crates/hir_ty/src/infer/expr.rs

   1 //! Type inference for expressions.
   2
   3 use std::iter::{repeat, repeat_with};
   4 use std::{mem, sync::Arc};
   5
   6 use hir_def::{
   7     builtin_type::Signedness,
   8     expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
   9     path::{GenericArg, GenericArgs},
  10     resolver::resolver_for_expr,
  11     AdtId, AssocContainerId, FieldId, Lookup,
  12 };
  13 use hir_expand::name::{name, Name};
  14 use syntax::ast::RangeOp;
  15 use test_utils::mark;
  16
  17 use crate::{
  18     autoderef, method_resolution, op,
  19     traits::{FnTrait, InEnvironment},
  20     utils::{generics, variant_data, Generics},
  21     ApplicationTy, Binders, CallableDefId, InferTy, IntTy, Mutability, Obligation, OpaqueTyId,
  22     Rawness, Substs, TraitRef, Ty, TypeCtor,
  23 };
  24
  25 use super::{
  26     find_breakable, BindingMode, BreakableContext, Diverges, Expectation, InferenceContext,
  27     InferenceDiagnostic, TypeMismatch,
  28 };
  29
  30 impl<'a> InferenceContext<'a> {
  31     pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
  32         let ty = self.infer_expr_inner(tgt_expr, expected);
  33         if ty.is_never() {
  34             // Any expression that produces a value of type `!` must have diverged
  35             self.diverges = Diverges::Always;
  36         }
  37         let could_unify = self.unify(&ty, &expected.ty);
  38         if !could_unify {
  39             self.result.type_mismatches.insert(
  40                 tgt_expr,
  41                 TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() },
  42             );
  43         }
  44         self.resolve_ty_as_possible(ty)
  45     }
  46
  47     /// Infer type of expression with possibly implicit coerce to the expected type.
  48     /// Return the type after possible coercion.
  49     pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
  50         let ty = self.infer_expr_inner(expr, &expected);
  51         let ty = if !self.coerce(&ty, &expected.coercion_target()) {
  52             self.result
  53                 .type_mismatches
  54                 .insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() });
  55             // Return actual type when type mismatch.
  56             // This is needed for diagnostic when return type mismatch.
  57             ty
  58         } else if expected.coercion_target() == &Ty::Unknown {
  59             ty
  60         } else {
  61             expected.ty.clone()
  62         };
  63
  64         self.resolve_ty_as_possible(ty)
  65     }
  66
  67     fn callable_sig_from_fn_trait(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
  68         let krate = self.resolver.krate()?;
  69         let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
  70         let output_assoc_type =
  71             self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
  72         let generic_params = generics(self.db.upcast(), fn_once_trait.into());
  73         if generic_params.len() != 2 {
  74             return None;
  75         }
  76
  77         let mut param_builder = Substs::builder(num_args);
  78         let mut arg_tys = vec![];
  79         for _ in 0..num_args {
  80             let arg = self.table.new_type_var();
  81             param_builder = param_builder.push(arg.clone());
  82             arg_tys.push(arg);
  83         }
  84         let parameters = param_builder.build();
  85         let arg_ty = Ty::Apply(ApplicationTy {
  86             ctor: TypeCtor::Tuple { cardinality: num_args as u16 },
  87             parameters,
  88         });
  89         let substs =
  90             Substs::build_for_generics(&generic_params).push(ty.clone()).push(arg_ty).build();
  91
  92         let trait_env = Arc::clone(&self.trait_env);
  93         let implements_fn_trait =
  94             Obligation::Trait(TraitRef { trait_: fn_once_trait, substs: substs.clone() });
  95         let goal = self.canonicalizer().canonicalize_obligation(InEnvironment {
  96             value: implements_fn_trait.clone(),
  97             environment: trait_env,
  98         });
  99         if self.db.trait_solve(krate, goal.value).is_some() {
 100             self.obligations.push(implements_fn_trait);
 101             let output_proj_ty =
 102                 crate::ProjectionTy { associated_ty: output_assoc_type, parameters: substs };
 103             let return_ty = self.normalize_projection_ty(output_proj_ty);
 104             Some((arg_tys, return_ty))
 105         } else {
 106             None
 107         }
 108     }
 109
 110     pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
 111         match ty.callable_sig(self.db) {
 112             Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
 113             None => self.callable_sig_from_fn_trait(ty, num_args),
 114         }
 115     }
 116
 117     fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
 118         let body = Arc::clone(&self.body); // avoid borrow checker problem
 119         let ty = match &body[tgt_expr] {
 120             Expr::Missing => Ty::Unknown,
 121             Expr::If { condition, then_branch, else_branch } => {
 122                 // if let is desugared to match, so this is always simple if
 123                 self.infer_expr(*condition, &Expectation::has_type(Ty::simple(TypeCtor::Bool)));
 124
 125                 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 126                 let mut both_arms_diverge = Diverges::Always;
 127
 128                 let then_ty = self.infer_expr_inner(*then_branch, &expected);
 129                 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
 130                 let else_ty = match else_branch {
 131                     Some(else_branch) => self.infer_expr_inner(*else_branch, &expected),
 132                     None => Ty::unit(),
 133                 };
 134                 both_arms_diverge &= self.diverges;
 135
