compiler/rustc_typeck/src/check/expr.rs

   1 //! Type checking expressions.
   2 //!
   3 //! See `mod.rs` for more context on type checking in general.
   4
   5 use crate::astconv::AstConv as _;
   6 use crate::check::cast;
   7 use crate::check::coercion::CoerceMany;
   8 use crate::check::fatally_break_rust;
   9 use crate::check::method::SelfSource;
  10 use crate::check::report_unexpected_variant_res;
  11 use crate::check::BreakableCtxt;
  12 use crate::check::Diverges;
  13 use crate::check::DynamicCoerceMany;
  14 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
  15 use crate::check::FnCtxt;
  16 use crate::check::Needs;
  17 use crate::check::TupleArgumentsFlag::DontTupleArguments;
  18 use crate::errors::{
  19     FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
  20     YieldExprOutsideOfGenerator,
  21 };
  22 use crate::type_error_struct;
  23
  24 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
  25 use rustc_ast as ast;
  26 use rustc_data_structures::fx::FxHashMap;
  27 use rustc_data_structures::stack::ensure_sufficient_stack;
  28 use rustc_errors::Diagnostic;
  29 use rustc_errors::ErrorReported;
  30 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
  31 use rustc_hir as hir;
  32 use rustc_hir::def::{CtorKind, DefKind, Res};
  33 use rustc_hir::def_id::DefId;
  34 use rustc_hir::intravisit::Visitor;
  35 use rustc_hir::{ExprKind, HirId, QPath};
  36 use rustc_infer::infer;
  37 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
  38 use rustc_infer::infer::InferOk;
  39 use rustc_middle::middle::stability;
  40 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
  41 use rustc_middle::ty::error::ExpectedFound;
  42 use rustc_middle::ty::error::TypeError::{FieldMisMatch, Sorts};
  43 use rustc_middle::ty::subst::SubstsRef;
  44 use rustc_middle::ty::{self, AdtKind, Ty, TypeFoldable};
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::edition::LATEST_STABLE_EDITION;
  47 use rustc_span::hygiene::DesugaringKind;
  48 use rustc_span::lev_distance::find_best_match_for_name;
  49 use rustc_span::source_map::Span;
  50 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  51 use rustc_span::{BytePos, Pos};
  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 Fn(&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         extend_err: impl Fn(&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             assert!(
  82                 !self.typeck_results.borrow().adjustments().contains_key(expr.hir_id),
  83                 "expression with never type wound up being adjusted"
  84             );
  85             let adj_ty = self.next_ty_var(TypeVariableOrigin {
  86                 kind: TypeVariableOriginKind::AdjustmentType,
  87                 span: expr.span,
  88             });
  89             self.apply_adjustments(
  90                 expr,
  91                 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
  92             );
  93             ty = adj_ty;
  94         }
  95
  96         if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
  97             let expr = expr.peel_drop_temps();
  98             self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
  99             extend_err(&mut err);
 100             err.emit();
 101         }
 102         ty
 103     }
 104
 105     pub(super) fn check_expr_coercable_to_type(
 106         &self,
 107         expr: &'tcx hir::Expr<'tcx>,
 108         expected: Ty<'tcx>,
 109         expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
 110     ) -> Ty<'tcx> {
 111         let ty = self.check_expr_with_hint(expr, expected);
 112         // checks don't need two phase
 113         self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
 114     }
 115
 116     pub(super) fn check_expr_with_hint(
 117         &self,
 118         expr: &'tcx hir::Expr<'tcx>,
 119         expected: Ty<'tcx>,
 120     ) -> Ty<'tcx> {
 121         self.check_expr_with_expectation(expr, ExpectHasType(expected))
 122     }
 123
 124     fn check_expr_with_expectation_and_needs(
 125         &self,
 126         expr: &'tcx hir::Expr<'tcx>,
 127         expected: Expectation<'tcx>,
 128         needs: Needs,
 129     ) -> Ty<'tcx> {
 130         let ty = self.check_expr_with_expectation(expr, expected);
 131
 132         // If the expression is used in a place whether mutable place is required
 133         // e.g. LHS of assignment, perform the conversion.
 134         if let Needs::MutPlace = needs {
 135             self.convert_place_derefs_to_mutable(expr);
 136         }
 137
 138         ty
 139     }
 140
 141     pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
 142         self.check_expr_with_expectation(expr, NoExpectation)
 143     }
 144
 145     pub(super) fn check_expr_with_needs(
 146         &self,
 147         expr: &'tcx hir::Expr<'tcx>,
 148         needs: Needs,
 149     ) -> Ty<'tcx> {
 150         self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
 151     }
 152
 153     /// Invariant:
 154     /// If an expression has any sub-expressions that result in a type error,
 155     /// inspecting that expression's type with `ty.references_error()` will return
 156     /// true. Likewise, if an expression is known to diverge, inspecting its
 157     /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
 158     /// strict, _|_ can appear in the type of an expression that does not,
 159     /// itself, diverge: for example, fn() -> _|_.)
 160     /// Note that inspecting a type's structure *directly* may expose the fact
 161     /// that there are actually multiple representations for `Error`, so avoid
 162     /// that when err needs to be handled differently.
 163     #[instrument(skip(self, expr), level = "debug")]
 164     pub(super) fn check_expr_with_expectation(
 165         &self,
 166         expr: &'tcx hir::Expr<'tcx>,
 167         expected: Expectation<'tcx>,
 168     ) -> Ty<'tcx> {
 169         self.check_expr_with_expectation_and_args(expr, expected, &[])
 170     }
 171
 172     /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
 173     /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
 174     pub(super) fn check_expr_with_expectation_and_args(
 175         &self,
 176         expr: &'tcx hir::Expr<'tcx>,
 177         expected: Expectation<'tcx>,
 178         args: &'tcx [hir::Expr<'tcx>],
 179     ) -> Ty<'tcx> {
 180         if self.tcx().sess.verbose() {
 181             // make this code only run with -Zverbose because it is probably slow
 182             if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
 183                 if !lint_str.contains('\n') {
 184                     debug!("expr text: {}", lint_str);
 185                 } else {
 186                     let mut lines = lint_str.lines();
 187                     if let Some(line0) = lines.next() {
 188                         let remaining_lines = lines.count();
 189                         debug!("expr text: {}", line0);
 190                         debug!("expr text: ...(and {} more lines)", remaining_lines);
 191                     }
 192                 }
 193             }
 194         }
 195
 196         // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
 197         // without the final expr (e.g. `try { return; }`). We don't want to generate an
 198         // unreachable_code lint for it since warnings for autogenerated code are confusing.
 199         let is_try_block_generated_unit_expr = match expr.kind {
 200             ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
 201                 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
 202             }
 203
 204             _ => false,
 205         };
 206
 207         // Warn for expressions after diverging siblings.
 208         if !is_try_block_generated_unit_expr {
 209             self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
 210         }
 211
 212         // Hide the outer diverging and has_errors flags.
 213         let old_diverges = self.diverges.replace(Diverges::Maybe);
 214         let old_has_errors = self.has_errors.replace(false);
 215
 216         let ty = ensure_sufficient_stack(|| match &expr.kind {
 217             hir::ExprKind::Path(
 218                 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
 219             ) => self.check_expr_path(qpath, expr, args),
 220             _ => self.check_expr_kind(expr, expected),
 221         });
 222
 223         // Warn for non-block expressions with diverging children.
 224         match expr.kind {
 225             ExprKind::Block(..)
 226             | ExprKind::If(..)
 227             | ExprKind::Let(..)
 228             | ExprKind::Loop(..)
 229             | ExprKind::Match(..) => {}
 230             // If `expr` is a result of desugaring the try block and is an ok-wrapped
 231             // diverging expression (e.g. it arose from desugaring of `try { return }`),
 232             // we skip issuing a warning because it is autogenerated code.
 233             ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
 234             ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
 235             ExprKind::MethodCall(segment, ..) => {
 236                 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
 237             }
 238             _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
 239         }
 240
 241         // Any expression that produces a value of type `!` must have diverged
 242         if ty.is_never() {
 243             self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
 244         }
 245
 246         // Record the type, which applies it effects.
 247         // We need to do this after the warning above, so that
 248         // we don't warn for the diverging expression itself.
 249         self.write_ty(expr.hir_id, ty);
 250
 251         // Combine the diverging and has_error flags.
 252         self.diverges.set(self.diverges.get() | old_diverges);
 253         self.has_errors.set(self.has_errors.get() | old_has_errors);
 254
 255         debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
 256         debug!("... {:?}, expected is {:?}", ty, expected);
 257
 258         ty
 259     }
 260
 261     #[instrument(skip(self, expr), level = "debug")]
 262     fn check_expr_kind(
 263         &self,
 264         expr: &'tcx hir::Expr<'tcx>,
 265         expected: Expectation<'tcx>,
 266     ) -> Ty<'tcx> {
 267         trace!("expr={:#?}", expr);
 268
 269         let tcx = self.tcx;
 270         match expr.kind {
 271             ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
 272             ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
 273             ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs),
 274             ExprKind::Assign(lhs, rhs, ref span) => {
 275                 self.check_expr_assign(expr, expected, lhs, rhs, span)
 276             }
 277             ExprKind::AssignOp(op, lhs, rhs) => self.check_binop_assign(expr, op, lhs, rhs),
 278             ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
 279             ExprKind::AddrOf(kind, mutbl, oprnd) => {
 280                 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
 281             }
 282             ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
 283                 self.check_lang_item_path(lang_item, expr, hir_id)
 284             }
 285             ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
 286             ExprKind::InlineAsm(asm) => self.check_expr_asm(asm),
 287             ExprKind::Break(destination, ref expr_opt) => {
 288                 self.check_expr_break(destination, expr_opt.as_deref(), expr)
 289             }
 290             ExprKind::Continue(destination) => {
 291                 if destination.target_id.is_ok() {
 292                     tcx.types.never
 293                 } else {
 294                     // There was an error; make type-check fail.
