crates/hir_ty/src/infer/expr.rs

   1 //! Type inference for expressions.
   2
   3 use std::iter::{repeat, repeat_with};
   4 use std::{mem, sync::Arc};
   5
   6 use chalk_ir::{cast::Cast, fold::Shift, ConstData, Mutability, TyVariableKind};
   7 use hir_def::{
   8     expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
   9     path::{GenericArg, GenericArgs},
  10     resolver::resolver_for_expr,
  11     type_ref::ConstScalar,
  12     AssocContainerId, FieldId, Lookup,
  13 };
  14 use hir_expand::name::{name, Name};
  15 use stdx::always;
  16 use syntax::ast::RangeOp;
  17
  18 use crate::{
  19     autoderef,
  20     lower::lower_to_chalk_mutability,
  21     mapping::from_chalk,
  22     method_resolution, op,
  23     primitive::{self, UintTy},
  24     static_lifetime, to_chalk_trait_id,
  25     traits::FnTrait,
  26     utils::{generics, Generics},
  27     AdtId, Binders, CallableDefId, ConcreteConst, ConstValue, FnPointer, FnSig, FnSubst,
  28     InEnvironment, Interner, ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty,
  29     TyBuilder, TyExt, TyKind,
  30 };
  31
  32 use super::{
  33     find_breakable, BindingMode, BreakableContext, Diverges, Expectation, InferenceContext,
  34     InferenceDiagnostic, TypeMismatch,
  35 };
  36
  37 impl<'a> InferenceContext<'a> {
  38     pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
  39         let ty = self.infer_expr_inner(tgt_expr, expected);
  40         if ty.is_never() {
  41             // Any expression that produces a value of type `!` must have diverged
  42             self.diverges = Diverges::Always;
  43         }
  44         let could_unify = self.unify(&ty, &expected.ty);
  45         if !could_unify {
  46             self.result.type_mismatches.insert(
  47                 tgt_expr,
  48                 TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() },
  49             );
  50         }
  51         self.resolve_ty_as_possible(ty)
  52     }
  53
  54     /// Infer type of expression with possibly implicit coerce to the expected type.
  55     /// Return the type after possible coercion.
  56     pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
  57         let ty = self.infer_expr_inner(expr, &expected);
  58         let ty = if !self.coerce(&ty, &expected.coercion_target()) {
  59             self.result
  60                 .type_mismatches
  61                 .insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() });
  62             // Return actual type when type mismatch.
  63             // This is needed for diagnostic when return type mismatch.
  64             ty
  65         } else if expected.coercion_target().is_unknown() {
  66             ty
  67         } else {
  68             expected.ty.clone()
  69         };
  70
  71         self.resolve_ty_as_possible(ty)
  72     }
  73
  74     fn callable_sig_from_fn_trait(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
  75         let krate = self.resolver.krate()?;
  76         let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
  77         let output_assoc_type =
  78             self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
  79
  80         let mut arg_tys = vec![];
  81         let arg_ty = TyBuilder::tuple(num_args)
  82             .fill(repeat_with(|| {
  83                 let arg = self.table.new_type_var();
  84                 arg_tys.push(arg.clone());
  85                 arg
  86             }))
  87             .build();
  88
  89         let projection = {
  90             let b = TyBuilder::assoc_type_projection(self.db, output_assoc_type);
  91             if b.remaining() != 2 {
  92                 return None;
  93             }
  94             b.push(ty.clone()).push(arg_ty).build()
  95         };
  96
  97         let trait_env = self.trait_env.env.clone();
  98         let obligation = InEnvironment {
  99             goal: projection.trait_ref(self.db).cast(&Interner),
 100             environment: trait_env,
 101         };
 102         let canonical = self.canonicalizer().canonicalize_obligation(obligation.clone());
 103         if self.db.trait_solve(krate, canonical.value).is_some() {
 104             self.push_obligation(obligation.goal);
 105             let return_ty = self.normalize_projection_ty(projection);
 106             Some((arg_tys, return_ty))
 107         } else {
 108             None
 109         }
 110     }
 111
 112     pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
 113         match ty.callable_sig(self.db) {
 114             Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
 115             None => self.callable_sig_from_fn_trait(ty, num_args),
 116         }
 117     }
 118
 119     fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
 120         self.db.check_canceled();
 121
 122         let body = Arc::clone(&self.body); // avoid borrow checker problem
 123         let ty = match &body[tgt_expr] {
 124             Expr::Missing => self.err_ty(),
 125             Expr::If { condition, then_branch, else_branch } => {
 126                 // if let is desugared to match, so this is always simple if
 127                 self.infer_expr(
 128                     *condition,
 129                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
 130                 );
 131
 132                 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 133                 let mut both_arms_diverge = Diverges::Always;
 134
 135                 let then_ty = self.infer_expr_inner(*then_branch, &expected);
 136                 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
 137                 let else_ty = match else_branch {
 138                     Some(else_branch) => self.infer_expr_inner(*else_branch, &expected),
 139                     None => TyBuilder::unit(),
 140                 };
 141                 both_arms_diverge &= self.diverges;
 142
 143                 self.diverges = condition_diverges | both_arms_diverge;
 144
 145                 self.coerce_merge_branch(&then_ty, &else_ty)
 146             }
 147             Expr::Block { statements, tail, label, id: _ } => {
 148                 let old_resolver = mem::replace(
 149                     &mut self.resolver,
 150                     resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
 151                 );
 152                 let ty = match label {
 153                     Some(_) => {
