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.
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, HasTypeFlags, 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};
22 use require_same_types;
23 use util::nodemap::FnvHashMap;
26 use std::collections::hash_map::Entry::{Occupied, Vacant};
28 use syntax::ext::mtwt;
29 use syntax::codemap::{Span, Spanned};
33 use rustc_front::print::pprust;
34 use rustc_front::util as hir_util;
36 pub fn check_pat<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
41 let tcx = pcx.fcx.ccx.tcx;
43 debug!("check_pat(pat={:?},expected={:?})",
49 fcx.write_ty(pat.id, expected);
51 hir::PatLit(ref lt) => {
52 check_expr(fcx, &**lt);
53 let expr_ty = fcx.expr_ty(&**lt);
55 // Byte string patterns behave the same way as array patterns
56 // They can denote both statically and dynamically sized byte arrays
57 let mut pat_ty = expr_ty;
58 if let hir::ExprLit(ref lt) = lt.node {
59 if let ast::LitByteStr(_) = lt.node {
60 let expected_ty = structurally_resolved_type(fcx, pat.span, expected);
61 if let ty::TyRef(_, mt) = expected_ty.sty {
62 if let ty::TySlice(_) = mt.ty.sty {
63 pat_ty = tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic),
64 tcx.mk_slice(tcx.types.u8))
70 fcx.write_ty(pat.id, pat_ty);
72 // somewhat surprising: in this case, the subtyping
73 // relation goes the opposite way as the other
74 // cases. Actually what we really want is not a subtyping
75 // relation at all but rather that there exists a LUB (so
76 // that they can be compared). However, in practice,
77 // constants are always scalars or strings. For scalars
78 // subtyping is irrelevant, and for strings `expr_ty` is
79 // type is `&'static str`, so if we say that
81 // &'static str <: expected
83 // that's equivalent to there existing a LUB.
84 demand::suptype(fcx, pat.span, expected, pat_ty);
86 hir::PatRange(ref begin, ref end) => {
87 check_expr(fcx, begin);
90 let lhs_ty = fcx.expr_ty(begin);
91 let rhs_ty = fcx.expr_ty(end);
93 // Check that both end-points are of numeric or char type.
94 let numeric_or_char = |ty: Ty| ty.is_numeric() || ty.is_char();
95 let lhs_compat = numeric_or_char(lhs_ty);
96 let rhs_compat = numeric_or_char(rhs_ty);
98 if !lhs_compat || !rhs_compat {
99 let span = if !lhs_compat && !rhs_compat {
101 } else if !lhs_compat {
107 // Note: spacing here is intentional, we want a space before "start" and "end".
108 span_err!(tcx.sess, span, E0029,
109 "only char and numeric types are allowed in range patterns\n \
110 start type: {}\n end type: {}",
111 fcx.infcx().ty_to_string(lhs_ty),
112 fcx.infcx().ty_to_string(rhs_ty)
117 // Check that the types of the end-points can be unified.
118 let types_unify = require_same_types(
119 tcx, Some(fcx.infcx()), false, pat.span, rhs_ty, lhs_ty,
120 || "mismatched types in range".to_string()
123 // It's ok to return without a message as `require_same_types` prints an error.
128 // Now that we know the types can be unified we find the unified type and use
129 // it to type the entire expression.
130 let common_type = fcx.infcx().resolve_type_vars_if_possible(&lhs_ty);
132 fcx.write_ty(pat.id, common_type);
134 // subtyping doesn't matter here, as the value is some kind of scalar
135 demand::eqtype(fcx, pat.span, expected, lhs_ty);
137 hir::PatEnum(..) | hir::PatIdent(..)
138 if pat_is_resolved_const(&tcx.def_map.borrow(), pat) => {
139 let const_did = tcx.def_map.borrow().get(&pat.id).unwrap().def_id();
140 let const_scheme = tcx.lookup_item_type(const_did);
141 assert!(const_scheme.generics.is_empty());
142 let const_ty = pcx.fcx.instantiate_type_scheme(pat.span,
145 fcx.write_ty(pat.id, const_ty);
147 // FIXME(#20489) -- we should limit the types here to scalars or something!
