crates/hir_ty/src/infer/expr.rs

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