "Box<".to_string()),
656                        (self.cast_span.shrink_to_hi(), ">".to_string()),
657                    ],
658                    Applicability::MachineApplicable,
659                );
660            }
661            _ => {
662                err.span_help(self.expr_span, "consider using a box or reference as appropriate");
663            }
664        }
665        err.emit()
666    }
667
668    fn trivial_cast_lint(&self, fcx: &FnCtxt<'a, 'tcx>) {
669        let (numeric, lint) = if self.cast_ty.is_numeric() && self.expr_ty.is_numeric() {
670            (true, lint::builtin::TRIVIAL_NUMERIC_CASTS)
671        } else {
672            (false, lint::builtin::TRIVIAL_CASTS)
673        };
674        let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
675        let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
676        fcx.tcx.emit_node_span_lint(
677            lint,
678            self.expr.hir_id,
679            self.span,
680            errors::TrivialCast { numeric, expr_ty, cast_ty },
681        );
682    }
683
684    #[instrument(skip(fcx), level = "debug")]
685    pub(crate) fn check(mut self, fcx: &FnCtxt<'a, 'tcx>) {
686        self.expr_ty = fcx.structurally_resolve_type(self.expr_span, self.expr_ty);
687        self.cast_ty = fcx.structurally_resolve_type(self.cast_span, self.cast_ty);
688
689        debug!("check_cast({}, {:?} as {:?})", self.expr.hir_id, self.expr_ty, self.cast_ty);
690
691        if !fcx.type_is_sized_modulo_regions(fcx.param_env, self.cast_ty)
692            && !self.cast_ty.has_infer_types()
693        {
694            self.report_cast_to_unsized_type(fcx);
695        } else if self.expr_ty.references_error() || self.cast_ty.references_error() {
696            // No sense in giving duplicate error messages
697        } else {
698            match self.try_coercion_cast(fcx) {
699                Ok(()) => {
700                    if self.expr_ty.is_raw_ptr() && self.cast_ty.is_raw_ptr() {
701                        // When casting a raw pointer to another raw pointer, we cannot convert the cast into
702                        // a coercion because the pointee types might only differ in regions, which HIR typeck
703                        // cannot distinguish. This would cause us to erroneously discard a cast which will
704                        // lead to a borrowck error like #113257.
705                        // We still did a coercion above to unify inference variables for `ptr as _` casts.
706                        // This does cause us to miss some trivial casts in the trivial cast lint.
707                        debug!(" -> PointerCast");
708                    } else {
709                        self.trivial_cast_lint(fcx);
710                        debug!(" -> CoercionCast");
711                        fcx.typeck_results
712                            .borrow_mut()
713                            .set_coercion_cast(self.expr.hir_id.local_id);
714                    }
715                }
716                Err(_) => {
717                    match self.do_check(fcx) {
718                        Ok(k) => {
719                            debug!(" -> {:?}", k);
720                        }
721                        Err(e) => self.report_cast_error(fcx, e),
722                    };
723                }
724            };
725        }
726    }
727    /// Checks a cast, and report an error if one exists. In some cases, this
728    /// can return Ok and create type errors in the fcx rather than returning
729    /// directly. coercion-cast is handled in check instead of here.
730    fn do_check(&self, fcx: &FnCtxt<'a, 'tcx>) -> Result<CastKind, CastError<'tcx>> {
731        use rustc_middle::ty::cast::CastTy::*;
732        use rustc_middle::ty::cast::IntTy::*;
733
734        let (t_from, t_cast) = match (CastTy::from_ty(self.expr_ty), CastTy::from_ty(self.cast_ty))
735        {
736            (Some(t_from), Some(t_cast)) => (t_from, t_cast),
737            // Function item types may need to be reified before casts.
738            (None, Some(t_cast)) => {
739                match *self.expr_ty.kind() {
740                    ty::FnDef(..) => {
741                        // Attempt a coercion to a fn pointer type.
