compiler/rustc_typeck/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;
   7 use crate::check::coercion::CoerceMany;
   8 use crate::check::fatally_break_rust;
   9 use crate::check::method::SelfSource;
  10 use crate::check::report_unexpected_variant_res;
  11 use crate::check::BreakableCtxt;
  12 use crate::check::Diverges;
  13 use crate::check::DynamicCoerceMany;
  14 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
  15 use crate::check::FnCtxt;
  16 use crate::check::Needs;
  17 use crate::check::TupleArgumentsFlag::DontTupleArguments;
  18 use crate::errors::{
  19     FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
  20     YieldExprOutsideOfGenerator,
  21 };
  22 use crate::type_error_struct;
  23
  24 use super::suggest_call_constructor;
  25 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
  26 use rustc_ast as ast;
  27 use rustc_data_structures::fx::FxHashMap;
  28 use rustc_data_structures::stack::ensure_sufficient_stack;
  29 use rustc_errors::{
  30     pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId,
  31     ErrorGuaranteed,
  32 };
  33 use rustc_hir as hir;
  34 use rustc_hir::def::{CtorKind, DefKind, Res};
  35 use rustc_hir::def_id::DefId;
  36 use rustc_hir::intravisit::Visitor;
  37 use rustc_hir::lang_items::LangItem;
  38 use rustc_hir::{Closure, ExprKind, HirId, QPath};
  39 use rustc_infer::infer;
  40 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
  41 use rustc_infer::infer::InferOk;
  42 use rustc_infer::traits::ObligationCause;
  43 use rustc_middle::middle::stability;
  44 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
  45 use rustc_middle::ty::error::TypeError::FieldMisMatch;
  46 use rustc_middle::ty::subst::SubstsRef;
  47 use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TypeVisitable};
  48 use rustc_session::parse::feature_err;
  49 use rustc_span::hygiene::DesugaringKind;
  50 use rustc_span::lev_distance::find_best_match_for_name;
  51 use rustc_span::source_map::{Span, Spanned};
  52 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  53 use rustc_target::spec::abi::Abi::RustIntrinsic;
  54 use rustc_trait_selection::infer::InferCtxtExt;
  55 use rustc_trait_selection::traits::{self, ObligationCauseCode};
  56
  57 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  58     fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
  59         let ty = self.check_expr_with_hint(expr, expected);
  60         self.demand_eqtype(expr.span, expected, ty);
  61     }
  62
  63     pub fn check_expr_has_type_or_error(
  64         &self,
  65         expr: &'tcx hir::Expr<'tcx>,
  66         expected: Ty<'tcx>,
  67         extend_err: impl FnMut(&mut Diagnostic),
  68     ) -> Ty<'tcx> {
  69         self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
  70     }
  71
  72     fn check_expr_meets_expectation_or_error(
  73         &self,
  74         expr: &'tcx hir::Expr<'tcx>,
  75         expected: Expectation<'tcx>,
  76         mut extend_err: impl FnMut(&mut Diagnostic),
  77     ) -> Ty<'tcx> {
  78         let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
  79         let mut ty = self.check_expr_with_expectation(expr, expected);
  80
  81         // While we don't allow *arbitrary* coercions here, we *do* allow
  82         // coercions from ! to `expected`.
  83         if ty.is_never() {
  84             if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
  85                 self.tcx().sess.delay_span_bug(
  86                     expr.span,
  87                     "expression with never type wound up being adjusted",
  88                 );
  89                 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
  90                     target.to_owned()
  91                 } else {
  92                     self.tcx().ty_error()
  93                 };
  94             }
  95
  96             let adj_ty = self.next_ty_var(TypeVariableOrigin {
  97                 kind: TypeVariableOriginKind::AdjustmentType,
  98                 span: expr.span,
  99             });
 100             self.apply_adjustments(
 101                 expr,
 102                 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
 103             );
 104             ty = adj_ty;
 105         }
 106
 107         if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
 108             let expr = expr.peel_drop_temps();
 109             self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
 110             extend_err(&mut err);
 111             err.emit();
 112         }
 113         ty
 114     }
 115
 116     pub(super) fn check_expr_coercable_to_type(
 117         &self,
 118         expr: &'tcx hir::Expr<'tcx>,
 119         expected: Ty<'tcx>,
 120         expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
 121     ) -> Ty<'tcx> {
 122         let ty = self.check_expr_with_hint(expr, expected);
 123         // checks don't need two phase
 124         self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
 125     }
 126
 127     pub(super) fn check_expr_with_hint(
 128         &self,
 129         expr: &'tcx hir::Expr<'tcx>,
 130         expected: Ty<'tcx>,
 131     ) -> Ty<'tcx> {
 132         self.check_expr_with_expectation(expr, ExpectHasType(expected))
 133     }
 134
 135     fn check_expr_with_expectation_and_needs(
 136         &self,
 137         expr: &'tcx hir::Expr<'tcx>,
 138         expected: Expectation<'tcx>,
 139         needs: Needs,
 140     ) -> Ty<'tcx> {
 141         let ty = self.check_expr_with_expectation(expr, expected);
 142
 143         // If the expression is used in a place whether mutable place is required
 144         // e.g. LHS of assignment, perform the conversion.
 145         if let Needs::MutPlace = needs {
 146             self.convert_place_derefs_to_mutable(expr);
 147         }
 148
 149         ty
 150     }
 151
 152     pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
 153         self.check_expr_with_expectation(expr, NoExpectation)
 154     }
 155
 156     pub(super) fn check_expr_with_needs(
 157         &self,
 158         expr: &'tcx hir::Expr<'tcx>,
 159         needs: Needs,
 160     ) -> Ty<'tcx> {
 161         self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
 162     }
 163
 164     /// Invariant:
 165     /// If an expression has any sub-expressions that result in a type error,
 166     /// inspecting that expression's type with `ty.references_error()` will return
 167     /// true. Likewise, if an expression is known to diverge, inspecting its
 168     /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
 169     /// strict, _|_ can appear in the type of an expression that does not,
 170     /// itself, diverge: for example, fn() -> _|_.)
 171     /// Note that inspecting a type's structure *directly* may expose the fact
 172     /// that there are actually multiple representations for `Error`, so avoid
 173     /// that when err needs to be handled differently.
 174     #[instrument(skip(self, expr), level = "debug")]
 175     pub(super) fn check_expr_with_expectation(
 176         &self,
 177         expr: &'tcx hir::Expr<'tcx>,
 178         expected: Expectation<'tcx>,
 179     ) -> Ty<'tcx> {
 180         self.check_expr_with_expectation_and_args(expr, expected, &[])
 181     }
 182
 183     /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
 184     /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
 185     pub(super) fn check_expr_with_expectation_and_args(
 186         &self,
 187         expr: &'tcx hir::Expr<'tcx>,
 188         expected: Expectation<'tcx>,
 189         args: &'tcx [hir::Expr<'tcx>],
 190     ) -> Ty<'tcx> {
 191         if self.tcx().sess.verbose() {
 192             // make this code only run with -Zverbose because it is probably slow
 193             if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
 194                 if !lint_str.contains('\n') {
 195                     debug!("expr text: {lint_str}");
 196                 } else {
 197                     let mut lines = lint_str.lines();
 198                     if let Some(line0) = lines.next() {
 199                         let remaining_lines = lines.count();
 200                         debug!("expr text: {line0}");
 201                         debug!("expr text: ...(and {remaining_lines} more lines)");
 202                     }
 203                 }
 204             }
 205         }
 206
 207         // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
 208         // without the final expr (e.g. `try { return; }`). We don't want to generate an
 209         // unreachable_code lint for it since warnings for autogenerated code are confusing.
 210         let is_try_block_generated_unit_expr = match expr.kind {
 211             ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
 212                 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
 213             }
 214
 215             _ => false,
 216         };
 217
 218         // Warn for expressions after diverging siblings.
 219         if !is_try_block_generated_unit_expr {
 220             self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
 221         }
 222
 223         // Hide the outer diverging and has_errors flags.
 224         let old_diverges = self.diverges.replace(Diverges::Maybe);
 225         let old_has_errors = self.has_errors.replace(false);
 226
 227         let ty = ensure_sufficient_stack(|| match &expr.kind {
 228             hir::ExprKind::Path(
 229                 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
 230             ) => self.check_expr_path(qpath, expr, args),
 231             _ => self.check_expr_kind(expr, expected),
 232         });
 233
 234         // Warn for non-block expressions with diverging children.
 235         match expr.kind {
 236             ExprKind::Block(..)
 237             | ExprKind::If(..)
 238             | ExprKind::Let(..)
 239             | ExprKind::Loop(..)
 240             | ExprKind::Match(..) => {}
 241             // If `expr` is a result of desugaring the try block and is an ok-wrapped
 242             // diverging expression (e.g. it arose from desugaring of `try { return }`),
 243             // we skip issuing a warning because it is autogenerated code.
 244             ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
 245             ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
 246             ExprKind::MethodCall(segment, ..) => {
 247                 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
 248             }
 249             _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
 250         }
 251
 252         // Any expression that produces a value of type `!` must have diverged
 253         if ty.is_never() {
 254             self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
 255         }
 256
 257         // Record the type, which applies it effects.
 258         // We need to do this after the warning above, so that
 259         // we don't warn for the diverging expression itself.
 260         self.write_ty(expr.hir_id, ty);
 261
 262         // Combine the diverging and has_error flags.
 263         self.diverges.set(self.diverges.get() | old_diverges);
 264         self.has_errors.set(self.has_errors.get() | old_has_errors);
 265
 266         debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
 267         debug!("... {:?}, expected is {:?}", ty, expected);
 268
 269         ty
 270     }
 271
 272     #[instrument(skip(self, expr), level = "debug")]
 273     fn check_expr_kind(
 274         &self,
 275         expr: &'tcx hir::Expr<'tcx>,
 276         expected: Expectation<'tcx>,
 277     ) -> Ty<'tcx> {
 278         trace!("expr={:#?}", expr);
 279
 280         let tcx = self.tcx;
 281         match expr.kind {
 282             ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
 283             ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
 284             ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
 285             ExprKind::Assign(lhs, rhs, span) => {
 286                 self.check_expr_assign(expr, expected, lhs, rhs, span)
 287             }
 288             ExprKind::AssignOp(op, lhs, rhs) => {
 289                 self.check_binop_assign(expr, op, lhs, rhs, expected)
 290             }
 291             ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
 292             ExprKind::AddrOf(kind, mutbl, oprnd) => {
 293                 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
 294             }
 295             ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
 296                 self.check_lang_item_path(lang_item, expr, hir_id)
 297             }
 298             ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
 299             ExprKind::InlineAsm(asm) => {
 300                 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
 301                 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
 302                 self.check_expr_asm(asm)
 303             }
 304             ExprKind::Break(destination, ref expr_opt) => {
 305                 self.check_expr_break(destination, expr_opt.as_deref(), expr)
 306             }
 307             ExprKind::Continue(destination) => {
 308                 if destination.target_id.is_ok() {
 309                     tcx.types.never
 310                 } else {
 311                     // There was an error; make type-check fail.
