compiler/rustc_hir_analysis/src/check/expr.rs

   1 //! Type checking expressions.
   2 //!
   3 //! See `mod.rs` for more context on type checking in general.
   4
   5 use crate::astconv::AstConv as _;
   6 use crate::check::cast::{self, CastCheckResult};
   7 use crate::check::coercion::CoerceMany;
   8 use crate::check::fatally_break_rust;
   9 use crate::check::method::SelfSource;
  10 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
  11 use crate::check::{
  12     report_unexpected_variant_res, BreakableCtxt, Diverges, DynamicCoerceMany, FnCtxt, Needs,
  13     TupleArgumentsFlag::DontTupleArguments,
  14 };
  15 use crate::errors::{
  16     FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
  17     YieldExprOutsideOfGenerator,
  18 };
  19 use crate::type_error_struct;
  20
  21 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
  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::{Closure, ExprKind, HirId, QPath};
  35 use rustc_infer::infer;
  36 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
  37 use rustc_infer::infer::InferOk;
  38 use rustc_infer::traits::ObligationCause;
  39 use rustc_middle::middle::stability;
  40 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
  41 use rustc_middle::ty::error::TypeError::FieldMisMatch;
  42 use rustc_middle::ty::subst::SubstsRef;
  43 use rustc_middle::ty::{self, AdtKind, Ty, TypeVisitable};
  44 use rustc_session::errors::ExprParenthesesNeeded;
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::hygiene::DesugaringKind;
  47 use rustc_span::lev_distance::find_best_match_for_name;
  48 use rustc_span::source_map::{Span, Spanned};
  49 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  50 use rustc_target::spec::abi::Abi::RustIntrinsic;
  51 use rustc_trait_selection::infer::InferCtxtExt;
  52 use rustc_trait_selection::traits::{self, ObligationCauseCode};
  53
  54 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  55     fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
  56         let ty = self.check_expr_with_hint(expr, expected);
  57         self.demand_eqtype(expr.span, expected, ty);
  58     }
  59
  60     pub fn check_expr_has_type_or_error(
  61         &self,
  62         expr: &'tcx hir::Expr<'tcx>,
  63         expected: Ty<'tcx>,
  64         extend_err: impl FnMut(&mut Diagnostic),
  65     ) -> Ty<'tcx> {
  66         self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
  67     }
  68
  69     fn check_expr_meets_expectation_or_error(
  70         &self,
  71         expr: &'tcx hir::Expr<'tcx>,
  72         expected: Expectation<'tcx>,
  73         mut extend_err: impl FnMut(&mut Diagnostic),
  74     ) -> Ty<'tcx> {
  75         let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
  76         let mut ty = self.check_expr_with_expectation(expr, expected);
  77
  78         // While we don't allow *arbitrary* coercions here, we *do* allow
  79         // coercions from ! to `expected`.
  80         if ty.is_never() {
  81             if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
  82                 self.tcx().sess.delay_span_bug(
  83                     expr.span,
  84                     "expression with never type wound up being adjusted",
  85                 );
  86                 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
  87                     target.to_owned()
  88                 } else {
  89                     self.tcx().ty_error()
  90                 };
  91             }
  92
  93             let adj_ty = self.next_ty_var(TypeVariableOrigin {
  94                 kind: TypeVariableOriginKind::AdjustmentType,
  95                 span: expr.span,
  96             });
  97             self.apply_adjustments(
  98                 expr,
  99                 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
 100             );
 101             ty = adj_ty;
 102         }
 103
 104         if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
 105             let expr = expr.peel_drop_temps();
 106             self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
 107             extend_err(&mut err);
 108             err.emit();
 109         }
 110         ty
 111     }
 112
 113     pub(super) fn check_expr_coercable_to_type(
 114         &self,
 115         expr: &'tcx hir::Expr<'tcx>,
 116         expected: Ty<'tcx>,
 117         expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
 118     ) -> Ty<'tcx> {
 119         let ty = self.check_expr_with_hint(expr, expected);
 120         // checks don't need two phase
 121         self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
 122     }
 123
 124     pub(super) fn check_expr_with_hint(
 125         &self,
 126         expr: &'tcx hir::Expr<'tcx>,
 127         expected: Ty<'tcx>,
 128     ) -> Ty<'tcx> {
 129         self.check_expr_with_expectation(expr, ExpectHasType(expected))
 130     }
 131
 132     fn check_expr_with_expectation_and_needs(
 133         &self,
 134         expr: &'tcx hir::Expr<'tcx>,
 135         expected: Expectation<'tcx>,
 136         needs: Needs,
 137     ) -> Ty<'tcx> {
 138         let ty = self.check_expr_with_expectation(expr, expected);
 139
 140         // If the expression is used in a place whether mutable place is required
 141         // e.g. LHS of assignment, perform the conversion.
 142         if let Needs::MutPlace = needs {
 143             self.convert_place_derefs_to_mutable(expr);
 144         }
 145
 146         ty
 147     }
 148
 149     pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
 150         self.check_expr_with_expectation(expr, NoExpectation)
 151     }
 152
 153     pub(super) fn check_expr_with_needs(
 154         &self,
 155         expr: &'tcx hir::Expr<'tcx>,
 156         needs: Needs,
 157     ) -> Ty<'tcx> {
 158         self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
 159     }
 160
 161     /// Invariant:
 162     /// If an expression has any sub-expressions that result in a type error,
 163     /// inspecting that expression's type with `ty.references_error()` will return
 164     /// true. Likewise, if an expression is known to diverge, inspecting its
 165     /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
 166     /// strict, _|_ can appear in the type of an expression that does not,
 167     /// itself, diverge: for example, fn() -> _|_.)
 168     /// Note that inspecting a type's structure *directly* may expose the fact
 169     /// that there are actually multiple representations for `Error`, so avoid
 170     /// that when err needs to be handled differently.
 171     #[instrument(skip(self, expr), level = "debug")]
 172     pub(super) fn check_expr_with_expectation(
 173         &self,
 174         expr: &'tcx hir::Expr<'tcx>,
 175         expected: Expectation<'tcx>,
 176     ) -> Ty<'tcx> {
 177         self.check_expr_with_expectation_and_args(expr, expected, &[])
 178     }
 179
 180     /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
 181     /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
 182     pub(super) fn check_expr_with_expectation_and_args(
 183         &self,
 184         expr: &'tcx hir::Expr<'tcx>,
 185         expected: Expectation<'tcx>,
 186         args: &'tcx [hir::Expr<'tcx>],
 187     ) -> Ty<'tcx> {
 188         if self.tcx().sess.verbose() {
 189             // make this code only run with -Zverbose because it is probably slow
 190             if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
 191                 if !lint_str.contains('\n') {
 192                     debug!("expr text: {lint_str}");
 193                 } else {
 194                     let mut lines = lint_str.lines();
 195                     if let Some(line0) = lines.next() {
 196                         let remaining_lines = lines.count();
 197                         debug!("expr text: {line0}");
 198                         debug!("expr text: ...(and {remaining_lines} more lines)");
 199                     }
 200                 }
 201             }
 202         }
 203
 204         // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
 205         // without the final expr (e.g. `try { return; }`). We don't want to generate an
 206         // unreachable_code lint for it since warnings for autogenerated code are confusing.
 207         let is_try_block_generated_unit_expr = match expr.kind {
 208             ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
 209                 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
 210             }
 211
 212             _ => false,
 213         };
 214
 215         // Warn for expressions after diverging siblings.
 216         if !is_try_block_generated_unit_expr {
 217             self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
 218         }
 219
 220         // Hide the outer diverging and has_errors flags.
 221         let old_diverges = self.diverges.replace(Diverges::Maybe);
 222         let old_has_errors = self.has_errors.replace(false);
 223
 224         let ty = ensure_sufficient_stack(|| match &expr.kind {
 225             hir::ExprKind::Path(
 226                 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
 227             ) => self.check_expr_path(qpath, expr, args),
 228             _ => self.check_expr_kind(expr, expected),
 229         });
 230
 231         // Warn for non-block expressions with diverging children.
 232         match expr.kind {
 233             ExprKind::Block(..)
 234             | ExprKind::If(..)
 235             | ExprKind::Let(..)
 236             | ExprKind::Loop(..)
 237             | ExprKind::Match(..) => {}
 238             // If `expr` is a result of desugaring the try block and is an ok-wrapped
 239             // diverging expression (e.g. it arose from desugaring of `try { return }`),
 240             // we skip issuing a warning because it is autogenerated code.
 241             ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
 242             ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
 243             ExprKind::MethodCall(segment, ..) => {
 244                 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
 245             }
 246             _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
 247         }
 248
 249         // Any expression that produces a value of type `!` must have diverged
 250         if ty.is_never() {
 251             self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
 252         }
 253
 254         // Record the type, which applies it effects.
 255         // We need to do this after the warning above, so that
 256         // we don't warn for the diverging expression itself.
 257         self.write_ty(expr.hir_id, ty);
 258
 259         // Combine the diverging and has_error flags.
 260         self.diverges.set(self.diverges.get() | old_diverges);
 261         self.has_errors.set(self.has_errors.get() | old_has_errors);
 262
 263         debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
 264         debug!("... {:?}, expected is {:?}", ty, expected);
 265
 266         ty
 267     }
 268
 269     #[instrument(skip(self, expr), level = "debug")]
 270     fn check_expr_kind(
 271         &self,
 272         expr: &'tcx hir::Expr<'tcx>,
 273         expected: Expectation<'tcx>,
 274     ) -> Ty<'tcx> {
 275         trace!("expr={:#?}", expr);
 276
 277         let tcx = self.tcx;
 278         match expr.kind {
 279             ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
 280             ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
 281             ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
 282             ExprKind::Assign(lhs, rhs, span) => {
 283                 self.check_expr_assign(expr, expected, lhs, rhs, span)
 284             }
 285             ExprKind::AssignOp(op, lhs, rhs) => {
 286                 self.check_binop_assign(expr, op, lhs, rhs, expected)
 287             }
 288             ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
 289             ExprKind::AddrOf(kind, mutbl, oprnd) => {
 290                 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
 291             }
 292             ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
 293                 self.check_lang_item_path(lang_item, expr, hir_id)
 294             }
 295             ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
 296             ExprKind::InlineAsm(asm) => {
 297                 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
 298                 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
 299                 self.check_expr_asm(asm)
 300             }
 301             ExprKind::Break(destination, ref expr_opt) => {
 302                 self.check_expr_break(destination, expr_opt.as_deref(), expr)
 303             }
 304             ExprKind::Continue(destination) => {
 305                 if destination.target_id.is_ok() {
 306                     tcx.types.never
 307                 } else {
 308                     // There was an error; make type-check fail.
