1 use crate::check
::FnCtxt
;
4 use rustc_data_structures
::fx
::FxHashMap
;
5 use rustc_errors
::{pluralize, struct_span_err, Applicability, DiagnosticBuilder}
;
7 use rustc_hir
::def
::{CtorKind, DefKind, Res}
;
8 use rustc_hir
::pat_util
::EnumerateAndAdjustIterator
;
9 use rustc_hir
::{HirId, Pat, PatKind}
;
10 use rustc_infer
::infer
;
11 use rustc_infer
::infer
::type_variable
::{TypeVariableOrigin, TypeVariableOriginKind}
;
12 use rustc_middle
::ty
::subst
::GenericArg
;
13 use rustc_middle
::ty
::{self, Adt, BindingMode, Ty, TypeFoldable}
;
14 use rustc_span
::hygiene
::DesugaringKind
;
15 use rustc_span
::lev_distance
::find_best_match_for_name
;
16 use rustc_span
::source_map
::{Span, Spanned}
;
17 use rustc_span
::symbol
::Ident
;
18 use rustc_trait_selection
::traits
::{ObligationCause, Pattern}
;
21 use std
::collections
::hash_map
::Entry
::{Occupied, Vacant}
;
23 use super::report_unexpected_variant_res
;
25 const CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ
: &str = "\
26 This error indicates that a pointer to a trait type cannot be implicitly dereferenced by a \
27 pattern. Every trait defines a type, but because the size of trait implementors isn't fixed, \
28 this type has no compile-time size. Therefore, all accesses to trait types must be through \
29 pointers. If you encounter this error you should try to avoid dereferencing the pointer.
31 You can read more about trait objects in the Trait Objects section of the Reference: \
32 https://doc.rust-lang.org/reference/types.html#trait-objects";
34 /// Information about the expected type at the top level of type checking a pattern.
36 /// **NOTE:** This is only for use by diagnostics. Do NOT use for type checking logic!
37 #[derive(Copy, Clone)]
38 struct TopInfo
<'tcx
> {
39 /// The `expected` type at the top level of type checking a pattern.
41 /// Was the origin of the `span` from a scrutinee expression?
43 /// Otherwise there is no scrutinee and it could be e.g. from the type of a formal parameter.
45 /// The span giving rise to the `expected` type, if one could be provided.
47 /// If `origin_expr` is `true`, then this is the span of the scrutinee as in:
49 /// - `match scrutinee { ... }`
50 /// - `let _ = scrutinee;`
52 /// This is used to point to add context in type errors.
53 /// In the following example, `span` corresponds to the `a + b` expression:
56 /// error[E0308]: mismatched types
57 /// --> src/main.rs:L:C
59 /// L | let temp: usize = match a + b {
60 /// | ----- this expression has type `usize`
61 /// L | Ok(num) => num,
62 /// | ^^^^^^^ expected `usize`, found enum `std::result::Result`
64 /// = note: expected type `usize`
65 /// found type `std::result::Result<_, _>`
68 /// This refers to the parent pattern. Used to provide extra diagnostic information on errors.
70 /// error[E0308]: mismatched types
71 /// --> $DIR/const-in-struct-pat.rs:8:17
74 /// | --------- unit struct defined here
76 /// L | let Thing { f } = t;
79 /// | expected struct `std::string::String`, found struct `f`
80 /// | `f` is interpreted as a unit struct, not a new binding
81 /// | help: bind the struct field to a different name instead: `f: other_f`
83 parent_pat
: Option
<&'tcx Pat
<'tcx
>>,
86 impl<'tcx
> FnCtxt
<'_
, 'tcx
> {
87 fn pattern_cause(&self, ti
: TopInfo
<'tcx
>, cause_span
: Span
) -> ObligationCause
<'tcx
> {
88 let code
= Pattern { span: ti.span, root_ty: ti.expected, origin_expr: ti.origin_expr }
;
89 self.cause(cause_span
, code
)
92 fn demand_eqtype_pat_diag(
98 ) -> Option
<DiagnosticBuilder
<'tcx
>> {
99 self.demand_eqtype_with_origin(&self.pattern_cause(ti
, cause_span
), expected
, actual
)
102 fn demand_eqtype_pat(
109 if let Some(mut err
) = self.demand_eqtype_pat_diag(cause_span
, expected
, actual
, ti
) {
115 const INITIAL_BM
: BindingMode
= BindingMode
::BindByValue(hir
::Mutability
::Not
);
117 /// Mode for adjusting the expected type and binding mode.
119 /// Peel off all immediate reference types.
121 /// Reset binding mode to the initial mode.
123 /// Pass on the input binding mode and expected type.
127 impl<'a
, 'tcx
> FnCtxt
<'a
, 'tcx
> {
128 /// Type check the given top level pattern against the `expected` type.
130 /// If a `Some(span)` is provided and `origin_expr` holds,
131 /// then the `span` represents the scrutinee's span.
132 /// The scrutinee is found in e.g. `match scrutinee { ... }` and `let pat = scrutinee;`.
134 /// Otherwise, `Some(span)` represents the span of a type expression
135 /// which originated the `expected` type.
136 pub fn check_pat_top(
138 pat
: &'tcx Pat
<'tcx
>,
143 let info
= TopInfo { expected, origin_expr, span, parent_pat: None }
;
144 self.check_pat(pat
, expected
, INITIAL_BM
, info
);
147 /// Type check the given `pat` against the `expected` type
148 /// with the provided `def_bm` (default binding mode).
150 /// Outside of this module, `check_pat_top` should always be used.
151 /// Conversely, inside this module, `check_pat_top` should never be used.
152 #[instrument(skip(self, ti))]
155 pat
: &'tcx Pat
<'tcx
>,
160 let path_res
= match &pat
.kind
{
161 PatKind
::Path(qpath
) => Some(self.resolve_ty_and_res_ufcs(qpath
, pat
.hir_id
, pat
.span
)),
164 let adjust_mode
= self.calc_adjust_mode(pat
, path_res
.map(|(res
, ..)| res
));
165 let (expected
, def_bm
) = self.calc_default_binding_mode(pat
, expected
, def_bm
, adjust_mode
);
167 let ty
= match pat
.kind
{
168 PatKind
::Wild
=> expected
,
169 PatKind
::Lit(lt
) => self.check_pat_lit(pat
.span
, lt
, expected
, ti
),
170 PatKind
::Range(lhs
, rhs
, _
) => self.check_pat_range(pat
.span
, lhs
, rhs
, expected
, ti
),
171 PatKind
::Binding(ba
, var_id
, _
, sub
) => {
172 self.check_pat_ident(pat
, ba
, var_id
, sub
, expected
, def_bm
, ti
)
174 PatKind
::TupleStruct(ref qpath
, subpats
, ddpos
) => {
175 self.check_pat_tuple_struct(pat
, qpath
, subpats
, ddpos
, expected
, def_bm
, ti
)
177 PatKind
::Path(_
) => self.check_pat_path(pat
, path_res
.unwrap(), expected
, ti
),
178 PatKind
::Struct(ref qpath
, fields
, etc
) => {
179 self.check_pat_struct(pat
, qpath
, fields
, etc
, expected
, def_bm
, ti
)
181 PatKind
::Or(pats
) => {
182 let parent_pat
= Some(pat
);
184 self.check_pat(pat
, expected
, def_bm
, TopInfo { parent_pat, ..ti }
);
188 PatKind
::Tuple(elements
, ddpos
) => {
189 self.check_pat_tuple(pat
.span
, elements
, ddpos
, expected
, def_bm
, ti
)
191 PatKind
::Box(inner
) => self.check_pat_box(pat
.span
, inner
, expected
, def_bm
, ti
),
192 PatKind
::Ref(inner
, mutbl
) => {
193 self.check_pat_ref(pat
, inner
, mutbl
, expected
, def_bm
, ti
)
195 PatKind
::Slice(before
, slice
, after
) => {
196 self.check_pat_slice(pat
.span
, before
, slice
, after
, expected
, def_bm
, ti
)
200 self.write_ty(pat
.hir_id
, ty
);
202 // (note_1): In most of the cases where (note_1) is referenced
203 // (literals and constants being the exception), we relate types
204 // using strict equality, even though subtyping would be sufficient.