 295                     tcx.ty_error()
 296                 }
 297             }
 298             ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
 299             ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
 300             ExprKind::Loop(body, _, source, _) => {
 301                 self.check_expr_loop(body, source, expected, expr)
 302             }
 303             ExprKind::Match(discrim, arms, match_src) => {
 304                 self.check_match(expr, &discrim, arms, expected, match_src)
 305             }
 306             ExprKind::Closure(capture, decl, body_id, _, gen) => {
 307                 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
 308             }
 309             ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
 310             ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
 311             ExprKind::MethodCall(segment, args, _) => {
 312                 self.check_method_call(expr, segment, args, expected)
 313             }
 314             ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
 315             ExprKind::Type(e, t) => {
 316                 let ty = self.to_ty_saving_user_provided_ty(&t);
 317                 self.check_expr_eq_type(&e, ty);
 318                 ty
 319             }
 320             ExprKind::If(cond, then_expr, opt_else_expr) => {
 321                 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
 322             }
 323             ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
 324             ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
 325             ExprKind::ConstBlock(ref anon_const) => {
 326                 self.check_expr_const_block(anon_const, expected, expr)
 327             }
 328             ExprKind::Repeat(element, ref count) => {
 329                 self.check_expr_repeat(element, count, expected, expr)
 330             }
 331             ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
 332             ExprKind::Struct(qpath, fields, ref base_expr) => {
 333                 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
 334             }
 335             ExprKind::Field(base, field) => self.check_field(expr, &base, field),
 336             ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
 337             ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
 338             hir::ExprKind::Err => tcx.ty_error(),
 339         }
 340     }
 341
 342     fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
 343         let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
 344             ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
 345             _ => NoExpectation,
 346         });
 347         let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
 348         self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
 349         self.tcx.mk_box(referent_ty)
 350     }
 351
 352     fn check_expr_unary(
 353         &self,
 354         unop: hir::UnOp,
 355         oprnd: &'tcx hir::Expr<'tcx>,
 356         expected: Expectation<'tcx>,
 357         expr: &'tcx hir::Expr<'tcx>,
 358     ) -> Ty<'tcx> {
 359         let tcx = self.tcx;
 360         let expected_inner = match unop {
 361             hir::UnOp::Not | hir::UnOp::Neg => expected,
 362             hir::UnOp::Deref => NoExpectation,
 363         };
 364         let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
 365
 366         if !oprnd_t.references_error() {
 367             oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
 368             match unop {
 369                 hir::UnOp::Deref => {
 370                     if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
 371                         oprnd_t = ty;
 372                     } else {
 373                         let mut err = type_error_struct!(
 374                             tcx.sess,
 375                             expr.span,
 376                             oprnd_t,
 377                             E0614,
 378                             "type `{}` cannot be dereferenced",
 379                             oprnd_t,
 380                         );
 381                         let sp = tcx.sess.source_map().start_point(expr.span);
 382                         if let Some(sp) =
 383                             tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
 384                         {
 385                             tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
 386                         }
 387                         err.emit();
 388                         oprnd_t = tcx.ty_error();
 389                     }
 390                 }
 391                 hir::UnOp::Not => {
 392                     let result = self.check_user_unop(expr, oprnd_t, unop);
 393                     // If it's builtin, we can reuse the type, this helps inference.
 394                     if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
 395                         oprnd_t = result;
 396                     }
 397                 }
 398                 hir::UnOp::Neg => {
 399                     let result = self.check_user_unop(expr, oprnd_t, unop);
 400                     // If it's builtin, we can reuse the type, this helps inference.
 401                     if !oprnd_t.is_numeric() {
 402                         oprnd_t = result;
 403                     }
 404                 }
 405             }
 406         }
 407         oprnd_t
 408     }
 409
 410     fn check_expr_addr_of(
 411         &self,
 412         kind: hir::BorrowKind,
 413         mutbl: hir::Mutability,
 414         oprnd: &'tcx hir::Expr<'tcx>,
 415         expected: Expectation<'tcx>,
 416         expr: &'tcx hir::Expr<'tcx>,
 417     ) -> Ty<'tcx> {
 418         let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
 419             match ty.kind() {
 420                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 421                     if oprnd.is_syntactic_place_expr() {
 422                         // Places may legitimately have unsized types.
 423                         // For example, dereferences of a fat pointer and
 424                         // the last field of a struct can be unsized.
 425                         ExpectHasType(*ty)
 426                     } else {
 427                         Expectation::rvalue_hint(self, *ty)
 428                     }
 429                 }
 430                 _ => NoExpectation,
 431             }
 432         });
 433         let ty =
 434             self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
 435
 436         let tm = ty::TypeAndMut { ty, mutbl };
 437         match kind {
 438             _ if tm.ty.references_error() => self.tcx.ty_error(),
 439             hir::BorrowKind::Raw => {
 440                 self.check_named_place_expr(oprnd);
 441                 self.tcx.mk_ptr(tm)
 442             }
 443             hir::BorrowKind::Ref => {
 444                 // Note: at this point, we cannot say what the best lifetime
 445                 // is to use for resulting pointer.  We want to use the
 446                 // shortest lifetime possible so as to avoid spurious borrowck
 447                 // errors.  Moreover, the longest lifetime will depend on the
 448                 // precise details of the value whose address is being taken
 449                 // (and how long it is valid), which we don't know yet until
 450                 // type inference is complete.
 451                 //
 452                 // Therefore, here we simply generate a region variable. The
 453                 // region inferencer will then select a suitable value.
 454                 // Finally, borrowck will infer the value of the region again,
 455                 // this time with enough precision to check that the value
 456                 // whose address was taken can actually be made to live as long
 457                 // as it needs to live.
 458                 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
 459                 self.tcx.mk_ref(region, tm)
 460             }
 461         }
 462     }
 463
 464     /// Does this expression refer to a place that either:
 465     /// * Is based on a local or static.
 466     /// * Contains a dereference
 467     /// Note that the adjustments for the children of `expr` should already
 468     /// have been resolved.
 469     fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
 470         let is_named = oprnd.is_place_expr(|base| {
 471             // Allow raw borrows if there are any deref adjustments.
 472             //
 473             // const VAL: (i32,) = (0,);
 474             // const REF: &(i32,) = &(0,);
 475             //
 476             // &raw const VAL.0;            // ERROR
 477             // &raw const REF.0;            // OK, same as &raw const (*REF).0;
 478             //
 479             // This is maybe too permissive, since it allows
 480             // `let u = &raw const Box::new((1,)).0`, which creates an
 481             // immediately dangling raw pointer.
 482             self.typeck_results
 483                 .borrow()
 484                 .adjustments()
 485                 .get(base.hir_id)
 486                 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
 487         });
 488         if !is_named {
 489             self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
 490         }
 491     }
 492
 493     fn check_lang_item_path(
 494         &self,
 495         lang_item: hir::LangItem,
 496         expr: &'tcx hir::Expr<'tcx>,
 497         hir_id: Option<hir::HirId>,
 498     ) -> Ty<'tcx> {
 499         self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
 500     }
 501
 502     pub(crate) fn check_expr_path(
 503         &self,
 504         qpath: &'tcx hir::QPath<'tcx>,
 505         expr: &'tcx hir::Expr<'tcx>,
 506         args: &'tcx [hir::Expr<'tcx>],
 507     ) -> Ty<'tcx> {
 508         let tcx = self.tcx;
 509         let (res, opt_ty, segs) =
 510             self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
 511         let ty = match res {
 512             Res::Err => {
 513                 self.set_tainted_by_errors();
 514                 tcx.ty_error()
 515             }
 516             Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
 517                 report_unexpected_variant_res(tcx, res, expr.span);
 518                 tcx.ty_error()
 519             }
 520             _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
 521         };
 522
 523         if let ty::FnDef(..) = ty.kind() {
 524             let fn_sig = ty.fn_sig(tcx);
 525             if !tcx.features().unsized_fn_params {
 526                 // We want to remove some Sized bounds from std functions,
 527                 // but don't want to expose the removal to stable Rust.
 528                 // i.e., we don't want to allow
 529                 //
 530                 // ```rust
 531                 // drop as fn(str);
 532                 // ```
 533                 //
 534                 // to work in stable even if the Sized bound on `drop` is relaxed.
 535                 for i in 0..fn_sig.inputs().skip_binder().len() {
 536                     // We just want to check sizedness, so instead of introducing
 537                     // placeholder lifetimes with probing, we just replace higher lifetimes
 538                     // with fresh vars.
 539                     let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
 540                     let input = self
 541                         .replace_bound_vars_with_fresh_vars(
 542                             span,
 543                             infer::LateBoundRegionConversionTime::FnCall,
 544                             fn_sig.input(i),
 545                         )
 546                         .0;
 547                     self.require_type_is_sized_deferred(
 548                         input,
 549                         span,
 550                         traits::SizedArgumentType(None),
 551                     );
 552                 }
 553             }
 554             // Here we want to prevent struct constructors from returning unsized types.
 555             // There were two cases this happened: fn pointer coercion in stable
 556             // and usual function call in presence of unsized_locals.
 557             // Also, as we just want to check sizedness, instead of introducing
 558             // placeholder lifetimes with probing, we just replace higher lifetimes
 559             // with fresh vars.
 560             let output = self
 561                 .replace_bound_vars_with_fresh_vars(
 562                     expr.span,
 563                     infer::LateBoundRegionConversionTime::FnCall,
 564                     fn_sig.output(),
 565                 )
 566                 .0;
 567             self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
 568         }
 569
 570         // We always require that the type provided as the value for
 571         // a type parameter outlives the moment of instantiation.
 572         let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
 573         self.add_wf_bounds(substs, expr);
 574
 575         ty
 576     }
 577
 578     fn check_expr_break(
 579         &self,
 580         destination: hir::Destination,
 581         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 582         expr: &'tcx hir::Expr<'tcx>,
 583     ) -> Ty<'tcx> {
 584         let tcx = self.tcx;
 585         if let Ok(target_id) = destination.target_id {
 586             let (e_ty, cause);
 587             if let Some(e) = expr_opt {
 588                 // If this is a break with a value, we need to type-check
 589                 // the expression. Get an expected type from the loop context.
 590                 let opt_coerce_to = {
 591                     // We should release `enclosing_breakables` before the `check_expr_with_hint`
 592                     // below, so can't move this block of code to the enclosing scope and share
 593                     // `ctxt` with the second `encloding_breakables` borrow below.
 594                     let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 595                     match enclosing_breakables.opt_find_breakable(target_id) {
 596                         Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
 597                         None => {
 598                             // Avoid ICE when `break` is inside a closure (#65383).
 599                             return tcx.ty_error_with_message(
 600                                 expr.span,
 601                                 "break was outside loop, but no error was emitted",
 602                             );
 603                         }
 604                     }
 605                 };
 606
 607                 // If the loop context is not a `loop { }`, then break with
 608                 // a value is illegal, and `opt_coerce_to` will be `None`.