 309                     tcx.ty_error()
 310                 }
 311             }
 312             ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
 313             ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
 314             ExprKind::Loop(body, _, source, _) => {
 315                 self.check_expr_loop(body, source, expected, expr)
 316             }
 317             ExprKind::Match(discrim, arms, match_src) => {
 318                 self.check_match(expr, &discrim, arms, expected, match_src)
 319             }
 320             ExprKind::Closure(&Closure { capture_clause, fn_decl, body, movability, .. }) => {
 321                 self.check_expr_closure(expr, capture_clause, &fn_decl, body, movability, expected)
 322             }
 323             ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
 324             ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
 325             ExprKind::MethodCall(segment, receiver, args, _) => {
 326                 self.check_method_call(expr, segment, receiver, args, expected)
 327             }
 328             ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
 329             ExprKind::Type(e, t) => {
 330                 let ty = self.to_ty_saving_user_provided_ty(&t);
 331                 self.check_expr_eq_type(&e, ty);
 332                 ty
 333             }
 334             ExprKind::If(cond, then_expr, opt_else_expr) => {
 335                 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
 336             }
 337             ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
 338             ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
 339             ExprKind::ConstBlock(ref anon_const) => {
 340                 self.check_expr_const_block(anon_const, expected, expr)
 341             }
 342             ExprKind::Repeat(element, ref count) => {
 343                 self.check_expr_repeat(element, count, expected, expr)
 344             }
 345             ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
 346             ExprKind::Struct(qpath, fields, ref base_expr) => {
 347                 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
 348             }
 349             ExprKind::Field(base, field) => self.check_field(expr, &base, field),
 350             ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
 351             ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
 352             hir::ExprKind::Err => tcx.ty_error(),
 353         }
 354     }
 355
 356     fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
 357         let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
 358             ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
 359             _ => NoExpectation,
 360         });
 361         let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
 362         self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
 363         self.tcx.mk_box(referent_ty)
 364     }
 365
 366     fn check_expr_unary(
 367         &self,
 368         unop: hir::UnOp,
 369         oprnd: &'tcx hir::Expr<'tcx>,
 370         expected: Expectation<'tcx>,
 371         expr: &'tcx hir::Expr<'tcx>,
 372     ) -> Ty<'tcx> {
 373         let tcx = self.tcx;
 374         let expected_inner = match unop {
 375             hir::UnOp::Not | hir::UnOp::Neg => expected,
 376             hir::UnOp::Deref => NoExpectation,
 377         };
 378         let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
 379
 380         if !oprnd_t.references_error() {
 381             oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
 382             match unop {
 383                 hir::UnOp::Deref => {
 384                     if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
 385                         oprnd_t = ty;
 386                     } else {
 387                         let mut err = type_error_struct!(
 388                             tcx.sess,
 389                             expr.span,
 390                             oprnd_t,
 391                             E0614,
 392                             "type `{oprnd_t}` cannot be dereferenced",
 393                         );
 394                         let sp = tcx.sess.source_map().start_point(expr.span);
 395                         if let Some(sp) =
 396                             tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
 397                         {
 398                             err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
 399                         }
 400                         err.emit();
 401                         oprnd_t = tcx.ty_error();
 402                     }
 403                 }
 404                 hir::UnOp::Not => {
 405                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 406                     // If it's builtin, we can reuse the type, this helps inference.
 407                     if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
 408                         oprnd_t = result;
 409                     }
 410                 }
 411                 hir::UnOp::Neg => {
 412                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 413                     // If it's builtin, we can reuse the type, this helps inference.
 414                     if !oprnd_t.is_numeric() {
 415                         oprnd_t = result;
 416                     }
 417                 }
 418             }
 419         }
 420         oprnd_t
 421     }
 422
 423     fn check_expr_addr_of(
 424         &self,
 425         kind: hir::BorrowKind,
 426         mutbl: hir::Mutability,
 427         oprnd: &'tcx hir::Expr<'tcx>,
 428         expected: Expectation<'tcx>,
 429         expr: &'tcx hir::Expr<'tcx>,
 430     ) -> Ty<'tcx> {
 431         let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
 432             match ty.kind() {
 433                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 434                     if oprnd.is_syntactic_place_expr() {
 435                         // Places may legitimately have unsized types.
 436                         // For example, dereferences of a fat pointer and
 437                         // the last field of a struct can be unsized.
 438                         ExpectHasType(*ty)
 439                     } else {
 440                         Expectation::rvalue_hint(self, *ty)
 441                     }
 442                 }
 443                 _ => NoExpectation,
 444             }
 445         });
 446         let ty =
 447             self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
 448
 449         let tm = ty::TypeAndMut { ty, mutbl };
 450         match kind {
 451             _ if tm.ty.references_error() => self.tcx.ty_error(),
 452             hir::BorrowKind::Raw => {
 453                 self.check_named_place_expr(oprnd);
 454                 self.tcx.mk_ptr(tm)
 455             }
 456             hir::BorrowKind::Ref => {
 457                 // Note: at this point, we cannot say what the best lifetime
 458                 // is to use for resulting pointer.  We want to use the
 459                 // shortest lifetime possible so as to avoid spurious borrowck
 460                 // errors.  Moreover, the longest lifetime will depend on the
 461                 // precise details of the value whose address is being taken
 462                 // (and how long it is valid), which we don't know yet until
 463                 // type inference is complete.
 464                 //
 465                 // Therefore, here we simply generate a region variable. The
 466                 // region inferencer will then select a suitable value.
 467                 // Finally, borrowck will infer the value of the region again,
 468                 // this time with enough precision to check that the value
 469                 // whose address was taken can actually be made to live as long
 470                 // as it needs to live.
 471                 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
 472                 self.tcx.mk_ref(region, tm)
 473             }
 474         }
 475     }
 476
 477     /// Does this expression refer to a place that either:
 478     /// * Is based on a local or static.
 479     /// * Contains a dereference
 480     /// Note that the adjustments for the children of `expr` should already
 481     /// have been resolved.
 482     fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
 483         let is_named = oprnd.is_place_expr(|base| {
 484             // Allow raw borrows if there are any deref adjustments.
 485             //
 486             // const VAL: (i32,) = (0,);
 487             // const REF: &(i32,) = &(0,);
 488             //
 489             // &raw const VAL.0;            // ERROR
 490             // &raw const REF.0;            // OK, same as &raw const (*REF).0;
 491             //
 492             // This is maybe too permissive, since it allows
 493             // `let u = &raw const Box::new((1,)).0`, which creates an
 494             // immediately dangling raw pointer.
 495             self.typeck_results
 496                 .borrow()
 497                 .adjustments()
 498                 .get(base.hir_id)
 499                 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
 500         });
 501         if !is_named {
 502             self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
 503         }
 504     }
 505
 506     fn check_lang_item_path(
 507         &self,
 508         lang_item: hir::LangItem,
 509         expr: &'tcx hir::Expr<'tcx>,
 510         hir_id: Option<hir::HirId>,
 511     ) -> Ty<'tcx> {
 512         self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
 513     }
 514
 515     pub(crate) fn check_expr_path(
 516         &self,
 517         qpath: &'tcx hir::QPath<'tcx>,
 518         expr: &'tcx hir::Expr<'tcx>,
 519         args: &'tcx [hir::Expr<'tcx>],
 520     ) -> Ty<'tcx> {
 521         let tcx = self.tcx;
 522         let (res, opt_ty, segs) =
 523             self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
 524         let ty = match res {
 525             Res::Err => {
 526                 self.set_tainted_by_errors();
 527                 tcx.ty_error()
 528             }
 529             Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
 530                 report_unexpected_variant_res(tcx, res, qpath, expr.span);
 531                 tcx.ty_error()
 532             }
 533             _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
 534         };
 535
 536         if let ty::FnDef(did, ..) = *ty.kind() {
 537             let fn_sig = ty.fn_sig(tcx);
 538             if tcx.fn_sig(did).abi() == RustIntrinsic && tcx.item_name(did) == sym::transmute {
 539                 let from = fn_sig.inputs().skip_binder()[0];
 540                 let to = fn_sig.output().skip_binder();
 541                 // We defer the transmute to the end of typeck, once all inference vars have
 542                 // been resolved or we errored. This is important as we can only check transmute
 543                 // on concrete types, but the output type may not be known yet (it would only
 544                 // be known if explicitly specified via turbofish).
 545                 self.deferred_transmute_checks.borrow_mut().push((from, to, expr.hir_id));
 546             }
 547             if !tcx.features().unsized_fn_params {
 548                 // We want to remove some Sized bounds from std functions,
 549                 // but don't want to expose the removal to stable Rust.
 550                 // i.e., we don't want to allow
 551                 //
 552                 // ```rust
 553                 // drop as fn(str);
 554                 // ```
 555                 //
 556                 // to work in stable even if the Sized bound on `drop` is relaxed.
 557                 for i in 0..fn_sig.inputs().skip_binder().len() {
 558                     // We just want to check sizedness, so instead of introducing
 559                     // placeholder lifetimes with probing, we just replace higher lifetimes
 560                     // with fresh vars.
 561                     let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
 562                     let input = self.replace_bound_vars_with_fresh_vars(
 563                         span,
 564                         infer::LateBoundRegionConversionTime::FnCall,
 565                         fn_sig.input(i),
 566                     );
 567                     self.require_type_is_sized_deferred(
 568                         input,
 569                         span,
 570                         traits::SizedArgumentType(None),
 571                     );
 572                 }
 573             }
 574             // Here we want to prevent struct constructors from returning unsized types.
 575             // There were two cases this happened: fn pointer coercion in stable
 576             // and usual function call in presence of unsized_locals.
 577             // Also, as we just want to check sizedness, instead of introducing
 578             // placeholder lifetimes with probing, we just replace higher lifetimes
 579             // with fresh vars.
 580             let output = self.replace_bound_vars_with_fresh_vars(
 581                 expr.span,
 582                 infer::LateBoundRegionConversionTime::FnCall,
 583                 fn_sig.output(),
 584             );
 585             self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
 586         }
 587
 588         // We always require that the type provided as the value for
 589         // a type parameter outlives the moment of instantiation.
 590         let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
 591         self.add_wf_bounds(substs, expr);
 592
 593         ty
 594     }
 595
 596     fn check_expr_break(
 597         &self,
 598         destination: hir::Destination,
 599         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 600         expr: &'tcx hir::Expr<'tcx>,
 601     ) -> Ty<'tcx> {
 602         let tcx = self.tcx;
 603         if let Ok(target_id) = destination.target_id {
 604             let (e_ty, cause);
 605             if let Some(e) = expr_opt {
 606                 // If this is a break with a value, we need to type-check
 607                 // the expression. Get an expected type from the loop context.
 608                 let opt_coerce_to = {
 609                     // We should release `enclosing_breakables` before the `check_expr_with_hint`
 610                     // below, so can't move this block of code to the enclosing scope and share
 611                     // `ctxt` with the second `enclosing_breakables` borrow below.
 612                     let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 613                     match enclosing_breakables.opt_find_breakable(target_id) {
 614                         Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
 615                         None => {
 616                             // Avoid ICE when `break` is inside a closure (#65383).
 617                             return tcx.ty_error_with_message(
 618                                 expr.span,
 619                                 "break was outside loop, but no error was emitted",
 620                             );
 621                         }
 622                     }
 623                 };
 624
 625                 // If the loop context is not a `loop { }`, then break with
 626                 // a value is illegal, and `opt_coerce_to` will be `None`.
 627                 // Just set expectation to error in that case.
 628                 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
 629
 630                 // Recurse without `enclosing_breakables` borrowed.
 631                 e_ty = self.check_expr_with_hint(e, coerce_to);
 632                 cause = self.misc(e.span);
 633             } else {
 634                 // Otherwise, this is a break *without* a value. That's
 635                 // always legal, and is equivalent to `break ()`.
 636                 e_ty = tcx.mk_unit();
 637                 cause = self.misc(expr.span);
 638             }
 639
 640             // Now that we have type-checked `expr_opt`, borrow
 641             // the `enclosing_loops` field and let's coerce the
 642             // type of `expr_opt` into what is expected.
 643             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 644             let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
 645                 // Avoid ICE when `break` is inside a closure (#65383).
 646                 return tcx.ty_error_with_message(
 647                     expr.span,
 648                     "break was outside loop, but no error was emitted",
 649                 );
 650             };
 651
 652             if let Some(ref mut coerce) = ctxt.coerce {
 653                 if let Some(ref e) = expr_opt {
 654                     coerce.coerce(self, &cause, e, e_ty);
 655                 } else {
 656                     assert!(e_ty.is_unit());
 657                     let ty = coerce.expected_ty();
 658                     coerce.coerce_forced_unit(
 659                         self,
 660                         &cause,
 661                         &mut |mut err| {
 662                             self.suggest_mismatched_types_on_tail(
 663                                 &mut err, expr, ty, e_ty, target_id,
 664                             );
 665                             if let Some(val) = ty_kind_suggestion(ty) {
 666                                 let label = destination
 667                                     .label
 668                                     .map(|l| format!(" {}", l.ident))
 669                                     .unwrap_or_else(String::new);
 670                                 err.span_suggestion(
 671                                     expr.span,
 672                                     "give it a value of the expected type",
 673                                     format!("break{label} {val}"),
 674                                     Applicability::HasPlaceholders,
 675                                 );
 676                             }
 677                         },
 678                         false,
 679                     );
 680                 }
 681             } else {
 682                 // If `ctxt.coerce` is `None`, we can just ignore
 683                 // the type of the expression.  This is because
 684                 // either this was a break *without* a value, in
 685                 // which case it is always a legal type (`()`), or
 686                 // else an error would have been flagged by the
 687                 // `loops` pass for using break with an expression
 688                 // where you are not supposed to.
