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, 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     AssocContainerId, FieldId, Lookup,
  12 };
  13 use hir_expand::name::{name, Name};
  14 use stdx::always;
  15 use syntax::ast::RangeOp;
  16
  17 use crate::{
  18     autoderef, consteval,
  19     infer::coerce::CoerceMany,
  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, FnPointer, FnSig, FnSubst, InEnvironment, Interner,
  28     ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
  29 };
  30
  31 use super::{
  32     find_breakable, BindingMode, BreakableContext, Diverges, Expectation, InferenceContext,
  33     InferenceDiagnostic, TypeMismatch,
  34 };
  35
  36 impl<'a> InferenceContext<'a> {
  37     pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
  38         let ty = self.infer_expr_inner(tgt_expr, expected);
  39         if self.resolve_ty_shallow(&ty).is_never() {
  40             // Any expression that produces a value of type `!` must have diverged
  41             self.diverges = Diverges::Always;
  42         }
  43         if let Some(expected_ty) = expected.only_has_type(&mut self.table) {
  44             let could_unify = self.unify(&ty, &expected_ty);
  45             if !could_unify {
  46                 self.result.type_mismatches.insert(
  47                     tgt_expr.into(),
  48                     TypeMismatch { expected: expected_ty, actual: ty.clone() },
  49                 );
  50             }
  51         }
  52         ty
  53     }
  54
  55     /// Infer type of expression with possibly implicit coerce to the expected type.
  56     /// Return the type after possible coercion.
  57     pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
  58         let ty = self.infer_expr_inner(expr, expected);
  59         let ty = if let Some(target) = expected.only_has_type(&mut self.table) {
  60             match self.coerce(Some(expr), &ty, &target) {
  61                 Ok(res) => res.value,
  62                 Err(_) => {
  63                     self.result
  64                         .type_mismatches
  65                         .insert(expr.into(), TypeMismatch { expected: target, actual: ty.clone() });
  66                     // Return actual type when type mismatch.
  67                     // This is needed for diagnostic when return type mismatch.
  68                     ty
  69                 }
  70             }
  71         } else {
  72             ty
  73         };
  74
  75         ty
  76     }
  77
  78     fn callable_sig_from_fn_trait(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
  79         let krate = self.resolver.krate()?;
  80         let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
  81         let output_assoc_type =
  82             self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
  83
  84         let mut arg_tys = vec![];
  85         let arg_ty = TyBuilder::tuple(num_args)
  86             .fill(repeat_with(|| {
  87                 let arg = self.table.new_type_var();
  88                 arg_tys.push(arg.clone());
  89                 arg
  90             }))
  91             .build();
  92
  93         let projection = {
  94             let b = TyBuilder::assoc_type_projection(self.db, output_assoc_type);
  95             if b.remaining() != 2 {
  96                 return None;
  97             }
  98             b.push(ty.clone()).push(arg_ty).build()
  99         };
 100
 101         let trait_env = self.trait_env.env.clone();
 102         let obligation = InEnvironment {
 103             goal: projection.trait_ref(self.db).cast(&Interner),
 104             environment: trait_env,
 105         };
 106         let canonical = self.canonicalize(obligation.clone());
 107         if self.db.trait_solve(krate, canonical.value.cast(&Interner)).is_some() {
 108             self.push_obligation(obligation.goal);
 109             let return_ty = self.table.normalize_projection_ty(projection);
 110             Some((arg_tys, return_ty))
 111         } else {
 112             None
 113         }
 114     }
 115
 116     pub(crate) fn callable_sig(&mut self, ty: &Ty, num_args: usize) -> Option<(Vec<Ty>, Ty)> {
 117         match ty.callable_sig(self.db) {
 118             Some(sig) => Some((sig.params().to_vec(), sig.ret().clone())),
 119             None => self.callable_sig_from_fn_trait(ty, num_args),
 120         }
 121     }
 122
 123     fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
 124         self.db.unwind_if_cancelled();
 125
 126         let body = Arc::clone(&self.body); // avoid borrow checker problem
 127         let ty = match &body[tgt_expr] {
 128             Expr::Missing => self.err_ty(),
 129             &Expr::If { condition, then_branch, else_branch } => {
 130                 // if let is desugared to match, so this is always simple if
 131                 self.infer_expr(
 132                     condition,
 133                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
 134                 );
 135
 136                 let condition_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 137                 let mut both_arms_diverge = Diverges::Always;
 138
 139                 let result_ty = self.table.new_type_var();
 140                 let then_ty = self.infer_expr_inner(then_branch, expected);
 141                 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
 142                 let mut coerce = CoerceMany::new(result_ty);
 143                 coerce.coerce(self, Some(then_branch), &then_ty);
 144                 let else_ty = match else_branch {
 145                     Some(else_branch) => self.infer_expr_inner(else_branch, expected),
 146                     None => TyBuilder::unit(),
 147                 };
 148                 both_arms_diverge &= self.diverges;
 149                 // FIXME: create a synthetic `else {}` so we have something to refer to here instead of None?
