1 //! Type inference for patterns.
6 use chalk_ir::Mutability;
8 expr::{BindingAnnotation, Expr, Literal, Pat, PatId, RecordFieldPat},
12 use hir_expand::name::Name;
14 use super::{BindingMode, Expectation, InferenceContext};
15 use crate::{lower::lower_to_chalk_mutability, utils::variant_data, Interner, Substs, Ty, TyKind};
17 impl<'a> InferenceContext<'a> {
18 fn infer_tuple_struct_pat(
23 default_bm: BindingMode,
25 ellipsis: Option<usize>,
27 let (ty, def) = self.resolve_variant(path);
28 let var_data = def.map(|it| variant_data(self.db.upcast(), it));
29 if let Some(variant) = def {
30 self.write_variant_resolution(id.into(), variant);
32 self.unify(&ty, expected);
34 let substs = ty.substs().cloned().unwrap_or_else(Substs::empty);
36 let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
37 let (pre, post) = match ellipsis {
38 Some(idx) => subpats.split_at(idx),
39 None => (&subpats[..], &[][..]),
41 let post_idx_offset = field_tys.iter().count() - post.len();
43 let pre_iter = pre.iter().enumerate();
44 let post_iter = (post_idx_offset..).zip(post.iter());
45 for (i, &subpat) in pre_iter.chain(post_iter) {
46 let expected_ty = var_data
48 .and_then(|d| d.field(&Name::new_tuple_field(i)))
49 .map_or(self.err_ty(), |field| field_tys[field].clone().subst(&substs));
50 let expected_ty = self.normalize_associated_types_in(expected_ty);
51 self.infer_pat(subpat, &expected_ty, default_bm);
60 subpats: &[RecordFieldPat],
62 default_bm: BindingMode,
65 let (ty, def) = self.resolve_variant(path);
66 let var_data = def.map(|it| variant_data(self.db.upcast(), it));
67 if let Some(variant) = def {
68 self.write_variant_resolution(id.into(), variant);
71 self.unify(&ty, expected);
73 let substs = ty.substs().cloned().unwrap_or_else(Substs::empty);
75 let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
76 for subpat in subpats {
77 let matching_field = var_data.as_ref().and_then(|it| it.field(&subpat.name));
78 if let Some(local_id) = matching_field {
79 let field_def = FieldId { parent: def.unwrap(), local_id };
80 self.result.record_pat_field_resolutions.insert(subpat.pat, field_def);
83 let expected_ty = matching_field
84 .map_or(self.err_ty(), |field| field_tys[field].clone().subst(&substs));
85 let expected_ty = self.normalize_associated_types_in(expected_ty);
86 self.infer_pat(subpat.pat, &expected_ty, default_bm);
92 pub(super) fn infer_pat(
96 mut default_bm: BindingMode,
98 let body = Arc::clone(&self.body); // avoid borrow checker problem
100 if is_non_ref_pat(&body, pat) {
101 while let Some((inner, mutability)) = expected.as_reference() {
103 default_bm = match default_bm {
104 BindingMode::Move => BindingMode::Ref(mutability),
105 BindingMode::Ref(Mutability::Not) => BindingMode::Ref(Mutability::Not),
106 BindingMode::Ref(Mutability::Mut) => BindingMode::Ref(mutability),
109 } else if let Pat::Ref { .. } = &body[pat] {
110 cov_mark::hit!(match_ergonomics_ref);
111 // When you encounter a `&pat` pattern, reset to Move.
112 // This is so that `w` is by value: `let (_, &w) = &(1, &2);`
113 default_bm = BindingMode::Move;
117 let default_bm = default_bm;
118 let expected = expected;
120 let ty = match &body[pat] {
121 &Pat::Tuple { ref args, ellipsis } => {
122 let expectations = match expected.as_tuple() {
123 Some(parameters) => &*parameters.0,
127 let (pre, post) = match ellipsis {
128 Some(idx) => args.split_at(idx),
129 None => (&args[..], &[][..]),
131 let n_uncovered_patterns = expectations.len().saturating_sub(args.len());
132 let err_ty = self.err_ty();
133 let mut expectations_iter = expectations.iter().chain(repeat(&err_ty));
134 let mut infer_pat = |(&pat, ty)| self.infer_pat(pat, ty, default_bm);
136 let mut inner_tys = Vec::with_capacity(n_uncovered_patterns + args.len());
137 inner_tys.extend(pre.iter().zip(expectations_iter.by_ref()).map(&mut infer_pat));
138 inner_tys.extend(expectations_iter.by_ref().take(n_uncovered_patterns).cloned());
139 inner_tys.extend(post.iter().zip(expectations_iter).map(infer_pat));
141 TyKind::Tuple(inner_tys.len(), Substs(inner_tys.into())).intern(&Interner)
143 Pat::Or(ref pats) => {
144 if let Some((first_pat, rest)) = pats.split_first() {
145 let ty = self.infer_pat(*first_pat, expected, default_bm);
147 self.infer_pat(*pat, expected, default_bm);
154 Pat::Ref { pat, mutability } => {
155 let mutability = lower_to_chalk_mutability(*mutability);
156 let expectation = match expected.as_reference() {
157 Some((inner_ty, exp_mut)) => {
158 if mutability != exp_mut {
159 // FIXME: emit type error?