 154                         let break_ty = self.table.new_type_var();
 155                         self.breakables.push(BreakableContext {
 156                             may_break: false,
 157                             break_ty: break_ty.clone(),
 158                             label: label.map(|label| self.body[label].name.clone()),
 159                         });
 160                         let ty =
 161                             self.infer_block(statements, *tail, &Expectation::has_type(break_ty));
 162                         let ctxt = self.breakables.pop().expect("breakable stack broken");
 163                         if ctxt.may_break {
 164                             ctxt.break_ty
 165                         } else {
 166                             ty
 167                         }
 168                     }
 169                     None => self.infer_block(statements, *tail, expected),
 170                 };
 171                 self.resolver = old_resolver;
 172                 ty
 173             }
 174             Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
 175             Expr::TryBlock { body } => {
 176                 let _inner = self.infer_expr(*body, expected);
 177                 // FIXME should be std::result::Result<{inner}, _>
 178                 self.err_ty()
 179             }
 180             Expr::Async { body } => {
 181                 // Use the first type parameter as the output type of future.
 182                 // existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
 183                 let inner_ty = self.infer_expr(*body, &Expectation::none());
 184                 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
 185                 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
 186                 TyKind::OpaqueType(opaque_ty_id, Substitution::from1(&Interner, inner_ty))
 187                     .intern(&Interner)
 188             }
 189             Expr::Loop { body, label } => {
 190                 self.breakables.push(BreakableContext {
 191                     may_break: false,
 192                     break_ty: self.table.new_type_var(),
 193                     label: label.map(|label| self.body[label].name.clone()),
 194                 });
 195                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 196
 197                 let ctxt = self.breakables.pop().expect("breakable stack broken");
 198                 if ctxt.may_break {
 199                     self.diverges = Diverges::Maybe;
 200                 }
 201
 202                 if ctxt.may_break {
 203                     ctxt.break_ty
 204                 } else {
 205                     TyKind::Never.intern(&Interner)
 206                 }
 207             }
 208             Expr::While { condition, body, label } => {
 209                 self.breakables.push(BreakableContext {
 210                     may_break: false,
 211                     break_ty: self.err_ty(),
 212                     label: label.map(|label| self.body[label].name.clone()),
 213                 });
 214                 // while let is desugared to a match loop, so this is always simple while
 215                 self.infer_expr(
 216                     *condition,
 217                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
 218                 );
 219                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 220                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 221                 // the body may not run, so it diverging doesn't mean we diverge
 222                 self.diverges = Diverges::Maybe;
 223                 TyBuilder::unit()
 224             }
 225             Expr::For { iterable, body, pat, label } => {
 226                 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
 227
 228                 self.breakables.push(BreakableContext {
 229                     may_break: false,
 230                     break_ty: self.err_ty(),
 231                     label: label.map(|label| self.body[label].name.clone()),
 232                 });
 233                 let pat_ty =
 234                     self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
 235
 236                 self.infer_pat(*pat, &pat_ty, BindingMode::default());
 237
 238                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 239                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 240                 // the body may not run, so it diverging doesn't mean we diverge
 241                 self.diverges = Diverges::Maybe;
 242                 TyBuilder::unit()
 243             }
 244             Expr::Lambda { body, args, ret_type, arg_types } => {
 245                 assert_eq!(args.len(), arg_types.len());
 246
 247                 let mut sig_tys = Vec::new();
 248
 249                 // collect explicitly written argument types
 250                 for arg_type in arg_types.iter() {
 251                     let arg_ty = if let Some(type_ref) = arg_type {
 252                         self.make_ty(type_ref)
 253                     } else {
 254                         self.table.new_type_var()
 255                     };
 256                     sig_tys.push(arg_ty);
 257                 }
 258
 259                 // add return type
 260                 let ret_ty = match ret_type {
 261                     Some(type_ref) => self.make_ty(type_ref),
 262                     None => self.table.new_type_var(),
 263                 };
 264                 sig_tys.push(ret_ty.clone());
 265                 let sig_ty = TyKind::Function(FnPointer {
 266                     num_binders: 0,
 267                     sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
 268                     substitution: FnSubst(
 269                         Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
 270                     ),
 271                 })
 272                 .intern(&Interner);
 273                 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
 274                 let closure_ty =
 275                     TyKind::Closure(closure_id, Substitution::from1(&Interner, sig_ty))
 276                         .intern(&Interner);
 277
 278                 // Eagerly try to relate the closure type with the expected
 279                 // type, otherwise we often won't have enough information to
 280                 // infer the body.
