crates/hir_ty/src/infer/pat.rs

   1 //! Type inference for patterns.
   2
   3 use std::iter::repeat;
   4 use std::sync::Arc;
   5
   6 use hir_def::{
   7     expr::{BindingAnnotation, Expr, Literal, Pat, PatId, RecordFieldPat},
   8     path::Path,
   9     type_ref::Mutability,
  10     FieldId,
  11 };
  12 use hir_expand::name::Name;
  13 use test_utils::mark;
  14
  15 use super::{BindingMode, Expectation, InferenceContext};
  16 use crate::{utils::variant_data, Substs, Ty, TypeCtor};
  17
  18 impl<'a> InferenceContext<'a> {
  19     fn infer_tuple_struct_pat(
  20         &mut self,
  21         path: Option<&Path>,
  22         subpats: &[PatId],
  23         expected: &Ty,
  24         default_bm: BindingMode,
  25         id: PatId,
  26     ) -> Ty {
  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);
  31         }
  32         self.unify(&ty, expected);
  33
  34         let substs = ty.substs().unwrap_or_else(Substs::empty);
  35
  36         let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
  37
  38         for (i, &subpat) in subpats.iter().enumerate() {
  39             let expected_ty = var_data
  40                 .as_ref()
  41                 .and_then(|d| d.field(&Name::new_tuple_field(i)))
  42                 .map_or(Ty::Unknown, |field| field_tys[field].clone().subst(&substs));
  43             let expected_ty = self.normalize_associated_types_in(expected_ty);
  44             self.infer_pat(subpat, &expected_ty, default_bm);
  45         }
  46
  47         ty
  48     }
  49
  50     fn infer_record_pat(
  51         &mut self,
  52         path: Option<&Path>,
  53         subpats: &[RecordFieldPat],
  54         expected: &Ty,
  55         default_bm: BindingMode,
  56         id: PatId,
  57     ) -> Ty {
  58         let (ty, def) = self.resolve_variant(path);
  59         let var_data = def.map(|it| variant_data(self.db.upcast(), it));
  60         if let Some(variant) = def {
  61             self.write_variant_resolution(id.into(), variant);
  62         }
  63
  64         self.unify(&ty, expected);
  65
  66         let substs = ty.substs().unwrap_or_else(Substs::empty);
  67
  68         let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
  69         for subpat in subpats {
  70             let matching_field = var_data.as_ref().and_then(|it| it.field(&subpat.name));
  71             if let Some(local_id) = matching_field {
  72                 let field_def = FieldId { parent: def.unwrap(), local_id };
  73                 self.result.record_pat_field_resolutions.insert(subpat.pat, field_def);
  74             }
  75
  76             let expected_ty =
  77                 matching_field.map_or(Ty::Unknown, |field| field_tys[field].clone().subst(&substs));
  78             let expected_ty = self.normalize_associated_types_in(expected_ty);
  79             self.infer_pat(subpat.pat, &expected_ty, default_bm);
  80         }
  81
  82         ty
  83     }
  84
  85     pub(super) fn infer_pat(
  86         &mut self,
  87         pat: PatId,
  88         mut expected: &Ty,
  89         mut default_bm: BindingMode,
  90     ) -> Ty {
  91         let body = Arc::clone(&self.body); // avoid borrow checker problem
  92
  93         if is_non_ref_pat(&body, pat) {
  94             while let Some((inner, mutability)) = expected.as_reference() {
  95                 expected = inner;
  96                 default_bm = match default_bm {
  97                     BindingMode::Move => BindingMode::Ref(mutability),
  98                     BindingMode::Ref(Mutability::Shared) => BindingMode::Ref(Mutability::Shared),
  99                     BindingMode::Ref(Mutability::Mut) => BindingMode::Ref(mutability),
 100                 }
 101             }
 102         } else if let Pat::Ref { .. } = &body[pat] {
 103             mark::hit!(match_ergonomics_ref);
 104             // When you encounter a `&pat` pattern, reset to Move.
 105             // This is so that `w` is by value: `let (_, &w) = &(1, &2);`
 106             default_bm = BindingMode::Move;
 107         }
 108
 109         // Lose mutability.
 110         let default_bm = default_bm;
 111         let expected = expected;
 112
 113         let ty = match &body[pat] {
 114             Pat::Tuple { ref args, .. } => {
 115                 let expectations = match expected.as_tuple() {
 116                     Some(parameters) => &*parameters.0,
 117                     _ => &[],
 118                 };
 119                 let expectations_iter = expectations.iter().chain(repeat(&Ty::Unknown));
 120
 121                 let inner_tys = args
 122                     .iter()
 123                     .zip(expectations_iter)
 124                     .map(|(&pat, ty)| self.infer_pat(pat, ty, default_bm))
 125                     .collect();
 126
 127                 Ty::apply(TypeCtor::Tuple { cardinality: args.len() as u16 }, Substs(inner_tys))
 128             }
 129             Pat::Or(ref pats) => {
 130                 if let Some((first_pat, rest)) = pats.split_first() {
 131                     let ty = self.infer_pat(*first_pat, expected, default_bm);
 132                     for pat in rest {
 133                         self.infer_pat(*pat, expected, default_bm);
 134                     }
 135                     ty
 136                 } else {
 137                     Ty::Unknown
 138                 }
 139             }
 140             Pat::Ref { pat, mutability } => {
 141                 let expectation = match expected.as_reference() {
 142                     Some((inner_ty, exp_mut)) => {
 143                         if *mutability != exp_mut {
 144                             // FIXME: emit type error?
