compiler/rustc_typeck/src/check/expr.rs

   1 //! Type checking expressions.
   2 //!
   3 //! See `mod.rs` for more context on type checking in general.
   4
   5 use crate::astconv::AstConv as _;
   6 use crate::check::cast;
   7 use crate::check::coercion::CoerceMany;
   8 use crate::check::fatally_break_rust;
   9 use crate::check::method::SelfSource;
  10 use crate::check::report_unexpected_variant_res;
  11 use crate::check::BreakableCtxt;
  12 use crate::check::Diverges;
  13 use crate::check::DynamicCoerceMany;
  14 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
  15 use crate::check::FnCtxt;
  16 use crate::check::Needs;
  17 use crate::check::TupleArgumentsFlag::DontTupleArguments;
  18 use crate::errors::{
  19     FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
  20     YieldExprOutsideOfGenerator,
  21 };
  22 use crate::type_error_struct;
  23
  24 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
  25 use rustc_ast as ast;
  26 use rustc_data_structures::fx::FxHashMap;
  27 use rustc_data_structures::stack::ensure_sufficient_stack;
  28 use rustc_errors::Diagnostic;
  29 use rustc_errors::ErrorGuaranteed;
  30 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
  31 use rustc_hir as hir;
  32 use rustc_hir::def::{CtorKind, DefKind, Res};
  33 use rustc_hir::def_id::DefId;
  34 use rustc_hir::intravisit::Visitor;
  35 use rustc_hir::{ExprKind, HirId, QPath};
  36 use rustc_infer::infer;
  37 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
  38 use rustc_infer::infer::InferOk;
  39 use rustc_middle::middle::stability;
  40 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
  41 use rustc_middle::ty::error::ExpectedFound;
  42 use rustc_middle::ty::error::TypeError::{FieldMisMatch, Sorts};
  43 use rustc_middle::ty::subst::SubstsRef;
  44 use rustc_middle::ty::{self, AdtKind, Ty, TypeFoldable};
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::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 Diagnostic),
  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 Diagnostic),
  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, 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 && let Some(last_expr) = body.expr {
 813                 span = last_expr.span;
 814             }
 815         }
 816         ret_coercion.borrow_mut().coerce(
 817             self,
 818             &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
 819             return_expr,
 820             return_expr_ty,
 821         );
 822     }
 823
 824     pub(crate) fn check_lhs_assignable(
 825         &self,
 826         lhs: &'tcx hir::Expr<'tcx>,
 827         err_code: &'static str,
 828         op_span: Span,
 829     ) {
 830         if lhs.is_syntactic_place_expr() {
 831             return;
 832         }
 833
 834         // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
 835         let mut err = self.tcx.sess.struct_span_err_with_code(
 836             op_span,
 837             "invalid left-hand side of assignment",
 838             DiagnosticId::Error(err_code.into()),
 839         );
 840         err.span_label(lhs.span, "cannot assign to this expression");
 841
 842         self.comes_from_while_condition(lhs.hir_id, |expr| {
 843             err.span_suggestion_verbose(
 844                 expr.span.shrink_to_lo(),
 845                 "you might have meant to use pattern destructuring",
 846                 "let ".to_string(),
 847                 Applicability::MachineApplicable,
 848             );
 849         });
 850
 851         err.emit();
 852     }
 853
 854     // Check if an expression `original_expr_id` comes from the condition of a while loop,
 855     // as opposed from the body of a while loop, which we can naively check by iterating
 856     // parents until we find a loop...
 857     pub(super) fn comes_from_while_condition(
 858         &self,
 859         original_expr_id: HirId,
 860         then: impl FnOnce(&hir::Expr<'_>),
 861     ) {
 862         let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
 863         while let Some(node) = self.tcx.hir().find(parent) {
 864             match node {
 865                 hir::Node::Expr(hir::Expr {
 866                     kind:
 867                         hir::ExprKind::Loop(
 868                             hir::Block {
 869                                 expr:
 870                                     Some(hir::Expr {
 871                                         kind:
 872                                             hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
 873                                         ..
 874                                     }),
 875                                 ..
 876                             },
 877                             _,
 878                             hir::LoopSource::While,
 879                             _,
 880                         ),
 881                     ..
 882                 }) => {
 883                     // Check if our original expression is a child of the condition of a while loop
 884                     let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
 885                         self.tcx.hir().find_parent_node(*id)
 886                     })
 887                     .take_while(|id| *id != parent)
 888                     .any(|id| id == expr.hir_id);
 889                     // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
 890                     // where `while let` was more likely intended.
 891                     if expr_is_ancestor {
 892                         then(expr);
 893                     }
 894                     break;
 895                 }
 896                 hir::Node::Item(_)
 897                 | hir::Node::ImplItem(_)
 898                 | hir::Node::TraitItem(_)
 899                 | hir::Node::Crate(_) => break,
 900                 _ => {
 901                     parent = self.tcx.hir().get_parent_node(parent);
 902                 }
 903             }
 904         }
 905     }
 906
 907     // A generic function for checking the 'then' and 'else' clauses in an 'if'
 908     // or 'if-else' expression.
 909     fn check_then_else(
 910         &self,
 911         cond_expr: &'tcx hir::Expr<'tcx>,
 912         then_expr: &'tcx hir::Expr<'tcx>,
 913         opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
 914         sp: Span,
 915         orig_expected: Expectation<'tcx>,
 916     ) -> Ty<'tcx> {
 917         let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
 918
 919         self.warn_if_unreachable(
 920             cond_expr.hir_id,
 921             then_expr.span,
 922             "block in `if` or `while` expression",
 923         );
 924
 925         let cond_diverges = self.diverges.get();
 926         self.diverges.set(Diverges::Maybe);
 927
 928         let expected = orig_expected.adjust_for_branches(self);
 929         let then_ty = self.check_expr_with_expectation(then_expr, expected);
 930         let then_diverges = self.diverges.get();
 931         self.diverges.set(Diverges::Maybe);
 932
 933         // We've already taken the expected type's preferences
 934         // into account when typing the `then` branch. To figure
 935         // out the initial shot at a LUB, we thus only consider
 936         // `expected` if it represents a *hard* constraint
 937         // (`only_has_type`); otherwise, we just go with a
 938         // fresh type variable.
 939         let coerce_to_ty = expected.coercion_target_type(self, sp);
 940         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
 941
 942         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
 943
 944         if let Some(else_expr) = opt_else_expr {
 945             let else_ty = if sp.desugaring_kind() == Some(DesugaringKind::LetElse) {
 946                 // todo introduce `check_expr_with_expectation(.., Expectation::LetElse)`
 947                 //   for errors that point to the offending expression rather than the entire block.
 948                 //   We could use `check_expr_eq_type(.., tcx.types.never)`, but then there is no
 949                 //   way to detect that the expected type originated from let-else and provide
 950                 //   a customized error.