205 // There are a few reasons for this, some of which are fairly subtle
206 // and which cost me (nmatsakis) an hour or two debugging to remember,
207 // so I thought I'd write them down this time.
209 // 1. There is no loss of expressiveness here, though it does
210 // cause some inconvenience. What we are saying is that the type
211 // of `x` becomes *exactly* what is expected. This can cause unnecessary
212 // errors in some cases, such as this one:
215 // fn foo<'x>(x: &'x i32) {
222 // The reason we might get an error is that `z` might be
223 // assigned a type like `&'x i32`, and then we would have
224 // a problem when we try to assign `&a` to `z`, because
225 // the lifetime of `&a` (i.e., the enclosing block) is
226 // shorter than `'x`.
228 // HOWEVER, this code works fine. The reason is that the
229 // expected type here is whatever type the user wrote, not
230 // the initializer's type. In this case the user wrote
231 // nothing, so we are going to create a type variable `Z`.
232 // Then we will assign the type of the initializer (`&'x i32`)
233 // as a subtype of `Z`: `&'x i32 <: Z`. And hence we
234 // will instantiate `Z` as a type `&'0 i32` where `'0` is
235 // a fresh region variable, with the constraint that `'x : '0`.
236 // So basically we're all set.
238 // Note that there are two tests to check that this remains true
239 // (`regions-reassign-{match,let}-bound-pointer.rs`).
241 // 2. Things go horribly wrong if we use subtype. The reason for
242 // THIS is a fairly subtle case involving bound regions. See the
243 // `givens` field in `region_constraints`, as well as the test
244 // `regions-relate-bound-regions-on-closures-to-inference-variables.rs`,
245 // for details. Short version is that we must sometimes detect
246 // relationships between specific region variables and regions
247 // bound in a closure signature, and that detection gets thrown
248 // off when we substitute fresh region variables here to enable
252 /// Compute the new expected type and default binding mode from the old ones
253 /// as well as the pattern form we are currently checking.
254 fn calc_default_binding_mode(
256 pat
: &'tcx Pat
<'tcx
>,
259 adjust_mode
: AdjustMode
,
260 ) -> (Ty
<'tcx
>, BindingMode
) {
262 AdjustMode
::Pass
=> (expected
, def_bm
),
263 AdjustMode
::Reset
=> (expected
, INITIAL_BM
),
264 AdjustMode
::Peel
=> self.peel_off_references(pat
, expected
, def_bm
),
268 /// How should the binding mode and expected type be adjusted?
270 /// When the pattern is a path pattern, `opt_path_res` must be `Some(res)`.
271 fn calc_adjust_mode(&self, pat
: &'tcx Pat
<'tcx
>, opt_path_res
: Option
<Res
>) -> AdjustMode
{
272 // When we perform destructuring assignment, we disable default match bindings, which are
273 // unintuitive in this context.
274 if !pat
.default_binding_modes
{
275 return AdjustMode
::Reset
;
278 // Type checking these product-like types successfully always require
279 // that the expected type be of those types and not reference types.
281 | PatKind
::TupleStruct(..)
285 | PatKind
::Slice(..) => AdjustMode
::Peel
,
286 // String and byte-string literals result in types `&str` and `&[u8]` respectively.
287 // All other literals result in non-reference types.
288 // As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo {}`.
289 PatKind
::Lit(lt
) => match self.check_expr(lt
).kind() {
290 ty
::Ref(..) => AdjustMode
::Pass
,
291 _
=> AdjustMode
::Peel
,
293 PatKind
::Path(_
) => match opt_path_res
.unwrap() {
294 // These constants can be of a reference type, e.g. `const X: &u8 = &0;`.
295 // Peeling the reference types too early will cause type checking failures.
296 // Although it would be possible to *also* peel the types of the constants too.
297 Res
::Def(DefKind
::Const
| DefKind
::AssocConst
, _
) => AdjustMode
::Pass
,
298 // In the `ValueNS`, we have `SelfCtor(..) | Ctor(_, Const), _)` remaining which
299 // could successfully compile. The former being `Self` requires a unit struct.
300 // In either case, and unlike constants, the pattern itself cannot be
301 // a reference type wherefore peeling doesn't give up any expressivity.
302 _
=> AdjustMode
::Peel
,
304 // When encountering a `& mut? pat` pattern, reset to "by value".
305 // This is so that `x` and `y` here are by value, as they appear to be:
308 // match &(&22, &44) {
314 PatKind
::Ref(..) => AdjustMode
::Reset
,
315 // A `_` pattern works with any expected type, so there's no need to do anything.
317 // Bindings also work with whatever the expected type is,
318 // and moreover if we peel references off, that will give us the wrong binding type.
319 // Also, we can have a subpattern `binding @ pat`.
320 // Each side of the `@` should be treated independently (like with OR-patterns).
321 | PatKind
::Binding(..)
322 // An OR-pattern just propagates to each individual alternative.
323 // This is maximally flexible, allowing e.g., `Some(mut x) | &Some(mut x)`.
324 // In that example, `Some(mut x)` results in `Peel` whereas `&Some(mut x)` in `Reset`.
325 | PatKind
::Or(_
) => AdjustMode
::Pass
,
329 /// Peel off as many immediately nested `& mut?` from the expected type as possible
330 /// and return the new expected type and binding default binding mode.
331 /// The adjustments vector, if non-empty is stored in a table.
332 fn peel_off_references(
334 pat
: &'tcx Pat
<'tcx
>,
336 mut def_bm
: BindingMode
,
337 ) -> (Ty
<'tcx
>, BindingMode
) {
338 let mut expected
= self.resolve_vars_with_obligations(&expected
);
340 // Peel off as many `&` or `&mut` from the scrutinee type as possible. For example,
341 // for `match &&&mut Some(5)` the loop runs three times, aborting when it reaches
342 // the `Some(5)` which is not of type Ref.
344 // For each ampersand peeled off, update the binding mode and push the original
345 // type into the adjustments vector.
347 // See the examples in `ui/match-defbm*.rs`.
348 let mut pat_adjustments
= vec
![];
349 while let ty
::Ref(_
, inner_ty
, inner_mutability
) = *expected
.kind() {
350 debug
!("inspecting {:?}", expected
);
352 debug
!("current discriminant is Ref, inserting implicit deref");
353 // Preserve the reference type. We'll need it later during THIR lowering.
354 pat_adjustments
.push(expected
);
357 def_bm
= ty
::BindByReference(match def_bm
{
358 // If default binding mode is by value, make it `ref` or `ref mut`
359 // (depending on whether we observe `&` or `&mut`).
361 // When `ref mut`, stay a `ref mut` (on `&mut`) or downgrade to `ref` (on `&`).
362 ty
::BindByReference(hir
::Mutability
::Mut
) => inner_mutability
,
363 // Once a `ref`, always a `ref`.
364 // This is because a `& &mut` cannot mutate the underlying value.
365 ty
::BindByReference(m @ hir
::Mutability
::Not
) => m
,
369 if !pat_adjustments
.is_empty() {
370 debug
!("default binding mode is now {:?}", def_bm
);
374 .pat_adjustments_mut()
375 .insert(pat
.hir_id
, pat_adjustments
);
384 lt
: &hir
::Expr
<'tcx
>,
388 // We've already computed the type above (when checking for a non-ref pat),
389 // so avoid computing it again.
