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, StashKey,
  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 arg_span = args.get(i).map(|a| a.span);
 565                     let span = arg_span.unwrap_or(expr.span);
 566                     let input = self.replace_bound_vars_with_fresh_vars(
 567                         span,
 568                         infer::LateBoundRegionConversionTime::FnCall,
 569                         fn_sig.input(i),
 570                     );
 571                     self.require_type_is_sized(
 572                         self.normalize_associated_types_in(span, input),
 573                         span,
 574                         traits::SizedArgumentType(arg_span),
 575                     );
 576                 }
 577             }
 578             // Here we want to prevent struct constructors from returning unsized types.
 579             // There were two cases this happened: fn pointer coercion in stable
 580             // and usual function call in presence of unsized_locals.
 581             // Also, as we just want to check sizedness, instead of introducing
 582             // placeholder lifetimes with probing, we just replace higher lifetimes
 583             // with fresh vars.
 584             let output = self.replace_bound_vars_with_fresh_vars(
 585                 expr.span,
 586                 infer::LateBoundRegionConversionTime::FnCall,
 587                 fn_sig.output(),
 588             );
 589             self.require_type_is_sized(
 590                 self.normalize_associated_types_in(expr.span, output),
 591                 expr.span,
 592                 traits::SizedReturnType,
 593             );
 594         }
 595
 596         // We always require that the type provided as the value for
 597         // a type parameter outlives the moment of instantiation.
 598         let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
 599         self.add_wf_bounds(substs, expr);
 600
 601         ty
 602     }
 603
 604     fn check_expr_break(
 605         &self,
 606         destination: hir::Destination,
 607         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 608         expr: &'tcx hir::Expr<'tcx>,
 609     ) -> Ty<'tcx> {
 610         let tcx = self.tcx;
 611         if let Ok(target_id) = destination.target_id {
 612             let (e_ty, cause);
 613             if let Some(e) = expr_opt {
 614                 // If this is a break with a value, we need to type-check
 615                 // the expression. Get an expected type from the loop context.
 616                 let opt_coerce_to = {
 617                     // We should release `enclosing_breakables` before the `check_expr_with_hint`
 618                     // below, so can't move this block of code to the enclosing scope and share
 619                     // `ctxt` with the second `enclosing_breakables` borrow below.
 620                     let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 621                     match enclosing_breakables.opt_find_breakable(target_id) {
 622                         Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
 623                         None => {
 624                             // Avoid ICE when `break` is inside a closure (#65383).
 625                             return tcx.ty_error_with_message(
 626                                 expr.span,
 627                                 "break was outside loop, but no error was emitted",
 628                             );
 629                         }
 630                     }
 631                 };
 632
 633                 // If the loop context is not a `loop { }`, then break with
 634                 // a value is illegal, and `opt_coerce_to` will be `None`.
 635                 // Just set expectation to error in that case.
 636                 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
 637
 638                 // Recurse without `enclosing_breakables` borrowed.
 639                 e_ty = self.check_expr_with_hint(e, coerce_to);
 640                 cause = self.misc(e.span);
 641             } else {
 642                 // Otherwise, this is a break *without* a value. That's
 643                 // always legal, and is equivalent to `break ()`.
 644                 e_ty = tcx.mk_unit();
 645                 cause = self.misc(expr.span);
 646             }
 647
 648             // Now that we have type-checked `expr_opt`, borrow
 649             // the `enclosing_loops` field and let's coerce the
 650             // type of `expr_opt` into what is expected.
 651             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 652             let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
 653                 // Avoid ICE when `break` is inside a closure (#65383).
 654                 return tcx.ty_error_with_message(
 655                     expr.span,
 656                     "break was outside loop, but no error was emitted",
 657                 );
 658             };
 659
 660             if let Some(ref mut coerce) = ctxt.coerce {
 661                 if let Some(ref e) = expr_opt {
 662                     coerce.coerce(self, &cause, e, e_ty);
 663                 } else {
 664                     assert!(e_ty.is_unit());
 665                     let ty = coerce.expected_ty();
 666                     coerce.coerce_forced_unit(
 667                         self,
 668                         &cause,
 669                         &mut |mut err| {
 670                             self.suggest_mismatched_types_on_tail(
 671                                 &mut err, expr, ty, e_ty, target_id,
 672                             );
 673                             if let Some(val) = ty_kind_suggestion(ty) {
 674                                 let label = destination
 675                                     .label
 676                                     .map(|l| format!(" {}", l.ident))
 677                                     .unwrap_or_else(String::new);
 678                                 err.span_suggestion(
 679                                     expr.span,
 680                                     "give it a value of the expected type",
 681                                     format!("break{label} {val}"),
 682                                     Applicability::HasPlaceholders,
 683                                 );
 684                             }
 685                         },
 686                         false,
 687                     );
 688                 }
 689             } else {
 690                 // If `ctxt.coerce` is `None`, we can just ignore
 691                 // the type of the expression.  This is because
 692                 // either this was a break *without* a value, in
 693                 // which case it is always a legal type (`()`), or
 694                 // else an error would have been flagged by the
 695                 // `loops` pass for using break with an expression
 696                 // where you are not supposed to.
 697                 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
 698             }
 699
 700             // If we encountered a `break`, then (no surprise) it may be possible to break from the
 701             // loop... unless the value being returned from the loop diverges itself, e.g.
 702             // `break return 5` or `break loop {}`.
 703             ctxt.may_break |= !self.diverges.get().is_always();
 704
 705             // the type of a `break` is always `!`, since it diverges
 706             tcx.types.never
 707         } else {
 708             // Otherwise, we failed to find the enclosing loop;
 709             // this can only happen if the `break` was not
 710             // inside a loop at all, which is caught by the
 711             // loop-checking pass.
 712             let err = self.tcx.ty_error_with_message(
 713                 expr.span,
 714                 "break was outside loop, but no error was emitted",
 715             );
 716
 717             // We still need to assign a type to the inner expression to
 718             // prevent the ICE in #43162.
 719             if let Some(e) = expr_opt {
 720                 self.check_expr_with_hint(e, err);
 721
 722                 // ... except when we try to 'break rust;'.
 723                 // ICE this expression in particular (see #43162).
 724                 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
 725                     if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
 726                         fatally_break_rust(self.tcx.sess);
 727                     }
 728                 }
 729             }
 730
 731             // There was an error; make type-check fail.
 732             err
 733         }
 734     }
 735
 736     fn check_expr_return(
 737         &self,
 738         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 739         expr: &'tcx hir::Expr<'tcx>,
 740     ) -> Ty<'tcx> {
 741         if self.ret_coercion.is_none() {
 742             let mut err = ReturnStmtOutsideOfFnBody {
 743                 span: expr.span,
 744                 encl_body_span: None,
 745                 encl_fn_span: None,
 746             };
 747
 748             let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
 749
 750             if let Some(hir::Node::Item(hir::Item {
 751                 kind: hir::ItemKind::Fn(..),
 752                 span: encl_fn_span,
 753                 ..
 754             }))
 755             | Some(hir::Node::TraitItem(hir::TraitItem {
 756                 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
 757                 span: encl_fn_span,
 758                 ..
 759             }))
 760             | Some(hir::Node::ImplItem(hir::ImplItem {
 761                 kind: hir::ImplItemKind::Fn(..),
 762                 span: encl_fn_span,
 763                 ..
 764             })) = self.tcx.hir().find_by_def_id(encl_item_id)
 765             {
 766                 // We are inside a function body, so reporting "return statement
 767                 // outside of function body" needs an explanation.
 768
 769                 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
 770
 771                 // If this didn't hold, we would not have to report an error in
 772                 // the first place.
 773                 assert_ne!(encl_item_id, encl_body_owner_id);
 774
 775                 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
 776                 let encl_body = self.tcx.hir().body(encl_body_id);
 777
 778                 err.encl_body_span = Some(encl_body.value.span);
 779                 err.encl_fn_span = Some(*encl_fn_span);
 780             }
 781
 782             self.tcx.sess.emit_err(err);
 783
 784             if let Some(e) = expr_opt {
 785                 // We still have to type-check `e` (issue #86188), but calling
 786                 // `check_return_expr` only works inside fn bodies.
 787                 self.check_expr(e);
 788             }
 789         } else if let Some(e) = expr_opt {
 790             if self.ret_coercion_span.get().is_none() {
 791                 self.ret_coercion_span.set(Some(e.span));
 792             }
 793             self.check_return_expr(e, true);
 794         } else {
 795             let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
 796             if self.ret_coercion_span.get().is_none() {
 797                 self.ret_coercion_span.set(Some(expr.span));
 798             }
 799             let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
 800             if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
 801                 coercion.coerce_forced_unit(
 802                     self,
 803                     &cause,
 804                     &mut |db| {
 805                         let span = fn_decl.output.span();
 806                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
 807                             db.span_label(
 808                                 span,
 809                                 format!("expected `{snippet}` because of this return type"),
 810                             );
 811                         }
 812                     },
 813                     true,
 814                 );
 815             } else {
 816                 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
 817             }
 818         }
 819         self.tcx.types.never
 820     }
 821
 822     /// `explicit_return` is `true` if we're checking an explicit `return expr`,
 823     /// and `false` if we're checking a trailing expression.