 281                 self.coerce(&closure_ty, &expected.ty);
 282
 283                 // Now go through the argument patterns
 284                 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
 285                     let resolved = self.resolve_ty_as_possible(arg_ty);
 286                     self.infer_pat(*arg_pat, &resolved, BindingMode::default());
 287                 }
 288
 289                 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 290                 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
 291
 292                 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
 293
 294                 self.diverges = prev_diverges;
 295                 self.return_ty = prev_ret_ty;
 296
 297                 closure_ty
 298             }
 299             Expr::Call { callee, args } => {
 300                 let callee_ty = self.infer_expr(*callee, &Expectation::none());
 301                 let canonicalized = self.canonicalizer().canonicalize_ty(callee_ty.clone());
 302                 let mut derefs = autoderef(
 303                     self.db,
 304                     self.resolver.krate(),
 305                     InEnvironment {
 306                         goal: canonicalized.value.clone(),
 307                         environment: self.trait_env.env.clone(),
 308                     },
 309                 );
 310                 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
 311                     .find_map(|callee_deref_ty| {
 312                         self.callable_sig(
 313                             &canonicalized.decanonicalize_ty(callee_deref_ty.value),
 314                             args.len(),
 315                         )
 316                     })
 317                     .unwrap_or((Vec::new(), self.err_ty()));
 318                 self.register_obligations_for_call(&callee_ty);
 319                 self.check_call_arguments(args, &param_tys);
 320                 self.normalize_associated_types_in(ret_ty)
 321             }
 322             Expr::MethodCall { receiver, args, method_name, generic_args } => self
 323                 .infer_method_call(
 324                     tgt_expr,
 325                     *receiver,
 326                     &args,
 327                     &method_name,
 328                     generic_args.as_deref(),
 329                 ),
 330             Expr::Match { expr, arms } => {
 331                 let input_ty = self.infer_expr(*expr, &Expectation::none());
 332
 333                 let mut result_ty = if arms.is_empty() {
 334                     TyKind::Never.intern(&Interner)
 335                 } else {
 336                     self.table.new_type_var()
 337                 };
 338
 339                 let matchee_diverges = self.diverges;
 340                 let mut all_arms_diverge = Diverges::Always;
 341
 342                 for arm in arms {
 343                     self.diverges = Diverges::Maybe;
 344                     let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
 345                     if let Some(guard_expr) = arm.guard {
 346                         self.infer_expr(
 347                             guard_expr,
 348                             &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
 349                         );
 350                     }
 351
 352                     let arm_ty = self.infer_expr_inner(arm.expr, &expected);
 353                     all_arms_diverge &= self.diverges;
 354                     result_ty = self.coerce_merge_branch(&result_ty, &arm_ty);
 355                 }
 356
 357                 self.diverges = matchee_diverges | all_arms_diverge;
 358
 359                 result_ty
 360             }
 361             Expr::Path(p) => {
 362                 // FIXME this could be more efficient...
