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;
27 use std::collections::hash_map::Entry::{Occupied, Vacant};
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 if let hir::PatEnum(ref path, ref subpats) = pat.node {
140 if !(subpats.is_some() && subpats.as_ref().unwrap().is_empty()) {
141 bad_struct_kind_err(tcx.sess, pat.span, path, false);
145 if let Some(pat_def) = tcx.def_map.borrow().get(&pat.id) {
146 let const_did = pat_def.def_id();
147 let const_scheme = tcx.lookup_item_type(const_did);
148 assert!(const_scheme.generics.is_empty());
149 let const_ty = pcx.fcx.instantiate_type_scheme(pat.span,
152 fcx.write_ty(pat.id, const_ty);
154 // FIXME(#20489) -- we should limit the types here to scalars or something!
156 // As with PatLit, what we really want here is that there
157 // exist a LUB, but for the cases that can occur, subtype
159 demand::suptype(fcx, pat.span, expected, const_ty);
161 fcx.write_error(pat.id);
164 hir::PatIdent(bm, ref path, ref sub) if pat_is_binding(&tcx.def_map.borrow(), pat) => {
165 let typ = fcx.local_ty(pat.span, pat.id);
167 hir::BindByRef(mutbl) => {
168 // if the binding is like
169 // ref x | ref const x | ref mut x
170 // then `x` is assigned a value of type `&M T` where M is the mutability
171 // and T is the expected type.
172 let region_var = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
173 let mt = ty::TypeAndMut { ty: expected, mutbl: mutbl };
174 let region_ty = tcx.mk_ref(tcx.mk_region(region_var), mt);
176 // `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)` is
177 // required. However, we use equality, which is stronger. See (*) for
179 demand::eqtype(fcx, pat.span, region_ty, typ);
181 // otherwise the type of x is the expected type T
182 hir::BindByValue(_) => {
183 // As above, `T <: typeof(x)` is required but we
184 // use equality, see (*) below.
185 demand::eqtype(fcx, pat.span, expected, typ);
189 fcx.write_ty(pat.id, typ);
191 // if there are multiple arms, make sure they all agree on
192 // what the type of the binding `x` ought to be
193 if let Some(&canon_id) = pcx.map.get(&path.node.name) {
194 if canon_id != pat.id {
195 let ct = fcx.local_ty(pat.span, canon_id);
196 demand::eqtype(fcx, pat.span, ct, typ);
199 if let Some(ref p) = *sub {
200 check_pat(pcx, &**p, expected);
204 hir::PatIdent(_, ref path, _) => {
205 let path = hir_util::ident_to_path(path.span, path.node);
206 check_pat_enum(pcx, pat, &path, Some(&[]), expected, false);
208 hir::PatEnum(ref path, ref subpats) => {
209 let subpats = subpats.as_ref().map(|v| &v[..]);
210 let is_tuple_struct_pat = !(subpats.is_some() && subpats.unwrap().is_empty());
211 check_pat_enum(pcx, pat, path, subpats, expected, is_tuple_struct_pat);
213 hir::PatQPath(ref qself, ref path) => {
214 let self_ty = fcx.to_ty(&qself.ty);
215 let path_res = if let Some(&d) = tcx.def_map.borrow().get(&pat.id) {
216 if d.base_def == def::DefErr {
217 fcx.write_error(pat.id);
221 } else if qself.position == 0 {
222 // This is just a sentinel for finish_resolving_def_to_ty.
