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 };
   8
   9 use chalk_ir::{
  10     cast::Cast, fold::Shift, DebruijnIndex, GenericArgData, Mutability, TyVariableKind,
  11 };
  12 use hir_def::{
  13     expr::{ArithOp, Array, BinaryOp, CmpOp, Expr, ExprId, Literal, Ordering, Statement, UnaryOp},
  14     generics::TypeOrConstParamData,
  15     path::{GenericArg, GenericArgs},
  16     resolver::resolver_for_expr,
  17     ConstParamId, FieldId, FunctionId, ItemContainerId, Lookup,
  18 };
  19 use hir_expand::name::{name, Name};
  20 use stdx::always;
  21 use syntax::ast::RangeOp;
  22
  23 use crate::{
  24     autoderef::{self, Autoderef},
  25     consteval,
  26     infer::coerce::CoerceMany,
  27     lower::{
  28         const_or_path_to_chalk, generic_arg_to_chalk, lower_to_chalk_mutability, ParamLoweringMode,
  29     },
  30     mapping::{from_chalk, ToChalk},
  31     method_resolution::{self, VisibleFromModule},
  32     primitive::{self, UintTy},
  33     static_lifetime, to_chalk_trait_id,
  34     utils::{generics, Generics},
  35     AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, Interner, Rawness, Scalar,
  36     Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
  37 };
  38
  39 use super::{
  40     coerce::auto_deref_adjust_steps, find_breakable, BindingMode, BreakableContext, Diverges,
  41     Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch,
  42 };
  43
  44 impl<'a> InferenceContext<'a> {
  45     pub(crate) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
  46         let ty = self.infer_expr_inner(tgt_expr, expected);
  47         if let Some(expected_ty) = expected.only_has_type(&mut self.table) {
  48             let could_unify = self.unify(&ty, &expected_ty);
  49             if !could_unify {
  50                 self.result.type_mismatches.insert(
  51                     tgt_expr.into(),
  52                     TypeMismatch { expected: expected_ty, actual: ty.clone() },
  53                 );
  54             }
  55         }
  56         ty
  57     }
  58
  59     /// Infer type of expression with possibly implicit coerce to the expected type.
  60     /// Return the type after possible coercion.
  61     pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
  62         let ty = self.infer_expr_inner(expr, expected);
  63         if let Some(target) = expected.only_has_type(&mut self.table) {
  64             match self.coerce(Some(expr), &ty, &target) {
  65                 Ok(res) => res,
  66                 Err(_) => {
  67                     self.result.type_mismatches.insert(
  68                         expr.into(),
  69                         TypeMismatch { expected: target.clone(), actual: ty.clone() },
  70                     );
  71                     target
  72                 }
  73             }
  74         } else {
  75             ty
  76         }
  77     }
  78
  79     fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
  80         self.db.unwind_if_cancelled();
  81
  82         let ty = match &self.body[tgt_expr] {
  83             Expr::Missing => self.err_ty(),
  84             &Expr::If { condition, then_branch, else_branch } => {
  85                 self.infer_expr(
  86                     condition,
  87                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(Interner)),
  88                 );
  89
  90                 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
  91                 let mut both_arms_diverge = Diverges::Always;
  92
  93                 let result_ty = self.table.new_type_var();
  94                 let then_ty = self.infer_expr_inner(then_branch, expected);
  95                 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
  96                 let mut coerce = CoerceMany::new(result_ty);
  97                 coerce.coerce(self, Some(then_branch), &then_ty);
  98                 let else_ty = match else_branch {
  99                     Some(else_branch) => self.infer_expr_inner(else_branch, expected),
 100                     None => TyBuilder::unit(),
 101                 };
 102                 both_arms_diverge &= self.diverges;
 103                 // FIXME: create a synthetic `else {}` so we have something to refer to here instead of None?
 104                 coerce.coerce(self, else_branch, &else_ty);
 105
 106                 self.diverges = condition_diverges | both_arms_diverge;
 107
 108                 coerce.complete()
 109             }
 110             &Expr::Let { pat, expr } => {
 111                 let input_ty = self.infer_expr(expr, &Expectation::none());
 112                 self.infer_pat(pat, &input_ty, BindingMode::default());
 113                 TyKind::Scalar(Scalar::Bool).intern(Interner)
 114             }
 115             Expr::Block { statements, tail, label, id: _ } => {
 116                 let old_resolver = mem::replace(
 117                     &mut self.resolver,
 118                     resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
 119                 );
 120                 let ty = match label {
 121                     Some(_) => {
 122                         let break_ty = self.table.new_type_var();
 123                         self.breakables.push(BreakableContext {
 124                             may_break: false,
 125                             coerce: CoerceMany::new(break_ty.clone()),
 126                             label: label.map(|label| self.body[label].name.clone()),
 127                         });
 128                         let ty = self.infer_block(
 129                             tgt_expr,
 130                             statements,
 131                             *tail,
 132                             &Expectation::has_type(break_ty),
 133                         );
 134                         let ctxt = self.breakables.pop().expect("breakable stack broken");
 135                         if ctxt.may_break {
 136                             ctxt.coerce.complete()
 137                         } else {
 138                             ty
 139                         }
 140                     }
 141                     None => self.infer_block(tgt_expr, statements, *tail, expected),
 142                 };
 143                 self.resolver = old_resolver;
 144                 ty
 145             }
 146             Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
 147             Expr::TryBlock { body } => {
 148                 let _inner = self.infer_expr(*body, expected);
 149                 // FIXME should be std::result::Result<{inner}, _>
 150                 self.err_ty()
 151             }
 152             Expr::Async { body } => {
 153                 let ret_ty = self.table.new_type_var();
 154                 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 155                 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
 156
 157                 let inner_ty = self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
 158
 159                 self.diverges = prev_diverges;
 160                 self.return_ty = prev_ret_ty;
 161
 162                 // Use the first type parameter as the output type of future.
