1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use middle::def::{self, Def};
12 use middle::infer::{self, TypeOrigin};
13 use middle::pat_util::{PatIdMap, pat_id_map, pat_is_binding};
14 use middle::pat_util::pat_is_resolved_const;
15 use middle::privacy::{AllPublic, LastMod};
16 use middle::subst::Substs;
17 use middle::ty::{self, Ty, TypeFoldable, LvaluePreference};
18 use check::{check_expr, check_expr_has_type, check_expr_with_expectation};
19 use check::{check_expr_coercable_to_type, demand, FnCtxt, Expectation};
20 use check::{check_expr_with_lvalue_pref};
21 use check::{instantiate_path, resolve_ty_and_def_ufcs, structurally_resolved_type};
23 use require_same_types;
24 use util::nodemap::FnvHashMap;
28 use std::collections::hash_map::Entry::{Occupied, Vacant};
30 use syntax::codemap::{Span, Spanned};
33 use rustc_front::hir::{self, PatKind};
34 use rustc_front::print::pprust;
35 use rustc_front::util as hir_util;
37 pub fn check_pat<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
42 let tcx = pcx.fcx.ccx.tcx;
44 debug!("check_pat(pat={:?},expected={:?})",
50 fcx.write_ty(pat.id, expected);
52 PatKind::Lit(ref lt) => {
54 let expr_ty = fcx.expr_ty(<);
56 // Byte string patterns behave the same way as array patterns
57 // They can denote both statically and dynamically sized byte arrays
58 let mut pat_ty = expr_ty;
59 if let hir::ExprLit(ref lt) = lt.node {
60 if let ast::LitKind::ByteStr(_) = lt.node {
61 let expected_ty = structurally_resolved_type(fcx, pat.span, expected);
62 if let ty::TyRef(_, mt) = expected_ty.sty {
63 if let ty::TySlice(_) = mt.ty.sty {
64 pat_ty = tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic),
65 tcx.mk_slice(tcx.types.u8))
71 fcx.write_ty(pat.id, pat_ty);
73 // somewhat surprising: in this case, the subtyping
74 // relation goes the opposite way as the other
75 // cases. Actually what we really want is not a subtyping
76 // relation at all but rather that there exists a LUB (so
77 // that they can be compared). However, in practice,
78 // constants are always scalars or strings. For scalars
79 // subtyping is irrelevant, and for strings `expr_ty` is
80 // type is `&'static str`, so if we say that
82 // &'static str <: expected
84 // that's equivalent to there existing a LUB.
85 demand::suptype(fcx, pat.span, expected, pat_ty);
87 PatKind::Range(ref begin, ref end) => {
88 check_expr(fcx, begin);
91 let lhs_ty = fcx.expr_ty(begin);
92 let rhs_ty = fcx.expr_ty(end);
94 // Check that both end-points are of numeric or char type.
95 let numeric_or_char = |ty: Ty| ty.is_numeric() || ty.is_char();
96 let lhs_compat = numeric_or_char(lhs_ty);
97 let rhs_compat = numeric_or_char(rhs_ty);
99 if !lhs_compat || !rhs_compat {
100 let span = if !lhs_compat && !rhs_compat {
102 } else if !lhs_compat {
108 // Note: spacing here is intentional, we want a space before "start" and "end".
109 span_err!(tcx.sess, span, E0029,
110 "only char and numeric types are allowed in range patterns\n \
111 start type: {}\n end type: {}",
112 fcx.infcx().ty_to_string(lhs_ty),
113 fcx.infcx().ty_to_string(rhs_ty)
118 // Check that the types of the end-points can be unified.
119 let types_unify = require_same_types(
120 tcx, Some(fcx.infcx()), false, pat.span, rhs_ty, lhs_ty,
121 || "mismatched types in range".to_string()
124 // It's ok to return without a message as `require_same_types` prints an error.
129 // Now that we know the types can be unified we find the unified type and use
130 // it to type the entire expression.
