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Diffstat (limited to 'compiler/rustc_typeck/src/check/pat.rs')
| -rw-r--r-- | compiler/rustc_typeck/src/check/pat.rs | 2142 |
1 files changed, 2142 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/check/pat.rs b/compiler/rustc_typeck/src/check/pat.rs new file mode 100644 index 000000000..837c32355 --- /dev/null +++ b/compiler/rustc_typeck/src/check/pat.rs @@ -0,0 +1,2142 @@ +use crate::check::FnCtxt; +use rustc_ast as ast; + +use rustc_data_structures::fx::FxHashMap; +use rustc_errors::{ + pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, + MultiSpan, +}; +use rustc_hir as hir; +use rustc_hir::def::{CtorKind, DefKind, Res}; +use rustc_hir::pat_util::EnumerateAndAdjustIterator; +use rustc_hir::{HirId, Pat, PatKind}; +use rustc_infer::infer; +use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; +use rustc_middle::middle::stability::EvalResult; +use rustc_middle::ty::{self, Adt, BindingMode, Ty, TypeVisitable}; +use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS; +use rustc_span::hygiene::DesugaringKind; +use rustc_span::lev_distance::find_best_match_for_name; +use rustc_span::source_map::{Span, Spanned}; +use rustc_span::symbol::{kw, sym, Ident}; +use rustc_span::{BytePos, DUMMY_SP}; +use rustc_trait_selection::autoderef::Autoderef; +use rustc_trait_selection::traits::{ObligationCause, Pattern}; +use ty::VariantDef; + +use std::cmp; +use std::collections::hash_map::Entry::{Occupied, Vacant}; + +use super::report_unexpected_variant_res; + +const CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ: &str = "\ +This error indicates that a pointer to a trait type cannot be implicitly dereferenced by a \ +pattern. Every trait defines a type, but because the size of trait implementors isn't fixed, \ +this type has no compile-time size. Therefore, all accesses to trait types must be through \ +pointers. If you encounter this error you should try to avoid dereferencing the pointer. + +You can read more about trait objects in the Trait Objects section of the Reference: \ +https://doc.rust-lang.org/reference/types.html#trait-objects"; + +/// Information about the expected type at the top level of type checking a pattern. +/// +/// **NOTE:** This is only for use by diagnostics. Do NOT use for type checking logic! +#[derive(Copy, Clone)] +struct TopInfo<'tcx> { + /// The `expected` type at the top level of type checking a pattern. + expected: Ty<'tcx>, + /// Was the origin of the `span` from a scrutinee expression? + /// + /// Otherwise there is no scrutinee and it could be e.g. from the type of a formal parameter. + origin_expr: bool, + /// The span giving rise to the `expected` type, if one could be provided. + /// + /// If `origin_expr` is `true`, then this is the span of the scrutinee as in: + /// + /// - `match scrutinee { ... }` + /// - `let _ = scrutinee;` + /// + /// This is used to point to add context in type errors. + /// In the following example, `span` corresponds to the `a + b` expression: + /// + /// ```text + /// error[E0308]: mismatched types + /// --> src/main.rs:L:C + /// | + /// L | let temp: usize = match a + b { + /// | ----- this expression has type `usize` + /// L | Ok(num) => num, + /// | ^^^^^^^ expected `usize`, found enum `std::result::Result` + /// | + /// = note: expected type `usize` + /// found type `std::result::Result<_, _>` + /// ``` + span: Option<Span>, +} + +impl<'tcx> FnCtxt<'_, 'tcx> { + fn pattern_cause(&self, ti: TopInfo<'tcx>, cause_span: Span) -> ObligationCause<'tcx> { + let code = Pattern { span: ti.span, root_ty: ti.expected, origin_expr: ti.origin_expr }; + self.cause(cause_span, code) + } + + fn demand_eqtype_pat_diag( + &self, + cause_span: Span, + expected: Ty<'tcx>, + actual: Ty<'tcx>, + ti: TopInfo<'tcx>, + ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> { + self.demand_eqtype_with_origin(&self.pattern_cause(ti, cause_span), expected, actual) + } + + fn demand_eqtype_pat( + &self, + cause_span: Span, + expected: Ty<'tcx>, + actual: Ty<'tcx>, + ti: TopInfo<'tcx>, + ) { + if let Some(mut err) = self.demand_eqtype_pat_diag(cause_span, expected, actual, ti) { + err.emit(); + } + } +} + +const INITIAL_BM: BindingMode = BindingMode::BindByValue(hir::Mutability::Not); + +/// Mode for adjusting the expected type and binding mode. +enum AdjustMode { + /// Peel off all immediate reference types. + Peel, + /// Reset binding mode to the initial mode. + Reset, + /// Pass on the input binding mode and expected type. + Pass, +} + +impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + /// Type check the given top level pattern against the `expected` type. + /// + /// If a `Some(span)` is provided and `origin_expr` holds, + /// then the `span` represents the scrutinee's span. + /// The scrutinee is found in e.g. `match scrutinee { ... }` and `let pat = scrutinee;`. + /// + /// Otherwise, `Some(span)` represents the span of a type expression + /// which originated the `expected` type. + pub fn check_pat_top( + &self, + pat: &'tcx Pat<'tcx>, + expected: Ty<'tcx>, + span: Option<Span>, + origin_expr: bool, + ) { + let info = TopInfo { expected, origin_expr, span }; + self.check_pat(pat, expected, INITIAL_BM, info); + } + + /// Type check the given `pat` against the `expected` type + /// with the provided `def_bm` (default binding mode). + /// + /// Outside of this module, `check_pat_top` should always be used. + /// Conversely, inside this module, `check_pat_top` should never be used. + #[instrument(level = "debug", skip(self, ti))] + fn check_pat( + &self, + pat: &'tcx Pat<'tcx>, + expected: Ty<'tcx>, + def_bm: BindingMode, + ti: TopInfo<'tcx>, + ) { + let path_res = match &pat.kind { + PatKind::Path(qpath) => { + Some(self.resolve_ty_and_res_fully_qualified_call(qpath, pat.hir_id, pat.span)) + } + _ => None, + }; + let adjust_mode = self.calc_adjust_mode(pat, path_res.map(|(res, ..)| res)); + let (expected, def_bm) = self.calc_default_binding_mode(pat, expected, def_bm, adjust_mode); + + let ty = match pat.kind { + PatKind::Wild => expected, + PatKind::Lit(lt) => self.check_pat_lit(pat.span, lt, expected, ti), + PatKind::Range(lhs, rhs, _) => self.check_pat_range(pat.span, lhs, rhs, expected, ti), + PatKind::Binding(ba, var_id, _, sub) => { + self.check_pat_ident(pat, ba, var_id, sub, expected, def_bm, ti) + } + PatKind::TupleStruct(ref qpath, subpats, ddpos) => { + self.check_pat_tuple_struct(pat, qpath, subpats, ddpos, expected, def_bm, ti) + } + PatKind::Path(ref qpath) => { + self.check_pat_path(pat, qpath, path_res.unwrap(), expected, ti) + } + PatKind::Struct(ref qpath, fields, has_rest_pat) => { + self.check_pat_struct(pat, qpath, fields, has_rest_pat, expected, def_bm, ti) + } + PatKind::Or(pats) => { + for pat in pats { + self.check_pat(pat, expected, def_bm, ti); + } + expected + } + PatKind::Tuple(elements, ddpos) => { + self.check_pat_tuple(pat.span, elements, ddpos, expected, def_bm, ti) + } + PatKind::Box(inner) => self.check_pat_box(pat.span, inner, expected, def_bm, ti), + PatKind::Ref(inner, mutbl) => { + self.check_pat_ref(pat, inner, mutbl, expected, def_bm, ti) + } + PatKind::Slice(before, slice, after) => { + self.check_pat_slice(pat.span, before, slice, after, expected, def_bm, ti) + } + }; + + self.write_ty(pat.hir_id, ty); + + // (note_1): In most of the cases where (note_1) is referenced + // (literals and constants being the exception), we relate types + // using strict equality, even though subtyping would be sufficient. + // There are a few reasons for this, some of which are fairly subtle + // and which cost me (nmatsakis) an hour or two debugging to remember, + // so I thought I'd write them down this time. + // + // 1. There is no loss of expressiveness here, though it does + // cause some inconvenience. What we are saying is that the type + // of `x` becomes *exactly* what is expected. This can cause unnecessary + // errors in some cases, such as this one: + // + // ``` + // fn foo<'x>(x: &'x i32) { + // let a = 1; + // let mut z = x; + // z = &a; + // } + // ``` + // + // The reason we might get an error is that `z` might be + // assigned a type like `&'x i32`, and then we would have + // a problem when we try to assign `&a` to `z`, because + // the lifetime of `&a` (i.e., the enclosing block) is + // shorter than `'x`. + // + // HOWEVER, this code works fine. The reason is that the + // expected type here is whatever type the user wrote, not + // the initializer's type. In this case the user wrote + // nothing, so we