 136                 self.diverges = condition_diverges | both_arms_diverge;
 137
 138                 self.coerce_merge_branch(&then_ty, &else_ty)
 139             }
 140             Expr::Block { statements, tail, label } => match label {
 141                 Some(_) => {
 142                     let break_ty = self.table.new_type_var();
 143                     self.breakables.push(BreakableContext {
 144                         may_break: false,
 145                         break_ty: break_ty.clone(),
 146                         label: label.map(|label| self.body[label].name.clone()),
 147                     });
 148                     let ty = self.infer_block(statements, *tail, &Expectation::has_type(break_ty));
 149                     let ctxt = self.breakables.pop().expect("breakable stack broken");
 150                     if ctxt.may_break {
 151                         ctxt.break_ty
 152                     } else {
 153                         ty
 154                     }
 155                 }
 156                 None => self.infer_block(statements, *tail, expected),
 157             },
 158             Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
 159             Expr::TryBlock { body } => {
 160                 let _inner = self.infer_expr(*body, expected);
 161                 // FIXME should be std::result::Result<{inner}, _>
 162                 Ty::Unknown
 163             }
 164             Expr::Async { body } => {
 165                 // Use the first type parameter as the output type of future.
 166                 // existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
 167                 let inner_ty = self.infer_expr(*body, &Expectation::none());
 168                 let opaque_ty_id = OpaqueTyId::AsyncBlockTypeImplTrait(self.owner, *body);
 169                 Ty::apply_one(TypeCtor::OpaqueType(opaque_ty_id), inner_ty)
 170             }
 171             Expr::Loop { body, label } => {
 172                 self.breakables.push(BreakableContext {
 173                     may_break: false,
 174                     break_ty: self.table.new_type_var(),
 175                     label: label.map(|label| self.body[label].name.clone()),
 176                 });
 177                 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
 178
 179                 let ctxt = self.breakables.pop().expect("breakable stack broken");
 180                 if ctxt.may_break {
 181                     self.diverges = Diverges::Maybe;
 182                 }
 183
 184                 if ctxt.may_break {
 185                     ctxt.break_ty
 186                 } else {
 187                     Ty::simple(TypeCtor::Never)
 188                 }
 189             }
 190             Expr::While { condition, body, label } => {
 191                 self.breakables.push(BreakableContext {
 192                     may_break: false,
 193                     break_ty: Ty::Unknown,
 194                     label: label.map(|label| self.body[label].name.clone()),
 195                 });
 196                 // while let is desugared to a match loop, so this is always simple while
 197                 self.infer_expr(*condition, &Expectation::has_type(Ty::simple(TypeCtor::Bool)));
 198                 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
 199                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 200                 // the body may not run, so it diverging doesn't mean we diverge
 201                 self.diverges = Diverges::Maybe;
 202                 Ty::unit()
 203             }
 204             Expr::For { iterable, body, pat, label } => {
 205                 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
 206
 207                 self.breakables.push(BreakableContext {
 208                     may_break: false,
 209                     break_ty: Ty::Unknown,
 210                     label: label.map(|label| self.body[label].name.clone()),
 211                 });
 212                 let pat_ty =
 213                     self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
 214
 215                 self.infer_pat(*pat, &pat_ty, BindingMode::default());
 216
 217                 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
 218                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 219                 // the body may not run, so it diverging doesn't mean we diverge
 220                 self.diverges = Diverges::Maybe;
 221                 Ty::unit()
 222             }
 223             Expr::Lambda { body, args, ret_type, arg_types } => {
 224                 assert_eq!(args.len(), arg_types.len());
 225
 226                 let mut sig_tys = Vec::new();
 227
 228                 // collect explicitly written argument types
 229                 for arg_type in arg_types.iter() {
 230                     let arg_ty = if let Some(type_ref) = arg_type {
 231                         self.make_ty(type_ref)
 232                     } else {
 233                         self.table.new_type_var()
 234                     };
 235                     sig_tys.push(arg_ty);
 236                 }
 237
 238                 // add return type
 239                 let ret_ty = match ret_type {
 240                     Some(type_ref) => self.make_ty(type_ref),
 241                     None => self.table.new_type_var(),
 242                 };
 243                 sig_tys.push(ret_ty.clone());
 244                 let sig_ty = Ty::apply(
 245                     TypeCtor::FnPtr { num_args: sig_tys.len() as u16 - 1, is_varargs: false },
 246                     Substs(sig_tys.clone().into()),
 247                 );
 248                 let closure_ty =
 249                     Ty::apply_one(TypeCtor::Closure { def: self.owner, expr: tgt_expr }, sig_ty);
 250
 251                 // Eagerly try to relate the closure type with the expected
 252                 // type, otherwise we often won't have enough information to
 253                 // infer the body.
