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