 363                 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
 364                 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(self.err_ty())
 365             }
 366             Expr::Continue { .. } => TyKind::Never.intern(&Interner),
 367             Expr::Break { expr, label } => {
 368                 let val_ty = if let Some(expr) = expr {
 369                     self.infer_expr(*expr, &Expectation::none())
 370                 } else {
 371                     TyBuilder::unit()
 372                 };
 373
 374                 let last_ty =
 375                     if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
 376                         ctxt.break_ty.clone()
 377                     } else {
 378                         self.err_ty()
 379                     };
 380
 381                 let merged_type = self.coerce_merge_branch(&last_ty, &val_ty);
 382
 383                 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
 384                     ctxt.break_ty = merged_type;
 385                     ctxt.may_break = true;
 386                 } else {
 387                     self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
 388                         expr: tgt_expr,
 389                     });
 390                 }
 391                 TyKind::Never.intern(&Interner)
 392             }
 393             Expr::Return { expr } => {
 394                 if let Some(expr) = expr {
 395                     self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
 396                 } else {
 397                     let unit = TyBuilder::unit();
 398                     self.coerce(&unit, &self.return_ty.clone());
 399                 }
 400                 TyKind::Never.intern(&Interner)
 401             }
 402             Expr::Yield { expr } => {
 403                 // FIXME: track yield type for coercion
 404                 if let Some(expr) = expr {
 405                     self.infer_expr(*expr, &Expectation::none());
 406                 }
 407                 TyKind::Never.intern(&Interner)
 408             }
 409             Expr::RecordLit { path, fields, spread } => {
 410                 let (ty, def_id) = self.resolve_variant(path.as_deref());
 411                 if let Some(variant) = def_id {
 412                     self.write_variant_resolution(tgt_expr.into(), variant);
 413                 }
 414
 415                 self.unify(&ty, &expected.ty);
 416
 417                 let substs = ty
 418                     .as_adt()
 419                     .map(|(_, s)| s.clone())
 420                     .unwrap_or_else(|| Substitution::empty(&Interner));
 421                 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
 422                 let variant_data = def_id.map(|it| it.variant_data(self.db.upcast()));
 423                 for field in fields.iter() {
 424                     let field_def =
 425                         variant_data.as_ref().and_then(|it| match it.field(&field.name) {
 426                             Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
 427                             None => {
 428                                 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
 429                                     expr: field.expr,
 430                                 });
 431                                 None
 432                             }
 433                         });
 434                     let field_ty = field_def.map_or(self.err_ty(), |it| {
 435                         field_types[it.local_id].clone().substitute(&Interner, &substs)
 436                     });
 437                     self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
 438                 }
 439                 if let Some(expr) = spread {
 440                     self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
 441                 }
 442                 ty
 443             }
 444             Expr::Field { expr, name } => {
 445                 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
 446                 let canonicalized = self.canonicalizer().canonicalize_ty(receiver_ty);
 447                 let ty = autoderef::autoderef(
 448                     self.db,
 449                     self.resolver.krate(),
 450                     InEnvironment {
 451                         goal: canonicalized.value.clone(),
 452                         environment: self.trait_env.env.clone(),
 453                     },
 454                 )
 455                 .find_map(|derefed_ty| {
 456                     let def_db = self.db.upcast();
 457                     let module = self.resolver.module();
 458                     let is_visible = |field_id: &FieldId| {
 459                         module
 460                             .map(|mod_id| {
 461                                 self.db.field_visibilities(field_id.parent)[field_id.local_id]
 462                                     .is_visible_from(def_db, mod_id)
 463                             })
 464                             .unwrap_or(true)
 465                     };
 466                     match canonicalized.decanonicalize_ty(derefed_ty.value).kind(&Interner) {
 467                         TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
 468                             substs
 469                                 .as_slice(&Interner)
 470                                 .get(idx)
 471                                 .map(|a| a.assert_ty_ref(&Interner))
 472                                 .cloned()
 473                         }),
 474                         TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
 475                             let local_id = self.db.struct_data(*s).variant_data.field(name)?;
 476                             let field = FieldId { parent: (*s).into(), local_id };
 477                             if is_visible(&field) {
 478                                 self.write_field_resolution(tgt_expr, field);
 479                                 Some(
 480                                     self.db.field_types((*s).into())[field.local_id]
 481                                         .clone()
 482                                         .substitute(&Interner, &parameters),
 483                                 )
 484                             } else {
 485                                 None
 486                             }
 487                         }
 488                         TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
 489                             let local_id = self.db.union_data(*u).variant_data.field(name)?;
 490                             let field = FieldId { parent: (*u).into(), local_id };
 491                             if is_visible(&field) {
 492                                 self.write_field_resolution(tgt_expr, field);
 493                                 Some(
 494                                     self.db.field_types((*u).into())[field.local_id]
 495                                         .clone()
 496                                         .substitute(&Interner, &parameters),
 497                                 )
 498                             } else {
 499                                 None
 500                             }
 501                         }
 502                         _ => None,
 503                     }
 504                 })
 505                 .unwrap_or(self.err_ty());
 506                 let ty = self.insert_type_vars(ty);
 507                 self.normalize_associated_types_in(ty)
 508             }
 509             Expr::Await { expr } => {
 510                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 511                 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
 512             }
 513             Expr::Try { expr } => {
 514                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 515                 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
 516             }
 517             Expr::Cast { expr, type_ref } => {
 518                 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 519                 let cast_ty = self.make_ty(type_ref);
 520                 // FIXME check the cast...