742                        let f = fcx.normalize(self.expr_span, self.expr_ty.fn_sig(fcx.tcx));
743                        let res = fcx.coerce(
744                            self.expr,
745                            self.expr_ty,
746                            Ty::new_fn_ptr(fcx.tcx, f),
747                            AllowTwoPhase::No,
748                            None,
749                        );
750                        if let Err(TypeError::IntrinsicCast) = res {
751                            return Err(CastError::IllegalCast);
752                        }
753                        if res.is_err() {
754                            return Err(CastError::NonScalar);
755                        }
756                        (FnPtr, t_cast)
757                    }
758                    // Special case some errors for references, and check for
759                    // array-ptr-casts. `Ref` is not a CastTy because the cast
760                    // is split into a coercion to a pointer type, followed by
761                    // a cast.
762                    ty::Ref(_, inner_ty, mutbl) => {
763                        return match t_cast {
764                            Int(_) | Float => match *inner_ty.kind() {
765                                ty::Int(_)
766                                | ty::Uint(_)
767                                | ty::Float(_)
768                                | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(_)) => {
769                                    Err(CastError::NeedDeref)
770                                }
771                                _ => Err(CastError::NeedViaPtr),
772                            },
773                            // array-ptr-cast
774                            Ptr(mt) => {
775                                if !fcx.type_is_sized_modulo_regions(fcx.param_env, mt.ty) {
776                                    return Err(CastError::IllegalCast);
777                                }
778                                self.check_ref_cast(fcx, TypeAndMut { mutbl, ty: inner_ty }, mt)
779                            }
780                            _ => Err(CastError::NonScalar),
781                        };
782                    }
783                    _ => return Err(CastError::NonScalar),
784                }
785            }
786            _ => return Err(CastError::NonScalar),
787        };
788        if let ty::Adt(adt_def, _) = *self.expr_ty.kind()
789            && !adt_def.did().is_local()
790            && adt_def.variants().iter().any(VariantDef::is_field_list_non_exhaustive)
791        {
792            return Err(CastError::ForeignNonExhaustiveAdt);
793        }
794        match (t_from, t_cast) {
795            // These types have invariants! can't cast into them.
796            (_, Int(CEnum) | FnPtr) => Err(CastError::NonScalar),
797
798            // * -> Bool
799            (_, Int(Bool)) => Err(CastError::CastToBool),
800
801            // * -> Char
802            (Int(U(ty::UintTy::U8)), Int(Char)) => Ok(CastKind::U8CharCast), // u8-char-cast
803            (_, Int(Char)) => Err(CastError::CastToChar),
804
805            // prim -> float,ptr
806            (Int(Bool) | Int(CEnum) | Int(Char), Float) => Err(CastError::NeedViaInt),
807
808            (Int(Bool) | Int(CEnum) | Int(Char) | Float, Ptr(_)) | (Ptr(_) | FnPtr, Float) => {
809                Err(CastError::IllegalCast)
810            }
811
812            // ptr -> ptr
813            (Ptr(m_e), Ptr(m_c)) => self.check_ptr_ptr_cast(fcx, m_e, m_c), // ptr-ptr-cast
814
815            // ptr-addr-cast
816            (Ptr(m_expr), Int(t_c)) => {
817                self.lossy_provenance_ptr2int_lint(fcx, t_c);
818                self.check_ptr_addr_cast(fcx, m_expr)
819            }
820            (FnPtr, Int(_)) => {
821                // FIXME(#95489): there should eventually be a lint for these casts
822                Ok(CastKind::FnPtrAddrCast)
823            }
824            // addr-ptr-cast
825            (Int(_), Ptr(mt)) => {
826                self.fuzzy_provenance_int2ptr_lint(fcx);
827                self.check_addr_ptr_cast(fcx, mt)
828            }
829            // fn-ptr-cast
830            (FnPtr, Ptr(mt)) => self.check_fptr_ptr_cast(fcx, mt),
831
832            // prim -> prim
833            (Int(CEnum), Int(_)) => {
834                self.err_if_cenum_impl_drop(fcx);
835                Ok(CastKind::EnumCast)
836            }
837            (Int(Char) | Int(Bool), Int(_)) => Ok(CastKind::PrimIntCast),
838
839            (Int(_) | Float, Int(_) | Float) => Ok(CastKind::NumericCast),
840        }
841    }
842
843    fn check_ptr_ptr_cast(
844        &self,
845        fcx: &FnCtxt<'a, 'tcx>,
846        m_src: ty::TypeAndMut<'tcx>,
847        m_dst: ty::TypeAndMut<'tcx>,
848    ) -> Result<CastKind, CastError<'tcx>> {
849        debug!("check_ptr_ptr_cast m_src={m_src:?} m_dst={m_dst:?}");
850        // ptr-ptr cast. metadata must match.
