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 chalk_ir::{cast::Cast, fold::Shift, Mutability, TyVariableKind};
   7 use hir_def::{
   8     expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
   9     path::{GenericArg, GenericArgs},
  10     resolver::resolver_for_expr,
  11     AssocContainerId, FieldId, Lookup,
  12 };
  13 use hir_expand::name::{name, Name};
  14 use stdx::always;
  15 use syntax::ast::RangeOp;
  16
  17 use crate::{
  18     autoderef, consteval,
  19     infer::coerce::CoerceMany,
  20     lower::lower_to_chalk_mutability,
  21     mapping::from_chalk,
  22     method_resolution, op,
  23     primitive::{self, UintTy},
  24     static_lifetime, to_chalk_trait_id,
  25     traits::FnTrait,
  26     utils::{generics, Generics},
  27     AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, InEnvironment, Interner,
  28     ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
  29 };
  30
  31 use super::{
  32     find_breakable, BindingMode, BreakableContext, Diverges, Expectation, InferenceContext,
  33     InferenceDiagnostic, TypeMismatch,
  34 };
  35
  36 impl<'a> InferenceContext<'a> {
  37     pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
  38         let ty = self.infer_expr_inner(tgt_expr, expected);
  39         if self.resolve_ty_shallow(&ty).is_never() {
  40             // Any expression that produces a value of type `!` must have diverged
  41             self.diverges = Diverges::Always;
  42         }
  43         if let Some(expected_ty) = expected.only_has_type(&mut self.table) {
  44             let could_unify = self.unify(&ty, &expected_ty);
  45             if !could_unify {
  46                 self.result.type_mismatches.insert(
  47                     tgt_expr.into(),
  48                     TypeMismatch { expected: expected_ty, actual: ty.clone() },
  49                 );
  50             }
  51         }
  52         ty
  53     }
  54
  55     /// Infer type of expression with possibly implicit coerce to the expected type.
  56     /// Return the type after possible coercion.
  57     pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
  58         let ty = self.infer_expr_inner(expr, expected);
  59         let ty = if let Some(target) = expected.only_has_type(&mut self.table) {
  60             match self.coerce(Some(expr), &ty, &target) {
  61                 Ok(res) => res.value,
  62                 Err(_) => {
  63                     self.result
  64                         .type_mismatches
  65                         .insert(expr.into(), TypeMismatch { expected: target, actual: ty.clone() });
  66                     // Return actual type when type mismatch.
  67                     // This is needed for diagnostic when return type mismatch.
  68                     ty
  69                 }
  70             }
  71         } else {
  72             ty
  73         };
  74
  75         ty
  76     }
  77
  78     fn callable_sig_from_fn_trait(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
  79         let krate = self.resolver.krate()?;
  80         let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
  81         let output_assoc_type =
  82             self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
  83
  84         let mut arg_tys = vec![];
  85         let arg_ty = TyBuilder::tuple(num_args)
  86             .fill(repeat_with(|| {
  87                 let arg = self.table.new_type_var();
  88                 arg_tys.push(arg.clone());
  89                 arg
  90             }))
  91             .build();
  92
  93         let projection = {
  94             let b = TyBuilder::assoc_type_projection(self.db, output_assoc_type);
  95             if b.remaining() != 2 {
  96                 return None;
  97             }
  98             b.push(ty.clone()).push(arg_ty).build()
  99         };
 100
 101         let trait_env = self.trait_env.env.clone();
 102         let obligation = InEnvironment {
 103             goal: projection.trait_ref(self.db).cast(&Interner),
 104             environment: trait_env,
 105         };
 106         let canonical = self.canonicalize(obligation.clone());
 107         if self.db.trait_solve(krate, canonical.value.cast(&Interner)).is_some() {
 108             self.push_obligation(obligation.goal);
 109             let return_ty = self.table.normalize_projection_ty(projection);
 110             Some((arg_tys, return_ty))
 111         } else {
 112             None
 113         }
 114     }
 115
 116     pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
 117         match ty.callable_sig(self.db) {
 118             Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
 119             None => self.callable_sig_from_fn_trait(ty, num_args),
 120         }
 121     }
 122
 123     fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
 124         self.db.unwind_if_cancelled();
 125
 126         let body = Arc::clone(&self.body); // avoid borrow checker problem
 127         let ty = match &body[tgt_expr] {
 128             Expr::Missing => self.err_ty(),
 129             &Expr::If { condition, then_branch, else_branch } => {
 130                 // if let is desugared to match, so this is always simple if
 131                 self.infer_expr(
 132                     condition,
 133                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
 134                 );
 135
 136                 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 137                 let mut both_arms_diverge = Diverges::Always;
 138
 139                 let result_ty = self.table.new_type_var();
 140                 let then_ty = self.infer_expr_inner(then_branch, expected);
 141                 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
 142                 let mut coerce = CoerceMany::new(result_ty);
 143                 coerce.coerce(self, Some(then_branch), &then_ty);
 144                 let else_ty = match else_branch {
 145                     Some(else_branch) => self.infer_expr_inner(else_branch, expected),
 146                     None => TyBuilder::unit(),
 147                 };
 148                 both_arms_diverge &= self.diverges;
 149                 // FIXME: create a synthetic `else {}` so we have something to refer to here instead of None?
