compiler/rustc_hir_typeck/src/expr.rs

   1 //! Type checking expressions.
   2 //!
   3 //! See `mod.rs` for more context on type checking in general.
   4
   5 use crate::cast;
   6 use crate::coercion::CoerceMany;
   7 use crate::coercion::DynamicCoerceMany;
   8 use crate::errors::TypeMismatchFruTypo;
   9 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
  10 use crate::errors::{
  11     FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
  12     YieldExprOutsideOfGenerator,
  13 };
  14 use crate::fatally_break_rust;
  15 use crate::method::SelfSource;
  16 use crate::type_error_struct;
  17 use crate::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
  18 use crate::{
  19     report_unexpected_variant_res, BreakableCtxt, Diverges, FnCtxt, Needs,
  20     TupleArgumentsFlag::DontTupleArguments,
  21 };
  22 use rustc_ast as ast;
  23 use rustc_data_structures::fx::FxHashMap;
  24 use rustc_data_structures::stack::ensure_sufficient_stack;
  25 use rustc_errors::{
  26     pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId,
  27     ErrorGuaranteed, StashKey,
  28 };
  29 use rustc_hir as hir;
  30 use rustc_hir::def::{CtorKind, DefKind, Res};
  31 use rustc_hir::def_id::DefId;
  32 use rustc_hir::intravisit::Visitor;
  33 use rustc_hir::lang_items::LangItem;
  34 use rustc_hir::{ExprKind, HirId, QPath};
  35 use rustc_hir_analysis::astconv::AstConv as _;
  36 use rustc_hir_analysis::check::ty_kind_suggestion;
  37 use rustc_infer::infer;
  38 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
  39 use rustc_infer::infer::InferOk;
  40 use rustc_infer::traits::ObligationCause;
  41 use rustc_middle::middle::stability;
  42 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
  43 use rustc_middle::ty::error::TypeError::FieldMisMatch;
  44 use rustc_middle::ty::subst::SubstsRef;
  45 use rustc_middle::ty::{self, AdtKind, Ty, TypeVisitable};
  46 use rustc_session::errors::ExprParenthesesNeeded;
  47 use rustc_session::parse::feature_err;
  48 use rustc_span::hygiene::DesugaringKind;
  49 use rustc_span::lev_distance::find_best_match_for_name;
  50 use rustc_span::source_map::{Span, Spanned};
  51 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  52 use rustc_target::spec::abi::Abi::RustIntrinsic;
  53 use rustc_trait_selection::infer::InferCtxtExt;
  54 use rustc_trait_selection::traits::{self, ObligationCauseCode};
  55
  56 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  57     fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
  58         let ty = self.check_expr_with_hint(expr, expected);
  59         self.demand_eqtype(expr.span, expected, ty);
  60     }
  61
  62     pub fn check_expr_has_type_or_error(
  63         &self,
  64         expr: &'tcx hir::Expr<'tcx>,
  65         expected: Ty<'tcx>,
  66         extend_err: impl FnMut(&mut Diagnostic),
  67     ) -> Ty<'tcx> {
  68         self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
  69     }
  70
  71     fn check_expr_meets_expectation_or_error(
  72         &self,
  73         expr: &'tcx hir::Expr<'tcx>,
  74         expected: Expectation<'tcx>,
  75         mut extend_err: impl FnMut(&mut Diagnostic),
  76     ) -> Ty<'tcx> {
  77         let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
  78         let mut ty = self.check_expr_with_expectation(expr, expected);
  79
  80         // While we don't allow *arbitrary* coercions here, we *do* allow
  81         // coercions from ! to `expected`.
  82         if ty.is_never() {
  83             if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
  84                 let reported = self.tcx().sess.delay_span_bug(
  85                     expr.span,
  86                     "expression with never type wound up being adjusted",
  87                 );
  88                 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
  89                     target.to_owned()
  90                 } else {
  91                     self.tcx().ty_error_with_guaranteed(reported)
  92                 };
  93             }
  94
  95             let adj_ty = self.next_ty_var(TypeVariableOrigin {
  96                 kind: TypeVariableOriginKind::AdjustmentType,
  97                 span: expr.span,
  98             });
  99             self.apply_adjustments(
 100                 expr,
 101                 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
 102             );
 103             ty = adj_ty;
 104         }
 105
 106         if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
 107             // FIXME(compiler-errors): We probably should fold some of the
 108             // `suggest_` functions from  `emit_coerce_suggestions` into here,
 109             // since some of those aren't necessarily just coerce suggestions.
 110             let _ = self.suggest_deref_ref_or_into(
 111                 &mut err,
 112                 expr.peel_drop_temps(),
 113                 expected_ty,
 114                 ty,
 115                 None,
 116             ) || self.suggest_option_to_bool(&mut err, expr, ty, expected_ty);
 117             extend_err(&mut err);
 118             err.emit();
 119         }
 120         ty
 121     }
 122
 123     pub(super) fn check_expr_coercable_to_type(
 124         &self,
 125         expr: &'tcx hir::Expr<'tcx>,
 126         expected: Ty<'tcx>,
 127         expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
 128     ) -> Ty<'tcx> {
 129         let ty = self.check_expr_with_hint(expr, expected);
 130         // checks don't need two phase
 131         self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
 132     }
 133
 134     pub(super) fn check_expr_with_hint(
 135         &self,
 136         expr: &'tcx hir::Expr<'tcx>,
 137         expected: Ty<'tcx>,
 138     ) -> Ty<'tcx> {
 139         self.check_expr_with_expectation(expr, ExpectHasType(expected))
 140     }
 141
 142     fn check_expr_with_expectation_and_needs(
 143         &self,
 144         expr: &'tcx hir::Expr<'tcx>,
 145         expected: Expectation<'tcx>,
 146         needs: Needs,
 147     ) -> Ty<'tcx> {
 148         let ty = self.check_expr_with_expectation(expr, expected);
 149
 150         // If the expression is used in a place whether mutable place is required
 151         // e.g. LHS of assignment, perform the conversion.
 152         if let Needs::MutPlace = needs {
 153             self.convert_place_derefs_to_mutable(expr);
 154         }
 155
 156         ty
 157     }
 158
 159     pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
 160         self.check_expr_with_expectation(expr, NoExpectation)
 161     }
 162
 163     pub(super) fn check_expr_with_needs(
 164         &self,
 165         expr: &'tcx hir::Expr<'tcx>,
 166         needs: Needs,
 167     ) -> Ty<'tcx> {
 168         self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
 169     }
 170
 171     /// Invariant:
 172     /// If an expression has any sub-expressions that result in a type error,
 173     /// inspecting that expression's type with `ty.references_error()` will return
 174     /// true. Likewise, if an expression is known to diverge, inspecting its
 175     /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
 176     /// strict, _|_ can appear in the type of an expression that does not,
 177     /// itself, diverge: for example, fn() -> _|_.)
 178     /// Note that inspecting a type's structure *directly* may expose the fact
 179     /// that there are actually multiple representations for `Error`, so avoid
 180     /// that when err needs to be handled differently.
 181     #[instrument(skip(self, expr), level = "debug")]
 182     pub(super) fn check_expr_with_expectation(
 183         &self,
 184         expr: &'tcx hir::Expr<'tcx>,
 185         expected: Expectation<'tcx>,
 186     ) -> Ty<'tcx> {
 187         self.check_expr_with_expectation_and_args(expr, expected, &[])
 188     }
 189
 190     /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
 191     /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
 192     pub(super) fn check_expr_with_expectation_and_args(
 193         &self,
 194         expr: &'tcx hir::Expr<'tcx>,
 195         expected: Expectation<'tcx>,
 196         args: &'tcx [hir::Expr<'tcx>],
 197     ) -> Ty<'tcx> {
 198         if self.tcx().sess.verbose() {
 199             // make this code only run with -Zverbose because it is probably slow
 200             if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
 201                 if !lint_str.contains('\n') {
 202                     debug!("expr text: {lint_str}");
 203                 } else {
 204                     let mut lines = lint_str.lines();
 205                     if let Some(line0) = lines.next() {
 206                         let remaining_lines = lines.count();
 207                         debug!("expr text: {line0}");
 208                         debug!("expr text: ...(and {remaining_lines} more lines)");
 209                     }
 210                 }
 211             }
 212         }
 213
 214         // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
 215         // without the final expr (e.g. `try { return; }`). We don't want to generate an
 216         // unreachable_code lint for it since warnings for autogenerated code are confusing.
 217         let is_try_block_generated_unit_expr = match expr.kind {
 218             ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
 219                 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
 220             }
 221
 222             _ => false,
 223         };
 224
 225         // Warn for expressions after diverging siblings.
 226         if !is_try_block_generated_unit_expr {
 227             self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
 228         }
 229
 230         // Hide the outer diverging and has_errors flags.
 231         let old_diverges = self.diverges.replace(Diverges::Maybe);
 232
 233         let ty = ensure_sufficient_stack(|| match &expr.kind {
 234             hir::ExprKind::Path(
 235                 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
 236             ) => self.check_expr_path(qpath, expr, args),
 237             _ => self.check_expr_kind(expr, expected),
 238         });
 239
 240         // Warn for non-block expressions with diverging children.
 241         match expr.kind {
 242             ExprKind::Block(..)
 243             | ExprKind::If(..)
 244             | ExprKind::Let(..)
 245             | ExprKind::Loop(..)
 246             | ExprKind::Match(..) => {}
 247             // If `expr` is a result of desugaring the try block and is an ok-wrapped
 248             // diverging expression (e.g. it arose from desugaring of `try { return }`),
 249             // we skip issuing a warning because it is autogenerated code.
 250             ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
 251             ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
 252             ExprKind::MethodCall(segment, ..) => {
 253                 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
 254             }
 255             _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
 256         }
 257
 258         // Any expression that produces a value of type `!` must have diverged
 259         if ty.is_never() {
 260             self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
 261         }
 262
 263         // Record the type, which applies it effects.
 264         // We need to do this after the warning above, so that
 265         // we don't warn for the diverging expression itself.
 266         self.write_ty(expr.hir_id, ty);
 267
 268         // Combine the diverging and has_error flags.
 269         self.diverges.set(self.diverges.get() | old_diverges);
 270
 271         debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
 272         debug!("... {:?}, expected is {:?}", ty, expected);
 273
 274         ty
 275     }
 276
 277     #[instrument(skip(self, expr), level = "debug")]
 278     fn check_expr_kind(
 279         &self,
 280         expr: &'tcx hir::Expr<'tcx>,
 281         expected: Expectation<'tcx>,
 282     ) -> Ty<'tcx> {
 283         trace!("expr={:#?}", expr);
 284
 285         let tcx = self.tcx;
 286         match expr.kind {
 287             ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
 288             ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
 289             ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
 290             ExprKind::Assign(lhs, rhs, span) => {
 291                 self.check_expr_assign(expr, expected, lhs, rhs, span)
 292             }
 293             ExprKind::AssignOp(op, lhs, rhs) => {
 294                 self.check_binop_assign(expr, op, lhs, rhs, expected)
 295             }
 296             ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
 297             ExprKind::AddrOf(kind, mutbl, oprnd) => {
 298                 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
 299             }
 300             ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
 301                 self.check_lang_item_path(lang_item, expr, hir_id)
 302             }
 303             ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
 304             ExprKind::InlineAsm(asm) => {
 305                 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
 306                 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
 307                 self.check_expr_asm(asm)
 308             }
 309             ExprKind::Break(destination, ref expr_opt) => {
 310                 self.check_expr_break(destination, expr_opt.as_deref(), expr)
 311             }
 312             ExprKind::Continue(destination) => {
 313                 if destination.target_id.is_ok() {
 314                     tcx.types.never
 315                 } else {
 316                     // There was an error; make type-check fail.