 689                 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
 690             }
 691
 692             // If we encountered a `break`, then (no surprise) it may be possible to break from the
 693             // loop... unless the value being returned from the loop diverges itself, e.g.
 694             // `break return 5` or `break loop {}`.
 695             ctxt.may_break |= !self.diverges.get().is_always();
 696
 697             // the type of a `break` is always `!`, since it diverges
 698             tcx.types.never
 699         } else {
 700             // Otherwise, we failed to find the enclosing loop;
 701             // this can only happen if the `break` was not
 702             // inside a loop at all, which is caught by the
 703             // loop-checking pass.
 704             let err = self.tcx.ty_error_with_message(
 705                 expr.span,
 706                 "break was outside loop, but no error was emitted",
 707             );
 708
 709             // We still need to assign a type to the inner expression to
 710             // prevent the ICE in #43162.
 711             if let Some(e) = expr_opt {
 712                 self.check_expr_with_hint(e, err);
 713
 714                 // ... except when we try to 'break rust;'.
 715                 // ICE this expression in particular (see #43162).
 716                 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
 717                     if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
 718                         fatally_break_rust(self.tcx.sess);
 719                     }
 720                 }
 721             }
 722
 723             // There was an error; make type-check fail.
 724             err
 725         }
 726     }
 727
 728     fn check_expr_return(
 729         &self,
 730         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 731         expr: &'tcx hir::Expr<'tcx>,
 732     ) -> Ty<'tcx> {
 733         if self.ret_coercion.is_none() {
 734             let mut err = ReturnStmtOutsideOfFnBody {
 735                 span: expr.span,
 736                 encl_body_span: None,
 737                 encl_fn_span: None,
 738             };
 739
 740             let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
 741
 742             if let Some(hir::Node::Item(hir::Item {
 743                 kind: hir::ItemKind::Fn(..),
 744                 span: encl_fn_span,
 745                 ..
 746             }))
 747             | Some(hir::Node::TraitItem(hir::TraitItem {
 748                 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
 749                 span: encl_fn_span,
 750                 ..
 751             }))
 752             | Some(hir::Node::ImplItem(hir::ImplItem {
 753                 kind: hir::ImplItemKind::Fn(..),
 754                 span: encl_fn_span,
 755                 ..
 756             })) = self.tcx.hir().find_by_def_id(encl_item_id.def_id)
 757             {
 758                 // We are inside a function body, so reporting "return statement
 759                 // outside of function body" needs an explanation.
 760
 761                 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
 762
 763                 // If this didn't hold, we would not have to report an error in
 764                 // the first place.
 765                 assert_ne!(encl_item_id.def_id, encl_body_owner_id);
 766
 767                 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
 768                 let encl_body = self.tcx.hir().body(encl_body_id);
 769
 770                 err.encl_body_span = Some(encl_body.value.span);
 771                 err.encl_fn_span = Some(*encl_fn_span);
 772             }
 773
 774             self.tcx.sess.emit_err(err);
 775
 776             if let Some(e) = expr_opt {
 777                 // We still have to type-check `e` (issue #86188), but calling
 778                 // `check_return_expr` only works inside fn bodies.
 779                 self.check_expr(e);
 780             }
 781         } else if let Some(e) = expr_opt {
 782             if self.ret_coercion_span.get().is_none() {
 783                 self.ret_coercion_span.set(Some(e.span));
 784             }
 785             self.check_return_expr(e, true);
 786         } else {
 787             let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
 788             if self.ret_coercion_span.get().is_none() {
 789                 self.ret_coercion_span.set(Some(expr.span));
 790             }
 791             let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
 792             if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
 793                 coercion.coerce_forced_unit(
 794                     self,
 795                     &cause,
 796                     &mut |db| {
 797                         let span = fn_decl.output.span();
 798                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
 799                             db.span_label(
 800                                 span,
 801                                 format!("expected `{snippet}` because of this return type"),
 802                             );
 803                         }
 804                     },
 805                     true,
 806                 );
 807             } else {
 808                 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
 809             }
 810         }
 811         self.tcx.types.never
 812     }
 813
 814     /// `explicit_return` is `true` if we're checking an explicit `return expr`,
 815     /// and `false` if we're checking a trailing expression.
 816     pub(super) fn check_return_expr(
 817         &self,
 818         return_expr: &'tcx hir::Expr<'tcx>,
 819         explicit_return: bool,
 820     ) {
 821         let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
 822             span_bug!(return_expr.span, "check_return_expr called outside fn body")
 823         });
 824
 825         let ret_ty = ret_coercion.borrow().expected_ty();
 826         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
 827         let mut span = return_expr.span;
 828         // Use the span of the trailing expression for our cause,
 829         // not the span of the entire function
 830         if !explicit_return {
 831             if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
 832                 span = last_expr.span;
 833             }
 834         }
 835         ret_coercion.borrow_mut().coerce(
 836             self,
 837             &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
 838             return_expr,
 839             return_expr_ty,
 840         );
 841
 842         if self.return_type_has_opaque {
 843             // Point any obligations that were registered due to opaque type
 844             // inference at the return expression.
 845             self.select_obligations_where_possible(false, |errors| {
 846                 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
 847             });
 848         }
 849     }
 850
 851     fn point_at_return_for_opaque_ty_error(
 852         &self,
 853         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
 854         span: Span,
 855         return_expr_ty: Ty<'tcx>,
 856     ) {
 857         // Don't point at the whole block if it's empty
 858         if span == self.tcx.hir().span(self.body_id) {
 859             return;
 860         }
 861         for err in errors {
 862             let cause = &mut err.obligation.cause;
 863             if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
 864                 let new_cause = ObligationCause::new(
 865                     cause.span,
 866                     cause.body_id,
 867                     ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
 868                 );
 869                 *cause = new_cause;
 870             }
 871         }
 872     }
 873
 874     pub(crate) fn check_lhs_assignable(
 875         &self,
 876         lhs: &'tcx hir::Expr<'tcx>,
 877         err_code: &'static str,
 878         op_span: Span,
 879         adjust_err: impl FnOnce(&mut Diagnostic),
 880     ) {
 881         if lhs.is_syntactic_place_expr() {
 882             return;
 883         }
 884
 885         // FIXME: Make this use Diagnostic once error codes can be dynamically set.
 886         let mut err = self.tcx.sess.struct_span_err_with_code(
 887             op_span,
 888             "invalid left-hand side of assignment",
 889             DiagnosticId::Error(err_code.into()),
 890         );
 891         err.span_label(lhs.span, "cannot assign to this expression");
 892
 893         self.comes_from_while_condition(lhs.hir_id, |expr| {
 894             err.span_suggestion_verbose(
 895                 expr.span.shrink_to_lo(),
 896                 "you might have meant to use pattern destructuring",
 897                 "let ",
 898                 Applicability::MachineApplicable,
 899             );
 900         });
 901
 902         adjust_err(&mut err);
 903
 904         err.emit();
 905     }
 906
 907     // Check if an expression `original_expr_id` comes from the condition of a while loop,
 908     // as opposed from the body of a while loop, which we can naively check by iterating
 909     // parents until we find a loop...
 910     pub(super) fn comes_from_while_condition(
 911         &self,
 912         original_expr_id: HirId,
 913         then: impl FnOnce(&hir::Expr<'_>),
 914     ) {
 915         let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
 916         while let Some(node) = self.tcx.hir().find(parent) {
 917             match node {
 918                 hir::Node::Expr(hir::Expr {
 919                     kind:
 920                         hir::ExprKind::Loop(
 921                             hir::Block {
 922                                 expr:
 923                                     Some(hir::Expr {
 924                                         kind:
 925                                             hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
 926                                         ..
 927                                     }),
 928                                 ..
 929                             },
 930                             _,
 931                             hir::LoopSource::While,
 932                             _,
 933                         ),
 934                     ..
 935                 }) => {
 936                     // Check if our original expression is a child of the condition of a while loop
 937                     let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
 938                         self.tcx.hir().find_parent_node(*id)
 939                     })
 940                     .take_while(|id| *id != parent)
 941                     .any(|id| id == expr.hir_id);
 942                     // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
 943                     // where `while let` was more likely intended.
 944                     if expr_is_ancestor {
 945                         then(expr);
 946                     }
 947                     break;
 948                 }
 949                 hir::Node::Item(_)
 950                 | hir::Node::ImplItem(_)
 951                 | hir::Node::TraitItem(_)
 952                 | hir::Node::Crate(_) => break,
 953                 _ => {
 954                     parent = self.tcx.hir().get_parent_node(parent);
 955                 }
 956             }
 957         }
 958     }
 959
 960     // A generic function for checking the 'then' and 'else' clauses in an 'if'
 961     // or 'if-else' expression.
 962     fn check_then_else(
 963         &self,
 964         cond_expr: &'tcx hir::Expr<'tcx>,
 965         then_expr: &'tcx hir::Expr<'tcx>,
 966         opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
 967         sp: Span,
 968         orig_expected: Expectation<'tcx>,
 969     ) -> Ty<'tcx> {
 970         let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
 971
 972         self.warn_if_unreachable(
 973             cond_expr.hir_id,
 974             then_expr.span,
 975             "block in `if` or `while` expression",
 976         );
 977
 978         let cond_diverges = self.diverges.get();
 979         self.diverges.set(Diverges::Maybe);
 980
 981         let expected = orig_expected.adjust_for_branches(self);
 982         let then_ty = self.check_expr_with_expectation(then_expr, expected);
 983         let then_diverges = self.diverges.get();
 984         self.diverges.set(Diverges::Maybe);
 985
 986         // We've already taken the expected type's preferences
 987         // into account when typing the `then` branch. To figure
 988         // out the initial shot at a LUB, we thus only consider
 989         // `expected` if it represents a *hard* constraint
 990         // (`only_has_type`); otherwise, we just go with a
 991         // fresh type variable.
 992         let coerce_to_ty = expected.coercion_target_type(self, sp);
 993         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
 994
 995         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
 996
 997         if let Some(else_expr) = opt_else_expr {
 998             let else_ty = self.check_expr_with_expectation(else_expr, expected);
 999             let else_diverges = self.diverges.get();
1000
1001             let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1002             let if_cause = self.if_cause(
1003                 sp,
1004                 cond_expr.span,
1005                 then_expr,
1006                 else_expr,
1007                 then_ty,
1008                 else_ty,
1009                 opt_suggest_box_span,
1010             );
1011
1012             coerce.coerce(self, &if_cause, else_expr, else_ty);
1013
1014             // We won't diverge unless both branches do (or the condition does).
1015             self.diverges.set(cond_diverges | then_diverges & else_diverges);
1016         } else {
1017             self.if_fallback_coercion(sp, then_expr, &mut coerce);
1018
1019             // If the condition is false we can't diverge.
1020             self.diverges.set(cond_diverges);
1021         }
1022
1023         let result_ty = coerce.complete(self);
1024         if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1025     }
1026
1027     /// Type check assignment expression `expr` of form `lhs = rhs`.
1028     /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1029     fn check_expr_assign(
1030         &self,
1031         expr: &'tcx hir::Expr<'tcx>,
1032         expected: Expectation<'tcx>,
1033         lhs: &'tcx hir::Expr<'tcx>,
1034         rhs: &'tcx hir::Expr<'tcx>,
1035         span: Span,
1036     ) -> Ty<'tcx> {
1037         let expected_ty = expected.coercion_target_type(self, expr.span);
1038         if expected_ty == self.tcx.types.bool {
1039             // The expected type is `bool` but this will result in `()` so we can reasonably
1040             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1041             // The likely cause of this is `if foo = bar { .. }`.