 145                         }
 146                         inner_ty
 147                     }
 148                     _ => &Ty::Unknown,
 149                 };
 150                 let subty = self.infer_pat(*pat, expectation, default_bm);
 151                 Ty::apply_one(TypeCtor::Ref(*mutability), subty)
 152             }
 153             Pat::TupleStruct { path: p, args: subpats, .. } => {
 154                 self.infer_tuple_struct_pat(p.as_ref(), subpats, expected, default_bm, pat)
 155             }
 156             Pat::Record { path: p, args: fields, ellipsis: _ } => {
 157                 self.infer_record_pat(p.as_ref(), fields, expected, default_bm, pat)
 158             }
 159             Pat::Path(path) => {
 160                 // FIXME use correct resolver for the surrounding expression
 161                 let resolver = self.resolver.clone();
 162                 self.infer_path(&resolver, &path, pat.into()).unwrap_or(Ty::Unknown)
 163             }
 164             Pat::Bind { mode, name: _, subpat } => {
 165                 let mode = if mode == &BindingAnnotation::Unannotated {
 166                     default_bm
 167                 } else {
 168                     BindingMode::convert(*mode)
 169                 };
 170                 let inner_ty = if let Some(subpat) = subpat {
 171                     self.infer_pat(*subpat, expected, default_bm)
 172                 } else {
 173                     expected.clone()
 174                 };
 175                 let inner_ty = self.insert_type_vars_shallow(inner_ty);
 176
 177                 let bound_ty = match mode {
 178                     BindingMode::Ref(mutability) => {
 179                         Ty::apply_one(TypeCtor::Ref(mutability), inner_ty.clone())
 180                     }
 181                     BindingMode::Move => inner_ty.clone(),
 182                 };
 183                 let bound_ty = self.resolve_ty_as_possible(bound_ty);
 184                 self.write_pat_ty(pat, bound_ty);
 185                 return inner_ty;
 186             }
 187             Pat::Slice { prefix, slice, suffix } => {
 188                 let (container_ty, elem_ty) = match &expected {
 189                     ty_app!(TypeCtor::Array, st) => (TypeCtor::Array, st.as_single().clone()),
 190                     ty_app!(TypeCtor::Slice, st) => (TypeCtor::Slice, st.as_single().clone()),
 191                     _ => (TypeCtor::Slice, Ty::Unknown),
 192                 };
 193
 194                 for pat_id in prefix.iter().chain(suffix) {
 195                     self.infer_pat(*pat_id, &elem_ty, default_bm);
 196                 }
 197
 198                 let pat_ty = Ty::apply_one(container_ty, elem_ty);
 199                 if let Some(slice_pat_id) = slice {
 200                     self.infer_pat(*slice_pat_id, &pat_ty, default_bm);
 201                 }
 202
 203                 pat_ty
 204             }
 205             Pat::Wild => expected.clone(),
 206             Pat::Range { start, end } => {
 207                 let start_ty = self.infer_expr(*start, &Expectation::has_type(expected.clone()));
 208                 let end_ty = self.infer_expr(*end, &Expectation::has_type(start_ty));
 209                 end_ty
 210             }
 211             Pat::Lit(expr) => self.infer_expr(*expr, &Expectation::has_type(expected.clone())),
 212             Pat::Box { inner } => match self.resolve_boxed_box() {
 213                 Some(box_adt) => {
 214                     let inner_expected = match expected.as_adt() {
 215                         Some((adt, substs)) if adt == box_adt => substs.as_single(),
 216                         _ => &Ty::Unknown,
 217                     };
 218
 219                     let inner_ty = self.infer_pat(*inner, inner_expected, default_bm);
 220                     Ty::apply_one(TypeCtor::Adt(box_adt), inner_ty)
 221                 }
 222                 None => Ty::Unknown,
 223             },
 224             Pat::Missing => Ty::Unknown,
 225         };
 226         // use a new type variable if we got Ty::Unknown here
 227         let ty = self.insert_type_vars_shallow(ty);
 228         if !self.unify(&ty, expected) {
 229             // FIXME record mismatch, we need to change the type of self.type_mismatches for that
 230         }
 231         let ty = self.resolve_ty_as_possible(ty);
 232         self.write_pat_ty(pat, ty.clone());
 233         ty
 234     }
 235 }
 236
 237 fn is_non_ref_pat(body: &hir_def::body::Body, pat: PatId) -> bool {
 238     match &body[pat] {
 239         Pat::Tuple { .. }
 240         | Pat::TupleStruct { .. }
 241         | Pat::Record { .. }
 242         | Pat::Range { .. }
 243         | Pat::Slice { .. } => true,
 244         Pat::Or(pats) => pats.iter().all(|p| is_non_ref_pat(body, *p)),
 245         // FIXME: Path/Lit might actually evaluate to ref, but inference is unimplemented.
 246         Pat::Path(..) => true,
 247         Pat::Lit(expr) => match body[*expr] {
 248             Expr::Literal(Literal::String(..)) => false,
 249             _ => true,
 250         },
 251         Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Box { .. } | Pat::Missing => false,
 252     }
 253 }