 150                 coerce.coerce(self, else_branch, &else_ty);
 151
 152                 self.diverges = condition_diverges | both_arms_diverge;
 153
 154                 coerce.complete()
 155             }
 156             Expr::Block { statements, tail, label, id: _ } => {
 157                 let old_resolver = mem::replace(
 158                     &mut self.resolver,
 159                     resolver_for_expr(self.db.upcast(), self.owner, tgt_expr),
 160                 );
 161                 let ty = match label {
 162                     Some(_) => {
 163                         let break_ty = self.table.new_type_var();
 164                         self.breakables.push(BreakableContext {
 165                             may_break: false,
 166                             break_ty: break_ty.clone(),
 167                             label: label.map(|label| self.body[label].name.clone()),
 168                         });
 169                         let ty = self.infer_block(
 170                             tgt_expr,
 171                             statements,
 172                             *tail,
 173                             &Expectation::has_type(break_ty),
 174                         );
 175                         let ctxt = self.breakables.pop().expect("breakable stack broken");
 176                         if ctxt.may_break {
 177                             ctxt.break_ty
 178                         } else {
 179                             ty
 180                         }
 181                     }
 182                     None => self.infer_block(tgt_expr, statements, *tail, expected),
 183                 };
 184                 self.resolver = old_resolver;
 185                 ty
 186             }
 187             Expr::Unsafe { body } | Expr::Const { body } => self.infer_expr(*body, expected),
 188             Expr::TryBlock { body } => {
 189                 let _inner = self.infer_expr(*body, expected);
 190                 // FIXME should be std::result::Result<{inner}, _>
 191                 self.err_ty()
 192             }
 193             Expr::Async { body } => {
 194                 // Use the first type parameter as the output type of future.
 195                 // existential type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
 196                 let inner_ty = self.infer_expr(*body, &Expectation::none());
 197                 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
 198                 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
 199                 TyKind::OpaqueType(opaque_ty_id, Substitution::from1(&Interner, inner_ty))
 200                     .intern(&Interner)
 201             }
 202             Expr::Loop { body, label } => {
 203                 self.breakables.push(BreakableContext {
 204                     may_break: false,
 205                     break_ty: self.table.new_type_var(),
 206                     label: label.map(|label| self.body[label].name.clone()),
 207                 });
 208                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 209
 210                 let ctxt = self.breakables.pop().expect("breakable stack broken");
 211                 if ctxt.may_break {
 212                     self.diverges = Diverges::Maybe;
 213                 }
 214
 215                 if ctxt.may_break {
 216                     ctxt.break_ty
 217                 } else {
 218                     TyKind::Never.intern(&Interner)
 219                 }
 220             }
 221             Expr::While { condition, body, label } => {
 222                 self.breakables.push(BreakableContext {
 223                     may_break: false,
 224                     break_ty: self.err_ty(),
 225
 226                     label: label.map(|label| self.body[label].name.clone()),
 227                 });
 228                 // while let is desugared to a match loop, so this is always simple while
 229                 self.infer_expr(
 230                     *condition,
 231                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
 232                 );
 233                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 234                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 235                 // the body may not run, so it diverging doesn't mean we diverge
 236                 self.diverges = Diverges::Maybe;
 237                 TyBuilder::unit()
 238             }
 239             Expr::For { iterable, body, pat, label } => {
 240                 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
 241
 242                 self.breakables.push(BreakableContext {
 243                     may_break: false,
 244                     break_ty: self.err_ty(),
 245                     label: label.map(|label| self.body[label].name.clone()),
 246                 });
 247                 let pat_ty =
 248                     self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
 249
 250                 self.infer_pat(*pat, &pat_ty, BindingMode::default());
 251
 252                 self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 253                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
 254                 // the body may not run, so it diverging doesn't mean we diverge
 255                 self.diverges = Diverges::Maybe;
 256                 TyBuilder::unit()
 257             }
 258             Expr::Lambda { body, args, ret_type, arg_types } => {
 259                 assert_eq!(args.len(), arg_types.len());
 260
 261                 let mut sig_tys = Vec::new();
 262
 263                 // collect explicitly written argument types
 264                 for arg_type in arg_types.iter() {
 265                     let arg_ty = if let Some(type_ref) = arg_type {
 266                         self.make_ty(type_ref)
 267                     } else {
 268                         self.table.new_type_var()
 269                     };
 270                     sig_tys.push(arg_ty);
 271                 }
 272
 273                 // add return type
 274                 let ret_ty = match ret_type {
 275                     Some(type_ref) => self.make_ty(type_ref),
 276                     None => self.table.new_type_var(),
 277                 };
 278                 sig_tys.push(ret_ty.clone());
 279                 let sig_ty = TyKind::Function(FnPointer {
 280                     num_binders: 0,
 281                     sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
 282                     substitution: FnSubst(
 283                         Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
 284                     ),
 285                 })
 286                 .intern(&Interner);
 287                 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
 288                 let closure_ty =
 289                     TyKind::Closure(closure_id, Substitution::from1(&Interner, sig_ty.clone()))
 290                         .intern(&Interner);
 291
 292                 // Eagerly try to relate the closure type with the expected
 293                 // type, otherwise we often won't have enough information to
 294                 // infer the body.
