compiler/rustc_hir_analysis/src/check/expr.rs

   1 //! Type checking expressions.
   2 //!
   3 //! See `mod.rs` for more context on type checking in general.
   4
   5 use crate::astconv::AstConv as _;
   6 use crate::check::cast::{self, CastCheckResult};
   7 use crate::check::coercion::CoerceMany;
   8 use crate::check::fatally_break_rust;
   9 use crate::check::method::SelfSource;
  10 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
  11 use crate::check::{
  12     report_unexpected_variant_res, BreakableCtxt, Diverges, DynamicCoerceMany, FnCtxt, Needs,
  13     TupleArgumentsFlag::DontTupleArguments,
  14 };
  15 use crate::errors::{
  16     FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
  17     YieldExprOutsideOfGenerator,
  18 };
  19 use crate::type_error_struct;
  20
  21 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
  22 use rustc_ast as ast;
  23 use rustc_data_structures::fx::FxHashMap;
  24 use rustc_data_structures::stack::ensure_sufficient_stack;
  25 use rustc_errors::{
  26     pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId,
  27     ErrorGuaranteed, StashKey,
  28 };
  29 use rustc_hir as hir;
  30 use rustc_hir::def::{CtorKind, DefKind, Res};
  31 use rustc_hir::def_id::DefId;
  32 use rustc_hir::intravisit::Visitor;
  33 use rustc_hir::lang_items::LangItem;
  34 use rustc_hir::{Closure, ExprKind, HirId, QPath};
  35 use rustc_infer::infer;
  36 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
  37 use rustc_infer::infer::InferOk;
  38 use rustc_infer::traits::ObligationCause;
  39 use rustc_middle::middle::stability;
  40 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
  41 use rustc_middle::ty::error::TypeError::FieldMisMatch;
  42 use rustc_middle::ty::subst::SubstsRef;
  43 use rustc_middle::ty::{self, AdtKind, Ty, TypeVisitable};
  44 use rustc_session::errors::ExprParenthesesNeeded;
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::hygiene::DesugaringKind;
  47 use rustc_span::lev_distance::find_best_match_for_name;
  48 use rustc_span::source_map::{Span, Spanned};
  49 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  50 use rustc_target::spec::abi::Abi::RustIntrinsic;
  51 use rustc_trait_selection::infer::InferCtxtExt;
  52 use rustc_trait_selection::traits::{self, ObligationCauseCode};
  53
  54 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  55     fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
  56         let ty = self.check_expr_with_hint(expr, expected);
  57         self.demand_eqtype(expr.span, expected, ty);
  58     }
  59
  60     pub fn check_expr_has_type_or_error(
  61         &self,
  62         expr: &'tcx hir::Expr<'tcx>,
  63         expected: Ty<'tcx>,
  64         extend_err: impl FnMut(&mut Diagnostic),
  65     ) -> Ty<'tcx> {
  66         self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
  67     }
  68
  69     fn check_expr_meets_expectation_or_error(
  70         &self,
  71         expr: &'tcx hir::Expr<'tcx>,
  72         expected: Expectation<'tcx>,
  73         mut extend_err: impl FnMut(&mut Diagnostic),
  74     ) -> Ty<'tcx> {
  75         let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
  76         let mut ty = self.check_expr_with_expectation(expr, expected);
  77
  78         // While we don't allow *arbitrary* coercions here, we *do* allow
  79         // coercions from ! to `expected`.
  80         if ty.is_never() {
  81             if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
  82                 self.tcx().sess.delay_span_bug(
  83                     expr.span,
  84                     "expression with never type wound up being adjusted",
  85                 );
  86                 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
  87                     target.to_owned()
  88                 } else {
  89                     self.tcx().ty_error()
  90                 };
  91             }
  92
  93             let adj_ty = self.next_ty_var(TypeVariableOrigin {
  94                 kind: TypeVariableOriginKind::AdjustmentType,
  95                 span: expr.span,
  96             });
  97             self.apply_adjustments(
  98                 expr,
  99                 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
 100             );
 101             ty = adj_ty;
 102         }
 103
 104         if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
 105             let expr = expr.peel_drop_temps();
 106             self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
 107             extend_err(&mut err);
 108             err.emit();
 109         }
 110         ty
 111     }
 112
 113     pub(super) fn check_expr_coercable_to_type(
 114         &self,
 115         expr: &'tcx hir::Expr<'tcx>,
 116         expected: Ty<'tcx>,
 117         expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
 118     ) -> Ty<'tcx> {
 119         let ty = self.check_expr_with_hint(expr, expected);
 120         // checks don't need two phase
 121         self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
 122     }
 123
 124     pub(super) fn check_expr_with_hint(
 125         &self,
 126         expr: &'tcx hir::Expr<'tcx>,
 127         expected: Ty<'tcx>,
 128     ) -> Ty<'tcx> {
 129         self.check_expr_with_expectation(expr, ExpectHasType(expected))
 130     }
 131
 132     fn check_expr_with_expectation_and_needs(
 133         &self,
 134         expr: &'tcx hir::Expr<'tcx>,
 135         expected: Expectation<'tcx>,
 136         needs: Needs,
 137     ) -> Ty<'tcx> {
 138         let ty = self.check_expr_with_expectation(expr, expected);
 139
 140         // If the expression is used in a place whether mutable place is required
 141         // e.g. LHS of assignment, perform the conversion.
 142         if let Needs::MutPlace = needs {
 143             self.convert_place_derefs_to_mutable(expr);
 144         }
 145
 146         ty
 147     }
 148
 149     pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
 150         self.check_expr_with_expectation(expr, NoExpectation)
 151     }
 152
 153     pub(super) fn check_expr_with_needs(
 154         &self,
 155         expr: &'tcx hir::Expr<'tcx>,
 156         needs: Needs,
 157     ) -> Ty<'tcx> {
 158         self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
 159     }
 160
 161     /// Invariant:
 162     /// If an expression has any sub-expressions that result in a type error,
 163     /// inspecting that expression's type with `ty.references_error()` will return
 164     /// true. Likewise, if an expression is known to diverge, inspecting its
 165     /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
 166     /// strict, _|_ can appear in the type of an expression that does not,
 167     /// itself, diverge: for example, fn() -> _|_.)
 168     /// Note that inspecting a type's structure *directly* may expose the fact
 169     /// that there are actually multiple representations for `Error`, so avoid
 170     /// that when err needs to be handled differently.
 171     #[instrument(skip(self, expr), level = "debug")]
 172     pub(super) fn check_expr_with_expectation(
 173         &self,
 174         expr: &'tcx hir::Expr<'tcx>,
 175         expected: Expectation<'tcx>,
 176     ) -> Ty<'tcx> {
 177         self.check_expr_with_expectation_and_args(expr, expected, &[])
 178     }
 179
 180     /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
 181     /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
 182     pub(super) fn check_expr_with_expectation_and_args(
 183         &self,
 184         expr: &'tcx hir::Expr<'tcx>,
 185         expected: Expectation<'tcx>,
 186         args: &'tcx [hir::Expr<'tcx>],
 187     ) -> Ty<'tcx> {
 188         if self.tcx().sess.verbose() {
 189             // make this code only run with -Zverbose because it is probably slow
 190             if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
 191                 if !lint_str.contains('\n') {
 192                     debug!("expr text: {lint_str}");
 193                 } else {
 194                     let mut lines = lint_str.lines();
 195                     if let Some(line0) = lines.next() {
 196                         let remaining_lines = lines.count();
 197                         debug!("expr text: {line0}");
 198                         debug!("expr text: ...(and {remaining_lines} more lines)");
 199                     }
 200                 }
 201             }
 202         }
 203
 204         // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
 205         // without the final expr (e.g. `try { return; }`). We don't want to generate an
 206         // unreachable_code lint for it since warnings for autogenerated code are confusing.
 207         let is_try_block_generated_unit_expr = match expr.kind {
 208             ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
 209                 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
 210             }
 211
 212             _ => false,
 213         };
 214
 215         // Warn for expressions after diverging siblings.
 216         if !is_try_block_generated_unit_expr {
 217             self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
 218         }
 219
 220         // Hide the outer diverging and has_errors flags.
 221         let old_diverges = self.diverges.replace(Diverges::Maybe);
 222         let old_has_errors = self.has_errors.replace(false);
 223
 224         let ty = ensure_sufficient_stack(|| match &expr.kind {
 225             hir::ExprKind::Path(
 226                 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
 227             ) => self.check_expr_path(qpath, expr, args),
 228             _ => self.check_expr_kind(expr, expected),
 229         });
 230
 231         // Warn for non-block expressions with diverging children.
 232         match expr.kind {
 233             ExprKind::Block(..)
 234             | ExprKind::If(..)
 235             | ExprKind::Let(..)
 236             | ExprKind::Loop(..)
 237             | ExprKind::Match(..) => {}
 238             // If `expr` is a result of desugaring the try block and is an ok-wrapped
 239             // diverging expression (e.g. it arose from desugaring of `try { return }`),
 240             // we skip issuing a warning because it is autogenerated code.
 241             ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
 242             ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
 243             ExprKind::MethodCall(segment, ..) => {
 244                 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
 245             }
 246             _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
 247         }
 248
 249         // Any expression that produces a value of type `!` must have diverged
 250         if ty.is_never() {
 251             self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
 252         }
 253
 254         // Record the type, which applies it effects.
 255         // We need to do this after the warning above, so that
 256         // we don't warn for the diverging expression itself.
 257         self.write_ty(expr.hir_id, ty);
 258
 259         // Combine the diverging and has_error flags.
 260         self.diverges.set(self.diverges.get() | old_diverges);
 261         self.has_errors.set(self.has_errors.get() | old_has_errors);
 262
 263         debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
 264         debug!("... {:?}, expected is {:?}", ty, expected);
 265
 266         ty
 267     }
 268
 269     #[instrument(skip(self, expr), level = "debug")]
 270     fn check_expr_kind(
 271         &self,
 272         expr: &'tcx hir::Expr<'tcx>,
 273         expected: Expectation<'tcx>,
 274     ) -> Ty<'tcx> {
 275         trace!("expr={:#?}", expr);
 276
 277         let tcx = self.tcx;
 278         match expr.kind {
 279             ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
 280             ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
 281             ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
 282             ExprKind::Assign(lhs, rhs, span) => {
 283                 self.check_expr_assign(expr, expected, lhs, rhs, span)
 284             }
 285             ExprKind::AssignOp(op, lhs, rhs) => {
 286                 self.check_binop_assign(expr, op, lhs, rhs, expected)
 287             }
 288             ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
 289             ExprKind::AddrOf(kind, mutbl, oprnd) => {
 290                 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
 291             }
 292             ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
 293                 self.check_lang_item_path(lang_item, expr, hir_id)
 294             }
 295             ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
 296             ExprKind::InlineAsm(asm) => {
 297                 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
 298                 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
 299                 self.check_expr_asm(asm)
 300             }
 301             ExprKind::Break(destination, ref expr_opt) => {
 302                 self.check_expr_break(destination, expr_opt.as_deref(), expr)
 303             }
 304             ExprKind::Continue(destination) => {
 305                 if destination.target_id.is_ok() {
 306                     tcx.types.never
 307                 } else {
 308                     // There was an error; make type-check fail.