 951                 let else_ty = self.check_expr(else_expr);
 952                 let cause = self.cause(else_expr.span, ObligationCauseCode::LetElse);
 953
 954                 if let Some(mut err) =
 955                     self.demand_eqtype_with_origin(&cause, self.tcx.types.never, else_ty)
 956                 {
 957                     err.emit();
 958                     self.tcx.ty_error()
 959                 } else {
 960                     else_ty
 961                 }
 962             } else {
 963                 self.check_expr_with_expectation(else_expr, expected)
 964             };
 965             let else_diverges = self.diverges.get();
 966
 967             let opt_suggest_box_span =
 968                 self.opt_suggest_box_span(else_expr.span, else_ty, orig_expected);
 969             let if_cause =
 970                 self.if_cause(sp, then_expr, else_expr, then_ty, else_ty, opt_suggest_box_span);
 971
 972             coerce.coerce(self, &if_cause, else_expr, else_ty);
 973
 974             // We won't diverge unless both branches do (or the condition does).
 975             self.diverges.set(cond_diverges | then_diverges & else_diverges);
 976         } else {
 977             self.if_fallback_coercion(sp, then_expr, &mut coerce);
 978
 979             // If the condition is false we can't diverge.
 980             self.diverges.set(cond_diverges);
 981         }
 982
 983         let result_ty = coerce.complete(self);
 984         if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
 985     }
 986
 987     /// Type check assignment expression `expr` of form `lhs = rhs`.
 988     /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
 989     fn check_expr_assign(
 990         &self,
 991         expr: &'tcx hir::Expr<'tcx>,
 992         expected: Expectation<'tcx>,
 993         lhs: &'tcx hir::Expr<'tcx>,
 994         rhs: &'tcx hir::Expr<'tcx>,
 995         span: Span,
 996     ) -> Ty<'tcx> {
 997         let expected_ty = expected.coercion_target_type(self, expr.span);
 998         if expected_ty == self.tcx.types.bool {
 999             // The expected type is `bool` but this will result in `()` so we can reasonably
1000             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1001             // The likely cause of this is `if foo = bar { .. }`.
1002             let actual_ty = self.tcx.mk_unit();
1003             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1004             let lhs_ty = self.check_expr(&lhs);
1005             let rhs_ty = self.check_expr(&rhs);
1006             let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1007                 (Applicability::MachineApplicable, true)
1008             } else {
1009                 (Applicability::MaybeIncorrect, false)
1010             };
1011             if !lhs.is_syntactic_place_expr() && !matches!(lhs.kind, hir::ExprKind::Lit(_)) {
1012                 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1013                 let hir = self.tcx.hir();
1014                 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1015                     hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1016                 {
1017                     err.span_suggestion_verbose(
1018                         expr.span.shrink_to_lo(),
1019                         "you might have meant to use pattern matching",
1020                         "let ".to_string(),
1021                         applicability,
1022                     );
1023                 };
1024             }
1025             if eq {
1026                 err.span_suggestion_verbose(
1027                     span,
1028                     "you might have meant to compare for equality",
1029                     "==".to_string(),
1030                     applicability,
1031                 );
1032             }
1033
1034             // If the assignment expression itself is ill-formed, don't
1035             // bother emitting another error
1036             if lhs_ty.references_error() || rhs_ty.references_error() {
1037                 err.delay_as_bug()
1038             } else {
1039                 err.emit();
1040             }
1041             return self.tcx.ty_error();
1042         }
1043
1044         self.check_lhs_assignable(lhs, "E0070", span);
1045
1046         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1047         let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty, Some(lhs));
1048
1049         self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1050
1051         if lhs_ty.references_error() || rhs_ty.references_error() {
1052             self.tcx.ty_error()
1053         } else {
1054             self.tcx.mk_unit()
1055         }
1056     }
1057
1058     fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1059         // for let statements, this is done in check_stmt
1060         let init = let_expr.init;
1061         self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1062         // otherwise check exactly as a let statement
1063         self.check_decl(let_expr.into());
1064         // but return a bool, for this is a boolean expression
1065         self.tcx.types.bool
1066     }
1067
1068     fn check_expr_loop(
1069         &self,
1070         body: &'tcx hir::Block<'tcx>,
1071         source: hir::LoopSource,
1072         expected: Expectation<'tcx>,
1073         expr: &'tcx hir::Expr<'tcx>,
1074     ) -> Ty<'tcx> {
1075         let coerce = match source {
1076             // you can only use break with a value from a normal `loop { }`
1077             hir::LoopSource::Loop => {
1078                 let coerce_to = expected.coercion_target_type(self, body.span);
1079                 Some(CoerceMany::new(coerce_to))
1080             }
1081
1082             hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1083         };
1084
1085         let ctxt = BreakableCtxt {
1086             coerce,
1087             may_break: false, // Will get updated if/when we find a `break`.
1088         };
1089
1090         let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1091             self.check_block_no_value(&body);
1092         });
1093
1094         if ctxt.may_break {
1095             // No way to know whether it's diverging because
1096             // of a `break` or an outer `break` or `return`.
1097             self.diverges.set(Diverges::Maybe);
1098         }
1099
1100         // If we permit break with a value, then result type is
1101         // the LUB of the breaks (possibly ! if none); else, it
1102         // is nil. This makes sense because infinite loops
1103         // (which would have type !) are only possible iff we
1104         // permit break with a value [1].
1105         if ctxt.coerce.is_none() && !ctxt.may_break {
1106             // [1]
1107             self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1108         }
1109         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1110     }
1111
1112     /// Checks a method call.
1113     fn check_method_call(
1114         &self,
1115         expr: &'tcx hir::Expr<'tcx>,
1116         segment: &hir::PathSegment<'_>,
1117         args: &'tcx [hir::Expr<'tcx>],
1118         expected: Expectation<'tcx>,
1119     ) -> Ty<'tcx> {
1120         let rcvr = &args[0];
1121         let rcvr_t = self.check_expr(&rcvr);
1122         // no need to check for bot/err -- callee does that
1123         let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
1124         let span = segment.ident.span;
1125
1126         let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1127             Ok(method) => {
1128                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1129                 // trigger this codepath causing `structuraly_resolved_type` to emit an error.
1130
1131                 self.write_method_call(expr.hir_id, method);
1132                 Ok(method)
1133             }
1134             Err(error) => {
1135                 if segment.ident.name != kw::Empty {
1136                     if let Some(mut err) = self.report_method_error(
1137                         span,
1138                         rcvr_t,
1139                         segment.ident,
1140                         SelfSource::MethodCall(&args[0]),
1141                         error,
1142                         Some(args),
1143                     ) {
1144                         err.emit();
1145                     }
1146                 }
1147                 Err(())
1148             }
1149         };
1150
1151         // Call the generic checker.
1152         self.check_method_argument_types(
1153             span,
1154             expr,
1155             method,
1156             &args[1..],
1157             DontTupleArguments,
1158             expected,
1159         )
1160     }
1161
1162     fn check_expr_cast(
1163         &self,
1164         e: &'tcx hir::Expr<'tcx>,
1165         t: &'tcx hir::Ty<'tcx>,
1166         expr: &'tcx hir::Expr<'tcx>,
1167     ) -> Ty<'tcx> {
1168         // Find the type of `e`. Supply hints based on the type we are casting to,
1169         // if appropriate.
1170         let t_cast = self.to_ty_saving_user_provided_ty(t);
1171         let t_cast = self.resolve_vars_if_possible(t_cast);
1172         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1173         let t_expr = self.resolve_vars_if_possible(t_expr);
1174
1175         // Eagerly check for some obvious errors.