1042             let actual_ty = self.tcx.mk_unit();
1043             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1044             let lhs_ty = self.check_expr(&lhs);
1045             let rhs_ty = self.check_expr(&rhs);
1046             let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1047                 (Applicability::MachineApplicable, true)
1048             } else if let ExprKind::Binary(
1049                 Spanned { node: hir::BinOpKind::And | hir::BinOpKind::Or, .. },
1050                 _,
1051                 rhs_expr,
1052             ) = lhs.kind
1053             {
1054                 // if x == 1 && y == 2 { .. }
1055                 //                 +
1056                 let actual_lhs_ty = self.check_expr(&rhs_expr);
1057                 (Applicability::MaybeIncorrect, self.can_coerce(rhs_ty, actual_lhs_ty))
1058             } else if let ExprKind::Binary(
1059                 Spanned { node: hir::BinOpKind::And | hir::BinOpKind::Or, .. },
1060                 lhs_expr,
1061                 _,
1062             ) = rhs.kind
1063             {
1064                 // if x == 1 && y == 2 { .. }
1065                 //       +
1066                 let actual_rhs_ty = self.check_expr(&lhs_expr);
1067                 (Applicability::MaybeIncorrect, self.can_coerce(actual_rhs_ty, lhs_ty))
1068             } else {
1069                 (Applicability::MaybeIncorrect, false)
1070             };
1071             if !lhs.is_syntactic_place_expr()
1072                 && lhs.is_approximately_pattern()
1073                 && !matches!(lhs.kind, hir::ExprKind::Lit(_))
1074             {
1075                 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1076                 let hir = self.tcx.hir();
1077                 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1078                     hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1079                 {
1080                     err.span_suggestion_verbose(
1081                         expr.span.shrink_to_lo(),
1082                         "you might have meant to use pattern matching",
1083                         "let ",
1084                         applicability,
1085                     );
1086                 };
1087             }
1088             if eq {
1089                 err.span_suggestion_verbose(
1090                     span.shrink_to_hi(),
1091                     "you might have meant to compare for equality",
1092                     '=',
1093                     applicability,
1094                 );
1095             }
1096
1097             // If the assignment expression itself is ill-formed, don't
1098             // bother emitting another error
1099             if lhs_ty.references_error() || rhs_ty.references_error() {
1100                 err.delay_as_bug()
1101             } else {
1102                 err.emit();
1103             }
1104             return self.tcx.ty_error();
1105         }
1106
1107         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1108
1109         let suggest_deref_binop = |err: &mut Diagnostic, rhs_ty: Ty<'tcx>| {
1110             if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1111                 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1112                 // unsized, do not suggest dereferencing it.
1113                 let lhs_deref_ty_is_sized = self
1114                     .infcx
1115                     .type_implements_trait(
1116                         self.tcx.lang_items().sized_trait().unwrap(),
1117                         lhs_deref_ty,
1118                         ty::List::empty(),
1119                         self.param_env,
1120                     )
1121                     .may_apply();
1122                 if lhs_deref_ty_is_sized && self.can_coerce(rhs_ty, lhs_deref_ty) {
1123                     err.span_suggestion_verbose(
1124                         lhs.span.shrink_to_lo(),
1125                         "consider dereferencing here to assign to the mutably borrowed value",
1126                         "*",
1127                         Applicability::MachineApplicable,
1128                     );
1129                 }
1130             }
1131         };
1132
1133         self.check_lhs_assignable(lhs, "E0070", span, |err| {
1134             let rhs_ty = self.check_expr(&rhs);
1135             suggest_deref_binop(err, rhs_ty);
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.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1149
1150         if lhs_ty.references_error() || rhs_ty.references_error() {
1151             self.tcx.ty_error()
1152         } else {
1153             self.tcx.mk_unit()
1154         }
1155     }
1156
1157     pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1158         // for let statements, this is done in check_stmt
1159         let init = let_expr.init;
1160         self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1161         // otherwise check exactly as a let statement
1162         self.check_decl(let_expr.into());
1163         // but return a bool, for this is a boolean expression
1164         self.tcx.types.bool
1165     }
1166
1167     fn check_expr_loop(
1168         &self,
1169         body: &'tcx hir::Block<'tcx>,
1170         source: hir::LoopSource,
1171         expected: Expectation<'tcx>,
1172         expr: &'tcx hir::Expr<'tcx>,
1173     ) -> Ty<'tcx> {
1174         let coerce = match source {
1175             // you can only use break with a value from a normal `loop { }`
1176             hir::LoopSource::Loop => {
1177                 let coerce_to = expected.coercion_target_type(self, body.span);
1178                 Some(CoerceMany::new(coerce_to))
1179             }
1180
1181             hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1182         };
1183
1184         let ctxt = BreakableCtxt {
1185             coerce,
1186             may_break: false, // Will get updated if/when we find a `break`.
1187         };
1188
1189         let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1190             self.check_block_no_value(&body);
1191         });
1192
1193         if ctxt.may_break {
1194             // No way to know whether it's diverging because
1195             // of a `break` or an outer `break` or `return`.
1196             self.diverges.set(Diverges::Maybe);
1197         }
1198
1199         // If we permit break with a value, then result type is
1200         // the LUB of the breaks (possibly ! if none); else, it
1201         // is nil. This makes sense because infinite loops
1202         // (which would have type !) are only possible iff we
1203         // permit break with a value [1].
1204         if ctxt.coerce.is_none() && !ctxt.may_break {
1205             // [1]
1206             self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1207         }
1208         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1209     }
1210
1211     /// Checks a method call.
1212     fn check_method_call(
1213         &self,
1214         expr: &'tcx hir::Expr<'tcx>,
1215         segment: &hir::PathSegment<'_>,
1216         rcvr: &'tcx hir::Expr<'tcx>,
1217         args: &'tcx [hir::Expr<'tcx>],
1218         expected: Expectation<'tcx>,
1219     ) -> Ty<'tcx> {
1220         let rcvr_t = self.check_expr(&rcvr);
1221         // no need to check for bot/err -- callee does that
1222         let rcvr_t = self.structurally_resolved_type(rcvr.span, rcvr_t);
1223         let span = segment.ident.span;
1224
1225         let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1226             Ok(method) => {
1227                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1228                 // trigger this codepath causing `structurally_resolved_type` to emit an error.
1229
1230                 self.write_method_call(expr.hir_id, method);
1231                 Ok(method)
1232             }
1233             Err(error) => {
1234                 if segment.ident.name != kw::Empty {
1235                     if let Some(mut err) = self.report_method_error(
1236                         span,
1237                         rcvr_t,
1238                         segment.ident,
1239                         SelfSource::MethodCall(rcvr),
1240                         error,
1241                         Some((rcvr, args)),
1242                     ) {
1243                         err.emit();
1244                     }
1245                 }
1246                 Err(())
1247             }
1248         };
1249
1250         // Call the generic checker.
1251         self.check_method_argument_types(span, expr, method, &args, DontTupleArguments, expected)
1252     }
1253
1254     fn check_expr_cast(
1255         &self,
1256         e: &'tcx hir::Expr<'tcx>,
1257         t: &'tcx hir::Ty<'tcx>,
1258         expr: &'tcx hir::Expr<'tcx>,
1259     ) -> Ty<'tcx> {
1260         // Find the type of `e`. Supply hints based on the type we are casting to,
1261         // if appropriate.
1262         let t_cast = self.to_ty_saving_user_provided_ty(t);
1263         let t_cast = self.resolve_vars_if_possible(t_cast);
1264         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1265         let t_expr = self.resolve_vars_if_possible(t_expr);
1266
1267         // Eagerly check for some obvious errors.
1268         if t_expr.references_error() || t_cast.references_error() {
1269             self.tcx.ty_error()
1270         } else {
1271             // Defer other checks until we're done type checking.
1272             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1273             match cast::check_cast(self, e, t_expr, t_cast, t.span, expr.span) {
1274                 CastCheckResult::Ok => t_cast,
1275                 CastCheckResult::Deferred(cast_check) => {
1276                     debug!(
1277                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1278                         t_cast, t_expr, cast_check,
1279                     );
1280                     deferred_cast_checks.push(cast_check);
1281                     t_cast
1282                 }
1283                 CastCheckResult::Err(ErrorGuaranteed { .. }) => self.tcx.ty_error(),
1284             }
1285         }
1286     }
1287
1288     fn check_expr_array(
1289         &self,
1290         args: &'tcx [hir::Expr<'tcx>],
1291         expected: Expectation<'tcx>,
1292         expr: &'tcx hir::Expr<'tcx>,
1293     ) -> Ty<'tcx> {
1294         let element_ty = if !args.is_empty() {
1295             let coerce_to = expected
1296                 .to_option(self)
1297                 .and_then(|uty| match *uty.kind() {
1298                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1299                     _ => None,
1300                 })
1301                 .unwrap_or_else(|| {
1302                     self.next_ty_var(TypeVariableOrigin {
1303                         kind: TypeVariableOriginKind::TypeInference,
1304                         span: expr.span,
1305                     })
1306                 });
1307             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1308             assert_eq!(self.diverges.get(), Diverges::Maybe);
1309             for e in args {
1310                 let e_ty = self.check_expr_with_hint(e, coerce_to);
1311                 let cause = self.misc(e.span);
1312                 coerce.coerce(self, &cause, e, e_ty);
1313             }
1314             coerce.complete(self)
1315         } else {
1316             self.next_ty_var(TypeVariableOrigin {
1317                 kind: TypeVariableOriginKind::TypeInference,
1318                 span: expr.span,
1319             })
1320         };
1321         let array_len = args.len() as u64;
1322         self.suggest_array_len(expr, array_len);
1323         self.tcx.mk_array(element_ty, array_len)
1324     }
1325
1326     fn suggest_array_len(&self, expr: &'tcx hir::Expr<'tcx>, array_len: u64) {
1327         let parent_node = self.tcx.hir().parent_iter(expr.hir_id).find(|(_, node)| {
1328             !matches!(node, hir::Node::Expr(hir::Expr { kind: hir::ExprKind::AddrOf(..), .. }))
1329         });
1330         let Some((_,
1331             hir::Node::Local(hir::Local { ty: Some(ty), .. })
1332             | hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _), .. }))
1333         ) = parent_node else {
1334             return
1335         };
1336         if let hir::TyKind::Array(_, length) = ty.peel_refs().kind
1337             && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
1338             && let Some(span) = self.tcx.hir().opt_span(hir_id)
1339         {
1340             match self.tcx.sess.diagnostic().steal_diagnostic(span, StashKey::UnderscoreForArrayLengths) {
1341                 Some(mut err) => {
1342                     err.span_suggestion(
1343                         span,
1344                         "consider specifying the array length",
1345                         array_len,
1346                         Applicability::MaybeIncorrect,
1347                     );
1348                     err.emit();
1349                 }
1350                 None => ()
1351             }
1352         }
1353     }
1354
1355     fn check_expr_const_block(
1356         &self,
1357         anon_const: &'tcx hir::AnonConst,
1358         expected: Expectation<'tcx>,
1359         _expr: &'tcx hir::Expr<'tcx>,
1360     ) -> Ty<'tcx> {
1361         let body = self.tcx.hir().body(anon_const.body);
1362
1363         // Create a new function context.
