1 use crate::{FnCtxt, RawTy}
;
3 use rustc_data_structures
::fx
::FxHashMap
;
5 pluralize
, struct_span_err
, Applicability
, Diagnostic
, DiagnosticBuilder
, ErrorGuaranteed
,
9 use rustc_hir
::def
::{CtorKind, DefKind, Res}
;
10 use rustc_hir
::pat_util
::EnumerateAndAdjustIterator
;
11 use rustc_hir
::{HirId, Pat, PatKind}
;
12 use rustc_infer
::infer
;
13 use rustc_infer
::infer
::type_variable
::{TypeVariableOrigin, TypeVariableOriginKind}
;
14 use rustc_middle
::middle
::stability
::EvalResult
;
15 use rustc_middle
::ty
::{self, Adt, BindingMode, Ty, TypeVisitable}
;
16 use rustc_session
::lint
::builtin
::NON_EXHAUSTIVE_OMITTED_PATTERNS
;
17 use rustc_span
::hygiene
::DesugaringKind
;
18 use rustc_span
::lev_distance
::find_best_match_for_name
;
19 use rustc_span
::source_map
::{Span, Spanned}
;
20 use rustc_span
::symbol
::{kw, sym, Ident}
;
21 use rustc_span
::{BytePos, DUMMY_SP}
;
22 use rustc_trait_selection
::traits
::{ObligationCause, Pattern}
;
26 use std
::collections
::hash_map
::Entry
::{Occupied, Vacant}
;
28 use super::report_unexpected_variant_res
;
30 const CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ
: &str = "\
31 This error indicates that a pointer to a trait type cannot be implicitly dereferenced by a \
32 pattern. Every trait defines a type, but because the size of trait implementors isn't fixed, \
33 this type has no compile-time size. Therefore, all accesses to trait types must be through \
34 pointers. If you encounter this error you should try to avoid dereferencing the pointer.
36 You can read more about trait objects in the Trait Objects section of the Reference: \
37 https://doc.rust-lang.org/reference/types.html#trait-objects";
39 /// Information about the expected type at the top level of type checking a pattern.
41 /// **NOTE:** This is only for use by diagnostics. Do NOT use for type checking logic!
42 #[derive(Copy, Clone)]
43 struct TopInfo
<'tcx
> {
44 /// The `expected` type at the top level of type checking a pattern.
46 /// Was the origin of the `span` from a scrutinee expression?
48 /// Otherwise there is no scrutinee and it could be e.g. from the type of a formal parameter.
50 /// The span giving rise to the `expected` type, if one could be provided.
52 /// If `origin_expr` is `true`, then this is the span of the scrutinee as in:
54 /// - `match scrutinee { ... }`
55 /// - `let _ = scrutinee;`
57 /// This is used to point to add context in type errors.
58 /// In the following example, `span` corresponds to the `a + b` expression:
61 /// error[E0308]: mismatched types
62 /// --> src/main.rs:L:C
64 /// L | let temp: usize = match a + b {
65 /// | ----- this expression has type `usize`
66 /// L | Ok(num) => num,
67 /// | ^^^^^^^ expected `usize`, found enum `std::result::Result`
69 /// = note: expected type `usize`
70 /// found type `std::result::Result<_, _>`
75 impl<'tcx
> FnCtxt
<'_
, 'tcx
> {
76 fn pattern_cause(&self, ti
: TopInfo
<'tcx
>, cause_span
: Span
) -> ObligationCause
<'tcx
> {
77 let code
= Pattern { span: ti.span, root_ty: ti.expected, origin_expr: ti.origin_expr }
;
78 self.cause(cause_span
, code
)
81 fn demand_eqtype_pat_diag(
87 ) -> Option
<DiagnosticBuilder
<'tcx
, ErrorGuaranteed
>> {
88 self.demand_eqtype_with_origin(&self.pattern_cause(ti
, cause_span
), expected
, actual
)
98 if let Some(mut err
) = self.demand_eqtype_pat_diag(cause_span
, expected
, actual
, ti
) {
104 const INITIAL_BM
: BindingMode
= BindingMode
::BindByValue(hir
::Mutability
::Not
);
106 /// Mode for adjusting the expected type and binding mode.
108 /// Peel off all immediate reference types.
110 /// Reset binding mode to the initial mode.
112 /// Pass on the input binding mode and expected type.
116 impl<'a
, 'tcx
> FnCtxt
<'a
, 'tcx
> {
117 /// Type check the given top level pattern against the `expected` type.
119 /// If a `Some(span)` is provided and `origin_expr` holds,
120 /// then the `span` represents the scrutinee's span.
121 /// The scrutinee is found in e.g. `match scrutinee { ... }` and `let pat = scrutinee;`.
123 /// Otherwise, `Some(span)` represents the span of a type expression
124 /// which originated the `expected` type.
125 pub fn check_pat_top(
127 pat
: &'tcx Pat
<'tcx
>,
132 let info
= TopInfo { expected, origin_expr, span }
;
133 self.check_pat(pat
, expected
, INITIAL_BM
, info
);
136 /// Type check the given `pat` against the `expected` type
137 /// with the provided `def_bm` (default binding mode).
139 /// Outside of this module, `check_pat_top` should always be used.
140 /// Conversely, inside this module, `check_pat_top` should never be used.
141 #[instrument(level = "debug", skip(self, ti))]
144 pat
: &'tcx Pat
<'tcx
>,
149 let path_res
= match &pat
.kind
{
150 PatKind
::Path(qpath
) => {
151 Some(self.resolve_ty_and_res_fully_qualified_call(qpath
, pat
.hir_id
, pat
.span
))
155 let adjust_mode
= self.calc_adjust_mode(pat
, path_res
.map(|(res
, ..)| res
));
156 let (expected
, def_bm
) = self.calc_default_binding_mode(pat
, expected
, def_bm
, adjust_mode
);
158 let ty
= match pat
.kind
{
159 PatKind
::Wild
=> expected
,
160 PatKind
::Lit(lt
) => self.check_pat_lit(pat
.span
, lt
, expected
, ti
),
161 PatKind
::Range(lhs
, rhs
, _
) => self.check_pat_range(pat
.span
, lhs
, rhs
, expected
, ti
),
162 PatKind
::Binding(ba
, var_id
, _
, sub
) => {
163 self.check_pat_ident(pat
, ba
, var_id
, sub
, expected
, def_bm
, ti
)
165 PatKind
::TupleStruct(ref qpath
, subpats
, ddpos
) => {
166 self.check_pat_tuple_struct(pat
, qpath
, subpats
, ddpos
, expected
, def_bm
, ti
)
168 PatKind
::Path(ref qpath
) => {
169 self.check_pat_path(pat
, qpath
, path_res
.unwrap(), expected
, ti
)
171 PatKind
::Struct(ref qpath
, fields
, has_rest_pat
) => {
172 self.check_pat_struct(pat
, qpath
, fields
, has_rest_pat
, expected
, def_bm
, ti
)
174 PatKind
::Or(pats
) => {
176 self.check_pat(pat
, expected
, def_bm
, ti
);
180 PatKind
::Tuple(elements
, ddpos
) => {
181 self.check_pat_tuple(pat
.span
, elements
, ddpos
, expected
, def_bm
, ti
)
183 PatKind
::Box(inner
) => self.check_pat_box(pat
.span
, inner
, expected
, def_bm
, ti
),
184 PatKind
::Ref(inner
, mutbl
) => {
185 self.check_pat_ref(pat
, inner
, mutbl
, expected
, def_bm
, ti
)
187 PatKind
::Slice(before
, slice
, after
) => {
188 self.check_pat_slice(pat
.span
, before
, slice
, after
, expected
, def_bm
, ti
)
192 self.write_ty(pat
.hir_id
, ty
);
194 // (note_1): In most of the cases where (note_1) is referenced
195 // (literals and constants being the exception), we relate types
196 // using strict equality, even though subtyping would be sufficient.
197 // There are a few reasons for this, some of which are fairly subtle
198 // and which cost me (nmatsakis) an hour or two debugging to remember,
199 // so I thought I'd write them down this time.
201 // 1. There is no loss of expressiveness here, though it does
202 // cause some inconvenience. What we are saying is that the type
203 // of `x` becomes *exactly* what is expected. This can cause unnecessary
204 // errors in some cases, such as this one:
207 // fn foo<'x>(x: &'x i32) {
214 // The reason we might get an error is that `z` might be
215 // assigned a type like `&'x i32`, and then we would have
216 // a problem when we try to assign `&a` to `z`, because
217 // the lifetime of `&a` (i.e., the enclosing block) is
218 // shorter than `'x`.
220 // HOWEVER, this code works fine. The reason is that the
221 // expected type here is whatever type the user wrote, not
222 // the initializer's type. In this case the user wrote
223 // nothing, so we are going to create a type variable `Z`.
224 // Then we will assign the type of the initializer (`&'x i32`)
225 // as a subtype of `Z`: `&'x i32 <: Z`. And hence we
226 // will instantiate `Z` as a type `&'0 i32` where `'0` is
227 // a fresh region variable, with the constraint that `'x : '0`.
228 // So basically we're all set.
230 // Note that there are two tests to check that this remains true
231 // (`regions-reassign-{match,let}-bound-pointer.rs`).
233 // 2. Things go horribly wrong if we use subtype. The reason for
234 // THIS is a fairly subtle case involving bound regions. See the
235 // `givens` field in `region_constraints`, as well as the test
236 // `regions-relate-bound-regions-on-closures-to-inference-variables.rs`,
237 // for details. Short version is that we must sometimes detect
238 // relationships between specific region variables and regions
239 // bound in a closure signature, and that detection gets thrown
240 // off when we substitute fresh region variables here to enable
244 /// Compute the new expected type and default binding mode from the old ones
245 /// as well as the pattern form we are currently checking.