 521                 cast_ty
 522             }
 523             Expr::Ref { expr, rawness, mutability } => {
 524                 let mutability = lower_to_chalk_mutability(*mutability);
 525                 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) =
 526                     &expected.ty.as_reference_or_ptr()
 527                 {
 528                     if *exp_mutability == Mutability::Mut && mutability == Mutability::Not {
 529                         // FIXME: throw type error - expected mut reference but found shared ref,
 530                         // which cannot be coerced
 531                     }
 532                     if *exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
 533                         // FIXME: throw type error - expected reference but found ptr,
 534                         // which cannot be coerced
 535                     }
 536                     Expectation::rvalue_hint(Ty::clone(exp_inner))
 537                 } else {
 538                     Expectation::none()
 539                 };
 540                 let inner_ty = self.infer_expr_inner(*expr, &expectation);
 541                 match rawness {
 542                     Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
 543                     Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
 544                 }
 545                 .intern(&Interner)
 546             }
 547             Expr::Box { expr } => {
 548                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 549                 if let Some(box_) = self.resolve_boxed_box() {
 550                     TyBuilder::adt(self.db, box_)
 551                         .push(inner_ty)
 552                         .fill_with_defaults(self.db, || self.table.new_type_var())
 553                         .build()
 554                 } else {
 555                     self.err_ty()
 556                 }
 557             }
 558             Expr::UnaryOp { expr, op } => {
 559                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 560                 match op {
 561                     UnaryOp::Deref => match self.resolver.krate() {
 562                         Some(krate) => {
 563                             let canonicalized = self.canonicalizer().canonicalize_ty(inner_ty);
 564                             match autoderef::deref(
 565                                 self.db,
 566                                 krate,
 567                                 InEnvironment {
 568                                     goal: &canonicalized.value,
 569                                     environment: self.trait_env.env.clone(),
 570                                 },
 571                             ) {
 572                                 Some(derefed_ty) => {
 573                                     canonicalized.decanonicalize_ty(derefed_ty.value)
 574                                 }
 575                                 None => self.err_ty(),
 576                             }
 577                         }
 578                         None => self.err_ty(),
 579                     },
 580                     UnaryOp::Neg => {
 581                         match inner_ty.kind(&Interner) {
 582                             // Fast path for builtins
 583                             TyKind::Scalar(Scalar::Int(_))
 584                             | TyKind::Scalar(Scalar::Uint(_))
 585                             | TyKind::Scalar(Scalar::Float(_))
 586                             | TyKind::InferenceVar(_, TyVariableKind::Integer)
 587                             | TyKind::InferenceVar(_, TyVariableKind::Float) => inner_ty,
 588                             // Otherwise we resolve via the std::ops::Neg trait
 589                             _ => self
 590                                 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
 591                         }
 592                     }
 593                     UnaryOp::Not => {
 594                         match inner_ty.kind(&Interner) {
 595                             // Fast path for builtins
 596                             TyKind::Scalar(Scalar::Bool)
 597                             | TyKind::Scalar(Scalar::Int(_))
 598                             | TyKind::Scalar(Scalar::Uint(_))
 599                             | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
 600                             // Otherwise we resolve via the std::ops::Not trait
 601                             _ => self
 602                                 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
 603                         }
 604                     }
 605                 }
 606             }
 607             Expr::BinaryOp { lhs, rhs, op } => match op {
 608                 Some(op) => {
 609                     let lhs_expectation = match op {
 610                         BinaryOp::LogicOp(..) => {
 611                             Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner))
 612                         }
 613                         _ => Expectation::none(),
 614                     };
 615                     let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
 616                     let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
 617                     let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
 618
 619                     let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
 620
 621                     if ret.is_unknown() {
 622                         cov_mark::hit!(infer_expr_inner_binary_operator_overload);
 623
 624                         self.resolve_associated_type_with_params(
 625                             lhs_ty,
 626                             self.resolve_binary_op_output(op),
 627                             &[rhs_ty],
 628                         )