223 let sentinel = fcx.tcx().map.local_def_id(ast::CRATE_NODE_ID);
224 def::PathResolution {
225 base_def: def::DefMod(sentinel),
226 last_private: LastMod(AllPublic),
227 depth: path.segments.len()
230 debug!("unbound path {:?}", pat);
231 fcx.write_error(pat.id);
234 if let Some((opt_ty, segments, def)) =
235 resolve_ty_and_def_ufcs(fcx, path_res, Some(self_ty),
236 path, pat.span, pat.id) {
237 if check_assoc_item_is_const(pcx, def, pat.span) {
238 let scheme = tcx.lookup_item_type(def.def_id());
239 let predicates = tcx.lookup_predicates(def.def_id());
240 instantiate_path(fcx, segments,
242 opt_ty, def, pat.span, pat.id);
243 let const_ty = fcx.node_ty(pat.id);
244 demand::suptype(fcx, pat.span, expected, const_ty);
246 fcx.write_error(pat.id)
250 hir::PatStruct(ref path, ref fields, etc) => {
251 check_pat_struct(pcx, pat, path, fields, etc, expected);
253 hir::PatTup(ref elements) => {
254 let element_tys: Vec<_> =
255 (0..elements.len()).map(|_| fcx.infcx().next_ty_var())
257 let pat_ty = tcx.mk_tup(element_tys.clone());
258 fcx.write_ty(pat.id, pat_ty);
259 demand::eqtype(fcx, pat.span, expected, pat_ty);
260 for (element_pat, element_ty) in elements.iter().zip(element_tys) {
261 check_pat(pcx, &**element_pat, element_ty);
264 hir::PatBox(ref inner) => {
265 let inner_ty = fcx.infcx().next_ty_var();
266 let uniq_ty = tcx.mk_box(inner_ty);
268 if check_dereferencable(pcx, pat.span, expected, &**inner) {
269 // Here, `demand::subtype` is good enough, but I don't
270 // think any errors can be introduced by using
272 demand::eqtype(fcx, pat.span, expected, uniq_ty);
273 fcx.write_ty(pat.id, uniq_ty);
274 check_pat(pcx, &**inner, inner_ty);
276 fcx.write_error(pat.id);
277 check_pat(pcx, &**inner, tcx.types.err);
280 hir::PatRegion(ref inner, mutbl) => {
281 let expected = fcx.infcx().shallow_resolve(expected);
282 if check_dereferencable(pcx, pat.span, expected, &**inner) {
283 // `demand::subtype` would be good enough, but using
284 // `eqtype` turns out to be equally general. See (*)
285 // below for details.
287 // Take region, inner-type from expected type if we
288 // can, to avoid creating needless variables. This
289 // also helps with the bad interactions of the given
290 // hack detailed in (*) below.
291 let (rptr_ty, inner_ty) = match expected.sty {
292 ty::TyRef(_, mt) if mt.mutbl == mutbl => {
296 let inner_ty = fcx.infcx().next_ty_var();
297 let mt = ty::TypeAndMut { ty: inner_ty, mutbl: mutbl };
298 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
299 let rptr_ty = tcx.mk_ref(tcx.mk_region(region), mt);
300 demand::eqtype(fcx, pat.span, expected, rptr_ty);
305 fcx.write_ty(pat.id, rptr_ty);
306 check_pat(pcx, &**inner, inner_ty);
308 fcx.write_error(pat.id);
309 check_pat(pcx, &**inner, tcx.types.err);
312 hir::PatVec(ref before, ref slice, ref after) => {
313 let expected_ty = structurally_resolved_type(fcx, pat.span, expected);
314 let inner_ty = fcx.infcx().next_ty_var();
315 let pat_ty = match expected_ty.sty {
316 ty::TyArray(_, size) => tcx.mk_array(inner_ty, {
317 let min_len = before.len() + after.len();
319 Some(_) => cmp::max(min_len, size),
324 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
325 tcx.mk_ref(tcx.mk_region(region), ty::TypeAndMut {
326 ty: tcx.mk_slice(inner_ty),
327 mutbl: expected_ty.builtin_deref(true, ty::NoPreference).map(|mt| mt.mutbl)
328 .unwrap_or(hir::MutImmutable)
333 fcx.write_ty(pat.id, pat_ty);
335 // `demand::subtype` would be good enough, but using
336 // `eqtype` turns out to be equally general. See (*)
337 // below for details.
338 demand::eqtype(fcx, pat.span, expected, pat_ty);
341 check_pat(pcx, &**elt, inner_ty);
343 if let Some(ref slice) = *slice {
344 let region = fcx.infcx().next_region_var(infer::PatternRegion(pat.span));
345 let mutbl = expected_ty.builtin_deref(true, ty::NoPreference)
346 .map_or(hir::MutImmutable, |mt| mt.mutbl);
348 let slice_ty = tcx.mk_ref(tcx.mk_region(region), ty::TypeAndMut {
349 ty: tcx.mk_slice(inner_ty),
352 check_pat(pcx, &**slice, slice_ty);
355 check_pat(pcx, &**elt, inner_ty);
361 // (*) In most of the cases above (literals and constants being
362 // the exception), we relate types using strict equality, evewn
363 // though subtyping would be sufficient. There are a few reasons
364 // for this, some of which are fairly subtle and which cost me
365 // (nmatsakis) an hour or two debugging to remember, so I thought
366 // I'd write them down this time.