246 fn calc_default_binding_mode(
248 pat
: &'tcx Pat
<'tcx
>,
251 adjust_mode
: AdjustMode
,
252 ) -> (Ty
<'tcx
>, BindingMode
) {
254 AdjustMode
::Pass
=> (expected
, def_bm
),
255 AdjustMode
::Reset
=> (expected
, INITIAL_BM
),
256 AdjustMode
::Peel
=> self.peel_off_references(pat
, expected
, def_bm
),
260 /// How should the binding mode and expected type be adjusted?
262 /// When the pattern is a path pattern, `opt_path_res` must be `Some(res)`.
263 fn calc_adjust_mode(&self, pat
: &'tcx Pat
<'tcx
>, opt_path_res
: Option
<Res
>) -> AdjustMode
{
264 // When we perform destructuring assignment, we disable default match bindings, which are
265 // unintuitive in this context.
266 if !pat
.default_binding_modes
{
267 return AdjustMode
::Reset
;
270 // Type checking these product-like types successfully always require
271 // that the expected type be of those types and not reference types.
273 | PatKind
::TupleStruct(..)
277 | PatKind
::Slice(..) => AdjustMode
::Peel
,
278 // String and byte-string literals result in types `&str` and `&[u8]` respectively.
279 // All other literals result in non-reference types.
280 // As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo {}`.
282 // Call `resolve_vars_if_possible` here for inline const blocks.
283 PatKind
::Lit(lt
) => match self.resolve_vars_if_possible(self.check_expr(lt
)).kind() {
284 ty
::Ref(..) => AdjustMode
::Pass
,
285 _
=> AdjustMode
::Peel
,
287 PatKind
::Path(_
) => match opt_path_res
.unwrap() {
288 // These constants can be of a reference type, e.g. `const X: &u8 = &0;`.
289 // Peeling the reference types too early will cause type checking failures.
290 // Although it would be possible to *also* peel the types of the constants too.
291 Res
::Def(DefKind
::Const
| DefKind
::AssocConst
, _
) => AdjustMode
::Pass
,
292 // In the `ValueNS`, we have `SelfCtor(..) | Ctor(_, Const), _)` remaining which
293 // could successfully compile. The former being `Self` requires a unit struct.
294 // In either case, and unlike constants, the pattern itself cannot be
295 // a reference type wherefore peeling doesn't give up any expressiveness.
296 _
=> AdjustMode
::Peel
,
298 // When encountering a `& mut? pat` pattern, reset to "by value".
299 // This is so that `x` and `y` here are by value, as they appear to be:
302 // match &(&22, &44) {
308 PatKind
::Ref(..) => AdjustMode
::Reset
,
309 // A `_` pattern works with any expected type, so there's no need to do anything.
311 // Bindings also work with whatever the expected type is,
312 // and moreover if we peel references off, that will give us the wrong binding type.
313 // Also, we can have a subpattern `binding @ pat`.
314 // Each side of the `@` should be treated independently (like with OR-patterns).
315 | PatKind
::Binding(..)
316 // An OR-pattern just propagates to each individual alternative.
317 // This is maximally flexible, allowing e.g., `Some(mut x) | &Some(mut x)`.
318 // In that example, `Some(mut x)` results in `Peel` whereas `&Some(mut x)` in `Reset`.
319 | PatKind
::Or(_
) => AdjustMode
::Pass
,
323 /// Peel off as many immediately nested `& mut?` from the expected type as possible
324 /// and return the new expected type and binding default binding mode.
325 /// The adjustments vector, if non-empty is stored in a table.
326 fn peel_off_references(
328 pat
: &'tcx Pat
<'tcx
>,
330 mut def_bm
: BindingMode
,
331 ) -> (Ty
<'tcx
>, BindingMode
) {
332 let mut expected
= self.resolve_vars_with_obligations(expected
);
334 // Peel off as many `&` or `&mut` from the scrutinee type as possible. For example,
335 // for `match &&&mut Some(5)` the loop runs three times, aborting when it reaches
336 // the `Some(5)` which is not of type Ref.
338 // For each ampersand peeled off, update the binding mode and push the original
339 // type into the adjustments vector.
341 // See the examples in `ui/match-defbm*.rs`.
342 let mut pat_adjustments
= vec
![];
343 while let ty
::Ref(_
, inner_ty
, inner_mutability
) = *expected
.kind() {
344 debug
!("inspecting {:?}", expected
);
346 debug
!("current discriminant is Ref, inserting implicit deref");
347 // Preserve the reference type. We'll need it later during THIR lowering.
348 pat_adjustments
.push(expected
);
351 def_bm
= ty
::BindByReference(match def_bm
{
352 // If default binding mode is by value, make it `ref` or `ref mut`
353 // (depending on whether we observe `&` or `&mut`).
355 // When `ref mut`, stay a `ref mut` (on `&mut`) or downgrade to `ref` (on `&`).
356 ty
::BindByReference(hir
::Mutability
::Mut
) => inner_mutability
,
357 // Once a `ref`, always a `ref`.
358 // This is because a `& &mut` cannot mutate the underlying value.
359 ty
::BindByReference(m @ hir
::Mutability
::Not
) => m
,
363 if !pat_adjustments
.is_empty() {
364 debug
!("default binding mode is now {:?}", def_bm
);
368 .pat_adjustments_mut()
369 .insert(pat
.hir_id
, pat_adjustments
);
378 lt
: &hir
::Expr
<'tcx
>,
382 // We've already computed the type above (when checking for a non-ref pat),
383 // so avoid computing it again.
384 let ty
= self.node_ty(lt
.hir_id
);
386 // Byte string patterns behave the same way as array patterns
387 // They can denote both statically and dynamically-sized byte arrays.
389 if let hir
::ExprKind
::Lit(Spanned { node: ast::LitKind::ByteStr(..), .. }
) = lt
.kind
{
390 let expected
= self.structurally_resolved_type(span
, expected
);
391 if let ty
::Ref(_
, inner_ty
, _
) = expected
.kind()
392 && matches
!(inner_ty
.kind(), ty
::Slice(_
))
395 trace
!(?lt
.hir_id
.local_id
, "polymorphic byte string lit");
398 .treat_byte_string_as_slice
399 .insert(lt
.hir_id
.local_id
);
400 pat_ty
= tcx
.mk_imm_ref(tcx
.lifetimes
.re_static
, tcx
.mk_slice(tcx
.types
.u8));
404 if self.tcx
.features().string_deref_patterns
&& let hir
::ExprKind
::Lit(Spanned { node: ast::LitKind::Str(..), .. }
) = lt
.kind
{
406 let expected
= self.resolve_vars_if_possible(expected
);
407 pat_ty
= match expected
.kind() {
408 ty
::Adt(def
, _
) if Some(def
.did()) == tcx
.lang_items().string() => expected
,
409 ty
::Str
=> tcx
.mk_static_str(),
414 // Somewhat surprising: in this case, the subtyping relation goes the
415 // opposite way as the other cases. Actually what we really want is not
416 // a subtyping relation at all but rather that there exists a LUB
417 // (so that they can be compared). However, in practice, constants are
418 // always scalars or strings. For scalars subtyping is irrelevant,
419 // and for strings `ty` is type is `&'static str`, so if we say that
421 // &'static str <: expected
423 // then that's equivalent to there existing a LUB.
424 let cause
= self.pattern_cause(ti
, span
);
425 if let Some(mut err
) = self.demand_suptype_with_origin(&cause
, expected
, pat_ty
) {
429 // In the case of `if`- and `while`-expressions we've already checked
430 // that `scrutinee: bool`. We know that the pattern is `true`,
431 // so an error here would be a duplicate and from the wrong POV.
432 s
.is_desugaring(DesugaringKind
::CondTemporary
)
444 lhs
: Option
<&'tcx hir
::Expr
<'tcx
>>,
445 rhs
: Option
<&'tcx hir
::Expr
<'tcx
>>,
449 let calc_side
= |opt_expr
: Option
<&'tcx hir
::Expr
<'tcx
>>| match opt_expr
{
452 let ty
= self.check_expr(expr
);
453 // Check that the end-point is possibly of numeric or char type.
454 // The early check here is not for correctness, but rather better
455 // diagnostics (e.g. when `&str` is being matched, `expected` will
456 // be peeled to `str` while ty here is still `&str`, if we don't
457 // err early here, a rather confusing unification error will be
460 !(ty
.is_numeric() || ty
.is_char() || ty
.is_ty_var() || ty
.references_error());
461 Some((fail
, ty
, expr
.span
))
464 let mut lhs
= calc_side(lhs
);
465 let mut rhs
= calc_side(rhs
);
467 if let (Some((true, ..)), _
) | (_
, Some((true, ..))) = (lhs
, rhs
) {
468 // There exists a side that didn't meet our criteria that the end-point
469 // be of a numeric or char type, as checked in `calc_side` above.
470 self.emit_err_pat_range(span
, lhs
, rhs
);
471 return self.tcx
.ty_error();
474 // Unify each side with `expected`.
475 // Subtyping doesn't matter here, as the value is some kind of scalar.
476 let demand_eqtype
= |x
: &mut _
, y
| {
477 if let Some((ref mut fail
, x_ty
, x_span
)) = *x
478 && let Some(mut err
) = self.demand_eqtype_pat_diag(x_span
, expected
, x_ty
, ti
)
480 if let Some((_
, y_ty
, y_span
)) = y
{
481 self.endpoint_has_type(&mut err
, y_span
, y_ty
);
487 demand_eqtype(&mut lhs
, rhs
);
488 demand_eqtype(&mut rhs
, lhs
);
490 if let (Some((true, ..)), _
) | (_
, Some((true, ..))) = (lhs
, rhs
) {
491 return self.tcx
.ty_error();
494 // Find the unified type and check if it's of numeric or char type again.