 295                 self.deduce_closure_type_from_expectations(
 296                     tgt_expr,
 297                     &closure_ty,
 298                     &sig_ty,
 299                     expected,
 300                 );
 301
 302                 // Now go through the argument patterns
 303                 for (arg_pat, arg_ty) in args.iter().zip(sig_tys) {
 304                     self.infer_pat(*arg_pat, &arg_ty, BindingMode::default());
 305                 }
 306
 307                 let prev_diverges = mem::replace(&mut self.diverges, Diverges::Maybe);
 308                 let prev_ret_ty = mem::replace(&mut self.return_ty, ret_ty.clone());
 309
 310                 self.infer_expr_coerce(*body, &Expectation::has_type(ret_ty));
 311
 312                 self.diverges = prev_diverges;
 313                 self.return_ty = prev_ret_ty;
 314
 315                 closure_ty
 316             }
 317             Expr::Call { callee, args } => {
 318                 let callee_ty = self.infer_expr(*callee, &Expectation::none());
 319                 let canonicalized = self.canonicalize(callee_ty.clone());
 320                 let mut derefs = autoderef(
 321                     self.db,
 322                     self.resolver.krate(),
 323                     InEnvironment {
 324                         goal: canonicalized.value.clone(),
 325                         environment: self.table.trait_env.env.clone(),
 326                     },
 327                 );
 328                 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
 329                     .find_map(|callee_deref_ty| {
 330                         self.callable_sig(
 331                             &canonicalized.decanonicalize_ty(callee_deref_ty.value),
 332                             args.len(),
 333                         )
 334                     })
 335                     .unwrap_or((Vec::new(), self.err_ty()));
 336                 self.register_obligations_for_call(&callee_ty);
 337                 self.check_call_arguments(args, &param_tys);
 338                 self.normalize_associated_types_in(ret_ty)
 339             }
 340             Expr::MethodCall { receiver, args, method_name, generic_args } => self
 341                 .infer_method_call(tgt_expr, *receiver, args, method_name, generic_args.as_deref()),
 342             Expr::Match { expr, arms } => {
 343                 let input_ty = self.infer_expr(*expr, &Expectation::none());
 344
 345                 let expected = expected.adjust_for_branches(&mut self.table);
 346
 347                 let result_ty = if arms.is_empty() {
 348                     TyKind::Never.intern(&Interner)
 349                 } else {
 350                     match &expected {
 351                         Expectation::HasType(ty) => ty.clone(),
 352                         _ => self.table.new_type_var(),
 353                     }
 354                 };
 355                 let mut coerce = CoerceMany::new(result_ty);
 356
 357                 let matchee_diverges = self.diverges;
 358                 let mut all_arms_diverge = Diverges::Always;
 359
 360                 for arm in arms {
 361                     self.diverges = Diverges::Maybe;
 362                     let _pat_ty = self.infer_pat(arm.pat, &input_ty, BindingMode::default());
 363                     if let Some(guard_expr) = arm.guard {
 364                         self.infer_expr(
 365                             guard_expr,
 366                             &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
 367                         );
 368                     }
 369
 370                     let arm_ty = self.infer_expr_inner(arm.expr, &expected);
 371                     all_arms_diverge &= self.diverges;
 372                     coerce.coerce(self, Some(arm.expr), &arm_ty);
 373                 }
 374
 375                 self.diverges = matchee_diverges | all_arms_diverge;
 376
 377                 coerce.complete()
 378             }
 379             Expr::Path(p) => {
 380                 // FIXME this could be more efficient...
 381                 let resolver = resolver_for_expr(self.db.upcast(), self.owner, tgt_expr);
 382                 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or_else(|| self.err_ty())
 383             }
 384             Expr::Continue { .. } => TyKind::Never.intern(&Interner),
 385             Expr::Break { expr, label } => {
 386                 let expr = *expr;
 387                 let last_ty =
 388                     if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
 389                         ctxt.break_ty.clone()
 390                     } else {
 391                         self.err_ty()
 392                     };
 393
 394                 let val_ty = if let Some(expr) = expr {
 395                     self.infer_expr(expr, &Expectation::none())
 396                 } else {
 397                     TyBuilder::unit()
 398                 };
 399
 400                 // FIXME: create a synthetic `()` during lowering so we have something to refer to here?
