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 #![allow(non_camel_case_types)]
13 use middle::pat_util::{PatIdMap, pat_id_map, pat_is_binding, pat_is_const};
15 use middle::typeck::check::demand;
16 use middle::typeck::check::{check_expr, check_expr_has_type, FnCtxt};
17 use middle::typeck::check::{instantiate_path, lookup_def};
18 use middle::typeck::check::{structure_of, valid_range_bounds};
19 use middle::typeck::infer;
20 use middle::typeck::require_same_types;
22 use collections::{HashMap, HashSet};
25 use syntax::parse::token;
26 use syntax::codemap::Span;
27 use syntax::print::pprust;
29 pub fn check_match(fcx: &FnCtxt,
33 let tcx = fcx.ccx.tcx;
35 let discrim_ty = fcx.infcx().next_ty_var();
36 check_expr_has_type(fcx, discrim, discrim_ty);
38 // Typecheck the patterns first, so that we get types for all the
40 for arm in arms.iter() {
41 let mut pcx = pat_ctxt {
43 map: pat_id_map(&tcx.def_map, *arm.pats.get(0)),
46 for p in arm.pats.iter() { check_pat(&mut pcx, *p, discrim_ty);}
49 // The result of the match is the common supertype of all the
50 // arms. Start out the value as bottom, since it's the, well,
51 // bottom the type lattice, and we'll be moving up the lattice as
52 // we process each arm. (Note that any match with 0 arms is matching
53 // on any empty type and is therefore unreachable; should the flow
54 // of execution reach it, we will fail, so bottom is an appropriate
56 let mut result_ty = ty::mk_bot();
58 // Now typecheck the blocks.
59 let mut saw_err = ty::type_is_error(discrim_ty);
60 for arm in arms.iter() {
61 let mut guard_err = false;
62 let mut guard_bot = false;
65 check_expr_has_type(fcx, e, ty::mk_bool());
66 let e_ty = fcx.expr_ty(e);
67 if ty::type_is_error(e_ty) {
70 else if ty::type_is_bot(e_ty) {
76 check_expr(fcx, arm.body);
77 let bty = fcx.node_ty(arm.body.id);
78 saw_err = saw_err || ty::type_is_error(bty);
80 fcx.write_error(arm.body.id);
84 fcx.write_bot(arm.body.id);
88 infer::common_supertype(
90 infer::MatchExpression(expr.span),
91 true, // result_ty is "expected" here
97 result_ty = ty::mk_err();
98 } else if ty::type_is_bot(discrim_ty) {
99 result_ty = ty::mk_bot();
102 fcx.write_ty(expr.id, result_ty);
105 pub struct pat_ctxt<'a> {
106 pub fcx: &'a FnCtxt<'a>,
110 pub fn check_pat_variant(pcx: &pat_ctxt, pat: &ast::Pat, path: &ast::Path,
111 subpats: &Option<Vec<@ast::Pat>>, expected: ty::t) {
113 // Typecheck the path.
115 let tcx = pcx.fcx.ccx.tcx;
117 let arg_types: Vec<ty::t> ;
120 // structure_of requires type variables to be resolved.
121 // So when we pass in <expected>, it's an error if it
122 // contains type variables.
124 // Check to see whether this is an enum or a struct.
125 match *structure_of(pcx.fcx, pat.span, expected) {
126 ty::ty_enum(_, ref expected_substs) => {
127 // Lookup the enum and variant def ids:
128 let v_def = lookup_def(pcx.fcx, pat.span, pat.id);
129 match ast_util::variant_def_ids(v_def) {
130 Some((enm, var)) => {
131 // Assign the pattern the type of the *enum*, not the variant.
132 let enum_tpt = ty::lookup_item_type(tcx, enm);
133 instantiate_path(pcx.fcx,
140 // check that the type of the value being matched is a subtype
141 // of the type of the pattern:
142 let pat_ty = fcx.node_ty(pat.id);
143 demand::subtype(fcx, pat.span, expected, pat_ty);
145 // Get the expected types of the arguments.
