1 //! Type checking expressions.
3 //! See `mod.rs` for more context on type checking in general.
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;
19 FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
20 YieldExprOutsideOfGenerator,
22 use crate::type_error_struct;
24 use super::suggest_call_constructor;
25 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
27 use rustc_data_structures::fx::FxHashMap;
28 use rustc_data_structures::stack::ensure_sufficient_stack;
29 use rustc_errors::Diagnostic;
30 use rustc_errors::EmissionGuarantee;
31 use rustc_errors::ErrorGuaranteed;
32 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
34 use rustc_hir::def::{CtorKind, DefKind, Res};
35 use rustc_hir::def_id::DefId;
36 use rustc_hir::intravisit::Visitor;
37 use rustc_hir::lang_items::LangItem;
38 use rustc_hir::{ExprKind, HirId, QPath};
39 use rustc_infer::infer;
40 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
41 use rustc_infer::infer::InferOk;
42 use rustc_middle::middle::stability;
43 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
44 use rustc_middle::ty::error::ExpectedFound;
45 use rustc_middle::ty::error::TypeError::{FieldMisMatch, Sorts};
46 use rustc_middle::ty::subst::SubstsRef;
47 use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TypeFoldable};
48 use rustc_session::parse::feature_err;
49 use rustc_span::hygiene::DesugaringKind;
50 use rustc_span::lev_distance::find_best_match_for_name;
51 use rustc_span::source_map::Span;
52 use rustc_span::symbol::{kw, sym, Ident, Symbol};
53 use rustc_span::{BytePos, Pos};
54 use rustc_target::spec::abi::Abi::RustIntrinsic;
55 use rustc_trait_selection::infer::InferCtxtExt;
56 use rustc_trait_selection::traits::{self, ObligationCauseCode};
58 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
59 fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
60 let ty = self.check_expr_with_hint(expr, expected);
61 self.demand_eqtype(expr.span, expected, ty);
64 pub fn check_expr_has_type_or_error(
66 expr: &'tcx hir::Expr<'tcx>,
68 extend_err: impl Fn(&mut Diagnostic),
70 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
73 fn check_expr_meets_expectation_or_error(
75 expr: &'tcx hir::Expr<'tcx>,
76 expected: Expectation<'tcx>,
77 extend_err: impl Fn(&mut Diagnostic),
79 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
80 let mut ty = self.check_expr_with_expectation(expr, expected);
82 // While we don't allow *arbitrary* coercions here, we *do* allow
83 // coercions from ! to `expected`.
85 if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
86 self.tcx().sess.delay_span_bug(
88 "expression with never type wound up being adjusted",
90 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
97 let adj_ty = self.next_ty_var(TypeVariableOrigin {
98 kind: TypeVariableOriginKind::AdjustmentType,
101 self.apply_adjustments(
103 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
108 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
109 let expr = expr.peel_drop_temps();
110 self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
111 extend_err(&mut err);
117 pub(super) fn check_expr_coercable_to_type(
119 expr: &'tcx hir::Expr<'tcx>,
121 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
123 let ty = self.check_expr_with_hint(expr, expected);
124 // checks don't need two phase
125 self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
128 pub(super) fn check_expr_with_hint(
130 expr: &'tcx hir::Expr<'tcx>,
133 self.check_expr_with_expectation(expr, ExpectHasType(expected))
136 fn check_expr_with_expectation_and_needs(
138 expr: &'tcx hir::Expr<'tcx>,
139 expected: Expectation<'tcx>,
142 let ty = self.check_expr_with_expectation(expr, expected);
144 // If the expression is used in a place whether mutable place is required
145 // e.g. LHS of assignment, perform the conversion.
146 if let Needs::MutPlace = needs {
147 self.convert_place_derefs_to_mutable(expr);
153 pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
154 self.check_expr_with_expectation(expr, NoExpectation)
157 pub(super) fn check_expr_with_needs(
159 expr: &'tcx hir::Expr<'tcx>,
162 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
166 /// If an expression has any sub-expressions that result in a type error,
167 /// inspecting that expression's type with `ty.references_error()` will return
168 /// true. Likewise, if an expression is known to diverge, inspecting its
169 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
170 /// strict, _|_ can appear in the type of an expression that does not,
171 /// itself, diverge: for example, fn() -> _|_.)
172 /// Note that inspecting a type's structure *directly* may expose the fact
173 /// that there are actually multiple representations for `Error`, so avoid
174 /// that when err needs to be handled differently.