are going to create a type variable `Z`. + // Then we will assign the type of the initializer (`&'x i32`) + // as a subtype of `Z`: `&'x i32 <: Z`. And hence we + // will instantiate `Z` as a type `&'0 i32` where `'0` is + // a fresh region variable, with the constraint that `'x : '0`. + // So basically we're all set. + // + // Note that there are two tests to check that this remains true + // (`regions-reassign-{match,let}-bound-pointer.rs`). + // + // 2. Things go horribly wrong if we use subtype. The reason for + // THIS is a fairly subtle case involving bound regions. See the + // `givens` field in `region_constraints`, as well as the test + // `regions-relate-bound-regions-on-closures-to-inference-variables.rs`, + // for details. Short version is that we must sometimes detect + // relationships between specific region variables and regions + // bound in a closure signature, and that detection gets thrown + // off when we substitute fresh region variables here to enable + // subtyping. + } + + /// Compute the new expected type and default binding mode from the old ones + /// as well as the pattern form we are currently checking. + fn calc_default_binding_mode( + &self, + pat: &'tcx Pat<'tcx>, + expected: Ty<'tcx>, + def_bm: BindingMode, + adjust_mode: AdjustMode, + ) -> (Ty<'tcx>, BindingMode) { + match adjust_mode { + AdjustMode::Pass => (expected, def_bm), + AdjustMode::Reset => (expected, INITIAL_BM), + AdjustMode::Peel => self.peel_off_references(pat, expected, def_bm), + } + } + + /// How should the binding mode and expected type be adjusted? + /// + /// When the pattern is a path pattern, `opt_path_res` must be `Some(res)`. + fn calc_adjust_mode(&self, pat: &'tcx Pat<'tcx>, opt_path_res: Option<Res>) -> AdjustMode { + // When we perform destructuring assignment, we disable default match bindings, which are + // unintuitive in this context. + if !pat.default_binding_modes { + return AdjustMode::Reset; + } + match &pat.kind { + // Type checking these product-like types successfully always require + // that the expected type be of those types and not reference types. + PatKind::Struct(..) + | PatKind::TupleStruct(..) + | PatKind::Tuple(..) + | PatKind::Box(_) + | PatKind::Range(..) + | PatKind::Slice(..) => AdjustMode::Peel, + // String and byte-string literals result in types `&str` and `&[u8]` respectively. + // All other literals result in non-reference types. + // As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo {}`. + // + // Call `resolve_vars_if_possible` here for inline const blocks. + PatKind::Lit(lt) => match self.resolve_vars_if_possible(self.check_expr(lt)).kind() { + ty::Ref(..) => AdjustMode::Pass, + _ => AdjustMode::Peel, + }, + PatKind::Path(_) => match opt_path_res.unwrap() { + // These constants can be of a reference type, e.g. `const X: &u8 = &0;`. + // Peeling the reference types too early will cause type checking failures. + // Although it would be possible to *also* peel the types of the constants too. + Res::Def(DefKind::Const | DefKind::AssocConst, _) => AdjustMode::Pass, + // In the `ValueNS`, we have `SelfCtor(..) | Ctor(_, Const), _)` remaining which + // could successfully compile. The former being `Self` requires a unit struct. + // In either case, and unlike constants, the pattern itself cannot be + // a reference type wherefore peeling doesn't give up any expressiveness. + _ => AdjustMode::Peel, + }, + // When encountering a `& mut? pat` pattern, reset to "by value". + // This is so that `x` and `y` here are by value, as they appear to be: + // + // ``` + // match &(&22, &44) { + // (&x, &y) => ... + // } + // ``` + // + // See issue #46688. + PatKind::Ref(..) => AdjustMode::Reset, + // A `_` pattern works with any expected type, so there's no need to do anything. + PatKind::Wild + // Bindings also work with whatever the expected type is, + // and moreover if we peel references off, that will give us the wrong binding type. + // Also, we can have a subpattern `binding @ pat`. + // Each side of the `@` should be treated independently (like with OR-patterns). + | PatKind::Binding(..) + // An OR-pattern just propagates to each individual alternative. + // This is maximally flexible, allowing e.g., `Some(mut x) | &Some(mut x)`. + // In that example, `Some(mut x)` results in `Peel` whereas `&Some(mut x)` in `Reset`. + | PatKind::Or(_) => AdjustMode::Pass, + } + } + + /// Peel off as many immediately nested `& mut?` from the expected type as possible + /// and return the new expected type and binding default binding mode. + /// The adjustments vector, if non-empty is stored in a table. + fn peel_off_references( + &self, + pat: &'tcx Pat<'tcx>, + expected: Ty<'tcx>, + mut def_bm: BindingMode, + ) -> (Ty<'tcx>, BindingMode) { + let mut expected = self.resolve_vars_with_obligations(expected); + + // Peel off as many `&` or `&mut` from the scrutinee type as possible. For example, + // for `match &&&mut Some(5)` the loop runs three times, aborting when it reaches + // the `Some(5)` which is not of type Ref. + // + // For each ampersand peeled off, update the binding mode and push the original + // type into the adjustments vector. + // + // See the examples in `ui/match-defbm*.rs`. + let mut pat_adjustments = vec![]; + while let ty::Ref(_, inner_ty, inner_mutability) = *expected.kind() { + debug!("inspecting {:?}", expected); + + debug!("current discriminant is Ref, inserting implicit deref"); + // Preserve the reference type. We'll need it later during THIR lowering. + pat_adjustments.push(expected); + + expected = inner_ty; + def_bm = ty::BindByReference(match def_bm { + // If default binding mode is by value, make it `ref` or `ref mut` + // (depending on whether we observe `&` or `&mut`). + ty::BindByValue(_) | + // When `ref mut`, stay a `ref mut` (on `&mut`) or downgrade to `ref` (on `&`). + ty::BindByReference(hir::Mutability::Mut) => inner_mutability, + // Once a `ref`, always a `ref`. + // This is because a `& &mut` cannot mutate the underlying value. + ty::BindByReference(m @ hir::Mutability::Not) => m, + }); + } + + if !pat_adjustments.is_empty() { + debug!("default binding mode is now {:?}", def_bm); + self.inh + .typeck_results + .borrow_mut() + .pat_adjustments_mut() + .insert(pat.hir_id, pat_adjustments); + } + + (expected, def_bm) + } + + fn check_pat_lit( + &self, + span: Span, + lt: &hir::Expr<'tcx>, + expected: Ty<'tcx>, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + // We've already computed the type above (when checking for a non-ref pat), + // so avoid computing it again. + let ty = self.node_ty(lt.hir_id); + + // Byte string patterns behave the same way as array patterns + // They can denote both statically and dynamically-sized byte arrays. + let mut pat_ty = ty; + if let hir::ExprKind::Lit(Spanned { node: ast::LitKind::ByteStr(_), .. }) = lt.kind { + let expected = self.structurally_resolved_type(span, expected); + if let ty::Ref(_, inner_ty, _) = expected.kind() + && matches!(inner_ty.kind(), ty::Slice(_)) + { + let tcx = self.tcx; + trace!(?lt.hir_id.local_id, "polymorphic byte string lit"); + self.typeck_results + .borrow_mut() + .treat_byte_string_as_slice + .insert(lt.hir_id.local_id); + pat_ty = tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_slice(tcx.types.u8)); + } + } + + // Somewhat surprising: in this case, the subtyping relation goes the + // opposite way as the other cases. Actually what we really want is not + // a subtyping relation at all but rather that there exists a LUB + // (so that they can be compared). However, in practice, constants are + // always scalars or strings. For scalars subtyping is irrelevant, + // and for strings `ty` is type is `&'static str`, so if we say that + // + // &'static str <: expected + // + // then that's equivalent to there existing a LUB. + let cause = self.pattern_cause(ti, span); + if let Some(mut err) = self.demand_suptype_with_origin(&cause, expected, pat_ty) { + err.emit_unless( + ti.span + .filter(|&s| { + // In the case of `if`- and `while`-expressions we've already checked + // that `scrutinee: bool`. We know that the pattern is `true`, + // so an error here would be a duplicate and from the wrong POV. + s.is_desugaring(DesugaringKind::CondTemporary) + }) + .is_some(), + ); + } + + pat_ty + } + + fn check_pat_range( + &self, + span: Span, + lhs: Option<&'tcx hir::Expr<'tcx>>, + rhs: Option<&'tcx hir::Expr<'tcx>>, + expected: Ty<'tcx>, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + let calc_side = |opt_expr: Option<&'tcx hir::Expr<'tcx>>| match opt_expr { + None => None, + Some(expr) => { + let ty = self.check_expr(expr); + // Check that the end-point is possibly of numeric or char type. + // The early check here is not for correctness, but rather better + // diagnostics (e.g. when `&str` is being matched, `expected` will + // be peeled to `str` while ty here is still `&str`, if we don't + // err early here, a rather confusing unification error will be + // emitted instead). + let fail = + !