 309                     tcx.ty_error()
 310                 }
 311             }
 312             ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
 313             ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
 314             ExprKind::Loop(body, _, source, _) => {
 315                 self.check_expr_loop(body, source, expected, expr)
 316             }
 317             ExprKind::Match(discrim, arms, match_src) => {
 318                 self.check_match(expr, &discrim, arms, expected, match_src)
 319             }
 320             ExprKind::Closure(&Closure { capture_clause, fn_decl, body, movability, .. }) => {
 321                 self.check_expr_closure(expr, capture_clause, &fn_decl, body, movability, expected)
 322             }
 323             ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
 324             ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
 325             ExprKind::MethodCall(segment, receiver, args, _) => {
 326                 self.check_method_call(expr, segment, receiver, args, expected)
 327             }
 328             ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
 329             ExprKind::Type(e, t) => {
 330                 let ty = self.to_ty_saving_user_provided_ty(&t);
 331                 self.check_expr_eq_type(&e, ty);
 332                 ty
 333             }
 334             ExprKind::If(cond, then_expr, opt_else_expr) => {
 335                 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
 336             }
 337             ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
 338             ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
 339             ExprKind::ConstBlock(ref anon_const) => {
 340                 self.check_expr_const_block(anon_const, expected, expr)
 341             }
 342             ExprKind::Repeat(element, ref count) => {
 343                 self.check_expr_repeat(element, count, expected, expr)
 344             }
 345             ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
 346             ExprKind::Struct(qpath, fields, ref base_expr) => {
 347                 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
 348             }
 349             ExprKind::Field(base, field) => self.check_field(expr, &base, field),
 350             ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
 351             ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
 352             hir::ExprKind::Err => tcx.ty_error(),
 353         }
 354     }
 355
 356     fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
 357         let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
 358             ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
 359             _ => NoExpectation,
 360         });
 361         let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
 362         self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
 363         self.tcx.mk_box(referent_ty)
 364     }
 365
 366     fn check_expr_unary(
 367         &self,
 368         unop: hir::UnOp,
 369         oprnd: &'tcx hir::Expr<'tcx>,
 370         expected: Expectation<'tcx>,
 371         expr: &'tcx hir::Expr<'tcx>,
 372     ) -> Ty<'tcx> {
 373         let tcx = self.tcx;
 374         let expected_inner = match unop {
 375             hir::UnOp::Not | hir::UnOp::Neg => expected,
 376             hir::UnOp::Deref => NoExpectation,
 377         };
 378         let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
 379
 380         if !oprnd_t.references_error() {
 381             oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
 382             match unop {
 383                 hir::UnOp::Deref => {
 384                     if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
 385                         oprnd_t = ty;
 386                     } else {
 387                         let mut err = type_error_struct!(
 388                             tcx.sess,
 389                             expr.span,
 390                             oprnd_t,
 391                             E0614,
 392                             "type `{oprnd_t}` cannot be dereferenced",
 393                         );
 394                         let sp = tcx.sess.source_map().start_point(expr.span);
 395                         if let Some(sp) =
 396                             tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
 397                         {
 398                             err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
 399                         }
 400                         err.emit();
 401                         oprnd_t = tcx.ty_error();
 402                     }
 403                 }
 404                 hir::UnOp::Not => {
 405                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 406                     // If it's builtin, we can reuse the type, this helps inference.
 407                     if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
 408                         oprnd_t = result;
 409                     }
 410                 }
 411                 hir::UnOp::Neg => {
 412                     let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
 413                     // If it's builtin, we can reuse the type, this helps inference.
 414                     if !oprnd_t.is_numeric() {
 415                         oprnd_t = result;
 416                     }
 417                 }
 418             }
 419         }
 420         oprnd_t
 421     }
 422
 423     fn check_expr_addr_of(
 424         &self,
 425         kind: hir::BorrowKind,
 426         mutbl: hir::Mutability,
 427         oprnd: &'tcx hir::Expr<'tcx>,
 428         expected: Expectation<'tcx>,
 429         expr: &'tcx hir::Expr<'tcx>,
 430     ) -> Ty<'tcx> {
 431         let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
 432             match ty.kind() {
 433                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 434                     if oprnd.is_syntactic_place_expr() {
 435                         // Places may legitimately have unsized types.
 436                         // For example, dereferences of a fat pointer and
 437                         // the last field of a struct can be unsized.
 438                         ExpectHasType(*ty)
 439                     } else {
 440                         Expectation::rvalue_hint(self, *ty)
 441                     }
 442                 }
 443                 _ => NoExpectation,
 444             }
 445         });
 446         let ty =
 447             self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
 448
 449         let tm = ty::TypeAndMut { ty, mutbl };
 450         match kind {
 451             _ if tm.ty.references_error() => self.tcx.ty_error(),
 452             hir::BorrowKind::Raw => {
 453                 self.check_named_place_expr(oprnd);
 454                 self.tcx.mk_ptr(tm)
 455             }
 456             hir::BorrowKind::Ref => {
 457                 // Note: at this point, we cannot say what the best lifetime
 458                 // is to use for resulting pointer.  We want to use the
 459                 // shortest lifetime possible so as to avoid spurious borrowck
 460                 // errors.  Moreover, the longest lifetime will depend on the
 461                 // precise details of the value whose address is being taken
 462                 // (and how long it is valid), which we don't know yet until
 463                 // type inference is complete.
 464                 //
 465                 // Therefore, here we simply generate a region variable. The
 466                 // region inferencer will then select a suitable value.
 467                 // Finally, borrowck will infer the value of the region again,
 468                 // this time with enough precision to check that the value
 469                 // whose address was taken can actually be made to live as long
 470                 // as it needs to live.
 471                 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
 472                 self.tcx.mk_ref(region, tm)
 473             }
 474         }
 475     }
 476
 477     /// Does this expression refer to a place that either:
 478     /// * Is based on a local or static.
 479     /// * Contains a dereference
 480     /// Note that the adjustments for the children of `expr` should already
 481     /// have been resolved.
 482     fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
 483         let is_named = oprnd.is_place_expr(|base| {
 484             // Allow raw borrows if there are any deref adjustments.
 485             //
 486             // const VAL: (i32,) = (0,);
 487             // const REF: &(i32,) = &(0,);
 488             //
 489             // &raw const VAL.0;            // ERROR
 490             // &raw const REF.0;            // OK, same as &raw const (*REF).0;
 491             //
 492             // This is maybe too permissive, since it allows
 493             // `let u = &raw const Box::new((1,)).0`, which creates an
 494             // immediately dangling raw pointer.
 495             self.typeck_results
 496                 .borrow()
 497                 .adjustments()
 498                 .get(base.hir_id)
 499                 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
 500         });
 501         if !is_named {
 502             self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
 503         }
 504     }
 505
 506     fn check_lang_item_path(
 507         &self,
 508         lang_item: hir::LangItem,
 509         expr: &'tcx hir::Expr<'tcx>,
 510         hir_id: Option<hir::HirId>,
 511     ) -> Ty<'tcx> {
 512         self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
 513     }
 514
 515     pub(crate) fn check_expr_path(
 516         &self,
 517         qpath: &'tcx hir::QPath<'tcx>,
 518         expr: &'tcx hir::Expr<'tcx>,
 519         args: &'tcx [hir::Expr<'tcx>],
 520     ) -> Ty<'tcx> {
 521         let tcx = self.tcx;
 522         let (res, opt_ty, segs) =
 523             self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
 524         let ty = match res {
 525             Res::Err => {
 526                 self.set_tainted_by_errors();
 527                 tcx.ty_error()
 528             }
 529             Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
 530                 report_unexpected_variant_res(tcx, res, qpath, expr.span);
 531                 tcx.ty_error()
 532             }
 533             _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
 534         };
 535
 536         if let ty::FnDef(did, ..) = *ty.kind() {
 537             let fn_sig = ty.fn_sig(tcx);
 538             if tcx.fn_sig(did).abi() == RustIntrinsic && tcx.item_name(did) == sym::transmute {
 539                 let from = fn_sig.inputs().skip_binder()[0];
 540                 let to = fn_sig.output().skip_binder();
 541                 // We defer the transmute to the end of typeck, once all inference vars have
 542                 // been resolved or we errored. This is important as we can only check transmute
 543                 // on concrete types, but the output type may not be known yet (it would only
 544                 // be known if explicitly specified via turbofish).
 545                 self.deferred_transmute_checks.borrow_mut().push((from, to, expr.hir_id));
 546             }
 547             if !tcx.features().unsized_fn_params {
 548                 // We want to remove some Sized bounds from std functions,
 549                 // but don't want to expose the removal to stable Rust.
 550                 // i.e., we don't want to allow
 551                 //
 552                 // ```rust
 553                 // drop as fn(str);
 554                 // ```
 555                 //
 556                 // to work in stable even if the Sized bound on `drop` is relaxed.
 557                 for i in 0..fn_sig.inputs().skip_binder().len() {
 558                     // We just want to check sizedness, so instead of introducing
 559                     // placeholder lifetimes with probing, we just replace higher lifetimes
 560                     // with fresh vars.
 561                     let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
 562                     let input = self.replace_bound_vars_with_fresh_vars(
 563                         span,
 564                         infer::LateBoundRegionConversionTime::FnCall,
 565                         fn_sig.input(i),
 566                     );
 567                     self.require_type_is_sized_deferred(
 568                         input,
 569                         span,
 570                         traits::SizedArgumentType(None),
 571                     );
 572                 }
 573             }
 574             // Here we want to prevent struct constructors from returning unsized types.
 575             // There were two cases this happened: fn pointer coercion in stable
 576             // and usual function call in presence of unsized_locals.
 577             // Also, as we just want to check sizedness, instead of introducing
 578             // placeholder lifetimes with probing, we just replace higher lifetimes
 579             // with fresh vars.
 580             let output = self.replace_bound_vars_with_fresh_vars(
 581                 expr.span,
 582                 infer::LateBoundRegionConversionTime::FnCall,
 583                 fn_sig.output(),
 584             );
 585             self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
 586         }
 587
 588         // We always require that the type provided as the value for
 589         // a type parameter outlives the moment of instantiation.
 590         let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
 591         self.add_wf_bounds(substs, expr);
 592
 593         ty
 594     }
 595
 596     fn check_expr_break(
 597         &self,
 598         destination: hir::Destination,
 599         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 600         expr: &'tcx hir::Expr<'tcx>,
 601     ) -> Ty<'tcx> {
 602         let tcx = self.tcx;
 603         if let Ok(target_id) = destination.target_id {
 604             let (e_ty, cause);
 605             if let Some(e) = expr_opt {
 606                 // If this is a break with a value, we need to type-check
 607                 // the expression. Get an expected type from the loop context.
 608                 let opt_coerce_to = {
 609                     // We should release `enclosing_breakables` before the `check_expr_with_hint`
 610                     // below, so can't move this block of code to the enclosing scope and share
 611                     // `ctxt` with the second `enclosing_breakables` borrow below.
 612                     let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 613                     match enclosing_breakables.opt_find_breakable(target_id) {
 614                         Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
 615                         None => {
 616                             // Avoid ICE when `break` is inside a closure (#65383).
 617                             return tcx.ty_error_with_message(
 618                                 expr.span,
 619                                 "break was outside loop, but no error was emitted",
 620                             );
 621                         }
 622                     }
 623                 };
 624
 625                 // If the loop context is not a `loop { }`, then break with
 626                 // a value is illegal, and `opt_coerce_to` will be `None`.
