| use crate::check::FnCtxt; |
| use rustc_ast::ast; |
| use rustc_ast::util::lev_distance::find_best_match_for_name; |
| use rustc_data_structures::fx::FxHashMap; |
| use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder}; |
| 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::ty::subst::GenericArg; |
| use rustc_middle::ty::{self, BindingMode, Ty, TypeFoldable}; |
| use rustc_span::hygiene::DesugaringKind; |
| use rustc_span::source_map::{Span, Spanned}; |
| use rustc_span::symbol::Ident; |
| use rustc_trait_selection::traits::{ObligationCause, Pattern}; |
| |
| 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>, |
| /// This refers to the parent pattern. Used to provide extra diagnostic information on errors. |
| /// ```text |
| /// error[E0308]: mismatched types |
| /// --> $DIR/const-in-struct-pat.rs:8:17 |
| /// | |
| /// L | struct f; |
| /// | --------- unit struct defined here |
| /// ... |
| /// L | let Thing { f } = t; |
| /// | ^ |
| /// | | |
| /// | expected struct `std::string::String`, found struct `f` |
| /// | `f` is interpreted as a unit struct, not a new binding |
| /// | help: bind the struct field to a different name instead: `f: other_f` |
| /// ``` |
| parent_pat: Option<&'tcx Pat<'tcx>>, |
| } |
| |
| 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>> { |
| 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, parent_pat: None }; |
| 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. |
| fn check_pat( |
| &self, |
| pat: &'tcx Pat<'tcx>, |
| expected: Ty<'tcx>, |
| def_bm: BindingMode, |
| ti: TopInfo<'tcx>, |
| ) { |
| debug!("check_pat(pat={:?},expected={:?},def_bm={:?})", pat, expected, def_bm); |
| |
| let path_res = match &pat.kind { |
| PatKind::Path(qpath) => Some(self.resolve_ty_and_res_ufcs(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(_) => self.check_pat_path(pat, path_res.unwrap(), expected, ti), |
| PatKind::Struct(ref qpath, fields, etc) => { |
| self.check_pat_struct(pat, qpath, fields, etc, expected, def_bm, ti) |
| } |
| PatKind::Or(pats) => { |
| let parent_pat = Some(pat); |
| for pat in pats { |
| self.check_pat(pat, expected, def_bm, TopInfo { parent_pat, ..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 { |
| 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 {}`. |
| PatKind::Lit(lt) => match 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 expressivity. |
| _ => 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 HAIR 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.tables.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(_, ty::TyS { kind: ty::Slice(_), .. }, _) = expected.kind { |
| let tcx = self.tcx; |
| 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, None), |
| Some(expr) => { |
| let ty = self.check_expr(expr); |
| // Check that the end-point is of numeric or char type. |
| let fail = !(ty.is_numeric() || ty.is_char() || ty.references_error()); |
| (Some(ty), Some((fail, ty, expr.span))) |
| } |
| }; |
| let (lhs_ty, lhs) = calc_side(lhs); |
| let (rhs_ty, 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(); |
| } |
| |
| // Now that we know the types can be unified we find the unified type |
| // and use it to type the entire expression. |
| let common_type = self.resolve_vars_if_possible(&lhs_ty.or(rhs_ty).unwrap_or(expected)); |
| |
| // Subtyping doesn't matter here, as the value is some kind of scalar. |
| let demand_eqtype = |x, y| { |
| if let Some((_, x_ty, x_span)) = x { |
| if 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(); |
| }; |
| } |
| }; |
| demand_eqtype(lhs, rhs); |
| demand_eqtype(rhs, lhs); |
| |
| common_type |
| } |
| |
| fn endpoint_has_type(&self, err: &mut DiagnosticBuilder<'_>, 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| 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 { |
| self.endpoint_has_type(&mut err, sp, ty); |
| } |
| }; |
| match (lhs, rhs) { |
| (Some((true, lhs_ty, lhs_sp)), Some((true, rhs_ty, rhs_sp))) => { |
