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             let _ = self.emit_type_mismatch_suggestions(
 108                 &mut err,
 109                 expr.peel_drop_temps(),
 110                 ty,
 111                 expected_ty,
 112                 None,
 113                 None,
 114             );
 115             extend_err(&mut err);
 116             err.emit();
 117         }
 118         ty
 119     }
 120
 121     pub(super) fn check_expr_coercable_to_type(
 122         &self,
 123         expr: &'tcx hir::Expr<'tcx>,
 124         expected: Ty<'tcx>,
 125         expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
 126     ) -> Ty<'tcx> {
 127         let ty = self.check_expr_with_hint(expr, expected);
 128         // checks don't need two phase
 129         self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
 130     }
 131
 132     pub(super) fn check_expr_with_hint(
 133         &self,
 134         expr: &'tcx hir::Expr<'tcx>,
 135         expected: Ty<'tcx>,
 136     ) -> Ty<'tcx> {
 137         self.check_expr_with_expectation(expr, ExpectHasType(expected))
 138     }
 139
 140     fn check_expr_with_expectation_and_needs(
 141         &self,
 142         expr: &'tcx hir::Expr<'tcx>,
 143         expected: Expectation<'tcx>,
 144         needs: Needs,
 145     ) -> Ty<'tcx> {
 146         let ty = self.check_expr_with_expectation(expr, expected);
 147
 148         // If the expression is used in a place whether mutable place is required
 149         // e.g. LHS of assignment, perform the conversion.
 150         if let Needs::MutPlace = needs {
 151             self.convert_place_derefs_to_mutable(expr);
 152         }
 153
 154         ty
 155     }
 156
 157     pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
 158         self.check_expr_with_expectation(expr, NoExpectation)
 159     }
 160
 161     pub(super) fn check_expr_with_needs(
 162         &self,
 163         expr: &'tcx hir::Expr<'tcx>,
 164         needs: Needs,
 165     ) -> Ty<'tcx> {
 166         self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
 167     }
 168
 169     /// Invariant:
 170     /// If an expression has any sub-expressions that result in a type error,
 171     /// inspecting that expression's type with `ty.references_error()` will return
 172     /// true. Likewise, if an expression is known to diverge, inspecting its
 173     /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
 174     /// strict, _|_ can appear in the type of an expression that does not,
 175     /// itself, diverge: for example, fn() -> _|_.)
 176     /// Note that inspecting a type's structure *directly* may expose the fact
 177     /// that there are actually multiple representations for `Error`, so avoid
 178     /// that when err needs to be handled differently.
 179     #[instrument(skip(self, expr), level = "debug")]
 180     pub(super) fn check_expr_with_expectation(
 181         &self,
 182         expr: &'tcx hir::Expr<'tcx>,
 183         expected: Expectation<'tcx>,
 184     ) -> Ty<'tcx> {
 185         self.check_expr_with_expectation_and_args(expr, expected, &[])
 186     }
 187
 188     /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
 189     /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
 190     pub(super) fn check_expr_with_expectation_and_args(
 191         &self,
 192         expr: &'tcx hir::Expr<'tcx>,
 193         expected: Expectation<'tcx>,
 194         args: &'tcx [hir::Expr<'tcx>],
 195     ) -> Ty<'tcx> {
 196         if self.tcx().sess.verbose() {
 197             // make this code only run with -Zverbose because it is probably slow
 198             if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
 199                 if !lint_str.contains('\n') {
 200                     debug!("expr text: {lint_str}");
 201                 } else {
 202                     let mut lines = lint_str.lines();
 203                     if let Some(line0) = lines.next() {
 204                         let remaining_lines = lines.count();
 205                         debug!("expr text: {line0}");
 206                         debug!("expr text: ...(and {remaining_lines} more lines)");
 207                     }
 208                 }
 209             }
 210         }
 211
 212         // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
 213         // without the final expr (e.g. `try { return; }`). We don't want to generate an
 214         // unreachable_code lint for it since warnings for autogenerated code are confusing.
 215         let is_try_block_generated_unit_expr = match expr.kind {
 216             ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
 217                 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
 218             }
 219
 220             _ => false,
 221         };
 222
 223         // Warn for expressions after diverging siblings.
 224         if !is_try_block_generated_unit_expr {
 225             self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
 226         }
 227
 228         // Hide the outer diverging and has_errors flags.
 229         let old_diverges = self.diverges.replace(Diverges::Maybe);
 230
 231         let ty = ensure_sufficient_stack(|| match &expr.kind {
 232             hir::ExprKind::Path(
 233                 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
 234             ) => self.check_expr_path(qpath, expr, args),
 235             _ => self.check_expr_kind(expr, expected),
 236         });
 237         let ty = self.resolve_vars_if_possible(ty);
 238
 239         // Warn for non-block expressions with diverging children.
 240         match expr.kind {
 241             ExprKind::Block(..)
 242             | ExprKind::If(..)
 243             | ExprKind::Let(..)
 244             | ExprKind::Loop(..)
 245             | ExprKind::Match(..) => {}
 246             // If `expr` is a result of desugaring the try block and is an ok-wrapped
 247             // diverging expression (e.g. it arose from desugaring of `try { return }`),
 248             // we skip issuing a warning because it is autogenerated code.
 249             ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
 250             ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
 251             ExprKind::MethodCall(segment, ..) => {
 252                 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
 253             }
 254             _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
 255         }
 256
 257         // Any expression that produces a value of type `!` must have diverged
 258         if ty.is_never() {
 259             self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
 260         }
 261
 262         // Record the type, which applies it effects.
 263         // We need to do this after the warning above, so that
 264         // we don't warn for the diverging expression itself.
 265         self.write_ty(expr.hir_id, ty);
 266
 267         // Combine the diverging and has_error flags.
 268         self.diverges.set(self.diverges.get() | old_diverges);
 269
 270         debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
 271         debug!("... {:?}, expected is {:?}", ty, expected);
 272
 273         ty
 274     }
 275
 276     #[instrument(skip(self, expr), level = "debug")]
 277     fn check_expr_kind(
 278         &self,
 279         expr: &'tcx hir::Expr<'tcx>,
 280         expected: Expectation<'tcx>,
 281     ) -> Ty<'tcx> {
 282         trace!("expr={:#?}", expr);
 283
 284         let tcx = self.tcx;
 285         match expr.kind {
 286             ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
 287             ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
 288             ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
 289             ExprKind::Assign(lhs, rhs, span) => {
 290                 self.check_expr_assign(expr, expected, lhs, rhs, span)
 291             }
 292             ExprKind::AssignOp(op, lhs, rhs) => {
 293                 self.check_binop_assign(expr, op, lhs, rhs, expected)
 294             }
 295             ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
 296             ExprKind::AddrOf(kind, mutbl, oprnd) => {
 297                 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
 298             }
 299             ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
 300                 self.check_lang_item_path(lang_item, expr, hir_id)
 301             }
 302             ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
 303             ExprKind::InlineAsm(asm) => {
 304                 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
 305                 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
 306                 self.check_expr_asm(asm)
 307             }
 308             ExprKind::Break(destination, ref expr_opt) => {
 309                 self.check_expr_break(destination, expr_opt.as_deref(), expr)
 310             }
 311             ExprKind::Continue(destination) => {
 312                 if destination.target_id.is_ok() {
 313                     tcx.types.never
 314                 } else {
 315                     // There was an error; make type-check fail.
 316                     tcx.ty_error()
 317                 }
 318             }
 319             ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
 320             ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
 321             ExprKind::Loop(body, _, source, _) => {
 322                 self.check_expr_loop(body, source, expected, expr)
 323             }
 324             ExprKind::Match(discrim, arms, match_src) => {
 325                 self.check_match(expr, &discrim, arms, expected, match_src)
 326             }
 327             ExprKind::Closure(closure) => self.check_expr_closure(closure, expr.span, expected),
 328             ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
 329             ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
 330             ExprKind::MethodCall(segment, receiver, args, _) => {
 331                 self.check_method_call(expr, segment, receiver, args, expected)
 332             }
 333             ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
 334             ExprKind::Type(e, t) => {
 335                 let ty = self.to_ty_saving_user_provided_ty(&t);
 336                 self.check_expr_eq_type(&e, ty);
 337                 ty
 338             }
 339             ExprKind::If(cond, then_expr, opt_else_expr) => {
 340                 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
 341             }
 342             ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
 343             ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
 344             ExprKind::ConstBlock(ref anon_const) => {
 345                 self.check_expr_const_block(anon_const, expected, expr)
 346             }
 347             ExprKind::Repeat(element, ref count) => {
 348                 self.check_expr_repeat(element, count, expected, expr)
 349             }
 350             ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
 351             ExprKind::Struct(qpath, fields, ref base_expr) => {
 352                 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
 353             }
 354             ExprKind::Field(base, field) => self.check_field(expr, &base, field, expected),
 355             ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
 356             ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
 357             hir::ExprKind::Err => tcx.ty_error(),
 358         }
 359     }
 360
 361     fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
 362         let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
 363             ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
 364             _ => NoExpectation,
 365         });
 366         let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
 367         self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
 368         self.tcx.mk_box(referent_ty)
 369     }
 370
 371     fn check_expr_unary(
 372         &self,
 373         unop: hir::UnOp,
 374         oprnd: &'tcx hir::Expr<'tcx>,
 375         expected: Expectation<'tcx>,
 376         expr: &'tcx hir::Expr<'tcx>,
 377     ) -> Ty<'tcx> {
 378         let tcx = self.tcx;
 379         let expected_inner = match unop {
 380             hir::UnOp::Not | hir::UnOp::Neg => expected,
 381             hir::UnOp::Deref => NoExpectation,
 382         };
 383         let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
 384
 385         if !oprnd_t.references_error() {
 386             oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
 387             match unop {
 388                 hir::UnOp::Deref => {
 389                     if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
 390                         oprnd_t = ty;
 391                     } else {
 392                         let mut err = type_error_struct!(
 393                             tcx.sess,
 394                             expr.span,
 395                             oprnd_t,
 396                             E0614,
 397                             "type `{oprnd_t}` cannot be dereferenced",
 398                         );
 399                         let sp = tcx.sess.source_map().start_point(expr.span).with_parent(None);
 400                         if let Some(sp) =
 401                             tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
 402                         {
 403                             err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
 404                         }
 405                         oprnd_t = tcx.ty_error_with_guaranteed(err.emit());
 406                     }
 407                 }
 408                 hir::UnOp::Not => {
 409                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 410                     // If it's builtin, we can reuse the type, this helps inference.