 163                 // existential type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
 164                 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
 165                 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
 166                 TyKind::OpaqueType(opaque_ty_id, Substitution::from1(Interner, inner_ty))
 167                     .intern(Interner)
 168             }
 169             Expr::Loop { body, label } => {
 170                 self.breakables.push(BreakableContext {
 171                     may_break: false,
 172                     coerce: CoerceMany::new(self.table.new_type_var()),
 173                     label: label.map(|label| self.body[label].name.clone()),
 174                 });
 175                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 176
 177                 let ctxt = self.breakables.pop().expect("breakable stack broken");
 178
 179                 if ctxt.may_break {
 180                     self.diverges = Diverges::Maybe;
 181                     ctxt.coerce.complete()
 182                 } else {
 183                     TyKind::Never.intern(Interner)
 184                 }
 185             }
 186             Expr::While { condition, body, label } => {
 187                 self.breakables.push(BreakableContext {
 188                     may_break: false,
 189                     coerce: CoerceMany::new(self.err_ty()),
 190                     label: label.map(|label| self.body[label].name.clone()),
 191                 });
 192                 self.infer_expr(
 193                     *condition,
 194                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(Interner)),
 195                 );
 196                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 197                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 198                 // the body may not run, so it diverging doesn't mean we diverge
 199                 self.diverges = Diverges::Maybe;
 200                 TyBuilder::unit()
 201             }
 202             Expr::For { iterable, body, pat, label } => {
 203                 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
 204
 205                 self.breakables.push(BreakableContext {
 206                     may_break: false,
 207                     coerce: CoerceMany::new(self.err_ty()),
 208                     label: label.map(|label| self.body[label].name.clone()),
 209                 });
 210                 let pat_ty =
 211                     self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
 212
 213                 self.infer_pat(*pat, &pat_ty, BindingMode::default());
 214
 215                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 216                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 217                 // the body may not run, so it diverging doesn't mean we diverge
 218                 self.diverges = Diverges::Maybe;
 219                 TyBuilder::unit()
 220             }
 221             Expr::Lambda { body, args, ret_type, arg_types } => {
 222                 assert_eq!(args.len(), arg_types.len());
 223
 224                 let mut sig_tys = Vec::new();
 225
 226                 // collect explicitly written argument types
 227                 for arg_type in arg_types.iter() {
 228                     let arg_ty = match arg_type {
 229                         Some(type_ref) => self.make_ty(type_ref),
 230                         None => self.table.new_type_var(),
 231                     };
 232                     sig_tys.push(arg_ty);
 233                 }
 234
 235                 // add return type
 236                 let ret_ty = match ret_type {
 237                     Some(type_ref) => self.make_ty(type_ref),
 238                     None => self.table.new_type_var(),
 239                 };
 240                 sig_tys.push(ret_ty.clone());
 241                 let sig_ty = TyKind::Function(FnPointer {
 242                     num_binders: 0,
 243                     sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
 244                     substitution: FnSubst(
 245                         Substitution::from_iter(Interner, sig_tys.clone()).shifted_in(Interner),
 246                     ),
 247                 })
 248                 .intern(Interner);
 249                 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
 250                 let closure_ty =
 251                     TyKind::Closure(closure_id, Substitution::from1(Interner, sig_ty.clone()))
 252                         .intern(Interner);
 253
 254                 // Eagerly try to relate the closure type with the expected
 255                 // type, otherwise we often won't have enough information to
 256                 // infer the body.
 257                 self.deduce_closure_type_from_expectations(
 258                     tgt_expr,
 259                     &closure_ty,
 260                     &sig_ty,
 261                     expected,
 262                 );
 263
 264                 // Now go through the argument patterns
 265                 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
 266                     self.infer_pat(*arg_pat, &arg_ty, BindingMode::default());
 267                 }
 268
 269                 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 270                 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
 271
 272                 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
 273
 274                 self.diverges = prev_diverges;
 275                 self.return_ty = prev_ret_ty;
 276
 277                 closure_ty
 278             }
 279             Expr::Call { callee, args } => {
 280                 let callee_ty = self.infer_expr(*callee, &Expectation::none());
 281                 let mut derefs = Autoderef::new(&mut self.table, callee_ty.clone());
 282                 let mut res = None;
 283                 let mut derefed_callee = callee_ty.clone();
 284                 // manual loop to be able to access `derefs.table`
 285                 while let Some((callee_deref_ty, _)) = derefs.next() {
 286                     res = derefs.table.callable_sig(&callee_deref_ty, args.len());
 287                     if res.is_some() {
 288                         derefed_callee = callee_deref_ty;
 289                         break;
 290                     }
 291                 }
 292                 // if the function is unresolved, we use is_varargs=true to
 293                 // suppress the arg count diagnostic here
 294                 let is_varargs =
 295                     derefed_callee.callable_sig(self.db).map_or(false, |sig| sig.is_varargs)
 296                         || res.is_none();
 297                 let (param_tys, ret_ty) = match res {
 298                     Some(res) => {
 299                         let adjustments = auto_deref_adjust_steps(&derefs);
 300                         self.write_expr_adj(*callee, adjustments);
 301                         res
 302                     }
 303                     None => (Vec::new(), self.err_ty()), // FIXME diagnostic
 304                 };
 305                 let indices_to_skip = self.check_legacy_const_generics(derefed_callee, args);
 306                 self.register_obligations_for_call(&callee_ty);
 307
 308                 let expected_inputs = self.expected_inputs_for_expected_output(
 309                     expected,
 310                     ret_ty.clone(),
 311                     param_tys.clone(),
 312                 );
 313
 314                 self.check_call_arguments(
 315                     tgt_expr,
 316                     args,
 317                     &expected_inputs,
 318                     &param_tys,
 319                     &indices_to_skip,
 320                     is_varargs,
 321                 );
 322                 self.normalize_associated_types_in(ret_ty)
 323             }
 324             Expr::MethodCall { receiver, args, method_name, generic_args } => self
 325                 .infer_method_call(
 326                     tgt_expr,
 327                     *receiver,
 328                     args,
 329                     method_name,
 330                     generic_args.as_deref(),
 331                     expected,
 332                 ),
 333             Expr::Match { expr, arms } => {
 334                 let input_ty = self.infer_expr(*expr, &Expectation::none());
 335
 336                 let expected = expected.adjust_for_branches(&mut self.table);
 337
 338                 let result_ty = if arms.is_empty() {
 339                     TyKind::Never.intern(Interner)
 340                 } else {
 341                     match &expected {
 342                         Expectation::HasType(ty) => ty.clone(),
 343                         _ => self.table.new_type_var(),
 344                     }
 345                 };
 346                 let mut coerce = CoerceMany::new(result_ty);
 347
 348                 let matchee_diverges = self.diverges;
 349                 let mut all_arms_diverge = Diverges::Always;
 350
 351                 for arm in arms.iter() {
 352                     self.diverges = Diverges::Maybe;
 353                     let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
 354                     if let Some(guard_expr) = arm.guard {
 355                         self.infer_expr(
 356                             guard_expr,
 357                             &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(Interner)),
 358                         );
 359                     }
 360
 361                     let arm_ty = self.infer_expr_inner(arm.expr, &expected);
 362                     all_arms_diverge &= self.diverges;
 363                     coerce.coerce(self, Some(arm.expr), &arm_ty);
 364                 }
 365
 366                 self.diverges = matchee_diverges | all_arms_diverge;
 367
 368                 coerce.complete()
 369             }
 370             Expr::Path(p) => {
 371                 // FIXME this could be more efficient...
 372                 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
 373                 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or_else(|| self.err_ty())
 374             }
 375             Expr::Continue { .. } => TyKind::Never.intern(Interner),
 376             Expr::Break { expr, label } => {
 377                 let mut coerce = match find_breakable(&mut self.breakables, label.as_ref()) {
 378                     Some(ctxt) => {
 379                         // avoiding the borrowck
 380                         mem::replace(
 381                             &mut ctxt.coerce,
 382                             CoerceMany::new(self.result.standard_types.unknown.clone()),
 383                         )
 384                     }
 385                     None => CoerceMany::new(self.result.standard_types.unknown.clone()),
 386                 };
 387
 388                 let val_ty = if let Some(expr) = *expr {
 389                     self.infer_expr(expr, &Expectation::none())
 390                 } else {
 391                     TyBuilder::unit()
 392                 };
 393
 394                 // FIXME: create a synthetic `()` during lowering so we have something to refer to here?
