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