compiler/rustc_typeck/src/check/expr.rs

   1 //! Type checking expressions.
   2 //!
   3 //! See `mod.rs` for more context on type checking in general.
   4
   5 use crate::astconv::AstConv as _;
   6 use crate::check::cast;
   7 use crate::check::coercion::CoerceMany;
   8 use crate::check::fatally_break_rust;
   9 use crate::check::method::SelfSource;
  10 use crate::check::report_unexpected_variant_res;
  11 use crate::check::BreakableCtxt;
  12 use crate::check::Diverges;
  13 use crate::check::DynamicCoerceMany;
  14 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
  15 use crate::check::FnCtxt;
  16 use crate::check::Needs;
  17 use crate::check::TupleArgumentsFlag::DontTupleArguments;
  18 use crate::errors::{
  19     FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
  20     YieldExprOutsideOfGenerator,
  21 };
  22 use crate::type_error_struct;
  23
  24 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
  25 use rustc_ast as ast;
  26 use rustc_data_structures::fx::FxHashMap;
  27 use rustc_data_structures::stack::ensure_sufficient_stack;
  28 use rustc_errors::ErrorReported;
  29 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::{CtorKind, DefKind, Res};
  32 use rustc_hir::def_id::DefId;
  33 use rustc_hir::intravisit::Visitor;
  34 use rustc_hir::{ExprKind, HirId, QPath};
  35 use rustc_infer::infer;
  36 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
  37 use rustc_infer::infer::InferOk;
  38 use rustc_middle::middle::stability;
  39 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
  40 use rustc_middle::ty::error::ExpectedFound;
  41 use rustc_middle::ty::error::TypeError::{FieldMisMatch, Sorts};
  42 use rustc_middle::ty::subst::SubstsRef;
  43 use rustc_middle::ty::{self, AdtKind, Ty, TypeFoldable};
  44 use rustc_session::parse::feature_err;
  45 use rustc_span::edition::LATEST_STABLE_EDITION;
  46 use rustc_span::hygiene::DesugaringKind;
  47 use rustc_span::lev_distance::find_best_match_for_name;
  48 use rustc_span::source_map::Span;
  49 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  50 use rustc_span::{BytePos, Pos};
  51 use rustc_trait_selection::traits::{self, ObligationCauseCode};
  52
  53 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  54     fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
  55         let ty = self.check_expr_with_hint(expr, expected);
  56         self.demand_eqtype(expr.span, expected, ty);
  57     }
  58
  59     pub fn check_expr_has_type_or_error(
  60         &self,
  61         expr: &'tcx hir::Expr<'tcx>,
  62         expected: Ty<'tcx>,
  63         extend_err: impl Fn(&mut DiagnosticBuilder<'_>),
  64     ) -> Ty<'tcx> {
  65         self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
  66     }
  67
  68     fn check_expr_meets_expectation_or_error(
  69         &self,
  70         expr: &'tcx hir::Expr<'tcx>,
  71         expected: Expectation<'tcx>,
  72         extend_err: impl Fn(&mut DiagnosticBuilder<'_>),
  73     ) -> Ty<'tcx> {
  74         let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
  75         let mut ty = self.check_expr_with_expectation(expr, expected);
  76
  77         // While we don't allow *arbitrary* coercions here, we *do* allow
  78         // coercions from ! to `expected`.
  79         if ty.is_never() {
  80             assert!(
  81                 !self.typeck_results.borrow().adjustments().contains_key(expr.hir_id),
  82                 "expression with never type wound up being adjusted"
  83             );
  84             let adj_ty = self.next_ty_var(TypeVariableOrigin {
  85                 kind: TypeVariableOriginKind::AdjustmentType,
  86                 span: expr.span,
  87             });
  88             self.apply_adjustments(
  89                 expr,
  90                 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
  91             );
  92             ty = adj_ty;
  93         }
  94
  95         if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
  96             let expr = expr.peel_drop_temps();
  97             self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
  98             extend_err(&mut err);
  99             err.emit();
 100         }
 101         ty
 102     }
 103
 104     pub(super) fn check_expr_coercable_to_type(
 105         &self,
 106         expr: &'tcx hir::Expr<'tcx>,
 107         expected: Ty<'tcx>,
 108         expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
 109     ) -> Ty<'tcx> {
 110         let ty = self.check_expr_with_hint(expr, expected);
 111         // checks don't need two phase
 112         self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
 113     }
 114
 115     pub(super) fn check_expr_with_hint(
 116         &self,
 117         expr: &'tcx hir::Expr<'tcx>,
 118         expected: Ty<'tcx>,
 119     ) -> Ty<'tcx> {
 120         self.check_expr_with_expectation(expr, ExpectHasType(expected))
 121     }
 122
 123     fn check_expr_with_expectation_and_needs(
 124         &self,
 125         expr: &'tcx hir::Expr<'tcx>,
 126         expected: Expectation<'tcx>,
 127         needs: Needs,
 128     ) -> Ty<'tcx> {
 129         let ty = self.check_expr_with_expectation(expr, expected);
 130
 131         // If the expression is used in a place whether mutable place is required
 132         // e.g. LHS of assignment, perform the conversion.
 133         if let Needs::MutPlace = needs {
 134             self.convert_place_derefs_to_mutable(expr);
 135         }
 136
 137         ty
 138     }
 139
 140     pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
 141         self.check_expr_with_expectation(expr, NoExpectation)
 142     }
 143
 144     pub(super) fn check_expr_with_needs(
 145         &self,
 146         expr: &'tcx hir::Expr<'tcx>,
 147         needs: Needs,
 148     ) -> Ty<'tcx> {
 149         self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
 150     }
 151
 152     /// Invariant:
 153     /// If an expression has any sub-expressions that result in a type error,
 154     /// inspecting that expression's type with `ty.references_error()` will return
 155     /// true. Likewise, if an expression is known to diverge, inspecting its
 156     /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
 157     /// strict, _|_ can appear in the type of an expression that does not,
 158     /// itself, diverge: for example, fn() -> _|_.)
 159     /// Note that inspecting a type's structure *directly* may expose the fact
 160     /// that there are actually multiple representations for `Error`, so avoid
 161     /// that when err needs to be handled differently.
 162     #[instrument(skip(self, expr), level = "debug")]
 163     pub(super) fn check_expr_with_expectation(
 164         &self,
 165         expr: &'tcx hir::Expr<'tcx>,
 166         expected: Expectation<'tcx>,
 167     ) -> Ty<'tcx> {
 168         self.check_expr_with_expectation_and_args(expr, expected, &[])
 169     }
 170
 171     /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
 172     /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
 173     pub(super) fn check_expr_with_expectation_and_args(
 174         &self,
 175         expr: &'tcx hir::Expr<'tcx>,
 176         expected: Expectation<'tcx>,
 177         args: &'tcx [hir::Expr<'tcx>],
 178     ) -> Ty<'tcx> {
 179         if self.tcx().sess.verbose() {
 180             // make this code only run with -Zverbose because it is probably slow
 181             if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
 182                 if !lint_str.contains('\n') {
 183                     debug!("expr text: {}", lint_str);
 184                 } else {
 185                     let mut lines = lint_str.lines();
 186                     if let Some(line0) = lines.next() {
 187                         let remaining_lines = lines.count();
 188                         debug!("expr text: {}", line0);
 189                         debug!("expr text: ...(and {} more lines)", remaining_lines);
 190                     }
 191                 }
 192             }
 193         }
 194
 195         // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
 196         // without the final expr (e.g. `try { return; }`). We don't want to generate an
 197         // unreachable_code lint for it since warnings for autogenerated code are confusing.
 198         let is_try_block_generated_unit_expr = match expr.kind {
 199             ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
 200                 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
 201             }
 202
 203             _ => false,
 204         };
 205
 206         // Warn for expressions after diverging siblings.
 207         if !is_try_block_generated_unit_expr {
 208             self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
 209         }
 210
 211         // Hide the outer diverging and has_errors flags.
 212         let old_diverges = self.diverges.replace(Diverges::Maybe);
 213         let old_has_errors = self.has_errors.replace(false);
 214
 215         let ty = ensure_sufficient_stack(|| match &expr.kind {
 216             hir::ExprKind::Path(
 217                 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
 218             ) => self.check_expr_path(qpath, expr, args),
 219             _ => self.check_expr_kind(expr, expected),
 220         });
 221
 222         // Warn for non-block expressions with diverging children.
 223         match expr.kind {
 224             ExprKind::Block(..)
 225             | ExprKind::If(..)
 226             | ExprKind::Let(..)
 227             | ExprKind::Loop(..)
 228             | ExprKind::Match(..) => {}
 229             // If `expr` is a result of desugaring the try block and is an ok-wrapped
 230             // diverging expression (e.g. it arose from desugaring of `try { return }`),
 231             // we skip issuing a warning because it is autogenerated code.
 232             ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
 233             ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
 234             ExprKind::MethodCall(segment, ..) => {
 235                 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
 236             }
 237             _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
 238         }
 239
 240         // Any expression that produces a value of type `!` must have diverged
 241         if ty.is_never() {
 242             self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
 243         }
 244
 245         // Record the type, which applies it effects.
 246         // We need to do this after the warning above, so that
 247         // we don't warn for the diverging expression itself.
 248         self.write_ty(expr.hir_id, ty);
 249
 250         // Combine the diverging and has_error flags.
 251         self.diverges.set(self.diverges.get() | old_diverges);
 252         self.has_errors.set(self.has_errors.get() | old_has_errors);
 253
 254         debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
 255         debug!("... {:?}, expected is {:?}", ty, expected);
 256
 257         ty
 258     }
 259
 260     #[instrument(skip(self, expr), level = "debug")]
 261     fn check_expr_kind(
 262         &self,
 263         expr: &'tcx hir::Expr<'tcx>,
 264         expected: Expectation<'tcx>,
 265     ) -> Ty<'tcx> {
 266         trace!("expr={:#?}", expr);
 267
 268         let tcx = self.tcx;
 269         match expr.kind {
 270             ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
 271             ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
 272             ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs),
 273             ExprKind::Assign(lhs, rhs, ref span) => {
 274                 self.check_expr_assign(expr, expected, lhs, rhs, span)
 275             }
 276             ExprKind::AssignOp(op, lhs, rhs) => self.check_binop_assign(expr, op, lhs, rhs),
 277             ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
 278             ExprKind::AddrOf(kind, mutbl, oprnd) => {
 279                 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
 280             }
 281             ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
 282                 self.check_lang_item_path(lang_item, expr, hir_id)
 283             }
 284             ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
 285             ExprKind::InlineAsm(asm) => self.check_expr_asm(asm),
 286             ExprKind::Break(destination, ref expr_opt) => {
 287                 self.check_expr_break(destination, expr_opt.as_deref(), expr)
 288             }
 289             ExprKind::Continue(destination) => {
 290                 if destination.target_id.is_ok() {
 291                     tcx.types.never
 292                 } else {
 293                     // There was an error; make type-check fail.