 411                     if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
 412                         oprnd_t = result;
 413                     }
 414                 }
 415                 hir::UnOp::Neg => {
 416                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 417                     // If it's builtin, we can reuse the type, this helps inference.
 418                     if !oprnd_t.is_numeric() {
 419                         oprnd_t = result;
 420                     }
 421                 }
 422             }
 423         }
 424         oprnd_t
 425     }
 426
 427     fn check_expr_addr_of(
 428         &self,
 429         kind: hir::BorrowKind,
 430         mutbl: hir::Mutability,
 431         oprnd: &'tcx hir::Expr<'tcx>,
 432         expected: Expectation<'tcx>,
 433         expr: &'tcx hir::Expr<'tcx>,
 434     ) -> Ty<'tcx> {
 435         let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
 436             match ty.kind() {
 437                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 438                     if oprnd.is_syntactic_place_expr() {
 439                         // Places may legitimately have unsized types.
 440                         // For example, dereferences of a fat pointer and
 441                         // the last field of a struct can be unsized.
 442                         ExpectHasType(*ty)
 443                     } else {
 444                         Expectation::rvalue_hint(self, *ty)
 445                     }
 446                 }
 447                 _ => NoExpectation,
 448             }
 449         });
 450         let ty =
 451             self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
 452
 453         let tm = ty::TypeAndMut { ty, mutbl };
 454         match kind {
 455             _ if tm.ty.references_error() => self.tcx.ty_error(),
 456             hir::BorrowKind::Raw => {
 457                 self.check_named_place_expr(oprnd);
 458                 self.tcx.mk_ptr(tm)
 459             }
 460             hir::BorrowKind::Ref => {
 461                 // Note: at this point, we cannot say what the best lifetime
 462                 // is to use for resulting pointer. We want to use the
 463                 // shortest lifetime possible so as to avoid spurious borrowck
 464                 // errors. Moreover, the longest lifetime will depend on the
 465                 // precise details of the value whose address is being taken
 466                 // (and how long it is valid), which we don't know yet until
 467                 // type inference is complete.
 468                 //
 469                 // Therefore, here we simply generate a region variable. The
 470                 // region inferencer will then select a suitable value.
 471                 // Finally, borrowck will infer the value of the region again,
 472                 // this time with enough precision to check that the value
 473                 // whose address was taken can actually be made to live as long
 474                 // as it needs to live.
 475                 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
 476                 self.tcx.mk_ref(region, tm)
 477             }
 478         }
 479     }
 480
 481     /// Does this expression refer to a place that either:
 482     /// * Is based on a local or static.
 483     /// * Contains a dereference
 484     /// Note that the adjustments for the children of `expr` should already
 485     /// have been resolved.
 486     fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
 487         let is_named = oprnd.is_place_expr(|base| {
 488             // Allow raw borrows if there are any deref adjustments.
 489             //
 490             // const VAL: (i32,) = (0,);
 491             // const REF: &(i32,) = &(0,);
 492             //
 493             // &raw const VAL.0;            // ERROR
 494             // &raw const REF.0;            // OK, same as &raw const (*REF).0;
 495             //
 496             // This is maybe too permissive, since it allows
 497             // `let u = &raw const Box::new((1,)).0`, which creates an
 498             // immediately dangling raw pointer.
 499             self.typeck_results
 500                 .borrow()
 501                 .adjustments()
 502                 .get(base.hir_id)
 503                 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
 504         });
 505         if !is_named {
 506             self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
 507         }
 508     }
 509
 510     fn check_lang_item_path(
 511         &self,
 512         lang_item: hir::LangItem,
 513         expr: &'tcx hir::Expr<'tcx>,
 514         hir_id: Option<hir::HirId>,
 515     ) -> Ty<'tcx> {
 516         self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
 517     }
 518
 519     pub(crate) fn check_expr_path(
 520         &self,
 521         qpath: &'tcx hir::QPath<'tcx>,
 522         expr: &'tcx hir::Expr<'tcx>,
 523         args: &'tcx [hir::Expr<'tcx>],
 524     ) -> Ty<'tcx> {
 525         let tcx = self.tcx;
 526         let (res, opt_ty, segs) =
 527             self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
 528         let ty = match res {
 529             Res::Err => {
 530                 self.suggest_assoc_method_call(segs);
 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::Variant, _) => {
 537                 let e = report_unexpected_variant_res(tcx, res, qpath, expr.span, "E0533", "value");
 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, return_expr.span);
 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         return_span: Span,
 866     ) {
 867         // Don't point at the whole block if it's empty
 868         if span == return_span {
 869             return;
 870         }
 871         for err in errors {
 872             let cause = &mut err.obligation.cause;
 873             if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
 874                 let new_cause = ObligationCause::new(
 875                     cause.span,
 876                     cause.body_id,
 877                     ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
 878                 );
 879                 *cause = new_cause;
 880             }
 881         }
 882     }
 883
 884     pub(crate) fn check_lhs_assignable(
 885         &self,
 886         lhs: &'tcx hir::Expr<'tcx>,
 887         err_code: &'static str,
 888         op_span: Span,
 889         adjust_err: impl FnOnce(&mut Diagnostic),
 890     ) {
 891         if lhs.is_syntactic_place_expr() {
 892             return;
 893         }
 894
 895         // FIXME: Make this use Diagnostic once error codes can be dynamically set.
 896         let mut err = self.tcx.sess.struct_span_err_with_code(
 897             op_span,
 898             "invalid left-hand side of assignment",
 899             DiagnosticId::Error(err_code.into()),
 900         );
 901         err.span_label(lhs.span, "cannot assign to this expression");
 902
 903         self.comes_from_while_condition(lhs.hir_id, |expr| {
 904             err.span_suggestion_verbose(
 905                 expr.span.shrink_to_lo(),
 906                 "you might have meant to use pattern destructuring",
 907                 "let ",
 908                 Applicability::MachineApplicable,
 909             );
 910         });
 911
 912         adjust_err(&mut err);
 913
 914         err.emit();
 915     }
 916
 917     // Check if an expression `original_expr_id` comes from the condition of a while loop,
 918     /// as opposed from the body of a while loop, which we can naively check by iterating
 919     /// parents until we find a loop...
 920     pub(super) fn comes_from_while_condition(
 921         &self,
 922         original_expr_id: HirId,
 923         then: impl FnOnce(&hir::Expr<'_>),
 924     ) {
 925         let mut parent = self.tcx.hir().parent_id(original_expr_id);
 926         while let Some(node) = self.tcx.hir().find(parent) {
 927             match node {
 928                 hir::Node::Expr(hir::Expr {
 929                     kind:
 930                         hir::ExprKind::Loop(
 931                             hir::Block {
 932                                 expr:
 933                                     Some(hir::Expr {
 934                                         kind:
 935                                             hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
 936                                         ..
 937                                     }),
 938                                 ..
 939                             },
 940                             _,
 941                             hir::LoopSource::While,
 942                             _,
 943                         ),
 944                     ..
 945                 }) => {
 946                     // Check if our original expression is a child of the condition of a while loop
 947                     let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
 948                         self.tcx.hir().opt_parent_id(*id)
 949                     })
 950                     .take_while(|id| *id != parent)
 951                     .any(|id| id == expr.hir_id);
 952                     // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
 953                     // where `while let` was more likely intended.
 954                     if expr_is_ancestor {
 955                         then(expr);
 956                     }
 957                     break;
 958                 }
 959                 hir::Node::Item(_)
 960                 | hir::Node::ImplItem(_)
 961                 | hir::Node::TraitItem(_)
 962                 | hir::Node::Crate(_) => break,
 963                 _ => {
 964                     parent = self.tcx.hir().parent_id(parent);
 965                 }
 966             }
 967         }
 968     }
 969
 970     // A generic function for checking the 'then' and 'else' clauses in an 'if'
 971     // or 'if-else' expression.
 972     fn check_then_else(
 973         &self,
 974         cond_expr: &'tcx hir::Expr<'tcx>,
 975         then_expr: &'tcx hir::Expr<'tcx>,
 976         opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
 977         sp: Span,
 978         orig_expected: Expectation<'tcx>,
 979     ) -> Ty<'tcx> {
 980         let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
 981
 982         self.warn_if_unreachable(
 983             cond_expr.hir_id,
 984             then_expr.span,
 985             "block in `if` or `while` expression",
 986         );
 987
 988         let cond_diverges = self.diverges.get();
 989         self.diverges.set(Diverges::Maybe);
 990
 991         let expected = orig_expected.adjust_for_branches(self);
 992         let then_ty = self.check_expr_with_expectation(then_expr, expected);
 993         let then_diverges = self.diverges.get();
 994         self.diverges.set(Diverges::Maybe);
 995
 996         // We've already taken the expected type's preferences
 997         // into account when typing the `then` branch. To figure
 998         // out the initial shot at a LUB, we thus only consider
 999         // `expected` if it represents a *hard* constraint
1000         // (`only_has_type`); otherwise, we just go with a
1001         // fresh type variable.
1002         let coerce_to_ty = expected.coercion_target_type(self, sp);
1003         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
1004
1005         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
1006
1007         if let Some(else_expr) = opt_else_expr {
1008             let else_ty = self.check_expr_with_expectation(else_expr, expected);
1009             let else_diverges = self.diverges.get();
1010
1011             let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1012             let if_cause = self.if_cause(
1013                 sp,
1014                 cond_expr.span,
1015                 then_expr,
1016                 else_expr,
1017                 then_ty,
1018                 else_ty,
1019                 opt_suggest_box_span,
1020             );
1021
1022             coerce.coerce(self, &if_cause, else_expr, else_ty);
1023
1024             // We won't diverge unless both branches do (or the condition does).
