| use crate::check::{FnCtxt, Expectation, Diverges, Needs}; |
| use crate::check::coercion::CoerceMany; |
| use crate::util::nodemap::FxHashMap; |
| use errors::{Applicability, DiagnosticBuilder}; |
| use rustc::hir::{self, PatKind, Pat, ExprKind}; |
| use rustc::hir::def::{Res, DefKind, CtorKind}; |
| use rustc::hir::pat_util::EnumerateAndAdjustIterator; |
| use rustc::infer; |
| use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; |
| use rustc::traits::{ObligationCause, ObligationCauseCode}; |
| use rustc::ty::{self, Ty, TypeFoldable}; |
| use rustc::ty::subst::Kind; |
| use syntax::ast; |
| use syntax::source_map::Spanned; |
| use syntax::ptr::P; |
| use syntax::util::lev_distance::find_best_match_for_name; |
| use syntax_pos::Span; |
| use syntax_pos::hygiene::CompilerDesugaringKind; |
| |
| use std::collections::hash_map::Entry::{Occupied, Vacant}; |
| use std::cmp; |
| |
| use super::report_unexpected_variant_res; |
| |
| impl<'a, 'tcx> FnCtxt<'a, 'tcx> { |
| /// `discrim_span` argument having a `Span` indicates that this pattern is part of a match |
| /// expression arm guard, and it points to the match discriminant to add context in type errors. |
| /// In the following example, `discrim_span` corresponds to the `a + b` expression: |
| /// |
| /// ```text |
| /// error[E0308]: mismatched types |
| /// --> src/main.rs:5:9 |
| /// | |
| /// 4 | let temp: usize = match a + b { |
| /// | ----- this expression has type `usize` |
| /// 5 | Ok(num) => num, |
| /// | ^^^^^^^ expected usize, found enum `std::result::Result` |
| /// | |
| /// = note: expected type `usize` |
| /// found type `std::result::Result<_, _>` |
| /// ``` |
| pub fn check_pat_walk( |
| &self, |
| pat: &'tcx hir::Pat, |
| mut expected: Ty<'tcx>, |
| mut def_bm: ty::BindingMode, |
| discrim_span: Option<Span>, |
| ) { |
| let tcx = self.tcx; |
| |
| debug!("check_pat_walk(pat={:?},expected={:?},def_bm={:?})", pat, expected, def_bm); |
| |
| let mut path_resolution = None; |
| let is_non_ref_pat = match pat.node { |
| PatKind::Struct(..) | |
| PatKind::TupleStruct(..) | |
| PatKind::Tuple(..) | |
| PatKind::Box(_) | |
| PatKind::Range(..) | |
| PatKind::Slice(..) => true, |
| PatKind::Lit(ref lt) => { |
| let ty = self.check_expr(lt); |
| match ty.sty { |
| ty::Ref(..) => false, |
| _ => true, |
| } |
| } |
| PatKind::Path(ref qpath) => { |
| let resolution = self.resolve_ty_and_res_ufcs(qpath, pat.hir_id, pat.span); |
| path_resolution = Some(resolution); |
| match resolution.0 { |
| Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) => false, |
| _ => true, |
| } |
| } |
| PatKind::Wild | |
| PatKind::Binding(..) | |
| PatKind::Ref(..) => false, |
| }; |
| if is_non_ref_pat { |
| debug!("pattern is non reference pattern"); |
| let mut exp_ty = self.resolve_type_vars_with_obligations(&expected); |
| |
| // Peel off as many `&` or `&mut` from the discriminant 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 `run-pass/match-defbm*.rs`. |
| let mut pat_adjustments = vec![]; |
| while let ty::Ref(_, inner_ty, inner_mutability) = exp_ty.sty { |
| debug!("inspecting {:?}", exp_ty); |
| |
| debug!("current discriminant is Ref, inserting implicit deref"); |
| // Preserve the reference type. We'll need it later during HAIR lowering. |
| pat_adjustments.push(exp_ty); |
| |
| exp_ty = inner_ty; |
| def_bm = 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(_) => |
| ty::BindByReference(inner_mutability), |
| |
| // Once a `ref`, always a `ref`. This is because a `& &mut` can't mutate |
| // the underlying value. |
| ty::BindByReference(hir::Mutability::MutImmutable) => |
| ty::BindByReference(hir::Mutability::MutImmutable), |
| |
| // When `ref mut`, stay a `ref mut` (on `&mut`) or downgrade to `ref` |
| // (on `&`). |
| ty::BindByReference(hir::Mutability::MutMutable) => |
| ty::BindByReference(inner_mutability), |
| }; |
| } |
| expected = exp_ty; |
| |
| if pat_adjustments.len() > 0 { |
| debug!("default binding mode is now {:?}", def_bm); |
| self.inh.tables.borrow_mut() |
| .pat_adjustments_mut() |
| .insert(pat.hir_id, pat_adjustments); |
| } |
| } else if let PatKind::Ref(..) = pat.node { |
| // When you encounter a `&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. |
| def_bm = ty::BindByValue(hir::MutImmutable); |
| } |
| |
| // Lose mutability now that we know binding mode and discriminant type. |
| let def_bm = def_bm; |
| let expected = expected; |
| |
| let ty = match pat.node { |
| PatKind::Wild => { |
| expected |
| } |
| PatKind::Lit(ref lt) => { |