131 let common_type = fcx.infcx().resolve_type_vars_if_possible(&lhs_ty);
133 fcx.write_ty(pat.id, common_type);
135 // subtyping doesn't matter here, as the value is some kind of scalar
136 demand::eqtype(fcx, pat.span, expected, lhs_ty);
138 PatKind::Path(..) | PatKind::Ident(..)
139 if pat_is_resolved_const(&tcx.def_map.borrow(), pat) => {
140 if let Some(pat_def) = tcx.def_map.borrow().get(&pat.id) {
141 let const_did = pat_def.def_id();
142 let const_scheme = tcx.lookup_item_type(const_did);
143 assert!(const_scheme.generics.is_empty());
144 let const_ty = pcx.fcx.instantiate_type_scheme(pat.span,
147 fcx.write_ty(pat.id, const_ty);
149 // FIXME(#20489) -- we should limit the types here to scalars or something!
151 // As with PatKind::Lit, what we really want here is that there
152 // exist a LUB, but for the cases that can occur, subtype
154 demand::suptype(fcx, pat.span, expected, const_ty);
156 fcx.write_error(pat.id);
159 PatKind::Ident(bm, ref path, ref sub) if pat_is_binding(&tcx.def_map.borrow(), pat) => {
160 let typ = fcx.local_ty(pat.span, pat.id);
162 hir::BindByRef(mutbl) => {
163 // if the binding is like
164 // ref x | ref const x | ref mut x
165 // then `x` is assigned a value of type `&M T` where M is the mutability
166 // and T is the expected type.
167 let region_var = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
168 let mt = ty::TypeAndMut { ty: expected, mutbl: mutbl };
169 let region_ty = tcx.mk_ref(tcx.mk_region(region_var), mt);
171 // `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)` is
172 // required. However, we use equality, which is stronger. See (*) for
174 demand::eqtype(fcx, pat.span, region_ty, typ);
176 // otherwise the type of x is the expected type T
177 hir::BindByValue(_) => {
178 // As above, `T <: typeof(x)` is required but we
179 // use equality, see (*) below.
180 demand::eqtype(fcx, pat.span, expected, typ);
184 fcx.write_ty(pat.id, typ);
186 // if there are multiple arms, make sure they all agree on
187 // what the type of the binding `x` ought to be
188 if let Some(&canon_id) = pcx.map.get(&path.node.name) {
189 if canon_id != pat.id {
190 let ct = fcx.local_ty(pat.span, canon_id);
191 demand::eqtype(fcx, pat.span, ct, typ);
194 if let Some(ref p) = *sub {
195 check_pat(pcx, &p, expected);
199 PatKind::Ident(_, ref path, _) => {
200 let path = hir_util::ident_to_path(path.span, path.node);
201 check_pat_enum(pcx, pat, &path, Some(&[]), expected, false);
203 PatKind::TupleStruct(ref path, ref subpats) => {
204 check_pat_enum(pcx, pat, path, subpats.as_ref().map(|v| &v[..]), expected, true);
206 PatKind::Path(ref path) => {
207 check_pat_enum(pcx, pat, path, None, expected, false);
209 PatKind::QPath(ref qself, ref path) => {
210 let self_ty = fcx.to_ty(&qself.ty);
211 let path_res = if let Some(&d) = tcx.def_map.borrow().get(&pat.id) {
212 if d.base_def == Def::Err {
213 fcx.write_error(pat.id);
217 } else if qself.position == 0 {
218 // This is just a sentinel for finish_resolving_def_to_ty.