 312                     tcx.ty_error()
 313                 }
 314             }
 315             ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
 316             ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
 317             ExprKind::Loop(body, _, source, _) => {
 318                 self.check_expr_loop(body, source, expected, expr)
 319             }
 320             ExprKind::Match(discrim, arms, match_src) => {
 321                 self.check_match(expr, &discrim, arms, expected, match_src)
 322             }
 323             ExprKind::Closure(&Closure { capture_clause, fn_decl, body, movability, .. }) => {
 324                 self.check_expr_closure(expr, capture_clause, &fn_decl, body, movability, expected)
 325             }
 326             ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
 327             ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
 328             ExprKind::MethodCall(segment, args, _) => {
 329                 self.check_method_call(expr, segment, args, expected)
 330             }
 331             ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
 332             ExprKind::Type(e, t) => {
 333                 let ty = self.to_ty_saving_user_provided_ty(&t);
 334                 self.check_expr_eq_type(&e, ty);
 335                 ty
 336             }
 337             ExprKind::If(cond, then_expr, opt_else_expr) => {
 338                 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
 339             }
 340             ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
 341             ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
 342             ExprKind::ConstBlock(ref anon_const) => {
 343                 self.check_expr_const_block(anon_const, expected, expr)
 344             }
 345             ExprKind::Repeat(element, ref count) => {
 346                 self.check_expr_repeat(element, count, expected, expr)
 347             }
 348             ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
 349             ExprKind::Struct(qpath, fields, ref base_expr) => {
 350                 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
 351             }
 352             ExprKind::Field(base, field) => self.check_field(expr, &base, field),
 353             ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
 354             ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
 355             hir::ExprKind::Err => tcx.ty_error(),
 356         }
 357     }
 358
 359     fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
 360         let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
 361             ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
 362             _ => NoExpectation,
 363         });
 364         let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
 365         self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
 366         self.tcx.mk_box(referent_ty)
 367     }
 368
 369     fn check_expr_unary(
 370         &self,
 371         unop: hir::UnOp,
 372         oprnd: &'tcx hir::Expr<'tcx>,
 373         expected: Expectation<'tcx>,
 374         expr: &'tcx hir::Expr<'tcx>,
 375     ) -> Ty<'tcx> {
 376         let tcx = self.tcx;
 377         let expected_inner = match unop {
 378             hir::UnOp::Not | hir::UnOp::Neg => expected,
 379             hir::UnOp::Deref => NoExpectation,
 380         };
 381         let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
 382
 383         if !oprnd_t.references_error() {
 384             oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
 385             match unop {
 386                 hir::UnOp::Deref => {
 387                     if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
 388                         oprnd_t = ty;
 389                     } else {
 390                         let mut err = type_error_struct!(
 391                             tcx.sess,
 392                             expr.span,
 393                             oprnd_t,
 394                             E0614,
 395                             "type `{oprnd_t}` cannot be dereferenced",
 396                         );
 397                         let sp = tcx.sess.source_map().start_point(expr.span);
 398                         if let Some(sp) =
 399                             tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
 400                         {
 401                             tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
 402                         }
 403                         err.emit();
 404                         oprnd_t = tcx.ty_error();
 405                     }
 406                 }
 407                 hir::UnOp::Not => {
 408                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 409                     // If it's builtin, we can reuse the type, this helps inference.
 410                     if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
 411                         oprnd_t = result;
 412                     }
 413                 }
 414                 hir::UnOp::Neg => {
 415                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 416                     // If it's builtin, we can reuse the type, this helps inference.
 417                     if !oprnd_t.is_numeric() {
 418                         oprnd_t = result;
 419                     }
 420                 }
 421             }
 422         }
 423         oprnd_t
 424     }
 425
 426     fn check_expr_addr_of(
 427         &self,
 428         kind: hir::BorrowKind,
 429         mutbl: hir::Mutability,
 430         oprnd: &'tcx hir::Expr<'tcx>,
 431         expected: Expectation<'tcx>,
 432         expr: &'tcx hir::Expr<'tcx>,
 433     ) -> Ty<'tcx> {
 434         let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
 435             match ty.kind() {
 436                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 437                     if oprnd.is_syntactic_place_expr() {
 438                         // Places may legitimately have unsized types.
 439                         // For example, dereferences of a fat pointer and
 440                         // the last field of a struct can be unsized.
 441                         ExpectHasType(*ty)
 442                     } else {
 443                         Expectation::rvalue_hint(self, *ty)
 444                     }
 445                 }
 446                 _ => NoExpectation,
 447             }
 448         });
 449         let ty =
 450             self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
 451
 452         let tm = ty::TypeAndMut { ty, mutbl };
 453         match kind {
 454             _ if tm.ty.references_error() => self.tcx.ty_error(),
 455             hir::BorrowKind::Raw => {
 456                 self.check_named_place_expr(oprnd);
 457                 self.tcx.mk_ptr(tm)
 458             }
 459             hir::BorrowKind::Ref => {
 460                 // Note: at this point, we cannot say what the best lifetime
 461                 // is to use for resulting pointer.  We want to use the
 462                 // shortest lifetime possible so as to avoid spurious borrowck
 463                 // errors.  Moreover, the longest lifetime will depend on the
 464                 // precise details of the value whose address is being taken
 465                 // (and how long it is valid), which we don't know yet until
 466                 // type inference is complete.
 467                 //
 468                 // Therefore, here we simply generate a region variable. The
 469                 // region inferencer will then select a suitable value.
 470                 // Finally, borrowck will infer the value of the region again,
 471                 // this time with enough precision to check that the value
 472                 // whose address was taken can actually be made to live as long
 473                 // as it needs to live.
 474                 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
 475                 self.tcx.mk_ref(region, tm)
 476             }
 477         }
 478     }
 479
 480     /// Does this expression refer to a place that either:
 481     /// * Is based on a local or static.
 482     /// * Contains a dereference
 483     /// Note that the adjustments for the children of `expr` should already
 484     /// have been resolved.
 485     fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
 486         let is_named = oprnd.is_place_expr(|base| {
 487             // Allow raw borrows if there are any deref adjustments.
 488             //
 489             // const VAL: (i32,) = (0,);
 490             // const REF: &(i32,) = &(0,);
 491             //
 492             // &raw const VAL.0;            // ERROR
 493             // &raw const REF.0;            // OK, same as &raw const (*REF).0;
 494             //
 495             // This is maybe too permissive, since it allows
 496             // `let u = &raw const Box::new((1,)).0`, which creates an
 497             // immediately dangling raw pointer.
 498             self.typeck_results
 499                 .borrow()
 500                 .adjustments()
 501                 .get(base.hir_id)
 502                 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
 503         });
 504         if !is_named {
 505             self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
 506         }
 507     }
 508
 509     fn check_lang_item_path(
 510         &self,
 511         lang_item: hir::LangItem,
 512         expr: &'tcx hir::Expr<'tcx>,
 513         hir_id: Option<hir::HirId>,
 514     ) -> Ty<'tcx> {
 515         self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
 516     }
 517
 518     pub(crate) fn check_expr_path(
 519         &self,
 520         qpath: &'tcx hir::QPath<'tcx>,
 521         expr: &'tcx hir::Expr<'tcx>,
 522         args: &'tcx [hir::Expr<'tcx>],
 523     ) -> Ty<'tcx> {
 524         let tcx = self.tcx;
 525         let (res, opt_ty, segs) =
 526             self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
 527         let ty = match res {
 528             Res::Err => {
 529                 self.set_tainted_by_errors();
 530                 tcx.ty_error()
 531             }
 532             Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
 533                 report_unexpected_variant_res(tcx, res, qpath, expr.span);
 534                 tcx.ty_error()
 535             }
 536             _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
 537         };
 538
 539         if let ty::FnDef(did, ..) = *ty.kind() {
 540             let fn_sig = ty.fn_sig(tcx);
 541             if tcx.fn_sig(did).abi() == RustIntrinsic && tcx.item_name(did) == sym::transmute {
 542                 let from = fn_sig.inputs().skip_binder()[0];
 543                 let to = fn_sig.output().skip_binder();
 544                 // We defer the transmute to the end of typeck, once all inference vars have
 545                 // been resolved or we errored. This is important as we can only check transmute
 546                 // on concrete types, but the output type may not be known yet (it would only
 547                 // be known if explicitly specified via turbofish).
 548                 self.deferred_transmute_checks.borrow_mut().push((from, to, expr.span));
 549             }
 550             if !tcx.features().unsized_fn_params {
 551                 // We want to remove some Sized bounds from std functions,
 552                 // but don't want to expose the removal to stable Rust.
 553                 // i.e., we don't want to allow
 554                 //
 555                 // ```rust
 556                 // drop as fn(str);
 557                 // ```
 558                 //
 559                 // to work in stable even if the Sized bound on `drop` is relaxed.
 560                 for i in 0..fn_sig.inputs().skip_binder().len() {
 561                     // We just want to check sizedness, so instead of introducing
 562                     // placeholder lifetimes with probing, we just replace higher lifetimes
 563                     // with fresh vars.
 564                     let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
 565                     let input = self.replace_bound_vars_with_fresh_vars(
 566                         span,
 567                         infer::LateBoundRegionConversionTime::FnCall,
 568                         fn_sig.input(i),
 569                     );
 570                     self.require_type_is_sized_deferred(
 571                         input,
 572                         span,
 573                         traits::SizedArgumentType(None),
 574                     );
 575                 }
 576             }
 577             // Here we want to prevent struct constructors from returning unsized types.
 578             // There were two cases this happened: fn pointer coercion in stable
 579             // and usual function call in presence of unsized_locals.
 580             // Also, as we just want to check sizedness, instead of introducing
 581             // placeholder lifetimes with probing, we just replace higher lifetimes
 582             // with fresh vars.
 583             let output = self.replace_bound_vars_with_fresh_vars(
 584                 expr.span,
 585                 infer::LateBoundRegionConversionTime::FnCall,
 586                 fn_sig.output(),
 587             );
 588             self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
 589         }
 590
 591         // We always require that the type provided as the value for
 592         // a type parameter outlives the moment of instantiation.
 593         let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
 594         self.add_wf_bounds(substs, expr);
 595
 596         ty
 597     }
 598
 599     fn check_expr_break(
 600         &self,
 601         destination: hir::Destination,
 602         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 603         expr: &'tcx hir::Expr<'tcx>,
 604     ) -> Ty<'tcx> {
 605         let tcx = self.tcx;
 606         if let Ok(target_id) = destination.target_id {
 607             let (e_ty, cause);
 608             if let Some(e) = expr_opt {
 609                 // If this is a break with a value, we need to type-check
 610                 // the expression. Get an expected type from the loop context.
 611                 let opt_coerce_to = {
 612                     // We should release `enclosing_breakables` before the `check_expr_with_hint`
 613                     // below, so can't move this block of code to the enclosing scope and share
 614                     // `ctxt` with the second `enclosing_breakables` borrow below.
 615                     let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 616                     match enclosing_breakables.opt_find_breakable(target_id) {
 617                         Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
 618                         None => {
 619                             // Avoid ICE when `break` is inside a closure (#65383).
 620                             return tcx.ty_error_with_message(
 621                                 expr.span,
 622                                 "break was outside loop, but no error was emitted",
 623                             );
 624                         }
 625                     }
 626                 };
 627
 628                 // If the loop context is not a `loop { }`, then break with
 629                 // a value is illegal, and `opt_coerce_to` will be `None`.
 630                 // Just set expectation to error in that case.
 631                 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
 632
 633                 // Recurse without `enclosing_breakables` borrowed.
 634                 e_ty = self.check_expr_with_hint(e, coerce_to);
 635                 cause = self.misc(e.span);
 636             } else {
 637                 // Otherwise, this is a break *without* a value. That's
 638                 // always legal, and is equivalent to `break ()`.
 639                 e_ty = tcx.mk_unit();
 640                 cause = self.misc(expr.span);
 641             }
 642
 643             // Now that we have type-checked `expr_opt`, borrow
 644             // the `enclosing_loops` field and let's coerce the
 645             // type of `expr_opt` into what is expected.