| // 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(ref lt) = lt.node { |
| if let ast::LitKind::ByteStr(_) = lt.node { |
| let expected_ty = self.structurally_resolved_type(pat.span, expected); |
| if let ty::Ref(_, r_ty, _) = expected_ty.sty { |
| if let ty::Slice(_) = r_ty.sty { |
| 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. |
| if let Some(mut err) = self.demand_suptype_diag(pat.span, expected, pat_ty) { |
| err.emit_unless(discrim_span |
| .filter(|&s| s.is_compiler_desugaring(CompilerDesugaringKind::IfTemporary)) |
| .is_some()); |
| } |
| |
| pat_ty |
| } |
| PatKind::Range(ref begin, ref end, _) => { |
| let lhs_ty = self.check_expr(begin); |
| let rhs_ty = self.check_expr(end); |
| |
| // Check that both end-points are of numeric or char type. |
| let numeric_or_char = |ty: Ty<'_>| ty.is_numeric() || ty.is_char(); |
| let lhs_compat = numeric_or_char(lhs_ty); |
| let rhs_compat = numeric_or_char(rhs_ty); |
| |
| if !lhs_compat || !rhs_compat { |
| let span = if !lhs_compat && !rhs_compat { |
| pat.span |
| } else if !lhs_compat { |
| begin.span |
| } else { |
| end.span |
| }; |
| |
| let mut err = struct_span_err!( |
| tcx.sess, |
| span, |
| E0029, |
| "only char and numeric types are allowed in range patterns" |
| ); |
| err.span_label(span, "ranges require char or numeric types"); |
| err.note(&format!("start type: {}", self.ty_to_string(lhs_ty))); |
| err.note(&format!("end type: {}", self.ty_to_string(rhs_ty))); |
| if 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(); |
| return; |
| } |
| |
| // 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); |
| |
| // Subtyping doesn't matter here, as the value is some kind of scalar. |
| self.demand_eqtype_pat(pat.span, expected, lhs_ty, discrim_span); |
| self.demand_eqtype_pat(pat.span, expected, rhs_ty, discrim_span); |
| common_type |
| } |
| PatKind::Binding(ba, var_id, _, ref sub) => { |
| let bm = if ba == hir::BindingAnnotation::Unannotated { |
| def_bm |
| } else { |
| ty::BindingMode::convert(ba) |
| }; |
| self.inh |
| .tables |
| .borrow_mut() |
| .pat_binding_modes_mut() |
| .insert(pat.hir_id, bm); |
| debug!("check_pat_walk: pat.hir_id={:?} bm={:?}", pat.hir_id, bm); |
| let local_ty = self.local_ty(pat.span, pat.hir_id).decl_ty; |
| match bm { |
| ty::BindByReference(mutbl) => { |
| // If the binding is like |
| // ref x | ref const 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. |
| let region_var = self.next_region_var(infer::PatternRegion(pat.span)); |
| let mt = ty::TypeAndMut { ty: expected, mutbl: mutbl }; |
| let region_ty = tcx.mk_ref(region_var, mt); |
| |
| // `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)` is |
| // required. However, we use equality, which is stronger. See (*) for |
| // an explanation. |
| self.demand_eqtype_pat(pat.span, region_ty, local_ty, discrim_span); |
| } |
| // Otherwise, the type of x is the expected type `T`. |
| ty::BindByValue(_) => { |
| // As above, `T <: typeof(x)` is required, but we |
| // use equality, see (*) below. |
| self.demand_eqtype_pat(pat.span, expected, local_ty, discrim_span); |
| } |
| } |
| |
| // 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 { |
| let vt = self.local_ty(pat.span, var_id).decl_ty; |
| self.demand_eqtype_pat(pat.span, vt, local_ty, discrim_span); |
| } |
| |
| if let Some(ref p) = *sub { |
| self.check_pat_walk(&p, expected, def_bm, discrim_span); |
| } |
| |
| local_ty |
| } |
| PatKind::TupleStruct(ref qpath, ref subpats, ddpos) => { |
| self.check_pat_tuple_struct( |
| pat, |
| qpath, |
| &subpats, |
| ddpos, |
| expected, |
| def_bm, |
| discrim_span, |
| ) |
| } |
| PatKind::Path(ref qpath) => { |
| self.check_pat_path(pat, path_resolution.unwrap(), qpath, expected) |
| } |
| PatKind::Struct(ref qpath, ref fields, etc) => { |
| self.check_pat_struct(pat, qpath, fields, etc, expected, def_bm, discrim_span) |
| } |
| PatKind::Tuple(ref elements, ddpos) => { |
| 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(pat.span, expected).sty { |
| expected_len = tys.len(); |
| } |
| } |
| let max_len = cmp::max(expected_len, elements.len()); |
| |
| let element_tys_iter = (0..max_len).map(|_| { |
| Kind::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: pat.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_diag(pat.span, expected, pat_ty) { |
| 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.types.err); |
| for (_, elem) in elements.iter().enumerate_and_adjust(max_len, ddpos) { |
| self.check_pat_walk(elem, &tcx.types.err, def_bm, discrim_span); |
| } |
| tcx.mk_tup(element_tys_iter) |