148 ty::enum_variant_with_id(tcx, enm, var);
149 let var_tpt = ty::lookup_item_type(tcx, var);
150 vinfo.args.iter().map(|t| {
151 if var_tpt.generics.type_param_defs().len() ==
152 expected_substs.tps.len()
154 ty::subst(tcx, expected_substs, *t)
157 *t // In this case, an error was already signaled
163 kind_name = "variant";
166 // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
167 fcx.infcx().type_error_message_str_with_expected(pat.span,
169 expected.map_or("".to_owned(), |e| {
170 format!("mismatched types: expected `{}` but found {}",
172 Some(expected), "a structure pattern".to_owned(),
174 fcx.write_error(pat.id);
175 kind_name = "[error]";
176 arg_types = subpats.clone()
179 .map(|_| ty::mk_err())
184 ty::ty_struct(struct_def_id, ref expected_substs) => {
185 // Lookup the struct ctor def id
186 let s_def = lookup_def(pcx.fcx, pat.span, pat.id);
187 let s_def_id = ast_util::def_id_of_def(s_def);
189 // Assign the pattern the type of the struct.
190 let ctor_tpt = ty::lookup_item_type(tcx, s_def_id);
191 let struct_tpt = if ty::is_fn_ty(ctor_tpt.ty) {
192 ty::ty_param_bounds_and_ty {ty: ty::ty_fn_ret(ctor_tpt.ty),
197 instantiate_path(pcx.fcx,
204 // Check that the type of the value being matched is a subtype of
205 // the type of the pattern.
206 let pat_ty = fcx.node_ty(pat.id);
207 demand::subtype(fcx, pat.span, expected, pat_ty);
209 // Get the expected types of the arguments.
210 let class_fields = ty::struct_fields(
211 tcx, struct_def_id, expected_substs);
212 arg_types = class_fields.iter().map(|field| field.mt.ty).collect();
214 kind_name = "structure";
217 // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
218 fcx.infcx().type_error_message_str_with_expected(pat.span,
220 expected.map_or("".to_owned(), |e| {
221 format!("mismatched types: expected `{}` but found {}",
223 Some(expected), "an enum or structure pattern".to_owned(),
225 fcx.write_error(pat.id);
226 kind_name = "[error]";
227 arg_types = subpats.clone()
230 .map(|_| ty::mk_err())
235 let arg_len = arg_types.len();
237 // Count the number of subpatterns.
240 None => subpats_len = arg_len,
241 Some(ref subpats) => subpats_len = subpats.len()
244 let mut error_happened = false;
248 if arg_len != subpats_len {
249 let s = format!("this pattern has \
250 {npat, plural, =1{# field} other{# fields}}, \
251 but the corresponding {kind} has \
252 {narg, plural, =1{# field} other{# fields}}",
256 tcx.sess.span_err(pat.span, s);
257 error_happened = true;
261 for pats in subpats.iter() {
262 for (subpat, arg_ty) in pats.iter().zip(arg_types.iter()) {
263 check_pat(pcx, *subpat, *arg_ty);
267 } else if subpats_len > 0 {
268 tcx.sess.span_err(pat.span,
269 format!("this pattern has \
270 {npat, plural, =1{# field} other{# fields}}, \
271 but the corresponding {kind} has no fields",
274 error_happened = true;
278 for pats in subpats.iter() {
279 for pat in pats.iter() {
280 check_pat(pcx, *pat, ty::mk_err());
286 /// `path` is the AST path item naming the type of this struct.
287 /// `fields` is the field patterns of the struct pattern.
288 /// `class_fields` describes the type of each field of the struct.
289 /// `class_id` is the ID of the struct.
290 /// `substitutions` are the type substitutions applied to this struct type
291 /// (e.g. K,V in HashMap<K,V>).
292 /// `etc` is true if the pattern said '...' and false otherwise.
293 pub fn check_struct_pat_fields(pcx: &pat_ctxt,
296 fields: &[ast::FieldPat],
297 class_fields: Vec<ty::field_ty> ,
298 class_id: ast::DefId,
299 substitutions: &ty::substs,
301 let tcx = pcx.fcx.ccx.tcx;
303 // Index the class fields. The second argument in the tuple is whether the
304 // field has been bound yet or not.