(ty.is_numeric() || ty.is_char() || ty.is_ty_var() || ty.references_error()); + Some((fail, ty, expr.span)) + } + }; + let mut lhs = calc_side(lhs); + let mut rhs = calc_side(rhs); + + if let (Some((true, ..)), _) | (_, Some((true, ..))) = (lhs, rhs) { + // There exists a side that didn't meet our criteria that the end-point + // be of a numeric or char type, as checked in `calc_side` above. + self.emit_err_pat_range(span, lhs, rhs); + return self.tcx.ty_error(); + } + + // Unify each side with `expected`. + // Subtyping doesn't matter here, as the value is some kind of scalar. + let demand_eqtype = |x: &mut _, y| { + if let Some((ref mut fail, x_ty, x_span)) = *x + && let Some(mut err) = self.demand_eqtype_pat_diag(x_span, expected, x_ty, ti) + { + if let Some((_, y_ty, y_span)) = y { + self.endpoint_has_type(&mut err, y_span, y_ty); + } + err.emit(); + *fail = true; + } + }; + demand_eqtype(&mut lhs, rhs); + demand_eqtype(&mut rhs, lhs); + + if let (Some((true, ..)), _) | (_, Some((true, ..))) = (lhs, rhs) { + return self.tcx.ty_error(); + } + + // Find the unified type and check if it's of numeric or char type again. + // This check is needed if both sides are inference variables. + // We require types to be resolved here so that we emit inference failure + // rather than "_ is not a char or numeric". + let ty = self.structurally_resolved_type(span, expected); + if !(ty.is_numeric() || ty.is_char() || ty.references_error()) { + if let Some((ref mut fail, _, _)) = lhs { + *fail = true; + } + if let Some((ref mut fail, _, _)) = rhs { + *fail = true; + } + self.emit_err_pat_range(span, lhs, rhs); + return self.tcx.ty_error(); + } + ty + } + + fn endpoint_has_type(&self, err: &mut Diagnostic, span: Span, ty: Ty<'_>) { + if !ty.references_error() { + err.span_label(span, &format!("this is of type `{}`", ty)); + } + } + + fn emit_err_pat_range( + &self, + span: Span, + lhs: Option<(bool, Ty<'tcx>, Span)>, + rhs: Option<(bool, Ty<'tcx>, Span)>, + ) { + let span = match (lhs, rhs) { + (Some((true, ..)), Some((true, ..))) => span, + (Some((true, _, sp)), _) => sp, + (_, Some((true, _, sp))) => sp, + _ => span_bug!(span, "emit_err_pat_range: no side failed or exists but still error?"), + }; + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0029, + "only `char` and numeric types are allowed in range patterns" + ); + let msg = |ty| { + let ty = self.resolve_vars_if_possible(ty); + format!("this is of type `{}` but it should be `char` or numeric", ty) + }; + let mut one_side_err = |first_span, first_ty, second: Option<(bool, Ty<'tcx>, Span)>| { + err.span_label(first_span, &msg(first_ty)); + if let Some((_, ty, sp)) = second { + let ty = self.resolve_vars_if_possible(ty); + self.endpoint_has_type(&mut err, sp, ty); + } + }; + match (lhs, rhs) { + (Some((true, lhs_ty, lhs_sp)), Some((true, rhs_ty, rhs_sp))) => { + err.span_label(lhs_sp, &msg(lhs_ty)); + err.span_label(rhs_sp, &msg(rhs_ty)); + } + (Some((true, lhs_ty, lhs_sp)), rhs) => one_side_err(lhs_sp, lhs_ty, rhs), + (lhs, Some((true, rhs_ty, rhs_sp))) => one_side_err(rhs_sp, rhs_ty, lhs), + _ => span_bug!(span, "Impossible, verified above."), + } + if self.tcx.sess.teach(&err.get_code().unwrap()) { + err.note( + "In a match expression, only numbers and characters can be matched \ + against a range. This is because the compiler checks that the range \ + is non-empty at compile-time, and is unable to evaluate arbitrary \ + comparison functions. If you want to capture values of an orderable \ + type between two end-points, you can use a guard.", + ); + } + err.emit(); + } + + fn check_pat_ident( + &self, + pat: &'tcx Pat<'tcx>, + ba: hir::BindingAnnotation, + var_id: HirId, + sub: Option<&'tcx Pat<'tcx>>, + expected: Ty<'tcx>, + def_bm: BindingMode, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + // Determine the binding mode... + let bm = match ba { + hir::BindingAnnotation::Unannotated => def_bm, + _ => BindingMode::convert(ba), + }; + // ...and store it in a side table: + self.inh.typeck_results.borrow_mut().pat_binding_modes_mut().insert(pat.hir_id, bm); + + debug!("check_pat_ident: pat.hir_id={:?} bm={:?}", pat.hir_id, bm); + + let local_ty = self.local_ty(pat.span, pat.hir_id).decl_ty; + let eq_ty = match bm { + ty::BindByReference(mutbl) => { + // If the binding is like `ref x | ref mut x`, + // then `x` is assigned a value of type `&M T` where M is the + // mutability and T is the expected type. + // + // `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)` + // is required. However, we use equality, which is stronger. + // See (note_1) for an explanation. + self.new_ref_ty(pat.span, mutbl, expected) + } + // Otherwise, the type of x is the expected type `T`. + ty::BindByValue(_) => { + // As above, `T <: typeof(x)` is required, but we use equality, see (note_1). + expected + } + }; + self.demand_eqtype_pat(pat.span, eq_ty, local_ty, ti); + + // If there are multiple arms, make sure they all agree on + // what the type of the binding `x` ought to be. + if var_id != pat.hir_id { + self.check_binding_alt_eq_ty(pat.span, var_id, local_ty, ti); + } + + if let Some(p) = sub { + self.check_pat(p, expected, def_bm, ti); + } + + local_ty + } + + fn check_binding_alt_eq_ty(&self, span: Span, var_id: HirId, ty: Ty<'tcx>, ti: TopInfo<'tcx>) { + let var_ty = self.local_ty(span, var_id).decl_ty; + if let Some(mut err) = self.demand_eqtype_pat_diag(span, var_ty, ty, ti) { + let hir = self.tcx.hir(); + let var_ty = self.resolve_vars_with_obligations(var_ty); + let msg = format!("first introduced with type `{var_ty}` here"); + err.span_label(hir.span(var_id), msg); + let in_match = hir.parent_iter(var_id).any(|(_, n)| { + matches!( + n, + hir::Node::Expr(hir::Expr { + kind: hir::ExprKind::Match(.., hir::MatchSource::Normal), + .. + }) + ) + }); + let pre = if in_match { "in the same arm, " } else { "" }; + err.note(&format!("{}a binding must have the same type in all alternatives", pre)); + // FIXME: check if `var_ty` and `ty` can be made the same type by adding or removing + // `ref` or `&` to the pattern. + err.emit(); + } + } + + // Precondition: pat is a Ref(_) pattern + fn borrow_pat_suggestion(&self, err: &mut Diagnostic, pat: &Pat<'_>) { + let tcx = self.tcx; + if let PatKind::Ref(inner, mutbl) = pat.kind + && let PatKind::Binding(_, _, binding, ..) = inner.kind { + let binding_parent_id = tcx.hir().get_parent_node(pat.hir_id); + let binding_parent = tcx.hir().get(binding_parent_id); + debug!(?inner, ?pat, ?binding_parent); + + let mutability = match mutbl { + ast::Mutability::Mut => "mut", + ast::Mutability::Not => "", + }; + + let mut_var_suggestion = 'block: { + if !matches!(mutbl, ast::Mutability::Mut) { + break 'block None; + } + + let ident_kind = match binding_parent { + hir::Node::Param(_) => "parameter", + hir::Node::Local(_) => "variable", + hir::Node::Arm(_) => "binding", + + // Provide diagnostics only if the parent pattern is struct-like, + // i.e. where `mut binding` makes sense + hir::Node::Pat(Pat { kind, .. }) => match kind { + PatKind::Struct(..) + | PatKind::TupleStruct(..) + | PatKind::Or(..) + | PatKind::Tuple(..) + | PatKind::Slice(..) => "binding", + + PatKind::Wild + | PatKind::Binding(..) + | PatKind::Path(..) + | PatKind::Box(..) + | PatKind::Ref(..) + | PatKind::Lit(..) + | PatKind::Range(..) => break 'block None, + }, + + // Don't provide suggestions in other cases + _ => break 'block None, + }; + + Some(( + pat.span, + format!("to declare a mutable {ident_kind} use"), + format!("mut {binding}"), + )) + + }; + + match binding_parent { + // Check that there is explicit type (ie this is not a closure param with inferred type) + // so we don't suggest moving something to the type that does not exist + hir::Node::Param(hir::Param { ty_span, .. }) if binding.span != *ty_span => { + err.multipart_suggestion_verbose( + format!("to take parameter `{binding}` by reference, move `&{mutability}` to the type"), + vec![ + (pat.span.until(inner.span), "".to_owned()), + (ty_span.shrink_to_lo(), format!