1176         if t_expr.references_error() || t_cast.references_error() {
1177             self.tcx.ty_error()
1178         } else {
1179             // Defer other checks until we're done type checking.
1180             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1181             match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1182                 Ok(cast_check) => {
1183                     debug!(
1184                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1185                         t_cast, t_expr, cast_check,
1186                     );
1187                     deferred_cast_checks.push(cast_check);
1188                     t_cast
1189                 }
1190                 Err(ErrorGuaranteed) => self.tcx.ty_error(),
1191             }
1192         }
1193     }
1194
1195     fn check_expr_array(
1196         &self,
1197         args: &'tcx [hir::Expr<'tcx>],
1198         expected: Expectation<'tcx>,
1199         expr: &'tcx hir::Expr<'tcx>,
1200     ) -> Ty<'tcx> {
1201         let element_ty = if !args.is_empty() {
1202             let coerce_to = expected
1203                 .to_option(self)
1204                 .and_then(|uty| match *uty.kind() {
1205                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1206                     _ => None,
1207                 })
1208                 .unwrap_or_else(|| {
1209                     self.next_ty_var(TypeVariableOrigin {
1210                         kind: TypeVariableOriginKind::TypeInference,
1211                         span: expr.span,
1212                     })
1213                 });
1214             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1215             assert_eq!(self.diverges.get(), Diverges::Maybe);
1216             for e in args {
1217                 let e_ty = self.check_expr_with_hint(e, coerce_to);
1218                 let cause = self.misc(e.span);
1219                 coerce.coerce(self, &cause, e, e_ty);
1220             }
1221             coerce.complete(self)
1222         } else {
1223             self.next_ty_var(TypeVariableOrigin {
1224                 kind: TypeVariableOriginKind::TypeInference,
1225                 span: expr.span,
1226             })
1227         };
1228         self.tcx.mk_array(element_ty, args.len() as u64)
1229     }
1230
1231     fn check_expr_const_block(
1232         &self,
1233         anon_const: &'tcx hir::AnonConst,
1234         expected: Expectation<'tcx>,
1235         _expr: &'tcx hir::Expr<'tcx>,
1236     ) -> Ty<'tcx> {
1237         let body = self.tcx.hir().body(anon_const.body);
1238
1239         // Create a new function context.
1240         let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1241         crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1242
1243         let ty = fcx.check_expr_with_expectation(&body.value, expected);
1244         fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1245         fcx.write_ty(anon_const.hir_id, ty);
1246         ty
1247     }
1248
1249     fn check_expr_repeat(
1250         &self,
1251         element: &'tcx hir::Expr<'tcx>,
1252         count: &'tcx hir::ArrayLen,
1253         expected: Expectation<'tcx>,
1254         _expr: &'tcx hir::Expr<'tcx>,
1255     ) -> Ty<'tcx> {
1256         let tcx = self.tcx;
1257         let count = self.array_length_to_const(count);
1258
1259         let uty = match expected {
1260             ExpectHasType(uty) => match *uty.kind() {
1261                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1262                 _ => None,
1263             },
1264             _ => None,
1265         };
1266
1267         let (element_ty, t) = match uty {
1268             Some(uty) => {
1269                 self.check_expr_coercable_to_type(&element, uty, None);
1270                 (uty, uty)
1271             }
1272             None => {
1273                 let ty = self.next_ty_var(TypeVariableOrigin {
1274                     kind: TypeVariableOriginKind::MiscVariable,
1275                     span: element.span,
1276                 });
1277                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1278                 (element_ty, ty)
1279             }
1280         };
1281
1282         if element_ty.references_error() {
1283             return tcx.ty_error();
1284         }
1285
1286         tcx.mk_ty(ty::Array(t, count))
1287     }
1288
1289     fn check_expr_tuple(
1290         &self,
1291         elts: &'tcx [hir::Expr<'tcx>],
1292         expected: Expectation<'tcx>,
1293         expr: &'tcx hir::Expr<'tcx>,
1294     ) -> Ty<'tcx> {
1295         let flds = expected.only_has_type(self).and_then(|ty| {
1296             let ty = self.resolve_vars_with_obligations(ty);
1297             match ty.kind() {
1298                 ty::Tuple(flds) => Some(&flds[..]),
1299                 _ => None,
1300             }
1301         });
1302
1303         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1304             Some(fs) if i < fs.len() => {
1305                 let ety = fs[i];
1306                 self.check_expr_coercable_to_type(&e, ety, None);
1307                 ety
1308             }
1309             _ => self.check_expr_with_expectation(&e, NoExpectation),
1310         });
1311         let tuple = self.tcx.mk_tup(elt_ts_iter);
1312         if tuple.references_error() {
1313             self.tcx.ty_error()
1314         } else {
1315             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1316             tuple
1317         }
1318     }
1319
1320     fn check_expr_struct(
1321         &self,
1322         expr: &hir::Expr<'_>,
1323         expected: Expectation<'tcx>,
1324         qpath: &QPath<'_>,
1325         fields: &'tcx [hir::ExprField<'tcx>],
1326         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1327     ) -> Ty<'tcx> {
1328         // Find the relevant variant
1329         let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1330             self.check_struct_fields_on_error(fields, base_expr);
1331             return self.tcx.ty_error();
1332         };
1333
1334         // Prohibit struct expressions when non-exhaustive flag is set.
1335         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1336         if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
1337             self.tcx
1338                 .sess
1339                 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1340         }
1341
1342         self.check_expr_struct_fields(
1343             adt_ty,
1344             expected,
1345             expr.hir_id,
1346             qpath.span(),
1347             variant,
1348             fields,
1349             base_expr,
1350             expr.span,
1351         );
1352
1353         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1354         adt_ty
1355     }
1356
1357     fn check_expr_struct_fields(
1358         &self,
1359         adt_ty: Ty<'tcx>,
1360         expected: Expectation<'tcx>,
1361         expr_id: hir::HirId,
1362         span: Span,
1363         variant: &'tcx ty::VariantDef,
1364         ast_fields: &'tcx [hir::ExprField<'tcx>],
1365         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1366         expr_span: Span,
1367     ) {
1368         let tcx = self.tcx;
1369
1370         let adt_ty_hint = self
1371             .expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
1372             .get(0)
1373             .cloned()
1374             .unwrap_or(adt_ty);
1375         // re-link the regions that EIfEO can erase.
1376         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1377
1378         let (substs, adt_kind, kind_name) = match adt_ty.kind() {
1379             ty::Adt(adt, substs) => (substs, adt.adt_kind(), adt.variant_descr()),
1380             _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields"),
1381         };
1382
1383         let mut remaining_fields = variant
1384             .fields
1385             .iter()
1386             .enumerate()
1387             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1388             .collect::<FxHashMap<_, _>>();
1389
1390         let mut seen_fields = FxHashMap::default();
1391
1392         let mut error_happened = false;
1393
1394         // Type-check each field.
1395         for field in ast_fields {
1396             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1397             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1398                 seen_fields.insert(ident, field.span);
1399                 self.write_field_index(field.hir_id, i);
1400
1401                 // We don't look at stability attributes on
1402                 // struct-like enums (yet...), but it's definitely not
1403                 // a bug to have constructed one.