 824     pub(super) fn check_return_expr(
 825         &self,
 826         return_expr: &'tcx hir::Expr<'tcx>,
 827         explicit_return: bool,
 828     ) {
 829         let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
 830             span_bug!(return_expr.span, "check_return_expr called outside fn body")
 831         });
 832
 833         let ret_ty = ret_coercion.borrow().expected_ty();
 834         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
 835         let mut span = return_expr.span;
 836         // Use the span of the trailing expression for our cause,
 837         // not the span of the entire function
 838         if !explicit_return {
 839             if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
 840                 span = last_expr.span;
 841             }
 842         }
 843         ret_coercion.borrow_mut().coerce(
 844             self,
 845             &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
 846             return_expr,
 847             return_expr_ty,
 848         );
 849
 850         if self.return_type_has_opaque {
 851             // Point any obligations that were registered due to opaque type
 852             // inference at the return expression.
 853             self.select_obligations_where_possible(false, |errors| {
 854                 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
 855             });
 856         }
 857     }
 858
 859     fn point_at_return_for_opaque_ty_error(
 860         &self,
 861         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
 862         span: Span,
 863         return_expr_ty: Ty<'tcx>,
 864     ) {
 865         // Don't point at the whole block if it's empty
 866         if span == self.tcx.hir().span(self.body_id) {
 867             return;
 868         }
 869         for err in errors {
 870             let cause = &mut err.obligation.cause;
 871             if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
 872                 let new_cause = ObligationCause::new(
 873                     cause.span,
 874                     cause.body_id,
 875                     ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
 876                 );
 877                 *cause = new_cause;
 878             }
 879         }
 880     }
 881
 882     pub(crate) fn check_lhs_assignable(
 883         &self,
 884         lhs: &'tcx hir::Expr<'tcx>,
 885         err_code: &'static str,
 886         op_span: Span,
 887         adjust_err: impl FnOnce(&mut Diagnostic),
 888     ) {
 889         if lhs.is_syntactic_place_expr() {
 890             return;
 891         }
 892
 893         // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
 894         let mut err = self.tcx.sess.struct_span_err_with_code(
 895             op_span,
 896             "invalid left-hand side of assignment",
 897             DiagnosticId::Error(err_code.into()),
 898         );
 899         err.span_label(lhs.span, "cannot assign to this expression");
 900
 901         self.comes_from_while_condition(lhs.hir_id, |expr| {
 902             err.span_suggestion_verbose(
 903                 expr.span.shrink_to_lo(),
 904                 "you might have meant to use pattern destructuring",
 905                 "let ",
 906                 Applicability::MachineApplicable,
 907             );
 908         });
 909
 910         adjust_err(&mut err);
 911
 912         err.emit();
 913     }
 914
 915     // Check if an expression `original_expr_id` comes from the condition of a while loop,
 916     // as opposed from the body of a while loop, which we can naively check by iterating
 917     // parents until we find a loop...
 918     pub(super) fn comes_from_while_condition(
 919         &self,
 920         original_expr_id: HirId,
 921         then: impl FnOnce(&hir::Expr<'_>),
 922     ) {
 923         let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
 924         while let Some(node) = self.tcx.hir().find(parent) {
 925             match node {
 926                 hir::Node::Expr(hir::Expr {
 927                     kind:
 928                         hir::ExprKind::Loop(
 929                             hir::Block {
 930                                 expr:
 931                                     Some(hir::Expr {
 932                                         kind:
 933                                             hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
 934                                         ..
 935                                     }),
 936                                 ..
 937                             },
 938                             _,
 939                             hir::LoopSource::While,
 940                             _,
 941                         ),
 942                     ..
 943                 }) => {
 944                     // Check if our original expression is a child of the condition of a while loop
 945                     let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
 946                         self.tcx.hir().find_parent_node(*id)
 947                     })
 948                     .take_while(|id| *id != parent)
 949                     .any(|id| id == expr.hir_id);
 950                     // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
 951                     // where `while let` was more likely intended.
 952                     if expr_is_ancestor {
 953                         then(expr);
 954                     }
 955                     break;
 956                 }
 957                 hir::Node::Item(_)
 958                 | hir::Node::ImplItem(_)
 959                 | hir::Node::TraitItem(_)
 960                 | hir::Node::Crate(_) => break,
 961                 _ => {
 962                     parent = self.tcx.hir().get_parent_node(parent);
 963                 }
 964             }
 965         }
 966     }
 967
 968     // A generic function for checking the 'then' and 'else' clauses in an 'if'
 969     // or 'if-else' expression.
 970     fn check_then_else(
 971         &self,
 972         cond_expr: &'tcx hir::Expr<'tcx>,
 973         then_expr: &'tcx hir::Expr<'tcx>,
 974         opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
 975         sp: Span,
 976         orig_expected: Expectation<'tcx>,
 977     ) -> Ty<'tcx> {
 978         let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
 979
 980         self.warn_if_unreachable(
 981             cond_expr.hir_id,
 982             then_expr.span,
 983             "block in `if` or `while` expression",
 984         );
 985
 986         let cond_diverges = self.diverges.get();
 987         self.diverges.set(Diverges::Maybe);
 988
 989         let expected = orig_expected.adjust_for_branches(self);
 990         let then_ty = self.check_expr_with_expectation(then_expr, expected);
 991         let then_diverges = self.diverges.get();
 992         self.diverges.set(Diverges::Maybe);
 993
 994         // We've already taken the expected type's preferences
 995         // into account when typing the `then` branch. To figure
 996         // out the initial shot at a LUB, we thus only consider
 997         // `expected` if it represents a *hard* constraint
 998         // (`only_has_type`); otherwise, we just go with a
 999         // fresh type variable.
1000         let coerce_to_ty = expected.coercion_target_type(self, sp);
1001         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
1002
1003         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
1004
1005         if let Some(else_expr) = opt_else_expr {
1006             let else_ty = self.check_expr_with_expectation(else_expr, expected);
1007             let else_diverges = self.diverges.get();
1008
1009             let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1010             let if_cause = self.if_cause(
1011                 sp,
1012                 cond_expr.span,
1013                 then_expr,
1014                 else_expr,
1015                 then_ty,
1016                 else_ty,
1017                 opt_suggest_box_span,
1018             );
1019
1020             coerce.coerce(self, &if_cause, else_expr, else_ty);
1021
1022             // We won't diverge unless both branches do (or the condition does).
1023             self.diverges.set(cond_diverges | then_diverges & else_diverges);
1024         } else {
1025             self.if_fallback_coercion(sp, then_expr, &mut coerce);
1026
1027             // If the condition is false we can't diverge.
1028             self.diverges.set(cond_diverges);
1029         }
1030
1031         let result_ty = coerce.complete(self);
1032         if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1033     }
1034
1035     /// Type check assignment expression `expr` of form `lhs = rhs`.
1036     /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1037     fn check_expr_assign(
1038         &self,
1039         expr: &'tcx hir::Expr<'tcx>,
1040         expected: Expectation<'tcx>,
1041         lhs: &'tcx hir::Expr<'tcx>,
1042         rhs: &'tcx hir::Expr<'tcx>,
1043         span: Span,
1044     ) -> Ty<'tcx> {
1045         let expected_ty = expected.coercion_target_type(self, expr.span);
1046         if expected_ty == self.tcx.types.bool {
1047             // The expected type is `bool` but this will result in `()` so we can reasonably
1048             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1049             // The likely cause of this is `if foo = bar { .. }`.
1050             let actual_ty = self.tcx.mk_unit();
1051             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1052             let lhs_ty = self.check_expr(&lhs);
1053             let rhs_ty = self.check_expr(&rhs);
1054             let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1055                 (Applicability::MachineApplicable, true)
1056             } else {
1057                 (Applicability::MaybeIncorrect, false)
1058             };
1059             if !lhs.is_syntactic_place_expr()
1060                 && lhs.is_approximately_pattern()
1061                 && !matches!(lhs.kind, hir::ExprKind::Lit(_))
1062             {
1063                 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1064                 let hir = self.tcx.hir();
1065                 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1066                     hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1067                 {
1068                     err.span_suggestion_verbose(
1069                         expr.span.shrink_to_lo(),
1070                         "you might have meant to use pattern matching",
1071                         "let ",
1072                         applicability,
1073                     );
1074                 };
1075             }
1076             if eq {
1077                 err.span_suggestion_verbose(
1078                     span,
1079                     "you might have meant to compare for equality",
1080                     "==",
1081                     applicability,
1082                 );
1083             }
1084
1085             // If the assignment expression itself is ill-formed, don't
1086             // bother emitting another error
1087             if lhs_ty.references_error() || rhs_ty.references_error() {
1088                 err.delay_as_bug()
1089             } else {
1090                 err.emit();
1091             }
1092             return self.tcx.ty_error();
1093         }
1094
1095         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1096
1097         let suggest_deref_binop = |err: &mut Diagnostic, rhs_ty: Ty<'tcx>| {
1098             if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1099                 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1100                 // unsized, do not suggest dereferencing it.
1101                 let lhs_deref_ty_is_sized = self
1102                     .infcx
1103                     .type_implements_trait(
1104                         self.tcx.lang_items().sized_trait().unwrap(),
1105                         lhs_deref_ty,
1106                         ty::List::empty(),
1107                         self.param_env,
1108                     )
1109                     .may_apply();
1110                 if lhs_deref_ty_is_sized && self.can_coerce(rhs_ty, lhs_deref_ty) {
1111                     err.span_suggestion_verbose(
1112                         lhs.span.shrink_to_lo(),
1113                         "consider dereferencing here to assign to the mutably borrowed value",
1114                         "*",
1115                         Applicability::MachineApplicable,
1116                     );
1117                 }
1118             }
1119         };
1120
1121         self.check_lhs_assignable(lhs, "E0070", span, |err| {
1122             let rhs_ty = self.check_expr(&rhs);
1123             suggest_deref_binop(err, rhs_ty);
1124         });
1125
1126         // This is (basically) inlined `check_expr_coercable_to_type`, but we want
1127         // to suggest an additional fixup here in `suggest_deref_binop`.