| } else { |
| for (i, elem) in elements.iter().enumerate_and_adjust(max_len, ddpos) { |
| self.check_pat_walk( |
| elem, |
| &element_tys[i].expect_ty(), |
| def_bm, |
| discrim_span, |
| ); |
| } |
| pat_ty |
| } |
| } |
| PatKind::Box(ref inner) => { |
| let inner_ty = self.next_ty_var(TypeVariableOrigin { |
| kind: TypeVariableOriginKind::TypeInference, |
| span: inner.span, |
| }); |
| let uniq_ty = tcx.mk_box(inner_ty); |
| |
| if self.check_dereferencable(pat.span, expected, &inner) { |
| // Here, `demand::subtype` is good enough, but I don't |
| // think any errors can be introduced by using |
| // `demand::eqtype`. |
| self.demand_eqtype_pat(pat.span, expected, uniq_ty, discrim_span); |
| self.check_pat_walk(&inner, inner_ty, def_bm, discrim_span); |
| uniq_ty |
| } else { |
| self.check_pat_walk(&inner, tcx.types.err, def_bm, discrim_span); |
| tcx.types.err |
| } |
| } |
| PatKind::Ref(ref inner, mutbl) => { |
| let expected = self.shallow_resolve(expected); |
| if self.check_dereferencable(pat.span, expected, &inner) { |
| // `demand::subtype` would be good enough, but using |
| // `eqtype` turns out to be equally general. See (*) |
| // below 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 (*) below. |
| debug!("check_pat_walk: expected={:?}", expected); |
| let (rptr_ty, inner_ty) = match expected.sty { |
| 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 mt = ty::TypeAndMut { ty: inner_ty, mutbl: mutbl }; |
| let region = self.next_region_var(infer::PatternRegion(pat.span)); |
| let rptr_ty = tcx.mk_ref(region, mt); |
| debug!("check_pat_walk: demanding {:?} = {:?}", expected, rptr_ty); |
| let err = self.demand_eqtype_diag(pat.span, expected, rptr_ty); |
| |
| // 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) |
| } |
| }; |
| |
| self.check_pat_walk(&inner, inner_ty, def_bm, discrim_span); |
| rptr_ty |
| } else { |
| self.check_pat_walk(&inner, tcx.types.err, def_bm, discrim_span); |
| tcx.types.err |
| } |
| } |
| PatKind::Slice(ref before, ref slice, ref after) => { |
| let expected_ty = self.structurally_resolved_type(pat.span, expected); |
| let (inner_ty, slice_ty) = match expected_ty.sty { |
| ty::Array(inner_ty, size) => { |
| if let Some(size) = size.assert_usize(tcx) { |
| let min_len = before.len() as u64 + after.len() as u64; |
| if slice.is_none() { |
| if min_len != size { |
| struct_span_err!( |
| tcx.sess, pat.span, E0527, |
| "pattern requires {} elements but array has {}", |
| min_len, size) |
| .span_label(pat.span, format!("expected {} elements", size)) |
| .emit(); |
| } |
| (inner_ty, tcx.types.err) |
| } else if let Some(rest) = size.checked_sub(min_len) { |
| (inner_ty, tcx.mk_array(inner_ty, rest)) |
| } else { |
| struct_span_err!(tcx.sess, pat.span, E0528, |
| "pattern requires at least {} elements but array has {}", |
| min_len, size) |
| .span_label(pat.span, |
| format!("pattern cannot match array of {} elements", size)) |
| .emit(); |
| (inner_ty, tcx.types.err) |
| } |
| } else { |
| struct_span_err!( |
| tcx.sess, |
| pat.span, |
| E0730, |
| "cannot pattern-match on an array without a fixed length", |
| ).emit(); |
| (inner_ty, tcx.types.err) |
| } |
| } |
| ty::Slice(inner_ty) => (inner_ty, expected_ty), |
| _ => { |
| if !expected_ty.references_error() { |
| let mut err = struct_span_err!( |
| tcx.sess, pat.span, E0529, |
| "expected an array or slice, found `{}`", |
| expected_ty); |
| if let ty::Ref(_, ty, _) = expected_ty.sty { |
| match ty.sty { |
| ty::Array(..) | ty::Slice(..) => { |
| err.help("the semantics of slice patterns changed \ |
| recently; see issue #23121"); |
| } |
| _ => {} |
| } |
| } |
| |
| err.span_label( pat.span, |
| format!("pattern cannot match with input type `{}`", expected_ty) |
| ).emit(); |
| } |
| (tcx.types.err, tcx.types.err) |
| } |
| }; |
| |
| for elt in before { |
| self.check_pat_walk(&elt, inner_ty, def_bm, discrim_span); |
| } |
| if let Some(ref slice) = *slice { |
| self.check_pat_walk(&slice, slice_ty, def_bm, discrim_span); |
| } |
| for elt in after { |
| self.check_pat_walk(&elt, inner_ty, def_bm, discrim_span); |
| } |
| expected_ty |
| } |
| }; |
| |
| self.write_ty(pat.hir_id, ty); |
| |
| // (*) In most of the cases above (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 int) { |
| // 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 int`, 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 |
| // int`) as a subtype of `Z`: `&'x int <: Z`. And hence we |
| // will instantiate `Z` as a type `&'0 int` 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. |
