src/librustc_typeck/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::{probe, MethodError, SelfSource};
  10 use crate::check::report_unexpected_variant_res;
  11 use crate::check::BreakableCtxt;
  12 use crate::check::Diverges;
  13 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
  14 use crate::check::FnCtxt;
  15 use crate::check::Needs;
  16 use crate::check::TupleArgumentsFlag::DontTupleArguments;
  17 use crate::type_error_struct;
  18
  19 use rustc_ast::ast;
  20 use rustc_ast::util::lev_distance::find_best_match_for_name;
  21 use rustc_data_structures::fx::FxHashMap;
  22 use rustc_errors::ErrorReported;
  23 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
  24 use rustc_hir as hir;
  25 use rustc_hir::def::{CtorKind, DefKind, Res};
  26 use rustc_hir::def_id::DefId;
  27 use rustc_hir::lang_items;
  28 use rustc_hir::{ExprKind, QPath};
  29 use rustc_infer::infer;
  30 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
  31 use rustc_middle::ty;
  32 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
  33 use rustc_middle::ty::Ty;
  34 use rustc_middle::ty::TypeFoldable;
  35 use rustc_middle::ty::{AdtKind, Visibility};
  36 use rustc_span::hygiene::DesugaringKind;
  37 use rustc_span::source_map::Span;
  38 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  39 use rustc_trait_selection::traits::{self, ObligationCauseCode};
  40
  41 use std::fmt::Display;
  42
  43 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  44     fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
  45         let ty = self.check_expr_with_hint(expr, expected);
  46         self.demand_eqtype(expr.span, expected, ty);
  47     }
  48
  49     pub fn check_expr_has_type_or_error(
  50         &self,
  51         expr: &'tcx hir::Expr<'tcx>,
  52         expected: Ty<'tcx>,
  53         extend_err: impl Fn(&mut DiagnosticBuilder<'_>),
  54     ) -> Ty<'tcx> {
  55         self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
  56     }
  57
  58     fn check_expr_meets_expectation_or_error(
  59         &self,
  60         expr: &'tcx hir::Expr<'tcx>,
  61         expected: Expectation<'tcx>,
  62         extend_err: impl Fn(&mut DiagnosticBuilder<'_>),
  63     ) -> Ty<'tcx> {
  64         let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
  65         let mut ty = self.check_expr_with_expectation(expr, expected);
  66
  67         // While we don't allow *arbitrary* coercions here, we *do* allow
  68         // coercions from ! to `expected`.
  69         if ty.is_never() {
  70             assert!(
  71                 !self.tables.borrow().adjustments().contains_key(expr.hir_id),
  72                 "expression with never type wound up being adjusted"
  73             );
  74             let adj_ty = self.next_diverging_ty_var(TypeVariableOrigin {
  75                 kind: TypeVariableOriginKind::AdjustmentType,
  76                 span: expr.span,
  77             });
  78             self.apply_adjustments(
  79                 expr,
  80                 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
  81             );
  82             ty = adj_ty;
  83         }
  84
  85         if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
  86             let expr = expr.peel_drop_temps();
  87             self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
  88             extend_err(&mut err);
  89             // Error possibly reported in `check_assign` so avoid emitting error again.
  90             err.emit_unless(self.is_assign_to_bool(expr, expected_ty));
  91         }
  92         ty
  93     }
  94
  95     pub(super) fn check_expr_coercable_to_type(
  96         &self,
  97         expr: &'tcx hir::Expr<'tcx>,
  98         expected: Ty<'tcx>,
  99         expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
 100     ) -> Ty<'tcx> {
 101         let ty = self.check_expr_with_hint(expr, expected);
 102         // checks don't need two phase
 103         self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
 104     }
 105
 106     pub(super) fn check_expr_with_hint(
 107         &self,
 108         expr: &'tcx hir::Expr<'tcx>,
 109         expected: Ty<'tcx>,
 110     ) -> Ty<'tcx> {
 111         self.check_expr_with_expectation(expr, ExpectHasType(expected))
 112     }
 113
 114     fn check_expr_with_expectation_and_needs(
 115         &self,
 116         expr: &'tcx hir::Expr<'tcx>,
 117         expected: Expectation<'tcx>,
 118         needs: Needs,
 119     ) -> Ty<'tcx> {
 120         let ty = self.check_expr_with_expectation(expr, expected);
 121
 122         // If the expression is used in a place whether mutable place is required
 123         // e.g. LHS of assignment, perform the conversion.
 124         if let Needs::MutPlace = needs {
 125             self.convert_place_derefs_to_mutable(expr);
 126         }
 127
 128         ty
 129     }
 130
 131     pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
 132         self.check_expr_with_expectation(expr, NoExpectation)
 133     }
 134
 135     pub(super) fn check_expr_with_needs(
 136         &self,
 137         expr: &'tcx hir::Expr<'tcx>,
 138         needs: Needs,
 139     ) -> Ty<'tcx> {
 140         self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
 141     }
 142
 143     /// Invariant:
 144     /// If an expression has any sub-expressions that result in a type error,
 145     /// inspecting that expression's type with `ty.references_error()` will return
 146     /// true. Likewise, if an expression is known to diverge, inspecting its
 147     /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
 148     /// strict, _|_ can appear in the type of an expression that does not,
 149     /// itself, diverge: for example, fn() -> _|_.)
 150     /// Note that inspecting a type's structure *directly* may expose the fact
 151     /// that there are actually multiple representations for `Error`, so avoid
 152     /// that when err needs to be handled differently.
 153     pub(super) fn check_expr_with_expectation(
 154         &self,
 155         expr: &'tcx hir::Expr<'tcx>,
 156         expected: Expectation<'tcx>,
 157     ) -> Ty<'tcx> {
 158         debug!(">> type-checking: expr={:?} expected={:?}", expr, expected);
 159
 160         // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
 161         // without the final expr (e.g. `try { return; }`). We don't want to generate an
 162         // unreachable_code lint for it since warnings for autogenerated code are confusing.
 163         let is_try_block_generated_unit_expr = match expr.kind {
 164             ExprKind::Call(_, ref args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
 165                 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
 166             }
 167
 168             _ => false,
 169         };
 170
 171         // Warn for expressions after diverging siblings.
 172         if !is_try_block_generated_unit_expr {
 173             self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
 174         }
 175
 176         // Hide the outer diverging and has_errors flags.
 177         let old_diverges = self.diverges.replace(Diverges::Maybe);
 178         let old_has_errors = self.has_errors.replace(false);
 179
 180         let ty = self.check_expr_kind(expr, expected);
 181
 182         // Warn for non-block expressions with diverging children.
 183         match expr.kind {
 184             ExprKind::Block(..) | ExprKind::Loop(..) | ExprKind::Match(..) => {}
 185             // If `expr` is a result of desugaring the try block and is an ok-wrapped
 186             // diverging expression (e.g. it arose from desugaring of `try { return }`),
 187             // we skip issuing a warning because it is autogenerated code.
 188             ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
 189             ExprKind::Call(ref callee, _) => {
 190                 self.warn_if_unreachable(expr.hir_id, callee.span, "call")
 191             }
 192             ExprKind::MethodCall(_, ref span, _, _) => {
 193                 self.warn_if_unreachable(expr.hir_id, *span, "call")
 194             }
 195             _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
 196         }
 197
 198         // Any expression that produces a value of type `!` must have diverged
 199         if ty.is_never() {
 200             self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
 201         }
 202
 203         // Record the type, which applies it effects.
 204         // We need to do this after the warning above, so that
 205         // we don't warn for the diverging expression itself.
 206         self.write_ty(expr.hir_id, ty);
 207
 208         // Combine the diverging and has_error flags.