495 // This check is needed if both sides are inference variables.
496 // We require types to be resolved here so that we emit inference failure
497 // rather than "_ is not a char or numeric".
498 let ty
= self.structurally_resolved_type(span
, expected
);
499 if !(ty
.is_numeric() || ty
.is_char() || ty
.references_error()) {
500 if let Some((ref mut fail
, _
, _
)) = lhs
{
503 if let Some((ref mut fail
, _
, _
)) = rhs
{
506 self.emit_err_pat_range(span
, lhs
, rhs
);
507 return self.tcx
.ty_error();
512 fn endpoint_has_type(&self, err
: &mut Diagnostic
, span
: Span
, ty
: Ty
<'_
>) {
513 if !ty
.references_error() {
514 err
.span_label(span
, &format
!("this is of type `{}`", ty
));
518 fn emit_err_pat_range(
521 lhs
: Option
<(bool
, Ty
<'tcx
>, Span
)>,
522 rhs
: Option
<(bool
, Ty
<'tcx
>, Span
)>,
524 let span
= match (lhs
, rhs
) {
525 (Some((true, ..)), Some((true, ..))) => span
,
526 (Some((true, _
, sp
)), _
) => sp
,
527 (_
, Some((true, _
, sp
))) => sp
,
528 _
=> span_bug
!(span
, "emit_err_pat_range: no side failed or exists but still error?"),
530 let mut err
= struct_span_err
!(
534 "only `char` and numeric types are allowed in range patterns"
537 let ty
= self.resolve_vars_if_possible(ty
);
538 format
!("this is of type `{}` but it should be `char` or numeric", ty
)
540 let mut one_side_err
= |first_span
, first_ty
, second
: Option
<(bool
, Ty
<'tcx
>, Span
)>| {
541 err
.span_label(first_span
, &msg(first_ty
));
542 if let Some((_
, ty
, sp
)) = second
{
543 let ty
= self.resolve_vars_if_possible(ty
);
544 self.endpoint_has_type(&mut err
, sp
, ty
);
548 (Some((true, lhs_ty
, lhs_sp
)), Some((true, rhs_ty
, rhs_sp
))) => {
549 err
.span_label(lhs_sp
, &msg(lhs_ty
));
550 err
.span_label(rhs_sp
, &msg(rhs_ty
));
552 (Some((true, lhs_ty
, lhs_sp
)), rhs
) => one_side_err(lhs_sp
, lhs_ty
, rhs
),
553 (lhs
, Some((true, rhs_ty
, rhs_sp
))) => one_side_err(rhs_sp
, rhs_ty
, lhs
),
554 _
=> span_bug
!(span
, "Impossible, verified above."),
556 if (lhs
, rhs
).references_error() {
557 err
.downgrade_to_delayed_bug();
559 if self.tcx
.sess
.teach(&err
.get_code().unwrap()) {
561 "In a match expression, only numbers and characters can be matched \
562 against a range. This is because the compiler checks that the range \
563 is non-empty at compile-time, and is unable to evaluate arbitrary \
564 comparison functions. If you want to capture values of an orderable \
565 type between two end-points, you can use a guard.",
573 pat
: &'tcx Pat
<'tcx
>,
574 ba
: hir
::BindingAnnotation
,
576 sub
: Option
<&'tcx Pat
<'tcx
>>,
581 // Determine the binding mode...
583 hir
::BindingAnnotation
::NONE
=> def_bm
,
584 _
=> BindingMode
::convert(ba
),
586 // ...and store it in a side table:
587 self.inh
.typeck_results
.borrow_mut().pat_binding_modes_mut().insert(pat
.hir_id
, bm
);
589 debug
!("check_pat_ident: pat.hir_id={:?} bm={:?}", pat
.hir_id
, bm
);
591 let local_ty
= self.local_ty(pat
.span
, pat
.hir_id
).decl_ty
;
592 let eq_ty
= match bm
{
593 ty
::BindByReference(mutbl
) => {
594 // If the binding is like `ref x | ref mut x`,
595 // then `x` is assigned a value of type `&M T` where M is the
596 // mutability and T is the expected type.
598 // `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)`
599 // is required. However, we use equality, which is stronger.
600 // See (note_1) for an explanation.
601 self.new_ref_ty(pat
.span
, mutbl
, expected
)
603 // Otherwise, the type of x is the expected type `T`.
604 ty
::BindByValue(_
) => {
605 // As above, `T <: typeof(x)` is required, but we use equality, see (note_1).
609 self.demand_eqtype_pat(pat
.span
, eq_ty
, local_ty
, ti
);
611 // If there are multiple arms, make sure they all agree on
612 // what the type of the binding `x` ought to be.
613 if var_id
!= pat
.hir_id
{
614 self.check_binding_alt_eq_ty(ba
, pat
.span
, var_id
, local_ty
, ti
);
617 if let Some(p
) = sub
{
618 self.check_pat(p
, expected
, def_bm
, ti
);
624 fn check_binding_alt_eq_ty(
626 ba
: hir
::BindingAnnotation
,
632 let var_ty
= self.local_ty(span
, var_id
).decl_ty
;
633 if let Some(mut err
) = self.demand_eqtype_pat_diag(span
, var_ty
, ty
, ti
) {
634 let hir
= self.tcx
.hir();
635 let var_ty
= self.resolve_vars_with_obligations(var_ty
);
636 let msg
= format
!("first introduced with type `{var_ty}` here");
637 err
.span_label(hir
.span(var_id
), msg
);
638 let in_match
= hir
.parent_iter(var_id
).any(|(_
, n
)| {
641 hir
::Node
::Expr(hir
::Expr
{
642 kind
: hir
::ExprKind
::Match(.., hir
::MatchSource
::Normal
),
647 let pre
= if in_match { "in the same arm, " }
else { "" }
;
648 err
.note(&format
!("{}a binding must have the same type in all alternatives", pre
));
649 self.suggest_adding_missing_ref_or_removing_ref(
653 self.resolve_vars_with_obligations(ty
),
660 fn suggest_adding_missing_ref_or_removing_ref(
662 err
: &mut Diagnostic
,
666 ba
: hir
::BindingAnnotation
,
668 match (expected
.kind(), actual
.kind(), ba
) {
669 (ty
::Ref(_
, inner_ty
, _
), _
, hir
::BindingAnnotation
::NONE
)
670 if self.can_eq(self.param_env
, *inner_ty
, actual
).is_ok() =>
672 err
.span_suggestion_verbose(
674 "consider adding `ref`",
676 Applicability
::MaybeIncorrect
,
679 (_
, ty
::Ref(_
, inner_ty
, _
), hir
::BindingAnnotation
::REF
)
680 if self.can_eq(self.param_env
, expected
, *inner_ty
).is_ok() =>
682 err
.span_suggestion_verbose(
683 span
.with_hi(span
.lo() + BytePos(4)),
684 "consider removing `ref`",
686 Applicability
::MaybeIncorrect
,
693 // Precondition: pat is a Ref(_) pattern
694 fn borrow_pat_suggestion(&self, err
: &mut Diagnostic
, pat
: &Pat
<'_
>) {
696 if let PatKind
::Ref(inner
, mutbl
) = pat
.kind
697 && let PatKind
::Binding(_
, _
, binding
, ..) = inner
.kind
{
698 let binding_parent_id
= tcx
.hir().parent_id(pat
.hir_id
);
699 let binding_parent
= tcx
.hir().get(binding_parent_id
);
700 debug
!(?inner
, ?pat
, ?binding_parent
);
702 let mutability
= match mutbl
{
703 ast
::Mutability
::Mut
=> "mut",
704 ast
::Mutability
::Not
=> "",
707 let mut_var_suggestion
= 'block
: {
712 let ident_kind
= match binding_parent
{
713 hir
::Node
::Param(_
) => "parameter",
714 hir
::Node
::Local(_
) => "variable",
715 hir
::Node
::Arm(_
) => "binding",
717 // Provide diagnostics only if the parent pattern is struct-like,
718 // i.e. where `mut binding` makes sense
719 hir
::Node
::Pat(Pat { kind, .. }
) => match kind
{
721 | PatKind
::TupleStruct(..)
724 | PatKind
::Slice(..) => "binding",
727 | PatKind
::Binding(..)
