1 //! Type inference for patterns.
6 use chalk_ir::Mutability;
8 expr::{BindingAnnotation, Expr, Literal, Pat, PatId, RecordFieldPat},
11 use hir_expand::name::Name;
13 use super::{BindingMode, Expectation, InferenceContext};
15 lower::lower_to_chalk_mutability, static_lifetime, Interner, Substitution, Ty, TyBuilder,
19 impl<'a> InferenceContext<'a> {
20 fn infer_tuple_struct_pat(
25 default_bm: BindingMode,
27 ellipsis: Option<usize>,
29 let (ty, def) = self.resolve_variant(path);
30 let var_data = def.map(|it| it.variant_data(self.db.upcast()));
31 if let Some(variant) = def {
32 self.write_variant_resolution(id.into(), variant);
34 self.unify(&ty, expected);
37 ty.as_adt().map(|(_, s)| s.clone()).unwrap_or_else(|| Substitution::empty(&Interner));
39 let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
40 let (pre, post) = match ellipsis {
41 Some(idx) => subpats.split_at(idx),
42 None => (subpats, &[][..]),
44 let post_idx_offset = field_tys.iter().count() - post.len();
46 let pre_iter = pre.iter().enumerate();
47 let post_iter = (post_idx_offset..).zip(post.iter());
48 for (i, &subpat) in pre_iter.chain(post_iter) {
49 let expected_ty = var_data
51 .and_then(|d| d.field(&Name::new_tuple_field(i)))
52 .map_or(self.err_ty(), |field| {
53 field_tys[field].clone().substitute(&Interner, &substs)
55 let expected_ty = self.normalize_associated_types_in(expected_ty);
56 self.infer_pat(subpat, &expected_ty, default_bm);
65 subpats: &[RecordFieldPat],
67 default_bm: BindingMode,
70 let (ty, def) = self.resolve_variant(path);
71 let var_data = def.map(|it| it.variant_data(self.db.upcast()));
72 if let Some(variant) = def {
73 self.write_variant_resolution(id.into(), variant);
76 self.unify(&ty, expected);
79 ty.as_adt().map(|(_, s)| s.clone()).unwrap_or_else(|| Substitution::empty(&Interner));
81 let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
82 for subpat in subpats {
83 let matching_field = var_data.as_ref().and_then(|it| it.field(&subpat.name));
84 let expected_ty = matching_field.map_or(self.err_ty(), |field| {
85 field_tys[field].clone().substitute(&Interner, &substs)
87 let expected_ty = self.normalize_associated_types_in(expected_ty);
88 self.infer_pat(subpat.pat, &expected_ty, default_bm);
94 pub(super) fn infer_pat(
98 mut default_bm: BindingMode,
100 let body = Arc::clone(&self.body); // avoid borrow checker problem
102 if is_non_ref_pat(&body, pat) {
103 while let Some((inner, _lifetime, mutability)) = expected.as_reference() {
105 default_bm = match default_bm {
106 BindingMode::Move => BindingMode::Ref(mutability),
107 BindingMode::Ref(Mutability::Not) => BindingMode::Ref(Mutability::Not),
108 BindingMode::Ref(Mutability::Mut) => BindingMode::Ref(mutability),
111 } else if let Pat::Ref { .. } = &body[pat] {
112 cov_mark::hit!(match_ergonomics_ref);
113 // When you encounter a `&pat` pattern, reset to Move.
114 // This is so that `w` is by value: `let (_, &w) = &(1, &2);`
115 default_bm = BindingMode::Move;
119 let default_bm = default_bm;
120 let expected = expected;
122 let ty = match &body[pat] {
123 &Pat::Tuple { ref args, ellipsis } => {
124 let expectations = match expected.as_tuple() {
125 Some(parameters) => &*parameters.as_slice(&Interner),
129 let (pre, post) = match ellipsis {
130 Some(idx) => args.split_at(idx),
131 None => (&args[..], &[][..]),
133 let n_uncovered_patterns = expectations.len().saturating_sub(args.len());
134 let err_ty = self.err_ty();
135 let mut expectations_iter =
136 expectations.iter().map(|a| a.assert_ty_ref(&Interner)).chain(repeat(&err_ty));
137 let mut infer_pat = |(&pat, ty)| self.infer_pat(pat, ty, default_bm);
139 let mut inner_tys = Vec::with_capacity(n_uncovered_patterns + args.len());
140 inner_tys.extend(pre.iter().zip(expectations_iter.by_ref()).map(&mut infer_pat));
141 inner_tys.extend(expectations_iter.by_ref().take(n_uncovered_patterns).cloned());
142 inner_tys.extend(post.iter().zip(expectations_iter).map(infer_pat));
144 TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys))
147 Pat::Or(ref pats) => {
148 if let Some((first_pat, rest)) = pats.split_first() {
149 let ty = self.infer_pat(*first_pat, expected, default_bm);
151 self.infer_pat(*pat, expected, default_bm);
158 Pat::Ref { pat, mutability } => {
159 let mutability = lower_to_chalk_mutability(*mutability);
160 let expectation = match expected.as_reference() {
161 Some((inner_ty, _lifetime, exp_mut)) => {
162 if mutability != exp_mut {
163 // FIXME: emit type error?
