crates/hir_ty/src/infer/expr.rs

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