1025             self.diverges.set(cond_diverges | then_diverges & else_diverges);
1026         } else {
1027             self.if_fallback_coercion(sp, then_expr, &mut coerce);
1028
1029             // If the condition is false we can't diverge.
1030             self.diverges.set(cond_diverges);
1031         }
1032
1033         let result_ty = coerce.complete(self);
1034         if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1035     }
1036
1037     /// Type check assignment expression `expr` of form `lhs = rhs`.
1038     /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1039     fn check_expr_assign(
1040         &self,
1041         expr: &'tcx hir::Expr<'tcx>,
1042         expected: Expectation<'tcx>,
1043         lhs: &'tcx hir::Expr<'tcx>,
1044         rhs: &'tcx hir::Expr<'tcx>,
1045         span: Span,
1046     ) -> Ty<'tcx> {
1047         let expected_ty = expected.coercion_target_type(self, expr.span);
1048         if expected_ty == self.tcx.types.bool {
1049             // The expected type is `bool` but this will result in `()` so we can reasonably
1050             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1051             // The likely cause of this is `if foo = bar { .. }`.
1052             let actual_ty = self.tcx.mk_unit();
1053             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1054             let lhs_ty = self.check_expr(&lhs);
1055             let rhs_ty = self.check_expr(&rhs);
1056             let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1057                 (Applicability::MachineApplicable, true)
1058             } else if let ExprKind::Binary(
1059                 Spanned { node: hir::BinOpKind::And | hir::BinOpKind::Or, .. },
1060                 _,
1061                 rhs_expr,
1062             ) = lhs.kind
1063             {
1064                 // if x == 1 && y == 2 { .. }
1065                 //                 +
1066                 let actual_lhs_ty = self.check_expr(&rhs_expr);
1067                 (Applicability::MaybeIncorrect, self.can_coerce(rhs_ty, actual_lhs_ty))
1068             } else if let ExprKind::Binary(
1069                 Spanned { node: hir::BinOpKind::And | hir::BinOpKind::Or, .. },
1070                 lhs_expr,
1071                 _,
1072             ) = rhs.kind
1073             {
1074                 // if x == 1 && y == 2 { .. }
1075                 //       +
1076                 let actual_rhs_ty = self.check_expr(&lhs_expr);
1077                 (Applicability::MaybeIncorrect, self.can_coerce(actual_rhs_ty, lhs_ty))
1078             } else {
1079                 (Applicability::MaybeIncorrect, false)
1080             };
1081             if !lhs.is_syntactic_place_expr()
1082                 && lhs.is_approximately_pattern()
1083                 && !matches!(lhs.kind, hir::ExprKind::Lit(_))
1084             {
1085                 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1086                 let hir = self.tcx.hir();
1087                 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1088                     hir.get_parent(hir.parent_id(expr.hir_id))
1089                 {
1090                     err.span_suggestion_verbose(
1091                         expr.span.shrink_to_lo(),
1092                         "you might have meant to use pattern matching",
1093                         "let ",
1094                         applicability,
1095                     );
1096                 };
1097             }
1098             if eq {
1099                 err.span_suggestion_verbose(
1100                     span.shrink_to_hi(),
1101                     "you might have meant to compare for equality",
1102                     '=',
1103                     applicability,
1104                 );
1105             }
1106
1107             // If the assignment expression itself is ill-formed, don't
1108             // bother emitting another error
1109             let reported = err.emit_unless(lhs_ty.references_error() || rhs_ty.references_error());
1110             return self.tcx.ty_error_with_guaranteed(reported);
1111         }
1112
1113         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1114
1115         let suggest_deref_binop = |err: &mut Diagnostic, rhs_ty: Ty<'tcx>| {
1116             if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1117                 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1118                 // unsized, do not suggest dereferencing it.
1119                 let lhs_deref_ty_is_sized = self
1120                     .infcx
1121                     .type_implements_trait(
1122                         self.tcx.require_lang_item(LangItem::Sized, None),
1123                         [lhs_deref_ty],
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                         expected,
1249                     ) {
1250                         err.emit();
1251                     }
1252                 }
1253                 Err(())
1254             }
1255         };
1256
1257         // Call the generic checker.
1258         self.check_method_argument_types(span, expr, method, &args, DontTupleArguments, expected)
1259     }
1260
1261     fn check_expr_cast(
1262         &self,
1263         e: &'tcx hir::Expr<'tcx>,
1264         t: &'tcx hir::Ty<'tcx>,
1265         expr: &'tcx hir::Expr<'tcx>,
1266     ) -> Ty<'tcx> {
1267         // Find the type of `e`. Supply hints based on the type we are casting to,
1268         // if appropriate.
1269         let t_cast = self.to_ty_saving_user_provided_ty(t);
1270         let t_cast = self.resolve_vars_if_possible(t_cast);
1271         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1272         let t_expr = self.resolve_vars_if_possible(t_expr);
1273
1274         // Eagerly check for some obvious errors.
1275         if t_expr.references_error() || t_cast.references_error() {
1276             self.tcx.ty_error()
1277         } else {
1278             // Defer other checks until we're done type checking.
1279             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1280             match cast::CastCheck::new(
1281                 self,
1282                 e,
1283                 t_expr,
1284                 t_cast,
1285                 t.span,
1286                 expr.span,
1287                 self.param_env.constness(),
1288             ) {
1289                 Ok(cast_check) => {
1290                     debug!(
1291                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1292                         t_cast, t_expr, cast_check,
1293                     );
1294                     deferred_cast_checks.push(cast_check);
1295                     t_cast
1296                 }
1297                 Err(_) => self.tcx.ty_error(),
1298             }
1299         }
1300     }
1301
1302     fn check_expr_array(
1303         &self,
1304         args: &'tcx [hir::Expr<'tcx>],
1305         expected: Expectation<'tcx>,
1306         expr: &'tcx hir::Expr<'tcx>,
1307     ) -> Ty<'tcx> {
1308         let element_ty = if !args.is_empty() {
1309             let coerce_to = expected
1310                 .to_option(self)
1311                 .and_then(|uty| match *uty.kind() {
1312                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1313                     _ => None,
1314                 })
1315                 .unwrap_or_else(|| {
1316                     self.next_ty_var(TypeVariableOrigin {
1317                         kind: TypeVariableOriginKind::TypeInference,
1318                         span: expr.span,
1319                     })
1320                 });
1321             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1322             assert_eq!(self.diverges.get(), Diverges::Maybe);
1323             for e in args {
1324                 let e_ty = self.check_expr_with_hint(e, coerce_to);
1325                 let cause = self.misc(e.span);
1326                 coerce.coerce(self, &cause, e, e_ty);
1327             }
1328             coerce.complete(self)
1329         } else {
1330             self.next_ty_var(TypeVariableOrigin {
1331                 kind: TypeVariableOriginKind::TypeInference,
1332                 span: expr.span,
1333             })
1334         };
1335         let array_len = args.len() as u64;
1336         self.suggest_array_len(expr, array_len);
1337         self.tcx.mk_array(element_ty, array_len)
1338     }
1339
1340     fn suggest_array_len(&self, expr: &'tcx hir::Expr<'tcx>, array_len: u64) {
1341         let parent_node = self.tcx.hir().parent_iter(expr.hir_id).find(|(_, node)| {
1342             !matches!(node, hir::Node::Expr(hir::Expr { kind: hir::ExprKind::AddrOf(..), .. }))
1343         });
1344         let Some((_,
1345             hir::Node::Local(hir::Local { ty: Some(ty), .. })
1346             | hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _), .. }))
1347         ) = parent_node else {
1348             return
1349         };
1350         if let hir::TyKind::Array(_, length) = ty.peel_refs().kind
1351             && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
1352             && let Some(span) = self.tcx.hir().opt_span(hir_id)
1353         {
1354             match self.tcx.sess.diagnostic().steal_diagnostic(span, StashKey::UnderscoreForArrayLengths) {
1355                 Some(mut err) => {
1356                     err.span_suggestion(
1357                         span,
1358                         "consider specifying the array length",
1359                         array_len,
1360                         Applicability::MaybeIncorrect,
1361                     );
1362                     err.emit();
1363                 }
1364                 None => ()
1365             }
1366         }
1367     }
1368
1369     fn check_expr_const_block(
1370         &self,
1371         anon_const: &'tcx hir::AnonConst,
1372         expected: Expectation<'tcx>,
1373         _expr: &'tcx hir::Expr<'tcx>,
1374     ) -> Ty<'tcx> {
1375         let body = self.tcx.hir().body(anon_const.body);
1376
1377         // Create a new function context.