219 let sentinel = fcx.tcx().map.local_def_id(ast::CRATE_NODE_ID);
220 def::PathResolution {
221 base_def: Def::Mod(sentinel),
222 last_private: LastMod(AllPublic),
223 depth: path.segments.len()
226 debug!("unbound path {:?}", pat);
227 fcx.write_error(pat.id);
230 if let Some((opt_ty, segments, def)) =
231 resolve_ty_and_def_ufcs(fcx, path_res, Some(self_ty),
232 path, pat.span, pat.id) {
233 if check_assoc_item_is_const(pcx, def, pat.span) {
234 let scheme = tcx.lookup_item_type(def.def_id());
235 let predicates = tcx.lookup_predicates(def.def_id());
236 instantiate_path(fcx, segments,
238 opt_ty, def, pat.span, pat.id);
239 let const_ty = fcx.node_ty(pat.id);
240 demand::suptype(fcx, pat.span, expected, const_ty);
242 fcx.write_error(pat.id)
246 PatKind::Struct(ref path, ref fields, etc) => {
247 check_pat_struct(pcx, pat, path, fields, etc, expected);
249 PatKind::Tup(ref elements) => {
250 let element_tys: Vec<_> =
251 (0..elements.len()).map(|_| fcx.infcx().next_ty_var())
253 let pat_ty = tcx.mk_tup(element_tys.clone());
254 fcx.write_ty(pat.id, pat_ty);
255 demand::eqtype(fcx, pat.span, expected, pat_ty);
256 for (element_pat, element_ty) in elements.iter().zip(element_tys) {
257 check_pat(pcx, &element_pat, element_ty);
260 PatKind::Box(ref inner) => {
261 let inner_ty = fcx.infcx().next_ty_var();
262 let uniq_ty = tcx.mk_box(inner_ty);
264 if check_dereferencable(pcx, pat.span, expected, &inner) {
265 // Here, `demand::subtype` is good enough, but I don't
266 // think any errors can be introduced by using
268 demand::eqtype(fcx, pat.span, expected, uniq_ty);
269 fcx.write_ty(pat.id, uniq_ty);
270 check_pat(pcx, &inner, inner_ty);
272 fcx.write_error(pat.id);
273 check_pat(pcx, &inner, tcx.types.err);
276 PatKind::Ref(ref inner, mutbl) => {
277 let expected = fcx.infcx().shallow_resolve(expected);
278 if check_dereferencable(pcx, pat.span, expected, &inner) {
279 // `demand::subtype` would be good enough, but using
280 // `eqtype` turns out to be equally general. See (*)
281 // below for details.
283 // Take region, inner-type from expected type if we
284 // can, to avoid creating needless variables. This
285 // also helps with the bad interactions of the given
286 // hack detailed in (*) below.
287 let (rptr_ty, inner_ty) = match expected.sty {
288 ty::TyRef(_, mt) if mt.mutbl == mutbl => {
292 let inner_ty = fcx.infcx().next_ty_var();
293 let mt = ty::TypeAndMut { ty: inner_ty, mutbl: mutbl };
294 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
295 let rptr_ty = tcx.mk_ref(tcx.mk_region(region), mt);
296 demand::eqtype(fcx, pat.span, expected, rptr_ty);
301 fcx.write_ty(pat.id, rptr_ty);
302 check_pat(pcx, &inner, inner_ty);
304 fcx.write_error(pat.id);
305 check_pat(pcx, &inner, tcx.types.err);
308 PatKind::Vec(ref before, ref slice, ref after) => {
309 let expected_ty = structurally_resolved_type(fcx, pat.span, expected);
310 let inner_ty = fcx.infcx().next_ty_var();
311 let pat_ty = match expected_ty.sty {
312 ty::TyArray(_, size) => tcx.mk_array(inner_ty, {
313 let min_len = before.len() + after.len();
315 Some(_) => cmp::max(min_len, size),
320 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
321 tcx.mk_ref(tcx.mk_region(region), ty::TypeAndMut {
322 ty: tcx.mk_slice(inner_ty),
323 mutbl: expected_ty.builtin_deref(true, ty::NoPreference).map(|mt| mt.mutbl)
324 .unwrap_or(hir::MutImmutable)
329 fcx.write_ty(pat.id, pat_ty);
331 // `demand::subtype` would be good enough, but using
332 // `eqtype` turns out to be equally general. See (*)
333 // below for details.