175 #[instrument(skip(self, expr), level = "debug")]
176 pub(super) fn check_expr_with_expectation(
178 expr: &'tcx hir::Expr<'tcx>,
179 expected: Expectation<'tcx>,
181 self.check_expr_with_expectation_and_args(expr, expected, &[])
184 /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
185 /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
186 pub(super) fn check_expr_with_expectation_and_args(
188 expr: &'tcx hir::Expr<'tcx>,
189 expected: Expectation<'tcx>,
190 args: &'tcx [hir::Expr<'tcx>],
192 if self.tcx().sess.verbose() {
193 // make this code only run with -Zverbose because it is probably slow
194 if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
195 if !lint_str.contains('\n') {
196 debug!("expr text: {lint_str}");
198 let mut lines = lint_str.lines();
199 if let Some(line0) = lines.next() {
200 let remaining_lines = lines.count();
201 debug!("expr text: {line0}");
202 debug!("expr text: ...(and {remaining_lines} more lines)");
208 // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
209 // without the final expr (e.g. `try { return; }`). We don't want to generate an
210 // unreachable_code lint for it since warnings for autogenerated code are confusing.
211 let is_try_block_generated_unit_expr = match expr.kind {
212 ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
213 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
219 // Warn for expressions after diverging siblings.
220 if !is_try_block_generated_unit_expr {
221 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
224 // Hide the outer diverging and has_errors flags.
225 let old_diverges = self.diverges.replace(Diverges::Maybe);
226 let old_has_errors = self.has_errors.replace(false);
228 let ty = ensure_sufficient_stack(|| match &expr.kind {
230 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
231 ) => self.check_expr_path(qpath, expr, args),
232 _ => self.check_expr_kind(expr, expected),
235 // Warn for non-block expressions with diverging children.
241 | ExprKind::Match(..) => {}
242 // If `expr` is a result of desugaring the try block and is an ok-wrapped
243 // diverging expression (e.g. it arose from desugaring of `try { return }`),
244 // we skip issuing a warning because it is autogenerated code.
245 ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
246 ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
247 ExprKind::MethodCall(segment, ..) => {
248 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
250 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
253 // Any expression that produces a value of type `!` must have diverged
255 self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
258 // Record the type, which applies it effects.
259 // We need to do this after the warning above, so that
260 // we don't warn for the diverging expression itself.
261 self.write_ty(expr.hir_id, ty);
263 // Combine the diverging and has_error flags.
264 self.diverges.set(self.diverges.get() | old_diverges);
265 self.has_errors.set(self.has_errors.get() | old_has_errors);
267 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
268 debug!("... {:?}, expected is {:?}", ty, expected);
273 #[instrument(skip(self, expr), level = "debug")]
274 pub(super) fn check_expr_kind(
276 expr: &'tcx hir::Expr<'tcx>,
277 expected: Expectation<'tcx>,
279 trace!("expr={:#?}", expr);
283 ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
284 ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
285 ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs),
286 ExprKind::Assign(lhs, rhs, span) => {
287 self.check_expr_assign(expr, expected, lhs, rhs, span)
289 ExprKind::AssignOp(op, lhs, rhs) => self.check_binop_assign(expr, op, lhs, rhs),
290 ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
291 ExprKind::AddrOf(kind, mutbl, oprnd) => {
292 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
294 ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
295 self.check_lang_item_path(lang_item, expr, hir_id)
297 ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
298 ExprKind::InlineAsm(asm) => {
299 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
300 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
301 self.check_expr_asm(asm)
303 ExprKind::Break(destination, ref expr_opt) => {
304 self.check_expr_break(destination, expr_opt.as_deref(), expr)
306 ExprKind::Continue(destination) => {
307 if destination.target_id.is_ok() {
310 // There was an error; make type-check fail.
314 ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
315 ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
316 ExprKind::Loop(body, _, source, _) => {
317 self.check_expr_loop(body, source, expected, expr)
319 ExprKind::Match(discrim, arms, match_src) => {
320 self.check_match(expr, &discrim, arms, expected, match_src)
322 ExprKind::Closure(capture, decl, body_id, _, gen) => {
323 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
325 ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
326 ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
327 ExprKind::MethodCall(segment, args, _) => {
328 self.check_method_call(expr, segment, args, expected)
330 ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
331 ExprKind::Type(e, t) => {
332 let ty = self.to_ty_saving_user_provided_ty(&t);
333 self.check_expr_eq_type(&e, ty);
336 ExprKind::If(cond, then_expr, opt_else_expr) => {
337 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
339 ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
340 ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
341 ExprKind::ConstBlock(ref anon_const) => {
342 self.check_expr_const_block(anon_const, expected, expr)
344 ExprKind::Repeat(element, ref count) => {
345 self.check_expr_repeat(element, count, expected, expr)
347 ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
348 ExprKind::Struct(qpath, fields, ref base_expr) => {
349 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
351 ExprKind::Field(base, field) => self.check_field(expr, &base, field),
352 ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
353 ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
354 hir::ExprKind::Err => tcx.ty_error(),
358 fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
359 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
360 ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
363 let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
364 self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
365 self.tcx.mk_box(referent_ty)
371 oprnd: &'tcx hir::Expr<'tcx>,
372 expected: Expectation<'tcx>,
373 expr: &'tcx hir::Expr<'tcx>,
376 let expected_inner = match unop {
377 hir::UnOp::Not | hir::UnOp::Neg => expected,
378 hir::UnOp::Deref => NoExpectation,
380 let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
382 if !oprnd_t.references_error() {
383 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
385 hir::UnOp::Deref => {
386 if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
389 let mut err = type_error_struct!(
394 "type `{oprnd_t}` cannot be dereferenced",
396 let sp = tcx.sess.source_map().start_point(expr.span);
398 tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
400 tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
403 oprnd_t = tcx.ty_error();
407 let result = self.check_user_unop(expr, oprnd_t, unop);
408 // If it's builtin, we can reuse the type, this helps inference.