 317                     tcx.ty_error()
 318                 }
 319             }
 320             ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
 321             ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
 322             ExprKind::Loop(body, _, source, _) => {
 323                 self.check_expr_loop(body, source, expected, expr)
 324             }
 325             ExprKind::Match(discrim, arms, match_src) => {
 326                 self.check_match(expr, &discrim, arms, expected, match_src)
 327             }
 328             ExprKind::Closure(closure) => self.check_expr_closure(closure, expr.span, expected),
 329             ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
 330             ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
 331             ExprKind::MethodCall(segment, receiver, args, _) => {
 332                 self.check_method_call(expr, segment, receiver, args, expected)
 333             }
 334             ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
 335             ExprKind::Type(e, t) => {
 336                 let ty = self.to_ty_saving_user_provided_ty(&t);
 337                 self.check_expr_eq_type(&e, ty);
 338                 ty
 339             }
 340             ExprKind::If(cond, then_expr, opt_else_expr) => {
 341                 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
 342             }
 343             ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
 344             ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
 345             ExprKind::ConstBlock(ref anon_const) => {
 346                 self.check_expr_const_block(anon_const, expected, expr)
 347             }
 348             ExprKind::Repeat(element, ref count) => {
 349                 self.check_expr_repeat(element, count, expected, expr)
 350             }
 351             ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
 352             ExprKind::Struct(qpath, fields, ref base_expr) => {
 353                 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
 354             }
 355             ExprKind::Field(base, field) => self.check_field(expr, &base, field),
 356             ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
 357             ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
 358             hir::ExprKind::Err => tcx.ty_error(),
 359         }
 360     }
 361
 362     fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
 363         let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
 364             ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
 365             _ => NoExpectation,
 366         });
 367         let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
 368         self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
 369         self.tcx.mk_box(referent_ty)
 370     }
 371
 372     fn check_expr_unary(
 373         &self,
 374         unop: hir::UnOp,
 375         oprnd: &'tcx hir::Expr<'tcx>,
 376         expected: Expectation<'tcx>,
 377         expr: &'tcx hir::Expr<'tcx>,
 378     ) -> Ty<'tcx> {
 379         let tcx = self.tcx;
 380         let expected_inner = match unop {
 381             hir::UnOp::Not | hir::UnOp::Neg => expected,
 382             hir::UnOp::Deref => NoExpectation,
 383         };
 384         let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
 385
 386         if !oprnd_t.references_error() {
 387             oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
 388             match unop {
 389                 hir::UnOp::Deref => {
 390                     if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
 391                         oprnd_t = ty;
 392                     } else {
 393                         let mut err = type_error_struct!(
 394                             tcx.sess,
 395                             expr.span,
 396                             oprnd_t,
 397                             E0614,
 398                             "type `{oprnd_t}` cannot be dereferenced",
 399                         );
 400                         let sp = tcx.sess.source_map().start_point(expr.span);
 401                         if let Some(sp) =
 402                             tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
 403                         {
 404                             err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
 405                         }
 406                         oprnd_t = tcx.ty_error_with_guaranteed(err.emit());
 407                     }
 408                 }
 409                 hir::UnOp::Not => {
 410                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 411                     // If it's builtin, we can reuse the type, this helps inference.
 412                     if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
 413                         oprnd_t = result;
 414                     }
 415                 }
 416                 hir::UnOp::Neg => {
 417                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 418                     // If it's builtin, we can reuse the type, this helps inference.
 419                     if !oprnd_t.is_numeric() {
 420                         oprnd_t = result;
 421                     }
 422                 }
 423             }
 424         }
 425         oprnd_t
 426     }
 427
 428     fn check_expr_addr_of(
 429         &self,
 430         kind: hir::BorrowKind,
 431         mutbl: hir::Mutability,
 432         oprnd: &'tcx hir::Expr<'tcx>,
 433         expected: Expectation<'tcx>,
 434         expr: &'tcx hir::Expr<'tcx>,
 435     ) -> Ty<'tcx> {
 436         let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
 437             match ty.kind() {
 438                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 439                     if oprnd.is_syntactic_place_expr() {
 440                         // Places may legitimately have unsized types.
 441                         // For example, dereferences of a fat pointer and
 442                         // the last field of a struct can be unsized.
 443                         ExpectHasType(*ty)
 444                     } else {
 445                         Expectation::rvalue_hint(self, *ty)
 446                     }
 447                 }
 448                 _ => NoExpectation,
 449             }
 450         });
 451         let ty =
 452             self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
 453
 454         let tm = ty::TypeAndMut { ty, mutbl };
 455         match kind {
 456             _ if tm.ty.references_error() => self.tcx.ty_error(),
 457             hir::BorrowKind::Raw => {
 458                 self.check_named_place_expr(oprnd);
 459                 self.tcx.mk_ptr(tm)
 460             }
 461             hir::BorrowKind::Ref => {
 462                 // Note: at this point, we cannot say what the best lifetime
 463                 // is to use for resulting pointer.  We want to use the
 464                 // shortest lifetime possible so as to avoid spurious borrowck
 465                 // errors.  Moreover, the longest lifetime will depend on the
 466                 // precise details of the value whose address is being taken
 467                 // (and how long it is valid), which we don't know yet until
 468                 // type inference is complete.
 469                 //
 470                 // Therefore, here we simply generate a region variable. The
 471                 // region inferencer will then select a suitable value.
 472                 // Finally, borrowck will infer the value of the region again,
 473                 // this time with enough precision to check that the value
 474                 // whose address was taken can actually be made to live as long
 475                 // as it needs to live.
 476                 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
 477                 self.tcx.mk_ref(region, tm)
 478             }
 479         }
 480     }
 481
 482     /// Does this expression refer to a place that either:
 483     /// * Is based on a local or static.
 484     /// * Contains a dereference
 485     /// Note that the adjustments for the children of `expr` should already
 486     /// have been resolved.
 487     fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
 488         let is_named = oprnd.is_place_expr(|base| {
 489             // Allow raw borrows if there are any deref adjustments.
 490             //
 491             // const VAL: (i32,) = (0,);
 492             // const REF: &(i32,) = &(0,);
 493             //
 494             // &raw const VAL.0;            // ERROR
 495             // &raw const REF.0;            // OK, same as &raw const (*REF).0;
 496             //
 497             // This is maybe too permissive, since it allows
 498             // `let u = &raw const Box::new((1,)).0`, which creates an
 499             // immediately dangling raw pointer.
 500             self.typeck_results
 501                 .borrow()
 502                 .adjustments()
 503                 .get(base.hir_id)
 504                 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
 505         });
 506         if !is_named {
 507             self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
 508         }
 509     }
 510
 511     fn check_lang_item_path(
 512         &self,
 513         lang_item: hir::LangItem,
 514         expr: &'tcx hir::Expr<'tcx>,
 515         hir_id: Option<hir::HirId>,
 516     ) -> Ty<'tcx> {
 517         self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
 518     }
 519
 520     pub(crate) fn check_expr_path(
 521         &self,
 522         qpath: &'tcx hir::QPath<'tcx>,
 523         expr: &'tcx hir::Expr<'tcx>,
 524         args: &'tcx [hir::Expr<'tcx>],
 525     ) -> Ty<'tcx> {
 526         let tcx = self.tcx;
 527         let (res, opt_ty, segs) =
 528             self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
 529         let ty = match res {
 530             Res::Err => {
 531                 let e =
 532                     self.tcx.sess.delay_span_bug(qpath.span(), "`Res::Err` but no error emitted");
 533                 self.set_tainted_by_errors(e);
 534                 tcx.ty_error_with_guaranteed(e)
 535             }
 536             Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
 537                 let e = report_unexpected_variant_res(tcx, res, qpath, expr.span);
 538                 tcx.ty_error_with_guaranteed(e)
 539             }
 540             _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
 541         };
 542
 543         if let ty::FnDef(did, ..) = *ty.kind() {
 544             let fn_sig = ty.fn_sig(tcx);
 545             if tcx.fn_sig(did).abi() == RustIntrinsic && tcx.item_name(did) == sym::transmute {
 546                 let from = fn_sig.inputs().skip_binder()[0];
 547                 let to = fn_sig.output().skip_binder();
 548                 // We defer the transmute to the end of typeck, once all inference vars have
 549                 // been resolved or we errored. This is important as we can only check transmute
 550                 // on concrete types, but the output type may not be known yet (it would only
 551                 // be known if explicitly specified via turbofish).
 552                 self.deferred_transmute_checks.borrow_mut().push((from, to, expr.hir_id));
 553             }
 554             if !tcx.features().unsized_fn_params {
 555                 // We want to remove some Sized bounds from std functions,
 556                 // but don't want to expose the removal to stable Rust.
 557                 // i.e., we don't want to allow
 558                 //
 559                 // ```rust
 560                 // drop as fn(str);
 561                 // ```
 562                 //
 563                 // to work in stable even if the Sized bound on `drop` is relaxed.
 564                 for i in 0..fn_sig.inputs().skip_binder().len() {
 565                     // We just want to check sizedness, so instead of introducing
 566                     // placeholder lifetimes with probing, we just replace higher lifetimes
 567                     // with fresh vars.
 568                     let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
 569                     let input = self.replace_bound_vars_with_fresh_vars(
 570                         span,
 571                         infer::LateBoundRegionConversionTime::FnCall,
 572                         fn_sig.input(i),
 573                     );
 574                     self.require_type_is_sized_deferred(
 575                         input,
 576                         span,
 577                         traits::SizedArgumentType(None),
 578                     );
 579                 }
 580             }
 581             // Here we want to prevent struct constructors from returning unsized types.
 582             // There were two cases this happened: fn pointer coercion in stable
 583             // and usual function call in presence of unsized_locals.
 584             // Also, as we just want to check sizedness, instead of introducing
 585             // placeholder lifetimes with probing, we just replace higher lifetimes
 586             // with fresh vars.
 587             let output = self.replace_bound_vars_with_fresh_vars(
 588                 expr.span,
 589                 infer::LateBoundRegionConversionTime::FnCall,
 590                 fn_sig.output(),
 591             );
 592             self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
 593         }
 594
 595         // We always require that the type provided as the value for
 596         // a type parameter outlives the moment of instantiation.
 597         let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
 598         self.add_wf_bounds(substs, expr);
 599
 600         ty
 601     }
 602
 603     fn check_expr_break(
 604         &self,
 605         destination: hir::Destination,
 606         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 607         expr: &'tcx hir::Expr<'tcx>,
 608     ) -> Ty<'tcx> {
 609         let tcx = self.tcx;
 610         if let Ok(target_id) = destination.target_id {
 611             let (e_ty, cause);
 612             if let Some(e) = expr_opt {
 613                 // If this is a break with a value, we need to type-check
 614                 // the expression. Get an expected type from the loop context.
 615                 let opt_coerce_to = {
 616                     // We should release `enclosing_breakables` before the `check_expr_with_hint`
 617                     // below, so can't move this block of code to the enclosing scope and share
 618                     // `ctxt` with the second `enclosing_breakables` borrow below.
 619                     let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 620                     match enclosing_breakables.opt_find_breakable(target_id) {
 621                         Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
 622                         None => {
 623                             // Avoid ICE when `break` is inside a closure (#65383).
 624                             return tcx.ty_error_with_message(
 625                                 expr.span,
 626                                 "break was outside loop, but no error was emitted",
 627                             );
 628                         }
 629                     }
 630                 };
 631
 632                 // If the loop context is not a `loop { }`, then break with
 633                 // a value is illegal, and `opt_coerce_to` will be `None`.
 634                 // Just set expectation to error in that case.
 635                 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
 636
 637                 // Recurse without `enclosing_breakables` borrowed.
 638                 e_ty = self.check_expr_with_hint(e, coerce_to);
 639                 cause = self.misc(e.span);
 640             } else {
 641                 // Otherwise, this is a break *without* a value. That's
 642                 // always legal, and is equivalent to `break ()`.
 643                 e_ty = tcx.mk_unit();
 644                 cause = self.misc(expr.span);
 645             }
 646
 647             // Now that we have type-checked `expr_opt`, borrow
 648             // the `enclosing_loops` field and let's coerce the
 649             // type of `expr_opt` into what is expected.
 650             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 651             let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
 652                 // Avoid ICE when `break` is inside a closure (#65383).