1378         let def_id = anon_const.def_id;
1379         let fcx = FnCtxt::new(self, self.param_env.with_const(), def_id);
1380         crate::GatherLocalsVisitor::new(&fcx).visit_body(body);
1381
1382         let ty = fcx.check_expr_with_expectation(&body.value, expected);
1383         fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1384         fcx.write_ty(anon_const.hir_id, ty);
1385         ty
1386     }
1387
1388     fn check_expr_repeat(
1389         &self,
1390         element: &'tcx hir::Expr<'tcx>,
1391         count: &'tcx hir::ArrayLen,
1392         expected: Expectation<'tcx>,
1393         expr: &'tcx hir::Expr<'tcx>,
1394     ) -> Ty<'tcx> {
1395         let tcx = self.tcx;
1396         let count = self.array_length_to_const(count);
1397         if let Some(count) = count.try_eval_usize(tcx, self.param_env) {
1398             self.suggest_array_len(expr, count);
1399         }
1400
1401         let uty = match expected {
1402             ExpectHasType(uty) => match *uty.kind() {
1403                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1404                 _ => None,
1405             },
1406             _ => None,
1407         };
1408
1409         let (element_ty, t) = match uty {
1410             Some(uty) => {
1411                 self.check_expr_coercable_to_type(&element, uty, None);
1412                 (uty, uty)
1413             }
1414             None => {
1415                 let ty = self.next_ty_var(TypeVariableOrigin {
1416                     kind: TypeVariableOriginKind::MiscVariable,
1417                     span: element.span,
1418                 });
1419                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1420                 (element_ty, ty)
1421             }
1422         };
1423
1424         if element_ty.references_error() {
1425             return tcx.ty_error();
1426         }
1427
1428         self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1429
1430         tcx.mk_ty(ty::Array(t, count))
1431     }
1432
1433     fn check_repeat_element_needs_copy_bound(
1434         &self,
1435         element: &hir::Expr<'_>,
1436         count: ty::Const<'tcx>,
1437         element_ty: Ty<'tcx>,
1438     ) {
1439         let tcx = self.tcx;
1440         // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1441         match &element.kind {
1442             hir::ExprKind::ConstBlock(..) => return,
1443             hir::ExprKind::Path(qpath) => {
1444                 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1445                 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1446                 {
1447                     return;
1448                 }
1449             }
1450             _ => {}
1451         }
1452         // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1453         // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1454         let is_const_fn = match element.kind {
1455             hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1456                 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1457                 _ => false,
1458             },
1459             _ => false,
1460         };
1461
1462         // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1463         // don't copy that one element, we move it. Only check for Copy if the length is larger.
1464         if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1465             let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1466             let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1467             self.require_type_meets(element_ty, element.span, code, lang_item);
1468         }
1469     }
1470
1471     fn check_expr_tuple(
1472         &self,
1473         elts: &'tcx [hir::Expr<'tcx>],
1474         expected: Expectation<'tcx>,
1475         expr: &'tcx hir::Expr<'tcx>,
1476     ) -> Ty<'tcx> {
1477         let flds = expected.only_has_type(self).and_then(|ty| {
1478             let ty = self.resolve_vars_with_obligations(ty);
1479             match ty.kind() {
1480                 ty::Tuple(flds) => Some(&flds[..]),
1481                 _ => None,
1482             }
1483         });
1484
1485         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1486             Some(fs) if i < fs.len() => {
1487                 let ety = fs[i];
1488                 self.check_expr_coercable_to_type(&e, ety, None);
1489                 ety
1490             }
1491             _ => self.check_expr_with_expectation(&e, NoExpectation),
1492         });
1493         let tuple = self.tcx.mk_tup(elt_ts_iter);
1494         if tuple.references_error() {
1495             self.tcx.ty_error()
1496         } else {
1497             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1498             tuple
1499         }
1500     }
1501
1502     fn check_expr_struct(
1503         &self,
1504         expr: &hir::Expr<'_>,
1505         expected: Expectation<'tcx>,
1506         qpath: &QPath<'_>,
1507         fields: &'tcx [hir::ExprField<'tcx>],
1508         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1509     ) -> Ty<'tcx> {
1510         // Find the relevant variant
1511         let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1512             self.check_struct_fields_on_error(fields, base_expr);
1513             return self.tcx.ty_error();
1514         };
1515
1516         // Prohibit struct expressions when non-exhaustive flag is set.
1517         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1518         if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1519             self.tcx
1520                 .sess
1521                 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1522         }
1523
1524         self.check_expr_struct_fields(
1525             adt_ty,
1526             expected,
1527             expr.hir_id,
1528             qpath.span(),
1529             variant,
1530             fields,
1531             base_expr,
1532             expr.span,
1533         );
1534
1535         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1536         adt_ty
1537     }
1538
1539     fn check_expr_struct_fields(
1540         &self,
1541         adt_ty: Ty<'tcx>,
1542         expected: Expectation<'tcx>,
1543         expr_id: hir::HirId,
1544         span: Span,
1545         variant: &'tcx ty::VariantDef,
1546         ast_fields: &'tcx [hir::ExprField<'tcx>],
1547         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1548         expr_span: Span,
1549     ) {
1550         let tcx = self.tcx;
1551
1552         let expected_inputs =
1553             self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1554         let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1555             expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1556         } else {
1557             adt_ty
1558         };
1559         // re-link the regions that EIfEO can erase.
1560         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1561
1562         let ty::Adt(adt, substs) = adt_ty.kind() else {
1563             span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1564         };
1565         let adt_kind = adt.adt_kind();
1566
1567         let mut remaining_fields = variant
1568             .fields
1569             .iter()
1570             .enumerate()
1571             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1572             .collect::<FxHashMap<_, _>>();
1573
1574         let mut seen_fields = FxHashMap::default();
1575
1576         let mut error_happened = false;
1577
1578         // Type-check each field.
1579         for (idx, field) in ast_fields.iter().enumerate() {
1580             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1581             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1582                 seen_fields.insert(ident, field.span);
1583                 self.write_field_index(field.hir_id, i);
1584
1585                 // We don't look at stability attributes on
1586                 // struct-like enums (yet...), but it's definitely not
1587                 // a bug to have constructed one.
1588                 if adt_kind != AdtKind::Enum {
1589                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1590                 }
1591
1592                 self.field_ty(field.span, v_field, substs)
1593             } else {
1594                 error_happened = true;
1595                 if let Some(prev_span) = seen_fields.get(&ident) {
1596                     tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1597                         span: field.ident.span,
1598                         prev_span: *prev_span,
1599                         ident,
1600                     });
1601                 } else {
1602                     self.report_unknown_field(
1603                         adt_ty,
1604                         variant,
1605                         field,
1606                         ast_fields,
1607                         adt.variant_descr(),
1608                         expr_span,
1609                     );
1610                 }
1611
1612                 tcx.ty_error()
1613             };
1614
1615             // Make sure to give a type to the field even if there's
1616             // an error, so we can continue type-checking.
1617             let ty = self.check_expr_with_hint(&field.expr, field_type);
1618             let (_, diag) =
1619                 self.demand_coerce_diag(&field.expr, ty, field_type, None, AllowTwoPhase::No);
1620
1621             if let Some(mut diag) = diag {
1622                 if idx == ast_fields.len() - 1 {
1623                     if remaining_fields.is_empty() {
1624                         self.suggest_fru_from_range(field, variant, substs, &mut diag);
1625                         diag.emit();
1626                     } else {
1627                         diag.stash(field.span, StashKey::MaybeFruTypo);
1628                     }
1629                 } else {
1630                     diag.emit();
1631                 }
1632             }
1633         }
1634
1635         // Make sure the programmer specified correct number of fields.
1636         if adt_kind == AdtKind::Union {
1637             if ast_fields.len() != 1 {
1638                 struct_span_err!(
1639                     tcx.sess,
1640                     span,
1641                     E0784,
1642                     "union expressions should have exactly one field",
1643                 )
1644                 .emit();
1645             }
1646         }
1647
1648         // If check_expr_struct_fields hit an error, do not attempt to populate
1649         // the fields with the base_expr. This could cause us to hit errors later
1650         // when certain fields are assumed to exist that in fact do not.
1651         if error_happened {
1652             if let Some(base_expr) = base_expr {
1653                 self.check_expr(base_expr);
1654             }
1655             return;
1656         }
1657
1658         if let Some(base_expr) = base_expr {
1659             // FIXME: We are currently creating two branches here in order to maintain
1660             // consistency. But they should be merged as much as possible.
1661             let fru_tys = if self.tcx.features().type_changing_struct_update {
1662                 if adt.is_struct() {
1663                     // Make some fresh substitutions for our ADT type.
1664                     let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1665                     // We do subtyping on the FRU fields first, so we can
1666                     // learn exactly what types we expect the base expr
1667                     // needs constrained to be compatible with the struct
1668                     // type we expect from the expectation value.
1669                     let fru_tys = variant
1670                         .fields
1671                         .iter()
1672                         .map(|f| {
1673                             let fru_ty = self.normalize(
1674                                 expr_span,
1675                                 self.field_ty(base_expr.span, f, fresh_substs),
1676                             );
1677                             let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1678                             if let Some(_) = remaining_fields.remove(&ident) {
1679                                 let target_ty = self.field_ty(base_expr.span, f, substs);
1680                                 let cause = self.misc(base_expr.span);
1681                                 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1682                                     Ok(InferOk { obligations, value: () }) => {
1683                                         self.register_predicates(obligations)
1684                                     }
1685                                     Err(_) => {
1686                                         // This should never happen, since we're just subtyping the
1687                                         // remaining_fields, but it's fine to emit this, I guess.
1688                                         self.err_ctxt()
1689                                             .report_mismatched_types(
1690                                                 &cause,
1691                                                 target_ty,
1692                                                 fru_ty,
1693                                                 FieldMisMatch(variant.name, ident.name),
1694                                             )
1695                                             .emit();
1696                                     }
1697                                 }
1698                             }
1699                             self.resolve_vars_if_possible(fru_ty)
1700                         })
1701                         .collect();
1702                     // The use of fresh substs that we have subtyped against
1703                     // our base ADT type's fields allows us to guide inference
1704                     // along so that, e.g.
1705                     // ```
1706                     // MyStruct<'a, F1, F2, const C: usize> {
1707                     //     f: F1,
1708                     //     // Other fields that reference `'a`, `F2`, and `C`
1709                     // }
1710                     //
1711                     // let x = MyStruct {
1712                     //    f: 1usize,
1713                     //    ..other_struct
1714                     // };
1715                     // ```
1716                     // will have the `other_struct` expression constrained to
1717                     // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1718                     // This is important to allow coercions to happen in
1719                     // `other_struct` itself. See `coerce-in-base-expr.rs`.
1720                     let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1721                     self.check_expr_has_type_or_error(
1722                         base_expr,
1723                         self.resolve_vars_if_possible(fresh_base_ty),
1724                         |_| {},
1725                     );
1726                     fru_tys
1727                 } else {
1728                     // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1729                     // type errors on that expression, too.