1404                 if adt_kind != AdtKind::Enum {
1405                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1406                 }
1407
1408                 self.field_ty(field.span, v_field, substs)
1409             } else {
1410                 error_happened = true;
1411                 if let Some(prev_span) = seen_fields.get(&ident) {
1412                     tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1413                         span: field.ident.span,
1414                         prev_span: *prev_span,
1415                         ident,
1416                     });
1417                 } else {
1418                     self.report_unknown_field(
1419                         adt_ty, variant, field, ast_fields, kind_name, expr_span,
1420                     );
1421                 }
1422
1423                 tcx.ty_error()
1424             };
1425
1426             // Make sure to give a type to the field even if there's
1427             // an error, so we can continue type-checking.
1428             self.check_expr_coercable_to_type(&field.expr, field_type, None);
1429         }
1430
1431         // Make sure the programmer specified correct number of fields.
1432         if kind_name == "union" {
1433             if ast_fields.len() != 1 {
1434                 struct_span_err!(
1435                     tcx.sess,
1436                     span,
1437                     E0784,
1438                     "union expressions should have exactly one field",
1439                 )
1440                 .emit();
1441             }
1442         }
1443
1444         // If check_expr_struct_fields hit an error, do not attempt to populate
1445         // the fields with the base_expr. This could cause us to hit errors later
1446         // when certain fields are assumed to exist that in fact do not.
1447         if error_happened {
1448             return;
1449         }
1450
1451         if let Some(base_expr) = base_expr {
1452             // FIXME: We are currently creating two branches here in order to maintain
1453             // consistency. But they should be merged as much as possible.
1454             let fru_tys = if self.tcx.features().type_changing_struct_update {
1455                 let base_ty = self.check_expr(base_expr);
1456                 match adt_ty.kind() {
1457                     ty::Adt(adt, substs) if adt.is_struct() => {
1458                         match base_ty.kind() {
1459                             ty::Adt(base_adt, base_subs) if adt == base_adt => {
1460                                 variant
1461                                     .fields
1462                                     .iter()
1463                                     .map(|f| {
1464                                         let fru_ty = self.normalize_associated_types_in(
1465                                             expr_span,
1466                                             self.field_ty(base_expr.span, f, base_subs),
1467                                         );
1468                                         let ident = self
1469                                             .tcx
1470                                             .adjust_ident(f.ident(self.tcx), variant.def_id);
1471                                         if let Some(_) = remaining_fields.remove(&ident) {
1472                                             let target_ty =
1473                                                 self.field_ty(base_expr.span, f, substs);
1474                                             let cause = self.misc(base_expr.span);
1475                                             match self
1476                                                 .at(&cause, self.param_env)
1477                                                 .sup(target_ty, fru_ty)
1478                                             {
1479                                                 Ok(InferOk { obligations, value: () }) => {
1480                                                     self.register_predicates(obligations)
1481                                                 }
1482                                                 // FIXME: Need better diagnostics for `FieldMisMatch` error
1483                                                 Err(_) => {
1484                                                     self.report_mismatched_types(
1485                                                         &cause,
1486                                                         target_ty,
1487                                                         fru_ty,
1488                                                         FieldMisMatch(variant.name, ident.name),
1489                                                     )
1490                                                     .emit();
1491                                                 }
1492                                             }
1493                                         }
1494                                         fru_ty
1495                                     })
1496                                     .collect()
1497                             }
1498                             _ => {
1499                                 self.report_mismatched_types(
1500                                     &self.misc(base_expr.span),
1501                                     adt_ty,
1502                                     base_ty,
1503                                     Sorts(ExpectedFound::new(true, adt_ty, base_ty)),
1504                                 )
1505                                 .emit();
1506                                 return;
1507                             }
1508                         }
1509                     }
1510                     _ => {
1511                         self.tcx
1512                             .sess
1513                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1514                         return;
1515                     }
1516                 }
1517             } else {
1518                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1519                     let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1520                     let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1521                         (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1522                         _ => false,
1523                     };
1524                     if self.tcx.sess.is_nightly_build() && same_adt {
1525                         feature_err(
1526                             &self.tcx.sess.parse_sess,
1527                             sym::type_changing_struct_update,
1528                             base_expr.span,
1529                             "type changing struct updating is experimental",
1530                         )
1531                         .emit();
1532                     }
1533                 });
1534                 match adt_ty.kind() {
1535                     ty::Adt(adt, substs) if adt.is_struct() => variant
1536                         .fields
1537                         .iter()
1538                         .map(|f| {
1539                             self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1540                         })
1541                         .collect(),
1542                     _ => {
1543                         self.tcx
1544                             .sess
1545                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1546                         return;
1547                     }
1548                 }
1549             };
1550             self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1551         } else if kind_name != "union" && !remaining_fields.is_empty() {
1552             let inaccessible_remaining_fields = remaining_fields.iter().any(|(_, (_, field))| {
1553                 !field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1554             });
1555
1556             if inaccessible_remaining_fields {
1557                 self.report_inaccessible_fields(adt_ty, span);
1558             } else {
1559                 self.report_missing_fields(adt_ty, span, remaining_fields);
1560             }
1561         }
1562     }
1563
1564     fn check_struct_fields_on_error(
1565         &self,
1566         fields: &'tcx [hir::ExprField<'tcx>],
1567         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1568     ) {
1569         for field in fields {
1570             self.check_expr(&field.expr);
1571         }
1572         if let Some(base) = *base_expr {
1573             self.check_expr(&base);
1574         }
1575     }
1576
1577     /// Report an error for a struct field expression when there are fields which aren't provided.
1578     ///
1579     /// ```text
1580     /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1581     ///  --> src/main.rs:8:5
1582     ///   |
1583     /// 8 |     foo::Foo {};
1584     ///   |     ^^^^^^^^ missing `you_can_use_this_field`
1585     ///
1586     /// error: aborting due to previous error
1587     /// ```
1588     fn report_missing_fields(
1589         &self,
1590         adt_ty: Ty<'tcx>,
1591         span: Span,
1592         remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1593     ) {
1594         let len = remaining_fields.len();
1595
1596         let mut displayable_field_names: Vec<&str> =
1597             remaining_fields.keys().map(|ident| ident.as_str()).collect();
1598         // sorting &str primitives here, sort_unstable is ok
1599         displayable_field_names.sort_unstable();
1600
1601         let mut truncated_fields_error = String::new();
1602         let remaining_fields_names = match &displayable_field_names[..] {
1603             [field1] => format!("`{}`", field1),
1604             [field1, field2] => format!("`{}` and `{}`", field1, field2),
1605             [field1, field2, field3] => format!("`{}`, `{}` and `{}`", field1, field2, field3),
1606             _ => {
1607                 truncated_fields_error =
1608                     format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1609                 displayable_field_names
1610                     .iter()
1611                     .take(3)
1612                     .map(|n| format!("`{}`", n))
1613                     .collect::<Vec<_>>()
1614                     .join(", ")
1615             }
1616         };
1617
1618         struct_span_err!(
1619             self.tcx.sess,
1620             span,
1621             E0063,
1622             "missing field{} {}{} in initializer of `{}`",
1623             pluralize!(len),
1624             remaining_fields_names,
1625             truncated_fields_error,
1626             adt_ty
1627         )
1628         .span_label(span, format!("missing {}{}", remaining_fields_names, truncated_fields_error))
1629         .emit();
1630     }
1631
1632     /// Report an error for a struct field expression when there are invisible fields.