 254                 self.coerce(&closure_ty, &expected.ty);
 255
 256                 // Now go through the argument patterns
 257                 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
 258                     let resolved = self.resolve_ty_as_possible(arg_ty);
 259                     self.infer_pat(*arg_pat, &resolved, BindingMode::default());
 260                 }
 261
 262                 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 263                 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
 264
 265                 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
 266
 267                 self.diverges = prev_diverges;
 268                 self.return_ty = prev_ret_ty;
 269
 270                 closure_ty
 271             }
 272             Expr::Call { callee, args } => {
 273                 let callee_ty = self.infer_expr(*callee, &Expectation::none());
 274                 let canonicalized = self.canonicalizer().canonicalize_ty(callee_ty.clone());
 275                 let mut derefs = autoderef(
 276                     self.db,
 277                     self.resolver.krate(),
 278                     InEnvironment {
 279                         value: canonicalized.value.clone(),
 280                         environment: self.trait_env.clone(),
 281                     },
 282                 );
 283                 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
 284                     .find_map(|callee_deref_ty| {
 285                         self.callable_sig(
 286                             &canonicalized.decanonicalize_ty(callee_deref_ty.value),
 287                             args.len(),
 288                         )
 289                     })
 290                     .unwrap_or((Vec::new(), Ty::Unknown));
 291                 self.register_obligations_for_call(&callee_ty);
 292                 self.check_call_arguments(args, &param_tys);
 293                 self.normalize_associated_types_in(ret_ty)
 294             }
 295             Expr::MethodCall { receiver, args, method_name, generic_args } => self
 296                 .infer_method_call(tgt_expr, *receiver, &args, &method_name, generic_args.as_ref()),
 297             Expr::Match { expr, arms } => {
 298                 let input_ty = self.infer_expr(*expr, &Expectation::none());
 299
 300                 let mut result_ty = if arms.is_empty() {
 301                     Ty::simple(TypeCtor::Never)
 302                 } else {
 303                     self.table.new_type_var()
 304                 };
 305
 306                 let matchee_diverges = self.diverges;
 307                 let mut all_arms_diverge = Diverges::Always;
 308
 309                 for arm in arms {
 310                     self.diverges = Diverges::Maybe;
 311                     let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
 312                     if let Some(guard_expr) = arm.guard {
 313                         self.infer_expr(
 314                             guard_expr,
 315                             &Expectation::has_type(Ty::simple(TypeCtor::Bool)),
 316                         );
 317                     }
 318
 319                     let arm_ty = self.infer_expr_inner(arm.expr, &expected);
 320                     all_arms_diverge &= self.diverges;
 321                     result_ty = self.coerce_merge_branch(&result_ty, &arm_ty);
 322                 }
 323
 324                 self.diverges = matchee_diverges | all_arms_diverge;
 325
 326                 result_ty
 327             }
 328             Expr::Path(p) => {
 329                 // FIXME this could be more efficient...