| } |
| |
| fn borrow_pat_suggestion( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| pat: &Pat, |
| inner: &Pat, |
| expected: Ty<'tcx>, |
| ) { |
| let tcx = self.tcx; |
| if let PatKind::Binding(..) = inner.node { |
| let parent_id = tcx.hir().get_parent_node(pat.hir_id); |
| let parent = tcx.hir().get(parent_id); |
| debug!("inner {:?} pat {:?} parent {:?}", inner, pat, parent); |
| match parent { |
| hir::Node::Item(hir::Item { node: hir::ItemKind::Fn(..), .. }) | |
| hir::Node::ForeignItem(hir::ForeignItem { |
| node: hir::ForeignItemKind::Fn(..), .. |
| }) | |
| hir::Node::TraitItem(hir::TraitItem { node: hir::TraitItemKind::Method(..), .. }) | |
| hir::Node::ImplItem(hir::ImplItem { node: hir::ImplItemKind::Method(..), .. }) => { |
| // this pat is likely an argument |
| if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(inner.span) { |
| // FIXME: turn into structured suggestion, will need a span that also |
| // includes the the arg's type. |
| err.help(&format!("did you mean `{}: &{}`?", snippet, expected)); |
| } |
| } |
| 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_dereferencable(&self, span: Span, expected: Ty<'tcx>, inner: &hir::Pat) -> bool { |
| if let PatKind::Binding(..) = inner.node { |
| if let Some(mt) = self.shallow_resolve(expected).builtin_deref(true) { |
| if let ty::Dynamic(..) = mt.ty.sty { |
| // 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("\ |
| 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"); |
| } |
| err.emit(); |
| return false |
| } |
| } |
| } |
| true |
| } |
| |
| pub fn check_match( |
| &self, |
| expr: &'tcx hir::Expr, |
| discrim: &'tcx hir::Expr, |
| arms: &'tcx [hir::Arm], |
| expected: Expectation<'tcx>, |
| match_src: hir::MatchSource, |
| ) -> Ty<'tcx> { |
| let tcx = self.tcx; |
| |
| use hir::MatchSource::*; |
| let (source_if, if_no_else, if_desugar) = match match_src { |
| IfDesugar { contains_else_clause } => (true, !contains_else_clause, true), |
| IfLetDesugar { contains_else_clause } => (true, !contains_else_clause, false), |
| _ => (false, false, false), |
| }; |
| |
| // Type check the descriminant and get its type. |
| let discrim_ty = if if_desugar { |
| // Here we want to ensure: |
| // |
| // 1. That default match bindings are *not* accepted in the condition of an |
| // `if` expression. E.g. given `fn foo() -> &bool;` we reject `if foo() { .. }`. |
| // |
| // 2. By expecting `bool` for `expr` we get nice diagnostics for e.g. `if x = y { .. }`. |
| // |
| // FIXME(60707): Consider removing hack with principled solution. |
| self.check_expr_has_type_or_error(discrim, self.tcx.types.bool) |
| } else { |
| self.demand_discriminant_type(arms, discrim) |
| }; |
| |
| // If there are no arms, that is a diverging match; a special case. |
| if arms.is_empty() { |
| self.diverges.set(self.diverges.get() | Diverges::Always); |
| return tcx.types.never; |
| } |
| |
| self.warn_arms_when_scrutinee_diverges(arms, source_if); |
| |
| // Otherwise, we have to union together the types that the |
| // arms produce and so forth. |
| let discrim_diverges = self.diverges.get(); |
| self.diverges.set(Diverges::Maybe); |
| |
| // rust-lang/rust#55810: Typecheck patterns first (via eager |
| // collection into `Vec`), so we get types for all bindings. |
| let all_arm_pats_diverge: Vec<_> = arms.iter().map(|arm| { |
| let mut all_pats_diverge = Diverges::WarnedAlways; |
| for p in &arm.pats { |
| self.diverges.set(Diverges::Maybe); |
| let binding_mode = ty::BindingMode::BindByValue(hir::Mutability::MutImmutable); |
| self.check_pat_walk(&p, discrim_ty, binding_mode, Some(discrim.span)); |
| all_pats_diverge &= self.diverges.get(); |
| } |
| |
| // As discussed with @eddyb, this is for disabling unreachable_code |
| // warnings on patterns (they're now subsumed by unreachable_patterns |
| // warnings). |
| match all_pats_diverge { |
| Diverges::Maybe => Diverges::Maybe, |
| Diverges::Always | Diverges::WarnedAlways => Diverges::WarnedAlways, |
| } |
| }).collect(); |
| |
| // Now typecheck the blocks. |
| // |
| // The result of the match is the common supertype of all the |
| // arms. Start out the value as bottom, since it's the, well, |
| // bottom the type lattice, and we'll be moving up the lattice as |
| // we process each arm. (Note that any match with 0 arms is matching |
| // on any empty type and is therefore unreachable; should the flow |
| // of execution reach it, we will panic, so bottom is an appropriate |
| // type in that case) |
| let mut all_arms_diverge = Diverges::WarnedAlways; |
