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.
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::codemap::{Span, Spanned};
32 use rustc_front::print::pprust;
33 use rustc_front::util as hir_util;
35 pub fn check_pat<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
40 let tcx = pcx.fcx.ccx.tcx;
42 debug!("check_pat(pat={:?},expected={:?})",
48 fcx.write_ty(pat.id, expected);
50 hir::PatLit(ref lt) => {
51 check_expr(fcx, &**lt);
52 let expr_ty = fcx.expr_ty(&**lt);
54 // Byte string patterns behave the same way as array patterns
55 // They can denote both statically and dynamically sized byte arrays
56 let mut pat_ty = expr_ty;
57 if let hir::ExprLit(ref lt) = lt.node {
58 if let ast::LitByteStr(_) = lt.node {
59 let expected_ty = structurally_resolved_type(fcx, pat.span, expected);
60 if let ty::TyRef(_, mt) = expected_ty.sty {
61 if let ty::TySlice(_) = mt.ty.sty {
62 pat_ty = tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic),
63 tcx.mk_slice(tcx.types.u8))
69 fcx.write_ty(pat.id, pat_ty);
71 // somewhat surprising: in this case, the subtyping
72 // relation goes the opposite way as the other
73 // cases. Actually what we really want is not a subtyping
74 // relation at all but rather that there exists a LUB (so
75 // that they can be compared). However, in practice,
76 // constants are always scalars or strings. For scalars
77 // subtyping is irrelevant, and for strings `expr_ty` is
78 // type is `&'static str`, so if we say that
80 // &'static str <: expected
82 // that's equivalent to there existing a LUB.
83 demand::suptype(fcx, pat.span, expected, pat_ty);
85 hir::PatRange(ref begin, ref end) => {
86 check_expr(fcx, begin);
89 let lhs_ty = fcx.expr_ty(begin);
90 let rhs_ty = fcx.expr_ty(end);
92 // Check that both end-points are of numeric or char type.
93 let numeric_or_char = |ty: Ty| ty.is_numeric() || ty.is_char();
94 let lhs_compat = numeric_or_char(lhs_ty);
95 let rhs_compat = numeric_or_char(rhs_ty);
97 if !lhs_compat || !rhs_compat {
98 let span = if !lhs_compat && !rhs_compat {
100 } else if !lhs_compat {
106 // Note: spacing here is intentional, we want a space before "start" and "end".
107 span_err!(tcx.sess, span, E0029,
108 "only char and numeric types are allowed in range patterns\n \
109 start type: {}\n end type: {}",
110 fcx.infcx().ty_to_string(lhs_ty),
111 fcx.infcx().ty_to_string(rhs_ty)
116 // Check that the types of the end-points can be unified.
117 let types_unify = require_same_types(
118 tcx, Some(fcx.infcx()), false, pat.span, rhs_ty, lhs_ty,
119 || "mismatched types in range".to_string()
122 // It's ok to return without a message as `require_same_types` prints an error.
127 // Now that we know the types can be unified we find the unified type and use
128 // it to type the entire expression.
129 let common_type = fcx.infcx().resolve_type_vars_if_possible(&lhs_ty);
131 fcx.write_ty(pat.id, common_type);
133 // subtyping doesn't matter here, as the value is some kind of scalar
134 demand::eqtype(fcx, pat.span, expected, lhs_ty);
136 hir::PatEnum(..) | hir::PatIdent(..)
137 if pat_is_resolved_const(&tcx.def_map.borrow(), pat) => {
138 let const_did = tcx.def_map.borrow().get(&pat.id).unwrap().def_id();
139 let const_scheme = tcx.lookup_item_type(const_did);
140 assert!(const_scheme.generics.is_empty());
141 let const_ty = pcx.fcx.instantiate_type_scheme(pat.span,
144 fcx.write_ty(pat.id, const_ty);
146 // FIXME(#20489) -- we should limit the types here to scalars or something!