 330                 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
 331                 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(Ty::Unknown)
 332             }
 333             Expr::Continue { .. } => Ty::simple(TypeCtor::Never),
 334             Expr::Break { expr, label } => {
 335                 let val_ty = if let Some(expr) = expr {
 336                     self.infer_expr(*expr, &Expectation::none())
 337                 } else {
 338                     Ty::unit()
 339                 };
 340
 341                 let last_ty =
 342                     if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
 343                         ctxt.break_ty.clone()
 344                     } else {
 345                         Ty::Unknown
 346                     };
 347
 348                 let merged_type = self.coerce_merge_branch(&last_ty, &val_ty);
 349
 350                 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
 351                     ctxt.break_ty = merged_type;
 352                     ctxt.may_break = true;
 353                 } else {
 354                     self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
 355                         expr: tgt_expr,
 356                     });
 357                 }
 358
 359                 Ty::simple(TypeCtor::Never)
 360             }
 361             Expr::Return { expr } => {
 362                 if let Some(expr) = expr {
 363                     self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
 364                 } else {
 365                     let unit = Ty::unit();
 366                     self.coerce(&unit, &self.return_ty.clone());
 367                 }
 368                 Ty::simple(TypeCtor::Never)
 369             }
 370             Expr::Yield { expr } => {
 371                 // FIXME: track yield type for coercion
 372                 if let Some(expr) = expr {
 373                     self.infer_expr(*expr, &Expectation::none());
 374                 }
 375                 Ty::simple(TypeCtor::Never)
 376             }
 377             Expr::RecordLit { path, fields, spread } => {
 378                 let (ty, def_id) = self.resolve_variant(path.as_ref());
 379                 if let Some(variant) = def_id {
 380                     self.write_variant_resolution(tgt_expr.into(), variant);
 381                 }
 382
 383                 self.unify(&ty, &expected.ty);
 384
 385                 let substs = ty.substs().unwrap_or_else(Substs::empty);
 386                 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
 387                 let variant_data = def_id.map(|it| variant_data(self.db.upcast(), it));
 388                 for (field_idx, field) in fields.iter().enumerate() {
 389                     let field_def =
 390                         variant_data.as_ref().and_then(|it| match it.field(&field.name) {
 391                             Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
 392                             None => {
 393                                 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
 394                                     expr: tgt_expr,
 395                                     field: field_idx,
 396                                 });
 397                                 None
 398                             }
 399                         });
 400                     if let Some(field_def) = field_def {
 401                         self.result.record_field_resolutions.insert(field.expr, field_def);
 402                     }
 403                     let field_ty = field_def
 404                         .map_or(Ty::Unknown, |it| field_types[it.local_id].clone().subst(&substs));
 405                     self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
 406                 }
 407                 if let Some(expr) = spread {
 408                     self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
 409                 }
 410                 ty
 411             }
 412             Expr::Field { expr, name } => {
 413                 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
 414                 let canonicalized = self.canonicalizer().canonicalize_ty(receiver_ty);
 415                 let ty = autoderef::autoderef(
 416                     self.db,
 417                     self.resolver.krate(),
 418                     InEnvironment {
 419                         value: canonicalized.value.clone(),
 420                         environment: self.trait_env.clone(),
 421                     },
 422                 )
 423                 .find_map(|derefed_ty| match canonicalized.decanonicalize_ty(derefed_ty.value) {
 424                     Ty::Apply(a_ty) => match a_ty.ctor {
 425                         TypeCtor::Tuple { .. } => name
 426                             .as_tuple_index()
 427                             .and_then(|idx| a_ty.parameters.0.get(idx).cloned()),
 428                         TypeCtor::Adt(AdtId::StructId(s)) => {
 429                             self.db.struct_data(s).variant_data.field(name).map(|local_id| {
 430                                 let field = FieldId { parent: s.into(), local_id };
 431                                 self.write_field_resolution(tgt_expr, field);
 432                                 self.db.field_types(s.into())[field.local_id]
 433                                     .clone()
 434                                     .subst(&a_ty.parameters)
 435                             })
 436                         }
 437                         TypeCtor::Adt(AdtId::UnionId(u)) => {
 438                             self.db.union_data(u).variant_data.field(name).map(|local_id| {
 439                                 let field = FieldId { parent: u.into(), local_id };
 440                                 self.write_field_resolution(tgt_expr, field);
 441                                 self.db.field_types(u.into())[field.local_id]
 442                                     .clone()
 443                                     .subst(&a_ty.parameters)
 444                             })
 445                         }
 446                         _ => None,
 447                     },
 448                     _ => None,
 449                 })
 450                 .unwrap_or(Ty::Unknown);
 451                 let ty = self.insert_type_vars(ty);
 452                 self.normalize_associated_types_in(ty)
 453             }
 454             Expr::Await { expr } => {
 455                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 456                 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
 457             }
 458             Expr::Try { expr } => {
 459                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 460                 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
 461             }
 462             Expr::Cast { expr, type_ref } => {
 463                 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 464                 let cast_ty = self.make_ty(type_ref);
 465                 // FIXME check the cast...