1730                     self.check_expr(base_expr);
1731                     self.tcx
1732                         .sess
1733                         .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1734                     return;
1735                 }
1736             } else {
1737                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1738                     let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1739                     let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1740                         (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1741                         _ => false,
1742                     };
1743                     if self.tcx.sess.is_nightly_build() && same_adt {
1744                         feature_err(
1745                             &self.tcx.sess.parse_sess,
1746                             sym::type_changing_struct_update,
1747                             base_expr.span,
1748                             "type changing struct updating is experimental",
1749                         )
1750                         .emit();
1751                     }
1752                 });
1753                 match adt_ty.kind() {
1754                     ty::Adt(adt, substs) if adt.is_struct() => variant
1755                         .fields
1756                         .iter()
1757                         .map(|f| self.normalize(expr_span, f.ty(self.tcx, substs)))
1758                         .collect(),
1759                     _ => {
1760                         self.tcx
1761                             .sess
1762                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1763                         return;
1764                     }
1765                 }
1766             };
1767             self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1768         } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1769             debug!(?remaining_fields);
1770             let private_fields: Vec<&ty::FieldDef> = variant
1771                 .fields
1772                 .iter()
1773                 .filter(|field| !field.vis.is_accessible_from(tcx.parent_module(expr_id), tcx))
1774                 .collect();
1775
1776             if !private_fields.is_empty() {
1777                 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1778             } else {
1779                 self.report_missing_fields(
1780                     adt_ty,
1781                     span,
1782                     remaining_fields,
1783                     variant,
1784                     ast_fields,
1785                     substs,
1786                 );
1787             }
1788         }
1789     }
1790
1791     fn check_struct_fields_on_error(
1792         &self,
1793         fields: &'tcx [hir::ExprField<'tcx>],
1794         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1795     ) {
1796         for field in fields {
1797             self.check_expr(&field.expr);
1798         }
1799         if let Some(base) = *base_expr {
1800             self.check_expr(&base);
1801         }
1802     }
1803
1804     /// Report an error for a struct field expression when there are fields which aren't provided.
1805     ///
1806     /// ```text
1807     /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1808     ///  --> src/main.rs:8:5
1809     ///   |
1810     /// 8 |     foo::Foo {};
1811     ///   |     ^^^^^^^^ missing `you_can_use_this_field`
1812     ///
1813     /// error: aborting due to previous error
1814     /// ```
1815     fn report_missing_fields(
1816         &self,
1817         adt_ty: Ty<'tcx>,
1818         span: Span,
1819         remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1820         variant: &'tcx ty::VariantDef,
1821         ast_fields: &'tcx [hir::ExprField<'tcx>],
1822         substs: SubstsRef<'tcx>,
1823     ) {
1824         let len = remaining_fields.len();
1825
1826         let mut displayable_field_names: Vec<&str> =
1827             remaining_fields.keys().map(|ident| ident.as_str()).collect();
1828         // sorting &str primitives here, sort_unstable is ok
1829         displayable_field_names.sort_unstable();
1830
1831         let mut truncated_fields_error = String::new();
1832         let remaining_fields_names = match &displayable_field_names[..] {
1833             [field1] => format!("`{}`", field1),
1834             [field1, field2] => format!("`{field1}` and `{field2}`"),
1835             [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1836             _ => {
1837                 truncated_fields_error =
1838                     format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1839                 displayable_field_names
1840                     .iter()
1841                     .take(3)
1842                     .map(|n| format!("`{n}`"))
1843                     .collect::<Vec<_>>()
1844                     .join(", ")
1845             }
1846         };
1847
1848         let mut err = struct_span_err!(
1849             self.tcx.sess,
1850             span,
1851             E0063,
1852             "missing field{} {}{} in initializer of `{}`",
1853             pluralize!(len),
1854             remaining_fields_names,
1855             truncated_fields_error,
1856             adt_ty
1857         );
1858         err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1859
1860         if let Some(last) = ast_fields.last() {
1861             self.suggest_fru_from_range(last, variant, substs, &mut err);
1862         }
1863
1864         err.emit();
1865     }
1866
1867     /// If the last field is a range literal, but it isn't supposed to be, then they probably
1868     /// meant to use functional update syntax.
1869     fn suggest_fru_from_range(
1870         &self,
1871         last_expr_field: &hir::ExprField<'tcx>,
1872         variant: &ty::VariantDef,
1873         substs: SubstsRef<'tcx>,
1874         err: &mut Diagnostic,
1875     ) {
1876         // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1877         if let ExprKind::Struct(
1878                 QPath::LangItem(LangItem::Range, ..),
1879                 [range_start, range_end],
1880                 _,
1881             ) = last_expr_field.expr.kind
1882             && let variant_field =
1883                 variant.fields.iter().find(|field| field.ident(self.tcx) == last_expr_field.ident)
1884             && let range_def_id = self.tcx.lang_items().range_struct()
1885             && variant_field
1886                 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1887                 .map(|adt| adt.did())
1888                 != range_def_id
1889         {
1890             // Suppress any range expr type mismatches
1891             if let Some(mut diag) = self
1892                 .tcx
1893                 .sess
1894                 .diagnostic()
1895                 .steal_diagnostic(last_expr_field.span, StashKey::MaybeFruTypo)
1896             {
1897                 diag.delay_as_bug();
1898             }
1899
1900             // Use a (somewhat arbitrary) filtering heuristic to avoid printing
1901             // expressions that are either too long, or have control character
1902             //such as newlines in them.
1903             let expr = self
1904                 .tcx
1905                 .sess
1906                 .source_map()
1907                 .span_to_snippet(range_end.expr.span)
1908                 .ok()
1909                 .filter(|s| s.len() < 25 && !s.contains(|c: char| c.is_control()));
1910
1911             let fru_span = self
1912                 .tcx
1913                 .sess
1914                 .source_map()
1915                 .span_extend_while(range_start.span, |c| c.is_whitespace())
1916                 .unwrap_or(range_start.span).shrink_to_hi().to(range_end.span);
1917
1918             err.subdiagnostic(TypeMismatchFruTypo {
1919                 expr_span: range_start.span,
1920                 fru_span,
1921                 expr,
1922             });
1923         }
1924     }
1925
1926     /// Report an error for a struct field expression when there are invisible fields.
1927     ///
1928     /// ```text
1929     /// error: cannot construct `Foo` with struct literal syntax due to private fields
1930     ///  --> src/main.rs:8:5
1931     ///   |
1932     /// 8 |     foo::Foo {};
1933     ///   |     ^^^^^^^^
1934     ///
1935     /// error: aborting due to previous error
1936     /// ```
1937     fn report_private_fields(
1938         &self,
1939         adt_ty: Ty<'tcx>,
1940         span: Span,
1941         private_fields: Vec<&ty::FieldDef>,
1942         used_fields: &'tcx [hir::ExprField<'tcx>],
1943     ) {
1944         let mut err = self.tcx.sess.struct_span_err(
1945             span,
1946             &format!(
1947                 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1948             ),
1949         );
1950         let (used_private_fields, remaining_private_fields): (
1951             Vec<(Symbol, Span, bool)>,
1952             Vec<(Symbol, Span, bool)>,
1953         ) = private_fields
1954             .iter()
1955             .map(|field| {
1956                 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1957                     Some(used_field) => (field.name, used_field.span, true),
1958                     None => (field.name, self.tcx.def_span(field.did), false),
1959                 }
1960             })
1961             .partition(|field| field.2);
1962         err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1963         if !remaining_private_fields.is_empty() {
1964             let remaining_private_fields_len = remaining_private_fields.len();
1965             let names = match &remaining_private_fields
1966                 .iter()
1967                 .map(|(name, _, _)| name)
1968                 .collect::<Vec<_>>()[..]