 646             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 647             let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
 648                 // Avoid ICE when `break` is inside a closure (#65383).
 649                 return tcx.ty_error_with_message(
 650                     expr.span,
 651                     "break was outside loop, but no error was emitted",
 652                 );
 653             };
 654
 655             if let Some(ref mut coerce) = ctxt.coerce {
 656                 if let Some(ref e) = expr_opt {
 657                     coerce.coerce(self, &cause, e, e_ty);
 658                 } else {
 659                     assert!(e_ty.is_unit());
 660                     let ty = coerce.expected_ty();
 661                     coerce.coerce_forced_unit(
 662                         self,
 663                         &cause,
 664                         &mut |mut err| {
 665                             self.suggest_mismatched_types_on_tail(
 666                                 &mut err, expr, ty, e_ty, target_id,
 667                             );
 668                             if let Some(val) = ty_kind_suggestion(ty) {
 669                                 let label = destination
 670                                     .label
 671                                     .map(|l| format!(" {}", l.ident))
 672                                     .unwrap_or_else(String::new);
 673                                 err.span_suggestion(
 674                                     expr.span,
 675                                     "give it a value of the expected type",
 676                                     format!("break{label} {val}"),
 677                                     Applicability::HasPlaceholders,
 678                                 );
 679                             }
 680                         },
 681                         false,
 682                     );
 683                 }
 684             } else {
 685                 // If `ctxt.coerce` is `None`, we can just ignore
 686                 // the type of the expression.  This is because
 687                 // either this was a break *without* a value, in
 688                 // which case it is always a legal type (`()`), or
 689                 // else an error would have been flagged by the
 690                 // `loops` pass for using break with an expression
 691                 // where you are not supposed to.
 692                 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
 693             }
 694
 695             // If we encountered a `break`, then (no surprise) it may be possible to break from the
 696             // loop... unless the value being returned from the loop diverges itself, e.g.
 697             // `break return 5` or `break loop {}`.
 698             ctxt.may_break |= !self.diverges.get().is_always();
 699
 700             // the type of a `break` is always `!`, since it diverges
 701             tcx.types.never
 702         } else {
 703             // Otherwise, we failed to find the enclosing loop;
 704             // this can only happen if the `break` was not
 705             // inside a loop at all, which is caught by the
 706             // loop-checking pass.
 707             let err = self.tcx.ty_error_with_message(
 708                 expr.span,
 709                 "break was outside loop, but no error was emitted",
 710             );
 711
 712             // We still need to assign a type to the inner expression to
 713             // prevent the ICE in #43162.
 714             if let Some(e) = expr_opt {
 715                 self.check_expr_with_hint(e, err);
 716
 717                 // ... except when we try to 'break rust;'.
 718                 // ICE this expression in particular (see #43162).
 719                 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
 720                     if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
 721                         fatally_break_rust(self.tcx.sess);
 722                     }
 723                 }
 724             }
 725
 726             // There was an error; make type-check fail.
 727             err
 728         }
 729     }
 730
 731     fn check_expr_return(
 732         &self,
 733         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 734         expr: &'tcx hir::Expr<'tcx>,
 735     ) -> Ty<'tcx> {
 736         if self.ret_coercion.is_none() {
 737             let mut err = ReturnStmtOutsideOfFnBody {
 738                 span: expr.span,
 739                 encl_body_span: None,
 740                 encl_fn_span: None,
 741             };
 742
 743             let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
 744
 745             if let Some(hir::Node::Item(hir::Item {
 746                 kind: hir::ItemKind::Fn(..),
 747                 span: encl_fn_span,
 748                 ..
 749             }))
 750             | Some(hir::Node::TraitItem(hir::TraitItem {
 751                 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
 752                 span: encl_fn_span,
 753                 ..
 754             }))
 755             | Some(hir::Node::ImplItem(hir::ImplItem {
 756                 kind: hir::ImplItemKind::Fn(..),
 757                 span: encl_fn_span,
 758                 ..
 759             })) = self.tcx.hir().find_by_def_id(encl_item_id)
 760             {
 761                 // We are inside a function body, so reporting "return statement
 762                 // outside of function body" needs an explanation.
 763
 764                 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
 765
 766                 // If this didn't hold, we would not have to report an error in
 767                 // the first place.
 768                 assert_ne!(encl_item_id, encl_body_owner_id);
 769
 770                 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
 771                 let encl_body = self.tcx.hir().body(encl_body_id);
 772
 773                 err.encl_body_span = Some(encl_body.value.span);
 774                 err.encl_fn_span = Some(*encl_fn_span);
 775             }
 776
 777             self.tcx.sess.emit_err(err);
 778
 779             if let Some(e) = expr_opt {
 780                 // We still have to type-check `e` (issue #86188), but calling
 781                 // `check_return_expr` only works inside fn bodies.
 782                 self.check_expr(e);
 783             }
 784         } else if let Some(e) = expr_opt {
 785             if self.ret_coercion_span.get().is_none() {
 786                 self.ret_coercion_span.set(Some(e.span));
 787             }
 788             self.check_return_expr(e, true);
 789         } else {
 790             let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
 791             if self.ret_coercion_span.get().is_none() {
 792                 self.ret_coercion_span.set(Some(expr.span));
 793             }
 794             let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
 795             if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
 796                 coercion.coerce_forced_unit(
 797                     self,
 798                     &cause,
 799                     &mut |db| {
 800                         let span = fn_decl.output.span();
 801                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
 802                             db.span_label(
 803                                 span,
 804                                 format!("expected `{snippet}` because of this return type"),
 805                             );
 806                         }
 807                     },
 808                     true,
 809                 );
 810             } else {
 811                 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
 812             }
 813         }
 814         self.tcx.types.never
 815     }
 816
 817     /// `explicit_return` is `true` if we're checking an explicit `return expr`,
 818     /// and `false` if we're checking a trailing expression.
 819     pub(super) fn check_return_expr(
 820         &self,
 821         return_expr: &'tcx hir::Expr<'tcx>,
 822         explicit_return: bool,
 823     ) {
 824         let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
 825             span_bug!(return_expr.span, "check_return_expr called outside fn body")
 826         });
 827
 828         let ret_ty = ret_coercion.borrow().expected_ty();
 829         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
 830         let mut span = return_expr.span;
 831         // Use the span of the trailing expression for our cause,
 832         // not the span of the entire function
 833         if !explicit_return {
 834             if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
 835                 span = last_expr.span;
 836             }
 837         }
 838         ret_coercion.borrow_mut().coerce(
 839             self,
 840             &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
 841             return_expr,
 842             return_expr_ty,
 843         );
 844
 845         if self.return_type_has_opaque {
 846             // Point any obligations that were registered due to opaque type
 847             // inference at the return expression.
 848             self.select_obligations_where_possible(false, |errors| {
 849                 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
 850             });
 851         }
 852     }
 853
 854     fn point_at_return_for_opaque_ty_error(
 855         &self,
 856         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
 857         span: Span,
 858         return_expr_ty: Ty<'tcx>,
 859     ) {
 860         // Don't point at the whole block if it's empty
 861         if span == self.tcx.hir().span(self.body_id) {
 862             return;
 863         }
 864         for err in errors {
 865             let cause = &mut err.obligation.cause;
 866             if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
 867                 let new_cause = ObligationCause::new(
 868                     cause.span,
 869                     cause.body_id,
 870                     ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
 871                 );
 872                 *cause = new_cause;
 873             }
 874         }
 875     }
 876
 877     pub(crate) fn check_lhs_assignable(
 878         &self,
 879         lhs: &'tcx hir::Expr<'tcx>,
 880         err_code: &'static str,
 881         op_span: Span,
 882         adjust_err: impl FnOnce(&mut Diagnostic),
 883     ) {
 884         if lhs.is_syntactic_place_expr() {
 885             return;
 886         }
 887
 888         // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
 889         let mut err = self.tcx.sess.struct_span_err_with_code(
 890             op_span,
 891             "invalid left-hand side of assignment",
 892             DiagnosticId::Error(err_code.into()),
 893         );
 894         err.span_label(lhs.span, "cannot assign to this expression");
 895
 896         self.comes_from_while_condition(lhs.hir_id, |expr| {
 897             err.span_suggestion_verbose(
 898                 expr.span.shrink_to_lo(),
 899                 "you might have meant to use pattern destructuring",
 900                 "let ",
 901                 Applicability::MachineApplicable,
 902             );
 903         });
 904
 905         adjust_err(&mut err);
 906
 907         err.emit();
 908     }
 909
 910     // Check if an expression `original_expr_id` comes from the condition of a while loop,
 911     // as opposed from the body of a while loop, which we can naively check by iterating
 912     // parents until we find a loop...
 913     pub(super) fn comes_from_while_condition(
 914         &self,
 915         original_expr_id: HirId,
 916         then: impl FnOnce(&hir::Expr<'_>),
 917     ) {
 918         let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
 919         while let Some(node) = self.tcx.hir().find(parent) {
 920             match node {
 921                 hir::Node::Expr(hir::Expr {
 922                     kind:
 923                         hir::ExprKind::Loop(
 924                             hir::Block {
 925                                 expr:
 926                                     Some(hir::Expr {
 927                                         kind:
 928                                             hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
 929                                         ..
 930                                     }),
 931                                 ..
 932                             },
 933                             _,
 934                             hir::LoopSource::While,
 935                             _,
 936                         ),
 937                     ..
 938                 }) => {
 939                     // Check if our original expression is a child of the condition of a while loop
 940                     let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
 941                         self.tcx.hir().find_parent_node(*id)
 942                     })
 943                     .take_while(|id| *id != parent)
 944                     .any(|id| id == expr.hir_id);
 945                     // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
 946                     // where `while let` was more likely intended.
 947                     if expr_is_ancestor {
 948                         then(expr);
 949                     }
 950                     break;
 951                 }
 952                 hir::Node::Item(_)
 953                 | hir::Node::ImplItem(_)
 954                 | hir::Node::TraitItem(_)
 955                 | hir::Node::Crate(_) => break,
 956                 _ => {
 957                     parent = self.tcx.hir().get_parent_node(parent);
 958                 }
 959             }
 960         }
 961     }
 962
 963     // A generic function for checking the 'then' and 'else' clauses in an 'if'
 964     // or 'if-else' expression.
 965     fn check_then_else(
 966         &self,
 967         cond_expr: &'tcx hir::Expr<'tcx>,
 968         then_expr: &'tcx hir::Expr<'tcx>,
 969         opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
 970         sp: Span,
 971         orig_expected: Expectation<'tcx>,
 972     ) -> Ty<'tcx> {
 973         let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
 974
 975         self.warn_if_unreachable(
 976             cond_expr.hir_id,
 977             then_expr.span,
 978             "block in `if` or `while` expression",
 979         );
 980
 981         let cond_diverges = self.diverges.get();
 982         self.diverges.set(Diverges::Maybe);
 983
 984         let expected = orig_expected.adjust_for_branches(self);
 985         let then_ty = self.check_expr_with_expectation(then_expr, expected);
 986         let then_diverges = self.diverges.get();
 987         self.diverges.set(Diverges::Maybe);
 988
 989         // We've already taken the expected type's preferences
 990         // into account when typing the `then` branch. To figure
 991         // out the initial shot at a LUB, we thus only consider
 992         // `expected` if it represents a *hard* constraint
 993         // (`only_has_type`); otherwise, we just go with a
 994         // fresh type variable.