 609                 // Just set expectation to error in that case.
 610                 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
 611
 612                 // Recurse without `enclosing_breakables` borrowed.
 613                 e_ty = self.check_expr_with_hint(e, coerce_to);
 614                 cause = self.misc(e.span);
 615             } else {
 616                 // Otherwise, this is a break *without* a value. That's
 617                 // always legal, and is equivalent to `break ()`.
 618                 e_ty = tcx.mk_unit();
 619                 cause = self.misc(expr.span);
 620             }
 621
 622             // Now that we have type-checked `expr_opt`, borrow
 623             // the `enclosing_loops` field and let's coerce the
 624             // type of `expr_opt` into what is expected.
 625             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 626             let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
 627                 // Avoid ICE when `break` is inside a closure (#65383).
 628                 return tcx.ty_error_with_message(
 629                     expr.span,
 630                     "break was outside loop, but no error was emitted",
 631                 );
 632             };
 633
 634             if let Some(ref mut coerce) = ctxt.coerce {
 635                 if let Some(ref e) = expr_opt {
 636                     coerce.coerce(self, &cause, e, e_ty);
 637                 } else {
 638                     assert!(e_ty.is_unit());
 639                     let ty = coerce.expected_ty();
 640                     coerce.coerce_forced_unit(
 641                         self,
 642                         &cause,
 643                         &mut |mut err| {
 644                             self.suggest_mismatched_types_on_tail(
 645                                 &mut err, expr, ty, e_ty, target_id,
 646                             );
 647                             if let Some(val) = ty_kind_suggestion(ty) {
 648                                 let label = destination
 649                                     .label
 650                                     .map(|l| format!(" {}", l.ident))
 651                                     .unwrap_or_else(String::new);
 652                                 err.span_suggestion(
 653                                     expr.span,
 654                                     "give it a value of the expected type",
 655                                     format!("break{} {}", label, val),
 656                                     Applicability::HasPlaceholders,
 657                                 );
 658                             }
 659                         },
 660                         false,
 661                     );
 662                 }
 663             } else {
 664                 // If `ctxt.coerce` is `None`, we can just ignore
 665                 // the type of the expression.  This is because
 666                 // either this was a break *without* a value, in
 667                 // which case it is always a legal type (`()`), or
 668                 // else an error would have been flagged by the
 669                 // `loops` pass for using break with an expression
 670                 // where you are not supposed to.
 671                 assert!(expr_opt.is_none() || self.tcx.sess.has_errors());
 672             }
 673
 674             // If we encountered a `break`, then (no surprise) it may be possible to break from the
 675             // loop... unless the value being returned from the loop diverges itself, e.g.
 676             // `break return 5` or `break loop {}`.
 677             ctxt.may_break |= !self.diverges.get().is_always();
 678
 679             // the type of a `break` is always `!`, since it diverges
 680             tcx.types.never
 681         } else {
 682             // Otherwise, we failed to find the enclosing loop;
 683             // this can only happen if the `break` was not
 684             // inside a loop at all, which is caught by the
 685             // loop-checking pass.
 686             let err = self.tcx.ty_error_with_message(
 687                 expr.span,
 688                 "break was outside loop, but no error was emitted",
 689             );
 690
 691             // We still need to assign a type to the inner expression to
 692             // prevent the ICE in #43162.
 693             if let Some(e) = expr_opt {
 694                 self.check_expr_with_hint(e, err);
 695
 696                 // ... except when we try to 'break rust;'.
 697                 // ICE this expression in particular (see #43162).
 698                 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
 699                     if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
 700                         fatally_break_rust(self.tcx.sess);
 701                     }
 702                 }
 703             }
 704
 705             // There was an error; make type-check fail.
 706             err
 707         }
 708     }
 709
 710     fn check_expr_return(
 711         &self,
 712         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 713         expr: &'tcx hir::Expr<'tcx>,
 714     ) -> Ty<'tcx> {
 715         if self.ret_coercion.is_none() {
 716             let mut err = ReturnStmtOutsideOfFnBody {
 717                 span: expr.span,
 718                 encl_body_span: None,
 719                 encl_fn_span: None,
 720             };
 721
 722             let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
 723
 724             if let Some(hir::Node::Item(hir::Item {
 725                 kind: hir::ItemKind::Fn(..),
 726                 span: encl_fn_span,
 727                 ..
 728             }))
 729             | Some(hir::Node::TraitItem(hir::TraitItem {
 730                 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
 731                 span: encl_fn_span,
 732                 ..
 733             }))
 734             | Some(hir::Node::ImplItem(hir::ImplItem {
 735                 kind: hir::ImplItemKind::Fn(..),
 736                 span: encl_fn_span,
 737                 ..
 738             })) = self.tcx.hir().find_by_def_id(encl_item_id)
 739             {
 740                 // We are inside a function body, so reporting "return statement
 741                 // outside of function body" needs an explanation.
 742
 743                 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
 744
 745                 // If this didn't hold, we would not have to report an error in
 746                 // the first place.
 747                 assert_ne!(hir::HirId::make_owner(encl_item_id), encl_body_owner_id);
 748
 749                 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
 750                 let encl_body = self.tcx.hir().body(encl_body_id);
 751
 752                 err.encl_body_span = Some(encl_body.value.span);
 753                 err.encl_fn_span = Some(*encl_fn_span);
 754             }
 755
 756             self.tcx.sess.emit_err(err);
 757
 758             if let Some(e) = expr_opt {
 759                 // We still have to type-check `e` (issue #86188), but calling
 760                 // `check_return_expr` only works inside fn bodies.
 761                 self.check_expr(e);
 762             }
 763         } else if let Some(e) = expr_opt {
 764             if self.ret_coercion_span.get().is_none() {
 765                 self.ret_coercion_span.set(Some(e.span));
 766             }
 767             self.check_return_expr(e, true);
 768         } else {
 769             let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
 770             if self.ret_coercion_span.get().is_none() {
 771                 self.ret_coercion_span.set(Some(expr.span));
 772             }
 773             let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
 774             if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
 775                 coercion.coerce_forced_unit(
 776                     self,
 777                     &cause,
 778                     &mut |db| {
 779                         let span = fn_decl.output.span();
 780                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
 781                             db.span_label(
 782                                 span,
 783                                 format!("expected `{}` because of this return type", snippet),
 784                             );
 785                         }
 786                     },
 787                     true,
 788                 );
 789             } else {
 790                 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
 791             }
 792         }
 793         self.tcx.types.never
 794     }
 795
 796     /// `explicit_return` is `true` if we're checkng an explicit `return expr`,
 797     /// and `false` if we're checking a trailing expression.
 798     pub(super) fn check_return_expr(
 799         &self,
 800         return_expr: &'tcx hir::Expr<'tcx>,
 801         explicit_return: bool,
 802     ) {
 803         let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
 804             span_bug!(return_expr.span, "check_return_expr called outside fn body")
 805         });
 806
 807         let ret_ty = ret_coercion.borrow().expected_ty();
 808         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
 809         let mut span = return_expr.span;
 810         // Use the span of the trailing expression for our cause,
 811         // not the span of the entire function
 812         if !explicit_return {
 813             if let ExprKind::Block(body, _) = return_expr.kind {
 814                 if let Some(last_expr) = body.expr {
 815                     span = last_expr.span;
 816                 }
 817             }
 818         }
 819         ret_coercion.borrow_mut().coerce(
 820             self,
 821             &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
 822             return_expr,
 823             return_expr_ty,
 824         );
 825     }
 826
 827     pub(crate) fn check_lhs_assignable(
 828         &self,
 829         lhs: &'tcx hir::Expr<'tcx>,
 830         err_code: &'static str,
 831         op_span: Span,
 832     ) {
 833         if lhs.is_syntactic_place_expr() {
 834             return;
 835         }
 836
 837         // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
 838         let mut err = self.tcx.sess.struct_span_err_with_code(
 839             op_span,
 840             "invalid left-hand side of assignment",
 841             DiagnosticId::Error(err_code.into()),
 842         );
 843         err.span_label(lhs.span, "cannot assign to this expression");
 844
 845         let mut parent = self.tcx.hir().get_parent_node(lhs.hir_id);
 846         while let Some(node) = self.tcx.hir().find(parent) {
 847             match node {
 848                 hir::Node::Expr(hir::Expr {
 849                     kind:
 850                         hir::ExprKind::Loop(
 851                             hir::Block {
 852                                 expr:
 853                                     Some(hir::Expr {
 854                                         kind:
 855                                             hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
 856                                         ..
 857                                     }),
 858                                 ..
 859                             },
 860                             _,
 861                             hir::LoopSource::While,
 862                             _,
 863                         ),
 864                     ..
 865                 }) => {
 866                     // Check if our lhs is a child of the condition of a while loop
 867                     let expr_is_ancestor = std::iter::successors(Some(lhs.hir_id), |id| {
 868                         self.tcx.hir().find_parent_node(*id)
 869                     })
 870                     .take_while(|id| *id != parent)
 871                     .any(|id| id == expr.hir_id);
 872                     // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
 873                     // where `while let` was more likely intended.
 874                     if expr_is_ancestor {
 875                         err.span_suggestion_verbose(
 876                             expr.span.shrink_to_lo(),
 877                             "you might have meant to use pattern destructuring",
 878                             "let ".to_string(),
 879                             Applicability::MachineApplicable,
 880                         );
 881                     }
 882                     break;
 883                 }
 884                 hir::Node::Item(_)
 885                 | hir::Node::ImplItem(_)
 886                 | hir::Node::TraitItem(_)
 887                 | hir::Node::Crate(_) => break,
 888                 _ => {
 889                     parent = self.tcx.hir().get_parent_node(parent);
 890                 }
 891             }
 892         }
 893
 894         err.emit();
 895     }
 896
 897     // A generic function for checking the 'then' and 'else' clauses in an 'if'
 898     // or 'if-else' expression.