| |
| let expected = expected.adjust_for_branches(self); |
| |
| let mut coercion = { |
| let coerce_first = match expected { |
| // We don't coerce to `()` so that if the match expression is a |
| // statement it's branches can have any consistent type. That allows |
| // us to give better error messages (pointing to a usually better |
| // arm for inconsistent arms or to the whole match when a `()` type |
| // is required). |
| Expectation::ExpectHasType(ety) if ety != self.tcx.mk_unit() => ety, |
| _ => self.next_ty_var(TypeVariableOrigin { |
| kind: TypeVariableOriginKind::MiscVariable, |
| span: expr.span, |
| }), |
| }; |
| CoerceMany::with_coercion_sites(coerce_first, arms) |
| }; |
| |
| let mut other_arms = vec![]; // used only for diagnostics |
| let mut prior_arm_ty = None; |
| for (i, (arm, pats_diverge)) in arms.iter().zip(all_arm_pats_diverge).enumerate() { |
| if let Some(g) = &arm.guard { |
| self.diverges.set(pats_diverge); |
| match g { |
| hir::Guard::If(e) => self.check_expr_has_type_or_error(e, tcx.types.bool), |
| }; |
| } |
| |
| self.diverges.set(pats_diverge); |
| let arm_ty = self.check_expr_with_expectation(&arm.body, expected); |
| all_arms_diverge &= self.diverges.get(); |
| |
| let span = expr.span; |
| |
| if source_if { |
| let then_expr = &arms[0].body; |
| match (i, if_no_else) { |
| (0, _) => coercion.coerce(self, &self.misc(span), then_expr, arm_ty), |
| (_, true) => self.if_fallback_coercion(span, then_expr, &mut coercion), |
| (_, _) => { |
| let then_ty = prior_arm_ty.unwrap(); |
| let cause = self.if_cause(span, then_expr, &arm.body, then_ty, arm_ty); |
| coercion.coerce(self, &cause, &arm.body, arm_ty); |
| } |
| } |
| } else { |
| let arm_span = if let hir::ExprKind::Block(blk, _) = &arm.body.node { |
| // Point at the block expr instead of the entire block |
| blk.expr.as_ref().map(|e| e.span).unwrap_or(arm.body.span) |
| } else { |
| arm.body.span |
| }; |
| let (span, code) = match i { |
| // The reason for the first arm to fail is not that the match arms diverge, |
| // but rather that there's a prior obligation that doesn't hold. |
| 0 => (arm_span, ObligationCauseCode::BlockTailExpression(arm.body.hir_id)), |
| _ => (span, ObligationCauseCode::MatchExpressionArm { |
| arm_span, |
| source: match_src, |
| prior_arms: other_arms.clone(), |
| last_ty: prior_arm_ty.unwrap(), |
| discrim_hir_id: discrim.hir_id, |
| }), |
| }; |
| let cause = self.cause(span, code); |
| coercion.coerce(self, &cause, &arm.body, arm_ty); |
| other_arms.push(arm_span); |
| if other_arms.len() > 5 { |
| other_arms.remove(0); |
| } |
| } |
| prior_arm_ty = Some(arm_ty); |
| } |
| |
| // We won't diverge unless the discriminant or all arms diverge. |
| self.diverges.set(discrim_diverges | all_arms_diverge); |
| |
| coercion.complete(self) |
| } |
| |
| /// When the previously checked expression (the scrutinee) diverges, |
| /// warn the user about the match arms being unreachable. |
| fn warn_arms_when_scrutinee_diverges(&self, arms: &'tcx [hir::Arm], source_if: bool) { |
| if self.diverges.get().always() { |
| let msg = if source_if { "block in `if` expression" } else { "arm" }; |
| for arm in arms { |
| self.warn_if_unreachable(arm.body.hir_id, arm.body.span, msg); |
| } |
| } |
| } |
| |
| /// Handle the fallback arm of a desugared if(-let) like a missing else. |
| fn if_fallback_coercion( |
| &self, |
| span: Span, |
| then_expr: &'tcx hir::Expr, |
| coercion: &mut CoerceMany<'tcx, '_, rustc::hir::Arm>, |
| ) { |
| // If this `if` expr is the parent's function return expr, |
| // the cause of the type coercion is the return type, point at it. (#25228) |
| let ret_reason = self.maybe_get_coercion_reason(then_expr.hir_id, span); |
| let cause = self.cause(span, ObligationCauseCode::IfExpressionWithNoElse); |
| coercion.coerce_forced_unit(self, &cause, &mut |err| { |
| if let Some((span, msg)) = &ret_reason { |
| err.span_label(*span, msg.as_str()); |
| } else if let ExprKind::Block(block, _) = &then_expr.node { |
| if let Some(expr) = &block.expr { |
| err.span_label(expr.span, "found here".to_string()); |
| } |
| } |
| err.note("`if` expressions without `else` evaluate to `()`"); |
| err.help("consider adding an `else` block that evaluates to the expected type"); |
| }, ret_reason.is_none()); |
| } |
| |
| fn maybe_get_coercion_reason(&self, hir_id: hir::HirId, span: Span) -> Option<(Span, String)> { |
| use hir::Node::{Block, Item, Local}; |
| |
| let hir = self.tcx.hir(); |
| let arm_id = hir.get_parent_node(hir_id); |