149 // As with PatLit, what we really want here is that there
150 // exist a LUB, but for the cases that can occur, subtype
152 demand::suptype(fcx, pat.span, expected, const_ty);
154 hir::PatIdent(bm, ref path, ref sub) if pat_is_binding(&tcx.def_map.borrow(), pat) => {
155 let typ = fcx.local_ty(pat.span, pat.id);
157 hir::BindByRef(mutbl) => {
158 // if the binding is like
159 // ref x | ref const x | ref mut x
160 // then `x` is assigned a value of type `&M T` where M is the mutability
161 // and T is the expected type.
162 let region_var = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
163 let mt = ty::TypeAndMut { ty: expected, mutbl: mutbl };
164 let region_ty = tcx.mk_ref(tcx.mk_region(region_var), mt);
166 // `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)` is
167 // required. However, we use equality, which is stronger. See (*) for
169 demand::eqtype(fcx, pat.span, region_ty, typ);
171 // otherwise the type of x is the expected type T
172 hir::BindByValue(_) => {
173 // As above, `T <: typeof(x)` is required but we
174 // use equality, see (*) below.
175 demand::eqtype(fcx, pat.span, expected, typ);
179 fcx.write_ty(pat.id, typ);
181 // if there are multiple arms, make sure they all agree on
182 // what the type of the binding `x` ought to be
183 let canon_id = *pcx.map.get(&mtwt::resolve(path.node)).unwrap();
184 if canon_id != pat.id {
185 let ct = fcx.local_ty(pat.span, canon_id);
186 demand::eqtype(fcx, pat.span, ct, typ);
189 if let Some(ref p) = *sub {
190 check_pat(pcx, &**p, expected);
193 hir::PatIdent(_, ref path, _) => {
194 let path = hir_util::ident_to_path(path.span, path.node);
195 check_pat_enum(pcx, pat, &path, Some(&[]), expected);
197 hir::PatEnum(ref path, ref subpats) => {
198 let subpats = subpats.as_ref().map(|v| &v[..]);
199 check_pat_enum(pcx, pat, path, subpats, expected);
201 hir::PatQPath(ref qself, ref path) => {
202 let self_ty = fcx.to_ty(&qself.ty);
203 let path_res = if let Some(&d) = tcx.def_map.borrow().get(&pat.id) {
205 } else if qself.position == 0 {
206 // This is just a sentinel for finish_resolving_def_to_ty.
207 let sentinel = fcx.tcx().map.local_def_id(ast::CRATE_NODE_ID);
208 def::PathResolution {
209 base_def: def::DefMod(sentinel),
210 last_private: LastMod(AllPublic),
211 depth: path.segments.len()
214 tcx.sess.span_bug(pat.span,
215 &format!("unbound path {:?}", pat))
217 if let Some((opt_ty, segments, def)) =
218 resolve_ty_and_def_ufcs(fcx, path_res, Some(self_ty),
219 path, pat.span, pat.id) {
220 if check_assoc_item_is_const(pcx, def, pat.span) {
221 let scheme = tcx.lookup_item_type(def.def_id());
222 let predicates = tcx.lookup_predicates(def.def_id());
223 instantiate_path(fcx, segments,
225 opt_ty, def, pat.span, pat.id);
226 let const_ty = fcx.node_ty(pat.id);
227 demand::suptype(fcx, pat.span, expected, const_ty);
229 fcx.write_error(pat.id)
233 hir::PatStruct(ref path, ref fields, etc) => {
234 check_pat_struct(pcx, pat, path, fields, etc, expected);
236 hir::PatTup(ref elements) => {
237 let element_tys: Vec<_> =
238 (0..elements.len()).map(|_| fcx.infcx().next_ty_var())
240 let pat_ty = tcx.mk_tup(element_tys.clone());
241 fcx.write_ty(pat.id, pat_ty);
242 demand::eqtype(fcx, pat.span, expected, pat_ty);
243 for (element_pat, element_ty) in elements.iter().zip(element_tys) {
244 check_pat(pcx, &**element_pat, element_ty);
247 hir::PatBox(ref inner) => {
248 let inner_ty = fcx.infcx().next_ty_var();
249 let uniq_ty = tcx.mk_box(inner_ty);
251 if check_dereferencable(pcx, pat.span, expected, &**inner) {
252 // Here, `demand::subtype` is good enough, but I don't
253 // think any errors can be introduced by using
255 demand::eqtype(fcx, pat.span, expected, uniq_ty);
256 fcx.write_ty(pat.id, uniq_ty);
257 check_pat(pcx, &**inner, inner_ty);
259 fcx.write_error(pat.id);
260 check_pat(pcx, &**inner, tcx.types.err);
263 hir::PatRegion(ref inner, mutbl) => {
264 let expected = fcx.infcx().shallow_resolve(expected);
265 if check_dereferencable(pcx, pat.span, expected, &**inner) {
266 // `demand::subtype` would be good enough, but using
267 // `eqtype` turns out to be equally general. See (*)
268 // below for details.
