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, TypeMismatch};
15 infer::{Adjust, Adjustment, AutoBorrow},
16 lower::lower_to_chalk_mutability,
17 static_lifetime, Interner, Substitution, Ty, TyBuilder, TyExt, TyKind,
20 impl<'a> InferenceContext<'a> {
21 fn infer_tuple_struct_pat(
26 default_bm: BindingMode,
28 ellipsis: Option<usize>,
30 let (ty, def) = self.resolve_variant(path, true);
31 let var_data = def.map(|it| it.variant_data(self.db.upcast()));
32 if let Some(variant) = def {
33 self.write_variant_resolution(id.into(), variant);
35 self.unify(&ty, expected);
38 ty.as_adt().map(|(_, s)| s.clone()).unwrap_or_else(|| Substitution::empty(&Interner));
40 let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
41 let (pre, post) = match ellipsis {
42 Some(idx) => subpats.split_at(idx),
43 None => (subpats, &[][..]),
45 let post_idx_offset = field_tys.iter().count() - post.len();
47 let pre_iter = pre.iter().enumerate();
48 let post_iter = (post_idx_offset..).zip(post.iter());
49 for (i, &subpat) in pre_iter.chain(post_iter) {
50 let expected_ty = var_data
52 .and_then(|d| d.field(&Name::new_tuple_field(i)))
53 .map_or(self.err_ty(), |field| {
54 field_tys[field].clone().substitute(&Interner, &substs)
56 let expected_ty = self.normalize_associated_types_in(expected_ty);
57 self.infer_pat(subpat, &expected_ty, default_bm);
66 subpats: &[RecordFieldPat],
68 default_bm: BindingMode,
71 let (ty, def) = self.resolve_variant(path, false);
72 let var_data = def.map(|it| it.variant_data(self.db.upcast()));
73 if let Some(variant) = def {
74 self.write_variant_resolution(id.into(), variant);
77 self.unify(&ty, expected);
80 ty.as_adt().map(|(_, s)| s.clone()).unwrap_or_else(|| Substitution::empty(&Interner));
82 let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
83 for subpat in subpats {
84 let matching_field = var_data.as_ref().and_then(|it| it.field(&subpat.name));
85 let expected_ty = matching_field.map_or(self.err_ty(), |field| {
86 field_tys[field].clone().substitute(&Interner, &substs)
88 let expected_ty = self.normalize_associated_types_in(expected_ty);
89 self.infer_pat(subpat.pat, &expected_ty, default_bm);
95 pub(super) fn infer_pat(
99 mut default_bm: BindingMode,
101 let body = Arc::clone(&self.body); // avoid borrow checker problem
102 let mut expected = self.resolve_ty_shallow(expected);
104 if is_non_ref_pat(&body, pat) {
105 let mut pat_adjustments = Vec::new();
106 while let Some((inner, _lifetime, mutability)) = expected.as_reference() {
107 pat_adjustments.push(Adjustment {
108 target: expected.clone(),
109 kind: Adjust::Borrow(AutoBorrow::Ref(mutability)),
111 expected = self.resolve_ty_shallow(inner);
112 default_bm = match default_bm {
113 BindingMode::Move => BindingMode::Ref(mutability),
114 BindingMode::Ref(Mutability::Not) => BindingMode::Ref(Mutability::Not),
115 BindingMode::Ref(Mutability::Mut) => BindingMode::Ref(mutability),
119 if !pat_adjustments.is_empty() {
120 pat_adjustments.shrink_to_fit();
121 self.result.pat_adjustments.insert(pat, pat_adjustments);
123 } else if let Pat::Ref { .. } = &body[pat] {
124 cov_mark::hit!(match_ergonomics_ref);
125 // When you encounter a `&pat` pattern, reset to Move.
126 // This is so that `w` is by value: `let (_, &w) = &(1, &2);`
127 default_bm = BindingMode::Move;
131 let default_bm = default_bm;
132 let expected = expected;
134 let ty = match &body[pat] {
135 &Pat::Tuple { ref args, ellipsis } => {
136 let expectations = match expected.as_tuple() {
137 Some(parameters) => &*parameters.as_slice(&Interner),
141 let ((pre, post), n_uncovered_patterns) = match ellipsis {
143 (args.split_at(idx), expectations.len().saturating_sub(args.len()))
145 None => ((&args[..], &[][..]), 0),
147 let err_ty = self.err_ty();
148 let mut expectations_iter =
149 expectations.iter().map(|a| a.assert_ty_ref(&Interner)).chain(repeat(&err_ty));
150 let mut infer_pat = |(&pat, ty)| self.infer_pat(pat, ty, default_bm);
152 let mut inner_tys = Vec::with_capacity(n_uncovered_patterns + args.len());
153 inner_tys.extend(pre.iter().zip(expectations_iter.by_ref()).map(&mut infer_pat));
154 inner_tys.extend(expectations_iter.by_ref().take(n_uncovered_patterns).cloned());
155 inner_tys.extend(post.iter().zip(expectations_iter).map(infer_pat));
157 TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys))
160 Pat::Or(ref pats) => {
161 if let Some((first_pat, rest)) = pats.split_first() {
162 let ty = self.infer_pat(*first_pat, &expected, default_bm);
164 self.infer_pat(*pat, &expected, default_bm);
171 Pat::Ref { pat, mutability } => {
172 let mutability = lower_to_chalk_mutability(*mutability);
173 let expectation = match expected.as_reference() {
174 Some((inner_ty, _lifetime, exp_mut)) => {
175 if mutability != exp_mut {
176 // FIXME: emit type error?