368 // 1. There is no loss of expressiveness here, though it does
369 // cause some inconvenience. What we are saying is that the type
370 // of `x` becomes *exactly* what is expected. This can cause unnecessary
371 // errors in some cases, such as this one:
372 // it will cause errors in a case like this:
375 // fn foo<'x>(x: &'x int) {
382 // The reason we might get an error is that `z` might be
383 // assigned a type like `&'x int`, and then we would have
384 // a problem when we try to assign `&a` to `z`, because
385 // the lifetime of `&a` (i.e., the enclosing block) is
386 // shorter than `'x`.
388 // HOWEVER, this code works fine. The reason is that the
389 // expected type here is whatever type the user wrote, not
390 // the initializer's type. In this case the user wrote
391 // nothing, so we are going to create a type variable `Z`.
392 // Then we will assign the type of the initializer (`&'x
393 // int`) as a subtype of `Z`: `&'x int <: Z`. And hence we
394 // will instantiate `Z` as a type `&'0 int` where `'0` is
395 // a fresh region variable, with the constraint that `'x :
396 // '0`. So basically we're all set.
398 // Note that there are two tests to check that this remains true
399 // (`regions-reassign-{match,let}-bound-pointer.rs`).
401 // 2. Things go horribly wrong if we use subtype. The reason for
402 // THIS is a fairly subtle case involving bound regions. See the
403 // `givens` field in `region_inference`, as well as the test
404 // `regions-relate-bound-regions-on-closures-to-inference-variables.rs`,
405 // for details. Short version is that we must sometimes detect
406 // relationships between specific region variables and regions
407 // bound in a closure signature, and that detection gets thrown
408 // off when we substitute fresh region variables here to enable
412 fn check_assoc_item_is_const(pcx: &pat_ctxt, def: def::Def, span: Span) -> bool {
414 def::DefAssociatedConst(..) => true,
415 def::DefMethod(..) => {
416 span_err!(pcx.fcx.ccx.tcx.sess, span, E0327,
417 "associated items in match patterns must be constants");
421 pcx.fcx.ccx.tcx.sess.span_bug(span, "non-associated item in
422 check_assoc_item_is_const");
427 pub fn check_dereferencable<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
428 span: Span, expected: Ty<'tcx>,
429 inner: &hir::Pat) -> bool {
431 let tcx = pcx.fcx.ccx.tcx;
432 if pat_is_binding(&tcx.def_map.borrow(), inner) {
433 let expected = fcx.infcx().shallow_resolve(expected);
434 expected.builtin_deref(true, ty::NoPreference).map_or(true, |mt| match mt.ty.sty {
436 // This is "x = SomeTrait" being reduced from
437 // "let &x = &SomeTrait" or "let box x = Box<SomeTrait>", an error.
438 span_err!(tcx.sess, span, E0033,
439 "type `{}` cannot be dereferenced",
440 fcx.infcx().ty_to_string(expected));
450 pub fn check_match<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
451 expr: &'tcx hir::Expr,
452 discrim: &'tcx hir::Expr,
453 arms: &'tcx [hir::Arm],
454 expected: Expectation<'tcx>,
455 match_src: hir::MatchSource) {
456 let tcx = fcx.ccx.tcx;
458 // Not entirely obvious: if matches may create ref bindings, we
459 // want to use the *precise* type of the discriminant, *not* some
460 // supertype, as the "discriminant type" (issue #23116).
461 let contains_ref_bindings = arms.iter()
462 .filter_map(|a| tcx.arm_contains_ref_binding(a))
463 .max_by_key(|m| match *m {
464 hir::MutMutable => 1,
465 hir::MutImmutable => 0,
468 if let Some(m) = contains_ref_bindings {
469 check_expr_with_lvalue_pref(fcx, discrim, LvaluePreference::from_mutbl(m));
470 discrim_ty = fcx.expr_ty(discrim);
472 // ...but otherwise we want to use any supertype of the
473 // discriminant. This is sort of a workaround, see note (*) in
474 // `check_pat` for some details.
475 discrim_ty = fcx.infcx().next_ty_var();
476 check_expr_has_type(fcx, discrim, discrim_ty);
479 // Typecheck the patterns first, so that we get types for all the
482 let mut pcx = pat_ctxt {
484 map: pat_id_map(&tcx.def_map, &*arm.pats[0]),
487 check_pat(&mut pcx, &**p, discrim_ty);
491 // Now typecheck the blocks.