 899     fn check_then_else(
 900         &self,
 901         cond_expr: &'tcx hir::Expr<'tcx>,
 902         then_expr: &'tcx hir::Expr<'tcx>,
 903         opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
 904         sp: Span,
 905         orig_expected: Expectation<'tcx>,
 906     ) -> Ty<'tcx> {
 907         let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
 908
 909         self.warn_if_unreachable(
 910             cond_expr.hir_id,
 911             then_expr.span,
 912             "block in `if` or `while` expression",
 913         );
 914
 915         let cond_diverges = self.diverges.get();
 916         self.diverges.set(Diverges::Maybe);
 917
 918         let expected = orig_expected.adjust_for_branches(self);
 919         let then_ty = self.check_expr_with_expectation(then_expr, expected);
 920         let then_diverges = self.diverges.get();
 921         self.diverges.set(Diverges::Maybe);
 922
 923         // We've already taken the expected type's preferences
 924         // into account when typing the `then` branch. To figure
 925         // out the initial shot at a LUB, we thus only consider
 926         // `expected` if it represents a *hard* constraint
 927         // (`only_has_type`); otherwise, we just go with a
 928         // fresh type variable.
 929         let coerce_to_ty = expected.coercion_target_type(self, sp);
 930         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
 931
 932         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
 933
 934         if let Some(else_expr) = opt_else_expr {
 935             let else_ty = if sp.desugaring_kind() == Some(DesugaringKind::LetElse) {
 936                 // todo introduce `check_expr_with_expectation(.., Expectation::LetElse)`
 937                 //   for errors that point to the offending expression rather than the entire block.
 938                 //   We could use `check_expr_eq_type(.., tcx.types.never)`, but then there is no
 939                 //   way to detect that the expected type originated from let-else and provide
 940                 //   a customized error.
 941                 let else_ty = self.check_expr(else_expr);
 942                 let cause = self.cause(else_expr.span, ObligationCauseCode::LetElse);
 943
 944                 if let Some(mut err) =
 945                     self.demand_eqtype_with_origin(&cause, self.tcx.types.never, else_ty)
 946                 {
 947                     err.emit();
 948                     self.tcx.ty_error()
 949                 } else {
 950                     else_ty
 951                 }
 952             } else {
 953                 self.check_expr_with_expectation(else_expr, expected)
 954             };
 955             let else_diverges = self.diverges.get();
 956
 957             let opt_suggest_box_span =
 958                 self.opt_suggest_box_span(else_expr.span, else_ty, orig_expected);
 959             let if_cause =
 960                 self.if_cause(sp, then_expr, else_expr, then_ty, else_ty, opt_suggest_box_span);
 961
 962             coerce.coerce(self, &if_cause, else_expr, else_ty);
 963
 964             // We won't diverge unless both branches do (or the condition does).
 965             self.diverges.set(cond_diverges | then_diverges & else_diverges);
 966         } else {
 967             self.if_fallback_coercion(sp, then_expr, &mut coerce);
 968
 969             // If the condition is false we can't diverge.
 970             self.diverges.set(cond_diverges);
 971         }
 972
 973         let result_ty = coerce.complete(self);
 974         if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
 975     }
 976
 977     /// Type check assignment expression `expr` of form `lhs = rhs`.
 978     /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
 979     fn check_expr_assign(
 980         &self,
 981         expr: &'tcx hir::Expr<'tcx>,
 982         expected: Expectation<'tcx>,
 983         lhs: &'tcx hir::Expr<'tcx>,
 984         rhs: &'tcx hir::Expr<'tcx>,
 985         span: &Span,
 986     ) -> Ty<'tcx> {
 987         let expected_ty = expected.coercion_target_type(self, expr.span);
 988         if expected_ty == self.tcx.types.bool {
 989             // The expected type is `bool` but this will result in `()` so we can reasonably
 990             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
 991             // The likely cause of this is `if foo = bar { .. }`.
 992             let actual_ty = self.tcx.mk_unit();
 993             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
 994             let lhs_ty = self.check_expr(&lhs);
 995             let rhs_ty = self.check_expr(&rhs);
 996             let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
 997                 (Applicability::MachineApplicable, true)
 998             } else {
 999                 (Applicability::MaybeIncorrect, false)
1000             };
1001             if !lhs.is_syntactic_place_expr() && !matches!(lhs.kind, hir::ExprKind::Lit(_)) {
1002                 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1003                 let hir = self.tcx.hir();
1004                 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1005                     hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1006                 {
1007                     err.span_suggestion_verbose(
1008                         expr.span.shrink_to_lo(),
1009                         "you might have meant to use pattern matching",
1010                         "let ".to_string(),
1011                         applicability,
1012                     );
1013                 };
1014             }
1015             if eq {
1016                 err.span_suggestion_verbose(
1017                     *span,
1018                     "you might have meant to compare for equality",
1019                     "==".to_string(),
1020                     applicability,
1021                 );
1022             }
1023
1024             // If the assignment expression itself is ill-formed, don't
1025             // bother emitting another error
1026             if lhs_ty.references_error() || rhs_ty.references_error() {
1027                 err.delay_as_bug()
1028             } else {
1029                 err.emit();
1030             }
1031             return self.tcx.ty_error();
1032         }
1033
1034         self.check_lhs_assignable(lhs, "E0070", *span);
1035
1036         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1037         let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty, Some(lhs));
1038
1039         self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1040
1041         if lhs_ty.references_error() || rhs_ty.references_error() {
1042             self.tcx.ty_error()
1043         } else {
1044             self.tcx.mk_unit()
1045         }
1046     }
1047
1048     fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1049         // for let statements, this is done in check_stmt
1050         let init = let_expr.init;
1051         self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1052         // otherwise check exactly as a let statement
1053         self.check_decl(let_expr.into());
1054         // but return a bool, for this is a boolean expression
1055         self.tcx.types.bool
1056     }
1057
1058     fn check_expr_loop(
1059         &self,
1060         body: &'tcx hir::Block<'tcx>,
1061         source: hir::LoopSource,
1062         expected: Expectation<'tcx>,
1063         expr: &'tcx hir::Expr<'tcx>,
1064     ) -> Ty<'tcx> {
1065         let coerce = match source {
1066             // you can only use break with a value from a normal `loop { }`
1067             hir::LoopSource::Loop => {
1068                 let coerce_to = expected.coercion_target_type(self, body.span);
1069                 Some(CoerceMany::new(coerce_to))
1070             }
1071
1072             hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1073         };
1074
1075         let ctxt = BreakableCtxt {
1076             coerce,
1077             may_break: false, // Will get updated if/when we find a `break`.
1078         };
1079
1080         let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1081             self.check_block_no_value(&body);
1082         });
1083
1084         if ctxt.may_break {
1085             // No way to know whether it's diverging because
1086             // of a `break` or an outer `break` or `return`.
1087             self.diverges.set(Diverges::Maybe);
1088         }
1089
1090         // If we permit break with a value, then result type is
1091         // the LUB of the breaks (possibly ! if none); else, it
1092         // is nil. This makes sense because infinite loops
1093         // (which would have type !) are only possible iff we
1094         // permit break with a value [1].
1095         if ctxt.coerce.is_none() && !ctxt.may_break {
1096             // [1]
1097             self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1098         }
1099         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1100     }
1101
1102     /// Checks a method call.
1103     fn check_method_call(
1104         &self,
1105         expr: &'tcx hir::Expr<'tcx>,
1106         segment: &hir::PathSegment<'_>,
1107         args: &'tcx [hir::Expr<'tcx>],
1108         expected: Expectation<'tcx>,
1109     ) -> Ty<'tcx> {
1110         let rcvr = &args[0];
1111         let rcvr_t = self.check_expr(&rcvr);
1112         // no need to check for bot/err -- callee does that
1113         let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
1114         let span = segment.ident.span;
1115
1116         let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1117             Ok(method) => {
1118                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1119                 // trigger this codepath causing `structuraly_resolved_type` to emit an error.
1120
1121                 self.write_method_call(expr.hir_id, method);
1122                 Ok(method)
1123             }
1124             Err(error) => {
1125                 if segment.ident.name != kw::Empty {
1126                     if let Some(mut err) = self.report_method_error(
1127                         span,
1128                         rcvr_t,
1129                         segment.ident,
1130                         SelfSource::MethodCall(&args[0]),
1131                         error,
1132                         Some(args),
1133                     ) {
1134                         err.emit();
1135                     }
1136                 }
1137                 Err(())
1138             }
1139         };
1140
1141         // Call the generic checker.
1142         self.check_method_argument_types(
1143             span,
1144             expr,
1145             method,
1146             &args[1..],
1147             DontTupleArguments,
1148             expected,
1149         )
1150     }
1151
1152     fn check_expr_cast(
1153         &self,
1154         e: &'tcx hir::Expr<'tcx>,
1155         t: &'tcx hir::Ty<'tcx>,
1156         expr: &'tcx hir::Expr<'tcx>,
1157     ) -> Ty<'tcx> {
1158         // Find the type of `e`. Supply hints based on the type we are casting to,
1159         // if appropriate.
1160         let t_cast = self.to_ty_saving_user_provided_ty(t);
1161         let t_cast = self.resolve_vars_if_possible(t_cast);
1162         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1163         let t_expr = self.resolve_vars_if_possible(t_expr);
1164
1165         // Eagerly check for some obvious errors.
1166         if t_expr.references_error() || t_cast.references_error() {
1167             self.tcx.ty_error()
1168         } else {
1169             // Defer other checks until we're done type checking.
1170             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1171             match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1172                 Ok(cast_check) => {
1173                     debug!(
1174                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1175                         t_cast, t_expr, cast_check,
1176                     );
1177                     deferred_cast_checks.push(cast_check);
1178                     t_cast
1179                 }
1180                 Err(ErrorReported) => self.tcx.ty_error(),
1181             }
1182         }
1183     }
1184
1185     fn check_expr_array(
1186         &self,
1187         args: &'tcx [hir::Expr<'tcx>],
1188         expected: Expectation<'tcx>,
1189         expr: &'tcx hir::Expr<'tcx>,
1190     ) -> Ty<'tcx> {
1191         let element_ty = if !args.is_empty() {
1192             let coerce_to = expected
1193                 .to_option(self)
1194                 .and_then(|uty| match *uty.kind() {
1195                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1196                     _ => None,
1197                 })
1198                 .unwrap_or_else(|| {
1199                     self.next_ty_var(TypeVariableOrigin {
1200                         kind: TypeVariableOriginKind::TypeInference,
1201                         span: expr.span,
1202                     })
1203                 });
1204             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1205             assert_eq!(self.diverges.get(), Diverges::Maybe);
1206             for e in args {
1207                 let e_ty = self.check_expr_with_hint(e, coerce_to);
1208                 let cause = self.misc(e.span);
1209                 coerce.coerce(self, &cause, e, e_ty);
1210             }
1211             coerce.complete(self)
1212         } else {
1213             self.next_ty_var(TypeVariableOrigin {
1214                 kind: TypeVariableOriginKind::TypeInference,
1215                 span: expr.span,
1216             })
1217         };
1218         self.tcx.mk_array(element_ty, args.len() as u64)
1219     }
1220
1221     fn check_expr_const_block(
1222         &self,
1223         anon_const: &'tcx hir::AnonConst,
1224         expected: Expectation<'tcx>,
1225         _expr: &'tcx hir::Expr<'tcx>,
1226     ) -> Ty<'tcx> {
1227         let body = self.tcx.hir().body(anon_const.body);
1228
1229         // Create a new function context.