270 // Take region, inner-type from expected type if we
271 // can, to avoid creating needless variables. This
272 // also helps with the bad interactions of the given
273 // hack detailed in (*) below.
274 let (rptr_ty, inner_ty) = match expected.sty {
275 ty::TyRef(_, mt) if mt.mutbl == mutbl => {
279 let inner_ty = fcx.infcx().next_ty_var();
280 let mt = ty::TypeAndMut { ty: inner_ty, mutbl: mutbl };
281 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
282 let rptr_ty = tcx.mk_ref(tcx.mk_region(region), mt);
283 demand::eqtype(fcx, pat.span, expected, rptr_ty);
288 fcx.write_ty(pat.id, rptr_ty);
289 check_pat(pcx, &**inner, inner_ty);
291 fcx.write_error(pat.id);
292 check_pat(pcx, &**inner, tcx.types.err);
295 hir::PatVec(ref before, ref slice, ref after) => {
296 let expected_ty = structurally_resolved_type(fcx, pat.span, expected);
297 let inner_ty = fcx.infcx().next_ty_var();
298 let pat_ty = match expected_ty.sty {
299 ty::TyArray(_, size) => tcx.mk_array(inner_ty, {
300 let min_len = before.len() + after.len();
302 Some(_) => cmp::max(min_len, size),
307 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
308 tcx.mk_ref(tcx.mk_region(region), ty::TypeAndMut {
309 ty: tcx.mk_slice(inner_ty),
310 mutbl: expected_ty.builtin_deref(true, ty::NoPreference).map(|mt| mt.mutbl)
311 .unwrap_or(hir::MutImmutable)
316 fcx.write_ty(pat.id, pat_ty);
318 // `demand::subtype` would be good enough, but using
319 // `eqtype` turns out to be equally general. See (*)
320 // below for details.
321 demand::eqtype(fcx, pat.span, expected, pat_ty);
324 check_pat(pcx, &**elt, inner_ty);
326 if let Some(ref slice) = *slice {
327 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
328 let mutbl = expected_ty.builtin_deref(true, ty::NoPreference)
329 .map_or(hir::MutImmutable, |mt| mt.mutbl);
331 let slice_ty = tcx.mk_ref(tcx.mk_region(region), ty::TypeAndMut {
332 ty: tcx.mk_slice(inner_ty),
335 check_pat(pcx, &**slice, slice_ty);
338 check_pat(pcx, &**elt, inner_ty);
344 // (*) In most of the cases above (literals and constants being
345 // the exception), we relate types using strict equality, evewn
346 // though subtyping would be sufficient. There are a few reasons
347 // for this, some of which are fairly subtle and which cost me
348 // (nmatsakis) an hour or two debugging to remember, so I thought
349 // I'd write them down this time.
351 // 1. There is no loss of expressiveness here, though it does
352 // cause some inconvenience. What we are saying is that the type
353 // of `x` becomes *exactly* what is expected. This can cause unnecessary
354 // errors in some cases, such as this one:
355 // it will cause errors in a case like this:
358 // fn foo<'x>(x: &'x int) {
365 // The reason we might get an error is that `z` might be
366 // assigned a type like `&'x int`, and then we would have
367 // a problem when we try to assign `&a` to `z`, because
368 // the lifetime of `&a` (i.e., the enclosing block) is
369 // shorter than `'x`.