 653                 return tcx.ty_error_with_message(
 654                     expr.span,
 655                     "break was outside loop, but no error was emitted",
 656                 );
 657             };
 658
 659             if let Some(ref mut coerce) = ctxt.coerce {
 660                 if let Some(ref e) = expr_opt {
 661                     coerce.coerce(self, &cause, e, e_ty);
 662                 } else {
 663                     assert!(e_ty.is_unit());
 664                     let ty = coerce.expected_ty();
 665                     coerce.coerce_forced_unit(
 666                         self,
 667                         &cause,
 668                         &mut |mut err| {
 669                             self.suggest_mismatched_types_on_tail(
 670                                 &mut err, expr, ty, e_ty, target_id,
 671                             );
 672                             if let Some(val) = ty_kind_suggestion(ty) {
 673                                 let label = destination
 674                                     .label
 675                                     .map(|l| format!(" {}", l.ident))
 676                                     .unwrap_or_else(String::new);
 677                                 err.span_suggestion(
 678                                     expr.span,
 679                                     "give it a value of the expected type",
 680                                     format!("break{label} {val}"),
 681                                     Applicability::HasPlaceholders,
 682                                 );
 683                             }
 684                         },
 685                         false,
 686                     );
 687                 }
 688             } else {
 689                 // If `ctxt.coerce` is `None`, we can just ignore
 690                 // the type of the expression.  This is because
 691                 // either this was a break *without* a value, in
 692                 // which case it is always a legal type (`()`), or
 693                 // else an error would have been flagged by the
 694                 // `loops` pass for using break with an expression
 695                 // where you are not supposed to.
 696                 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
 697             }
 698
 699             // If we encountered a `break`, then (no surprise) it may be possible to break from the
 700             // loop... unless the value being returned from the loop diverges itself, e.g.
 701             // `break return 5` or `break loop {}`.
 702             ctxt.may_break |= !self.diverges.get().is_always();
 703
 704             // the type of a `break` is always `!`, since it diverges
 705             tcx.types.never
 706         } else {
 707             // Otherwise, we failed to find the enclosing loop;
 708             // this can only happen if the `break` was not
 709             // inside a loop at all, which is caught by the
 710             // loop-checking pass.
 711             let err = self.tcx.ty_error_with_message(
 712                 expr.span,
 713                 "break was outside loop, but no error was emitted",
 714             );
 715
 716             // We still need to assign a type to the inner expression to
 717             // prevent the ICE in #43162.
 718             if let Some(e) = expr_opt {
 719                 self.check_expr_with_hint(e, err);
 720
 721                 // ... except when we try to 'break rust;'.
 722                 // ICE this expression in particular (see #43162).
 723                 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
 724                     if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
 725                         fatally_break_rust(self.tcx.sess);
 726                     }
 727                 }
 728             }
 729
 730             // There was an error; make type-check fail.
 731             err
 732         }
 733     }
 734
 735     fn check_expr_return(
 736         &self,
 737         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 738         expr: &'tcx hir::Expr<'tcx>,
 739     ) -> Ty<'tcx> {
 740         if self.ret_coercion.is_none() {
 741             let mut err = ReturnStmtOutsideOfFnBody {
 742                 span: expr.span,
 743                 encl_body_span: None,
 744                 encl_fn_span: None,
 745             };
 746
 747             let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
 748
 749             if let Some(hir::Node::Item(hir::Item {
 750                 kind: hir::ItemKind::Fn(..),
 751                 span: encl_fn_span,
 752                 ..
 753             }))
 754             | Some(hir::Node::TraitItem(hir::TraitItem {
 755                 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
 756                 span: encl_fn_span,
 757                 ..
 758             }))
 759             | Some(hir::Node::ImplItem(hir::ImplItem {
 760                 kind: hir::ImplItemKind::Fn(..),
 761                 span: encl_fn_span,
 762                 ..
 763             })) = self.tcx.hir().find_by_def_id(encl_item_id.def_id)
 764             {
 765                 // We are inside a function body, so reporting "return statement
 766                 // outside of function body" needs an explanation.
 767
 768                 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
 769
 770                 // If this didn't hold, we would not have to report an error in
 771                 // the first place.
 772                 assert_ne!(encl_item_id.def_id, encl_body_owner_id);
 773
 774                 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
 775                 let encl_body = self.tcx.hir().body(encl_body_id);
 776
 777                 err.encl_body_span = Some(encl_body.value.span);
 778                 err.encl_fn_span = Some(*encl_fn_span);
 779             }
 780
 781             self.tcx.sess.emit_err(err);
 782
 783             if let Some(e) = expr_opt {
 784                 // We still have to type-check `e` (issue #86188), but calling
 785                 // `check_return_expr` only works inside fn bodies.
 786                 self.check_expr(e);
 787             }
 788         } else if let Some(e) = expr_opt {
 789             if self.ret_coercion_span.get().is_none() {
 790                 self.ret_coercion_span.set(Some(e.span));
 791             }
 792             self.check_return_expr(e, true);
 793         } else {
 794             let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
 795             if self.ret_coercion_span.get().is_none() {
 796                 self.ret_coercion_span.set(Some(expr.span));
 797             }
 798             let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
 799             if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
 800                 coercion.coerce_forced_unit(
 801                     self,
 802                     &cause,
 803                     &mut |db| {
 804                         let span = fn_decl.output.span();
 805                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
 806                             db.span_label(
 807                                 span,
 808                                 format!("expected `{snippet}` because of this return type"),
 809                             );
 810                         }
 811                     },
 812                     true,
 813                 );
 814             } else {
 815                 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
 816             }
 817         }
 818         self.tcx.types.never
 819     }
 820
 821     /// `explicit_return` is `true` if we're checking an explicit `return expr`,
 822     /// and `false` if we're checking a trailing expression.
 823     pub(super) fn check_return_expr(
 824         &self,
 825         return_expr: &'tcx hir::Expr<'tcx>,
 826         explicit_return: bool,
 827     ) {
 828         let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
 829             span_bug!(return_expr.span, "check_return_expr called outside fn body")
 830         });
 831
 832         let ret_ty = ret_coercion.borrow().expected_ty();
 833         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
 834         let mut span = return_expr.span;
 835         // Use the span of the trailing expression for our cause,
 836         // not the span of the entire function
 837         if !explicit_return {
 838             if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
 839                 span = last_expr.span;
 840             }
 841         }
 842         ret_coercion.borrow_mut().coerce(
 843             self,
 844             &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
 845             return_expr,
 846             return_expr_ty,
 847         );
 848
 849         if let Some(fn_sig) = self.body_fn_sig()
 850             && fn_sig.output().has_opaque_types()
 851         {
 852             // Point any obligations that were registered due to opaque type
 853             // inference at the return expression.
 854             self.select_obligations_where_possible(|errors| {
 855                 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
 856             });
 857         }
 858     }
 859
 860     fn point_at_return_for_opaque_ty_error(
 861         &self,
 862         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
 863         span: Span,
 864         return_expr_ty: Ty<'tcx>,
 865     ) {
 866         // Don't point at the whole block if it's empty
 867         if span == self.tcx.hir().span(self.body_id) {
 868             return;
 869         }
 870         for err in errors {
 871             let cause = &mut err.obligation.cause;
 872             if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
 873                 let new_cause = ObligationCause::new(
 874                     cause.span,
 875                     cause.body_id,
 876                     ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
 877                 );
 878                 *cause = new_cause;
 879             }
 880         }
 881     }
 882
 883     pub(crate) fn check_lhs_assignable(
 884         &self,
 885         lhs: &'tcx hir::Expr<'tcx>,
 886         err_code: &'static str,
 887         op_span: Span,
 888         adjust_err: impl FnOnce(&mut Diagnostic),
 889     ) {
 890         if lhs.is_syntactic_place_expr() {
 891             return;
 892         }
 893
 894         // FIXME: Make this use Diagnostic once error codes can be dynamically set.
 895         let mut err = self.tcx.sess.struct_span_err_with_code(
 896             op_span,
 897             "invalid left-hand side of assignment",
 898             DiagnosticId::Error(err_code.into()),
 899         );
 900         err.span_label(lhs.span, "cannot assign to this expression");
 901
 902         self.comes_from_while_condition(lhs.hir_id, |expr| {
 903             err.span_suggestion_verbose(
 904                 expr.span.shrink_to_lo(),
 905                 "you might have meant to use pattern destructuring",
 906                 "let ",
 907                 Applicability::MachineApplicable,
 908             );
 909         });
 910
 911         adjust_err(&mut err);
 912
 913         err.emit();
 914     }
 915
 916     // Check if an expression `original_expr_id` comes from the condition of a while loop,
 917     // as opposed from the body of a while loop, which we can naively check by iterating
 918     // parents until we find a loop...
 919     pub(super) fn comes_from_while_condition(
 920         &self,
 921         original_expr_id: HirId,
 922         then: impl FnOnce(&hir::Expr<'_>),
 923     ) {
 924         let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
 925         while let Some(node) = self.tcx.hir().find(parent) {
 926             match node {
 927                 hir::Node::Expr(hir::Expr {
 928                     kind:
 929                         hir::ExprKind::Loop(
 930                             hir::Block {
 931                                 expr:
 932                                     Some(hir::Expr {
 933                                         kind:
 934                                             hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
 935                                         ..
 936                                     }),
 937                                 ..
 938                             },
 939                             _,
 940                             hir::LoopSource::While,
 941                             _,
 942                         ),
 943                     ..
 944                 }) => {
 945                     // Check if our original expression is a child of the condition of a while loop
 946                     let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
 947                         self.tcx.hir().find_parent_node(*id)
 948                     })
 949                     .take_while(|id| *id != parent)
 950                     .any(|id| id == expr.hir_id);
 951                     // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
 952                     // where `while let` was more likely intended.
 953                     if expr_is_ancestor {
 954                         then(expr);
 955                     }
 956                     break;
 957                 }
 958                 hir::Node::Item(_)
 959                 | hir::Node::ImplItem(_)
 960                 | hir::Node::TraitItem(_)
 961                 | hir::Node::Crate(_) => break,
 962                 _ => {
 963                     parent = self.tcx.hir().get_parent_node(parent);
 964                 }
 965             }
 966         }
 967     }
 968
 969     // A generic function for checking the 'then' and 'else' clauses in an 'if'
 970     // or 'if-else' expression.
 971     fn check_then_else(
 972         &self,
 973         cond_expr: &'tcx hir::Expr<'tcx>,
 974         then_expr: &'tcx hir::Expr<'tcx>,
 975         opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
 976         sp: Span,
 977         orig_expected: Expectation<'tcx>,
 978     ) -> Ty<'tcx> {
 979         let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
 980
 981         self.warn_if_unreachable(
 982             cond_expr.hir_id,
 983             then_expr.span,
 984             "block in `if` or `while` expression",
 985         );
 986
 987         let cond_diverges = self.diverges.get();
 988         self.diverges.set(Diverges::Maybe);
 989
 990         let expected = orig_expected.adjust_for_branches(self);
 991         let then_ty = self.check_expr_with_expectation(then_expr, expected);
 992         let then_diverges = self.diverges.get();
 993         self.diverges.set(Diverges::Maybe);
 994
 995         // We've already taken the expected type's preferences
 996         // into account when typing the `then` branch. To figure
 997         // out the initial shot at a LUB, we thus only consider
 998         // `expected` if it represents a *hard* constraint
 999         // (`only_has_type`); otherwise, we just go with a
1000         // fresh type variable.
1001         let coerce_to_ty = expected.coercion_target_type(self, sp);
1002         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
1003
1004         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
1005
1006         if let Some(else_expr) = opt_else_expr {
1007             let else_ty = self.check_expr_with_expectation(else_expr, expected);
1008             let else_diverges = self.diverges.get();
1009
1010             let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1011             let if_cause = self.if_cause(
1012                 sp,
1013                 cond_expr.span,
1014                 then_expr,
1015                 else_expr,
1016                 then_ty,
1017                 else_ty,
1018                 opt_suggest_box_span,
1019             );
1020
1021             coerce.coerce(self, &if_cause, else_expr, else_ty);
1022
1023             // We won't diverge unless both branches do (or the condition does).
1024             self.diverges.set(cond_diverges | then_diverges & else_diverges);
1025         } else {
1026             self.if_fallback_coercion(sp, then_expr, &mut coerce);
1027
1028             // If the condition is false we can't diverge.
1029             self.diverges.set(cond_diverges);
1030         }
1031
1032         let result_ty = coerce.complete(self);
1033         if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1034     }
1035
1036     /// Type check assignment expression `expr` of form `lhs = rhs`.