 209         self.diverges.set(self.diverges.get() | old_diverges);
 210         self.has_errors.set(self.has_errors.get() | old_has_errors);
 211
 212         debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
 213         debug!("... {:?}, expected is {:?}", ty, expected);
 214
 215         ty
 216     }
 217
 218     fn check_expr_kind(
 219         &self,
 220         expr: &'tcx hir::Expr<'tcx>,
 221         expected: Expectation<'tcx>,
 222     ) -> Ty<'tcx> {
 223         debug!("check_expr_kind(expr={:?}, expected={:?})", expr, expected);
 224
 225         let tcx = self.tcx;
 226         match expr.kind {
 227             ExprKind::Box(ref subexpr) => self.check_expr_box(subexpr, expected),
 228             ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
 229             ExprKind::Binary(op, ref lhs, ref rhs) => self.check_binop(expr, op, lhs, rhs),
 230             ExprKind::Assign(ref lhs, ref rhs, ref span) => {
 231                 self.check_expr_assign(expr, expected, lhs, rhs, span)
 232             }
 233             ExprKind::AssignOp(op, ref lhs, ref rhs) => self.check_binop_assign(expr, op, lhs, rhs),
 234             ExprKind::Unary(unop, ref oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
 235             ExprKind::AddrOf(kind, mutbl, ref oprnd) => {
 236                 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
 237             }
 238             ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr),
 239             ExprKind::InlineAsm(asm) => self.check_expr_asm(asm),
 240             ExprKind::LlvmInlineAsm(ref asm) => {
 241                 for expr in asm.outputs_exprs.iter().chain(asm.inputs_exprs.iter()) {
 242                     self.check_expr(expr);
 243                 }
 244                 tcx.mk_unit()
 245             }
 246             ExprKind::Break(destination, ref expr_opt) => {
 247                 self.check_expr_break(destination, expr_opt.as_deref(), expr)
 248             }
 249             ExprKind::Continue(destination) => {
 250                 if destination.target_id.is_ok() {
 251                     tcx.types.never
 252                 } else {
 253                     // There was an error; make type-check fail.
 254                     tcx.ty_error()
 255                 }
 256             }
 257             ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
 258             ExprKind::Loop(ref body, _, source) => {
 259                 self.check_expr_loop(body, source, expected, expr)
 260             }
 261             ExprKind::Match(ref discrim, ref arms, match_src) => {
 262                 self.check_match(expr, &discrim, arms, expected, match_src)
 263             }
 264             ExprKind::Closure(capture, ref decl, body_id, _, gen) => {
 265                 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
 266             }
 267             ExprKind::Block(ref body, _) => self.check_block_with_expected(&body, expected),
 268             ExprKind::Call(ref callee, ref args) => self.check_call(expr, &callee, args, expected),
 269             ExprKind::MethodCall(ref segment, span, ref args, _) => {
 270                 self.check_method_call(expr, segment, span, args, expected)
 271             }
 272             ExprKind::Cast(ref e, ref t) => self.check_expr_cast(e, t, expr),
 273             ExprKind::Type(ref e, ref t) => {
 274                 let ty = self.to_ty_saving_user_provided_ty(&t);
 275                 self.check_expr_eq_type(&e, ty);
 276                 ty
 277             }
 278             ExprKind::DropTemps(ref e) => self.check_expr_with_expectation(e, expected),
 279             ExprKind::Array(ref args) => self.check_expr_array(args, expected, expr),
 280             ExprKind::Repeat(ref element, ref count) => {
 281                 self.check_expr_repeat(element, count, expected, expr)
 282             }
 283             ExprKind::Tup(ref elts) => self.check_expr_tuple(elts, expected, expr),
 284             ExprKind::Struct(ref qpath, fields, ref base_expr) => {
 285                 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
 286             }
 287             ExprKind::Field(ref base, field) => self.check_field(expr, &base, field),
 288             ExprKind::Index(ref base, ref idx) => self.check_expr_index(base, idx, expr),
 289             ExprKind::Yield(ref value, ref src) => self.check_expr_yield(value, expr, src),
 290             hir::ExprKind::Err => tcx.ty_error(),
 291         }
 292     }
 293
 294     fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
 295         let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind {
 296             ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
 297             _ => NoExpectation,
 298         });
 299         let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
 300         self.tcx.mk_box(referent_ty)
 301     }
 302
 303     fn check_expr_unary(
 304         &self,
 305         unop: hir::UnOp,
 306         oprnd: &'tcx hir::Expr<'tcx>,
 307         expected: Expectation<'tcx>,
 308         expr: &'tcx hir::Expr<'tcx>,
 309     ) -> Ty<'tcx> {
 310         let tcx = self.tcx;
 311         let expected_inner = match unop {
 312             hir::UnOp::UnNot | hir::UnOp::UnNeg => expected,
 313             hir::UnOp::UnDeref => NoExpectation,
 314         };
 315         let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
 316
 317         if !oprnd_t.references_error() {
 318             oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
 319             match unop {
 320                 hir::UnOp::UnDeref => {
 321                     if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
 322                         oprnd_t = ty;
 323                     } else {
 324                         let mut err = type_error_struct!(
 325                             tcx.sess,
 326                             expr.span,
 327                             oprnd_t,
 328                             E0614,
 329                             "type `{}` cannot be dereferenced",
 330                             oprnd_t,
 331                         );
 332                         let sp = tcx.sess.source_map().start_point(expr.span);
 333                         if let Some(sp) =
 334                             tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
 335                         {
 336                             tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp, None);
 337                         }
 338                         err.emit();
 339                         oprnd_t = tcx.ty_error();
 340                     }
 341                 }
 342                 hir::UnOp::UnNot => {
 343                     let result = self.check_user_unop(expr, oprnd_t, unop);
 344                     // If it's builtin, we can reuse the type, this helps inference.
 345                     if !(oprnd_t.is_integral() || oprnd_t.kind == ty::Bool) {
 346                         oprnd_t = result;
 347                     }
 348                 }
 349                 hir::UnOp::UnNeg => {
 350                     let result = self.check_user_unop(expr, oprnd_t, unop);
 351                     // If it's builtin, we can reuse the type, this helps inference.
 352                     if !oprnd_t.is_numeric() {
 353                         oprnd_t = result;
 354                     }
 355                 }
 356             }
 357         }
 358         oprnd_t
 359     }
 360
 361     fn check_expr_addr_of(
 362         &self,
 363         kind: hir::BorrowKind,
 364         mutbl: hir::Mutability,
 365         oprnd: &'tcx hir::Expr<'tcx>,
 366         expected: Expectation<'tcx>,
 367         expr: &'tcx hir::Expr<'tcx>,
 368     ) -> Ty<'tcx> {
 369         let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
 370             match ty.kind {
 371                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 372                     if oprnd.is_syntactic_place_expr() {
 373                         // Places may legitimately have unsized types.
 374                         // For example, dereferences of a fat pointer and
 375                         // the last field of a struct can be unsized.
 376                         ExpectHasType(ty)
 377                     } else {
 378                         Expectation::rvalue_hint(self, ty)
 379                     }
 380                 }
 381                 _ => NoExpectation,
 382             }
 383         });
 384         let ty =
 385             self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
 386
 387         let tm = ty::TypeAndMut { ty, mutbl };
 388         match kind {
 389             _ if tm.ty.references_error() => self.tcx.ty_error(),
 390             hir::BorrowKind::Raw => {
 391                 self.check_named_place_expr(oprnd);
 392                 self.tcx.mk_ptr(tm)
 393             }
 394             hir::BorrowKind::Ref => {
 395                 // Note: at this point, we cannot say what the best lifetime
 396                 // is to use for resulting pointer.  We want to use the
 397                 // shortest lifetime possible so as to avoid spurious borrowck
 398                 // errors.  Moreover, the longest lifetime will depend on the
 399                 // precise details of the value whose address is being taken
 400                 // (and how long it is valid), which we don't know yet until
 401                 // type inference is complete.
 402                 //
 403                 // Therefore, here we simply generate a region variable. The
 404                 // region inferencer will then select a suitable value.
 405                 // Finally, borrowck will infer the value of the region again,
 406                 // this time with enough precision to check that the value
 407                 // whose address was taken can actually be made to live as long
 408                 // as it needs to live.
 409                 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
 410                 self.tcx.mk_ref(region, tm)
 411             }
 412         }
 413     }
 414
 415     /// Does this expression refer to a place that either:
 416     /// * Is based on a local or static.
 417     /// * Contains a dereference
 418     /// Note that the adjustments for the children of `expr` should already
 419     /// have been resolved.
 420     fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
 421         let is_named = oprnd.is_place_expr(|base| {
 422             // Allow raw borrows if there are any deref adjustments.
 423             //
 424             // const VAL: (i32,) = (0,);
 425             // const REF: &(i32,) = &(0,);
 426             //
 427             // &raw const VAL.0;            // ERROR
 428             // &raw const REF.0;            // OK, same as &raw const (*REF).0;
 429             //
 430             // This is maybe too permissive, since it allows
 431             // `let u = &raw const Box::new((1,)).0`, which creates an
 432             // immediately dangling raw pointer.