 401                 let merged_type = CoerceMany::once(self, last_ty, expr, &val_ty);
 402
 403                 if let Some(ctxt) = find_breakable(&mut self.breakables, label.as_ref()) {
 404                     ctxt.break_ty = merged_type;
 405                     ctxt.may_break = true;
 406                 } else {
 407                     self.push_diagnostic(InferenceDiagnostic::BreakOutsideOfLoop {
 408                         expr: tgt_expr,
 409                     });
 410                 }
 411                 TyKind::Never.intern(&Interner)
 412             }
 413             Expr::Return { expr } => {
 414                 if let Some(expr) = expr {
 415                     self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
 416                 } else {
 417                     let unit = TyBuilder::unit();
 418                     let _ = self.coerce(Some(tgt_expr), &unit, &self.return_ty.clone());
 419                 }
 420                 TyKind::Never.intern(&Interner)
 421             }
 422             Expr::Yield { expr } => {
 423                 // FIXME: track yield type for coercion
 424                 if let Some(expr) = expr {
 425                     self.infer_expr(*expr, &Expectation::none());
 426                 }
 427                 TyKind::Never.intern(&Interner)
 428             }
 429             Expr::RecordLit { path, fields, spread } => {
 430                 let (ty, def_id) = self.resolve_variant(path.as_deref());
 431                 if let Some(variant) = def_id {
 432                     self.write_variant_resolution(tgt_expr.into(), variant);
 433                 }
 434
 435                 if let Some(t) = expected.only_has_type(&mut self.table) {
 436                     self.unify(&ty, &t);
 437                 }
 438
 439                 let substs = ty
 440                     .as_adt()
 441                     .map(|(_, s)| s.clone())
 442                     .unwrap_or_else(|| Substitution::empty(&Interner));
 443                 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
 444                 let variant_data = def_id.map(|it| it.variant_data(self.db.upcast()));
 445                 for field in fields.iter() {
 446                     let field_def =
 447                         variant_data.as_ref().and_then(|it| match it.field(&field.name) {
 448                             Some(local_id) => Some(FieldId { parent: def_id.unwrap(), local_id }),
 449                             None => {
 450                                 self.push_diagnostic(InferenceDiagnostic::NoSuchField {
 451                                     expr: field.expr,
 452                                 });
 453                                 None
 454                             }
 455                         });
 456                     let field_ty = field_def.map_or(self.err_ty(), |it| {
 457                         field_types[it.local_id].clone().substitute(&Interner, &substs)
 458                     });
 459                     self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
 460                 }
 461                 if let Some(expr) = spread {
 462                     self.infer_expr(*expr, &Expectation::has_type(ty.clone()));
 463                 }
 464                 ty
 465             }
 466             Expr::Field { expr, name } => {
 467                 let receiver_ty = self.infer_expr_inner(*expr, &Expectation::none());
 468                 let canonicalized = self.canonicalize(receiver_ty);
 469                 let ty = autoderef::autoderef(
 470                     self.db,
 471                     self.resolver.krate(),
 472                     InEnvironment {
 473                         goal: canonicalized.value.clone(),
 474                         environment: self.trait_env.env.clone(),
 475                     },
 476                 )
 477                 .find_map(|derefed_ty| {
 478                     let def_db = self.db.upcast();
 479                     let module = self.resolver.module();
 480                     let is_visible = |field_id: &FieldId| {
 481                         module
 482                             .map(|mod_id| {
 483                                 self.db.field_visibilities(field_id.parent)[field_id.local_id]
 484                                     .is_visible_from(def_db, mod_id)
 485                             })
 486                             .unwrap_or(true)
 487                     };
 488                     match canonicalized.decanonicalize_ty(derefed_ty.value).kind(&Interner) {
 489                         TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
 490                             substs
 491                                 .as_slice(&Interner)
 492                                 .get(idx)
 493                                 .map(|a| a.assert_ty_ref(&Interner))
 494                                 .cloned()
 495                         }),
 496                         TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
 497                             let local_id = self.db.struct_data(*s).variant_data.field(name)?;
 498                             let field = FieldId { parent: (*s).into(), local_id };
 499                             if is_visible(&field) {
 500                                 self.write_field_resolution(tgt_expr, field);
 501                                 Some(
 502                                     self.db.field_types((*s).into())[field.local_id]
 503                                         .clone()
 504                                         .substitute(&Interner, &parameters),
 505                                 )
 506                             } else {
 507                                 None
 508                             }
 509                         }
 510                         TyKind::Adt(AdtId(hir_def::AdtId::UnionId(u)), parameters) => {
 511                             let local_id = self.db.union_data(*u).variant_data.field(name)?;
 512                             let field = FieldId { parent: (*u).into(), local_id };
 513                             if is_visible(&field) {
 514                                 self.write_field_resolution(tgt_expr, field);
 515                                 Some(
 516                                     self.db.field_types((*u).into())[field.local_id]
 517                                         .clone()
 518                                         .substitute(&Interner, &parameters),
 519                                 )
 520                             } else {
 521                                 None
 522                             }
 523                         }
 524                         _ => None,
 525                     }
 526                 })
 527                 .unwrap_or_else(|| self.err_ty());
 528                 let ty = self.insert_type_vars(ty);
 529                 self.normalize_associated_types_in(ty)
 530             }
 531             Expr::Await { expr } => {
 532                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 533                 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
 534             }
 535             Expr::Try { expr } => {
 536                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 537                 self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
 538             }
 539             Expr::Cast { expr, type_ref } => {
 540                 // FIXME: propagate the "castable to" expectation (and find a test case that shows this is necessary)
 541                 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 542                 let cast_ty = self.make_ty(type_ref);
 543                 // FIXME check the cast...