| err.span_label(lhs_sp, &msg(lhs_ty)); |
| err.span_label(rhs_sp, &msg(rhs_ty)); |
| } |
| (Some((true, lhs_ty, lhs_sp)), rhs) => one_side_err(lhs_sp, lhs_ty, rhs), |
| (lhs, Some((true, rhs_ty, rhs_sp))) => one_side_err(rhs_sp, rhs_ty, lhs), |
| _ => span_bug!(span, "Impossible, verified above."), |
| } |
| if self.tcx.sess.teach(&err.get_code().unwrap()) { |
| err.note( |
| "In a match expression, only numbers and characters can be matched \ |
| against a range. This is because the compiler checks that the range \ |
| is non-empty at compile-time, and is unable to evaluate arbitrary \ |
| comparison functions. If you want to capture values of an orderable \ |
| type between two end-points, you can use a guard.", |
| ); |
| } |
| err.emit(); |
| } |
| |
| fn check_pat_ident( |
| &self, |
| pat: &'tcx Pat<'tcx>, |
| ba: hir::BindingAnnotation, |
| var_id: HirId, |
| sub: Option<&'tcx Pat<'tcx>>, |
| expected: Ty<'tcx>, |
| def_bm: BindingMode, |
| ti: TopInfo<'tcx>, |
| ) -> Ty<'tcx> { |
| // Determine the binding mode... |
| let bm = match ba { |
| hir::BindingAnnotation::Unannotated => def_bm, |
| _ => BindingMode::convert(ba), |
| }; |
| // ...and store it in a side table: |
| self.inh.tables.borrow_mut().pat_binding_modes_mut().insert(pat.hir_id, bm); |
| |
| debug!("check_pat_ident: pat.hir_id={:?} bm={:?}", pat.hir_id, bm); |
| |
| let local_ty = self.local_ty(pat.span, pat.hir_id).decl_ty; |
| let eq_ty = match bm { |
| ty::BindByReference(mutbl) => { |
| // If the binding is like `ref x | ref mut x`, |
| // then `x` is assigned a value of type `&M T` where M is the |
| // mutability and T is the expected type. |
| // |
| // `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)` |
| // is required. However, we use equality, which is stronger. |
| // See (note_1) for an explanation. |
| self.new_ref_ty(pat.span, mutbl, expected) |
| } |
| // Otherwise, the type of x is the expected type `T`. |
| ty::BindByValue(_) => { |
| // As above, `T <: typeof(x)` is required, but we use equality, see (note_1). |
| expected |
| } |
| }; |
| self.demand_eqtype_pat(pat.span, eq_ty, local_ty, ti); |
| |
| // If there are multiple arms, make sure they all agree on |
| // what the type of the binding `x` ought to be. |
| if var_id != pat.hir_id { |
| self.check_binding_alt_eq_ty(pat.span, var_id, local_ty, ti); |
| } |
| |
| if let Some(p) = sub { |
| self.check_pat(&p, expected, def_bm, TopInfo { parent_pat: Some(&pat), ..ti }); |
| } |
| |
| local_ty |
| } |
| |
| fn check_binding_alt_eq_ty(&self, span: Span, var_id: HirId, ty: Ty<'tcx>, ti: TopInfo<'tcx>) { |
| let var_ty = self.local_ty(span, var_id).decl_ty; |
| if let Some(mut err) = self.demand_eqtype_pat_diag(span, var_ty, ty, ti) { |
| let hir = self.tcx.hir(); |
| let var_ty = self.resolve_vars_with_obligations(var_ty); |
| let msg = format!("first introduced with type `{}` here", var_ty); |
| 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)); |
| err.emit(); |
| } |
| } |
| |
| fn borrow_pat_suggestion( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| pat: &Pat<'_>, |
| inner: &Pat<'_>, |
| expected: Ty<'tcx>, |
| ) { |
| let tcx = self.tcx; |
| if let PatKind::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 {:?} parent {:?}", inner, pat, binding_parent); |
| match binding_parent { |
| hir::Node::Param(hir::Param { span, .. }) => { |
| if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(inner.span) { |
| err.span_suggestion( |
| *span, |
| &format!("did you mean `{}`", snippet), |
| format!(" &{}", expected), |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| hir::Node::Arm(_) | hir::Node::Pat(_) => { |
| // rely on match ergonomics or it might be nested `&&pat` |
| if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(inner.span) { |
| err.span_suggestion( |
| pat.span, |
| "you can probably remove the explicit borrow", |