 150                 coerce.coerce(self, else_branch, &else_ty);
 151
 152                 self.diverges = condition_diverges | both_arms_diverge;
 153
 154                 coerce.complete()
 155             }
 156             Expr::Block { statements, tail, label, id: _ } => {
 157                 let old_resolver = mem::replace(
 158                     &mut self.resolver,
 159                     resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
 160                 );
 161                 let ty = match label {
 162                     Some(_) => {
 163                         let break_ty = self.table.new_type_var();
 164                         self.breakables.push(BreakableContext {
 165                             may_break: false,
 166                             coerce: CoerceMany::new(break_ty.clone()),
 167                             label: label.map(|label| self.body[label].name.clone()),
 168                         });
 169                         let ty = self.infer_block(
 170                             tgt_expr,
 171                             statements,
 172                             *tail,
 173                             &Expectation::has_type(break_ty),
 174                         );
 175                         let ctxt = self.breakables.pop().expect("breakable stack broken");
 176                         if ctxt.may_break {
 177                             ctxt.coerce.complete()
 178                         } else {
 179                             ty
 180                         }
 181                     }
 182                     None => self.infer_block(tgt_expr, statements, *tail, expected),
 183                 };
 184                 self.resolver = old_resolver;
 185                 ty
 186             }
 187             Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
 188             Expr::TryBlock { body } => {
 189                 let _inner = self.infer_expr(*body, expected);
 190                 // FIXME should be std::result::Result<{inner}, _>
 191                 self.err_ty()
 192             }
 193             Expr::Async { body } => {
 194                 // Use the first type parameter as the output type of future.
 195                 // existential type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
 196                 let inner_ty = self.infer_expr(*body, &Expectation::none());
 197                 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
 198                 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
 199                 TyKind::OpaqueType(opaque_ty_id, Substitution::from1(&Interner, inner_ty))
 200                     .intern(&Interner)
 201             }
 202             Expr::Loop { body, label } => {
 203                 self.breakables.push(BreakableContext {
 204                     may_break: false,
 205                     coerce: CoerceMany::new(self.table.new_type_var()),
 206                     label: label.map(|label| self.body[label].name.clone()),
 207                 });
 208                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 209
 210                 let ctxt = self.breakables.pop().expect("breakable stack broken");
 211
 212                 if ctxt.may_break {
 213                     self.diverges = Diverges::Maybe;
 214                     ctxt.coerce.complete()
 215                 } else {
 216                     TyKind::Never.intern(&Interner)
 217                 }
 218             }
 219             Expr::While { condition, body, label } => {
 220                 self.breakables.push(BreakableContext {
 221                     may_break: false,
 222                     coerce: CoerceMany::new(self.err_ty()),
 223                     label: label.map(|label| self.body[label].name.clone()),
 224                 });
 225                 // while let is desugared to a match loop, so this is always simple while
 226                 self.infer_expr(
 227                     *condition,
 228                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
 229                 );
 230                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 231                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 232                 // the body may not run, so it diverging doesn't mean we diverge
 233                 self.diverges = Diverges::Maybe;
 234                 TyBuilder::unit()
 235             }
 236             Expr::For { iterable, body, pat, label } => {
 237                 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
 238
 239                 self.breakables.push(BreakableContext {
 240                     may_break: false,
 241                     coerce: CoerceMany::new(self.err_ty()),
 242                     label: label.map(|label| self.body[label].name.clone()),
 243                 });
 244                 let pat_ty =
 245                     self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
 246
 247                 self.infer_pat(*pat, &pat_ty, BindingMode::default());
 248
 249                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 250                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 251                 // the body may not run, so it diverging doesn't mean we diverge
 252                 self.diverges = Diverges::Maybe;
 253                 TyBuilder::unit()
 254             }
 255             Expr::Lambda { body, args, ret_type, arg_types } => {
 256                 assert_eq!(args.len(), arg_types.len());
 257
 258                 let mut sig_tys = Vec::new();
 259
 260                 // collect explicitly written argument types
 261                 for arg_type in arg_types.iter() {
 262                     let arg_ty = if let Some(type_ref) = arg_type {
 263                         self.make_ty(type_ref)
 264                     } else {
 265                         self.table.new_type_var()
 266                     };
 267                     sig_tys.push(arg_ty);
 268                 }
 269
 270                 // add return type
 271                 let ret_ty = match ret_type {
 272                     Some(type_ref) => self.make_ty(type_ref),
 273                     None => self.table.new_type_var(),
 274                 };
 275                 sig_tys.push(ret_ty.clone());
 276                 let sig_ty = TyKind::Function(FnPointer {
 277                     num_binders: 0,
 278                     sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
 279                     substitution: FnSubst(
 280                         Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
 281                     ),
 282                 })
 283                 .intern(&Interner);
 284                 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
 285                 let closure_ty =
 286                     TyKind::Closure(closure_id, Substitution::from1(&Interner, sig_ty.clone()))
 287                         .intern(&Interner);
 288
 289                 // Eagerly try to relate the closure type with the expected
 290                 // type, otherwise we often won't have enough information to
 291                 // infer the body.