| let match_id = hir.get_parent_node(arm_id); |
| let containing_id = hir.get_parent_node(match_id); |
| |
| let node = hir.get(containing_id); |
| if let Block(block) = node { |
| // check that the body's parent is an fn |
| let parent = hir.get( |
| hir.get_parent_node( |
| hir.get_parent_node(block.hir_id), |
| ), |
| ); |
| if let (Some(expr), Item(hir::Item { |
| node: hir::ItemKind::Fn(..), .. |
| })) = (&block.expr, parent) { |
| // check that the `if` expr without `else` is the fn body's expr |
| if expr.span == span { |
| return self.get_fn_decl(hir_id).map(|(fn_decl, _)| ( |
| fn_decl.output.span(), |
| format!("expected `{}` because of this return type", fn_decl.output), |
| )); |
| } |
| } |
| } |
| if let Local(hir::Local { ty: Some(_), pat, .. }) = node { |
| return Some((pat.span, "expected because of this assignment".to_string())); |
| } |
| None |
| } |
| |
| fn if_cause( |
| &self, |
| span: Span, |
| then_expr: &'tcx hir::Expr, |
| else_expr: &'tcx hir::Expr, |
| then_ty: Ty<'tcx>, |
| else_ty: Ty<'tcx>, |
| ) -> ObligationCause<'tcx> { |
| let mut outer_sp = if self.tcx.sess.source_map().is_multiline(span) { |
| // The `if`/`else` isn't in one line in the output, include some context to make it |
| // clear it is an if/else expression: |
| // ``` |
| // LL | let x = if true { |
| // | _____________- |
| // LL || 10i32 |
| // || ----- expected because of this |
| // LL || } else { |
| // LL || 10u32 |
| // || ^^^^^ expected i32, found u32 |
| // LL || }; |
| // ||_____- if and else have incompatible types |
| // ``` |
| Some(span) |
| } else { |
| // The entire expression is in one line, only point at the arms |
| // ``` |
| // LL | let x = if true { 10i32 } else { 10u32 }; |
| // | ----- ^^^^^ expected i32, found u32 |
| // | | |
| // | expected because of this |
| // ``` |
| None |
| }; |
| |
| let mut remove_semicolon = None; |
| let error_sp = if let ExprKind::Block(block, _) = &else_expr.node { |
| if let Some(expr) = &block.expr { |
| expr.span |
| } else if let Some(stmt) = block.stmts.last() { |
| // possibly incorrect trailing `;` in the else arm |
| remove_semicolon = self.could_remove_semicolon(block, then_ty); |
| stmt.span |
| } else { // empty block; point at its entirety |
| // Avoid overlapping spans that aren't as readable: |
| // ``` |
| // 2 | let x = if true { |
| // | _____________- |
| // 3 | | 3 |
| // | | - expected because of this |
| // 4 | | } else { |
| // | |____________^ |
| // 5 | || |
| // 6 | || }; |
| // | || ^ |
| // | ||_____| |
| // | |______if and else have incompatible types |
| // | expected integer, found () |
| // ``` |
| // by not pointing at the entire expression: |
| // ``` |
| // 2 | let x = if true { |
| // | ------- if and else have incompatible types |
| // 3 | 3 |
| // | - expected because of this |
| // 4 | } else { |
| // | ____________^ |
| // 5 | | |
| // 6 | | }; |
| // | |_____^ expected integer, found () |
| // ``` |
| if outer_sp.is_some() { |
| outer_sp = Some(self.tcx.sess.source_map().def_span(span)); |
| } |
| else_expr.span |
| } |
| } else { // shouldn't happen unless the parser has done something weird |
| else_expr.span |
| }; |
| |
| // Compute `Span` of `then` part of `if`-expression. |
| let then_sp = if let ExprKind::Block(block, _) = &then_expr.node { |
| if let Some(expr) = &block.expr { |
| expr.span |
| } else if let Some(stmt) = block.stmts.last() { |
| // possibly incorrect trailing `;` in the else arm |
| remove_semicolon = remove_semicolon.or(self.could_remove_semicolon(block, else_ty)); |
| stmt.span |
| } else { // empty block; point at its entirety |
| outer_sp = None; // same as in `error_sp`; cleanup output |
| then_expr.span |
| } |
| } else { // shouldn't happen unless the parser has done something weird |
| then_expr.span |
| }; |
| |
| // Finally construct the cause: |
| self.cause(error_sp, ObligationCauseCode::IfExpression { |
| then: then_sp, |
| outer: outer_sp, |
| semicolon: remove_semicolon, |
| }) |
| } |
| |
| fn demand_discriminant_type( |
| &self, |
| arms: &'tcx [hir::Arm], |
| discrim: &'tcx hir::Expr, |
| ) -> Ty<'tcx> { |
| // Not entirely obvious: if matches may create ref bindings, we want to |
| // use the *precise* type of the discriminant, *not* some supertype, as |
| // the "discriminant type" (issue #23116). |
| // |
| // arielb1 [writes here in this comment thread][c] that there |
| // is certainly *some* potential danger, e.g., for an example |
| // like: |
| // |
| // [c]: https://github.com/rust-lang/rust/pull/43399#discussion_r130223956 |
| // |
