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