 433             self.tables.borrow().adjustments().get(base.hir_id).map_or(false, |x| {
 434                 x.iter().any(|adj| if let Adjust::Deref(_) = adj.kind { true } else { false })
 435             })
 436         });
 437         if !is_named {
 438             struct_span_err!(
 439                 self.tcx.sess,
 440                 oprnd.span,
 441                 E0745,
 442                 "cannot take address of a temporary"
 443             )
 444             .span_label(oprnd.span, "temporary value")
 445             .emit();
 446         }
 447     }
 448
 449     fn check_expr_path(&self, qpath: &hir::QPath<'_>, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
 450         let tcx = self.tcx;
 451         let (res, opt_ty, segs) = self.resolve_ty_and_res_ufcs(qpath, expr.hir_id, expr.span);
 452         let ty = match res {
 453             Res::Err => {
 454                 self.set_tainted_by_errors();
 455                 tcx.ty_error()
 456             }
 457             Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
 458                 report_unexpected_variant_res(tcx, res, expr.span);
 459                 tcx.ty_error()
 460             }
 461             _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
 462         };
 463
 464         if let ty::FnDef(..) = ty.kind {
 465             let fn_sig = ty.fn_sig(tcx);
 466             if !tcx.features().unsized_locals {
 467                 // We want to remove some Sized bounds from std functions,
 468                 // but don't want to expose the removal to stable Rust.
 469                 // i.e., we don't want to allow
 470                 //
 471                 // ```rust
 472                 // drop as fn(str);
 473                 // ```
 474                 //
 475                 // to work in stable even if the Sized bound on `drop` is relaxed.
 476                 for i in 0..fn_sig.inputs().skip_binder().len() {
 477                     // We just want to check sizedness, so instead of introducing
 478                     // placeholder lifetimes with probing, we just replace higher lifetimes
 479                     // with fresh vars.
 480                     let input = self
 481                         .replace_bound_vars_with_fresh_vars(
 482                             expr.span,
 483                             infer::LateBoundRegionConversionTime::FnCall,
 484                             &fn_sig.input(i),
 485                         )
 486                         .0;
 487                     self.require_type_is_sized_deferred(
 488                         input,
 489                         expr.span,
 490                         traits::SizedArgumentType,
 491                     );
 492                 }
 493             }
 494             // Here we want to prevent struct constructors from returning unsized types.
 495             // There were two cases this happened: fn pointer coercion in stable
 496             // and usual function call in presence of unsized_locals.
 497             // Also, as we just want to check sizedness, instead of introducing
 498             // placeholder lifetimes with probing, we just replace higher lifetimes
 499             // with fresh vars.
 500             let output = self
 501                 .replace_bound_vars_with_fresh_vars(
 502                     expr.span,
 503                     infer::LateBoundRegionConversionTime::FnCall,
 504                     &fn_sig.output(),
 505                 )
 506                 .0;
 507             self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
 508         }
 509
 510         // We always require that the type provided as the value for
 511         // a type parameter outlives the moment of instantiation.
 512         let substs = self.tables.borrow().node_substs(expr.hir_id);
 513         self.add_wf_bounds(substs, expr);
 514
 515         ty
 516     }
 517
 518     fn check_expr_break(
 519         &self,
 520         destination: hir::Destination,
 521         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 522         expr: &'tcx hir::Expr<'tcx>,
 523     ) -> Ty<'tcx> {
 524         let tcx = self.tcx;
 525         if let Ok(target_id) = destination.target_id {
 526             let (e_ty, cause);
 527             if let Some(ref e) = expr_opt {
 528                 // If this is a break with a value, we need to type-check
 529                 // the expression. Get an expected type from the loop context.
 530                 let opt_coerce_to = {
 531                     // We should release `enclosing_breakables` before the `check_expr_with_hint`
 532                     // below, so can't move this block of code to the enclosing scope and share
 533                     // `ctxt` with the second `encloding_breakables` borrow below.
 534                     let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 535                     match enclosing_breakables.opt_find_breakable(target_id) {
 536                         Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
 537                         None => {
 538                             // Avoid ICE when `break` is inside a closure (#65383).
 539                             return tcx.ty_error_with_message(
 540                                 expr.span,
 541                                 "break was outside loop, but no error was emitted",
 542                             );
 543                         }
 544                     }
 545                 };
 546
 547                 // If the loop context is not a `loop { }`, then break with
 548                 // a value is illegal, and `opt_coerce_to` will be `None`.
 549                 // Just set expectation to error in that case.
 550                 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
 551
 552                 // Recurse without `enclosing_breakables` borrowed.
 553                 e_ty = self.check_expr_with_hint(e, coerce_to);
 554                 cause = self.misc(e.span);
 555             } else {
 556                 // Otherwise, this is a break *without* a value. That's
 557                 // always legal, and is equivalent to `break ()`.
 558                 e_ty = tcx.mk_unit();
 559                 cause = self.misc(expr.span);
 560             }
 561
 562             // Now that we have type-checked `expr_opt`, borrow
 563             // the `enclosing_loops` field and let's coerce the
 564             // type of `expr_opt` into what is expected.
 565             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 566             let ctxt = match enclosing_breakables.opt_find_breakable(target_id) {
 567                 Some(ctxt) => ctxt,
 568                 None => {
 569                     // Avoid ICE when `break` is inside a closure (#65383).
 570                     return tcx.ty_error_with_message(
 571                         expr.span,
 572                         "break was outside loop, but no error was emitted",
 573                     );
 574                 }
 575             };
 576
 577             if let Some(ref mut coerce) = ctxt.coerce {
 578                 if let Some(ref e) = expr_opt {
 579                     coerce.coerce(self, &cause, e, e_ty);
 580                 } else {
 581                     assert!(e_ty.is_unit());
 582                     let ty = coerce.expected_ty();
 583                     coerce.coerce_forced_unit(
 584                         self,
 585                         &cause,
 586                         &mut |mut err| {
 587                             self.suggest_mismatched_types_on_tail(
 588                                 &mut err, expr, ty, e_ty, cause.span, target_id,
 589                             );
 590                             if let Some(val) = ty_kind_suggestion(ty) {
 591                                 let label = destination
 592                                     .label
 593                                     .map(|l| format!(" {}", l.ident))
 594                                     .unwrap_or_else(String::new);
 595                                 err.span_suggestion(
 596                                     expr.span,
 597                                     "give it a value of the expected type",
 598                                     format!("break{} {}", label, val),
 599                                     Applicability::HasPlaceholders,
 600                                 );
 601                             }
 602                         },
 603                         false,
 604                     );
 605                 }
 606             } else {
 607                 // If `ctxt.coerce` is `None`, we can just ignore
 608                 // the type of the expression.  This is because
 609                 // either this was a break *without* a value, in
 610                 // which case it is always a legal type (`()`), or
 611                 // else an error would have been flagged by the
 612                 // `loops` pass for using break with an expression
 613                 // where you are not supposed to.
 614                 assert!(expr_opt.is_none() || self.tcx.sess.has_errors());
 615             }
 616
 617             ctxt.may_break = true;
 618
 619             // the type of a `break` is always `!`, since it diverges
 620             tcx.types.never
 621         } else {
 622             // Otherwise, we failed to find the enclosing loop;
 623             // this can only happen if the `break` was not
 624             // inside a loop at all, which is caught by the
 625             // loop-checking pass.
 626             let err = self.tcx.ty_error_with_message(
 627                 expr.span,
 628                 "break was outside loop, but no error was emitted",
 629             );
 630
 631             // We still need to assign a type to the inner expression to
 632             // prevent the ICE in #43162.
 633             if let Some(ref e) = expr_opt {
 634                 self.check_expr_with_hint(e, err);
 635
 636                 // ... except when we try to 'break rust;'.
 637                 // ICE this expression in particular (see #43162).
 638                 if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.kind {
 639                     if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
 640                         fatally_break_rust(self.tcx.sess);
 641                     }
 642                 }
 643             }
 644
 645             // There was an error; make type-check fail.