1364         let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1365         crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1366
1367         let ty = fcx.check_expr_with_expectation(&body.value, expected);
1368         fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1369         fcx.write_ty(anon_const.hir_id, ty);
1370         ty
1371     }
1372
1373     fn check_expr_repeat(
1374         &self,
1375         element: &'tcx hir::Expr<'tcx>,
1376         count: &'tcx hir::ArrayLen,
1377         expected: Expectation<'tcx>,
1378         expr: &'tcx hir::Expr<'tcx>,
1379     ) -> Ty<'tcx> {
1380         let tcx = self.tcx;
1381         let count = self.array_length_to_const(count);
1382         if let Some(count) = count.try_eval_usize(tcx, self.param_env) {
1383             self.suggest_array_len(expr, count);
1384         }
1385
1386         let uty = match expected {
1387             ExpectHasType(uty) => match *uty.kind() {
1388                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1389                 _ => None,
1390             },
1391             _ => None,
1392         };
1393
1394         let (element_ty, t) = match uty {
1395             Some(uty) => {
1396                 self.check_expr_coercable_to_type(&element, uty, None);
1397                 (uty, uty)
1398             }
1399             None => {
1400                 let ty = self.next_ty_var(TypeVariableOrigin {
1401                     kind: TypeVariableOriginKind::MiscVariable,
1402                     span: element.span,
1403                 });
1404                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1405                 (element_ty, ty)
1406             }
1407         };
1408
1409         if element_ty.references_error() {
1410             return tcx.ty_error();
1411         }
1412
1413         self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1414
1415         tcx.mk_ty(ty::Array(t, count))
1416     }
1417
1418     fn check_repeat_element_needs_copy_bound(
1419         &self,
1420         element: &hir::Expr<'_>,
1421         count: ty::Const<'tcx>,
1422         element_ty: Ty<'tcx>,
1423     ) {
1424         let tcx = self.tcx;
1425         // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1426         match &element.kind {
1427             hir::ExprKind::ConstBlock(..) => return,
1428             hir::ExprKind::Path(qpath) => {
1429                 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1430                 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1431                 {
1432                     return;
1433                 }
1434             }
1435             _ => {}
1436         }
1437         // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1438         // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1439         let is_const_fn = match element.kind {
1440             hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1441                 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1442                 _ => false,
1443             },
1444             _ => false,
1445         };
1446
1447         // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1448         // don't copy that one element, we move it. Only check for Copy if the length is larger.
1449         if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1450             let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1451             let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1452             self.require_type_meets(element_ty, element.span, code, lang_item);
1453         }
1454     }
1455
1456     fn check_expr_tuple(
1457         &self,
1458         elts: &'tcx [hir::Expr<'tcx>],
1459         expected: Expectation<'tcx>,
1460         expr: &'tcx hir::Expr<'tcx>,
1461     ) -> Ty<'tcx> {
1462         let flds = expected.only_has_type(self).and_then(|ty| {
1463             let ty = self.resolve_vars_with_obligations(ty);
1464             match ty.kind() {
1465                 ty::Tuple(flds) => Some(&flds[..]),
1466                 _ => None,
1467             }
1468         });
1469
1470         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1471             Some(fs) if i < fs.len() => {
1472                 let ety = fs[i];
1473                 self.check_expr_coercable_to_type(&e, ety, None);
1474                 ety
1475             }
1476             _ => self.check_expr_with_expectation(&e, NoExpectation),
1477         });
1478         let tuple = self.tcx.mk_tup(elt_ts_iter);
1479         if tuple.references_error() {
1480             self.tcx.ty_error()
1481         } else {
1482             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1483             tuple
1484         }
1485     }
1486
1487     fn check_expr_struct(
1488         &self,
1489         expr: &hir::Expr<'_>,
1490         expected: Expectation<'tcx>,
1491         qpath: &QPath<'_>,
1492         fields: &'tcx [hir::ExprField<'tcx>],
1493         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1494     ) -> Ty<'tcx> {
1495         // Find the relevant variant
1496         let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1497             self.check_struct_fields_on_error(fields, base_expr);
1498             return self.tcx.ty_error();
1499         };
1500
1501         // Prohibit struct expressions when non-exhaustive flag is set.
1502         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1503         if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1504             self.tcx
1505                 .sess
1506                 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1507         }
1508
1509         self.check_expr_struct_fields(
1510             adt_ty,
1511             expected,
1512             expr.hir_id,
1513             qpath.span(),
1514             variant,
1515             fields,
1516             base_expr,
1517             expr.span,
1518         );
1519
1520         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1521         adt_ty
1522     }
1523
1524     fn check_expr_struct_fields(
1525         &self,
1526         adt_ty: Ty<'tcx>,
1527         expected: Expectation<'tcx>,
1528         expr_id: hir::HirId,
1529         span: Span,
1530         variant: &'tcx ty::VariantDef,
1531         ast_fields: &'tcx [hir::ExprField<'tcx>],
1532         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1533         expr_span: Span,
1534     ) {
1535         let tcx = self.tcx;
1536
1537         let expected_inputs =
1538             self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1539         let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1540             expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1541         } else {
1542             adt_ty
1543         };
1544         // re-link the regions that EIfEO can erase.
1545         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1546
1547         let ty::Adt(adt, substs) = adt_ty.kind() else {
1548             span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1549         };
1550         let adt_kind = adt.adt_kind();
1551
1552         let mut remaining_fields = variant
1553             .fields
1554             .iter()
1555             .enumerate()
1556             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1557             .collect::<FxHashMap<_, _>>();
1558
1559         let mut seen_fields = FxHashMap::default();
1560
1561         let mut error_happened = false;
1562
1563         // Type-check each field.
1564         for (idx, field) in ast_fields.iter().enumerate() {
1565             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1566             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1567                 seen_fields.insert(ident, field.span);
1568                 self.write_field_index(field.hir_id, i);
1569
1570                 // We don't look at stability attributes on
1571                 // struct-like enums (yet...), but it's definitely not
1572                 // a bug to have constructed one.
1573                 if adt_kind != AdtKind::Enum {
1574                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1575                 }
1576
1577                 self.field_ty(field.span, v_field, substs)
1578             } else {
1579                 error_happened = true;
1580                 if let Some(prev_span) = seen_fields.get(&ident) {
1581                     tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1582                         span: field.ident.span,
1583                         prev_span: *prev_span,
1584                         ident,
1585                     });
1586                 } else {
1587                     self.report_unknown_field(
1588                         adt_ty,
1589                         variant,
1590                         field,
1591                         ast_fields,
1592                         adt.variant_descr(),
1593                         expr_span,
1594                     );
1595                 }
1596
1597                 tcx.ty_error()
1598             };
1599
1600             // Make sure to give a type to the field even if there's
1601             // an error, so we can continue type-checking.
1602             let ty = self.check_expr_with_hint(&field.expr, field_type);
1603             let (_, diag) =
1604                 self.demand_coerce_diag(&field.expr, ty, field_type, None, AllowTwoPhase::No);
1605
1606             if let Some(mut diag) = diag {
1607                 if idx == ast_fields.len() - 1 && remaining_fields.is_empty() {
1608                     self.suggest_fru_from_range(field, variant, substs, &mut diag);
1609                 }
1610                 diag.emit();
1611             }
1612         }
1613
1614         // Make sure the programmer specified correct number of fields.
1615         if adt_kind == AdtKind::Union {
1616             if ast_fields.len() != 1 {
1617                 struct_span_err!(
1618                     tcx.sess,
1619                     span,
1620                     E0784,
1621                     "union expressions should have exactly one field",
1622                 )
1623                 .emit();
1624             }
1625         }
1626
1627         // If check_expr_struct_fields hit an error, do not attempt to populate
1628         // the fields with the base_expr. This could cause us to hit errors later
1629         // when certain fields are assumed to exist that in fact do not.
1630         if error_happened {
1631             return;
1632         }
1633
1634         if let Some(base_expr) = base_expr {
1635             // FIXME: We are currently creating two branches here in order to maintain
1636             // consistency. But they should be merged as much as possible.
1637             let fru_tys = if self.tcx.features().type_changing_struct_update {
1638                 if adt.is_struct() {
1639                     // Make some fresh substitutions for our ADT type.
1640                     let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1641                     // We do subtyping on the FRU fields first, so we can
1642                     // learn exactly what types we expect the base expr
1643                     // needs constrained to be compatible with the struct
1644                     // type we expect from the expectation value.
1645                     let fru_tys = variant
1646                         .fields
1647                         .iter()
1648                         .map(|f| {
1649                             let fru_ty = self.normalize_associated_types_in(
1650                                 expr_span,
1651                                 self.field_ty(base_expr.span, f, fresh_substs),
1652                             );
1653                             let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1654                             if let Some(_) = remaining_fields.remove(&ident) {
1655                                 let target_ty = self.field_ty(base_expr.span, f, substs);
1656                                 let cause = self.misc(base_expr.span);
1657                                 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1658                                     Ok(InferOk { obligations, value: () }) => {
1659                                         self.register_predicates(obligations)
1660                                     }
1661                                     Err(_) => {
1662                                         // This should never happen, since we're just subtyping the
1663                                         // remaining_fields, but it's fine to emit this, I guess.
1664                                         self.err_ctxt()
1665                                             .report_mismatched_types(
1666                                                 &cause,
1667                                                 target_ty,
1668                                                 fru_ty,
1669                                                 FieldMisMatch(variant.name, ident.name),
1670                                             )
1671                                             .emit();
1672                                     }
1673                                 }
1674                             }
1675                             self.resolve_vars_if_possible(fru_ty)
1676                         })
1677                         .collect();
1678                     // The use of fresh substs that we have subtyped against
1679                     // our base ADT type's fields allows us to guide inference
1680                     // along so that, e.g.
1681                     // ```
1682                     // MyStruct<'a, F1, F2, const C: usize> {
1683                     //     f: F1,
1684                     //     // Other fields that reference `'a`, `F2`, and `C`
1685                     // }
1686                     //
1687                     // let x = MyStruct {
1688                     //    f: 1usize,
1689                     //    ..other_struct
1690                     // };
1691                     // ```
1692                     // will have the `other_struct` expression constrained to
1693                     // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1694                     // This is important to allow coercions to happen in
1695                     // `other_struct` itself. See `coerce-in-base-expr.rs`.
1696                     let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1697                     self.check_expr_has_type_or_error(
1698                         base_expr,
1699                         self.resolve_vars_if_possible(fresh_base_ty),
1700                         |_| {},
1701                     );
1702                     fru_tys
1703                 } else {
1704                     // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1705                     // type errors on that expression, too.
1706                     self.check_expr(base_expr);
1707                     self.tcx
1708                         .sess
1709                         .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1710                     return;
1711                 }
1712             } else {
1713                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1714                     let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1715                     let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1716                         (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1717                         _ => false,
1718                     };
1719                     if self.tcx.sess.is_nightly_build() && same_adt {
1720                         feature_err(
1721                             &self.tcx.sess.parse_sess,
1722                             sym::type_changing_struct_update,
1723                             base_expr.span,
1724                             "type changing struct updating is experimental",
1725                         )
1726                         .emit();
1727                     }
1728                 });
1729                 match adt_ty.kind() {
1730                     ty::Adt(adt, substs) if adt.is_struct() => variant
1731                         .fields
1732                         .iter()
1733                         .map(|f| {
1734                             self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1735                         })
1736                         .collect(),
1737                     _ => {
1738                         self.tcx
1739                             .sess
1740                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1741                         return;
1742                     }
1743                 }
1744             };
1745             self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1746         } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1747             debug!(?remaining_fields);
1748             let private_fields: Vec<&ty::FieldDef> = variant
1749                 .fields
1750                 .iter()
1751                 .filter(|field| !field.vis.is_accessible_from(tcx.parent_module(expr_id), tcx))
1752                 .collect();
1753
1754             if !private_fields.is_empty() {
1755                 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1756             } else {
1757                 self.report_missing_fields(
1758                     adt_ty,
1759                     span,
1760                     remaining_fields,
1761                     variant,
1762                     ast_fields,
1763                     substs,
1764                 );
1765             }
1766         }
1767     }
1768
1769     fn check_struct_fields_on_error(
1770         &self,
1771         fields: &'tcx [hir::ExprField<'tcx>],
1772         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1773     ) {
1774         for field in fields {
1775             self.check_expr(&field.expr);
1776         }
1777         if let Some(base) = *base_expr {
1778             self.check_expr(&base);
1779         }
1780     }
1781
1782     /// Report an error for a struct field expression when there are fields which aren't provided.