1037     /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1038     fn check_expr_assign(
1039         &self,
1040         expr: &'tcx hir::Expr<'tcx>,
1041         expected: Expectation<'tcx>,
1042         lhs: &'tcx hir::Expr<'tcx>,
1043         rhs: &'tcx hir::Expr<'tcx>,
1044         span: Span,
1045     ) -> Ty<'tcx> {
1046         let expected_ty = expected.coercion_target_type(self, expr.span);
1047         if expected_ty == self.tcx.types.bool {
1048             // The expected type is `bool` but this will result in `()` so we can reasonably
1049             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1050             // The likely cause of this is `if foo = bar { .. }`.
1051             let actual_ty = self.tcx.mk_unit();
1052             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1053             let lhs_ty = self.check_expr(&lhs);
1054             let rhs_ty = self.check_expr(&rhs);
1055             let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1056                 (Applicability::MachineApplicable, true)
1057             } else if let ExprKind::Binary(
1058                 Spanned { node: hir::BinOpKind::And | hir::BinOpKind::Or, .. },
1059                 _,
1060                 rhs_expr,
1061             ) = lhs.kind
1062             {
1063                 // if x == 1 && y == 2 { .. }
1064                 //                 +
1065                 let actual_lhs_ty = self.check_expr(&rhs_expr);
1066                 (Applicability::MaybeIncorrect, self.can_coerce(rhs_ty, actual_lhs_ty))
1067             } else if let ExprKind::Binary(
1068                 Spanned { node: hir::BinOpKind::And | hir::BinOpKind::Or, .. },
1069                 lhs_expr,
1070                 _,
1071             ) = rhs.kind
1072             {
1073                 // if x == 1 && y == 2 { .. }
1074                 //       +
1075                 let actual_rhs_ty = self.check_expr(&lhs_expr);
1076                 (Applicability::MaybeIncorrect, self.can_coerce(actual_rhs_ty, lhs_ty))
1077             } else {
1078                 (Applicability::MaybeIncorrect, false)
1079             };
1080             if !lhs.is_syntactic_place_expr()
1081                 && lhs.is_approximately_pattern()
1082                 && !matches!(lhs.kind, hir::ExprKind::Lit(_))
1083             {
1084                 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1085                 let hir = self.tcx.hir();
1086                 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1087                     hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1088                 {
1089                     err.span_suggestion_verbose(
1090                         expr.span.shrink_to_lo(),
1091                         "you might have meant to use pattern matching",
1092                         "let ",
1093                         applicability,
1094                     );
1095                 };
1096             }
1097             if eq {
1098                 err.span_suggestion_verbose(
1099                     span.shrink_to_hi(),
1100                     "you might have meant to compare for equality",
1101                     '=',
1102                     applicability,
1103                 );
1104             }
1105
1106             // If the assignment expression itself is ill-formed, don't
1107             // bother emitting another error
1108             let reported = err.emit_unless(lhs_ty.references_error() || rhs_ty.references_error());
1109             return self.tcx.ty_error_with_guaranteed(reported);
1110         }
1111
1112         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1113
1114         let suggest_deref_binop = |err: &mut Diagnostic, rhs_ty: Ty<'tcx>| {
1115             if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1116                 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1117                 // unsized, do not suggest dereferencing it.
1118                 let lhs_deref_ty_is_sized = self
1119                     .infcx
1120                     .type_implements_trait(
1121                         self.tcx.lang_items().sized_trait().unwrap(),
1122                         lhs_deref_ty,
1123                         ty::List::empty(),
1124                         self.param_env,
1125                     )
1126                     .may_apply();
1127                 if lhs_deref_ty_is_sized && self.can_coerce(rhs_ty, lhs_deref_ty) {
1128                     err.span_suggestion_verbose(
1129                         lhs.span.shrink_to_lo(),
1130                         "consider dereferencing here to assign to the mutably borrowed value",
1131                         "*",
1132                         Applicability::MachineApplicable,
1133                     );
1134                 }
1135             }
1136         };
1137
1138         // This is (basically) inlined `check_expr_coercable_to_type`, but we want
1139         // to suggest an additional fixup here in `suggest_deref_binop`.
1140         let rhs_ty = self.check_expr_with_hint(&rhs, lhs_ty);
1141         if let (_, Some(mut diag)) =
1142             self.demand_coerce_diag(rhs, rhs_ty, lhs_ty, Some(lhs), AllowTwoPhase::No)
1143         {
1144             suggest_deref_binop(&mut diag, rhs_ty);
1145             diag.emit();
1146         }
1147
1148         self.check_lhs_assignable(lhs, "E0070", span, |err| {
1149             if let Some(rhs_ty) = self.typeck_results.borrow().expr_ty_opt(rhs) {
1150                 suggest_deref_binop(err, rhs_ty);
1151             }
1152         });
1153
1154         self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1155
1156         if lhs_ty.references_error() || rhs_ty.references_error() {
1157             self.tcx.ty_error()
1158         } else {
1159             self.tcx.mk_unit()
1160         }
1161     }
1162
1163     pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1164         // for let statements, this is done in check_stmt
1165         let init = let_expr.init;
1166         self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1167         // otherwise check exactly as a let statement
1168         self.check_decl(let_expr.into());
1169         // but return a bool, for this is a boolean expression
1170         self.tcx.types.bool
1171     }
1172
1173     fn check_expr_loop(
1174         &self,
1175         body: &'tcx hir::Block<'tcx>,
1176         source: hir::LoopSource,
1177         expected: Expectation<'tcx>,
1178         expr: &'tcx hir::Expr<'tcx>,
1179     ) -> Ty<'tcx> {
1180         let coerce = match source {
1181             // you can only use break with a value from a normal `loop { }`
1182             hir::LoopSource::Loop => {
1183                 let coerce_to = expected.coercion_target_type(self, body.span);
1184                 Some(CoerceMany::new(coerce_to))
1185             }
1186
1187             hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1188         };
1189
1190         let ctxt = BreakableCtxt {
1191             coerce,
1192             may_break: false, // Will get updated if/when we find a `break`.
1193         };
1194
1195         let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1196             self.check_block_no_value(&body);
1197         });
1198
1199         if ctxt.may_break {
1200             // No way to know whether it's diverging because
1201             // of a `break` or an outer `break` or `return`.
1202             self.diverges.set(Diverges::Maybe);
1203         }
1204
1205         // If we permit break with a value, then result type is
1206         // the LUB of the breaks (possibly ! if none); else, it
1207         // is nil. This makes sense because infinite loops
1208         // (which would have type !) are only possible iff we
1209         // permit break with a value [1].
1210         if ctxt.coerce.is_none() && !ctxt.may_break {
1211             // [1]
1212             self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1213         }
1214         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1215     }
1216
1217     /// Checks a method call.
1218     fn check_method_call(
1219         &self,
1220         expr: &'tcx hir::Expr<'tcx>,
1221         segment: &hir::PathSegment<'_>,
1222         rcvr: &'tcx hir::Expr<'tcx>,
1223         args: &'tcx [hir::Expr<'tcx>],
1224         expected: Expectation<'tcx>,
1225     ) -> Ty<'tcx> {
1226         let rcvr_t = self.check_expr(&rcvr);
1227         // no need to check for bot/err -- callee does that
1228         let rcvr_t = self.structurally_resolved_type(rcvr.span, rcvr_t);
1229         let span = segment.ident.span;
1230
1231         let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1232             Ok(method) => {
1233                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1234                 // trigger this codepath causing `structurally_resolved_type` to emit an error.
1235
1236                 self.write_method_call(expr.hir_id, method);
1237                 Ok(method)
1238             }
1239             Err(error) => {
1240                 if segment.ident.name != kw::Empty {
1241                     if let Some(mut err) = self.report_method_error(
1242                         span,
1243                         rcvr_t,
1244                         segment.ident,
1245                         SelfSource::MethodCall(rcvr),
1246                         error,
1247                         Some((rcvr, args)),
1248                     ) {
1249                         err.emit();
1250                     }
1251                 }
1252                 Err(())
1253             }
1254         };
1255
1256         // Call the generic checker.
1257         self.check_method_argument_types(span, expr, method, &args, DontTupleArguments, expected)
1258     }
1259
1260     fn check_expr_cast(
1261         &self,
1262         e: &'tcx hir::Expr<'tcx>,
1263         t: &'tcx hir::Ty<'tcx>,
1264         expr: &'tcx hir::Expr<'tcx>,
1265     ) -> Ty<'tcx> {
1266         // Find the type of `e`. Supply hints based on the type we are casting to,
1267         // if appropriate.
1268         let t_cast = self.to_ty_saving_user_provided_ty(t);
1269         let t_cast = self.resolve_vars_if_possible(t_cast);
1270         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1271         let t_expr = self.resolve_vars_if_possible(t_expr);
1272
1273         // Eagerly check for some obvious errors.
1274         if t_expr.references_error() || t_cast.references_error() {
1275             self.tcx.ty_error()
1276         } else {
1277             // Defer other checks until we're done type checking.
1278             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1279             match cast::CastCheck::new(
1280                 self,
1281                 e,
1282                 t_expr,
1283                 t_cast,
1284                 t.span,
1285                 expr.span,
1286                 self.param_env.constness(),
1287             ) {
1288                 Ok(cast_check) => {
1289                     debug!(
1290                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1291                         t_cast, t_expr, cast_check,
1292                     );
1293                     deferred_cast_checks.push(cast_check);
1294                     t_cast
1295                 }
1296                 Err(_) => self.tcx.ty_error(),
1297             }
1298         }
1299     }
1300
1301     fn check_expr_array(
1302         &self,
1303         args: &'tcx [hir::Expr<'tcx>],
1304         expected: Expectation<'tcx>,
1305         expr: &'tcx hir::Expr<'tcx>,
1306     ) -> Ty<'tcx> {
1307         let element_ty = if !args.is_empty() {
1308             let coerce_to = expected
1309                 .to_option(self)
1310                 .and_then(|uty| match *uty.kind() {
1311                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1312                     _ => None,
1313                 })
1314                 .unwrap_or_else(|| {
1315                     self.next_ty_var(TypeVariableOrigin {
1316                         kind: TypeVariableOriginKind::TypeInference,
1317                         span: expr.span,
1318                     })
1319                 });
1320             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1321             assert_eq!(self.diverges.get(), Diverges::Maybe);
1322             for e in args {
1323                 let e_ty = self.check_expr_with_hint(e, coerce_to);
1324                 let cause = self.misc(e.span);
1325                 coerce.coerce(self, &cause, e, e_ty);
1326             }
1327             coerce.complete(self)
1328         } else {
1329             self.next_ty_var(TypeVariableOrigin {
1330                 kind: TypeVariableOriginKind::TypeInference,
1331                 span: expr.span,
1332             })
1333         };
1334         let array_len = args.len() as u64;
1335         self.suggest_array_len(expr, array_len);
1336         self.tcx.mk_array(element_ty, array_len)
1337     }
1338
1339     fn suggest_array_len(&self, expr: &'tcx hir::Expr<'tcx>, array_len: u64) {
1340         let parent_node = self.tcx.hir().parent_iter(expr.hir_id).find(|(_, node)| {
1341             !matches!(node, hir::Node::Expr(hir::Expr { kind: hir::ExprKind::AddrOf(..), .. }))
1342         });
1343         let Some((_,
1344             hir::Node::Local(hir::Local { ty: Some(ty), .. })
1345             | hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _), .. }))
1346         ) = parent_node else {
1347             return
1348         };
1349         if let hir::TyKind::Array(_, length) = ty.peel_refs().kind
1350             && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
1351             && let Some(span) = self.tcx.hir().opt_span(hir_id)
1352         {
1353             match self.tcx.sess.diagnostic().steal_diagnostic(span, StashKey::UnderscoreForArrayLengths) {
1354                 Some(mut err) => {
1355                     err.span_suggestion(
1356                         span,
1357                         "consider specifying the array length",
1358                         array_len,
1359                         Applicability::MaybeIncorrect,
1360                     );
1361                     err.emit();
1362                 }
1363                 None => ()
1364             }
1365         }
1366     }
1367
1368     fn check_expr_const_block(
1369         &self,
1370         anon_const: &'tcx hir::AnonConst,
1371         expected: Expectation<'tcx>,
1372         _expr: &'tcx hir::Expr<'tcx>,
1373     ) -> Ty<'tcx> {
1374         let body = self.tcx.hir().body(anon_const.body);
1375
1376         // Create a new function context.