 395                 coerce.coerce(self, *expr, &val_ty);
 396
 397                 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
 398                     ctxt.coerce = coerce;
 399                     ctxt.may_break = true;
 400                 } else {
 401                     self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
 402                         expr: tgt_expr,
 403                     });
 404                 };
 405
 406                 TyKind::Never.intern(Interner)
 407             }
 408             Expr::Return { expr } => {
 409                 if let Some(expr) = expr {
 410                     self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
 411                 } else {
 412                     let unit = TyBuilder::unit();
 413                     let _ = self.coerce(Some(tgt_expr), &unit, &self.return_ty.clone());
 414                 }
 415                 TyKind::Never.intern(Interner)
 416             }
 417             Expr::Yield { expr } => {
 418                 // FIXME: track yield type for coercion
 419                 if let Some(expr) = expr {
 420                     self.infer_expr(*expr, &Expectation::none());
 421                 }
 422                 TyKind::Never.intern(Interner)
 423             }
 424             Expr::RecordLit { path, fields, spread } => {
 425                 let (ty, def_id) = self.resolve_variant(path.as_deref(), false);
 426                 if let Some(variant) = def_id {
 427                     self.write_variant_resolution(tgt_expr.into(), variant);
 428                 }
 429
 430                 if let Some(t) = expected.only_has_type(&mut self.table) {
 431                     self.unify(&ty, &t);
 432                 }
 433
 434                 let substs = ty
 435                     .as_adt()
 436                     .map(|(_, s)| s.clone())
 437                     .unwrap_or_else(|| Substitution::empty(Interner));
 438                 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
 439                 let variant_data = def_id.map(|it| it.variant_data(self.db.upcast()));
 440                 for field in fields.iter() {
 441                     let field_def =
 442                         variant_data.as_ref().and_then(|it| match it.field(&field.name) {
 443                             Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
 444                             None => {
 445                                 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
 446                                     expr: field.expr,
 447                                 });
 448                                 None
 449                             }
 450                         });
 451                     let field_ty = field_def.map_or(self.err_ty(), |it| {
 452                         field_types[it.local_id].clone().substitute(Interner, &substs)
 453                     });
 454                     self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
 455                 }
 456                 if let Some(expr) = spread {
 457                     self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
 458                 }
 459                 ty
 460             }
 461             Expr::Field { expr, name } => {
 462                 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
 463
 464                 let mut autoderef = Autoderef::new(&mut self.table, receiver_ty);
 465                 let ty = autoderef.by_ref().find_map(|(derefed_ty, _)| {
 466                     let (field_id, parameters) = match derefed_ty.kind(Interner) {
 467                         TyKind::Tuple(_, substs) => {
 468                             return name.as_tuple_index().and_then(|idx| {
 469                                 substs
 470                                     .as_slice(Interner)
 471                                     .get(idx)
 472                                     .map(|a| a.assert_ty_ref(Interner))
 473                                     .cloned()
 474                             });
 475                         }
 476                         TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
 477                             let local_id = self.db.struct_data(*s).variant_data.field(name)?;
 478                             let field = FieldId { parent: (*s).into(), local_id };
 479                             (field, parameters.clone())
 480                         }
 481                         TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
 482                             let local_id = self.db.union_data(*u).variant_data.field(name)?;
 483                             let field = FieldId { parent: (*u).into(), local_id };
 484                             (field, parameters.clone())
 485                         }
 486                         _ => return None,
 487                     };
 488                     let is_visible = self.db.field_visibilities(field_id.parent)[field_id.local_id]
 489                         .is_visible_from(self.db.upcast(), self.resolver.module());
 490                     if !is_visible {
 491                         // Write down the first field resolution even if it is not visible
 492                         // This aids IDE features for private fields like goto def and in
 493                         // case of autoderef finding an applicable field, this will be
 494                         // overwritten in a following cycle
 495                         if let Entry::Vacant(entry) = self.result.field_resolutions.entry(tgt_expr)
 496                         {
 497                             entry.insert(field_id);
 498                         }
 499                         return None;
 500                     }
 501                     // can't have `write_field_resolution` here because `self.table` is borrowed :(
 502                     self.result.field_resolutions.insert(tgt_expr, field_id);
 503                     let ty = self.db.field_types(field_id.parent)[field_id.local_id]
 504                         .clone()
 505                         .substitute(Interner, &parameters);
 506                     Some(ty)
 507                 });
 508                 let ty = match ty {
 509                     Some(ty) => {
 510                         let adjustments = auto_deref_adjust_steps(&autoderef);
 511                         self.write_expr_adj(*expr, adjustments);
 512                         let ty = self.insert_type_vars(ty);
 513                         let ty = self.normalize_associated_types_in(ty);
 514                         ty
 515                     }
 516                     _ => self.err_ty(),
 517                 };
 518                 ty
 519             }
 520             Expr::Await { expr } => {
 521                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 522                 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
 523             }
 524             Expr::Try { expr } => {
 525                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 526                 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
 527             }
 528             Expr::Cast { expr, type_ref } => {
 529                 // FIXME: propagate the "castable to" expectation (and find a test case that shows this is necessary)
 530                 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 531                 let cast_ty = self.make_ty(type_ref);
 532                 // FIXME check the cast...