 629                     } else {
 630                         ret
 631                     }
 632                 }
 633                 _ => self.err_ty(),
 634             },
 635             Expr::Range { lhs, rhs, range_type } => {
 636                 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
 637                 let rhs_expect = lhs_ty
 638                     .as_ref()
 639                     .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
 640                 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
 641                 match (range_type, lhs_ty, rhs_ty) {
 642                     (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
 643                         Some(adt) => TyBuilder::adt(self.db, adt).build(),
 644                         None => self.err_ty(),
 645                     },
 646                     (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
 647                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 648                         None => self.err_ty(),
 649                     },
 650                     (RangeOp::Inclusive, None, Some(ty)) => {
 651                         match self.resolve_range_to_inclusive() {
 652                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 653                             None => self.err_ty(),
 654                         }
 655                     }
 656                     (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
 657                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 658                         None => self.err_ty(),
 659                     },
 660                     (RangeOp::Inclusive, Some(_), Some(ty)) => {
 661                         match self.resolve_range_inclusive() {
 662                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 663                             None => self.err_ty(),
 664                         }
 665                     }
 666                     (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
 667                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 668                         None => self.err_ty(),
 669                     },
 670                     (RangeOp::Inclusive, _, None) => self.err_ty(),
 671                 }
 672             }
 673             Expr::Index { base, index } => {
 674                 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
 675                 let index_ty = self.infer_expr(*index, &Expectation::none());
 676
 677                 if let (Some(index_trait), Some(krate)) =
 678                     (self.resolve_ops_index(), self.resolver.krate())
 679                 {
 680                     let canonicalized = self.canonicalizer().canonicalize_ty(base_ty);
 681                     let self_ty = method_resolution::resolve_indexing_op(
 682                         self.db,
 683                         &canonicalized.value,
 684                         self.trait_env.clone(),
 685                         krate,
 686                         index_trait,
 687                     );
 688                     let self_ty =
 689                         self_ty.map_or(self.err_ty(), |t| canonicalized.decanonicalize_ty(t.value));
 690                     self.resolve_associated_type_with_params(
 691                         self_ty,
 692                         self.resolve_ops_index_output(),
 693                         &[index_ty],
 694                     )
 695                 } else {
 696                     self.err_ty()
 697                 }
 698             }
 699             Expr::Tuple { exprs } => {
 700                 let mut tys = match expected.ty.kind(&Interner) {
 701                     TyKind::Tuple(_, substs) => substs
 702                         .iter(&Interner)
 703                         .map(|a| a.assert_ty_ref(&Interner).clone())
 704                         .chain(repeat_with(|| self.table.new_type_var()))
 705                         .take(exprs.len())
 706                         .collect::<Vec<_>>(),
 707                     _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
 708                 };
 709
 710                 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
 711                     self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
 712                 }
 713
 714                 TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
 715             }
 716             Expr::Array(array) => {
 717                 let elem_ty = match expected.ty.kind(&Interner) {
 718                     TyKind::Array(st, _) | TyKind::Slice(st) => st.clone(),
 719                     _ => self.table.new_type_var(),
 720                 };
 721
 722                 let len = match array {
 723                     Array::ElementList(items) => {
 724                         for expr in items.iter() {
 725                             self.infer_expr_coerce(*expr, &Expectation::has_type(elem_ty.clone()));
 726                         }
 727                         Some(items.len())
 728                     }
 729                     Array::Repeat { initializer, repeat } => {
 730                         self.infer_expr_coerce(
 731                             *initializer,
 732                             &Expectation::has_type(elem_ty.clone()),
 733                         );
 734                         self.infer_expr(
 735                             *repeat,
 736                             &Expectation::has_type(
 737                                 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
 738                             ),
 739                         );
 740                         // FIXME: we don't know the length here because hir Exprs don't actually
 741                         // get the value out of the AST, even though it is there.