371 // HOWEVER, this code works fine. The reason is that the
372 // expected type here is whatever type the user wrote, not
373 // the initializer's type. In this case the user wrote
374 // nothing, so we are going to create a type variable `Z`.
375 // Then we will assign the type of the initializer (`&'x
376 // int`) as a subtype of `Z`: `&'x int <: Z`. And hence we
377 // will instantiate `Z` as a type `&'0 int` where `'0` is
378 // a fresh region variable, with the constraint that `'x :
379 // '0`. So basically we're all set.
381 // Note that there are two tests to check that this remains true
382 // (`regions-reassign-{match,let}-bound-pointer.rs`).
384 // 2. Things go horribly wrong if we use subtype. The reason for
385 // THIS is a fairly subtle case involving bound regions. See the
386 // `givens` field in `region_inference`, as well as the test
387 // `regions-relate-bound-regions-on-closures-to-inference-variables.rs`,
388 // for details. Short version is that we must sometimes detect
389 // relationships between specific region variables and regions
390 // bound in a closure signature, and that detection gets thrown
391 // off when we substitute fresh region variables here to enable
395 fn check_assoc_item_is_const(pcx: &pat_ctxt, def: def::Def, span: Span) -> bool {
397 def::DefAssociatedConst(..) => true,
398 def::DefMethod(..) => {
399 span_err!(pcx.fcx.ccx.tcx.sess, span, E0327,
400 "associated items in match patterns must be constants");
404 pcx.fcx.ccx.tcx.sess.span_bug(span, "non-associated item in
405 check_assoc_item_is_const");
410 pub fn check_dereferencable<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
411 span: Span, expected: Ty<'tcx>,
412 inner: &hir::Pat) -> bool {
414 let tcx = pcx.fcx.ccx.tcx;
415 if pat_is_binding(&tcx.def_map.borrow(), inner) {
416 let expected = fcx.infcx().shallow_resolve(expected);
417 expected.builtin_deref(true, ty::NoPreference).map_or(true, |mt| match mt.ty.sty {
419 // This is "x = SomeTrait" being reduced from
420 // "let &x = &SomeTrait" or "let box x = Box<SomeTrait>", an error.
421 span_err!(tcx.sess, span, E0033,
422 "type `{}` cannot be dereferenced",
423 fcx.infcx().ty_to_string(expected));
433 pub fn check_match<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
434 expr: &'tcx hir::Expr,
435 discrim: &'tcx hir::Expr,
436 arms: &'tcx [hir::Arm],
437 expected: Expectation<'tcx>,
438 match_src: hir::MatchSource) {
439 let tcx = fcx.ccx.tcx;
441 // Not entirely obvious: if matches may create ref bindings, we
442 // want to use the *precise* type of the discriminant, *not* some
443 // supertype, as the "discriminant type" (issue #23116).
444 let contains_ref_bindings = arms.iter()
445 .filter_map(|a| tcx.arm_contains_ref_binding(a))
446 .max_by(|m| match *m {
447 hir::MutMutable => 1,
448 hir::MutImmutable => 0,
451 if let Some(m) = contains_ref_bindings {
452 check_expr_with_lvalue_pref(fcx, discrim, LvaluePreference::from_mutbl(m));
453 discrim_ty = fcx.expr_ty(discrim);
455 // ...but otherwise we want to use any supertype of the
456 // discriminant. This is sort of a workaround, see note (*) in
457 // `check_pat` for some details.
458 discrim_ty = fcx.infcx().next_ty_var();
459 check_expr_has_type(fcx, discrim, discrim_ty);
462 // Typecheck the patterns first, so that we get types for all the
465 let mut pcx = pat_ctxt {
467 map: pat_id_map(&tcx.def_map, &*arm.pats[0]),
470 check_pat(&mut pcx, &**p, discrim_ty);
474 // Now typecheck the blocks.