1230         let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1231         crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1232
1233         let ty = fcx.check_expr_with_expectation(&body.value, expected);
1234         fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1235         fcx.write_ty(anon_const.hir_id, ty);
1236         ty
1237     }
1238
1239     fn check_expr_repeat(
1240         &self,
1241         element: &'tcx hir::Expr<'tcx>,
1242         count: &'tcx hir::ArrayLen,
1243         expected: Expectation<'tcx>,
1244         _expr: &'tcx hir::Expr<'tcx>,
1245     ) -> Ty<'tcx> {
1246         let tcx = self.tcx;
1247         let count = self.array_length_to_const(count);
1248
1249         let uty = match expected {
1250             ExpectHasType(uty) => match *uty.kind() {
1251                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1252                 _ => None,
1253             },
1254             _ => None,
1255         };
1256
1257         let (element_ty, t) = match uty {
1258             Some(uty) => {
1259                 self.check_expr_coercable_to_type(&element, uty, None);
1260                 (uty, uty)
1261             }
1262             None => {
1263                 let ty = self.next_ty_var(TypeVariableOrigin {
1264                     kind: TypeVariableOriginKind::MiscVariable,
1265                     span: element.span,
1266                 });
1267                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1268                 (element_ty, ty)
1269             }
1270         };
1271
1272         if element_ty.references_error() {
1273             return tcx.ty_error();
1274         }
1275
1276         tcx.mk_ty(ty::Array(t, count))
1277     }
1278
1279     fn check_expr_tuple(
1280         &self,
1281         elts: &'tcx [hir::Expr<'tcx>],
1282         expected: Expectation<'tcx>,
1283         expr: &'tcx hir::Expr<'tcx>,
1284     ) -> Ty<'tcx> {
1285         let flds = expected.only_has_type(self).and_then(|ty| {
1286             let ty = self.resolve_vars_with_obligations(ty);
1287             match ty.kind() {
1288                 ty::Tuple(flds) => Some(&flds[..]),
1289                 _ => None,
1290             }
1291         });
1292
1293         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1294             Some(fs) if i < fs.len() => {
1295                 let ety = fs[i];
1296                 self.check_expr_coercable_to_type(&e, ety, None);
1297                 ety
1298             }
1299             _ => self.check_expr_with_expectation(&e, NoExpectation),
1300         });
1301         let tuple = self.tcx.mk_tup(elt_ts_iter);
1302         if tuple.references_error() {
1303             self.tcx.ty_error()
1304         } else {
1305             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1306             tuple
1307         }
1308     }
1309
1310     fn check_expr_struct(
1311         &self,
1312         expr: &hir::Expr<'_>,
1313         expected: Expectation<'tcx>,
1314         qpath: &QPath<'_>,
1315         fields: &'tcx [hir::ExprField<'tcx>],
1316         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1317     ) -> Ty<'tcx> {
1318         // Find the relevant variant
1319         let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1320             self.check_struct_fields_on_error(fields, base_expr);
1321             return self.tcx.ty_error();
1322         };
1323
1324         // Prohibit struct expressions when non-exhaustive flag is set.
1325         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1326         if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
1327             self.tcx
1328                 .sess
1329                 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1330         }
1331
1332         self.check_expr_struct_fields(
1333             adt_ty,
1334             expected,
1335             expr.hir_id,
1336             qpath.span(),
1337             variant,
1338             fields,
1339             base_expr,
1340             expr.span,
1341         );
1342
1343         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1344         adt_ty
1345     }
1346
1347     fn check_expr_struct_fields(
1348         &self,
1349         adt_ty: Ty<'tcx>,
1350         expected: Expectation<'tcx>,
1351         expr_id: hir::HirId,
1352         span: Span,
1353         variant: &'tcx ty::VariantDef,
1354         ast_fields: &'tcx [hir::ExprField<'tcx>],
1355         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1356         expr_span: Span,
1357     ) {
1358         let tcx = self.tcx;
1359
1360         let adt_ty_hint = self
1361             .expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
1362             .get(0)
1363             .cloned()
1364             .unwrap_or(adt_ty);
1365         // re-link the regions that EIfEO can erase.
1366         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1367
1368         let (substs, adt_kind, kind_name) = match adt_ty.kind() {
1369             ty::Adt(adt, substs) => (substs, adt.adt_kind(), adt.variant_descr()),
1370             _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields"),
1371         };
1372
1373         let mut remaining_fields = variant
1374             .fields
1375             .iter()
1376             .enumerate()
1377             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1378             .collect::<FxHashMap<_, _>>();
1379
1380         let mut seen_fields = FxHashMap::default();
1381
1382         let mut error_happened = false;
1383
1384         // Type-check each field.
1385         for field in ast_fields {
1386             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1387             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1388                 seen_fields.insert(ident, field.span);
1389                 self.write_field_index(field.hir_id, i);
1390
1391                 // We don't look at stability attributes on
1392                 // struct-like enums (yet...), but it's definitely not
1393                 // a bug to have constructed one.
1394                 if adt_kind != AdtKind::Enum {
1395                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1396                 }
1397
1398                 self.field_ty(field.span, v_field, substs)
1399             } else {
1400                 error_happened = true;
1401                 if let Some(prev_span) = seen_fields.get(&ident) {
1402                     tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1403                         span: field.ident.span,
1404                         prev_span: *prev_span,
1405                         ident,
1406                     });
1407                 } else {
1408                     self.report_unknown_field(
1409                         adt_ty, variant, field, ast_fields, kind_name, expr_span,
1410                     );
1411                 }
1412
1413                 tcx.ty_error()
1414             };
1415
1416             // Make sure to give a type to the field even if there's
1417             // an error, so we can continue type-checking.
1418             self.check_expr_coercable_to_type(&field.expr, field_type, None);
1419         }
1420
1421         // Make sure the programmer specified correct number of fields.
1422         if kind_name == "union" {
1423             if ast_fields.len() != 1 {
1424                 struct_span_err!(
1425                     tcx.sess,
1426                     span,
1427                     E0784,
1428                     "union expressions should have exactly one field",
1429                 )
1430                 .emit();
1431             }
1432         }
1433
1434         // If check_expr_struct_fields hit an error, do not attempt to populate
1435         // the fields with the base_expr. This could cause us to hit errors later
1436         // when certain fields are assumed to exist that in fact do not.
1437         if error_happened {
1438             return;
1439         }
1440
1441         if let Some(base_expr) = base_expr {
1442             // FIXME: We are currently creating two branches here in order to maintain
1443             // consistency. But they should be merged as much as possible.
1444             let fru_tys = if self.tcx.features().type_changing_struct_update {
1445                 let base_ty = self.check_expr(base_expr);
1446                 match adt_ty.kind() {
1447                     ty::Adt(adt, substs) if adt.is_struct() => {
1448                         match base_ty.kind() {
1449                             ty::Adt(base_adt, base_subs) if adt == base_adt => {
1450                                 variant
1451                                     .fields
1452                                     .iter()
1453                                     .map(|f| {
1454                                         let fru_ty = self.normalize_associated_types_in(
1455                                             expr_span,
1456                                             self.field_ty(base_expr.span, f, base_subs),
1457                                         );
1458                                         let ident = self
1459                                             .tcx
1460                                             .adjust_ident(f.ident(self.tcx), variant.def_id);
1461                                         if let Some(_) = remaining_fields.remove(&ident) {
1462                                             let target_ty =
1463                                                 self.field_ty(base_expr.span, f, substs);
1464                                             let cause = self.misc(base_expr.span);
1465                                             match self
1466                                                 .at(&cause, self.param_env)
1467                                                 .sup(target_ty, fru_ty)
1468                                             {
1469                                                 Ok(InferOk { obligations, value: () }) => {
1470                                                     self.register_predicates(obligations)
1471                                                 }
1472                                                 // FIXME: Need better diagnostics for `FieldMisMatch` error
1473                                                 Err(_) => {
1474                                                     self.report_mismatched_types(
1475                                                         &cause,
1476                                                         target_ty,
1477                                                         fru_ty,
1478                                                         FieldMisMatch(variant.name, ident.name),
1479                                                     )
1480                                                     .emit();
1481                                                 }
1482                                             }
1483                                         }
1484                                         fru_ty
1485                                     })
1486                                     .collect()
1487                             }
1488                             _ => {
1489                                 self.report_mismatched_types(
1490                                     &self.misc(base_expr.span),
1491                                     adt_ty,
1492                                     base_ty,
1493                                     Sorts(ExpectedFound::new(true, adt_ty, base_ty)),
1494                                 )
1495                                 .emit();
1496                                 return;
1497                             }
1498                         }
1499                     }
1500                     _ => {
1501                         self.tcx
1502                             .sess
1503                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1504                         return;
1505                     }
1506                 }
1507             } else {
1508                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1509                     let base_ty = self.typeck_results.borrow().node_type(base_expr.hir_id);
1510                     let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1511                         (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1512                         _ => false,
1513                     };
1514                     if self.tcx.sess.is_nightly_build() && same_adt {
1515                         feature_err(
1516                             &self.tcx.sess.parse_sess,
1517                             sym::type_changing_struct_update,
1518                             base_expr.span,
1519                             "type changing struct updating is experimental",
1520                         )
1521                         .emit();
1522                     }
1523                 });
1524                 match adt_ty.kind() {
1525                     ty::Adt(adt, substs) if adt.is_struct() => variant
1526                         .fields
1527                         .iter()
1528                         .map(|f| {
1529                             self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1530                         })
1531                         .collect(),
1532                     _ => {
1533                         self.tcx
1534                             .sess
1535                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1536                         return;
1537                     }
1538                 }
1539             };
1540             self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1541         } else if kind_name != "union" && !remaining_fields.is_empty() {
1542             let inaccessible_remaining_fields = remaining_fields.iter().any(|(_, (_, field))| {
1543                 !field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1544             });
1545
1546             if inaccessible_remaining_fields {
1547                 self.report_inaccessible_fields(adt_ty, span);
1548             } else {
1549                 self.report_missing_fields(adt_ty, span, remaining_fields);
1550             }
1551         }
1552     }
1553
1554     fn check_struct_fields_on_error(
1555         &self,
1556         fields: &'tcx [hir::ExprField<'tcx>],
1557         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1558     ) {
1559         for field in fields {
1560             self.check_expr(&field.expr);
1561         }
1562         if let Some(base) = *base_expr {
1563             self.check_expr(&base);
1564         }
1565     }
1566
1567     /// Report an error for a struct field expression when there are fields which aren't provided.
