--- /dev/null
+use crate::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::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).is_ok() =>
+ {
+ 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).is_ok() =>
+ {
+ 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().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::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 = || {
+ 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.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.
+ 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: 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(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), 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, "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::<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),
+ }
+ }
+}
projects / rustc.git / blobdiff