390 let ty
= self.node_ty(lt
.hir_id
);
392 // Byte string patterns behave the same way as array patterns
393 // They can denote both statically and dynamically-sized byte arrays.
395 if let hir
::ExprKind
::Lit(Spanned { node: ast::LitKind::ByteStr(_), .. }
) = lt
.kind
{
396 let expected
= self.structurally_resolved_type(span
, expected
);
397 if let ty
::Ref(_
, inner_ty
, _
) = expected
.kind() {
398 if matches
!(inner_ty
.kind(), ty
::Slice(_
)) {
400 trace
!(?lt
.hir_id
.local_id
, "polymorphic byte string lit");
403 .treat_byte_string_as_slice
404 .insert(lt
.hir_id
.local_id
);
405 pat_ty
= tcx
.mk_imm_ref(tcx
.lifetimes
.re_static
, tcx
.mk_slice(tcx
.types
.u8));
410 // Somewhat surprising: in this case, the subtyping relation goes the
411 // opposite way as the other cases. Actually what we really want is not
412 // a subtyping relation at all but rather that there exists a LUB
413 // (so that they can be compared). However, in practice, constants are
414 // always scalars or strings. For scalars subtyping is irrelevant,
415 // and for strings `ty` is type is `&'static str`, so if we say that
417 // &'static str <: expected
419 // then that's equivalent to there existing a LUB.
420 let cause
= self.pattern_cause(ti
, span
);
421 if let Some(mut err
) = self.demand_suptype_with_origin(&cause
, expected
, pat_ty
) {
425 // In the case of `if`- and `while`-expressions we've already checked
426 // that `scrutinee: bool`. We know that the pattern is `true`,
427 // so an error here would be a duplicate and from the wrong POV.
428 s
.is_desugaring(DesugaringKind
::CondTemporary
)
440 lhs
: Option
<&'tcx hir
::Expr
<'tcx
>>,
441 rhs
: Option
<&'tcx hir
::Expr
<'tcx
>>,
445 let calc_side
= |opt_expr
: Option
<&'tcx hir
::Expr
<'tcx
>>| match opt_expr
{
446 None
=> (None
, None
),
448 let ty
= self.check_expr(expr
);
449 // Check that the end-point is of numeric or char type.
450 let fail
= !(ty
.is_numeric() || ty
.is_char() || ty
.references_error());
451 (Some(ty
), Some((fail
, ty
, expr
.span
)))
454 let (lhs_ty
, lhs
) = calc_side(lhs
);
455 let (rhs_ty
, rhs
) = calc_side(rhs
);
457 if let (Some((true, ..)), _
) | (_
, Some((true, ..))) = (lhs
, rhs
) {
458 // There exists a side that didn't meet our criteria that the end-point
459 // be of a numeric or char type, as checked in `calc_side` above.
460 self.emit_err_pat_range(span
, lhs
, rhs
);
461 return self.tcx
.ty_error();
464 // Now that we know the types can be unified we find the unified type
465 // and use it to type the entire expression.
466 let common_type
= self.resolve_vars_if_possible(lhs_ty
.or(rhs_ty
).unwrap_or(expected
));
468 // Subtyping doesn't matter here, as the value is some kind of scalar.
469 let demand_eqtype
= |x
, y
| {
470 if let Some((_
, x_ty
, x_span
)) = x
{
471 if let Some(mut err
) = self.demand_eqtype_pat_diag(x_span
, expected
, x_ty
, ti
) {
472 if let Some((_
, y_ty
, y_span
)) = y
{
473 self.endpoint_has_type(&mut err
, y_span
, y_ty
);
479 demand_eqtype(lhs
, rhs
);
480 demand_eqtype(rhs
, lhs
);
485 fn endpoint_has_type(&self, err
: &mut DiagnosticBuilder
<'_
>, span
: Span
, ty
: Ty
<'_
>) {
486 if !ty
.references_error() {
487 err
.span_label(span
, &format
!("this is of type `{}`", ty
));
491 fn emit_err_pat_range(
494 lhs
: Option
<(bool
, Ty
<'tcx
>, Span
)>,
495 rhs
: Option
<(bool
, Ty
<'tcx
>, Span
)>,
497 let span
= match (lhs
, rhs
) {
498 (Some((true, ..)), Some((true, ..))) => span
,
499 (Some((true, _
, sp
)), _
) => sp
,
500 (_
, Some((true, _
, sp
))) => sp
,
501 _
=> span_bug
!(span
, "emit_err_pat_range: no side failed or exists but still error?"),
503 let mut err
= struct_span_err
!(
507 "only `char` and numeric types are allowed in range patterns"
509 let msg
= |ty
| format
!("this is of type `{}` but it should be `char` or numeric", ty
);
510 let mut one_side_err
= |first_span
, first_ty
, second
: Option
<(bool
, Ty
<'tcx
>, Span
)>| {
511 err
.span_label(first_span
, &msg(first_ty
));
512 if let Some((_
, ty
, sp
)) = second
{
513 self.endpoint_has_type(&mut err
, sp
, ty
);
517 (Some((true, lhs_ty
, lhs_sp
)), Some((true, rhs_ty
, rhs_sp
))) => {
518 err
.span_label(lhs_sp
, &msg(lhs_ty
));
519 err
.span_label(rhs_sp
, &msg(rhs_ty
));
521 (Some((true, lhs_ty
, lhs_sp
)), rhs
) => one_side_err(lhs_sp
, lhs_ty
, rhs
),
522 (lhs
, Some((true, rhs_ty
, rhs_sp
))) => one_side_err(rhs_sp
, rhs_ty
, lhs
),
523 _
=> span_bug
!(span
, "Impossible, verified above."),
525 if self.tcx
.sess
.teach(&err
.get_code().unwrap()) {
527 "In a match expression, only numbers and characters can be matched \
528 against a range. This is because the compiler checks that the range \
529 is non-empty at compile-time, and is unable to evaluate arbitrary \
530 comparison functions. If you want to capture values of an orderable \
531 type between two end-points, you can use a guard.",
539 pat
: &'tcx Pat
<'tcx
>,
540 ba
: hir
::BindingAnnotation
,
542 sub
: Option
<&'tcx Pat
<'tcx
>>,
547 // Determine the binding mode...
549 hir
::BindingAnnotation
::Unannotated
=> def_bm
,
550 _
=> BindingMode
::convert(ba
),
552 // ...and store it in a side table:
553 self.inh
.typeck_results
.borrow_mut().pat_binding_modes_mut().insert(pat
.hir_id
, bm
);
555 debug
!("check_pat_ident: pat.hir_id={:?} bm={:?}", pat
.hir_id
, bm
);
557 let local_ty
= self.local_ty(pat
.span
, pat
.hir_id
).decl_ty
;
558 let eq_ty
= match bm
{
559 ty
::BindByReference(mutbl
) => {
560 // If the binding is like `ref x | ref mut x`,
561 // then `x` is assigned a value of type `&M T` where M is the
562 // mutability and T is the expected type.
564 // `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)`
565 // is required. However, we use equality, which is stronger.
566 // See (note_1) for an explanation.
567 self.new_ref_ty(pat
.span
, mutbl
, expected
)
569 // Otherwise, the type of x is the expected type `T`.
570 ty
::BindByValue(_
) => {
571 // As above, `T <: typeof(x)` is required, but we use equality, see (note_1).
575 self.demand_eqtype_pat(pat
.span
, eq_ty
, local_ty
, ti
);
577 // If there are multiple arms, make sure they all agree on
578 // what the type of the binding `x` ought to be.