 646             err
 647         }
 648     }
 649
 650     fn check_expr_return(
 651         &self,
 652         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 653         expr: &'tcx hir::Expr<'tcx>,
 654     ) -> Ty<'tcx> {
 655         if self.ret_coercion.is_none() {
 656             struct_span_err!(
 657                 self.tcx.sess,
 658                 expr.span,
 659                 E0572,
 660                 "return statement outside of function body",
 661             )
 662             .emit();
 663         } else if let Some(ref e) = expr_opt {
 664             if self.ret_coercion_span.borrow().is_none() {
 665                 *self.ret_coercion_span.borrow_mut() = Some(e.span);
 666             }
 667             self.check_return_expr(e);
 668         } else {
 669             let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
 670             if self.ret_coercion_span.borrow().is_none() {
 671                 *self.ret_coercion_span.borrow_mut() = Some(expr.span);
 672             }
 673             let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
 674             if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
 675                 coercion.coerce_forced_unit(
 676                     self,
 677                     &cause,
 678                     &mut |db| {
 679                         let span = fn_decl.output.span();
 680                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
 681                             db.span_label(
 682                                 span,
 683                                 format!("expected `{}` because of this return type", snippet),
 684                             );
 685                         }
 686                     },
 687                     true,
 688                 );
 689             } else {
 690                 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
 691             }
 692         }
 693         self.tcx.types.never
 694     }
 695
 696     pub(super) fn check_return_expr(&self, return_expr: &'tcx hir::Expr<'tcx>) {
 697         let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
 698             span_bug!(return_expr.span, "check_return_expr called outside fn body")
 699         });
 700
 701         let ret_ty = ret_coercion.borrow().expected_ty();
 702         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty.clone());
 703         ret_coercion.borrow_mut().coerce(
 704             self,
 705             &self.cause(return_expr.span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
 706             return_expr,
 707             return_expr_ty,
 708         );
 709     }
 710
 711     fn is_destructuring_place_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> bool {
 712         match &expr.kind {
 713             ExprKind::Array(comps) | ExprKind::Tup(comps) => {
 714                 comps.iter().all(|e| self.is_destructuring_place_expr(e))
 715             }
 716             ExprKind::Struct(_path, fields, rest) => {
 717                 rest.as_ref().map(|e| self.is_destructuring_place_expr(e)).unwrap_or(true)
 718                     && fields.iter().all(|f| self.is_destructuring_place_expr(&f.expr))
 719             }
 720             _ => expr.is_syntactic_place_expr(),
 721         }
 722     }
 723
 724     pub(crate) fn check_lhs_assignable(
 725         &self,
 726         lhs: &'tcx hir::Expr<'tcx>,
 727         err_code: &'static str,
 728         expr_span: &Span,
 729     ) {
 730         if !lhs.is_syntactic_place_expr() {
 731             let mut err = self.tcx.sess.struct_span_err_with_code(
 732                 *expr_span,
 733                 "invalid left-hand side of assignment",
 734                 DiagnosticId::Error(err_code.into()),
 735             );
 736             err.span_label(lhs.span, "cannot assign to this expression");
 737             if self.is_destructuring_place_expr(lhs) {
 738                 err.note("destructuring assignments are not currently supported");
 739                 err.note("for more information, see https://github.com/rust-lang/rfcs/issues/372");
 740             }
 741             err.emit();
 742         }
 743     }
 744
 745     /// Type check assignment expression `expr` of form `lhs = rhs`.
 746     /// The expected type is `()` and is passsed to the function for the purposes of diagnostics.
 747     fn check_expr_assign(
 748         &self,
 749         expr: &'tcx hir::Expr<'tcx>,
 750         expected: Expectation<'tcx>,
 751         lhs: &'tcx hir::Expr<'tcx>,
 752         rhs: &'tcx hir::Expr<'tcx>,
 753         span: &Span,
 754     ) -> Ty<'tcx> {
 755         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
 756         let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty, Some(lhs));
 757
 758         let expected_ty = expected.coercion_target_type(self, expr.span);
 759         if expected_ty == self.tcx.types.bool {
 760             // The expected type is `bool` but this will result in `()` so we can reasonably
 761             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
 762             // The likely cause of this is `if foo = bar { .. }`.
 763             let actual_ty = self.tcx.mk_unit();
 764             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
 765             let msg = "try comparing for equality";
 766             let left = self.tcx.sess.source_map().span_to_snippet(lhs.span);
 767             let right = self.tcx.sess.source_map().span_to_snippet(rhs.span);
 768             if let (Ok(left), Ok(right)) = (left, right) {
 769                 let help = format!("{} == {}", left, right);
 770                 err.span_suggestion(expr.span, msg, help, Applicability::MaybeIncorrect);
 771             } else {
 772                 err.help(msg);
 773             }
 774             err.emit();
 775         } else {
 776             self.check_lhs_assignable(lhs, "E0070", span);
 777         }
 778
 779         self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
 780
 781         if lhs_ty.references_error() || rhs_ty.references_error() {
 782             self.tcx.ty_error()
 783         } else {
 784             self.tcx.mk_unit()
 785         }
 786     }
 787
 788     fn check_expr_loop(
 789         &self,
 790         body: &'tcx hir::Block<'tcx>,
 791         source: hir::LoopSource,
 792         expected: Expectation<'tcx>,
 793         expr: &'tcx hir::Expr<'tcx>,
 794     ) -> Ty<'tcx> {
 795         let coerce = match source {
 796             // you can only use break with a value from a normal `loop { }`
 797             hir::LoopSource::Loop => {
 798                 let coerce_to = expected.coercion_target_type(self, body.span);
 799                 Some(CoerceMany::new(coerce_to))
 800             }
 801
 802             hir::LoopSource::While | hir::LoopSource::WhileLet | hir::LoopSource::ForLoop => None,
 803         };
 804
 805         let ctxt = BreakableCtxt {
 806             coerce,
 807             may_break: false, // Will get updated if/when we find a `break`.
 808         };
 809
 810         let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
 811             self.check_block_no_value(&body);
 812         });
 813
 814         if ctxt.may_break {
 815             // No way to know whether it's diverging because
 816             // of a `break` or an outer `break` or `return`.
 817             self.diverges.set(Diverges::Maybe);
 818         }
 819
 820         // If we permit break with a value, then result type is
 821         // the LUB of the breaks (possibly ! if none); else, it
 822         // is nil. This makes sense because infinite loops
 823         // (which would have type !) are only possible iff we
 824         // permit break with a value [1].
 825         if ctxt.coerce.is_none() && !ctxt.may_break {
 826             // [1]
 827             self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
 828         }
 829         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
 830     }
 831
 832     /// Checks a method call.
 833     fn check_method_call(
 834         &self,
 835         expr: &'tcx hir::Expr<'tcx>,
 836         segment: &hir::PathSegment<'_>,
 837         span: Span,
 838         args: &'tcx [hir::Expr<'tcx>],
 839         expected: Expectation<'tcx>,
 840     ) -> Ty<'tcx> {
 841         let rcvr = &args[0];
 842         let rcvr_t = self.check_expr(&rcvr);
 843         // no need to check for bot/err -- callee does that
 844         let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
 845
 846         let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr) {
 847             Ok(method) => {
 848                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
 849                 // trigger this codepath causing `structuraly_resolved_type` to emit an error.
 850
 851                 self.write_method_call(expr.hir_id, method);
 852                 Ok(method)
 853             }
 854             Err(error) => {
 855                 if segment.ident.name != kw::Invalid {
 856                     self.report_extended_method_error(segment, span, args, rcvr_t, error);
 857                 }
 858                 Err(())
 859             }
 860         };
 861
 862         // Call the generic checker.