1128         let rhs_ty = self.check_expr_with_hint(&rhs, lhs_ty);
1129         if let (_, Some(mut diag)) =
1130             self.demand_coerce_diag(rhs, rhs_ty, lhs_ty, Some(lhs), AllowTwoPhase::No)
1131         {
1132             suggest_deref_binop(&mut diag, rhs_ty);
1133             diag.emit();
1134         }
1135
1136         self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1137
1138         if lhs_ty.references_error() || rhs_ty.references_error() {
1139             self.tcx.ty_error()
1140         } else {
1141             self.tcx.mk_unit()
1142         }
1143     }
1144
1145     pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1146         // for let statements, this is done in check_stmt
1147         let init = let_expr.init;
1148         self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1149         // otherwise check exactly as a let statement
1150         self.check_decl(let_expr.into());
1151         // but return a bool, for this is a boolean expression
1152         self.tcx.types.bool
1153     }
1154
1155     fn check_expr_loop(
1156         &self,
1157         body: &'tcx hir::Block<'tcx>,
1158         source: hir::LoopSource,
1159         expected: Expectation<'tcx>,
1160         expr: &'tcx hir::Expr<'tcx>,
1161     ) -> Ty<'tcx> {
1162         let coerce = match source {
1163             // you can only use break with a value from a normal `loop { }`
1164             hir::LoopSource::Loop => {
1165                 let coerce_to = expected.coercion_target_type(self, body.span);
1166                 Some(CoerceMany::new(coerce_to))
1167             }
1168
1169             hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1170         };
1171
1172         let ctxt = BreakableCtxt {
1173             coerce,
1174             may_break: false, // Will get updated if/when we find a `break`.
1175         };
1176
1177         let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1178             self.check_block_no_value(&body);
1179         });
1180
1181         if ctxt.may_break {
1182             // No way to know whether it's diverging because
1183             // of a `break` or an outer `break` or `return`.
1184             self.diverges.set(Diverges::Maybe);
1185         }
1186
1187         // If we permit break with a value, then result type is
1188         // the LUB of the breaks (possibly ! if none); else, it
1189         // is nil. This makes sense because infinite loops
1190         // (which would have type !) are only possible iff we
1191         // permit break with a value [1].
1192         if ctxt.coerce.is_none() && !ctxt.may_break {
1193             // [1]
1194             self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1195         }
1196         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1197     }
1198
1199     /// Checks a method call.
1200     fn check_method_call(
1201         &self,
1202         expr: &'tcx hir::Expr<'tcx>,
1203         segment: &hir::PathSegment<'_>,
1204         args: &'tcx [hir::Expr<'tcx>],
1205         expected: Expectation<'tcx>,
1206     ) -> Ty<'tcx> {
1207         let rcvr = &args[0];
1208         let rcvr_t = self.check_expr(&rcvr);
1209         // no need to check for bot/err -- callee does that
1210         let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
1211         let span = segment.ident.span;
1212
1213         let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1214             Ok(method) => {
1215                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1216                 // trigger this codepath causing `structurally_resolved_type` to emit an error.
1217
1218                 self.write_method_call(expr.hir_id, method);
1219                 Ok(method)
1220             }
1221             Err(error) => {
1222                 if segment.ident.name != kw::Empty {
1223                     if let Some(mut err) = self.report_method_error(
1224                         span,
1225                         rcvr_t,
1226                         segment.ident,
1227                         SelfSource::MethodCall(&args[0]),
1228                         error,
1229                         Some(args),
1230                     ) {
1231                         err.emit();
1232                     }
1233                 }
1234                 Err(())
1235             }
1236         };
1237
1238         // Call the generic checker.
1239         self.check_method_argument_types(
1240             span,
1241             expr,
1242             method,
1243             &args[1..],
1244             DontTupleArguments,
1245             expected,
1246         )
1247     }
1248
1249     fn check_expr_cast(
1250         &self,
1251         e: &'tcx hir::Expr<'tcx>,
1252         t: &'tcx hir::Ty<'tcx>,
1253         expr: &'tcx hir::Expr<'tcx>,
1254     ) -> Ty<'tcx> {
1255         // Find the type of `e`. Supply hints based on the type we are casting to,
1256         // if appropriate.
1257         let t_cast = self.to_ty_saving_user_provided_ty(t);
1258         let t_cast = self.resolve_vars_if_possible(t_cast);
1259         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1260         let t_expr = self.resolve_vars_if_possible(t_expr);
1261
1262         // Eagerly check for some obvious errors.
1263         if t_expr.references_error() || t_cast.references_error() {
1264             self.tcx.ty_error()
1265         } else {
1266             // Defer other checks until we're done type checking.
1267             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1268             match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1269                 Ok(cast_check) => {
1270                     debug!(
1271                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1272                         t_cast, t_expr, cast_check,
1273                     );
1274                     deferred_cast_checks.push(cast_check);
1275                     t_cast
1276                 }
1277                 Err(_) => self.tcx.ty_error(),
1278             }
1279         }
1280     }
1281
1282     fn check_expr_array(
1283         &self,
1284         args: &'tcx [hir::Expr<'tcx>],
1285         expected: Expectation<'tcx>,
1286         expr: &'tcx hir::Expr<'tcx>,
1287     ) -> Ty<'tcx> {
1288         let element_ty = if !args.is_empty() {
1289             let coerce_to = expected
1290                 .to_option(self)
1291                 .and_then(|uty| match *uty.kind() {
1292                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1293                     _ => None,
1294                 })
1295                 .unwrap_or_else(|| {
1296                     self.next_ty_var(TypeVariableOrigin {
1297                         kind: TypeVariableOriginKind::TypeInference,
1298                         span: expr.span,
1299                     })
1300                 });
1301             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1302             assert_eq!(self.diverges.get(), Diverges::Maybe);
1303             for e in args {
1304                 let e_ty = self.check_expr_with_hint(e, coerce_to);
1305                 let cause = self.misc(e.span);
1306                 coerce.coerce(self, &cause, e, e_ty);
1307             }
1308             coerce.complete(self)
1309         } else {
1310             self.next_ty_var(TypeVariableOrigin {
1311                 kind: TypeVariableOriginKind::TypeInference,
1312                 span: expr.span,
1313             })
1314         };
1315         let array_len = args.len() as u64;
1316         self.suggest_array_len(expr, array_len);
1317         self.tcx.mk_array(element_ty, array_len)
1318     }
1319
1320     fn suggest_array_len(&self, expr: &'tcx hir::Expr<'tcx>, array_len: u64) {
1321         if let Some(parent_hir_id) = self.tcx.hir().find_parent_node(expr.hir_id) {
1322             let ty = match self.tcx.hir().find(parent_hir_id) {
1323                 Some(
1324                     hir::Node::Local(hir::Local { ty: Some(ty), .. })
1325                     | hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _), .. }),
1326                 ) => Some(ty),
1327                 _ => None,
1328             };
1329             if let Some(ty) = ty
1330                 && let hir::TyKind::Array(_, length) = ty.kind
1331                 && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
1332                 && let Some(span) = self.tcx.hir().opt_span(hir_id)
1333             {
1334                 match self.tcx.sess.diagnostic().steal_diagnostic(span, StashKey::UnderscoreForArrayLengths) {
1335                     Some(mut err) => {
1336                         err.span_suggestion(
1337                             span,
1338                             "consider specifying the array length",
1339                             array_len,
1340                             Applicability::MaybeIncorrect,
1341                         );
1342                         err.emit();
1343                     }
1344                     None => ()
1345                 }
1346             }
1347         }
1348     }
1349
1350     fn check_expr_const_block(
1351         &self,
1352         anon_const: &'tcx hir::AnonConst,
1353         expected: Expectation<'tcx>,
1354         _expr: &'tcx hir::Expr<'tcx>,
1355     ) -> Ty<'tcx> {
1356         let body = self.tcx.hir().body(anon_const.body);
1357
1358         // Create a new function context.
