crates/hir_ty/src/infer/expr.rs

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