851
852        let src_kind = fcx.tcx.erase_and_anonymize_regions(fcx.pointer_kind(m_src.ty, self.span)?);
853        let dst_kind = fcx.tcx.erase_and_anonymize_regions(fcx.pointer_kind(m_dst.ty, self.span)?);
854
855        // We can't cast if target pointer kind is unknown
856        let Some(dst_kind) = dst_kind else {
857            return Err(CastError::UnknownCastPtrKind);
858        };
859
860        // Cast to thin pointer is OK
861        if dst_kind == PointerKind::Thin {
862            return Ok(CastKind::PtrPtrCast);
863        }
864
865        // We can't cast to wide pointer if source pointer kind is unknown
866        let Some(src_kind) = src_kind else {
867            return Err(CastError::UnknownCastPtrKind);
868        };
869
870        match (src_kind, dst_kind) {
871            // thin -> fat? report invalid cast (don't complain about vtable kinds)
872            (PointerKind::Thin, _) => Err(CastError::SizedUnsizedCast),
873
874            // trait object -> trait object? need to do additional checks
875            (PointerKind::VTable(src_tty), PointerKind::VTable(dst_tty)) => {
876                match (src_tty.principal(), dst_tty.principal()) {
877                    // A<dyn Src<...> + SrcAuto> -> B<dyn Dst<...> + DstAuto>. need to make sure
878                    // - `Src` and `Dst` traits are the same
879                    // - traits have the same generic arguments
880                    // - projections are the same
881                    // - `SrcAuto` (+auto traits implied by `Src`) is a superset of `DstAuto`
882                    //
883                    // Note that trait upcasting goes through a different mechanism (`coerce_unsized`)
884                    // and is unaffected by this check.
885                    (Some(src_principal), Some(_)) => {
886                        let tcx = fcx.tcx;
887
888                        // We need to reconstruct trait object types.
889                        // `m_src` and `m_dst` won't work for us here because they will potentially
890                        // contain wrappers, which we do not care about.
891                        //
892                        // e.g. we want to allow `dyn T -> (dyn T,)`, etc.
893                        //
894                        // We also need to skip auto traits to emit an FCW and not an error.
895                        let src_obj = Ty::new_dynamic(
896                            tcx,
897                            tcx.mk_poly_existential_predicates(
898                                &src_tty.without_auto_traits().collect::<Vec<_>>(),
899                            ),
900                            tcx.lifetimes.re_erased,
901                        );
902                        let dst_obj = Ty::new_dynamic(
903                            tcx,
904                            tcx.mk_poly_existential_predicates(
905                                &dst_tty.without_auto_traits().collect::<Vec<_>>(),
906                            ),
907                            tcx.lifetimes.re_erased,
908                        );
909
910                        // `dyn Src = dyn Dst`, this checks for matching traits/generics/projections
911                        // This is `fcx.demand_eqtype`, but inlined to give a better error.
912                        let cause = fcx.misc(self.span);
913                        if fcx
914                            .at(&cause, fcx.param_env)
915                            .eq(DefineOpaqueTypes::Yes, src_obj, dst_obj)
916                            .map(|infer_ok| fcx.register_infer_ok_obligations(infer_ok))
917                            .is_err()
918                        {
919                            return Err(CastError::DifferingKinds { src_kind, dst_kind });
920                        }
921
922                        // Check that `SrcAuto` (+auto traits implied by `Src`) is a superset of `DstAuto`.