 742                         None
 743                     }
 744                 };
 745
 746                 let cd = ConstData {
 747                     ty: TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
 748                     value: ConstValue::Concrete(chalk_ir::ConcreteConst {
 749                         interned: len
 750                             .map(|len| ConstScalar::Usize(len as u64))
 751                             .unwrap_or(ConstScalar::Unknown),
 752                     }),
 753                 };
 754                 TyKind::Array(elem_ty, cd.intern(&Interner)).intern(&Interner)
 755             }
 756             Expr::Literal(lit) => match lit {
 757                 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
 758                 Literal::String(..) => {
 759                     TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(&Interner))
 760                         .intern(&Interner)
 761                 }
 762                 Literal::ByteString(bs) => {
 763                     let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
 764
 765                     let len = ConstData {
 766                         ty: TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
 767                         value: ConstValue::Concrete(ConcreteConst {
 768                             interned: ConstScalar::Usize(bs.len() as u64),
 769                         }),
 770                     }
 771                     .intern(&Interner);
 772
 773                     let array_type = TyKind::Array(byte_type, len).intern(&Interner);
 774                     TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(&Interner)
 775                 }
 776                 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
 777                 Literal::Int(_v, ty) => match ty {
 778                     Some(int_ty) => {
 779                         TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
 780                             .intern(&Interner)
 781                     }
 782                     None => self.table.new_integer_var(),
 783                 },
 784                 Literal::Uint(_v, ty) => match ty {
 785                     Some(int_ty) => {
 786                         TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
 787                             .intern(&Interner)
 788                     }
 789                     None => self.table.new_integer_var(),
 790                 },
 791                 Literal::Float(_v, ty) => match ty {
 792                     Some(float_ty) => {
 793                         TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
 794                             .intern(&Interner)
 795                     }
 796                     None => self.table.new_float_var(),
 797                 },
 798             },
 799             Expr::MacroStmts { tail } => self.infer_expr(*tail, expected),
 800         };
 801         // use a new type variable if we got unknown here
 802         let ty = self.insert_type_vars_shallow(ty);
 803         let ty = self.resolve_ty_as_possible(ty);
 804         self.write_expr_ty(tgt_expr, ty.clone());
 805         ty
 806     }
 807
 808     fn infer_block(
 809         &mut self,
 810         statements: &[Statement],
 811         tail: Option<ExprId>,
 812         expected: &Expectation,
 813     ) -> Ty {
 814         for stmt in statements {
 815             match stmt {
 816                 Statement::Let { pat, type_ref, initializer } => {
 817                     let decl_ty =
 818                         type_ref.as_ref().map(|tr| self.make_ty(tr)).unwrap_or(self.err_ty());
 819
 820                     // Always use the declared type when specified
 821                     let mut ty = decl_ty.clone();
 822
 823                     if let Some(expr) = initializer {
 824                         let actual_ty =
 825                             self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
 826                         if decl_ty.is_unknown() {
 827                             ty = actual_ty;
 828                         }
 829                     }
 830
 831                     let ty = self.resolve_ty_as_possible(ty);
 832                     self.infer_pat(*pat, &ty, BindingMode::default());
 833                 }
 834                 Statement::Expr { expr, .. } => {
 835                     self.infer_expr(*expr, &Expectation::none());
 836                 }
 837             }
 838         }
 839
 840         let ty = if let Some(expr) = tail {
 841             self.infer_expr_coerce(expr, expected)
 842         } else {
 843             // Citing rustc: if there is no explicit tail expression,
 844             // that is typically equivalent to a tail expression
 845             // of `()` -- except if the block diverges. In that
 846             // case, there is no value supplied from the tail
 847             // expression (assuming there are no other breaks,
 848             // this implies that the type of the block will be
 849             // `!`).
 850             if self.diverges.is_always() {
 851                 // we don't even make an attempt at coercion
 852                 self.table.new_maybe_never_var()
 853             } else {
 854                 self.coerce(&TyBuilder::unit(), &expected.coercion_target());
 855                 TyBuilder::unit()
 856             }
 857         };
 858         ty
 859     }
 860
 861     fn infer_method_call(
 862         &mut self,
 863         tgt_expr: ExprId,
 864         receiver: ExprId,
 865         args: &[ExprId],
 866         method_name: &Name,
 867         generic_args: Option<&GenericArgs>,
 868     ) -> Ty {
 869         let receiver_ty = self.infer_expr(receiver, &Expectation::none());
 870         let canonicalized_receiver = self.canonicalizer().canonicalize_ty(receiver_ty.clone());
 871
 872         let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
 873
 874         let resolved = self.resolver.krate().and_then(|krate| {
 875             method_resolution::lookup_method(
 876                 &canonicalized_receiver.value,
 877                 self.db,
 878                 self.trait_env.clone(),
 879                 krate,
 880                 &traits_in_scope,
 881                 self.resolver.module(),
 882                 method_name,
 883             )
 884         });
 885         let (derefed_receiver_ty, method_ty, def_generics) = match resolved {
 886             Some((ty, func)) => {
 887                 let ty = canonicalized_receiver.decanonicalize_ty(ty);
 888                 self.write_method_resolution(tgt_expr, func);
 889                 (ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
 890             }
 891             None => (receiver_ty, Binders::empty(&Interner, self.err_ty()), None),
 892         };
 893         let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty);
 894         let method_ty = method_ty.substitute(&Interner, &substs);
 895         let method_ty = self.insert_type_vars(method_ty);
 896         self.register_obligations_for_call(&method_ty);
 897         let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
 898             Some(sig) => {
 899                 if !sig.params().is_empty() {
 900                     (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
 901                 } else {
 902                     (self.err_ty(), Vec::new(), sig.ret().clone())
 903                 }
 904             }
 905             None => (self.err_ty(), Vec::new(), self.err_ty()),
 906         };
 907         // Apply autoref so the below unification works correctly
 908         // FIXME: return correct autorefs from lookup_method
 909         let actual_receiver_ty = match expected_receiver_ty.as_reference() {
 910             Some((_, lifetime, mutability)) => {
 911                 TyKind::Ref(mutability, lifetime, derefed_receiver_ty).intern(&Interner)
 912             }
 913             _ => derefed_receiver_ty,
 914         };
 915         self.unify(&expected_receiver_ty, &actual_receiver_ty);
 916
 917         self.check_call_arguments(args, &param_tys);
 918         self.normalize_associated_types_in(ret_ty)
 919     }
 920
 921     fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
 922         // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
 923         // We do this in a pretty awful way: first we type-check any arguments
 924         // that are not closures, then we type-check the closures. This is so
 925         // that we have more information about the types of arguments when we
 926         // type-check the functions. This isn't really the right way to do this.