579 if var_id
!= pat
.hir_id
{
580 self.check_binding_alt_eq_ty(pat
.span
, var_id
, local_ty
, ti
);
583 if let Some(p
) = sub
{
584 self.check_pat(&p
, expected
, def_bm
, TopInfo { parent_pat: Some(&pat), ..ti }
);
590 fn check_binding_alt_eq_ty(&self, span
: Span
, var_id
: HirId
, ty
: Ty
<'tcx
>, ti
: TopInfo
<'tcx
>) {
591 let var_ty
= self.local_ty(span
, var_id
).decl_ty
;
592 if let Some(mut err
) = self.demand_eqtype_pat_diag(span
, var_ty
, ty
, ti
) {
593 let hir
= self.tcx
.hir();
594 let var_ty
= self.resolve_vars_with_obligations(var_ty
);
595 let msg
= format
!("first introduced with type `{}` here", var_ty
);
596 err
.span_label(hir
.span(var_id
), msg
);
597 let in_match
= hir
.parent_iter(var_id
).any(|(_
, n
)| {
600 hir
::Node
::Expr(hir
::Expr
{
601 kind
: hir
::ExprKind
::Match(.., hir
::MatchSource
::Normal
),
606 let pre
= if in_match { "in the same arm, " }
else { "" }
;
607 err
.note(&format
!("{}a binding must have the same type in all alternatives", pre
));
612 fn borrow_pat_suggestion(
614 err
: &mut DiagnosticBuilder
<'_
>,
620 if let PatKind
::Binding(..) = inner
.kind
{
621 let binding_parent_id
= tcx
.hir().get_parent_node(pat
.hir_id
);
622 let binding_parent
= tcx
.hir().get(binding_parent_id
);
623 debug
!("inner {:?} pat {:?} parent {:?}", inner
, pat
, binding_parent
);
624 match binding_parent
{
625 hir
::Node
::Param(hir
::Param { span, .. }
) => {
626 if let Ok(snippet
) = tcx
.sess
.source_map().span_to_snippet(inner
.span
) {
629 &format
!("did you mean `{}`", snippet
),
630 format
!(" &{}", expected
),
631 Applicability
::MachineApplicable
,
635 hir
::Node
::Arm(_
) | hir
::Node
::Pat(_
) => {
636 // rely on match ergonomics or it might be nested `&&pat`
637 if let Ok(snippet
) = tcx
.sess
.source_map().span_to_snippet(inner
.span
) {
640 "you can probably remove the explicit borrow",
642 Applicability
::MaybeIncorrect
,
646 _
=> {}
// don't provide suggestions in other cases #55175
651 pub fn check_dereferenceable(&self, span
: Span
, expected
: Ty
<'tcx
>, inner
: &Pat
<'_
>) -> bool
{
652 if let PatKind
::Binding(..) = inner
.kind
{
653 if let Some(mt
) = self.shallow_resolve(expected
).builtin_deref(true) {
654 if let ty
::Dynamic(..) = mt
.ty
.kind() {
655 // This is "x = SomeTrait" being reduced from
656 // "let &x = &SomeTrait" or "let box x = Box<SomeTrait>", an error.
657 let type_str
= self.ty_to_string(expected
);
658 let mut err
= struct_span_err
!(
662 "type `{}` cannot be dereferenced",
665 err
.span_label(span
, format
!("type `{}` cannot be dereferenced", type_str
));
666 if self.tcx
.sess
.teach(&err
.get_code().unwrap()) {
667 err
.note(CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ
);
679 pat
: &'tcx Pat
<'tcx
>,
680 qpath
: &hir
::QPath
<'_
>,
681 fields
: &'tcx
[hir
::FieldPat
<'tcx
>],
687 // Resolve the path and check the definition for errors.
688 let (variant
, pat_ty
) = if let Some(variant_ty
) = self.check_struct_path(qpath
, pat
.hir_id
)
692 let err
= self.tcx
.ty_error();
693 for field
in fields
{
694 let ti
= TopInfo { parent_pat: Some(&pat), ..ti }
;
695 self.check_pat(&field
.pat
, err
, def_bm
, ti
);
700 // Type-check the path.
701 self.demand_eqtype_pat(pat
.span
, expected
, pat_ty
, ti
);
703 // Type-check subpatterns.
704 if self.check_struct_pat_fields(pat_ty
, &pat
, variant
, fields
, etc
, def_bm
, ti
) {
714 path_resolution
: (Res
, Option
<Ty
<'tcx
>>, &'b
[hir
::PathSegment
<'b
>]),
720 // We have already resolved the path.
721 let (res
, opt_ty
, segments
) = path_resolution
;
724 self.set_tainted_by_errors();
725 return tcx
.ty_error();
727 Res
::Def(DefKind
::AssocFn
| DefKind
::Ctor(_
, CtorKind
::Fictive
| CtorKind
::Fn
), _
) => {
728 report_unexpected_variant_res(tcx
, res
, pat
.span
);
729 return tcx
.ty_error();
733 DefKind
::Ctor(_
, CtorKind
::Const
)
735 | DefKind
::AssocConst
736 | DefKind
::ConstParam
,
739 _
=> bug
!("unexpected pattern resolution: {:?}", res
),
742 // Type-check the path.
743 let (pat_ty
, pat_res
) =
744 self.instantiate_value_path(segments
, opt_ty
, res
, pat
.span
, pat
.hir_id
);
746 self.demand_suptype_with_origin(&self.pattern_cause(ti
, pat
.span
), expected
, pat_ty
)
748 self.emit_bad_pat_path(err
, pat
.span
, res
, pat_res
, pat_ty
, segments
, ti
.parent_pat
);
753 fn maybe_suggest_range_literal(
755 e
: &mut DiagnosticBuilder
<'_
>,
756 opt_def_id
: Option
<hir
::def_id
::DefId
>,
760 Some(def_id
) => match self.tcx
.hir().get_if_local(def_id
) {
761 Some(hir
::Node
::Item(hir
::Item
{
762 kind
: hir
::ItemKind
::Const(_
, body_id
), ..