("&{}", mutbl.prefix_str())), + ], + Applicability::MachineApplicable + ); + + if let Some((sp, msg, sugg)) = mut_var_suggestion { + err.span_note(sp, format!("{msg}: `{sugg}`")); + } + } + hir::Node::Param(_) | hir::Node::Arm(_) | hir::Node::Pat(_) => { + // rely on match ergonomics or it might be nested `&&pat` + err.span_suggestion_verbose( + pat.span.until(inner.span), + format!("consider removing `&{mutability}` from the pattern"), + "", + Applicability::MaybeIncorrect, + ); + + if let Some((sp, msg, sugg)) = mut_var_suggestion { + err.span_note(sp, format!("{msg}: `{sugg}`")); + } + } + _ if let Some((sp, msg, sugg)) = mut_var_suggestion => { + err.span_suggestion(sp, msg, sugg, Applicability::MachineApplicable); + } + _ => {} // don't provide suggestions in other cases #55175 + } + } + } + + pub fn check_dereferenceable(&self, span: Span, expected: Ty<'tcx>, inner: &Pat<'_>) -> bool { + if let PatKind::Binding(..) = inner.kind + && let Some(mt) = self.shallow_resolve(expected).builtin_deref(true) + && let ty::Dynamic(..) = mt.ty.kind() + { + // This is "x = SomeTrait" being reduced from + // "let &x = &SomeTrait" or "let box x = Box<SomeTrait>", an error. + let type_str = self.ty_to_string(expected); + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0033, + "type `{}` cannot be dereferenced", + type_str + ); + err.span_label(span, format!("type `{type_str}` cannot be dereferenced")); + if self.tcx.sess.teach(&err.get_code().unwrap()) { + err.note(CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ); + } + err.emit(); + return false; + } + true + } + + fn check_pat_struct( + &self, + pat: &'tcx Pat<'tcx>, + qpath: &hir::QPath<'_>, + fields: &'tcx [hir::PatField<'tcx>], + has_rest_pat: bool, + expected: Ty<'tcx>, + def_bm: BindingMode, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + // Resolve the path and check the definition for errors. + let Some((variant, pat_ty)) = self.check_struct_path(qpath, pat.hir_id) else { + let err = self.tcx.ty_error(); + for field in fields { + let ti = ti; + self.check_pat(field.pat, err, def_bm, ti); + } + return err; + }; + + // Type-check the path. + self.demand_eqtype_pat(pat.span, expected, pat_ty, ti); + + // Type-check subpatterns. + if self.check_struct_pat_fields(pat_ty, &pat, variant, fields, has_rest_pat, def_bm, ti) { + pat_ty + } else { + self.tcx.ty_error() + } + } + + fn check_pat_path( + &self, + pat: &Pat<'tcx>, + qpath: &hir::QPath<'_>, + path_resolution: (Res, Option<Ty<'tcx>>, &'tcx [hir::PathSegment<'tcx>]), + expected: Ty<'tcx>, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + let tcx = self.tcx; + + // We have already resolved the path. + let (res, opt_ty, segments) = path_resolution; + match res { + Res::Err => { + self.set_tainted_by_errors(); + return tcx.ty_error(); + } + Res::Def(DefKind::AssocFn | DefKind::Ctor(_, CtorKind::Fictive | CtorKind::Fn), _) => { + report_unexpected_variant_res(tcx, res, qpath, pat.span); + return tcx.ty_error(); + } + Res::SelfCtor(..) + | Res::Def( + DefKind::Ctor(_, CtorKind::Const) + | DefKind::Const + | DefKind::AssocConst + | DefKind::ConstParam, + _, + ) => {} // OK + _ => bug!("unexpected pattern resolution: {:?}", res), + } + + // Type-check the path. + let (pat_ty, pat_res) = + self.instantiate_value_path(segments, opt_ty, res, pat.span, pat.hir_id); + if let Some(err) = + self.demand_suptype_with_origin(&self.pattern_cause(ti, pat.span), expected, pat_ty) + { + self.emit_bad_pat_path(err, pat, res, pat_res, pat_ty, segments); + } + pat_ty + } + + fn maybe_suggest_range_literal( + &self, + e: &mut Diagnostic, + opt_def_id: Option<hir::def_id::DefId>, + ident: Ident, + ) -> bool { + match opt_def_id { + Some(def_id) => match self.tcx.hir().get_if_local(def_id) { + Some(hir::Node::Item(hir::Item { + kind: hir::ItemKind::Const(_, body_id), .. + })) => match self.tcx.hir().get(body_id.hir_id) { + hir::Node::Expr(expr) => { + if hir::is_range_literal(expr) { + let span = self.tcx.hir().span(body_id.hir_id); + if let Ok(snip) = self.tcx.sess.source_map().span_to_snippet(span) { + e.span_suggestion_verbose( + ident.span, + "you may want to move the range into the match block", + snip, + Applicability::MachineApplicable, + ); + return true; + } + } + } + _ => (), + }, + _ => (), + }, + _ => (), + } + false + } + + fn emit_bad_pat_path( + &self, + mut e: DiagnosticBuilder<'_, ErrorGuaranteed>, + pat: &hir::Pat<'tcx>, + res: Res, + pat_res: Res, + pat_ty: Ty<'tcx>, + segments: &'tcx [hir::PathSegment<'tcx>], + ) { + let pat_span = pat.span; + if let Some(span) = self.tcx.hir().res_span(pat_res) { + e.span_label(span, &format!("{} defined here", res.descr())); + if let [hir::PathSegment { ident, .. }] = &*segments { + e.span_label( + pat_span, + &format!( + "`{}` is interpreted as {} {}, not a new binding", + ident, + res.article(), + res.descr(), + ), + ); + match self.tcx.hir().get(self.tcx.hir().get_parent_node(pat.hir_id)) { + hir::Node::Pat(Pat { kind: hir::PatKind::Struct(..), .. }) => { + e.span_suggestion_verbose( + ident.span.shrink_to_hi(), + "bind the struct field to a different name instead", + format!(": other_{}", ident.as_str().to_lowercase()), + Applicability::HasPlaceholders, + ); + } + _ => { + let (type_def_id, item_def_id) = match pat_ty.kind() { + Adt(def, _) => match res { + Res::Def(DefKind::Const, def_id) => (Some(def.did()), Some(def_id)), + _ => (None, None), + }, + _ => (None, None), + }; + + let ranges = &[ + self.tcx.lang_items().range_struct(), + self.tcx.lang_items().range_from_struct(), + self.tcx.lang_items().range_to_struct(), + self.tcx.lang_items().range_full_struct(), + self.tcx.lang_items().range_inclusive_struct(), + self.tcx.lang_items().range_to_inclusive_struct(), + ]; + if type_def_id != None && ranges.contains(&type_def_id) { + if !self.maybe_suggest_range_literal(&mut e, item_def_id, *ident) { + let msg = "constants only support matching by type, \ + if you meant to match against a range of values, \ + consider using a range pattern like `min ..= max` in the match block"; + e.note(msg); + } + } else { + let msg = "introduce a new binding instead"; + let sugg = format!("other_{}", ident.as_str().to_lowercase()); + e.span_suggestion( + ident.span, + msg, + sugg, + Applicability::HasPlaceholders, + ); + } + } + }; + } + } + e.emit(); + } + + fn check_pat_tuple_struct( + &self, + pat: &'tcx Pat<'tcx>, + qpath: &'tcx hir::QPath<'tcx>, + subpats: &'tcx [Pat<'tcx>], + ddpos: Option<usize>, + expected: Ty<'tcx>, + def_bm: BindingMode, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + let tcx = self.tcx; + let on_error = || { + for pat in subpats { + self.check_pat(pat, tcx.ty_error(), def_bm, ti); + } + }; + let report_unexpected_res = |res: Res| { + let sm = tcx.sess.source_map(); + let path_str = sm + .span_to_snippet(sm.span_until_char(pat.span, '(')) + .map_or_else(|_| String::new(), |s| format!(" `{}`", s.trim_end())); + let msg = format!( + "expected tuple struct or tuple variant, found {}{}", + res.descr(), + path_str + ); + + let mut err = struct_span_err!(tcx.sess, pat.span, E0164, "{msg}"); + match res { + Res::Def(DefKind::Fn | DefKind::AssocFn, _) => { + err.span_label(pat.span, "`fn` calls are not allowed in patterns"); + err.help( + "for more information, visit \ + https://doc.rust-lang.org/book/ch18-00-patterns.html", + ); + } + _ => { + err.span_label(pat.span, "not a tuple variant or struct"); + } + } + err.emit(); + on_error(); + }; + + // Resolve the path and check the definition for errors. + let (res, opt_ty, segments) = + self.resolve_ty_and_res_fully_qualified_call(qpath, pat.hir_id, pat.span); + if res == Res::Err { + self.set_tainted_by_errors(); + on_error(); + return self.tcx.ty_error(); + } + + // Type-check the path. + let (pat_ty, res) = + self.instantiate_value_path(segments, opt_ty, res, pat.span, pat.hir_id); + if !pat_ty.is_fn() { + report_unexpected_res(res); + return tcx.ty_error(); + } + + let variant = match res { + Res::Err => { + self.set_tainted_by_errors(); + on_error(); + return tcx.ty_error(); + } + Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) => { + report_unexpected_res(res); + return tcx.ty_error(); + } + Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) => tcx.expect_variant_res(res), + _ => bug!("unexpected pattern resolution: {:?