| // ``` |
| // let Foo(x) = f()[0]; |
| // ``` |
| // |
| // Then if the pattern matches by reference, we want to match |
| // `f()[0]` as a lexpr, so we can't allow it to be |
| // coerced. But if the pattern matches by value, `f()[0]` is |
| // still syntactically a lexpr, but we *do* want to allow |
| // coercions. |
| // |
| // However, *likely* we are ok with allowing coercions to |
| // happen if there are no explicit ref mut patterns - all |
| // implicit ref mut patterns must occur behind a reference, so |
| // they will have the "correct" variance and lifetime. |
| // |
| // This does mean that the following pattern would be legal: |
| // |
| // ``` |
| // struct Foo(Bar); |
| // struct Bar(u32); |
| // impl Deref for Foo { |
| // type Target = Bar; |
| // fn deref(&self) -> &Bar { &self.0 } |
| // } |
| // impl DerefMut for Foo { |
| // fn deref_mut(&mut self) -> &mut Bar { &mut self.0 } |
| // } |
| // fn foo(x: &mut Foo) { |
| // { |
| // let Bar(z): &mut Bar = x; |
| // *z = 42; |
| // } |
| // assert_eq!(foo.0.0, 42); |
| // } |
| // ``` |
| // |
| // FIXME(tschottdorf): don't call contains_explicit_ref_binding, which |
| // is problematic as the HIR is being scraped, but ref bindings may be |
| // implicit after #42640. We need to make sure that pat_adjustments |
| // (once introduced) is populated by the time we get here. |
| // |
| // See #44848. |
| let contains_ref_bindings = arms.iter() |
| .filter_map(|a| a.contains_explicit_ref_binding()) |
| .max_by_key(|m| match *m { |
| hir::MutMutable => 1, |
| hir::MutImmutable => 0, |
| }); |
| |
| if let Some(m) = contains_ref_bindings { |
| self.check_expr_with_needs(discrim, Needs::maybe_mut_place(m)) |
| } else { |
| // ...but otherwise we want to use any supertype of the |
| // discriminant. This is sort of a workaround, see note (*) in |
| // `check_pat` for some details. |
| let discrim_ty = self.next_ty_var(TypeVariableOrigin { |
| kind: TypeVariableOriginKind::TypeInference, |
| span: discrim.span, |
| }); |
| self.check_expr_has_type_or_error(discrim, discrim_ty); |
| discrim_ty |
| } |
| } |
| |
| fn check_pat_struct( |
| &self, |
| pat: &'tcx hir::Pat, |
| qpath: &hir::QPath, |
| fields: &'tcx [Spanned<hir::FieldPat>], |
| etc: bool, |
| expected: Ty<'tcx>, |
| def_bm: ty::BindingMode, |
| discrim_span: Option<Span>, |
| ) -> 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 { |
| for field in fields { |
| self.check_pat_walk(&field.node.pat, self.tcx.types.err, def_bm, discrim_span); |
| } |
| return self.tcx.types.err; |
| }; |
| |
| // Type-check the path. |
| self.demand_eqtype_pat(pat.span, expected, pat_ty, discrim_span); |
| |
| // Type-check subpatterns. |
| if self.check_struct_pat_fields(pat_ty, pat.hir_id, pat.span, variant, fields, etc, def_bm) |
| { |
| pat_ty |
| } else { |
| self.tcx.types.err |
| } |
| } |
| |
| fn check_pat_path( |
| &self, |
| pat: &hir::Pat, |
| path_resolution: (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment]), |
| qpath: &hir::QPath, |
| expected: Ty<'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.types.err; |
| } |
| Res::Def(DefKind::Method, _) | |
| Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) | |
| Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) => { |
| report_unexpected_variant_res(tcx, res, pat.span, qpath); |
| return tcx.types.err; |
| } |
| Res::Def(DefKind::Ctor(_, CtorKind::Const), _) | Res::SelfCtor(..) | |
| Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) => {} // OK |
| _ => bug!("unexpected pattern resolution: {:?}", res) |
| } |
| |
| // Type-check the path. |
| let pat_ty = self.instantiate_value_path(segments, opt_ty, res, pat.span, pat.hir_id).0; |
| self.demand_suptype(pat.span, expected, pat_ty); |
| pat_ty |
| } |
| |
| fn check_pat_tuple_struct( |
| &self, |
| pat: &hir::Pat, |
| qpath: &hir::QPath, |
| subpats: &'tcx [P<hir::Pat>], |
| ddpos: Option<usize>, |
| expected: Ty<'tcx>, |
| def_bm: ty::BindingMode, |
| match_arm_pat_span: Option<Span>, |
| ) -> Ty<'tcx> { |
| let tcx = self.tcx; |
| let on_error = || { |
| for pat in subpats { |
| self.check_pat_walk(&pat, tcx.types.err, def_bm, match_arm_pat_span); |
| } |
| }; |
| let report_unexpected_res = |res: Res| { |
| let msg = format!("expected tuple struct/variant, found {} `{}`", |
| res.descr(), |
| hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false))); |
| let mut err = struct_span_err!(tcx.sess, pat.span, E0164, "{}", msg); |
| match (res, &pat.node) { |
| (Res::Def(DefKind::Fn, _), _) | (Res::Def(DefKind::Method, _), _) => { |