1633     ///
1634     /// ```text
1635     /// error: cannot construct `Foo` with struct literal syntax due to inaccessible fields
1636     ///  --> src/main.rs:8:5
1637     ///   |
1638     /// 8 |     foo::Foo {};
1639     ///   |     ^^^^^^^^
1640     ///
1641     /// error: aborting due to previous error
1642     /// ```
1643     fn report_inaccessible_fields(&self, adt_ty: Ty<'tcx>, span: Span) {
1644         self.tcx.sess.span_err(
1645             span,
1646             &format!(
1647                 "cannot construct `{}` with struct literal syntax due to inaccessible fields",
1648                 adt_ty,
1649             ),
1650         );
1651     }
1652
1653     fn report_unknown_field(
1654         &self,
1655         ty: Ty<'tcx>,
1656         variant: &'tcx ty::VariantDef,
1657         field: &hir::ExprField<'_>,
1658         skip_fields: &[hir::ExprField<'_>],
1659         kind_name: &str,
1660         expr_span: Span,
1661     ) {
1662         if variant.is_recovered() {
1663             self.set_tainted_by_errors();
1664             return;
1665         }
1666         let mut err = self.type_error_struct_with_diag(
1667             field.ident.span,
1668             |actual| match ty.kind() {
1669                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1670                     self.tcx.sess,
1671                     field.ident.span,
1672                     E0559,
1673                     "{} `{}::{}` has no field named `{}`",
1674                     kind_name,
1675                     actual,
1676                     variant.name,
1677                     field.ident
1678                 ),
1679                 _ => struct_span_err!(
1680                     self.tcx.sess,
1681                     field.ident.span,
1682                     E0560,
1683                     "{} `{}` has no field named `{}`",
1684                     kind_name,
1685                     actual,
1686                     field.ident
1687                 ),
1688             },
1689             ty,
1690         );
1691
1692         let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1693         match variant.ctor_kind {
1694             CtorKind::Fn => match ty.kind() {
1695                 ty::Adt(adt, ..) if adt.is_enum() => {
1696                     err.span_label(
1697                         variant_ident_span,
1698                         format!(
1699                             "`{adt}::{variant}` defined here",
1700                             adt = ty,
1701                             variant = variant.name,
1702                         ),
1703                     );
1704                     err.span_label(field.ident.span, "field does not exist");
1705                     err.span_suggestion_verbose(
1706                         expr_span,
1707                         &format!(
1708                             "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1709                             adt = ty,
1710                             variant = variant.name,
1711                         ),
1712                         format!(
1713                             "{adt}::{variant}(/* fields */)",
1714                             adt = ty,
1715                             variant = variant.name,
1716                         ),
1717                         Applicability::HasPlaceholders,
1718                     );
1719                 }
1720                 _ => {
1721                     err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1722                     err.span_label(field.ident.span, "field does not exist");
1723                     err.span_suggestion_verbose(
1724                         expr_span,
1725                         &format!(
1726                             "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1727                             adt = ty,
1728                             kind_name = kind_name,
1729                         ),
1730                         format!("{adt}(/* fields */)", adt = ty),
1731                         Applicability::HasPlaceholders,
1732                     );
1733                 }
1734             },
1735             _ => {
1736                 // prevent all specified fields from being suggested
1737                 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
1738                 if let Some(field_name) = self.suggest_field_name(
1739                     variant,
1740                     field.ident.name,
1741                     skip_fields.collect(),
1742                     expr_span,
1743                 ) {
1744                     err.span_suggestion(
1745                         field.ident.span,
1746                         "a field with a similar name exists",
1747                         field_name.to_string(),
1748                         Applicability::MaybeIncorrect,
1749                     );
1750                 } else {
1751                     match ty.kind() {
1752                         ty::Adt(adt, ..) => {
1753                             if adt.is_enum() {
1754                                 err.span_label(
1755                                     field.ident.span,
1756                                     format!("`{}::{}` does not have this field", ty, variant.name),
1757                                 );
1758                             } else {
1759                                 err.span_label(
1760                                     field.ident.span,
1761                                     format!("`{}` does not have this field", ty),
1762                                 );
1763                             }
1764                             let available_field_names =
1765                                 self.available_field_names(variant, expr_span);
1766                             if !available_field_names.is_empty() {
1767                                 err.note(&format!(
1768                                     "available fields are: {}",
1769                                     self.name_series_display(available_field_names)
1770                                 ));
1771                             }
1772                         }
1773                         _ => bug!("non-ADT passed to report_unknown_field"),
1774                     }
1775                 };
1776             }
1777         }
1778         err.emit();
1779     }
1780
1781     // Return a hint about the closest match in field names
1782     fn suggest_field_name(
1783         &self,
1784         variant: &'tcx ty::VariantDef,
1785         field: Symbol,
1786         skip: Vec<Symbol>,
1787         // The span where stability will be checked
1788         span: Span,
1789     ) -> Option<Symbol> {
1790         let names = variant
1791             .fields
1792             .iter()
1793             .filter_map(|field| {
1794                 // ignore already set fields and private fields from non-local crates
1795                 // and unstable fields.
1796                 if skip.iter().any(|&x| x == field.name)
1797                     || (!variant.def_id.is_local() && !field.vis.is_public())
1798                     || matches!(
1799                         self.tcx.eval_stability(field.did, None, span, None),
1800                         stability::EvalResult::Deny { .. }
1801                     )
1802                 {
1803                     None
1804                 } else {
1805                     Some(field.name)
1806                 }
1807             })
1808             .collect::<Vec<Symbol>>();
1809
1810         find_best_match_for_name(&names, field, None)
1811     }
1812
1813     fn available_field_names(
1814         &self,
1815         variant: &'tcx ty::VariantDef,
1816         access_span: Span,
1817     ) -> Vec<Symbol> {
1818         variant
1819             .fields
1820             .iter()
1821             .filter(|field| {
1822                 let def_scope = self
1823                     .tcx
1824                     .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
1825                     .1;
1826                 field.vis.is_accessible_from(def_scope, self.tcx)
1827                     && !matches!(
1828                         self.tcx.eval_stability(field.did, None, access_span, None),
1829                         stability::EvalResult::Deny { .. }
1830                     )
1831             })
1832             .filter(|field| !self.tcx.is_doc_hidden(field.did))
1833             .map(|field| field.name)
1834             .collect()
1835     }
1836
1837     fn name_series_display(&self, names: Vec<Symbol>) -> String {
1838         // dynamic limit, to never omit just one field
1839         let limit = if names.len() == 6 { 6 } else { 5 };
1840         let mut display =
1841             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
1842         if names.len() > limit {
1843             display = format!("{} ... and {} others", display, names.len() - limit);
1844         }
1845         display
1846     }
1847
1848     // Check field access expressions
1849     fn check_field(
1850         &self,
1851         expr: &'tcx hir::Expr<'tcx>,
1852         base: &'tcx hir::Expr<'tcx>,
1853         field: Ident,
1854     ) -> Ty<'tcx> {
1855         debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
1856         let expr_t = self.check_expr(base);
1857         let expr_t = self.structurally_resolved_type(base.span, expr_t);
1858         let mut private_candidate = None;
1859         let mut autoderef = self.autoderef(expr.span, expr_t);
1860         while let Some((base_t, _)) = autoderef.next() {
1861             debug!("base_t: {:?}", base_t);
1862             match base_t.kind() {
1863                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
1864                     debug!("struct named {:?}", base_t);
1865                     let (ident, def_scope) =
1866                         self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
1867                     let fields = &base_def.non_enum_variant().fields;
1868                     if let Some(index) = fields
1869                         .iter()
1870                         .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
1871                     {
1872                         let field = &fields[index];
1873                         let field_ty = self.field_ty(expr.span, field, substs);
1874                         // Save the index of all fields regardless of their visibility in case
1875                         // of error recovery.