}", res), + }; + + // Replace constructor type with constructed type for tuple struct patterns. + let pat_ty = pat_ty.fn_sig(tcx).output(); + let pat_ty = pat_ty.no_bound_vars().expect("expected fn type"); + + // Type-check the tuple struct pattern against the expected type. + let diag = self.demand_eqtype_pat_diag(pat.span, expected, pat_ty, ti); + let had_err = if let Some(mut err) = diag { + err.emit(); + true + } else { + false + }; + + // Type-check subpatterns. + if subpats.len() == variant.fields.len() + || subpats.len() < variant.fields.len() && ddpos.is_some() + { + let ty::Adt(_, substs) = pat_ty.kind() else { + bug!("unexpected pattern type {:?}", pat_ty); + }; + for (i, subpat) in subpats.iter().enumerate_and_adjust(variant.fields.len(), ddpos) { + let field_ty = self.field_ty(subpat.span, &variant.fields[i], substs); + self.check_pat(subpat, field_ty, def_bm, ti); + + self.tcx.check_stability( + variant.fields[i].did, + Some(pat.hir_id), + subpat.span, + None, + ); + } + } else { + // Pattern has wrong number of fields. + self.e0023(pat.span, res, qpath, subpats, &variant.fields, expected, had_err); + on_error(); + return tcx.ty_error(); + } + pat_ty + } + + fn e0023( + &self, + pat_span: Span, + res: Res, + qpath: &hir::QPath<'_>, + subpats: &'tcx [Pat<'tcx>], + fields: &'tcx [ty::FieldDef], + expected: Ty<'tcx>, + had_err: bool, + ) { + let subpats_ending = pluralize!(subpats.len()); + let fields_ending = pluralize!(fields.len()); + + let subpat_spans = if subpats.is_empty() { + vec![pat_span] + } else { + subpats.iter().map(|p| p.span).collect() + }; + let last_subpat_span = *subpat_spans.last().unwrap(); + let res_span = self.tcx.def_span(res.def_id()); + let def_ident_span = self.tcx.def_ident_span(res.def_id()).unwrap_or(res_span); + let field_def_spans = if fields.is_empty() { + vec![res_span] + } else { + fields.iter().map(|f| f.ident(self.tcx).span).collect() + }; + let last_field_def_span = *field_def_spans.last().unwrap(); + + let mut err = struct_span_err!( + self.tcx.sess, + MultiSpan::from_spans(subpat_spans), + E0023, + "this pattern has {} field{}, but the corresponding {} has {} field{}", + subpats.len(), + subpats_ending, + res.descr(), + fields.len(), + fields_ending, + ); + err.span_label( + last_subpat_span, + &format!("expected {} field{}, found {}", fields.len(), fields_ending, subpats.len()), + ); + if self.tcx.sess.source_map().is_multiline(qpath.span().between(last_subpat_span)) { + err.span_label(qpath.span(), ""); + } + if self.tcx.sess.source_map().is_multiline(def_ident_span.between(last_field_def_span)) { + err.span_label(def_ident_span, format!("{} defined here", res.descr())); + } + for span in &field_def_spans[..field_def_spans.len() - 1] { + err.span_label(*span, ""); + } + err.span_label( + last_field_def_span, + &format!("{} has {} field{}", res.descr(), fields.len(), fields_ending), + ); + + // Identify the case `Some(x, y)` where the expected type is e.g. `Option<(T, U)>`. + // More generally, the expected type wants a tuple variant with one field of an + // N-arity-tuple, e.g., `V_i((p_0, .., p_N))`. Meanwhile, the user supplied a pattern + // with the subpatterns directly in the tuple variant pattern, e.g., `V_i(p_0, .., p_N)`. + let missing_parentheses = match (&expected.kind(), fields, had_err) { + // #67037: only do this if we could successfully type-check the expected type against + // the tuple struct pattern. Otherwise the substs could get out of range on e.g., + // `let P() = U;` where `P != U` with `struct P<T>(T);`. + (ty::Adt(_, substs), [field], false) => { + let field_ty = self.field_ty(pat_span, field, substs); + match field_ty.kind() { + ty::Tuple(fields) => fields.len() == subpats.len(), + _ => false, + } + } + _ => false, + }; + if missing_parentheses { + let (left, right) = match subpats { + // This is the zero case; we aim to get the "hi" part of the `QPath`'s + // span as the "lo" and then the "hi" part of the pattern's span as the "hi". + // This looks like: + // + // help: missing parentheses + // | + // L | let A(()) = A(()); + // | ^ ^ + [] => (qpath.span().shrink_to_hi(), pat_span), + // Easy case. Just take the "lo" of the first sub-pattern and the "hi" of the + // last sub-pattern. In the case of `A(x)` the first and last may coincide. + // This looks like: + // + // help: missing parentheses + // | + // L | let A((x, y)) = A((1, 2)); + // | ^ ^ + [first, ..] => (first.span.shrink_to_lo(), subpats.last().unwrap().span), + }; + err.multipart_suggestion( + "missing parentheses", + vec![(left, "(".to_string()), (right.shrink_to_hi(), ")".to_string())], + Applicability::MachineApplicable, + ); + } else if fields.len() > subpats.len() && pat_span != DUMMY_SP { + let after_fields_span = pat_span.with_hi(pat_span.hi() - BytePos(1)).shrink_to_hi(); + let all_fields_span = match subpats { + [] => after_fields_span, + [field] => field.span, + [first, .., last] => first.span.to(last.span), + }; + + // Check if all the fields in the pattern are wildcards. + let all_wildcards = subpats.iter().all(|pat| matches!(pat.kind, PatKind::Wild)); + let first_tail_wildcard = + subpats.iter().enumerate().fold(None, |acc, (pos, pat)| match (acc, &pat.kind) { + (None, PatKind::Wild) => Some(pos), + (Some(_), PatKind::Wild) => acc, + _ => None, + }); + let tail_span = match first_tail_wildcard { + None => after_fields_span, + Some(0) => subpats[0].span.to(after_fields_span), + Some(pos) => subpats[pos - 1].span.shrink_to_hi().to(after_fields_span), + }; + + // FIXME: heuristic-based suggestion to check current types for where to add `_`. + let mut wildcard_sugg = vec!["_"; fields.len() - subpats.len()].join(", "); + if !subpats.is_empty() { + wildcard_sugg = String::from(", ") + &wildcard_sugg; + } + + err.span_suggestion_verbose( + after_fields_span, + "use `_` to explicitly ignore each field", + wildcard_sugg, + Applicability::MaybeIncorrect, + ); + + // Only suggest `..` if more than one field is missing + // or the pattern consists of all wildcards. + if fields.len() - subpats.len() > 1 || all_wildcards { + if subpats.is_empty() || all_wildcards { + err.span_suggestion_verbose( + all_fields_span, + "use `..` to ignore all fields", + "..", + Applicability::MaybeIncorrect, + ); + } else { + err.span_suggestion_verbose( + tail_span, + "use `..` to ignore the rest of the fields", + ", ..", + Applicability::MaybeIncorrect, + ); + } + } + } + + err.emit(); + } + + fn check_pat_tuple( + &self, + span: Span, + elements: &'tcx [Pat<'tcx>], + ddpos: Option<usize>, + expected: Ty<'tcx>, + def_bm: BindingMode, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + let tcx = self.tcx; + let mut expected_len = elements.len(); + if ddpos.is_some() { + // Require known type only when `..` is present. + if let ty::Tuple(tys) = self.structurally_resolved_type(span, expected).kind() { + expected_len = tys.len(); + } + } + let max_len = cmp::max(expected_len, elements.len()); + + let element_tys_iter = (0..max_len).map(|_| { + self.next_ty_var( + // FIXME: `MiscVariable` for now -- obtaining the span and name information + // from all tuple elements isn't trivial. + TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span }, + ) + }); + let element_tys = tcx.mk_type_list(element_tys_iter); + let pat_ty = tcx.mk_ty(ty::Tuple(element_tys)); + if let Some(mut err) = self.demand_eqtype_pat_diag(span, expected, pat_ty, ti) { + err.emit(); + // Walk subpatterns with an expected type of `err` in this case to silence + // further errors being emitted when using the bindings. #50333 + let element_tys_iter = (0..max_len).map(|_| tcx.ty_error()); + for (_, elem) in elements.iter().enumerate_and_adjust(max_len, ddpos) { + self.check_pat(elem, tcx.ty_error(), def_bm, ti); + } + tcx.mk_tup(element_tys_iter) + } else { + for (i, elem) in elements.iter().enumerate_and_adjust(max_len, ddpos) { + self.check_pat(elem, element_tys[i], def_bm, ti); + } + pat_ty + } + } + + fn check_struct_pat_fields( + &self, + adt_ty: Ty<'tcx>, + pat: &'tcx Pat<'tcx>, + variant: &'tcx ty::VariantDef, + fields: &'tcx [hir::PatField<'tcx>], + has_rest_pat: bool, + def_bm: BindingMode, + ti: TopInfo<'tcx>, + ) -> bool { + let tcx = self.tcx; + + let ty::Adt(adt, substs) = adt_ty.kind() else { + span_bug!