 466                 cast_ty
 467             }
 468             Expr::Ref { expr, rawness, mutability } => {
 469                 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) =
 470                     &expected.ty.as_reference_or_ptr()
 471                 {
 472                     if *exp_mutability == Mutability::Mut && *mutability == Mutability::Shared {
 473                         // FIXME: throw type error - expected mut reference but found shared ref,
 474                         // which cannot be coerced
 475                     }
 476                     if *exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
 477                         // FIXME: throw type error - expected reference but found ptr,
 478                         // which cannot be coerced
 479                     }
 480                     Expectation::rvalue_hint(Ty::clone(exp_inner))
 481                 } else {
 482                     Expectation::none()
 483                 };
 484                 let inner_ty = self.infer_expr_inner(*expr, &expectation);
 485                 let ty = match rawness {
 486                     Rawness::RawPtr => TypeCtor::RawPtr(*mutability),
 487                     Rawness::Ref => TypeCtor::Ref(*mutability),
 488                 };
 489                 Ty::apply_one(ty, inner_ty)
 490             }
 491             Expr::Box { expr } => {
 492                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 493                 if let Some(box_) = self.resolve_boxed_box() {
 494                     let mut sb = Substs::build_for_type_ctor(self.db, TypeCtor::Adt(box_));
 495                     sb = sb.push(inner_ty);
 496                     sb = sb.fill(repeat_with(|| self.table.new_type_var()));
 497                     Ty::apply(TypeCtor::Adt(box_), sb.build())
 498                 } else {
 499                     Ty::Unknown
 500                 }
 501             }
 502             Expr::UnaryOp { expr, op } => {
 503                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 504                 match op {
 505                     UnaryOp::Deref => match self.resolver.krate() {
 506                         Some(krate) => {
 507                             let canonicalized = self.canonicalizer().canonicalize_ty(inner_ty);
 508                             match autoderef::deref(
 509                                 self.db,
 510                                 krate,
 511                                 InEnvironment {
 512                                     value: &canonicalized.value,
 513                                     environment: self.trait_env.clone(),
 514                                 },
 515                             ) {
 516                                 Some(derefed_ty) => {
 517                                     canonicalized.decanonicalize_ty(derefed_ty.value)
 518                                 }
 519                                 None => Ty::Unknown,
 520                             }
 521                         }
 522                         None => Ty::Unknown,
 523                     },
 524                     UnaryOp::Neg => {
 525                         match &inner_ty {
 526                             // Fast path for builtins
 527                             Ty::Apply(ApplicationTy {
 528                                 ctor: TypeCtor::Int(IntTy { signedness: Signedness::Signed, .. }),
 529                                 ..
 530                             })
 531                             | Ty::Apply(ApplicationTy { ctor: TypeCtor::Float(_), .. })
 532                             | Ty::Infer(InferTy::IntVar(..))
 533                             | Ty::Infer(InferTy::FloatVar(..)) => inner_ty,
 534                             // Otherwise we resolve via the std::ops::Neg trait
 535                             _ => self
 536                                 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
 537                         }
 538                     }
 539                     UnaryOp::Not => {
 540                         match &inner_ty {
 541                             // Fast path for builtins
 542                             Ty::Apply(ApplicationTy { ctor: TypeCtor::Bool, .. })
 543                             | Ty::Apply(ApplicationTy { ctor: TypeCtor::Int(_), .. })
 544                             | Ty::Infer(InferTy::IntVar(..)) => inner_ty,
 545                             // Otherwise we resolve via the std::ops::Not trait
 546                             _ => self
 547                                 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
 548                         }
 549                     }
 550                 }
 551             }
 552             Expr::BinaryOp { lhs, rhs, op } => match op {
 553                 Some(op) => {
 554                     let lhs_expectation = match op {
 555                         BinaryOp::LogicOp(..) => Expectation::has_type(Ty::simple(TypeCtor::Bool)),
 556                         _ => Expectation::none(),
 557                     };
 558                     let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
 559                     let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
 560                     let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
 561
 562                     let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
 563
 564                     if ret == Ty::Unknown {
 565                         mark::hit!(infer_expr_inner_binary_operator_overload);
 566
 567                         self.resolve_associated_type_with_params(
 568                             lhs_ty,
 569                             self.resolve_binary_op_output(op),
 570                             &[rhs_ty],
 571                         )
 572                     } else {
 573                         ret
 574                     }
 575                 }
 576                 _ => Ty::Unknown,
 577             },
 578             Expr::Range { lhs, rhs, range_type } => {
 579                 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
 580                 let rhs_expect = lhs_ty