 292                 self.deduce_closure_type_from_expectations(
 293                     tgt_expr,
 294                     &closure_ty,
 295                     &sig_ty,
 296                     expected,
 297                 );
 298
 299                 // Now go through the argument patterns
 300                 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
 301                     self.infer_pat(*arg_pat, &arg_ty, BindingMode::default());
 302                 }
 303
 304                 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 305                 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
 306
 307                 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
 308
 309                 self.diverges = prev_diverges;
 310                 self.return_ty = prev_ret_ty;
 311
 312                 closure_ty
 313             }
 314             Expr::Call { callee, args } => {
 315                 let callee_ty = self.infer_expr(*callee, &Expectation::none());
 316                 let canonicalized = self.canonicalize(callee_ty.clone());
 317                 let mut derefs = autoderef(
 318                     self.db,
 319                     self.resolver.krate(),
 320                     InEnvironment {
 321                         goal: canonicalized.value.clone(),
 322                         environment: self.table.trait_env.env.clone(),
 323                     },
 324                 );
 325                 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
 326                     .find_map(|callee_deref_ty| {
 327                         self.callable_sig(
 328                             &canonicalized.decanonicalize_ty(callee_deref_ty.value),
 329                             args.len(),
 330                         )
 331                     })
 332                     .unwrap_or((Vec::new(), self.err_ty()));
 333                 self.register_obligations_for_call(&callee_ty);
 334                 self.check_call_arguments(args, &param_tys);
 335                 self.normalize_associated_types_in(ret_ty)
 336             }
 337             Expr::MethodCall { receiver, args, method_name, generic_args } => self
 338                 .infer_method_call(tgt_expr, *receiver, args, method_name, generic_args.as_deref()),
 339             Expr::Match { expr, arms } => {
 340                 let input_ty = self.infer_expr(*expr, &Expectation::none());
 341
 342                 let expected = expected.adjust_for_branches(&mut self.table);
 343
 344                 let result_ty = if arms.is_empty() {
 345                     TyKind::Never.intern(&Interner)
 346                 } else {
 347                     match &expected {
 348                         Expectation::HasType(ty) => ty.clone(),
 349                         _ => self.table.new_type_var(),
 350                     }
 351                 };
 352                 let mut coerce = CoerceMany::new(result_ty);
 353
 354                 let matchee_diverges = self.diverges;
 355                 let mut all_arms_diverge = Diverges::Always;
 356
 357                 for arm in arms {
 358                     self.diverges = Diverges::Maybe;
 359                     let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
 360                     if let Some(guard_expr) = arm.guard {
 361                         self.infer_expr(
 362                             guard_expr,
 363                             &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
 364                         );
 365                     }
 366
 367                     let arm_ty = self.infer_expr_inner(arm.expr, &expected);
 368                     all_arms_diverge &= self.diverges;
 369                     coerce.coerce(self, Some(arm.expr), &arm_ty);
 370                 }
 371
 372                 self.diverges = matchee_diverges | all_arms_diverge;
 373
 374                 coerce.complete()
 375             }
 376             Expr::Path(p) => {
 377                 // FIXME this could be more efficient...