1359         let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1360         crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1361
1362         let ty = fcx.check_expr_with_expectation(&body.value, expected);
1363         fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1364         fcx.write_ty(anon_const.hir_id, ty);
1365         ty
1366     }
1367
1368     fn check_expr_repeat(
1369         &self,
1370         element: &'tcx hir::Expr<'tcx>,
1371         count: &'tcx hir::ArrayLen,
1372         expected: Expectation<'tcx>,
1373         expr: &'tcx hir::Expr<'tcx>,
1374     ) -> Ty<'tcx> {
1375         let tcx = self.tcx;
1376         let count = self.array_length_to_const(count);
1377         if let Some(count) = count.try_eval_usize(tcx, self.param_env) {
1378             self.suggest_array_len(expr, count);
1379         }
1380
1381         let uty = match expected {
1382             ExpectHasType(uty) => match *uty.kind() {
1383                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1384                 _ => None,
1385             },
1386             _ => None,
1387         };
1388
1389         let (element_ty, t) = match uty {
1390             Some(uty) => {
1391                 self.check_expr_coercable_to_type(&element, uty, None);
1392                 (uty, uty)
1393             }
1394             None => {
1395                 let ty = self.next_ty_var(TypeVariableOrigin {
1396                     kind: TypeVariableOriginKind::MiscVariable,
1397                     span: element.span,
1398                 });
1399                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1400                 (element_ty, ty)
1401             }
1402         };
1403
1404         if element_ty.references_error() {
1405             return tcx.ty_error();
1406         }
1407
1408         self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1409
1410         tcx.mk_ty(ty::Array(t, count))
1411     }
1412
1413     fn check_repeat_element_needs_copy_bound(
1414         &self,
1415         element: &hir::Expr<'_>,
1416         count: ty::Const<'tcx>,
1417         element_ty: Ty<'tcx>,
1418     ) {
1419         let tcx = self.tcx;
1420         // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1421         match &element.kind {
1422             hir::ExprKind::ConstBlock(..) => return,
1423             hir::ExprKind::Path(qpath) => {
1424                 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1425                 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1426                 {
1427                     return;
1428                 }
1429             }
1430             _ => {}
1431         }
1432         // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1433         // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1434         let is_const_fn = match element.kind {
1435             hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1436                 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1437                 _ => false,
1438             },
1439             _ => false,
1440         };
1441
1442         // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1443         // don't copy that one element, we move it. Only check for Copy if the length is larger.
1444         if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1445             let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1446             let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1447             self.require_type_meets(element_ty, element.span, code, lang_item);
1448         }
1449     }
1450
1451     fn check_expr_tuple(
1452         &self,
1453         elts: &'tcx [hir::Expr<'tcx>],
1454         expected: Expectation<'tcx>,
1455         expr: &'tcx hir::Expr<'tcx>,
1456     ) -> Ty<'tcx> {
1457         let flds = expected.only_has_type(self).and_then(|ty| {
1458             let ty = self.resolve_vars_with_obligations(ty);
1459             match ty.kind() {
1460                 ty::Tuple(flds) => Some(&flds[..]),
1461                 _ => None,
1462             }
1463         });
1464
1465         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1466             Some(fs) if i < fs.len() => {
1467                 let ety = fs[i];
1468                 self.check_expr_coercable_to_type(&e, ety, None);
1469                 ety
1470             }
1471             _ => self.check_expr_with_expectation(&e, NoExpectation),
1472         });
1473         let tuple = self.tcx.mk_tup(elt_ts_iter);
1474         if tuple.references_error() {
1475             self.tcx.ty_error()
1476         } else {
1477             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1478             tuple
1479         }
1480     }
1481
1482     fn check_expr_struct(
1483         &self,
1484         expr: &hir::Expr<'_>,
1485         expected: Expectation<'tcx>,
1486         qpath: &QPath<'_>,
1487         fields: &'tcx [hir::ExprField<'tcx>],
1488         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1489     ) -> Ty<'tcx> {
1490         // Find the relevant variant
1491         let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1492             self.check_struct_fields_on_error(fields, base_expr);
1493             return self.tcx.ty_error();
1494         };
1495
1496         // Prohibit struct expressions when non-exhaustive flag is set.
1497         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1498         if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1499             self.tcx
1500                 .sess
1501                 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1502         }
1503
1504         self.check_expr_struct_fields(
1505             adt_ty,
1506             expected,
1507             expr.hir_id,
1508             qpath.span(),
1509             variant,
1510             fields,
1511             base_expr,
1512             expr.span,
1513         );
1514
1515         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1516         adt_ty
1517     }
1518
1519     fn check_expr_struct_fields(
1520         &self,
1521         adt_ty: Ty<'tcx>,
1522         expected: Expectation<'tcx>,
1523         expr_id: hir::HirId,
1524         span: Span,
1525         variant: &'tcx ty::VariantDef,
1526         ast_fields: &'tcx [hir::ExprField<'tcx>],
1527         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1528         expr_span: Span,
1529     ) {
1530         let tcx = self.tcx;
1531
1532         let expected_inputs =
1533             self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1534         let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1535             expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1536         } else {
1537             adt_ty
1538         };
1539         // re-link the regions that EIfEO can erase.
1540         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1541
1542         let ty::Adt(adt, substs) = adt_ty.kind() else {
1543             span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1544         };
1545         let adt_kind = adt.adt_kind();
1546
1547         let mut remaining_fields = variant
1548             .fields
1549             .iter()
1550             .enumerate()
1551             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1552             .collect::<FxHashMap<_, _>>();
1553
1554         let mut seen_fields = FxHashMap::default();
1555
1556         let mut error_happened = false;
1557
1558         // Type-check each field.
1559         for field in ast_fields {
1560             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1561             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1562                 seen_fields.insert(ident, field.span);
1563                 self.write_field_index(field.hir_id, i);
1564
1565                 // We don't look at stability attributes on
1566                 // struct-like enums (yet...), but it's definitely not
1567                 // a bug to have constructed one.
1568                 if adt_kind != AdtKind::Enum {
1569                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1570                 }
1571
1572                 self.field_ty(field.span, v_field, substs)
1573             } else {
1574                 error_happened = true;
1575                 if let Some(prev_span) = seen_fields.get(&ident) {
1576                     tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1577                         span: field.ident.span,
1578                         prev_span: *prev_span,
1579                         ident,
1580                     });
1581                 } else {
1582                     self.report_unknown_field(
1583                         adt_ty,
1584                         variant,
1585                         field,
1586                         ast_fields,
1587                         adt.variant_descr(),
1588                         expr_span,
1589                     );
1590                 }
1591
1592                 tcx.ty_error()
1593             };
1594
1595             // Make sure to give a type to the field even if there's
1596             // an error, so we can continue type-checking.
1597             self.check_expr_coercable_to_type(&field.expr, field_type, None);
1598         }
1599
1600         // Make sure the programmer specified correct number of fields.
1601         if adt_kind == AdtKind::Union {
1602             if ast_fields.len() != 1 {
1603                 struct_span_err!(
1604                     tcx.sess,
1605                     span,
1606                     E0784,
1607                     "union expressions should have exactly one field",
1608                 )
1609                 .emit();
1610             }
1611         }
1612
1613         // If check_expr_struct_fields hit an error, do not attempt to populate
1614         // the fields with the base_expr. This could cause us to hit errors later
1615         // when certain fields are assumed to exist that in fact do not.
1616         if error_happened {
1617             return;
1618         }
1619
1620         if let Some(base_expr) = base_expr {
1621             // FIXME: We are currently creating two branches here in order to maintain
1622             // consistency. But they should be merged as much as possible.
1623             let fru_tys = if self.tcx.features().type_changing_struct_update {
1624                 if adt.is_struct() {
1625                     // Make some fresh substitutions for our ADT type.
1626                     let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1627                     // We do subtyping on the FRU fields first, so we can
1628                     // learn exactly what types we expect the base expr
1629                     // needs constrained to be compatible with the struct
1630                     // type we expect from the expectation value.
1631                     let fru_tys = variant
1632                         .fields
1633                         .iter()
1634                         .map(|f| {
1635                             let fru_ty = self.normalize_associated_types_in(
1636                                 expr_span,
1637                                 self.field_ty(base_expr.span, f, fresh_substs),
1638                             );
1639                             let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1640                             if let Some(_) = remaining_fields.remove(&ident) {
1641                                 let target_ty = self.field_ty(base_expr.span, f, substs);
1642                                 let cause = self.misc(base_expr.span);
1643                                 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1644                                     Ok(InferOk { obligations, value: () }) => {
1645                                         self.register_predicates(obligations)
1646                                     }
1647                                     Err(_) => {
1648                                         // This should never happen, since we're just subtyping the
1649                                         // remaining_fields, but it's fine to emit this, I guess.
1650                                         self.report_mismatched_types(
1651                                             &cause,
1652                                             target_ty,
1653                                             fru_ty,
1654                                             FieldMisMatch(variant.name, ident.name),
1655                                         )
1656                                         .emit();
1657                                     }
1658                                 }
1659                             }
1660                             self.resolve_vars_if_possible(fru_ty)
1661                         })
1662                         .collect();
1663                     // The use of fresh substs that we have subtyped against
1664                     // our base ADT type's fields allows us to guide inference
1665                     // along so that, e.g.
1666                     // ```
1667                     // MyStruct<'a, F1, F2, const C: usize> {
1668                     //     f: F1,
1669                     //     // Other fields that reference `'a`, `F2`, and `C`
1670                     // }
1671                     //
1672                     // let x = MyStruct {
1673                     //    f: 1usize,
1674                     //    ..other_struct
1675                     // };
1676                     // ```
1677                     // will have the `other_struct` expression constrained to
1678                     // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1679                     // This is important to allow coercions to happen in
1680                     // `other_struct` itself. See `coerce-in-base-expr.rs`.
1681                     let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1682                     self.check_expr_has_type_or_error(
1683                         base_expr,
1684                         self.resolve_vars_if_possible(fresh_base_ty),
1685                         |_| {},
1686                     );
1687                     fru_tys
1688                 } else {
1689                     // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1690                     // type errors on that expression, too.