1377         let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1378         crate::GatherLocalsVisitor::new(&fcx).visit_body(body);
1379
1380         let ty = fcx.check_expr_with_expectation(&body.value, expected);
1381         fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1382         fcx.write_ty(anon_const.hir_id, ty);
1383         ty
1384     }
1385
1386     fn check_expr_repeat(
1387         &self,
1388         element: &'tcx hir::Expr<'tcx>,
1389         count: &'tcx hir::ArrayLen,
1390         expected: Expectation<'tcx>,
1391         expr: &'tcx hir::Expr<'tcx>,
1392     ) -> Ty<'tcx> {
1393         let tcx = self.tcx;
1394         let count = self.array_length_to_const(count);
1395         if let Some(count) = count.try_eval_usize(tcx, self.param_env) {
1396             self.suggest_array_len(expr, count);
1397         }
1398
1399         let uty = match expected {
1400             ExpectHasType(uty) => match *uty.kind() {
1401                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1402                 _ => None,
1403             },
1404             _ => None,
1405         };
1406
1407         let (element_ty, t) = match uty {
1408             Some(uty) => {
1409                 self.check_expr_coercable_to_type(&element, uty, None);
1410                 (uty, uty)
1411             }
1412             None => {
1413                 let ty = self.next_ty_var(TypeVariableOrigin {
1414                     kind: TypeVariableOriginKind::MiscVariable,
1415                     span: element.span,
1416                 });
1417                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1418                 (element_ty, ty)
1419             }
1420         };
1421
1422         if element_ty.references_error() {
1423             return tcx.ty_error();
1424         }
1425
1426         self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1427
1428         tcx.mk_ty(ty::Array(t, count))
1429     }
1430
1431     fn check_repeat_element_needs_copy_bound(
1432         &self,
1433         element: &hir::Expr<'_>,
1434         count: ty::Const<'tcx>,
1435         element_ty: Ty<'tcx>,
1436     ) {
1437         let tcx = self.tcx;
1438         // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1439         match &element.kind {
1440             hir::ExprKind::ConstBlock(..) => return,
1441             hir::ExprKind::Path(qpath) => {
1442                 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1443                 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1444                 {
1445                     return;
1446                 }
1447             }
1448             _ => {}
1449         }
1450         // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1451         // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1452         let is_const_fn = match element.kind {
1453             hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1454                 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1455                 _ => false,
1456             },
1457             _ => false,
1458         };
1459
1460         // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1461         // don't copy that one element, we move it. Only check for Copy if the length is larger.
1462         if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1463             let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1464             let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1465             self.require_type_meets(element_ty, element.span, code, lang_item);
1466         }
1467     }
1468
1469     fn check_expr_tuple(
1470         &self,
1471         elts: &'tcx [hir::Expr<'tcx>],
1472         expected: Expectation<'tcx>,
1473         expr: &'tcx hir::Expr<'tcx>,
1474     ) -> Ty<'tcx> {
1475         let flds = expected.only_has_type(self).and_then(|ty| {
1476             let ty = self.resolve_vars_with_obligations(ty);
1477             match ty.kind() {
1478                 ty::Tuple(flds) => Some(&flds[..]),
1479                 _ => None,
1480             }
1481         });
1482
1483         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1484             Some(fs) if i < fs.len() => {
1485                 let ety = fs[i];
1486                 self.check_expr_coercable_to_type(&e, ety, None);
1487                 ety
1488             }
1489             _ => self.check_expr_with_expectation(&e, NoExpectation),
1490         });
1491         let tuple = self.tcx.mk_tup(elt_ts_iter);
1492         if tuple.references_error() {
1493             self.tcx.ty_error()
1494         } else {
1495             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1496             tuple
1497         }
1498     }
1499
1500     fn check_expr_struct(
1501         &self,
1502         expr: &hir::Expr<'_>,
1503         expected: Expectation<'tcx>,
1504         qpath: &QPath<'_>,
1505         fields: &'tcx [hir::ExprField<'tcx>],
1506         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1507     ) -> Ty<'tcx> {
1508         // Find the relevant variant
1509         let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1510             self.check_struct_fields_on_error(fields, base_expr);
1511             return self.tcx.ty_error();
1512         };
1513
1514         // Prohibit struct expressions when non-exhaustive flag is set.
1515         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1516         if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1517             self.tcx
1518                 .sess
1519                 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1520         }
1521
1522         self.check_expr_struct_fields(
1523             adt_ty,
1524             expected,
1525             expr.hir_id,
1526             qpath.span(),
1527             variant,
1528             fields,
1529             base_expr,
1530             expr.span,
1531         );
1532
1533         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1534         adt_ty
1535     }
1536
1537     fn check_expr_struct_fields(
1538         &self,
1539         adt_ty: Ty<'tcx>,
1540         expected: Expectation<'tcx>,
1541         expr_id: hir::HirId,
1542         span: Span,
1543         variant: &'tcx ty::VariantDef,
1544         ast_fields: &'tcx [hir::ExprField<'tcx>],
1545         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1546         expr_span: Span,
1547     ) {
1548         let tcx = self.tcx;
1549
1550         let expected_inputs =
1551             self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1552         let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1553             expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1554         } else {
1555             adt_ty
1556         };
1557         // re-link the regions that EIfEO can erase.
1558         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1559
1560         let ty::Adt(adt, substs) = adt_ty.kind() else {
1561             span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1562         };
1563         let adt_kind = adt.adt_kind();
1564
1565         let mut remaining_fields = variant
1566             .fields
1567             .iter()
1568             .enumerate()
1569             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1570             .collect::<FxHashMap<_, _>>();
1571
1572         let mut seen_fields = FxHashMap::default();
1573
1574         let mut error_happened = false;
1575
1576         // Type-check each field.
1577         for (idx, field) in ast_fields.iter().enumerate() {
1578             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1579             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1580                 seen_fields.insert(ident, field.span);
1581                 self.write_field_index(field.hir_id, i);
1582
1583                 // We don't look at stability attributes on
1584                 // struct-like enums (yet...), but it's definitely not
1585                 // a bug to have constructed one.
1586                 if adt_kind != AdtKind::Enum {
1587                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1588                 }
1589
1590                 self.field_ty(field.span, v_field, substs)
1591             } else {
1592                 error_happened = true;
1593                 if let Some(prev_span) = seen_fields.get(&ident) {
1594                     tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1595                         span: field.ident.span,
1596                         prev_span: *prev_span,
1597                         ident,
1598                     });
1599                 } else {
1600                     self.report_unknown_field(
1601                         adt_ty,
1602                         variant,
1603                         field,
1604                         ast_fields,
1605                         adt.variant_descr(),
1606                         expr_span,
1607                     );
1608                 }
1609
1610                 tcx.ty_error()
1611             };
1612
1613             // Make sure to give a type to the field even if there's
1614             // an error, so we can continue type-checking.
1615             let ty = self.check_expr_with_hint(&field.expr, field_type);
1616             let (_, diag) =
1617                 self.demand_coerce_diag(&field.expr, ty, field_type, None, AllowTwoPhase::No);
1618
1619             if let Some(mut diag) = diag {
1620                 if idx == ast_fields.len() - 1 {
1621                     if remaining_fields.is_empty() {
1622                         self.suggest_fru_from_range(field, variant, substs, &mut diag);
1623                         diag.emit();
1624                     } else {
1625                         diag.stash(field.span, StashKey::MaybeFruTypo);
1626                     }
1627                 } else {
1628                     diag.emit();
1629                 }
1630             }
1631         }
1632
1633         // Make sure the programmer specified correct number of fields.
1634         if adt_kind == AdtKind::Union {
1635             if ast_fields.len() != 1 {
1636                 struct_span_err!(
1637                     tcx.sess,
1638                     span,
1639                     E0784,
1640                     "union expressions should have exactly one field",
1641                 )
1642                 .emit();
1643             }
1644         }
1645
1646         // If check_expr_struct_fields hit an error, do not attempt to populate
1647         // the fields with the base_expr. This could cause us to hit errors later
1648         // when certain fields are assumed to exist that in fact do not.
1649         if error_happened {
1650             return;
1651         }
1652
1653         if let Some(base_expr) = base_expr {
1654             // FIXME: We are currently creating two branches here in order to maintain
1655             // consistency. But they should be merged as much as possible.
1656             let fru_tys = if self.tcx.features().type_changing_struct_update {
1657                 if adt.is_struct() {
1658                     // Make some fresh substitutions for our ADT type.
1659                     let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1660                     // We do subtyping on the FRU fields first, so we can
1661                     // learn exactly what types we expect the base expr
1662                     // needs constrained to be compatible with the struct
1663                     // type we expect from the expectation value.
1664                     let fru_tys = variant
1665                         .fields
1666                         .iter()
1667                         .map(|f| {
1668                             let fru_ty = self.normalize_associated_types_in(
1669                                 expr_span,
1670                                 self.field_ty(base_expr.span, f, fresh_substs),
1671                             );
1672                             let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1673                             if let Some(_) = remaining_fields.remove(&ident) {
1674                                 let target_ty = self.field_ty(base_expr.span, f, substs);
1675                                 let cause = self.misc(base_expr.span);
1676                                 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1677                                     Ok(InferOk { obligations, value: () }) => {
1678                                         self.register_predicates(obligations)
1679                                     }
1680                                     Err(_) => {
1681                                         // This should never happen, since we're just subtyping the
1682                                         // remaining_fields, but it's fine to emit this, I guess.
1683                                         self.err_ctxt()
1684                                             .report_mismatched_types(
1685                                                 &cause,
1686                                                 target_ty,
1687                                                 fru_ty,
1688                                                 FieldMisMatch(variant.name, ident.name),
1689                                             )
1690                                             .emit();
1691                                     }
1692                                 }
1693                             }
1694                             self.resolve_vars_if_possible(fru_ty)
1695                         })
1696                         .collect();
1697                     // The use of fresh substs that we have subtyped against
1698                     // our base ADT type's fields allows us to guide inference
1699                     // along so that, e.g.
1700                     // ```
1701                     // MyStruct<'a, F1, F2, const C: usize> {
1702                     //     f: F1,
1703                     //     // Other fields that reference `'a`, `F2`, and `C`
1704                     // }
1705                     //
1706                     // let x = MyStruct {
1707                     //    f: 1usize,
1708                     //    ..other_struct
1709                     // };
1710                     // ```
1711                     // will have the `other_struct` expression constrained to
1712                     // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1713                     // This is important to allow coercions to happen in
1714                     // `other_struct` itself. See `coerce-in-base-expr.rs`.
1715                     let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1716                     self.check_expr_has_type_or_error(
1717                         base_expr,
1718                         self.resolve_vars_if_possible(fresh_base_ty),
1719                         |_| {},
1720                     );
1721                     fru_tys
1722                 } else {
1723                     // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1724                     // type errors on that expression, too.
1725                     self.check_expr(base_expr);
1726                     self.tcx
1727                         .sess
1728                         .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1729                     return;
1730                 }
1731             } else {
1732                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1733                     let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1734                     let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1735                         (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1736                         _ => false,
1737                     };
1738                     if self.tcx.sess.is_nightly_build() && same_adt {
1739                         feature_err(
1740                             &self.tcx.sess.parse_sess,
1741                             sym::type_changing_struct_update,
1742                             base_expr.span,
1743                             "type changing struct updating is experimental",
1744                         )
1745                         .emit();
1746                     }
1747                 });
1748                 match adt_ty.kind() {
1749                     ty::Adt(adt, substs) if adt.is_struct() => variant
1750                         .fields
1751                         .iter()
1752                         .map(|f| {
1753                             self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1754                         })
1755                         .collect(),
1756                     _ => {
1757                         self.tcx
1758                             .sess
1759                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1760                         return;
1761                     }
1762                 }
1763             };
1764             self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1765         } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1766             debug!(?remaining_fields);
1767             let private_fields: Vec<&ty::FieldDef> = variant
1768                 .fields
1769                 .iter()
1770                 .filter(|field| !field.vis.is_accessible_from(tcx.parent_module(expr_id), tcx))
1771                 .collect();
1772
1773             if !private_fields.is_empty() {
1774                 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1775             } else {
1776                 self.report_missing_fields(
1777                     adt_ty,
1778                     span,
1779                     remaining_fields,
1780                     variant,
1781                     ast_fields,
1782                     substs,
1783                 );
1784             }
1785         }
1786     }
1787
1788     fn check_struct_fields_on_error(
1789         &self,
1790         fields: &'tcx [hir::ExprField<'tcx>],
1791         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1792     ) {
1793         for field in fields {
1794             self.check_expr(&field.expr);
1795         }
1796         if let Some(base) = *base_expr {
1797             self.check_expr(&base);
1798         }
1799     }
1800
1801     /// Report an error for a struct field expression when there are fields which aren't provided.