1568     ///
1569     /// ```text
1570     /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1571     ///  --> src/main.rs:8:5
1572     ///   |
1573     /// 8 |     foo::Foo {};
1574     ///   |     ^^^^^^^^ missing `you_can_use_this_field`
1575     ///
1576     /// error: aborting due to previous error
1577     /// ```
1578     fn report_missing_fields(
1579         &self,
1580         adt_ty: Ty<'tcx>,
1581         span: Span,
1582         remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1583     ) {
1584         let len = remaining_fields.len();
1585
1586         let mut displayable_field_names: Vec<&str> =
1587             remaining_fields.keys().map(|ident| ident.as_str()).collect();
1588         // sorting &str primitives here, sort_unstable is ok
1589         displayable_field_names.sort_unstable();
1590
1591         let mut truncated_fields_error = String::new();
1592         let remaining_fields_names = match &displayable_field_names[..] {
1593             [field1] => format!("`{}`", field1),
1594             [field1, field2] => format!("`{}` and `{}`", field1, field2),
1595             [field1, field2, field3] => format!("`{}`, `{}` and `{}`", field1, field2, field3),
1596             _ => {
1597                 truncated_fields_error =
1598                     format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1599                 displayable_field_names
1600                     .iter()
1601                     .take(3)
1602                     .map(|n| format!("`{}`", n))
1603                     .collect::<Vec<_>>()
1604                     .join(", ")
1605             }
1606         };
1607
1608         struct_span_err!(
1609             self.tcx.sess,
1610             span,
1611             E0063,
1612             "missing field{} {}{} in initializer of `{}`",
1613             pluralize!(len),
1614             remaining_fields_names,
1615             truncated_fields_error,
1616             adt_ty
1617         )
1618         .span_label(span, format!("missing {}{}", remaining_fields_names, truncated_fields_error))
1619         .emit();
1620     }
1621
1622     /// Report an error for a struct field expression when there are invisible fields.
1623     ///
1624     /// ```text
1625     /// error: cannot construct `Foo` with struct literal syntax due to inaccessible fields
1626     ///  --> src/main.rs:8:5
1627     ///   |
1628     /// 8 |     foo::Foo {};
1629     ///   |     ^^^^^^^^
1630     ///
1631     /// error: aborting due to previous error
1632     /// ```
1633     fn report_inaccessible_fields(&self, adt_ty: Ty<'tcx>, span: Span) {
1634         self.tcx.sess.span_err(
1635             span,
1636             &format!(
1637                 "cannot construct `{}` with struct literal syntax due to inaccessible fields",
1638                 adt_ty,
1639             ),
1640         );
1641     }
1642
1643     fn report_unknown_field(
1644         &self,
1645         ty: Ty<'tcx>,
1646         variant: &'tcx ty::VariantDef,
1647         field: &hir::ExprField<'_>,
1648         skip_fields: &[hir::ExprField<'_>],
1649         kind_name: &str,
1650         expr_span: Span,
1651     ) {
1652         if variant.is_recovered() {
1653             self.set_tainted_by_errors();
1654             return;
1655         }
1656         let mut err = self.type_error_struct_with_diag(
1657             field.ident.span,
1658             |actual| match ty.kind() {
1659                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1660                     self.tcx.sess,
1661                     field.ident.span,
1662                     E0559,
1663                     "{} `{}::{}` has no field named `{}`",
1664                     kind_name,
1665                     actual,
1666                     variant.name,
1667                     field.ident
1668                 ),
1669                 _ => struct_span_err!(
1670                     self.tcx.sess,
1671                     field.ident.span,
1672                     E0560,
1673                     "{} `{}` has no field named `{}`",
1674                     kind_name,
1675                     actual,
1676                     field.ident
1677                 ),
1678             },
1679             ty,
1680         );
1681
1682         let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1683         match variant.ctor_kind {
1684             CtorKind::Fn => match ty.kind() {
1685                 ty::Adt(adt, ..) if adt.is_enum() => {
1686                     err.span_label(
1687                         variant_ident_span,
1688                         format!(
1689                             "`{adt}::{variant}` defined here",
1690                             adt = ty,
1691                             variant = variant.name,
1692                         ),
1693                     );
1694                     err.span_label(field.ident.span, "field does not exist");
1695                     err.span_suggestion_verbose(
1696                         expr_span,
1697                         &format!(
1698                             "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1699                             adt = ty,
1700                             variant = variant.name,
1701                         ),
1702                         format!(
1703                             "{adt}::{variant}(/* fields */)",
1704                             adt = ty,
1705                             variant = variant.name,
1706                         ),
1707                         Applicability::HasPlaceholders,
1708                     );
1709                 }
1710                 _ => {
1711                     err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1712                     err.span_label(field.ident.span, "field does not exist");
1713                     err.span_suggestion_verbose(
1714                         expr_span,
1715                         &format!(
1716                             "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1717                             adt = ty,
1718                             kind_name = kind_name,
1719                         ),
1720                         format!("{adt}(/* fields */)", adt = ty),
1721                         Applicability::HasPlaceholders,
1722                     );
1723                 }
1724             },
1725             _ => {
1726                 // prevent all specified fields from being suggested
1727                 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
1728                 if let Some(field_name) = self.suggest_field_name(
1729                     variant,
1730                     field.ident.name,
1731                     skip_fields.collect(),
1732                     expr_span,
1733                 ) {
1734                     err.span_suggestion(
1735                         field.ident.span,
1736                         "a field with a similar name exists",
1737                         field_name.to_string(),
1738                         Applicability::MaybeIncorrect,
1739                     );
1740                 } else {
1741                     match ty.kind() {
1742                         ty::Adt(adt, ..) => {
1743                             if adt.is_enum() {
1744                                 err.span_label(
1745                                     field.ident.span,
1746                                     format!("`{}::{}` does not have this field", ty, variant.name),
1747                                 );
1748                             } else {
1749                                 err.span_label(
1750                                     field.ident.span,
1751                                     format!("`{}` does not have this field", ty),
1752                                 );
1753                             }
1754                             let available_field_names =
1755                                 self.available_field_names(variant, expr_span);
1756                             if !available_field_names.is_empty() {
1757                                 err.note(&format!(
1758                                     "available fields are: {}",
1759                                     self.name_series_display(available_field_names)
1760                                 ));
1761                             }
1762                         }
1763                         _ => bug!("non-ADT passed to report_unknown_field"),
1764                     }
1765                 };
1766             }
1767         }
1768         err.emit();
1769     }
1770
1771     // Return a hint about the closest match in field names
1772     fn suggest_field_name(
1773         &self,
1774         variant: &'tcx ty::VariantDef,
1775         field: Symbol,
1776         skip: Vec<Symbol>,
1777         // The span where stability will be checked
1778         span: Span,
1779     ) -> Option<Symbol> {
1780         let names = variant
1781             .fields
1782             .iter()
1783             .filter_map(|field| {
1784                 // ignore already set fields and private fields from non-local crates
1785                 // and unstable fields.
1786                 if skip.iter().any(|&x| x == field.name)
1787                     || (!variant.def_id.is_local() && !field.vis.is_public())
1788                     || matches!(
1789                         self.tcx.eval_stability(field.did, None, span, None),
1790                         stability::EvalResult::Deny { .. }
1791                     )
1792                 {
1793                     None
1794                 } else {
1795                     Some(field.name)
1796                 }
1797             })
1798             .collect::<Vec<Symbol>>();
1799
1800         find_best_match_for_name(&names, field, None)
1801     }
1802
1803     fn available_field_names(
1804         &self,
1805         variant: &'tcx ty::VariantDef,
1806         access_span: Span,
1807     ) -> Vec<Symbol> {
1808         variant
1809             .fields
1810             .iter()
1811             .filter(|field| {
1812                 let def_scope = self
1813                     .tcx
1814                     .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
1815                     .1;
1816                 field.vis.is_accessible_from(def_scope, self.tcx)
1817                     && !matches!(
1818                         self.tcx.eval_stability(field.did, None, access_span, None),
1819                         stability::EvalResult::Deny { .. }
1820                     )
1821             })
1822             .filter(|field| !self.tcx.is_doc_hidden(field.did))
1823             .map(|field| field.name)
1824             .collect()
1825     }
1826
1827     fn name_series_display(&self, names: Vec<Symbol>) -> String {
1828         // dynamic limit, to never omit just one field
1829         let limit = if names.len() == 6 { 6 } else { 5 };
1830         let mut display =
1831             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
1832         if names.len() > limit {
1833             display = format!("{} ... and {} others", display, names.len() - limit);
1834         }
1835         display
1836     }
1837
1838     // Check field access expressions
1839     fn check_field(
1840         &self,
1841         expr: &'tcx hir::Expr<'tcx>,
1842         base: &'tcx hir::Expr<'tcx>,
1843         field: Ident,
1844     ) -> Ty<'tcx> {
1845         debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
1846         let expr_t = self.check_expr(base);
1847         let expr_t = self.structurally_resolved_type(base.span, expr_t);
1848         let mut private_candidate = None;
1849         let mut autoderef = self.autoderef(expr.span, expr_t);
1850         while let Some((base_t, _)) = autoderef.next() {
1851             debug!("base_t: {:?}", base_t);
1852             match base_t.kind() {
1853                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
1854                     debug!("struct named {:?}", base_t);
1855                     let (ident, def_scope) =
1856                         self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
1857                     let fields = &base_def.non_enum_variant().fields;
1858                     if let Some(index) = fields
1859                         .iter()
1860                         .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
1861                     {
1862                         let field = &fields[index];
1863                         let field_ty = self.field_ty(expr.span, field, substs);
1864                         // Save the index of all fields regardless of their visibility in case
1865                         // of error recovery.