180 _ => self.result.standard_types.unknown.clone(),
182 let subty = self.infer_pat(*pat, &expectation, default_bm);
183 TyKind::Ref(mutability, static_lifetime(), subty).intern(&Interner)
185 Pat::TupleStruct { path: p, args: subpats, ellipsis } => self.infer_tuple_struct_pat(
193 Pat::Record { path: p, args: fields, ellipsis: _ } => {
194 self.infer_record_pat(p.as_deref(), fields, &expected, default_bm, pat)
197 // FIXME use correct resolver for the surrounding expression
198 let resolver = self.resolver.clone();
199 self.infer_path(&resolver, path, pat.into()).unwrap_or_else(|| self.err_ty())
201 Pat::Bind { mode, name: _, subpat } => {
202 let mode = if mode == &BindingAnnotation::Unannotated {
205 BindingMode::convert(*mode)
207 let inner_ty = if let Some(subpat) = subpat {
208 self.infer_pat(*subpat, &expected, default_bm)
212 let inner_ty = self.insert_type_vars_shallow(inner_ty);
214 let bound_ty = match mode {
215 BindingMode::Ref(mutability) => {
216 TyKind::Ref(mutability, static_lifetime(), inner_ty.clone())
219 BindingMode::Move => inner_ty.clone(),
221 self.write_pat_ty(pat, bound_ty);
224 Pat::Slice { prefix, slice, suffix } => {
225 let elem_ty = match expected.kind(&Interner) {
226 TyKind::Array(st, _) | TyKind::Slice(st) => st.clone(),
230 for pat_id in prefix.iter().chain(suffix) {
231 self.infer_pat(*pat_id, &elem_ty, default_bm);
234 let pat_ty = match expected.kind(&Interner) {
235 TyKind::Array(_, const_) => TyKind::Array(elem_ty, const_.clone()),
236 _ => TyKind::Slice(elem_ty),
239 if let Some(slice_pat_id) = slice {
240 self.infer_pat(*slice_pat_id, &pat_ty, default_bm);
245 Pat::Wild => expected.clone(),
246 Pat::Range { start, end } => {
247 let start_ty = self.infer_expr(*start, &Expectation::has_type(expected.clone()));
248 let end_ty = self.infer_expr(*end, &Expectation::has_type(start_ty));
251 Pat::Lit(expr) => self.infer_expr(*expr, &Expectation::has_type(expected.clone())),
252 Pat::Box { inner } => match self.resolve_boxed_box() {
254 let (inner_ty, alloc_ty) = match expected.as_adt() {
255 Some((adt, subst)) if adt == box_adt => (
256 subst.at(&Interner, 0).assert_ty_ref(&Interner).clone(),
257 subst.as_slice(&Interner).get(1).and_then(|a| a.ty(&Interner).cloned()),
259 _ => (self.result.standard_types.unknown.clone(), None),
262 let inner_ty = self.infer_pat(*inner, &inner_ty, default_bm);
263 let mut b = TyBuilder::adt(self.db, box_adt).push(inner_ty);
265 if let Some(alloc_ty) = alloc_ty {
266 b = b.push(alloc_ty);
268 b.fill_with_defaults(self.db, || self.table.new_type_var()).build()
270 None => self.err_ty(),
272 Pat::ConstBlock(expr) => {
273 self.infer_expr(*expr, &Expectation::has_type(expected.clone()))
275 Pat::Missing => self.err_ty(),
277 // use a new type variable if we got error type here
278 let ty = self.insert_type_vars_shallow(ty);
279 if !self.unify(&ty, &expected) {
282 .insert(pat.into(), TypeMismatch { expected, actual: ty.clone() });
284 self.write_pat_ty(pat, ty.clone());
289 fn is_non_ref_pat(body: &hir_def::body::Body, pat: PatId) -> bool {
292 | Pat::TupleStruct { .. }
295 | Pat::Slice { .. } => true,
296 Pat::Or(pats) => pats.iter().all(|p| is_non_ref_pat(body, *p)),
297 // FIXME: ConstBlock/Path/Lit might actually evaluate to ref, but inference is unimplemented.
298 Pat::Path(..) => true,
299 Pat::ConstBlock(..) => true,
300 Pat::Lit(expr) => match body[*expr] {
301 Expr::Literal(Literal::String(..)) => false,
305 mode: BindingAnnotation::Mutable | BindingAnnotation::Unannotated,
306 subpat: Some(subpat),
308 } => is_non_ref_pat(body, *subpat),
309 Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Box { .. } | Pat::Missing => false,