476 // The result of the match is the common supertype of all the
477 // arms. Start out the value as bottom, since it's the, well,
478 // bottom the type lattice, and we'll be moving up the lattice as
479 // we process each arm. (Note that any match with 0 arms is matching
480 // on any empty type and is therefore unreachable; should the flow
481 // of execution reach it, we will panic, so bottom is an appropriate
482 // type in that case)
483 let expected = expected.adjust_for_branches(fcx);
484 let result_ty = arms.iter().fold(fcx.infcx().next_diverging_ty_var(), |result_ty, arm| {
485 let bty = match expected {
486 // We don't coerce to `()` so that if the match expression is a
487 // statement it's branches can have any consistent type. That allows
488 // us to give better error messages (pointing to a usually better
489 // arm for inconsistent arms or to the whole match when a `()` type
491 Expectation::ExpectHasType(ety) if ety != fcx.tcx().mk_nil() => {
492 check_expr_coercable_to_type(fcx, &*arm.body, ety);
496 check_expr_with_expectation(fcx, &*arm.body, expected);
497 fcx.node_ty(arm.body.id)
501 if let Some(ref e) = arm.guard {
502 check_expr_has_type(fcx, &**e, tcx.types.bool);
505 if result_ty.references_error() || bty.references_error() {
508 let (origin, expected, found) = match match_src {
509 /* if-let construct without an else block */
510 hir::MatchSource::IfLetDesugar { contains_else_clause }
511 if !contains_else_clause => (
512 TypeOrigin::IfExpressionWithNoElse(expr.span),
517 TypeOrigin::MatchExpressionArm(expr.span, arm.body.span, match_src),
523 infer::common_supertype(
533 fcx.write_ty(expr.id, result_ty);
536 pub struct pat_ctxt<'a, 'tcx: 'a> {
537 pub fcx: &'a FnCtxt<'a, 'tcx>,
541 pub fn check_pat_struct<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>, pat: &'tcx hir::Pat,
542 path: &hir::Path, fields: &'tcx [Spanned<hir::FieldPat>],
543 etc: bool, expected: Ty<'tcx>) {
545 let tcx = pcx.fcx.ccx.tcx;
547 let def = tcx.def_map.borrow().get(&pat.id).unwrap().full_def();
548 let variant = match fcx.def_struct_variant(def, path.span) {
549 Some((_, variant)) => variant,
551 let name = pprust::path_to_string(path);
552 span_err!(tcx.sess, pat.span, E0163,
553 "`{}` does not name a struct or a struct variant", name);
554 fcx.write_error(pat.id);
556 for field in fields {
557 check_pat(pcx, &field.node.pat, tcx.types.err);
563 let pat_ty = pcx.fcx.instantiate_type(def.def_id(), path);
564 let item_substs = match pat_ty.sty {
565 ty::TyStruct(_, substs) | ty::TyEnum(_, substs) => substs,
566 _ => tcx.sess.span_bug(pat.span, "struct variant is not an ADT")
568 demand::eqtype(fcx, pat.span, expected, pat_ty);
569 check_struct_pat_fields(pcx, pat.span, fields, variant, &item_substs, etc);
571 fcx.write_ty(pat.id, pat_ty);
572 fcx.write_substs(pat.id, ty::ItemSubsts { substs: item_substs.clone() });
575 pub fn check_pat_enum<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
578 subpats: Option<&'tcx [P<hir::Pat>]>,
581 // Typecheck the path.
583 let tcx = pcx.fcx.ccx.tcx;
585 let path_res = *tcx.def_map.borrow().get(&pat.id).unwrap();
587 let (opt_ty, segments, def) = match resolve_ty_and_def_ufcs(fcx, path_res,
590 Some(resolution) => resolution,
591 // Error handling done inside resolve_ty_and_def_ufcs, so if
592 // resolution fails just return.
596 // Items that were partially resolved before should have been resolved to
597 // associated constants (i.e. not methods).
598 if path_res.depth != 0 && !check_assoc_item_is_const(pcx, def, pat.span) {
599 fcx.write_error(pat.id);
603 let enum_def = def.variant_def_ids()
604 .map_or_else(|| def.def_id(), |(enum_def, _)| enum_def);
606 let ctor_scheme = tcx.lookup_item_type(enum_def);
607 let ctor_predicates = tcx.lookup_predicates(enum_def);
608 let path_scheme = if ctor_scheme.ty.is_fn() {
609 let fn_ret = tcx.no_late_bound_regions(&ctor_scheme.ty.fn_ret()).unwrap();
612 generics: ctor_scheme.generics,
617 instantiate_path(pcx.fcx, segments,
618 path_scheme, &ctor_predicates,
619 opt_ty, def, pat.span, pat.id);
621 // If we didn't have a fully resolved path to start with, we had an
622 // associated const, and we should quit now, since the rest of this
623 // function uses checks specific to structs and enums.