 378                 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
 379                 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or_else(|| self.err_ty())
 380             }
 381             Expr::Continue { .. } => TyKind::Never.intern(&Interner),
 382             Expr::Break { expr, label } => {
 383                 let mut coerce = match find_breakable(&mut self.breakables, label.as_ref()) {
 384                     Some(ctxt) => {
 385                         // avoiding the borrowck
 386                         mem::replace(
 387                             &mut ctxt.coerce,
 388                             CoerceMany::new(self.result.standard_types.unknown.clone()),
 389                         )
 390                     }
 391                     None => CoerceMany::new(self.result.standard_types.unknown.clone()),
 392                 };
 393
 394                 let val_ty = if let Some(expr) = *expr {
 395                     self.infer_expr(expr, &Expectation::none())
 396                 } else {
 397                     TyBuilder::unit()
 398                 };
 399
 400                 // FIXME: create a synthetic `()` during lowering so we have something to refer to here?
 401                 coerce.coerce(self, *expr, &val_ty);
 402
 403                 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
 404                     ctxt.coerce = coerce;
 405                     ctxt.may_break = true;
 406                 } else {
 407                     self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
 408                         expr: tgt_expr,
 409                     });
 410                 };
 411
 412                 TyKind::Never.intern(&Interner)
 413             }
 414             Expr::Return { expr } => {
 415                 if let Some(expr) = expr {
 416                     self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
 417                 } else {
 418                     let unit = TyBuilder::unit();
 419                     let _ = self.coerce(Some(tgt_expr), &unit, &self.return_ty.clone());
 420                 }
 421                 TyKind::Never.intern(&Interner)
 422             }
 423             Expr::Yield { expr } => {
 424                 // FIXME: track yield type for coercion
 425                 if let Some(expr) = expr {
 426                     self.infer_expr(*expr, &Expectation::none());
 427                 }
 428                 TyKind::Never.intern(&Interner)
 429             }
 430             Expr::RecordLit { path, fields, spread } => {
 431                 let (ty, def_id) = self.resolve_variant(path.as_deref());
 432                 if let Some(variant) = def_id {
 433                     self.write_variant_resolution(tgt_expr.into(), variant);
 434                 }
 435
 436                 if let Some(t) = expected.only_has_type(&mut self.table) {
 437                     self.unify(&ty, &t);
 438                 }
 439
 440                 let substs = ty
 441                     .as_adt()
 442                     .map(|(_, s)| s.clone())
 443                     .unwrap_or_else(|| Substitution::empty(&Interner));
 444                 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
 445                 let variant_data = def_id.map(|it| it.variant_data(self.db.upcast()));
 446                 for field in fields.iter() {
 447                     let field_def =
 448                         variant_data.as_ref().and_then(|it| match it.field(&field.name) {
 449                             Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
 450                             None => {
 451                                 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
 452                                     expr: field.expr,
 453                                 });
 454                                 None
 455                             }
 456                         });
 457                     let field_ty = field_def.map_or(self.err_ty(), |it| {
 458                         field_types[it.local_id].clone().substitute(&Interner, &substs)
 459                     });
 460                     self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
 461                 }
 462                 if let Some(expr) = spread {
 463                     self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
 464                 }
 465                 ty
 466             }
 467             Expr::Field { expr, name } => {
 468                 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
 469                 let canonicalized = self.canonicalize(receiver_ty);
 470                 let ty = autoderef::autoderef(
 471                     self.db,
 472                     self.resolver.krate(),
 473                     InEnvironment {
 474                         goal: canonicalized.value.clone(),
 475                         environment: self.trait_env.env.clone(),
 476                     },
 477                 )
 478                 .find_map(|derefed_ty| {
 479                     let def_db = self.db.upcast();
 480                     let module = self.resolver.module();
 481                     let is_visible = |field_id: &FieldId| {
 482                         module
 483                             .map(|mod_id| {
 484                                 self.db.field_visibilities(field_id.parent)[field_id.local_id]
 485                                     .is_visible_from(def_db, mod_id)
 486                             })
 487                             .unwrap_or(true)
 488                     };
 489                     match canonicalized.decanonicalize_ty(derefed_ty.value).kind(&Interner) {
 490                         TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
 491                             substs
 492                                 .as_slice(&Interner)
 493                                 .get(idx)
 494                                 .map(|a| a.assert_ty_ref(&Interner))
 495                                 .cloned()
 496                         }),
 497                         TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
 498                             let local_id = self.db.struct_data(*s).variant_data.field(name)?;
 499                             let field = FieldId { parent: (*s).into(), local_id };
 500                             if is_visible(&field) {
 501                                 self.write_field_resolution(tgt_expr, field);
 502                                 Some(
 503                                     self.db.field_types((*s).into())[field.local_id]
 504                                         .clone()
 505                                         .substitute(&Interner, &parameters),
 506                                 )
 507                             } else {
 508                                 None
 509                             }
 510                         }
 511                         TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
 512                             let local_id = self.db.union_data(*u).variant_data.field(name)?;
 513                             let field = FieldId { parent: (*u).into(), local_id };
 514                             if is_visible(&field) {
 515                                 self.write_field_resolution(tgt_expr, field);
 516                                 Some(
 517                                     self.db.field_types((*u).into())[field.local_id]
 518                                         .clone()
 519                                         .substitute(&Interner, &parameters),
 520                                 )
 521                             } else {
 522                                 None
 523                             }
 524                         }
 525                         _ => None,
 526                     }
 527                 })
 528                 .unwrap_or_else(|| self.err_ty());
 529                 let ty = self.insert_type_vars(ty);
 530                 self.normalize_associated_types_in(ty)
 531             }
 532             Expr::Await { expr } => {
 533                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 534                 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
 535             }
 536             Expr::Try { expr } => {
 537                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 538                 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
 539             }
 540             Expr::Cast { expr, type_ref } => {
 541                 // FIXME: propagate the "castable to" expectation (and find a test case that shows this is necessary)
 542                 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 543                 let cast_ty = self.make_ty(type_ref);
 544                 // FIXME check the cast...