| snippet, |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| _ => {} // 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 { |
| if let Some(mt) = self.shallow_resolve(expected).builtin_deref(true) { |
| if 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 `{}` cannot be dereferenced", type_str)); |
| 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::FieldPat<'tcx>], |
| etc: 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) = if let Some(variant_ty) = self.check_struct_path(qpath, pat.hir_id) |
| { |
| variant_ty |
| } else { |
| let err = self.tcx.ty_error(); |
| for field in fields { |
| let ti = TopInfo { parent_pat: Some(&pat), ..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, etc, def_bm, ti) { |
| pat_ty |
| } else { |
| self.tcx.ty_error() |
| } |
| } |
| |
| fn check_pat_path( |
| &self, |
| pat: &Pat<'_>, |
| path_resolution: (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment<'b>]), |
| 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, 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.span, res, pat_res, segments, ti.parent_pat); |
| } |
| pat_ty |
| } |
| |
| fn emit_bad_pat_path( |
| &self, |
| mut e: DiagnosticBuilder<'_>, |
| pat_span: Span, |
| res: Res, |
| pat_res: Res, |
| segments: &'b [hir::PathSegment<'b>], |
| parent_pat: Option<&Pat<'_>>, |
| ) { |
| 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 parent_pat { |
| Some(Pat { kind: hir::PatKind::Struct(..), .. }) => { |
| e.span_suggestion_verbose( |
| ident.span.shrink_to_hi(), |
| "bind the struct field to a different name instead", |
| format!(": other_{}", ident.as_str().to_lowercase()), |
| Applicability::HasPlaceholders, |
| ); |
| } |
| _ => { |
| let 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: &hir::QPath<'_>, |
| subpats: &'tcx [&'tcx Pat<'tcx>], |
| ddpos: Option<usize>, |
| expected: Ty<'tcx>, |
| def_bm: BindingMode, |
| ti: TopInfo<'tcx>, |
| ) -> Ty<'tcx> { |
| let tcx = self.tcx; |
| let on_error = || { |
| let parent_pat = Some(pat); |
| for pat in subpats { |
| self.check_pat(&pat, tcx.ty_error(), def_bm, TopInfo { parent_pat, ..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(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_ufcs(qpath, pat.hir_id, pat.span); |
| if res == Res::Err { |
| self.set_tainted_by_errors(); |
| on_error(); |
| return self.tcx.ty_error(); |
| } |
| |
| // Type-check the path. |
| let (pat_ty, res) = |
| self.instantiate_value_path(segments, opt_ty, res, pat.span, pat.hir_id); |
| if !pat_ty.is_fn() { |
| report_unexpected_res(res); |
| return tcx.ty_error(); |
| } |
| |
| let variant = match res { |
| Res::Err => { |
| self.set_tainted_by_errors(); |
| on_error(); |
| return tcx.ty_error(); |
| } |
| Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) => { |
| report_unexpected_res(res); |
| return tcx.ty_error(); |
| } |
| Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) => tcx.expect_variant_res(res), |
| _ => bug!("unexpected pattern resolution: {:?}", res), |
| }; |
| |
| // Replace constructor type with constructed type for tuple struct patterns. |
| let pat_ty = pat_ty.fn_sig(tcx).output(); |
| let pat_ty = pat_ty.no_bound_vars().expect("expected fn type"); |
| |
| // Type-check the tuple struct pattern against the expected type. |
| let diag = self.demand_eqtype_pat_diag(pat.span, expected, pat_ty, ti); |
| let had_err = if let Some(mut err) = diag { |
| err.emit(); |
| true |
| } else { |
| false |
| }; |
| |
| // Type-check subpatterns. |
| if subpats.len() == variant.fields.len() |
| || subpats.len() < variant.fields.len() && ddpos.is_some() |
| { |
| let substs = match pat_ty.kind { |
| ty::Adt(_, substs) => substs, |
| _ => 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, TopInfo { parent_pat: Some(&pat), ..ti }); |
| |
| self.tcx.check_stability(variant.fields[i].did, Some(pat.hir_id), subpat.span); |
| } |