1876                         self.write_field_index(expr.hir_id, index);
1877                         let adjustments = self.adjust_steps(&autoderef);
1878                         if field.vis.is_accessible_from(def_scope, self.tcx) {
1879                             self.apply_adjustments(base, adjustments);
1880                             self.register_predicates(autoderef.into_obligations());
1881
1882                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
1883                             return field_ty;
1884                         }
1885                         private_candidate = Some((adjustments, base_def.did, field_ty));
1886                     }
1887                 }
1888                 ty::Tuple(tys) => {
1889                     let fstr = field.as_str();
1890                     if let Ok(index) = fstr.parse::<usize>() {
1891                         if fstr == index.to_string() {
1892                             if let Some(&field_ty) = tys.get(index) {
1893                                 let adjustments = self.adjust_steps(&autoderef);
1894                                 self.apply_adjustments(base, adjustments);
1895                                 self.register_predicates(autoderef.into_obligations());
1896
1897                                 self.write_field_index(expr.hir_id, index);
1898                                 return field_ty;
1899                             }
1900                         }
1901                     }
1902                 }
1903                 _ => {}
1904             }
1905         }
1906         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
1907
1908         if let Some((adjustments, did, field_ty)) = private_candidate {
1909             // (#90483) apply adjustments to avoid ExprUseVisitor from
1910             // creating erroneous projection.
1911             self.apply_adjustments(base, adjustments);
1912             self.ban_private_field_access(expr, expr_t, field, did);
1913             return field_ty;
1914         }
1915
1916         if field.name == kw::Empty {
1917         } else if self.method_exists(field, expr_t, expr.hir_id, true) {
1918             self.ban_take_value_of_method(expr, expr_t, field);
1919         } else if !expr_t.is_primitive_ty() {
1920             self.ban_nonexisting_field(field, base, expr, expr_t);
1921         } else {
1922             type_error_struct!(
1923                 self.tcx().sess,
1924                 field.span,
1925                 expr_t,
1926                 E0610,
1927                 "`{}` is a primitive type and therefore doesn't have fields",
1928                 expr_t
1929             )
1930             .emit();
1931         }
1932
1933         self.tcx().ty_error()
1934     }
1935
1936     fn suggest_await_on_field_access(
1937         &self,
1938         err: &mut Diagnostic,
1939         field_ident: Ident,
1940         base: &'tcx hir::Expr<'tcx>,
1941         ty: Ty<'tcx>,
1942     ) {
1943         let output_ty = match self.infcx.get_impl_future_output_ty(ty) {
1944             Some(output_ty) => self.resolve_vars_if_possible(output_ty),
1945             _ => return,
1946         };
1947         let mut add_label = true;
1948         if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
1949             // no field access on enum type
1950             if !def.is_enum() {
1951                 if def
1952                     .non_enum_variant()
1953                     .fields
1954                     .iter()
1955                     .any(|field| field.ident(self.tcx) == field_ident)
1956                 {
1957                     add_label = false;
1958                     err.span_label(
1959                         field_ident.span,
1960                         "field not available in `impl Future`, but it is available in its `Output`",
1961                     );
1962                     err.span_suggestion_verbose(
1963                         base.span.shrink_to_hi(),
1964                         "consider `await`ing on the `Future` and access the field of its `Output`",
1965                         ".await".to_string(),
1966                         Applicability::MaybeIncorrect,
1967                     );
1968                 }
1969             }
1970         }
1971         if add_label {
1972             err.span_label(field_ident.span, &format!("field not found in `{}`", ty));
1973         }
1974     }
1975
1976     fn ban_nonexisting_field(
1977         &self,
1978         field: Ident,
1979         base: &'tcx hir::Expr<'tcx>,
1980         expr: &'tcx hir::Expr<'tcx>,
1981         expr_t: Ty<'tcx>,
1982     ) {
1983         debug!(
1984             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
1985             field, base, expr, expr_t
1986         );
1987         let mut err = self.no_such_field_err(field, expr_t, base.hir_id);
1988
1989         match *expr_t.peel_refs().kind() {
1990             ty::Array(_, len) => {
1991                 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
1992             }
1993             ty::RawPtr(..) => {
1994                 self.suggest_first_deref_field(&mut err, expr, base, field);
1995             }
1996             ty::Adt(def, _) if !def.is_enum() => {
1997                 self.suggest_fields_on_recordish(&mut err, def, field, expr.span);
1998             }
1999             ty::Param(param_ty) => {
2000                 self.point_at_param_definition(&mut err, param_ty);
2001             }
2002             ty::Opaque(_, _) => {
2003                 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
2004             }
2005             _ => {}
2006         }
2007
2008         if field.name == kw::Await {
2009             // We know by construction that `<expr>.await` is either on Rust 2015
2010             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2011             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2012             err.help_use_latest_edition();
2013         }
2014
2015         err.emit();
2016     }
2017
2018     fn ban_private_field_access(
2019         &self,
2020         expr: &hir::Expr<'_>,
2021         expr_t: Ty<'tcx>,
2022         field: Ident,
2023         base_did: DefId,
2024     ) {
2025         let struct_path = self.tcx().def_path_str(base_did);
2026         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2027         let mut err = struct_span_err!(
2028             self.tcx().sess,
2029             field.span,
2030             E0616,
2031             "field `{}` of {} `{}` is private",
2032             field,
2033             kind_name,
2034             struct_path
2035         );
2036         err.span_label(field.span, "private field");
2037         // Also check if an accessible method exists, which is often what is meant.