1691                     self.check_expr(base_expr);
1692                     self.tcx
1693                         .sess
1694                         .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1695                     return;
1696                 }
1697             } else {
1698                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1699                     let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1700                     let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1701                         (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1702                         _ => false,
1703                     };
1704                     if self.tcx.sess.is_nightly_build() && same_adt {
1705                         feature_err(
1706                             &self.tcx.sess.parse_sess,
1707                             sym::type_changing_struct_update,
1708                             base_expr.span,
1709                             "type changing struct updating is experimental",
1710                         )
1711                         .emit();
1712                     }
1713                 });
1714                 match adt_ty.kind() {
1715                     ty::Adt(adt, substs) if adt.is_struct() => variant
1716                         .fields
1717                         .iter()
1718                         .map(|f| {
1719                             self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1720                         })
1721                         .collect(),
1722                     _ => {
1723                         self.tcx
1724                             .sess
1725                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1726                         return;
1727                     }
1728                 }
1729             };
1730             self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1731         } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1732             debug!(?remaining_fields);
1733             let private_fields: Vec<&ty::FieldDef> = variant
1734                 .fields
1735                 .iter()
1736                 .filter(|field| {
1737                     !field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1738                 })
1739                 .collect();
1740
1741             if !private_fields.is_empty() {
1742                 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1743             } else {
1744                 self.report_missing_fields(
1745                     adt_ty,
1746                     span,
1747                     remaining_fields,
1748                     variant,
1749                     ast_fields,
1750                     substs,
1751                 );
1752             }
1753         }
1754     }
1755
1756     fn check_struct_fields_on_error(
1757         &self,
1758         fields: &'tcx [hir::ExprField<'tcx>],
1759         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1760     ) {
1761         for field in fields {
1762             self.check_expr(&field.expr);
1763         }
1764         if let Some(base) = *base_expr {
1765             self.check_expr(&base);
1766         }
1767     }
1768
1769     /// Report an error for a struct field expression when there are fields which aren't provided.
1770     ///
1771     /// ```text
1772     /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1773     ///  --> src/main.rs:8:5
1774     ///   |
1775     /// 8 |     foo::Foo {};
1776     ///   |     ^^^^^^^^ missing `you_can_use_this_field`
1777     ///
1778     /// error: aborting due to previous error
1779     /// ```
1780     fn report_missing_fields(
1781         &self,
1782         adt_ty: Ty<'tcx>,
1783         span: Span,
1784         remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1785         variant: &'tcx ty::VariantDef,
1786         ast_fields: &'tcx [hir::ExprField<'tcx>],
1787         substs: SubstsRef<'tcx>,
1788     ) {
1789         let len = remaining_fields.len();
1790
1791         let mut displayable_field_names: Vec<&str> =
1792             remaining_fields.keys().map(|ident| ident.as_str()).collect();
1793         // sorting &str primitives here, sort_unstable is ok
1794         displayable_field_names.sort_unstable();
1795
1796         let mut truncated_fields_error = String::new();
1797         let remaining_fields_names = match &displayable_field_names[..] {
1798             [field1] => format!("`{}`", field1),
1799             [field1, field2] => format!("`{field1}` and `{field2}`"),
1800             [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1801             _ => {
1802                 truncated_fields_error =
1803                     format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1804                 displayable_field_names
1805                     .iter()
1806                     .take(3)
1807                     .map(|n| format!("`{n}`"))
1808                     .collect::<Vec<_>>()
1809                     .join(", ")
1810             }
1811         };
1812
1813         let mut err = struct_span_err!(
1814             self.tcx.sess,
1815             span,
1816             E0063,
1817             "missing field{} {}{} in initializer of `{}`",
1818             pluralize!(len),
1819             remaining_fields_names,
1820             truncated_fields_error,
1821             adt_ty
1822         );
1823         err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1824
1825         // If the last field is a range literal, but it isn't supposed to be, then they probably
1826         // meant to use functional update syntax.
1827         //
1828         // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1829         if let Some((
1830             last,
1831             ExprKind::Struct(
1832                 QPath::LangItem(LangItem::Range, ..),
1833                 &[ref range_start, ref range_end],
1834                 _,
1835             ),
1836         )) = ast_fields.last().map(|last| (last, &last.expr.kind)) &&
1837         let variant_field =
1838             variant.fields.iter().find(|field| field.ident(self.tcx) == last.ident) &&
1839         let range_def_id = self.tcx.lang_items().range_struct() &&
1840         variant_field
1841             .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1842             .map(|adt| adt.did())
1843             != range_def_id
1844         {
1845             let instead = self
1846                 .tcx
1847                 .sess
1848                 .source_map()
1849                 .span_to_snippet(range_end.expr.span)
1850                 .map(|s| format!(" from `{s}`"))
1851                 .unwrap_or_default();
1852             err.span_suggestion(
1853                 range_start.span.shrink_to_hi(),
1854                 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1855                 ",",
1856                 Applicability::MaybeIncorrect,
1857             );
1858         }
1859
1860         err.emit();
1861     }
1862
1863     /// Report an error for a struct field expression when there are invisible fields.
1864     ///
1865     /// ```text
1866     /// error: cannot construct `Foo` with struct literal syntax due to private fields
1867     ///  --> src/main.rs:8:5
1868     ///   |
1869     /// 8 |     foo::Foo {};
1870     ///   |     ^^^^^^^^
1871     ///
1872     /// error: aborting due to previous error
1873     /// ```
1874     fn report_private_fields(
1875         &self,
1876         adt_ty: Ty<'tcx>,
1877         span: Span,
1878         private_fields: Vec<&ty::FieldDef>,
1879         used_fields: &'tcx [hir::ExprField<'tcx>],
1880     ) {
1881         let mut err = self.tcx.sess.struct_span_err(
1882             span,
1883             &format!(
1884                 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1885             ),
1886         );
1887         let (used_private_fields, remaining_private_fields): (
1888             Vec<(Symbol, Span, bool)>,
1889             Vec<(Symbol, Span, bool)>,
1890         ) = private_fields
1891             .iter()
1892             .map(|field| {
1893                 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1894                     Some(used_field) => (field.name, used_field.span, true),
1895                     None => (field.name, self.tcx.def_span(field.did), false),
1896                 }
1897             })
1898             .partition(|field| field.2);
1899         err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1900         if !remaining_private_fields.is_empty() {
1901             let remaining_private_fields_len = remaining_private_fields.len();
1902             let names = match &remaining_private_fields
1903                 .iter()
1904                 .map(|(name, _, _)| name)
1905                 .collect::<Vec<_>>()[..]
1906             {
1907                 _ if remaining_private_fields_len > 6 => String::new(),
1908                 [name] => format!("`{name}` "),
1909                 [names @ .., last] => {
1910                     let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1911                     format!("{} and `{last}` ", names.join(", "))
1912                 }
1913                 [] => unreachable!(),
1914             };
1915             err.note(format!(
1916                 "... and other private field{s} {names}that {were} not provided",
1917                 s = pluralize!(remaining_private_fields_len),
1918                 were = pluralize!("was", remaining_private_fields_len),
1919             ));
1920         }
1921         err.emit();
1922     }
1923
1924     fn report_unknown_field(
1925         &self,
1926         ty: Ty<'tcx>,
1927         variant: &'tcx ty::VariantDef,
1928         field: &hir::ExprField<'_>,
1929         skip_fields: &[hir::ExprField<'_>],
1930         kind_name: &str,
1931         expr_span: Span,
1932     ) {
1933         if variant.is_recovered() {
1934             self.set_tainted_by_errors();
1935             return;
1936         }
1937         let mut err = self.type_error_struct_with_diag(
1938             field.ident.span,
1939             |actual| match ty.kind() {
1940                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1941                     self.tcx.sess,
1942                     field.ident.span,
1943                     E0559,
1944                     "{} `{}::{}` has no field named `{}`",
1945                     kind_name,
1946                     actual,
1947                     variant.name,
1948                     field.ident
1949                 ),
1950                 _ => struct_span_err!(
1951                     self.tcx.sess,
1952                     field.ident.span,
1953                     E0560,
1954                     "{} `{}` has no field named `{}`",
1955                     kind_name,
1956                     actual,
1957                     field.ident
1958                 ),
1959             },
1960             ty,
1961         );
1962
1963         let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1964         match variant.ctor_kind {
1965             CtorKind::Fn => match ty.kind() {
1966                 ty::Adt(adt, ..) if adt.is_enum() => {
1967                     err.span_label(
1968                         variant_ident_span,
1969                         format!(
1970                             "`{adt}::{variant}` defined here",
1971                             adt = ty,
1972                             variant = variant.name,
1973                         ),
1974                     );
1975                     err.span_label(field.ident.span, "field does not exist");
1976                     err.span_suggestion_verbose(
1977                         expr_span,
1978                         &format!(
1979                             "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1980                             adt = ty,
1981                             variant = variant.name,
1982                         ),
1983                         format!(
1984                             "{adt}::{variant}(/* fields */)",
1985                             adt = ty,
1986                             variant = variant.name,
1987                         ),
1988                         Applicability::HasPlaceholders,
1989                     );
1990                 }
1991                 _ => {
1992                     err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1993                     err.span_label(field.ident.span, "field does not exist");
1994                     err.span_suggestion_verbose(
1995                         expr_span,
1996                         &format!(
1997                             "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1998                             adt = ty,
1999                             kind_name = kind_name,
2000                         ),
2001                         format!("{adt}(/* fields */)", adt = ty),
2002                         Applicability::HasPlaceholders,
2003                     );
2004                 }
2005             },
2006             _ => {
2007                 // prevent all specified fields from being suggested
2008                 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
2009                 if let Some(field_name) = self.suggest_field_name(
2010                     variant,
2011                     field.ident.name,
2012                     skip_fields.collect(),
2013                     expr_span,
2014                 ) {
2015                     err.span_suggestion(
2016                         field.ident.span,
2017                         "a field with a similar name exists",
2018                         field_name,
2019                         Applicability::MaybeIncorrect,
2020                     );
2021                 } else {
2022                     match ty.kind() {
2023                         ty::Adt(adt, ..) => {
2024                             if adt.is_enum() {
2025                                 err.span_label(
2026                                     field.ident.span,
2027                                     format!("`{}::{}` does not have this field", ty, variant.name),
2028                                 );
2029                             } else {
2030                                 err.span_label(
2031                                     field.ident.span,
2032                                     format!("`{ty}` does not have this field"),
2033                                 );
2034                             }
2035                             let available_field_names =
2036                                 self.available_field_names(variant, expr_span);
2037                             if !available_field_names.is_empty() {
2038                                 err.note(&format!(
2039                                     "available fields are: {}",
2040                                     self.name_series_display(available_field_names)
2041                                 ));
2042                             }
2043                         }
2044                         _ => bug!("non-ADT passed to report_unknown_field"),
2045                     }
2046                 };
2047             }
2048         }
2049         err.emit();
2050     }
2051
2052     // Return a hint about the closest match in field names
2053     fn suggest_field_name(
2054         &self,
2055         variant: &'tcx ty::VariantDef,
2056         field: Symbol,
2057         skip: Vec<Symbol>,
2058         // The span where stability will be checked
2059         span: Span,
2060     ) -> Option<Symbol> {
2061         let names = variant
2062             .fields
2063             .iter()
2064             .filter_map(|field| {
2065                 // ignore already set fields and private fields from non-local crates
2066                 // and unstable fields.