148 // As with PatLit, what we really want here is that there
149 // exist a LUB, but for the cases that can occur, subtype
151 demand::suptype(fcx, pat.span, expected, const_ty);
153 hir::PatIdent(bm, ref path, ref sub) if pat_is_binding(&tcx.def_map.borrow(), pat) => {
154 let typ = fcx.local_ty(pat.span, pat.id);
156 hir::BindByRef(mutbl) => {
157 // if the binding is like
158 // ref x | ref const x | ref mut x
159 // then `x` is assigned a value of type `&M T` where M is the mutability
160 // and T is the expected type.
161 let region_var = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
162 let mt = ty::TypeAndMut { ty: expected, mutbl: mutbl };
163 let region_ty = tcx.mk_ref(tcx.mk_region(region_var), mt);
165 // `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)` is
166 // required. However, we use equality, which is stronger. See (*) for
168 demand::eqtype(fcx, pat.span, region_ty, typ);
170 // otherwise the type of x is the expected type T
171 hir::BindByValue(_) => {
172 // As above, `T <: typeof(x)` is required but we
173 // use equality, see (*) below.
174 demand::eqtype(fcx, pat.span, expected, typ);
178 fcx.write_ty(pat.id, typ);
180 // if there are multiple arms, make sure they all agree on
181 // what the type of the binding `x` ought to be
182 let canon_id = *pcx.map.get(&path.node.name).unwrap();
183 if canon_id != pat.id {
184 let ct = fcx.local_ty(pat.span, canon_id);
185 demand::eqtype(fcx, pat.span, ct, typ);
188 if let Some(ref p) = *sub {
189 check_pat(pcx, &**p, expected);
192 hir::PatIdent(_, ref path, _) => {
193 let path = hir_util::ident_to_path(path.span, path.node);
194 check_pat_enum(pcx, pat, &path, Some(&[]), expected);
196 hir::PatEnum(ref path, ref subpats) => {
197 let subpats = subpats.as_ref().map(|v| &v[..]);
198 check_pat_enum(pcx, pat, path, subpats, expected);
200 hir::PatQPath(ref qself, ref path) => {
201 let self_ty = fcx.to_ty(&qself.ty);
202 let path_res = if let Some(&d) = tcx.def_map.borrow().get(&pat.id) {
204 } else if qself.position == 0 {
205 // This is just a sentinel for finish_resolving_def_to_ty.
206 let sentinel = fcx.tcx().map.local_def_id(ast::CRATE_NODE_ID);
207 def::PathResolution {
208 base_def: def::DefMod(sentinel),
209 last_private: LastMod(AllPublic),
210 depth: path.segments.len()
213 tcx.sess.span_bug(pat.span,
214 &format!("unbound path {:?}", pat))
216 if let Some((opt_ty, segments, def)) =
217 resolve_ty_and_def_ufcs(fcx, path_res, Some(self_ty),
218 path, pat.span, pat.id) {
219 if check_assoc_item_is_const(pcx, def, pat.span) {
220 let scheme = tcx.lookup_item_type(def.def_id());
221 let predicates = tcx.lookup_predicates(def.def_id());
222 instantiate_path(fcx, segments,
224 opt_ty, def, pat.span, pat.id);
225 let const_ty = fcx.node_ty(pat.id);
226 demand::suptype(fcx, pat.span, expected, const_ty);
228 fcx.write_error(pat.id)
232 hir::PatStruct(ref path, ref fields, etc) => {
233 check_pat_struct(pcx, pat, path, fields, etc, expected);
235 hir::PatTup(ref elements) => {
236 let element_tys: Vec<_> =
237 (0..elements.len()).map(|_| fcx.infcx().next_ty_var())
239 let pat_ty = tcx.mk_tup(element_tys.clone());
240 fcx.write_ty(pat.id, pat_ty);
241 demand::eqtype(fcx, pat.span, expected, pat_ty);
242 for (element_pat, element_ty) in elements.iter().zip(element_tys) {
243 check_pat(pcx, &**element_pat, element_ty);
246 hir::PatBox(ref inner) => {
247 let inner_ty = fcx.infcx().next_ty_var();
248 let uniq_ty = tcx.mk_box(inner_ty);
250 if check_dereferencable(pcx, pat.span, expected, &**inner) {
251 // Here, `demand::subtype` is good enough, but I don't
252 // think any errors can be introduced by using
254 demand::eqtype(fcx, pat.span, expected, uniq_ty);
255 fcx.write_ty(pat.id, uniq_ty);
256 check_pat(pcx, &**inner, inner_ty);
258 fcx.write_error(pat.id);
259 check_pat(pcx, &**inner, tcx.types.err);
262 hir::PatRegion(ref inner, mutbl) => {
263 let expected = fcx.infcx().shallow_resolve(expected);
264 if check_dereferencable(pcx, pat.span, expected, &**inner) {
265 // `demand::subtype` would be good enough, but using
266 // `eqtype` turns out to be equally general. See (*)
267 // below for details.