 545                 cast_ty
 546             }
 547             Expr::Ref { expr, rawness, mutability } => {
 548                 let mutability = lower_to_chalk_mutability(*mutability);
 549                 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) = expected
 550                     .only_has_type(&mut self.table)
 551                     .as_ref()
 552                     .and_then(|t| t.as_reference_or_ptr())
 553                 {
 554                     if exp_mutability == Mutability::Mut && mutability == Mutability::Not {
 555                         // FIXME: record type error - expected mut reference but found shared ref,
 556                         // which cannot be coerced
 557                     }
 558                     if exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
 559                         // FIXME: record type error - expected reference but found ptr,
 560                         // which cannot be coerced
 561                     }
 562                     Expectation::rvalue_hint(Ty::clone(exp_inner))
 563                 } else {
 564                     Expectation::none()
 565                 };
 566                 let inner_ty = self.infer_expr_inner(*expr, &expectation);
 567                 match rawness {
 568                     Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
 569                     Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
 570                 }
 571                 .intern(&Interner)
 572             }
 573             Expr::Box { expr } => {
 574                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 575                 if let Some(box_) = self.resolve_boxed_box() {
 576                     TyBuilder::adt(self.db, box_)
 577                         .push(inner_ty)
 578                         .fill_with_defaults(self.db, || self.table.new_type_var())
 579                         .build()
 580                 } else {
 581                     self.err_ty()
 582                 }
 583             }
 584             Expr::UnaryOp { expr, op } => {
 585                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 586                 let inner_ty = self.resolve_ty_shallow(&inner_ty);
 587                 match op {
 588                     UnaryOp::Deref => match self.resolver.krate() {
 589                         Some(krate) => {
 590                             let canonicalized = self.canonicalize(inner_ty);
 591                             match autoderef::deref(
 592                                 self.db,
 593                                 krate,
 594                                 InEnvironment {
 595                                     goal: &canonicalized.value,
 596                                     environment: self.trait_env.env.clone(),
 597                                 },
 598                             ) {
 599                                 Some(derefed_ty) => {
 600                                     canonicalized.decanonicalize_ty(derefed_ty.value)
 601                                 }
 602                                 None => self.err_ty(),
 603                             }
 604                         }
 605                         None => self.err_ty(),
 606                     },
 607                     UnaryOp::Neg => {
 608                         match inner_ty.kind(&Interner) {
 609                             // Fast path for builtins
 610                             TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_))
 611                             | TyKind::InferenceVar(
 612                                 _,
 613                                 TyVariableKind::Integer | TyVariableKind::Float,
 614                             ) => inner_ty,
 615                             // Otherwise we resolve via the std::ops::Neg trait
 616                             _ => self
 617                                 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
 618                         }
 619                     }
 620                     UnaryOp::Not => {
 621                         match inner_ty.kind(&Interner) {
 622                             // Fast path for builtins
 623                             TyKind::Scalar(Scalar::Bool | Scalar::Int(_) | Scalar::Uint(_))
 624                             | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
 625                             // Otherwise we resolve via the std::ops::Not trait
 626                             _ => self
 627                                 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
 628                         }
 629                     }
 630                 }
 631             }
 632             Expr::BinaryOp { lhs, rhs, op } => match op {
 633                 Some(op) => {
 634                     let lhs_expectation = match op {
 635                         BinaryOp::LogicOp(..) => {
 636                             Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner))
 637                         }
 638                         _ => Expectation::none(),
 639                     };
 640                     let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
 641                     let lhs_ty = self.resolve_ty_shallow(&lhs_ty);
 642                     let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
 643                     let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
 644                     let rhs_ty = self.resolve_ty_shallow(&rhs_ty);
 645
 646                     let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
 647
 648                     if ret.is_unknown() {
 649                         cov_mark::hit!(infer_expr_inner_binary_operator_overload);
 650
 651                         self.resolve_associated_type_with_params(
 652                             lhs_ty,
 653                             self.resolve_binary_op_output(op),
 654                             &[rhs_ty],
 655                         )
 656                     } else {