493 // The result of the match is the common supertype of all the
494 // arms. Start out the value as bottom, since it's the, well,
495 // bottom the type lattice, and we'll be moving up the lattice as
496 // we process each arm. (Note that any match with 0 arms is matching
497 // on any empty type and is therefore unreachable; should the flow
498 // of execution reach it, we will panic, so bottom is an appropriate
499 // type in that case)
500 let expected = expected.adjust_for_branches(fcx);
501 let result_ty = arms.iter().fold(fcx.infcx().next_diverging_ty_var(), |result_ty, arm| {
502 let bty = match expected {
503 // We don't coerce to `()` so that if the match expression is a
504 // statement it's branches can have any consistent type. That allows
505 // us to give better error messages (pointing to a usually better
506 // arm for inconsistent arms or to the whole match when a `()` type
508 Expectation::ExpectHasType(ety) if ety != fcx.tcx().mk_nil() => {
509 check_expr_coercable_to_type(fcx, &*arm.body, ety);
513 check_expr_with_expectation(fcx, &*arm.body, expected);
514 fcx.node_ty(arm.body.id)
518 if let Some(ref e) = arm.guard {
519 check_expr_has_type(fcx, &**e, tcx.types.bool);
522 if result_ty.references_error() || bty.references_error() {
525 let (origin, expected, found) = match match_src {
526 /* if-let construct without an else block */
527 hir::MatchSource::IfLetDesugar { contains_else_clause }
528 if !contains_else_clause => (
529 TypeOrigin::IfExpressionWithNoElse(expr.span),
534 TypeOrigin::MatchExpressionArm(expr.span, arm.body.span, match_src),
540 infer::common_supertype(
550 fcx.write_ty(expr.id, result_ty);
553 pub struct pat_ctxt<'a, 'tcx: 'a> {
554 pub fcx: &'a FnCtxt<'a, 'tcx>,
558 pub fn check_pat_struct<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>, pat: &'tcx hir::Pat,
559 path: &hir::Path, fields: &'tcx [Spanned<hir::FieldPat>],
560 etc: bool, expected: Ty<'tcx>) {
562 let tcx = pcx.fcx.ccx.tcx;
564 let def = tcx.def_map.borrow().get(&pat.id).unwrap().full_def();
565 let variant = match fcx.def_struct_variant(def, path.span) {
566 Some((_, variant)) => variant,
568 let name = pprust::path_to_string(path);
569 span_err!(tcx.sess, pat.span, E0163,
570 "`{}` does not name a struct or a struct variant", name);
571 fcx.write_error(pat.id);
573 for field in fields {
574 check_pat(pcx, &field.node.pat, tcx.types.err);
580 let pat_ty = pcx.fcx.instantiate_type(def.def_id(), path);
581 let item_substs = match pat_ty.sty {
582 ty::TyStruct(_, substs) | ty::TyEnum(_, substs) => substs,
583 _ => tcx.sess.span_bug(pat.span, "struct variant is not an ADT")
585 demand::eqtype(fcx, pat.span, expected, pat_ty);
586 check_struct_pat_fields(pcx, pat.span, fields, variant, &item_substs, etc);
588 fcx.write_ty(pat.id, pat_ty);
589 fcx.write_substs(pat.id, ty::ItemSubsts { substs: item_substs.clone() });
592 // This function exists due to the warning "diagnostic code E0164 already used"
593 fn bad_struct_kind_err(sess: &Session, span: Span, path: &hir::Path, is_warning: bool) {
594 let name = pprust::path_to_string(path);
595 span_err_or_warn!(is_warning, sess, span, E0164,
596 "`{}` does not name a tuple variant or a tuple struct", name);
599 pub fn check_pat_enum<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
602 subpats: Option<&'tcx [P<hir::Pat>]>,
604 is_tuple_struct_pat: bool)
606 // Typecheck the path.
608 let tcx = pcx.fcx.ccx.tcx;
610 let path_res = match tcx.def_map.borrow().get(&pat.id) {
611 Some(&path_res) if path_res.base_def != def::DefErr => path_res,
613 fcx.write_error(pat.id);
615 if let Some(subpats) = subpats {
617 check_pat(pcx, &**pat, tcx.types.err);
625 let (opt_ty, segments, def) = match resolve_ty_and_def_ufcs(fcx, path_res,
628 Some(resolution) => resolution,
629 // Error handling done inside resolve_ty_and_def_ufcs, so if
630 // resolution fails just return.
634 // Items that were partially resolved before should have been resolved to
635 // associated constants (i.e. not methods).