1783     ///
1784     /// ```text
1785     /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1786     ///  --> src/main.rs:8:5
1787     ///   |
1788     /// 8 |     foo::Foo {};
1789     ///   |     ^^^^^^^^ missing `you_can_use_this_field`
1790     ///
1791     /// error: aborting due to previous error
1792     /// ```
1793     fn report_missing_fields(
1794         &self,
1795         adt_ty: Ty<'tcx>,
1796         span: Span,
1797         remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1798         variant: &'tcx ty::VariantDef,
1799         ast_fields: &'tcx [hir::ExprField<'tcx>],
1800         substs: SubstsRef<'tcx>,
1801     ) {
1802         let len = remaining_fields.len();
1803
1804         let mut displayable_field_names: Vec<&str> =
1805             remaining_fields.keys().map(|ident| ident.as_str()).collect();
1806         // sorting &str primitives here, sort_unstable is ok
1807         displayable_field_names.sort_unstable();
1808
1809         let mut truncated_fields_error = String::new();
1810         let remaining_fields_names = match &displayable_field_names[..] {
1811             [field1] => format!("`{}`", field1),
1812             [field1, field2] => format!("`{field1}` and `{field2}`"),
1813             [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1814             _ => {
1815                 truncated_fields_error =
1816                     format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1817                 displayable_field_names
1818                     .iter()
1819                     .take(3)
1820                     .map(|n| format!("`{n}`"))
1821                     .collect::<Vec<_>>()
1822                     .join(", ")
1823             }
1824         };
1825
1826         let mut err = struct_span_err!(
1827             self.tcx.sess,
1828             span,
1829             E0063,
1830             "missing field{} {}{} in initializer of `{}`",
1831             pluralize!(len),
1832             remaining_fields_names,
1833             truncated_fields_error,
1834             adt_ty
1835         );
1836         err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1837
1838         if let Some(last) = ast_fields.last() {
1839             self.suggest_fru_from_range(last, variant, substs, &mut err);
1840         }
1841
1842         err.emit();
1843     }
1844
1845     /// If the last field is a range literal, but it isn't supposed to be, then they probably
1846     /// meant to use functional update syntax.
1847     fn suggest_fru_from_range(
1848         &self,
1849         last_expr_field: &hir::ExprField<'tcx>,
1850         variant: &ty::VariantDef,
1851         substs: SubstsRef<'tcx>,
1852         err: &mut Diagnostic,
1853     ) {
1854         // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1855         if let ExprKind::Struct(
1856                 QPath::LangItem(LangItem::Range, ..),
1857                 &[ref range_start, ref range_end],
1858                 _,
1859             ) = last_expr_field.expr.kind
1860             && let variant_field =
1861                 variant.fields.iter().find(|field| field.ident(self.tcx) == last_expr_field.ident)
1862             && let range_def_id = self.tcx.lang_items().range_struct()
1863             && variant_field
1864                 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1865                 .map(|adt| adt.did())
1866                 != range_def_id
1867         {
1868             let instead = self
1869                 .tcx
1870                 .sess
1871                 .source_map()
1872                 .span_to_snippet(range_end.expr.span)
1873                 .map(|s| format!(" from `{s}`"))
1874                 .unwrap_or_default();
1875             err.span_suggestion(
1876                 range_start.span.shrink_to_hi(),
1877                 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1878                 ",",
1879                 Applicability::MaybeIncorrect,
1880             );
1881         }
1882     }
1883
1884     /// Report an error for a struct field expression when there are invisible fields.
1885     ///
1886     /// ```text
1887     /// error: cannot construct `Foo` with struct literal syntax due to private fields
1888     ///  --> src/main.rs:8:5
1889     ///   |
1890     /// 8 |     foo::Foo {};
1891     ///   |     ^^^^^^^^
1892     ///
1893     /// error: aborting due to previous error
1894     /// ```
1895     fn report_private_fields(
1896         &self,
1897         adt_ty: Ty<'tcx>,
1898         span: Span,
1899         private_fields: Vec<&ty::FieldDef>,
1900         used_fields: &'tcx [hir::ExprField<'tcx>],
1901     ) {
1902         let mut err = self.tcx.sess.struct_span_err(
1903             span,
1904             &format!(
1905                 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1906             ),
1907         );
1908         let (used_private_fields, remaining_private_fields): (
1909             Vec<(Symbol, Span, bool)>,
1910             Vec<(Symbol, Span, bool)>,
1911         ) = private_fields
1912             .iter()
1913             .map(|field| {
1914                 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1915                     Some(used_field) => (field.name, used_field.span, true),
1916                     None => (field.name, self.tcx.def_span(field.did), false),
1917                 }
1918             })
1919             .partition(|field| field.2);
1920         err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1921         if !remaining_private_fields.is_empty() {
1922             let remaining_private_fields_len = remaining_private_fields.len();
1923             let names = match &remaining_private_fields
1924                 .iter()
1925                 .map(|(name, _, _)| name)
1926                 .collect::<Vec<_>>()[..]
1927             {
1928                 _ if remaining_private_fields_len > 6 => String::new(),
1929                 [name] => format!("`{name}` "),
1930                 [names @ .., last] => {
1931                     let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1932                     format!("{} and `{last}` ", names.join(", "))
1933                 }
1934                 [] => unreachable!(),
1935             };
1936             err.note(format!(
1937                 "... and other private field{s} {names}that {were} not provided",
1938                 s = pluralize!(remaining_private_fields_len),
1939                 were = pluralize!("was", remaining_private_fields_len),
1940             ));
1941         }
1942         err.emit();
1943     }
1944
1945     fn report_unknown_field(
1946         &self,
1947         ty: Ty<'tcx>,
1948         variant: &'tcx ty::VariantDef,
1949         field: &hir::ExprField<'_>,
1950         skip_fields: &[hir::ExprField<'_>],
1951         kind_name: &str,
1952         expr_span: Span,
1953     ) {
1954         if variant.is_recovered() {
1955             self.set_tainted_by_errors();
1956             return;
1957         }
1958         let mut err = self.err_ctxt().type_error_struct_with_diag(
1959             field.ident.span,
1960             |actual| match ty.kind() {
1961                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1962                     self.tcx.sess,
1963                     field.ident.span,
1964                     E0559,
1965                     "{} `{}::{}` has no field named `{}`",
1966                     kind_name,
1967                     actual,
1968                     variant.name,
1969                     field.ident
1970                 ),
1971                 _ => struct_span_err!(
1972                     self.tcx.sess,
1973                     field.ident.span,
1974                     E0560,
1975                     "{} `{}` has no field named `{}`",
1976                     kind_name,
1977                     actual,
1978                     field.ident
1979                 ),
1980             },
1981             ty,
1982         );
1983
1984         let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1985         match variant.ctor_kind {
1986             CtorKind::Fn => match ty.kind() {
1987                 ty::Adt(adt, ..) if adt.is_enum() => {
1988                     err.span_label(
1989                         variant_ident_span,
1990                         format!(
1991                             "`{adt}::{variant}` defined here",
1992                             adt = ty,
1993                             variant = variant.name,
1994                         ),
1995                     );
1996                     err.span_label(field.ident.span, "field does not exist");
1997                     err.span_suggestion_verbose(
1998                         expr_span,
1999                         &format!(
2000                             "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
2001                             adt = ty,
2002                             variant = variant.name,
2003                         ),
2004                         format!(
2005                             "{adt}::{variant}(/* fields */)",
2006                             adt = ty,
2007                             variant = variant.name,
2008                         ),
2009                         Applicability::HasPlaceholders,
2010                     );
2011                 }
2012                 _ => {
2013                     err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
2014                     err.span_label(field.ident.span, "field does not exist");
2015                     err.span_suggestion_verbose(
2016                         expr_span,
2017                         &format!(
2018                             "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
2019                             adt = ty,
2020                             kind_name = kind_name,
2021                         ),
2022                         format!("{adt}(/* fields */)", adt = ty),
2023                         Applicability::HasPlaceholders,
2024                     );
2025                 }
2026             },
2027             _ => {
2028                 // prevent all specified fields from being suggested
2029                 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
2030                 if let Some(field_name) = self.suggest_field_name(
2031                     variant,
2032                     field.ident.name,
2033                     skip_fields.collect(),
2034                     expr_span,
2035                 ) {
2036                     err.span_suggestion(
2037                         field.ident.span,
2038                         "a field with a similar name exists",
2039                         field_name,
2040                         Applicability::MaybeIncorrect,
2041                     );
2042                 } else {
2043                     match ty.kind() {
2044                         ty::Adt(adt, ..) => {
2045                             if adt.is_enum() {
2046                                 err.span_label(
2047                                     field.ident.span,
2048                                     format!("`{}::{}` does not have this field", ty, variant.name),
2049                                 );
2050                             } else {
2051                                 err.span_label(
2052                                     field.ident.span,
2053                                     format!("`{ty}` does not have this field"),
2054                                 );
2055                             }
2056                             let available_field_names =
2057                                 self.available_field_names(variant, expr_span);
2058                             if !available_field_names.is_empty() {
2059                                 err.note(&format!(
2060                                     "available fields are: {}",
2061                                     self.name_series_display(available_field_names)
2062                                 ));
2063                             }
2064                         }
2065                         _ => bug!("non-ADT passed to report_unknown_field"),
2066                     }
2067                 };
2068             }
2069         }
2070         err.emit();
2071     }
2072
2073     // Return a hint about the closest match in field names
2074     fn suggest_field_name(
2075         &self,
2076         variant: &'tcx ty::VariantDef,
2077         field: Symbol,
2078         skip: Vec<Symbol>,
2079         // The span where stability will be checked
2080         span: Span,
2081     ) -> Option<Symbol> {
2082         let names = variant
2083             .fields
2084             .iter()
2085             .filter_map(|field| {
2086                 // ignore already set fields and private fields from non-local crates
2087                 // and unstable fields.
2088                 if skip.iter().any(|&x| x == field.name)
2089                     || (!variant.def_id.is_local() && !field.vis.is_public())
2090                     || matches!(
2091                         self.tcx.eval_stability(field.did, None, span, None),
2092                         stability::EvalResult::Deny { .. }
2093                     )
2094                 {
2095                     None
2096                 } else {
2097                     Some(field.name)
2098                 }
2099             })
2100             .collect::<Vec<Symbol>>();
2101
2102         find_best_match_for_name(&names, field, None)
2103     }
2104
2105     fn available_field_names(
2106         &self,
2107         variant: &'tcx ty::VariantDef,
2108         access_span: Span,
2109     ) -> Vec<Symbol> {
2110         variant
2111             .fields
2112             .iter()
2113             .filter(|field| {
2114                 let def_scope = self
2115                     .tcx
2116                     .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2117                     .1;
2118                 field.vis.is_accessible_from(def_scope, self.tcx)
2119                     && !matches!(
2120                         self.tcx.eval_stability(field.did, None, access_span, None),
2121                         stability::EvalResult::Deny { .. }
2122                     )
2123             })
2124             .filter(|field| !self.tcx.is_doc_hidden(field.did))
2125             .map(|field| field.name)
2126             .collect()
2127     }
2128
2129     fn name_series_display(&self, names: Vec<Symbol>) -> String {
2130         // dynamic limit, to never omit just one field
2131         let limit = if names.len() == 6 { 6 } else { 5 };
2132         let mut display =
2133             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2134         if names.len() > limit {
2135             display = format!("{} ... and {} others", display, names.len() - limit);
2136         }
2137         display
2138     }
2139
2140     // Check field access expressions
2141     fn check_field(
2142         &self,
2143         expr: &'tcx hir::Expr<'tcx>,
2144         base: &'tcx hir::Expr<'tcx>,
2145         field: Ident,
2146     ) -> Ty<'tcx> {
2147         debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2148         let base_ty = self.check_expr(base);
2149         let base_ty = self.structurally_resolved_type(base.span, base_ty);
2150         let mut private_candidate = None;
2151         let mut autoderef = self.autoderef(expr.span, base_ty);
2152         while let Some((deref_base_ty, _)) = autoderef.next() {
2153             debug!("deref_base_ty: {:?}", deref_base_ty);
2154             match deref_base_ty.kind() {
2155                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2156                     debug!("struct named {:?}", deref_base_ty);
2157                     let (ident, def_scope) =
2158                         self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2159                     let fields = &base_def.non_enum_variant().fields;
2160                     if let Some(index) = fields
2161                         .iter()
2162                         .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2163                     {
2164                         let field = &fields[index];
2165                         let field_ty = self.field_ty(expr.span, field, substs);
2166                         // Save the index of all fields regardless of their visibility in case
2167                         // of error recovery.