732 | PatKind
::Range(..) => break 'block None
,
735 // Don't provide suggestions in other cases
736 _
=> break 'block None
,
741 format
!("to declare a mutable {ident_kind} use"),
742 format
!("mut {binding}"),
747 match binding_parent
{
748 // Check that there is explicit type (ie this is not a closure param with inferred type)
749 // so we don't suggest moving something to the type that does not exist
750 hir
::Node
::Param(hir
::Param { ty_span, .. }
) if binding
.span
!= *ty_span
=> {
751 err
.multipart_suggestion_verbose(
752 format
!("to take parameter `{binding}` by reference, move `&{mutability}` to the type"),
754 (pat
.span
.until(inner
.span
), "".to_owned()),
755 (ty_span
.shrink_to_lo(), mutbl
.ref_prefix_str().to_owned()),
757 Applicability
::MachineApplicable
760 if let Some((sp
, msg
, sugg
)) = mut_var_suggestion
{
761 err
.span_note(sp
, format
!("{msg}: `{sugg}`"));
764 hir
::Node
::Pat(pt
) if let PatKind
::TupleStruct(_
, pat_arr
, _
) = pt
.kind
=> {
765 for i
in pat_arr
.iter() {
766 if let PatKind
::Ref(the_ref
, _
) = i
.kind
767 && let PatKind
::Binding(mt
, _
, ident
, _
) = the_ref
.kind
{
768 let hir
::BindingAnnotation(_
, mtblty
) = mt
;
769 err
.span_suggestion_verbose(
771 format
!("consider removing `&{mutability}` from the pattern"),
772 mtblty
.prefix_str().to_string() + &ident
.name
.to_string(),
773 Applicability
::MaybeIncorrect
,
777 if let Some((sp
, msg
, sugg
)) = mut_var_suggestion
{
778 err
.span_note(sp
, format
!("{msg}: `{sugg}`"));
781 hir
::Node
::Param(_
) | hir
::Node
::Arm(_
) | hir
::Node
::Pat(_
) => {
782 // rely on match ergonomics or it might be nested `&&pat`
783 err
.span_suggestion_verbose(
784 pat
.span
.until(inner
.span
),
785 format
!("consider removing `&{mutability}` from the pattern"),
787 Applicability
::MaybeIncorrect
,
790 if let Some((sp
, msg
, sugg
)) = mut_var_suggestion
{
791 err
.span_note(sp
, format
!("{msg}: `{sugg}`"));
794 _
if let Some((sp
, msg
, sugg
)) = mut_var_suggestion
=> {
795 err
.span_suggestion(sp
, msg
, sugg
, Applicability
::MachineApplicable
);
797 _
=> {}
// don't provide suggestions in other cases #55175
802 pub fn check_dereferenceable(&self, span
: Span
, expected
: Ty
<'tcx
>, inner
: &Pat
<'_
>) -> bool
{
803 if let PatKind
::Binding(..) = inner
.kind
804 && let Some(mt
) = self.shallow_resolve(expected
).builtin_deref(true)
805 && let ty
::Dynamic(..) = mt
.ty
.kind()
807 // This is "x = SomeTrait" being reduced from
808 // "let &x = &SomeTrait" or "let box x = Box<SomeTrait>", an error.
809 let type_str
= self.ty_to_string(expected
);
810 let mut err
= struct_span_err
!(
814 "type `{}` cannot be dereferenced",
817 err
.span_label(span
, format
!("type `{type_str}` cannot be dereferenced"));
818 if self.tcx
.sess
.teach(&err
.get_code().unwrap()) {
819 err
.note(CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ
);
829 pat
: &'tcx Pat
<'tcx
>,
830 qpath
: &hir
::QPath
<'_
>,
831 fields
: &'tcx
[hir
::PatField
<'tcx
>],
837 // Resolve the path and check the definition for errors.
838 let Some((variant
, pat_ty
)) = self.check_struct_path(qpath
, pat
.hir_id
) else {
839 let err
= self.tcx
.ty_error();
840 for field
in fields
{
842 self.check_pat(field
.pat
, err
, def_bm
, ti
);
847 // Type-check the path.
848 self.demand_eqtype_pat(pat
.span
, expected
, pat_ty
, ti
);
850 // Type-check subpatterns.
851 if self.check_struct_pat_fields(pat_ty
, &pat
, variant
, fields
, has_rest_pat
, def_bm
, ti
) {
861 qpath
: &hir
::QPath
<'_
>,
862 path_resolution
: (Res
, Option
<RawTy
<'tcx
>>, &'tcx
[hir
::PathSegment
<'tcx
>]),
868 // We have already resolved the path.
869 let (res
, opt_ty
, segments
) = path_resolution
;
872 let e
= tcx
.sess
.delay_span_bug(qpath
.span(), "`Res::Err` but no error emitted");
873 self.set_tainted_by_errors(e
);
874 return tcx
.ty_error_with_guaranteed(e
);
876 Res
::Def(DefKind
::AssocFn
| DefKind
::Ctor(_
, CtorKind
::Fn
) | DefKind
::Variant
, _
) => {
877 let expected
= "unit struct, unit variant or constant";
878 let e
= report_unexpected_variant_res(tcx
, res
, qpath
, pat
.span
, "E0533", expected
);
879 return tcx
.ty_error_with_guaranteed(e
);
883 DefKind
::Ctor(_
, CtorKind
::Const
)
885 | DefKind
::AssocConst
886 | DefKind
::ConstParam
,
889 _
=> bug
!("unexpected pattern resolution: {:?}", res
),
892 // Type-check the path.
893 let (pat_ty
, pat_res
) =
894 self.instantiate_value_path(segments
, opt_ty
, res
, pat
.span
, pat
.hir_id
);
896 self.demand_suptype_with_origin(&self.pattern_cause(ti
, pat
.span
), expected
, pat_ty
)
898 self.emit_bad_pat_path(err
, pat
, res
, pat_res
, pat_ty
, segments
);
903 fn maybe_suggest_range_literal(
906 opt_def_id
: Option
<hir
::def_id
::DefId
>,
910 Some(def_id
) => match self.tcx
.hir().get_if_local(def_id
) {
911 Some(hir
::Node
::Item(hir
::Item
{
912 kind
: hir
::ItemKind
::Const(_
, body_id
), ..
913 })) => match self.tcx
.hir().get(body_id
.hir_id
) {
914 hir
::Node
::Expr(expr
) => {
915 if hir
::is_range_literal(expr
) {
916 let span
= self.tcx
.hir().span(body_id
.hir_id
);
917 if let Ok(snip
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
918 e
.span_suggestion_verbose(
920 "you may want to move the range into the match block",
922 Applicability
::MachineApplicable
,
937 fn emit_bad_pat_path(
939 mut e
: DiagnosticBuilder
<'_
, ErrorGuaranteed
>,
940 pat
: &hir
::Pat
<'tcx
>,
944 segments
: &'tcx
[hir
::PathSegment
<'tcx
>],
946 let pat_span
= pat
.span
;
947 if let Some(span
) = self.tcx
.hir().res_span(pat_res
) {
948 e
.span_label(span
, &format
!("{} defined here", res
.descr()));
949 if let [hir
::PathSegment { ident, .. }
] = &*segments
{
953 "`{}` is interpreted as {} {}, not a new binding",
959 match self.tcx
.hir().get_parent(pat
.hir_id
) {
960 hir
::Node
::PatField(..) => {
961 e
.span_suggestion_verbose(
962 ident
.span
.shrink_to_hi(),
963 "bind the struct field to a different name instead",
964 format
!(": other_{}", ident
.as_str().to_lowercase()),
965 Applicability
::HasPlaceholders
,
969 let (type_def_id
, item_def_id
) = match pat_ty
.kind() {
970 Adt(def
, _
) => match res
{
971 Res
::Def(DefKind
::Const
, def_id
) => (Some(def
.did()), Some(def_id
)),
978 self.tcx
.lang_items().range_struct(),
979 self.tcx
.lang_items().range_from_struct(),
980 self.tcx
.lang_items().range_to_struct(),
981 self.tcx
.lang_items().range_full_struct(),
982 self.tcx
.lang_items().range_inclusive_struct(),
983 self.tcx
.lang_items().range_to_inclusive_struct(),
985 if type_def_id
!= None
&& ranges
.contains(&type_def_id
) {
986 if !self.maybe_suggest_range_literal(&mut e
, item_def_id
, *ident
) {
987 let msg
= "constants only support matching by type, \
988 if you meant to match against a range of values, \
989 consider using a range pattern like `min ..= max` in the match block";
993 let msg
= "introduce a new binding instead";
994 let sugg
= format
!("other_{}", ident
.as_str().to_lowercase());
999 Applicability
::HasPlaceholders
,
1009 fn check_pat_tuple_struct(
1011 pat
: &'tcx Pat
<'tcx
>,
1012 qpath
: &'tcx hir
::QPath
<'tcx
>,
1013 subpats
: &'tcx
[Pat
<'tcx
>],
1014 ddpos
: hir
::DotDotPos
,
1016 def_bm
: BindingMode
,
1020 let on_error
= |e
| {
1021 for pat
in subpats
{
1022 self.check_pat(pat
, tcx
.ty_error_with_guaranteed(e
), def_bm
, ti
);
1025 let report_unexpected_res
= |res
: Res
| {
1026 let expected
= "tuple struct or tuple variant";
1027 let e
= report_unexpected_variant_res(tcx
, res
, qpath
, pat
.span
, "E0164", expected
);
1032 // Resolve the path and check the definition for errors.
1033 let (res
, opt_ty
, segments
) =
1034 self.resolve_ty_and_res_fully_qualified_call(qpath
, pat
.hir_id
, pat
.span
);
1035 if res
== Res
::Err
{
1036 let e
= tcx
.sess
.delay_span_bug(pat
.span
, "`Res::Err` but no error emitted");
1037 self.set_tainted_by_errors(e
);
1039 return tcx
.ty_error_with_guaranteed(e
);
1042 // Type-check the path.
1044 self.instantiate_value_path(segments
, opt_ty
, res
, pat
.span
, pat
.hir_id
);
1045 if !pat_ty
.is_fn() {
1046 let e
= report_unexpected_res(res
);
1047 return tcx
.ty_error_with_guaranteed(e
);
1050 let variant
= match res
{
1052 let e
= tcx
.sess
.delay_span_bug(pat
.span
, "`Res::Err` but no error emitted");
1053 self.set_tainted_by_errors(e
);
1055 return tcx
.ty_error_with_guaranteed(e
);
1057 Res
::Def(DefKind
::AssocConst
| DefKind
::AssocFn
, _
) => {
1058 let e
= report_unexpected_res(res
);
1059 return tcx
.ty_error_with_guaranteed(e
);
1061 Res
::Def(DefKind
::Ctor(_
, CtorKind
::Fn
), _
) => tcx
.expect_variant_res(res
),
1062 _
=> bug
!("unexpected pattern resolution: {:?}", res
),
1065 // Replace constructor type with constructed type for tuple struct patterns.