 863         self.check_method_argument_types(
 864             span,
 865             expr,
 866             method,
 867             &args[1..],
 868             DontTupleArguments,
 869             expected,
 870         )
 871     }
 872
 873     fn report_extended_method_error(
 874         &self,
 875         segment: &hir::PathSegment<'_>,
 876         span: Span,
 877         args: &'tcx [hir::Expr<'tcx>],
 878         rcvr_t: Ty<'tcx>,
 879         error: MethodError<'tcx>,
 880     ) {
 881         let rcvr = &args[0];
 882         let try_alt_rcvr = |err: &mut DiagnosticBuilder<'_>, new_rcvr_t| {
 883             if let Some(new_rcvr_t) = new_rcvr_t {
 884                 if let Ok(pick) = self.lookup_probe(
 885                     span,
 886                     segment.ident,
 887                     new_rcvr_t,
 888                     rcvr,
 889                     probe::ProbeScope::AllTraits,
 890                 ) {
 891                     debug!("try_alt_rcvr: pick candidate {:?}", pick);
 892                     // Make sure the method is defined for the *actual* receiver:
 893                     // we don't want to treat `Box<Self>` as a receiver if
 894                     // it only works because of an autoderef to `&self`
 895                     if pick.autoderefs == 0 {
 896                         err.span_label(
 897                             pick.item.ident.span,
 898                             &format!("the method is available for `{}` here", new_rcvr_t),
 899                         );
 900                     }
 901                 }
 902             }
 903         };
 904
 905         if let Some(mut err) = self.report_method_error(
 906             span,
 907             rcvr_t,
 908             segment.ident,
 909             SelfSource::MethodCall(rcvr),
 910             error,
 911             Some(args),
 912         ) {
 913             if let ty::Adt(..) = rcvr_t.kind {
 914                 // Try alternative arbitrary self types that could fulfill this call.
 915                 // FIXME: probe for all types that *could* be arbitrary self-types, not
 916                 // just this list.
 917                 try_alt_rcvr(&mut err, self.tcx.mk_lang_item(rcvr_t, lang_items::OwnedBoxLangItem));
 918                 try_alt_rcvr(&mut err, self.tcx.mk_lang_item(rcvr_t, lang_items::PinTypeLangItem));
 919                 try_alt_rcvr(&mut err, self.tcx.mk_diagnostic_item(rcvr_t, sym::Arc));
 920                 try_alt_rcvr(&mut err, self.tcx.mk_diagnostic_item(rcvr_t, sym::Rc));
 921             }
 922             err.emit();
 923         }
 924     }
 925
 926     fn check_expr_cast(
 927         &self,
 928         e: &'tcx hir::Expr<'tcx>,
 929         t: &'tcx hir::Ty<'tcx>,
 930         expr: &'tcx hir::Expr<'tcx>,
 931     ) -> Ty<'tcx> {
 932         // Find the type of `e`. Supply hints based on the type we are casting to,
 933         // if appropriate.
 934         let t_cast = self.to_ty_saving_user_provided_ty(t);
 935         let t_cast = self.resolve_vars_if_possible(&t_cast);
 936         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
 937         let t_cast = self.resolve_vars_if_possible(&t_cast);
 938
 939         // Eagerly check for some obvious errors.
 940         if t_expr.references_error() || t_cast.references_error() {
 941             self.tcx.ty_error()
 942         } else {
 943             // Defer other checks until we're done type checking.
 944             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
 945             match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
 946                 Ok(cast_check) => {
 947                     deferred_cast_checks.push(cast_check);
 948                     t_cast
 949                 }
 950                 Err(ErrorReported) => self.tcx.ty_error(),
 951             }
 952         }
 953     }
 954
 955     fn check_expr_array(
 956         &self,
 957         args: &'tcx [hir::Expr<'tcx>],
 958         expected: Expectation<'tcx>,
 959         expr: &'tcx hir::Expr<'tcx>,
 960     ) -> Ty<'tcx> {
 961         let element_ty = if !args.is_empty() {
 962             let coerce_to = expected
 963                 .to_option(self)
 964                 .and_then(|uty| match uty.kind {
 965                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
 966                     _ => None,
 967                 })
 968                 .unwrap_or_else(|| {
 969                     self.next_ty_var(TypeVariableOrigin {
 970                         kind: TypeVariableOriginKind::TypeInference,
 971                         span: expr.span,
 972                     })
 973                 });
 974             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
 975             assert_eq!(self.diverges.get(), Diverges::Maybe);
 976             for e in args {
 977                 let e_ty = self.check_expr_with_hint(e, coerce_to);
 978                 let cause = self.misc(e.span);
 979                 coerce.coerce(self, &cause, e, e_ty);
 980             }
 981             coerce.complete(self)
 982         } else {
 983             self.next_ty_var(TypeVariableOrigin {
 984                 kind: TypeVariableOriginKind::TypeInference,
 985                 span: expr.span,
 986             })
 987         };
 988         self.tcx.mk_array(element_ty, args.len() as u64)
 989     }
 990
 991     fn check_expr_repeat(
 992         &self,
 993         element: &'tcx hir::Expr<'tcx>,
 994         count: &'tcx hir::AnonConst,
 995         expected: Expectation<'tcx>,
 996         _expr: &'tcx hir::Expr<'tcx>,
 997     ) -> Ty<'tcx> {
 998         let tcx = self.tcx;
 999         let count = self.to_const(count);
1000
1001         let uty = match expected {
1002             ExpectHasType(uty) => match uty.kind {
1003                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1004                 _ => None,
1005             },
1006             _ => None,
1007         };
1008
1009         let (element_ty, t) = match uty {
1010             Some(uty) => {
1011                 self.check_expr_coercable_to_type(&element, uty, None);
1012                 (uty, uty)
1013             }
1014             None => {
1015                 let ty = self.next_ty_var(TypeVariableOrigin {
1016                     kind: TypeVariableOriginKind::MiscVariable,
1017                     span: element.span,
1018                 });
1019                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1020                 (element_ty, ty)
1021             }
1022         };
1023
1024         if element_ty.references_error() {
1025             return tcx.ty_error();
1026         }
1027
1028         tcx.mk_ty(ty::Array(t, count))
1029     }
1030
1031     fn check_expr_tuple(
1032         &self,
1033         elts: &'tcx [hir::Expr<'tcx>],
1034         expected: Expectation<'tcx>,
1035         expr: &'tcx hir::Expr<'tcx>,
1036     ) -> Ty<'tcx> {
1037         let flds = expected.only_has_type(self).and_then(|ty| {
1038             let ty = self.resolve_vars_with_obligations(ty);
1039             match ty.kind {
1040                 ty::Tuple(ref flds) => Some(&flds[..]),
1041                 _ => None,
1042             }
1043         });
1044
1045         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1046             Some(ref fs) if i < fs.len() => {
1047                 let ety = fs[i].expect_ty();
1048                 self.check_expr_coercable_to_type(&e, ety, None);
1049                 ety
1050             }
1051             _ => self.check_expr_with_expectation(&e, NoExpectation),
1052         });
1053         let tuple = self.tcx.mk_tup(elt_ts_iter);
1054         if tuple.references_error() {
1055             self.tcx.ty_error()
1056         } else {
1057             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1058             tuple
1059         }
1060     }
1061
1062     fn check_expr_struct(
1063         &self,
1064         expr: &hir::Expr<'_>,
1065         expected: Expectation<'tcx>,
1066         qpath: &QPath<'_>,
1067         fields: &'tcx [hir::Field<'tcx>],
1068         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1069     ) -> Ty<'tcx> {
1070         // Find the relevant variant
1071         let (variant, adt_ty) = if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id)
1072         {
1073             variant_ty
1074         } else {
1075             self.check_struct_fields_on_error(fields, base_expr);
1076             return self.tcx.ty_error();
1077         };
1078
1079         let path_span = match *qpath {
1080             QPath::Resolved(_, ref path) => path.span,
1081             QPath::TypeRelative(ref qself, _) => qself.span,
1082         };
1083
1084         // Prohibit struct expressions when non-exhaustive flag is set.
1085         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1086         if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
1087             struct_span_err!(
1088                 self.tcx.sess,
1089                 expr.span,
1090                 E0639,
1091                 "cannot create non-exhaustive {} using struct expression",
1092                 adt.variant_descr()
1093             )
1094             .emit();
1095         }
1096
1097         let error_happened = self.check_expr_struct_fields(
1098             adt_ty,
1099             expected,
1100             expr.hir_id,
1101             path_span,
1102             variant,
1103             fields,
1104             base_expr.is_none(),
1105         );
1106         if let &Some(ref base_expr) = base_expr {
1107             // If check_expr_struct_fields hit an error, do not attempt to populate
1108             // the fields with the base_expr. This could cause us to hit errors later
1109             // when certain fields are assumed to exist that in fact do not.