 627                 // Just set expectation to error in that case.
 628                 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
 629
 630                 // Recurse without `enclosing_breakables` borrowed.
 631                 e_ty = self.check_expr_with_hint(e, coerce_to);
 632                 cause = self.misc(e.span);
 633             } else {
 634                 // Otherwise, this is a break *without* a value. That's
 635                 // always legal, and is equivalent to `break ()`.
 636                 e_ty = tcx.mk_unit();
 637                 cause = self.misc(expr.span);
 638             }
 639
 640             // Now that we have type-checked `expr_opt`, borrow
 641             // the `enclosing_loops` field and let's coerce the
 642             // type of `expr_opt` into what is expected.
 643             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 644             let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
 645                 // Avoid ICE when `break` is inside a closure (#65383).
 646                 return tcx.ty_error_with_message(
 647                     expr.span,
 648                     "break was outside loop, but no error was emitted",
 649                 );
 650             };
 651
 652             if let Some(ref mut coerce) = ctxt.coerce {
 653                 if let Some(ref e) = expr_opt {
 654                     coerce.coerce(self, &cause, e, e_ty);
 655                 } else {
 656                     assert!(e_ty.is_unit());
 657                     let ty = coerce.expected_ty();
 658                     coerce.coerce_forced_unit(
 659                         self,
 660                         &cause,
 661                         &mut |mut err| {
 662                             self.suggest_mismatched_types_on_tail(
 663                                 &mut err, expr, ty, e_ty, target_id,
 664                             );
 665                             if let Some(val) = ty_kind_suggestion(ty) {
 666                                 let label = destination
 667                                     .label
 668                                     .map(|l| format!(" {}", l.ident))
 669                                     .unwrap_or_else(String::new);
 670                                 err.span_suggestion(
 671                                     expr.span,
 672                                     "give it a value of the expected type",
 673                                     format!("break{label} {val}"),
 674                                     Applicability::HasPlaceholders,
 675                                 );
 676                             }
 677                         },
 678                         false,
 679                     );
 680                 }
 681             } else {
 682                 // If `ctxt.coerce` is `None`, we can just ignore
 683                 // the type of the expression.  This is because
 684                 // either this was a break *without* a value, in
 685                 // which case it is always a legal type (`()`), or
 686                 // else an error would have been flagged by the
 687                 // `loops` pass for using break with an expression
 688                 // where you are not supposed to.
 689                 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
 690             }
 691
 692             // If we encountered a `break`, then (no surprise) it may be possible to break from the
 693             // loop... unless the value being returned from the loop diverges itself, e.g.
 694             // `break return 5` or `break loop {}`.
 695             ctxt.may_break |= !self.diverges.get().is_always();
 696
 697             // the type of a `break` is always `!`, since it diverges
 698             tcx.types.never
 699         } else {
 700             // Otherwise, we failed to find the enclosing loop;
 701             // this can only happen if the `break` was not
 702             // inside a loop at all, which is caught by the
 703             // loop-checking pass.
 704             let err = self.tcx.ty_error_with_message(
 705                 expr.span,
 706                 "break was outside loop, but no error was emitted",
 707             );
 708
 709             // We still need to assign a type to the inner expression to
 710             // prevent the ICE in #43162.
 711             if let Some(e) = expr_opt {
 712                 self.check_expr_with_hint(e, err);
 713
 714                 // ... except when we try to 'break rust;'.
 715                 // ICE this expression in particular (see #43162).
 716                 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
 717                     if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
 718                         fatally_break_rust(self.tcx.sess);
 719                     }
 720                 }
 721             }
 722
 723             // There was an error; make type-check fail.
 724             err
 725         }
 726     }
 727
 728     fn check_expr_return(
 729         &self,
 730         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 731         expr: &'tcx hir::Expr<'tcx>,
 732     ) -> Ty<'tcx> {
 733         if self.ret_coercion.is_none() {
 734             let mut err = ReturnStmtOutsideOfFnBody {
 735                 span: expr.span,
 736                 encl_body_span: None,
 737                 encl_fn_span: None,
 738             };
 739
 740             let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
 741
 742             if let Some(hir::Node::Item(hir::Item {
 743                 kind: hir::ItemKind::Fn(..),
 744                 span: encl_fn_span,
 745                 ..
 746             }))
 747             | Some(hir::Node::TraitItem(hir::TraitItem {
 748                 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
 749                 span: encl_fn_span,
 750                 ..
 751             }))
 752             | Some(hir::Node::ImplItem(hir::ImplItem {
 753                 kind: hir::ImplItemKind::Fn(..),
 754                 span: encl_fn_span,
 755                 ..
 756             })) = self.tcx.hir().find_by_def_id(encl_item_id.def_id)
 757             {
 758                 // We are inside a function body, so reporting "return statement
 759                 // outside of function body" needs an explanation.
 760
 761                 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
 762
 763                 // If this didn't hold, we would not have to report an error in
 764                 // the first place.
 765                 assert_ne!(encl_item_id.def_id, encl_body_owner_id);
 766
 767                 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
 768                 let encl_body = self.tcx.hir().body(encl_body_id);
 769
 770                 err.encl_body_span = Some(encl_body.value.span);
 771                 err.encl_fn_span = Some(*encl_fn_span);
 772             }
 773
 774             self.tcx.sess.emit_err(err);
 775
 776             if let Some(e) = expr_opt {
 777                 // We still have to type-check `e` (issue #86188), but calling
 778                 // `check_return_expr` only works inside fn bodies.
 779                 self.check_expr(e);
 780             }
 781         } else if let Some(e) = expr_opt {
 782             if self.ret_coercion_span.get().is_none() {
 783                 self.ret_coercion_span.set(Some(e.span));
 784             }
 785             self.check_return_expr(e, true);
 786         } else {
 787             let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
 788             if self.ret_coercion_span.get().is_none() {
 789                 self.ret_coercion_span.set(Some(expr.span));
 790             }
 791             let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
 792             if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
 793                 coercion.coerce_forced_unit(
 794                     self,
 795                     &cause,
 796                     &mut |db| {
 797                         let span = fn_decl.output.span();
 798                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
 799                             db.span_label(
 800                                 span,
 801                                 format!("expected `{snippet}` because of this return type"),
 802                             );
 803                         }
 804                     },
 805                     true,
 806                 );
 807             } else {
 808                 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
 809             }
 810         }
 811         self.tcx.types.never
 812     }
 813
 814     /// `explicit_return` is `true` if we're checking an explicit `return expr`,
 815     /// and `false` if we're checking a trailing expression.
 816     pub(super) fn check_return_expr(
 817         &self,
 818         return_expr: &'tcx hir::Expr<'tcx>,
 819         explicit_return: bool,
 820     ) {
 821         let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
 822             span_bug!(return_expr.span, "check_return_expr called outside fn body")
 823         });
 824
 825         let ret_ty = ret_coercion.borrow().expected_ty();
 826         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
 827         let mut span = return_expr.span;
 828         // Use the span of the trailing expression for our cause,
 829         // not the span of the entire function
 830         if !explicit_return {
 831             if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
 832                 span = last_expr.span;
 833             }
 834         }
 835         ret_coercion.borrow_mut().coerce(
 836             self,
 837             &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
 838             return_expr,
 839             return_expr_ty,
 840         );
 841
 842         if self.return_type_has_opaque {
 843             // Point any obligations that were registered due to opaque type
 844             // inference at the return expression.
 845             self.select_obligations_where_possible(false, |errors| {
 846                 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
 847             });
 848         }
 849     }
 850
 851     fn point_at_return_for_opaque_ty_error(
 852         &self,
 853         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
 854         span: Span,
 855         return_expr_ty: Ty<'tcx>,
 856     ) {
 857         // Don't point at the whole block if it's empty
 858         if span == self.tcx.hir().span(self.body_id) {
 859             return;
 860         }
 861         for err in errors {
 862             let cause = &mut err.obligation.cause;
 863             if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
 864                 let new_cause = ObligationCause::new(
 865                     cause.span,
 866                     cause.body_id,
 867                     ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
 868                 );
 869                 *cause = new_cause;
 870             }
 871         }
 872     }
 873
 874     pub(crate) fn check_lhs_assignable(
 875         &self,
 876         lhs: &'tcx hir::Expr<'tcx>,
 877         err_code: &'static str,
 878         op_span: Span,
 879         adjust_err: impl FnOnce(&mut Diagnostic),
 880     ) {
 881         if lhs.is_syntactic_place_expr() {
 882             return;
 883         }
 884
 885         // FIXME: Make this use Diagnostic once error codes can be dynamically set.
 886         let mut err = self.tcx.sess.struct_span_err_with_code(
 887             op_span,
 888             "invalid left-hand side of assignment",
 889             DiagnosticId::Error(err_code.into()),
 890         );
 891         err.span_label(lhs.span, "cannot assign to this expression");
 892
 893         self.comes_from_while_condition(lhs.hir_id, |expr| {
 894             err.span_suggestion_verbose(
 895                 expr.span.shrink_to_lo(),
 896                 "you might have meant to use pattern destructuring",
 897                 "let ",
 898                 Applicability::MachineApplicable,
 899             );
 900         });
 901
 902         adjust_err(&mut err);
 903
 904         err.emit();
 905     }
 906
 907     // Check if an expression `original_expr_id` comes from the condition of a while loop,
 908     // as opposed from the body of a while loop, which we can naively check by iterating
 909     // parents until we find a loop...
 910     pub(super) fn comes_from_while_condition(
 911         &self,
 912         original_expr_id: HirId,
 913         then: impl FnOnce(&hir::Expr<'_>),
 914     ) {
 915         let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
 916         while let Some(node) = self.tcx.hir().find(parent) {
 917             match node {
 918                 hir::Node::Expr(hir::Expr {
 919                     kind:
 920                         hir::ExprKind::Loop(
 921                             hir::Block {
 922                                 expr:
 923                                     Some(hir::Expr {
 924                                         kind:
 925                                             hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
 926                                         ..
 927                                     }),
 928                                 ..
 929                             },
 930                             _,
 931                             hir::LoopSource::While,
 932                             _,
 933                         ),
 934                     ..
 935                 }) => {
 936                     // Check if our original expression is a child of the condition of a while loop
 937                     let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
 938                         self.tcx.hir().find_parent_node(*id)
 939                     })
 940                     .take_while(|id| *id != parent)
 941                     .any(|id| id == expr.hir_id);
 942                     // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
 943                     // where `while let` was more likely intended.
 944                     if expr_is_ancestor {
 945                         then(expr);
 946                     }
 947                     break;
 948                 }
 949                 hir::Node::Item(_)
 950                 | hir::Node::ImplItem(_)
 951                 | hir::Node::TraitItem(_)
 952                 | hir::Node::Crate(_) => break,
 953                 _ => {
 954                     parent = self.tcx.hir().get_parent_node(parent);
 955                 }
 956             }
 957         }
 958     }
 959
 960     // A generic function for checking the 'then' and 'else' clauses in an 'if'
 961     // or 'if-else' expression.