1066 let pat_ty
= pat_ty
.fn_sig(tcx
).output();
1067 let pat_ty
= pat_ty
.no_bound_vars().expect("expected fn type");
1069 // Type-check the tuple struct pattern against the expected type.
1070 let diag
= self.demand_eqtype_pat_diag(pat
.span
, expected
, pat_ty
, ti
);
1071 let had_err
= if let Some(mut err
) = diag
{
1078 // Type-check subpatterns.
1079 if subpats
.len() == variant
.fields
.len()
1080 || subpats
.len() < variant
.fields
.len() && ddpos
.as_opt_usize().is_some()
1082 let ty
::Adt(_
, substs
) = pat_ty
.kind() else {
1083 bug
!("unexpected pattern type {:?}", pat_ty
);
1085 for (i
, subpat
) in subpats
.iter().enumerate_and_adjust(variant
.fields
.len(), ddpos
) {
1086 let field_ty
= self.field_ty(subpat
.span
, &variant
.fields
[i
], substs
);
1087 self.check_pat(subpat
, field_ty
, def_bm
, ti
);
1089 self.tcx
.check_stability(
1090 variant
.fields
[i
].did
,
1097 // Pattern has wrong number of fields.
1098 let e
= self.e0023(pat
.span
, res
, qpath
, subpats
, &variant
.fields
, expected
, had_err
);
1100 return tcx
.ty_error_with_guaranteed(e
);
1109 qpath
: &hir
::QPath
<'_
>,
1110 subpats
: &'tcx
[Pat
<'tcx
>],
1111 fields
: &'tcx
[ty
::FieldDef
],
1114 ) -> ErrorGuaranteed
{
1115 let subpats_ending
= pluralize
!(subpats
.len());
1116 let fields_ending
= pluralize
!(fields
.len());
1118 let subpat_spans
= if subpats
.is_empty() {
1121 subpats
.iter().map(|p
| p
.span
).collect()
1123 let last_subpat_span
= *subpat_spans
.last().unwrap();
1124 let res_span
= self.tcx
.def_span(res
.def_id());
1125 let def_ident_span
= self.tcx
.def_ident_span(res
.def_id()).unwrap_or(res_span
);
1126 let field_def_spans
= if fields
.is_empty() {
1129 fields
.iter().map(|f
| f
.ident(self.tcx
).span
).collect()
1131 let last_field_def_span
= *field_def_spans
.last().unwrap();
1133 let mut err
= struct_span_err
!(
1135 MultiSpan
::from_spans(subpat_spans
),
1137 "this pattern has {} field{}, but the corresponding {} has {} field{}",
1146 &format
!("expected {} field{}, found {}", fields
.len(), fields_ending
, subpats
.len()),
1148 if self.tcx
.sess
.source_map().is_multiline(qpath
.span().between(last_subpat_span
)) {
1149 err
.span_label(qpath
.span(), "");
1151 if self.tcx
.sess
.source_map().is_multiline(def_ident_span
.between(last_field_def_span
)) {
1152 err
.span_label(def_ident_span
, format
!("{} defined here", res
.descr()));
1154 for span
in &field_def_spans
[..field_def_spans
.len() - 1] {
1155 err
.span_label(*span
, "");
1158 last_field_def_span
,
1159 &format
!("{} has {} field{}", res
.descr(), fields
.len(), fields_ending
),
1162 // Identify the case `Some(x, y)` where the expected type is e.g. `Option<(T, U)>`.
1163 // More generally, the expected type wants a tuple variant with one field of an
1164 // N-arity-tuple, e.g., `V_i((p_0, .., p_N))`. Meanwhile, the user supplied a pattern
1165 // with the subpatterns directly in the tuple variant pattern, e.g., `V_i(p_0, .., p_N)`.
1166 let missing_parentheses
= match (&expected
.kind(), fields
, had_err
) {
1167 // #67037: only do this if we could successfully type-check the expected type against
1168 // the tuple struct pattern. Otherwise the substs could get out of range on e.g.,
1169 // `let P() = U;` where `P != U` with `struct P<T>(T);`.
1170 (ty
::Adt(_
, substs
), [field
], false) => {
1171 let field_ty
= self.field_ty(pat_span
, field
, substs
);
1172 match field_ty
.kind() {
1173 ty
::Tuple(fields
) => fields
.len() == subpats
.len(),
1179 if missing_parentheses
{
1180 let (left
, right
) = match subpats
{
1181 // This is the zero case; we aim to get the "hi" part of the `QPath`'s
1182 // span as the "lo" and then the "hi" part of the pattern's span as the "hi".
1185 // help: missing parentheses
1187 // L | let A(()) = A(());
1189 [] => (qpath
.span().shrink_to_hi(), pat_span
),
1190 // Easy case. Just take the "lo" of the first sub-pattern and the "hi" of the
1191 // last sub-pattern. In the case of `A(x)` the first and last may coincide.
1194 // help: missing parentheses
1196 // L | let A((x, y)) = A((1, 2));
1198 [first
, ..] => (first
.span
.shrink_to_lo(), subpats
.last().unwrap().span
),
1200 err
.multipart_suggestion(
1201 "missing parentheses",
1202 vec
![(left
, "(".to_string()), (right
.shrink_to_hi(), ")".to_string())],
1203 Applicability
::MachineApplicable
,
1205 } else if fields
.len() > subpats
.len() && pat_span
!= DUMMY_SP
{
1206 let after_fields_span
= pat_span
.with_hi(pat_span
.hi() - BytePos(1)).shrink_to_hi();
1207 let all_fields_span
= match subpats
{
1208 [] => after_fields_span
,
1209 [field
] => field
.span
,
1210 [first
, .., last
] => first
.span
.to(last
.span
),
1213 // Check if all the fields in the pattern are wildcards.
1214 let all_wildcards
= subpats
.iter().all(|pat
| matches
!(pat
.kind
, PatKind
::Wild
));
1215 let first_tail_wildcard
=
1216 subpats
.iter().enumerate().fold(None
, |acc
, (pos
, pat
)| match (acc
, &pat
.kind
) {
1217 (None
, PatKind
::Wild
) => Some(pos
),
1218 (Some(_
), PatKind
::Wild
) => acc
,
1221 let tail_span
= match first_tail_wildcard
{
1222 None
=> after_fields_span
,
1223 Some(0) => subpats
[0].span
.to(after_fields_span
),
1224 Some(pos
) => subpats
[pos
- 1].span
.shrink_to_hi().to(after_fields_span
),
1227 // FIXME: heuristic-based suggestion to check current types for where to add `_`.
1228 let mut wildcard_sugg
= vec
!["_"; fields
.len() - subpats
.len()].join(", ");
1229 if !subpats
.is_empty() {
1230 wildcard_sugg
= String
::from(", ") + &wildcard_sugg
;
1233 err
.span_suggestion_verbose(
1235 "use `_` to explicitly ignore each field",
1237 Applicability
::MaybeIncorrect
,
1240 // Only suggest `..` if more than one field is missing
1241 // or the pattern consists of all wildcards.
1242 if fields
.len() - subpats
.len() > 1 || all_wildcards
{
1243 if subpats
.is_empty() || all_wildcards
{
1244 err
.span_suggestion_verbose(
1246 "use `..` to ignore all fields",
1248 Applicability
::MaybeIncorrect
,
1251 err
.span_suggestion_verbose(
1253 "use `..` to ignore the rest of the fields",
1255 Applicability
::MaybeIncorrect
,
1267 elements
: &'tcx
[Pat
<'tcx
>],
1268 ddpos
: hir
::DotDotPos
,
1270 def_bm
: BindingMode
,
1274 let mut expected_len
= elements
.len();
1275 if ddpos
.as_opt_usize().is_some() {
1276 // Require known type only when `..` is present.
1277 if let ty
::Tuple(tys
) = self.structurally_resolved_type(span
, expected
).kind() {
1278 expected_len
= tys
.len();
1281 let max_len
= cmp
::max(expected_len
, elements
.len());
1283 let element_tys_iter
= (0..max_len
).map(|_
| {
1285 // FIXME: `MiscVariable` for now -- obtaining the span and name information
1286 // from all tuple elements isn't trivial.
1287 TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span }
,
1290 let element_tys
= tcx
.mk_type_list(element_tys_iter
);
1291 let pat_ty
= tcx
.mk_ty(ty
::Tuple(element_tys
));
1292 if let Some(mut err
) = self.demand_eqtype_pat_diag(span
, expected
, pat_ty
, ti
) {
1293 let reported
= err
.emit();
1294 // Walk subpatterns with an expected type of `err` in this case to silence
1295 // further errors being emitted when using the bindings. #50333
1296 let element_tys_iter
= (0..max_len
).map(|_
| tcx
.ty_error_with_guaranteed(reported
));
1297 for (_
, elem
) in elements
.iter().enumerate_and_adjust(max_len
, ddpos
) {
1298 self.check_pat(elem
, tcx
.ty_error_with_guaranteed(reported
), def_bm
, ti
);
1300 tcx
.mk_tup(element_tys_iter
)
1302 for (i
, elem
) in elements
.iter().enumerate_and_adjust(max_len
, ddpos
) {
1303 self.check_pat(elem
, element_tys
[i
], def_bm
, ti
);
1309 fn check_struct_pat_fields(
1312 pat
: &'tcx Pat
<'tcx
>,
1313 variant
: &'tcx ty
::VariantDef
,
1314 fields
: &'tcx
[hir
::PatField
<'tcx
>],
1316 def_bm
: BindingMode
,
1321 let ty
::Adt(adt
, substs
) = adt_ty
.kind() else {
1322 span_bug
!(pat
.span
, "struct pattern is not an ADT");
1325 // Index the struct fields' types.