 294                     tcx.ty_error()
 295                 }
 296             }
 297             ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
 298             ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
 299             ExprKind::Loop(body, _, source, _) => {
 300                 self.check_expr_loop(body, source, expected, expr)
 301             }
 302             ExprKind::Match(discrim, arms, match_src) => {
 303                 self.check_match(expr, &discrim, arms, expected, match_src)
 304             }
 305             ExprKind::Closure(capture, decl, body_id, _, gen) => {
 306                 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
 307             }
 308             ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
 309             ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
 310             ExprKind::MethodCall(segment, args, _) => {
 311                 self.check_method_call(expr, segment, args, expected)
 312             }
 313             ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
 314             ExprKind::Type(e, t) => {
 315                 let ty = self.to_ty_saving_user_provided_ty(&t);
 316                 self.check_expr_eq_type(&e, ty);
 317                 ty
 318             }
 319             ExprKind::If(cond, then_expr, opt_else_expr) => {
 320                 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
 321             }
 322             ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
 323             ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
 324             ExprKind::ConstBlock(ref anon_const) => {
 325                 self.check_expr_const_block(anon_const, expected, expr)
 326             }
 327             ExprKind::Repeat(element, ref count) => {
 328                 self.check_expr_repeat(element, count, expected, expr)
 329             }
 330             ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
 331             ExprKind::Struct(qpath, fields, ref base_expr) => {
 332                 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
 333             }
 334             ExprKind::Field(base, field) => self.check_field(expr, &base, field),
 335             ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
 336             ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
 337             hir::ExprKind::Err => tcx.ty_error(),
 338         }
 339     }
 340
 341     fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
 342         let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
 343             ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
 344             _ => NoExpectation,
 345         });
 346         let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
 347         self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
 348         self.tcx.mk_box(referent_ty)
 349     }
 350
 351     fn check_expr_unary(
 352         &self,
 353         unop: hir::UnOp,
 354         oprnd: &'tcx hir::Expr<'tcx>,
 355         expected: Expectation<'tcx>,
 356         expr: &'tcx hir::Expr<'tcx>,
 357     ) -> Ty<'tcx> {
 358         let tcx = self.tcx;
 359         let expected_inner = match unop {
 360             hir::UnOp::Not | hir::UnOp::Neg => expected,
 361             hir::UnOp::Deref => NoExpectation,
 362         };
 363         let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
 364
 365         if !oprnd_t.references_error() {
 366             oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
 367             match unop {
 368                 hir::UnOp::Deref => {
 369                     if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
 370                         oprnd_t = ty;
 371                     } else {
 372                         let mut err = type_error_struct!(
 373                             tcx.sess,
 374                             expr.span,
 375                             oprnd_t,
 376                             E0614,
 377                             "type `{}` cannot be dereferenced",
 378                             oprnd_t,
 379                         );
 380                         let sp = tcx.sess.source_map().start_point(expr.span);
 381                         if let Some(sp) =
 382                             tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
 383                         {
 384                             tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
 385                         }
 386                         err.emit();
 387                         oprnd_t = tcx.ty_error();
 388                     }
 389                 }
 390                 hir::UnOp::Not => {
 391                     let result = self.check_user_unop(expr, oprnd_t, unop);
 392                     // If it's builtin, we can reuse the type, this helps inference.
 393                     if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
 394                         oprnd_t = result;
 395                     }
 396                 }
 397                 hir::UnOp::Neg => {
 398                     let result = self.check_user_unop(expr, oprnd_t, unop);
 399                     // If it's builtin, we can reuse the type, this helps inference.
 400                     if !oprnd_t.is_numeric() {
 401                         oprnd_t = result;
 402                     }
 403                 }
 404             }
 405         }
 406         oprnd_t
 407     }
 408
 409     fn check_expr_addr_of(
 410         &self,
 411         kind: hir::BorrowKind,
 412         mutbl: hir::Mutability,
 413         oprnd: &'tcx hir::Expr<'tcx>,
 414         expected: Expectation<'tcx>,
 415         expr: &'tcx hir::Expr<'tcx>,
 416     ) -> Ty<'tcx> {
 417         let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
 418             match ty.kind() {
 419                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 420                     if oprnd.is_syntactic_place_expr() {
 421                         // Places may legitimately have unsized types.
 422                         // For example, dereferences of a fat pointer and
 423                         // the last field of a struct can be unsized.
 424                         ExpectHasType(ty)
 425                     } else {
 426                         Expectation::rvalue_hint(self, ty)
 427                     }
 428                 }
 429                 _ => NoExpectation,
 430             }
 431         });
 432         let ty =
 433             self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
 434
 435         let tm = ty::TypeAndMut { ty, mutbl };
 436         match kind {
 437             _ if tm.ty.references_error() => self.tcx.ty_error(),
 438             hir::BorrowKind::Raw => {
 439                 self.check_named_place_expr(oprnd);
 440                 self.tcx.mk_ptr(tm)
 441             }
 442             hir::BorrowKind::Ref => {
 443                 // Note: at this point, we cannot say what the best lifetime
 444                 // is to use for resulting pointer.  We want to use the
 445                 // shortest lifetime possible so as to avoid spurious borrowck
 446                 // errors.  Moreover, the longest lifetime will depend on the
 447                 // precise details of the value whose address is being taken
 448                 // (and how long it is valid), which we don't know yet until
 449                 // type inference is complete.
 450                 //
 451                 // Therefore, here we simply generate a region variable. The
 452                 // region inferencer will then select a suitable value.
 453                 // Finally, borrowck will infer the value of the region again,
 454                 // this time with enough precision to check that the value
 455                 // whose address was taken can actually be made to live as long
 456                 // as it needs to live.
 457                 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
 458                 self.tcx.mk_ref(region, tm)
 459             }
 460         }
 461     }
 462
 463     /// Does this expression refer to a place that either:
 464     /// * Is based on a local or static.
 465     /// * Contains a dereference
 466     /// Note that the adjustments for the children of `expr` should already
 467     /// have been resolved.
 468     fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
 469         let is_named = oprnd.is_place_expr(|base| {
 470             // Allow raw borrows if there are any deref adjustments.
 471             //
 472             // const VAL: (i32,) = (0,);
 473             // const REF: &(i32,) = &(0,);
 474             //
 475             // &raw const VAL.0;            // ERROR
 476             // &raw const REF.0;            // OK, same as &raw const (*REF).0;
 477             //
 478             // This is maybe too permissive, since it allows
 479             // `let u = &raw const Box::new((1,)).0`, which creates an
 480             // immediately dangling raw pointer.
 481             self.typeck_results
 482                 .borrow()
 483                 .adjustments()
 484                 .get(base.hir_id)
 485                 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
 486         });
 487         if !is_named {
 488             self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span })
 489         }
 490     }
 491
 492     fn check_lang_item_path(
 493         &self,
 494         lang_item: hir::LangItem,
 495         expr: &'tcx hir::Expr<'tcx>,
 496         hir_id: Option<hir::HirId>,
 497     ) -> Ty<'tcx> {
 498         self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
 499     }
 500
 501     pub(crate) fn check_expr_path(
 502         &self,
 503         qpath: &'tcx hir::QPath<'tcx>,
 504         expr: &'tcx hir::Expr<'tcx>,
 505         args: &'tcx [hir::Expr<'tcx>],
 506     ) -> Ty<'tcx> {
 507         let tcx = self.tcx;
 508         let (res, opt_ty, segs) =
 509             self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
 510         let ty = match res {
 511             Res::Err => {
 512                 self.set_tainted_by_errors();
 513                 tcx.ty_error()
 514             }
 515             Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
 516                 report_unexpected_variant_res(tcx, res, expr.span);
 517                 tcx.ty_error()
 518             }
 519             _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
 520         };
 521
 522         if let ty::FnDef(..) = ty.kind() {
 523             let fn_sig = ty.fn_sig(tcx);
 524             if !tcx.features().unsized_fn_params {
 525                 // We want to remove some Sized bounds from std functions,
 526                 // but don't want to expose the removal to stable Rust.
 527                 // i.e., we don't want to allow
 528                 //
 529                 // ```rust
 530                 // drop as fn(str);
 531                 // ```
 532                 //
 533                 // to work in stable even if the Sized bound on `drop` is relaxed.
 534                 for i in 0..fn_sig.inputs().skip_binder().len() {
 535                     // We just want to check sizedness, so instead of introducing
 536                     // placeholder lifetimes with probing, we just replace higher lifetimes
 537                     // with fresh vars.
 538                     let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
 539                     let input = self
 540                         .replace_bound_vars_with_fresh_vars(
 541                             span,
 542                             infer::LateBoundRegionConversionTime::FnCall,
 543                             fn_sig.input(i),
 544                         )
 545                         .0;
 546                     self.require_type_is_sized_deferred(
 547                         input,
 548                         span,
 549                         traits::SizedArgumentType(None),
 550                     );
 551                 }
 552             }
 553             // Here we want to prevent struct constructors from returning unsized types.
 554             // There were two cases this happened: fn pointer coercion in stable
 555             // and usual function call in presence of unsized_locals.
 556             // Also, as we just want to check sizedness, instead of introducing
 557             // placeholder lifetimes with probing, we just replace higher lifetimes
 558             // with fresh vars.
 559             let output = self
 560                 .replace_bound_vars_with_fresh_vars(
 561                     expr.span,
 562                     infer::LateBoundRegionConversionTime::FnCall,
 563                     fn_sig.output(),
 564                 )
 565                 .0;
 566             self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
 567         }
 568
 569         // We always require that the type provided as the value for
 570         // a type parameter outlives the moment of instantiation.
 571         let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
 572         self.add_wf_bounds(substs, expr);
 573
 574         ty
 575     }
 576
 577     fn check_expr_break(
 578         &self,
 579         destination: hir::Destination,
 580         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 581         expr: &'tcx hir::Expr<'tcx>,
 582     ) -> Ty<'tcx> {
 583         let tcx = self.tcx;
 584         if let Ok(target_id) = destination.target_id {
 585             let (e_ty, cause);
 586             if let Some(e) = expr_opt {
 587                 // If this is a break with a value, we need to type-check
 588                 // the expression. Get an expected type from the loop context.