| } 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 [&'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 res_span = self.tcx.def_span(res.def_id()); |
| let mut err = struct_span_err!( |
| self.tcx.sess, |
| pat_span, |
| E0023, |
| "this pattern has {} field{}, but the corresponding {} has {} field{}", |
| subpats.len(), |
| subpats_ending, |
| res.descr(), |
| fields.len(), |
| fields_ending, |
| ); |
| err.span_label( |
| pat_span, |
| format!("expected {} field{}, found {}", fields.len(), fields_ending, subpats.len(),), |
| ) |
| .span_label(res_span, format!("{} defined here", res.descr())); |
| |
| // 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_parenthesis = 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(_) => field_ty.tuple_fields().count() == subpats.len(), |
| _ => false, |
| } |
| } |
| _ => false, |
| }; |
| if missing_parenthesis { |
| 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 parenthesis |
| // | |
| // L | let A(()) = A(()); |
| // | ^ ^ |
| [] => { |
| let qpath_span = match qpath { |
| hir::QPath::Resolved(_, path) => path.span, |
| hir::QPath::TypeRelative(_, ps) => ps.ident.span, |
| }; |
| (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 parenthesis |
| // | |
| // L | let A((x, y)) = A((1, 2)); |
| // | ^ ^ |
| [first, ..] => (first.span.shrink_to_lo(), subpats.last().unwrap().span), |
| }; |
| err.multipart_suggestion( |
| "missing parenthesis", |
| vec![(left, "(".to_string()), (right.shrink_to_hi(), ")".to_string())], |
| Applicability::MachineApplicable, |
| ); |
| } |
| |
| err.emit(); |
| } |
| |
| fn check_pat_tuple( |
| &self, |
| span: Span, |
| elements: &'tcx [&'tcx Pat<'tcx>], |
| ddpos: Option<usize>, |
| expected: Ty<'tcx>, |
| def_bm: BindingMode, |
| ti: TopInfo<'tcx>, |
| ) -> Ty<'tcx> { |
| let tcx = self.tcx; |
| let mut expected_len = elements.len(); |
| if ddpos.is_some() { |
| // Require known type only when `..` is present. |
| if let ty::Tuple(ref 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(|_| { |
| GenericArg::from(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_substs(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].expect_ty(), 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::FieldPat<'tcx>], |
| etc: bool, |
| def_bm: BindingMode, |
| ti: TopInfo<'tcx>, |
| ) -> bool { |
| let tcx = self.tcx; |
| |
| let (substs, adt) = match adt_ty.kind { |
| ty::Adt(adt, substs) => (substs, adt), |
| _ => 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.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); |
| self.field_ty(span, f, substs) |
| }) |
| .unwrap_or_else(|| { |
| inexistent_fields.push(field.ident); |
| no_field_errors = false; |
| tcx.ty_error() |
| }) |
| } |
| }; |
| |
| self.check_pat(&field.pat, field_ty, def_bm, TopInfo { parent_pat: Some(&pat), ..ti }); |
| } |
| |
| let mut unmentioned_fields = variant |
| .fields |
| .iter() |
| .map(|field| field.ident.normalize_to_macros_2_0()) |
| .filter(|ident| !used_fields.contains_key(&ident)) |
| .collect::<Vec<_>>(); |
| |
| if !inexistent_fields.is_empty() && !variant.recovered { |
| self.error_inexistent_fields( |
| adt.variant_descr(), |
| &inexistent_fields, |
| &mut unmentioned_fields, |
| variant, |
| ); |
| } |
| |
| // Require `..` if struct has non_exhaustive attribute. |
| if variant.is_field_list_non_exhaustive() && !adt.did.is_local() && !etc { |
| self.error_foreign_non_exhaustive_spat(pat, adt.variant_descr(), fields.is_empty()); |
| } |
| |
| // Report an error if incorrect number of the fields were 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 etc { |
| tcx.sess.struct_span_err(pat.span, "`..` cannot be used in union patterns").emit(); |
| } |
| } else if !etc && !unmentioned_fields.is_empty() { |
| self.error_unmentioned_fields(pat.span, &unmentioned_fields, variant); |
| } |
| no_field_errors |
| } |
| |
| 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 {} marked as non-exhaustive", |
| descr |
| ); |