1326 let field_map
= variant
1330 .map(|(i
, field
)| (field
.ident(self.tcx
).normalize_to_macros_2_0(), (i
, field
)))
1331 .collect
::<FxHashMap
<_
, _
>>();
1333 // Keep track of which fields have already appeared in the pattern.
1334 let mut used_fields
= FxHashMap
::default();
1335 let mut no_field_errors
= true;
1337 let mut inexistent_fields
= vec
![];
1338 // Typecheck each field.
1339 for field
in fields
{
1340 let span
= field
.span
;
1341 let ident
= tcx
.adjust_ident(field
.ident
, variant
.def_id
);
1342 let field_ty
= match used_fields
.entry(ident
) {
1343 Occupied(occupied
) => {
1344 self.error_field_already_bound(span
, field
.ident
, *occupied
.get());
1345 no_field_errors
= false;
1349 vacant
.insert(span
);
1353 self.write_field_index(field
.hir_id
, *i
);
1354 self.tcx
.check_stability(f
.did
, Some(pat
.hir_id
), span
, None
);
1355 self.field_ty(span
, f
, substs
)
1357 .unwrap_or_else(|| {
1358 inexistent_fields
.push(field
);
1359 no_field_errors
= false;
1365 self.check_pat(field
.pat
, field_ty
, def_bm
, ti
);
1368 let mut unmentioned_fields
= variant
1371 .map(|field
| (field
, field
.ident(self.tcx
).normalize_to_macros_2_0()))
1372 .filter(|(_
, ident
)| !used_fields
.contains_key(ident
))
1373 .collect
::<Vec
<_
>>();
1375 let inexistent_fields_err
= if !(inexistent_fields
.is_empty() || variant
.is_recovered())
1376 && !inexistent_fields
.iter().any(|field
| field
.ident
.name
== kw
::Underscore
)
1378 Some(self.error_inexistent_fields(
1379 adt
.variant_descr(),
1381 &mut unmentioned_fields
,
1389 // Require `..` if struct has non_exhaustive attribute.
1390 let non_exhaustive
= variant
.is_field_list_non_exhaustive() && !adt
.did().is_local();
1391 if non_exhaustive
&& !has_rest_pat
{
1392 self.error_foreign_non_exhaustive_spat(pat
, adt
.variant_descr(), fields
.is_empty());
1395 let mut unmentioned_err
= None
;
1396 // Report an error if an incorrect number of fields was specified.
1398 if fields
.len() != 1 {
1400 .struct_span_err(pat
.span
, "union patterns should have exactly one field")
1404 tcx
.sess
.struct_span_err(pat
.span
, "`..` cannot be used in union patterns").emit();
1406 } else if !unmentioned_fields
.is_empty() {
1407 let accessible_unmentioned_fields
: Vec
<_
> = unmentioned_fields
1410 .filter(|(field
, _
)| {
1411 field
.vis
.is_accessible_from(tcx
.parent_module(pat
.hir_id
), tcx
)
1413 tcx
.eval_stability(field
.did
, None
, DUMMY_SP
, None
),
1414 EvalResult
::Deny { .. }
1416 // We only want to report the error if it is hidden and not local
1417 && !(tcx
.is_doc_hidden(field
.did
) && !field
.did
.is_local())
1422 if accessible_unmentioned_fields
.is_empty() {
1423 unmentioned_err
= Some(self.error_no_accessible_fields(pat
, fields
));
1425 unmentioned_err
= Some(self.error_unmentioned_fields(
1427 &accessible_unmentioned_fields
,
1428 accessible_unmentioned_fields
.len() != unmentioned_fields
.len(),
1432 } else if non_exhaustive
&& !accessible_unmentioned_fields
.is_empty() {
1433 self.lint_non_exhaustive_omitted_patterns(
1435 &accessible_unmentioned_fields
,
1440 match (inexistent_fields_err
, unmentioned_err
) {
1441 (Some(mut i
), Some(mut u
)) => {
1442 if let Some(mut e
) = self.error_tuple_variant_as_struct_pat(pat
, fields
, variant
) {
1443 // We don't want to show the nonexistent fields error when this was
1444 // `Foo { a, b }` when it should have been `Foo(a, b)`.
1453 (None
, Some(mut u
)) => {
1454 if let Some(mut e
) = self.error_tuple_variant_as_struct_pat(pat
, fields
, variant
) {
1461 (Some(mut err
), None
) => {
1464 (None
, None
) if let Some(mut err
) =
1465 self.error_tuple_variant_index_shorthand(variant
, pat
, fields
) =>
1474 fn error_tuple_variant_index_shorthand(
1476 variant
: &VariantDef
,
1478 fields
: &[hir
::PatField
<'_
>],
1479 ) -> Option
<DiagnosticBuilder
<'_
, ErrorGuaranteed
>> {
1480 // if this is a tuple struct, then all field names will be numbers
1481 // so if any fields in a struct pattern use shorthand syntax, they will
1482 // be invalid identifiers (for example, Foo { 0, 1 }).
1483 if let (Some(CtorKind
::Fn
), PatKind
::Struct(qpath
, field_patterns
, ..)) =
1484 (variant
.ctor_kind(), &pat
.kind
)
1486 let has_shorthand_field_name
= field_patterns
.iter().any(|field
| field
.is_shorthand
);
1487 if has_shorthand_field_name
{
1488 let path
= rustc_hir_pretty
::to_string(rustc_hir_pretty
::NO_ANN
, |s
| {
1489 s
.print_qpath(qpath
, false)
1491 let mut err
= struct_span_err
!(
1495 "tuple variant `{path}` written as struct variant",
1497 err
.span_suggestion_verbose(
1498 qpath
.span().shrink_to_hi().to(pat
.span
.shrink_to_hi()),
1499 "use the tuple variant pattern syntax instead",
1500 format
!("({})", self.get_suggested_tuple_struct_pattern(fields
, variant
)),
1501 Applicability
::MaybeIncorrect
,
1509 fn error_foreign_non_exhaustive_spat(&self, pat
: &Pat
<'_
>, descr
: &str, no_fields
: bool
) {
1510 let sess
= self.tcx
.sess
;
1511 let sm
= sess
.source_map();
1512 let sp_brace
= sm
.end_point(pat
.span
);
1513 let sp_comma
= sm
.end_point(pat
.span
.with_hi(sp_brace
.hi()));
1514 let sugg
= if no_fields
|| sp_brace
!= sp_comma { ".. }
" } else { ", .. }" };
1516 let mut err
= struct_span_err
!(
1520 "`..` required with {descr} marked as non-exhaustive",
1522 err
.span_suggestion_verbose(
1524 "add `..` at the end of the field list to ignore all other fields",
1526 Applicability
::MachineApplicable
,
1531 fn error_field_already_bound(&self, span
: Span
, ident
: Ident
, other_field
: Span
) {
1536 "field `{}` bound multiple times in the pattern",
1539 .span_label(span
, format
!("multiple uses of `{ident}` in pattern"))
1540 .span_label(other_field
, format
!("first use of `{ident}`"))
1544 fn error_inexistent_fields(
1547 inexistent_fields
: &[&hir
::PatField
<'tcx
>],
1548 unmentioned_fields
: &mut Vec
<(&'tcx ty
::FieldDef
, Ident
)>,
1549 variant
: &ty
::VariantDef
,
1550 substs
: &'tcx ty
::List
<ty
::subst
::GenericArg
<'tcx
>>,
1551 ) -> DiagnosticBuilder
<'tcx
, ErrorGuaranteed
> {
1553 let (field_names
, t
, plural
) = if inexistent_fields
.len() == 1 {
1554 (format
!("a field named `{}`", inexistent_fields
[0].ident
), "this", "")
1561 .map(|field
| format
!("`{}`", field
.ident
))
1562 .collect
::<Vec
<String
>>()
1569 let spans
= inexistent_fields
.iter().map(|field
| field
.ident
.span
).collect
::<Vec
<_
>>();
1570 let mut err
= struct_span_err
!(
1574 "{} `{}` does not have {}",
1576 tcx
.def_path_str(variant
.def_id
),
1579 if let Some(pat_field
) = inexistent_fields
.last() {
1581 pat_field
.ident
.span
,
1583 "{} `{}` does not have {} field{}",
1585 tcx
.def_path_str(variant
.def_id
),
1591 if unmentioned_fields
.len() == 1 {
1593 unmentioned_fields
.iter().map(|(_
, field
)| field
.name
).collect
::<Vec
<_
>>();
1594 let suggested_name
= find_best_match_for_name(&input
, pat_field
.ident
.name
, None
);
1595 if let Some(suggested_name
) = suggested_name
{
1596 err
.span_suggestion(
1597 pat_field
.ident
.span
,
1598 "a field with a similar name exists",
1600 Applicability
::MaybeIncorrect
,
1603 // When we have a tuple struct used with struct we don't want to suggest using
1604 // the (valid) struct syntax with numeric field names. Instead we want to
1605 // suggest the expected syntax. We infer that this is the case by parsing the
1606 // `Ident` into an unsized integer. The suggestion will be emitted elsewhere in
1607 // `smart_resolve_context_dependent_help`.
1608 if suggested_name
.to_ident_string().parse
::<usize>().is_err() {
1609 // We don't want to throw `E0027` in case we have thrown `E0026` for them.
