crates/hir_ty/src/infer/expr.rs

   1 //! Type inference for expressions.
   2
   3 use std::{
   4     collections::hash_map::Entry,
   5     iter::{repeat, repeat_with},
   6     mem,
   7     sync::Arc,
   8 };
   9
  10 use chalk_ir::{
  11     cast::Cast, fold::Shift, DebruijnIndex, GenericArgData, Mutability, TyVariableKind,
  12 };
  13 use hir_def::{
  14     expr::{ArithOp, Array, BinaryOp, CmpOp, Expr, ExprId, Literal, Ordering, Statement, UnaryOp},
  15     generics::TypeOrConstParamData,
  16     path::{GenericArg, GenericArgs},
  17     resolver::resolver_for_expr,
  18     ConstParamId, FieldId, FunctionId, ItemContainerId, Lookup,
  19 };
  20 use hir_expand::name::{name, Name};
  21 use stdx::always;
  22 use syntax::ast::RangeOp;
  23
  24 use crate::{
  25     autoderef::{self, Autoderef},
  26     consteval,
  27     infer::coerce::CoerceMany,
  28     lower::{
  29         const_or_path_to_chalk, generic_arg_to_chalk, lower_to_chalk_mutability, ParamLoweringMode,
  30     },
  31     mapping::{from_chalk, ToChalk},
  32     method_resolution,
  33     primitive::{self, UintTy},
  34     static_lifetime, to_chalk_trait_id,
  35     utils::{generics, Generics},
  36     AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, Interner, Rawness, Scalar,
  37     Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
  38 };
  39
  40 use super::{
  41     coerce::auto_deref_adjust_steps, find_breakable, BindingMode, BreakableContext, Diverges,
  42     Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch,
  43 };
  44
  45 impl<'a> InferenceContext<'a> {
  46     pub(crate) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
  47         let ty = self.infer_expr_inner(tgt_expr, expected);
  48         if self.resolve_ty_shallow(&ty).is_never() {
  49             // Any expression that produces a value of type `!` must have diverged
  50             self.diverges = Diverges::Always;
  51         }
  52         if let Some(expected_ty) = expected.only_has_type(&mut self.table) {
  53             let could_unify = self.unify(&ty, &expected_ty);
  54             if !could_unify {
  55                 self.result.type_mismatches.insert(
  56                     tgt_expr.into(),
  57                     TypeMismatch { expected: expected_ty, actual: ty.clone() },
  58                 );
  59             }
  60         }
  61         ty
  62     }
  63
  64     /// Infer type of expression with possibly implicit coerce to the expected type.
  65     /// Return the type after possible coercion.
  66     pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
  67         let ty = self.infer_expr_inner(expr, expected);
  68         if let Some(target) = expected.only_has_type(&mut self.table) {
  69             match self.coerce(Some(expr), &ty, &target) {
  70                 Ok(res) => res,
  71                 Err(_) => {
  72                     self.result.type_mismatches.insert(
  73                         expr.into(),
  74                         TypeMismatch { expected: target.clone(), actual: ty.clone() },
  75                     );
  76                     target
  77                 }
  78             }
  79         } else {
  80             ty
  81         }
  82     }
  83
  84     fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
  85         self.db.unwind_if_cancelled();
  86
  87         let body = Arc::clone(&self.body); // avoid borrow checker problem
  88         let ty = match &body[tgt_expr] {
  89             Expr::Missing => self.err_ty(),
  90             &Expr::If { condition, then_branch, else_branch } => {
  91                 self.infer_expr(
  92                     condition,
  93                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(Interner)),
  94                 );
  95
  96                 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
  97                 let mut both_arms_diverge = Diverges::Always;
  98
  99                 let result_ty = self.table.new_type_var();
 100                 let then_ty = self.infer_expr_inner(then_branch, expected);
 101                 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
 102                 let mut coerce = CoerceMany::new(result_ty);
 103                 coerce.coerce(self, Some(then_branch), &then_ty);
 104                 let else_ty = match else_branch {
 105                     Some(else_branch) => self.infer_expr_inner(else_branch, expected),
 106                     None => TyBuilder::unit(),
 107                 };
 108                 both_arms_diverge &= self.diverges;
 109                 // FIXME: create a synthetic `else {}` so we have something to refer to here instead of None?
 110                 coerce.coerce(self, else_branch, &else_ty);
 111
 112                 self.diverges = condition_diverges | both_arms_diverge;
 113
 114                 coerce.complete()
 115             }
 116             &Expr::Let { pat, expr } => {
 117                 let input_ty = self.infer_expr(expr, &Expectation::none());
 118                 self.infer_pat(pat, &input_ty, BindingMode::default());
 119                 TyKind::Scalar(Scalar::Bool).intern(Interner)
 120             }
 121             Expr::Block { statements, tail, label, id: _ } => {
 122                 let old_resolver = mem::replace(
 123                     &mut self.resolver,
 124                     resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
 125                 );
 126                 let ty = match label {
 127                     Some(_) => {
 128                         let break_ty = self.table.new_type_var();
 129                         self.breakables.push(BreakableContext {
 130                             may_break: false,
 131                             coerce: CoerceMany::new(break_ty.clone()),
 132                             label: label.map(|label| self.body[label].name.clone()),
 133                         });
 134                         let ty = self.infer_block(
 135                             tgt_expr,
 136                             statements,
 137                             *tail,
 138                             &Expectation::has_type(break_ty),
 139                         );
 140                         let ctxt = self.breakables.pop().expect("breakable stack broken");
 141                         if ctxt.may_break {
 142                             ctxt.coerce.complete()
 143                         } else {
 144                             ty
 145                         }
 146                     }
 147                     None => self.infer_block(tgt_expr, statements, *tail, expected),
 148                 };
 149                 self.resolver = old_resolver;
 150                 ty
 151             }
 152             Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
 153             Expr::TryBlock { body } => {
 154                 let _inner = self.infer_expr(*body, expected);
 155                 // FIXME should be std::result::Result<{inner}, _>
 156                 self.err_ty()
 157             }
 158             Expr::Async { body } => {
 159                 let ret_ty = self.table.new_type_var();
 160                 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 161                 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
 162
 163                 let inner_ty = self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
 164
 165                 self.diverges = prev_diverges;
 166                 self.return_ty = prev_ret_ty;
 167
 168                 // Use the first type parameter as the output type of future.
