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