 962     fn check_then_else(
 963         &self,
 964         cond_expr: &'tcx hir::Expr<'tcx>,
 965         then_expr: &'tcx hir::Expr<'tcx>,
 966         opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
 967         sp: Span,
 968         orig_expected: Expectation<'tcx>,
 969     ) -> Ty<'tcx> {
 970         let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
 971
 972         self.warn_if_unreachable(
 973             cond_expr.hir_id,
 974             then_expr.span,
 975             "block in `if` or `while` expression",
 976         );
 977
 978         let cond_diverges = self.diverges.get();
 979         self.diverges.set(Diverges::Maybe);
 980
 981         let expected = orig_expected.adjust_for_branches(self);
 982         let then_ty = self.check_expr_with_expectation(then_expr, expected);
 983         let then_diverges = self.diverges.get();
 984         self.diverges.set(Diverges::Maybe);
 985
 986         // We've already taken the expected type's preferences
 987         // into account when typing the `then` branch. To figure
 988         // out the initial shot at a LUB, we thus only consider
 989         // `expected` if it represents a *hard* constraint
 990         // (`only_has_type`); otherwise, we just go with a
 991         // fresh type variable.
 992         let coerce_to_ty = expected.coercion_target_type(self, sp);
 993         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
 994
 995         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
 996
 997         if let Some(else_expr) = opt_else_expr {
 998             let else_ty = self.check_expr_with_expectation(else_expr, expected);
 999             let else_diverges = self.diverges.get();
1000
1001             let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1002             let if_cause = self.if_cause(
1003                 sp,
1004                 cond_expr.span,
1005                 then_expr,
1006                 else_expr,
1007                 then_ty,
1008                 else_ty,
1009                 opt_suggest_box_span,
1010             );
1011
1012             coerce.coerce(self, &if_cause, else_expr, else_ty);
1013
1014             // We won't diverge unless both branches do (or the condition does).
1015             self.diverges.set(cond_diverges | then_diverges & else_diverges);
1016         } else {
1017             self.if_fallback_coercion(sp, then_expr, &mut coerce);
1018
1019             // If the condition is false we can't diverge.
1020             self.diverges.set(cond_diverges);
1021         }
1022
1023         let result_ty = coerce.complete(self);
1024         if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1025     }
1026
1027     /// Type check assignment expression `expr` of form `lhs = rhs`.
1028     /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1029     fn check_expr_assign(
1030         &self,
1031         expr: &'tcx hir::Expr<'tcx>,
1032         expected: Expectation<'tcx>,
1033         lhs: &'tcx hir::Expr<'tcx>,
1034         rhs: &'tcx hir::Expr<'tcx>,
1035         span: Span,
1036     ) -> Ty<'tcx> {
1037         let expected_ty = expected.coercion_target_type(self, expr.span);
1038         if expected_ty == self.tcx.types.bool {
1039             // The expected type is `bool` but this will result in `()` so we can reasonably
1040             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1041             // The likely cause of this is `if foo = bar { .. }`.
1042             let actual_ty = self.tcx.mk_unit();
1043             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1044             let lhs_ty = self.check_expr(&lhs);
1045             let rhs_ty = self.check_expr(&rhs);
1046             let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1047                 (Applicability::MachineApplicable, true)
1048             } else if let ExprKind::Binary(
1049                 Spanned { node: hir::BinOpKind::And | hir::BinOpKind::Or, .. },
1050                 _,
1051                 rhs_expr,
1052             ) = lhs.kind
1053             {
1054                 let actual_lhs_ty = self.check_expr(&rhs_expr);
1055                 (Applicability::MaybeIncorrect, self.can_coerce(rhs_ty, actual_lhs_ty))
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.shrink_to_hi(),
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         rcvr: &'tcx hir::Expr<'tcx>,
1205         args: &'tcx [hir::Expr<'tcx>],
1206         expected: Expectation<'tcx>,
1207     ) -> Ty<'tcx> {
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(rcvr.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(rcvr),
1228                         error,
1229                         Some((rcvr, args)),
1230                     ) {
1231                         err.emit();
1232                     }
1233                 }
1234                 Err(())
1235             }
1236         };
1237
1238         // Call the generic checker.
1239         self.check_method_argument_types(span, expr, method, &args, DontTupleArguments, expected)
1240     }
1241
1242     fn check_expr_cast(
1243         &self,
1244         e: &'tcx hir::Expr<'tcx>,
1245         t: &'tcx hir::Ty<'tcx>,
1246         expr: &'tcx hir::Expr<'tcx>,
1247     ) -> Ty<'tcx> {
1248         // Find the type of `e`. Supply hints based on the type we are casting to,
1249         // if appropriate.
1250         let t_cast = self.to_ty_saving_user_provided_ty(t);
1251         let t_cast = self.resolve_vars_if_possible(t_cast);
1252         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1253         let t_expr = self.resolve_vars_if_possible(t_expr);
1254
1255         // Eagerly check for some obvious errors.
1256         if t_expr.references_error() || t_cast.references_error() {
1257             self.tcx.ty_error()
1258         } else {
1259             // Defer other checks until we're done type checking.
1260             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1261             match cast::check_cast(self, e, t_expr, t_cast, t.span, expr.span) {
1262                 CastCheckResult::Ok => t_cast,
1263                 CastCheckResult::Deferred(cast_check) => {
1264                     debug!(
1265                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1266                         t_cast, t_expr, cast_check,
1267                     );
1268                     deferred_cast_checks.push(cast_check);
1269                     t_cast
1270                 }
1271                 CastCheckResult::Err(ErrorGuaranteed { .. }) => self.tcx.ty_error(),
1272             }
1273         }
1274     }
1275
1276     fn check_expr_array(
1277         &self,
1278         args: &'tcx [hir::Expr<'tcx>],
1279         expected: Expectation<'tcx>,
1280         expr: &'tcx hir::Expr<'tcx>,
1281     ) -> Ty<'tcx> {
1282         let element_ty = if !args.is_empty() {
1283             let coerce_to = expected
1284                 .to_option(self)
1285                 .and_then(|uty| match *uty.kind() {
1286                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1287                     _ => None,
1288                 })
1289                 .unwrap_or_else(|| {
1290                     self.next_ty_var(TypeVariableOrigin {
1291                         kind: TypeVariableOriginKind::TypeInference,
1292                         span: expr.span,
1293                     })
1294                 });
1295             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1296             assert_eq!(self.diverges.get(), Diverges::Maybe);
1297             for e in args {
1298                 let e_ty = self.check_expr_with_hint(e, coerce_to);
1299                 let cause = self.misc(e.span);
1300                 coerce.coerce(self, &cause, e, e_ty);
1301             }
1302             coerce.complete(self)
1303         } else {
1304             self.next_ty_var(TypeVariableOrigin {
1305                 kind: TypeVariableOriginKind::TypeInference,
1306                 span: expr.span,
1307             })
1308         };
1309         let array_len = args.len() as u64;
1310         self.suggest_array_len(expr, array_len);
1311         self.tcx.mk_array(element_ty, array_len)
1312     }
1313
1314     fn suggest_array_len(&self, expr: &'tcx hir::Expr<'tcx>, array_len: u64) {
1315         let parent_node = self.tcx.hir().parent_iter(expr.hir_id).find(|(_, node)| {
1316             !matches!(node, hir::Node::Expr(hir::Expr { kind: hir::ExprKind::AddrOf(..), .. }))
1317         });
1318         let Some((_,
1319             hir::Node::Local(hir::Local { ty: Some(ty), .. })
1320             | hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _), .. }))
1321         ) = parent_node else {
1322             return
1323         };
1324         if let hir::TyKind::Array(_, length) = ty.peel_refs().kind
1325             && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
1326             && let Some(span) = self.tcx.hir().opt_span(hir_id)
1327         {
1328             match self.tcx.sess.diagnostic().steal_diagnostic(span, StashKey::UnderscoreForArrayLengths) {
1329                 Some(mut err) => {
1330                     err.span_suggestion(
1331                         span,
1332                         "consider specifying the array length",
1333                         array_len,
1334                         Applicability::MaybeIncorrect,
1335                     );
1336                     err.emit();
1337                 }
1338                 None => ()
1339             }
1340         }
1341     }
1342
1343     fn check_expr_const_block(
1344         &self,
1345         anon_const: &'tcx hir::AnonConst,
1346         expected: Expectation<'tcx>,
1347         _expr: &'tcx hir::Expr<'tcx>,
1348     ) -> Ty<'tcx> {
1349         let body = self.tcx.hir().body(anon_const.body);
1350
1351         // Create a new function context.
1352         let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1353         crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1354
1355         let ty = fcx.check_expr_with_expectation(&body.value, expected);
1356         fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1357         fcx.write_ty(anon_const.hir_id, ty);
1358         ty
1359     }
1360
1361     fn check_expr_repeat(
1362         &self,
1363         element: &'tcx hir::Expr<'tcx>,
1364         count: &'tcx hir::ArrayLen,
1365         expected: Expectation<'tcx>,
1366         expr: &'tcx hir::Expr<'tcx>,
1367     ) -> Ty<'tcx> {
1368         let tcx = self.tcx;
1369         let count = self.array_length_to_const(count);
1370         if let Some(count) = count.try_eval_usize(tcx, self.param_env) {
1371             self.suggest_array_len(expr, count);
1372         }
1373
1374         let uty = match expected {
1375             ExpectHasType(uty) => match *uty.kind() {
1376                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1377                 _ => None,
1378             },
1379             _ => None,
1380         };
1381
1382         let (element_ty, t) = match uty {
1383             Some(uty) => {
1384                 self.check_expr_coercable_to_type(&element, uty, None);
1385                 (uty, uty)
1386             }
1387             None => {
1388                 let ty = self.next_ty_var(TypeVariableOrigin {
1389                     kind: TypeVariableOriginKind::MiscVariable,
1390                     span: element.span,
1391                 });
1392                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1393                 (element_ty, ty)
1394             }
1395         };
1396
1397         if element_ty.references_error() {
1398             return tcx.ty_error();
1399         }
1400
1401         self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1402
1403         tcx.mk_ty(ty::Array(t, count))
1404     }
1405
1406     fn check_repeat_element_needs_copy_bound(
1407         &self,
1408         element: &hir::Expr<'_>,
1409         count: ty::Const<'tcx>,
1410         element_ty: Ty<'tcx>,
1411     ) {
1412         let tcx = self.tcx;
1413         // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1414         match &element.kind {
1415             hir::ExprKind::ConstBlock(..) => return,
1416             hir::ExprKind::Path(qpath) => {
1417                 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1418                 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1419                 {
1420                     return;
1421                 }
1422             }
1423             _ => {}
1424         }
1425         // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1426         // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1427         let is_const_fn = match element.kind {
1428             hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1429                 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1430                 _ => false,
1431             },
1432             _ => false,
1433         };
1434
1435         // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1436         // don't copy that one element, we move it. Only check for Copy if the length is larger.