163 _ => &Ty(TyKind::Unknown),
165 let subty = self.infer_pat(*pat, expectation, default_bm);
166 TyKind::Ref(mutability, Substs::single(subty)).intern(&Interner)
168 Pat::TupleStruct { path: p, args: subpats, ellipsis } => self.infer_tuple_struct_pat(
176 Pat::Record { path: p, args: fields, ellipsis: _ } => {
177 self.infer_record_pat(p.as_ref(), fields, expected, default_bm, pat)
180 // FIXME use correct resolver for the surrounding expression
181 let resolver = self.resolver.clone();
182 self.infer_path(&resolver, &path, pat.into()).unwrap_or(self.err_ty())
184 Pat::Bind { mode, name: _, subpat } => {
185 let mode = if mode == &BindingAnnotation::Unannotated {
188 BindingMode::convert(*mode)
190 let inner_ty = if let Some(subpat) = subpat {
191 self.infer_pat(*subpat, expected, default_bm)
195 let inner_ty = self.insert_type_vars_shallow(inner_ty);
197 let bound_ty = match mode {
198 BindingMode::Ref(mutability) => {
199 TyKind::Ref(mutability, Substs::single(inner_ty.clone())).intern(&Interner)
201 BindingMode::Move => inner_ty.clone(),
203 let bound_ty = self.resolve_ty_as_possible(bound_ty);
204 self.write_pat_ty(pat, bound_ty);
207 Pat::Slice { prefix, slice, suffix } => {
208 let (container_ty, elem_ty): (fn(_) -> _, _) = match expected.interned(&Interner) {
209 TyKind::Array(st) => (TyKind::Array, st.as_single().clone()),
210 TyKind::Slice(st) => (TyKind::Slice, st.as_single().clone()),
211 _ => (TyKind::Slice, self.err_ty()),
214 for pat_id in prefix.iter().chain(suffix) {
215 self.infer_pat(*pat_id, &elem_ty, default_bm);
218 let pat_ty = container_ty(Substs::single(elem_ty)).intern(&Interner);
219 if let Some(slice_pat_id) = slice {
220 self.infer_pat(*slice_pat_id, &pat_ty, default_bm);
225 Pat::Wild => expected.clone(),
226 Pat::Range { start, end } => {
227 let start_ty = self.infer_expr(*start, &Expectation::has_type(expected.clone()));
228 let end_ty = self.infer_expr(*end, &Expectation::has_type(start_ty));
231 Pat::Lit(expr) => self.infer_expr(*expr, &Expectation::has_type(expected.clone())),
232 Pat::Box { inner } => match self.resolve_boxed_box() {
234 let inner_expected = match expected.as_adt() {
235 Some((adt, substs)) if adt == box_adt => substs.as_single(),
236 _ => &Ty(TyKind::Unknown),
239 let inner_ty = self.infer_pat(*inner, inner_expected, default_bm);
240 Ty::adt_ty(box_adt, Substs::single(inner_ty))
242 None => self.err_ty(),
244 Pat::ConstBlock(expr) => {
245 self.infer_expr(*expr, &Expectation::has_type(expected.clone()))
247 Pat::Missing => self.err_ty(),
249 // use a new type variable if we got error type here
250 let ty = self.insert_type_vars_shallow(ty);
251 if !self.unify(&ty, expected) {
252 // FIXME record mismatch, we need to change the type of self.type_mismatches for that
254 let ty = self.resolve_ty_as_possible(ty);
255 self.write_pat_ty(pat, ty.clone());
260 fn is_non_ref_pat(body: &hir_def::body::Body, pat: PatId) -> bool {
263 | Pat::TupleStruct { .. }
266 | Pat::Slice { .. } => true,
267 Pat::Or(pats) => pats.iter().all(|p| is_non_ref_pat(body, *p)),
268 // FIXME: ConstBlock/Path/Lit might actually evaluate to ref, but inference is unimplemented.
269 Pat::Path(..) => true,
270 Pat::ConstBlock(..) => true,
271 Pat::Lit(expr) => match body[*expr] {
272 Expr::Literal(Literal::String(..)) => false,
275 Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Box { .. } | Pat::Missing => false,