334 demand::eqtype(fcx, pat.span, expected, pat_ty);
337 check_pat(pcx, &elt, inner_ty);
339 if let Some(ref slice) = *slice {
340 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
341 let mutbl = expected_ty.builtin_deref(true, ty::NoPreference)
342 .map_or(hir::MutImmutable, |mt| mt.mutbl);
344 let slice_ty = tcx.mk_ref(tcx.mk_region(region), ty::TypeAndMut {
345 ty: tcx.mk_slice(inner_ty),
348 check_pat(pcx, &slice, slice_ty);
351 check_pat(pcx, &elt, inner_ty);
357 // (*) In most of the cases above (literals and constants being
358 // the exception), we relate types using strict equality, evewn
359 // though subtyping would be sufficient. There are a few reasons
360 // for this, some of which are fairly subtle and which cost me
361 // (nmatsakis) an hour or two debugging to remember, so I thought
362 // I'd write them down this time.
364 // 1. There is no loss of expressiveness here, though it does
365 // cause some inconvenience. What we are saying is that the type
366 // of `x` becomes *exactly* what is expected. This can cause unnecessary
367 // errors in some cases, such as this one:
368 // it will cause errors in a case like this:
371 // fn foo<'x>(x: &'x int) {
378 // The reason we might get an error is that `z` might be
379 // assigned a type like `&'x int`, and then we would have
380 // a problem when we try to assign `&a` to `z`, because
381 // the lifetime of `&a` (i.e., the enclosing block) is
382 // shorter than `'x`.
384 // HOWEVER, this code works fine. The reason is that the
385 // expected type here is whatever type the user wrote, not
386 // the initializer's type. In this case the user wrote
387 // nothing, so we are going to create a type variable `Z`.
388 // Then we will assign the type of the initializer (`&'x
389 // int`) as a subtype of `Z`: `&'x int <: Z`. And hence we
390 // will instantiate `Z` as a type `&'0 int` where `'0` is
391 // a fresh region variable, with the constraint that `'x :
392 // '0`. So basically we're all set.
394 // Note that there are two tests to check that this remains true
395 // (`regions-reassign-{match,let}-bound-pointer.rs`).
397 // 2. Things go horribly wrong if we use subtype. The reason for
398 // THIS is a fairly subtle case involving bound regions. See the
399 // `givens` field in `region_inference`, as well as the test
400 // `regions-relate-bound-regions-on-closures-to-inference-variables.rs`,
401 // for details. Short version is that we must sometimes detect
402 // relationships between specific region variables and regions
403 // bound in a closure signature, and that detection gets thrown
404 // off when we substitute fresh region variables here to enable
408 fn check_assoc_item_is_const(pcx: &pat_ctxt, def: Def, span: Span) -> bool {
410 Def::AssociatedConst(..) => true,
412 span_err!(pcx.fcx.ccx.tcx.sess, span, E0327,
413 "associated items in match patterns must be constants");
417 pcx.fcx.ccx.tcx.sess.span_bug(span, "non-associated item in
418 check_assoc_item_is_const");
423 pub fn check_dereferencable<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
424 span: Span, expected: Ty<'tcx>,
425 inner: &hir::Pat) -> bool {
427 let tcx = pcx.fcx.ccx.tcx;
428 if pat_is_binding(&tcx.def_map.borrow(), inner) {
429 let expected = fcx.infcx().shallow_resolve(expected);
430 expected.builtin_deref(true, ty::NoPreference).map_or(true, |mt| match mt.ty.sty {
432 // This is "x = SomeTrait" being reduced from
433 // "let &x = &SomeTrait" or "let box x = Box<SomeTrait>", an error.