 544                 cast_ty
 545             }
 546             Expr::Ref { expr, rawness, mutability } => {
 547                 let mutability = lower_to_chalk_mutability(*mutability);
 548                 let expectation = if let Some((exp_inner, exp_rawness, exp_mutability)) = expected
 549                     .only_has_type(&mut self.table)
 550                     .as_ref()
 551                     .and_then(|t| t.as_reference_or_ptr())
 552                 {
 553                     if exp_mutability == Mutability::Mut && mutability == Mutability::Not {
 554                         // FIXME: record type error - expected mut reference but found shared ref,
 555                         // which cannot be coerced
 556                     }
 557                     if exp_rawness == Rawness::Ref && *rawness == Rawness::RawPtr {
 558                         // FIXME: record type error - expected reference but found ptr,
 559                         // which cannot be coerced
 560                     }
 561                     Expectation::rvalue_hint(Ty::clone(exp_inner))
 562                 } else {
 563                     Expectation::none()
 564                 };
 565                 let inner_ty = self.infer_expr_inner(*expr, &expectation);
 566                 match rawness {
 567                     Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
 568                     Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
 569                 }
 570                 .intern(&Interner)
 571             }
 572             Expr::Box { expr } => {
 573                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 574                 if let Some(box_) = self.resolve_boxed_box() {
 575                     TyBuilder::adt(self.db, box_)
 576                         .push(inner_ty)
 577                         .fill_with_defaults(self.db, || self.table.new_type_var())
 578                         .build()
 579                 } else {
 580                     self.err_ty()
 581                 }
 582             }
 583             Expr::UnaryOp { expr, op } => {
 584                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
 585                 let inner_ty = self.resolve_ty_shallow(&inner_ty);
 586                 match op {
 587                     UnaryOp::Deref => match self.resolver.krate() {
 588                         Some(krate) => {
 589                             let canonicalized = self.canonicalize(inner_ty);
 590                             match autoderef::deref(
 591                                 self.db,
 592                                 krate,
 593                                 InEnvironment {
 594                                     goal: &canonicalized.value,
 595                                     environment: self.trait_env.env.clone(),
 596                                 },
 597                             ) {
 598                                 Some(derefed_ty) => {
 599                                     canonicalized.decanonicalize_ty(derefed_ty.value)
 600                                 }
 601                                 None => self.err_ty(),
 602                             }
 603                         }
 604                         None => self.err_ty(),
 605                     },
 606                     UnaryOp::Neg => {
 607                         match inner_ty.kind(&Interner) {
 608                             // Fast path for builtins
 609                             TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_) | Scalar::Float(_))
 610                             | TyKind::InferenceVar(
 611                                 _,
 612                                 TyVariableKind::Integer | TyVariableKind::Float,
 613                             ) => inner_ty,
 614                             // Otherwise we resolve via the std::ops::Neg trait
 615                             _ => self
 616                                 .resolve_associated_type(inner_ty, self.resolve_ops_neg_output()),
 617                         }
 618                     }
 619                     UnaryOp::Not => {
 620                         match inner_ty.kind(&Interner) {
 621                             // Fast path for builtins
 622                             TyKind::Scalar(Scalar::Bool | Scalar::Int(_) | Scalar::Uint(_))
 623                             | TyKind::InferenceVar(_, TyVariableKind::Integer) => inner_ty,
 624                             // Otherwise we resolve via the std::ops::Not trait
 625                             _ => self
 626                                 .resolve_associated_type(inner_ty, self.resolve_ops_not_output()),
 627                         }
 628                     }
 629                 }
 630             }
 631             Expr::BinaryOp { lhs, rhs, op } => match op {
 632                 Some(op) => {
 633                     let lhs_expectation = match op {
 634                         BinaryOp::LogicOp(..) => {
 635                             Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner))
 636                         }
 637                         _ => Expectation::none(),
 638                     };
 639                     let lhs_ty = self.infer_expr(*lhs, &lhs_expectation);
 640                     let lhs_ty = self.resolve_ty_shallow(&lhs_ty);
 641                     let rhs_expectation = op::binary_op_rhs_expectation(*op, lhs_ty.clone());
 642                     let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation));
 643                     let rhs_ty = self.resolve_ty_shallow(&rhs_ty);
 644
 645                     let ret = op::binary_op_return_ty(*op, lhs_ty.clone(), rhs_ty.clone());
 646
 647                     if ret.is_unknown() {
 648                         cov_mark::hit!(infer_expr_inner_binary_operator_overload);
 649
 650                         self.resolve_associated_type_with_params(
 651                             lhs_ty,
 652                             self.resolve_binary_op_output(op),
 653                             &[rhs_ty],
 654                         )
 655                     } else {
 656                         ret
 657                     }
 658                 }
 659                 _ => self.err_ty(),
 660             },
 661             Expr::Range { lhs, rhs, range_type } => {
 662                 let lhs_ty = lhs.map(|e| self.infer_expr_inner(e, &Expectation::none()));
 663                 let rhs_expect = lhs_ty
 664                     .as_ref()
 665                     .map_or_else(Expectation::none, |ty| Expectation::has_type(ty.clone()));
 666                 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