 533                 cast_ty
 534             }
 535             Expr::Ref { expr, rawness, mutability } => {
 536                 let mutability = lower_to_chalk_mutability(*mutability);
 537                 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) = expected
 538                     .only_has_type(&mut self.table)
 539                     .as_ref()
 540                     .and_then(|t| t.as_reference_or_ptr())
 541                 {
 542                     if exp_mutability == Mutability::Mut && mutability == Mutability::Not {
 543                         // FIXME: record type error - expected mut reference but found shared ref,
 544                         // which cannot be coerced
 545                     }
 546                     if exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
 547                         // FIXME: record type error - expected reference but found ptr,
 548                         // which cannot be coerced
 549                     }
 550                     Expectation::rvalue_hint(&mut self.table, Ty::clone(exp_inner))
 551                 } else {
 552                     Expectation::none()
 553                 };
 554                 let inner_ty = self.infer_expr_inner(*expr, &expectation);
 555                 match rawness {
 556                     Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
 557                     Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
 558                 }
 559                 .intern(Interner)
 560             }
 561             &Expr::Box { expr } => self.infer_expr_box(expr, expected),
 562             Expr::UnaryOp { expr, op } => {
 563                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 564                 let inner_ty = self.resolve_ty_shallow(&inner_ty);
 565                 match op {
 566                     UnaryOp::Deref => {
 567                         autoderef::deref(&mut self.table, inner_ty).unwrap_or_else(|| self.err_ty())
 568                     }
 569                     UnaryOp::Neg => {
 570                         match inner_ty.kind(Interner) {
 571                             // Fast path for builtins
 572                             TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_))
 573                             | TyKind::InferenceVar(
 574                                 _,
 575                                 TyVariableKind::Integer | TyVariableKind::Float,
 576                             ) => inner_ty,
 577                             // Otherwise we resolve via the std::ops::Neg trait
 578                             _ => self
 579                                 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
 580                         }
 581                     }
 582                     UnaryOp::Not => {
 583                         match inner_ty.kind(Interner) {
 584                             // Fast path for builtins
 585                             TyKind::Scalar(Scalar::Bool | Scalar::Int(_) | Scalar::Uint(_))
 586                             | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
 587                             // Otherwise we resolve via the std::ops::Not trait
 588                             _ => self
 589                                 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
 590                         }
 591                     }
 592                 }
 593             }
 594             Expr::BinaryOp { lhs, rhs, op } => match op {
 595                 Some(BinaryOp::Assignment { op: None }) => {
 596                     let lhs_ty = self.infer_expr(*lhs, &Expectation::none());
 597                     self.infer_expr_coerce(*rhs, &Expectation::has_type(lhs_ty));
 598                     self.result.standard_types.unit.clone()
 599                 }
 600                 Some(BinaryOp::LogicOp(_)) => {
 601                     let bool_ty = self.result.standard_types.bool_.clone();
 602                     self.infer_expr_coerce(*lhs, &Expectation::HasType(bool_ty.clone()));
 603                     let lhs_diverges = self.diverges;
 604                     self.infer_expr_coerce(*rhs, &Expectation::HasType(bool_ty.clone()));
 605                     // Depending on the LHS' value, the RHS can never execute.
 606                     self.diverges = lhs_diverges;
 607                     bool_ty
 608                 }
 609                 Some(op) => self.infer_overloadable_binop(*lhs, *op, *rhs, tgt_expr),
 610                 _ => self.err_ty(),
 611             },
 612             Expr::Range { lhs, rhs, range_type } => {
 613                 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
 614                 let rhs_expect = lhs_ty
 615                     .as_ref()
 616                     .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
 617                 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
 618                 match (range_type, lhs_ty, rhs_ty) {
 619                     (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
 620                         Some(adt) => TyBuilder::adt(self.db, adt).build(),
 621                         None => self.err_ty(),
 622                     },
 623                     (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
 624                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 625                         None => self.err_ty(),
 626                     },
 627                     (RangeOp::Inclusive, None, Some(ty)) => {
 628                         match self.resolve_range_to_inclusive() {
 629                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 630                             None => self.err_ty(),
 631                         }
 632                     }
 633                     (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
 634                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 635                         None => self.err_ty(),
 636                     },
 637                     (RangeOp::Inclusive, Some(_), Some(ty)) => {
 638                         match self.resolve_range_inclusive() {
 639                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 640                             None => self.err_ty(),
 641                         }
 642                     }
 643                     (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
 644                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 645                         None => self.err_ty(),
 646                     },
 647                     (RangeOp::Inclusive, _, None) => self.err_ty(),
 648                 }
 649             }
 650             Expr::Index { base, index } => {
 651                 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
 652                 let index_ty = self.infer_expr(*index, &Expectation::none());
 653
 654                 if let Some(index_trait) = self.resolve_ops_index() {
 655                     let canonicalized = self.canonicalize(base_ty.clone());
 656                     let receiver_adjustments = method_resolution::resolve_indexing_op(
 657                         self.db,
 658                         self.trait_env.clone(),
 659                         canonicalized.value,
 660                         index_trait,
 661                     );
 662                     let (self_ty, adj) = receiver_adjustments
 663                         .map_or((self.err_ty(), Vec::new()), |adj| {
 664                             adj.apply(&mut self.table, base_ty)
 665                         });
 666                     self.write_expr_adj(*base, adj);
 667                     self.resolve_associated_type_with_params(
 668                         self_ty,
 669                         self.resolve_ops_index_output(),
 670                         &[GenericArgData::Ty(index_ty).intern(Interner)],
 671                     )
 672                 } else {
 673                     self.err_ty()
 674                 }
 675             }
 676             Expr::Tuple { exprs } => {
 677                 let mut tys = match expected
 678                     .only_has_type(&mut self.table)
 679                     .as_ref()
 680                     .map(|t| t.kind(Interner))
 681                 {
 682                     Some(TyKind::Tuple(_, substs)) => substs
 683                         .iter(Interner)
 684                         .map(|a| a.assert_ty_ref(Interner).clone())
 685                         .chain(repeat_with(|| self.table.new_type_var()))
 686                         .take(exprs.len())
 687                         .collect::<Vec<_>>(),
 688                     _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
 689                 };
 690
 691                 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
 692                     self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
 693                 }
 694
 695                 TyKind::Tuple(tys.len(), Substitution::from_iter(Interner, tys)).intern(Interner)
 696             }
 697             Expr::Array(array) => {
 698                 let elem_ty =
 699                     match expected.to_option(&mut self.table).as_ref().map(|t| t.kind(Interner)) {
 700                         Some(TyKind::Array(st, _) | TyKind::Slice(st)) => st.clone(),
 701                         _ => self.table.new_type_var(),
 702                     };
 703                 let mut coerce = CoerceMany::new(elem_ty.clone());
 704
 705                 let expected = Expectation::has_type(elem_ty.clone());
 706                 let len = match array {
