use crate::{FnCtxt, RawTy}; 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, TypeVisitableExt}; use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS; use rustc_span::edit_distance::find_best_match_for_name; use rustc_span::hygiene::DesugaringKind; use rustc_span::source_map::{Span, Spanned}; use rustc_span::symbol::{kw, sym, Ident}; use rustc_span::{BytePos, DUMMY_SP}; 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: Option<&'tcx hir::Expr<'tcx>>, /// 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, } 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.is_some() }; self.cause(cause_span, code) } fn demand_eqtype_pat_diag( &self, cause_span: Span, expected: Ty<'tcx>, actual: Ty<'tcx>, ti: TopInfo<'tcx>, ) -> Option> { let mut diag = self.demand_eqtype_with_origin(&self.pattern_cause(ti, cause_span), expected, actual)?; if let Some(expr) = ti.origin_expr { self.suggest_fn_call(&mut diag, expr, expected, |output| { self.can_eq(self.param_env, output, actual) }); } Some(diag) } 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, origin_expr: Option<&'tcx hir::Expr<'tcx>>, ) { 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) -> 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)); } } if self.tcx.features().string_deref_patterns && let hir::ExprKind::Lit(Spanned { node: ast::LitKind::Str(..), .. }) = lt.kind { let tcx = self.tcx; let expected = self.resolve_vars_if_possible(expected); pat_ty = match expected.kind() { ty::Adt(def, _) if Some(def.did()) == tcx.lang_items().string() => expected, ty::Str => tcx.mk_static_str(), _ => pat_ty, }; } // 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. let guar = self.emit_err_pat_range(span, lhs, rhs); return self.tcx.ty_error(guar); } // 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_misc(); } // 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; } let guar = self.emit_err_pat_range(span, lhs, rhs); return self.tcx.ty_error(guar); } 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)>, ) -> ErrorGuaranteed { 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 (lhs, rhs).references_error() { err.downgrade_to_delayed_bug(); } 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::NONE => 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(ba, 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, ba: hir::BindingAnnotation, 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)); self.suggest_adding_missing_ref_or_removing_ref( &mut err, span, var_ty, self.resolve_vars_with_obligations(ty), ba, ); err.emit(); } } fn suggest_adding_missing_ref_or_removing_ref( &self, err: &mut Diagnostic, span: Span, expected: Ty<'tcx>, actual: Ty<'tcx>, ba: hir::BindingAnnotation, ) { match (expected.kind(), actual.kind(), ba) { (ty::Ref(_, inner_ty, _), _, hir::BindingAnnotation::NONE) if self.can_eq(self.param_env, *inner_ty, actual) => { err.span_suggestion_verbose( span.shrink_to_lo(), "consider adding `ref`", "ref ", Applicability::MaybeIncorrect, ); } (_, ty::Ref(_, inner_ty, _), hir::BindingAnnotation::REF) if self.can_eq(self.param_env, expected, *inner_ty) => { err.span_suggestion_verbose( span.with_hi(span.lo() + BytePos(4)), "consider removing `ref`", "", Applicability::MaybeIncorrect, ); } _ => (), } } // 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().parent_id(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 mutbl.is_not() { 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(), mutbl.ref_prefix_str().to_owned()), ], Applicability::MachineApplicable ); if let Some((sp, msg, sugg)) = mut_var_suggestion { err.span_note(sp, format!("{msg}: `{sugg}`")); } } hir::Node::Pat(pt) if let PatKind::TupleStruct(_, pat_arr, _) = pt.kind => { for i in pat_arr.iter() { if let PatKind::Ref(the_ref, _) = i.kind && let PatKind::Binding(mt, _, ident, _) = the_ref.kind { let hir::BindingAnnotation(_, mtblty) = mt; err.span_suggestion_verbose( i.span, format!("consider removing `&{mutability}` from the pattern"), mtblty.prefix_str().to_string() + &ident.name.to_string(), Applicability::MaybeIncorrect, ); } } 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<'_>, ) -> Result<(), ErrorGuaranteed> { 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", 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); } return Err(err.emit()); } Ok(()) } 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 (variant, pat_ty) = match self.check_struct_path(qpath, pat.hir_id) { Ok(data) => data, Err(guar) => { let err = self.tcx.ty_error(guar); 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_misc() } } fn check_pat_path( &self, pat: &Pat<'tcx>, qpath: &hir::QPath<'_>, path_resolution: (Res, Option>, &'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 => { let e = tcx.sess.delay_span_bug(qpath.span(), "`Res::Err` but no error emitted"); self.set_tainted_by_errors(e); return tcx.ty_error(e); } Res::Def(DefKind::AssocFn | DefKind::Ctor(_, CtorKind::Fn) | DefKind::Variant, _) => { let expected = "unit struct, unit variant or constant"; let e = report_unexpected_variant_res(tcx, res, qpath, pat.span, "E0533", expected); return tcx.ty_error(e); } 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, 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_parent(pat.hir_id) { hir::Node::PatField(..) => { 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: hir::DotDotPos, expected: Ty<'tcx>, def_bm: BindingMode, ti: TopInfo<'tcx>, ) -> Ty<'tcx> { let tcx = self.tcx; let on_error = |e| { for pat in subpats { self.check_pat(pat, tcx.ty_error(e), def_bm, ti); } }; let report_unexpected_res = |res: Res| { let expected = "tuple struct or tuple variant"; let e = report_unexpected_variant_res(tcx, res, qpath, pat.span, "E0164", expected); on_error(e); e }; // 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 { let e = tcx.sess.delay_span_bug(pat.span, "`Res::Err` but no error emitted"); self.set_tainted_by_errors(e); on_error(e); return tcx.ty_error(e); } // 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() { let e = report_unexpected_res(res); return tcx.ty_error(e); } let variant = match res { Res::Err => { let e = tcx.sess.delay_span_bug(pat.span, "`Res::Err` but no error emitted"); self.set_tainted_by_errors(e); on_error(e); return tcx.ty_error(e); } Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) => { let e = report_unexpected_res(res); return tcx.ty_error(e); } 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.as_opt_usize().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. let e = self.e0023(pat.span, res, qpath, subpats, &variant.fields, expected, had_err); on_error(e); return tcx.ty_error(e); } 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, ) -> ErrorGuaranteed { 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);`. (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: hir::DotDotPos, expected: Ty<'tcx>, def_bm: BindingMode, ti: TopInfo<'tcx>, ) -> Ty<'tcx> { let tcx = self.tcx; let mut expected_len = elements.len(); if ddpos.as_opt_usize().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_from_iter(element_tys_iter); let pat_ty = tcx.mk_tup(element_tys); if let Some(mut err) = self.demand_eqtype_pat_diag(span, expected, pat_ty, ti) { let reported = 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(reported)); for (_, elem) in elements.iter().enumerate_and_adjust(max_len, ddpos) { self.check_pat(elem, tcx.ty_error(reported), def_bm, ti); } tcx.mk_tup_from_iter(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::>(); // 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) => { no_field_errors = false; let guar = self.error_field_already_bound(span, field.ident, *occupied.get()); tcx.ty_error(guar) } 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_misc() }) } }; 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::>(); 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), 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> { // 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 (Some(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, ) -> ErrorGuaranteed { 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>, ) -> 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::>() .join(", ") ), "these", "s", ) }; let spans = inexistent_fields.iter().map(|field| field.ident.span).collect::>(); 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::>(); 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::().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> { if let (Some(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::>().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::>(); 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::>() .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::>(), ); self.tcx.struct_span_lint_hir(NON_EXHAUSTIVE_OMITTED_PATTERNS, pat.hir_id, pat.span, "some fields are not explicitly listed", |lint| { 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 }); } /// 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::>() .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::>() .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) = match self.check_dereferenceable(span, expected, inner) { Ok(()) => { // 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) } Err(guar) => { let err = tcx.ty_error(guar); (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 (ref_ty, inner_ty) = match self.check_dereferenceable(pat.span, expected, inner) { Ok(()) => { // `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 ref_ty = self.new_ref_ty(pat.span, mutbl, inner_ty); debug!("check_pat_ref: demanding {:?} = {:?}", expected, ref_ty); let err = self.demand_eqtype_pat_diag(pat.span, expected, ref_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(); } (ref_ty, inner_ty) } } } Err(guar) => { let err = tcx.ty_error(guar); (err, err) } }; self.check_pat(inner, inner_ty, def_bm, ti); ref_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. _ => { let guar = expected .error_reported() .err() .unwrap_or_else(|| self.error_expected_array_or_slice(span, expected, ti)); let err = self.tcx.ty_error(guar); (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>) { let guar = if let Some(len) = len.try_eval_target_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(guar)), arr_ty) } fn error_scrutinee_inconsistent_length( &self, span: Span, min_len: u64, size: u64, ) -> ErrorGuaranteed { 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, ) -> ErrorGuaranteed { 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) -> ErrorGuaranteed { 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>, ) -> ErrorGuaranteed { 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 self.autoderef(span, expected_ty) .any(|(ty, _)| matches!(ty.kind(), ty::Slice(..) | ty::Array(..))) && let Some(span) = ti.span && let Some(_) = 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(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, 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(*ty), ty::Slice(..) | ty::Array(..) => (true, ty), _ => (false, ty), } } }