269 // Take region, inner-type from expected type if we
270 // can, to avoid creating needless variables. This
271 // also helps with the bad interactions of the given
272 // hack detailed in (*) below.
273 let (rptr_ty, inner_ty) = match expected.sty {
274 ty::TyRef(_, mt) if mt.mutbl == mutbl => {
278 let inner_ty = fcx.infcx().next_ty_var();
279 let mt = ty::TypeAndMut { ty: inner_ty, mutbl: mutbl };
280 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
281 let rptr_ty = tcx.mk_ref(tcx.mk_region(region), mt);
282 demand::eqtype(fcx, pat.span, expected, rptr_ty);
287 fcx.write_ty(pat.id, rptr_ty);
288 check_pat(pcx, &**inner, inner_ty);
290 fcx.write_error(pat.id);
291 check_pat(pcx, &**inner, tcx.types.err);
294 hir::PatVec(ref before, ref slice, ref after) => {
295 let expected_ty = structurally_resolved_type(fcx, pat.span, expected);
296 let inner_ty = fcx.infcx().next_ty_var();
297 let pat_ty = match expected_ty.sty {
298 ty::TyArray(_, size) => tcx.mk_array(inner_ty, {
299 let min_len = before.len() + after.len();
301 Some(_) => cmp::max(min_len, size),
306 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
307 tcx.mk_ref(tcx.mk_region(region), ty::TypeAndMut {
308 ty: tcx.mk_slice(inner_ty),
309 mutbl: expected_ty.builtin_deref(true, ty::NoPreference).map(|mt| mt.mutbl)
310 .unwrap_or(hir::MutImmutable)
315 fcx.write_ty(pat.id, pat_ty);
317 // `demand::subtype` would be good enough, but using
318 // `eqtype` turns out to be equally general. See (*)
319 // below for details.
320 demand::eqtype(fcx, pat.span, expected, pat_ty);
323 check_pat(pcx, &**elt, inner_ty);
325 if let Some(ref slice) = *slice {
326 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
327 let mutbl = expected_ty.builtin_deref(true, ty::NoPreference)
328 .map_or(hir::MutImmutable, |mt| mt.mutbl);
330 let slice_ty = tcx.mk_ref(tcx.mk_region(region), ty::TypeAndMut {
331 ty: tcx.mk_slice(inner_ty),
334 check_pat(pcx, &**slice, slice_ty);
337 check_pat(pcx, &**elt, inner_ty);
343 // (*) In most of the cases above (literals and constants being
344 // the exception), we relate types using strict equality, evewn
345 // though subtyping would be sufficient. There are a few reasons
346 // for this, some of which are fairly subtle and which cost me
347 // (nmatsakis) an hour or two debugging to remember, so I thought
348 // I'd write them down this time.
350 // 1. There is no loss of expressiveness here, though it does
351 // cause some inconvenience. What we are saying is that the type
352 // of `x` becomes *exactly* what is expected. This can cause unnecessary
353 // errors in some cases, such as this one:
354 // it will cause errors in a case like this:
357 // fn foo<'x>(x: &'x int) {
364 // The reason we might get an error is that `z` might be
365 // assigned a type like `&'x int`, and then we would have
366 // a problem when we try to assign `&a` to `z`, because
367 // the lifetime of `&a` (i.e., the enclosing block) is
368 // shorter than `'x`.
370 // HOWEVER, this code works fine. The reason is that the
371 // expected type here is whatever type the user wrote, not
372 // the initializer's type. In this case the user wrote
373 // nothing, so we are going to create a type variable `Z`.