 707                     Array::ElementList(items) => {
 708                         for &expr in items.iter() {
 709                             let cur_elem_ty = self.infer_expr_inner(expr, &expected);
 710                             coerce.coerce(self, Some(expr), &cur_elem_ty);
 711                         }
 712                         consteval::usize_const(Some(items.len() as u64))
 713                     }
 714                     &Array::Repeat { initializer, repeat } => {
 715                         self.infer_expr_coerce(initializer, &Expectation::has_type(elem_ty));
 716                         self.infer_expr(
 717                             repeat,
 718                             &Expectation::has_type(
 719                                 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(Interner),
 720                             ),
 721                         );
 722
 723                         if let Some(g_def) = self.owner.as_generic_def_id() {
 724                             let generics = generics(self.db.upcast(), g_def);
 725                             consteval::eval_to_const(
 726                                 repeat,
 727                                 ParamLoweringMode::Placeholder,
 728                                 self,
 729                                 || generics,
 730                                 DebruijnIndex::INNERMOST,
 731                             )
 732                         } else {
 733                             consteval::usize_const(None)
 734                         }
 735                     }
 736                 };
 737
 738                 TyKind::Array(coerce.complete(), len).intern(Interner)
 739             }
 740             Expr::Literal(lit) => match lit {
 741                 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(Interner),
 742                 Literal::String(..) => {
 743                     TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(Interner))
 744                         .intern(Interner)
 745                 }
 746                 Literal::ByteString(bs) => {
 747                     let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(Interner);
 748
 749                     let len = consteval::usize_const(Some(bs.len() as u64));
 750
 751                     let array_type = TyKind::Array(byte_type, len).intern(Interner);
 752                     TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(Interner)
 753                 }
 754                 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(Interner),
 755                 Literal::Int(_v, ty) => match ty {
 756                     Some(int_ty) => {
 757                         TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
 758                             .intern(Interner)
 759                     }
 760                     None => self.table.new_integer_var(),
 761                 },
 762                 Literal::Uint(_v, ty) => match ty {
 763                     Some(int_ty) => {
 764                         TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
 765                             .intern(Interner)
 766                     }
 767                     None => self.table.new_integer_var(),
 768                 },
 769                 Literal::Float(_v, ty) => match ty {
 770                     Some(float_ty) => {
 771                         TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
 772                             .intern(Interner)
 773                     }
 774                     None => self.table.new_float_var(),
 775                 },
 776             },
 777             Expr::MacroStmts { tail } => self.infer_expr_inner(*tail, expected),
 778         };
 779         // use a new type variable if we got unknown here
 780         let ty = self.insert_type_vars_shallow(ty);
 781         self.write_expr_ty(tgt_expr, ty.clone());
 782         if self.resolve_ty_shallow(&ty).is_never() {
 783             // Any expression that produces a value of type `!` must have diverged
 784             self.diverges = Diverges::Always;
 785         }
 786         ty
 787     }
 788
 789     fn infer_expr_box(&mut self, inner_expr: ExprId, expected: &Expectation) -> Ty {
 790         if let Some(box_id) = self.resolve_boxed_box() {
 791             let table = &mut self.table;
 792             let inner_exp = expected
 793                 .to_option(table)
 794                 .as_ref()
 795                 .map(|e| e.as_adt())
 796                 .flatten()
 797                 .filter(|(e_adt, _)| e_adt == &box_id)
 798                 .map(|(_, subts)| {
 799                     let g = subts.at(Interner, 0);
 800                     Expectation::rvalue_hint(table, Ty::clone(g.assert_ty_ref(Interner)))
 801                 })
 802                 .unwrap_or_else(Expectation::none);
 803
 804             let inner_ty = self.infer_expr_inner(inner_expr, &inner_exp);
 805             TyBuilder::adt(self.db, box_id)
 806                 .push(inner_ty)
 807                 .fill_with_defaults(self.db, || self.table.new_type_var())
 808                 .build()
 809         } else {
 810             self.err_ty()
 811         }
 812     }
 813
 814     fn infer_overloadable_binop(
 815         &mut self,
 816         lhs: ExprId,
 817         op: BinaryOp,
 818         rhs: ExprId,
 819         tgt_expr: ExprId,
 820     ) -> Ty {
 821         let lhs_expectation = Expectation::none();
 822         let lhs_ty = self.infer_expr(lhs, &lhs_expectation);
 823         let rhs_ty = self.table.new_type_var();
 824
 825         let func = self.resolve_binop_method(op);
 826         let func = match func {
 827             Some(func) => func,
 828             None => {
 829                 let rhs_ty = self.builtin_binary_op_rhs_expectation(op, lhs_ty.clone());
 830                 let rhs_ty = self.infer_expr_coerce(rhs, &Expectation::from_option(rhs_ty));
 831                 return self
 832                     .builtin_binary_op_return_ty(op, lhs_ty, rhs_ty)
 833                     .unwrap_or_else(|| self.err_ty());
 834             }
 835         };
 836
 837         let subst = TyBuilder::subst_for_def(self.db, func)
 838             .push(lhs_ty.clone())
 839             .push(rhs_ty.clone())
 840             .build();
 841         self.write_method_resolution(tgt_expr, func, subst.clone());
 842
 843         let method_ty = self.db.value_ty(func.into()).substitute(Interner, &subst);
 844         self.register_obligations_for_call(&method_ty);
 845
 846         self.infer_expr_coerce(rhs, &Expectation::has_type(rhs_ty.clone()));
 847
 848         let ret_ty = match method_ty.callable_sig(self.db) {
 849             Some(sig) => sig.ret().clone(),
 850             None => self.err_ty(),
 851         };
 852
 853         let ret_ty = self.normalize_associated_types_in(ret_ty);
 854
 855         // FIXME: record autoref adjustments
 856
 857         // use knowledge of built-in binary ops, which can sometimes help inference
 858         if let Some(builtin_rhs) = self.builtin_binary_op_rhs_expectation(op, lhs_ty.clone()) {
 859             self.unify(&builtin_rhs, &rhs_ty);
 860         }
 861         if let Some(builtin_ret) = self.builtin_binary_op_return_ty(op, lhs_ty, rhs_ty) {
 862             self.unify(&builtin_ret, &ret_ty);
 863         }
 864
 865         ret_ty
 866     }
 867
 868     fn infer_block(
 869         &mut self,
 870         expr: ExprId,
 871         statements: &[Statement],
 872         tail: Option<ExprId>,
 873         expected: &Expectation,
 874     ) -> Ty {
 875         for stmt in statements {
 876             match stmt {
 877                 Statement::Let { pat, type_ref, initializer, else_branch } => {
 878                     let decl_ty = type_ref
 879                         .as_ref()
 880                         .map(|tr| self.make_ty(tr))
 881                         .unwrap_or_else(|| self.err_ty());
 882
 883                     // Always use the declared type when specified
 884                     let mut ty = decl_ty.clone();
 885
 886                     if let Some(expr) = initializer {
 887                         let actual_ty =
 888                             self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
 889                         if decl_ty.is_unknown() {
 890                             ty = actual_ty;
 891                         }
 892                     }
 893
 894                     if let Some(expr) = else_branch {
 895                         self.infer_expr_coerce(
 896                             *expr,
 897                             &Expectation::has_type(Ty::new(Interner, TyKind::Never)),
 898                         );
 899                     }
 900
 901                     self.infer_pat(*pat, &ty, BindingMode::default());
 902                 }
 903                 Statement::Expr { expr, .. } => {
 904                     self.infer_expr(*expr, &Expectation::none());
 905                 }
 906             }
 907         }
 908
 909         if let Some(expr) = tail {
 910             self.infer_expr_coerce(expr, expected)
 911         } else {
 912             // Citing rustc: if there is no explicit tail expression,
 913             // that is typically equivalent to a tail expression
 914             // of `()` -- except if the block diverges. In that
 915             // case, there is no value supplied from the tail
 916             // expression (assuming there are no other breaks,
 917             // this implies that the type of the block will be
 918             // `!`).