| 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.types.err; |
| } |
| |
| // 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 self.tcx.types.err; |
| } |
| |
| let variant = match res { |
| Res::Err => { |
| self.set_tainted_by_errors(); |
| on_error(); |
| return tcx.types.err; |
| } |
| Res::Def(DefKind::AssocConst, _) | Res::Def(DefKind::Method, _) => { |
| report_unexpected_res(res); |
| return tcx.types.err; |
| } |
| 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"); |
| |
| self.demand_eqtype_pat(pat.span, expected, pat_ty, match_arm_pat_span); |
| |
| // Type-check subpatterns. |
| if subpats.len() == variant.fields.len() || |
| subpats.len() < variant.fields.len() && ddpos.is_some() { |
| let substs = match pat_ty.sty { |
| 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_walk(&subpat, field_ty, def_bm, match_arm_pat_span); |
| |
| self.tcx.check_stability(variant.fields[i].did, Some(pat.hir_id), subpat.span); |
| } |
| } else { |
| let subpats_ending = if subpats.len() == 1 { "" } else { "s" }; |
| let fields_ending = if variant.fields.len() == 1 { "" } else { "s" }; |
| struct_span_err!(tcx.sess, pat.span, E0023, |
| "this pattern has {} field{}, but the corresponding {} has {} field{}", |
| subpats.len(), subpats_ending, res.descr(), |
| variant.fields.len(), fields_ending) |
| .span_label(pat.span, format!("expected {} field{}, found {}", |
| variant.fields.len(), fields_ending, subpats.len())) |
| .emit(); |
| on_error(); |
| return tcx.types.err; |
| } |
| pat_ty |
| } |
| |
| fn check_struct_pat_fields( |
| &self, |
| adt_ty: Ty<'tcx>, |
| pat_id: hir::HirId, |
| span: Span, |
| variant: &'tcx ty::VariantDef, |
| fields: &'tcx [Spanned<hir::FieldPat>], |
| etc: bool, |
| def_bm: ty::BindingMode, |
| ) -> bool { |
| let tcx = self.tcx; |
| |
| let (substs, adt) = match adt_ty.sty { |
| ty::Adt(adt, substs) => (substs, adt), |
| _ => span_bug!(span, "struct pattern is not an ADT") |
| }; |
| let kind_name = adt.variant_descr(); |
| |
| // Index the struct fields' types. |
| let field_map = variant.fields |
| .iter() |
| .enumerate() |
| .map(|(i, field)| (field.ident.modern(), (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 &Spanned { node: ref field, span } in fields { |
| let ident = tcx.adjust_ident(field.ident, variant.def_id); |
| let field_ty = match used_fields.entry(ident) { |
| Occupied(occupied) => { |
| struct_span_err!(tcx.sess, span, E0025, |
| "field `{}` bound multiple times \ |
| in the pattern", |
| field.ident) |
| .span_label(span, |
| format!("multiple uses of `{}` in pattern", field.ident)) |
| .span_label(*occupied.get(), format!("first use of `{}`", field.ident)) |
| .emit(); |
| no_field_errors = false; |
| tcx.types.err |
| } |
| 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_id), span); |
| self.field_ty(span, f, substs) |
| }) |
| .unwrap_or_else(|| { |
| inexistent_fields.push(field.ident); |
| no_field_errors = false; |
| tcx.types.err |
| }) |
| } |
| }; |
| |
| self.check_pat_walk(&field.pat, field_ty, def_bm, None); |
| } |
| let mut unmentioned_fields = variant.fields |
| .iter() |
| .map(|field| field.ident.modern()) |
| .filter(|ident| !used_fields.contains_key(&ident)) |
| .collect::<Vec<_>>(); |
| if inexistent_fields.len() > 0 && !variant.recovered { |
| 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.as_str() != suggested_name.as_str()); |
| } |
| } |
| } |
| 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(); |
| } |
| |
| // Require `..` if struct has non_exhaustive attribute. |
| if variant.is_field_list_non_exhaustive() && !adt.did.is_local() && !etc { |
| span_err!(tcx.sess, span, E0638, |
| "`..` required with {} marked as non-exhaustive", |
| kind_name); |
| } |
| |
| // Report an error if incorrect number of the fields were specified. |
| if kind_name == "union" { |
| if fields.len() != 1 { |
| tcx.sess.span_err(span, "union patterns should have exactly one field"); |
| } |
| if etc { |
| tcx.sess.span_err(span, "`..` cannot be used in union patterns"); |
| } |
| } else if !etc { |
| if unmentioned_fields.len() > 0 { |
| let field_names = if unmentioned_fields.len() == 1 { |
| format!("field `{}`", unmentioned_fields[0]) |
| } else { |
| format!("fields {}", |
| unmentioned_fields.iter() |
| .map(|name| format!("`{}`", name)) |
| .collect::<Vec<String>>() |
| .join(", ")) |
| }; |
| let mut diag = struct_span_err!(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 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(); |
| } |
| } |
| no_field_errors |
| } |
| } |