 657                         ret
 658                     }
 659                 }
 660                 _ => self.err_ty(),
 661             },
 662             Expr::Range { lhs, rhs, range_type } => {
 663                 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
 664                 let rhs_expect = lhs_ty
 665                     .as_ref()
 666                     .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
 667                 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
 668                 match (range_type, lhs_ty, rhs_ty) {
 669                     (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
 670                         Some(adt) => TyBuilder::adt(self.db, adt).build(),
 671                         None => self.err_ty(),
 672                     },
 673                     (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
 674                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 675                         None => self.err_ty(),
 676                     },
 677                     (RangeOp::Inclusive, None, Some(ty)) => {
 678                         match self.resolve_range_to_inclusive() {
 679                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 680                             None => self.err_ty(),
 681                         }
 682                     }
 683                     (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
 684                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 685                         None => self.err_ty(),
 686                     },
 687                     (RangeOp::Inclusive, Some(_), Some(ty)) => {
 688                         match self.resolve_range_inclusive() {
 689                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 690                             None => self.err_ty(),
 691                         }
 692                     }
 693                     (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
 694                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 695                         None => self.err_ty(),
 696                     },
 697                     (RangeOp::Inclusive, _, None) => self.err_ty(),
 698                 }
 699             }
 700             Expr::Index { base, index } => {
 701                 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
 702                 let index_ty = self.infer_expr(*index, &Expectation::none());
 703
 704                 if let (Some(index_trait), Some(krate)) =
 705                     (self.resolve_ops_index(), self.resolver.krate())
 706                 {
 707                     let canonicalized = self.canonicalize(base_ty);
 708                     let self_ty = method_resolution::resolve_indexing_op(
 709                         self.db,
 710                         &canonicalized.value,
 711                         self.trait_env.clone(),
 712                         krate,
 713                         index_trait,
 714                     );
 715                     let self_ty =
 716                         self_ty.map_or(self.err_ty(), |t| canonicalized.decanonicalize_ty(t.value));
 717                     self.resolve_associated_type_with_params(
 718                         self_ty,
 719                         self.resolve_ops_index_output(),
 720                         &[index_ty],
 721                     )
 722                 } else {
 723                     self.err_ty()
 724                 }
 725             }
 726             Expr::Tuple { exprs } => {
 727                 let mut tys = match expected
 728                     .only_has_type(&mut self.table)
 729                     .as_ref()
 730                     .map(|t| t.kind(&Interner))
 731                 {
 732                     Some(TyKind::Tuple(_, substs)) => substs
 733                         .iter(&Interner)
 734                         .map(|a| a.assert_ty_ref(&Interner).clone())
 735                         .chain(repeat_with(|| self.table.new_type_var()))
 736                         .take(exprs.len())
 737                         .collect::<Vec<_>>(),
 738                     _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
 739                 };
 740
 741                 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
 742                     self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
 743                 }
 744
 745                 TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
 746             }
 747             Expr::Array(array) => {
 748                 let elem_ty =
 749                     match expected.to_option(&mut self.table).as_ref().map(|t| t.kind(&Interner)) {
 750                         Some(TyKind::Array(st, _) | TyKind::Slice(st)) => st.clone(),
 751                         _ => self.table.new_type_var(),
 752                     };
 753                 let mut coerce = CoerceMany::new(elem_ty.clone());
 754
 755                 let expected = Expectation::has_type(elem_ty.clone());
 756                 let len = match array {
 757                     Array::ElementList(items) => {
 758                         for &expr in items.iter() {
 759                             let cur_elem_ty = self.infer_expr_inner(expr, &expected);
 760                             coerce.coerce(self, Some(expr), &cur_elem_ty);
 761                         }
 762                         Some(items.len() as u64)
 763                     }
 764                     &Array::Repeat { initializer, repeat } => {
 765                         self.infer_expr_coerce(initializer, &Expectation::has_type(elem_ty));
 766                         self.infer_expr(
 767                             repeat,
 768                             &Expectation::has_type(
 769                                 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
 770                             ),
 771                         );
 772
 773                         let repeat_expr = &self.body.exprs[repeat];