 919             if self.diverges.is_always() {
 920                 // we don't even make an attempt at coercion
 921                 self.table.new_maybe_never_var()
 922             } else {
 923                 if let Some(t) = expected.only_has_type(&mut self.table) {
 924                     if self.coerce(Some(expr), &TyBuilder::unit(), &t).is_err() {
 925                         self.result.type_mismatches.insert(
 926                             expr.into(),
 927                             TypeMismatch { expected: t.clone(), actual: TyBuilder::unit() },
 928                         );
 929                     }
 930                     t
 931                 } else {
 932                     TyBuilder::unit()
 933                 }
 934             }
 935         }
 936     }
 937
 938     fn infer_method_call(
 939         &mut self,
 940         tgt_expr: ExprId,
 941         receiver: ExprId,
 942         args: &[ExprId],
 943         method_name: &Name,
 944         generic_args: Option<&GenericArgs>,
 945         expected: &Expectation,
 946     ) -> Ty {
 947         let receiver_ty = self.infer_expr(receiver, &Expectation::none());
 948         let canonicalized_receiver = self.canonicalize(receiver_ty.clone());
 949
 950         let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
 951
 952         let resolved = method_resolution::lookup_method(
 953             &canonicalized_receiver.value,
 954             self.db,
 955             self.trait_env.clone(),
 956             &traits_in_scope,
 957             VisibleFromModule::Filter(self.resolver.module()),
 958             method_name,
 959         );
 960         let (receiver_ty, method_ty, substs) = match resolved {
 961             Some((adjust, func)) => {
 962                 let (ty, adjustments) = adjust.apply(&mut self.table, receiver_ty);
 963                 let generics = generics(self.db.upcast(), func.into());
 964                 let substs = self.substs_for_method_call(generics, generic_args);
 965                 self.write_expr_adj(receiver, adjustments);
 966                 self.write_method_resolution(tgt_expr, func, substs.clone());
 967                 (ty, self.db.value_ty(func.into()), substs)
 968             }
 969             None => (
 970                 receiver_ty,
 971                 Binders::empty(Interner, self.err_ty()),
 972                 Substitution::empty(Interner),
 973             ),
 974         };
 975         let method_ty = method_ty.substitute(Interner, &substs);
 976         self.register_obligations_for_call(&method_ty);
 977         let (formal_receiver_ty, param_tys, ret_ty, is_varargs) =
 978             match method_ty.callable_sig(self.db) {
 979                 Some(sig) => {
 980                     if !sig.params().is_empty() {
 981                         (
 982                             sig.params()[0].clone(),
 983                             sig.params()[1..].to_vec(),
 984                             sig.ret().clone(),
 985                             sig.is_varargs,
 986                         )
 987                     } else {
 988                         (self.err_ty(), Vec::new(), sig.ret().clone(), sig.is_varargs)
 989                     }
 990                 }
 991                 None => (self.err_ty(), Vec::new(), self.err_ty(), true),
 992             };
 993         self.unify(&formal_receiver_ty, &receiver_ty);
 994
 995         let expected_inputs =
 996             self.expected_inputs_for_expected_output(expected, ret_ty.clone(), param_tys.clone());
 997
 998         self.check_call_arguments(tgt_expr, args, &expected_inputs, &param_tys, &[], is_varargs);
 999         self.normalize_associated_types_in(ret_ty)
1000     }
1001
1002     fn expected_inputs_for_expected_output(
1003         &mut self,
1004         expected_output: &Expectation,
1005         output: Ty,
1006         inputs: Vec<Ty>,
1007     ) -> Vec<Ty> {
1008         if let Some(expected_ty) = expected_output.to_option(&mut self.table) {
1009             self.table.fudge_inference(|table| {
1010                 if table.try_unify(&expected_ty, &output).is_ok() {
1011                     table.resolve_with_fallback(inputs, &|var, kind, _, _| match kind {
1012                         chalk_ir::VariableKind::Ty(tk) => var.to_ty(Interner, tk).cast(Interner),
1013                         chalk_ir::VariableKind::Lifetime => {
1014                             var.to_lifetime(Interner).cast(Interner)
1015                         }
1016                         chalk_ir::VariableKind::Const(ty) => {
1017                             var.to_const(Interner, ty).cast(Interner)
1018                         }
1019                     })
1020                 } else {
1021                     Vec::new()
1022                 }
1023             })
1024         } else {
1025             Vec::new()
1026         }
1027     }
1028
1029     fn check_call_arguments(
1030         &mut self,
1031         expr: ExprId,
1032         args: &[ExprId],
1033         expected_inputs: &[Ty],
1034         param_tys: &[Ty],
1035         skip_indices: &[u32],
1036         is_varargs: bool,
1037     ) {
1038         if args.len() != param_tys.len() + skip_indices.len() && !is_varargs {
1039             self.push_diagnostic(InferenceDiagnostic::MismatchedArgCount {
1040                 call_expr: expr,
1041                 expected: param_tys.len() + skip_indices.len(),
1042                 found: args.len(),
1043             });
1044         }
1045
1046         // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
1047         // We do this in a pretty awful way: first we type-check any arguments
1048         // that are not closures, then we type-check the closures. This is so
1049         // that we have more information about the types of arguments when we
1050         // type-check the functions. This isn't really the right way to do this.
1051         for &check_closures in &[false, true] {
1052             let mut skip_indices = skip_indices.into_iter().copied().fuse().peekable();
1053             let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
1054             let expected_iter = expected_inputs
1055                 .iter()
1056                 .cloned()
1057                 .chain(param_iter.clone().skip(expected_inputs.len()));
1058             for (idx, ((&arg, param_ty), expected_ty)) in
1059                 args.iter().zip(param_iter).zip(expected_iter).enumerate()
1060             {
1061                 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
1062                 if is_closure != check_closures {
1063                     continue;
1064                 }
1065
1066                 while skip_indices.peek().map_or(false, |i| *i < idx as u32) {
1067                     skip_indices.next();
1068                 }
1069                 if skip_indices.peek().copied() == Some(idx as u32) {
1070                     continue;
1071                 }
1072
1073                 // the difference between param_ty and expected here is that
1074                 // expected is the parameter when the expected *return* type is
1075                 // taken into account. So in `let _: &[i32] = identity(&[1, 2])`
1076                 // the expected type is already `&[i32]`, whereas param_ty is
1077                 // still an unbound type variable. We don't always want to force
1078                 // the parameter to coerce to the expected type (for example in
1079                 // `coerce_unsize_expected_type_4`).
1080                 let param_ty = self.normalize_associated_types_in(param_ty);
1081                 let expected = Expectation::rvalue_hint(&mut self.table, expected_ty);
1082                 // infer with the expected type we have...