1110             if !error_happened {
1111                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {});
1112                 match adt_ty.kind {
1113                     ty::Adt(adt, substs) if adt.is_struct() => {
1114                         let fru_field_types = adt
1115                             .non_enum_variant()
1116                             .fields
1117                             .iter()
1118                             .map(|f| {
1119                                 self.normalize_associated_types_in(
1120                                     expr.span,
1121                                     &f.ty(self.tcx, substs),
1122                                 )
1123                             })
1124                             .collect();
1125
1126                         self.tables
1127                             .borrow_mut()
1128                             .fru_field_types_mut()
1129                             .insert(expr.hir_id, fru_field_types);
1130                     }
1131                     _ => {
1132                         struct_span_err!(
1133                             self.tcx.sess,
1134                             base_expr.span,
1135                             E0436,
1136                             "functional record update syntax requires a struct"
1137                         )
1138                         .emit();
1139                     }
1140                 }
1141             }
1142         }
1143         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1144         adt_ty
1145     }
1146
1147     fn check_expr_struct_fields(
1148         &self,
1149         adt_ty: Ty<'tcx>,
1150         expected: Expectation<'tcx>,
1151         expr_id: hir::HirId,
1152         span: Span,
1153         variant: &'tcx ty::VariantDef,
1154         ast_fields: &'tcx [hir::Field<'tcx>],
1155         check_completeness: bool,
1156     ) -> bool {
1157         let tcx = self.tcx;
1158
1159         let adt_ty_hint = self
1160             .expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
1161             .get(0)
1162             .cloned()
1163             .unwrap_or(adt_ty);
1164         // re-link the regions that EIfEO can erase.
1165         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1166
1167         let (substs, adt_kind, kind_name) = match &adt_ty.kind {
1168             &ty::Adt(adt, substs) => (substs, adt.adt_kind(), adt.variant_descr()),
1169             _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields"),
1170         };
1171
1172         let mut remaining_fields = variant
1173             .fields
1174             .iter()
1175             .enumerate()
1176             .map(|(i, field)| (field.ident.normalize_to_macros_2_0(), (i, field)))
1177             .collect::<FxHashMap<_, _>>();
1178
1179         let mut seen_fields = FxHashMap::default();
1180
1181         let mut error_happened = false;
1182
1183         // Type-check each field.
1184         for field in ast_fields {
1185             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1186             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1187                 seen_fields.insert(ident, field.span);
1188                 self.write_field_index(field.hir_id, i);
1189
1190                 // We don't look at stability attributes on
1191                 // struct-like enums (yet...), but it's definitely not
1192                 // a bug to have constructed one.
1193                 if adt_kind != AdtKind::Enum {
1194                     tcx.check_stability(v_field.did, Some(expr_id), field.span);
1195                 }
1196
1197                 self.field_ty(field.span, v_field, substs)
1198             } else {
1199                 error_happened = true;
1200                 if let Some(prev_span) = seen_fields.get(&ident) {
1201                     let mut err = struct_span_err!(
1202                         self.tcx.sess,
1203                         field.ident.span,
1204                         E0062,
1205                         "field `{}` specified more than once",
1206                         ident
1207                     );
1208
1209                     err.span_label(field.ident.span, "used more than once");
1210                     err.span_label(*prev_span, format!("first use of `{}`", ident));
1211
1212                     err.emit();
1213                 } else {
1214                     self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name, span);
1215                 }
1216
1217                 tcx.ty_error()
1218             };
1219
1220             // Make sure to give a type to the field even if there's
1221             // an error, so we can continue type-checking.
1222             self.check_expr_coercable_to_type(&field.expr, field_type, None);
1223         }
1224
1225         // Make sure the programmer specified correct number of fields.
1226         if kind_name == "union" {
1227             if ast_fields.len() != 1 {
1228                 tcx.sess.span_err(span, "union expressions should have exactly one field");
1229             }
1230         } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
1231             let len = remaining_fields.len();
1232
1233             let mut displayable_field_names =
1234                 remaining_fields.keys().map(|ident| ident.as_str()).collect::<Vec<_>>();
1235
1236             displayable_field_names.sort();
1237
1238             let truncated_fields_error = if len <= 3 {
1239                 String::new()
1240             } else {
1241                 format!(" and {} other field{}", (len - 3), if len - 3 == 1 { "" } else { "s" })
1242             };
1243
1244             let remaining_fields_names = displayable_field_names
1245                 .iter()
1246                 .take(3)
1247                 .map(|n| format!("`{}`", n))
1248                 .collect::<Vec<_>>()
1249                 .join(", ");
1250
1251             struct_span_err!(
1252                 tcx.sess,
1253                 span,
1254                 E0063,
1255                 "missing field{} {}{} in initializer of `{}`",
1256                 pluralize!(remaining_fields.len()),
1257                 remaining_fields_names,
1258                 truncated_fields_error,
1259                 adt_ty
1260             )
1261             .span_label(
1262                 span,
1263                 format!("missing {}{}", remaining_fields_names, truncated_fields_error),
1264             )
1265             .emit();
1266         }
1267         error_happened
1268     }
1269
1270     fn check_struct_fields_on_error(
1271         &self,
1272         fields: &'tcx [hir::Field<'tcx>],
1273         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1274     ) {
1275         for field in fields {
1276             self.check_expr(&field.expr);
1277         }
1278         if let Some(ref base) = *base_expr {
1279             self.check_expr(&base);
1280         }
1281     }
1282
1283     fn report_unknown_field(
1284         &self,
1285         ty: Ty<'tcx>,
1286         variant: &'tcx ty::VariantDef,
1287         field: &hir::Field<'_>,
1288         skip_fields: &[hir::Field<'_>],
1289         kind_name: &str,
1290         ty_span: Span,
1291     ) {
1292         if variant.recovered {
1293             self.set_tainted_by_errors();
1294             return;
1295         }
1296         let mut err = self.type_error_struct_with_diag(
1297             field.ident.span,
1298             |actual| match ty.kind {
1299                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1300                     self.tcx.sess,
1301                     field.ident.span,
1302                     E0559,
1303                     "{} `{}::{}` has no field named `{}`",
1304                     kind_name,
1305                     actual,
1306                     variant.ident,
1307                     field.ident
1308                 ),
1309                 _ => struct_span_err!(
1310                     self.tcx.sess,
1311                     field.ident.span,
1312                     E0560,
1313                     "{} `{}` has no field named `{}`",
1314                     kind_name,
1315                     actual,
1316                     field.ident
1317                 ),
1318             },
1319             ty,
1320         );
1321         match variant.ctor_kind {
1322             CtorKind::Fn => {
1323                 err.span_label(variant.ident.span, format!("`{adt}` defined here", adt = ty));
1324                 err.span_label(field.ident.span, "field does not exist");
1325                 err.span_label(
1326                     ty_span,
1327                     format!(
1328                         "`{adt}` is a tuple {kind_name}, \
1329                          use the appropriate syntax: `{adt}(/* fields */)`",
1330                         adt = ty,
1331                         kind_name = kind_name
1332                     ),
1333                 );
1334             }
1335             _ => {
1336                 // prevent all specified fields from being suggested
1337                 let skip_fields = skip_fields.iter().map(|ref x| x.ident.name);
1338                 if let Some(field_name) =
1339                     Self::suggest_field_name(variant, &field.ident.as_str(), skip_fields.collect())
1340                 {
1341                     err.span_suggestion(
1342                         field.ident.span,
1343                         "a field with a similar name exists",