1437         if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1438             let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1439             let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1440             self.require_type_meets(element_ty, element.span, code, lang_item);
1441         }
1442     }
1443
1444     fn check_expr_tuple(
1445         &self,
1446         elts: &'tcx [hir::Expr<'tcx>],
1447         expected: Expectation<'tcx>,
1448         expr: &'tcx hir::Expr<'tcx>,
1449     ) -> Ty<'tcx> {
1450         let flds = expected.only_has_type(self).and_then(|ty| {
1451             let ty = self.resolve_vars_with_obligations(ty);
1452             match ty.kind() {
1453                 ty::Tuple(flds) => Some(&flds[..]),
1454                 _ => None,
1455             }
1456         });
1457
1458         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1459             Some(fs) if i < fs.len() => {
1460                 let ety = fs[i];
1461                 self.check_expr_coercable_to_type(&e, ety, None);
1462                 ety
1463             }
1464             _ => self.check_expr_with_expectation(&e, NoExpectation),
1465         });
1466         let tuple = self.tcx.mk_tup(elt_ts_iter);
1467         if tuple.references_error() {
1468             self.tcx.ty_error()
1469         } else {
1470             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1471             tuple
1472         }
1473     }
1474
1475     fn check_expr_struct(
1476         &self,
1477         expr: &hir::Expr<'_>,
1478         expected: Expectation<'tcx>,
1479         qpath: &QPath<'_>,
1480         fields: &'tcx [hir::ExprField<'tcx>],
1481         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1482     ) -> Ty<'tcx> {
1483         // Find the relevant variant
1484         let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1485             self.check_struct_fields_on_error(fields, base_expr);
1486             return self.tcx.ty_error();
1487         };
1488
1489         // Prohibit struct expressions when non-exhaustive flag is set.
1490         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1491         if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1492             self.tcx
1493                 .sess
1494                 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1495         }
1496
1497         self.check_expr_struct_fields(
1498             adt_ty,
1499             expected,
1500             expr.hir_id,
1501             qpath.span(),
1502             variant,
1503             fields,
1504             base_expr,
1505             expr.span,
1506         );
1507
1508         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1509         adt_ty
1510     }
1511
1512     fn check_expr_struct_fields(
1513         &self,
1514         adt_ty: Ty<'tcx>,
1515         expected: Expectation<'tcx>,
1516         expr_id: hir::HirId,
1517         span: Span,
1518         variant: &'tcx ty::VariantDef,
1519         ast_fields: &'tcx [hir::ExprField<'tcx>],
1520         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1521         expr_span: Span,
1522     ) {
1523         let tcx = self.tcx;
1524
1525         let expected_inputs =
1526             self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1527         let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1528             expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1529         } else {
1530             adt_ty
1531         };
1532         // re-link the regions that EIfEO can erase.
1533         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1534
1535         let ty::Adt(adt, substs) = adt_ty.kind() else {
1536             span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1537         };
1538         let adt_kind = adt.adt_kind();
1539
1540         let mut remaining_fields = variant
1541             .fields
1542             .iter()
1543             .enumerate()
1544             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1545             .collect::<FxHashMap<_, _>>();
1546
1547         let mut seen_fields = FxHashMap::default();
1548
1549         let mut error_happened = false;
1550
1551         // Type-check each field.
1552         for (idx, field) in ast_fields.iter().enumerate() {
1553             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1554             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1555                 seen_fields.insert(ident, field.span);
1556                 self.write_field_index(field.hir_id, i);
1557
1558                 // We don't look at stability attributes on
1559                 // struct-like enums (yet...), but it's definitely not
1560                 // a bug to have constructed one.
1561                 if adt_kind != AdtKind::Enum {
1562                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1563                 }
1564
1565                 self.field_ty(field.span, v_field, substs)
1566             } else {
1567                 error_happened = true;
1568                 if let Some(prev_span) = seen_fields.get(&ident) {
1569                     tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1570                         span: field.ident.span,
1571                         prev_span: *prev_span,
1572                         ident,
1573                     });
1574                 } else {
1575                     self.report_unknown_field(
1576                         adt_ty,
1577                         variant,
1578                         field,
1579                         ast_fields,
1580                         adt.variant_descr(),
1581                         expr_span,
1582                     );
1583                 }
1584
1585                 tcx.ty_error()
1586             };
1587
1588             // Make sure to give a type to the field even if there's
1589             // an error, so we can continue type-checking.
1590             let ty = self.check_expr_with_hint(&field.expr, field_type);
1591             let (_, diag) =
1592                 self.demand_coerce_diag(&field.expr, ty, field_type, None, AllowTwoPhase::No);
1593
1594             if let Some(mut diag) = diag {
1595                 if idx == ast_fields.len() - 1 && remaining_fields.is_empty() {
1596                     self.suggest_fru_from_range(field, variant, substs, &mut diag);
1597                 }
1598                 diag.emit();
1599             }
1600         }
1601
1602         // Make sure the programmer specified correct number of fields.
1603         if adt_kind == AdtKind::Union {
1604             if ast_fields.len() != 1 {
1605                 struct_span_err!(
1606                     tcx.sess,
1607                     span,
1608                     E0784,
1609                     "union expressions should have exactly one field",
1610                 )
1611                 .emit();
1612             }
1613         }
1614
1615         // If check_expr_struct_fields hit an error, do not attempt to populate
1616         // the fields with the base_expr. This could cause us to hit errors later
1617         // when certain fields are assumed to exist that in fact do not.
1618         if error_happened {
1619             return;
1620         }
1621
1622         if let Some(base_expr) = base_expr {
1623             // FIXME: We are currently creating two branches here in order to maintain
1624             // consistency. But they should be merged as much as possible.
1625             let fru_tys = if self.tcx.features().type_changing_struct_update {
1626                 if adt.is_struct() {
1627                     // Make some fresh substitutions for our ADT type.
1628                     let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1629                     // We do subtyping on the FRU fields first, so we can
1630                     // learn exactly what types we expect the base expr
1631                     // needs constrained to be compatible with the struct
1632                     // type we expect from the expectation value.
1633                     let fru_tys = variant
1634                         .fields
1635                         .iter()
1636                         .map(|f| {
1637                             let fru_ty = self.normalize_associated_types_in(
1638                                 expr_span,
1639                                 self.field_ty(base_expr.span, f, fresh_substs),
1640                             );
1641                             let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1642                             if let Some(_) = remaining_fields.remove(&ident) {
1643                                 let target_ty = self.field_ty(base_expr.span, f, substs);
1644                                 let cause = self.misc(base_expr.span);
1645                                 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1646                                     Ok(InferOk { obligations, value: () }) => {
1647                                         self.register_predicates(obligations)
1648                                     }
1649                                     Err(_) => {
1650                                         // This should never happen, since we're just subtyping the
1651                                         // remaining_fields, but it's fine to emit this, I guess.
1652                                         self.err_ctxt()
1653                                             .report_mismatched_types(
1654                                                 &cause,
1655                                                 target_ty,
1656                                                 fru_ty,
1657                                                 FieldMisMatch(variant.name, ident.name),
1658                                             )
1659                                             .emit();
1660                                     }
1661                                 }
1662                             }
1663                             self.resolve_vars_if_possible(fru_ty)
1664                         })
1665                         .collect();
1666                     // The use of fresh substs that we have subtyped against
1667                     // our base ADT type's fields allows us to guide inference
1668                     // along so that, e.g.
1669                     // ```
1670                     // MyStruct<'a, F1, F2, const C: usize> {
1671                     //     f: F1,
1672                     //     // Other fields that reference `'a`, `F2`, and `C`
1673                     // }
1674                     //
1675                     // let x = MyStruct {
1676                     //    f: 1usize,
1677                     //    ..other_struct
1678                     // };
1679                     // ```
1680                     // will have the `other_struct` expression constrained to
1681                     // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1682                     // This is important to allow coercions to happen in
1683                     // `other_struct` itself. See `coerce-in-base-expr.rs`.
1684                     let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1685                     self.check_expr_has_type_or_error(
1686                         base_expr,
1687                         self.resolve_vars_if_possible(fresh_base_ty),
1688                         |_| {},
1689                     );
1690                     fru_tys
1691                 } else {
1692                     // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1693                     // type errors on that expression, too.
1694                     self.check_expr(base_expr);
1695                     self.tcx
1696                         .sess
1697                         .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1698                     return;
1699                 }
1700             } else {
1701                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1702                     let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1703                     let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1704                         (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1705                         _ => false,
1706                     };
1707                     if self.tcx.sess.is_nightly_build() && same_adt {
1708                         feature_err(
1709                             &self.tcx.sess.parse_sess,
1710                             sym::type_changing_struct_update,
1711                             base_expr.span,
1712                             "type changing struct updating is experimental",
1713                         )
1714                         .emit();
1715                     }
1716                 });
1717                 match adt_ty.kind() {
1718                     ty::Adt(adt, substs) if adt.is_struct() => variant
1719                         .fields
1720                         .iter()
1721                         .map(|f| {
1722                             self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1723                         })
1724                         .collect(),
1725                     _ => {
1726                         self.tcx
1727                             .sess
1728                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1729                         return;
1730                     }
1731                 }
1732             };
1733             self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1734         } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1735             debug!(?remaining_fields);
1736             let private_fields: Vec<&ty::FieldDef> = variant
1737                 .fields
1738                 .iter()
1739                 .filter(|field| !field.vis.is_accessible_from(tcx.parent_module(expr_id), tcx))
1740                 .collect();
1741
1742             if !private_fields.is_empty() {
1743                 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1744             } else {
1745                 self.report_missing_fields(
1746                     adt_ty,
1747                     span,
1748                     remaining_fields,
1749                     variant,
1750                     ast_fields,
1751                     substs,
1752                 );
1753             }
1754         }
1755     }
1756
1757     fn check_struct_fields_on_error(
1758         &self,
1759         fields: &'tcx [hir::ExprField<'tcx>],
1760         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1761     ) {
1762         for field in fields {
1763             self.check_expr(&field.expr);
1764         }
1765         if let Some(base) = *base_expr {
1766             self.check_expr(&base);
1767         }
1768     }
1769
1770     /// Report an error for a struct field expression when there are fields which aren't provided.
1771     ///
1772     /// ```text
1773     /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1774     ///  --> src/main.rs:8:5
1775     ///   |
1776     /// 8 |     foo::Foo {};
1777     ///   |     ^^^^^^^^ missing `you_can_use_this_field`
1778     ///
1779     /// error: aborting due to previous error
1780     /// ```
1781     fn report_missing_fields(
1782         &self,
1783         adt_ty: Ty<'tcx>,
1784         span: Span,
1785         remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1786         variant: &'tcx ty::VariantDef,
1787         ast_fields: &'tcx [hir::ExprField<'tcx>],
1788         substs: SubstsRef<'tcx>,
1789     ) {
1790         let len = remaining_fields.len();
1791
1792         let mut displayable_field_names: Vec<&str> =
1793             remaining_fields.keys().map(|ident| ident.as_str()).collect();
1794         // sorting &str primitives here, sort_unstable is ok
1795         displayable_field_names.sort_unstable();
1796
1797         let mut truncated_fields_error = String::new();
1798         let remaining_fields_names = match &displayable_field_names[..] {
1799             [field1] => format!("`{}`", field1),
1800             [field1, field2] => format!("`{field1}` and `{field2}`"),
1801             [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1802             _ => {
1803                 truncated_fields_error =
1804                     format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1805                 displayable_field_names
1806                     .iter()
1807                     .take(3)
1808                     .map(|n| format!("`{n}`"))
1809                     .collect::<Vec<_>>()
1810                     .join(", ")
1811             }
1812         };
1813
1814         let mut err = struct_span_err!(
1815             self.tcx.sess,
1816             span,
1817             E0063,
1818             "missing field{} {}{} in initializer of `{}`",
1819             pluralize!(len),
1820             remaining_fields_names,
1821             truncated_fields_error,
1822             adt_ty
1823         );
1824         err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1825
1826         if let Some(last) = ast_fields.last() {
1827             self.suggest_fru_from_range(last, variant, substs, &mut err);
1828         }
1829
1830         err.emit();
1831     }
1832
1833     /// If the last field is a range literal, but it isn't supposed to be, then they probably
1834     /// meant to use functional update syntax.