 995         let coerce_to_ty = expected.coercion_target_type(self, sp);
 996         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
 997
 998         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
 999
1000         if let Some(else_expr) = opt_else_expr {
1001             let else_ty = self.check_expr_with_expectation(else_expr, expected);
1002             let else_diverges = self.diverges.get();
1003
1004             let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1005             let if_cause = self.if_cause(
1006                 sp,
1007                 cond_expr.span,
1008                 then_expr,
1009                 else_expr,
1010                 then_ty,
1011                 else_ty,
1012                 opt_suggest_box_span,
1013             );
1014
1015             coerce.coerce(self, &if_cause, else_expr, else_ty);
1016
1017             // We won't diverge unless both branches do (or the condition does).
1018             self.diverges.set(cond_diverges | then_diverges & else_diverges);
1019         } else {
1020             self.if_fallback_coercion(sp, then_expr, &mut coerce);
1021
1022             // If the condition is false we can't diverge.
1023             self.diverges.set(cond_diverges);
1024         }
1025
1026         let result_ty = coerce.complete(self);
1027         if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1028     }
1029
1030     /// Type check assignment expression `expr` of form `lhs = rhs`.
1031     /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1032     fn check_expr_assign(
1033         &self,
1034         expr: &'tcx hir::Expr<'tcx>,
1035         expected: Expectation<'tcx>,
1036         lhs: &'tcx hir::Expr<'tcx>,
1037         rhs: &'tcx hir::Expr<'tcx>,
1038         span: Span,
1039     ) -> Ty<'tcx> {
1040         let expected_ty = expected.coercion_target_type(self, expr.span);
1041         if expected_ty == self.tcx.types.bool {
1042             // The expected type is `bool` but this will result in `()` so we can reasonably
1043             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1044             // The likely cause of this is `if foo = bar { .. }`.
1045             let actual_ty = self.tcx.mk_unit();
1046             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1047             let lhs_ty = self.check_expr(&lhs);
1048             let rhs_ty = self.check_expr(&rhs);
1049             let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1050                 (Applicability::MachineApplicable, true)
1051             } else {
1052                 (Applicability::MaybeIncorrect, false)
1053             };
1054             if !lhs.is_syntactic_place_expr()
1055                 && lhs.is_approximately_pattern()
1056                 && !matches!(lhs.kind, hir::ExprKind::Lit(_))
1057             {
1058                 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1059                 let hir = self.tcx.hir();
1060                 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1061                     hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1062                 {
1063                     err.span_suggestion_verbose(
1064                         expr.span.shrink_to_lo(),
1065                         "you might have meant to use pattern matching",
1066                         "let ",
1067                         applicability,
1068                     );
1069                 };
1070             }
1071             if eq {
1072                 err.span_suggestion_verbose(
1073                     span,
1074                     "you might have meant to compare for equality",
1075                     "==",
1076                     applicability,
1077                 );
1078             }
1079
1080             // If the assignment expression itself is ill-formed, don't
1081             // bother emitting another error
1082             if lhs_ty.references_error() || rhs_ty.references_error() {
1083                 err.delay_as_bug()
1084             } else {
1085                 err.emit();
1086             }
1087             return self.tcx.ty_error();
1088         }
1089
1090         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1091
1092         let suggest_deref_binop = |err: &mut Diagnostic, rhs_ty: Ty<'tcx>| {
1093             if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1094                 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1095                 // unsized, do not suggest dereferencing it.
1096                 let lhs_deref_ty_is_sized = self
1097                     .infcx
1098                     .type_implements_trait(
1099                         self.tcx.lang_items().sized_trait().unwrap(),
1100                         lhs_deref_ty,
1101                         ty::List::empty(),
1102                         self.param_env,
1103                     )
1104                     .may_apply();
1105                 if lhs_deref_ty_is_sized && self.can_coerce(rhs_ty, lhs_deref_ty) {
1106                     err.span_suggestion_verbose(
1107                         lhs.span.shrink_to_lo(),
1108                         "consider dereferencing here to assign to the mutably borrowed value",
1109                         "*",
1110                         Applicability::MachineApplicable,
1111                     );
1112                 }
1113             }
1114         };
1115
1116         self.check_lhs_assignable(lhs, "E0070", span, |err| {
1117             let rhs_ty = self.check_expr(&rhs);
1118             suggest_deref_binop(err, rhs_ty);
1119         });
1120
1121         // This is (basically) inlined `check_expr_coercable_to_type`, but we want
1122         // to suggest an additional fixup here in `suggest_deref_binop`.
1123         let rhs_ty = self.check_expr_with_hint(&rhs, lhs_ty);
1124         if let (_, Some(mut diag)) =
1125             self.demand_coerce_diag(rhs, rhs_ty, lhs_ty, Some(lhs), AllowTwoPhase::No)
1126         {
1127             suggest_deref_binop(&mut diag, rhs_ty);
1128             diag.emit();
1129         }
1130
1131         self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1132
1133         if lhs_ty.references_error() || rhs_ty.references_error() {
1134             self.tcx.ty_error()
1135         } else {
1136             self.tcx.mk_unit()
1137         }
1138     }
1139
1140     pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1141         // for let statements, this is done in check_stmt
1142         let init = let_expr.init;
1143         self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1144         // otherwise check exactly as a let statement
1145         self.check_decl(let_expr.into());
1146         // but return a bool, for this is a boolean expression
1147         self.tcx.types.bool
1148     }
1149
1150     fn check_expr_loop(
1151         &self,
1152         body: &'tcx hir::Block<'tcx>,
1153         source: hir::LoopSource,
1154         expected: Expectation<'tcx>,
1155         expr: &'tcx hir::Expr<'tcx>,
1156     ) -> Ty<'tcx> {
1157         let coerce = match source {
1158             // you can only use break with a value from a normal `loop { }`
1159             hir::LoopSource::Loop => {
1160                 let coerce_to = expected.coercion_target_type(self, body.span);
1161                 Some(CoerceMany::new(coerce_to))
1162             }
1163
1164             hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1165         };
1166
1167         let ctxt = BreakableCtxt {
1168             coerce,
1169             may_break: false, // Will get updated if/when we find a `break`.
1170         };
1171
1172         let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1173             self.check_block_no_value(&body);
1174         });
1175
1176         if ctxt.may_break {
1177             // No way to know whether it's diverging because
1178             // of a `break` or an outer `break` or `return`.
1179             self.diverges.set(Diverges::Maybe);
1180         }
1181
1182         // If we permit break with a value, then result type is
1183         // the LUB of the breaks (possibly ! if none); else, it
1184         // is nil. This makes sense because infinite loops
1185         // (which would have type !) are only possible iff we
1186         // permit break with a value [1].
1187         if ctxt.coerce.is_none() && !ctxt.may_break {
1188             // [1]
1189             self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1190         }
1191         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1192     }
1193
1194     /// Checks a method call.
1195     fn check_method_call(
1196         &self,
1197         expr: &'tcx hir::Expr<'tcx>,
1198         segment: &hir::PathSegment<'_>,
1199         args: &'tcx [hir::Expr<'tcx>],
1200         expected: Expectation<'tcx>,
1201     ) -> Ty<'tcx> {
1202         let rcvr = &args[0];
1203         let rcvr_t = self.check_expr(&rcvr);
1204         // no need to check for bot/err -- callee does that
1205         let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
1206         let span = segment.ident.span;
1207
1208         let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1209             Ok(method) => {
1210                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1211                 // trigger this codepath causing `structurally_resolved_type` to emit an error.
1212
1213                 self.write_method_call(expr.hir_id, method);
1214                 Ok(method)
1215             }
1216             Err(error) => {
1217                 if segment.ident.name != kw::Empty {
1218                     if let Some(mut err) = self.report_method_error(
1219                         span,
1220                         rcvr_t,
1221                         segment.ident,
1222                         SelfSource::MethodCall(&args[0]),
1223                         error,
1224                         Some(args),
1225                     ) {
1226                         err.emit();
1227                     }
1228                 }
1229                 Err(())
1230             }
1231         };
1232
1233         // Call the generic checker.
1234         self.check_method_argument_types(
1235             span,
1236             expr,
1237             method,
1238             &args[1..],
1239             DontTupleArguments,
1240             expected,
1241         )
1242     }
1243
1244     fn check_expr_cast(
1245         &self,
1246         e: &'tcx hir::Expr<'tcx>,
1247         t: &'tcx hir::Ty<'tcx>,
1248         expr: &'tcx hir::Expr<'tcx>,
1249     ) -> Ty<'tcx> {
1250         // Find the type of `e`. Supply hints based on the type we are casting to,
1251         // if appropriate.
1252         let t_cast = self.to_ty_saving_user_provided_ty(t);
1253         let t_cast = self.resolve_vars_if_possible(t_cast);
1254         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1255         let t_expr = self.resolve_vars_if_possible(t_expr);
1256
1257         // Eagerly check for some obvious errors.
1258         if t_expr.references_error() || t_cast.references_error() {
1259             self.tcx.ty_error()
1260         } else {
1261             // Defer other checks until we're done type checking.
1262             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1263             match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1264                 Ok(cast_check) => {
1265                     debug!(
1266                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1267                         t_cast, t_expr, cast_check,
1268                     );
1269                     deferred_cast_checks.push(cast_check);
1270                     t_cast
1271                 }
1272                 Err(_) => self.tcx.ty_error(),
1273             }
1274         }
1275     }
1276
1277     fn check_expr_array(
1278         &self,
1279         args: &'tcx [hir::Expr<'tcx>],
1280         expected: Expectation<'tcx>,
1281         expr: &'tcx hir::Expr<'tcx>,
1282     ) -> Ty<'tcx> {
1283         let element_ty = if !args.is_empty() {
1284             let coerce_to = expected
1285                 .to_option(self)
1286                 .and_then(|uty| match *uty.kind() {
1287                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1288                     _ => None,
1289                 })
1290                 .unwrap_or_else(|| {
1291                     self.next_ty_var(TypeVariableOrigin {
1292                         kind: TypeVariableOriginKind::TypeInference,
1293                         span: expr.span,
1294                     })
1295                 });
1296             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1297             assert_eq!(self.diverges.get(), Diverges::Maybe);
1298             for e in args {
1299                 let e_ty = self.check_expr_with_hint(e, coerce_to);
1300                 let cause = self.misc(e.span);
1301                 coerce.coerce(self, &cause, e, e_ty);
1302             }
1303             coerce.complete(self)
1304         } else {
1305             self.next_ty_var(TypeVariableOrigin {
1306                 kind: TypeVariableOriginKind::TypeInference,
1307                 span: expr.span,
1308             })
1309         };
1310         self.tcx.mk_array(element_ty, args.len() as u64)
1311     }
1312
1313     fn check_expr_const_block(
1314         &self,
1315         anon_const: &'tcx hir::AnonConst,
1316         expected: Expectation<'tcx>,
1317         _expr: &'tcx hir::Expr<'tcx>,
1318     ) -> Ty<'tcx> {
1319         let body = self.tcx.hir().body(anon_const.body);
1320
1321         // Create a new function context.