1610 unmentioned_fields
.retain(|&(_
, x
)| x
.name
!= suggested_name
);
1612 } else if inexistent_fields
.len() == 1 {
1613 match pat_field
.pat
.kind
{
1615 if !self.can_coerce(
1616 self.typeck_results
.borrow().expr_ty(expr
),
1618 unmentioned_fields
[0].1.span
,
1619 unmentioned_fields
[0].0,
1624 let unmentioned_field
= unmentioned_fields
[0].1.name
;
1625 err
.span_suggestion_short(
1626 pat_field
.ident
.span
,
1628 "`{}` has a field named `{}`",
1629 tcx
.def_path_str(variant
.def_id
),
1632 unmentioned_field
.to_string(),
1633 Applicability
::MaybeIncorrect
,
1640 if tcx
.sess
.teach(&err
.get_code().unwrap()) {
1642 "This error indicates that a struct pattern attempted to \
1643 extract a non-existent field from a struct. Struct fields \
1644 are identified by the name used before the colon : so struct \
1645 patterns should resemble the declaration of the struct type \
1647 If you are using shorthand field patterns but want to refer \
1648 to the struct field by a different name, you should rename \
1655 fn error_tuple_variant_as_struct_pat(
1658 fields
: &'tcx
[hir
::PatField
<'tcx
>],
1659 variant
: &ty
::VariantDef
,
1660 ) -> Option
<DiagnosticBuilder
<'tcx
, ErrorGuaranteed
>> {
1661 if let (Some(CtorKind
::Fn
), PatKind
::Struct(qpath
, ..)) = (variant
.ctor_kind(), &pat
.kind
) {
1662 let path
= rustc_hir_pretty
::to_string(rustc_hir_pretty
::NO_ANN
, |s
| {
1663 s
.print_qpath(qpath
, false)
1665 let mut err
= struct_span_err
!(
1669 "tuple variant `{}` written as struct variant",
1672 let (sugg
, appl
) = if fields
.len() == variant
.fields
.len() {
1674 self.get_suggested_tuple_struct_pattern(fields
, variant
),
1675 Applicability
::MachineApplicable
,
1679 variant
.fields
.iter().map(|_
| "_").collect
::<Vec
<&str>>().join(", "),
1680 Applicability
::MaybeIncorrect
,
1683 err
.span_suggestion_verbose(
1684 qpath
.span().shrink_to_hi().to(pat
.span
.shrink_to_hi()),
1685 "use the tuple variant pattern syntax instead",
1686 format
!("({})", sugg
),
1694 fn get_suggested_tuple_struct_pattern(
1696 fields
: &[hir
::PatField
<'_
>],
1697 variant
: &VariantDef
,
1699 let variant_field_idents
=
1700 variant
.fields
.iter().map(|f
| f
.ident(self.tcx
)).collect
::<Vec
<Ident
>>();
1704 match self.tcx
.sess
.source_map().span_to_snippet(field
.pat
.span
) {
1706 // Field names are numbers, but numbers
1707 // are not valid identifiers
1708 if variant_field_idents
.contains(&field
.ident
) {
1714 Err(_
) => rustc_hir_pretty
::to_string(rustc_hir_pretty
::NO_ANN
, |s
| {
1715 s
.print_pat(field
.pat
)
1719 .collect
::<Vec
<String
>>()
1723 /// Returns a diagnostic reporting a struct pattern which is missing an `..` due to
1724 /// inaccessible fields.
1727 /// error: pattern requires `..` due to inaccessible fields
1728 /// --> src/main.rs:10:9
1730 /// LL | let foo::Foo {} = foo::Foo::default();
1733 /// help: add a `..`
1735 /// LL | let foo::Foo { .. } = foo::Foo::default();
1738 fn error_no_accessible_fields(
1741 fields
: &'tcx
[hir
::PatField
<'tcx
>],
1742 ) -> DiagnosticBuilder
<'tcx
, ErrorGuaranteed
> {
1746 .struct_span_err(pat
.span
, "pattern requires `..` due to inaccessible fields");
1748 if let Some(field
) = fields
.last() {
1749 err
.span_suggestion_verbose(
1750 field
.span
.shrink_to_hi(),
1751 "ignore the inaccessible and unused fields",
1753 Applicability
::MachineApplicable
,
1756 let qpath_span
= if let PatKind
::Struct(qpath
, ..) = &pat
.kind
{
1759 bug
!("`error_no_accessible_fields` called on non-struct pattern");
1762 // Shrink the span to exclude the `foo:Foo` in `foo::Foo { }`.
1763 let span
= pat
.span
.with_lo(qpath_span
.shrink_to_hi().hi());
1764 err
.span_suggestion_verbose(
1766 "ignore the inaccessible and unused fields",
1768 Applicability
::MachineApplicable
,
1774 /// Report that a pattern for a `#[non_exhaustive]` struct marked with `non_exhaustive_omitted_patterns`
1775 /// is not exhaustive enough.
1777 /// Nb: the partner lint for enums lives in `compiler/rustc_mir_build/src/thir/pattern/usefulness.rs`.
1778 fn lint_non_exhaustive_omitted_patterns(
1781 unmentioned_fields
: &[(&ty
::FieldDef
, Ident
)],
1784 fn joined_uncovered_patterns(witnesses
: &[&Ident
]) -> String
{
1785 const LIMIT
: usize = 3;
1788 [witness
] => format
!("`{}`", witness
),
1789 [head @
.., tail
] if head
.len() < LIMIT
=> {
1790 let head
: Vec
<_
> = head
.iter().map(<_
>::to_string
).collect();
1791 format
!("`{}` and `{}`", head
.join("`, `"), tail
)
1794 let (head
, tail
) = witnesses
.split_at(LIMIT
);
1795 let head
: Vec
<_
> = head
.iter().map(<_
>::to_string
).collect();
1796 format
!("`{}` and {} more", head
.join("`, `"), tail
.len())
1800 let joined_patterns
= joined_uncovered_patterns(
1801 &unmentioned_fields
.iter().map(|(_
, i
)| i
).collect
::<Vec
<_
>>(),
1804 self.tcx
.struct_span_lint_hir(NON_EXHAUSTIVE_OMITTED_PATTERNS
, pat
.hir_id
, pat
.span
, "some fields are not explicitly listed", |lint
| {
1805 lint
.span_label(pat
.span
, format
!("field{} {} not listed", rustc_errors
::pluralize
!(unmentioned_fields
.len()), joined_patterns
));
1807 "ensure that all fields are mentioned explicitly by adding the suggested fields",
1810 "the pattern is of type `{}` and the `non_exhaustive_omitted_patterns` attribute was found",
1818 /// Returns a diagnostic reporting a struct pattern which does not mention some fields.
1821 /// error[E0027]: pattern does not mention field `bar`
1822 /// --> src/main.rs:15:9
1824 /// LL | let foo::Foo {} = foo::Foo::new();
1825 /// | ^^^^^^^^^^^ missing field `bar`
1827 fn error_unmentioned_fields(
1830 unmentioned_fields
: &[(&ty
::FieldDef
, Ident
)],
1831 have_inaccessible_fields
: bool
,
1832 fields
: &'tcx
[hir
::PatField
<'tcx
>],
1833 ) -> DiagnosticBuilder
<'tcx
, ErrorGuaranteed
> {
1834 let inaccessible
= if have_inaccessible_fields { " and inaccessible fields" }
else { "" }
;
1835 let field_names
= if unmentioned_fields
.len() == 1 {
1836 format
!("field `{}`{}", unmentioned_fields
[0].1, inaccessible
)
1838 let fields
= unmentioned_fields
1840 .map(|(_
, name
)| format
!("`{}`", name
))
1841 .collect
::<Vec
<String
>>()
1843 format
!("fields {}{}", fields
, inaccessible
)
1845 let mut err
= struct_span_err
!(
1849 "pattern does not mention {}",
1852 err
.span_label(pat
.span
, format
!("missing {}", field_names
));
1853 let len
= unmentioned_fields
.len();
1854 let (prefix
, postfix
, sp
) = match fields
{
1855 [] => match &pat
.kind
{
1856 PatKind
::Struct(path
, [], false) => {
1857 (" { ", " }", path
.span().shrink_to_hi().until(pat
.span
.shrink_to_hi()))
1862 // Account for last field having a trailing comma or parse recovery at the tail of
1863 // the pattern to avoid invalid suggestion (#78511).
1864 let tail
= field
.span
.shrink_to_hi().with_hi(pat
.span
.hi());
1866 PatKind
::Struct(..) => (", ", " }", tail
),
1871 err
.span_suggestion(
1874 "include the missing field{} in the pattern{}",
1876 if have_inaccessible_fields { " and ignore the inaccessible fields" }
else { "" }
1883 .map(|(_
, name
)| name
.to_string())
1884 .collect
::<Vec
<_
>>()
1886 if have_inaccessible_fields { ", .." }
else { "" }
,
1889 Applicability
::MachineApplicable
,
1891 err
.span_suggestion(
1894 "if you don't care about {these} missing field{s}, you can explicitly ignore {them}",
1895 these
= pluralize
!("this", len
),
1896 s
= pluralize
!(len
),
1897 them
= if len
== 1 { "it" }
else { "them" }
,
1899 format
!("{}..{}", prefix
, postfix
),
1900 Applicability
::MachineApplicable
,
1908 inner
: &'tcx Pat
<'tcx
>,
1910 def_bm
: BindingMode
,
1914 let (box_ty
, inner_ty
) = if self.check_dereferenceable(span
, expected
, inner
) {
1915 // Here, `demand::subtype` is good enough, but I don't
1916 // think any errors can be introduced by using `demand::eqtype`.
1917 let inner_ty
= self.next_ty_var(TypeVariableOrigin
{
1918 kind
: TypeVariableOriginKind
::TypeInference
,
1921 let box_ty
= tcx
.mk_box(inner_ty
);
1922 self.demand_eqtype_pat(span
, expected
, box_ty
, ti
);
1925 let err
= tcx
.ty_error();
1928 self.check_pat(inner
, inner_ty
, def_bm
, ti
);
1932 // Precondition: Pat is Ref(inner)
1935 pat
: &'tcx Pat
<'tcx
>,
1936 inner
: &'tcx Pat
<'tcx
>,
1937 mutbl
: hir
::Mutability
,
1939 def_bm
: BindingMode
,
1943 let expected
= self.shallow_resolve(expected
);
1944 let (ref_ty
, inner_ty
) = if self.check_dereferenceable(pat
.span
, expected
, inner
) {
1945 // `demand::subtype` would be good enough, but using `eqtype` turns
1946 // out to be equally general. See (note_1) for details.