1344                         field_name.to_string(),
1345                         Applicability::MaybeIncorrect,
1346                     );
1347                 } else {
1348                     match ty.kind {
1349                         ty::Adt(adt, ..) => {
1350                             if adt.is_enum() {
1351                                 err.span_label(
1352                                     field.ident.span,
1353                                     format!("`{}::{}` does not have this field", ty, variant.ident),
1354                                 );
1355                             } else {
1356                                 err.span_label(
1357                                     field.ident.span,
1358                                     format!("`{}` does not have this field", ty),
1359                                 );
1360                             }
1361                             let available_field_names = self.available_field_names(variant);
1362                             if !available_field_names.is_empty() {
1363                                 err.note(&format!(
1364                                     "available fields are: {}",
1365                                     self.name_series_display(available_field_names)
1366                                 ));
1367                             }
1368                         }
1369                         _ => bug!("non-ADT passed to report_unknown_field"),
1370                     }
1371                 };
1372             }
1373         }
1374         err.emit();
1375     }
1376
1377     // Return an hint about the closest match in field names
1378     fn suggest_field_name(
1379         variant: &'tcx ty::VariantDef,
1380         field: &str,
1381         skip: Vec<Symbol>,
1382     ) -> Option<Symbol> {
1383         let names = variant.fields.iter().filter_map(|field| {
1384             // ignore already set fields and private fields from non-local crates
1385             if skip.iter().any(|&x| x == field.ident.name)
1386                 || (!variant.def_id.is_local() && field.vis != Visibility::Public)
1387             {
1388                 None
1389             } else {
1390                 Some(&field.ident.name)
1391             }
1392         });
1393
1394         find_best_match_for_name(names, field, None)
1395     }
1396
1397     fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<Symbol> {
1398         variant
1399             .fields
1400             .iter()
1401             .filter(|field| {
1402                 let def_scope = self
1403                     .tcx
1404                     .adjust_ident_and_get_scope(field.ident, variant.def_id, self.body_id)
1405                     .1;
1406                 field.vis.is_accessible_from(def_scope, self.tcx)
1407             })
1408             .map(|field| field.ident.name)
1409             .collect()
1410     }
1411
1412     fn name_series_display(&self, names: Vec<Symbol>) -> String {
1413         // dynamic limit, to never omit just one field
1414         let limit = if names.len() == 6 { 6 } else { 5 };
1415         let mut display =
1416             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
1417         if names.len() > limit {
1418             display = format!("{} ... and {} others", display, names.len() - limit);
1419         }
1420         display
1421     }
1422
1423     // Check field access expressions
1424     fn check_field(
1425         &self,
1426         expr: &'tcx hir::Expr<'tcx>,
1427         base: &'tcx hir::Expr<'tcx>,
1428         field: Ident,
1429     ) -> Ty<'tcx> {
1430         let expr_t = self.check_expr(base);
1431         let expr_t = self.structurally_resolved_type(base.span, expr_t);
1432         let mut private_candidate = None;
1433         let mut autoderef = self.autoderef(expr.span, expr_t);
1434         while let Some((base_t, _)) = autoderef.next() {
1435             match base_t.kind {
1436                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
1437                     debug!("struct named {:?}", base_t);
1438                     let (ident, def_scope) =
1439                         self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
1440                     let fields = &base_def.non_enum_variant().fields;
1441                     if let Some(index) =
1442                         fields.iter().position(|f| f.ident.normalize_to_macros_2_0() == ident)
1443                     {
1444                         let field = &fields[index];
1445                         let field_ty = self.field_ty(expr.span, field, substs);
1446                         // Save the index of all fields regardless of their visibility in case
1447                         // of error recovery.
1448                         self.write_field_index(expr.hir_id, index);
1449                         if field.vis.is_accessible_from(def_scope, self.tcx) {
1450                             let adjustments = self.adjust_steps(&autoderef);
1451                             self.apply_adjustments(base, adjustments);
1452                             self.register_predicates(autoderef.into_obligations());
1453
1454                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span);
1455                             return field_ty;
1456                         }
1457                         private_candidate = Some((base_def.did, field_ty));
1458                     }
1459                 }
1460                 ty::Tuple(ref tys) => {
1461                     let fstr = field.as_str();
1462                     if let Ok(index) = fstr.parse::<usize>() {
1463                         if fstr == index.to_string() {
1464                             if let Some(field_ty) = tys.get(index) {
1465                                 let adjustments = self.adjust_steps(&autoderef);
1466                                 self.apply_adjustments(base, adjustments);
1467                                 self.register_predicates(autoderef.into_obligations());
1468
1469                                 self.write_field_index(expr.hir_id, index);
1470                                 return field_ty.expect_ty();
1471                             }
1472                         }
1473                     }
1474                 }
1475                 _ => {}
1476             }
1477         }
1478         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
1479
1480         if let Some((did, field_ty)) = private_candidate {
1481             self.ban_private_field_access(expr, expr_t, field, did);
1482             return field_ty;
1483         }
1484
1485         if field.name == kw::Invalid {
1486         } else if self.method_exists(field, expr_t, expr.hir_id, true) {
1487             self.ban_take_value_of_method(expr, expr_t, field);
1488         } else if !expr_t.is_primitive_ty() {
1489             self.ban_nonexisting_field(field, base, expr, expr_t);
1490         } else {
1491             type_error_struct!(
1492                 self.tcx().sess,
1493                 field.span,
1494                 expr_t,
1495                 E0610,
1496                 "`{}` is a primitive type and therefore doesn't have fields",
1497                 expr_t
1498             )
1499             .emit();
1500         }
1501
1502         self.tcx().ty_error()
1503     }
1504
1505     fn ban_nonexisting_field(
1506         &self,
1507         field: Ident,
1508         base: &'tcx hir::Expr<'tcx>,
1509         expr: &'tcx hir::Expr<'tcx>,
1510         expr_t: Ty<'tcx>,
1511     ) {
1512         let mut err = self.no_such_field_err(field.span, field, expr_t);
1513
1514         match expr_t.peel_refs().kind {
1515             ty::Array(_, len) => {
1516                 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
1517             }
1518             ty::RawPtr(..) => {
1519                 self.suggest_first_deref_field(&mut err, expr, base, field);
1520             }
1521             ty::Adt(def, _) if !def.is_enum() => {
1522                 self.suggest_fields_on_recordish(&mut err, def, field);
1523             }
1524             ty::Param(param_ty) => {
1525                 self.point_at_param_definition(&mut err, param_ty);
1526             }
1527             _ => {}
1528         }
1529
1530         if field.name == kw::Await {
1531             // We know by construction that `<expr>.await` is either on Rust 2015
1532             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
1533             err.note("to `.await` a `Future`, switch to Rust 2018");
1534             err.help("set `edition = \"2018\"` in `Cargo.toml`");
1535             err.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
1536         }
1537
1538         err.emit();
1539     }
1540
1541     fn ban_private_field_access(
1542         &self,
1543         expr: &hir::Expr<'_>,
1544         expr_t: Ty<'tcx>,
1545         field: Ident,
1546         base_did: DefId,
1547     ) {
1548         let struct_path = self.tcx().def_path_str(base_did);
1549         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
1550         let mut err = struct_span_err!(
1551             self.tcx().sess,
1552             field.span,
1553             E0616,
1554             "field `{}` of {} `{}` is private",
1555             field,
1556             kind_name,
1557             struct_path
1558         );
1559         err.span_label(field.span, "private field");
1560         // Also check if an accessible method exists, which is often what is meant.