763 })) => match self.tcx
.hir().get(body_id
.hir_id
) {
764 hir
::Node
::Expr(expr
) => {
765 if hir
::is_range_literal(expr
) {
766 let span
= self.tcx
.hir().span(body_id
.hir_id
);
767 if let Ok(snip
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
768 e
.span_suggestion_verbose(
770 "you may want to move the range into the match block",
772 Applicability
::MachineApplicable
,
787 fn emit_bad_pat_path(
789 mut e
: DiagnosticBuilder
<'_
>,
794 segments
: &'b
[hir
::PathSegment
<'b
>],
795 parent_pat
: Option
<&Pat
<'_
>>,
797 if let Some(span
) = self.tcx
.hir().res_span(pat_res
) {
798 e
.span_label(span
, &format
!("{} defined here", res
.descr()));
799 if let [hir
::PathSegment { ident, .. }
] = &*segments
{
803 "`{}` is interpreted as {} {}, not a new binding",
810 Some(Pat { kind: hir::PatKind::Struct(..), .. }
) => {
811 e
.span_suggestion_verbose(
812 ident
.span
.shrink_to_hi(),
813 "bind the struct field to a different name instead",
814 format
!(": other_{}", ident
.as_str().to_lowercase()),
815 Applicability
::HasPlaceholders
,
819 let (type_def_id
, item_def_id
) = match pat_ty
.kind() {
820 Adt(def
, _
) => match res
{
821 Res
::Def(DefKind
::Const
, def_id
) => (Some(def
.did
), Some(def_id
)),
828 self.tcx
.lang_items().range_struct(),
829 self.tcx
.lang_items().range_from_struct(),
830 self.tcx
.lang_items().range_to_struct(),
831 self.tcx
.lang_items().range_full_struct(),
832 self.tcx
.lang_items().range_inclusive_struct(),
833 self.tcx
.lang_items().range_to_inclusive_struct(),
835 if type_def_id
!= None
&& ranges
.contains(&type_def_id
) {
836 if !self.maybe_suggest_range_literal(&mut e
, item_def_id
, *ident
) {
837 let msg
= "constants only support matching by type, \
838 if you meant to match against a range of values, \
839 consider using a range pattern like `min ..= max` in the match block";
843 let msg
= "introduce a new binding instead";
844 let sugg
= format
!("other_{}", ident
.as_str().to_lowercase());
849 Applicability
::HasPlaceholders
,
859 fn check_pat_tuple_struct(
861 pat
: &'tcx Pat
<'tcx
>,
862 qpath
: &hir
::QPath
<'_
>,
863 subpats
: &'tcx
[&'tcx Pat
<'tcx
>],
864 ddpos
: Option
<usize>,
871 let parent_pat
= Some(pat
);
873 self.check_pat(&pat
, tcx
.ty_error(), def_bm
, TopInfo { parent_pat, ..ti }
);
876 let report_unexpected_res
= |res
: Res
| {
877 let sm
= tcx
.sess
.source_map();
879 .span_to_snippet(sm
.span_until_char(pat
.span
, '
('
))
880 .map_or(String
::new(), |s
| format
!(" `{}`", s
.trim_end()));
882 "expected tuple struct or tuple variant, found {}{}",
887 let mut err
= struct_span_err
!(tcx
.sess
, pat
.span
, E0164
, "{}", msg
);
889 Res
::Def(DefKind
::Fn
| DefKind
::AssocFn
, _
) => {
890 err
.span_label(pat
.span
, "`fn` calls are not allowed in patterns");
892 "for more information, visit \
893 https://doc.rust-lang.org/book/ch18-00-patterns.html",
897 err
.span_label(pat
.span
, "not a tuple variant or struct");
904 // Resolve the path and check the definition for errors.
905 let (res
, opt_ty
, segments
) = self.resolve_ty_and_res_ufcs(qpath
, pat
.hir_id
, pat
.span
);
907 self.set_tainted_by_errors();
909 return self.tcx
.ty_error();
912 // Type-check the path.
914 self.instantiate_value_path(segments
, opt_ty
, res
, pat
.span
, pat
.hir_id
);
916 report_unexpected_res(res
);
917 return tcx
.ty_error();
920 let variant
= match res
{
922 self.set_tainted_by_errors();
924 return tcx
.ty_error();
926 Res
::Def(DefKind
::AssocConst
| DefKind
::AssocFn
, _
) => {
927 report_unexpected_res(res
);
928 return tcx
.ty_error();
930 Res
::Def(DefKind
::Ctor(_
, CtorKind
::Fn
), _
) => tcx
.expect_variant_res(res
),
931 _
=> bug
!("unexpected pattern resolution: {:?}", res
),
934 // Replace constructor type with constructed type for tuple struct patterns.
935 let pat_ty
= pat_ty
.fn_sig(tcx
).output();
936 let pat_ty
= pat_ty
.no_bound_vars().expect("expected fn type");
938 // Type-check the tuple struct pattern against the expected type.
939 let diag
= self.demand_eqtype_pat_diag(pat
.span
, expected
, pat_ty
, ti
);
940 let had_err
= if let Some(mut err
) = diag
{
947 // Type-check subpatterns.
948 if subpats
.len() == variant
.fields
.len()
949 || subpats
.len() < variant
.fields
.len() && ddpos
.is_some()
951 let substs
= match pat_ty
.kind() {
952 ty
::Adt(_
, substs
) => substs
,
953 _
=> bug
!("unexpected pattern type {:?}", pat_ty
),
955 for (i
, subpat
) in subpats
.iter().enumerate_and_adjust(variant
.fields
.len(), ddpos
) {
956 let field_ty
= self.field_ty(subpat
.span
, &variant
.fields
[i
], substs
);
957 self.check_pat(&subpat
, field_ty
, def_bm
, TopInfo { parent_pat: Some(&pat), ..ti }
);
959 self.tcx
.check_stability(variant
.fields
[i
].did
, Some(pat
.hir_id
), subpat
.span
);
962 // Pattern has wrong number of fields.
963 self.e0023(pat
.span
, res
, qpath
, subpats
, &variant
.fields
, expected
, had_err
);
965 return tcx
.ty_error();
974 qpath
: &hir
::QPath
<'_
>,
975 subpats
: &'tcx
[&'tcx Pat
<'tcx
>],
976 fields
: &'tcx
[ty
::FieldDef
],
980 let subpats_ending
= pluralize
!(subpats
.len());
981 let fields_ending
= pluralize
!(fields
.len());
982 let res_span
= self.tcx
.def_span(res
.def_id());
983 let mut err
= struct_span_err
!(
987 "this pattern has {} field{}, but the corresponding {} has {} field{}",
996 format
!("expected {} field{}, found {}", fields
.len(), fields_ending
, subpats
.len(),),
998 .span_label(res_span
, format
!("{} defined here", res
.descr()));
1000 // Identify the case `Some(x, y)` where the expected type is e.g. `Option<(T, U)>`.
1001 // More generally, the expected type wants a tuple variant with one field of an
1002 // N-arity-tuple, e.g., `V_i((p_0, .., p_N))`. Meanwhile, the user supplied a pattern
1003 // with the subpatterns directly in the tuple variant pattern, e.g., `V_i(p_0, .., p_N)`.
1004 let missing_parenthesis
= match (&expected
.kind(), fields
, had_err
) {
1005 // #67037: only do this if we could successfully type-check the expected type against
1006 // the tuple struct pattern. Otherwise the substs could get out of range on e.g.,
1007 // `let P() = U;` where `P != U` with `struct P<T>(T);`.
1008 (ty
::Adt(_
, substs
), [field
], false) => {
1009 let field_ty
= self.field_ty(pat_span
, field
, substs
);
1010 match field_ty
.kind() {
1011 ty
::Tuple(_
) => field_ty
.tuple_fields().count() == subpats
.len(),
1017 if missing_parenthesis
{
1018 let (left
, right
) = match subpats
{
1019 // This is the zero case; we aim to get the "hi" part of the `QPath`'s
1020 // span as the "lo" and then the "hi" part of the pattern's span as the "hi".
1023 // help: missing parenthesis
1025 // L | let A(()) = A(());
1027 [] => (qpath
.span().shrink_to_hi(), pat_span
),
1028 // Easy case. Just take the "lo" of the first sub-pattern and the "hi" of the
1029 // last sub-pattern. In the case of `A(x)` the first and last may coincide.
1032 // help: missing parenthesis
1034 // L | let A((x, y)) = A((1, 2));
1036 [first
, ..] => (first
.span
.shrink_to_lo(), subpats
.last().unwrap().span
),
1038 err
.multipart_suggestion(
1039 "missing parenthesis",
1040 vec
![(left
, "(".to_string()), (right
.shrink_to_hi(), ")".to_string())],
1041 Applicability
::MachineApplicable
,
1051 elements
: &'tcx
[&'tcx Pat
<'tcx
>],
1052 ddpos
: Option
<usize>,
1054 def_bm
: BindingMode
,
1058 let mut expected_len
= elements
.len();
1059 if ddpos
.is_some() {
1060 // Require known type only when `..` is present.