 169                 // existential type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
 170                 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
 171                 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
 172                 TyKind::OpaqueType(opaque_ty_id, Substitution::from1(Interner, inner_ty))
 173                     .intern(Interner)
 174             }
 175             Expr::Loop { body, label } => {
 176                 self.breakables.push(BreakableContext {
 177                     may_break: false,
 178                     coerce: CoerceMany::new(self.table.new_type_var()),
 179                     label: label.map(|label| self.body[label].name.clone()),
 180                 });
 181                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 182
 183                 let ctxt = self.breakables.pop().expect("breakable stack broken");
 184
 185                 if ctxt.may_break {
 186                     self.diverges = Diverges::Maybe;
 187                     ctxt.coerce.complete()
 188                 } else {
 189                     TyKind::Never.intern(Interner)
 190                 }
 191             }
 192             Expr::While { condition, body, label } => {
 193                 self.breakables.push(BreakableContext {
 194                     may_break: false,
 195                     coerce: CoerceMany::new(self.err_ty()),
 196                     label: label.map(|label| self.body[label].name.clone()),
 197                 });
 198                 self.infer_expr(
 199                     *condition,
 200                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(Interner)),
 201                 );
 202                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 203                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 204                 // the body may not run, so it diverging doesn't mean we diverge
 205                 self.diverges = Diverges::Maybe;
 206                 TyBuilder::unit()
 207             }
 208             Expr::For { iterable, body, pat, label } => {
 209                 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
 210
 211                 self.breakables.push(BreakableContext {
 212                     may_break: false,
 213                     coerce: CoerceMany::new(self.err_ty()),
 214                     label: label.map(|label| self.body[label].name.clone()),
 215                 });
 216                 let pat_ty =
 217                     self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
 218
 219                 self.infer_pat(*pat, &pat_ty, BindingMode::default());
 220
 221                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 222                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 223                 // the body may not run, so it diverging doesn't mean we diverge
 224                 self.diverges = Diverges::Maybe;
 225                 TyBuilder::unit()
 226             }
 227             Expr::Lambda { body, args, ret_type, arg_types } => {
 228                 assert_eq!(args.len(), arg_types.len());
 229
 230                 let mut sig_tys = Vec::new();
 231
 232                 // collect explicitly written argument types
 233                 for arg_type in arg_types.iter() {
 234                     let arg_ty = match arg_type {
 235                         Some(type_ref) => self.make_ty(type_ref),
 236                         None => self.table.new_type_var(),
 237                     };
 238                     sig_tys.push(arg_ty);
 239                 }
 240
 241                 // add return type
 242                 let ret_ty = match ret_type {
 243                     Some(type_ref) => self.make_ty(type_ref),
 244                     None => self.table.new_type_var(),
 245                 };
 246                 sig_tys.push(ret_ty.clone());
 247                 let sig_ty = TyKind::Function(FnPointer {
 248                     num_binders: 0,
 249                     sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
 250                     substitution: FnSubst(
 251                         Substitution::from_iter(Interner, sig_tys.clone()).shifted_in(Interner),
 252                     ),
 253                 })
 254                 .intern(Interner);
 255                 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
 256                 let closure_ty =
 257                     TyKind::Closure(closure_id, Substitution::from1(Interner, sig_ty.clone()))
 258                         .intern(Interner);
 259
 260                 // Eagerly try to relate the closure type with the expected
 261                 // type, otherwise we often won't have enough information to
 262                 // infer the body.
 263                 self.deduce_closure_type_from_expectations(
 264                     tgt_expr,
 265                     &closure_ty,
 266                     &sig_ty,
 267                     expected,
 268                 );
 269
 270                 // Now go through the argument patterns
 271                 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
 272                     self.infer_pat(*arg_pat, &arg_ty, BindingMode::default());
 273                 }
 274
 275                 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 276                 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
 277
 278                 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
 279
 280                 self.diverges = prev_diverges;
 281                 self.return_ty = prev_ret_ty;
 282
 283                 closure_ty
 284             }
 285             Expr::Call { callee, args } => {
 286                 let callee_ty = self.infer_expr(*callee, &Expectation::none());
 287                 let mut derefs = Autoderef::new(&mut self.table, callee_ty.clone());
 288                 let mut res = None;
 289                 let mut derefed_callee = callee_ty.clone();
 290                 // manual loop to be able to access `derefs.table`
 291                 while let Some((callee_deref_ty, _)) = derefs.next() {
 292                     res = derefs.table.callable_sig(&callee_deref_ty, args.len());
 293                     if res.is_some() {
 294                         derefed_callee = callee_deref_ty;
 295                         break;
 296                     }
 297                 }
 298                 // if the function is unresolved, we use is_varargs=true to
 299                 // suppress the arg count diagnostic here
 300                 let is_varargs =
 301                     derefed_callee.callable_sig(self.db).map_or(false, |sig| sig.is_varargs)
 302                         || res.is_none();
 303                 let (param_tys, ret_ty) = match res {
 304                     Some(res) => {
 305                         let adjustments = auto_deref_adjust_steps(&derefs);
 306                         self.write_expr_adj(*callee, adjustments);
 307                         res
 308                     }
 309                     None => (Vec::new(), self.err_ty()), // FIXME diagnostic
 310                 };
 311                 let indices_to_skip = self.check_legacy_const_generics(derefed_callee, args);
 312                 self.register_obligations_for_call(&callee_ty);
 313
 314                 let expected_inputs = self.expected_inputs_for_expected_output(
 315                     expected,
 316                     ret_ty.clone(),
 317                     param_tys.clone(),
 318                 );
 319
 320                 self.check_call_arguments(
 321                     tgt_expr,
 322                     args,
 323                     &expected_inputs,
 324                     &param_tys,
 325                     &indices_to_skip,
 326                     is_varargs,
 327                 );
 328                 self.normalize_associated_types_in(ret_ty)
 329             }
 330             Expr::MethodCall { receiver, args, method_name, generic_args } => self
 331                 .infer_method_call(
 332                     tgt_expr,
 333                     *receiver,
 334                     args,
 335                     method_name,
 336                     generic_args.as_deref(),
 337                     expected,
 338                 ),
 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.iter() {
 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(), false);
 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
 470                 let mut autoderef = Autoderef::new(&mut self.table, receiver_ty);
 471                 let ty = autoderef.by_ref().find_map(|(derefed_ty, _)| {
 472                     let (field_id, parameters) = match derefed_ty.kind(Interner) {
 473                         TyKind::Tuple(_, substs) => {