 589                 let opt_coerce_to = {
 590                     // We should release `enclosing_breakables` before the `check_expr_with_hint`
 591                     // below, so can't move this block of code to the enclosing scope and share
 592                     // `ctxt` with the second `encloding_breakables` borrow below.
 593                     let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 594                     match enclosing_breakables.opt_find_breakable(target_id) {
 595                         Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
 596                         None => {
 597                             // Avoid ICE when `break` is inside a closure (#65383).
 598                             return tcx.ty_error_with_message(
 599                                 expr.span,
 600                                 "break was outside loop, but no error was emitted",
 601                             );
 602                         }
 603                     }
 604                 };
 605
 606                 // If the loop context is not a `loop { }`, then break with
 607                 // a value is illegal, and `opt_coerce_to` will be `None`.
 608                 // Just set expectation to error in that case.
 609                 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
 610
 611                 // Recurse without `enclosing_breakables` borrowed.
 612                 e_ty = self.check_expr_with_hint(e, coerce_to);
 613                 cause = self.misc(e.span);
 614             } else {
 615                 // Otherwise, this is a break *without* a value. That's
 616                 // always legal, and is equivalent to `break ()`.
 617                 e_ty = tcx.mk_unit();
 618                 cause = self.misc(expr.span);
 619             }
 620
 621             // Now that we have type-checked `expr_opt`, borrow
 622             // the `enclosing_loops` field and let's coerce the
 623             // type of `expr_opt` into what is expected.
 624             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
 625             let ctxt = match enclosing_breakables.opt_find_breakable(target_id) {
 626                 Some(ctxt) => ctxt,
 627                 None => {
 628                     // Avoid ICE when `break` is inside a closure (#65383).
 629                     return tcx.ty_error_with_message(
 630                         expr.span,
 631                         "break was outside loop, but no error was emitted",
 632                     );
 633                 }
 634             };
 635
 636             if let Some(ref mut coerce) = ctxt.coerce {
 637                 if let Some(ref e) = expr_opt {
 638                     coerce.coerce(self, &cause, e, e_ty);
 639                 } else {
 640                     assert!(e_ty.is_unit());
 641                     let ty = coerce.expected_ty();
 642                     coerce.coerce_forced_unit(
 643                         self,
 644                         &cause,
 645                         &mut |mut err| {
 646                             self.suggest_mismatched_types_on_tail(
 647                                 &mut err, expr, ty, e_ty, target_id,
 648                             );
 649                             if let Some(val) = ty_kind_suggestion(ty) {
 650                                 let label = destination
 651                                     .label
 652                                     .map(|l| format!(" {}", l.ident))
 653                                     .unwrap_or_else(String::new);
 654                                 err.span_suggestion(
 655                                     expr.span,
 656                                     "give it a value of the expected type",
 657                                     format!("break{} {}", label, val),
 658                                     Applicability::HasPlaceholders,
 659                                 );
 660                             }
 661                         },
 662                         false,
 663                     );
 664                 }
 665             } else {
 666                 // If `ctxt.coerce` is `None`, we can just ignore
 667                 // the type of the expression.  This is because
 668                 // either this was a break *without* a value, in
 669                 // which case it is always a legal type (`()`), or
 670                 // else an error would have been flagged by the
 671                 // `loops` pass for using break with an expression
 672                 // where you are not supposed to.
 673                 assert!(expr_opt.is_none() || self.tcx.sess.has_errors());
 674             }
 675
 676             // If we encountered a `break`, then (no surprise) it may be possible to break from the
 677             // loop... unless the value being returned from the loop diverges itself, e.g.
 678             // `break return 5` or `break loop {}`.
 679             ctxt.may_break |= !self.diverges.get().is_always();
 680
 681             // the type of a `break` is always `!`, since it diverges
 682             tcx.types.never
 683         } else {
 684             // Otherwise, we failed to find the enclosing loop;
 685             // this can only happen if the `break` was not
 686             // inside a loop at all, which is caught by the
 687             // loop-checking pass.
 688             let err = self.tcx.ty_error_with_message(
 689                 expr.span,
 690                 "break was outside loop, but no error was emitted",
 691             );
 692
 693             // We still need to assign a type to the inner expression to
 694             // prevent the ICE in #43162.
 695             if let Some(e) = expr_opt {
 696                 self.check_expr_with_hint(e, err);
 697
 698                 // ... except when we try to 'break rust;'.
 699                 // ICE this expression in particular (see #43162).
 700                 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
 701                     if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
 702                         fatally_break_rust(self.tcx.sess);
 703                     }
 704                 }
 705             }
 706
 707             // There was an error; make type-check fail.
 708             err
 709         }
 710     }
 711
 712     fn check_expr_return(
 713         &self,
 714         expr_opt: Option<&'tcx hir::Expr<'tcx>>,
 715         expr: &'tcx hir::Expr<'tcx>,
 716     ) -> Ty<'tcx> {
 717         if self.ret_coercion.is_none() {
 718             let mut err = ReturnStmtOutsideOfFnBody {
 719                 span: expr.span,
 720                 encl_body_span: None,
 721                 encl_fn_span: None,
 722             };
 723
 724             let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
 725
 726             if let Some(hir::Node::Item(hir::Item {
 727                 kind: hir::ItemKind::Fn(..),
 728                 span: encl_fn_span,
 729                 ..
 730             }))
 731             | Some(hir::Node::TraitItem(hir::TraitItem {
 732                 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
 733                 span: encl_fn_span,
 734                 ..
 735             }))
 736             | Some(hir::Node::ImplItem(hir::ImplItem {
 737                 kind: hir::ImplItemKind::Fn(..),
 738                 span: encl_fn_span,
 739                 ..
 740             })) = self.tcx.hir().find_by_def_id(encl_item_id)
 741             {
 742                 // We are inside a function body, so reporting "return statement
 743                 // outside of function body" needs an explanation.
 744
 745                 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
 746
 747                 // If this didn't hold, we would not have to report an error in
 748                 // the first place.
 749                 assert_ne!(hir::HirId::make_owner(encl_item_id), encl_body_owner_id);
 750
 751                 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
 752                 let encl_body = self.tcx.hir().body(encl_body_id);
 753
 754                 err.encl_body_span = Some(encl_body.value.span);
 755                 err.encl_fn_span = Some(*encl_fn_span);
 756             }
 757
 758             self.tcx.sess.emit_err(err);
 759
 760             if let Some(e) = expr_opt {
 761                 // We still have to type-check `e` (issue #86188), but calling
 762                 // `check_return_expr` only works inside fn bodies.
 763                 self.check_expr(e);
 764             }
 765         } else if let Some(e) = expr_opt {
 766             if self.ret_coercion_span.get().is_none() {
 767                 self.ret_coercion_span.set(Some(e.span));
 768             }
 769             self.check_return_expr(e, true);
 770         } else {
 771             let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
 772             if self.ret_coercion_span.get().is_none() {
 773                 self.ret_coercion_span.set(Some(expr.span));
 774             }
 775             let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
 776             if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
 777                 coercion.coerce_forced_unit(
 778                     self,
 779                     &cause,
 780                     &mut |db| {
 781                         let span = fn_decl.output.span();
 782                         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
 783                             db.span_label(
 784                                 span,
 785                                 format!("expected `{}` because of this return type", snippet),
 786                             );
 787                         }
 788                     },
 789                     true,
 790                 );
 791             } else {
 792                 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
 793             }
 794         }
 795         self.tcx.types.never
 796     }
 797
 798     /// `explicit_return` is `true` if we're checkng an explicit `return expr`,
 799     /// and `false` if we're checking a trailing expression.
 800     pub(super) fn check_return_expr(
 801         &self,
 802         return_expr: &'tcx hir::Expr<'tcx>,
 803         explicit_return: bool,
 804     ) {
 805         let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
 806             span_bug!(return_expr.span, "check_return_expr called outside fn body")
 807         });
 808
 809         let ret_ty = ret_coercion.borrow().expected_ty();
 810         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
 811         let mut span = return_expr.span;
 812         // Use the span of the trailing expression for our cause,
 813         // not the span of the entire function
 814         if !explicit_return {
 815             if let ExprKind::Block(body, _) = return_expr.kind {
 816                 if let Some(last_expr) = body.expr {
 817                     span = last_expr.span;
 818                 }
 819             }
 820         }
 821         ret_coercion.borrow_mut().coerce(
 822             self,
 823             &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
 824             return_expr,
 825             return_expr_ty,
 826         );
 827     }
 828
 829     pub(crate) fn check_lhs_assignable(
 830         &self,
 831         lhs: &'tcx hir::Expr<'tcx>,
 832         err_code: &'static str,
 833         op_span: Span,
 834     ) {
 835         if lhs.is_syntactic_place_expr() {
 836             return;
 837         }
 838
 839         // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
 840         let mut err = self.tcx.sess.struct_span_err_with_code(
 841             op_span,
 842             "invalid left-hand side of assignment",
 843             DiagnosticId::Error(err_code.into()),
 844         );
 845         err.span_label(lhs.span, "cannot assign to this expression");
 846
 847         let mut parent = self.tcx.hir().get_parent_node(lhs.hir_id);
 848         while let Some(node) = self.tcx.hir().find(parent) {
 849             match node {
 850                 hir::Node::Expr(hir::Expr {
 851                     kind:
 852                         hir::ExprKind::Loop(
 853                             hir::Block {
 854                                 expr:
 855                                     Some(hir::Expr {
 856                                         kind:
 857                                             hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
 858                                         ..
 859                                     }),
 860                                 ..
 861                             },
 862                             _,
 863                             hir::LoopSource::While,
 864                             _,
 865                         ),
 866                     ..
 867                 }) => {
 868                     // Check if our lhs is a child of the condition of a while loop
 869                     let expr_is_ancestor = std::iter::successors(Some(lhs.hir_id), |id| {
 870                         self.tcx.hir().find_parent_node(*id)
 871                     })
 872                     .take_while(|id| *id != parent)
 873                     .any(|id| id == expr.hir_id);
 874                     // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
 875                     // where `while let` was more likely intended.
 876                     if expr_is_ancestor {
 877                         err.span_suggestion_verbose(
 878                             expr.span.shrink_to_lo(),
 879                             "you might have meant to use pattern destructuring",
 880                             "let ".to_string(),
 881                             Applicability::MachineApplicable,
 882                         );
 883                     }
 884                     break;
 885                 }
 886                 hir::Node::Item(_)
 887                 | hir::Node::ImplItem(_)
 888                 | hir::Node::TraitItem(_)
 889                 | hir::Node::Crate(_) => break,
 890                 _ => {
 891                     parent = self.tcx.hir().get_parent_node(parent);
 892                 }
 893             }
 894         }
 895
 896         err.emit();
 897     }
 898
 899     // A generic function for checking the 'then' and 'else' clauses in an 'if'
 900     // or 'if-else' expression.