1948 // Take region, inner-type from expected type if we can,
1949 // to avoid creating needless variables. This also helps with
1950 // the bad interactions of the given hack detailed in (note_1).
1951 debug
!("check_pat_ref: expected={:?}", expected
);
1952 match *expected
.kind() {
1953 ty
::Ref(_
, r_ty
, r_mutbl
) if r_mutbl
== mutbl
=> (expected
, r_ty
),
1955 let inner_ty
= self.next_ty_var(TypeVariableOrigin
{
1956 kind
: TypeVariableOriginKind
::TypeInference
,
1959 let ref_ty
= self.new_ref_ty(pat
.span
, mutbl
, inner_ty
);
1960 debug
!("check_pat_ref: demanding {:?} = {:?}", expected
, ref_ty
);
1961 let err
= self.demand_eqtype_pat_diag(pat
.span
, expected
, ref_ty
, ti
);
1963 // Look for a case like `fn foo(&foo: u32)` and suggest
1964 // `fn foo(foo: &u32)`
1965 if let Some(mut err
) = err
{
1966 self.borrow_pat_suggestion(&mut err
, pat
);
1973 let err
= tcx
.ty_error();
1976 self.check_pat(inner
, inner_ty
, def_bm
, ti
);
1980 /// Create a reference type with a fresh region variable.
1981 fn new_ref_ty(&self, span
: Span
, mutbl
: hir
::Mutability
, ty
: Ty
<'tcx
>) -> Ty
<'tcx
> {
1982 let region
= self.next_region_var(infer
::PatternRegion(span
));
1983 let mt
= ty
::TypeAndMut { ty, mutbl }
;
1984 self.tcx
.mk_ref(region
, mt
)
1987 /// Type check a slice pattern.
1989 /// Syntactically, these look like `[pat_0, ..., pat_n]`.
1990 /// Semantically, we are type checking a pattern with structure:
1991 /// ```ignore (not-rust)
1992 /// [before_0, ..., before_n, (slice, after_0, ... after_n)?]
1994 /// The type of `slice`, if it is present, depends on the `expected` type.
1995 /// If `slice` is missing, then so is `after_i`.
1996 /// If `slice` is present, it can still represent 0 elements.
2000 before
: &'tcx
[Pat
<'tcx
>],
2001 slice
: Option
<&'tcx Pat
<'tcx
>>,
2002 after
: &'tcx
[Pat
<'tcx
>],
2004 def_bm
: BindingMode
,
2007 let expected
= self.structurally_resolved_type(span
, expected
);
2008 let (element_ty
, opt_slice_ty
, inferred
) = match *expected
.kind() {
2009 // An array, so we might have something like `let [a, b, c] = [0, 1, 2];`.
2010 ty
::Array(element_ty
, len
) => {
2011 let min
= before
.len() as u64 + after
.len() as u64;
2012 let (opt_slice_ty
, expected
) =
2013 self.check_array_pat_len(span
, element_ty
, expected
, slice
, len
, min
);
2014 // `opt_slice_ty.is_none()` => `slice.is_none()`.
2015 // Note, though, that opt_slice_ty could be `Some(error_ty)`.
2016 assert
!(opt_slice_ty
.is_some() || slice
.is_none());
2017 (element_ty
, opt_slice_ty
, expected
)
2019 ty
::Slice(element_ty
) => (element_ty
, Some(expected
), expected
),
2020 // The expected type must be an array or slice, but was neither, so error.
2022 if !expected
.references_error() {
2023 self.error_expected_array_or_slice(span
, expected
, ti
);
2025 let err
= self.tcx
.ty_error();
2026 (err
, Some(err
), err
)
2030 // Type check all the patterns before `slice`.
2032 self.check_pat(elt
, element_ty
, def_bm
, ti
);
2034 // Type check the `slice`, if present, against its expected type.
2035 if let Some(slice
) = slice
{
2036 self.check_pat(slice
, opt_slice_ty
.unwrap(), def_bm
, ti
);
2038 // Type check the elements after `slice`, if present.
2040 self.check_pat(elt
, element_ty
, def_bm
, ti
);
2045 /// Type check the length of an array pattern.
2047 /// Returns both the type of the variable length pattern (or `None`), and the potentially
2048 /// inferred array type. We only return `None` for the slice type if `slice.is_none()`.
2049 fn check_array_pat_len(
2052 element_ty
: Ty
<'tcx
>,
2054 slice
: Option
<&'tcx Pat
<'tcx
>>,
2055 len
: ty
::Const
<'tcx
>,
2057 ) -> (Option
<Ty
<'tcx
>>, Ty
<'tcx
>) {
2058 if let Some(len
) = len
.try_eval_usize(self.tcx
, self.param_env
) {
2059 // Now we know the length...
2060 if slice
.is_none() {
2061 // ...and since there is no variable-length pattern,
2062 // we require an exact match between the number of elements
2063 // in the array pattern and as provided by the matched type.
2065 return (None
, arr_ty
);
2068 self.error_scrutinee_inconsistent_length(span
, min_len
, len
);
2069 } else if let Some(pat_len
) = len
.checked_sub(min_len
) {
2070 // The variable-length pattern was there,
2071 // so it has an array type with the remaining elements left as its size...
2072 return (Some(self.tcx
.mk_array(element_ty
, pat_len
)), arr_ty
);
2074 // ...however, in this case, there were no remaining elements.
2075 // That is, the slice pattern requires more than the array type offers.
2076 self.error_scrutinee_with_rest_inconsistent_length(span
, min_len
, len
);
2078 } else if slice
.is_none() {
2079 // We have a pattern with a fixed length,
2080 // which we can use to infer the length of the array.
2081 let updated_arr_ty
= self.tcx
.mk_array(element_ty
, min_len
);
2082 self.demand_eqtype(span
, updated_arr_ty
, arr_ty
);
2083 return (None
, updated_arr_ty
);
2085 // We have a variable-length pattern and don't know the array length.
2086 // This happens if we have e.g.,
2087 // `let [a, b, ..] = arr` where `arr: [T; N]` where `const N: usize`.
2088 self.error_scrutinee_unfixed_length(span
);
2091 // If we get here, we must have emitted an error.
2092 (Some(self.tcx
.ty_error()), arr_ty
)
2095 fn error_scrutinee_inconsistent_length(&self, span
: Span
, min_len
: u64, size
: u64) {
2100 "pattern requires {} element{} but array has {}",
2102 pluralize
!(min_len
),
2105 .span_label(span
, format
!("expected {} element{}", size
, pluralize
!(size
)))
2109 fn error_scrutinee_with_rest_inconsistent_length(&self, span
: Span
, min_len
: u64, size
: u64) {
2114 "pattern requires at least {} element{} but array has {}",
2116 pluralize
!(min_len
),
2121 format
!("pattern cannot match array of {} element{}", size
, pluralize
!(size
),),
2126 fn error_scrutinee_unfixed_length(&self, span
: Span
) {
2131 "cannot pattern-match on an array without a fixed length",
2136 fn error_expected_array_or_slice(&self, span
: Span
, expected_ty
: Ty
<'tcx
>, ti
: TopInfo
<'tcx
>) {
2137 let mut err
= struct_span_err
!(
2141 "expected an array or slice, found `{expected_ty}`"
2143 if let ty
::Ref(_
, ty
, _
) = expected_ty
.kind()
2144 && let ty
::Array(..) | ty
::Slice(..) = ty
.kind()
2146 err
.help("the semantics of slice patterns changed recently; see issue #62254");
2147 } else if self.autoderef(span
, expected_ty
)
2148 .any(|(ty
, _
)| matches
!(ty
.kind(), ty
::Slice(..) | ty
::Array(..)))
2149 && let (Some(span
), true) = (ti
.span
, ti
.origin_expr
)
2150 && let Ok(snippet
) = self.tcx
.sess
.source_map().span_to_snippet(span
)
2152 let ty
= self.resolve_vars_if_possible(ti
.expected
);
2153 let is_slice_or_array_or_vector
= self.is_slice_or_array_or_vector(ty
);
2154 match is_slice_or_array_or_vector
.1.kind() {
2156 if self.tcx
.is_diagnostic_item(sym
::Option
, adt_def
.did())
2157 || self.tcx
.is_diagnostic_item(sym
::Result
, adt_def
.did()) =>
2159 // Slicing won't work here, but `.as_deref()` might (issue #91328).
2160 err
.span_suggestion(
2162 "consider using `as_deref` here",
2163 format
!("{snippet}.as_deref()"),
2164 Applicability
::MaybeIncorrect
,
2169 if is_slice_or_array_or_vector
.0 {
2170 err
.span_suggestion(
2172 "consider slicing here",
2173 format
!("{snippet}[..]"),
2174 Applicability
::MachineApplicable
,
2178 err
.span_label(span
, format
!("pattern cannot match with input type `{expected_ty}`"));
2182 fn is_slice_or_array_or_vector(&self, ty
: Ty
<'tcx
>) -> (bool
, Ty
<'tcx
>) {
2184 ty
::Adt(adt_def
, _
) if self.tcx
.is_diagnostic_item(sym
::Vec
, adt_def
.did()) => {
2187 ty
::Ref(_
, ty
, _
) => self.is_slice_or_array_or_vector(*ty
),
2188 ty
::Slice(..) | ty
::Array(..) => (true, ty
),