1061 if let ty
::Tuple(ref tys
) = self.structurally_resolved_type(span
, expected
).kind() {
1062 expected_len
= tys
.len();
1065 let max_len
= cmp
::max(expected_len
, elements
.len());
1067 let element_tys_iter
= (0..max_len
).map(|_
| {
1068 GenericArg
::from(self.next_ty_var(
1069 // FIXME: `MiscVariable` for now -- obtaining the span and name information
1070 // from all tuple elements isn't trivial.
1071 TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span }
,
1074 let element_tys
= tcx
.mk_substs(element_tys_iter
);
1075 let pat_ty
= tcx
.mk_ty(ty
::Tuple(element_tys
));
1076 if let Some(mut err
) = self.demand_eqtype_pat_diag(span
, expected
, pat_ty
, ti
) {
1078 // Walk subpatterns with an expected type of `err` in this case to silence
1079 // further errors being emitted when using the bindings. #50333
1080 let element_tys_iter
= (0..max_len
).map(|_
| tcx
.ty_error());
1081 for (_
, elem
) in elements
.iter().enumerate_and_adjust(max_len
, ddpos
) {
1082 self.check_pat(elem
, &tcx
.ty_error(), def_bm
, ti
);
1084 tcx
.mk_tup(element_tys_iter
)
1086 for (i
, elem
) in elements
.iter().enumerate_and_adjust(max_len
, ddpos
) {
1087 self.check_pat(elem
, &element_tys
[i
].expect_ty(), def_bm
, ti
);
1093 fn check_struct_pat_fields(
1096 pat
: &'tcx Pat
<'tcx
>,
1097 variant
: &'tcx ty
::VariantDef
,
1098 fields
: &'tcx
[hir
::FieldPat
<'tcx
>],
1100 def_bm
: BindingMode
,
1105 let (substs
, adt
) = match adt_ty
.kind() {
1106 ty
::Adt(adt
, substs
) => (substs
, adt
),
1107 _
=> span_bug
!(pat
.span
, "struct pattern is not an ADT"),
1110 // Index the struct fields' types.
1111 let field_map
= variant
1115 .map(|(i
, field
)| (field
.ident
.normalize_to_macros_2_0(), (i
, field
)))
1116 .collect
::<FxHashMap
<_
, _
>>();
1118 // Keep track of which fields have already appeared in the pattern.
1119 let mut used_fields
= FxHashMap
::default();
1120 let mut no_field_errors
= true;
1122 let mut inexistent_fields
= vec
![];
1123 // Typecheck each field.
1124 for field
in fields
{
1125 let span
= field
.span
;
1126 let ident
= tcx
.adjust_ident(field
.ident
, variant
.def_id
);
1127 let field_ty
= match used_fields
.entry(ident
) {
1128 Occupied(occupied
) => {
1129 self.error_field_already_bound(span
, field
.ident
, *occupied
.get());
1130 no_field_errors
= false;
1134 vacant
.insert(span
);
1138 self.write_field_index(field
.hir_id
, *i
);
1139 self.tcx
.check_stability(f
.did
, Some(pat
.hir_id
), span
);
1140 self.field_ty(span
, f
, substs
)
1142 .unwrap_or_else(|| {
1143 inexistent_fields
.push(field
.ident
);
1144 no_field_errors
= false;
1150 self.check_pat(&field
.pat
, field_ty
, def_bm
, TopInfo { parent_pat: Some(&pat), ..ti }
);
1153 let mut unmentioned_fields
= variant
1156 .map(|field
| (field
, field
.ident
.normalize_to_macros_2_0()))
1157 .filter(|(_
, ident
)| !used_fields
.contains_key(&ident
))
1158 .collect
::<Vec
<_
>>();
1160 let inexistent_fields_err
= if !(inexistent_fields
.is_empty() || variant
.is_recovered()) {
1161 Some(self.error_inexistent_fields(
1162 adt
.variant_descr(),
1164 &mut unmentioned_fields
,
1171 // Require `..` if struct has non_exhaustive attribute.
1172 if variant
.is_field_list_non_exhaustive() && !adt
.did
.is_local() && !etc
{
1173 self.error_foreign_non_exhaustive_spat(pat
, adt
.variant_descr(), fields
.is_empty());
1176 let mut unmentioned_err
= None
;
1177 // Report an error if an incorrect number of fields was specified.
1179 if fields
.len() != 1 {
1181 .struct_span_err(pat
.span
, "union patterns should have exactly one field")
1185 tcx
.sess
.struct_span_err(pat
.span
, "`..` cannot be used in union patterns").emit();
1187 } else if !etc
&& !unmentioned_fields
.is_empty() {
1188 let no_accessible_unmentioned_fields
= !unmentioned_fields
.iter().any(|(field
, _
)| {
1189 field
.vis
.is_accessible_from(tcx
.parent_module(pat
.hir_id
).to_def_id(), tcx
)
1192 if no_accessible_unmentioned_fields
{
1193 unmentioned_err
= Some(self.error_no_accessible_fields(pat
, &fields
));
1196 Some(self.error_unmentioned_fields(pat
, &unmentioned_fields
, &fields
));
1199 match (inexistent_fields_err
, unmentioned_err
) {
1200 (Some(mut i
), Some(mut u
)) => {
1201 if let Some(mut e
) = self.error_tuple_variant_as_struct_pat(pat
, fields
, variant
) {
1202 // We don't want to show the inexistent fields error when this was
1203 // `Foo { a, b }` when it should have been `Foo(a, b)`.
1212 (None
, Some(mut err
)) | (Some(mut err
), None
) => {
1220 fn error_foreign_non_exhaustive_spat(&self, pat
: &Pat
<'_
>, descr
: &str, no_fields
: bool
) {
1221 let sess
= self.tcx
.sess
;
1222 let sm
= sess
.source_map();
1223 let sp_brace
= sm
.end_point(pat
.span
);
1224 let sp_comma
= sm
.end_point(pat
.span
.with_hi(sp_brace
.hi()));
1225 let sugg
= if no_fields
|| sp_brace
!= sp_comma { ".. }
" } else { ", .. }" };
1227 let mut err
= struct_span_err
!(
1231 "`..` required with {} marked as non-exhaustive",
1234 err
.span_suggestion_verbose(
1236 "add `..` at the end of the field list to ignore all other fields",
1238 Applicability
::MachineApplicable
,
1243 fn error_field_already_bound(&self, span
: Span
, ident
: Ident
, other_field
: Span
) {
1248 "field `{}` bound multiple times in the pattern",
1251 .span_label(span
, format
!("multiple uses of `{}` in pattern", ident
))
1252 .span_label(other_field
, format
!("first use of `{}`", ident
))
1256 fn error_inexistent_fields(
1259 inexistent_fields
: &[Ident
],
1260 unmentioned_fields
: &mut Vec
<(&ty
::FieldDef
, Ident
)>,
1261 variant
: &ty
::VariantDef
,
1262 ) -> DiagnosticBuilder
<'tcx
> {
1264 let (field_names
, t
, plural
) = if inexistent_fields
.len() == 1 {
1265 (format
!("a field named `{}`", inexistent_fields
[0]), "this", "")
1272 .map(|ident
| format
!("`{}`", ident
))
1273 .collect
::<Vec
<String
>>()
1280 let spans
= inexistent_fields
.iter().map(|ident
| ident
.span
).collect
::<Vec
<_
>>();
1281 let mut err
= struct_span_err
!(
1285 "{} `{}` does not have {}",
1287 tcx
.def_path_str(variant
.def_id
),
1290 if let Some(ident
) = inexistent_fields
.last() {
1294 "{} `{}` does not have {} field{}",
1296 tcx
.def_path_str(variant
.def_id
),
1303 unmentioned_fields
.iter().map(|(_
, field
)| field
.name
).collect
::<Vec
<_
>>();
1304 let suggested_name
= find_best_match_for_name(&input
, ident
.name
, None
);
1305 if let Some(suggested_name
) = suggested_name
{
1306 err
.span_suggestion(
1308 "a field with a similar name exists",
1309 suggested_name
.to_string(),
1310 Applicability
::MaybeIncorrect
,
1313 // When we have a tuple struct used with struct we don't want to suggest using
1314 // the (valid) struct syntax with numeric field names. Instead we want to
1315 // suggest the expected syntax. We infer that this is the case by parsing the
1316 // `Ident` into an unsized integer. The suggestion will be emitted elsewhere in
1317 // `smart_resolve_context_dependent_help`.