 901     fn check_then_else(
 902         &self,
 903         cond_expr: &'tcx hir::Expr<'tcx>,
 904         then_expr: &'tcx hir::Expr<'tcx>,
 905         opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
 906         sp: Span,
 907         orig_expected: Expectation<'tcx>,
 908     ) -> Ty<'tcx> {
 909         let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
 910
 911         self.warn_if_unreachable(
 912             cond_expr.hir_id,
 913             then_expr.span,
 914             "block in `if` or `while` expression",
 915         );
 916
 917         let cond_diverges = self.diverges.get();
 918         self.diverges.set(Diverges::Maybe);
 919
 920         let expected = orig_expected.adjust_for_branches(self);
 921         let then_ty = self.check_expr_with_expectation(then_expr, expected);
 922         let then_diverges = self.diverges.get();
 923         self.diverges.set(Diverges::Maybe);
 924
 925         // We've already taken the expected type's preferences
 926         // into account when typing the `then` branch. To figure
 927         // out the initial shot at a LUB, we thus only consider
 928         // `expected` if it represents a *hard* constraint
 929         // (`only_has_type`); otherwise, we just go with a
 930         // fresh type variable.
 931         let coerce_to_ty = expected.coercion_target_type(self, sp);
 932         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
 933
 934         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
 935
 936         if let Some(else_expr) = opt_else_expr {
 937             let else_ty = if sp.desugaring_kind() == Some(DesugaringKind::LetElse) {
 938                 // todo introduce `check_expr_with_expectation(.., Expectation::LetElse)`
 939                 //   for errors that point to the offending expression rather than the entire block.
 940                 //   We could use `check_expr_eq_type(.., tcx.types.never)`, but then there is no
 941                 //   way to detect that the expected type originated from let-else and provide
 942                 //   a customized error.
 943                 let else_ty = self.check_expr(else_expr);
 944                 let cause = self.cause(else_expr.span, ObligationCauseCode::LetElse);
 945
 946                 if let Some(mut err) =
 947                     self.demand_eqtype_with_origin(&cause, self.tcx.types.never, else_ty)
 948                 {
 949                     err.emit();
 950                     self.tcx.ty_error()
 951                 } else {
 952                     else_ty
 953                 }
 954             } else {
 955                 self.check_expr_with_expectation(else_expr, expected)
 956             };
 957             let else_diverges = self.diverges.get();
 958
 959             let opt_suggest_box_span = self.opt_suggest_box_span(else_ty, orig_expected);
 960             let if_cause =
 961                 self.if_cause(sp, then_expr, else_expr, then_ty, else_ty, opt_suggest_box_span);
 962
 963             coerce.coerce(self, &if_cause, else_expr, else_ty);
 964
 965             // We won't diverge unless both branches do (or the condition does).
 966             self.diverges.set(cond_diverges | then_diverges & else_diverges);
 967         } else {
 968             self.if_fallback_coercion(sp, then_expr, &mut coerce);
 969
 970             // If the condition is false we can't diverge.
 971             self.diverges.set(cond_diverges);
 972         }
 973
 974         let result_ty = coerce.complete(self);
 975         if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
 976     }
 977
 978     /// Type check assignment expression `expr` of form `lhs = rhs`.
 979     /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
 980     fn check_expr_assign(
 981         &self,
 982         expr: &'tcx hir::Expr<'tcx>,
 983         expected: Expectation<'tcx>,
 984         lhs: &'tcx hir::Expr<'tcx>,
 985         rhs: &'tcx hir::Expr<'tcx>,
 986         span: &Span,
 987     ) -> Ty<'tcx> {
 988         let expected_ty = expected.coercion_target_type(self, expr.span);
 989         if expected_ty == self.tcx.types.bool {
 990             // The expected type is `bool` but this will result in `()` so we can reasonably
 991             // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
 992             // The likely cause of this is `if foo = bar { .. }`.
 993             let actual_ty = self.tcx.mk_unit();
 994             let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
 995             let lhs_ty = self.check_expr(&lhs);
 996             let rhs_ty = self.check_expr(&rhs);
 997             let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
 998                 (Applicability::MachineApplicable, true)
 999             } else {
1000                 (Applicability::MaybeIncorrect, false)
1001             };
1002             if !lhs.is_syntactic_place_expr() && !matches!(lhs.kind, hir::ExprKind::Lit(_)) {
1003                 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1004                 let hir = self.tcx.hir();
1005                 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1006                     hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1007                 {
1008                     err.span_suggestion_verbose(
1009                         expr.span.shrink_to_lo(),
1010                         "you might have meant to use pattern matching",
1011                         "let ".to_string(),
1012                         applicability,
1013                     );
1014                 };
1015             }
1016             if eq {
1017                 err.span_suggestion_verbose(
1018                     *span,
1019                     "you might have meant to compare for equality",
1020                     "==".to_string(),
1021                     applicability,
1022                 );
1023             }
1024
1025             // If the assignment expression itself is ill-formed, don't
1026             // bother emitting another error
1027             if lhs_ty.references_error() || rhs_ty.references_error() {
1028                 err.delay_as_bug()
1029             } else {
1030                 err.emit();
1031             }
1032             return self.tcx.ty_error();
1033         }
1034
1035         self.check_lhs_assignable(lhs, "E0070", *span);
1036
1037         let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1038         let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty, Some(lhs));
1039
1040         self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1041
1042         if lhs_ty.references_error() || rhs_ty.references_error() {
1043             self.tcx.ty_error()
1044         } else {
1045             self.tcx.mk_unit()
1046         }
1047     }
1048
1049     fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1050         // for let statements, this is done in check_stmt
1051         let init = let_expr.init;
1052         self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1053         // otherwise check exactly as a let statement
1054         self.check_decl(let_expr.into());
1055         // but return a bool, for this is a boolean expression
1056         self.tcx.types.bool
1057     }
1058
1059     fn check_expr_loop(
1060         &self,
1061         body: &'tcx hir::Block<'tcx>,
1062         source: hir::LoopSource,
1063         expected: Expectation<'tcx>,
1064         expr: &'tcx hir::Expr<'tcx>,
1065     ) -> Ty<'tcx> {
1066         let coerce = match source {
1067             // you can only use break with a value from a normal `loop { }`
1068             hir::LoopSource::Loop => {
1069                 let coerce_to = expected.coercion_target_type(self, body.span);
1070                 Some(CoerceMany::new(coerce_to))
1071             }
1072
1073             hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1074         };
1075
1076         let ctxt = BreakableCtxt {
1077             coerce,
1078             may_break: false, // Will get updated if/when we find a `break`.
1079         };
1080
1081         let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1082             self.check_block_no_value(&body);
1083         });
1084
1085         if ctxt.may_break {
1086             // No way to know whether it's diverging because
1087             // of a `break` or an outer `break` or `return`.
1088             self.diverges.set(Diverges::Maybe);
1089         }
1090
1091         // If we permit break with a value, then result type is
1092         // the LUB of the breaks (possibly ! if none); else, it
1093         // is nil. This makes sense because infinite loops
1094         // (which would have type !) are only possible iff we
1095         // permit break with a value [1].
1096         if ctxt.coerce.is_none() && !ctxt.may_break {
1097             // [1]
1098             self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1099         }
1100         ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1101     }
1102
1103     /// Checks a method call.
1104     fn check_method_call(
1105         &self,
1106         expr: &'tcx hir::Expr<'tcx>,
1107         segment: &hir::PathSegment<'_>,
1108         args: &'tcx [hir::Expr<'tcx>],
1109         expected: Expectation<'tcx>,
1110     ) -> Ty<'tcx> {
1111         let rcvr = &args[0];
1112         let rcvr_t = self.check_expr(&rcvr);
1113         // no need to check for bot/err -- callee does that
1114         let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
1115         let span = segment.ident.span;
1116
1117         let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1118             Ok(method) => {
1119                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1120                 // trigger this codepath causing `structuraly_resolved_type` to emit an error.
1121
1122                 self.write_method_call(expr.hir_id, method);
1123                 Ok(method)
1124             }
1125             Err(error) => {
1126                 if segment.ident.name != kw::Empty {
1127                     if let Some(mut err) = self.report_method_error(
1128                         span,
1129                         rcvr_t,
1130                         segment.ident,
1131                         SelfSource::MethodCall(&args[0]),
1132                         error,
1133                         Some(args),
1134                     ) {
1135                         err.emit();
1136                     }
1137                 }
1138                 Err(())
1139             }
1140         };
1141
1142         // Call the generic checker.
1143         self.check_method_argument_types(
1144             span,
1145             expr,
1146             method,
1147             &args[1..],
1148             DontTupleArguments,
1149             expected,
1150         )
1151     }
1152
1153     fn check_expr_cast(
1154         &self,
1155         e: &'tcx hir::Expr<'tcx>,
1156         t: &'tcx hir::Ty<'tcx>,
1157         expr: &'tcx hir::Expr<'tcx>,
1158     ) -> Ty<'tcx> {
1159         // Find the type of `e`. Supply hints based on the type we are casting to,
1160         // if appropriate.
1161         let t_cast = self.to_ty_saving_user_provided_ty(t);
1162         let t_cast = self.resolve_vars_if_possible(t_cast);
1163         let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1164         let t_expr = self.resolve_vars_if_possible(t_expr);
1165
1166         // Eagerly check for some obvious errors.
1167         if t_expr.references_error() || t_cast.references_error() {
1168             self.tcx.ty_error()
1169         } else {
1170             // Defer other checks until we're done type checking.