374 // Then we will assign the type of the initializer (`&'x
375 // int`) as a subtype of `Z`: `&'x int <: Z`. And hence we
376 // will instantiate `Z` as a type `&'0 int` where `'0` is
377 // a fresh region variable, with the constraint that `'x :
378 // '0`. So basically we're all set.
380 // Note that there are two tests to check that this remains true
381 // (`regions-reassign-{match,let}-bound-pointer.rs`).
383 // 2. Things go horribly wrong if we use subtype. The reason for
384 // THIS is a fairly subtle case involving bound regions. See the
385 // `givens` field in `region_inference`, as well as the test
386 // `regions-relate-bound-regions-on-closures-to-inference-variables.rs`,
387 // for details. Short version is that we must sometimes detect
388 // relationships between specific region variables and regions
389 // bound in a closure signature, and that detection gets thrown
390 // off when we substitute fresh region variables here to enable
394 fn check_assoc_item_is_const(pcx: &pat_ctxt, def: def::Def, span: Span) -> bool {
396 def::DefAssociatedConst(..) => true,
397 def::DefMethod(..) => {
398 span_err!(pcx.fcx.ccx.tcx.sess, span, E0327,
399 "associated items in match patterns must be constants");
403 pcx.fcx.ccx.tcx.sess.span_bug(span, "non-associated item in
404 check_assoc_item_is_const");
409 pub fn check_dereferencable<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
410 span: Span, expected: Ty<'tcx>,
411 inner: &hir::Pat) -> bool {
413 let tcx = pcx.fcx.ccx.tcx;
414 if pat_is_binding(&tcx.def_map.borrow(), inner) {
415 let expected = fcx.infcx().shallow_resolve(expected);
416 expected.builtin_deref(true, ty::NoPreference).map_or(true, |mt| match mt.ty.sty {
418 // This is "x = SomeTrait" being reduced from
419 // "let &x = &SomeTrait" or "let box x = Box<SomeTrait>", an error.
420 span_err!(tcx.sess, span, E0033,
421 "type `{}` cannot be dereferenced",
422 fcx.infcx().ty_to_string(expected));
432 pub fn check_match<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
433 expr: &'tcx hir::Expr,
434 discrim: &'tcx hir::Expr,
435 arms: &'tcx [hir::Arm],
436 expected: Expectation<'tcx>,
437 match_src: hir::MatchSource) {
438 let tcx = fcx.ccx.tcx;
440 // Not entirely obvious: if matches may create ref bindings, we
441 // want to use the *precise* type of the discriminant, *not* some
442 // supertype, as the "discriminant type" (issue #23116).
443 let contains_ref_bindings = arms.iter()
444 .filter_map(|a| tcx.arm_contains_ref_binding(a))
445 .max_by(|m| match *m {
446 hir::MutMutable => 1,
447 hir::MutImmutable => 0,
450 if let Some(m) = contains_ref_bindings {
451 check_expr_with_lvalue_pref(fcx, discrim, LvaluePreference::from_mutbl(m));
452 discrim_ty = fcx.expr_ty(discrim);
454 // ...but otherwise we want to use any supertype of the
455 // discriminant. This is sort of a workaround, see note (*) in
456 // `check_pat` for some details.
457 discrim_ty = fcx.infcx().next_ty_var();
458 check_expr_has_type(fcx, discrim, discrim_ty);
461 // Typecheck the patterns first, so that we get types for all the
464 let mut pcx = pat_ctxt {
466 map: pat_id_map(&tcx.def_map, &*arm.pats[0]),
469 check_pat(&mut pcx, &**p, discrim_ty);
473 // Now typecheck the blocks.