 474                             return name.as_tuple_index().and_then(|idx| {
 475                                 substs
 476                                     .as_slice(Interner)
 477                                     .get(idx)
 478                                     .map(|a| a.assert_ty_ref(Interner))
 479                                     .cloned()
 480                             });
 481                         }
 482                         TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
 483                             let local_id = self.db.struct_data(*s).variant_data.field(name)?;
 484                             let field = FieldId { parent: (*s).into(), local_id };
 485                             (field, parameters.clone())
 486                         }
 487                         TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
 488                             let local_id = self.db.union_data(*u).variant_data.field(name)?;
 489                             let field = FieldId { parent: (*u).into(), local_id };
 490                             (field, parameters.clone())
 491                         }
 492                         _ => return None,
 493                     };
 494                     let module = self.resolver.module();
 495                     let is_visible = module
 496                         .map(|mod_id| {
 497                             self.db.field_visibilities(field_id.parent)[field_id.local_id]
 498                                 .is_visible_from(self.db.upcast(), mod_id)
 499                         })
 500                         .unwrap_or(true);
 501                     if !is_visible {
 502                         // Write down the first field resolution even if it is not visible
 503                         // This aids IDE features for private fields like goto def and in
 504                         // case of autoderef finding an applicable field, this will be
 505                         // overwritten in a following cycle
 506                         if let Entry::Vacant(entry) = self.result.field_resolutions.entry(tgt_expr)
 507                         {
 508                             entry.insert(field_id);
 509                         }
 510                         return None;
 511                     }
 512                     // can't have `write_field_resolution` here because `self.table` is borrowed :(
 513                     self.result.field_resolutions.insert(tgt_expr, field_id);
 514                     let ty = self.db.field_types(field_id.parent)[field_id.local_id]
 515                         .clone()
 516                         .substitute(Interner, &parameters);
 517                     Some(ty)
 518                 });
 519                 let ty = match ty {
 520                     Some(ty) => {
 521                         let adjustments = auto_deref_adjust_steps(&autoderef);
 522                         self.write_expr_adj(*expr, adjustments);
 523                         let ty = self.insert_type_vars(ty);
 524                         let ty = self.normalize_associated_types_in(ty);
 525                         ty
 526                     }
 527                     _ => self.err_ty(),
 528                 };
 529                 ty
 530             }
 531             Expr::Await { expr } => {
 532                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 533                 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
 534             }
 535             Expr::Try { expr } => {
 536                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 537                 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
 538             }
 539             Expr::Cast { expr, type_ref } => {
 540                 // FIXME: propagate the "castable to" expectation (and find a test case that shows this is necessary)
 541                 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 542                 let cast_ty = self.make_ty(type_ref);
 543                 // FIXME check the cast...
 544                 cast_ty
 545             }
 546             Expr::Ref { expr, rawness, mutability } => {
 547                 let mutability = lower_to_chalk_mutability(*mutability);
 548                 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) = expected
 549                     .only_has_type(&mut self.table)
 550                     .as_ref()
 551                     .and_then(|t| t.as_reference_or_ptr())
 552                 {
 553                     if exp_mutability == Mutability::Mut && mutability == Mutability::Not {
 554                         // FIXME: record type error - expected mut reference but found shared ref,
 555                         // which cannot be coerced
 556                     }
 557                     if exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
 558                         // FIXME: record type error - expected reference but found ptr,
 559                         // which cannot be coerced
 560                     }
 561                     Expectation::rvalue_hint(&mut self.table, Ty::clone(exp_inner))
 562                 } else {
 563                     Expectation::none()
 564                 };
 565                 let inner_ty = self.infer_expr_inner(*expr, &expectation);
 566                 match rawness {
 567                     Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
 568                     Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
 569                 }
 570                 .intern(Interner)
 571             }
 572             Expr::Box { expr } => {
 573                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 574                 if let Some(box_) = self.resolve_boxed_box() {
 575                     TyBuilder::adt(self.db, box_)
 576                         .push(inner_ty)
 577                         .fill_with_defaults(self.db, || self.table.new_type_var())
 578                         .build()
 579                 } else {
 580                     self.err_ty()
 581                 }
 582             }
 583             Expr::UnaryOp { expr, op } => {
 584                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 585                 let inner_ty = self.resolve_ty_shallow(&inner_ty);
 586                 match op {
 587                     UnaryOp::Deref => {
 588                         autoderef::deref(&mut self.table, inner_ty).unwrap_or_else(|| self.err_ty())
 589                     }
 590                     UnaryOp::Neg => {
 591                         match inner_ty.kind(Interner) {
 592                             // Fast path for builtins
 593                             TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_))
 594                             | TyKind::InferenceVar(
 595                                 _,
 596                                 TyVariableKind::Integer | TyVariableKind::Float,
 597                             ) => inner_ty,
 598                             // Otherwise we resolve via the std::ops::Neg trait
 599                             _ => self
 600                                 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
 601                         }
 602                     }
 603                     UnaryOp::Not => {
 604                         match inner_ty.kind(Interner) {
 605                             // Fast path for builtins
 606                             TyKind::Scalar(Scalar::Bool | Scalar::Int(_) | Scalar::Uint(_))
 607                             | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
 608                             // Otherwise we resolve via the std::ops::Not trait
 609                             _ => self
 610                                 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
 611                         }
 612                     }
 613                 }
 614             }
 615             Expr::BinaryOp { lhs, rhs, op } => match op {
 616                 Some(BinaryOp::Assignment { op: None }) => {
 617                     let lhs_ty = self.infer_expr(*lhs, &Expectation::none());
 618                     self.infer_expr_coerce(*rhs, &Expectation::has_type(lhs_ty));
 619                     self.result.standard_types.unit.clone()
 620                 }
 621                 Some(BinaryOp::LogicOp(_)) => {
 622                     let bool_ty = self.result.standard_types.bool_.clone();
 623                     self.infer_expr_coerce(*lhs, &Expectation::HasType(bool_ty.clone()));
 624                     let lhs_diverges = self.diverges;
 625                     self.infer_expr_coerce(*rhs, &Expectation::HasType(bool_ty.clone()));
 626                     // Depending on the LHS' value, the RHS can never execute.