1171             let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1172             match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1173                 Ok(cast_check) => {
1174                     debug!(
1175                         "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1176                         t_cast, t_expr, cast_check,
1177                     );
1178                     deferred_cast_checks.push(cast_check);
1179                     t_cast
1180                 }
1181                 Err(ErrorReported) => self.tcx.ty_error(),
1182             }
1183         }
1184     }
1185
1186     fn check_expr_array(
1187         &self,
1188         args: &'tcx [hir::Expr<'tcx>],
1189         expected: Expectation<'tcx>,
1190         expr: &'tcx hir::Expr<'tcx>,
1191     ) -> Ty<'tcx> {
1192         let element_ty = if !args.is_empty() {
1193             let coerce_to = expected
1194                 .to_option(self)
1195                 .and_then(|uty| match *uty.kind() {
1196                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1197                     _ => None,
1198                 })
1199                 .unwrap_or_else(|| {
1200                     self.next_ty_var(TypeVariableOrigin {
1201                         kind: TypeVariableOriginKind::TypeInference,
1202                         span: expr.span,
1203                     })
1204                 });
1205             let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1206             assert_eq!(self.diverges.get(), Diverges::Maybe);
1207             for e in args {
1208                 let e_ty = self.check_expr_with_hint(e, coerce_to);
1209                 let cause = self.misc(e.span);
1210                 coerce.coerce(self, &cause, e, e_ty);
1211             }
1212             coerce.complete(self)
1213         } else {
1214             self.next_ty_var(TypeVariableOrigin {
1215                 kind: TypeVariableOriginKind::TypeInference,
1216                 span: expr.span,
1217             })
1218         };
1219         self.tcx.mk_array(element_ty, args.len() as u64)
1220     }
1221
1222     fn check_expr_const_block(
1223         &self,
1224         anon_const: &'tcx hir::AnonConst,
1225         expected: Expectation<'tcx>,
1226         _expr: &'tcx hir::Expr<'tcx>,
1227     ) -> Ty<'tcx> {
1228         let body = self.tcx.hir().body(anon_const.body);
1229
1230         // Create a new function context.
1231         let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1232         crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1233
1234         let ty = fcx.check_expr_with_expectation(&body.value, expected);
1235         fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1236         fcx.write_ty(anon_const.hir_id, ty);
1237         ty
1238     }
1239
1240     fn check_expr_repeat(
1241         &self,
1242         element: &'tcx hir::Expr<'tcx>,
1243         count: &'tcx hir::ArrayLen,
1244         expected: Expectation<'tcx>,
1245         _expr: &'tcx hir::Expr<'tcx>,
1246     ) -> Ty<'tcx> {
1247         let tcx = self.tcx;
1248         let count = self.array_length_to_const(count);
1249
1250         let uty = match expected {
1251             ExpectHasType(uty) => match *uty.kind() {
1252                 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1253                 _ => None,
1254             },
1255             _ => None,
1256         };
1257
1258         let (element_ty, t) = match uty {
1259             Some(uty) => {
1260                 self.check_expr_coercable_to_type(&element, uty, None);
1261                 (uty, uty)
1262             }
1263             None => {
1264                 let ty = self.next_ty_var(TypeVariableOrigin {
1265                     kind: TypeVariableOriginKind::MiscVariable,
1266                     span: element.span,
1267                 });
1268                 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1269                 (element_ty, ty)
1270             }
1271         };
1272
1273         if element_ty.references_error() {
1274             return tcx.ty_error();
1275         }
1276
1277         tcx.mk_ty(ty::Array(t, count))
1278     }
1279
1280     fn check_expr_tuple(
1281         &self,
1282         elts: &'tcx [hir::Expr<'tcx>],
1283         expected: Expectation<'tcx>,
1284         expr: &'tcx hir::Expr<'tcx>,
1285     ) -> Ty<'tcx> {
1286         let flds = expected.only_has_type(self).and_then(|ty| {
1287             let ty = self.resolve_vars_with_obligations(ty);
1288             match ty.kind() {
1289                 ty::Tuple(flds) => Some(&flds[..]),
1290                 _ => None,
1291             }
1292         });
1293
1294         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1295             Some(fs) if i < fs.len() => {
1296                 let ety = fs[i].expect_ty();
1297                 self.check_expr_coercable_to_type(&e, ety, None);
1298                 ety
1299             }
1300             _ => self.check_expr_with_expectation(&e, NoExpectation),
1301         });
1302         let tuple = self.tcx.mk_tup(elt_ts_iter);
1303         if tuple.references_error() {
1304             self.tcx.ty_error()
1305         } else {
1306             self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1307             tuple
1308         }
1309     }
1310
1311     fn check_expr_struct(
1312         &self,
1313         expr: &hir::Expr<'_>,
1314         expected: Expectation<'tcx>,
1315         qpath: &QPath<'_>,
1316         fields: &'tcx [hir::ExprField<'tcx>],
1317         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1318     ) -> Ty<'tcx> {
1319         // Find the relevant variant
1320         let (variant, adt_ty) = if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id)
1321         {
1322             variant_ty
1323         } else {
1324             self.check_struct_fields_on_error(fields, base_expr);
1325             return self.tcx.ty_error();
1326         };
1327
1328         // Prohibit struct expressions when non-exhaustive flag is set.
1329         let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1330         if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
1331             self.tcx
1332                 .sess
1333                 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1334         }
1335
1336         self.check_expr_struct_fields(
1337             adt_ty,
1338             expected,
1339             expr.hir_id,
1340             qpath.span(),
1341             variant,
1342             fields,
1343             base_expr,
1344             expr.span,
1345         );
1346
1347         self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1348         adt_ty
1349     }
1350
1351     fn check_expr_struct_fields(
1352         &self,
1353         adt_ty: Ty<'tcx>,
1354         expected: Expectation<'tcx>,
1355         expr_id: hir::HirId,
1356         span: Span,
1357         variant: &'tcx ty::VariantDef,
1358         ast_fields: &'tcx [hir::ExprField<'tcx>],
1359         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1360         expr_span: Span,
1361     ) {
1362         let tcx = self.tcx;
1363
1364         let adt_ty_hint = self
1365             .expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
1366             .get(0)
1367             .cloned()
1368             .unwrap_or(adt_ty);
1369         // re-link the regions that EIfEO can erase.
1370         self.demand_eqtype(span, adt_ty_hint, adt_ty);
1371
1372         let (substs, adt_kind, kind_name) = match adt_ty.kind() {
1373             ty::Adt(adt, substs) => (substs, adt.adt_kind(), adt.variant_descr()),
1374             _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields"),
1375         };
1376
1377         let mut remaining_fields = variant
1378             .fields
1379             .iter()
1380             .enumerate()
1381             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1382             .collect::<FxHashMap<_, _>>();
1383
1384         let mut seen_fields = FxHashMap::default();
1385
1386         let mut error_happened = false;
1387
1388         // Type-check each field.
1389         for field in ast_fields {
1390             let ident = tcx.adjust_ident(field.ident, variant.def_id);
1391             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1392                 seen_fields.insert(ident, field.span);
1393                 self.write_field_index(field.hir_id, i);
1394
1395                 // We don't look at stability attributes on
1396                 // struct-like enums (yet...), but it's definitely not
1397                 // a bug to have constructed one.
1398                 if adt_kind != AdtKind::Enum {
1399                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1400                 }
1401
1402                 self.field_ty(field.span, v_field, substs)
1403             } else {
1404                 error_happened = true;
1405                 if let Some(prev_span) = seen_fields.get(&ident) {
1406                     tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1407                         span: field.ident.span,
1408                         prev_span: *prev_span,
1409                         ident,
1410                     });
1411                 } else {
1412                     self.report_unknown_field(
1413                         adt_ty, variant, field, ast_fields, kind_name, expr_span,
1414                     );
1415                 }
1416
1417                 tcx.ty_error()
1418             };
1419
1420             // Make sure to give a type to the field even if there's
1421             // an error, so we can continue type-checking.
1422             self.check_expr_coercable_to_type(&field.expr, field_type, None);
1423         }
1424
1425         // Make sure the programmer specified correct number of fields.
1426         if kind_name == "union" {
1427             if ast_fields.len() != 1 {
1428                 struct_span_err!(
1429                     tcx.sess,
1430                     span,
1431                     E0784,
1432                     "union expressions should have exactly one field",
1433                 )
1434                 .emit();
1435             }
1436         }
1437
1438         // If check_expr_struct_fields hit an error, do not attempt to populate
1439         // the fields with the base_expr. This could cause us to hit errors later
1440         // when certain fields are assumed to exist that in fact do not.
1441         if error_happened {
1442             return;
1443         }
1444
1445         if let Some(base_expr) = base_expr {
1446             // FIXME: We are currently creating two branches here in order to maintain
1447             // consistency. But they should be merged as much as possible.
1448             let fru_tys = if self.tcx.features().type_changing_struct_update {
1449                 let base_ty = self.check_expr(base_expr);
1450                 match adt_ty.kind() {
1451                     ty::Adt(adt, substs) if adt.is_struct() => {
1452                         match base_ty.kind() {
1453                             ty::Adt(base_adt, base_subs) if adt == base_adt => {
1454                                 variant
1455                                     .fields
1456                                     .iter()
1457                                     .map(|f| {
1458                                         let fru_ty = self.normalize_associated_types_in(
1459                                             expr_span,
1460                                             self.field_ty(base_expr.span, f, base_subs),
1461                                         );
1462                                         let ident = self
1463                                             .tcx
1464                                             .adjust_ident(f.ident(self.tcx), variant.def_id);
1465                                         if let Some(_) = remaining_fields.remove(&ident) {
1466                                             let target_ty =
1467                                                 self.field_ty(base_expr.span, f, substs);
1468                                             let cause = self.misc(base_expr.span);
1469                                             match self
1470                                                 .at(&cause, self.param_env)
1471                                                 .sup(target_ty, fru_ty)
1472                                             {
1473                                                 Ok(InferOk { obligations, value: () }) => {
1474                                                     self.register_predicates(obligations)
1475                                                 }
1476                                                 // FIXME: Need better diagnostics for `FieldMisMatch` error
1477                                                 Err(_) => self
1478                                                     .report_mismatched_types(
1479                                                         &cause,
1480                                                         target_ty,
1481                                                         fru_ty,
1482                                                         FieldMisMatch(variant.name, ident.name),
1483                                                     )
1484                                                     .emit(),
1485                                             }
1486                                         }
1487                                         fru_ty
1488                                     })
1489                                     .collect()
1490                             }
1491                             _ => {
1492                                 return self
1493                                     .report_mismatched_types(
1494                                         &self.misc(base_expr.span),
1495                                         adt_ty,
1496                                         base_ty,
1497                                         Sorts(ExpectedFound::new(true, adt_ty, base_ty)),
1498                                     )
1499                                     .emit();
1500                             }
1501                         }
1502                     }
1503                     _ => {
1504                         return self
1505                             .tcx
1506                             .sess
1507                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1508                     }
1509                 }
1510             } else {
1511                 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1512                     let base_ty = self.typeck_results.borrow().node_type(base_expr.hir_id);
1513                     let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1514                         (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1515                         _ => false,
1516                     };
1517                     if self.tcx.sess.is_nightly_build() && same_adt {
1518                         feature_err(
1519                             &self.tcx.sess.parse_sess,
1520                             sym::type_changing_struct_update,
1521                             base_expr.span,
1522                             "type changing struct updating is experimental",
1523                         )
1524                         .emit();
1525                     }
1526                 });
1527                 match adt_ty.kind() {
1528                     ty::Adt(adt, substs) if adt.is_struct() => variant
1529                         .fields
1530                         .iter()
1531                         .map(|f| {
1532                             self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1533                         })
1534                         .collect(),
1535                     _ => {
1536                         return self
1537                             .tcx
1538                             .sess
1539                             .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1540                     }
1541                 }
1542             };
1543             self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1544         } else if kind_name != "union" && !remaining_fields.is_empty() {
1545             let inaccessible_remaining_fields = remaining_fields.iter().any(|(_, (_, field))| {
1546                 !field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1547             });
1548
1549             if inaccessible_remaining_fields {
1550                 self.report_inaccessible_fields(adt_ty, span);
1551             } else {
1552                 self.report_missing_fields(adt_ty, span, remaining_fields);
1553             }
1554         }
1555     }
1556
1557     fn check_struct_fields_on_error(
1558         &self,
1559         fields: &'tcx [hir::ExprField<'tcx>],
1560         base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1561     ) {
1562         for field in fields {
1563             self.check_expr(&field.expr);
1564         }
1565         if let Some(base) = *base_expr {
1566             self.check_expr(&base);
1567         }
1568     }
1569
1570     /// Report an error for a struct field expression when there are fields which aren't provided.