 774                         consteval::eval_usize(repeat_expr)
 775                     }
 776                 };
 777
 778                 TyKind::Array(coerce.complete(), consteval::usize_const(len)).intern(&Interner)
 779             }
 780             Expr::Literal(lit) => match lit {
 781                 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
 782                 Literal::String(..) => {
 783                     TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(&Interner))
 784                         .intern(&Interner)
 785                 }
 786                 Literal::ByteString(bs) => {
 787                     let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
 788
 789                     let len = consteval::usize_const(Some(bs.len() as u64));
 790
 791                     let array_type = TyKind::Array(byte_type, len).intern(&Interner);
 792                     TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(&Interner)
 793                 }
 794                 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
 795                 Literal::Int(_v, ty) => match ty {
 796                     Some(int_ty) => {
 797                         TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
 798                             .intern(&Interner)
 799                     }
 800                     None => self.table.new_integer_var(),
 801                 },
 802                 Literal::Uint(_v, ty) => match ty {
 803                     Some(int_ty) => {
 804                         TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
 805                             .intern(&Interner)
 806                     }
 807                     None => self.table.new_integer_var(),
 808                 },
 809                 Literal::Float(_v, ty) => match ty {
 810                     Some(float_ty) => {
 811                         TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
 812                             .intern(&Interner)
 813                     }
 814                     None => self.table.new_float_var(),
 815                 },
 816             },
 817             Expr::MacroStmts { tail } => self.infer_expr_inner(*tail, expected),
 818         };
 819         // use a new type variable if we got unknown here
 820         let ty = self.insert_type_vars_shallow(ty);
 821         self.write_expr_ty(tgt_expr, ty.clone());
 822         ty
 823     }
 824
 825     fn infer_block(
 826         &mut self,
 827         expr: ExprId,
 828         statements: &[Statement],
 829         tail: Option<ExprId>,
 830         expected: &Expectation,
 831     ) -> Ty {
 832         for stmt in statements {
 833             match stmt {
 834                 Statement::Let { pat, type_ref, initializer } => {
 835                     let decl_ty = type_ref
 836                         .as_ref()
 837                         .map(|tr| self.make_ty(tr))
 838                         .unwrap_or_else(|| self.err_ty());
 839
 840                     // Always use the declared type when specified
 841                     let mut ty = decl_ty.clone();
 842
 843                     if let Some(expr) = initializer {
 844                         let actual_ty =
 845                             self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
 846                         if decl_ty.is_unknown() {
 847                             ty = actual_ty;
 848                         }
 849                     }
 850
 851                     self.infer_pat(*pat, &ty, BindingMode::default());
 852                 }
 853                 Statement::Expr { expr, .. } => {
 854                     self.infer_expr(*expr, &Expectation::none());
 855                 }
 856             }
 857         }
 858
 859         let ty = if let Some(expr) = tail {
 860             self.infer_expr_coerce(expr, expected)
 861         } else {
 862             // Citing rustc: if there is no explicit tail expression,
 863             // that is typically equivalent to a tail expression
 864             // of `()` -- except if the block diverges. In that
 865             // case, there is no value supplied from the tail
 866             // expression (assuming there are no other breaks,
 867             // this implies that the type of the block will be
 868             // `!`).
 869             if self.diverges.is_always() {
 870                 // we don't even make an attempt at coercion
 871                 self.table.new_maybe_never_var()
 872             } else {
 873                 if let Some(t) = expected.only_has_type(&mut self.table) {
 874                     let _ = self.coerce(Some(expr), &TyBuilder::unit(), &t);
 875                 }
 876                 TyBuilder::unit()
 877             }
 878         };
 879         ty
 880     }
 881
 882     fn infer_method_call(
 883         &mut self,
 884         tgt_expr: ExprId,
 885         receiver: ExprId,
 886         args: &[ExprId],
 887         method_name: &Name,
 888         generic_args: Option<&GenericArgs>,
 889     ) -> Ty {
 890         let receiver_ty = self.infer_expr(receiver, &Expectation::none());
 891         let canonicalized_receiver = self.canonicalize(receiver_ty.clone());
 892
 893         let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
 894
 895         let resolved = self.resolver.krate().and_then(|krate| {
 896             method_resolution::lookup_method(
 897                 &canonicalized_receiver.value,
 898                 self.db,
 899                 self.trait_env.clone(),
 900                 krate,
 901                 &traits_in_scope,
 902                 self.resolver.module(),
 903                 method_name,
 904             )
 905         });
 906         let (receiver_ty, method_ty, substs) = match resolved {
 907             Some((ty, func)) => {
 908                 let ty = canonicalized_receiver.decanonicalize_ty(ty);
 909                 let generics = generics(self.db.upcast(), func.into());
 910                 let substs = self.substs_for_method_call(generics, generic_args, &ty);