475 // The result of the match is the common supertype of all the
476 // arms. Start out the value as bottom, since it's the, well,
477 // bottom the type lattice, and we'll be moving up the lattice as
478 // we process each arm. (Note that any match with 0 arms is matching
479 // on any empty type and is therefore unreachable; should the flow
480 // of execution reach it, we will panic, so bottom is an appropriate
481 // type in that case)
482 let expected = expected.adjust_for_branches(fcx);
483 let result_ty = arms.iter().fold(fcx.infcx().next_diverging_ty_var(), |result_ty, arm| {
484 let bty = match expected {
485 // We don't coerce to `()` so that if the match expression is a
486 // statement it's branches can have any consistent type. That allows
487 // us to give better error messages (pointing to a usually better
488 // arm for inconsistent arms or to the whole match when a `()` type
490 Expectation::ExpectHasType(ety) if ety != fcx.tcx().mk_nil() => {
491 check_expr_coercable_to_type(fcx, &*arm.body, ety);
495 check_expr_with_expectation(fcx, &*arm.body, expected);
496 fcx.node_ty(arm.body.id)
500 if let Some(ref e) = arm.guard {
501 check_expr_has_type(fcx, &**e, tcx.types.bool);
504 if result_ty.references_error() || bty.references_error() {
507 let (origin, expected, found) = match match_src {
508 /* if-let construct without an else block */
509 hir::MatchSource::IfLetDesugar { contains_else_clause }
510 if !contains_else_clause => (
511 infer::IfExpressionWithNoElse(expr.span),
516 infer::MatchExpressionArm(expr.span, arm.body.span, match_src),
522 infer::common_supertype(
532 fcx.write_ty(expr.id, result_ty);
535 pub struct pat_ctxt<'a, 'tcx: 'a> {
536 pub fcx: &'a FnCtxt<'a, 'tcx>,
540 pub fn check_pat_struct<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>, pat: &'tcx hir::Pat,
541 path: &hir::Path, fields: &'tcx [Spanned<hir::FieldPat>],
542 etc: bool, expected: Ty<'tcx>) {
544 let tcx = pcx.fcx.ccx.tcx;
546 let def = tcx.def_map.borrow().get(&pat.id).unwrap().full_def();
547 let variant = match fcx.def_struct_variant(def, path.span) {
548 Some((_, variant)) => variant,
550 let name = pprust::path_to_string(path);
551 span_err!(tcx.sess, pat.span, E0163,
552 "`{}` does not name a struct or a struct variant", name);
553 fcx.write_error(pat.id);
555 for field in fields {
556 check_pat(pcx, &field.node.pat, tcx.types.err);
562 let pat_ty = pcx.fcx.instantiate_type(def.def_id(), path);
563 let item_substs = match pat_ty.sty {
564 ty::TyStruct(_, substs) | ty::TyEnum(_, substs) => substs,
565 _ => tcx.sess.span_bug(pat.span, "struct variant is not an ADT")
567 demand::eqtype(fcx, pat.span, expected, pat_ty);
568 check_struct_pat_fields(pcx, pat.span, fields, variant, &item_substs, etc);
570 fcx.write_ty(pat.id, pat_ty);
571 fcx.write_substs(pat.id, ty::ItemSubsts { substs: item_substs.clone() });
574 pub fn check_pat_enum<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
577 subpats: Option<&'tcx [P<hir::Pat>]>,
580 // Typecheck the path.
582 let tcx = pcx.fcx.ccx.tcx;
584 let path_res = *tcx.def_map.borrow().get(&pat.id).unwrap();
586 let (opt_ty, segments, def) = match resolve_ty_and_def_ufcs(fcx, path_res,
589 Some(resolution) => resolution,
590 // Error handling done inside resolve_ty_and_def_ufcs, so if
591 // resolution fails just return.
595 // Items that were partially resolved before should have been resolved to
596 // associated constants (i.e. not methods).
597 if path_res.depth != 0 && !check_assoc_item_is_const(pcx, def, pat.span) {
598 fcx.write_error(pat.id);
602 let enum_def = def.variant_def_ids()
603 .map_or_else(|| def.def_id(), |(enum_def, _)| enum_def);
605 let ctor_scheme = tcx.lookup_item_type(enum_def);
606 let ctor_predicates = tcx.lookup_predicates(enum_def);
607 let path_scheme = if ctor_scheme.ty.is_fn() {
608 let fn_ret = tcx.no_late_bound_regions(&ctor_scheme.ty.fn_ret()).unwrap();
611 generics: ctor_scheme.generics,
616 instantiate_path(pcx.fcx, segments,
617 path_scheme, &ctor_predicates,
618 opt_ty, def, pat.span, pat.id);
620 // If we didn't have a fully resolved path to start with, we had an
621 // associated const, and we should quit now, since the rest of this
622 // function uses checks specific to structs and enums.