167 _ => self.result.standard_types.unknown.clone(),
169 let subty = self.infer_pat(*pat, &expectation, default_bm);
170 TyKind::Ref(mutability, static_lifetime(), subty).intern(&Interner)
172 Pat::TupleStruct { path: p, args: subpats, ellipsis } => self.infer_tuple_struct_pat(
180 Pat::Record { path: p, args: fields, ellipsis: _ } => {
181 self.infer_record_pat(p.as_deref(), fields, expected, default_bm, pat)
184 // FIXME use correct resolver for the surrounding expression
185 let resolver = self.resolver.clone();
186 self.infer_path(&resolver, &path, pat.into()).unwrap_or(self.err_ty())
188 Pat::Bind { mode, name: _, subpat } => {
189 let mode = if mode == &BindingAnnotation::Unannotated {
192 BindingMode::convert(*mode)
194 let inner_ty = if let Some(subpat) = subpat {
195 self.infer_pat(*subpat, expected, default_bm)
199 let inner_ty = self.insert_type_vars_shallow(inner_ty);
201 let bound_ty = match mode {
202 BindingMode::Ref(mutability) => {
203 TyKind::Ref(mutability, static_lifetime(), inner_ty.clone())
206 BindingMode::Move => inner_ty.clone(),
208 let bound_ty = self.resolve_ty_as_possible(bound_ty);
209 self.write_pat_ty(pat, bound_ty);
212 Pat::Slice { prefix, slice, suffix } => {
213 let elem_ty = match expected.kind(&Interner) {
214 TyKind::Array(st, _) | TyKind::Slice(st) => st.clone(),
218 for pat_id in prefix.iter().chain(suffix) {
219 self.infer_pat(*pat_id, &elem_ty, default_bm);
222 let pat_ty = match expected.kind(&Interner) {
223 TyKind::Array(_, const_) => TyKind::Array(elem_ty, const_.clone()),
224 _ => TyKind::Slice(elem_ty),
227 if let Some(slice_pat_id) = slice {
228 self.infer_pat(*slice_pat_id, &pat_ty, default_bm);
233 Pat::Wild => expected.clone(),
234 Pat::Range { start, end } => {
235 let start_ty = self.infer_expr(*start, &Expectation::has_type(expected.clone()));
236 let end_ty = self.infer_expr(*end, &Expectation::has_type(start_ty));
239 Pat::Lit(expr) => self.infer_expr(*expr, &Expectation::has_type(expected.clone())),
240 Pat::Box { inner } => match self.resolve_boxed_box() {
242 let (inner_ty, alloc_ty) = match expected.as_adt() {
243 Some((adt, subst)) if adt == box_adt => (
244 subst.at(&Interner, 0).assert_ty_ref(&Interner).clone(),
245 subst.as_slice(&Interner).get(1).and_then(|a| a.ty(&Interner).cloned()),
247 _ => (self.result.standard_types.unknown.clone(), None),
250 let inner_ty = self.infer_pat(*inner, &inner_ty, default_bm);
251 let mut b = TyBuilder::adt(self.db, box_adt).push(inner_ty);
253 if let Some(alloc_ty) = alloc_ty {
254 b = b.push(alloc_ty);
256 b.fill_with_defaults(self.db, || self.table.new_type_var()).build()
258 None => self.err_ty(),
260 Pat::ConstBlock(expr) => {
261 self.infer_expr(*expr, &Expectation::has_type(expected.clone()))
263 Pat::Missing => self.err_ty(),
265 // use a new type variable if we got error type here
266 let ty = self.insert_type_vars_shallow(ty);
267 if !self.unify(&ty, expected) {
268 // FIXME record mismatch, we need to change the type of self.type_mismatches for that
270 let ty = self.resolve_ty_as_possible(ty);
271 self.write_pat_ty(pat, ty.clone());
276 fn is_non_ref_pat(body: &hir_def::body::Body, pat: PatId) -> bool {
279 | Pat::TupleStruct { .. }
282 | Pat::Slice { .. } => true,
283 Pat::Or(pats) => pats.iter().all(|p| is_non_ref_pat(body, *p)),
284 // FIXME: ConstBlock/Path/Lit might actually evaluate to ref, but inference is unimplemented.
285 Pat::Path(..) => true,
286 Pat::ConstBlock(..) => true,
287 Pat::Lit(expr) => match body[*expr] {
288 Expr::Literal(Literal::String(..)) => false,
291 Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Box { .. } | Pat::Missing => false,