| err.span_suggestion_verbose( |
| sp_comma, |
| "add `..` at the end of the field list to ignore all other fields", |
| sugg.to_string(), |
| 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 `{}` in pattern", ident)) |
| .span_label(other_field, format!("first use of `{}`", ident)) |
| .emit(); |
| } |
| |
| fn error_inexistent_fields( |
| &self, |
| kind_name: &str, |
| inexistent_fields: &[Ident], |
| unmentioned_fields: &mut Vec<Ident>, |
| variant: &ty::VariantDef, |
| ) { |
| let tcx = self.tcx; |
| let (field_names, t, plural) = if inexistent_fields.len() == 1 { |
| (format!("a field named `{}`", inexistent_fields[0]), "this", "") |
| } else { |
| ( |
| format!( |
| "fields named {}", |
| inexistent_fields |
| .iter() |
| .map(|ident| format!("`{}`", ident)) |
| .collect::<Vec<String>>() |
| .join(", ") |
| ), |
| "these", |
| "s", |
| ) |
| }; |
| let spans = inexistent_fields.iter().map(|ident| 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(ident) = inexistent_fields.last() { |
| err.span_label( |
| ident.span, |
| format!( |
| "{} `{}` does not have {} field{}", |
| kind_name, |
| tcx.def_path_str(variant.def_id), |
| t, |
| plural |
| ), |
| ); |
| if plural == "" { |
| let input = unmentioned_fields.iter().map(|field| &field.name); |
| let suggested_name = find_best_match_for_name(input, &ident.as_str(), None); |
| if let Some(suggested_name) = suggested_name { |
| err.span_suggestion( |
| ident.span, |
| "a field with a similar name exists", |
| suggested_name.to_string(), |
| Applicability::MaybeIncorrect, |
| ); |
| |
| // we don't want to throw `E0027` in case we have thrown `E0026` for them |
| unmentioned_fields.retain(|&x| x.name != suggested_name); |
| } |
| } |
| } |
| 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.emit(); |
| } |
| |
| fn error_unmentioned_fields( |
| &self, |
| span: Span, |
| unmentioned_fields: &[Ident], |
| variant: &ty::VariantDef, |
| ) { |
| let field_names = if unmentioned_fields.len() == 1 { |
| format!("field `{}`", unmentioned_fields[0]) |
| } else { |
| let fields = unmentioned_fields |
| .iter() |
| .map(|name| format!("`{}`", name)) |
| .collect::<Vec<String>>() |
| .join(", "); |
| format!("fields {}", fields) |
| }; |
| let mut diag = struct_span_err!( |
| self.tcx.sess, |
| span, |
| E0027, |
| "pattern does not mention {}", |
| field_names |
| ); |
| diag.span_label(span, format!("missing {}", field_names)); |
| if variant.ctor_kind == CtorKind::Fn { |
| diag.note("trying to match a tuple variant with a struct variant pattern"); |
| } |
| if self.tcx.sess.teach(&diag.get_code().unwrap()) { |
| diag.note( |
| "This error indicates that a pattern for a struct fails to specify a \ |
| sub-pattern for every one of the struct's fields. Ensure that each field \ |
| from the struct's definition is mentioned in the pattern, or use `..` to \ |
| ignore unwanted fields.", |
| ); |
| } |
| diag.emit(); |
| } |
| |
| 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 |
| } |
| |
| 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, &inner, &expected); |
| err.emit(); |
| } |
| (rptr_ty, inner_ty) |
| } |
| } |
| } else { |
| let err = tcx.ty_error(); |
| (err, err) |
| }; |
| self.check_pat(&inner, inner_ty, def_bm, TopInfo { parent_pat: Some(&pat), ..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: |
| /// ``` |
| /// [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 [&'tcx Pat<'tcx>], |
| slice: Option<&'tcx Pat<'tcx>>, |
| after: &'tcx [&'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); |
| } |
| 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>) { |
| 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 { |
| if let ty::Array(..) | ty::Slice(..) = ty.kind { |
| err.help("the semantics of slice patterns changed recently; see issue #62254"); |
| } |
| } |
| err.span_label(span, format!("pattern cannot match with input type `{}`", expected_ty)); |
| err.emit(); |
| } |
| } |