1322         let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1323         crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1324
1325         let ty = fcx.check_expr_with_expectation(&body.value, expected);
1326         fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1327         fcx.write_ty(anon_const.hir_id, ty);
1328         ty
1329     }
1330
1331     fn check_expr_repeat(
1332         &self,
1333         element: &'tcx hir::Expr<'tcx>,
1334         count: &'tcx hir::ArrayLen,
1335         expected: Expectation<'tcx>,
1336         _expr: &'tcx hir::Expr<'tcx>,
1337     ) -> Ty<'tcx> {
1338         let tcx = self.tcx;
1339         let count = self.array_length_to_const(count);
1340
1341         let uty = match expected {
1342             ExpectHasType(uty) => match *uty.kind() {
1343                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1344                 _ => None,
1345             },
1346             _ => None,
1347         };
1348
1349         let (element_ty, t) = match uty {
1350             Some(uty) => {
1351                 self.check_expr_coercable_to_type(&element, uty, None);
1352                 (uty, uty)
1353             }
1354             None => {
1355                 let ty = self.next_ty_var(TypeVariableOrigin {
1356                     kind: TypeVariableOriginKind::MiscVariable,
1357                     span: element.span,
1358                 });
1359                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1360                 (element_ty, ty)
1361             }
1362         };
1363
1364         if element_ty.references_error() {
1365             return tcx.ty_error();
1366         }
1367
1368         self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1369
1370         tcx.mk_ty(ty::Array(t, count))
1371     }
1372
1373     fn check_repeat_element_needs_copy_bound(
1374         &self,
1375         element: &hir::Expr<'_>,
1376         count: ty::Const<'tcx>,
1377         element_ty: Ty<'tcx>,
1378     ) {
1379         let tcx = self.tcx;
1380         // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1381         match &element.kind {
1382             hir::ExprKind::ConstBlock(..) => return,
1383             hir::ExprKind::Path(qpath) => {
1384                 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1385                 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1386                 {
1387                     return;
1388                 }
1389             }
1390             _ => {}
1391         }
1392         // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1393         // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1394         let is_const_fn = match element.kind {
1395             hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1396                 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1397                 _ => false,
1398             },
1399             _ => false,
1400         };
1401
1402         // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1403         // don't copy that one element, we move it. Only check for Copy if the length is larger.
1404         if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1405             let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1406             let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1407             self.require_type_meets(element_ty, element.span, code, lang_item);
1408         }
1409     }
1410
1411     fn check_expr_tuple(
1412         &self,
1413         elts: &'tcx [hir::Expr<'tcx>],
1414         expected: Expectation<'tcx>,
1415         expr: &'tcx hir::Expr<'tcx>,
1416     ) -> Ty<'tcx> {
1417         let flds = expected.only_has_type(self).and_then(|ty| {
1418             let ty = self.resolve_vars_with_obligations(ty);
1419             match ty.kind() {
1420                 ty::Tuple(flds) => Some(&flds[..]),
1421                 _ => None,
1422             }
1423         });
1424
1425         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1426             Some(fs) if i < fs.len() => {
1427                 let ety = fs[i];
1428                 self.check_expr_coercable_to_type(&e, ety, None);
1429                 ety
1430             }
1431             _ => self.check_expr_with_expectation(&e, NoExpectation),
1432         });
1433         let tuple = self.tcx.mk_tup(elt_ts_iter);
1434         if tuple.references_error() {
1435             self.tcx.ty_error()
1436         } else {
1437             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1438             tuple
1439         }
1440     }
1441
1442     fn check_expr_struct(
1443         &self,
1444         expr: &hir::Expr<'_>,
1445         expected: Expectation<'tcx>,
1446         qpath: &QPath<'_>,
1447         fields: &'tcx [hir::ExprField<'tcx>],
1448         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1449     ) -> Ty<'tcx> {
1450         // Find the relevant variant
1451         let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1452             self.check_struct_fields_on_error(fields, base_expr);
1453             return self.tcx.ty_error();
1454         };
1455
1456         // Prohibit struct expressions when non-exhaustive flag is set.
1457         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1458         if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1459             self.tcx
1460                 .sess
1461                 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1462         }
1463
1464         self.check_expr_struct_fields(
1465             adt_ty,
1466             expected,
1467             expr.hir_id,
1468             qpath.span(),
1469             variant,
1470             fields,
1471             base_expr,
1472             expr.span,
1473         );
1474
1475         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1476         adt_ty
1477     }
1478
1479     fn check_expr_struct_fields(
1480         &self,
1481         adt_ty: Ty<'tcx>,
1482         expected: Expectation<'tcx>,
1483         expr_id: hir::HirId,
1484         span: Span,
1485         variant: &'tcx ty::VariantDef,
1486         ast_fields: &'tcx [hir::ExprField<'tcx>],
1487         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1488         expr_span: Span,
1489     ) {
1490         let tcx = self.tcx;
1491
1492         let expected_inputs =
1493             self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1494         let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1495             expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1496         } else {
1497             adt_ty
1498         };
1499         // re-link the regions that EIfEO can erase.
1500         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1501
1502         let ty::Adt(adt, substs) = adt_ty.kind() else {
1503             span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1504         };
1505         let adt_kind = adt.adt_kind();
1506
1507         let mut remaining_fields = variant
1508             .fields
1509             .iter()
1510             .enumerate()
1511             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1512             .collect::<FxHashMap<_, _>>();
1513
1514         let mut seen_fields = FxHashMap::default();
1515
1516         let mut error_happened = false;
1517
1518         // Type-check each field.
1519         for field in ast_fields {
1520             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1521             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1522                 seen_fields.insert(ident, field.span);
1523                 self.write_field_index(field.hir_id, i);
1524
1525                 // We don't look at stability attributes on
1526                 // struct-like enums (yet...), but it's definitely not
1527                 // a bug to have constructed one.
1528                 if adt_kind != AdtKind::Enum {
1529                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1530                 }
1531
1532                 self.field_ty(field.span, v_field, substs)
1533             } else {
1534                 error_happened = true;
1535                 if let Some(prev_span) = seen_fields.get(&ident) {
1536                     tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1537                         span: field.ident.span,
1538                         prev_span: *prev_span,
1539                         ident,
1540                     });
1541                 } else {
1542                     self.report_unknown_field(
1543                         adt_ty,
1544                         variant,
1545                         field,
1546                         ast_fields,
1547                         adt.variant_descr(),
1548                         expr_span,
1549                     );
1550                 }
1551
1552                 tcx.ty_error()
1553             };
1554
1555             // Make sure to give a type to the field even if there's
1556             // an error, so we can continue type-checking.
1557             self.check_expr_coercable_to_type(&field.expr, field_type, None);
1558         }
1559
1560         // Make sure the programmer specified correct number of fields.
1561         if adt_kind == AdtKind::Union {
1562             if ast_fields.len() != 1 {
1563                 struct_span_err!(
1564                     tcx.sess,
1565                     span,
1566                     E0784,
1567                     "union expressions should have exactly one field",
1568                 )
1569                 .emit();
1570             }
1571         }
1572
1573         // If check_expr_struct_fields hit an error, do not attempt to populate
1574         // the fields with the base_expr. This could cause us to hit errors later
1575         // when certain fields are assumed to exist that in fact do not.
1576         if error_happened {
1577             return;
1578         }
1579
1580         if let Some(base_expr) = base_expr {
1581             // FIXME: We are currently creating two branches here in order to maintain
1582             // consistency. But they should be merged as much as possible.
1583             let fru_tys = if self.tcx.features().type_changing_struct_update {
1584                 if adt.is_struct() {
1585                     // Make some fresh substitutions for our ADT type.
1586                     let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1587                     // We do subtyping on the FRU fields first, so we can
1588                     // learn exactly what types we expect the base expr
1589                     // needs constrained to be compatible with the struct
1590                     // type we expect from the expectation value.
1591                     let fru_tys = variant
1592                         .fields
1593                         .iter()
1594                         .map(|f| {
1595                             let fru_ty = self.normalize_associated_types_in(
1596                                 expr_span,
1597                                 self.field_ty(base_expr.span, f, fresh_substs),
1598                             );
1599                             let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1600                             if let Some(_) = remaining_fields.remove(&ident) {
1601                                 let target_ty = self.field_ty(base_expr.span, f, substs);
1602                                 let cause = self.misc(base_expr.span);
1603                                 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1604                                     Ok(InferOk { obligations, value: () }) => {
1605                                         self.register_predicates(obligations)
1606                                     }
1607                                     Err(_) => {
1608                                         // This should never happen, since we're just subtyping the
1609                                         // remaining_fields, but it's fine to emit this, I guess.
1610                                         self.report_mismatched_types(
1611                                             &cause,
1612                                             target_ty,
1613                                             fru_ty,
1614                                             FieldMisMatch(variant.name, ident.name),
1615                                         )
1616                                         .emit();
1617                                     }
1618                                 }
1619                             }
1620                             self.resolve_vars_if_possible(fru_ty)
1621                         })
1622                         .collect();
1623                     // The use of fresh substs that we have subtyped against
1624                     // our base ADT type's fields allows us to guide inference
1625                     // along so that, e.g.
1626                     // ```
1627                     // MyStruct<'a, F1, F2, const C: usize> {
1628                     //     f: F1,
1629                     //     // Other fields that reference `'a`, `F2`, and `C`
1630                     // }
1631                     //
1632                     // let x = MyStruct {
1633                     //    f: 1usize,
1634                     //    ..other_struct
1635                     // };
1636                     // ```
1637                     // will have the `other_struct` expression constrained to
1638                     // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1639                     // This is important to allow coercions to happen in
1640                     // `other_struct` itself. See `coerce-in-base-expr.rs`.
1641                     let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1642                     self.check_expr_has_type_or_error(
1643                         base_expr,
1644                         self.resolve_vars_if_possible(fresh_base_ty),
1645                         |_| {},
1646                     );
1647                     fru_tys
1648                 } else {
1649                     // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1650                     // type errors on that expression, too.
1651                     self.check_expr(base_expr);
1652                     self.tcx
1653                         .sess
1654                         .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1655                     return;
1656                 }
1657             } else {
1658                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1659                     let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1660                     let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1661                         (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1662                         _ => false,
1663                     };
1664                     if self.tcx.sess.is_nightly_build() && same_adt {
1665                         feature_err(
1666                             &self.tcx.sess.parse_sess,
1667                             sym::type_changing_struct_update,
1668                             base_expr.span,
1669                             "type changing struct updating is experimental",
1670                         )
1671                         .emit();
1672                     }
1673                 });
1674                 match adt_ty.kind() {
1675                     ty::Adt(adt, substs) if adt.is_struct() => variant
1676                         .fields
1677                         .iter()
1678                         .map(|f| {
1679                             self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1680                         })
1681                         .collect(),
1682                     _ => {
1683                         self.tcx
1684                             .sess
1685                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1686                         return;
1687                     }
1688                 }
1689             };
1690             self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1691         } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1692             debug!(?remaining_fields);
1693             let private_fields: Vec<&ty::FieldDef> = variant
1694                 .fields
1695                 .iter()
1696                 .filter(|field| {
1697                     !field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1698                 })
1699                 .collect();
1700
1701             if !private_fields.is_empty() {
1702                 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1703             } else {
1704                 self.report_missing_fields(
1705                     adt_ty,
1706                     span,
1707                     remaining_fields,
1708                     variant,
1709                     ast_fields,
1710                     substs,
1711                 );
1712             }
1713         }
1714     }
1715
1716     fn check_struct_fields_on_error(
1717         &self,
1718         fields: &'tcx [hir::ExprField<'tcx>],
1719         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1720     ) {
1721         for field in fields {
1722             self.check_expr(&field.expr);
1723         }
1724         if let Some(base) = *base_expr {
1725             self.check_expr(&base);
1726         }
1727     }
1728
1729     /// Report an error for a struct field expression when there are fields which aren't provided.