1083                 let ty = self.infer_expr_inner(arg, &expected);
1084
1085                 // then coerce to either the expected type or just the formal parameter type
1086                 let coercion_target = if let Some(ty) = expected.only_has_type(&mut self.table) {
1087                     // if we are coercing to the expectation, unify with the
1088                     // formal parameter type to connect everything
1089                     self.unify(&ty, &param_ty);
1090                     ty
1091                 } else {
1092                     param_ty
1093                 };
1094                 if !coercion_target.is_unknown() {
1095                     if self.coerce(Some(arg), &ty, &coercion_target).is_err() {
1096                         self.result.type_mismatches.insert(
1097                             arg.into(),
1098                             TypeMismatch { expected: coercion_target, actual: ty.clone() },
1099                         );
1100                     }
1101                 }
1102             }
1103         }
1104     }
1105
1106     fn substs_for_method_call(
1107         &mut self,
1108         def_generics: Generics,
1109         generic_args: Option<&GenericArgs>,
1110     ) -> Substitution {
1111         let (parent_params, self_params, type_params, const_params, impl_trait_params) =
1112             def_generics.provenance_split();
1113         assert_eq!(self_params, 0); // method shouldn't have another Self param
1114         let total_len = parent_params + type_params + const_params + impl_trait_params;
1115         let mut substs = Vec::with_capacity(total_len);
1116         // Parent arguments are unknown
1117         for (id, param) in def_generics.iter_parent() {
1118             match param {
1119                 TypeOrConstParamData::TypeParamData(_) => {
1120                     substs.push(GenericArgData::Ty(self.table.new_type_var()).intern(Interner));
1121                 }
1122                 TypeOrConstParamData::ConstParamData(_) => {
1123                     let ty = self.db.const_param_ty(ConstParamId::from_unchecked(id));
1124                     substs
1125                         .push(GenericArgData::Const(self.table.new_const_var(ty)).intern(Interner));
1126                 }
1127             }
1128         }
1129         // handle provided arguments
1130         if let Some(generic_args) = generic_args {
1131             // if args are provided, it should be all of them, but we can't rely on that
1132             for (arg, kind_id) in generic_args
1133                 .args
1134                 .iter()
1135                 .filter(|arg| !matches!(arg, GenericArg::Lifetime(_)))
1136                 .take(type_params + const_params)
1137                 .zip(def_generics.iter_id().skip(parent_params))
1138             {
1139                 if let Some(g) = generic_arg_to_chalk(
1140                     self.db,
1141                     kind_id,
1142                     arg,
1143                     self,
1144                     |this, type_ref| this.make_ty(type_ref),
1145                     |this, c, ty| {
1146                         const_or_path_to_chalk(
1147                             this.db,
1148                             &this.resolver,
1149                             ty,
1150                             c,
1151                             ParamLoweringMode::Placeholder,
1152                             || generics(this.db.upcast(), (&this.resolver).generic_def().unwrap()),
1153                             DebruijnIndex::INNERMOST,
1154                         )
1155                     },
1156                 ) {
1157                     substs.push(g);
1158                 }
1159             }
1160         };
1161         for (id, data) in def_generics.iter().skip(substs.len()) {
1162             match data {
1163                 TypeOrConstParamData::TypeParamData(_) => {
1164                     substs.push(GenericArgData::Ty(self.table.new_type_var()).intern(Interner))
1165                 }
1166                 TypeOrConstParamData::ConstParamData(_) => {
1167                     substs.push(
1168                         GenericArgData::Const(self.table.new_const_var(
1169                             self.db.const_param_ty(ConstParamId::from_unchecked(id)),
1170                         ))
1171                         .intern(Interner),
1172                     )
1173                 }
1174             }
1175         }
1176         assert_eq!(substs.len(), total_len);
1177         Substitution::from_iter(Interner, substs)
1178     }
1179
1180     fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
1181         let callable_ty = self.resolve_ty_shallow(callable_ty);
1182         if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(Interner) {
1183             let def: CallableDefId = from_chalk(self.db, *fn_def);
1184             let generic_predicates = self.db.generic_predicates(def.into());
1185             for predicate in generic_predicates.iter() {
1186                 let (predicate, binders) = predicate
1187                     .clone()
1188                     .substitute(Interner, parameters)
1189                     .into_value_and_skipped_binders();
1190                 always!(binders.len(Interner) == 0); // quantified where clauses not yet handled
1191                 self.push_obligation(predicate.cast(Interner));
1192             }
1193             // add obligation for trait implementation, if this is a trait method
1194             match def {
1195                 CallableDefId::FunctionId(f) => {
1196                     if let ItemContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container {
1197                         // construct a TraitRef
1198                         let substs = crate::subst_prefix(
1199                             &*parameters,
1200                             generics(self.db.upcast(), trait_.into()).len(),
1201                         );
1202                         self.push_obligation(
1203                             TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
1204                                 .cast(Interner),
1205                         );
1206                     }
1207                 }
1208                 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}
1209             }
1210         }
1211     }
1212
1213     /// Returns the argument indices to skip.
1214     fn check_legacy_const_generics(&mut self, callee: Ty, args: &[ExprId]) -> Vec<u32> {
1215         let (func, subst) = match callee.kind(Interner) {
1216             TyKind::FnDef(fn_id, subst) => {
1217                 let callable = CallableDefId::from_chalk(self.db, *fn_id);
1218                 let func = match callable {
1219                     CallableDefId::FunctionId(f) => f,
1220                     _ => return Vec::new(),
1221                 };
1222                 (func, subst)
1223             }
1224             _ => return Vec::new(),
1225         };
1226
1227         let data = self.db.function_data(func);
1228         if data.legacy_const_generics_indices.is_empty() {
1229             return Vec::new();
1230         }
1231
1232         // only use legacy const generics if the param count matches with them
1233         if data.params.len() + data.legacy_const_generics_indices.len() != args.len() {
1234             if args.len() <= data.params.len() {
1235                 return Vec::new();
1236             } else {
1237                 // there are more parameters than there should be without legacy
1238                 // const params; use them
1239                 let mut indices = data.legacy_const_generics_indices.clone();
1240                 indices.sort();
1241                 return indices;
1242             }
1243         }
1244
1245         // check legacy const parameters
1246         for (subst_idx, arg_idx) in data.legacy_const_generics_indices.iter().copied().enumerate() {
1247             let arg = match subst.at(Interner, subst_idx).constant(Interner) {