 667                 match (range_type, lhs_ty, rhs_ty) {
 668                     (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
 669                         Some(adt) => TyBuilder::adt(self.db, adt).build(),
 670                         None => self.err_ty(),
 671                     },
 672                     (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
 673                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 674                         None => self.err_ty(),
 675                     },
 676                     (RangeOp::Inclusive, None, Some(ty)) => {
 677                         match self.resolve_range_to_inclusive() {
 678                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 679                             None => self.err_ty(),
 680                         }
 681                     }
 682                     (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
 683                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 684                         None => self.err_ty(),
 685                     },
 686                     (RangeOp::Inclusive, Some(_), Some(ty)) => {
 687                         match self.resolve_range_inclusive() {
 688                             Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 689                             None => self.err_ty(),
 690                         }
 691                     }
 692                     (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
 693                         Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
 694                         None => self.err_ty(),
 695                     },
 696                     (RangeOp::Inclusive, _, None) => self.err_ty(),
 697                 }
 698             }
 699             Expr::Index { base, index } => {
 700                 let base_ty = self.infer_expr_inner(*base, &Expectation::none());
 701                 let index_ty = self.infer_expr(*index, &Expectation::none());
 702
 703                 if let (Some(index_trait), Some(krate)) =
 704                     (self.resolve_ops_index(), self.resolver.krate())
 705                 {
 706                     let canonicalized = self.canonicalize(base_ty);
 707                     let self_ty = method_resolution::resolve_indexing_op(
 708                         self.db,
 709                         &canonicalized.value,
 710                         self.trait_env.clone(),
 711                         krate,
 712                         index_trait,
 713                     );
 714                     let self_ty =
 715                         self_ty.map_or(self.err_ty(), |t| canonicalized.decanonicalize_ty(t.value));
 716                     self.resolve_associated_type_with_params(
 717                         self_ty,
 718                         self.resolve_ops_index_output(),
 719                         &[index_ty],
 720                     )
 721                 } else {
 722                     self.err_ty()
 723                 }
 724             }
 725             Expr::Tuple { exprs } => {
 726                 let mut tys = match expected
 727                     .only_has_type(&mut self.table)
 728                     .as_ref()
 729                     .map(|t| t.kind(&Interner))
 730                 {
 731                     Some(TyKind::Tuple(_, substs)) => substs
 732                         .iter(&Interner)
 733                         .map(|a| a.assert_ty_ref(&Interner).clone())
 734                         .chain(repeat_with(|| self.table.new_type_var()))
 735                         .take(exprs.len())
 736                         .collect::<Vec<_>>(),
 737                     _ => (0..exprs.len()).map(|_| self.table.new_type_var()).collect(),
 738                 };
 739
 740                 for (expr, ty) in exprs.iter().zip(tys.iter_mut()) {
 741                     self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
 742                 }
 743
 744                 TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
 745             }
 746             Expr::Array(array) => {
 747                 let elem_ty =
 748                     match expected.to_option(&mut self.table).as_ref().map(|t| t.kind(&Interner)) {
 749                         Some(TyKind::Array(st, _) | TyKind::Slice(st)) => st.clone(),
 750                         _ => self.table.new_type_var(),
 751                     };
 752                 let mut coerce = CoerceMany::new(elem_ty.clone());
 753
 754                 let expected = Expectation::has_type(elem_ty.clone());
 755                 let len = match array {
 756                     Array::ElementList(items) => {
 757                         for &expr in items.iter() {
 758                             let cur_elem_ty = self.infer_expr_inner(expr, &expected);
 759                             coerce.coerce(self, Some(expr), &cur_elem_ty);
 760                         }
 761                         Some(items.len() as u64)
 762                     }
 763                     &Array::Repeat { initializer, repeat } => {
 764                         self.infer_expr_coerce(initializer, &Expectation::has_type(elem_ty));
 765                         self.infer_expr(
 766                             repeat,
 767                             &Expectation::has_type(
 768                                 TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner),
 769                             ),
 770                         );
 771
 772                         let repeat_expr = &self.body.exprs[repeat];
 773                         consteval::eval_usize(repeat_expr)
 774                     }
 775                 };
 776
 777                 TyKind::Array(coerce.complete(), consteval::usize_const(len)).intern(&Interner)
 778             }
 779             Expr::Literal(lit) => match lit {
 780                 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
 781                 Literal::String(..) => {
 782                     TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(&Interner))
 783                         .intern(&Interner)
 784                 }
 785                 Literal::ByteString(bs) => {
 786                     let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
 787
 788                     let len = consteval::usize_const(Some(bs.len() as u64));
 789
 790                     let array_type = TyKind::Array(byte_type, len).intern(&Interner);
 791                     TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(&Interner)
 792                 }
 793                 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
 794                 Literal::Int(_v, ty) => match ty {
 795                     Some(int_ty) => {