2067                 if skip.iter().any(|&x| x == field.name)
2068                     || (!variant.def_id.is_local() && !field.vis.is_public())
2069                     || matches!(
2070                         self.tcx.eval_stability(field.did, None, span, None),
2071                         stability::EvalResult::Deny { .. }
2072                     )
2073                 {
2074                     None
2075                 } else {
2076                     Some(field.name)
2077                 }
2078             })
2079             .collect::<Vec<Symbol>>();
2080
2081         find_best_match_for_name(&names, field, None)
2082     }
2083
2084     fn available_field_names(
2085         &self,
2086         variant: &'tcx ty::VariantDef,
2087         access_span: Span,
2088     ) -> Vec<Symbol> {
2089         variant
2090             .fields
2091             .iter()
2092             .filter(|field| {
2093                 let def_scope = self
2094                     .tcx
2095                     .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2096                     .1;
2097                 field.vis.is_accessible_from(def_scope, self.tcx)
2098                     && !matches!(
2099                         self.tcx.eval_stability(field.did, None, access_span, None),
2100                         stability::EvalResult::Deny { .. }
2101                     )
2102             })
2103             .filter(|field| !self.tcx.is_doc_hidden(field.did))
2104             .map(|field| field.name)
2105             .collect()
2106     }
2107
2108     fn name_series_display(&self, names: Vec<Symbol>) -> String {
2109         // dynamic limit, to never omit just one field
2110         let limit = if names.len() == 6 { 6 } else { 5 };
2111         let mut display =
2112             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2113         if names.len() > limit {
2114             display = format!("{} ... and {} others", display, names.len() - limit);
2115         }
2116         display
2117     }
2118
2119     // Check field access expressions
2120     fn check_field(
2121         &self,
2122         expr: &'tcx hir::Expr<'tcx>,
2123         base: &'tcx hir::Expr<'tcx>,
2124         field: Ident,
2125     ) -> Ty<'tcx> {
2126         debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2127         let expr_t = self.check_expr(base);
2128         let expr_t = self.structurally_resolved_type(base.span, expr_t);
2129         let mut private_candidate = None;
2130         let mut autoderef = self.autoderef(expr.span, expr_t);
2131         while let Some((base_t, _)) = autoderef.next() {
2132             debug!("base_t: {:?}", base_t);
2133             match base_t.kind() {
2134                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2135                     debug!("struct named {:?}", base_t);
2136                     let (ident, def_scope) =
2137                         self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2138                     let fields = &base_def.non_enum_variant().fields;
2139                     if let Some(index) = fields
2140                         .iter()
2141                         .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2142                     {
2143                         let field = &fields[index];
2144                         let field_ty = self.field_ty(expr.span, field, substs);
2145                         // Save the index of all fields regardless of their visibility in case
2146                         // of error recovery.
2147                         self.write_field_index(expr.hir_id, index);
2148                         let adjustments = self.adjust_steps(&autoderef);
2149                         if field.vis.is_accessible_from(def_scope, self.tcx) {
2150                             self.apply_adjustments(base, adjustments);
2151                             self.register_predicates(autoderef.into_obligations());
2152
2153                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2154                             return field_ty;
2155                         }
2156                         private_candidate = Some((adjustments, base_def.did(), field_ty));
2157                     }
2158                 }
2159                 ty::Tuple(tys) => {
2160                     let fstr = field.as_str();
2161                     if let Ok(index) = fstr.parse::<usize>() {
2162                         if fstr == index.to_string() {
2163                             if let Some(&field_ty) = tys.get(index) {
2164                                 let adjustments = self.adjust_steps(&autoderef);
2165                                 self.apply_adjustments(base, adjustments);
2166                                 self.register_predicates(autoderef.into_obligations());
2167
2168                                 self.write_field_index(expr.hir_id, index);
2169                                 return field_ty;
2170                             }
2171                         }
2172                     }
2173                 }
2174                 _ => {}
2175             }
2176         }
2177         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2178
2179         if let Some((adjustments, did, field_ty)) = private_candidate {
2180             // (#90483) apply adjustments to avoid ExprUseVisitor from
2181             // creating erroneous projection.
2182             self.apply_adjustments(base, adjustments);
2183             self.ban_private_field_access(expr, expr_t, field, did);
2184             return field_ty;
2185         }
2186
2187         if field.name == kw::Empty {
2188         } else if self.method_exists(field, expr_t, expr.hir_id, true) {
2189             self.ban_take_value_of_method(expr, expr_t, field);
2190         } else if !expr_t.is_primitive_ty() {
2191             self.ban_nonexisting_field(field, base, expr, expr_t);
2192         } else {
2193             let field_name = field.to_string();
2194             let mut err = type_error_struct!(
2195                 self.tcx().sess,
2196                 field.span,
2197                 expr_t,
2198                 E0610,
2199                 "`{expr_t}` is a primitive type and therefore doesn't have fields",
2200             );
2201             let is_valid_suffix = |field: &str| {
2202                 if field == "f32" || field == "f64" {
2203                     return true;
2204                 }
2205                 let mut chars = field.chars().peekable();
2206                 match chars.peek() {
2207                     Some('e') | Some('E') => {
2208                         chars.next();
2209                         if let Some(c) = chars.peek()
2210                             && !c.is_numeric() && *c != '-' && *c != '+'
2211                         {
2212                             return false;
2213                         }
2214                         while let Some(c) = chars.peek() {
2215                             if !c.is_numeric() {
2216                                 break;
2217                             }
2218                             chars.next();
2219                         }
2220                     }
2221                     _ => (),
2222                 }
2223                 let suffix = chars.collect::<String>();
2224                 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2225             };
2226             let maybe_partial_suffix = |field: &str| -> Option<&str> {
2227                 let first_chars = ['f', 'l'];
2228                 if field.len() >= 1
2229                     && field.to_lowercase().starts_with(first_chars)
2230                     && field[1..].chars().all(|c| c.is_ascii_digit())
2231                 {
2232                     if field.to_lowercase().starts_with(['f']) { Some("f32") } else { Some("f64") }
2233                 } else {
2234                     None
2235                 }
2236             };
2237             if let ty::Infer(ty::IntVar(_)) = expr_t.kind()
2238                 && let ExprKind::Lit(Spanned {
2239                     node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2240                     ..
2241                 }) = base.kind
2242                 && !base.span.from_expansion()
2243             {
2244                 if is_valid_suffix(&field_name) {
2245                     err.span_suggestion_verbose(
2246                         field.span.shrink_to_lo(),
2247                         "if intended to be a floating point literal, consider adding a `0` after the period",
2248                         '0',
2249                         Applicability::MaybeIncorrect,
2250                     );
2251                 } else if let Some(correct_suffix) = maybe_partial_suffix(&field_name) {
2252                     err.span_suggestion_verbose(
2253                         field.span,
2254                         format!("if intended to be a floating point literal, consider adding a `0` after the period and a `{correct_suffix}` suffix"),
2255                         format!("0{correct_suffix}"),
2256                         Applicability::MaybeIncorrect,
2257                     );
2258                 }
2259             }
2260             err.emit();
2261         }
2262
2263         self.tcx().ty_error()
2264     }
2265
2266     fn check_call_constructor(
2267         &self,
2268         err: &mut Diagnostic,
2269         base: &'tcx hir::Expr<'tcx>,
2270         def_id: DefId,
2271     ) {
2272         if let Some(local_id) = def_id.as_local() {
2273             let hir_id = self.tcx.hir().local_def_id_to_hir_id(local_id);
2274             let node = self.tcx.hir().get(hir_id);
2275
2276             if let Some(fields) = node.tuple_fields() {
2277                 let kind = match self.tcx.opt_def_kind(local_id) {
2278                     Some(DefKind::Ctor(of, _)) => of,
2279                     _ => return,
2280                 };
2281
2282                 suggest_call_constructor(base.span, kind, fields.len(), err);
2283             }
2284         } else {
2285             // The logic here isn't smart but `associated_item_def_ids`
2286             // doesn't work nicely on local.