 581                     .as_ref()
 582                     .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
 583                 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
 584                 match (range_type, lhs_ty, rhs_ty) {
 585                     (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
 586                         Some(adt) => Ty::simple(TypeCtor::Adt(adt)),
 587                         None => Ty::Unknown,
 588                     },
 589                     (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
 590                         Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
 591                         None => Ty::Unknown,
 592                     },
 593                     (RangeOp::Inclusive, None, Some(ty)) => {
 594                         match self.resolve_range_to_inclusive() {
 595                             Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
 596                             None => Ty::Unknown,
 597                         }
 598                     }
 599                     (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
 600                         Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
 601                         None => Ty::Unknown,
 602                     },
 603                     (RangeOp::Inclusive, Some(_), Some(ty)) => {
 604                         match self.resolve_range_inclusive() {
 605                             Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
 606                             None => Ty::Unknown,
 607                         }
 608                     }
 609                     (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
 610                         Some(adt) => Ty::apply_one(TypeCtor::Adt(adt), ty),
 611                         None => Ty::Unknown,
 612                     },
 613                     (RangeOp::Inclusive, _, None) => Ty::Unknown,
 614                 }
 615             }
 616             Expr::Index { base, index } => {
 617                 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
 618                 let index_ty = self.infer_expr(*index, &Expectation::none());
 619
 620                 if let (Some(index_trait), Some(krate)) =
 621                     (self.resolve_ops_index(), self.resolver.krate())
 622                 {
 623                     let canonicalized = self.canonicalizer().canonicalize_ty(base_ty);
 624                     let self_ty = method_resolution::resolve_indexing_op(
 625                         self.db,
 626                         &canonicalized.value,
 627                         self.trait_env.clone(),
 628                         krate,
 629                         index_trait,
 630                     );
 631                     let self_ty =
 632                         self_ty.map_or(Ty::Unknown, |t| canonicalized.decanonicalize_ty(t.value));
 633                     self.resolve_associated_type_with_params(
 634                         self_ty,
 635                         self.resolve_ops_index_output(),
 636                         &[index_ty],
 637                     )
 638                 } else {
 639                     Ty::Unknown
 640                 }
 641             }
 642             Expr::Tuple { exprs } => {
 643                 let mut tys = match &expected.ty {
 644                     ty_app!(TypeCtor::Tuple { .. }, st) => st
 645                         .iter()
 646                         .cloned()
 647                         .chain(repeat_with(|| self.table.new_type_var()))
 648                         .take(exprs.len())
 649                         .collect::<Vec<_>>(),
 650                     _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
 651                 };
 652
 653                 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
 654                     self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
 655                 }
 656
 657                 Ty::apply(TypeCtor::Tuple { cardinality: tys.len() as u16 }, Substs(tys.into()))
 658             }
 659             Expr::Array(array) => {
 660                 let elem_ty = match &expected.ty {
 661                     // FIXME: remove when https://github.com/rust-lang/rust/issues/80501 is fixed
 662                     #[allow(unreachable_patterns)]
 663                     ty_app!(TypeCtor::Array, st) | ty_app!(TypeCtor::Slice, st) => {
 664                         st.as_single().clone()
 665                     }
 666                     _ => self.table.new_type_var(),
 667                 };
 668
 669                 match array {
 670                     Array::ElementList(items) => {
 671                         for expr in items.iter() {
 672                             self.infer_expr_coerce(*expr, &Expectation::has_type(elem_ty.clone()));
 673                         }
 674                     }
 675                     Array::Repeat { initializer, repeat } => {
 676                         self.infer_expr_coerce(
 677                             *initializer,
 678                             &Expectation::has_type(elem_ty.clone()),
 679                         );
 680                         self.infer_expr(
 681                             *repeat,
 682                             &Expectation::has_type(Ty::simple(TypeCtor::Int(IntTy::usize()))),
 683                         );
 684                     }
 685                 }
 686
 687                 Ty::apply_one(TypeCtor::Array, elem_ty)
 688             }
 689             Expr::Literal(lit) => match lit {
 690                 Literal::Bool(..) => Ty::simple(TypeCtor::Bool),
 691                 Literal::String(..) => {
 692                     Ty::apply_one(TypeCtor::Ref(Mutability::Shared), Ty::simple(TypeCtor::Str))
 693                 }
 694                 Literal::ByteString(..) => {
 695                     let byte_type = Ty::simple(TypeCtor::Int(IntTy::u8()));
 696                     let array_type = Ty::apply_one(TypeCtor::Array, byte_type);
 697                     Ty::apply_one(TypeCtor::Ref(Mutability::Shared), array_type)
 698                 }