 627                     self.diverges = lhs_diverges;
 628                     bool_ty
 629                 }
 630                 Some(op) => self.infer_overloadable_binop(*lhs, *op, *rhs, tgt_expr),
 631                 _ => self.err_ty(),
 632             },
 633             Expr::Range { lhs, rhs, range_type } => {
 634                 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
 635                 let rhs_expect = lhs_ty
 636                     .as_ref()
 637                     .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
 638                 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
 639                 match (range_type, lhs_ty, rhs_ty) {
 640                     (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
 641                         Some(adt) => TyBuilder::adt(self.db, adt).build(),
 642                         None => self.err_ty(),
 643                     },
 644                     (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
 645                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 646                         None => self.err_ty(),
 647                     },
 648                     (RangeOp::Inclusive, None, Some(ty)) => {
 649                         match self.resolve_range_to_inclusive() {
 650                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 651                             None => self.err_ty(),
 652                         }
 653                     }
 654                     (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
 655                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 656                         None => self.err_ty(),
 657                     },
 658                     (RangeOp::Inclusive, Some(_), Some(ty)) => {
 659                         match self.resolve_range_inclusive() {
 660                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 661                             None => self.err_ty(),
 662                         }
 663                     }
 664                     (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
 665                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 666                         None => self.err_ty(),
 667                     },
 668                     (RangeOp::Inclusive, _, None) => self.err_ty(),
 669                 }
 670             }
 671             Expr::Index { base, index } => {
 672                 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
 673                 let index_ty = self.infer_expr(*index, &Expectation::none());
 674
 675                 if let Some(index_trait) = self.resolve_ops_index() {
 676                     let canonicalized = self.canonicalize(base_ty.clone());
 677                     let receiver_adjustments = method_resolution::resolve_indexing_op(
 678                         self.db,
 679                         self.trait_env.clone(),
 680                         canonicalized.value,
 681                         index_trait,
 682                     );
 683                     let (self_ty, adj) = receiver_adjustments
 684                         .map_or((self.err_ty(), Vec::new()), |adj| {
 685                             adj.apply(&mut self.table, base_ty)
 686                         });
 687                     self.write_expr_adj(*base, adj);
 688                     self.resolve_associated_type_with_params(
 689                         self_ty,
 690                         self.resolve_ops_index_output(),
 691                         &[GenericArgData::Ty(index_ty).intern(Interner)],
 692                     )
 693                 } else {
 694                     self.err_ty()
 695                 }
 696             }
 697             Expr::Tuple { exprs } => {
 698                 let mut tys = match expected
 699                     .only_has_type(&mut self.table)
 700                     .as_ref()
 701                     .map(|t| t.kind(Interner))
 702                 {
 703                     Some(TyKind::Tuple(_, substs)) => substs
 704                         .iter(Interner)
 705                         .map(|a| a.assert_ty_ref(Interner).clone())
 706                         .chain(repeat_with(|| self.table.new_type_var()))
 707                         .take(exprs.len())
 708                         .collect::<Vec<_>>(),
 709                     _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
 710                 };
 711
 712                 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
 713                     self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
 714                 }
 715
 716                 TyKind::Tuple(tys.len(), Substitution::from_iter(Interner, tys)).intern(Interner)
 717             }
 718             Expr::Array(array) => {
 719                 let elem_ty =
 720                     match expected.to_option(&mut self.table).as_ref().map(|t| t.kind(Interner)) {
 721                         Some(TyKind::Array(st, _) | TyKind::Slice(st)) => st.clone(),
 722                         _ => self.table.new_type_var(),
 723                     };
 724                 let mut coerce = CoerceMany::new(elem_ty.clone());
 725
 726                 let expected = Expectation::has_type(elem_ty.clone());
 727                 let len = match array {
 728                     Array::ElementList(items) => {
 729                         for &expr in items.iter() {
 730                             let cur_elem_ty = self.infer_expr_inner(expr, &expected);
 731                             coerce.coerce(self, Some(expr), &cur_elem_ty);
 732                         }
 733                         consteval::usize_const(Some(items.len() as u64))
 734                     }
 735                     &Array::Repeat { initializer, repeat } => {
 736                         self.infer_expr_coerce(initializer, &Expectation::has_type(elem_ty));
 737                         self.infer_expr(
 738                             repeat,
 739                             &Expectation::has_type(
 740                                 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(Interner),
 741                             ),
 742                         );
 743
 744                         if let Some(g_def) = self.owner.as_generic_def_id() {
 745                             let generics = generics(self.db.upcast(), g_def);
 746                             consteval::eval_to_const(
 747                                 repeat,
 748                                 ParamLoweringMode::Placeholder,
 749                                 self,
 750                                 || generics,
 751                                 DebruijnIndex::INNERMOST,
 752                             )
 753                         } else {
 754                             consteval::usize_const(None)
 755                         }
 756                     }
 757                 };
 758
 759                 TyKind::Array(coerce.complete(), len).intern(Interner)
 760             }
 761             Expr::Literal(lit) => match lit {
 762                 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(Interner),