1969             {
1970                 _ if remaining_private_fields_len > 6 => String::new(),
1971                 [name] => format!("`{name}` "),
1972                 [names @ .., last] => {
1973                     let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1974                     format!("{} and `{last}` ", names.join(", "))
1975                 }
1976                 [] => unreachable!(),
1977             };
1978             err.note(format!(
1979                 "... and other private field{s} {names}that {were} not provided",
1980                 s = pluralize!(remaining_private_fields_len),
1981                 were = pluralize!("was", remaining_private_fields_len),
1982             ));
1983         }
1984         err.emit();
1985     }
1986
1987     fn report_unknown_field(
1988         &self,
1989         ty: Ty<'tcx>,
1990         variant: &'tcx ty::VariantDef,
1991         field: &hir::ExprField<'_>,
1992         skip_fields: &[hir::ExprField<'_>],
1993         kind_name: &str,
1994         expr_span: Span,
1995     ) {
1996         if variant.is_recovered() {
1997             self.set_tainted_by_errors(
1998                 self.tcx
1999                     .sess
2000                     .delay_span_bug(expr_span, "parser recovered but no error was emitted"),
2001             );
2002             return;
2003         }
2004         let mut err = self.err_ctxt().type_error_struct_with_diag(
2005             field.ident.span,
2006             |actual| match ty.kind() {
2007                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
2008                     self.tcx.sess,
2009                     field.ident.span,
2010                     E0559,
2011                     "{} `{}::{}` has no field named `{}`",
2012                     kind_name,
2013                     actual,
2014                     variant.name,
2015                     field.ident
2016                 ),
2017                 _ => struct_span_err!(
2018                     self.tcx.sess,
2019                     field.ident.span,
2020                     E0560,
2021                     "{} `{}` has no field named `{}`",
2022                     kind_name,
2023                     actual,
2024                     field.ident
2025                 ),
2026             },
2027             ty,
2028         );
2029
2030         let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
2031         match variant.ctor_kind() {
2032             Some(CtorKind::Fn) => match ty.kind() {
2033                 ty::Adt(adt, ..) if adt.is_enum() => {
2034                     err.span_label(
2035                         variant_ident_span,
2036                         format!(
2037                             "`{adt}::{variant}` defined here",
2038                             adt = ty,
2039                             variant = variant.name,
2040                         ),
2041                     );
2042                     err.span_label(field.ident.span, "field does not exist");
2043                     err.span_suggestion_verbose(
2044                         expr_span,
2045                         &format!(
2046                             "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
2047                             adt = ty,
2048                             variant = variant.name,
2049                         ),
2050                         format!(
2051                             "{adt}::{variant}(/* fields */)",
2052                             adt = ty,
2053                             variant = variant.name,
2054                         ),
2055                         Applicability::HasPlaceholders,
2056                     );
2057                 }
2058                 _ => {
2059                     err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
2060                     err.span_label(field.ident.span, "field does not exist");
2061                     err.span_suggestion_verbose(
2062                         expr_span,
2063                         &format!(
2064                             "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
2065                             adt = ty,
2066                             kind_name = kind_name,
2067                         ),
2068                         format!("{adt}(/* fields */)", adt = ty),
2069                         Applicability::HasPlaceholders,
2070                     );
2071                 }
2072             },
2073             _ => {
2074                 // prevent all specified fields from being suggested
2075                 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
2076                 if let Some(field_name) = self.suggest_field_name(
2077                     variant,
2078                     field.ident.name,
2079                     skip_fields.collect(),
2080                     expr_span,
2081                 ) {
2082                     err.span_suggestion(
2083                         field.ident.span,
2084                         "a field with a similar name exists",
2085                         field_name,
2086                         Applicability::MaybeIncorrect,
2087                     );
2088                 } else {
2089                     match ty.kind() {
2090                         ty::Adt(adt, ..) => {
2091                             if adt.is_enum() {
2092                                 err.span_label(
2093                                     field.ident.span,
2094                                     format!("`{}::{}` does not have this field", ty, variant.name),
2095                                 );
2096                             } else {
2097                                 err.span_label(
2098                                     field.ident.span,
2099                                     format!("`{ty}` does not have this field"),
2100                                 );
2101                             }
2102                             let available_field_names =
2103                                 self.available_field_names(variant, expr_span);
2104                             if !available_field_names.is_empty() {
2105                                 err.note(&format!(
2106                                     "available fields are: {}",
2107                                     self.name_series_display(available_field_names)
2108                                 ));
2109                             }
2110                         }
2111                         _ => bug!("non-ADT passed to report_unknown_field"),
2112                     }
2113                 };
2114             }
2115         }
2116         err.emit();
2117     }
2118
2119     // Return a hint about the closest match in field names
2120     fn suggest_field_name(
2121         &self,
2122         variant: &'tcx ty::VariantDef,
2123         field: Symbol,
2124         skip: Vec<Symbol>,
2125         // The span where stability will be checked
2126         span: Span,
2127     ) -> Option<Symbol> {
2128         let names = variant
2129             .fields
2130             .iter()
2131             .filter_map(|field| {
2132                 // ignore already set fields and private fields from non-local crates
2133                 // and unstable fields.
2134                 if skip.iter().any(|&x| x == field.name)
2135                     || (!variant.def_id.is_local() && !field.vis.is_public())
2136                     || matches!(
2137                         self.tcx.eval_stability(field.did, None, span, None),
2138                         stability::EvalResult::Deny { .. }
2139                     )
2140                 {
2141                     None
2142                 } else {
2143                     Some(field.name)
2144                 }
2145             })
2146             .collect::<Vec<Symbol>>();
2147
2148         find_best_match_for_name(&names, field, None)
2149     }
2150
2151     fn available_field_names(
2152         &self,
2153         variant: &'tcx ty::VariantDef,
2154         access_span: Span,
2155     ) -> Vec<Symbol> {
2156         let body_owner_hir_id = self.tcx.hir().local_def_id_to_hir_id(self.body_id);
2157         variant
2158             .fields
2159             .iter()
2160             .filter(|field| {
2161                 let def_scope = self
2162                     .tcx
2163                     .adjust_ident_and_get_scope(
2164                         field.ident(self.tcx),
2165                         variant.def_id,
2166                         body_owner_hir_id,
2167                     )
2168                     .1;
2169                 field.vis.is_accessible_from(def_scope, self.tcx)
2170                     && !matches!(
2171                         self.tcx.eval_stability(field.did, None, access_span, None),
2172                         stability::EvalResult::Deny { .. }
2173                     )
2174             })
2175             .filter(|field| !self.tcx.is_doc_hidden(field.did))
2176             .map(|field| field.name)
2177             .collect()
2178     }
2179
2180     fn name_series_display(&self, names: Vec<Symbol>) -> String {
2181         // dynamic limit, to never omit just one field
2182         let limit = if names.len() == 6 { 6 } else { 5 };
2183         let mut display =
2184             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2185         if names.len() > limit {
2186             display = format!("{} ... and {} others", display, names.len() - limit);
2187         }
2188         display
2189     }
2190
2191     // Check field access expressions
2192     fn check_field(
2193         &self,
2194         expr: &'tcx hir::Expr<'tcx>,
2195         base: &'tcx hir::Expr<'tcx>,
2196         field: Ident,
2197         expected: Expectation<'tcx>,
2198     ) -> Ty<'tcx> {
2199         debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2200         let base_ty = self.check_expr(base);
2201         let base_ty = self.structurally_resolved_type(base.span, base_ty);
2202         let mut private_candidate = None;
2203         let mut autoderef = self.autoderef(expr.span, base_ty);
2204         while let Some((deref_base_ty, _)) = autoderef.next() {
2205             debug!("deref_base_ty: {:?}", deref_base_ty);
2206             match deref_base_ty.kind() {
2207                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2208                     debug!("struct named {:?}", deref_base_ty);
2209                     let body_hir_id = self.tcx.hir().local_def_id_to_hir_id(self.body_id);
2210                     let (ident, def_scope) =
2211                         self.tcx.adjust_ident_and_get_scope(field, base_def.did(), body_hir_id);
2212                     let fields = &base_def.non_enum_variant().fields;
2213                     if let Some(index) = fields
2214                         .iter()
2215                         .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2216                     {
2217                         let field = &fields[index];
2218                         let field_ty = self.field_ty(expr.span, field, substs);
2219                         // Save the index of all fields regardless of their visibility in case
2220                         // of error recovery.
2221                         self.write_field_index(expr.hir_id, index);
2222                         let adjustments = self.adjust_steps(&autoderef);
2223                         if field.vis.is_accessible_from(def_scope, self.tcx) {
2224                             self.apply_adjustments(base, adjustments);
2225                             self.register_predicates(autoderef.into_obligations());
2226
2227                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2228                             return field_ty;
2229                         }
2230                         private_candidate = Some((adjustments, base_def.did()));
2231                     }
2232                 }
2233                 ty::Tuple(tys) => {
2234                     let fstr = field.as_str();
2235                     if let Ok(index) = fstr.parse::<usize>() {
2236                         if fstr == index.to_string() {
2237                             if let Some(&field_ty) = tys.get(index) {
2238                                 let adjustments = self.adjust_steps(&autoderef);
2239                                 self.apply_adjustments(base, adjustments);
2240                                 self.register_predicates(autoderef.into_obligations());
2241
2242                                 self.write_field_index(expr.hir_id, index);
2243                                 return field_ty;
2244                             }
2245                         }
2246                     }
2247                 }
2248                 _ => {}
2249             }
2250         }
2251         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2252
2253         if let Some((adjustments, did)) = private_candidate {
2254             // (#90483) apply adjustments to avoid ExprUseVisitor from
2255             // creating erroneous projection.
2256             self.apply_adjustments(base, adjustments);
2257             self.ban_private_field_access(expr, base_ty, field, did, expected.only_has_type(self));
2258             return self.tcx().ty_error();
2259         }
2260
2261         if field.name == kw::Empty {
2262         } else if self.method_exists(
2263             field,
2264             base_ty,
2265             expr.hir_id,
2266             true,
2267             expected.only_has_type(self),
2268         ) {
2269             self.ban_take_value_of_method(expr, base_ty, field);
2270         } else if !base_ty.is_primitive_ty() {
2271             self.ban_nonexisting_field(field, base, expr, base_ty);
2272         } else {
2273             let field_name = field.to_string();
2274             let mut err = type_error_struct!(
2275                 self.tcx().sess,
2276                 field.span,
2277                 base_ty,
2278                 E0610,
2279                 "`{base_ty}` is a primitive type and therefore doesn't have fields",
2280             );
2281             let is_valid_suffix = |field: &str| {
2282                 if field == "f32" || field == "f64" {
2283                     return true;
2284                 }
2285                 let mut chars = field.chars().peekable();
2286                 match chars.peek() {
2287                     Some('e') | Some('E') => {
2288                         chars.next();
2289                         if let Some(c) = chars.peek()
2290                             && !c.is_numeric() && *c != '-' && *c != '+'
2291                         {
2292                             return false;
2293                         }
2294                         while let Some(c) = chars.peek() {
2295                             if !c.is_numeric() {
2296                                 break;
2297                             }
2298                             chars.next();
2299                         }
2300                     }
2301                     _ => (),
2302                 }
2303                 let suffix = chars.collect::<String>();
2304                 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2305             };
2306             let maybe_partial_suffix = |field: &str| -> Option<&str> {
2307                 let first_chars = ['f', 'l'];
2308                 if field.len() >= 1
2309                     && field.to_lowercase().starts_with(first_chars)
2310                     && field[1..].chars().all(|c| c.is_ascii_digit())
2311                 {
2312                     if field.to_lowercase().starts_with(['f']) { Some("f32") } else { Some("f64") }
2313                 } else {
2314                     None
2315                 }
2316             };
2317             if let ty::Infer(ty::IntVar(_)) = base_ty.kind()
2318                 && let ExprKind::Lit(Spanned {
2319                     node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2320                     ..