624 if path_res.depth != 0 {
625 let pat_ty = fcx.node_ty(pat.id);
626 demand::suptype(fcx, pat.span, expected, pat_ty);
630 let pat_ty = fcx.node_ty(pat.id);
631 demand::eqtype(fcx, pat.span, expected, pat_ty);
634 let real_path_ty = fcx.node_ty(pat.id);
635 let (arg_tys, kind_name): (Vec<_>, &'static str) = match real_path_ty.sty {
636 ty::TyEnum(enum_def, expected_substs)
637 if def == def::DefVariant(enum_def.did, def.def_id(), false) =>
639 let variant = enum_def.variant_of_def(def);
642 .map(|f| fcx.instantiate_type_scheme(pat.span,
648 ty::TyStruct(struct_def, expected_substs) => {
649 (struct_def.struct_variant()
652 .map(|f| fcx.instantiate_type_scheme(pat.span,
659 let name = pprust::path_to_string(path);
660 span_err!(tcx.sess, pat.span, E0164,
661 "`{}` does not name a non-struct variant or a tuple struct", name);
662 fcx.write_error(pat.id);
664 if let Some(subpats) = subpats {
666 check_pat(pcx, &**pat, tcx.types.err);
673 if let Some(subpats) = subpats {
674 if subpats.len() == arg_tys.len() {
675 for (subpat, arg_ty) in subpats.iter().zip(arg_tys) {
676 check_pat(pcx, &**subpat, arg_ty);
678 } else if arg_tys.is_empty() {
679 span_err!(tcx.sess, pat.span, E0024,
680 "this pattern has {} field{}, but the corresponding {} has no fields",
681 subpats.len(), if subpats.len() == 1 {""} else {"s"}, kind_name);
684 check_pat(pcx, &**pat, tcx.types.err);
687 span_err!(tcx.sess, pat.span, E0023,
688 "this pattern has {} field{}, but the corresponding {} has {} field{}",
689 subpats.len(), if subpats.len() == 1 {""} else {"s"},
691 arg_tys.len(), if arg_tys.len() == 1 {""} else {"s"});
694 check_pat(pcx, &**pat, tcx.types.err);
700 /// `path` is the AST path item naming the type of this struct.
701 /// `fields` is the field patterns of the struct pattern.
702 /// `struct_fields` describes the type of each field of the struct.
703 /// `struct_id` is the ID of the struct.
704 /// `etc` is true if the pattern said '...' and false otherwise.
705 pub fn check_struct_pat_fields<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
707 fields: &'tcx [Spanned<hir::FieldPat>],
708 variant: ty::VariantDef<'tcx>,
709 substs: &Substs<'tcx>,
711 let tcx = pcx.fcx.ccx.tcx;
713 // Index the struct fields' types.
714 let field_map = variant.fields
716 .map(|field| (field.name, field))
717 .collect::<FnvHashMap<_, _>>();
719 // Keep track of which fields have already appeared in the pattern.
720 let mut used_fields = FnvHashMap();
722 // Typecheck each field.
723 for &Spanned { node: ref field, span } in fields {
724 let field_ty = match used_fields.entry(field.name) {
725 Occupied(occupied) => {
726 span_err!(tcx.sess, span, E0025,
727 "field `{}` bound multiple times in the pattern",
729 span_note!(tcx.sess, *occupied.get(),
730 "field `{}` previously bound here",
736 field_map.get(&field.name)
737 .map(|f| pcx.fcx.field_ty(span, f, substs))
739 span_err!(tcx.sess, span, E0026,
740 "struct `{}` does not have a field named `{}`",
741 tcx.item_path_str(variant.did),
748 check_pat(pcx, &*field.pat, field_ty);
751 // Report an error if not all the fields were specified.
753 for field in variant.fields
755 .filter(|field| !used_fields.contains_key(&field.name)) {
756 span_err!(tcx.sess, span, E0027,
757 "pattern does not mention field `{}`",