434 span_err!(tcx.sess, span, E0033,
435 "type `{}` cannot be dereferenced",
436 fcx.infcx().ty_to_string(expected));
446 pub fn check_match<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
447 expr: &'tcx hir::Expr,
448 discrim: &'tcx hir::Expr,
449 arms: &'tcx [hir::Arm],
450 expected: Expectation<'tcx>,
451 match_src: hir::MatchSource) {
452 let tcx = fcx.ccx.tcx;
454 // Not entirely obvious: if matches may create ref bindings, we
455 // want to use the *precise* type of the discriminant, *not* some
456 // supertype, as the "discriminant type" (issue #23116).
457 let contains_ref_bindings = arms.iter()
458 .filter_map(|a| tcx.arm_contains_ref_binding(a))
459 .max_by_key(|m| match *m {
460 hir::MutMutable => 1,
461 hir::MutImmutable => 0,
464 if let Some(m) = contains_ref_bindings {
465 check_expr_with_lvalue_pref(fcx, discrim, LvaluePreference::from_mutbl(m));
466 discrim_ty = fcx.expr_ty(discrim);
468 // ...but otherwise we want to use any supertype of the
469 // discriminant. This is sort of a workaround, see note (*) in
470 // `check_pat` for some details.
471 discrim_ty = fcx.infcx().next_ty_var();
472 check_expr_has_type(fcx, discrim, discrim_ty);
475 // Typecheck the patterns first, so that we get types for all the
478 let mut pcx = pat_ctxt {
480 map: pat_id_map(&tcx.def_map, &arm.pats[0]),
483 check_pat(&mut pcx, &p, discrim_ty);
487 // Now typecheck the blocks.
489 // The result of the match is the common supertype of all the
490 // arms. Start out the value as bottom, since it's the, well,
491 // bottom the type lattice, and we'll be moving up the lattice as
492 // we process each arm. (Note that any match with 0 arms is matching
493 // on any empty type and is therefore unreachable; should the flow
494 // of execution reach it, we will panic, so bottom is an appropriate
495 // type in that case)
496 let expected = expected.adjust_for_branches(fcx);
497 let result_ty = arms.iter().fold(fcx.infcx().next_diverging_ty_var(), |result_ty, arm| {
498 let bty = match expected {
499 // We don't coerce to `()` so that if the match expression is a
500 // statement it's branches can have any consistent type. That allows
501 // us to give better error messages (pointing to a usually better
502 // arm for inconsistent arms or to the whole match when a `()` type
504 Expectation::ExpectHasType(ety) if ety != fcx.tcx().mk_nil() => {
505 check_expr_coercable_to_type(fcx, &arm.body, ety);
509 check_expr_with_expectation(fcx, &arm.body, expected);
510 fcx.node_ty(arm.body.id)
514 if let Some(ref e) = arm.guard {
515 check_expr_has_type(fcx, &e, tcx.types.bool);
518 if result_ty.references_error() || bty.references_error() {
521 let (origin, expected, found) = match match_src {
522 /* if-let construct without an else block */
523 hir::MatchSource::IfLetDesugar { contains_else_clause }
524 if !contains_else_clause => (
525 TypeOrigin::IfExpressionWithNoElse(expr.span),
530 TypeOrigin::MatchExpressionArm(expr.span, arm.body.span, match_src),
536 infer::common_supertype(
546 fcx.write_ty(expr.id, result_ty);
549 pub struct pat_ctxt<'a, 'tcx: 'a> {
550 pub fcx: &'a FnCtxt<'a, 'tcx>,
554 pub fn check_pat_struct<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>, pat: &'tcx hir::Pat,
555 path: &hir::Path, fields: &'tcx [Spanned<hir::FieldPat>],
556 etc: bool, expected: Ty<'tcx>) {
558 let tcx = pcx.fcx.ccx.tcx;
560 let def = tcx.def_map.borrow().get(&pat.id).unwrap().full_def();
561 let variant = match fcx.def_struct_variant(def, path.span) {
562 Some((_, variant)) => variant,
564 let name = pprust::path_to_string(path);
565 span_err!(tcx.sess, pat.span, E0163,
566 "`{}` does not name a struct or a struct variant", name);