1835     fn suggest_fru_from_range(
1836         &self,
1837         last_expr_field: &hir::ExprField<'tcx>,
1838         variant: &ty::VariantDef,
1839         substs: SubstsRef<'tcx>,
1840         err: &mut Diagnostic,
1841     ) {
1842         // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1843         if let ExprKind::Struct(
1844                 QPath::LangItem(LangItem::Range, ..),
1845                 &[ref range_start, ref range_end],
1846                 _,
1847             ) = last_expr_field.expr.kind
1848             && let variant_field =
1849                 variant.fields.iter().find(|field| field.ident(self.tcx) == last_expr_field.ident)
1850             && let range_def_id = self.tcx.lang_items().range_struct()
1851             && variant_field
1852                 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1853                 .map(|adt| adt.did())
1854                 != range_def_id
1855         {
1856             let instead = self
1857                 .tcx
1858                 .sess
1859                 .source_map()
1860                 .span_to_snippet(range_end.expr.span)
1861                 .map(|s| format!(" from `{s}`"))
1862                 .unwrap_or_default();
1863             err.span_suggestion(
1864                 range_start.span.shrink_to_hi(),
1865                 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1866                 ",",
1867                 Applicability::MaybeIncorrect,
1868             );
1869         }
1870     }
1871
1872     /// Report an error for a struct field expression when there are invisible fields.
1873     ///
1874     /// ```text
1875     /// error: cannot construct `Foo` with struct literal syntax due to private fields
1876     ///  --> src/main.rs:8:5
1877     ///   |
1878     /// 8 |     foo::Foo {};
1879     ///   |     ^^^^^^^^
1880     ///
1881     /// error: aborting due to previous error
1882     /// ```
1883     fn report_private_fields(
1884         &self,
1885         adt_ty: Ty<'tcx>,
1886         span: Span,
1887         private_fields: Vec<&ty::FieldDef>,
1888         used_fields: &'tcx [hir::ExprField<'tcx>],
1889     ) {
1890         let mut err = self.tcx.sess.struct_span_err(
1891             span,
1892             &format!(
1893                 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1894             ),
1895         );
1896         let (used_private_fields, remaining_private_fields): (
1897             Vec<(Symbol, Span, bool)>,
1898             Vec<(Symbol, Span, bool)>,
1899         ) = private_fields
1900             .iter()
1901             .map(|field| {
1902                 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1903                     Some(used_field) => (field.name, used_field.span, true),
1904                     None => (field.name, self.tcx.def_span(field.did), false),
1905                 }
1906             })
1907             .partition(|field| field.2);
1908         err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1909         if !remaining_private_fields.is_empty() {
1910             let remaining_private_fields_len = remaining_private_fields.len();
1911             let names = match &remaining_private_fields
1912                 .iter()
1913                 .map(|(name, _, _)| name)
1914                 .collect::<Vec<_>>()[..]
1915             {
1916                 _ if remaining_private_fields_len > 6 => String::new(),
1917                 [name] => format!("`{name}` "),
1918                 [names @ .., last] => {
1919                     let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1920                     format!("{} and `{last}` ", names.join(", "))
1921                 }
1922                 [] => unreachable!(),
1923             };
1924             err.note(format!(
1925                 "... and other private field{s} {names}that {were} not provided",
1926                 s = pluralize!(remaining_private_fields_len),
1927                 were = pluralize!("was", remaining_private_fields_len),
1928             ));
1929         }
1930         err.emit();
1931     }
1932
1933     fn report_unknown_field(
1934         &self,
1935         ty: Ty<'tcx>,
1936         variant: &'tcx ty::VariantDef,
1937         field: &hir::ExprField<'_>,
1938         skip_fields: &[hir::ExprField<'_>],
1939         kind_name: &str,
1940         expr_span: Span,
1941     ) {
1942         if variant.is_recovered() {
1943             self.set_tainted_by_errors();
1944             return;
1945         }
1946         let mut err = self.err_ctxt().type_error_struct_with_diag(
1947             field.ident.span,
1948             |actual| match ty.kind() {
1949                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1950                     self.tcx.sess,
1951                     field.ident.span,
1952                     E0559,
1953                     "{} `{}::{}` has no field named `{}`",
1954                     kind_name,
1955                     actual,
1956                     variant.name,
1957                     field.ident
1958                 ),
1959                 _ => struct_span_err!(
1960                     self.tcx.sess,
1961                     field.ident.span,
1962                     E0560,
1963                     "{} `{}` has no field named `{}`",
1964                     kind_name,
1965                     actual,
1966                     field.ident
1967                 ),
1968             },
1969             ty,
1970         );
1971
1972         let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1973         match variant.ctor_kind {
1974             CtorKind::Fn => match ty.kind() {
1975                 ty::Adt(adt, ..) if adt.is_enum() => {
1976                     err.span_label(
1977                         variant_ident_span,
1978                         format!(
1979                             "`{adt}::{variant}` defined here",
1980                             adt = ty,
1981                             variant = variant.name,
1982                         ),
1983                     );
1984                     err.span_label(field.ident.span, "field does not exist");
1985                     err.span_suggestion_verbose(
1986                         expr_span,
1987                         &format!(
1988                             "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1989                             adt = ty,
1990                             variant = variant.name,
1991                         ),
1992                         format!(
1993                             "{adt}::{variant}(/* fields */)",
1994                             adt = ty,
1995                             variant = variant.name,
1996                         ),
1997                         Applicability::HasPlaceholders,
1998                     );
1999                 }
2000                 _ => {
2001                     err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
2002                     err.span_label(field.ident.span, "field does not exist");
2003                     err.span_suggestion_verbose(
2004                         expr_span,
2005                         &format!(
2006                             "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
2007                             adt = ty,
2008                             kind_name = kind_name,
2009                         ),
2010                         format!("{adt}(/* fields */)", adt = ty),
2011                         Applicability::HasPlaceholders,
2012                     );
2013                 }
2014             },
2015             _ => {
2016                 // prevent all specified fields from being suggested
2017                 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
2018                 if let Some(field_name) = self.suggest_field_name(
2019                     variant,
2020                     field.ident.name,
2021                     skip_fields.collect(),
2022                     expr_span,
2023                 ) {
2024                     err.span_suggestion(
2025                         field.ident.span,
2026                         "a field with a similar name exists",
2027                         field_name,
2028                         Applicability::MaybeIncorrect,
2029                     );
2030                 } else {
2031                     match ty.kind() {
2032                         ty::Adt(adt, ..) => {
2033                             if adt.is_enum() {
2034                                 err.span_label(
2035                                     field.ident.span,
2036                                     format!("`{}::{}` does not have this field", ty, variant.name),
2037                                 );
2038                             } else {
2039                                 err.span_label(
2040                                     field.ident.span,
2041                                     format!("`{ty}` does not have this field"),
2042                                 );
2043                             }
2044                             let available_field_names =
2045                                 self.available_field_names(variant, expr_span);
2046                             if !available_field_names.is_empty() {
2047                                 err.note(&format!(
2048                                     "available fields are: {}",
2049                                     self.name_series_display(available_field_names)
2050                                 ));
2051                             }
2052                         }
2053                         _ => bug!("non-ADT passed to report_unknown_field"),
2054                     }
2055                 };
2056             }
2057         }
2058         err.emit();
2059     }
2060
2061     // Return a hint about the closest match in field names
2062     fn suggest_field_name(
2063         &self,
2064         variant: &'tcx ty::VariantDef,
2065         field: Symbol,
2066         skip: Vec<Symbol>,
2067         // The span where stability will be checked
2068         span: Span,
2069     ) -> Option<Symbol> {
2070         let names = variant
2071             .fields
2072             .iter()
2073             .filter_map(|field| {
2074                 // ignore already set fields and private fields from non-local crates
2075                 // and unstable fields.
2076                 if skip.iter().any(|&x| x == field.name)
2077                     || (!variant.def_id.is_local() && !field.vis.is_public())
2078                     || matches!(
2079                         self.tcx.eval_stability(field.did, None, span, None),
2080                         stability::EvalResult::Deny { .. }
2081                     )
2082                 {
2083                     None
2084                 } else {
2085                     Some(field.name)
2086                 }
2087             })
2088             .collect::<Vec<Symbol>>();
2089
2090         find_best_match_for_name(&names, field, None)
2091     }
2092
2093     fn available_field_names(
2094         &self,
2095         variant: &'tcx ty::VariantDef,
2096         access_span: Span,
2097     ) -> Vec<Symbol> {
2098         variant
2099             .fields
2100             .iter()
2101             .filter(|field| {
2102                 let def_scope = self
2103                     .tcx
2104                     .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2105                     .1;
2106                 field.vis.is_accessible_from(def_scope, self.tcx)
2107                     && !matches!(
2108                         self.tcx.eval_stability(field.did, None, access_span, None),
2109                         stability::EvalResult::Deny { .. }
2110                     )
2111             })
2112             .filter(|field| !self.tcx.is_doc_hidden(field.did))
2113             .map(|field| field.name)
2114             .collect()
2115     }
2116
2117     fn name_series_display(&self, names: Vec<Symbol>) -> String {
2118         // dynamic limit, to never omit just one field
2119         let limit = if names.len() == 6 { 6 } else { 5 };
2120         let mut display =
2121             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2122         if names.len() > limit {
2123             display = format!("{} ... and {} others", display, names.len() - limit);
2124         }
2125         display
2126     }
2127
2128     // Check field access expressions
2129     fn check_field(
2130         &self,
2131         expr: &'tcx hir::Expr<'tcx>,
2132         base: &'tcx hir::Expr<'tcx>,
2133         field: Ident,
2134     ) -> Ty<'tcx> {
2135         debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2136         let base_ty = self.check_expr(base);
2137         let base_ty = self.structurally_resolved_type(base.span, base_ty);
2138         let mut private_candidate = None;
2139         let mut autoderef = self.autoderef(expr.span, base_ty);
2140         while let Some((deref_base_ty, _)) = autoderef.next() {
2141             debug!("deref_base_ty: {:?}", deref_base_ty);
2142             match deref_base_ty.kind() {
2143                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2144                     debug!("struct named {:?}", deref_base_ty);
2145                     let (ident, def_scope) =
2146                         self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2147                     let fields = &base_def.non_enum_variant().fields;
2148                     if let Some(index) = fields
2149                         .iter()
2150                         .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2151                     {
2152                         let field = &fields[index];
2153                         let field_ty = self.field_ty(expr.span, field, substs);
2154                         // Save the index of all fields regardless of their visibility in case
2155                         // of error recovery.