1802     ///
1803     /// ```text
1804     /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1805     ///  --> src/main.rs:8:5
1806     ///   |
1807     /// 8 |     foo::Foo {};
1808     ///   |     ^^^^^^^^ missing `you_can_use_this_field`
1809     ///
1810     /// error: aborting due to previous error
1811     /// ```
1812     fn report_missing_fields(
1813         &self,
1814         adt_ty: Ty<'tcx>,
1815         span: Span,
1816         remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1817         variant: &'tcx ty::VariantDef,
1818         ast_fields: &'tcx [hir::ExprField<'tcx>],
1819         substs: SubstsRef<'tcx>,
1820     ) {
1821         let len = remaining_fields.len();
1822
1823         let mut displayable_field_names: Vec<&str> =
1824             remaining_fields.keys().map(|ident| ident.as_str()).collect();
1825         // sorting &str primitives here, sort_unstable is ok
1826         displayable_field_names.sort_unstable();
1827
1828         let mut truncated_fields_error = String::new();
1829         let remaining_fields_names = match &displayable_field_names[..] {
1830             [field1] => format!("`{}`", field1),
1831             [field1, field2] => format!("`{field1}` and `{field2}`"),
1832             [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1833             _ => {
1834                 truncated_fields_error =
1835                     format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1836                 displayable_field_names
1837                     .iter()
1838                     .take(3)
1839                     .map(|n| format!("`{n}`"))
1840                     .collect::<Vec<_>>()
1841                     .join(", ")
1842             }
1843         };
1844
1845         let mut err = struct_span_err!(
1846             self.tcx.sess,
1847             span,
1848             E0063,
1849             "missing field{} {}{} in initializer of `{}`",
1850             pluralize!(len),
1851             remaining_fields_names,
1852             truncated_fields_error,
1853             adt_ty
1854         );
1855         err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1856
1857         if let Some(last) = ast_fields.last() {
1858             self.suggest_fru_from_range(last, variant, substs, &mut err);
1859         }
1860
1861         err.emit();
1862     }
1863
1864     /// If the last field is a range literal, but it isn't supposed to be, then they probably
1865     /// meant to use functional update syntax.
1866     fn suggest_fru_from_range(
1867         &self,
1868         last_expr_field: &hir::ExprField<'tcx>,
1869         variant: &ty::VariantDef,
1870         substs: SubstsRef<'tcx>,
1871         err: &mut Diagnostic,
1872     ) {
1873         // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1874         if let ExprKind::Struct(
1875                 QPath::LangItem(LangItem::Range, ..),
1876                 &[ref range_start, ref range_end],
1877                 _,
1878             ) = last_expr_field.expr.kind
1879             && let variant_field =
1880                 variant.fields.iter().find(|field| field.ident(self.tcx) == last_expr_field.ident)
1881             && let range_def_id = self.tcx.lang_items().range_struct()
1882             && variant_field
1883                 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1884                 .map(|adt| adt.did())
1885                 != range_def_id
1886         {
1887             // Suppress any range expr type mismatches
1888             if let Some(mut diag) = self
1889                 .tcx
1890                 .sess
1891                 .diagnostic()
1892                 .steal_diagnostic(last_expr_field.span, StashKey::MaybeFruTypo)
1893             {
1894                 diag.delay_as_bug();
1895             }
1896
1897             // Use a (somewhat arbitrary) filtering heuristic to avoid printing
1898             // expressions that are either too long, or have control character
1899             //such as newlines in them.
1900             let expr = self
1901                 .tcx
1902                 .sess
1903                 .source_map()
1904                 .span_to_snippet(range_end.expr.span)
1905                 .ok()
1906                 .filter(|s| s.len() < 25 && !s.contains(|c: char| c.is_control()));
1907
1908             let fru_span = self
1909                 .tcx
1910                 .sess
1911                 .source_map()
1912                 .span_extend_while(range_start.span, |c| c.is_whitespace())
1913                 .unwrap_or(range_start.span).shrink_to_hi().to(range_end.span);
1914
1915             err.subdiagnostic(TypeMismatchFruTypo {
1916                 expr_span: range_start.span,
1917                 fru_span,
1918                 expr,
1919             });
1920         }
1921     }
1922
1923     /// Report an error for a struct field expression when there are invisible fields.
1924     ///
1925     /// ```text
1926     /// error: cannot construct `Foo` with struct literal syntax due to private fields
1927     ///  --> src/main.rs:8:5
1928     ///   |
1929     /// 8 |     foo::Foo {};
1930     ///   |     ^^^^^^^^
1931     ///
1932     /// error: aborting due to previous error
1933     /// ```
1934     fn report_private_fields(
1935         &self,
1936         adt_ty: Ty<'tcx>,
1937         span: Span,
1938         private_fields: Vec<&ty::FieldDef>,
1939         used_fields: &'tcx [hir::ExprField<'tcx>],
1940     ) {
1941         let mut err = self.tcx.sess.struct_span_err(
1942             span,
1943             &format!(
1944                 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1945             ),
1946         );
1947         let (used_private_fields, remaining_private_fields): (
1948             Vec<(Symbol, Span, bool)>,
1949             Vec<(Symbol, Span, bool)>,
1950         ) = private_fields
1951             .iter()
1952             .map(|field| {
1953                 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1954                     Some(used_field) => (field.name, used_field.span, true),
1955                     None => (field.name, self.tcx.def_span(field.did), false),
1956                 }
1957             })
1958             .partition(|field| field.2);
1959         err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1960         if !remaining_private_fields.is_empty() {
1961             let remaining_private_fields_len = remaining_private_fields.len();
1962             let names = match &remaining_private_fields
1963                 .iter()
1964                 .map(|(name, _, _)| name)
1965                 .collect::<Vec<_>>()[..]
1966             {
1967                 _ if remaining_private_fields_len > 6 => String::new(),
1968                 [name] => format!("`{name}` "),
1969                 [names @ .., last] => {
1970                     let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1971                     format!("{} and `{last}` ", names.join(", "))
1972                 }
1973                 [] => unreachable!(),
1974             };
1975             err.note(format!(
1976                 "... and other private field{s} {names}that {were} not provided",
1977                 s = pluralize!(remaining_private_fields_len),
1978                 were = pluralize!("was", remaining_private_fields_len),
1979             ));
1980         }
1981         err.emit();
1982     }
1983
1984     fn report_unknown_field(
1985         &self,
1986         ty: Ty<'tcx>,
1987         variant: &'tcx ty::VariantDef,
1988         field: &hir::ExprField<'_>,
1989         skip_fields: &[hir::ExprField<'_>],
1990         kind_name: &str,
1991         expr_span: Span,
1992     ) {
1993         if variant.is_recovered() {
1994             self.set_tainted_by_errors(
1995                 self.tcx
1996                     .sess
1997                     .delay_span_bug(expr_span, "parser recovered but no error was emitted"),
1998             );
1999             return;
2000         }
2001         let mut err = self.err_ctxt().type_error_struct_with_diag(
2002             field.ident.span,
2003             |actual| match ty.kind() {
2004                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
2005                     self.tcx.sess,
2006                     field.ident.span,
2007                     E0559,
2008                     "{} `{}::{}` has no field named `{}`",
2009                     kind_name,
2010                     actual,
2011                     variant.name,
2012                     field.ident
2013                 ),
2014                 _ => struct_span_err!(
2015                     self.tcx.sess,
2016                     field.ident.span,
2017                     E0560,
2018                     "{} `{}` has no field named `{}`",
2019                     kind_name,
2020                     actual,
2021                     field.ident
2022                 ),
2023             },
2024             ty,
2025         );
2026
2027         let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
2028         match variant.ctor_kind {
2029             CtorKind::Fn => match ty.kind() {
2030                 ty::Adt(adt, ..) if adt.is_enum() => {
2031                     err.span_label(
2032                         variant_ident_span,
2033                         format!(
2034                             "`{adt}::{variant}` defined here",
2035                             adt = ty,
2036                             variant = variant.name,
2037                         ),
2038                     );
2039                     err.span_label(field.ident.span, "field does not exist");
2040                     err.span_suggestion_verbose(
2041                         expr_span,
2042                         &format!(
2043                             "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
2044                             adt = ty,
2045                             variant = variant.name,
2046                         ),
2047                         format!(
2048                             "{adt}::{variant}(/* fields */)",
2049                             adt = ty,
2050                             variant = variant.name,
2051                         ),
2052                         Applicability::HasPlaceholders,
2053                     );
2054                 }
2055                 _ => {
2056                     err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
2057                     err.span_label(field.ident.span, "field does not exist");
2058                     err.span_suggestion_verbose(
2059                         expr_span,
2060                         &format!(
2061                             "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
2062                             adt = ty,
2063                             kind_name = kind_name,
2064                         ),
2065                         format!("{adt}(/* fields */)", adt = ty),
2066                         Applicability::HasPlaceholders,
2067                     );
2068                 }
2069             },
2070             _ => {
2071                 // prevent all specified fields from being suggested
2072                 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
2073                 if let Some(field_name) = self.suggest_field_name(
2074                     variant,
2075                     field.ident.name,
2076                     skip_fields.collect(),
2077                     expr_span,
2078                 ) {
2079                     err.span_suggestion(
2080                         field.ident.span,
2081                         "a field with a similar name exists",
2082                         field_name,
2083                         Applicability::MaybeIncorrect,
2084                     );
2085                 } else {
2086                     match ty.kind() {
2087                         ty::Adt(adt, ..) => {
2088                             if adt.is_enum() {
2089                                 err.span_label(
2090                                     field.ident.span,
2091                                     format!("`{}::{}` does not have this field", ty, variant.name),
2092                                 );
2093                             } else {
2094                                 err.span_label(
2095                                     field.ident.span,
2096                                     format!("`{ty}` does not have this field"),
2097                                 );
2098                             }
2099                             let available_field_names =
2100                                 self.available_field_names(variant, expr_span);
2101                             if !available_field_names.is_empty() {
2102                                 err.note(&format!(
2103                                     "available fields are: {}",
2104                                     self.name_series_display(available_field_names)
2105                                 ));
2106                             }
2107                         }
2108                         _ => bug!("non-ADT passed to report_unknown_field"),
2109                     }
2110                 };
2111             }
2112         }
2113         err.emit();
2114     }
2115
2116     // Return a hint about the closest match in field names
2117     fn suggest_field_name(
2118         &self,
2119         variant: &'tcx ty::VariantDef,
2120         field: Symbol,
2121         skip: Vec<Symbol>,
2122         // The span where stability will be checked
2123         span: Span,
2124     ) -> Option<Symbol> {
2125         let names = variant
2126             .fields
2127             .iter()
2128             .filter_map(|field| {
2129                 // ignore already set fields and private fields from non-local crates
2130                 // and unstable fields.