923                        // Emit an FCW otherwise.
924                        let src_auto: FxHashSet<_> = src_tty
925                            .auto_traits()
926                            .chain(
927                                elaborate::supertrait_def_ids(tcx, src_principal.def_id())
928                                    .filter(|def_id| tcx.trait_is_auto(*def_id)),
929                            )
930                            .collect();
931
932                        let added = dst_tty
933                            .auto_traits()
934                            .filter(|trait_did| !src_auto.contains(trait_did))
935                            .collect::<Vec<_>>();
936
937                        if !added.is_empty() {
938                            return Err(CastError::PtrPtrAddingAutoTrait(added));
939                        }
940
941                        Ok(CastKind::PtrPtrCast)
942                    }
943
944                    // dyn Auto -> dyn Auto'? ok.
945                    (None, None) => Ok(CastKind::PtrPtrCast),
946
947                    // dyn Trait -> dyn Auto? not ok (for now).
948                    //
949                    // Although dropping the principal is already allowed for unsizing coercions
950                    // (e.g. `*const (dyn Trait + Auto)` to `*const dyn Auto`), dropping it is
951                    // currently **NOT** allowed for (non-coercion) ptr-to-ptr casts (e.g
952                    // `*const Foo` to `*const Bar` where `Foo` has a `dyn Trait + Auto` tail
953                    // and `Bar` has a `dyn Auto` tail), because the underlying MIR operations
954                    // currently work very differently:
955                    //
956                    // * A MIR unsizing coercion on raw pointers to trait objects (`*const dyn Src`
957                    //   to `*const dyn Dst`) is currently equivalent to downcasting the source to
958                    //   the concrete sized type that it was originally unsized from first (via a
959                    //   ptr-to-ptr cast from `*const Src` to `*const T` with `T: Sized`) and then
960                    //   unsizing this thin pointer to the target type (unsizing `*const T` to
961                    //   `*const Dst`). In particular, this means that the pointer's metadata
962                    //   (vtable) will semantically change, e.g. for const eval and miri, even
963                    //   though the vtables will always be merged for codegen.
964                    //
965                    // * A MIR ptr-to-ptr cast is currently equivalent to a transmute and does not
966                    //   change the pointer metadata (vtable) at all.
967                    //
968                    // In addition to this potentially surprising difference between coercion and
969                    // non-coercion casts, casting away the principal with a MIR ptr-to-ptr cast
970                    // is currently considered undefined behavior:
971                    //
972                    // As a validity invariant of pointers to trait objects, we currently require
973                    // that the principal of the vtable in the pointer metadata exactly matches
974                    // the principal of the pointee type, where "no principal" is also considered
975                    // a kind of principal.
976                    (Some(_), None) => Err(CastError::DifferingKinds { src_kind, dst_kind }),
977
978                    // dyn Auto -> dyn Trait? not ok.