2156                         self.write_field_index(expr.hir_id, index);
2157                         let adjustments = self.adjust_steps(&autoderef);
2158                         if field.vis.is_accessible_from(def_scope, self.tcx) {
2159                             self.apply_adjustments(base, adjustments);
2160                             self.register_predicates(autoderef.into_obligations());
2161
2162                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2163                             return field_ty;
2164                         }
2165                         private_candidate = Some((adjustments, base_def.did(), field_ty));
2166                     }
2167                 }
2168                 ty::Tuple(tys) => {
2169                     let fstr = field.as_str();
2170                     if let Ok(index) = fstr.parse::<usize>() {
2171                         if fstr == index.to_string() {
2172                             if let Some(&field_ty) = tys.get(index) {
2173                                 let adjustments = self.adjust_steps(&autoderef);
2174                                 self.apply_adjustments(base, adjustments);
2175                                 self.register_predicates(autoderef.into_obligations());
2176
2177                                 self.write_field_index(expr.hir_id, index);
2178                                 return field_ty;
2179                             }
2180                         }
2181                     }
2182                 }
2183                 _ => {}
2184             }
2185         }
2186         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2187
2188         if let Some((adjustments, did, field_ty)) = private_candidate {
2189             // (#90483) apply adjustments to avoid ExprUseVisitor from
2190             // creating erroneous projection.
2191             self.apply_adjustments(base, adjustments);
2192             self.ban_private_field_access(expr, base_ty, field, did);
2193             return field_ty;
2194         }
2195
2196         if field.name == kw::Empty {
2197         } else if self.method_exists(field, base_ty, expr.hir_id, true) {
2198             self.ban_take_value_of_method(expr, base_ty, field);
2199         } else if !base_ty.is_primitive_ty() {
2200             self.ban_nonexisting_field(field, base, expr, base_ty);
2201         } else {
2202             let field_name = field.to_string();
2203             let mut err = type_error_struct!(
2204                 self.tcx().sess,
2205                 field.span,
2206                 base_ty,
2207                 E0610,
2208                 "`{base_ty}` is a primitive type and therefore doesn't have fields",
2209             );
2210             let is_valid_suffix = |field: &str| {
2211                 if field == "f32" || field == "f64" {
2212                     return true;
2213                 }
2214                 let mut chars = field.chars().peekable();
2215                 match chars.peek() {
2216                     Some('e') | Some('E') => {
2217                         chars.next();
2218                         if let Some(c) = chars.peek()
2219                             && !c.is_numeric() && *c != '-' && *c != '+'
2220                         {
2221                             return false;
2222                         }
2223                         while let Some(c) = chars.peek() {
2224                             if !c.is_numeric() {
2225                                 break;
2226                             }
2227                             chars.next();
2228                         }
2229                     }
2230                     _ => (),
2231                 }
2232                 let suffix = chars.collect::<String>();
2233                 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2234             };
2235             let maybe_partial_suffix = |field: &str| -> Option<&str> {
2236                 let first_chars = ['f', 'l'];
2237                 if field.len() >= 1
2238                     && field.to_lowercase().starts_with(first_chars)
2239                     && field[1..].chars().all(|c| c.is_ascii_digit())
2240                 {
2241                     if field.to_lowercase().starts_with(['f']) { Some("f32") } else { Some("f64") }
2242                 } else {
2243                     None
2244                 }
2245             };
2246             if let ty::Infer(ty::IntVar(_)) = base_ty.kind()
2247                 && let ExprKind::Lit(Spanned {
2248                     node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2249                     ..
2250                 }) = base.kind
2251                 && !base.span.from_expansion()
2252             {
2253                 if is_valid_suffix(&field_name) {
2254                     err.span_suggestion_verbose(
2255                         field.span.shrink_to_lo(),
2256                         "if intended to be a floating point literal, consider adding a `0` after the period",
2257                         '0',
2258                         Applicability::MaybeIncorrect,
2259                     );
2260                 } else if let Some(correct_suffix) = maybe_partial_suffix(&field_name) {
2261                     err.span_suggestion_verbose(
2262                         field.span,
2263                         format!("if intended to be a floating point literal, consider adding a `0` after the period and a `{correct_suffix}` suffix"),
2264                         format!("0{correct_suffix}"),
2265                         Applicability::MaybeIncorrect,
2266                     );
2267                 }
2268             }
2269             err.emit();
2270         }
2271
2272         self.tcx().ty_error()
2273     }
2274
2275     fn suggest_await_on_field_access(
2276         &self,
2277         err: &mut Diagnostic,
2278         field_ident: Ident,
2279         base: &'tcx hir::Expr<'tcx>,
2280         ty: Ty<'tcx>,
2281     ) {
2282         let output_ty = match self.get_impl_future_output_ty(ty) {
2283             Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2284             _ => return,
2285         };
2286         let mut add_label = true;
2287         if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2288             // no field access on enum type
2289             if !def.is_enum() {
2290                 if def
2291                     .non_enum_variant()
2292                     .fields
2293                     .iter()
2294                     .any(|field| field.ident(self.tcx) == field_ident)
2295                 {
2296                     add_label = false;
2297                     err.span_label(
2298                         field_ident.span,
2299                         "field not available in `impl Future`, but it is available in its `Output`",
2300                     );
2301                     err.span_suggestion_verbose(
2302                         base.span.shrink_to_hi(),
2303                         "consider `await`ing on the `Future` and access the field of its `Output`",
2304                         ".await",
2305                         Applicability::MaybeIncorrect,
2306                     );
2307                 }
2308             }
2309         }
2310         if add_label {
2311             err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2312         }
2313     }
2314
2315     fn ban_nonexisting_field(
2316         &self,
2317         ident: Ident,
2318         base: &'tcx hir::Expr<'tcx>,
2319         expr: &'tcx hir::Expr<'tcx>,
2320         base_ty: Ty<'tcx>,
2321     ) {
2322         debug!(
2323             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, base_ty={:?}",
2324             ident, base, expr, base_ty
2325         );
2326         let mut err = self.no_such_field_err(ident, base_ty, base.hir_id);
2327
2328         match *base_ty.peel_refs().kind() {
2329             ty::Array(_, len) => {
2330                 self.maybe_suggest_array_indexing(&mut err, expr, base, ident, len);
2331             }
2332             ty::RawPtr(..) => {
2333                 self.suggest_first_deref_field(&mut err, expr, base, ident);
2334             }
2335             ty::Adt(def, _) if !def.is_enum() => {
2336                 self.suggest_fields_on_recordish(&mut err, def, ident, expr.span);
2337             }
2338             ty::Param(param_ty) => {
2339                 self.point_at_param_definition(&mut err, param_ty);
2340             }
2341             ty::Opaque(_, _) => {
2342                 self.suggest_await_on_field_access(&mut err, ident, base, base_ty.peel_refs());
2343             }
2344             _ => {}
2345         }
2346
2347         self.suggest_fn_call(&mut err, base, base_ty, |output_ty| {
2348             if let ty::Adt(def, _) = output_ty.kind() && !def.is_enum() {
2349                 def.non_enum_variant().fields.iter().any(|field| {
2350                     field.ident(self.tcx) == ident
2351                         && field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
2352                 })
2353             } else if let ty::Tuple(tys) = output_ty.kind()
2354                 && let Ok(idx) = ident.as_str().parse::<usize>()
2355             {
2356                 idx < tys.len()
2357             } else {
2358                 false
2359             }
2360         });
2361
2362         if ident.name == kw::Await {
2363             // We know by construction that `<expr>.await` is either on Rust 2015
2364             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2365             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2366             err.help_use_latest_edition();
2367         }
2368
2369         err.emit();
2370     }
2371
2372     fn ban_private_field_access(
2373         &self,
2374         expr: &hir::Expr<'_>,
2375         expr_t: Ty<'tcx>,
2376         field: Ident,
2377         base_did: DefId,
2378     ) {
2379         let struct_path = self.tcx().def_path_str(base_did);
2380         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2381         let mut err = struct_span_err!(
2382             self.tcx().sess,
2383             field.span,
2384             E0616,
2385             "field `{field}` of {kind_name} `{struct_path}` is private",
2386         );
2387         err.span_label(field.span, "private field");
2388         // Also check if an accessible method exists, which is often what is meant.
2389         if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2390         {
2391             self.suggest_method_call(
2392                 &mut err,
2393                 &format!("a method `{field}` also exists, call it with parentheses"),
2394                 field,
2395                 expr_t,
2396                 expr,
2397                 None,
2398             );
2399         }
2400         err.emit();
2401     }
2402
2403     fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2404         let mut err = type_error_struct!(
2405             self.tcx().sess,
2406             field.span,
2407             expr_t,
2408             E0615,
2409             "attempted to take value of method `{field}` on type `{expr_t}`",
2410         );
2411         err.span_label(field.span, "method, not a field");
2412         let expr_is_call =
2413             if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2414                 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2415             {
2416                 expr.hir_id == callee.hir_id
2417             } else {
2418                 false
2419             };
2420         let expr_snippet =
2421             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2422         let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2423         let after_open = expr.span.lo() + rustc_span::BytePos(1);
2424         let before_close = expr.span.hi() - rustc_span::BytePos(1);
2425
2426         if expr_is_call && is_wrapped {
2427             err.multipart_suggestion(
2428                 "remove wrapping parentheses to call the method",
2429                 vec![
2430                     (expr.span.with_hi(after_open), String::new()),
2431                     (expr.span.with_lo(before_close), String::new()),
2432                 ],
2433                 Applicability::MachineApplicable,
2434             );
2435         } else if !self.expr_in_place(expr.hir_id) {
2436             // Suggest call parentheses inside the wrapping parentheses
2437             let span = if is_wrapped {
2438                 expr.span.with_lo(after_open).with_hi(before_close)
2439             } else {
2440                 expr.span
2441             };
2442             self.suggest_method_call(
2443                 &mut err,
2444                 "use parentheses to call the method",
2445                 field,
2446                 expr_t,
2447                 expr,
2448                 Some(span),
2449             );
2450         } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2451             && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2452             && let ExprKind::Field(base_expr, _) = expr.kind
2453             && adt_def.variants().len() == 1
2454             && adt_def
2455                 .variants()
2456                 .iter()
2457                 .next()
2458                 .unwrap()
2459                 .fields
2460                 .iter()
2461                 .any(|f| f.ident(self.tcx) == field)
2462         {
2463             err.multipart_suggestion(
2464                 "to access the field, dereference first",
2465                 vec![
2466                     (base_expr.span.shrink_to_lo(), "(*".to_string()),
2467                     (base_expr.span.shrink_to_hi(), ")".to_string()),
2468                 ],
2469                 Applicability::MaybeIncorrect,
2470             );
2471         } else {
2472             err.help("methods are immutable and cannot be assigned to");
2473         }
2474
2475         err.emit();
2476     }
2477
2478     fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2479         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2480         let generic_param = generics.type_param(&param, self.tcx);
2481         if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2482             return;
2483         }
2484         let param_def_id = generic_param.def_id;
2485         let param_hir_id = match param_def_id.as_local() {
2486             Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2487             None => return,
2488         };
2489         let param_span = self.tcx.hir().span(param_hir_id);
2490         let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2491
2492         err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2493     }
2494
2495     fn suggest_fields_on_recordish(
2496         &self,
2497         err: &mut Diagnostic,
2498         def: ty::AdtDef<'tcx>,
2499         field: Ident,
2500         access_span: Span,
2501     ) {
2502         if let Some(suggested_field_name) =
2503             self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2504         {
2505             err.span_suggestion(
2506                 field.span,
2507                 "a field with a similar name exists",
2508                 suggested_field_name,
2509                 Applicability::MaybeIncorrect,
2510             );
2511         } else {
2512             err.span_label(field.span, "unknown field");
2513             let struct_variant_def = def.non_enum_variant();
2514             let field_names = self.available_field_names(struct_variant_def, access_span);
2515             if !field_names.is_empty() {
2516                 err.note(&format!(
2517                     "available fields are: {}",
2518                     self.name_series_display(field_names),
2519                 ));
2520             }
2521         }
2522     }
2523
2524     fn maybe_suggest_array_indexing(
2525         &self,
2526         err: &mut Diagnostic,
2527         expr: &hir::Expr<'_>,
2528         base: &hir::Expr<'_>,
2529         field: Ident,
2530         len: ty::Const<'tcx>,
2531     ) {
2532         if let (Some(len), Ok(user_index)) =
2533             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2534             && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2535         {
2536             let help = "instead of using tuple indexing, use array indexing";
2537             let suggestion = format!("{base}[{field}]");
2538             let applicability = if len < user_index {
2539                 Applicability::MachineApplicable
2540             } else {
2541                 Applicability::MaybeIncorrect
2542             };
2543             err.span_suggestion(expr.span, help, suggestion, applicability);
2544         }
2545     }
2546
2547     fn suggest_first_deref_field(
2548         &self,
2549         err: &mut Diagnostic,
2550         expr: &hir::Expr<'_>,
2551         base: &hir::Expr<'_>,
2552         field: Ident,
2553     ) {
2554         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2555             let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2556             let suggestion = format!("(*{base}).{field}");
2557             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2558         }
2559     }
2560
2561     fn no_such_field_err(
2562         &self,
2563         field: Ident,
2564         expr_t: Ty<'tcx>,
2565         id: HirId,
2566     ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2567         let span = field.span;
2568         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2569
2570         let mut err = type_error_struct!(
2571             self.tcx().sess,
2572             field.span,
2573             expr_t,
2574             E0609,
2575             "no field `{field}` on type `{expr_t}`",
2576         );
2577
2578         // try to add a suggestion in case the field is a nested field of a field of the Adt
2579         let mod_id = self.tcx.parent_module(id).to_def_id();
2580         if let Some((fields, substs)) =
2581             self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2582         {
2583             let candidate_fields: Vec<_> = fields
2584                 .filter_map(|candidate_field| {
2585                     self.check_for_nested_field_satisfying(
2586                         span,
2587                         &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2588                         candidate_field,
2589                         substs,
2590                         vec![],
2591                         mod_id,
2592                     )
2593                 })
2594                 .map(|mut field_path| {
2595                     field_path.pop();
2596                     field_path
2597                         .iter()
2598                         .map(|id| id.name.to_ident_string())
2599                         .collect::<Vec<String>>()
2600                         .join(".")