567 fcx.write_error(pat.id);
569 for field in fields {
570 check_pat(pcx, &field.node.pat, tcx.types.err);
576 let pat_ty = pcx.fcx.instantiate_type(def.def_id(), path);
577 let item_substs = match pat_ty.sty {
578 ty::TyStruct(_, substs) | ty::TyEnum(_, substs) => substs,
579 _ => tcx.sess.span_bug(pat.span, "struct variant is not an ADT")
581 demand::eqtype(fcx, pat.span, expected, pat_ty);
582 check_struct_pat_fields(pcx, pat.span, fields, variant, &item_substs, etc);
584 fcx.write_ty(pat.id, pat_ty);
585 fcx.write_substs(pat.id, ty::ItemSubsts { substs: item_substs.clone() });
588 // This function exists due to the warning "diagnostic code E0164 already used"
589 fn bad_struct_kind_err(sess: &Session, pat: &hir::Pat, path: &hir::Path, lint: bool) {
590 let name = pprust::path_to_string(path);
591 let msg = format!("`{}` does not name a tuple variant or a tuple struct", name);
593 sess.add_lint(lint::builtin::MATCH_OF_UNIT_VARIANT_VIA_PAREN_DOTDOT,
598 span_err!(sess, pat.span, E0164, "{}", msg);
602 pub fn check_pat_enum<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
605 subpats: Option<&'tcx [P<hir::Pat>]>,
607 is_tuple_struct_pat: bool)
609 // Typecheck the path.
611 let tcx = pcx.fcx.ccx.tcx;
613 let path_res = match tcx.def_map.borrow().get(&pat.id) {
614 Some(&path_res) if path_res.base_def != Def::Err => path_res,
616 fcx.write_error(pat.id);
618 if let Some(subpats) = subpats {
620 check_pat(pcx, &pat, tcx.types.err);
628 let (opt_ty, segments, def) = match resolve_ty_and_def_ufcs(fcx, path_res,
631 Some(resolution) => resolution,
632 // Error handling done inside resolve_ty_and_def_ufcs, so if
633 // resolution fails just return.
637 // Items that were partially resolved before should have been resolved to
638 // associated constants (i.e. not methods).
639 if path_res.depth != 0 && !check_assoc_item_is_const(pcx, def, pat.span) {
640 fcx.write_error(pat.id);
644 let enum_def = def.variant_def_ids()
645 .map_or_else(|| def.def_id(), |(enum_def, _)| enum_def);
647 let ctor_scheme = tcx.lookup_item_type(enum_def);
648 let ctor_predicates = tcx.lookup_predicates(enum_def);
649 let path_scheme = if ctor_scheme.ty.is_fn() {
650 let fn_ret = tcx.no_late_bound_regions(&ctor_scheme.ty.fn_ret()).unwrap();
653 generics: ctor_scheme.generics,
658 instantiate_path(pcx.fcx, segments,
659 path_scheme, &ctor_predicates,
660 opt_ty, def, pat.span, pat.id);
662 let report_bad_struct_kind = |is_warning| {
663 bad_struct_kind_err(tcx.sess, pat, path, is_warning);
664 if is_warning { return; }
665 fcx.write_error(pat.id);
666 if let Some(subpats) = subpats {
668 check_pat(pcx, &pat, tcx.types.err);
673 // If we didn't have a fully resolved path to start with, we had an
674 // associated const, and we should quit now, since the rest of this
675 // function uses checks specific to structs and enums.
676 if path_res.depth != 0 {
677 if is_tuple_struct_pat {
678 report_bad_struct_kind(false);
680 let pat_ty = fcx.node_ty(pat.id);
681 demand::suptype(fcx, pat.span, expected, pat_ty);
686 let pat_ty = fcx.node_ty(pat.id);
687 demand::eqtype(fcx, pat.span, expected, pat_ty);
689 let real_path_ty = fcx.node_ty(pat.id);
690 let (arg_tys, kind_name): (Vec<_>, &'static str) = match real_path_ty.sty {
691 ty::TyEnum(enum_def, expected_substs) => {
692 let variant = enum_def.variant_of_def(def);
693 if variant.kind() == ty::VariantKind::Struct {
694 report_bad_struct_kind(false);
697 if is_tuple_struct_pat && variant.kind() != ty::VariantKind::Tuple {
698 // Matching unit variants with tuple variant patterns (`UnitVariant(..)`)
699 // is allowed for backward compatibility.