623 if path_res.depth != 0 {
624 let pat_ty = fcx.node_ty(pat.id);
625 demand::suptype(fcx, pat.span, expected, pat_ty);
629 let pat_ty = fcx.node_ty(pat.id);
630 demand::eqtype(fcx, pat.span, expected, pat_ty);
633 let real_path_ty = fcx.node_ty(pat.id);
634 let (arg_tys, kind_name): (Vec<_>, &'static str) = match real_path_ty.sty {
635 ty::TyEnum(enum_def, expected_substs)
636 if def == def::DefVariant(enum_def.did, def.def_id(), false) =>
638 let variant = enum_def.variant_of_def(def);
641 .map(|f| fcx.instantiate_type_scheme(pat.span,
647 ty::TyStruct(struct_def, expected_substs) => {
648 (struct_def.struct_variant()
651 .map(|f| fcx.instantiate_type_scheme(pat.span,
658 let name = pprust::path_to_string(path);
659 span_err!(tcx.sess, pat.span, E0164,
660 "`{}` does not name a non-struct variant or a tuple struct", name);
661 fcx.write_error(pat.id);
663 if let Some(subpats) = subpats {
665 check_pat(pcx, &**pat, tcx.types.err);
672 if let Some(subpats) = subpats {
673 if subpats.len() == arg_tys.len() {
674 for (subpat, arg_ty) in subpats.iter().zip(arg_tys) {
675 check_pat(pcx, &**subpat, arg_ty);
677 } else if arg_tys.is_empty() {
678 span_err!(tcx.sess, pat.span, E0024,
679 "this pattern has {} field{}, but the corresponding {} has no fields",
680 subpats.len(), if subpats.len() == 1 {""} else {"s"}, kind_name);
683 check_pat(pcx, &**pat, tcx.types.err);
686 span_err!(tcx.sess, pat.span, E0023,
687 "this pattern has {} field{}, but the corresponding {} has {} field{}",
688 subpats.len(), if subpats.len() == 1 {""} else {"s"},
690 arg_tys.len(), if arg_tys.len() == 1 {""} else {"s"});
693 check_pat(pcx, &**pat, tcx.types.err);
699 /// `path` is the AST path item naming the type of this struct.
700 /// `fields` is the field patterns of the struct pattern.
701 /// `struct_fields` describes the type of each field of the struct.
702 /// `struct_id` is the ID of the struct.
703 /// `etc` is true if the pattern said '...' and false otherwise.
704 pub fn check_struct_pat_fields<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
706 fields: &'tcx [Spanned<hir::FieldPat>],
707 variant: ty::VariantDef<'tcx>,
708 substs: &Substs<'tcx>,
710 let tcx = pcx.fcx.ccx.tcx;
712 // Index the struct fields' types.
713 let field_map = variant.fields
715 .map(|field| (field.name, field))
716 .collect::<FnvHashMap<_, _>>();
718 // Keep track of which fields have already appeared in the pattern.
719 let mut used_fields = FnvHashMap();
721 // Typecheck each field.
722 for &Spanned { node: ref field, span } in fields {
723 let field_ty = match used_fields.entry(field.name) {
724 Occupied(occupied) => {
725 span_err!(tcx.sess, span, E0025,
726 "field `{}` bound multiple times in the pattern",
728 span_note!(tcx.sess, *occupied.get(),
729 "field `{}` previously bound here",
735 field_map.get(&field.name)
736 .map(|f| pcx.fcx.field_ty(span, f, substs))
738 span_err!(tcx.sess, span, E0026,
739 "struct `{}` does not have a field named `{}`",
740 tcx.item_path_str(variant.did),
747 check_pat(pcx, &*field.pat, field_ty);
750 // Report an error if not all the fields were specified.
752 for field in variant.fields
754 .filter(|field| !used_fields.contains_key(&field.name)) {
755 span_err!(tcx.sess, span, E0027,
756 "pattern does not mention field `{}`",