2287             if let DefKind::Ctor(of, _) = self.tcx.def_kind(def_id) {
2288                 let parent_def_id = self.tcx.parent(def_id);
2289                 let fields = self.tcx.associated_item_def_ids(parent_def_id);
2290                 suggest_call_constructor(base.span, of, fields.len(), err);
2291             }
2292         }
2293     }
2294
2295     fn suggest_await_on_field_access(
2296         &self,
2297         err: &mut Diagnostic,
2298         field_ident: Ident,
2299         base: &'tcx hir::Expr<'tcx>,
2300         ty: Ty<'tcx>,
2301     ) {
2302         let output_ty = match self.get_impl_future_output_ty(ty) {
2303             Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2304             _ => return,
2305         };
2306         let mut add_label = true;
2307         if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2308             // no field access on enum type
2309             if !def.is_enum() {
2310                 if def
2311                     .non_enum_variant()
2312                     .fields
2313                     .iter()
2314                     .any(|field| field.ident(self.tcx) == field_ident)
2315                 {
2316                     add_label = false;
2317                     err.span_label(
2318                         field_ident.span,
2319                         "field not available in `impl Future`, but it is available in its `Output`",
2320                     );
2321                     err.span_suggestion_verbose(
2322                         base.span.shrink_to_hi(),
2323                         "consider `await`ing on the `Future` and access the field of its `Output`",
2324                         ".await",
2325                         Applicability::MaybeIncorrect,
2326                     );
2327                 }
2328             }
2329         }
2330         if add_label {
2331             err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2332         }
2333     }
2334
2335     fn ban_nonexisting_field(
2336         &self,
2337         field: Ident,
2338         base: &'tcx hir::Expr<'tcx>,
2339         expr: &'tcx hir::Expr<'tcx>,
2340         expr_t: Ty<'tcx>,
2341     ) {
2342         debug!(
2343             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
2344             field, base, expr, expr_t
2345         );
2346         let mut err = self.no_such_field_err(field, expr_t, base.hir_id);
2347
2348         match *expr_t.peel_refs().kind() {
2349             ty::Array(_, len) => {
2350                 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
2351             }
2352             ty::RawPtr(..) => {
2353                 self.suggest_first_deref_field(&mut err, expr, base, field);
2354             }
2355             ty::Adt(def, _) if !def.is_enum() => {
2356                 self.suggest_fields_on_recordish(&mut err, def, field, expr.span);
2357             }
2358             ty::Param(param_ty) => {
2359                 self.point_at_param_definition(&mut err, param_ty);
2360             }
2361             ty::Opaque(_, _) => {
2362                 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
2363             }
2364             ty::FnDef(def_id, _) => {
2365                 self.check_call_constructor(&mut err, base, def_id);
2366             }
2367             _ => {}
2368         }
2369
2370         if field.name == kw::Await {
2371             // We know by construction that `<expr>.await` is either on Rust 2015
2372             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2373             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2374             err.help_use_latest_edition();
2375         }
2376
2377         err.emit();
2378     }
2379
2380     fn ban_private_field_access(
2381         &self,
2382         expr: &hir::Expr<'_>,
2383         expr_t: Ty<'tcx>,
2384         field: Ident,
2385         base_did: DefId,
2386     ) {
2387         let struct_path = self.tcx().def_path_str(base_did);
2388         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2389         let mut err = struct_span_err!(
2390             self.tcx().sess,
2391             field.span,
2392             E0616,
2393             "field `{field}` of {kind_name} `{struct_path}` is private",
2394         );
2395         err.span_label(field.span, "private field");
2396         // Also check if an accessible method exists, which is often what is meant.
2397         if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2398         {
2399             self.suggest_method_call(
2400                 &mut err,
2401                 &format!("a method `{field}` also exists, call it with parentheses"),
2402                 field,
2403                 expr_t,
2404                 expr,
2405                 None,
2406             );
2407         }
2408         err.emit();
2409     }
2410
2411     fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2412         let mut err = type_error_struct!(
2413             self.tcx().sess,
2414             field.span,
2415             expr_t,
2416             E0615,
2417             "attempted to take value of method `{field}` on type `{expr_t}`",
2418         );
2419         err.span_label(field.span, "method, not a field");
2420         let expr_is_call =
2421             if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2422                 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2423             {
2424                 expr.hir_id == callee.hir_id
2425             } else {
2426                 false
2427             };
2428         let expr_snippet =
2429             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2430         let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2431         let after_open = expr.span.lo() + rustc_span::BytePos(1);
2432         let before_close = expr.span.hi() - rustc_span::BytePos(1);
2433
2434         if expr_is_call && is_wrapped {
2435             err.multipart_suggestion(
2436                 "remove wrapping parentheses to call the method",
2437                 vec![
2438                     (expr.span.with_hi(after_open), String::new()),
2439                     (expr.span.with_lo(before_close), String::new()),
2440                 ],
2441                 Applicability::MachineApplicable,
2442             );
2443         } else if !self.expr_in_place(expr.hir_id) {
2444             // Suggest call parentheses inside the wrapping parentheses
2445             let span = if is_wrapped {
2446                 expr.span.with_lo(after_open).with_hi(before_close)
2447             } else {
2448                 expr.span
2449             };
2450             self.suggest_method_call(
2451                 &mut err,
2452                 "use parentheses to call the method",
2453                 field,
2454                 expr_t,
2455                 expr,
2456                 Some(span),
2457             );
2458         } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2459             && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2460             && let ExprKind::Field(base_expr, _) = expr.kind
2461             && adt_def.variants().len() == 1
2462             && adt_def
2463                 .variants()
2464                 .iter()
2465                 .next()
2466                 .unwrap()
2467                 .fields
2468                 .iter()
2469                 .any(|f| f.ident(self.tcx) == field)
2470         {
2471             err.multipart_suggestion(
2472                 "to access the field, dereference first",
2473                 vec![
2474                     (base_expr.span.shrink_to_lo(), "(*".to_string()),
2475                     (base_expr.span.shrink_to_hi(), ")".to_string()),
2476                 ],
2477                 Applicability::MaybeIncorrect,
2478             );
2479         } else {
2480             err.help("methods are immutable and cannot be assigned to");
2481         }
2482
2483         err.emit();
2484     }
2485
2486     fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2487         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2488         let generic_param = generics.type_param(&param, self.tcx);
2489         if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2490             return;
2491         }
2492         let param_def_id = generic_param.def_id;
2493         let param_hir_id = match param_def_id.as_local() {
2494             Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2495             None => return,
2496         };
2497         let param_span = self.tcx.hir().span(param_hir_id);
2498         let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2499
2500         err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2501     }
2502
2503     fn suggest_fields_on_recordish(
2504         &self,
2505         err: &mut Diagnostic,
2506         def: ty::AdtDef<'tcx>,
2507         field: Ident,
2508         access_span: Span,
2509     ) {
2510         if let Some(suggested_field_name) =
2511             self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2512         {
2513             err.span_suggestion(
2514                 field.span,
2515                 "a field with a similar name exists",
2516                 suggested_field_name,
2517                 Applicability::MaybeIncorrect,
2518             );
2519         } else {
2520             err.span_label(field.span, "unknown field");
2521             let struct_variant_def = def.non_enum_variant();
2522             let field_names = self.available_field_names(struct_variant_def, access_span);
2523             if !field_names.is_empty() {
2524                 err.note(&format!(
2525                     "available fields are: {}",
2526                     self.name_series_display(field_names),
2527                 ));
2528             }
2529         }
2530     }
2531
2532     fn maybe_suggest_array_indexing(
2533         &self,
2534         err: &mut Diagnostic,
2535         expr: &hir::Expr<'_>,
2536         base: &hir::Expr<'_>,
2537         field: Ident,
2538         len: ty::Const<'tcx>,
2539     ) {
2540         if let (Some(len), Ok(user_index)) =
2541             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2542             && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2543         {
2544             let help = "instead of using tuple indexing, use array indexing";
2545             let suggestion = format!("{base}[{field}]");
2546             let applicability = if len < user_index {
2547                 Applicability::MachineApplicable
2548             } else {
2549                 Applicability::MaybeIncorrect
2550             };
2551             err.span_suggestion(expr.span, help, suggestion, applicability);
2552         }
2553     }
2554
2555     fn suggest_first_deref_field(
2556         &self,
2557         err: &mut Diagnostic,
2558         expr: &hir::Expr<'_>,
2559         base: &hir::Expr<'_>,
2560         field: Ident,
2561     ) {
2562         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2563             let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2564             let suggestion = format!("(*{base}).{field}");
2565             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2566         }
2567     }
2568
2569     fn no_such_field_err(
2570         &self,
2571         field: Ident,
2572         expr_t: Ty<'tcx>,
2573         id: HirId,
2574     ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2575         let span = field.span;
2576         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2577
2578         let mut err = type_error_struct!(
2579             self.tcx().sess,
2580             field.span,
2581             expr_t,
2582             E0609,
2583             "no field `{field}` on type `{expr_t}`",
2584         );
2585
2586         // try to add a suggestion in case the field is a nested field of a field of the Adt
2587         let mod_id = self.tcx.parent_module(id).to_def_id();
2588         if let Some((fields, substs)) =
2589             self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2590         {
2591             for candidate_field in fields {
2592                 if let Some(mut field_path) = self.check_for_nested_field_satisfying(
2593                     span,
2594                     &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2595                     candidate_field,
2596                     substs,
2597                     vec![],
2598                     mod_id,
2599                 ) {
2600                     // field_path includes `field` that we're looking for, so pop it.