 763                 Literal::String(..) => {
 764                     TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(Interner))
 765                         .intern(Interner)
 766                 }
 767                 Literal::ByteString(bs) => {
 768                     let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(Interner);
 769
 770                     let len = consteval::usize_const(Some(bs.len() as u64));
 771
 772                     let array_type = TyKind::Array(byte_type, len).intern(Interner);
 773                     TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(Interner)
 774                 }
 775                 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(Interner),
 776                 Literal::Int(_v, ty) => match ty {
 777                     Some(int_ty) => {
 778                         TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
 779                             .intern(Interner)
 780                     }
 781                     None => self.table.new_integer_var(),
 782                 },
 783                 Literal::Uint(_v, ty) => match ty {
 784                     Some(int_ty) => {
 785                         TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
 786                             .intern(Interner)
 787                     }
 788                     None => self.table.new_integer_var(),
 789                 },
 790                 Literal::Float(_v, ty) => match ty {
 791                     Some(float_ty) => {
 792                         TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
 793                             .intern(Interner)
 794                     }
 795                     None => self.table.new_float_var(),
 796                 },
 797             },
 798             Expr::MacroStmts { tail } => self.infer_expr_inner(*tail, expected),
 799         };
 800         // use a new type variable if we got unknown here
 801         let ty = self.insert_type_vars_shallow(ty);
 802         self.write_expr_ty(tgt_expr, ty.clone());
 803         ty
 804     }
 805
 806     fn infer_overloadable_binop(
 807         &mut self,
 808         lhs: ExprId,
 809         op: BinaryOp,
 810         rhs: ExprId,
 811         tgt_expr: ExprId,
 812     ) -> Ty {
 813         let lhs_expectation = Expectation::none();
 814         let lhs_ty = self.infer_expr(lhs, &lhs_expectation);
 815         let rhs_ty = self.table.new_type_var();
 816
 817         let func = self.resolve_binop_method(op);
 818         let func = match func {
 819             Some(func) => func,
 820             None => {
 821                 let rhs_ty = self.builtin_binary_op_rhs_expectation(op, lhs_ty.clone());
 822                 let rhs_ty = self.infer_expr_coerce(rhs, &Expectation::from_option(rhs_ty));
 823                 return self
 824                     .builtin_binary_op_return_ty(op, lhs_ty, rhs_ty)
 825                     .unwrap_or_else(|| self.err_ty());
 826             }
 827         };
 828
 829         let subst = TyBuilder::subst_for_def(self.db, func)
 830             .push(lhs_ty.clone())
 831             .push(rhs_ty.clone())
 832             .build();
 833         self.write_method_resolution(tgt_expr, func, subst.clone());
 834
 835         let method_ty = self.db.value_ty(func.into()).substitute(Interner, &subst);
 836         self.register_obligations_for_call(&method_ty);
 837
 838         self.infer_expr_coerce(rhs, &Expectation::has_type(rhs_ty.clone()));
 839
 840         let ret_ty = match method_ty.callable_sig(self.db) {
 841             Some(sig) => sig.ret().clone(),
 842             None => self.err_ty(),
 843         };
 844
 845         let ret_ty = self.normalize_associated_types_in(ret_ty);
 846
 847         // FIXME: record autoref adjustments
 848
 849         // use knowledge of built-in binary ops, which can sometimes help inference
 850         if let Some(builtin_rhs) = self.builtin_binary_op_rhs_expectation(op, lhs_ty.clone()) {
 851             self.unify(&builtin_rhs, &rhs_ty);
 852         }
 853         if let Some(builtin_ret) = self.builtin_binary_op_return_ty(op, lhs_ty, rhs_ty) {
 854             self.unify(&builtin_ret, &ret_ty);
 855         }
 856
 857         ret_ty
 858     }
 859
 860     fn infer_block(
 861         &mut self,
 862         expr: ExprId,
 863         statements: &[Statement],
 864         tail: Option<ExprId>,
 865         expected: &Expectation,
 866     ) -> Ty {
 867         for stmt in statements {
 868             match stmt {
 869                 Statement::Let { pat, type_ref, initializer, else_branch } => {
 870                     let decl_ty = type_ref
 871                         .as_ref()
 872                         .map(|tr| self.make_ty(tr))
 873                         .unwrap_or_else(|| self.err_ty());
 874
 875                     // Always use the declared type when specified
 876                     let mut ty = decl_ty.clone();
 877
 878                     if let Some(expr) = initializer {
 879                         let actual_ty =
 880                             self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
 881                         if decl_ty.is_unknown() {
 882                             ty = actual_ty;
 883                         }
 884                     }
 885
 886                     if let Some(expr) = else_branch {
 887                         self.infer_expr_coerce(
 888                             *expr,
 889                             &Expectation::has_type(Ty::new(Interner, TyKind::Never)),
 890                         );
 891                     }
 892
 893                     self.infer_pat(*pat, &ty, BindingMode::default());
 894                 }
 895                 Statement::Expr { expr, .. } => {
 896                     self.infer_expr(*expr, &Expectation::none());
 897                 }
 898             }
 899         }
 900
 901         if let Some(expr) = tail {
 902             self.infer_expr_coerce(expr, expected)
 903         } else {
 904             // Citing rustc: if there is no explicit tail expression,
 905             // that is typically equivalent to a tail expression
 906             // of `()` -- except if the block diverges. In that
 907             // case, there is no value supplied from the tail
 908             // expression (assuming there are no other breaks,
 909             // this implies that the type of the block will be
 910             // `!`).
 911             if self.diverges.is_always() {
 912                 // we don't even make an attempt at coercion
 913                 self.table.new_maybe_never_var()
 914             } else {
 915                 if let Some(t) = expected.only_has_type(&mut self.table) {
 916                     if self.coerce(Some(expr), &TyBuilder::unit(), &t).is_err() {
 917                         self.result.type_mismatches.insert(
 918                             expr.into(),
 919                             TypeMismatch { expected: t.clone(), actual: TyBuilder::unit() },
 920                         );