2131                 if skip.iter().any(|&x| x == field.name)
2132                     || (!variant.def_id.is_local() && !field.vis.is_public())
2133                     || matches!(
2134                         self.tcx.eval_stability(field.did, None, span, None),
2135                         stability::EvalResult::Deny { .. }
2136                     )
2137                 {
2138                     None
2139                 } else {
2140                     Some(field.name)
2141                 }
2142             })
2143             .collect::<Vec<Symbol>>();
2144
2145         find_best_match_for_name(&names, field, None)
2146     }
2147
2148     fn available_field_names(
2149         &self,
2150         variant: &'tcx ty::VariantDef,
2151         access_span: Span,
2152     ) -> Vec<Symbol> {
2153         variant
2154             .fields
2155             .iter()
2156             .filter(|field| {
2157                 let def_scope = self
2158                     .tcx
2159                     .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2160                     .1;
2161                 field.vis.is_accessible_from(def_scope, self.tcx)
2162                     && !matches!(
2163                         self.tcx.eval_stability(field.did, None, access_span, None),
2164                         stability::EvalResult::Deny { .. }
2165                     )
2166             })
2167             .filter(|field| !self.tcx.is_doc_hidden(field.did))
2168             .map(|field| field.name)
2169             .collect()
2170     }
2171
2172     fn name_series_display(&self, names: Vec<Symbol>) -> String {
2173         // dynamic limit, to never omit just one field
2174         let limit = if names.len() == 6 { 6 } else { 5 };
2175         let mut display =
2176             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2177         if names.len() > limit {
2178             display = format!("{} ... and {} others", display, names.len() - limit);
2179         }
2180         display
2181     }
2182
2183     // Check field access expressions
2184     fn check_field(
2185         &self,
2186         expr: &'tcx hir::Expr<'tcx>,
2187         base: &'tcx hir::Expr<'tcx>,
2188         field: Ident,
2189     ) -> Ty<'tcx> {
2190         debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2191         let base_ty = self.check_expr(base);
2192         let base_ty = self.structurally_resolved_type(base.span, base_ty);
2193         let mut private_candidate = None;
2194         let mut autoderef = self.autoderef(expr.span, base_ty);
2195         while let Some((deref_base_ty, _)) = autoderef.next() {
2196             debug!("deref_base_ty: {:?}", deref_base_ty);
2197             match deref_base_ty.kind() {
2198                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2199                     debug!("struct named {:?}", deref_base_ty);
2200                     let (ident, def_scope) =
2201                         self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2202                     let fields = &base_def.non_enum_variant().fields;
2203                     if let Some(index) = fields
2204                         .iter()
2205                         .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2206                     {
2207                         let field = &fields[index];
2208                         let field_ty = self.field_ty(expr.span, field, substs);
2209                         // Save the index of all fields regardless of their visibility in case
2210                         // of error recovery.
2211                         self.write_field_index(expr.hir_id, index);
2212                         let adjustments = self.adjust_steps(&autoderef);
2213                         if field.vis.is_accessible_from(def_scope, self.tcx) {
2214                             self.apply_adjustments(base, adjustments);
2215                             self.register_predicates(autoderef.into_obligations());
2216
2217                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2218                             return field_ty;
2219                         }
2220                         private_candidate = Some((adjustments, base_def.did(), field_ty));
2221                     }
2222                 }
2223                 ty::Tuple(tys) => {
2224                     let fstr = field.as_str();
2225                     if let Ok(index) = fstr.parse::<usize>() {
2226                         if fstr == index.to_string() {
2227                             if let Some(&field_ty) = tys.get(index) {
2228                                 let adjustments = self.adjust_steps(&autoderef);
2229                                 self.apply_adjustments(base, adjustments);
2230                                 self.register_predicates(autoderef.into_obligations());
2231
2232                                 self.write_field_index(expr.hir_id, index);
2233                                 return field_ty;
2234                             }
2235                         }
2236                     }
2237                 }
2238                 _ => {}
2239             }
2240         }
2241         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2242
2243         if let Some((adjustments, did, field_ty)) = private_candidate {
2244             // (#90483) apply adjustments to avoid ExprUseVisitor from
2245             // creating erroneous projection.
2246             self.apply_adjustments(base, adjustments);
2247             self.ban_private_field_access(expr, base_ty, field, did);
2248             return field_ty;
2249         }
2250
2251         if field.name == kw::Empty {
2252         } else if self.method_exists(field, base_ty, expr.hir_id, true) {
2253             self.ban_take_value_of_method(expr, base_ty, field);
2254         } else if !base_ty.is_primitive_ty() {
2255             self.ban_nonexisting_field(field, base, expr, base_ty);
2256         } else {
2257             let field_name = field.to_string();
2258             let mut err = type_error_struct!(
2259                 self.tcx().sess,
2260                 field.span,
2261                 base_ty,
2262                 E0610,
2263                 "`{base_ty}` is a primitive type and therefore doesn't have fields",
2264             );
2265             let is_valid_suffix = |field: &str| {
2266                 if field == "f32" || field == "f64" {
2267                     return true;
2268                 }
2269                 let mut chars = field.chars().peekable();
2270                 match chars.peek() {
2271                     Some('e') | Some('E') => {
2272                         chars.next();
2273                         if let Some(c) = chars.peek()
2274                             && !c.is_numeric() && *c != '-' && *c != '+'
2275                         {
2276                             return false;
2277                         }
2278                         while let Some(c) = chars.peek() {
2279                             if !c.is_numeric() {
2280                                 break;
2281                             }
2282                             chars.next();
2283                         }
2284                     }
2285                     _ => (),
2286                 }
2287                 let suffix = chars.collect::<String>();
2288                 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2289             };
2290             let maybe_partial_suffix = |field: &str| -> Option<&str> {
2291                 let first_chars = ['f', 'l'];
2292                 if field.len() >= 1
2293                     && field.to_lowercase().starts_with(first_chars)
2294                     && field[1..].chars().all(|c| c.is_ascii_digit())
2295                 {
2296                     if field.to_lowercase().starts_with(['f']) { Some("f32") } else { Some("f64") }
2297                 } else {
2298                     None
2299                 }
2300             };
2301             if let ty::Infer(ty::IntVar(_)) = base_ty.kind()
2302                 && let ExprKind::Lit(Spanned {
2303                     node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2304                     ..
2305                 }) = base.kind
2306                 && !base.span.from_expansion()
2307             {
2308                 if is_valid_suffix(&field_name) {
2309                     err.span_suggestion_verbose(
2310                         field.span.shrink_to_lo(),
2311                         "if intended to be a floating point literal, consider adding a `0` after the period",
2312                         '0',
2313                         Applicability::MaybeIncorrect,
2314                     );
2315                 } else if let Some(correct_suffix) = maybe_partial_suffix(&field_name) {
2316                     err.span_suggestion_verbose(
2317                         field.span,
2318                         format!("if intended to be a floating point literal, consider adding a `0` after the period and a `{correct_suffix}` suffix"),
2319                         format!("0{correct_suffix}"),
2320                         Applicability::MaybeIncorrect,
2321                     );
2322                 }
2323             }
2324             err.emit();
2325         }
2326
2327         self.tcx().ty_error()
2328     }
2329
2330     fn suggest_await_on_field_access(
2331         &self,
2332         err: &mut Diagnostic,
2333         field_ident: Ident,
2334         base: &'tcx hir::Expr<'tcx>,
2335         ty: Ty<'tcx>,
2336     ) {
2337         let output_ty = match self.get_impl_future_output_ty(ty) {
2338             Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2339             _ => return,
2340         };
2341         let mut add_label = true;
2342         if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2343             // no field access on enum type
2344             if !def.is_enum() {
2345                 if def
2346                     .non_enum_variant()
2347                     .fields
2348                     .iter()
2349                     .any(|field| field.ident(self.tcx) == field_ident)
2350                 {
2351                     add_label = false;
2352                     err.span_label(
2353                         field_ident.span,
2354                         "field not available in `impl Future`, but it is available in its `Output`",
2355                     );
2356                     err.span_suggestion_verbose(
2357                         base.span.shrink_to_hi(),
2358                         "consider `await`ing on the `Future` and access the field of its `Output`",
2359                         ".await",
2360                         Applicability::MaybeIncorrect,
2361                     );
2362                 }
2363             }
2364         }
2365         if add_label {
2366             err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2367         }
2368     }
2369
2370     fn ban_nonexisting_field(
2371         &self,
2372         ident: Ident,
2373         base: &'tcx hir::Expr<'tcx>,
2374         expr: &'tcx hir::Expr<'tcx>,
2375         base_ty: Ty<'tcx>,
2376     ) {
2377         debug!(
2378             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, base_ty={:?}",
2379             ident, base, expr, base_ty
2380         );
2381         let mut err = self.no_such_field_err(ident, base_ty, base.hir_id);
2382
2383         match *base_ty.peel_refs().kind() {
2384             ty::Array(_, len) => {
2385                 self.maybe_suggest_array_indexing(&mut err, expr, base, ident, len);
2386             }
2387             ty::RawPtr(..) => {
2388                 self.suggest_first_deref_field(&mut err, expr, base, ident);
2389             }
2390             ty::Adt(def, _) if !def.is_enum() => {
2391                 self.suggest_fields_on_recordish(&mut err, def, ident, expr.span);
2392             }
2393             ty::Param(param_ty) => {
2394                 self.point_at_param_definition(&mut err, param_ty);
2395             }
2396             ty::Opaque(_, _) => {
2397                 self.suggest_await_on_field_access(&mut err, ident, base, base_ty.peel_refs());
2398             }
2399             _ => {}
2400         }
2401
2402         self.suggest_fn_call(&mut err, base, base_ty, |output_ty| {
2403             if let ty::Adt(def, _) = output_ty.kind() && !def.is_enum() {
2404                 def.non_enum_variant().fields.iter().any(|field| {
2405                     field.ident(self.tcx) == ident
2406                         && field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
2407                 })
2408             } else if let ty::Tuple(tys) = output_ty.kind()
2409                 && let Ok(idx) = ident.as_str().parse::<usize>()
2410             {
2411                 idx < tys.len()
2412             } else {
2413                 false
2414             }
2415         });
2416
2417         if ident.name == kw::Await {
2418             // We know by construction that `<expr>.await` is either on Rust 2015
2419             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2420             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2421             err.help_use_latest_edition();
2422         }
2423
2424         err.emit();
2425     }
2426
2427     fn ban_private_field_access(
2428         &self,
2429         expr: &hir::Expr<'_>,
2430         expr_t: Ty<'tcx>,
2431         field: Ident,
2432         base_did: DefId,
2433     ) {
2434         let struct_path = self.tcx().def_path_str(base_did);
2435         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2436         let mut err = struct_span_err!(
2437             self.tcx().sess,
2438             field.span,
2439             E0616,
2440             "field `{field}` of {kind_name} `{struct_path}` is private",
2441         );
2442         err.span_label(field.span, "private field");
2443         // Also check if an accessible method exists, which is often what is meant.