2601                     field_path.pop();
2602
2603                     let field_path_str = field_path
2604                         .iter()
2605                         .map(|id| id.name.to_ident_string())
2606                         .collect::<Vec<String>>()
2607                         .join(".");
2608                     debug!("field_path_str: {:?}", field_path_str);
2609
2610                     err.span_suggestion_verbose(
2611                         field.span.shrink_to_lo(),
2612                         "one of the expressions' fields has a field of the same name",
2613                         format!("{field_path_str}."),
2614                         Applicability::MaybeIncorrect,
2615                     );
2616                 }
2617             }
2618         }
2619         err
2620     }
2621
2622     pub(crate) fn get_field_candidates_considering_privacy(
2623         &self,
2624         span: Span,
2625         base_ty: Ty<'tcx>,
2626         mod_id: DefId,
2627     ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2628         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2629
2630         for (base_t, _) in self.autoderef(span, base_ty) {
2631             match base_t.kind() {
2632                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2633                     let tcx = self.tcx;
2634                     let fields = &base_def.non_enum_variant().fields;
2635                     // Some struct, e.g. some that impl `Deref`, have all private fields
2636                     // because you're expected to deref them to access the _real_ fields.
2637                     // This, for example, will help us suggest accessing a field through a `Box<T>`.
2638                     if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2639                         continue;
2640                     }
2641                     return Some((
2642                         fields
2643                             .iter()
2644                             .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2645                             // For compile-time reasons put a limit on number of fields we search
2646                             .take(100),
2647                         substs,
2648                     ));
2649                 }
2650                 _ => {}
2651             }
2652         }
2653         None
2654     }
2655
2656     /// This method is called after we have encountered a missing field error to recursively
2657     /// search for the field
2658     pub(crate) fn check_for_nested_field_satisfying(
2659         &self,
2660         span: Span,
2661         matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2662         candidate_field: &ty::FieldDef,
2663         subst: SubstsRef<'tcx>,
2664         mut field_path: Vec<Ident>,
2665         mod_id: DefId,
2666     ) -> Option<Vec<Ident>> {
2667         debug!(
2668             "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2669             span, candidate_field, field_path
2670         );
2671
2672         if field_path.len() > 3 {
2673             // For compile-time reasons and to avoid infinite recursion we only check for fields
2674             // up to a depth of three
2675             None
2676         } else {
2677             field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2678             let field_ty = candidate_field.ty(self.tcx, subst);
2679             if matches(candidate_field, field_ty) {
2680                 return Some(field_path);
2681             } else if let Some((nested_fields, subst)) =
2682                 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2683             {
2684                 // recursively search fields of `candidate_field` if it's a ty::Adt
2685                 for field in nested_fields {
2686                     if let Some(field_path) = self.check_for_nested_field_satisfying(
2687                         span,
2688                         matches,
2689                         field,
2690                         subst,
2691                         field_path.clone(),
2692                         mod_id,
2693                     ) {
2694                         return Some(field_path);
2695                     }
2696                 }
2697             }
2698             None
2699         }
2700     }
2701
2702     fn check_expr_index(
2703         &self,
2704         base: &'tcx hir::Expr<'tcx>,
2705         idx: &'tcx hir::Expr<'tcx>,
2706         expr: &'tcx hir::Expr<'tcx>,
2707     ) -> Ty<'tcx> {
2708         let base_t = self.check_expr(&base);
2709         let idx_t = self.check_expr(&idx);
2710
2711         if base_t.references_error() {
2712             base_t
2713         } else if idx_t.references_error() {
2714             idx_t
2715         } else {
2716             let base_t = self.structurally_resolved_type(base.span, base_t);
2717             match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2718                 Some((index_ty, element_ty)) => {
2719                     // two-phase not needed because index_ty is never mutable
2720                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2721                     self.select_obligations_where_possible(false, |errors| {
2722                         self.point_at_index_if_possible(errors, idx.span)
2723                     });
2724                     element_ty
2725                 }
2726                 None => {
2727                     let mut err = type_error_struct!(
2728                         self.tcx.sess,
2729                         expr.span,
2730                         base_t,
2731                         E0608,
2732                         "cannot index into a value of type `{base_t}`",
2733                     );
2734                     // Try to give some advice about indexing tuples.
2735                     if let ty::Tuple(..) = base_t.kind() {
2736                         let mut needs_note = true;
2737                         // If the index is an integer, we can show the actual
2738                         // fixed expression:
2739                         if let ExprKind::Lit(ref lit) = idx.kind {
2740                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2741                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2742                                 if let Ok(snip) = snip {
2743                                     err.span_suggestion(
2744                                         expr.span,
2745                                         "to access tuple elements, use",
2746                                         format!("{snip}.{i}"),
2747                                         Applicability::MachineApplicable,
2748                                     );
2749                                     needs_note = false;
2750                                 }
2751                             }
2752                         }
2753                         if needs_note {
2754                             err.help(
2755                                 "to access tuple elements, use tuple indexing \
2756                                         syntax (e.g., `tuple.0`)",
2757                             );
2758                         }
2759                     }
2760                     err.emit();
2761                     self.tcx.ty_error()
2762                 }
2763             }
2764         }
2765     }
2766
2767     fn point_at_index_if_possible(
2768         &self,
2769         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2770         span: Span,
2771     ) {
2772         for error in errors {
2773             match error.obligation.predicate.kind().skip_binder() {
2774                 ty::PredicateKind::Trait(predicate)
2775                     if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2776                 }
2777                 _ => continue,
2778             }
2779             error.obligation.cause.span = span;
2780         }
2781     }
2782
2783     fn check_expr_yield(
2784         &self,
2785         value: &'tcx hir::Expr<'tcx>,
2786         expr: &'tcx hir::Expr<'tcx>,
2787         src: &'tcx hir::YieldSource,
2788     ) -> Ty<'tcx> {
2789         match self.resume_yield_tys {
2790             Some((resume_ty, yield_ty)) => {
2791                 self.check_expr_coercable_to_type(&value, yield_ty, None);
2792
2793                 resume_ty
2794             }
2795             // Given that this `yield` expression was generated as a result of lowering a `.await`,
2796             // we know that the yield type must be `()`; however, the context won't contain this
2797             // information. Hence, we check the source of the yield expression here and check its
2798             // value's type against `()` (this check should always hold).
2799             None if src.is_await() => {
2800                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2801                 self.tcx.mk_unit()
2802             }
2803             _ => {
2804                 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2805                 // Avoid expressions without types during writeback (#78653).
2806                 self.check_expr(value);
2807                 self.tcx.mk_unit()
2808             }
2809         }
2810     }
2811
2812     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2813         let needs = if is_input { Needs::None } else { Needs::MutPlace };
2814         let ty = self.check_expr_with_needs(expr, needs);
2815         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2816
2817         if !is_input && !expr.is_syntactic_place_expr() {
2818             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2819             err.span_label(expr.span, "cannot assign to this expression");
2820             err.emit();
2821         }
2822
2823         // If this is an input value, we require its type to be fully resolved
2824         // at this point. This allows us to provide helpful coercions which help
2825         // pass the type candidate list in a later pass.
2826         //
2827         // We don't require output types to be resolved at this point, which
2828         // allows them to be inferred based on how they are used later in the
2829         // function.
2830         if is_input {
2831             let ty = self.structurally_resolved_type(expr.span, ty);
2832             match *ty.kind() {
2833                 ty::FnDef(..) => {
2834                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2835                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2836                 }
2837                 ty::Ref(_, base_ty, mutbl) => {
2838                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2839                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2840                 }
2841                 _ => {}
2842             }
2843         }
2844     }
2845
2846     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2847         for (op, _op_sp) in asm.operands {
2848             match op {
2849                 hir::InlineAsmOperand::In { expr, .. } => {
2850                     self.check_expr_asm_operand(expr, true);
2851                 }
2852                 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2853                 | hir::InlineAsmOperand::InOut { expr, .. } => {
2854                     self.check_expr_asm_operand(expr, false);
2855                 }
2856                 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2857                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2858                     self.check_expr_asm_operand(in_expr, true);
2859                     if let Some(out_expr) = out_expr {
2860                         self.check_expr_asm_operand(out_expr, false);
2861                     }
2862                 }
2863                 // `AnonConst`s have their own body and is type-checked separately.
2864                 // As they don't flow into the type system we don't need them to
2865                 // be well-formed.
2866                 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2867                 hir::InlineAsmOperand::SymStatic { .. } => {}
2868             }
2869         }
2870         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2871             self.tcx.types.never
2872         } else {
2873             self.tcx.mk_unit()
2874         }
2875     }
2876 }
2877
2878 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2879     Some(match ty.kind() {
2880         ty::Bool => "true",
2881         ty::Char => "'a'",
2882         ty::Int(_) | ty::Uint(_) => "42",
2883         ty::Float(_) => "3.14159",
2884         ty::Error(_) | ty::Never => return None,
2885         _ => "value",
2886     })
2887 }