2038         if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2039         {
2040             self.suggest_method_call(
2041                 &mut err,
2042                 &format!("a method `{}` also exists, call it with parentheses", field),
2043                 field,
2044                 expr_t,
2045                 expr,
2046                 None,
2047             );
2048         }
2049         err.emit();
2050     }
2051
2052     fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2053         let mut err = type_error_struct!(
2054             self.tcx().sess,
2055             field.span,
2056             expr_t,
2057             E0615,
2058             "attempted to take value of method `{}` on type `{}`",
2059             field,
2060             expr_t
2061         );
2062         err.span_label(field.span, "method, not a field");
2063         let expr_is_call =
2064             if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2065                 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2066             {
2067                 expr.hir_id == callee.hir_id
2068             } else {
2069                 false
2070             };
2071         let expr_snippet =
2072             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or(String::new());
2073         let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2074         let after_open = expr.span.lo() + rustc_span::BytePos(1);
2075         let before_close = expr.span.hi() - rustc_span::BytePos(1);
2076
2077         if expr_is_call && is_wrapped {
2078             err.multipart_suggestion(
2079                 "remove wrapping parentheses to call the method",
2080                 vec![
2081                     (expr.span.with_hi(after_open), String::new()),
2082                     (expr.span.with_lo(before_close), String::new()),
2083                 ],
2084                 Applicability::MachineApplicable,
2085             );
2086         } else if !self.expr_in_place(expr.hir_id) {
2087             // Suggest call parentheses inside the wrapping parentheses
2088             let span = if is_wrapped {
2089                 expr.span.with_lo(after_open).with_hi(before_close)
2090             } else {
2091                 expr.span
2092             };
2093             self.suggest_method_call(
2094                 &mut err,
2095                 "use parentheses to call the method",
2096                 field,
2097                 expr_t,
2098                 expr,
2099                 Some(span),
2100             );
2101         } else {
2102             let mut found = false;
2103
2104             if let ty::RawPtr(ty_and_mut) = expr_t.kind() {
2105                 if let ty::Adt(adt_def, _) = ty_and_mut.ty.kind() {
2106                     if adt_def.variants.len() == 1
2107                         && adt_def
2108                             .variants
2109                             .iter()
2110                             .next()
2111                             .unwrap()
2112                             .fields
2113                             .iter()
2114                             .any(|f| f.ident(self.tcx) == field)
2115                     {
2116                         if let Some(dot_loc) = expr_snippet.rfind('.') {
2117                             found = true;
2118                             err.span_suggestion(
2119                                 expr.span.with_hi(expr.span.lo() + BytePos::from_usize(dot_loc)),
2120                                 "to access the field, dereference first",
2121                                 format!("(*{})", &expr_snippet[0..dot_loc]),
2122                                 Applicability::MaybeIncorrect,
2123                             );
2124                         }
2125                     }
2126                 }
2127             }
2128
2129             if !found {
2130                 err.help("methods are immutable and cannot be assigned to");
2131             }
2132         }
2133
2134         err.emit();
2135     }
2136
2137     fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2138         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2139         let generic_param = generics.type_param(&param, self.tcx);
2140         if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2141             return;
2142         }
2143         let param_def_id = generic_param.def_id;
2144         let param_hir_id = match param_def_id.as_local() {
2145             Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2146             None => return,
2147         };
2148         let param_span = self.tcx.hir().span(param_hir_id);
2149         let param_name = self.tcx.hir().ty_param_name(param_hir_id);
2150
2151         err.span_label(param_span, &format!("type parameter '{}' declared here", param_name));
2152     }
2153
2154     fn suggest_fields_on_recordish(
2155         &self,
2156         err: &mut Diagnostic,
2157         def: &'tcx ty::AdtDef,
2158         field: Ident,
2159         access_span: Span,
2160     ) {
2161         if let Some(suggested_field_name) =
2162             self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2163         {
2164             err.span_suggestion(
2165                 field.span,
2166                 "a field with a similar name exists",
2167                 suggested_field_name.to_string(),
2168                 Applicability::MaybeIncorrect,
2169             );
2170         } else {
2171             err.span_label(field.span, "unknown field");
2172             let struct_variant_def = def.non_enum_variant();
2173             let field_names = self.available_field_names(struct_variant_def, access_span);
2174             if !field_names.is_empty() {
2175                 err.note(&format!(
2176                     "available fields are: {}",
2177                     self.name_series_display(field_names),
2178                 ));
2179             }
2180         }
2181     }
2182
2183     fn maybe_suggest_array_indexing(
2184         &self,
2185         err: &mut Diagnostic,
2186         expr: &hir::Expr<'_>,
2187         base: &hir::Expr<'_>,
2188         field: Ident,
2189         len: ty::Const<'tcx>,
2190     ) {
2191         if let (Some(len), Ok(user_index)) =
2192             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2193         {
2194             if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2195                 let help = "instead of using tuple indexing, use array indexing";
2196                 let suggestion = format!("{}[{}]", base, field);
2197                 let applicability = if len < user_index {
2198                     Applicability::MachineApplicable
2199                 } else {
2200                     Applicability::MaybeIncorrect
2201                 };
2202                 err.span_suggestion(expr.span, help, suggestion, applicability);
2203             }
2204         }
2205     }
2206
2207     fn suggest_first_deref_field(
2208         &self,
2209         err: &mut Diagnostic,
2210         expr: &hir::Expr<'_>,
2211         base: &hir::Expr<'_>,
2212         field: Ident,
2213     ) {
2214         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2215             let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
2216             let suggestion = format!("(*{}).{}", base, field);
2217             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2218         }
2219     }
2220
2221     fn no_such_field_err(
2222         &self,
2223         field: Ident,
2224         expr_t: Ty<'tcx>,
2225         id: HirId,
2226     ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2227         let span = field.span;
2228         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2229
2230         let mut err = type_error_struct!(
2231             self.tcx().sess,
2232             field.span,
2233             expr_t,
2234             E0609,
2235             "no field `{}` on type `{}`",
2236             field,
2237             expr_t
2238         );
2239
2240         // try to add a suggestion in case the field is a nested field of a field of the Adt
2241         if let Some((fields, substs)) = self.get_field_candidates(span, expr_t) {
2242             for candidate_field in fields.iter() {
2243                 if let Some(field_path) = self.check_for_nested_field(
2244                     span,
2245                     field,
2246                     candidate_field,
2247                     substs,
2248                     vec![],
2249                     self.tcx.parent_module(id).to_def_id(),
2250                 ) {
2251                     let field_path_str = field_path
2252                         .iter()
2253                         .map(|id| id.name.to_ident_string())
2254                         .collect::<Vec<String>>()
2255                         .join(".");
2256                     debug!("field_path_str: {:?}", field_path_str);
2257
2258                     err.span_suggestion_verbose(
2259                         field.span.shrink_to_lo(),
2260                         "one of the expressions' fields has a field of the same name",
2261                         format!("{}.", field_path_str),
2262                         Applicability::MaybeIncorrect,
2263                     );
2264                 }
2265             }
2266         }
2267         err
2268     }
2269
2270     fn get_field_candidates(
2271         &self,
2272         span: Span,
2273         base_t: Ty<'tcx>,
2274     ) -> Option<(&Vec<ty::FieldDef>, SubstsRef<'tcx>)> {
2275         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_t);
2276
2277         for (base_t, _) in self.autoderef(span, base_t) {
2278             match base_t.kind() {
2279                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2280                     let fields = &base_def.non_enum_variant().fields;
2281                     // For compile-time reasons put a limit on number of fields we search
2282                     if fields.len() > 100 {
2283                         return None;
2284                     }
2285                     return Some((fields, substs));