1866                         self.write_field_index(expr.hir_id, index);
1867                         let adjustments = self.adjust_steps(&autoderef);
1868                         if field.vis.is_accessible_from(def_scope, self.tcx) {
1869                             self.apply_adjustments(base, adjustments);
1870                             self.register_predicates(autoderef.into_obligations());
1871
1872                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
1873                             return field_ty;
1874                         }
1875                         private_candidate = Some((adjustments, base_def.did, field_ty));
1876                     }
1877                 }
1878                 ty::Tuple(tys) => {
1879                     let fstr = field.as_str();
1880                     if let Ok(index) = fstr.parse::<usize>() {
1881                         if fstr == index.to_string() {
1882                             if let Some(&field_ty) = tys.get(index) {
1883                                 let adjustments = self.adjust_steps(&autoderef);
1884                                 self.apply_adjustments(base, adjustments);
1885                                 self.register_predicates(autoderef.into_obligations());
1886
1887                                 self.write_field_index(expr.hir_id, index);
1888                                 return field_ty;
1889                             }
1890                         }
1891                     }
1892                 }
1893                 _ => {}
1894             }
1895         }
1896         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
1897
1898         if let Some((adjustments, did, field_ty)) = private_candidate {
1899             // (#90483) apply adjustments to avoid ExprUseVisitor from
1900             // creating erroneous projection.
1901             self.apply_adjustments(base, adjustments);
1902             self.ban_private_field_access(expr, expr_t, field, did);
1903             return field_ty;
1904         }
1905
1906         if field.name == kw::Empty {
1907         } else if self.method_exists(field, expr_t, expr.hir_id, true) {
1908             self.ban_take_value_of_method(expr, expr_t, field);
1909         } else if !expr_t.is_primitive_ty() {
1910             self.ban_nonexisting_field(field, base, expr, expr_t);
1911         } else {
1912             type_error_struct!(
1913                 self.tcx().sess,
1914                 field.span,
1915                 expr_t,
1916                 E0610,
1917                 "`{}` is a primitive type and therefore doesn't have fields",
1918                 expr_t
1919             )
1920             .emit();
1921         }
1922
1923         self.tcx().ty_error()
1924     }
1925
1926     fn suggest_await_on_field_access(
1927         &self,
1928         err: &mut Diagnostic,
1929         field_ident: Ident,
1930         base: &'tcx hir::Expr<'tcx>,
1931         ty: Ty<'tcx>,
1932     ) {
1933         let output_ty = match self.infcx.get_impl_future_output_ty(ty) {
1934             Some(output_ty) => self.resolve_vars_if_possible(output_ty),
1935             _ => return,
1936         };
1937         let mut add_label = true;
1938         if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
1939             // no field access on enum type
1940             if !def.is_enum() {
1941                 if def
1942                     .non_enum_variant()
1943                     .fields
1944                     .iter()
1945                     .any(|field| field.ident(self.tcx) == field_ident)
1946                 {
1947                     add_label = false;
1948                     err.span_label(
1949                         field_ident.span,
1950                         "field not available in `impl Future`, but it is available in its `Output`",
1951                     );
1952                     err.span_suggestion_verbose(
1953                         base.span.shrink_to_hi(),
1954                         "consider `await`ing on the `Future` and access the field of its `Output`",
1955                         ".await".to_string(),
1956                         Applicability::MaybeIncorrect,
1957                     );
1958                 }
1959             }
1960         }
1961         if add_label {
1962             err.span_label(field_ident.span, &format!("field not found in `{}`", ty));
1963         }
1964     }
1965
1966     fn ban_nonexisting_field(
1967         &self,
1968         field: Ident,
1969         base: &'tcx hir::Expr<'tcx>,
1970         expr: &'tcx hir::Expr<'tcx>,
1971         expr_t: Ty<'tcx>,
1972     ) {
1973         debug!(
1974             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
1975             field, base, expr, expr_t
1976         );
1977         let mut err = self.no_such_field_err(field, expr_t, base.hir_id);
1978
1979         match *expr_t.peel_refs().kind() {
1980             ty::Array(_, len) => {
1981                 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
1982             }
1983             ty::RawPtr(..) => {
1984                 self.suggest_first_deref_field(&mut err, expr, base, field);
1985             }
1986             ty::Adt(def, _) if !def.is_enum() => {
1987                 self.suggest_fields_on_recordish(&mut err, def, field, expr.span);
1988             }
1989             ty::Param(param_ty) => {
1990                 self.point_at_param_definition(&mut err, param_ty);
1991             }
1992             ty::Opaque(_, _) => {
1993                 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
1994             }
1995             _ => {}
1996         }
1997
1998         if field.name == kw::Await {
1999             // We know by construction that `<expr>.await` is either on Rust 2015
2000             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2001             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2002             err.help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION));
2003             err.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
2004         }
2005
2006         err.emit();
2007     }
2008
2009     fn ban_private_field_access(
2010         &self,
2011         expr: &hir::Expr<'_>,
2012         expr_t: Ty<'tcx>,
2013         field: Ident,
2014         base_did: DefId,
2015     ) {
2016         let struct_path = self.tcx().def_path_str(base_did);
2017         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2018         let mut err = struct_span_err!(
2019             self.tcx().sess,
2020             field.span,
2021             E0616,
2022             "field `{}` of {} `{}` is private",
2023             field,
2024             kind_name,
2025             struct_path
2026         );
2027         err.span_label(field.span, "private field");
2028         // Also check if an accessible method exists, which is often what is meant.
2029         if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2030         {
2031             self.suggest_method_call(
2032                 &mut err,
2033                 &format!("a method `{}` also exists, call it with parentheses", field),
2034                 field,
2035                 expr_t,
2036                 expr,
2037                 None,
2038             );
2039         }
2040         err.emit();
2041     }
2042
2043     fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2044         let mut err = type_error_struct!(
2045             self.tcx().sess,
2046             field.span,
2047             expr_t,
2048             E0615,
2049             "attempted to take value of method `{}` on type `{}`",
2050             field,
2051             expr_t
2052         );
2053         err.span_label(field.span, "method, not a field");
2054         let expr_is_call =
2055             if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2056                 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2057             {
2058                 expr.hir_id == callee.hir_id
2059             } else {
2060                 false
2061             };
2062         let expr_snippet =
2063             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or(String::new());
2064         let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2065         let after_open = expr.span.lo() + rustc_span::BytePos(1);
2066         let before_close = expr.span.hi() - rustc_span::BytePos(1);
2067
2068         if expr_is_call && is_wrapped {
2069             err.multipart_suggestion(
2070                 "remove wrapping parentheses to call the method",
2071                 vec![
2072                     (expr.span.with_hi(after_open), String::new()),
2073                     (expr.span.with_lo(before_close), String::new()),
2074                 ],
2075                 Applicability::MachineApplicable,
2076             );
2077         } else if !self.expr_in_place(expr.hir_id) {
2078             // Suggest call parentheses inside the wrapping parentheses
2079             let span = if is_wrapped {
2080                 expr.span.with_lo(after_open).with_hi(before_close)
2081             } else {
2082                 expr.span
2083             };
2084             self.suggest_method_call(
2085                 &mut err,
2086                 "use parentheses to call the method",
2087                 field,
2088                 expr_t,
2089                 expr,
2090                 Some(span),
2091             );
2092         } else {
2093             let mut found = false;
2094
2095             if let ty::RawPtr(ty_and_mut) = expr_t.kind() {
2096                 if let ty::Adt(adt_def, _) = ty_and_mut.ty.kind() {
2097                     if adt_def.variants.len() == 1
2098                         && adt_def
2099                             .variants
2100                             .iter()
2101                             .next()
2102                             .unwrap()
2103                             .fields
2104                             .iter()
2105                             .any(|f| f.ident(self.tcx) == field)
2106                     {
2107                         if let Some(dot_loc) = expr_snippet.rfind('.') {
2108                             found = true;
2109                             err.span_suggestion(
2110                                 expr.span.with_hi(expr.span.lo() + BytePos::from_usize(dot_loc)),
2111                                 "to access the field, dereference first",
2112                                 format!("(*{})", &expr_snippet[0..dot_loc]),
2113                                 Applicability::MaybeIncorrect,
2114                             );
2115                         }
2116                     }
2117                 }
2118             }
2119
2120             if !found {
2121                 err.help("methods are immutable and cannot be assigned to");
2122             }
2123         }
2124
2125         err.emit();
2126     }
2127
2128     fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2129         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2130         let generic_param = generics.type_param(&param, self.tcx);
2131         if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2132             return;
2133         }
2134         let param_def_id = generic_param.def_id;
2135         let param_hir_id = match param_def_id.as_local() {
2136             Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2137             None => return,
2138         };
2139         let param_span = self.tcx.hir().span(param_hir_id);
2140         let param_name = self.tcx.hir().ty_param_name(param_hir_id);
2141
2142         err.span_label(param_span, &format!("type parameter '{}' declared here", param_name));
2143     }
2144
2145     fn suggest_fields_on_recordish(
2146         &self,
2147         err: &mut Diagnostic,
2148         def: &'tcx ty::AdtDef,
2149         field: Ident,
2150         access_span: Span,
2151     ) {
2152         if let Some(suggested_field_name) =
2153             self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2154         {
2155             err.span_suggestion(
2156                 field.span,
2157                 "a field with a similar name exists",
2158                 suggested_field_name.to_string(),
2159                 Applicability::MaybeIncorrect,
2160             );
2161         } else {
2162             err.span_label(field.span, "unknown field");
2163             let struct_variant_def = def.non_enum_variant();
2164             let field_names = self.available_field_names(struct_variant_def, access_span);
2165             if !field_names.is_empty() {
2166                 err.note(&format!(
2167                     "available fields are: {}",
2168                     self.name_series_display(field_names),
2169                 ));
2170             }
2171         }
2172     }
2173
2174     fn maybe_suggest_array_indexing(
2175         &self,
2176         err: &mut Diagnostic,
2177         expr: &hir::Expr<'_>,
2178         base: &hir::Expr<'_>,
2179         field: Ident,
2180         len: ty::Const<'tcx>,
2181     ) {
2182         if let (Some(len), Ok(user_index)) =
2183             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2184         {
2185             if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2186                 let help = "instead of using tuple indexing, use array indexing";
2187                 let suggestion = format!("{}[{}]", base, field);
2188                 let applicability = if len < user_index {