1730     ///
1731     /// ```text
1732     /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1733     ///  --> src/main.rs:8:5
1734     ///   |
1735     /// 8 |     foo::Foo {};
1736     ///   |     ^^^^^^^^ missing `you_can_use_this_field`
1737     ///
1738     /// error: aborting due to previous error
1739     /// ```
1740     fn report_missing_fields(
1741         &self,
1742         adt_ty: Ty<'tcx>,
1743         span: Span,
1744         remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1745         variant: &'tcx ty::VariantDef,
1746         ast_fields: &'tcx [hir::ExprField<'tcx>],
1747         substs: SubstsRef<'tcx>,
1748     ) {
1749         let len = remaining_fields.len();
1750
1751         let mut displayable_field_names: Vec<&str> =
1752             remaining_fields.keys().map(|ident| ident.as_str()).collect();
1753         // sorting &str primitives here, sort_unstable is ok
1754         displayable_field_names.sort_unstable();
1755
1756         let mut truncated_fields_error = String::new();
1757         let remaining_fields_names = match &displayable_field_names[..] {
1758             [field1] => format!("`{}`", field1),
1759             [field1, field2] => format!("`{field1}` and `{field2}`"),
1760             [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1761             _ => {
1762                 truncated_fields_error =
1763                     format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1764                 displayable_field_names
1765                     .iter()
1766                     .take(3)
1767                     .map(|n| format!("`{n}`"))
1768                     .collect::<Vec<_>>()
1769                     .join(", ")
1770             }
1771         };
1772
1773         let mut err = struct_span_err!(
1774             self.tcx.sess,
1775             span,
1776             E0063,
1777             "missing field{} {}{} in initializer of `{}`",
1778             pluralize!(len),
1779             remaining_fields_names,
1780             truncated_fields_error,
1781             adt_ty
1782         );
1783         err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1784
1785         // If the last field is a range literal, but it isn't supposed to be, then they probably
1786         // meant to use functional update syntax.
1787         //
1788         // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1789         if let Some((
1790             last,
1791             ExprKind::Struct(
1792                 QPath::LangItem(LangItem::Range, ..),
1793                 &[ref range_start, ref range_end],
1794                 _,
1795             ),
1796         )) = ast_fields.last().map(|last| (last, &last.expr.kind)) &&
1797         let variant_field =
1798             variant.fields.iter().find(|field| field.ident(self.tcx) == last.ident) &&
1799         let range_def_id = self.tcx.lang_items().range_struct() &&
1800         variant_field
1801             .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1802             .map(|adt| adt.did())
1803             != range_def_id
1804         {
1805             let instead = self
1806                 .tcx
1807                 .sess
1808                 .source_map()
1809                 .span_to_snippet(range_end.expr.span)
1810                 .map(|s| format!(" from `{s}`"))
1811                 .unwrap_or_default();
1812             err.span_suggestion(
1813                 range_start.span.shrink_to_hi(),
1814                 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1815                 ",",
1816                 Applicability::MaybeIncorrect,
1817             );
1818         }
1819
1820         err.emit();
1821     }
1822
1823     /// Report an error for a struct field expression when there are invisible fields.
1824     ///
1825     /// ```text
1826     /// error: cannot construct `Foo` with struct literal syntax due to private fields
1827     ///  --> src/main.rs:8:5
1828     ///   |
1829     /// 8 |     foo::Foo {};
1830     ///   |     ^^^^^^^^
1831     ///
1832     /// error: aborting due to previous error
1833     /// ```
1834     fn report_private_fields(
1835         &self,
1836         adt_ty: Ty<'tcx>,
1837         span: Span,
1838         private_fields: Vec<&ty::FieldDef>,
1839         used_fields: &'tcx [hir::ExprField<'tcx>],
1840     ) {
1841         let mut err = self.tcx.sess.struct_span_err(
1842             span,
1843             &format!(
1844                 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1845             ),
1846         );
1847         let (used_private_fields, remaining_private_fields): (
1848             Vec<(Symbol, Span, bool)>,
1849             Vec<(Symbol, Span, bool)>,
1850         ) = private_fields
1851             .iter()
1852             .map(|field| {
1853                 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1854                     Some(used_field) => (field.name, used_field.span, true),
1855                     None => (field.name, self.tcx.def_span(field.did), false),
1856                 }
1857             })
1858             .partition(|field| field.2);
1859         err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1860         if !remaining_private_fields.is_empty() {
1861             let remaining_private_fields_len = remaining_private_fields.len();
1862             let names = match &remaining_private_fields
1863                 .iter()
1864                 .map(|(name, _, _)| name)
1865                 .collect::<Vec<_>>()[..]
1866             {
1867                 _ if remaining_private_fields_len > 6 => String::new(),
1868                 [name] => format!("`{name}` "),
1869                 [names @ .., last] => {
1870                     let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1871                     format!("{} and `{last}` ", names.join(", "))
1872                 }
1873                 [] => unreachable!(),
1874             };
1875             err.note(format!(
1876                 "... and other private field{s} {names}that {were} not provided",
1877                 s = pluralize!(remaining_private_fields_len),
1878                 were = pluralize!("was", remaining_private_fields_len),
1879             ));
1880         }
1881         err.emit();
1882     }
1883
1884     fn report_unknown_field(
1885         &self,
1886         ty: Ty<'tcx>,
1887         variant: &'tcx ty::VariantDef,
1888         field: &hir::ExprField<'_>,
1889         skip_fields: &[hir::ExprField<'_>],
1890         kind_name: &str,
1891         expr_span: Span,
1892     ) {
1893         if variant.is_recovered() {
1894             self.set_tainted_by_errors();
1895             return;
1896         }
1897         let mut err = self.type_error_struct_with_diag(
1898             field.ident.span,
1899             |actual| match ty.kind() {
1900                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1901                     self.tcx.sess,
1902                     field.ident.span,
1903                     E0559,
1904                     "{} `{}::{}` has no field named `{}`",
1905                     kind_name,
1906                     actual,
1907                     variant.name,
1908                     field.ident
1909                 ),
1910                 _ => struct_span_err!(
1911                     self.tcx.sess,
1912                     field.ident.span,
1913                     E0560,
1914                     "{} `{}` has no field named `{}`",
1915                     kind_name,
1916                     actual,
1917                     field.ident
1918                 ),
1919             },
1920             ty,
1921         );
1922
1923         let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1924         match variant.ctor_kind {
1925             CtorKind::Fn => match ty.kind() {
1926                 ty::Adt(adt, ..) if adt.is_enum() => {
1927                     err.span_label(
1928                         variant_ident_span,
1929                         format!(
1930                             "`{adt}::{variant}` defined here",
1931                             adt = ty,
1932                             variant = variant.name,
1933                         ),
1934                     );
1935                     err.span_label(field.ident.span, "field does not exist");
1936                     err.span_suggestion_verbose(
1937                         expr_span,
1938                         &format!(
1939                             "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1940                             adt = ty,
1941                             variant = variant.name,
1942                         ),
1943                         format!(
1944                             "{adt}::{variant}(/* fields */)",
1945                             adt = ty,
1946                             variant = variant.name,
1947                         ),
1948                         Applicability::HasPlaceholders,
1949                     );
1950                 }
1951                 _ => {
1952                     err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1953                     err.span_label(field.ident.span, "field does not exist");
1954                     err.span_suggestion_verbose(
1955                         expr_span,
1956                         &format!(
1957                             "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1958                             adt = ty,
1959                             kind_name = kind_name,
1960                         ),
1961                         format!("{adt}(/* fields */)", adt = ty),
1962                         Applicability::HasPlaceholders,
1963                     );
1964                 }
1965             },
1966             _ => {
1967                 // prevent all specified fields from being suggested
1968                 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
1969                 if let Some(field_name) = self.suggest_field_name(
1970                     variant,
1971                     field.ident.name,
1972                     skip_fields.collect(),
1973                     expr_span,
1974                 ) {
1975                     err.span_suggestion(
1976                         field.ident.span,
1977                         "a field with a similar name exists",
1978                         field_name,
1979                         Applicability::MaybeIncorrect,
1980                     );
1981                 } else {
1982                     match ty.kind() {
1983                         ty::Adt(adt, ..) => {
1984                             if adt.is_enum() {
1985                                 err.span_label(
1986                                     field.ident.span,
1987                                     format!("`{}::{}` does not have this field", ty, variant.name),
1988                                 );
1989                             } else {
1990                                 err.span_label(
1991                                     field.ident.span,
1992                                     format!("`{ty}` does not have this field"),
1993                                 );
1994                             }
1995                             let available_field_names =
1996                                 self.available_field_names(variant, expr_span);
1997                             if !available_field_names.is_empty() {
1998                                 err.note(&format!(
1999                                     "available fields are: {}",
2000                                     self.name_series_display(available_field_names)
2001                                 ));
2002                             }
2003                         }
2004                         _ => bug!("non-ADT passed to report_unknown_field"),
2005                     }
2006                 };
2007             }
2008         }
2009         err.emit();
2010     }
2011
2012     // Return a hint about the closest match in field names
2013     fn suggest_field_name(
2014         &self,
2015         variant: &'tcx ty::VariantDef,
2016         field: Symbol,
2017         skip: Vec<Symbol>,
2018         // The span where stability will be checked
2019         span: Span,
2020     ) -> Option<Symbol> {
2021         let names = variant
2022             .fields
2023             .iter()
2024             .filter_map(|field| {
2025                 // ignore already set fields and private fields from non-local crates
2026                 // and unstable fields.
2027                 if skip.iter().any(|&x| x == field.name)
2028                     || (!variant.def_id.is_local() && !field.vis.is_public())
2029                     || matches!(
2030                         self.tcx.eval_stability(field.did, None, span, None),
2031                         stability::EvalResult::Deny { .. }
2032                     )
2033                 {
2034                     None
2035                 } else {
2036                     Some(field.name)
2037                 }
2038             })
2039             .collect::<Vec<Symbol>>();
2040
2041         find_best_match_for_name(&names, field, None)
2042     }
2043
2044     fn available_field_names(
2045         &self,
2046         variant: &'tcx ty::VariantDef,
2047         access_span: Span,
2048     ) -> Vec<Symbol> {
2049         variant
2050             .fields
2051             .iter()
2052             .filter(|field| {
2053                 let def_scope = self
2054                     .tcx
2055                     .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2056                     .1;
2057                 field.vis.is_accessible_from(def_scope, self.tcx)
2058                     && !matches!(
2059                         self.tcx.eval_stability(field.did, None, access_span, None),
2060                         stability::EvalResult::Deny { .. }
2061                     )
2062             })
2063             .filter(|field| !self.tcx.is_doc_hidden(field.did))
2064             .map(|field| field.name)
2065             .collect()
2066     }
2067
2068     fn name_series_display(&self, names: Vec<Symbol>) -> String {
2069         // dynamic limit, to never omit just one field
2070         let limit = if names.len() == 6 { 6 } else { 5 };
2071         let mut display =
2072             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2073         if names.len() > limit {
2074             display = format!("{} ... and {} others", display, names.len() - limit);
2075         }
2076         display
2077     }
2078
2079     // Check field access expressions
2080     fn check_field(
2081         &self,
2082         expr: &'tcx hir::Expr<'tcx>,
2083         base: &'tcx hir::Expr<'tcx>,
2084         field: Ident,
2085     ) -> Ty<'tcx> {
2086         debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2087         let expr_t = self.check_expr(base);
2088         let expr_t = self.structurally_resolved_type(base.span, expr_t);
2089         let mut private_candidate = None;
2090         let mut autoderef = self.autoderef(expr.span, expr_t);
2091         while let Some((base_t, _)) = autoderef.next() {
2092             debug!("base_t: {:?}", base_t);
2093             match base_t.kind() {
2094                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2095                     debug!("struct named {:?}", base_t);
2096                     let (ident, def_scope) =
2097                         self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2098                     let fields = &base_def.non_enum_variant().fields;
2099                     if let Some(index) = fields
2100                         .iter()
2101                         .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2102                     {
2103                         let field = &fields[index];
2104                         let field_ty = self.field_ty(expr.span, field, substs);
2105                         // Save the index of all fields regardless of their visibility in case
2106                         // of error recovery.