2286                 }
2287                 _ => {}
2288             }
2289         }
2290         None
2291     }
2292
2293     /// This method is called after we have encountered a missing field error to recursively
2294     /// search for the field
2295     fn check_for_nested_field(
2296         &self,
2297         span: Span,
2298         target_field: Ident,
2299         candidate_field: &ty::FieldDef,
2300         subst: SubstsRef<'tcx>,
2301         mut field_path: Vec<Ident>,
2302         id: DefId,
2303     ) -> Option<Vec<Ident>> {
2304         debug!(
2305             "check_for_nested_field(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2306             span, candidate_field, field_path
2307         );
2308
2309         if candidate_field.ident(self.tcx) == target_field {
2310             Some(field_path)
2311         } else if field_path.len() > 3 {
2312             // For compile-time reasons and to avoid infinite recursion we only check for fields
2313             // up to a depth of three
2314             None
2315         } else {
2316             // recursively search fields of `candidate_field` if it's a ty::Adt
2317
2318             field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2319             let field_ty = candidate_field.ty(self.tcx, subst);
2320             if let Some((nested_fields, subst)) = self.get_field_candidates(span, field_ty) {
2321                 for field in nested_fields.iter() {
2322                     let accessible = field.vis.is_accessible_from(id, self.tcx);
2323                     if accessible {
2324                         let ident = field.ident(self.tcx).normalize_to_macros_2_0();
2325                         if ident == target_field {
2326                             return Some(field_path);
2327                         }
2328                         let field_path = field_path.clone();
2329                         if let Some(path) = self.check_for_nested_field(
2330                             span,
2331                             target_field,
2332                             field,
2333                             subst,
2334                             field_path,
2335                             id,
2336                         ) {
2337                             return Some(path);
2338                         }
2339                     }
2340                 }
2341             }
2342             None
2343         }
2344     }
2345
2346     fn check_expr_index(
2347         &self,
2348         base: &'tcx hir::Expr<'tcx>,
2349         idx: &'tcx hir::Expr<'tcx>,
2350         expr: &'tcx hir::Expr<'tcx>,
2351     ) -> Ty<'tcx> {
2352         let base_t = self.check_expr(&base);
2353         let idx_t = self.check_expr(&idx);
2354
2355         if base_t.references_error() {
2356             base_t
2357         } else if idx_t.references_error() {
2358             idx_t
2359         } else {
2360             let base_t = self.structurally_resolved_type(base.span, base_t);
2361             match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2362                 Some((index_ty, element_ty)) => {
2363                     // two-phase not needed because index_ty is never mutable
2364                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2365                     element_ty
2366                 }
2367                 None => {
2368                     let mut err = type_error_struct!(
2369                         self.tcx.sess,
2370                         expr.span,
2371                         base_t,
2372                         E0608,
2373                         "cannot index into a value of type `{}`",
2374                         base_t
2375                     );
2376                     // Try to give some advice about indexing tuples.
2377                     if let ty::Tuple(..) = base_t.kind() {
2378                         let mut needs_note = true;
2379                         // If the index is an integer, we can show the actual
2380                         // fixed expression:
2381                         if let ExprKind::Lit(ref lit) = idx.kind {
2382                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2383                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2384                                 if let Ok(snip) = snip {
2385                                     err.span_suggestion(
2386                                         expr.span,
2387                                         "to access tuple elements, use",
2388                                         format!("{}.{}", snip, i),
2389                                         Applicability::MachineApplicable,
2390                                     );
2391                                     needs_note = false;
2392                                 }
2393                             }
2394                         }
2395                         if needs_note {
2396                             err.help(
2397                                 "to access tuple elements, use tuple indexing \
2398                                         syntax (e.g., `tuple.0`)",
2399                             );
2400                         }
2401                     }
2402                     err.emit();
2403                     self.tcx.ty_error()
2404                 }
2405             }
2406         }
2407     }
2408
2409     fn check_expr_yield(
2410         &self,
2411         value: &'tcx hir::Expr<'tcx>,
2412         expr: &'tcx hir::Expr<'tcx>,
2413         src: &'tcx hir::YieldSource,
2414     ) -> Ty<'tcx> {
2415         match self.resume_yield_tys {
2416             Some((resume_ty, yield_ty)) => {
2417                 self.check_expr_coercable_to_type(&value, yield_ty, None);
2418
2419                 resume_ty
2420             }
2421             // Given that this `yield` expression was generated as a result of lowering a `.await`,
2422             // we know that the yield type must be `()`; however, the context won't contain this
2423             // information. Hence, we check the source of the yield expression here and check its
2424             // value's type against `()` (this check should always hold).
2425             None if src.is_await() => {
2426                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2427                 self.tcx.mk_unit()
2428             }
2429             _ => {
2430                 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2431                 // Avoid expressions without types during writeback (#78653).
2432                 self.check_expr(value);
2433                 self.tcx.mk_unit()
2434             }
2435         }
2436     }
2437
2438     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2439         let needs = if is_input { Needs::None } else { Needs::MutPlace };
2440         let ty = self.check_expr_with_needs(expr, needs);
2441         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2442
2443         if !is_input && !expr.is_syntactic_place_expr() {
2444             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2445             err.span_label(expr.span, "cannot assign to this expression");
2446             err.emit();
2447         }
2448
2449         // If this is an input value, we require its type to be fully resolved
2450         // at this point. This allows us to provide helpful coercions which help
2451         // pass the type candidate list in a later pass.
2452         //
2453         // We don't require output types to be resolved at this point, which
2454         // allows them to be inferred based on how they are used later in the
2455         // function.
2456         if is_input {
2457             let ty = self.structurally_resolved_type(expr.span, ty);
2458             match *ty.kind() {
2459                 ty::FnDef(..) => {
2460                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2461                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2462                 }
2463                 ty::Ref(_, base_ty, mutbl) => {
2464                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2465                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2466                 }
2467                 _ => {}
2468             }
2469         }
2470     }
2471
2472     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2473         for (op, _op_sp) in asm.operands {
2474             match op {
2475                 hir::InlineAsmOperand::In { expr, .. } => {
2476                     self.check_expr_asm_operand(expr, true);
2477                 }
2478                 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2479                 | hir::InlineAsmOperand::InOut { expr, .. } => {
2480                     self.check_expr_asm_operand(expr, false);
2481                 }
2482                 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2483                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2484                     self.check_expr_asm_operand(in_expr, true);
2485                     if let Some(out_expr) = out_expr {
2486                         self.check_expr_asm_operand(out_expr, false);
2487                     }
2488                 }
2489                 hir::InlineAsmOperand::Const { anon_const } => {
2490                     self.to_const(anon_const);
2491                 }
2492                 hir::InlineAsmOperand::Sym { expr } => {
2493                     self.check_expr(expr);
2494                 }
2495             }
2496         }
2497         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2498             self.tcx.types.never
2499         } else {
2500             self.tcx.mk_unit()
2501         }
2502     }
2503 }
2504
2505 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2506     Some(match ty.kind() {
2507         ty::Bool => "true",
2508         ty::Char => "'a'",
2509         ty::Int(_) | ty::Uint(_) => "42",
2510         ty::Float(_) => "3.14159",
2511         ty::Error(_) | ty::Never => return None,
2512         _ => "value",
2513     })
2514 }