409 if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
414 let result = self.check_user_unop(expr, oprnd_t, unop);
415 // If it's builtin, we can reuse the type, this helps inference.
416 if !oprnd_t.is_numeric() {
425 fn check_expr_addr_of(
427 kind: hir::BorrowKind,
428 mutbl: hir::Mutability,
429 oprnd: &'tcx hir::Expr<'tcx>,
430 expected: Expectation<'tcx>,
431 expr: &'tcx hir::Expr<'tcx>,
433 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
435 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
436 if oprnd.is_syntactic_place_expr() {
437 // Places may legitimately have unsized types.
438 // For example, dereferences of a fat pointer and
439 // the last field of a struct can be unsized.
442 Expectation::rvalue_hint(self, *ty)
449 self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
451 let tm = ty::TypeAndMut { ty, mutbl };
453 _ if tm.ty.references_error() => self.tcx.ty_error(),
454 hir::BorrowKind::Raw => {
455 self.check_named_place_expr(oprnd);
458 hir::BorrowKind::Ref => {
459 // Note: at this point, we cannot say what the best lifetime
460 // is to use for resulting pointer. We want to use the
461 // shortest lifetime possible so as to avoid spurious borrowck
462 // errors. Moreover, the longest lifetime will depend on the
463 // precise details of the value whose address is being taken
464 // (and how long it is valid), which we don't know yet until
465 // type inference is complete.
467 // Therefore, here we simply generate a region variable. The
468 // region inferencer will then select a suitable value.
469 // Finally, borrowck will infer the value of the region again,
470 // this time with enough precision to check that the value
471 // whose address was taken can actually be made to live as long
472 // as it needs to live.
473 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
474 self.tcx.mk_ref(region, tm)
479 /// Does this expression refer to a place that either:
480 /// * Is based on a local or static.
481 /// * Contains a dereference
482 /// Note that the adjustments for the children of `expr` should already
483 /// have been resolved.
484 fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
485 let is_named = oprnd.is_place_expr(|base| {
486 // Allow raw borrows if there are any deref adjustments.
488 // const VAL: (i32,) = (0,);
489 // const REF: &(i32,) = &(0,);
491 // &raw const VAL.0; // ERROR
492 // &raw const REF.0; // OK, same as &raw const (*REF).0;
494 // This is maybe too permissive, since it allows
495 // `let u = &raw const Box::new((1,)).0`, which creates an
496 // immediately dangling raw pointer.
501 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
504 self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
508 fn check_lang_item_path(
510 lang_item: hir::LangItem,
511 expr: &'tcx hir::Expr<'tcx>,
512 hir_id: Option<hir::HirId>,
514 self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
517 pub(crate) fn check_expr_path(
519 qpath: &'tcx hir::QPath<'tcx>,
520 expr: &'tcx hir::Expr<'tcx>,
521 args: &'tcx [hir::Expr<'tcx>],
524 let (res, opt_ty, segs) =
525 self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
528 self.set_tainted_by_errors();
531 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
532 report_unexpected_variant_res(tcx, res, expr.span);
535 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
538 if let ty::FnDef(did, ..) = *ty.kind() {
539 let fn_sig = ty.fn_sig(tcx);
540 if tcx.fn_sig(did).abi() == RustIntrinsic && tcx.item_name(did) == sym::transmute {
541 let from = fn_sig.inputs().skip_binder()[0];
542 let to = fn_sig.output().skip_binder();
543 // We defer the transmute to the end of typeck, once all inference vars have
544 // been resolved or we errored. This is important as we can only check transmute
545 // on concrete types, but the output type may not be known yet (it would only
546 // be known if explicitly specified via turbofish).
547 self.deferred_transmute_checks.borrow_mut().push((from, to, expr.span));
549 if !tcx.features().unsized_fn_params {
550 // We want to remove some Sized bounds from std functions,
551 // but don't want to expose the removal to stable Rust.
552 // i.e., we don't want to allow
558 // to work in stable even if the Sized bound on `drop` is relaxed.