1318 if suggested_name
.to_ident_string().parse
::<usize>().is_err() {
1319 // We don't want to throw `E0027` in case we have thrown `E0026` for them.
1320 unmentioned_fields
.retain(|&(_
, x
)| x
.name
!= suggested_name
);
1325 if tcx
.sess
.teach(&err
.get_code().unwrap()) {
1327 "This error indicates that a struct pattern attempted to \
1328 extract a non-existent field from a struct. Struct fields \
1329 are identified by the name used before the colon : so struct \
1330 patterns should resemble the declaration of the struct type \
1332 If you are using shorthand field patterns but want to refer \
1333 to the struct field by a different name, you should rename \
1340 fn error_tuple_variant_as_struct_pat(
1343 fields
: &'tcx
[hir
::FieldPat
<'tcx
>],
1344 variant
: &ty
::VariantDef
,
1345 ) -> Option
<DiagnosticBuilder
<'tcx
>> {
1346 if let (CtorKind
::Fn
, PatKind
::Struct(qpath
, ..)) = (variant
.ctor_kind
, &pat
.kind
) {
1347 let path
= rustc_hir_pretty
::to_string(rustc_hir_pretty
::NO_ANN
, |s
| {
1348 s
.print_qpath(qpath
, false)
1350 let mut err
= struct_span_err
!(
1354 "tuple variant `{}` written as struct variant",
1357 let (sugg
, appl
) = if fields
.len() == variant
.fields
.len() {
1361 .map(|f
| match self.tcx
.sess
.source_map().span_to_snippet(f
.pat
.span
) {
1363 Err(_
) => rustc_hir_pretty
::to_string(rustc_hir_pretty
::NO_ANN
, |s
| {
1367 .collect
::<Vec
<String
>>()
1369 Applicability
::MachineApplicable
,
1373 variant
.fields
.iter().map(|_
| "_").collect
::<Vec
<&str>>().join(", "),
1374 Applicability
::MaybeIncorrect
,
1377 err
.span_suggestion(
1379 "use the tuple variant pattern syntax instead",
1380 format
!("{}({})", path
, sugg
),
1388 /// Returns a diagnostic reporting a struct pattern which is missing an `..` due to
1389 /// inaccessible fields.
1392 /// error: pattern requires `..` due to inaccessible fields
1393 /// --> src/main.rs:10:9
1395 /// LL | let foo::Foo {} = foo::Foo::default();
1398 /// help: add a `..`
1400 /// LL | let foo::Foo { .. } = foo::Foo::default();
1403 fn error_no_accessible_fields(
1406 fields
: &'tcx
[hir
::FieldPat
<'tcx
>],
1407 ) -> DiagnosticBuilder
<'tcx
> {
1411 .struct_span_err(pat
.span
, "pattern requires `..` due to inaccessible fields");
1413 if let Some(field
) = fields
.last() {
1414 err
.span_suggestion_verbose(
1415 field
.span
.shrink_to_hi(),
1416 "ignore the inaccessible and unused fields",
1418 Applicability
::MachineApplicable
,
1421 let qpath_span
= if let PatKind
::Struct(qpath
, ..) = &pat
.kind
{
1424 bug
!("`error_no_accessible_fields` called on non-struct pattern");
1427 // Shrink the span to exclude the `foo:Foo` in `foo::Foo { }`.
1428 let span
= pat
.span
.with_lo(qpath_span
.shrink_to_hi().hi());
1429 err
.span_suggestion_verbose(
1431 "ignore the inaccessible and unused fields",
1432 " { .. }".to_string(),
1433 Applicability
::MachineApplicable
,
1439 /// Returns a diagnostic reporting a struct pattern which does not mention some fields.
1442 /// error[E0027]: pattern does not mention field `you_cant_use_this_field`
1443 /// --> src/main.rs:15:9
1445 /// LL | let foo::Foo {} = foo::Foo::new();
1446 /// | ^^^^^^^^^^^ missing field `you_cant_use_this_field`
1448 fn error_unmentioned_fields(
1451 unmentioned_fields
: &[(&ty
::FieldDef
, Ident
)],
1452 fields
: &'tcx
[hir
::FieldPat
<'tcx
>],
1453 ) -> DiagnosticBuilder
<'tcx
> {
1454 let field_names
= if unmentioned_fields
.len() == 1 {
1455 format
!("field `{}`", unmentioned_fields
[0].1)
1457 let fields
= unmentioned_fields
1459 .map(|(_
, name
)| format
!("`{}`", name
))
1460 .collect
::<Vec
<String
>>()
1462 format
!("fields {}", fields
)
1464 let mut err
= struct_span_err
!(
1468 "pattern does not mention {}",
1471 err
.span_label(pat
.span
, format
!("missing {}", field_names
));
1472 let len
= unmentioned_fields
.len();
1473 let (prefix
, postfix
, sp
) = match fields
{
1474 [] => match &pat
.kind
{
1475 PatKind
::Struct(path
, [], false) => {
1476 (" { ", " }", path
.span().shrink_to_hi().until(pat
.span
.shrink_to_hi()))
1482 PatKind
::Struct(_
, [_
, ..], _
) => ", ",
1486 field
.span
.shrink_to_hi(),
1489 err
.span_suggestion(
1492 "include the missing field{} in the pattern",
1493 if len
== 1 { "" }
else { "s" }
,
1500 .map(|(_
, name
)| name
.to_string())
1501 .collect
::<Vec
<_
>>()
1505 Applicability
::MachineApplicable
,
1507 err
.span_suggestion(
1510 "if you don't care about {} missing field{}, you can explicitly ignore {}",
1511 if len
== 1 { "this" }
else { "these" }
,
1512 if len
== 1 { "" }
else { "s" }
,
1513 if len
== 1 { "it" }
else { "them" }
,
1515 format
!("{}..{}", prefix
, postfix
),
1516 Applicability
::MachineApplicable
,
1524 inner
: &'tcx Pat
<'tcx
>,
1526 def_bm
: BindingMode
,
1530 let (box_ty
, inner_ty
) = if self.check_dereferenceable(span
, expected
, &inner
) {
1531 // Here, `demand::subtype` is good enough, but I don't
1532 // think any errors can be introduced by using `demand::eqtype`.
1533 let inner_ty
= self.next_ty_var(TypeVariableOrigin
{
1534 kind
: TypeVariableOriginKind
::TypeInference
,
1537 let box_ty
= tcx
.mk_box(inner_ty
);
1538 self.demand_eqtype_pat(span
, expected
, box_ty
, ti
);
1541 let err
= tcx
.ty_error();
1544 self.check_pat(&inner
, inner_ty
, def_bm
, ti
);
1550 pat
: &'tcx Pat
<'tcx
>,
1551 inner
: &'tcx Pat
<'tcx
>,
1552 mutbl
: hir
::Mutability
,
1554 def_bm
: BindingMode
,
1558 let expected
= self.shallow_resolve(expected
);
1559 let (rptr_ty
, inner_ty
) = if self.check_dereferenceable(pat
.span
, expected
, &inner
) {
1560 // `demand::subtype` would be good enough, but using `eqtype` turns
1561 // out to be equally general. See (note_1) for details.