2444         if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2445         {
2446             self.suggest_method_call(
2447                 &mut err,
2448                 &format!("a method `{field}` also exists, call it with parentheses"),
2449                 field,
2450                 expr_t,
2451                 expr,
2452                 None,
2453             );
2454         }
2455         err.emit();
2456     }
2457
2458     fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2459         let mut err = type_error_struct!(
2460             self.tcx().sess,
2461             field.span,
2462             expr_t,
2463             E0615,
2464             "attempted to take value of method `{field}` on type `{expr_t}`",
2465         );
2466         err.span_label(field.span, "method, not a field");
2467         let expr_is_call =
2468             if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2469                 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2470             {
2471                 expr.hir_id == callee.hir_id
2472             } else {
2473                 false
2474             };
2475         let expr_snippet =
2476             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2477         let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2478         let after_open = expr.span.lo() + rustc_span::BytePos(1);
2479         let before_close = expr.span.hi() - rustc_span::BytePos(1);
2480
2481         if expr_is_call && is_wrapped {
2482             err.multipart_suggestion(
2483                 "remove wrapping parentheses to call the method",
2484                 vec![
2485                     (expr.span.with_hi(after_open), String::new()),
2486                     (expr.span.with_lo(before_close), String::new()),
2487                 ],
2488                 Applicability::MachineApplicable,
2489             );
2490         } else if !self.expr_in_place(expr.hir_id) {
2491             // Suggest call parentheses inside the wrapping parentheses
2492             let span = if is_wrapped {
2493                 expr.span.with_lo(after_open).with_hi(before_close)
2494             } else {
2495                 expr.span
2496             };
2497             self.suggest_method_call(
2498                 &mut err,
2499                 "use parentheses to call the method",
2500                 field,
2501                 expr_t,
2502                 expr,
2503                 Some(span),
2504             );
2505         } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2506             && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2507             && let ExprKind::Field(base_expr, _) = expr.kind
2508             && adt_def.variants().len() == 1
2509             && adt_def
2510                 .variants()
2511                 .iter()
2512                 .next()
2513                 .unwrap()
2514                 .fields
2515                 .iter()
2516                 .any(|f| f.ident(self.tcx) == field)
2517         {
2518             err.multipart_suggestion(
2519                 "to access the field, dereference first",
2520                 vec![
2521                     (base_expr.span.shrink_to_lo(), "(*".to_string()),
2522                     (base_expr.span.shrink_to_hi(), ")".to_string()),
2523                 ],
2524                 Applicability::MaybeIncorrect,
2525             );
2526         } else {
2527             err.help("methods are immutable and cannot be assigned to");
2528         }
2529
2530         err.emit();
2531     }
2532
2533     fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2534         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2535         let generic_param = generics.type_param(&param, self.tcx);
2536         if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2537             return;
2538         }
2539         let param_def_id = generic_param.def_id;
2540         let param_hir_id = match param_def_id.as_local() {
2541             Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2542             None => return,
2543         };
2544         let param_span = self.tcx.hir().span(param_hir_id);
2545         let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2546
2547         err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2548     }
2549
2550     fn suggest_fields_on_recordish(
2551         &self,
2552         err: &mut Diagnostic,
2553         def: ty::AdtDef<'tcx>,
2554         field: Ident,
2555         access_span: Span,
2556     ) {
2557         if let Some(suggested_field_name) =
2558             self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2559         {
2560             err.span_suggestion(
2561                 field.span,
2562                 "a field with a similar name exists",
2563                 suggested_field_name,
2564                 Applicability::MaybeIncorrect,
2565             );
2566         } else {
2567             err.span_label(field.span, "unknown field");
2568             let struct_variant_def = def.non_enum_variant();
2569             let field_names = self.available_field_names(struct_variant_def, access_span);
2570             if !field_names.is_empty() {
2571                 err.note(&format!(
2572                     "available fields are: {}",
2573                     self.name_series_display(field_names),
2574                 ));
2575             }
2576         }
2577     }
2578
2579     fn maybe_suggest_array_indexing(
2580         &self,
2581         err: &mut Diagnostic,
2582         expr: &hir::Expr<'_>,
2583         base: &hir::Expr<'_>,
2584         field: Ident,
2585         len: ty::Const<'tcx>,
2586     ) {
2587         if let (Some(len), Ok(user_index)) =
2588             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2589             && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2590         {
2591             let help = "instead of using tuple indexing, use array indexing";
2592             let suggestion = format!("{base}[{field}]");
2593             let applicability = if len < user_index {
2594                 Applicability::MachineApplicable
2595             } else {
2596                 Applicability::MaybeIncorrect
2597             };
2598             err.span_suggestion(expr.span, help, suggestion, applicability);
2599         }
2600     }
2601
2602     fn suggest_first_deref_field(
2603         &self,
2604         err: &mut Diagnostic,
2605         expr: &hir::Expr<'_>,
2606         base: &hir::Expr<'_>,
2607         field: Ident,
2608     ) {
2609         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2610             let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2611             let suggestion = format!("(*{base}).{field}");
2612             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2613         }
2614     }
2615
2616     fn no_such_field_err(
2617         &self,
2618         field: Ident,
2619         expr_t: Ty<'tcx>,
2620         id: HirId,
2621     ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2622         let span = field.span;
2623         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2624
2625         let mut err = type_error_struct!(
2626             self.tcx().sess,
2627             field.span,
2628             expr_t,
2629             E0609,
2630             "no field `{field}` on type `{expr_t}`",
2631         );
2632
2633         // try to add a suggestion in case the field is a nested field of a field of the Adt
2634         let mod_id = self.tcx.parent_module(id).to_def_id();
2635         if let Some((fields, substs)) =
2636             self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2637         {
2638             let candidate_fields: Vec<_> = fields
2639                 .filter_map(|candidate_field| {
2640                     self.check_for_nested_field_satisfying(
2641                         span,
2642                         &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2643                         candidate_field,
2644                         substs,
2645                         vec![],
2646                         mod_id,
2647                     )
2648                 })
2649                 .map(|mut field_path| {
2650                     field_path.pop();
2651                     field_path
2652                         .iter()
2653                         .map(|id| id.name.to_ident_string())
2654                         .collect::<Vec<String>>()
2655                         .join(".")
2656                 })
2657                 .collect::<Vec<_>>();
2658
2659             let len = candidate_fields.len();
2660             if len > 0 {
2661                 err.span_suggestions(
2662                     field.span.shrink_to_lo(),
2663                     format!(
2664                         "{} of the expressions' fields {} a field of the same name",
2665                         if len > 1 { "some" } else { "one" },
2666                         if len > 1 { "have" } else { "has" },
2667                     ),
2668                     candidate_fields.iter().map(|path| format!("{path}.")),
2669                     Applicability::MaybeIncorrect,
2670                 );
2671             }
2672         }
2673         err
2674     }
2675
2676     pub(crate) fn get_field_candidates_considering_privacy(
2677         &self,
2678         span: Span,
2679         base_ty: Ty<'tcx>,
2680         mod_id: DefId,
2681     ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2682         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2683
2684         for (base_t, _) in self.autoderef(span, base_ty) {
2685             match base_t.kind() {
2686                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2687                     let tcx = self.tcx;
2688                     let fields = &base_def.non_enum_variant().fields;
2689                     // Some struct, e.g. some that impl `Deref`, have all private fields
2690                     // because you're expected to deref them to access the _real_ fields.
2691                     // This, for example, will help us suggest accessing a field through a `Box<T>`.
2692                     if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2693                         continue;
2694                     }
2695                     return Some((
2696                         fields
2697                             .iter()
2698                             .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2699                             // For compile-time reasons put a limit on number of fields we search
2700                             .take(100),
2701                         substs,
2702                     ));
2703                 }
2704                 _ => {}
2705             }
2706         }
2707         None
2708     }
2709
2710     /// This method is called after we have encountered a missing field error to recursively
2711     /// search for the field
2712     pub(crate) fn check_for_nested_field_satisfying(
2713         &self,
2714         span: Span,
2715         matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2716         candidate_field: &ty::FieldDef,
2717         subst: SubstsRef<'tcx>,
2718         mut field_path: Vec<Ident>,
2719         mod_id: DefId,
2720     ) -> Option<Vec<Ident>> {
2721         debug!(
2722             "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2723             span, candidate_field, field_path
2724         );
2725
2726         if field_path.len() > 3 {
2727             // For compile-time reasons and to avoid infinite recursion we only check for fields
2728             // up to a depth of three
2729             None
2730         } else {
2731             field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2732             let field_ty = candidate_field.ty(self.tcx, subst);
2733             if matches(candidate_field, field_ty) {
2734                 return Some(field_path);
2735             } else if let Some((nested_fields, subst)) =
2736                 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2737             {
2738                 // recursively search fields of `candidate_field` if it's a ty::Adt
2739                 for field in nested_fields {
2740                     if let Some(field_path) = self.check_for_nested_field_satisfying(
2741                         span,
2742                         matches,
2743                         field,
2744                         subst,
2745                         field_path.clone(),
2746                         mod_id,
2747                     ) {
2748                         return Some(field_path);
2749                     }
2750                 }
2751             }
2752             None
2753         }
2754     }
2755
2756     fn check_expr_index(
2757         &self,
2758         base: &'tcx hir::Expr<'tcx>,
2759         idx: &'tcx hir::Expr<'tcx>,
2760         expr: &'tcx hir::Expr<'tcx>,
2761     ) -> Ty<'tcx> {
2762         let base_t = self.check_expr(&base);
2763         let idx_t = self.check_expr(&idx);
2764
2765         if base_t.references_error() {
2766             base_t
2767         } else if idx_t.references_error() {
2768             idx_t
2769         } else {
2770             let base_t = self.structurally_resolved_type(base.span, base_t);
2771             match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2772                 Some((index_ty, element_ty)) => {
2773                     // two-phase not needed because index_ty is never mutable
2774                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2775                     self.select_obligations_where_possible(|errors| {
2776                         self.point_at_index_if_possible(errors, idx.span)
2777                     });
2778                     element_ty
2779                 }
2780                 None => {
2781                     let mut err = type_error_struct!(
2782                         self.tcx.sess,
2783                         expr.span,
2784                         base_t,
2785                         E0608,
2786                         "cannot index into a value of type `{base_t}`",
2787                     );
2788                     // Try to give some advice about indexing tuples.
2789                     if let ty::Tuple(..) = base_t.kind() {
2790                         let mut needs_note = true;
2791                         // If the index is an integer, we can show the actual
2792                         // fixed expression:
2793                         if let ExprKind::Lit(ref lit) = idx.kind {
2794                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2795                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2796                                 if let Ok(snip) = snip {
2797                                     err.span_suggestion(
2798                                         expr.span,
2799                                         "to access tuple elements, use",
2800                                         format!("{snip}.{i}"),
2801                                         Applicability::MachineApplicable,
2802                                     );
2803                                     needs_note = false;
2804                                 }
2805                             }
2806                         }
2807                         if needs_note {
2808                             err.help(
2809                                 "to access tuple elements, use tuple indexing \
2810                                         syntax (e.g., `tuple.0`)",
2811                             );
2812                         }
2813                     }
2814                     let reported = err.emit();
2815                     self.tcx.ty_error_with_guaranteed(reported)
2816                 }
2817             }
2818         }
2819     }
2820
2821     fn point_at_index_if_possible(
2822         &self,
2823         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2824         span: Span,
2825     ) {
2826         for error in errors {
2827             match error.obligation.predicate.kind().skip_binder() {
2828                 ty::PredicateKind::Trait(predicate)
2829                     if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2830                 }
2831                 _ => continue,
2832             }
2833             error.obligation.cause.span = span;
2834         }
2835     }
2836
2837     fn check_expr_yield(
2838         &self,
2839         value: &'tcx hir::Expr<'tcx>,
2840         expr: &'tcx hir::Expr<'tcx>,
2841         src: &'tcx hir::YieldSource,
2842     ) -> Ty<'tcx> {
2843         match self.resume_yield_tys {
2844             Some((resume_ty, yield_ty)) => {
2845                 self.check_expr_coercable_to_type(&value, yield_ty, None);
2846
2847                 resume_ty
2848             }
2849             // Given that this `yield` expression was generated as a result of lowering a `.await`,
2850             // we know that the yield type must be `()`; however, the context won't contain this
2851             // information. Hence, we check the source of the yield expression here and check its
2852             // value's type against `()` (this check should always hold).
2853             None if src.is_await() => {
2854                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2855                 self.tcx.mk_unit()
2856             }
2857             _ => {
2858                 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2859                 // Avoid expressions without types during writeback (#78653).
2860                 self.check_expr(value);
2861                 self.tcx.mk_unit()
2862             }
2863         }
2864     }
2865
2866     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2867         let needs = if is_input { Needs::None } else { Needs::MutPlace };
2868         let ty = self.check_expr_with_needs(expr, needs);
2869         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2870
2871         if !is_input && !expr.is_syntactic_place_expr() {
2872             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2873             err.span_label(expr.span, "cannot assign to this expression");
2874             err.emit();
2875         }
2876
2877         // If this is an input value, we require its type to be fully resolved
2878         // at this point. This allows us to provide helpful coercions which help
2879         // pass the type candidate list in a later pass.
2880         //
2881         // We don't require output types to be resolved at this point, which
2882         // allows them to be inferred based on how they are used later in the
2883         // function.
2884         if is_input {
2885             let ty = self.structurally_resolved_type(expr.span, ty);
2886             match *ty.kind() {
2887                 ty::FnDef(..) => {
2888                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2889                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2890                 }
2891                 ty::Ref(_, base_ty, mutbl) => {
2892                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2893                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2894                 }
2895                 _ => {}
2896             }
2897         }
2898     }
2899
2900     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2901         for (op, _op_sp) in asm.operands {
2902             match op {
2903                 hir::InlineAsmOperand::In { expr, .. } => {
2904                     self.check_expr_asm_operand(expr, true);
2905                 }
2906                 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2907                 | hir::InlineAsmOperand::InOut { expr, .. } => {
2908                     self.check_expr_asm_operand(expr, false);
2909                 }
2910                 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2911                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2912                     self.check_expr_asm_operand(in_expr, true);
2913                     if let Some(out_expr) = out_expr {
2914                         self.check_expr_asm_operand(out_expr, false);
2915                     }
2916                 }
2917                 // `AnonConst`s have their own body and is type-checked separately.
2918                 // As they don't flow into the type system we don't need them to
2919                 // be well-formed.
2920                 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2921                 hir::InlineAsmOperand::SymStatic { .. } => {}
2922             }
2923         }
2924         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2925             self.tcx.types.never
2926         } else {
2927             self.tcx.mk_unit()
2928         }
2929     }
2930 }