(pat.span, "struct pattern is not an ADT"); + }; + + // Index the struct fields' types. + let field_map = variant + .fields + .iter() + .enumerate() + .map(|(i, field)| (field.ident(self.tcx).normalize_to_macros_2_0(), (i, field))) + .collect::<FxHashMap<_, _>>(); + + // Keep track of which fields have already appeared in the pattern. + let mut used_fields = FxHashMap::default(); + let mut no_field_errors = true; + + let mut inexistent_fields = vec![]; + // Typecheck each field. + for field in fields { + let span = field.span; + let ident = tcx.adjust_ident(field.ident, variant.def_id); + let field_ty = match used_fields.entry(ident) { + Occupied(occupied) => { + self.error_field_already_bound(span, field.ident, *occupied.get()); + no_field_errors = false; + tcx.ty_error() + } + Vacant(vacant) => { + vacant.insert(span); + field_map + .get(&ident) + .map(|(i, f)| { + self.write_field_index(field.hir_id, *i); + self.tcx.check_stability(f.did, Some(pat.hir_id), span, None); + self.field_ty(span, f, substs) + }) + .unwrap_or_else(|| { + inexistent_fields.push(field); + no_field_errors = false; + tcx.ty_error() + }) + } + }; + + self.check_pat(field.pat, field_ty, def_bm, ti); + } + + let mut unmentioned_fields = variant + .fields + .iter() + .map(|field| (field, field.ident(self.tcx).normalize_to_macros_2_0())) + .filter(|(_, ident)| !used_fields.contains_key(ident)) + .collect::<Vec<_>>(); + + let inexistent_fields_err = if !(inexistent_fields.is_empty() || variant.is_recovered()) + && !inexistent_fields.iter().any(|field| field.ident.name == kw::Underscore) + { + Some(self.error_inexistent_fields( + adt.variant_descr(), + &inexistent_fields, + &mut unmentioned_fields, + variant, + substs, + )) + } else { + None + }; + + // Require `..` if struct has non_exhaustive attribute. + let non_exhaustive = variant.is_field_list_non_exhaustive() && !adt.did().is_local(); + if non_exhaustive && !has_rest_pat { + self.error_foreign_non_exhaustive_spat(pat, adt.variant_descr(), fields.is_empty()); + } + + let mut unmentioned_err = None; + // Report an error if an incorrect number of fields was specified. + if adt.is_union() { + if fields.len() != 1 { + tcx.sess + .struct_span_err(pat.span, "union patterns should have exactly one field") + .emit(); + } + if has_rest_pat { + tcx.sess.struct_span_err(pat.span, "`..` cannot be used in union patterns").emit(); + } + } else if !unmentioned_fields.is_empty() { + let accessible_unmentioned_fields: Vec<_> = unmentioned_fields + .iter() + .copied() + .filter(|(field, _)| { + field.vis.is_accessible_from(tcx.parent_module(pat.hir_id).to_def_id(), tcx) + && !matches!( + tcx.eval_stability(field.did, None, DUMMY_SP, None), + EvalResult::Deny { .. } + ) + // We only want to report the error if it is hidden and not local + && !(tcx.is_doc_hidden(field.did) && !field.did.is_local()) + }) + .collect(); + + if !has_rest_pat { + if accessible_unmentioned_fields.is_empty() { + unmentioned_err = Some(self.error_no_accessible_fields(pat, fields)); + } else { + unmentioned_err = Some(self.error_unmentioned_fields( + pat, + &accessible_unmentioned_fields, + accessible_unmentioned_fields.len() != unmentioned_fields.len(), + fields, + )); + } + } else if non_exhaustive && !accessible_unmentioned_fields.is_empty() { + self.lint_non_exhaustive_omitted_patterns( + pat, + &accessible_unmentioned_fields, + adt_ty, + ) + } + } + match (inexistent_fields_err, unmentioned_err) { + (Some(mut i), Some(mut u)) => { + if let Some(mut e) = self.error_tuple_variant_as_struct_pat(pat, fields, variant) { + // We don't want to show the nonexistent fields error when this was + // `Foo { a, b }` when it should have been `Foo(a, b)`. + i.delay_as_bug(); + u.delay_as_bug(); + e.emit(); + } else { + i.emit(); + u.emit(); + } + } + (None, Some(mut u)) => { + if let Some(mut e) = self.error_tuple_variant_as_struct_pat(pat, fields, variant) { + u.delay_as_bug(); + e.emit(); + } else { + u.emit(); + } + } + (Some(mut err), None) => { + err.emit(); + } + (None, None) if let Some(mut err) = + self.error_tuple_variant_index_shorthand(variant, pat, fields) => + { + err.emit(); + } + (None, None) => {} + } + no_field_errors + } + + fn error_tuple_variant_index_shorthand( + &self, + variant: &VariantDef, + pat: &'_ Pat<'_>, + fields: &[hir::PatField<'_>], + ) -> Option<DiagnosticBuilder<'_, ErrorGuaranteed>> { + // if this is a tuple struct, then all field names will be numbers + // so if any fields in a struct pattern use shorthand syntax, they will + // be invalid identifiers (for example, Foo { 0, 1 }). + if let (CtorKind::Fn, PatKind::Struct(qpath, field_patterns, ..)) = + (variant.ctor_kind, &pat.kind) + { + let has_shorthand_field_name = field_patterns.iter().any(|field| field.is_shorthand); + if has_shorthand_field_name { + let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| { + s.print_qpath(qpath, false) + }); + let mut err = struct_span_err!( + self.tcx.sess, + pat.span, + E0769, + "tuple variant `{path}` written as struct variant", + ); + err.span_suggestion_verbose( + qpath.span().shrink_to_hi().to(pat.span.shrink_to_hi()), + "use the tuple variant pattern syntax instead", + format!("({})", self.get_suggested_tuple_struct_pattern(fields, variant)), + Applicability::MaybeIncorrect, + ); + return Some(err); + } + } + None + } + + fn error_foreign_non_exhaustive_spat(&self, pat: &Pat<'_>, descr: &str, no_fields: bool) { + let sess = self.tcx.sess; + let sm = sess.source_map(); + let sp_brace = sm.end_point(pat.span); + let sp_comma = sm.end_point(pat.span.with_hi(sp_brace.hi())); + let sugg = if no_fields || sp_brace != sp_comma { ".. }" } else { ", .. }" }; + + let mut err = struct_span_err!( + sess, + pat.span, + E0638, + "`..` required with {descr} marked as non-exhaustive", + ); + err.span_suggestion_verbose( + sp_comma, + "add `..` at the end of the field list to ignore all other fields", + sugg, + Applicability::MachineApplicable, + ); + err.emit(); + } + + fn error_field_already_bound(&self, span: Span, ident: Ident, other_field: Span) { + struct_span_err!( + self.tcx.sess, + span, + E0025, + "field `{}` bound multiple times in the pattern", + ident + ) + .span_label(span, format!("multiple uses of `{ident}` in pattern")) + .span_label(other_field, format!("first use of `{ident}`")) + .emit(); + } + + fn error_inexistent_fields( + &self, + kind_name: &str, + inexistent_fields: &[&hir::PatField<'tcx>], + unmentioned_fields: &mut Vec<(&'tcx ty::FieldDef, Ident)>, + variant: &ty::VariantDef, + substs: &'tcx ty::List<ty::subst::GenericArg<'tcx>>, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let tcx = self.tcx; + let (field_names, t, plural) = if inexistent_fields.len() == 1 { + (format!("a field named `{}`", inexistent_fields[0].ident), "this", "") + } else { + ( + format!( + "fields named {}", + inexistent_fields + .iter() + .map(|field| format!("`{}`", field.ident)) + .collect::<Vec<String>>() + .join(", ") + ), + "these", + "s", + ) + }; + let spans = inexistent_fields.iter().map(|field| field.ident.span).collect::<Vec<_>>(); + let mut err = struct_span_err!( + tcx.sess, + spans, + E0026, + "{} `{}` does not have {}", + kind_name, + tcx.def_path_str(variant.def_id), + field_names + ); + if let Some(pat_field) = inexistent_fields.last() { + err.span_label( + pat_field.ident.span, + format!( + "{} `{}` does not have {} field{}", + kind_name, + tcx.def_path_str(variant.def_id), + t, + plural + ), + ); + + if unmentioned_fields.len() == 1 { + let input = + unmentioned_fields.iter().map(|(_, field)| field.name).collect::<Vec<_>>(); + let suggested_name = find_best_match_for_name(&input, pat_field.ident.name, None); + if let Some(suggested_name) = suggested_name { + err.span_suggestion( + pat_field.ident.span, + "a field with a similar name exists", + suggested_name, + Applicability::MaybeIncorrect, + ); + + // When we have a tuple struct used with struct we don't want to suggest using + // the (valid) struct syntax with numeric field names. Instead we want to + // suggest the expected syntax. We infer that this is the case by parsing the + // `Ident` into an unsized integer. The suggestion will be emitted elsewhere in + // `smart_resolve_context_dependent_help`. + if suggested_name.to_ident_string().parse::<usize>().is_err() { + // We don't want to throw `E0027` in case we have thrown `E0026` for them. + unmentioned_fields.retain(|&(_, x)| x.name != suggested_name); + } + } else if inexistent_fields.len() == 1 { + match pat_field.pat.kind { + PatKind::Lit(expr) + if !self.can_coerce( + self.typeck_results.borrow().expr_ty(expr), + self.field_ty( + unmentioned_fields[0].1.span, + unmentioned_fields[0].0, + substs, + ), + ) => {} + _ => { + let unmentioned_field = unmentioned_fields[0].1.name; + err.span_suggestion_short( + pat_field.ident.span, + &format!