1563 // Take region, inner-type from expected type if we can,
1564 // to avoid creating needless variables. This also helps with
1565 // the bad interactions of the given hack detailed in (note_1).
1566 debug
!("check_pat_ref: expected={:?}", expected
);
1567 match *expected
.kind() {
1568 ty
::Ref(_
, r_ty
, r_mutbl
) if r_mutbl
== mutbl
=> (expected
, r_ty
),
1570 let inner_ty
= self.next_ty_var(TypeVariableOrigin
{
1571 kind
: TypeVariableOriginKind
::TypeInference
,
1574 let rptr_ty
= self.new_ref_ty(pat
.span
, mutbl
, inner_ty
);
1575 debug
!("check_pat_ref: demanding {:?} = {:?}", expected
, rptr_ty
);
1576 let err
= self.demand_eqtype_pat_diag(pat
.span
, expected
, rptr_ty
, ti
);
1578 // Look for a case like `fn foo(&foo: u32)` and suggest
1579 // `fn foo(foo: &u32)`
1580 if let Some(mut err
) = err
{
1581 self.borrow_pat_suggestion(&mut err
, &pat
, &inner
, &expected
);
1588 let err
= tcx
.ty_error();
1591 self.check_pat(&inner
, inner_ty
, def_bm
, TopInfo { parent_pat: Some(&pat), ..ti }
);
1595 /// Create a reference type with a fresh region variable.
1596 fn new_ref_ty(&self, span
: Span
, mutbl
: hir
::Mutability
, ty
: Ty
<'tcx
>) -> Ty
<'tcx
> {
1597 let region
= self.next_region_var(infer
::PatternRegion(span
));
1598 let mt
= ty
::TypeAndMut { ty, mutbl }
;
1599 self.tcx
.mk_ref(region
, mt
)
1602 /// Type check a slice pattern.
1604 /// Syntactically, these look like `[pat_0, ..., pat_n]`.
1605 /// Semantically, we are type checking a pattern with structure:
1607 /// [before_0, ..., before_n, (slice, after_0, ... after_n)?]
1609 /// The type of `slice`, if it is present, depends on the `expected` type.
1610 /// If `slice` is missing, then so is `after_i`.
1611 /// If `slice` is present, it can still represent 0 elements.
1615 before
: &'tcx
[&'tcx Pat
<'tcx
>],
1616 slice
: Option
<&'tcx Pat
<'tcx
>>,
1617 after
: &'tcx
[&'tcx Pat
<'tcx
>],
1619 def_bm
: BindingMode
,
1622 let expected
= self.structurally_resolved_type(span
, expected
);
1623 let (element_ty
, opt_slice_ty
, inferred
) = match *expected
.kind() {
1624 // An array, so we might have something like `let [a, b, c] = [0, 1, 2];`.
1625 ty
::Array(element_ty
, len
) => {
1626 let min
= before
.len() as u64 + after
.len() as u64;
1627 let (opt_slice_ty
, expected
) =
1628 self.check_array_pat_len(span
, element_ty
, expected
, slice
, len
, min
);
1629 // `opt_slice_ty.is_none()` => `slice.is_none()`.
1630 // Note, though, that opt_slice_ty could be `Some(error_ty)`.
1631 assert
!(opt_slice_ty
.is_some() || slice
.is_none());
1632 (element_ty
, opt_slice_ty
, expected
)
1634 ty
::Slice(element_ty
) => (element_ty
, Some(expected
), expected
),
1635 // The expected type must be an array or slice, but was neither, so error.
1637 if !expected
.references_error() {
1638 self.error_expected_array_or_slice(span
, expected
);
1640 let err
= self.tcx
.ty_error();
1641 (err
, Some(err
), err
)
1645 // Type check all the patterns before `slice`.
1647 self.check_pat(&elt
, element_ty
, def_bm
, ti
);
1649 // Type check the `slice`, if present, against its expected type.
1650 if let Some(slice
) = slice
{
1651 self.check_pat(&slice
, opt_slice_ty
.unwrap(), def_bm
, ti
);
1653 // Type check the elements after `slice`, if present.
1655 self.check_pat(&elt
, element_ty
, def_bm
, ti
);
1660 /// Type check the length of an array pattern.
1662 /// Returns both the type of the variable length pattern (or `None`), and the potentially
1663 /// inferred array type. We only return `None` for the slice type if `slice.is_none()`.
1664 fn check_array_pat_len(
1667 element_ty
: Ty
<'tcx
>,
1669 slice
: Option
<&'tcx Pat
<'tcx
>>,
1670 len
: &ty
::Const
<'tcx
>,
1672 ) -> (Option
<Ty
<'tcx
>>, Ty
<'tcx
>) {
1673 if let Some(len
) = len
.try_eval_usize(self.tcx
, self.param_env
) {
1674 // Now we know the length...
1675 if slice
.is_none() {
1676 // ...and since there is no variable-length pattern,
1677 // we require an exact match between the number of elements
1678 // in the array pattern and as provided by the matched type.
1680 return (None
, arr_ty
);
1683 self.error_scrutinee_inconsistent_length(span
, min_len
, len
);
1684 } else if let Some(pat_len
) = len
.checked_sub(min_len
) {
1685 // The variable-length pattern was there,
1686 // so it has an array type with the remaining elements left as its size...
1687 return (Some(self.tcx
.mk_array(element_ty
, pat_len
)), arr_ty
);
1689 // ...however, in this case, there were no remaining elements.
1690 // That is, the slice pattern requires more than the array type offers.
1691 self.error_scrutinee_with_rest_inconsistent_length(span
, min_len
, len
);
1693 } else if slice
.is_none() {
1694 // We have a pattern with a fixed length,
1695 // which we can use to infer the length of the array.
1696 let updated_arr_ty
= self.tcx
.mk_array(element_ty
, min_len
);
1697 self.demand_eqtype(span
, updated_arr_ty
, arr_ty
);
1698 return (None
, updated_arr_ty
);
1700 // We have a variable-length pattern and don't know the array length.
1701 // This happens if we have e.g.,
1702 // `let [a, b, ..] = arr` where `arr: [T; N]` where `const N: usize`.
1703 self.error_scrutinee_unfixed_length(span
);
1706 // If we get here, we must have emitted an error.
1707 (Some(self.tcx
.ty_error()), arr_ty
)
1710 fn error_scrutinee_inconsistent_length(&self, span
: Span
, min_len
: u64, size
: u64) {
1715 "pattern requires {} element{} but array has {}",
1717 pluralize
!(min_len
),
1720 .span_label(span
, format
!("expected {} element{}", size
, pluralize
!(size
)))
1724 fn error_scrutinee_with_rest_inconsistent_length(&self, span
: Span
, min_len
: u64, size
: u64) {
1729 "pattern requires at least {} element{} but array has {}",
1731 pluralize
!(min_len
),
1736 format
!("pattern cannot match array of {} element{}", size
, pluralize
!(size
),),
1741 fn error_scrutinee_unfixed_length(&self, span
: Span
) {
1746 "cannot pattern-match on an array without a fixed length",
1751 fn error_expected_array_or_slice(&self, span
: Span
, expected_ty
: Ty
<'tcx
>) {
1752 let mut err
= struct_span_err
!(
1756 "expected an array or slice, found `{}`",
1759 if let ty
::Ref(_
, ty
, _
) = expected_ty
.kind() {
1760 if let ty
::Array(..) | ty
::Slice(..) = ty
.kind() {
1761 err
.help("the semantics of slice patterns changed recently; see issue #62254");
1764 err
.span_label(span
, format
!("pattern cannot match with input type `{}`", expected_ty
));