979                    (None, Some(_)) => Err(CastError::DifferingKinds { src_kind, dst_kind }),
980                }
981            }
982
983            // fat -> fat? metadata kinds must match
984            (src_kind, dst_kind) if src_kind == dst_kind => Ok(CastKind::PtrPtrCast),
985
986            (_, _) => Err(CastError::DifferingKinds { src_kind, dst_kind }),
987        }
988    }
989
990    fn check_fptr_ptr_cast(
991        &self,
992        fcx: &FnCtxt<'a, 'tcx>,
993        m_cast: ty::TypeAndMut<'tcx>,
994    ) -> Result<CastKind, CastError<'tcx>> {
995        // fptr-ptr cast. must be to thin ptr
996
997        match fcx.pointer_kind(m_cast.ty, self.span)? {
998            None => Err(CastError::UnknownCastPtrKind),
999            Some(PointerKind::Thin) => Ok(CastKind::FnPtrPtrCast),
1000            _ => Err(CastError::IllegalCast),
1001        }
1002    }
1003
1004    fn check_ptr_addr_cast(
1005        &self,
1006        fcx: &FnCtxt<'a, 'tcx>,
1007        m_expr: ty::TypeAndMut<'tcx>,
1008    ) -> Result<CastKind, CastError<'tcx>> {
1009        // ptr-addr cast. must be from thin ptr
1010
1011        match fcx.pointer_kind(m_expr.ty, self.span)? {
1012            None => Err(CastError::UnknownExprPtrKind),
1013            Some(PointerKind::Thin) => Ok(CastKind::PtrAddrCast),
1014            _ => Err(CastError::NeedViaThinPtr),
1015        }
1016    }
1017
1018    fn check_ref_cast(
1019        &self,
1020        fcx: &FnCtxt<'a, 'tcx>,
1021        mut m_expr: ty::TypeAndMut<'tcx>,
1022        mut m_cast: ty::TypeAndMut<'tcx>,
1023    ) -> Result<CastKind, CastError<'tcx>> {
1024        // array-ptr-cast: allow mut-to-mut, mut-to-const, const-to-const
1025        m_expr.ty = fcx.try_structurally_resolve_type(self.expr_span, m_expr.ty);
1026        m_cast.ty = fcx.try_structurally_resolve_type(self.cast_span, m_cast.ty);
1027
1028        if m_expr.mutbl >= m_cast.mutbl
1029            && let ty::Array(ety, _) = m_expr.ty.kind()
1030            && fcx.can_eq(fcx.param_env, *ety, m_cast.ty)
1031        {
1032            // Due to historical reasons we allow directly casting references of
1033            // arrays into raw pointers of their element type.
1034
1035            // Coerce to a raw pointer so that we generate RawPtr in MIR.
1036            let array_ptr_type = Ty::new_ptr(fcx.tcx, m_expr.ty, m_expr.mutbl);
1037            fcx.coerce(self.expr, self.expr_ty, array_ptr_type, AllowTwoPhase::No, None)
1038                .unwrap_or_else(|_| {
1039                    bug!(
1040                        "could not cast from reference to array to pointer to array ({:?} to {:?})",
1041                        self.expr_ty,
1042                        array_ptr_type,
1043                    )
1044                });
1045
1046            // this will report a type mismatch if needed
1047            fcx.demand_eqtype(self.span, *ety, m_cast.ty);
1048            return Ok(CastKind::ArrayPtrCast);
1049        }
1050
1051        Err(CastError::IllegalCast)
1052    }
1053
1054    fn check_addr_ptr_cast(
1055        &self,
1056        fcx: &FnCtxt<'a, 'tcx>,
1057        m_cast: TypeAndMut<'tcx>,
1058    ) -> Result<CastKind, CastError<'tcx>> {
1059        // ptr-addr cast. pointer must be thin.
1060        match fcx.pointer_kind(m_cast.ty, self.span)? {
1061            None => Err(CastError::UnknownCastPtrKind),
1062            Some(PointerKind::Thin) => Ok(CastKind::AddrPtrCast),
1063            Some(PointerKind::VTable(_)) => Err(CastError::IntToWideCast(Some("a vtable"))),
1064            Some(PointerKind::Length) => Err(CastError::IntToWideCast(Some("a length"))),
1065            Some(PointerKind::OfAlias(_) | PointerKind::OfParam(_)) => {
1066                Err(CastError::IntToWideCast(None))
1067            }
1068        }
1069    }
1070
1071    fn try_coercion_cast(&self, fcx: &FnCtxt<'a, 'tcx>) -> Result<(), ty::error::TypeError<'tcx>> {
1072        match fcx.coerce(self.expr, self.expr_ty, self.cast_ty, AllowTwoPhase::No, None) {
1073            Ok(_) => Ok(()),