2107                         self.write_field_index(expr.hir_id, index);
2108                         let adjustments = self.adjust_steps(&autoderef);
2109                         if field.vis.is_accessible_from(def_scope, self.tcx) {
2110                             self.apply_adjustments(base, adjustments);
2111                             self.register_predicates(autoderef.into_obligations());
2112
2113                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2114                             return field_ty;
2115                         }
2116                         private_candidate = Some((adjustments, base_def.did(), field_ty));
2117                     }
2118                 }
2119                 ty::Tuple(tys) => {
2120                     let fstr = field.as_str();
2121                     if let Ok(index) = fstr.parse::<usize>() {
2122                         if fstr == index.to_string() {
2123                             if let Some(&field_ty) = tys.get(index) {
2124                                 let adjustments = self.adjust_steps(&autoderef);
2125                                 self.apply_adjustments(base, adjustments);
2126                                 self.register_predicates(autoderef.into_obligations());
2127
2128                                 self.write_field_index(expr.hir_id, index);
2129                                 return field_ty;
2130                             }
2131                         }
2132                     }
2133                 }
2134                 _ => {}
2135             }
2136         }
2137         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2138
2139         if let Some((adjustments, did, field_ty)) = private_candidate {
2140             // (#90483) apply adjustments to avoid ExprUseVisitor from
2141             // creating erroneous projection.
2142             self.apply_adjustments(base, adjustments);
2143             self.ban_private_field_access(expr, expr_t, field, did);
2144             return field_ty;
2145         }
2146
2147         if field.name == kw::Empty {
2148         } else if self.method_exists(field, expr_t, expr.hir_id, true) {
2149             self.ban_take_value_of_method(expr, expr_t, field);
2150         } else if !expr_t.is_primitive_ty() {
2151             self.ban_nonexisting_field(field, base, expr, expr_t);
2152         } else {
2153             let field_name = field.to_string();
2154             let mut err = type_error_struct!(
2155                 self.tcx().sess,
2156                 field.span,
2157                 expr_t,
2158                 E0610,
2159                 "`{expr_t}` is a primitive type and therefore doesn't have fields",
2160             );
2161             let is_valid_suffix = |field: String| {
2162                 if field == "f32" || field == "f64" {
2163                     return true;
2164                 }
2165                 let mut chars = field.chars().peekable();
2166                 match chars.peek() {
2167                     Some('e') | Some('E') => {
2168                         chars.next();
2169                         if let Some(c) = chars.peek()
2170                             && !c.is_numeric() && *c != '-' && *c != '+'
2171                         {
2172                             return false;
2173                         }
2174                         while let Some(c) = chars.peek() {
2175                             if !c.is_numeric() {
2176                                 break;
2177                             }
2178                             chars.next();
2179                         }
2180                     }
2181                     _ => (),
2182                 }
2183                 let suffix = chars.collect::<String>();
2184                 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2185             };
2186             if let ty::Infer(ty::IntVar(_)) = expr_t.kind()
2187                 && let ExprKind::Lit(Spanned {
2188                     node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2189                     ..
2190                 }) = base.kind
2191                 && !base.span.from_expansion()
2192                 && is_valid_suffix(field_name)
2193             {
2194                 err.span_suggestion_verbose(
2195                     field.span.shrink_to_lo(),
2196                     "If the number is meant to be a floating point number, consider adding a `0` after the period",
2197                     '0',
2198                     Applicability::MaybeIncorrect,
2199                 );
2200             }
2201             err.emit();
2202         }
2203
2204         self.tcx().ty_error()
2205     }
2206
2207     fn check_call_constructor(
2208         &self,
2209         err: &mut Diagnostic,
2210         base: &'tcx hir::Expr<'tcx>,
2211         def_id: DefId,
2212     ) {
2213         if let Some(local_id) = def_id.as_local() {
2214             let hir_id = self.tcx.hir().local_def_id_to_hir_id(local_id);
2215             let node = self.tcx.hir().get(hir_id);
2216
2217             if let Some(fields) = node.tuple_fields() {
2218                 let kind = match self.tcx.opt_def_kind(local_id) {
2219                     Some(DefKind::Ctor(of, _)) => of,
2220                     _ => return,
2221                 };
2222
2223                 suggest_call_constructor(base.span, kind, fields.len(), err);
2224             }
2225         } else {
2226             // The logic here isn't smart but `associated_item_def_ids`
2227             // doesn't work nicely on local.
2228             if let DefKind::Ctor(of, _) = self.tcx.def_kind(def_id) {
2229                 let parent_def_id = self.tcx.parent(def_id);
2230                 let fields = self.tcx.associated_item_def_ids(parent_def_id);
2231                 suggest_call_constructor(base.span, of, fields.len(), err);
2232             }
2233         }
2234     }
2235
2236     fn suggest_await_on_field_access(
2237         &self,
2238         err: &mut Diagnostic,
2239         field_ident: Ident,
2240         base: &'tcx hir::Expr<'tcx>,
2241         ty: Ty<'tcx>,
2242     ) {
2243         let output_ty = match self.get_impl_future_output_ty(ty) {
2244             Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2245             _ => return,
2246         };
2247         let mut add_label = true;
2248         if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2249             // no field access on enum type
2250             if !def.is_enum() {
2251                 if def
2252                     .non_enum_variant()
2253                     .fields
2254                     .iter()
2255                     .any(|field| field.ident(self.tcx) == field_ident)
2256                 {
2257                     add_label = false;
2258                     err.span_label(
2259                         field_ident.span,
2260                         "field not available in `impl Future`, but it is available in its `Output`",
2261                     );
2262                     err.span_suggestion_verbose(
2263                         base.span.shrink_to_hi(),
2264                         "consider `await`ing on the `Future` and access the field of its `Output`",
2265                         ".await",
2266                         Applicability::MaybeIncorrect,
2267                     );
2268                 }
2269             }
2270         }
2271         if add_label {
2272             err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2273         }
2274     }
2275
2276     fn ban_nonexisting_field(
2277         &self,
2278         field: Ident,
2279         base: &'tcx hir::Expr<'tcx>,
2280         expr: &'tcx hir::Expr<'tcx>,
2281         expr_t: Ty<'tcx>,
2282     ) {
2283         debug!(
2284             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
2285             field, base, expr, expr_t
2286         );
2287         let mut err = self.no_such_field_err(field, expr_t, base.hir_id);
2288
2289         match *expr_t.peel_refs().kind() {
2290             ty::Array(_, len) => {
2291                 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
2292             }
2293             ty::RawPtr(..) => {
2294                 self.suggest_first_deref_field(&mut err, expr, base, field);
2295             }
2296             ty::Adt(def, _) if !def.is_enum() => {
2297                 self.suggest_fields_on_recordish(&mut err, def, field, expr.span);
2298             }
2299             ty::Param(param_ty) => {
2300                 self.point_at_param_definition(&mut err, param_ty);
2301             }
2302             ty::Opaque(_, _) => {
2303                 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
2304             }
2305             ty::FnDef(def_id, _) => {
2306                 self.check_call_constructor(&mut err, base, def_id);
2307             }
2308             _ => {}
2309         }
2310
2311         if field.name == kw::Await {
2312             // We know by construction that `<expr>.await` is either on Rust 2015
2313             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2314             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2315             err.help_use_latest_edition();
2316         }
2317
2318         err.emit();
2319     }
2320
2321     fn ban_private_field_access(
2322         &self,
2323         expr: &hir::Expr<'_>,
2324         expr_t: Ty<'tcx>,
2325         field: Ident,
2326         base_did: DefId,
2327     ) {
2328         let struct_path = self.tcx().def_path_str(base_did);
2329         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2330         let mut err = struct_span_err!(
2331             self.tcx().sess,
2332             field.span,
2333             E0616,
2334             "field `{field}` of {kind_name} `{struct_path}` is private",
2335         );
2336         err.span_label(field.span, "private field");
2337         // Also check if an accessible method exists, which is often what is meant.
2338         if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2339         {
2340             self.suggest_method_call(
2341                 &mut err,
2342                 &format!("a method `{field}` also exists, call it with parentheses"),
2343                 field,
2344                 expr_t,
2345                 expr,
2346                 None,
2347             );
2348         }
2349         err.emit();
2350     }
2351
2352     fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2353         let mut err = type_error_struct!(
2354             self.tcx().sess,
2355             field.span,
2356             expr_t,
2357             E0615,
2358             "attempted to take value of method `{field}` on type `{expr_t}`",
2359         );
2360         err.span_label(field.span, "method, not a field");
2361         let expr_is_call =
2362             if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2363                 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2364             {
2365                 expr.hir_id == callee.hir_id
2366             } else {
2367                 false
2368             };
2369         let expr_snippet =
2370             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2371         let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2372         let after_open = expr.span.lo() + rustc_span::BytePos(1);
2373         let before_close = expr.span.hi() - rustc_span::BytePos(1);
2374
2375         if expr_is_call && is_wrapped {
2376             err.multipart_suggestion(
2377                 "remove wrapping parentheses to call the method",
2378                 vec![
2379                     (expr.span.with_hi(after_open), String::new()),
2380                     (expr.span.with_lo(before_close), String::new()),
2381                 ],
2382                 Applicability::MachineApplicable,
2383             );
2384         } else if !self.expr_in_place(expr.hir_id) {
2385             // Suggest call parentheses inside the wrapping parentheses
2386             let span = if is_wrapped {
2387                 expr.span.with_lo(after_open).with_hi(before_close)
2388             } else {
2389                 expr.span
2390             };
2391             self.suggest_method_call(
2392                 &mut err,
2393                 "use parentheses to call the method",
2394                 field,
2395                 expr_t,
2396                 expr,
2397                 Some(span),
2398             );
2399         } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2400             && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2401             && let ExprKind::Field(base_expr, _) = expr.kind
2402             && adt_def.variants().len() == 1
2403             && adt_def
2404                 .variants()
2405                 .iter()
2406                 .next()
2407                 .unwrap()
2408                 .fields
2409                 .iter()
2410                 .any(|f| f.ident(self.tcx) == field)
2411         {
2412             err.multipart_suggestion(
2413                 "to access the field, dereference first",
2414                 vec![
2415                     (base_expr.span.shrink_to_lo(), "(*".to_string()),
2416                     (base_expr.span.shrink_to_hi(), ")".to_string()),
2417                 ],
2418                 Applicability::MaybeIncorrect,
2419             );
2420         } else {
2421             err.help("methods are immutable and cannot be assigned to");
2422         }
2423
2424         err.emit();
2425     }
2426
2427     fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2428         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2429         let generic_param = generics.type_param(&param, self.tcx);
2430         if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2431             return;
2432         }
2433         let param_def_id = generic_param.def_id;
2434         let param_hir_id = match param_def_id.as_local() {
2435             Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2436             None => return,
2437         };
2438         let param_span = self.tcx.hir().span(param_hir_id);
2439         let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2440
2441         err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2442     }
2443
2444     fn suggest_fields_on_recordish(
2445         &self,
2446         err: &mut Diagnostic,
2447         def: ty::AdtDef<'tcx>,
2448         field: Ident,
2449         access_span: Span,
2450     ) {
2451         if let Some(suggested_field_name) =
2452             self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2453         {
2454             err.span_suggestion(
2455                 field.span,
2456                 "a field with a similar name exists",
2457                 suggested_field_name,
2458                 Applicability::MaybeIncorrect,
2459             );
2460         } else {
2461             err.span_label(field.span, "unknown field");
2462             let struct_variant_def = def.non_enum_variant();
2463             let field_names = self.available_field_names(struct_variant_def, access_span);
2464             if !field_names.is_empty() {
2465                 err.note(&format!(
2466                     "available fields are: {}",
2467                     self.name_series_display(field_names),
2468                 ));
2469             }
2470         }
2471     }
2472
2473     fn maybe_suggest_array_indexing(
2474         &self,
2475         err: &mut Diagnostic,
2476         expr: &hir::Expr<'_>,
2477         base: &hir::Expr<'_>,
2478         field: Ident,
2479         len: ty::Const<'tcx>,
2480     ) {
2481         if let (Some(len), Ok(user_index)) =
2482             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2483             && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2484         {
2485             let help = "instead of using tuple indexing, use array indexing";
2486             let suggestion = format!("{base}[{field}]");
2487             let applicability = if len < user_index {
2488                 Applicability::MachineApplicable
2489             } else {
2490                 Applicability::MaybeIncorrect
2491             };
2492             err.span_suggestion(expr.span, help, suggestion, applicability);
2493         }
2494     }
2495
2496     fn suggest_first_deref_field(
2497         &self,
2498         err: &mut Diagnostic,
2499         expr: &hir::Expr<'_>,
2500         base: &hir::Expr<'_>,
2501         field: Ident,
2502     ) {
2503         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2504             let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2505             let suggestion = format!("(*{base}).{field}");
2506             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2507         }
2508     }
2509
2510     fn no_such_field_err(
2511         &self,
2512         field: Ident,
2513         expr_t: Ty<'tcx>,
2514         id: HirId,
2515     ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2516         let span = field.span;
2517         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2518
2519         let mut err = type_error_struct!(
2520             self.tcx().sess,
2521             field.span,
2522             expr_t,
2523             E0609,
2524             "no field `{field}` on type `{expr_t}`",
2525         );
2526
2527         // try to add a suggestion in case the field is a nested field of a field of the Adt
2528         let mod_id = self.tcx.parent_module(id).to_def_id();
2529         if let Some((fields, substs)) =
2530             self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2531         {
2532             for candidate_field in fields {
2533                 if let Some(mut field_path) = self.check_for_nested_field_satisfying(
2534                     span,
2535                     &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2536                     candidate_field,
2537                     substs,
2538                     vec![],
2539                     mod_id,
2540                 ) {
2541                     // field_path includes `field` that we're looking for, so pop it.