1248                 Some(c) => c,
1249                 None => continue, // not a const parameter?
1250             };
1251             if arg_idx >= args.len() as u32 {
1252                 continue;
1253             }
1254             let _ty = arg.data(Interner).ty.clone();
1255             let expected = Expectation::none(); // FIXME use actual const ty, when that is lowered correctly
1256             self.infer_expr(args[arg_idx as usize], &expected);
1257             // FIXME: evaluate and unify with the const
1258         }
1259         let mut indices = data.legacy_const_generics_indices.clone();
1260         indices.sort();
1261         indices
1262     }
1263
1264     fn builtin_binary_op_return_ty(&mut self, op: BinaryOp, lhs_ty: Ty, rhs_ty: Ty) -> Option<Ty> {
1265         let lhs_ty = self.resolve_ty_shallow(&lhs_ty);
1266         let rhs_ty = self.resolve_ty_shallow(&rhs_ty);
1267         match op {
1268             BinaryOp::LogicOp(_) | BinaryOp::CmpOp(_) => {
1269                 Some(TyKind::Scalar(Scalar::Bool).intern(Interner))
1270             }
1271             BinaryOp::Assignment { .. } => Some(TyBuilder::unit()),
1272             BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) => {
1273                 // all integer combinations are valid here
1274                 if matches!(
1275                     lhs_ty.kind(Interner),
1276                     TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_))
1277                         | TyKind::InferenceVar(_, TyVariableKind::Integer)
1278                 ) && matches!(
1279                     rhs_ty.kind(Interner),
1280                     TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_))
1281                         | TyKind::InferenceVar(_, TyVariableKind::Integer)
1282                 ) {
1283                     Some(lhs_ty)
1284                 } else {
1285                     None
1286                 }
1287             }
1288             BinaryOp::ArithOp(_) => match (lhs_ty.kind(Interner), rhs_ty.kind(Interner)) {
1289                 // (int, int) | (uint, uint) | (float, float)
1290                 (TyKind::Scalar(Scalar::Int(_)), TyKind::Scalar(Scalar::Int(_)))
1291                 | (TyKind::Scalar(Scalar::Uint(_)), TyKind::Scalar(Scalar::Uint(_)))
1292                 | (TyKind::Scalar(Scalar::Float(_)), TyKind::Scalar(Scalar::Float(_))) => {
1293                     Some(rhs_ty)
1294                 }
1295                 // ({int}, int) | ({int}, uint)
1296                 (
1297                     TyKind::InferenceVar(_, TyVariableKind::Integer),
1298                     TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_)),
1299                 ) => Some(rhs_ty),
1300                 // (int, {int}) | (uint, {int})
1301                 (
1302                     TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_)),
1303                     TyKind::InferenceVar(_, TyVariableKind::Integer),
1304                 ) => Some(lhs_ty),
1305                 // ({float} | float)
1306                 (
1307                     TyKind::InferenceVar(_, TyVariableKind::Float),
1308                     TyKind::Scalar(Scalar::Float(_)),
1309                 ) => Some(rhs_ty),
1310                 // (float, {float})
1311                 (
1312                     TyKind::Scalar(Scalar::Float(_)),
1313                     TyKind::InferenceVar(_, TyVariableKind::Float),
1314                 ) => Some(lhs_ty),
1315                 // ({int}, {int}) | ({float}, {float})
1316                 (
1317                     TyKind::InferenceVar(_, TyVariableKind::Integer),
1318                     TyKind::InferenceVar(_, TyVariableKind::Integer),
1319                 )
1320                 | (
1321                     TyKind::InferenceVar(_, TyVariableKind::Float),
1322                     TyKind::InferenceVar(_, TyVariableKind::Float),
1323                 ) => Some(rhs_ty),
1324                 _ => None,
1325             },
1326         }
1327     }
1328
1329     fn builtin_binary_op_rhs_expectation(&mut self, op: BinaryOp, lhs_ty: Ty) -> Option<Ty> {
1330         Some(match op {
1331             BinaryOp::LogicOp(..) => TyKind::Scalar(Scalar::Bool).intern(Interner),
1332             BinaryOp::Assignment { op: None } => lhs_ty,
1333             BinaryOp::CmpOp(CmpOp::Eq { .. }) => match self
1334                 .resolve_ty_shallow(&lhs_ty)
1335                 .kind(Interner)
1336             {
1337                 TyKind::Scalar(_) | TyKind::Str => lhs_ty,
1338                 TyKind::InferenceVar(_, TyVariableKind::Integer | TyVariableKind::Float) => lhs_ty,
1339                 _ => return None,
1340             },
1341             BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) => return None,
1342             BinaryOp::CmpOp(CmpOp::Ord { .. })
1343             | BinaryOp::Assignment { op: Some(_) }
1344             | BinaryOp::ArithOp(_) => match self.resolve_ty_shallow(&lhs_ty).kind(Interner) {
1345                 TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_)) => lhs_ty,
1346                 TyKind::InferenceVar(_, TyVariableKind::Integer | TyVariableKind::Float) => lhs_ty,
1347                 _ => return None,
1348             },
1349         })
1350     }
1351
1352     fn resolve_binop_method(&self, op: BinaryOp) -> Option<FunctionId> {
1353         let (name, lang_item) = match op {
1354             BinaryOp::LogicOp(_) => return None,
1355             BinaryOp::ArithOp(aop) => match aop {
1356                 ArithOp::Add => (name!(add), name!(add)),
1357                 ArithOp::Mul => (name!(mul), name!(mul)),
1358                 ArithOp::Sub => (name!(sub), name!(sub)),
1359                 ArithOp::Div => (name!(div), name!(div)),
1360                 ArithOp::Rem => (name!(rem), name!(rem)),
1361                 ArithOp::Shl => (name!(shl), name!(shl)),
1362                 ArithOp::Shr => (name!(shr), name!(shr)),
1363                 ArithOp::BitXor => (name!(bitxor), name!(bitxor)),
1364                 ArithOp::BitOr => (name!(bitor), name!(bitor)),
1365                 ArithOp::BitAnd => (name!(bitand), name!(bitand)),
1366             },
1367             BinaryOp::Assignment { op: Some(aop) } => match aop {
1368                 ArithOp::Add => (name!(add_assign), name!(add_assign)),
1369                 ArithOp::Mul => (name!(mul_assign), name!(mul_assign)),
1370                 ArithOp::Sub => (name!(sub_assign), name!(sub_assign)),
1371                 ArithOp::Div => (name!(div_assign), name!(div_assign)),
1372                 ArithOp::Rem => (name!(rem_assign), name!(rem_assign)),
1373                 ArithOp::Shl => (name!(shl_assign), name!(shl_assign)),
1374                 ArithOp::Shr => (name!(shr_assign), name!(shr_assign)),
1375                 ArithOp::BitXor => (name!(bitxor_assign), name!(bitxor_assign)),
1376                 ArithOp::BitOr => (name!(bitor_assign), name!(bitor_assign)),
1377                 ArithOp::BitAnd => (name!(bitand_assign), name!(bitand_assign)),
1378             },
1379             BinaryOp::CmpOp(cop) => match cop {
1380                 CmpOp::Eq { negated: false } => (name!(eq), name!(eq)),
1381                 CmpOp::Eq { negated: true } => (name!(ne), name!(eq)),
1382                 CmpOp::Ord { ordering: Ordering::Less, strict: false } => {
1383                     (name!(le), name!(partial_ord))
1384                 }
1385                 CmpOp::Ord { ordering: Ordering::Less, strict: true } => {
1386                     (name!(lt), name!(partial_ord))
1387                 }
1388                 CmpOp::Ord { ordering: Ordering::Greater, strict: false } => {
1389                     (name!(ge), name!(partial_ord))
1390                 }
1391                 CmpOp::Ord { ordering: Ordering::Greater, strict: true } => {
1392                     (name!(gt), name!(partial_ord))
1393                 }
1394             },
1395             BinaryOp::Assignment { op: None } => return None,
1396         };
1397
1398         let trait_ = self.resolve_lang_item(lang_item)?.as_trait()?;
1399
1400         self.db.trait_data(trait_).method_by_name(&name)
1401     }
1402 }