700 let is_special_case = variant.kind() == ty::VariantKind::Unit;
701 report_bad_struct_kind(is_special_case);
702 if !is_special_case {
708 .map(|f| fcx.instantiate_type_scheme(pat.span,
714 ty::TyStruct(struct_def, expected_substs) => {
715 let variant = struct_def.struct_variant();
716 if is_tuple_struct_pat && variant.kind() != ty::VariantKind::Tuple {
717 // Matching unit structs with tuple variant patterns (`UnitVariant(..)`)
718 // is allowed for backward compatibility.
719 let is_special_case = variant.kind() == ty::VariantKind::Unit;
720 report_bad_struct_kind(is_special_case);
725 .map(|f| fcx.instantiate_type_scheme(pat.span,
732 report_bad_struct_kind(false);
737 if let Some(subpats) = subpats {
738 if subpats.len() == arg_tys.len() {
739 for (subpat, arg_ty) in subpats.iter().zip(arg_tys) {
740 check_pat(pcx, &subpat, arg_ty);
742 } else if arg_tys.is_empty() {
743 span_err!(tcx.sess, pat.span, E0024,
744 "this pattern has {} field{}, but the corresponding {} has no fields",
745 subpats.len(), if subpats.len() == 1 {""} else {"s"}, kind_name);
748 check_pat(pcx, &pat, tcx.types.err);
751 span_err!(tcx.sess, pat.span, E0023,
752 "this pattern has {} field{}, but the corresponding {} has {} field{}",
753 subpats.len(), if subpats.len() == 1 {""} else {"s"},
755 arg_tys.len(), if arg_tys.len() == 1 {""} else {"s"});
758 check_pat(pcx, &pat, tcx.types.err);
764 /// `path` is the AST path item naming the type of this struct.
765 /// `fields` is the field patterns of the struct pattern.
766 /// `struct_fields` describes the type of each field of the struct.
767 /// `struct_id` is the ID of the struct.
768 /// `etc` is true if the pattern said '...' and false otherwise.
769 pub fn check_struct_pat_fields<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
771 fields: &'tcx [Spanned<hir::FieldPat>],
772 variant: ty::VariantDef<'tcx>,
773 substs: &Substs<'tcx>,
775 let tcx = pcx.fcx.ccx.tcx;
777 // Index the struct fields' types.
778 let field_map = variant.fields
780 .map(|field| (field.name, field))
781 .collect::<FnvHashMap<_, _>>();
783 // Keep track of which fields have already appeared in the pattern.
784 let mut used_fields = FnvHashMap();
786 // Typecheck each field.
787 for &Spanned { node: ref field, span } in fields {
788 let field_ty = match used_fields.entry(field.name) {
789 Occupied(occupied) => {
790 let mut err = struct_span_err!(tcx.sess, span, E0025,
791 "field `{}` bound multiple times in the pattern",
793 span_note!(&mut err, *occupied.get(),
794 "field `{}` previously bound here",
801 field_map.get(&field.name)
802 .map(|f| pcx.fcx.field_ty(span, f, substs))
804 span_err!(tcx.sess, span, E0026,
805 "struct `{}` does not have a field named `{}`",
806 tcx.item_path_str(variant.did),
813 check_pat(pcx, &field.pat, field_ty);
816 // Report an error if not all the fields were specified.
818 for field in variant.fields
820 .filter(|field| !used_fields.contains_key(&field.name)) {
821 span_err!(tcx.sess, span, E0027,
822 "pattern does not mention field `{}`",