 927         for &check_closures in &[false, true] {
 928             let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
 929             for (&arg, param_ty) in args.iter().zip(param_iter) {
 930                 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
 931                 if is_closure != check_closures {
 932                     continue;
 933                 }
 934
 935                 let param_ty = self.normalize_associated_types_in(param_ty);
 936                 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
 937             }
 938         }
 939     }
 940
 941     fn substs_for_method_call(
 942         &mut self,
 943         def_generics: Option<Generics>,
 944         generic_args: Option<&GenericArgs>,
 945         receiver_ty: &Ty,
 946     ) -> Substitution {
 947         let (parent_params, self_params, type_params, impl_trait_params) =
 948             def_generics.as_ref().map_or((0, 0, 0, 0), |g| g.provenance_split());
 949         assert_eq!(self_params, 0); // method shouldn't have another Self param
 950         let total_len = parent_params + type_params + impl_trait_params;
 951         let mut substs = Vec::with_capacity(total_len);
 952         // Parent arguments are unknown, except for the receiver type
 953         if let Some(parent_generics) = def_generics.as_ref().map(|p| p.iter_parent()) {
 954             for (_id, param) in parent_generics {
 955                 if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
 956                     substs.push(receiver_ty.clone());
 957                 } else {
 958                     substs.push(self.err_ty());
 959                 }
 960             }
 961         }
 962         // handle provided type arguments
 963         if let Some(generic_args) = generic_args {
 964             // if args are provided, it should be all of them, but we can't rely on that
 965             for arg in generic_args
 966                 .args
 967                 .iter()
 968                 .filter(|arg| matches!(arg, GenericArg::Type(_)))
 969                 .take(type_params)
 970             {
 971                 match arg {
 972                     GenericArg::Type(type_ref) => {
 973                         let ty = self.make_ty(type_ref);
 974                         substs.push(ty);
 975                     }
 976                     GenericArg::Lifetime(_) => {}
 977                 }
 978             }
 979         };
 980         let supplied_params = substs.len();
 981         for _ in supplied_params..total_len {
 982             substs.push(self.err_ty());
 983         }
 984         assert_eq!(substs.len(), total_len);
 985         Substitution::from_iter(&Interner, substs)
 986     }
 987
 988     fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
 989         if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
 990             let def: CallableDefId = from_chalk(self.db, *fn_def);
 991             let generic_predicates = self.db.generic_predicates(def.into());
 992             for predicate in generic_predicates.iter() {
 993                 let (predicate, binders) = predicate
 994                     .clone()
 995                     .substitute(&Interner, parameters)
 996                     .into_value_and_skipped_binders();
 997                 always!(binders.len(&Interner) == 0); // quantified where clauses not yet handled
 998                 self.push_obligation(predicate.cast(&Interner));
 999             }
1000             // add obligation for trait implementation, if this is a trait method
1001             match def {
1002                 CallableDefId::FunctionId(f) => {
1003                     if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
1004                     {
1005                         // construct a TraitRef
1006                         let substs = crate::subst_prefix(
1007                             &*parameters,
1008                             generics(self.db.upcast(), trait_.into()).len(),
1009                         );
1010                         self.push_obligation(
1011                             TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
1012                                 .cast(&Interner),
1013                         );
1014                     }
1015                 }
1016                 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}
1017             }
1018         }
1019     }
1020 }