305 let mut field_map = HashMap::new();
306 for (i, class_field) in class_fields.iter().enumerate() {
307 field_map.insert(class_field.name, (i, false));
310 // Typecheck each field.
311 let mut found_fields = HashSet::new();
312 for field in fields.iter() {
313 match field_map.find_mut(&field.ident.name) {
314 Some(&(_, true)) => {
315 tcx.sess.span_err(span,
316 format!("field `{}` bound twice in pattern",
317 token::get_ident(field.ident)));
319 Some(&(index, ref mut used)) => {
321 let class_field = *class_fields.get(index);
322 let field_type = ty::lookup_field_type(tcx,
326 check_pat(pcx, field.pat, field_type);
327 found_fields.insert(index);
330 let name = pprust::path_to_str(path);
331 // Check the pattern anyway, so that attempts to look
332 // up its type won't fail
333 check_pat(pcx, field.pat, ty::mk_err());
334 tcx.sess.span_err(span,
335 format!("struct `{}` does not have a field named `{}`",
337 token::get_ident(field.ident)));
342 // Report an error if not all the fields were specified.
344 for (i, field) in class_fields.iter().enumerate() {
345 if found_fields.contains(&i) {
349 tcx.sess.span_err(span,
350 format!("pattern does not mention field `{}`",
351 token::get_name(field.name)));
356 pub fn check_struct_pat(pcx: &pat_ctxt, pat_id: ast::NodeId, span: Span,
357 expected: ty::t, path: &ast::Path,
358 fields: &[ast::FieldPat], etc: bool,
359 struct_id: ast::DefId,
360 substitutions: &ty::substs) {
362 let tcx = pcx.fcx.ccx.tcx;
364 let class_fields = ty::lookup_struct_fields(tcx, struct_id);
366 // Check to ensure that the struct is the one specified.
367 match tcx.def_map.borrow().find(&pat_id) {
368 Some(&ast::DefStruct(supplied_def_id))
369 if supplied_def_id == struct_id => {
372 Some(&ast::DefStruct(..)) | Some(&ast::DefVariant(..)) => {
373 let name = pprust::path_to_str(path);
374 tcx.sess.span_err(span,
375 format!("mismatched types: expected `{}` but found `{}`",
376 fcx.infcx().ty_to_str(expected),
380 tcx.sess.span_bug(span, "resolve didn't write in struct ID");
384 check_struct_pat_fields(pcx, span, path, fields, class_fields, struct_id,
388 pub fn check_struct_like_enum_variant_pat(pcx: &pat_ctxt,
393 fields: &[ast::FieldPat],
396 substitutions: &ty::substs) {
398 let tcx = pcx.fcx.ccx.tcx;
400 // Find the variant that was specified.
401 match tcx.def_map.borrow().find(&pat_id) {
402 Some(&ast::DefVariant(found_enum_id, variant_id, _))
403 if found_enum_id == enum_id => {
404 // Get the struct fields from this struct-like enum variant.
405 let class_fields = ty::lookup_struct_fields(tcx, variant_id);
407 check_struct_pat_fields(pcx, span, path, fields, class_fields,
408 variant_id, substitutions, etc);
410 Some(&ast::DefStruct(..)) | Some(&ast::DefVariant(..)) => {
411 let name = pprust::path_to_str(path);
412 tcx.sess.span_err(span,
413 format!("mismatched types: expected `{}` but \
415 fcx.infcx().ty_to_str(expected),
419 tcx.sess.span_bug(span, "resolve didn't write in variant");
424 // Pattern checking is top-down rather than bottom-up so that bindings get
425 // their types immediately.