1074            Err(err) => Err(err),
1075        }
1076    }
1077
1078    fn err_if_cenum_impl_drop(&self, fcx: &FnCtxt<'a, 'tcx>) {
1079        if let ty::Adt(d, _) = self.expr_ty.kind()
1080            && d.has_dtor(fcx.tcx)
1081        {
1082            let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
1083            let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
1084
1085            fcx.dcx().emit_err(errors::CastEnumDrop { span: self.span, expr_ty, cast_ty });
1086        }
1087    }
1088
1089    fn lossy_provenance_ptr2int_lint(&self, fcx: &FnCtxt<'a, 'tcx>, t_c: ty::cast::IntTy) {
1090        let expr_prec = fcx.precedence(self.expr);
1091        let needs_parens = expr_prec < ExprPrecedence::Unambiguous;
1092
1093        let needs_cast = !matches!(t_c, ty::cast::IntTy::U(ty::UintTy::Usize));
1094        let cast_span = self.expr_span.shrink_to_hi().to(self.cast_span);
1095        let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
1096        let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
1097        let expr_span = self.expr_span.shrink_to_lo();
1098        let sugg = match (needs_parens, needs_cast) {
1099            (true, true) => errors::LossyProvenancePtr2IntSuggestion::NeedsParensCast {
1100                expr_span,
1101                cast_span,
1102                cast_ty,
1103            },
1104            (true, false) => {
1105                errors::LossyProvenancePtr2IntSuggestion::NeedsParens { expr_span, cast_span }
1106            }
1107            (false, true) => {
1108                errors::LossyProvenancePtr2IntSuggestion::NeedsCast { cast_span, cast_ty }
1109            }
1110            (false, false) => errors::LossyProvenancePtr2IntSuggestion::Other { cast_span },
1111        };
1112
1113        let lint = errors::LossyProvenancePtr2Int { expr_ty, cast_ty, sugg };
1114        fcx.tcx.emit_node_span_lint(
1115            lint::builtin::LOSSY_PROVENANCE_CASTS,
1116            self.expr.hir_id,
1117            self.span,
1118            lint,
1119        );
1120    }
1121
1122    fn fuzzy_provenance_int2ptr_lint(&self, fcx: &FnCtxt<'a, 'tcx>) {
1123        let sugg = errors::LossyProvenanceInt2PtrSuggestion {
1124            lo: self.expr_span.shrink_to_lo(),
1125            hi: self.expr_span.shrink_to_hi().to(self.cast_span),
1126        };
1127        let expr_ty = fcx.resolve_vars_if_possible(self.expr_ty);
1128        let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
1129        let lint = errors::LossyProvenanceInt2Ptr { expr_ty, cast_ty, sugg };
1130        fcx.tcx.emit_node_span_lint(
1131            lint::builtin::FUZZY_PROVENANCE_CASTS,
1132            self.expr.hir_id,
1133            self.span,
1134            lint,
1135        );
1136    }
1137
1138    /// Attempt to suggest using `.is_empty` when trying to cast from a
1139    /// collection type to a boolean.
1140    fn try_suggest_collection_to_bool(&self, fcx: &FnCtxt<'a, 'tcx>, err: &mut Diag<'_>) {
1141        if self.cast_ty.is_bool() {
1142            let derefed = fcx
1143                .autoderef(self.expr_span, self.expr_ty)
1144                .silence_errors()
1145                .find(|t| matches!(t.0.kind(), ty::Str | ty::Slice(..)));
1146
1147            if let Some((deref_ty, _)) = derefed {
1148                // Give a note about what the expr derefs to.
1149                if deref_ty != self.expr_ty.peel_refs() {
1150                    err.subdiagnostic(errors::DerefImplsIsEmpty { span: self.expr_span, deref_ty });
1151                }
1152
1153                // Create a multipart suggestion: add `!` and `.is_empty()` in
1154                // place of the cast.
1155                err.subdiagnostic(errors::UseIsEmpty {
1156                    lo: self.expr_span.shrink_to_lo(),
1157                    hi: self.span.with_lo(self.expr_span.hi()),
1158                    expr_ty: self.expr_ty,
1159                });
1160            }
1161        }
1162    }
1163}
rustc_hir_typeck/cast.rs

rustc_hir_typeck/
cast.rs
