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