426 pub fn check_pat(pcx: &pat_ctxt, pat: &ast::Pat, expected: ty::t) {
428 let tcx = pcx.fcx.ccx.tcx;
431 ast::PatWild | ast::PatWildMulti => {
432 fcx.write_ty(pat.id, expected);
435 check_expr_has_type(fcx, lt, expected);
436 fcx.write_ty(pat.id, fcx.expr_ty(lt));
438 ast::PatRange(begin, end) => {
439 check_expr_has_type(fcx, begin, expected);
440 check_expr_has_type(fcx, end, expected);
442 fcx.infcx().resolve_type_vars_if_possible(fcx.expr_ty(begin));
444 fcx.infcx().resolve_type_vars_if_possible(fcx.expr_ty(end));
445 debug!("pat_range beginning type: {:?}", b_ty);
446 debug!("pat_range ending type: {:?}", e_ty);
447 if !require_same_types(
448 tcx, Some(fcx.infcx()), false, pat.span, b_ty, e_ty,
449 || "mismatched types in range".to_owned())
452 } else if !ty::type_is_numeric(b_ty) && !ty::type_is_char(b_ty) {
453 tcx.sess.span_err(pat.span, "non-numeric type used in range");
455 match valid_range_bounds(fcx.ccx, begin, end) {
457 tcx.sess.span_err(begin.span,
458 "lower range bound must be less than upper");
461 tcx.sess.span_err(begin.span,
462 "mismatched types in range");
467 fcx.write_ty(pat.id, b_ty);
470 ast::PatIdent(..) if pat_is_const(&tcx.def_map, pat) => {
471 let const_did = ast_util::def_id_of_def(tcx.def_map.borrow()
473 let const_tpt = ty::lookup_item_type(tcx, const_did);
474 demand::suptype(fcx, pat.span, expected, const_tpt.ty);
475 fcx.write_ty(pat.id, const_tpt.ty);
477 ast::PatIdent(bm, ref name, sub) if pat_is_binding(&tcx.def_map, pat) => {
478 let typ = fcx.local_ty(pat.span, pat.id);
481 ast::BindByRef(mutbl) => {
482 // if the binding is like
483 // ref x | ref const x | ref mut x
484 // then the type of x is &M T where M is the mutability
485 // and T is the expected type
487 fcx.infcx().next_region_var(
488 infer::PatternRegion(pat.span));
489 let mt = ty::mt {ty: expected, mutbl: mutbl};
490 let region_ty = ty::mk_rptr(tcx, region_var, mt);
491 demand::eqtype(fcx, pat.span, region_ty, typ);
493 // otherwise the type of x is the expected type T
494 ast::BindByValue(_) => {
495 demand::eqtype(fcx, pat.span, expected, typ);
499 let canon_id = *pcx.map.get(&ast_util::path_to_ident(name));
500 if canon_id != pat.id {
501 let ct = fcx.local_ty(pat.span, canon_id);
502 demand::eqtype(fcx, pat.span, ct, typ);
504 fcx.write_ty(pat.id, typ);
506 debug!("(checking match) writing type for pat id {}", pat.id);
509 Some(p) => check_pat(pcx, p, expected),
513 ast::PatIdent(_, ref path, _) => {
514 check_pat_variant(pcx, pat, path, &Some(Vec::new()), expected);
516 ast::PatEnum(ref path, ref subpats) => {
517 check_pat_variant(pcx, pat, path, subpats, expected);
519 ast::PatStruct(ref path, ref fields, etc) => {
520 // Grab the class data that we care about.
521 let structure = structure_of(fcx, pat.span, expected);
522 let mut error_happened = false;
524 ty::ty_struct(cid, ref substs) => {
525 check_struct_pat(pcx, pat.id, pat.span, expected, path,
526 fields.as_slice(), etc, cid, substs);
528 ty::ty_enum(eid, ref substs) => {
529 check_struct_like_enum_variant_pat(pcx,
540 // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
541 fcx.infcx().type_error_message_str_with_expected(pat.span,
543 expected.map_or("".to_owned(), |e| {
544 format!("mismatched types: expected `{}` but found {}",
546 Some(expected), "a structure pattern".to_owned(),
548 match tcx.def_map.borrow().find(&pat.id) {
549 Some(&ast::DefStruct(supplied_def_id)) => {
550 check_struct_pat(pcx,
561 regions: ty::ErasedRegions,
564 _ => () // Error, but we're already in an error case
566 error_happened = true;
570 // Finally, write in the type.