2168                         self.write_field_index(expr.hir_id, index);
2169                         let adjustments = self.adjust_steps(&autoderef);
2170                         if field.vis.is_accessible_from(def_scope, self.tcx) {
2171                             self.apply_adjustments(base, adjustments);
2172                             self.register_predicates(autoderef.into_obligations());
2173
2174                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2175                             return field_ty;
2176                         }
2177                         private_candidate = Some((adjustments, base_def.did(), field_ty));
2178                     }
2179                 }
2180                 ty::Tuple(tys) => {
2181                     let fstr = field.as_str();
2182                     if let Ok(index) = fstr.parse::<usize>() {
2183                         if fstr == index.to_string() {
2184                             if let Some(&field_ty) = tys.get(index) {
2185                                 let adjustments = self.adjust_steps(&autoderef);
2186                                 self.apply_adjustments(base, adjustments);
2187                                 self.register_predicates(autoderef.into_obligations());
2188
2189                                 self.write_field_index(expr.hir_id, index);
2190                                 return field_ty;
2191                             }
2192                         }
2193                     }
2194                 }
2195                 _ => {}
2196             }
2197         }
2198         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2199
2200         if let Some((adjustments, did, field_ty)) = private_candidate {
2201             // (#90483) apply adjustments to avoid ExprUseVisitor from
2202             // creating erroneous projection.
2203             self.apply_adjustments(base, adjustments);
2204             self.ban_private_field_access(expr, base_ty, field, did);
2205             return field_ty;
2206         }
2207
2208         if field.name == kw::Empty {
2209         } else if self.method_exists(field, base_ty, expr.hir_id, true) {
2210             self.ban_take_value_of_method(expr, base_ty, field);
2211         } else if !base_ty.is_primitive_ty() {
2212             self.ban_nonexisting_field(field, base, expr, base_ty);
2213         } else {
2214             let field_name = field.to_string();
2215             let mut err = type_error_struct!(
2216                 self.tcx().sess,
2217                 field.span,
2218                 base_ty,
2219                 E0610,
2220                 "`{base_ty}` is a primitive type and therefore doesn't have fields",
2221             );
2222             let is_valid_suffix = |field: &str| {
2223                 if field == "f32" || field == "f64" {
2224                     return true;
2225                 }
2226                 let mut chars = field.chars().peekable();
2227                 match chars.peek() {
2228                     Some('e') | Some('E') => {
2229                         chars.next();
2230                         if let Some(c) = chars.peek()
2231                             && !c.is_numeric() && *c != '-' && *c != '+'
2232                         {
2233                             return false;
2234                         }
2235                         while let Some(c) = chars.peek() {
2236                             if !c.is_numeric() {
2237                                 break;
2238                             }
2239                             chars.next();
2240                         }
2241                     }
2242                     _ => (),
2243                 }
2244                 let suffix = chars.collect::<String>();
2245                 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2246             };
2247             let maybe_partial_suffix = |field: &str| -> Option<&str> {
2248                 let first_chars = ['f', 'l'];
2249                 if field.len() >= 1
2250                     && field.to_lowercase().starts_with(first_chars)
2251                     && field[1..].chars().all(|c| c.is_ascii_digit())
2252                 {
2253                     if field.to_lowercase().starts_with(['f']) { Some("f32") } else { Some("f64") }
2254                 } else {
2255                     None
2256                 }
2257             };
2258             if let ty::Infer(ty::IntVar(_)) = base_ty.kind()
2259                 && let ExprKind::Lit(Spanned {
2260                     node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2261                     ..
2262                 }) = base.kind
2263                 && !base.span.from_expansion()
2264             {
2265                 if is_valid_suffix(&field_name) {
2266                     err.span_suggestion_verbose(
2267                         field.span.shrink_to_lo(),
2268                         "if intended to be a floating point literal, consider adding a `0` after the period",
2269                         '0',
2270                         Applicability::MaybeIncorrect,
2271                     );
2272                 } else if let Some(correct_suffix) = maybe_partial_suffix(&field_name) {
2273                     err.span_suggestion_verbose(
2274                         field.span,
2275                         format!("if intended to be a floating point literal, consider adding a `0` after the period and a `{correct_suffix}` suffix"),
2276                         format!("0{correct_suffix}"),
2277                         Applicability::MaybeIncorrect,
2278                     );
2279                 }
2280             }
2281             err.emit();
2282         }
2283
2284         self.tcx().ty_error()
2285     }
2286
2287     fn suggest_await_on_field_access(
2288         &self,
2289         err: &mut Diagnostic,
2290         field_ident: Ident,
2291         base: &'tcx hir::Expr<'tcx>,
2292         ty: Ty<'tcx>,
2293     ) {
2294         let output_ty = match self.get_impl_future_output_ty(ty) {
2295             Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2296             _ => return,
2297         };
2298         let mut add_label = true;
2299         if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2300             // no field access on enum type
2301             if !def.is_enum() {
2302                 if def
2303                     .non_enum_variant()
2304                     .fields
2305                     .iter()
2306                     .any(|field| field.ident(self.tcx) == field_ident)
2307                 {
2308                     add_label = false;
2309                     err.span_label(
2310                         field_ident.span,
2311                         "field not available in `impl Future`, but it is available in its `Output`",
2312                     );
2313                     err.span_suggestion_verbose(
2314                         base.span.shrink_to_hi(),
2315                         "consider `await`ing on the `Future` and access the field of its `Output`",
2316                         ".await",
2317                         Applicability::MaybeIncorrect,
2318                     );
2319                 }
2320             }
2321         }
2322         if add_label {
2323             err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2324         }
2325     }
2326
2327     fn ban_nonexisting_field(
2328         &self,
2329         ident: Ident,
2330         base: &'tcx hir::Expr<'tcx>,
2331         expr: &'tcx hir::Expr<'tcx>,
2332         base_ty: Ty<'tcx>,
2333     ) {
2334         debug!(
2335             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, base_ty={:?}",
2336             ident, base, expr, base_ty
2337         );
2338         let mut err = self.no_such_field_err(ident, base_ty, base.hir_id);
2339
2340         match *base_ty.peel_refs().kind() {
2341             ty::Array(_, len) => {
2342                 self.maybe_suggest_array_indexing(&mut err, expr, base, ident, len);
2343             }
2344             ty::RawPtr(..) => {
2345                 self.suggest_first_deref_field(&mut err, expr, base, ident);
2346             }
2347             ty::Adt(def, _) if !def.is_enum() => {
2348                 self.suggest_fields_on_recordish(&mut err, def, ident, expr.span);
2349             }
2350             ty::Param(param_ty) => {
2351                 self.point_at_param_definition(&mut err, param_ty);
2352             }
2353             ty::Opaque(_, _) => {
2354                 self.suggest_await_on_field_access(&mut err, ident, base, base_ty.peel_refs());
2355             }
2356             _ => {}
2357         }
2358
2359         self.suggest_fn_call(&mut err, base, base_ty, |output_ty| {
2360             if let ty::Adt(def, _) = output_ty.kind() && !def.is_enum() {
2361                 def.non_enum_variant().fields.iter().any(|field| {
2362                     field.ident(self.tcx) == ident
2363                         && field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
2364                 })
2365             } else if let ty::Tuple(tys) = output_ty.kind()
2366                 && let Ok(idx) = ident.as_str().parse::<usize>()
2367             {
2368                 idx < tys.len()
2369             } else {
2370                 false
2371             }
2372         });
2373
2374         if ident.name == kw::Await {
2375             // We know by construction that `<expr>.await` is either on Rust 2015
2376             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2377             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2378             err.help_use_latest_edition();
2379         }
2380
2381         err.emit();
2382     }
2383
2384     fn ban_private_field_access(
2385         &self,
2386         expr: &hir::Expr<'_>,
2387         expr_t: Ty<'tcx>,
2388         field: Ident,
2389         base_did: DefId,
2390     ) {
2391         let struct_path = self.tcx().def_path_str(base_did);
2392         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2393         let mut err = struct_span_err!(
2394             self.tcx().sess,
2395             field.span,
2396             E0616,
2397             "field `{field}` of {kind_name} `{struct_path}` is private",
2398         );
2399         err.span_label(field.span, "private field");
2400         // Also check if an accessible method exists, which is often what is meant.
2401         if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2402         {
2403             self.suggest_method_call(
2404                 &mut err,
2405                 &format!("a method `{field}` also exists, call it with parentheses"),
2406                 field,
2407                 expr_t,
2408                 expr,
2409                 None,
2410             );
2411         }
2412         err.emit();
2413     }
2414
2415     fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2416         let mut err = type_error_struct!(
2417             self.tcx().sess,
2418             field.span,
2419             expr_t,
2420             E0615,
2421             "attempted to take value of method `{field}` on type `{expr_t}`",
2422         );
2423         err.span_label(field.span, "method, not a field");
2424         let expr_is_call =
2425             if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2426                 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2427             {
2428                 expr.hir_id == callee.hir_id
2429             } else {
2430                 false
2431             };
2432         let expr_snippet =
2433             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2434         let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2435         let after_open = expr.span.lo() + rustc_span::BytePos(1);
2436         let before_close = expr.span.hi() - rustc_span::BytePos(1);
2437
2438         if expr_is_call && is_wrapped {
2439             err.multipart_suggestion(
2440                 "remove wrapping parentheses to call the method",
2441                 vec![
2442                     (expr.span.with_hi(after_open), String::new()),
2443                     (expr.span.with_lo(before_close), String::new()),
2444                 ],
2445                 Applicability::MachineApplicable,
2446             );
2447         } else if !self.expr_in_place(expr.hir_id) {
2448             // Suggest call parentheses inside the wrapping parentheses
2449             let span = if is_wrapped {
2450                 expr.span.with_lo(after_open).with_hi(before_close)
2451             } else {
2452                 expr.span
2453             };
2454             self.suggest_method_call(
2455                 &mut err,
2456                 "use parentheses to call the method",
2457                 field,
2458                 expr_t,
2459                 expr,
2460                 Some(span),
2461             );
2462         } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2463             && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2464             && let ExprKind::Field(base_expr, _) = expr.kind
2465             && adt_def.variants().len() == 1
2466             && adt_def
2467                 .variants()
2468                 .iter()
2469                 .next()
2470                 .unwrap()
2471                 .fields
2472                 .iter()
2473                 .any(|f| f.ident(self.tcx) == field)
2474         {
2475             err.multipart_suggestion(
2476                 "to access the field, dereference first",
2477                 vec![
2478                     (base_expr.span.shrink_to_lo(), "(*".to_string()),
2479                     (base_expr.span.shrink_to_hi(), ")".to_string()),
2480                 ],
2481                 Applicability::MaybeIncorrect,
2482             );
2483         } else {
2484             err.help("methods are immutable and cannot be assigned to");
2485         }
2486
2487         err.emit();
2488     }
2489
2490     fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2491         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2492         let generic_param = generics.type_param(&param, self.tcx);
2493         if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2494             return;
2495         }
2496         let param_def_id = generic_param.def_id;
2497         let param_hir_id = match param_def_id.as_local() {
2498             Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2499             None => return,
2500         };
2501         let param_span = self.tcx.hir().span(param_hir_id);
2502         let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2503
2504         err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2505     }
2506
2507     fn suggest_fields_on_recordish(
2508         &self,
2509         err: &mut Diagnostic,
2510         def: ty::AdtDef<'tcx>,
2511         field: Ident,
2512         access_span: Span,
2513     ) {
2514         if let Some(suggested_field_name) =
2515             self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2516         {
2517             err.span_suggestion(
2518                 field.span,
2519                 "a field with a similar name exists",
2520                 suggested_field_name,
2521                 Applicability::MaybeIncorrect,
2522             );
2523         } else {
2524             err.span_label(field.span, "unknown field");
2525             let struct_variant_def = def.non_enum_variant();
2526             let field_names = self.available_field_names(struct_variant_def, access_span);
2527             if !field_names.is_empty() {
2528                 err.note(&format!(
2529                     "available fields are: {}",
2530                     self.name_series_display(field_names),
2531                 ));
2532             }
2533         }
2534     }
2535
2536     fn maybe_suggest_array_indexing(
2537         &self,
2538         err: &mut Diagnostic,
2539         expr: &hir::Expr<'_>,
2540         base: &hir::Expr<'_>,
2541         field: Ident,
2542         len: ty::Const<'tcx>,
2543     ) {
2544         if let (Some(len), Ok(user_index)) =
2545             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2546             && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2547         {
2548             let help = "instead of using tuple indexing, use array indexing";
2549             let suggestion = format!("{base}[{field}]");
2550             let applicability = if len < user_index {
2551                 Applicability::MachineApplicable
2552             } else {
2553                 Applicability::MaybeIncorrect
2554             };
2555             err.span_suggestion(expr.span, help, suggestion, applicability);
2556         }
2557     }
2558
2559     fn suggest_first_deref_field(
2560         &self,
2561         err: &mut Diagnostic,
2562         expr: &hir::Expr<'_>,
2563         base: &hir::Expr<'_>,
2564         field: Ident,
2565     ) {
2566         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2567             let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2568             let suggestion = format!("(*{base}).{field}");
2569             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2570         }
2571     }
2572
2573     fn no_such_field_err(
2574         &self,
2575         field: Ident,
2576         expr_t: Ty<'tcx>,
2577         id: HirId,
2578     ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2579         let span = field.span;
2580         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2581
2582         let mut err = type_error_struct!(
2583             self.tcx().sess,
2584             field.span,
2585             expr_t,
2586             E0609,
2587             "no field `{field}` on type `{expr_t}`",
2588         );
2589
2590         // try to add a suggestion in case the field is a nested field of a field of the Adt
2591         let mod_id = self.tcx.parent_module(id).to_def_id();
2592         if let Some((fields, substs)) =
2593             self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2594         {
2595             let candidate_fields: Vec<_> = fields
2596                 .filter_map(|candidate_field| {
2597                     self.check_for_nested_field_satisfying(
2598                         span,
2599                         &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2600                         candidate_field,
2601                         substs,
2602                         vec![],
2603                         mod_id,
2604                     )
2605                 })
2606                 .map(|mut field_path| {
2607                     field_path.pop();
2608                     field_path
2609                         .iter()
2610                         .map(|id| id.name.to_ident_string())
2611                         .collect::<Vec<String>>()
2612                         .join(".")