1561         if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
1562         {
1563             self.suggest_method_call(
1564                 &mut err,
1565                 &format!("a method `{}` also exists, call it with parentheses", field),
1566                 field,
1567                 expr_t,
1568                 expr,
1569             );
1570         }
1571         err.emit();
1572     }
1573
1574     fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
1575         let mut err = type_error_struct!(
1576             self.tcx().sess,
1577             field.span,
1578             expr_t,
1579             E0615,
1580             "attempted to take value of method `{}` on type `{}`",
1581             field,
1582             expr_t
1583         );
1584         err.span_label(field.span, "method, not a field");
1585         if !self.expr_in_place(expr.hir_id) {
1586             self.suggest_method_call(
1587                 &mut err,
1588                 "use parentheses to call the method",
1589                 field,
1590                 expr_t,
1591                 expr,
1592             );
1593         } else {
1594             err.help("methods are immutable and cannot be assigned to");
1595         }
1596
1597         err.emit();
1598     }
1599
1600     fn point_at_param_definition(&self, err: &mut DiagnosticBuilder<'_>, param: ty::ParamTy) {
1601         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
1602         let generic_param = generics.type_param(&param, self.tcx);
1603         if let ty::GenericParamDefKind::Type { synthetic: Some(..), .. } = generic_param.kind {
1604             return;
1605         }
1606         let param_def_id = generic_param.def_id;
1607         let param_hir_id = match param_def_id.as_local() {
1608             Some(x) => self.tcx.hir().as_local_hir_id(x),
1609             None => return,
1610         };
1611         let param_span = self.tcx.hir().span(param_hir_id);
1612         let param_name = self.tcx.hir().ty_param_name(param_hir_id);
1613
1614         err.span_label(param_span, &format!("type parameter '{}' declared here", param_name));
1615     }
1616
1617     fn suggest_fields_on_recordish(
1618         &self,
1619         err: &mut DiagnosticBuilder<'_>,
1620         def: &'tcx ty::AdtDef,
1621         field: Ident,
1622     ) {
1623         if let Some(suggested_field_name) =
1624             Self::suggest_field_name(def.non_enum_variant(), &field.as_str(), vec![])
1625         {
1626             err.span_suggestion(
1627                 field.span,
1628                 "a field with a similar name exists",
1629                 suggested_field_name.to_string(),
1630                 Applicability::MaybeIncorrect,
1631             );
1632         } else {
1633             err.span_label(field.span, "unknown field");
1634             let struct_variant_def = def.non_enum_variant();
1635             let field_names = self.available_field_names(struct_variant_def);
1636             if !field_names.is_empty() {
1637                 err.note(&format!(
1638                     "available fields are: {}",
1639                     self.name_series_display(field_names),
1640                 ));
1641             }
1642         }
1643     }
1644
1645     fn maybe_suggest_array_indexing(
1646         &self,
1647         err: &mut DiagnosticBuilder<'_>,
1648         expr: &hir::Expr<'_>,
1649         base: &hir::Expr<'_>,
1650         field: Ident,
1651         len: &ty::Const<'tcx>,
1652     ) {
1653         if let (Some(len), Ok(user_index)) =
1654             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
1655         {
1656             if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
1657                 let help = "instead of using tuple indexing, use array indexing";
1658                 let suggestion = format!("{}[{}]", base, field);
1659                 let applicability = if len < user_index {
1660                     Applicability::MachineApplicable
1661                 } else {
1662                     Applicability::MaybeIncorrect
1663                 };
1664                 err.span_suggestion(expr.span, help, suggestion, applicability);
1665             }
1666         }
1667     }
1668
1669     fn suggest_first_deref_field(
1670         &self,
1671         err: &mut DiagnosticBuilder<'_>,
1672         expr: &hir::Expr<'_>,
1673         base: &hir::Expr<'_>,
1674         field: Ident,
1675     ) {
1676         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
1677             let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
1678             let suggestion = format!("(*{}).{}", base, field);
1679             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
1680         }
1681     }
1682
1683     fn no_such_field_err<T: Display>(
1684         &self,
1685         span: Span,
1686         field: T,
1687         expr_t: &ty::TyS<'_>,
1688     ) -> DiagnosticBuilder<'_> {
1689         type_error_struct!(
1690             self.tcx().sess,
1691             span,
1692             expr_t,
1693             E0609,
1694             "no field `{}` on type `{}`",
1695             field,
1696             expr_t
1697         )
1698     }
1699
1700     fn check_expr_index(
1701         &self,
1702         base: &'tcx hir::Expr<'tcx>,
1703         idx: &'tcx hir::Expr<'tcx>,
1704         expr: &'tcx hir::Expr<'tcx>,
1705     ) -> Ty<'tcx> {
1706         let base_t = self.check_expr(&base);
1707         let idx_t = self.check_expr(&idx);
1708
1709         if base_t.references_error() {
1710             base_t
1711         } else if idx_t.references_error() {
1712             idx_t
1713         } else {
1714             let base_t = self.structurally_resolved_type(base.span, base_t);
1715             match self.lookup_indexing(expr, base, base_t, idx_t) {
1716                 Some((index_ty, element_ty)) => {
1717                     // two-phase not needed because index_ty is never mutable
1718                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
1719                     element_ty
1720                 }
1721                 None => {
1722                     let mut err = type_error_struct!(
1723                         self.tcx.sess,
1724                         expr.span,
1725                         base_t,
1726                         E0608,
1727                         "cannot index into a value of type `{}`",
1728                         base_t
1729                     );
1730                     // Try to give some advice about indexing tuples.
1731                     if let ty::Tuple(..) = base_t.kind {
1732                         let mut needs_note = true;
1733                         // If the index is an integer, we can show the actual
1734                         // fixed expression:
1735                         if let ExprKind::Lit(ref lit) = idx.kind {
1736                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
1737                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
1738                                 if let Ok(snip) = snip {
1739                                     err.span_suggestion(
1740                                         expr.span,
1741                                         "to access tuple elements, use",
1742                                         format!("{}.{}", snip, i),
1743                                         Applicability::MachineApplicable,
1744                                     );
1745                                     needs_note = false;
1746                                 }
1747                             }
1748                         }
1749                         if needs_note {
1750                             err.help(
1751                                 "to access tuple elements, use tuple indexing \
1752                                         syntax (e.g., `tuple.0`)",
1753                             );
1754                         }
1755                     }
1756                     err.emit();
1757                     self.tcx.ty_error()
1758                 }
1759             }
1760         }
1761     }
1762
1763     fn check_expr_yield(
1764         &self,
1765         value: &'tcx hir::Expr<'tcx>,
1766         expr: &'tcx hir::Expr<'tcx>,
1767         src: &'tcx hir::YieldSource,
1768     ) -> Ty<'tcx> {
1769         match self.resume_yield_tys {
1770             Some((resume_ty, yield_ty)) => {
1771                 self.check_expr_coercable_to_type(&value, yield_ty, None);
1772
1773                 resume_ty
1774             }
1775             // Given that this `yield` expression was generated as a result of lowering a `.await`,
1776             // we know that the yield type must be `()`; however, the context won't contain this
1777             // information. Hence, we check the source of the yield expression here and check its
1778             // value's type against `()` (this check should always hold).
1779             None if src.is_await() => {
1780                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
1781                 self.tcx.mk_unit()
1782             }
1783             _ => {
1784                 struct_span_err!(
1785                     self.tcx.sess,
1786                     expr.span,
1787                     E0627,
1788                     "yield expression outside of generator literal"
1789                 )
1790                 .emit();
1791                 self.tcx.mk_unit()
1792             }
1793         }
1794     }
1795
1796     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
1797         let needs = if is_input { Needs::None } else { Needs::MutPlace };
1798         let ty = self.check_expr_with_needs(expr, needs);
1799         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
1800
1801         if !is_input && !expr.is_syntactic_place_expr() {
1802             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
1803             err.span_label(expr.span, "cannot assign to this expression");
1804             err.emit();
1805         }
1806
1807         // If this is an input value, we require its type to be fully resolved
1808         // at this point. This allows us to provide helpful coercions which help
1809         // pass the type candidate list in a later pass.
1810         //
1811         // We don't require output types to be resolved at this point, which
1812         // allows them to be inferred based on how they are used later in the
1813         // function.
1814         if is_input {
1815             let ty = self.structurally_resolved_type(expr.span, &ty);
1816             match ty.kind {
1817                 ty::FnDef(..) => {
1818                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
1819                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
1820                 }
1821                 ty::Ref(_, base_ty, mutbl) => {
1822                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
1823                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
1824                 }
1825                 _ => {}
1826             }
1827         }
1828     }
1829
1830     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
1831         for op in asm.operands {
1832             match op {
1833                 hir::InlineAsmOperand::In { expr, .. } | hir::InlineAsmOperand::Const { expr } => {
1834                     self.check_expr_asm_operand(expr, true);
1835                 }
1836                 hir::InlineAsmOperand::Out { expr, .. } => {
1837                     if let Some(expr) = expr {
1838                         self.check_expr_asm_operand(expr, false);
1839                     }
1840                 }
1841                 hir::InlineAsmOperand::InOut { expr, .. } => {
1842                     self.check_expr_asm_operand(expr, false);
1843                 }
1844                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
1845                     self.check_expr_asm_operand(in_expr, true);
1846                     if let Some(out_expr) = out_expr {
1847                         self.check_expr_asm_operand(out_expr, false);
1848                     }
1849                 }
1850                 hir::InlineAsmOperand::Sym { expr } => {
1851                     self.check_expr(expr);
1852                 }
1853             }
1854         }
1855         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
1856             self.tcx.types.never
1857         } else {
1858             self.tcx.mk_unit()
1859         }
1860     }
1861 }
1862
1863 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
1864     Some(match ty.kind {
1865         ty::Bool => "true",
1866         ty::Char => "'a'",
1867         ty::Int(_) | ty::Uint(_) => "42",
1868         ty::Float(_) => "3.14159",
1869         ty::Error(_) | ty::Never => return None,
1870         _ => "value",
1871     })
1872 }