crates/hir_ty/src/infer/expr.rs

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