 796                         TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(*int_ty)))
 797                             .intern(&Interner)
 798                     }
 799                     None => self.table.new_integer_var(),
 800                 },
 801                 Literal::Uint(_v, ty) => match ty {
 802                     Some(int_ty) => {
 803                         TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(*int_ty)))
 804                             .intern(&Interner)
 805                     }
 806                     None => self.table.new_integer_var(),
 807                 },
 808                 Literal::Float(_v, ty) => match ty {
 809                     Some(float_ty) => {
 810                         TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(*float_ty)))
 811                             .intern(&Interner)
 812                     }
 813                     None => self.table.new_float_var(),
 814                 },
 815             },
 816             Expr::MacroStmts { tail } => self.infer_expr_inner(*tail, expected),
 817         };
 818         // use a new type variable if we got unknown here
 819         let ty = self.insert_type_vars_shallow(ty);
 820         self.write_expr_ty(tgt_expr, ty.clone());
 821         ty
 822     }
 823
 824     fn infer_block(
 825         &mut self,
 826         expr: ExprId,
 827         statements: &[Statement],
 828         tail: Option<ExprId>,
 829         expected: &Expectation,
 830     ) -> Ty {
 831         for stmt in statements {
 832             match stmt {
 833                 Statement::Let { pat, type_ref, initializer } => {
 834                     let decl_ty = type_ref
 835                         .as_ref()
 836                         .map(|tr| self.make_ty(tr))
 837                         .unwrap_or_else(|| self.err_ty());
 838
 839                     // Always use the declared type when specified
 840                     let mut ty = decl_ty.clone();
 841
 842                     if let Some(expr) = initializer {
 843                         let actual_ty =
 844                             self.infer_expr_coerce(*expr, &Expectation::has_type(decl_ty.clone()));
 845                         if decl_ty.is_unknown() {
 846                             ty = actual_ty;
 847                         }
 848                     }
 849
 850                     self.infer_pat(*pat, &ty, BindingMode::default());
 851                 }
 852                 Statement::Expr { expr, .. } => {
 853                     self.infer_expr(*expr, &Expectation::none());
 854                 }
 855             }
 856         }
 857
 858         let ty = if let Some(expr) = tail {
 859             self.infer_expr_coerce(expr, expected)
 860         } else {
 861             // Citing rustc: if there is no explicit tail expression,
 862             // that is typically equivalent to a tail expression
 863             // of `()` -- except if the block diverges. In that
 864             // case, there is no value supplied from the tail
 865             // expression (assuming there are no other breaks,
 866             // this implies that the type of the block will be
 867             // `!`).
 868             if self.diverges.is_always() {
 869                 // we don't even make an attempt at coercion
 870                 self.table.new_maybe_never_var()
 871             } else {
 872                 if let Some(t) = expected.only_has_type(&mut self.table) {
 873                     let _ = self.coerce(Some(expr), &TyBuilder::unit(), &t);
 874                 }
 875                 TyBuilder::unit()
 876             }
 877         };
 878         ty
 879     }
 880
 881     fn infer_method_call(
 882         &mut self,
 883         tgt_expr: ExprId,
 884         receiver: ExprId,
 885         args: &[ExprId],
 886         method_name: &Name,
 887         generic_args: Option<&GenericArgs>,
 888     ) -> Ty {
 889         let receiver_ty = self.infer_expr(receiver, &Expectation::none());
 890         let canonicalized_receiver = self.canonicalize(receiver_ty.clone());
 891
 892         let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
 893
 894         let resolved = self.resolver.krate().and_then(|krate| {
 895             method_resolution::lookup_method(
 896                 &canonicalized_receiver.value,
 897                 self.db,
 898                 self.trait_env.clone(),
 899                 krate,
 900                 &traits_in_scope,
 901                 self.resolver.module(),
 902                 method_name,
 903             )
 904         });
 905         let (receiver_ty, method_ty, substs) = match resolved {
 906             Some((ty, func)) => {
 907                 let ty = canonicalized_receiver.decanonicalize_ty(ty);
 908                 let generics = generics(self.db.upcast(), func.into());
 909                 let substs = self.substs_for_method_call(generics, generic_args, &ty);
 910                 self.write_method_resolution(tgt_expr, func, substs.clone());
 911                 (ty, self.db.value_ty(func.into()), substs)
 912             }
 913             None => (
 914                 receiver_ty,
 915                 Binders::empty(&Interner, self.err_ty()),
 916                 Substitution::empty(&Interner),
 917             ),
 918         };
 919         let method_ty = method_ty.substitute(&Interner, &substs);
 920         self.register_obligations_for_call(&method_ty);
 921         let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
 922             Some(sig) => {
 923                 if !sig.params().is_empty() {
 924                     (sig.params()[0].clone(), sig.params()[1..].to_vec(), sig.ret().clone())
 925                 } else {
 926                     (self.err_ty(), Vec::new(), sig.ret().clone())
 927                 }
 928             }
 929             None => (self.err_ty(), Vec::new(), self.err_ty()),
 930         };
 931         self.unify(&expected_receiver_ty, &receiver_ty);
 932
 933         self.check_call_arguments(args, &param_tys);
 934         self.normalize_associated_types_in(ret_ty)
 935     }
 936
 937     fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
 938         // Quoting https://github.com/rust-lang/rust/blob/6ef275e6c3cb1384ec78128eceeb4963ff788dca/src/librustc_typeck/check/mod.rs#L3325 --
 939         // We do this in a pretty awful way: first we type-check any arguments
 940         // that are not closures, then we type-check the closures. This is so
 941         // that we have more information about the types of arguments when we
 942         // type-check the functions. This isn't really the right way to do this.