1571     ///
1572     /// ```text
1573     /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1574     ///  --> src/main.rs:8:5
1575     ///   |
1576     /// 8 |     foo::Foo {};
1577     ///   |     ^^^^^^^^ missing `you_can_use_this_field`
1578     ///
1579     /// error: aborting due to previous error
1580     /// ```
1581     fn report_missing_fields(
1582         &self,
1583         adt_ty: Ty<'tcx>,
1584         span: Span,
1585         remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1586     ) {
1587         let len = remaining_fields.len();
1588
1589         let mut displayable_field_names: Vec<&str> =
1590             remaining_fields.keys().map(|ident| ident.as_str()).collect();
1591         // sorting &str primitives here, sort_unstable is ok
1592         displayable_field_names.sort_unstable();
1593
1594         let mut truncated_fields_error = String::new();
1595         let remaining_fields_names = match &displayable_field_names[..] {
1596             [field1] => format!("`{}`", field1),
1597             [field1, field2] => format!("`{}` and `{}`", field1, field2),
1598             [field1, field2, field3] => format!("`{}`, `{}` and `{}`", field1, field2, field3),
1599             _ => {
1600                 truncated_fields_error =
1601                     format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1602                 displayable_field_names
1603                     .iter()
1604                     .take(3)
1605                     .map(|n| format!("`{}`", n))
1606                     .collect::<Vec<_>>()
1607                     .join(", ")
1608             }
1609         };
1610
1611         struct_span_err!(
1612             self.tcx.sess,
1613             span,
1614             E0063,
1615             "missing field{} {}{} in initializer of `{}`",
1616             pluralize!(len),
1617             remaining_fields_names,
1618             truncated_fields_error,
1619             adt_ty
1620         )
1621         .span_label(span, format!("missing {}{}", remaining_fields_names, truncated_fields_error))
1622         .emit();
1623     }
1624
1625     /// Report an error for a struct field expression when there are invisible fields.
1626     ///
1627     /// ```text
1628     /// error: cannot construct `Foo` with struct literal syntax due to inaccessible fields
1629     ///  --> src/main.rs:8:5
1630     ///   |
1631     /// 8 |     foo::Foo {};
1632     ///   |     ^^^^^^^^
1633     ///
1634     /// error: aborting due to previous error
1635     /// ```
1636     fn report_inaccessible_fields(&self, adt_ty: Ty<'tcx>, span: Span) {
1637         self.tcx.sess.span_err(
1638             span,
1639             &format!(
1640                 "cannot construct `{}` with struct literal syntax due to inaccessible fields",
1641                 adt_ty,
1642             ),
1643         );
1644     }
1645
1646     fn report_unknown_field(
1647         &self,
1648         ty: Ty<'tcx>,
1649         variant: &'tcx ty::VariantDef,
1650         field: &hir::ExprField<'_>,
1651         skip_fields: &[hir::ExprField<'_>],
1652         kind_name: &str,
1653         expr_span: Span,
1654     ) {
1655         if variant.is_recovered() {
1656             self.set_tainted_by_errors();
1657             return;
1658         }
1659         let mut err = self.type_error_struct_with_diag(
1660             field.ident.span,
1661             |actual| match ty.kind() {
1662                 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1663                     self.tcx.sess,
1664                     field.ident.span,
1665                     E0559,
1666                     "{} `{}::{}` has no field named `{}`",
1667                     kind_name,
1668                     actual,
1669                     variant.name,
1670                     field.ident
1671                 ),
1672                 _ => struct_span_err!(
1673                     self.tcx.sess,
1674                     field.ident.span,
1675                     E0560,
1676                     "{} `{}` has no field named `{}`",
1677                     kind_name,
1678                     actual,
1679                     field.ident
1680                 ),
1681             },
1682             ty,
1683         );
1684
1685         let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1686         match variant.ctor_kind {
1687             CtorKind::Fn => match ty.kind() {
1688                 ty::Adt(adt, ..) if adt.is_enum() => {
1689                     err.span_label(
1690                         variant_ident_span,
1691                         format!(
1692                             "`{adt}::{variant}` defined here",
1693                             adt = ty,
1694                             variant = variant.name,
1695                         ),
1696                     );
1697                     err.span_label(field.ident.span, "field does not exist");
1698                     err.span_suggestion_verbose(
1699                         expr_span,
1700                         &format!(
1701                             "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1702                             adt = ty,
1703                             variant = variant.name,
1704                         ),
1705                         format!(
1706                             "{adt}::{variant}(/* fields */)",
1707                             adt = ty,
1708                             variant = variant.name,
1709                         ),
1710                         Applicability::HasPlaceholders,
1711                     );
1712                 }
1713                 _ => {
1714                     err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1715                     err.span_label(field.ident.span, "field does not exist");
1716                     err.span_suggestion_verbose(
1717                         expr_span,
1718                         &format!(
1719                             "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1720                             adt = ty,
1721                             kind_name = kind_name,
1722                         ),
1723                         format!("{adt}(/* fields */)", adt = ty),
1724                         Applicability::HasPlaceholders,
1725                     );
1726                 }
1727             },
1728             _ => {
1729                 // prevent all specified fields from being suggested
1730                 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
1731                 if let Some(field_name) = self.suggest_field_name(
1732                     variant,
1733                     field.ident.name,
1734                     skip_fields.collect(),
1735                     expr_span,
1736                 ) {
1737                     err.span_suggestion(
1738                         field.ident.span,
1739                         "a field with a similar name exists",
1740                         field_name.to_string(),
1741                         Applicability::MaybeIncorrect,
1742                     );
1743                 } else {
1744                     match ty.kind() {
1745                         ty::Adt(adt, ..) => {
1746                             if adt.is_enum() {
1747                                 err.span_label(
1748                                     field.ident.span,
1749                                     format!("`{}::{}` does not have this field", ty, variant.name),
1750                                 );
1751                             } else {
1752                                 err.span_label(
1753                                     field.ident.span,
1754                                     format!("`{}` does not have this field", ty),
1755                                 );
1756                             }
1757                             let available_field_names =
1758                                 self.available_field_names(variant, expr_span);
1759                             if !available_field_names.is_empty() {
1760                                 err.note(&format!(
1761                                     "available fields are: {}",
1762                                     self.name_series_display(available_field_names)
1763                                 ));
1764                             }
1765                         }
1766                         _ => bug!("non-ADT passed to report_unknown_field"),
1767                     }
1768                 };
1769             }
1770         }
1771         err.emit();
1772     }
1773
1774     // Return a hint about the closest match in field names
1775     fn suggest_field_name(
1776         &self,
1777         variant: &'tcx ty::VariantDef,
1778         field: Symbol,
1779         skip: Vec<Symbol>,
1780         // The span where stability will be checked
1781         span: Span,
1782     ) -> Option<Symbol> {
1783         let names = variant
1784             .fields
1785             .iter()
1786             .filter_map(|field| {
1787                 // ignore already set fields and private fields from non-local crates
1788                 // and unstable fields.
1789                 if skip.iter().any(|&x| x == field.name)
1790                     || (!variant.def_id.is_local() && !field.vis.is_public())
1791                     || matches!(
1792                         self.tcx.eval_stability(field.did, None, span, None),
1793                         stability::EvalResult::Deny { .. }
1794                     )
1795                 {
1796                     None
1797                 } else {
1798                     Some(field.name)
1799                 }
1800             })
1801             .collect::<Vec<Symbol>>();
1802
1803         find_best_match_for_name(&names, field, None)
1804     }
1805
1806     fn available_field_names(
1807         &self,
1808         variant: &'tcx ty::VariantDef,
1809         access_span: Span,
1810     ) -> Vec<Symbol> {
1811         variant
1812             .fields
1813             .iter()
1814             .filter(|field| {
1815                 let def_scope = self
1816                     .tcx
1817                     .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
1818                     .1;
1819                 field.vis.is_accessible_from(def_scope, self.tcx)
1820                     && !matches!(
1821                         self.tcx.eval_stability(field.did, None, access_span, None),
1822                         stability::EvalResult::Deny { .. }
1823                     )
1824             })
1825             .filter(|field| !self.tcx.is_doc_hidden(field.did))
1826             .map(|field| field.name)
1827             .collect()
1828     }
1829
1830     fn name_series_display(&self, names: Vec<Symbol>) -> String {
1831         // dynamic limit, to never omit just one field
1832         let limit = if names.len() == 6 { 6 } else { 5 };
1833         let mut display =
1834             names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
1835         if names.len() > limit {
1836             display = format!("{} ... and {} others", display, names.len() - limit);
1837         }
1838         display
1839     }
1840
1841     // Check field access expressions
1842     fn check_field(
1843         &self,
1844         expr: &'tcx hir::Expr<'tcx>,
1845         base: &'tcx hir::Expr<'tcx>,
1846         field: Ident,
1847     ) -> Ty<'tcx> {
1848         debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
1849         let expr_t = self.check_expr(base);
1850         let expr_t = self.structurally_resolved_type(base.span, expr_t);
1851         let mut private_candidate = None;
1852         let mut autoderef = self.autoderef(expr.span, expr_t);
1853         while let Some((base_t, _)) = autoderef.next() {
1854             debug!("base_t: {:?}", base_t);
1855             match base_t.kind() {
1856                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
1857                     debug!("struct named {:?}", base_t);
1858                     let (ident, def_scope) =
1859                         self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
1860                     let fields = &base_def.non_enum_variant().fields;
1861                     if let Some(index) = fields
1862                         .iter()
1863                         .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
1864                     {
1865                         let field = &fields[index];
1866                         let field_ty = self.field_ty(expr.span, field, substs);
1867                         // Save the index of all fields regardless of their visibility in case
1868                         // of error recovery.
