aboutsummaryrefslogtreecommitdiff
path: root/crates/hir_ty/src/infer/pat.rs
blob: b15f4977dd950f8789f519014e6c6ba367c22dfb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
//! Type inference for patterns.

use std::iter::repeat;
use std::sync::Arc;

use chalk_ir::Mutability;
use hir_def::{
    expr::{BindingAnnotation, Expr, Literal, Pat, PatId, RecordFieldPat},
    path::Path,
};
use hir_expand::name::Name;

use super::{BindingMode, Expectation, InferenceContext, TypeMismatch};
use crate::{
    lower::lower_to_chalk_mutability, static_lifetime, Interner, Substitution, Ty, TyBuilder,
    TyExt, TyKind,
};

impl<'a> InferenceContext<'a> {
    fn infer_tuple_struct_pat(
        &mut self,
        path: Option<&Path>,
        subpats: &[PatId],
        expected: &Ty,
        default_bm: BindingMode,
        id: PatId,
        ellipsis: Option<usize>,
    ) -> Ty {
        let (ty, def) = self.resolve_variant(path);
        let var_data = def.map(|it| it.variant_data(self.db.upcast()));
        if let Some(variant) = def {
            self.write_variant_resolution(id.into(), variant);
        }
        self.unify(&ty, expected);

        let substs =
            ty.as_adt().map(|(_, s)| s.clone()).unwrap_or_else(|| Substitution::empty(&Interner));

        let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
        let (pre, post) = match ellipsis {
            Some(idx) => subpats.split_at(idx),
            None => (subpats, &[][..]),
        };
        let post_idx_offset = field_tys.iter().count() - post.len();

        let pre_iter = pre.iter().enumerate();
        let post_iter = (post_idx_offset..).zip(post.iter());
        for (i, &subpat) in pre_iter.chain(post_iter) {
            let expected_ty = var_data
                .as_ref()
                .and_then(|d| d.field(&Name::new_tuple_field(i)))
                .map_or(self.err_ty(), |field| {
                    field_tys[field].clone().substitute(&Interner, &substs)
                });
            let expected_ty = self.normalize_associated_types_in(expected_ty);
            self.infer_pat(subpat, &expected_ty, default_bm);
        }

        ty
    }

    fn infer_record_pat(
        &mut self,
        path: Option<&Path>,
        subpats: &[RecordFieldPat],
        expected: &Ty,
        default_bm: BindingMode,
        id: PatId,
    ) -> Ty {
        let (ty, def) = self.resolve_variant(path);
        let var_data = def.map(|it| it.variant_data(self.db.upcast()));
        if let Some(variant) = def {
            self.write_variant_resolution(id.into(), variant);
        }

        self.unify(&ty, expected);

        let substs =
            ty.as_adt().map(|(_, s)| s.clone()).unwrap_or_else(|| Substitution::empty(&Interner));

        let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
        for subpat in subpats {
            let matching_field = var_data.as_ref().and_then(|it| it.field(&subpat.name));
            let expected_ty = matching_field.map_or(self.err_ty(), |field| {
                field_tys[field].clone().substitute(&Interner, &substs)
            });
            let expected_ty = self.normalize_associated_types_in(expected_ty);
            self.infer_pat(subpat.pat, &expected_ty, default_bm);
        }

        ty
    }

    pub(super) fn infer_pat(
        &mut self,
        pat: PatId,
        mut expected: &Ty,
        mut default_bm: BindingMode,
    ) -> Ty {
        let body = Arc::clone(&self.body); // avoid borrow checker problem

        if is_non_ref_pat(&body, pat) {
            while let Some((inner, _lifetime, mutability)) = expected.as_reference() {
                expected = inner;
                default_bm = match default_bm {
                    BindingMode::Move => BindingMode::Ref(mutability),
                    BindingMode::Ref(Mutability::Not) => BindingMode::Ref(Mutability::Not),
                    BindingMode::Ref(Mutability::Mut) => BindingMode::Ref(mutability),
                }
            }
        } else if let Pat::Ref { .. } = &body[pat] {
            cov_mark::hit!(match_ergonomics_ref);
            // When you encounter a `&pat` pattern, reset to Move.
            // This is so that `w` is by value: `let (_, &w) = &(1, &2);`
            default_bm = BindingMode::Move;
        }

        // Lose mutability.
        let default_bm = default_bm;
        let expected = expected;

        let ty = match &body[pat] {
            &Pat::Tuple { ref args, ellipsis } => {
                let expectations = match expected.as_tuple() {
                    Some(parameters) => &*parameters.as_slice(&Interner),
                    _ => &[],
                };

                let ((pre, post), n_uncovered_patterns) = match ellipsis {
                    Some(idx) => {
                        (args.split_at(idx), expectations.len().saturating_sub(args.len()))
                    }
                    None => ((&args[..], &[][..]), 0),
                };
                let err_ty = self.err_ty();
                let mut expectations_iter =
                    expectations.iter().map(|a| a.assert_ty_ref(&Interner)).chain(repeat(&err_ty));
                let mut infer_pat = |(&pat, ty)| self.infer_pat(pat, ty, default_bm);

                let mut inner_tys = Vec::with_capacity(n_uncovered_patterns + args.len());
                inner_tys.extend(pre.iter().zip(expectations_iter.by_ref()).map(&mut infer_pat));
                inner_tys.extend(expectations_iter.by_ref().take(n_uncovered_patterns).cloned());
                inner_tys.extend(post.iter().zip(expectations_iter).map(infer_pat));

                TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys))
                    .intern(&Interner)
            }
            Pat::Or(ref pats) => {
                if let Some((first_pat, rest)) = pats.split_first() {
                    let ty = self.infer_pat(*first_pat, expected, default_bm);
                    for pat in rest {
                        self.infer_pat(*pat, expected, default_bm);
                    }
                    ty
                } else {
                    self.err_ty()
                }
            }
            Pat::Ref { pat, mutability } => {
                let mutability = lower_to_chalk_mutability(*mutability);
                let expectation = match expected.as_reference() {
                    Some((inner_ty, _lifetime, exp_mut)) => {
                        if mutability != exp_mut {
                            // FIXME: emit type error?
                        }
                        inner_ty.clone()
                    }
                    _ => self.result.standard_types.unknown.clone(),
                };
                let subty = self.infer_pat(*pat, &expectation, default_bm);
                TyKind::Ref(mutability, static_lifetime(), subty).intern(&Interner)
            }
            Pat::TupleStruct { path: p, args: subpats, ellipsis } => self.infer_tuple_struct_pat(
                p.as_deref(),
                subpats,
                expected,
                default_bm,
                pat,
                *ellipsis,
            ),
            Pat::Record { path: p, args: fields, ellipsis: _ } => {
                self.infer_record_pat(p.as_deref(), fields, expected, default_bm, pat)
            }
            Pat::Path(path) => {
                // FIXME use correct resolver for the surrounding expression
                let resolver = self.resolver.clone();
                self.infer_path(&resolver, &path, pat.into()).unwrap_or(self.err_ty())
            }
            Pat::Bind { mode, name: _, subpat } => {
                let mode = if mode == &BindingAnnotation::Unannotated {
                    default_bm
                } else {
                    BindingMode::convert(*mode)
                };
                let inner_ty = if let Some(subpat) = subpat {
                    self.infer_pat(*subpat, expected, default_bm)
                } else {
                    expected.clone()
                };
                let inner_ty = self.insert_type_vars_shallow(inner_ty);

                let bound_ty = match mode {
                    BindingMode::Ref(mutability) => {
                        TyKind::Ref(mutability, static_lifetime(), inner_ty.clone())
                            .intern(&Interner)
                    }
                    BindingMode::Move => inner_ty.clone(),
                };
                let bound_ty = self.resolve_ty_as_possible(bound_ty);
                self.write_pat_ty(pat, bound_ty);
                return inner_ty;
            }
            Pat::Slice { prefix, slice, suffix } => {
                let elem_ty = match expected.kind(&Interner) {
                    TyKind::Array(st, _) | TyKind::Slice(st) => st.clone(),
                    _ => self.err_ty(),
                };

                for pat_id in prefix.iter().chain(suffix) {
                    self.infer_pat(*pat_id, &elem_ty, default_bm);
                }

                let pat_ty = match expected.kind(&Interner) {
                    TyKind::Array(_, const_) => TyKind::Array(elem_ty, const_.clone()),
                    _ => TyKind::Slice(elem_ty),
                }
                .intern(&Interner);
                if let Some(slice_pat_id) = slice {
                    self.infer_pat(*slice_pat_id, &pat_ty, default_bm);
                }

                pat_ty
            }
            Pat::Wild => expected.clone(),
            Pat::Range { start, end } => {
                let start_ty = self.infer_expr(*start, &Expectation::has_type(expected.clone()));
                let end_ty = self.infer_expr(*end, &Expectation::has_type(start_ty));
                end_ty
            }
            Pat::Lit(expr) => self.infer_expr(*expr, &Expectation::has_type(expected.clone())),
            Pat::Box { inner } => match self.resolve_boxed_box() {
                Some(box_adt) => {
                    let (inner_ty, alloc_ty) = match expected.as_adt() {
                        Some((adt, subst)) if adt == box_adt => (
                            subst.at(&Interner, 0).assert_ty_ref(&Interner).clone(),
                            subst.as_slice(&Interner).get(1).and_then(|a| a.ty(&Interner).cloned()),
                        ),
                        _ => (self.result.standard_types.unknown.clone(), None),
                    };

                    let inner_ty = self.infer_pat(*inner, &inner_ty, default_bm);
                    let mut b = TyBuilder::adt(self.db, box_adt).push(inner_ty);

                    if let Some(alloc_ty) = alloc_ty {
                        b = b.push(alloc_ty);
                    }
                    b.fill_with_defaults(self.db, || self.table.new_type_var()).build()
                }
                None => self.err_ty(),
            },
            Pat::ConstBlock(expr) => {
                self.infer_expr(*expr, &Expectation::has_type(expected.clone()))
            }
            Pat::Missing => self.err_ty(),
        };
        // use a new type variable if we got error type here
        let ty = self.insert_type_vars_shallow(ty);
        if !self.unify(&ty, expected) {
            self.result.type_mismatches.insert(
                pat.into(),
                TypeMismatch { expected: expected.clone(), actual: ty.clone() },
            );
        }
        let ty = self.resolve_ty_as_possible(ty);
        self.write_pat_ty(pat, ty.clone());
        ty
    }
}

fn is_non_ref_pat(body: &hir_def::body::Body, pat: PatId) -> bool {
    match &body[pat] {
        Pat::Tuple { .. }
        | Pat::TupleStruct { .. }
        | Pat::Record { .. }
        | Pat::Range { .. }
        | Pat::Slice { .. } => true,
        Pat::Or(pats) => pats.iter().all(|p| is_non_ref_pat(body, *p)),
        // FIXME: ConstBlock/Path/Lit might actually evaluate to ref, but inference is unimplemented.
        Pat::Path(..) => true,
        Pat::ConstBlock(..) => true,
        Pat::Lit(expr) => match body[*expr] {
            Expr::Literal(Literal::String(..)) => false,
            _ => true,
        },
        Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Box { .. } | Pat::Missing => false,
    }
}