( + "`{}` has a field named `{}`", + tcx.def_path_str(variant.def_id), + unmentioned_field + ), + unmentioned_field.to_string(), + Applicability::MaybeIncorrect, + ); + } + } + } + } + } + if tcx.sess.teach(&err.get_code().unwrap()) { + err.note( + "This error indicates that a struct pattern attempted to \ + extract a non-existent field from a struct. Struct fields \ + are identified by the name used before the colon : so struct \ + patterns should resemble the declaration of the struct type \ + being matched.\n\n\ + If you are using shorthand field patterns but want to refer \ + to the struct field by a different name, you should rename \ + it explicitly.", + ); + } + err + } + + fn error_tuple_variant_as_struct_pat( + &self, + pat: &Pat<'_>, + fields: &'tcx [hir::PatField<'tcx>], + variant: &ty::VariantDef, + ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> { + if let (CtorKind::Fn, PatKind::Struct(qpath, ..)) = (variant.ctor_kind, &pat.kind) { + let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| { + s.print_qpath(qpath, false) + }); + let mut err = struct_span_err!( + self.tcx.sess, + pat.span, + E0769, + "tuple variant `{}` written as struct variant", + path + ); + let (sugg, appl) = if fields.len() == variant.fields.len() { + ( + self.get_suggested_tuple_struct_pattern(fields, variant), + Applicability::MachineApplicable, + ) + } else { + ( + variant.fields.iter().map(|_| "_").collect::<Vec<&str>>().join(", "), + Applicability::MaybeIncorrect, + ) + }; + err.span_suggestion_verbose( + qpath.span().shrink_to_hi().to(pat.span.shrink_to_hi()), + "use the tuple variant pattern syntax instead", + format!("({})", sugg), + appl, + ); + return Some(err); + } + None + } + + fn get_suggested_tuple_struct_pattern( + &self, + fields: &[hir::PatField<'_>], + variant: &VariantDef, + ) -> String { + let variant_field_idents = + variant.fields.iter().map(|f| f.ident(self.tcx)).collect::<Vec<Ident>>(); + fields + .iter() + .map(|field| { + match self.tcx.sess.source_map().span_to_snippet(field.pat.span) { + Ok(f) => { + // Field names are numbers, but numbers + // are not valid identifiers + if variant_field_idents.contains(&field.ident) { + String::from("_") + } else { + f + } + } + Err(_) => rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| { + s.print_pat(field.pat) + }), + } + }) + .collect::<Vec<String>>() + .join(", ") + } + + /// Returns a diagnostic reporting a struct pattern which is missing an `..` due to + /// inaccessible fields. + /// + /// ```text + /// error: pattern requires `..` due to inaccessible fields + /// --> src/main.rs:10:9 + /// | + /// LL | let foo::Foo {} = foo::Foo::default(); + /// | ^^^^^^^^^^^ + /// | + /// help: add a `..` + /// | + /// LL | let foo::Foo { .. } = foo::Foo::default(); + /// | ^^^^^^ + /// ``` + fn error_no_accessible_fields( + &self, + pat: &Pat<'_>, + fields: &'tcx [hir::PatField<'tcx>], + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let mut err = self + .tcx + .sess + .struct_span_err(pat.span, "pattern requires `..` due to inaccessible fields"); + + if let Some(field) = fields.last() { + err.span_suggestion_verbose( + field.span.shrink_to_hi(), + "ignore the inaccessible and unused fields", + ", ..", + Applicability::MachineApplicable, + ); + } else { + let qpath_span = if let PatKind::Struct(qpath, ..) = &pat.kind { + qpath.span() + } else { + bug!("`error_no_accessible_fields` called on non-struct pattern"); + }; + + // Shrink the span to exclude the `foo:Foo` in `foo::Foo { }`. + let span = pat.span.with_lo(qpath_span.shrink_to_hi().hi()); + err.span_suggestion_verbose( + span, + "ignore the inaccessible and unused fields", + " { .. }", + Applicability::MachineApplicable, + ); + } + err + } + + /// Report that a pattern for a `#[non_exhaustive]` struct marked with `non_exhaustive_omitted_patterns` + /// is not exhaustive enough. + /// + /// Nb: the partner lint for enums lives in `compiler/rustc_mir_build/src/thir/pattern/usefulness.rs`. + fn lint_non_exhaustive_omitted_patterns( + &self, + pat: &Pat<'_>, + unmentioned_fields: &[(&ty::FieldDef, Ident)], + ty: Ty<'tcx>, + ) { + fn joined_uncovered_patterns(witnesses: &[&Ident]) -> String { + const LIMIT: usize = 3; + match witnesses { + [] => bug!(), + [witness] => format!("`{}`", witness), + [head @ .., tail] if head.len() < LIMIT => { + let head: Vec<_> = head.iter().map(<_>::to_string).collect(); + format!("`{}` and `{}`", head.join("`, `"), tail) + } + _ => { + let (head, tail) = witnesses.split_at(LIMIT); + let head: Vec<_> = head.iter().map(<_>::to_string).collect(); + format!("`{}` and {} more", head.join("`, `"), tail.len()) + } + } + } + let joined_patterns = joined_uncovered_patterns( + &unmentioned_fields.iter().map(|(_, i)| i).collect::<Vec<_>>(), + ); + + self.tcx.struct_span_lint_hir(NON_EXHAUSTIVE_OMITTED_PATTERNS, pat.hir_id, pat.span, |build| { + let mut lint = build.build("some fields are not explicitly listed"); + lint.span_label(pat.span, format!("field{} {} not listed", rustc_errors::pluralize!(unmentioned_fields.len()), joined_patterns)); + + lint.help( + "ensure that all fields are mentioned explicitly by adding the suggested fields", + ); + lint.note(&format!( + "the pattern is of type `{}` and the `non_exhaustive_omitted_patterns` attribute was found", + ty, + )); + lint.emit(); + }); + } + + /// Returns a diagnostic reporting a struct pattern which does not mention some fields. + /// + /// ```text + /// error[E0027]: pattern does not mention field `bar` + /// --> src/main.rs:15:9 + /// | + /// LL | let foo::Foo {} = foo::Foo::new(); + /// | ^^^^^^^^^^^ missing field `bar` + /// ``` + fn error_unmentioned_fields( + &self, + pat: &Pat<'_>, + unmentioned_fields: &[(&ty::FieldDef, Ident)], + have_inaccessible_fields: bool, + fields: &'tcx [hir::PatField<'tcx>], + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let inaccessible = if have_inaccessible_fields { " and inaccessible fields" } else { "" }; + let field_names = if unmentioned_fields.len() == 1 { + format!("field `{}`{}", unmentioned_fields[0].1, inaccessible) + } else { + let fields = unmentioned_fields + .iter() + .map(|(_, name)| format!("`{}`", name)) + .collect::<Vec<String>>() + .join(", "); + format!("fields {}{}", fields, inaccessible) + }; + let mut err = struct_span_err!( + self.tcx.sess, + pat.span, + E0027, + "pattern does not mention {}", + field_names + ); + err.span_label(pat.span, format!("missing {}", field_names)); + let len = unmentioned_fields.len(); + let (prefix, postfix, sp) = match fields { + [] => match &pat.kind { + PatKind::Struct(path, [], false) => { + (" { ", " }", path.span().shrink_to_hi().until(pat.span.shrink_to_hi())) + } + _ => return err, + }, + [.., field] => { + // Account for last field having a trailing comma or parse recovery at the tail of + // the pattern to avoid invalid suggestion (#78511). + let tail = field.span.shrink_to_hi().with_hi(pat.span.hi()); + match &pat.kind { + PatKind::Struct(..) => (", ", " }", tail), + _ => return err, + } + } + }; + err.span_suggestion( + sp, + &format!( + "include the missing field{} in the pattern{}", + pluralize!(len), + if have_inaccessible_fields { " and ignore the inaccessible fields" } else { "" } + ), + format!( + "{}{}{}{}", + prefix, + unmentioned_fields + .iter() + .map(|(_, name)| name.to_string()) + .collect::<Vec<_>>() + .join(", "), + if have_inaccessible_fields { ", .." } else { "" }, + postfix, + ), + Applicability::MachineApplicable, + ); + err.span_suggestion( + sp, + &format!( + "if you don't care about {these} missing field{s}, you can explicitly ignore {them}", + these = pluralize!("this", len), + s = pluralize!(len), + them = if len == 1 { "it" } else { "them" }, + ), + format!("{}..{}", prefix, postfix), + Applicability::MachineApplicable, + ); + err + } + + fn check_pat_box( + &self, + span: Span, + inner: &'tcx Pat<'tcx>, + expected: Ty<'tcx>, + def_bm: BindingMode, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + let tcx = self.tcx; + let (box_ty, inner_ty) = if self.check_dereferenceable(span, expected, inner) { + // Here, `demand::subtype` is good enough, but I don't + // think any errors can be introduced by using `demand::eqtype`. + let inner_ty = self.next_ty_var(TypeVariableOrigin { + kind: TypeVariableOriginKind::TypeInference, + span: inner.span, + }); + let box_ty = tcx.mk_box(inner_ty); + self.demand_eqtype_pat(span, expected, box_ty, ti); + (box_ty, inner_ty) + } else { + let err = tcx.ty_error(); + (err, err) + }; + self.check_pat(inner, inner_ty, def_bm, ti); + box_ty + } + + // Precondition: Pat is Ref(inner) + fn check_pat_ref( + &self, + pat: &'tcx Pat<'tcx>, + inner: &'tcx Pat<'tcx>, + mutbl: hir::Mutability, + expected: Ty<'tcx>, + def_bm: BindingMode, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + let tcx = self.tcx; + let expected = self.shallow_resolve(expected); + let (rptr_ty, inner_ty) = if self.check_dereferenceable(pat.span, expected, inner) { + // `demand::subtype` would be good enough, but using `eqtype` turns + // out to be equally general. See (note_1) for details. + + // Take region, inner-type from expected type if we can, + // to avoid creating needless variables. This also helps with + // the bad interactions of the given hack detailed in (note_1). + debug!