2321                 }) = base.kind
2322                 && !base.span.from_expansion()
2323             {
2324                 if is_valid_suffix(&field_name) {
2325                     err.span_suggestion_verbose(
2326                         field.span.shrink_to_lo(),
2327                         "if intended to be a floating point literal, consider adding a `0` after the period",
2328                         '0',
2329                         Applicability::MaybeIncorrect,
2330                     );
2331                 } else if let Some(correct_suffix) = maybe_partial_suffix(&field_name) {
2332                     err.span_suggestion_verbose(
2333                         field.span,
2334                         format!("if intended to be a floating point literal, consider adding a `0` after the period and a `{correct_suffix}` suffix"),
2335                         format!("0{correct_suffix}"),
2336                         Applicability::MaybeIncorrect,
2337                     );
2338                 }
2339             }
2340             err.emit();
2341         }
2342
2343         self.tcx().ty_error()
2344     }
2345
2346     fn suggest_await_on_field_access(
2347         &self,
2348         err: &mut Diagnostic,
2349         field_ident: Ident,
2350         base: &'tcx hir::Expr<'tcx>,
2351         ty: Ty<'tcx>,
2352     ) {
2353         let Some(output_ty) = self.get_impl_future_output_ty(ty) else { return; };
2354         let mut add_label = true;
2355         if let ty::Adt(def, _) = output_ty.kind() {
2356             // no field access on enum type
2357             if !def.is_enum() {
2358                 if def
2359                     .non_enum_variant()
2360                     .fields
2361                     .iter()
2362                     .any(|field| field.ident(self.tcx) == field_ident)
2363                 {
2364                     add_label = false;
2365                     err.span_label(
2366                         field_ident.span,
2367                         "field not available in `impl Future`, but it is available in its `Output`",
2368                     );
2369                     err.span_suggestion_verbose(
2370                         base.span.shrink_to_hi(),
2371                         "consider `await`ing on the `Future` and access the field of its `Output`",
2372                         ".await",
2373                         Applicability::MaybeIncorrect,
2374                     );
2375                 }
2376             }
2377         }
2378         if add_label {
2379             err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2380         }
2381     }
2382
2383     fn ban_nonexisting_field(
2384         &self,
2385         ident: Ident,
2386         base: &'tcx hir::Expr<'tcx>,
2387         expr: &'tcx hir::Expr<'tcx>,
2388         base_ty: Ty<'tcx>,
2389     ) {
2390         debug!(
2391             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, base_ty={:?}",
2392             ident, base, expr, base_ty
2393         );
2394         let mut err = self.no_such_field_err(ident, base_ty, base.hir_id);
2395
2396         match *base_ty.peel_refs().kind() {
2397             ty::Array(_, len) => {
2398                 self.maybe_suggest_array_indexing(&mut err, expr, base, ident, len);
2399             }
2400             ty::RawPtr(..) => {
2401                 self.suggest_first_deref_field(&mut err, expr, base, ident);
2402             }
2403             ty::Adt(def, _) if !def.is_enum() => {
2404                 self.suggest_fields_on_recordish(&mut err, def, ident, expr.span);
2405             }
2406             ty::Param(param_ty) => {
2407                 self.point_at_param_definition(&mut err, param_ty);
2408             }
2409             ty::Alias(ty::Opaque, _) => {
2410                 self.suggest_await_on_field_access(&mut err, ident, base, base_ty.peel_refs());
2411             }
2412             _ => {}
2413         }
2414
2415         self.suggest_fn_call(&mut err, base, base_ty, |output_ty| {
2416             if let ty::Adt(def, _) = output_ty.kind() && !def.is_enum() {
2417                 def.non_enum_variant().fields.iter().any(|field| {
2418                     field.ident(self.tcx) == ident
2419                         && field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
2420                 })
2421             } else if let ty::Tuple(tys) = output_ty.kind()
2422                 && let Ok(idx) = ident.as_str().parse::<usize>()
2423             {
2424                 idx < tys.len()
2425             } else {
2426                 false
2427             }
2428         });
2429
2430         if ident.name == kw::Await {
2431             // We know by construction that `<expr>.await` is either on Rust 2015
2432             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2433             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2434             err.help_use_latest_edition();
2435         }
2436
2437         err.emit();
2438     }
2439
2440     fn ban_private_field_access(
2441         &self,
2442         expr: &hir::Expr<'tcx>,
2443         expr_t: Ty<'tcx>,
2444         field: Ident,
2445         base_did: DefId,
2446         return_ty: Option<Ty<'tcx>>,
2447     ) {
2448         let struct_path = self.tcx().def_path_str(base_did);
2449         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2450         let mut err = struct_span_err!(
2451             self.tcx().sess,
2452             field.span,
2453             E0616,
2454             "field `{field}` of {kind_name} `{struct_path}` is private",
2455         );
2456         err.span_label(field.span, "private field");
2457         // Also check if an accessible method exists, which is often what is meant.
2458         if self.method_exists(field, expr_t, expr.hir_id, false, return_ty)
2459             && !self.expr_in_place(expr.hir_id)
2460         {
2461             self.suggest_method_call(
2462                 &mut err,
2463                 &format!("a method `{field}` also exists, call it with parentheses"),
2464                 field,
2465                 expr_t,
2466                 expr,
2467                 None,
2468             );
2469         }
2470         err.emit();
2471     }
2472
2473     fn ban_take_value_of_method(&self, expr: &hir::Expr<'tcx>, expr_t: Ty<'tcx>, field: Ident) {
2474         let mut err = type_error_struct!(
2475             self.tcx().sess,
2476             field.span,
2477             expr_t,
2478             E0615,
2479             "attempted to take value of method `{field}` on type `{expr_t}`",
2480         );
2481         err.span_label(field.span, "method, not a field");
2482         let expr_is_call =
2483             if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2484                 self.tcx.hir().get_parent(expr.hir_id)
2485             {
2486                 expr.hir_id == callee.hir_id
2487             } else {
2488                 false
2489             };
2490         let expr_snippet =
2491             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2492         let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2493         let after_open = expr.span.lo() + rustc_span::BytePos(1);
2494         let before_close = expr.span.hi() - rustc_span::BytePos(1);
2495
2496         if expr_is_call && is_wrapped {
2497             err.multipart_suggestion(
2498                 "remove wrapping parentheses to call the method",
2499                 vec![
2500                     (expr.span.with_hi(after_open), String::new()),
2501                     (expr.span.with_lo(before_close), String::new()),
2502                 ],
2503                 Applicability::MachineApplicable,
2504             );
2505         } else if !self.expr_in_place(expr.hir_id) {
2506             // Suggest call parentheses inside the wrapping parentheses
2507             let span = if is_wrapped {
2508                 expr.span.with_lo(after_open).with_hi(before_close)
2509             } else {
2510                 expr.span
2511             };
2512             self.suggest_method_call(
2513                 &mut err,
2514                 "use parentheses to call the method",
2515                 field,
2516                 expr_t,
2517                 expr,
2518                 Some(span),
2519             );
2520         } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2521             && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2522             && let ExprKind::Field(base_expr, _) = expr.kind
2523             && adt_def.variants().len() == 1
2524             && adt_def
2525                 .variants()
2526                 .iter()
2527                 .next()
2528                 .unwrap()
2529                 .fields
2530                 .iter()
2531                 .any(|f| f.ident(self.tcx) == field)
2532         {
2533             err.multipart_suggestion(
2534                 "to access the field, dereference first",
2535                 vec![
2536                     (base_expr.span.shrink_to_lo(), "(*".to_string()),
2537                     (base_expr.span.shrink_to_hi(), ")".to_string()),
2538                 ],
2539                 Applicability::MaybeIncorrect,
2540             );
2541         } else {
2542             err.help("methods are immutable and cannot be assigned to");
2543         }
2544
2545         err.emit();
2546     }
2547
2548     fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2549         let generics = self.tcx.generics_of(self.body_id);
2550         let generic_param = generics.type_param(&param, self.tcx);
2551         if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2552             return;
2553         }
2554         let param_def_id = generic_param.def_id;
2555         let param_hir_id = match param_def_id.as_local() {
2556             Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2557             None => return,
2558         };
2559         let param_span = self.tcx.hir().span(param_hir_id);
2560         let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2561
2562         err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2563     }
2564
2565     fn suggest_fields_on_recordish(
2566         &self,
2567         err: &mut Diagnostic,
2568         def: ty::AdtDef<'tcx>,
2569         field: Ident,
2570         access_span: Span,
2571     ) {
2572         if let Some(suggested_field_name) =
2573             self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2574         {
2575             err.span_suggestion(
2576                 field.span,
2577                 "a field with a similar name exists",
2578                 suggested_field_name,
2579                 Applicability::MaybeIncorrect,
2580             );
2581         } else {
2582             err.span_label(field.span, "unknown field");
2583             let struct_variant_def = def.non_enum_variant();
2584             let field_names = self.available_field_names(struct_variant_def, access_span);
2585             if !field_names.is_empty() {
2586                 err.note(&format!(
2587                     "available fields are: {}",
2588                     self.name_series_display(field_names),
2589                 ));
2590             }
2591         }
2592     }
2593
2594     fn maybe_suggest_array_indexing(
2595         &self,
2596         err: &mut Diagnostic,
2597         expr: &hir::Expr<'_>,
2598         base: &hir::Expr<'_>,
2599         field: Ident,
2600         len: ty::Const<'tcx>,
2601     ) {
2602         if let (Some(len), Ok(user_index)) =
2603             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2604             && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2605         {
2606             let help = "instead of using tuple indexing, use array indexing";
2607             let suggestion = format!("{base}[{field}]");
2608             let applicability = if len < user_index {
2609                 Applicability::MachineApplicable
2610             } else {
2611                 Applicability::MaybeIncorrect
2612             };
2613             err.span_suggestion(expr.span, help, suggestion, applicability);
2614         }
2615     }
2616
2617     fn suggest_first_deref_field(
2618         &self,
2619         err: &mut Diagnostic,
2620         expr: &hir::Expr<'_>,
2621         base: &hir::Expr<'_>,
2622         field: Ident,
2623     ) {
2624         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2625             let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2626             let suggestion = format!("(*{base}).{field}");
2627             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2628         }
2629     }
2630
2631     fn no_such_field_err(
2632         &self,
2633         field: Ident,
2634         expr_t: Ty<'tcx>,
2635         id: HirId,
2636     ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2637         let span = field.span;
2638         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2639
2640         let mut err = type_error_struct!(
2641             self.tcx().sess,
2642             field.span,
2643             expr_t,
2644             E0609,
2645             "no field `{field}` on type `{expr_t}`",
2646         );
2647
2648         // try to add a suggestion in case the field is a nested field of a field of the Adt
2649         let mod_id = self.tcx.parent_module(id).to_def_id();
2650         if let Some((fields, substs)) =
2651             self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2652         {
2653             let candidate_fields: Vec<_> = fields
2654                 .filter_map(|candidate_field| {
2655                     self.check_for_nested_field_satisfying(
2656                         span,
2657                         &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2658                         candidate_field,
2659                         substs,
2660                         vec![],
2661                         mod_id,
2662                     )
2663                 })
2664                 .map(|mut field_path| {
2665                     field_path.pop();
2666                     field_path
2667                         .iter()
2668                         .map(|id| id.name.to_ident_string())
2669                         .collect::<Vec<String>>()
2670                         .join(".")