 699                 Literal::Char(..) => Ty::simple(TypeCtor::Char),
 700                 Literal::Int(_v, ty) => match ty {
 701                     Some(int_ty) => Ty::simple(TypeCtor::Int((*int_ty).into())),
 702                     None => self.table.new_integer_var(),
 703                 },
 704                 Literal::Float(_v, ty) => match ty {
 705                     Some(float_ty) => Ty::simple(TypeCtor::Float((*float_ty).into())),
 706                     None => self.table.new_float_var(),
 707                 },
 708             },
 709         };
 710         // use a new type variable if we got Ty::Unknown here
 711         let ty = self.insert_type_vars_shallow(ty);
 712         let ty = self.resolve_ty_as_possible(ty);
 713         self.write_expr_ty(tgt_expr, ty.clone());
 714         ty
 715     }
 716
 717     fn infer_block(
 718         &mut self,
 719         statements: &[Statement],
 720         tail: Option<ExprId>,
 721         expected: &Expectation,
 722     ) -> Ty {
 723         for stmt in statements {
 724             match stmt {
 725                 Statement::Let { pat, type_ref, initializer } => {
 726                     let decl_ty =
 727                         type_ref.as_ref().map(|tr| self.make_ty(tr)).unwrap_or(Ty::Unknown);
 728
 729                     // Always use the declared type when specified
 730                     let mut ty = decl_ty.clone();
 731
 732                     if let Some(expr) = initializer {
 733                         let actual_ty =
 734                             self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
 735                         if decl_ty == Ty::Unknown {
 736                             ty = actual_ty;
 737                         }
 738                     }
 739
 740                     let ty = self.resolve_ty_as_possible(ty);
 741                     self.infer_pat(*pat, &ty, BindingMode::default());
 742                 }
 743                 Statement::Expr(expr) => {
 744                     self.infer_expr(*expr, &Expectation::none());
 745                 }
 746             }
 747         }
 748
 749         let ty = if let Some(expr) = tail {
 750             self.infer_expr_coerce(expr, expected)
 751         } else {
 752             // Citing rustc: if there is no explicit tail expression,
 753             // that is typically equivalent to a tail expression
 754             // of `()` -- except if the block diverges. In that
 755             // case, there is no value supplied from the tail
 756             // expression (assuming there are no other breaks,
 757             // this implies that the type of the block will be
 758             // `!`).
 759             if self.diverges.is_always() {
 760                 // we don't even make an attempt at coercion
 761                 self.table.new_maybe_never_type_var()
 762             } else {
 763                 self.coerce(&Ty::unit(), expected.coercion_target());
 764                 Ty::unit()
 765             }
 766         };
 767         ty
 768     }
 769
 770     fn infer_method_call(
 771         &mut self,
 772         tgt_expr: ExprId,
 773         receiver: ExprId,
 774         args: &[ExprId],
 775         method_name: &Name,
 776         generic_args: Option<&GenericArgs>,
 777     ) -> Ty {
 778         let receiver_ty = self.infer_expr(receiver, &Expectation::none());
 779         let canonicalized_receiver = self.canonicalizer().canonicalize_ty(receiver_ty.clone());
 780
 781         let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
 782
 783         let resolved = self.resolver.krate().and_then(|krate| {
 784             method_resolution::lookup_method(
 785                 &canonicalized_receiver.value,
 786                 self.db,
 787                 self.trait_env.clone(),
 788                 krate,
 789                 &traits_in_scope,
 790                 method_name,
 791             )
 792         });
 793         let (derefed_receiver_ty, method_ty, def_generics) = match resolved {
 794             Some((ty, func)) => {
 795                 let ty = canonicalized_receiver.decanonicalize_ty(ty);
 796                 self.write_method_resolution(tgt_expr, func);
 797                 (ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
 798             }
 799             None => (receiver_ty, Binders::new(0, Ty::Unknown), None),
 800         };
 801         let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty);
 802         let method_ty = method_ty.subst(&substs);
 803         let method_ty = self.insert_type_vars(method_ty);
 804         self.register_obligations_for_call(&method_ty);
 805         let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
 806             Some(sig) => {
 807                 if !sig.params().is_empty() {
 808                     (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
 809                 } else {
 810                     (Ty::Unknown, Vec::new(), sig.ret().clone())
 811                 }
 812             }
 813             None => (Ty::Unknown, Vec::new(), Ty::Unknown),
 814         };
 815         // Apply autoref so the below unification works correctly
 816         // FIXME: return correct autorefs from lookup_method
 817         let actual_receiver_ty = match expected_receiver_ty.as_reference() {
 818             Some((_, mutability)) => Ty::apply_one(TypeCtor::Ref(mutability), derefed_receiver_ty),
 819             _ => derefed_receiver_ty,
 820         };
 821         self.unify(&expected_receiver_ty, &actual_receiver_ty);
 822
 823         self.check_call_arguments(args, &param_tys);
 824         self.normalize_associated_types_in(ret_ty)
 825     }
 826
 827     fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
 828         // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
 829         // We do this in a pretty awful way: first we type-check any arguments
 830         // that are not closures, then we type-check the closures. This is so
 831         // that we have more information about the types of arguments when we
 832         // type-check the functions. This isn't really the right way to do this.