2613                 })
2614                 .collect::<Vec<_>>();
2615
2616             let len = candidate_fields.len();
2617             if len > 0 {
2618                 err.span_suggestions(
2619                     field.span.shrink_to_lo(),
2620                     format!(
2621                         "{} of the expressions' fields {} a field of the same name",
2622                         if len > 1 { "some" } else { "one" },
2623                         if len > 1 { "have" } else { "has" },
2624                     ),
2625                     candidate_fields.iter().map(|path| format!("{path}.")),
2626                     Applicability::MaybeIncorrect,
2627                 );
2628             }
2629         }
2630         err
2631     }
2632
2633     pub(crate) fn get_field_candidates_considering_privacy(
2634         &self,
2635         span: Span,
2636         base_ty: Ty<'tcx>,
2637         mod_id: DefId,
2638     ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2639         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2640
2641         for (base_t, _) in self.autoderef(span, base_ty) {
2642             match base_t.kind() {
2643                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2644                     let tcx = self.tcx;
2645                     let fields = &base_def.non_enum_variant().fields;
2646                     // Some struct, e.g. some that impl `Deref`, have all private fields
2647                     // because you're expected to deref them to access the _real_ fields.
2648                     // This, for example, will help us suggest accessing a field through a `Box<T>`.
2649                     if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2650                         continue;
2651                     }
2652                     return Some((
2653                         fields
2654                             .iter()
2655                             .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2656                             // For compile-time reasons put a limit on number of fields we search
2657                             .take(100),
2658                         substs,
2659                     ));
2660                 }
2661                 _ => {}
2662             }
2663         }
2664         None
2665     }
2666
2667     /// This method is called after we have encountered a missing field error to recursively
2668     /// search for the field
2669     pub(crate) fn check_for_nested_field_satisfying(
2670         &self,
2671         span: Span,
2672         matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2673         candidate_field: &ty::FieldDef,
2674         subst: SubstsRef<'tcx>,
2675         mut field_path: Vec<Ident>,
2676         mod_id: DefId,
2677     ) -> Option<Vec<Ident>> {
2678         debug!(
2679             "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2680             span, candidate_field, field_path
2681         );
2682
2683         if field_path.len() > 3 {
2684             // For compile-time reasons and to avoid infinite recursion we only check for fields
2685             // up to a depth of three
2686             None
2687         } else {
2688             field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2689             let field_ty = candidate_field.ty(self.tcx, subst);
2690             if matches(candidate_field, field_ty) {
2691                 return Some(field_path);
2692             } else if let Some((nested_fields, subst)) =
2693                 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2694             {
2695                 // recursively search fields of `candidate_field` if it's a ty::Adt
2696                 for field in nested_fields {
2697                     if let Some(field_path) = self.check_for_nested_field_satisfying(
2698                         span,
2699                         matches,
2700                         field,
2701                         subst,
2702                         field_path.clone(),
2703                         mod_id,
2704                     ) {
2705                         return Some(field_path);
2706                     }
2707                 }
2708             }
2709             None
2710         }
2711     }
2712
2713     fn check_expr_index(
2714         &self,
2715         base: &'tcx hir::Expr<'tcx>,
2716         idx: &'tcx hir::Expr<'tcx>,
2717         expr: &'tcx hir::Expr<'tcx>,
2718     ) -> Ty<'tcx> {
2719         let base_t = self.check_expr(&base);
2720         let idx_t = self.check_expr(&idx);
2721
2722         if base_t.references_error() {
2723             base_t
2724         } else if idx_t.references_error() {
2725             idx_t
2726         } else {
2727             let base_t = self.structurally_resolved_type(base.span, base_t);
2728             match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2729                 Some((index_ty, element_ty)) => {
2730                     // two-phase not needed because index_ty is never mutable
2731                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2732                     self.select_obligations_where_possible(false, |errors| {
2733                         self.point_at_index_if_possible(errors, idx.span)
2734                     });
2735                     element_ty
2736                 }
2737                 None => {
2738                     let mut err = type_error_struct!(
2739                         self.tcx.sess,
2740                         expr.span,
2741                         base_t,
2742                         E0608,
2743                         "cannot index into a value of type `{base_t}`",
2744                     );
2745                     // Try to give some advice about indexing tuples.
2746                     if let ty::Tuple(..) = base_t.kind() {
2747                         let mut needs_note = true;
2748                         // If the index is an integer, we can show the actual
2749                         // fixed expression:
2750                         if let ExprKind::Lit(ref lit) = idx.kind {
2751                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2752                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2753                                 if let Ok(snip) = snip {
2754                                     err.span_suggestion(
2755                                         expr.span,
2756                                         "to access tuple elements, use",
2757                                         format!("{snip}.{i}"),
2758                                         Applicability::MachineApplicable,
2759                                     );
2760                                     needs_note = false;
2761                                 }
2762                             }
2763                         }
2764                         if needs_note {
2765                             err.help(
2766                                 "to access tuple elements, use tuple indexing \
2767                                         syntax (e.g., `tuple.0`)",
2768                             );
2769                         }
2770                     }
2771                     err.emit();
2772                     self.tcx.ty_error()
2773                 }
2774             }
2775         }
2776     }
2777
2778     fn point_at_index_if_possible(
2779         &self,
2780         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2781         span: Span,
2782     ) {
2783         for error in errors {
2784             match error.obligation.predicate.kind().skip_binder() {
2785                 ty::PredicateKind::Trait(predicate)
2786                     if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2787                 }
2788                 _ => continue,
2789             }
2790             error.obligation.cause.span = span;
2791         }
2792     }
2793
2794     fn check_expr_yield(
2795         &self,
2796         value: &'tcx hir::Expr<'tcx>,
2797         expr: &'tcx hir::Expr<'tcx>,
2798         src: &'tcx hir::YieldSource,
2799     ) -> Ty<'tcx> {
2800         match self.resume_yield_tys {
2801             Some((resume_ty, yield_ty)) => {
2802                 self.check_expr_coercable_to_type(&value, yield_ty, None);
2803
2804                 resume_ty
2805             }
2806             // Given that this `yield` expression was generated as a result of lowering a `.await`,
2807             // we know that the yield type must be `()`; however, the context won't contain this
2808             // information. Hence, we check the source of the yield expression here and check its
2809             // value's type against `()` (this check should always hold).
2810             None if src.is_await() => {
2811                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2812                 self.tcx.mk_unit()
2813             }
2814             _ => {
2815                 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2816                 // Avoid expressions without types during writeback (#78653).
2817                 self.check_expr(value);
2818                 self.tcx.mk_unit()
2819             }
2820         }
2821     }
2822
2823     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2824         let needs = if is_input { Needs::None } else { Needs::MutPlace };
2825         let ty = self.check_expr_with_needs(expr, needs);
2826         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2827
2828         if !is_input && !expr.is_syntactic_place_expr() {
2829             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2830             err.span_label(expr.span, "cannot assign to this expression");
2831             err.emit();
2832         }
2833
2834         // If this is an input value, we require its type to be fully resolved
2835         // at this point. This allows us to provide helpful coercions which help
2836         // pass the type candidate list in a later pass.
2837         //
2838         // We don't require output types to be resolved at this point, which
2839         // allows them to be inferred based on how they are used later in the
2840         // function.
2841         if is_input {
2842             let ty = self.structurally_resolved_type(expr.span, ty);
2843             match *ty.kind() {
2844                 ty::FnDef(..) => {
2845                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2846                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2847                 }
2848                 ty::Ref(_, base_ty, mutbl) => {
2849                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2850                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2851                 }
2852                 _ => {}
2853             }
2854         }
2855     }
2856
2857     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2858         for (op, _op_sp) in asm.operands {
2859             match op {
2860                 hir::InlineAsmOperand::In { expr, .. } => {
2861                     self.check_expr_asm_operand(expr, true);
2862                 }
2863                 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2864                 | hir::InlineAsmOperand::InOut { expr, .. } => {
2865                     self.check_expr_asm_operand(expr, false);
2866                 }
2867                 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2868                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2869                     self.check_expr_asm_operand(in_expr, true);
2870                     if let Some(out_expr) = out_expr {
2871                         self.check_expr_asm_operand(out_expr, false);
2872                     }
2873                 }
2874                 // `AnonConst`s have their own body and is type-checked separately.
2875                 // As they don't flow into the type system we don't need them to
2876                 // be well-formed.
2877                 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2878                 hir::InlineAsmOperand::SymStatic { .. } => {}
2879             }
2880         }
2881         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2882             self.tcx.types.never
2883         } else {
2884             self.tcx.mk_unit()
2885         }
2886     }
2887 }
2888
2889 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2890     Some(match ty.kind() {
2891         ty::Bool => "true",
2892         ty::Char => "'a'",
2893         ty::Int(_) | ty::Uint(_) => "42",
2894         ty::Float(_) => "3.14159",
2895         ty::Error(_) | ty::Never => return None,
2896         _ => "value",
2897     })
2898 }