2542                     field_path.pop();
2543
2544                     let field_path_str = field_path
2545                         .iter()
2546                         .map(|id| id.name.to_ident_string())
2547                         .collect::<Vec<String>>()
2548                         .join(".");
2549                     debug!("field_path_str: {:?}", field_path_str);
2550
2551                     err.span_suggestion_verbose(
2552                         field.span.shrink_to_lo(),
2553                         "one of the expressions' fields has a field of the same name",
2554                         format!("{field_path_str}."),
2555                         Applicability::MaybeIncorrect,
2556                     );
2557                 }
2558             }
2559         }
2560         err
2561     }
2562
2563     pub(crate) fn get_field_candidates_considering_privacy(
2564         &self,
2565         span: Span,
2566         base_ty: Ty<'tcx>,
2567         mod_id: DefId,
2568     ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2569         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2570
2571         for (base_t, _) in self.autoderef(span, base_ty) {
2572             match base_t.kind() {
2573                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2574                     let tcx = self.tcx;
2575                     let fields = &base_def.non_enum_variant().fields;
2576                     // Some struct, e.g. some that impl `Deref`, have all private fields
2577                     // because you're expected to deref them to access the _real_ fields.
2578                     // This, for example, will help us suggest accessing a field through a `Box<T>`.
2579                     if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2580                         continue;
2581                     }
2582                     return Some((
2583                         fields
2584                             .iter()
2585                             .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2586                             // For compile-time reasons put a limit on number of fields we search
2587                             .take(100),
2588                         substs,
2589                     ));
2590                 }
2591                 _ => {}
2592             }
2593         }
2594         None
2595     }
2596
2597     /// This method is called after we have encountered a missing field error to recursively
2598     /// search for the field
2599     pub(crate) fn check_for_nested_field_satisfying(
2600         &self,
2601         span: Span,
2602         matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2603         candidate_field: &ty::FieldDef,
2604         subst: SubstsRef<'tcx>,
2605         mut field_path: Vec<Ident>,
2606         mod_id: DefId,
2607     ) -> Option<Vec<Ident>> {
2608         debug!(
2609             "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2610             span, candidate_field, field_path
2611         );
2612
2613         if field_path.len() > 3 {
2614             // For compile-time reasons and to avoid infinite recursion we only check for fields
2615             // up to a depth of three
2616             None
2617         } else {
2618             field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2619             let field_ty = candidate_field.ty(self.tcx, subst);
2620             if matches(candidate_field, field_ty) {
2621                 return Some(field_path);
2622             } else if let Some((nested_fields, subst)) =
2623                 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2624             {
2625                 // recursively search fields of `candidate_field` if it's a ty::Adt
2626                 for field in nested_fields {
2627                     if let Some(field_path) = self.check_for_nested_field_satisfying(
2628                         span,
2629                         matches,
2630                         field,
2631                         subst,
2632                         field_path.clone(),
2633                         mod_id,
2634                     ) {
2635                         return Some(field_path);
2636                     }
2637                 }
2638             }
2639             None
2640         }
2641     }
2642
2643     fn check_expr_index(
2644         &self,
2645         base: &'tcx hir::Expr<'tcx>,
2646         idx: &'tcx hir::Expr<'tcx>,
2647         expr: &'tcx hir::Expr<'tcx>,
2648     ) -> Ty<'tcx> {
2649         let base_t = self.check_expr(&base);
2650         let idx_t = self.check_expr(&idx);
2651
2652         if base_t.references_error() {
2653             base_t
2654         } else if idx_t.references_error() {
2655             idx_t
2656         } else {
2657             let base_t = self.structurally_resolved_type(base.span, base_t);
2658             match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2659                 Some((index_ty, element_ty)) => {
2660                     // two-phase not needed because index_ty is never mutable
2661                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2662                     self.select_obligations_where_possible(false, |errors| {
2663                         self.point_at_index_if_possible(errors, idx.span)
2664                     });
2665                     element_ty
2666                 }
2667                 None => {
2668                     let mut err = type_error_struct!(
2669                         self.tcx.sess,
2670                         expr.span,
2671                         base_t,
2672                         E0608,
2673                         "cannot index into a value of type `{base_t}`",
2674                     );
2675                     // Try to give some advice about indexing tuples.
2676                     if let ty::Tuple(..) = base_t.kind() {
2677                         let mut needs_note = true;
2678                         // If the index is an integer, we can show the actual
2679                         // fixed expression:
2680                         if let ExprKind::Lit(ref lit) = idx.kind {
2681                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2682                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2683                                 if let Ok(snip) = snip {
2684                                     err.span_suggestion(
2685                                         expr.span,
2686                                         "to access tuple elements, use",
2687                                         format!("{snip}.{i}"),
2688                                         Applicability::MachineApplicable,
2689                                     );
2690                                     needs_note = false;
2691                                 }
2692                             }
2693                         }
2694                         if needs_note {
2695                             err.help(
2696                                 "to access tuple elements, use tuple indexing \
2697                                         syntax (e.g., `tuple.0`)",
2698                             );
2699                         }
2700                     }
2701                     err.emit();
2702                     self.tcx.ty_error()
2703                 }
2704             }
2705         }
2706     }
2707
2708     fn point_at_index_if_possible(
2709         &self,
2710         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2711         span: Span,
2712     ) {
2713         for error in errors {
2714             match error.obligation.predicate.kind().skip_binder() {
2715                 ty::PredicateKind::Trait(predicate)
2716                     if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2717                 }
2718                 _ => continue,
2719             }
2720             error.obligation.cause.span = span;
2721         }
2722     }
2723
2724     fn check_expr_yield(
2725         &self,
2726         value: &'tcx hir::Expr<'tcx>,
2727         expr: &'tcx hir::Expr<'tcx>,
2728         src: &'tcx hir::YieldSource,
2729     ) -> Ty<'tcx> {
2730         match self.resume_yield_tys {
2731             Some((resume_ty, yield_ty)) => {
2732                 self.check_expr_coercable_to_type(&value, yield_ty, None);
2733
2734                 resume_ty
2735             }
2736             // Given that this `yield` expression was generated as a result of lowering a `.await`,
2737             // we know that the yield type must be `()`; however, the context won't contain this
2738             // information. Hence, we check the source of the yield expression here and check its
2739             // value's type against `()` (this check should always hold).
2740             None if src.is_await() => {
2741                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2742                 self.tcx.mk_unit()
2743             }
2744             _ => {
2745                 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2746                 // Avoid expressions without types during writeback (#78653).
2747                 self.check_expr(value);
2748                 self.tcx.mk_unit()
2749             }
2750         }
2751     }
2752
2753     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2754         let needs = if is_input { Needs::None } else { Needs::MutPlace };
2755         let ty = self.check_expr_with_needs(expr, needs);
2756         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2757
2758         if !is_input && !expr.is_syntactic_place_expr() {
2759             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2760             err.span_label(expr.span, "cannot assign to this expression");
2761             err.emit();
2762         }
2763
2764         // If this is an input value, we require its type to be fully resolved
2765         // at this point. This allows us to provide helpful coercions which help
2766         // pass the type candidate list in a later pass.
2767         //
2768         // We don't require output types to be resolved at this point, which
2769         // allows them to be inferred based on how they are used later in the
2770         // function.
2771         if is_input {
2772             let ty = self.structurally_resolved_type(expr.span, ty);
2773             match *ty.kind() {
2774                 ty::FnDef(..) => {
2775                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2776                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2777                 }
2778                 ty::Ref(_, base_ty, mutbl) => {
2779                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2780                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2781                 }
2782                 _ => {}
2783             }
2784         }
2785     }
2786
2787     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2788         for (op, _op_sp) in asm.operands {
2789             match op {
2790                 hir::InlineAsmOperand::In { expr, .. } => {
2791                     self.check_expr_asm_operand(expr, true);
2792                 }
2793                 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2794                 | hir::InlineAsmOperand::InOut { expr, .. } => {
2795                     self.check_expr_asm_operand(expr, false);
2796                 }
2797                 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2798                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2799                     self.check_expr_asm_operand(in_expr, true);
2800                     if let Some(out_expr) = out_expr {
2801                         self.check_expr_asm_operand(out_expr, false);
2802                     }
2803                 }
2804                 // `AnonConst`s have their own body and is type-checked separately.
2805                 // As they don't flow into the type system we don't need them to
2806                 // be well-formed.
2807                 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2808                 hir::InlineAsmOperand::SymStatic { .. } => {}
2809             }
2810         }
2811         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2812             self.tcx.types.never
2813         } else {
2814             self.tcx.mk_unit()
2815         }
2816     }
2817 }
2818
2819 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2820     Some(match ty.kind() {
2821         ty::Bool => "true",
2822         ty::Char => "'a'",
2823         ty::Int(_) | ty::Uint(_) => "42",
2824         ty::Float(_) => "3.14159",
2825         ty::Error(_) | ty::Never => return None,
2826         _ => "value",
2827     })
2828 }