 921                     }
 922                     t
 923                 } else {
 924                     TyBuilder::unit()
 925                 }
 926             }
 927         }
 928     }
 929
 930     fn infer_method_call(
 931         &mut self,
 932         tgt_expr: ExprId,
 933         receiver: ExprId,
 934         args: &[ExprId],
 935         method_name: &Name,
 936         generic_args: Option<&GenericArgs>,
 937         expected: &Expectation,
 938     ) -> Ty {
 939         let receiver_ty = self.infer_expr(receiver, &Expectation::none());
 940         let canonicalized_receiver = self.canonicalize(receiver_ty.clone());
 941
 942         let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
 943
 944         let resolved = method_resolution::lookup_method(
 945             &canonicalized_receiver.value,
 946             self.db,
 947             self.trait_env.clone(),
 948             &traits_in_scope,
 949             self.resolver.module().into(),
 950             method_name,
 951         );
 952         let (receiver_ty, method_ty, substs) = match resolved {
 953             Some((adjust, func)) => {
 954                 let (ty, adjustments) = adjust.apply(&mut self.table, receiver_ty);
 955                 let generics = generics(self.db.upcast(), func.into());
 956                 let substs = self.substs_for_method_call(generics, generic_args);
 957                 self.write_expr_adj(receiver, adjustments);
 958                 self.write_method_resolution(tgt_expr, func, substs.clone());
 959                 (ty, self.db.value_ty(func.into()), substs)
 960             }
 961             None => (
 962                 receiver_ty,
 963                 Binders::empty(Interner, self.err_ty()),
 964                 Substitution::empty(Interner),
 965             ),
 966         };
 967         let method_ty = method_ty.substitute(Interner, &substs);
 968         self.register_obligations_for_call(&method_ty);
 969         let (formal_receiver_ty, param_tys, ret_ty, is_varargs) =
 970             match method_ty.callable_sig(self.db) {
 971                 Some(sig) => {
 972                     if !sig.params().is_empty() {
 973                         (
 974                             sig.params()[0].clone(),
 975                             sig.params()[1..].to_vec(),
 976                             sig.ret().clone(),
 977                             sig.is_varargs,
 978                         )
 979                     } else {
 980                         (self.err_ty(), Vec::new(), sig.ret().clone(), sig.is_varargs)
 981                     }
 982                 }
 983                 None => (self.err_ty(), Vec::new(), self.err_ty(), true),
 984             };
 985         self.unify(&formal_receiver_ty, &receiver_ty);
 986
 987         let expected_inputs =
 988             self.expected_inputs_for_expected_output(expected, ret_ty.clone(), param_tys.clone());
 989
 990         self.check_call_arguments(tgt_expr, args, &expected_inputs, &param_tys, &[], is_varargs);
 991         self.normalize_associated_types_in(ret_ty)
 992     }
 993
 994     fn expected_inputs_for_expected_output(
 995         &mut self,
 996         expected_output: &Expectation,
 997         output: Ty,
 998         inputs: Vec<Ty>,
 999     ) -> Vec<Ty> {
1000         if let Some(expected_ty) = expected_output.to_option(&mut self.table) {
1001             self.table.fudge_inference(|table| {
1002                 if table.try_unify(&expected_ty, &output).is_ok() {
1003                     table.resolve_with_fallback(inputs, &|var, kind, _, _| match kind {
1004                         chalk_ir::VariableKind::Ty(tk) => var.to_ty(Interner, tk).cast(Interner),
1005                         chalk_ir::VariableKind::Lifetime => {
1006                             var.to_lifetime(Interner).cast(Interner)
1007                         }
1008                         chalk_ir::VariableKind::Const(ty) => {
1009                             var.to_const(Interner, ty).cast(Interner)
1010                         }
1011                     })
1012                 } else {
1013                     Vec::new()
1014                 }
1015             })
1016         } else {
1017             Vec::new()
1018         }
1019     }
1020
1021     fn check_call_arguments(
1022         &mut self,
1023         expr: ExprId,
1024         args: &[ExprId],
1025         expected_inputs: &[Ty],
1026         param_tys: &[Ty],
1027         skip_indices: &[u32],
1028         is_varargs: bool,
1029     ) {
1030         if args.len() != param_tys.len() + skip_indices.len() && !is_varargs {
1031             self.push_diagnostic(InferenceDiagnostic::MismatchedArgCount {
1032                 call_expr: expr,
1033                 expected: param_tys.len() + skip_indices.len(),
1034                 found: args.len(),
1035             });
1036         }
1037
1038         // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
1039         // We do this in a pretty awful way: first we type-check any arguments
1040         // that are not closures, then we type-check the closures. This is so
1041         // that we have more information about the types of arguments when we
1042         // type-check the functions. This isn't really the right way to do this.
1043         for &check_closures in &[false, true] {
1044             let mut skip_indices = skip_indices.into_iter().copied().fuse().peekable();
1045             let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
1046             let expected_iter = expected_inputs
1047                 .iter()
1048                 .cloned()
1049                 .chain(param_iter.clone().skip(expected_inputs.len()));
1050             for (idx, ((&arg, param_ty), expected_ty)) in
1051                 args.iter().zip(param_iter).zip(expected_iter).enumerate()
1052             {
1053                 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
1054                 if is_closure != check_closures {
1055                     continue;
1056                 }
1057
1058                 while skip_indices.peek().map_or(false, |i| *i < idx as u32) {
1059                     skip_indices.next();
1060                 }
1061                 if skip_indices.peek().copied() == Some(idx as u32) {
1062                     continue;
1063                 }
1064
1065                 // the difference between param_ty and expected here is that
1066                 // expected is the parameter when the expected *return* type is
1067                 // taken into account. So in `let _: &[i32] = identity(&[1, 2])`
1068                 // the expected type is already `&[i32]`, whereas param_ty is
1069                 // still an unbound type variable. We don't always want to force
1070                 // the parameter to coerce to the expected type (for example in
1071                 // `coerce_unsize_expected_type_4`).
1072                 let param_ty = self.normalize_associated_types_in(param_ty);
1073                 let expected = Expectation::rvalue_hint(&mut self.table, expected_ty);
1074                 // infer with the expected type we have...