2601                 })
2602                 .collect::<Vec<_>>();
2603
2604             let len = candidate_fields.len();
2605             if len > 0 {
2606                 err.span_suggestions(
2607                     field.span.shrink_to_lo(),
2608                     format!(
2609                         "{} of the expressions' fields {} a field of the same name",
2610                         if len > 1 { "some" } else { "one" },
2611                         if len > 1 { "have" } else { "has" },
2612                     ),
2613                     candidate_fields.iter().map(|path| format!("{path}.")),
2614                     Applicability::MaybeIncorrect,
2615                 );
2616             }
2617         }
2618         err
2619     }
2620
2621     pub(crate) fn get_field_candidates_considering_privacy(
2622         &self,
2623         span: Span,
2624         base_ty: Ty<'tcx>,
2625         mod_id: DefId,
2626     ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2627         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2628
2629         for (base_t, _) in self.autoderef(span, base_ty) {
2630             match base_t.kind() {
2631                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2632                     let tcx = self.tcx;
2633                     let fields = &base_def.non_enum_variant().fields;
2634                     // Some struct, e.g. some that impl `Deref`, have all private fields
2635                     // because you're expected to deref them to access the _real_ fields.
2636                     // This, for example, will help us suggest accessing a field through a `Box<T>`.
2637                     if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2638                         continue;
2639                     }
2640                     return Some((
2641                         fields
2642                             .iter()
2643                             .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2644                             // For compile-time reasons put a limit on number of fields we search
2645                             .take(100),
2646                         substs,
2647                     ));
2648                 }
2649                 _ => {}
2650             }
2651         }
2652         None
2653     }
2654
2655     /// This method is called after we have encountered a missing field error to recursively
2656     /// search for the field
2657     pub(crate) fn check_for_nested_field_satisfying(
2658         &self,
2659         span: Span,
2660         matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2661         candidate_field: &ty::FieldDef,
2662         subst: SubstsRef<'tcx>,
2663         mut field_path: Vec<Ident>,
2664         mod_id: DefId,
2665     ) -> Option<Vec<Ident>> {
2666         debug!(
2667             "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2668             span, candidate_field, field_path
2669         );
2670
2671         if field_path.len() > 3 {
2672             // For compile-time reasons and to avoid infinite recursion we only check for fields
2673             // up to a depth of three
2674             None
2675         } else {
2676             field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2677             let field_ty = candidate_field.ty(self.tcx, subst);
2678             if matches(candidate_field, field_ty) {
2679                 return Some(field_path);
2680             } else if let Some((nested_fields, subst)) =
2681                 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2682             {
2683                 // recursively search fields of `candidate_field` if it's a ty::Adt
2684                 for field in nested_fields {
2685                     if let Some(field_path) = self.check_for_nested_field_satisfying(
2686                         span,
2687                         matches,
2688                         field,
2689                         subst,
2690                         field_path.clone(),
2691                         mod_id,
2692                     ) {
2693                         return Some(field_path);
2694                     }
2695                 }
2696             }
2697             None
2698         }
2699     }
2700
2701     fn check_expr_index(
2702         &self,
2703         base: &'tcx hir::Expr<'tcx>,
2704         idx: &'tcx hir::Expr<'tcx>,
2705         expr: &'tcx hir::Expr<'tcx>,
2706     ) -> Ty<'tcx> {
2707         let base_t = self.check_expr(&base);
2708         let idx_t = self.check_expr(&idx);
2709
2710         if base_t.references_error() {
2711             base_t
2712         } else if idx_t.references_error() {
2713             idx_t
2714         } else {
2715             let base_t = self.structurally_resolved_type(base.span, base_t);
2716             match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2717                 Some((index_ty, element_ty)) => {
2718                     // two-phase not needed because index_ty is never mutable
2719                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2720                     self.select_obligations_where_possible(false, |errors| {
2721                         self.point_at_index_if_possible(errors, idx.span)
2722                     });
2723                     element_ty
2724                 }
2725                 None => {
2726                     let mut err = type_error_struct!(
2727                         self.tcx.sess,
2728                         expr.span,
2729                         base_t,
2730                         E0608,
2731                         "cannot index into a value of type `{base_t}`",
2732                     );
2733                     // Try to give some advice about indexing tuples.
2734                     if let ty::Tuple(..) = base_t.kind() {
2735                         let mut needs_note = true;
2736                         // If the index is an integer, we can show the actual
2737                         // fixed expression:
2738                         if let ExprKind::Lit(ref lit) = idx.kind {
2739                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2740                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2741                                 if let Ok(snip) = snip {
2742                                     err.span_suggestion(
2743                                         expr.span,
2744                                         "to access tuple elements, use",
2745                                         format!("{snip}.{i}"),
2746                                         Applicability::MachineApplicable,
2747                                     );
2748                                     needs_note = false;
2749                                 }
2750                             }
2751                         }
2752                         if needs_note {
2753                             err.help(
2754                                 "to access tuple elements, use tuple indexing \
2755                                         syntax (e.g., `tuple.0`)",
2756                             );
2757                         }
2758                     }
2759                     err.emit();
2760                     self.tcx.ty_error()
2761                 }
2762             }
2763         }
2764     }
2765
2766     fn point_at_index_if_possible(
2767         &self,
2768         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2769         span: Span,
2770     ) {
2771         for error in errors {
2772             match error.obligation.predicate.kind().skip_binder() {
2773                 ty::PredicateKind::Trait(predicate)
2774                     if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2775                 }
2776                 _ => continue,
2777             }
2778             error.obligation.cause.span = span;
2779         }
2780     }
2781
2782     fn check_expr_yield(
2783         &self,
2784         value: &'tcx hir::Expr<'tcx>,
2785         expr: &'tcx hir::Expr<'tcx>,
2786         src: &'tcx hir::YieldSource,
2787     ) -> Ty<'tcx> {
2788         match self.resume_yield_tys {
2789             Some((resume_ty, yield_ty)) => {
2790                 self.check_expr_coercable_to_type(&value, yield_ty, None);
2791
2792                 resume_ty
2793             }
2794             // Given that this `yield` expression was generated as a result of lowering a `.await`,
2795             // we know that the yield type must be `()`; however, the context won't contain this
2796             // information. Hence, we check the source of the yield expression here and check its
2797             // value's type against `()` (this check should always hold).
2798             None if src.is_await() => {
2799                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2800                 self.tcx.mk_unit()
2801             }
2802             _ => {
2803                 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2804                 // Avoid expressions without types during writeback (#78653).
2805                 self.check_expr(value);
2806                 self.tcx.mk_unit()
2807             }
2808         }
2809     }
2810
2811     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2812         let needs = if is_input { Needs::None } else { Needs::MutPlace };
2813         let ty = self.check_expr_with_needs(expr, needs);
2814         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2815
2816         if !is_input && !expr.is_syntactic_place_expr() {
2817             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2818             err.span_label(expr.span, "cannot assign to this expression");
2819             err.emit();
2820         }
2821
2822         // If this is an input value, we require its type to be fully resolved
2823         // at this point. This allows us to provide helpful coercions which help
2824         // pass the type candidate list in a later pass.
2825         //
2826         // We don't require output types to be resolved at this point, which
2827         // allows them to be inferred based on how they are used later in the
2828         // function.
2829         if is_input {
2830             let ty = self.structurally_resolved_type(expr.span, ty);
2831             match *ty.kind() {
2832                 ty::FnDef(..) => {
2833                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2834                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2835                 }
2836                 ty::Ref(_, base_ty, mutbl) => {
2837                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2838                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2839                 }
2840                 _ => {}
2841             }
2842         }
2843     }
2844
2845     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2846         for (op, _op_sp) in asm.operands {
2847             match op {
2848                 hir::InlineAsmOperand::In { expr, .. } => {
2849                     self.check_expr_asm_operand(expr, true);
2850                 }
2851                 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2852                 | hir::InlineAsmOperand::InOut { expr, .. } => {
2853                     self.check_expr_asm_operand(expr, false);
2854                 }
2855                 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2856                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2857                     self.check_expr_asm_operand(in_expr, true);
2858                     if let Some(out_expr) = out_expr {
2859                         self.check_expr_asm_operand(out_expr, false);
2860                     }
2861                 }
2862                 // `AnonConst`s have their own body and is type-checked separately.
2863                 // As they don't flow into the type system we don't need them to
2864                 // be well-formed.
2865                 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2866                 hir::InlineAsmOperand::SymStatic { .. } => {}
2867             }
2868         }
2869         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2870             self.tcx.types.never
2871         } else {
2872             self.tcx.mk_unit()
2873         }
2874     }
2875 }
2876
2877 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2878     Some(match ty.kind() {
2879         ty::Bool => "true",
2880         ty::Char => "'a'",
2881         ty::Int(_) | ty::Uint(_) => "42",
2882         ty::Float(_) => "3.14159",
2883         ty::Error(_) | ty::Never => return None,
2884         _ => "value",
2885     })
2886 }