2189                     Applicability::MachineApplicable
2190                 } else {
2191                     Applicability::MaybeIncorrect
2192                 };
2193                 err.span_suggestion(expr.span, help, suggestion, applicability);
2194             }
2195         }
2196     }
2197
2198     fn suggest_first_deref_field(
2199         &self,
2200         err: &mut Diagnostic,
2201         expr: &hir::Expr<'_>,
2202         base: &hir::Expr<'_>,
2203         field: Ident,
2204     ) {
2205         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2206             let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
2207             let suggestion = format!("(*{}).{}", base, field);
2208             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2209         }
2210     }
2211
2212     fn no_such_field_err(
2213         &self,
2214         field: Ident,
2215         expr_t: Ty<'tcx>,
2216         id: HirId,
2217     ) -> DiagnosticBuilder<'_, ErrorReported> {
2218         let span = field.span;
2219         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2220
2221         let mut err = type_error_struct!(
2222             self.tcx().sess,
2223             field.span,
2224             expr_t,
2225             E0609,
2226             "no field `{}` on type `{}`",
2227             field,
2228             expr_t
2229         );
2230
2231         // try to add a suggestion in case the field is a nested field of a field of the Adt
2232         if let Some((fields, substs)) = self.get_field_candidates(span, expr_t) {
2233             for candidate_field in fields.iter() {
2234                 if let Some(field_path) = self.check_for_nested_field(
2235                     span,
2236                     field,
2237                     candidate_field,
2238                     substs,
2239                     vec![],
2240                     self.tcx.parent_module(id).to_def_id(),
2241                 ) {
2242                     let field_path_str = field_path
2243                         .iter()
2244                         .map(|id| id.name.to_ident_string())
2245                         .collect::<Vec<String>>()
2246                         .join(".");
2247                     debug!("field_path_str: {:?}", field_path_str);
2248
2249                     err.span_suggestion_verbose(
2250                         field.span.shrink_to_lo(),
2251                         "one of the expressions' fields has a field of the same name",
2252                         format!("{}.", field_path_str),
2253                         Applicability::MaybeIncorrect,
2254                     );
2255                 }
2256             }
2257         }
2258         err
2259     }
2260
2261     fn get_field_candidates(
2262         &self,
2263         span: Span,
2264         base_t: Ty<'tcx>,
2265     ) -> Option<(&Vec<ty::FieldDef>, SubstsRef<'tcx>)> {
2266         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_t);
2267
2268         for (base_t, _) in self.autoderef(span, base_t) {
2269             match base_t.kind() {
2270                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2271                     let fields = &base_def.non_enum_variant().fields;
2272                     // For compile-time reasons put a limit on number of fields we search
2273                     if fields.len() > 100 {
2274                         return None;
2275                     }
2276                     return Some((fields, substs));
2277                 }
2278                 _ => {}
2279             }
2280         }
2281         None
2282     }
2283
2284     /// This method is called after we have encountered a missing field error to recursively
2285     /// search for the field
2286     fn check_for_nested_field(
2287         &self,
2288         span: Span,
2289         target_field: Ident,
2290         candidate_field: &ty::FieldDef,
2291         subst: SubstsRef<'tcx>,
2292         mut field_path: Vec<Ident>,
2293         id: DefId,
2294     ) -> Option<Vec<Ident>> {
2295         debug!(
2296             "check_for_nested_field(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2297             span, candidate_field, field_path
2298         );
2299
2300         if candidate_field.ident(self.tcx) == target_field {
2301             Some(field_path)
2302         } else if field_path.len() > 3 {
2303             // For compile-time reasons and to avoid infinite recursion we only check for fields
2304             // up to a depth of three
2305             None
2306         } else {
2307             // recursively search fields of `candidate_field` if it's a ty::Adt
2308
2309             field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2310             let field_ty = candidate_field.ty(self.tcx, subst);
2311             if let Some((nested_fields, subst)) = self.get_field_candidates(span, field_ty) {
2312                 for field in nested_fields.iter() {
2313                     let accessible = field.vis.is_accessible_from(id, self.tcx);
2314                     if accessible {
2315                         let ident = field.ident(self.tcx).normalize_to_macros_2_0();
2316                         if ident == target_field {
2317                             return Some(field_path);
2318                         }
2319                         let field_path = field_path.clone();
2320                         if let Some(path) = self.check_for_nested_field(
2321                             span,
2322                             target_field,
2323                             field,
2324                             subst,
2325                             field_path,
2326                             id,
2327                         ) {
2328                             return Some(path);
2329                         }
2330                     }
2331                 }
2332             }
2333             None
2334         }
2335     }
2336
2337     fn check_expr_index(
2338         &self,
2339         base: &'tcx hir::Expr<'tcx>,
2340         idx: &'tcx hir::Expr<'tcx>,
2341         expr: &'tcx hir::Expr<'tcx>,
2342     ) -> Ty<'tcx> {
2343         let base_t = self.check_expr(&base);
2344         let idx_t = self.check_expr(&idx);
2345
2346         if base_t.references_error() {
2347             base_t
2348         } else if idx_t.references_error() {
2349             idx_t
2350         } else {
2351             let base_t = self.structurally_resolved_type(base.span, base_t);
2352             match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2353                 Some((index_ty, element_ty)) => {
2354                     // two-phase not needed because index_ty is never mutable
2355                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2356                     element_ty
2357                 }
2358                 None => {
2359                     let mut err = type_error_struct!(
2360                         self.tcx.sess,
2361                         expr.span,
2362                         base_t,
2363                         E0608,
2364                         "cannot index into a value of type `{}`",
2365                         base_t
2366                     );
2367                     // Try to give some advice about indexing tuples.
2368                     if let ty::Tuple(..) = base_t.kind() {
2369                         let mut needs_note = true;
2370                         // If the index is an integer, we can show the actual
2371                         // fixed expression:
2372                         if let ExprKind::Lit(ref lit) = idx.kind {
2373                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2374                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2375                                 if let Ok(snip) = snip {
2376                                     err.span_suggestion(
2377                                         expr.span,
2378                                         "to access tuple elements, use",
2379                                         format!("{}.{}", snip, i),
2380                                         Applicability::MachineApplicable,
2381                                     );
2382                                     needs_note = false;
2383                                 }
2384                             }
2385                         }
2386                         if needs_note {
2387                             err.help(
2388                                 "to access tuple elements, use tuple indexing \
2389                                         syntax (e.g., `tuple.0`)",
2390                             );
2391                         }
2392                     }
2393                     err.emit();
2394                     self.tcx.ty_error()
2395                 }
2396             }
2397         }
2398     }
2399
2400     fn check_expr_yield(
2401         &self,
2402         value: &'tcx hir::Expr<'tcx>,
2403         expr: &'tcx hir::Expr<'tcx>,
2404         src: &'tcx hir::YieldSource,
2405     ) -> Ty<'tcx> {
2406         match self.resume_yield_tys {
2407             Some((resume_ty, yield_ty)) => {
2408                 self.check_expr_coercable_to_type(&value, yield_ty, None);
2409
2410                 resume_ty
2411             }
2412             // Given that this `yield` expression was generated as a result of lowering a `.await`,
2413             // we know that the yield type must be `()`; however, the context won't contain this
2414             // information. Hence, we check the source of the yield expression here and check its
2415             // value's type against `()` (this check should always hold).
2416             None if src.is_await() => {
2417                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2418                 self.tcx.mk_unit()
2419             }
2420             _ => {
2421                 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2422                 // Avoid expressions without types during writeback (#78653).
2423                 self.check_expr(value);
2424                 self.tcx.mk_unit()
2425             }
2426         }
2427     }
2428
2429     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2430         let needs = if is_input { Needs::None } else { Needs::MutPlace };
2431         let ty = self.check_expr_with_needs(expr, needs);
2432         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2433
2434         if !is_input && !expr.is_syntactic_place_expr() {
2435             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2436             err.span_label(expr.span, "cannot assign to this expression");
2437             err.emit();
2438         }
2439
2440         // If this is an input value, we require its type to be fully resolved
2441         // at this point. This allows us to provide helpful coercions which help
2442         // pass the type candidate list in a later pass.
2443         //
2444         // We don't require output types to be resolved at this point, which
2445         // allows them to be inferred based on how they are used later in the
2446         // function.
2447         if is_input {
2448             let ty = self.structurally_resolved_type(expr.span, ty);
2449             match *ty.kind() {
2450                 ty::FnDef(..) => {
2451                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2452                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2453                 }
2454                 ty::Ref(_, base_ty, mutbl) => {
2455                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2456                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2457                 }
2458                 _ => {}
2459             }
2460         }
2461     }
2462
2463     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2464         for (op, _op_sp) in asm.operands {
2465             match op {
2466                 hir::InlineAsmOperand::In { expr, .. } => {
2467                     self.check_expr_asm_operand(expr, true);
2468                 }
2469                 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2470                 | hir::InlineAsmOperand::InOut { expr, .. } => {
2471                     self.check_expr_asm_operand(expr, false);
2472                 }
2473                 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2474                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2475                     self.check_expr_asm_operand(in_expr, true);
2476                     if let Some(out_expr) = out_expr {
2477                         self.check_expr_asm_operand(out_expr, false);
2478                     }
2479                 }
2480                 hir::InlineAsmOperand::Const { anon_const } => {
2481                     self.to_const(anon_const);
2482                 }
2483                 hir::InlineAsmOperand::Sym { expr } => {
2484                     self.check_expr(expr);
2485                 }
2486             }
2487         }
2488         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2489             self.tcx.types.never
2490         } else {
2491             self.tcx.mk_unit()
2492         }
2493     }
2494 }
2495
2496 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2497     Some(match ty.kind() {
2498         ty::Bool => "true",
2499         ty::Char => "'a'",
2500         ty::Int(_) | ty::Uint(_) => "42",
2501         ty::Float(_) => "3.14159",
2502         ty::Error(_) | ty::Never => return None,
2503         _ => "value",
2504     })
2505 }