 833         for &check_closures in &[false, true] {
 834             let param_iter = param_tys.iter().cloned().chain(repeat(Ty::Unknown));
 835             for (&arg, param_ty) in args.iter().zip(param_iter) {
 836                 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
 837                 if is_closure != check_closures {
 838                     continue;
 839                 }
 840
 841                 let param_ty = self.normalize_associated_types_in(param_ty);
 842                 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
 843             }
 844         }
 845     }
 846
 847     fn substs_for_method_call(
 848         &mut self,
 849         def_generics: Option<Generics>,
 850         generic_args: Option<&GenericArgs>,
 851         receiver_ty: &Ty,
 852     ) -> Substs {
 853         let (parent_params, self_params, type_params, impl_trait_params) =
 854             def_generics.as_ref().map_or((0, 0, 0, 0), |g| g.provenance_split());
 855         assert_eq!(self_params, 0); // method shouldn't have another Self param
 856         let total_len = parent_params + type_params + impl_trait_params;
 857         let mut substs = Vec::with_capacity(total_len);
 858         // Parent arguments are unknown, except for the receiver type
 859         if let Some(parent_generics) = def_generics.as_ref().map(|p| p.iter_parent()) {
 860             for (_id, param) in parent_generics {
 861                 if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
 862                     substs.push(receiver_ty.clone());
 863                 } else {
 864                     substs.push(Ty::Unknown);
 865                 }
 866             }
 867         }
 868         // handle provided type arguments
 869         if let Some(generic_args) = generic_args {
 870             // if args are provided, it should be all of them, but we can't rely on that
 871             for arg in generic_args
 872                 .args
 873                 .iter()
 874                 .filter(|arg| matches!(arg, GenericArg::Type(_)))
 875                 .take(type_params)
 876             {
 877                 match arg {
 878                     GenericArg::Type(type_ref) => {
 879                         let ty = self.make_ty(type_ref);
 880                         substs.push(ty);
 881                     }
 882                     GenericArg::Lifetime(_) => {}
 883                 }
 884             }
 885         };
 886         let supplied_params = substs.len();
 887         for _ in supplied_params..total_len {
 888             substs.push(Ty::Unknown);
 889         }
 890         assert_eq!(substs.len(), total_len);
 891         Substs(substs.into())
 892     }
 893
 894     fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
 895         if let Ty::Apply(a_ty) = callable_ty {
 896             if let TypeCtor::FnDef(def) = a_ty.ctor {
 897                 let generic_predicates = self.db.generic_predicates(def.into());
 898                 for predicate in generic_predicates.iter() {
 899                     let predicate = predicate.clone().subst(&a_ty.parameters);
 900                     if let Some(obligation) = Obligation::from_predicate(predicate) {
 901                         self.obligations.push(obligation);
 902                     }
 903                 }
 904                 // add obligation for trait implementation, if this is a trait method
 905                 match def {
 906                     CallableDefId::FunctionId(f) => {
 907                         if let AssocContainerId::TraitId(trait_) =
 908                             f.lookup(self.db.upcast()).container
 909                         {
 910                             // construct a TraitDef
 911                             let substs = a_ty
 912                                 .parameters
 913                                 .prefix(generics(self.db.upcast(), trait_.into()).len());
 914                             self.obligations.push(Obligation::Trait(TraitRef { trait_, substs }));
 915                         }
 916                     }
 917                     CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}
 918                 }
 919             }
 920         }
 921     }
 922 }