1075                 let ty = self.infer_expr_inner(arg, &expected);
1076
1077                 // then coerce to either the expected type or just the formal parameter type
1078                 let coercion_target = if let Some(ty) = expected.only_has_type(&mut self.table) {
1079                     // if we are coercing to the expectation, unify with the
1080                     // formal parameter type to connect everything
1081                     self.unify(&ty, &param_ty);
1082                     ty
1083                 } else {
1084                     param_ty
1085                 };
1086                 if !coercion_target.is_unknown() {
1087                     if self.coerce(Some(arg), &ty, &coercion_target).is_err() {
1088                         self.result.type_mismatches.insert(
1089                             arg.into(),
1090                             TypeMismatch { expected: coercion_target, actual: ty.clone() },
1091                         );
1092                     }
1093                 }
1094             }
1095         }
1096     }
1097
1098     fn substs_for_method_call(
1099         &mut self,
1100         def_generics: Generics,
1101         generic_args: Option<&GenericArgs>,
1102     ) -> Substitution {
1103         let (parent_params, self_params, type_params, const_params, impl_trait_params) =
1104             def_generics.provenance_split();
1105         assert_eq!(self_params, 0); // method shouldn't have another Self param
1106         let total_len = parent_params + type_params + const_params + impl_trait_params;
1107         let mut substs = Vec::with_capacity(total_len);
1108         // Parent arguments are unknown
1109         for (id, param) in def_generics.iter_parent() {
1110             match param {
1111                 TypeOrConstParamData::TypeParamData(_) => {
1112                     substs.push(GenericArgData::Ty(self.table.new_type_var()).intern(Interner));
1113                 }
1114                 TypeOrConstParamData::ConstParamData(_) => {
1115                     let ty = self.db.const_param_ty(ConstParamId::from_unchecked(id));
1116                     substs
1117                         .push(GenericArgData::Const(self.table.new_const_var(ty)).intern(Interner));
1118                 }
1119             }
1120         }
1121         // handle provided arguments
1122         if let Some(generic_args) = generic_args {
1123             // if args are provided, it should be all of them, but we can't rely on that
1124             for (arg, kind_id) in generic_args
1125                 .args
1126                 .iter()
1127                 .filter(|arg| !matches!(arg, GenericArg::Lifetime(_)))
1128                 .take(type_params + const_params)
1129                 .zip(def_generics.iter_id().skip(parent_params))
1130             {
1131                 if let Some(g) = generic_arg_to_chalk(
1132                     self.db,
1133                     kind_id,
1134                     arg,
1135                     self,
1136                     |this, type_ref| this.make_ty(type_ref),
1137                     |this, c| {
1138                         const_or_path_to_chalk(
1139                             this.db,
1140                             &this.resolver,
1141                             c,
1142                             ParamLoweringMode::Placeholder,
1143                             || generics(this.db.upcast(), (&this.resolver).generic_def().unwrap()),
1144                             DebruijnIndex::INNERMOST,
1145                         )
1146                     },
1147                 ) {
1148                     substs.push(g);
1149                 }
1150             }
1151         };
1152         for (id, data) in def_generics.iter().skip(substs.len()) {
1153             match data {
1154                 TypeOrConstParamData::TypeParamData(_) => {
1155                     substs.push(GenericArgData::Ty(self.table.new_type_var()).intern(Interner))
1156                 }
1157                 TypeOrConstParamData::ConstParamData(_) => {
1158                     substs.push(
1159                         GenericArgData::Const(self.table.new_const_var(
1160                             self.db.const_param_ty(ConstParamId::from_unchecked(id)),
1161                         ))
1162                         .intern(Interner),
1163                     )
1164                 }
1165             }
1166         }
1167         assert_eq!(substs.len(), total_len);
1168         Substitution::from_iter(Interner, substs)
1169     }
1170
1171     fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
1172         let callable_ty = self.resolve_ty_shallow(callable_ty);
1173         if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(Interner) {
1174             let def: CallableDefId = from_chalk(self.db, *fn_def);
1175             let generic_predicates = self.db.generic_predicates(def.into());
1176             for predicate in generic_predicates.iter() {
1177                 let (predicate, binders) = predicate
1178                     .clone()
1179                     .substitute(Interner, parameters)
1180                     .into_value_and_skipped_binders();
1181                 always!(binders.len(Interner) == 0); // quantified where clauses not yet handled
1182                 self.push_obligation(predicate.cast(Interner));
1183             }
1184             // add obligation for trait implementation, if this is a trait method
1185             match def {
1186                 CallableDefId::FunctionId(f) => {
1187                     if let ItemContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container {
1188                         // construct a TraitRef
1189                         let substs = crate::subst_prefix(
1190                             &*parameters,
1191                             generics(self.db.upcast(), trait_.into()).len(),
1192                         );
1193                         self.push_obligation(
1194                             TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
1195                                 .cast(Interner),
1196                         );
1197                     }
1198                 }
1199                 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}
1200             }
1201         }
1202     }
1203
1204     /// Returns the argument indices to skip.
1205     fn check_legacy_const_generics(&mut self, callee: Ty, args: &[ExprId]) -> Vec<u32> {
1206         let (func, subst) = match callee.kind(Interner) {
1207             TyKind::FnDef(fn_id, subst) => {
1208                 let callable = CallableDefId::from_chalk(self.db, *fn_id);
1209                 let func = match callable {
1210                     CallableDefId::FunctionId(f) => f,
1211                     _ => return Vec::new(),
1212                 };
1213                 (func, subst)
1214             }
1215             _ => return Vec::new(),
1216         };
1217
1218         let data = self.db.function_data(func);
1219         if data.legacy_const_generics_indices.is_empty() {
1220             return Vec::new();
1221         }
1222
1223         // only use legacy const generics if the param count matches with them
1224         if data.params.len() + data.legacy_const_generics_indices.len() != args.len() {
1225             if args.len() <= data.params.len() {
1226                 return Vec::new();
1227             } else {
1228                 // there are more parameters than there should be without legacy
1229                 // const params; use them
1230                 let mut indices = data.legacy_const_generics_indices.clone();
1231                 indices.sort();
1232                 return indices;
1233             }
1234         }
1235
1236         // check legacy const parameters
1237         for (subst_idx, arg_idx) in data.legacy_const_generics_indices.iter().copied().enumerate() {
1238             let arg = match subst.at(Interner, subst_idx).constant(Interner) {