636 if path_res.depth != 0 && !check_assoc_item_is_const(pcx, def, pat.span) {
637 fcx.write_error(pat.id);
641 let enum_def = def.variant_def_ids()
642 .map_or_else(|| def.def_id(), |(enum_def, _)| enum_def);
644 let ctor_scheme = tcx.lookup_item_type(enum_def);
645 let ctor_predicates = tcx.lookup_predicates(enum_def);
646 let path_scheme = if ctor_scheme.ty.is_fn() {
647 let fn_ret = tcx.no_late_bound_regions(&ctor_scheme.ty.fn_ret()).unwrap();
650 generics: ctor_scheme.generics,
655 instantiate_path(pcx.fcx, segments,
656 path_scheme, &ctor_predicates,
657 opt_ty, def, pat.span, pat.id);
659 let report_bad_struct_kind = |is_warning| {
660 bad_struct_kind_err(tcx.sess, pat.span, path, is_warning);
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 if def == def::DefVariant(enum_def.did, def.def_id(), false) =>
694 let variant = enum_def.variant_of_def(def);
695 if is_tuple_struct_pat && variant.kind() != ty::VariantKind::Tuple {
696 // Matching unit variants with tuple variant patterns (`UnitVariant(..)`)
697 // is allowed for backward compatibility.
698 let is_special_case = variant.kind() == ty::VariantKind::Unit;
699 report_bad_struct_kind(is_special_case);
700 if !is_special_case {
703 span_note!(tcx.sess, pat.span,
704 "this warning will become a HARD ERROR in a future release. \
705 See RFC 218 for details.");
710 .map(|f| fcx.instantiate_type_scheme(pat.span,
716 ty::TyStruct(struct_def, expected_substs) => {
717 let variant = struct_def.struct_variant();
718 if is_tuple_struct_pat && variant.kind() != ty::VariantKind::Tuple {
719 report_bad_struct_kind(false);
724 .map(|f| fcx.instantiate_type_scheme(pat.span,
731 report_bad_struct_kind(false);
736 if let Some(subpats) = subpats {
737 if subpats.len() == arg_tys.len() {
738 for (subpat, arg_ty) in subpats.iter().zip(arg_tys) {
739 check_pat(pcx, &**subpat, arg_ty);
741 } else if arg_tys.is_empty() {
742 span_err!(tcx.sess, pat.span, E0024,
743 "this pattern has {} field{}, but the corresponding {} has no fields",
744 subpats.len(), if subpats.len() == 1 {""} else {"s"}, kind_name);
747 check_pat(pcx, &**pat, tcx.types.err);
750 span_err!(tcx.sess, pat.span, E0023,
751 "this pattern has {} field{}, but the corresponding {} has {} field{}",
752 subpats.len(), if subpats.len() == 1 {""} else {"s"},
754 arg_tys.len(), if arg_tys.len() == 1 {""} else {"s"});
757 check_pat(pcx, &**pat, tcx.types.err);
763 /// `path` is the AST path item naming the type of this struct.
764 /// `fields` is the field patterns of the struct pattern.
765 /// `struct_fields` describes the type of each field of the struct.
766 /// `struct_id` is the ID of the struct.
767 /// `etc` is true if the pattern said '...' and false otherwise.
768 pub fn check_struct_pat_fields<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
770 fields: &'tcx [Spanned<hir::FieldPat>],
771 variant: ty::VariantDef<'tcx>,
772 substs: &Substs<'tcx>,
774 let tcx = pcx.fcx.ccx.tcx;
776 // Index the struct fields' types.
777 let field_map = variant.fields
779 .map(|field| (field.name, field))
780 .collect::<FnvHashMap<_, _>>();
782 // Keep track of which fields have already appeared in the pattern.
783 let mut used_fields = FnvHashMap();
785 // Typecheck each field.
786 for &Spanned { node: ref field, span } in fields {
787 let field_ty = match used_fields.entry(field.name) {
788 Occupied(occupied) => {
789 span_err!(tcx.sess, span, E0025,
790 "field `{}` bound multiple times in the pattern",
792 span_note!(tcx.sess, *occupied.get(),
793 "field `{}` previously bound here",
799 field_map.get(&field.name)
800 .map(|f| pcx.fcx.field_ty(span, f, substs))
802 span_err!(tcx.sess, span, E0026,
803 "struct `{}` does not have a field named `{}`",
804 tcx.item_path_str(variant.did),
811 check_pat(pcx, &*field.pat, field_ty);
814 // Report an error if not all the fields were specified.
816 for field in variant.fields
818 .filter(|field| !used_fields.contains_key(&field.name)) {
819 span_err!(tcx.sess, span, E0027,
820 "pattern does not mention field `{}`",