2671                 })
2672                 .collect::<Vec<_>>();
2673
2674             let len = candidate_fields.len();
2675             if len > 0 {
2676                 err.span_suggestions(
2677                     field.span.shrink_to_lo(),
2678                     format!(
2679                         "{} of the expressions' fields {} a field of the same name",
2680                         if len > 1 { "some" } else { "one" },
2681                         if len > 1 { "have" } else { "has" },
2682                     ),
2683                     candidate_fields.iter().map(|path| format!("{path}.")),
2684                     Applicability::MaybeIncorrect,
2685                 );
2686             }
2687         }
2688         err
2689     }
2690
2691     pub(crate) fn get_field_candidates_considering_privacy(
2692         &self,
2693         span: Span,
2694         base_ty: Ty<'tcx>,
2695         mod_id: DefId,
2696     ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2697         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2698
2699         for (base_t, _) in self.autoderef(span, base_ty) {
2700             match base_t.kind() {
2701                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2702                     let tcx = self.tcx;
2703                     let fields = &base_def.non_enum_variant().fields;
2704                     // Some struct, e.g. some that impl `Deref`, have all private fields
2705                     // because you're expected to deref them to access the _real_ fields.
2706                     // This, for example, will help us suggest accessing a field through a `Box<T>`.
2707                     if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2708                         continue;
2709                     }
2710                     return Some((
2711                         fields
2712                             .iter()
2713                             .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2714                             // For compile-time reasons put a limit on number of fields we search
2715                             .take(100),
2716                         substs,
2717                     ));
2718                 }
2719                 _ => {}
2720             }
2721         }
2722         None
2723     }
2724
2725     /// This method is called after we have encountered a missing field error to recursively
2726     /// search for the field
2727     pub(crate) fn check_for_nested_field_satisfying(
2728         &self,
2729         span: Span,
2730         matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2731         candidate_field: &ty::FieldDef,
2732         subst: SubstsRef<'tcx>,
2733         mut field_path: Vec<Ident>,
2734         mod_id: DefId,
2735     ) -> Option<Vec<Ident>> {
2736         debug!(
2737             "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2738             span, candidate_field, field_path
2739         );
2740
2741         if field_path.len() > 3 {
2742             // For compile-time reasons and to avoid infinite recursion we only check for fields
2743             // up to a depth of three
2744             None
2745         } else {
2746             field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2747             let field_ty = candidate_field.ty(self.tcx, subst);
2748             if matches(candidate_field, field_ty) {
2749                 return Some(field_path);
2750             } else if let Some((nested_fields, subst)) =
2751                 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2752             {
2753                 // recursively search fields of `candidate_field` if it's a ty::Adt
2754                 for field in nested_fields {
2755                     if let Some(field_path) = self.check_for_nested_field_satisfying(
2756                         span,
2757                         matches,
2758                         field,
2759                         subst,
2760                         field_path.clone(),
2761                         mod_id,
2762                     ) {
2763                         return Some(field_path);
2764                     }
2765                 }
2766             }
2767             None
2768         }
2769     }
2770
2771     fn check_expr_index(
2772         &self,
2773         base: &'tcx hir::Expr<'tcx>,
2774         idx: &'tcx hir::Expr<'tcx>,
2775         expr: &'tcx hir::Expr<'tcx>,
2776     ) -> Ty<'tcx> {
2777         let base_t = self.check_expr(&base);
2778         let idx_t = self.check_expr(&idx);
2779
2780         if base_t.references_error() {
2781             base_t
2782         } else if idx_t.references_error() {
2783             idx_t
2784         } else {
2785             let base_t = self.structurally_resolved_type(base.span, base_t);
2786             match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2787                 Some((index_ty, element_ty)) => {
2788                     // two-phase not needed because index_ty is never mutable
2789                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2790                     self.select_obligations_where_possible(|errors| {
2791                         self.point_at_index_if_possible(errors, idx.span)
2792                     });
2793                     element_ty
2794                 }
2795                 None => {
2796                     let mut err = type_error_struct!(
2797                         self.tcx.sess,
2798                         expr.span,
2799                         base_t,
2800                         E0608,
2801                         "cannot index into a value of type `{base_t}`",
2802                     );
2803                     // Try to give some advice about indexing tuples.
2804                     if let ty::Tuple(..) = base_t.kind() {
2805                         let mut needs_note = true;
2806                         // If the index is an integer, we can show the actual
2807                         // fixed expression:
2808                         if let ExprKind::Lit(ref lit) = idx.kind {
2809                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2810                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2811                                 if let Ok(snip) = snip {
2812                                     err.span_suggestion(
2813                                         expr.span,
2814                                         "to access tuple elements, use",
2815                                         format!("{snip}.{i}"),
2816                                         Applicability::MachineApplicable,
2817                                     );
2818                                     needs_note = false;
2819                                 }
2820                             }
2821                         }
2822                         if needs_note {
2823                             err.help(
2824                                 "to access tuple elements, use tuple indexing \
2825                                         syntax (e.g., `tuple.0`)",
2826                             );
2827                         }
2828                     }
2829                     let reported = err.emit();
2830                     self.tcx.ty_error_with_guaranteed(reported)
2831                 }
2832             }
2833         }
2834     }
2835
2836     fn point_at_index_if_possible(
2837         &self,
2838         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2839         span: Span,
2840     ) {
2841         for error in errors {
2842             match error.obligation.predicate.kind().skip_binder() {
2843                 ty::PredicateKind::Clause(ty::Clause::Trait(predicate))
2844                     if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2845                 }
2846                 _ => continue,
2847             }
2848             error.obligation.cause.span = span;
2849         }
2850     }
2851
2852     fn check_expr_yield(
2853         &self,
2854         value: &'tcx hir::Expr<'tcx>,
2855         expr: &'tcx hir::Expr<'tcx>,
2856         src: &'tcx hir::YieldSource,
2857     ) -> Ty<'tcx> {
2858         match self.resume_yield_tys {
2859             Some((resume_ty, yield_ty)) => {
2860                 self.check_expr_coercable_to_type(&value, yield_ty, None);
2861
2862                 resume_ty
2863             }
2864             // Given that this `yield` expression was generated as a result of lowering a `.await`,
2865             // we know that the yield type must be `()`; however, the context won't contain this
2866             // information. Hence, we check the source of the yield expression here and check its
2867             // value's type against `()` (this check should always hold).
2868             None if src.is_await() => {
2869                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2870                 self.tcx.mk_unit()
2871             }
2872             _ => {
2873                 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2874                 // Avoid expressions without types during writeback (#78653).
2875                 self.check_expr(value);
2876                 self.tcx.mk_unit()
2877             }
2878         }
2879     }
2880
2881     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2882         let needs = if is_input { Needs::None } else { Needs::MutPlace };
2883         let ty = self.check_expr_with_needs(expr, needs);
2884         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2885
2886         if !is_input && !expr.is_syntactic_place_expr() {
2887             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2888             err.span_label(expr.span, "cannot assign to this expression");
2889             err.emit();
2890         }
2891
2892         // If this is an input value, we require its type to be fully resolved
2893         // at this point. This allows us to provide helpful coercions which help
2894         // pass the type candidate list in a later pass.
2895         //
2896         // We don't require output types to be resolved at this point, which
2897         // allows them to be inferred based on how they are used later in the
2898         // function.
2899         if is_input {
2900             let ty = self.structurally_resolved_type(expr.span, ty);
2901             match *ty.kind() {
2902                 ty::FnDef(..) => {
2903                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2904                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2905                 }
2906                 ty::Ref(_, base_ty, mutbl) => {
2907                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2908                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2909                 }
2910                 _ => {}
2911             }
2912         }
2913     }
2914
2915     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2916         for (op, _op_sp) in asm.operands {
2917             match op {
2918                 hir::InlineAsmOperand::In { expr, .. } => {
2919                     self.check_expr_asm_operand(expr, true);
2920                 }
2921                 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2922                 | hir::InlineAsmOperand::InOut { expr, .. } => {
2923                     self.check_expr_asm_operand(expr, false);
2924                 }
2925                 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2926                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2927                     self.check_expr_asm_operand(in_expr, true);
2928                     if let Some(out_expr) = out_expr {
2929                         self.check_expr_asm_operand(out_expr, false);
2930                     }
2931                 }
2932                 // `AnonConst`s have their own body and is type-checked separately.
2933                 // As they don't flow into the type system we don't need them to
2934                 // be well-formed.
2935                 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2936                 hir::InlineAsmOperand::SymStatic { .. } => {}
2937             }
2938         }
2939         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2940             self.tcx.types.never
2941         } else {
2942             self.tcx.mk_unit()
2943         }
2944     }
2945 }