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