1869                         self.write_field_index(expr.hir_id, index);
1870                         let adjustments = self.adjust_steps(&autoderef);
1871                         if field.vis.is_accessible_from(def_scope, self.tcx) {
1872                             self.apply_adjustments(base, adjustments);
1873                             self.register_predicates(autoderef.into_obligations());
1874
1875                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
1876                             return field_ty;
1877                         }
1878                         private_candidate = Some((adjustments, base_def.did, field_ty));
1879                     }
1880                 }
1881                 ty::Tuple(tys) => {
1882                     let fstr = field.as_str();
1883                     if let Ok(index) = fstr.parse::<usize>() {
1884                         if fstr == index.to_string() {
1885                             if let Some(field_ty) = tys.get(index) {
1886                                 let adjustments = self.adjust_steps(&autoderef);
1887                                 self.apply_adjustments(base, adjustments);
1888                                 self.register_predicates(autoderef.into_obligations());
1889
1890                                 self.write_field_index(expr.hir_id, index);
1891                                 return field_ty.expect_ty();
1892                             }
1893                         }
1894                     }
1895                 }
1896                 _ => {}
1897             }
1898         }
1899         self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
1900
1901         if let Some((adjustments, did, field_ty)) = private_candidate {
1902             // (#90483) apply adjustments to avoid ExprUseVisitor from
1903             // creating erroneous projection.
1904             self.apply_adjustments(base, adjustments);
1905             self.ban_private_field_access(expr, expr_t, field, did);
1906             return field_ty;
1907         }
1908
1909         if field.name == kw::Empty {
1910         } else if self.method_exists(field, expr_t, expr.hir_id, true) {
1911             self.ban_take_value_of_method(expr, expr_t, field);
1912         } else if !expr_t.is_primitive_ty() {
1913             self.ban_nonexisting_field(field, base, expr, expr_t);
1914         } else {
1915             type_error_struct!(
1916                 self.tcx().sess,
1917                 field.span,
1918                 expr_t,
1919                 E0610,
1920                 "`{}` is a primitive type and therefore doesn't have fields",
1921                 expr_t
1922             )
1923             .emit();
1924         }
1925
1926         self.tcx().ty_error()
1927     }
1928
1929     fn suggest_await_on_field_access(
1930         &self,
1931         err: &mut DiagnosticBuilder<'_>,
1932         field_ident: Ident,
1933         base: &'tcx hir::Expr<'tcx>,
1934         ty: Ty<'tcx>,
1935     ) {
1936         let output_ty = match self.infcx.get_impl_future_output_ty(ty) {
1937             Some(output_ty) => self.resolve_vars_if_possible(output_ty),
1938             _ => return,
1939         };
1940         let mut add_label = true;
1941         if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
1942             // no field access on enum type
1943             if !def.is_enum() {
1944                 if def
1945                     .non_enum_variant()
1946                     .fields
1947                     .iter()
1948                     .any(|field| field.ident(self.tcx) == field_ident)
1949                 {
1950                     add_label = false;
1951                     err.span_label(
1952                         field_ident.span,
1953                         "field not available in `impl Future`, but it is available in its `Output`",
1954                     );
1955                     err.span_suggestion_verbose(
1956                         base.span.shrink_to_hi(),
1957                         "consider `await`ing on the `Future` and access the field of its `Output`",
1958                         ".await".to_string(),
1959                         Applicability::MaybeIncorrect,
1960                     );
1961                 }
1962             }
1963         }
1964         if add_label {
1965             err.span_label(field_ident.span, &format!("field not found in `{}`", ty));
1966         }
1967     }
1968
1969     fn ban_nonexisting_field(
1970         &self,
1971         field: Ident,
1972         base: &'tcx hir::Expr<'tcx>,
1973         expr: &'tcx hir::Expr<'tcx>,
1974         expr_t: Ty<'tcx>,
1975     ) {
1976         debug!(
1977             "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
1978             field, base, expr, expr_t
1979         );
1980         let mut err = self.no_such_field_err(field, expr_t, base.hir_id);
1981
1982         match *expr_t.peel_refs().kind() {
1983             ty::Array(_, len) => {
1984                 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
1985             }
1986             ty::RawPtr(..) => {
1987                 self.suggest_first_deref_field(&mut err, expr, base, field);
1988             }
1989             ty::Adt(def, _) if !def.is_enum() => {
1990                 self.suggest_fields_on_recordish(&mut err, def, field, expr.span);
1991             }
1992             ty::Param(param_ty) => {
1993                 self.point_at_param_definition(&mut err, param_ty);
1994             }
1995             ty::Opaque(_, _) => {
1996                 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
1997             }
1998             _ => {}
1999         }
2000
2001         if field.name == kw::Await {
2002             // We know by construction that `<expr>.await` is either on Rust 2015
2003             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2004             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2005             err.help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION));
2006             err.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
2007         }
2008
2009         err.emit();
2010     }
2011
2012     fn ban_private_field_access(
2013         &self,
2014         expr: &hir::Expr<'_>,
2015         expr_t: Ty<'tcx>,
2016         field: Ident,
2017         base_did: DefId,
2018     ) {
2019         let struct_path = self.tcx().def_path_str(base_did);
2020         let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2021         let mut err = struct_span_err!(
2022             self.tcx().sess,
2023             field.span,
2024             E0616,
2025             "field `{}` of {} `{}` is private",
2026             field,
2027             kind_name,
2028             struct_path
2029         );
2030         err.span_label(field.span, "private field");
2031         // Also check if an accessible method exists, which is often what is meant.
2032         if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2033         {
2034             self.suggest_method_call(
2035                 &mut err,
2036                 &format!("a method `{}` also exists, call it with parentheses", field),
2037                 field,
2038                 expr_t,
2039                 expr,
2040                 None,
2041             );
2042         }
2043         err.emit();
2044     }
2045
2046     fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2047         let mut err = type_error_struct!(
2048             self.tcx().sess,
2049             field.span,
2050             expr_t,
2051             E0615,
2052             "attempted to take value of method `{}` on type `{}`",
2053             field,
2054             expr_t
2055         );
2056         err.span_label(field.span, "method, not a field");
2057         let expr_is_call =
2058             if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2059                 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2060             {
2061                 expr.hir_id == callee.hir_id
2062             } else {
2063                 false
2064             };
2065         let expr_snippet =
2066             self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or(String::new());
2067         let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2068         let after_open = expr.span.lo() + rustc_span::BytePos(1);
2069         let before_close = expr.span.hi() - rustc_span::BytePos(1);
2070
2071         if expr_is_call && is_wrapped {
2072             err.multipart_suggestion(
2073                 "remove wrapping parentheses to call the method",
2074                 vec![
2075                     (expr.span.with_hi(after_open), String::new()),
2076                     (expr.span.with_lo(before_close), String::new()),
2077                 ],
2078                 Applicability::MachineApplicable,
2079             );
2080         } else if !self.expr_in_place(expr.hir_id) {
2081             // Suggest call parentheses inside the wrapping parentheses
2082             let span = if is_wrapped {
2083                 expr.span.with_lo(after_open).with_hi(before_close)
2084             } else {
2085                 expr.span
2086             };
2087             self.suggest_method_call(
2088                 &mut err,
2089                 "use parentheses to call the method",
2090                 field,
2091                 expr_t,
2092                 expr,
2093                 Some(span),
2094             );
2095         } else {
2096             let mut found = false;
2097
2098             if let ty::RawPtr(ty_and_mut) = expr_t.kind() {
2099                 if let ty::Adt(adt_def, _) = ty_and_mut.ty.kind() {
2100                     if adt_def.variants.len() == 1
2101                         && adt_def
2102                             .variants
2103                             .iter()
2104                             .next()
2105                             .unwrap()
2106                             .fields
2107                             .iter()
2108                             .any(|f| f.ident(self.tcx) == field)
2109                     {
2110                         if let Some(dot_loc) = expr_snippet.rfind('.') {
2111                             found = true;
2112                             err.span_suggestion(
2113                                 expr.span.with_hi(expr.span.lo() + BytePos::from_usize(dot_loc)),
2114                                 "to access the field, dereference first",
2115                                 format!("(*{})", &expr_snippet[0..dot_loc]),
2116                                 Applicability::MaybeIncorrect,
2117                             );
2118                         }
2119                     }
2120                 }
2121             }
2122
2123             if !found {
2124                 err.help("methods are immutable and cannot be assigned to");
2125             }
2126         }
2127
2128         err.emit();
2129     }
2130
2131     fn point_at_param_definition(&self, err: &mut DiagnosticBuilder<'_>, param: ty::ParamTy) {
2132         let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2133         let generic_param = generics.type_param(&param, self.tcx);
2134         if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2135             return;
2136         }
2137         let param_def_id = generic_param.def_id;
2138         let param_hir_id = match param_def_id.as_local() {
2139             Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2140             None => return,
2141         };
2142         let param_span = self.tcx.hir().span(param_hir_id);
2143         let param_name = self.tcx.hir().ty_param_name(param_hir_id);
2144
2145         err.span_label(param_span, &format!("type parameter '{}' declared here", param_name));
2146     }
2147
2148     fn suggest_fields_on_recordish(
2149         &self,
2150         err: &mut DiagnosticBuilder<'_>,
2151         def: &'tcx ty::AdtDef,
2152         field: Ident,
2153         access_span: Span,
2154     ) {
2155         if let Some(suggested_field_name) =
2156             self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2157         {
2158             err.span_suggestion(
2159                 field.span,
2160                 "a field with a similar name exists",
2161                 suggested_field_name.to_string(),
2162                 Applicability::MaybeIncorrect,
2163             );
2164         } else {
2165             err.span_label(field.span, "unknown field");
2166             let struct_variant_def = def.non_enum_variant();
2167             let field_names = self.available_field_names(struct_variant_def, access_span);
2168             if !field_names.is_empty() {
2169                 err.note(&format!(
2170                     "available fields are: {}",
2171                     self.name_series_display(field_names),
2172                 ));
2173             }
2174         }
2175     }
2176
2177     fn maybe_suggest_array_indexing(
2178         &self,
2179         err: &mut DiagnosticBuilder<'_>,
2180         expr: &hir::Expr<'_>,
2181         base: &hir::Expr<'_>,
2182         field: Ident,
2183         len: &ty::Const<'tcx>,
2184     ) {
2185         if let (Some(len), Ok(user_index)) =
2186             (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2187         {
2188             if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2189                 let help = "instead of using tuple indexing, use array indexing";
2190                 let suggestion = format!("{}[{}]", base, field);
2191                 let applicability = if len < user_index {