1239                 Some(c) => c,
1240                 None => continue, // not a const parameter?
1241             };
1242             if arg_idx >= args.len() as u32 {
1243                 continue;
1244             }
1245             let _ty = arg.data(Interner).ty.clone();
1246             let expected = Expectation::none(); // FIXME use actual const ty, when that is lowered correctly
1247             self.infer_expr(args[arg_idx as usize], &expected);
1248             // FIXME: evaluate and unify with the const
1249         }
1250         let mut indices = data.legacy_const_generics_indices.clone();
1251         indices.sort();
1252         indices
1253     }
1254
1255     fn builtin_binary_op_return_ty(&mut self, op: BinaryOp, lhs_ty: Ty, rhs_ty: Ty) -> Option<Ty> {
1256         let lhs_ty = self.resolve_ty_shallow(&lhs_ty);
1257         let rhs_ty = self.resolve_ty_shallow(&rhs_ty);
1258         match op {
1259             BinaryOp::LogicOp(_) | BinaryOp::CmpOp(_) => {
1260                 Some(TyKind::Scalar(Scalar::Bool).intern(Interner))
1261             }
1262             BinaryOp::Assignment { .. } => Some(TyBuilder::unit()),
1263             BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) => {
1264                 // all integer combinations are valid here
1265                 if matches!(
1266                     lhs_ty.kind(Interner),
1267                     TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_))
1268                         | TyKind::InferenceVar(_, TyVariableKind::Integer)
1269                 ) && matches!(
1270                     rhs_ty.kind(Interner),
1271                     TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_))
1272                         | TyKind::InferenceVar(_, TyVariableKind::Integer)
1273                 ) {
1274                     Some(lhs_ty)
1275                 } else {
1276                     None
1277                 }
1278             }
1279             BinaryOp::ArithOp(_) => match (lhs_ty.kind(Interner), rhs_ty.kind(Interner)) {
1280                 // (int, int) | (uint, uint) | (float, float)
1281                 (TyKind::Scalar(Scalar::Int(_)), TyKind::Scalar(Scalar::Int(_)))
1282                 | (TyKind::Scalar(Scalar::Uint(_)), TyKind::Scalar(Scalar::Uint(_)))
1283                 | (TyKind::Scalar(Scalar::Float(_)), TyKind::Scalar(Scalar::Float(_))) => {
1284                     Some(rhs_ty)
1285                 }
1286                 // ({int}, int) | ({int}, uint)
1287                 (
1288                     TyKind::InferenceVar(_, TyVariableKind::Integer),
1289                     TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_)),
1290                 ) => Some(rhs_ty),
1291                 // (int, {int}) | (uint, {int})
1292                 (
1293                     TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_)),
1294                     TyKind::InferenceVar(_, TyVariableKind::Integer),
1295                 ) => Some(lhs_ty),
1296                 // ({float} | float)
1297                 (
1298                     TyKind::InferenceVar(_, TyVariableKind::Float),
1299                     TyKind::Scalar(Scalar::Float(_)),
1300                 ) => Some(rhs_ty),
1301                 // (float, {float})
1302                 (
1303                     TyKind::Scalar(Scalar::Float(_)),
1304                     TyKind::InferenceVar(_, TyVariableKind::Float),
1305                 ) => Some(lhs_ty),
1306                 // ({int}, {int}) | ({float}, {float})
1307                 (
1308                     TyKind::InferenceVar(_, TyVariableKind::Integer),
1309                     TyKind::InferenceVar(_, TyVariableKind::Integer),
1310                 )
1311                 | (
1312                     TyKind::InferenceVar(_, TyVariableKind::Float),
1313                     TyKind::InferenceVar(_, TyVariableKind::Float),
1314                 ) => Some(rhs_ty),
1315                 _ => None,
1316             },
1317         }
1318     }
1319
1320     fn builtin_binary_op_rhs_expectation(&mut self, op: BinaryOp, lhs_ty: Ty) -> Option<Ty> {
1321         Some(match op {
1322             BinaryOp::LogicOp(..) => TyKind::Scalar(Scalar::Bool).intern(Interner),
1323             BinaryOp::Assignment { op: None } => lhs_ty,
1324             BinaryOp::CmpOp(CmpOp::Eq { .. }) => match self
1325                 .resolve_ty_shallow(&lhs_ty)
1326                 .kind(Interner)
1327             {
1328                 TyKind::Scalar(_) | TyKind::Str => lhs_ty,
1329                 TyKind::InferenceVar(_, TyVariableKind::Integer | TyVariableKind::Float) => lhs_ty,
1330                 _ => return None,
1331             },
1332             BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) => return None,
1333             BinaryOp::CmpOp(CmpOp::Ord { .. })
1334             | BinaryOp::Assignment { op: Some(_) }
1335             | BinaryOp::ArithOp(_) => match self.resolve_ty_shallow(&lhs_ty).kind(Interner) {
1336                 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_)) => lhs_ty,
1337                 TyKind::InferenceVar(_, TyVariableKind::Integer | TyVariableKind::Float) => lhs_ty,
1338                 _ => return None,
1339             },
1340         })
1341     }
1342
1343     fn resolve_binop_method(&self, op: BinaryOp) -> Option<FunctionId> {
1344         let (name, lang_item) = match op {
1345             BinaryOp::LogicOp(_) => return None,
1346             BinaryOp::ArithOp(aop) => match aop {
1347                 ArithOp::Add => (name!(add), name!(add)),
1348                 ArithOp::Mul => (name!(mul), name!(mul)),
1349                 ArithOp::Sub => (name!(sub), name!(sub)),
1350                 ArithOp::Div => (name!(div), name!(div)),
1351                 ArithOp::Rem => (name!(rem), name!(rem)),
1352                 ArithOp::Shl => (name!(shl), name!(shl)),
1353                 ArithOp::Shr => (name!(shr), name!(shr)),
1354                 ArithOp::BitXor => (name!(bitxor), name!(bitxor)),
1355                 ArithOp::BitOr => (name!(bitor), name!(bitor)),
1356                 ArithOp::BitAnd => (name!(bitand), name!(bitand)),
1357             },
1358             BinaryOp::Assignment { op: Some(aop) } => match aop {
1359                 ArithOp::Add => (name!(add_assign), name!(add_assign)),
1360                 ArithOp::Mul => (name!(mul_assign), name!(mul_assign)),
1361                 ArithOp::Sub => (name!(sub_assign), name!(sub_assign)),
1362                 ArithOp::Div => (name!(div_assign), name!(div_assign)),
1363                 ArithOp::Rem => (name!(rem_assign), name!(rem_assign)),
1364                 ArithOp::Shl => (name!(shl_assign), name!(shl_assign)),
1365                 ArithOp::Shr => (name!(shr_assign), name!(shr_assign)),
1366                 ArithOp::BitXor => (name!(bitxor_assign), name!(bitxor_assign)),
1367                 ArithOp::BitOr => (name!(bitor_assign), name!(bitor_assign)),
1368                 ArithOp::BitAnd => (name!(bitand_assign), name!(bitand_assign)),
1369             },
1370             BinaryOp::CmpOp(cop) => match cop {
1371                 CmpOp::Eq { negated: false } => (name!(eq), name!(eq)),
1372                 CmpOp::Eq { negated: true } => (name!(ne), name!(eq)),
1373                 CmpOp::Ord { ordering: Ordering::Less, strict: false } => {
1374                     (name!(le), name!(partial_ord))
1375                 }
1376                 CmpOp::Ord { ordering: Ordering::Less, strict: true } => {
1377                     (name!(lt), name!(partial_ord))
1378                 }
1379                 CmpOp::Ord { ordering: Ordering::Greater, strict: false } => {
1380                     (name!(ge), name!(partial_ord))
1381                 }
1382                 CmpOp::Ord { ordering: Ordering::Greater, strict: true } => {
1383                     (name!(gt), name!(partial_ord))
1384                 }
1385             },
1386             BinaryOp::Assignment { op: None } => return None,
1387         };
1388
1389         let trait_ = self.resolve_lang_item(lang_item)?.as_trait()?;
1390
1391         self.db.trait_data(trait_).method_by_name(&name)
1392     }
1393 }