 911                 self.write_method_resolution(tgt_expr, func, substs.clone());
 912                 (ty, self.db.value_ty(func.into()), substs)
 913             }
 914             None => (
 915                 receiver_ty,
 916                 Binders::empty(&Interner, self.err_ty()),
 917                 Substitution::empty(&Interner),
 918             ),
 919         };
 920         let method_ty = method_ty.substitute(&Interner, &substs);
 921         self.register_obligations_for_call(&method_ty);
 922         let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
 923             Some(sig) => {
 924                 if !sig.params().is_empty() {
 925                     (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
 926                 } else {
 927                     (self.err_ty(), Vec::new(), sig.ret().clone())
 928                 }
 929             }
 930             None => (self.err_ty(), Vec::new(), self.err_ty()),
 931         };
 932         self.unify(&expected_receiver_ty, &receiver_ty);
 933
 934         self.check_call_arguments(args, &param_tys);
 935         self.normalize_associated_types_in(ret_ty)
 936     }
 937
 938     fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
 939         // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
 940         // We do this in a pretty awful way: first we type-check any arguments
 941         // that are not closures, then we type-check the closures. This is so
 942         // that we have more information about the types of arguments when we
 943         // type-check the functions. This isn't really the right way to do this.
 944         for &check_closures in &[false, true] {
 945             let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
 946             for (&arg, param_ty) in args.iter().zip(param_iter) {
 947                 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
 948                 if is_closure != check_closures {
 949                     continue;
 950                 }
 951
 952                 let param_ty = self.normalize_associated_types_in(param_ty);
 953                 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
 954             }
 955         }
 956     }
 957
 958     fn substs_for_method_call(
 959         &mut self,
 960         def_generics: Generics,
 961         generic_args: Option<&GenericArgs>,
 962         receiver_ty: &Ty,
 963     ) -> Substitution {
 964         let (parent_params, self_params, type_params, impl_trait_params) =
 965             def_generics.provenance_split();
 966         assert_eq!(self_params, 0); // method shouldn't have another Self param
 967         let total_len = parent_params + type_params + impl_trait_params;
 968         let mut substs = Vec::with_capacity(total_len);
 969         // Parent arguments are unknown, except for the receiver type
 970         for (_id, param) in def_generics.iter_parent() {
 971             if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
 972                 substs.push(receiver_ty.clone());
 973             } else {
 974                 substs.push(self.table.new_type_var());
 975             }
 976         }
 977         // handle provided type arguments
 978         if let Some(generic_args) = generic_args {
 979             // if args are provided, it should be all of them, but we can't rely on that
 980             for arg in generic_args
 981                 .args
 982                 .iter()
 983                 .filter(|arg| matches!(arg, GenericArg::Type(_)))
 984                 .take(type_params)
 985             {
 986                 match arg {
 987                     GenericArg::Type(type_ref) => {
 988                         let ty = self.make_ty(type_ref);
 989                         substs.push(ty);
 990                     }
 991                     GenericArg::Lifetime(_) => {}
 992                 }
 993             }
 994         };
 995         let supplied_params = substs.len();
 996         for _ in supplied_params..total_len {
 997             substs.push(self.table.new_type_var());
 998         }
 999         assert_eq!(substs.len(), total_len);
1000         Substitution::from_iter(&Interner, substs)
1001     }
1002
1003     fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
1004         let callable_ty = self.resolve_ty_shallow(callable_ty);
1005         if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
1006             let def: CallableDefId = from_chalk(self.db, *fn_def);
1007             let generic_predicates = self.db.generic_predicates(def.into());
1008             for predicate in generic_predicates.iter() {
1009                 let (predicate, binders) = predicate
1010                     .clone()
1011                     .substitute(&Interner, parameters)
1012                     .into_value_and_skipped_binders();
1013                 always!(binders.len(&Interner) == 0); // quantified where clauses not yet handled
1014                 self.push_obligation(predicate.cast(&Interner));
1015             }
1016             // add obligation for trait implementation, if this is a trait method
1017             match def {
1018                 CallableDefId::FunctionId(f) => {
1019                     if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
1020                     {
1021                         // construct a TraitRef
1022                         let substs = crate::subst_prefix(
1023                             &*parameters,
1024                             generics(self.db.upcast(), trait_.into()).len(),
1025                         );
1026                         self.push_obligation(
1027                             TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
1028                                 .cast(&Interner),
1029                         );
1030                     }
1031                 }
1032                 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}
1033             }
1034         }
1035     }
1036 }