572 fcx.write_error(pat.id);
574 fcx.write_ty(pat.id, expected);
577 ast::PatTup(ref elts) => {
578 let s = structure_of(fcx, pat.span, expected);
579 let e_count = elts.len();
581 ty::ty_tup(ref ex_elts) if e_count == ex_elts.len() => {
582 for (i, elt) in elts.iter().enumerate() {
583 check_pat(pcx, *elt, *ex_elts.get(i));
585 fcx.write_ty(pat.id, expected);
588 for elt in elts.iter() {
589 check_pat(pcx, *elt, ty::mk_err());
591 // use terr_tuple_size if both types are tuples
592 let type_error = match *s {
593 ty::ty_tup(ref ex_elts) =>
594 ty::terr_tuple_size(ty::expected_found{expected: ex_elts.len(),
596 _ => ty::terr_mismatch
598 // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
599 fcx.infcx().type_error_message_str_with_expected(pat.span, |expected, actual| {
600 expected.map_or("".to_owned(), |e| {
601 format!("mismatched types: expected `{}` but found {}",
603 Some(expected), "tuple".to_owned(), Some(&type_error));
604 fcx.write_error(pat.id);
608 ast::PatUniq(inner) => {
609 check_pointer_pat(pcx, Send, inner, pat.id, pat.span, expected);
611 ast::PatRegion(inner) => {
612 check_pointer_pat(pcx, Borrowed, inner, pat.id, pat.span, expected);
614 ast::PatVec(ref before, slice, ref after) => {
615 let default_region_var =
616 fcx.infcx().next_region_var(
617 infer::PatternRegion(pat.span));
620 for &elt in before.iter() {
621 check_pat(pcx, elt, ty::mk_err());
623 for &elt in slice.iter() {
624 check_pat(pcx, elt, ty::mk_err());
626 for &elt in after.iter() {
627 check_pat(pcx, elt, ty::mk_err());
629 // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
630 fcx.infcx().type_error_message_str_with_expected(
633 expected.map_or("".to_owned(), |e| {
634 format!("mismatched types: expected `{}` but found {}",
637 "a vector pattern".to_owned(),
639 fcx.write_error(pat.id);
642 let (elt_type, region_var, mutbl) = match *structure_of(fcx,
645 ty::ty_vec(mt, Some(_)) => (mt.ty, default_region_var, ast::MutImmutable),
646 ty::ty_uniq(t) => match ty::get(t).sty {
647 ty::ty_vec(mt, None) => {
648 fcx.type_error_message(pat.span,
650 "unique vector patterns are no \
651 longer supported".to_owned()
655 (mt.ty, default_region_var, ast::MutImmutable)
662 ty::ty_rptr(r, mt) => match ty::get(mt.ty).sty {
663 ty::ty_vec(mt, None) => (mt.ty, r, mt.mutbl),
674 for elt in before.iter() {
675 check_pat(pcx, *elt, elt_type);
679 let slice_ty = ty::mk_slice(tcx,
681 ty::mt {ty: elt_type, mutbl: mutbl});
682 check_pat(pcx, slice_pat, slice_ty);
686 for elt in after.iter() {
687 check_pat(pcx, *elt, elt_type);
689 fcx.write_ty(pat.id, expected);
694 // Helper function to check @, box and & patterns
695 pub fn check_pointer_pat(pcx: &pat_ctxt,
696 pointer_kind: PointerKind,
702 let check_inner: |ty::t| = |e_inner| {
703 check_pat(pcx, inner, e_inner);
704 fcx.write_ty(pat_id, expected);
706 match *structure_of(fcx, span, expected) {
707 ty::ty_uniq(e_inner) if pointer_kind == Send => {
708 check_inner(e_inner);
710 ty::ty_rptr(_, e_inner) if pointer_kind == Borrowed => {
711 check_inner(e_inner.ty);
714 check_pat(pcx, inner, ty::mk_err());
715 // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
716 fcx.infcx().type_error_message_str_with_expected(
719 expected.map_or("".to_owned(), |e| {
720 format!("mismatched types: expected `{}` but found {}",
723 format!("{} pattern", match pointer_kind {
725 Borrowed => "an `&`-pointer"
728 fcx.write_error(pat_id);
734 pub enum PointerKind { Send, Borrowed }