 943         for &check_closures in &[false, true] {
 944             let param_iter = param_tys.iter().cloned().chain(repeat(self.err_ty()));
 945             for (&arg, param_ty) in args.iter().zip(param_iter) {
 946                 let is_closure = matches!(&self.body[arg], Expr::Lambda { .. });
 947                 if is_closure != check_closures {
 948                     continue;
 949                 }
 950
 951                 let param_ty = self.normalize_associated_types_in(param_ty);
 952                 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
 953             }
 954         }
 955     }
 956
 957     fn substs_for_method_call(
 958         &mut self,
 959         def_generics: Generics,
 960         generic_args: Option<&GenericArgs>,
 961         receiver_ty: &Ty,
 962     ) -> Substitution {
 963         let (parent_params, self_params, type_params, impl_trait_params) =
 964             def_generics.provenance_split();
 965         assert_eq!(self_params, 0); // method shouldn't have another Self param
 966         let total_len = parent_params + type_params + impl_trait_params;
 967         let mut substs = Vec::with_capacity(total_len);
 968         // Parent arguments are unknown, except for the receiver type
 969         for (_id, param) in def_generics.iter_parent() {
 970             if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
 971                 substs.push(receiver_ty.clone());
 972             } else {
 973                 substs.push(self.table.new_type_var());
 974             }
 975         }
 976         // handle provided type arguments
 977         if let Some(generic_args) = generic_args {
 978             // if args are provided, it should be all of them, but we can't rely on that
 979             for arg in generic_args
 980                 .args
 981                 .iter()
 982                 .filter(|arg| matches!(arg, GenericArg::Type(_)))
 983                 .take(type_params)
 984             {
 985                 match arg {
 986                     GenericArg::Type(type_ref) => {
 987                         let ty = self.make_ty(type_ref);
 988                         substs.push(ty);
 989                     }
 990                     GenericArg::Lifetime(_) => {}
 991                 }
 992             }
 993         };
 994         let supplied_params = substs.len();
 995         for _ in supplied_params..total_len {
 996             substs.push(self.table.new_type_var());
 997         }
 998         assert_eq!(substs.len(), total_len);
 999         Substitution::from_iter(&Interner, substs)
1000     }
1001
1002     fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
1003         let callable_ty = self.resolve_ty_shallow(callable_ty);
1004         if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
1005             let def: CallableDefId = from_chalk(self.db, *fn_def);
1006             let generic_predicates = self.db.generic_predicates(def.into());
1007             for predicate in generic_predicates.iter() {
1008                 let (predicate, binders) = predicate
1009                     .clone()
1010                     .substitute(&Interner, parameters)
1011                     .into_value_and_skipped_binders();
1012                 always!(binders.len(&Interner) == 0); // quantified where clauses not yet handled
1013                 self.push_obligation(predicate.cast(&Interner));
1014             }
1015             // add obligation for trait implementation, if this is a trait method
1016             match def {
1017                 CallableDefId::FunctionId(f) => {
1018                     if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
1019                     {
1020                         // construct a TraitRef
1021                         let substs = crate::subst_prefix(
1022                             &*parameters,
1023                             generics(self.db.upcast(), trait_.into()).len(),
1024                         );
1025                         self.push_obligation(
1026                             TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
1027                                 .cast(&Interner),
1028                         );
1029                     }
1030                 }
1031                 CallableDefId::StructId(_) | CallableDefId::EnumVariantId(_) => {}
1032             }
1033         }
1034     }
1035 }