("check_pat_ref: expected={:?}", expected); + match *expected.kind() { + ty::Ref(_, r_ty, r_mutbl) if r_mutbl == mutbl => (expected, r_ty), + _ => { + let inner_ty = self.next_ty_var(TypeVariableOrigin { + kind: TypeVariableOriginKind::TypeInference, + span: inner.span, + }); + let rptr_ty = self.new_ref_ty(pat.span, mutbl, inner_ty); + debug!("check_pat_ref: demanding {:?} = {:?}", expected, rptr_ty); + let err = self.demand_eqtype_pat_diag(pat.span, expected, rptr_ty, ti); + + // Look for a case like `fn foo(&foo: u32)` and suggest + // `fn foo(foo: &u32)` + if let Some(mut err) = err { + self.borrow_pat_suggestion(&mut err, pat); + err.emit(); + } + (rptr_ty, inner_ty) + } + } + } else { + let err = tcx.ty_error(); + (err, err) + }; + self.check_pat(inner, inner_ty, def_bm, ti); + rptr_ty + } + + /// Create a reference type with a fresh region variable. + fn new_ref_ty(&self, span: Span, mutbl: hir::Mutability, ty: Ty<'tcx>) -> Ty<'tcx> { + let region = self.next_region_var(infer::PatternRegion(span)); + let mt = ty::TypeAndMut { ty, mutbl }; + self.tcx.mk_ref(region, mt) + } + + /// Type check a slice pattern. + /// + /// Syntactically, these look like `[pat_0, ..., pat_n]`. + /// Semantically, we are type checking a pattern with structure: + /// ```ignore (not-rust) + /// [before_0, ..., before_n, (slice, after_0, ... after_n)?] + /// ``` + /// The type of `slice`, if it is present, depends on the `expected` type. + /// If `slice` is missing, then so is `after_i`. + /// If `slice` is present, it can still represent 0 elements. + fn check_pat_slice( + &self, + span: Span, + before: &'tcx [Pat<'tcx>], + slice: Option<&'tcx Pat<'tcx>>, + after: &'tcx [Pat<'tcx>], + expected: Ty<'tcx>, + def_bm: BindingMode, + ti: TopInfo<'tcx>, + ) -> Ty<'tcx> { + let expected = self.structurally_resolved_type(span, expected); + let (element_ty, opt_slice_ty, inferred) = match *expected.kind() { + // An array, so we might have something like `let [a, b, c] = [0, 1, 2];`. + ty::Array(element_ty, len) => { + let min = before.len() as u64 + after.len() as u64; + let (opt_slice_ty, expected) = + self.check_array_pat_len(span, element_ty, expected, slice, len, min); + // `opt_slice_ty.is_none()` => `slice.is_none()`. + // Note, though, that opt_slice_ty could be `Some(error_ty)`. + assert!(opt_slice_ty.is_some() || slice.is_none()); + (element_ty, opt_slice_ty, expected) + } + ty::Slice(element_ty) => (element_ty, Some(expected), expected), + // The expected type must be an array or slice, but was neither, so error. + _ => { + if !expected.references_error() { + self.error_expected_array_or_slice(span, expected, ti); + } + let err = self.tcx.ty_error(); + (err, Some(err), err) + } + }; + + // Type check all the patterns before `slice`. + for elt in before { + self.check_pat(elt, element_ty, def_bm, ti); + } + // Type check the `slice`, if present, against its expected type. + if let Some(slice) = slice { + self.check_pat(slice, opt_slice_ty.unwrap(), def_bm, ti); + } + // Type check the elements after `slice`, if present. + for elt in after { + self.check_pat(elt, element_ty, def_bm, ti); + } + inferred + } + + /// Type check the length of an array pattern. + /// + /// Returns both the type of the variable length pattern (or `None`), and the potentially + /// inferred array type. We only return `None` for the slice type if `slice.is_none()`. + fn check_array_pat_len( + &self, + span: Span, + element_ty: Ty<'tcx>, + arr_ty: Ty<'tcx>, + slice: Option<&'tcx Pat<'tcx>>, + len: ty::Const<'tcx>, + min_len: u64, + ) -> (Option<Ty<'tcx>>, Ty<'tcx>) { + if let Some(len) = len.try_eval_usize(self.tcx, self.param_env) { + // Now we know the length... + if slice.is_none() { + // ...and since there is no variable-length pattern, + // we require an exact match between the number of elements + // in the array pattern and as provided by the matched type. + if min_len == len { + return (None, arr_ty); + } + + self.error_scrutinee_inconsistent_length(span, min_len, len); + } else if let Some(pat_len) = len.checked_sub(min_len) { + // The variable-length pattern was there, + // so it has an array type with the remaining elements left as its size... + return (Some(self.tcx.mk_array(element_ty, pat_len)), arr_ty); + } else { + // ...however, in this case, there were no remaining elements. + // That is, the slice pattern requires more than the array type offers. + self.error_scrutinee_with_rest_inconsistent_length(span, min_len, len); + } + } else if slice.is_none() { + // We have a pattern with a fixed length, + // which we can use to infer the length of the array. + let updated_arr_ty = self.tcx.mk_array(element_ty, min_len); + self.demand_eqtype(span, updated_arr_ty, arr_ty); + return (None, updated_arr_ty); + } else { + // We have a variable-length pattern and don't know the array length. + // This happens if we have e.g., + // `let [a, b, ..] = arr` where `arr: [T; N]` where `const N: usize`. + self.error_scrutinee_unfixed_length(span); + } + + // If we get here, we must have emitted an error. + (Some(self.tcx.ty_error()), arr_ty) + } + + fn error_scrutinee_inconsistent_length(&self, span: Span, min_len: u64, size: u64) { + struct_span_err!( + self.tcx.sess, + span, + E0527, + "pattern requires {} element{} but array has {}", + min_len, + pluralize!(min_len), + size, + ) + .span_label(span, format!("expected {} element{}", size, pluralize!(size))) + .emit(); + } + + fn error_scrutinee_with_rest_inconsistent_length(&self, span: Span, min_len: u64, size: u64) { + struct_span_err!( + self.tcx.sess, + span, + E0528, + "pattern requires at least {} element{} but array has {}", + min_len, + pluralize!(min_len), + size, + ) + .span_label( + span, + format!("pattern cannot match array of {} element{}", size, pluralize!(size),), + ) + .emit(); + } + + fn error_scrutinee_unfixed_length(&self, span: Span) { + struct_span_err!( + self.tcx.sess, + span, + E0730, + "cannot pattern-match on an array without a fixed length", + ) + .emit(); + } + + fn error_expected_array_or_slice(&self, span: Span, expected_ty: Ty<'tcx>, ti: TopInfo<'tcx>) { + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0529, + "expected an array or slice, found `{expected_ty}`" + ); + if let ty::Ref(_, ty, _) = expected_ty.kind() + && let ty::Array(..) | ty::Slice(..) = ty.kind() + { + err.help("the semantics of slice patterns changed recently; see issue #62254"); + } else if Autoderef::new(&self.infcx, self.param_env, self.body_id, span, expected_ty, span) + .any(|(ty, _)| matches!(ty.kind(), ty::Slice(..) | ty::Array(..))) + && let (Some(span), true) = (ti.span, ti.origin_expr) + && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) + { + let ty = self.resolve_vars_if_possible(ti.expected); + let is_slice_or_array_or_vector = self.is_slice_or_array_or_vector(&mut err, snippet.clone(), ty); + match is_slice_or_array_or_vector.1.kind() { + ty::Adt(adt_def, _) + if self.tcx.is_diagnostic_item(sym::Option, adt_def.did()) + || self.tcx.is_diagnostic_item(sym::Result, adt_def.did()) => + { + // Slicing won't work here, but `.as_deref()` might (issue #91328). + err.span_suggestion( + span, + "consider using `as_deref` here", + format!("{snippet}.as_deref()"), + Applicability::MaybeIncorrect, + ); + } + _ => () + } + if is_slice_or_array_or_vector.0 { + err.span_suggestion( + span, + "consider slicing here", + format!("{snippet}[..]"), + Applicability::MachineApplicable, + ); + } + } + err.span_label(span, format!("pattern cannot match with input type `{expected_ty}`")); + err.emit(); + } + + fn is_slice_or_array_or_vector( + &self, + err: &mut Diagnostic, + snippet: String, + ty: Ty<'tcx>, + ) -> (bool, Ty<'tcx>) { + match ty.kind() { + ty::Adt(adt_def, _) if self.tcx.is_diagnostic_item(sym::Vec, adt_def.did()) => { + (true, ty) + } + ty::Ref(_, ty, _) => self.is_slice_or_array_or_vector(err, snippet, *ty), + ty::Slice(..) | ty::Array(..) => (true, ty), + _ => (false, ty), + } + } +} |