2192                     Applicability::MachineApplicable
2193                 } else {
2194                     Applicability::MaybeIncorrect
2195                 };
2196                 err.span_suggestion(expr.span, help, suggestion, applicability);
2197             }
2198         }
2199     }
2200
2201     fn suggest_first_deref_field(
2202         &self,
2203         err: &mut DiagnosticBuilder<'_>,
2204         expr: &hir::Expr<'_>,
2205         base: &hir::Expr<'_>,
2206         field: Ident,
2207     ) {
2208         if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2209             let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
2210             let suggestion = format!("(*{}).{}", base, field);
2211             err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2212         }
2213     }
2214
2215     fn no_such_field_err(
2216         &self,
2217         field: Ident,
2218         expr_t: &'tcx ty::TyS<'tcx>,
2219         id: HirId,
2220     ) -> DiagnosticBuilder<'_> {
2221         let span = field.span;
2222         debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2223
2224         let mut err = type_error_struct!(
2225             self.tcx().sess,
2226             field.span,
2227             expr_t,
2228             E0609,
2229             "no field `{}` on type `{}`",
2230             field,
2231             expr_t
2232         );
2233
2234         // try to add a suggestion in case the field is a nested field of a field of the Adt
2235         if let Some((fields, substs)) = self.get_field_candidates(span, &expr_t) {
2236             for candidate_field in fields.iter() {
2237                 if let Some(field_path) = self.check_for_nested_field(
2238                     span,
2239                     field,
2240                     candidate_field,
2241                     substs,
2242                     vec![],
2243                     self.tcx.parent_module(id).to_def_id(),
2244                 ) {
2245                     let field_path_str = field_path
2246                         .iter()
2247                         .map(|id| id.name.to_ident_string())
2248                         .collect::<Vec<String>>()
2249                         .join(".");
2250                     debug!("field_path_str: {:?}", field_path_str);
2251
2252                     err.span_suggestion_verbose(
2253                         field.span.shrink_to_lo(),
2254                         "one of the expressions' fields has a field of the same name",
2255                         format!("{}.", field_path_str),
2256                         Applicability::MaybeIncorrect,
2257                     );
2258                 }
2259             }
2260         }
2261         err
2262     }
2263
2264     fn get_field_candidates(
2265         &self,
2266         span: Span,
2267         base_t: Ty<'tcx>,
2268     ) -> Option<(&Vec<ty::FieldDef>, SubstsRef<'tcx>)> {
2269         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_t);
2270
2271         for (base_t, _) in self.autoderef(span, base_t) {
2272             match base_t.kind() {
2273                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2274                     let fields = &base_def.non_enum_variant().fields;
2275                     // For compile-time reasons put a limit on number of fields we search
2276                     if fields.len() > 100 {
2277                         return None;
2278                     }
2279                     return Some((fields, substs));
2280                 }
2281                 _ => {}
2282             }
2283         }
2284         None
2285     }
2286
2287     /// This method is called after we have encountered a missing field error to recursively
2288     /// search for the field
2289     fn check_for_nested_field(
2290         &self,
2291         span: Span,
2292         target_field: Ident,
2293         candidate_field: &ty::FieldDef,
2294         subst: SubstsRef<'tcx>,
2295         mut field_path: Vec<Ident>,
2296         id: DefId,
2297     ) -> Option<Vec<Ident>> {
2298         debug!(
2299             "check_for_nested_field(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2300             span, candidate_field, field_path
2301         );
2302
2303         if candidate_field.ident(self.tcx) == target_field {
2304             Some(field_path)
2305         } else if field_path.len() > 3 {
2306             // For compile-time reasons and to avoid infinite recursion we only check for fields
2307             // up to a depth of three
2308             None
2309         } else {
2310             // recursively search fields of `candidate_field` if it's a ty::Adt
2311
2312             field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2313             let field_ty = candidate_field.ty(self.tcx, subst);
2314             if let Some((nested_fields, subst)) = self.get_field_candidates(span, &field_ty) {
2315                 for field in nested_fields.iter() {
2316                     let accessible = field.vis.is_accessible_from(id, self.tcx);
2317                     if accessible {
2318                         let ident = field.ident(self.tcx).normalize_to_macros_2_0();
2319                         if ident == target_field {
2320                             return Some(field_path);
2321                         }
2322                         let field_path = field_path.clone();
2323                         if let Some(path) = self.check_for_nested_field(
2324                             span,
2325                             target_field,
2326                             field,
2327                             subst,
2328                             field_path,
2329                             id,
2330                         ) {
2331                             return Some(path);
2332                         }
2333                     }
2334                 }
2335             }
2336             None
2337         }
2338     }
2339
2340     fn check_expr_index(
2341         &self,
2342         base: &'tcx hir::Expr<'tcx>,
2343         idx: &'tcx hir::Expr<'tcx>,
2344         expr: &'tcx hir::Expr<'tcx>,
2345     ) -> Ty<'tcx> {
2346         let base_t = self.check_expr(&base);
2347         let idx_t = self.check_expr(&idx);
2348
2349         if base_t.references_error() {
2350             base_t
2351         } else if idx_t.references_error() {
2352             idx_t
2353         } else {
2354             let base_t = self.structurally_resolved_type(base.span, base_t);
2355             match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2356                 Some((index_ty, element_ty)) => {
2357                     // two-phase not needed because index_ty is never mutable
2358                     self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2359                     element_ty
2360                 }
2361                 None => {
2362                     let mut err = type_error_struct!(
2363                         self.tcx.sess,
2364                         expr.span,
2365                         base_t,
2366                         E0608,
2367                         "cannot index into a value of type `{}`",
2368                         base_t
2369                     );
2370                     // Try to give some advice about indexing tuples.
2371                     if let ty::Tuple(..) = base_t.kind() {
2372                         let mut needs_note = true;
2373                         // If the index is an integer, we can show the actual
2374                         // fixed expression:
2375                         if let ExprKind::Lit(ref lit) = idx.kind {
2376                             if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2377                                 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2378                                 if let Ok(snip) = snip {
2379                                     err.span_suggestion(
2380                                         expr.span,
2381                                         "to access tuple elements, use",
2382                                         format!("{}.{}", snip, i),
2383                                         Applicability::MachineApplicable,
2384                                     );
2385                                     needs_note = false;
2386                                 }
2387                             }
2388                         }
2389                         if needs_note {
2390                             err.help(
2391                                 "to access tuple elements, use tuple indexing \
2392                                         syntax (e.g., `tuple.0`)",
2393                             );
2394                         }
2395                     }
2396                     err.emit();
2397                     self.tcx.ty_error()
2398                 }
2399             }
2400         }
2401     }
2402
2403     fn check_expr_yield(
2404         &self,
2405         value: &'tcx hir::Expr<'tcx>,
2406         expr: &'tcx hir::Expr<'tcx>,
2407         src: &'tcx hir::YieldSource,
2408     ) -> Ty<'tcx> {
2409         match self.resume_yield_tys {
2410             Some((resume_ty, yield_ty)) => {
2411                 self.check_expr_coercable_to_type(&value, yield_ty, None);
2412
2413                 resume_ty
2414             }
2415             // Given that this `yield` expression was generated as a result of lowering a `.await`,
2416             // we know that the yield type must be `()`; however, the context won't contain this
2417             // information. Hence, we check the source of the yield expression here and check its
2418             // value's type against `()` (this check should always hold).
2419             None if src.is_await() => {
2420                 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2421                 self.tcx.mk_unit()
2422             }
2423             _ => {
2424                 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2425                 // Avoid expressions without types during writeback (#78653).
2426                 self.check_expr(value);
2427                 self.tcx.mk_unit()
2428             }
2429         }
2430     }
2431
2432     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2433         let needs = if is_input { Needs::None } else { Needs::MutPlace };
2434         let ty = self.check_expr_with_needs(expr, needs);
2435         self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2436
2437         if !is_input && !expr.is_syntactic_place_expr() {
2438             let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2439             err.span_label(expr.span, "cannot assign to this expression");
2440             err.emit();
2441         }
2442
2443         // If this is an input value, we require its type to be fully resolved
2444         // at this point. This allows us to provide helpful coercions which help
2445         // pass the type candidate list in a later pass.
2446         //
2447         // We don't require output types to be resolved at this point, which
2448         // allows them to be inferred based on how they are used later in the
2449         // function.
2450         if is_input {
2451             let ty = self.structurally_resolved_type(expr.span, &ty);
2452             match *ty.kind() {
2453                 ty::FnDef(..) => {
2454                     let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2455                     self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2456                 }
2457                 ty::Ref(_, base_ty, mutbl) => {
2458                     let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2459                     self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2460                 }
2461                 _ => {}
2462             }
2463         }
2464     }
2465
2466     fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2467         for (op, _op_sp) in asm.operands {
2468             match op {
2469                 hir::InlineAsmOperand::In { expr, .. } => {
2470                     self.check_expr_asm_operand(expr, true);
2471                 }
2472                 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2473                 | hir::InlineAsmOperand::InOut { expr, .. } => {
2474                     self.check_expr_asm_operand(expr, false);
2475                 }
2476                 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2477                 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2478                     self.check_expr_asm_operand(in_expr, true);
2479                     if let Some(out_expr) = out_expr {
2480                         self.check_expr_asm_operand(out_expr, false);
2481                     }
2482                 }
2483                 hir::InlineAsmOperand::Const { anon_const } => {
2484                     self.to_const(anon_const);
2485                 }
2486                 hir::InlineAsmOperand::Sym { expr } => {
2487                     self.check_expr(expr);
2488                 }
2489             }
2490         }
2491         if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2492             self.tcx.types.never
2493         } else {
2494             self.tcx.mk_unit()
2495         }
2496     }
2497 }
2498
2499 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2500     Some(match ty.kind() {
2501         ty::Bool => "true",
2502         ty::Char => "'a'",
2503         ty::Int(_) | ty::Uint(_) => "42",
2504         ty::Float(_) => "3.14159",
2505         ty::Error(_) | ty::Never => return None,
2506         _ => "value",
2507     })
2508 }