559 for i in 0..fn_sig.inputs().skip_binder().len() {
560 // We just want to check sizedness, so instead of introducing
561 // placeholder lifetimes with probing, we just replace higher lifetimes
563 let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
565 .replace_bound_vars_with_fresh_vars(
567 infer::LateBoundRegionConversionTime::FnCall,
571 self.require_type_is_sized_deferred(
574 traits::SizedArgumentType(None),
578 // Here we want to prevent struct constructors from returning unsized types.
579 // There were two cases this happened: fn pointer coercion in stable
580 // and usual function call in presence of unsized_locals.
581 // Also, as we just want to check sizedness, instead of introducing
582 // placeholder lifetimes with probing, we just replace higher lifetimes
585 .replace_bound_vars_with_fresh_vars(
587 infer::LateBoundRegionConversionTime::FnCall,
591 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
594 // We always require that the type provided as the value for
595 // a type parameter outlives the moment of instantiation.
596 let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
597 self.add_wf_bounds(substs, expr);
604 destination: hir::Destination,
605 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
606 expr: &'tcx hir::Expr<'tcx>,
609 if let Ok(target_id) = destination.target_id {
611 if let Some(e) = expr_opt {
612 // If this is a break with a value, we need to type-check
613 // the expression. Get an expected type from the loop context.
614 let opt_coerce_to = {
615 // We should release `enclosing_breakables` before the `check_expr_with_hint`
616 // below, so can't move this block of code to the enclosing scope and share
617 // `ctxt` with the second `enclosing_breakables` borrow below.
618 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
619 match enclosing_breakables.opt_find_breakable(target_id) {
620 Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
622 // Avoid ICE when `break` is inside a closure (#65383).
623 return tcx.ty_error_with_message(
625 "break was outside loop, but no error was emitted",
631 // If the loop context is not a `loop { }`, then break with
632 // a value is illegal, and `opt_coerce_to` will be `None`.
633 // Just set expectation to error in that case.
634 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
636 // Recurse without `enclosing_breakables` borrowed.
637 e_ty = self.check_expr_with_hint(e, coerce_to);
638 cause = self.misc(e.span);
640 // Otherwise, this is a break *without* a value. That's
641 // always legal, and is equivalent to `break ()`.
642 e_ty = tcx.mk_unit();
643 cause = self.misc(expr.span);
646 // Now that we have type-checked `expr_opt`, borrow
647 // the `enclosing_loops` field and let's coerce the
648 // type of `expr_opt` into what is expected.
649 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
650 let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
651 // Avoid ICE when `break` is inside a closure (#65383).
652 return tcx.ty_error_with_message(
654 "break was outside loop, but no error was emitted",
658 if let Some(ref mut coerce) = ctxt.coerce {
659 if let Some(ref e) = expr_opt {
660 coerce.coerce(self, &cause, e, e_ty);
662 assert!(e_ty.is_unit());
663 let ty = coerce.expected_ty();
664 coerce.coerce_forced_unit(
668 self.suggest_mismatched_types_on_tail(
669 &mut err, expr, ty, e_ty, target_id,
671 if let Some(val) = ty_kind_suggestion(ty) {
672 let label = destination
674 .map(|l| format!(" {}", l.ident))
675 .unwrap_or_else(String::new);
678 "give it a value of the expected type",
679 format!("break{label} {val}"),
680 Applicability::HasPlaceholders,
688 // If `ctxt.coerce` is `None`, we can just ignore
689 // the type of the expression. This is because
690 // either this was a break *without* a value, in
691 // which case it is always a legal type (`()`), or
692 // else an error would have been flagged by the
693 // `loops` pass for using break with an expression
694 // where you are not supposed to.
695 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
698 // If we encountered a `break`, then (no surprise) it may be possible to break from the
699 // loop... unless the value being returned from the loop diverges itself, e.g.
700 // `break return 5` or `break loop {}`.
701 ctxt.may_break |= !self.diverges.get().is_always();
703 // the type of a `break` is always `!`, since it diverges
706 // Otherwise, we failed to find the enclosing loop;
707 // this can only happen if the `break` was not
708 // inside a loop at all, which is caught by the
709 // loop-checking pass.
710 let err = self.tcx.ty_error_with_message(
712 "break was outside loop, but no error was emitted",
715 // We still need to assign a type to the inner expression to
716 // prevent the ICE in #43162.
717 if let Some(e) = expr_opt {
718 self.check_expr_with_hint(e, err);
720 // ... except when we try to 'break rust;'.
721 // ICE this expression in particular (see #43162).
722 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
723 if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
724 fatally_break_rust(self.tcx.sess);
729 // There was an error; make type-check fail.
734 fn check_expr_return(
736 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
737 expr: &'tcx hir::Expr<'tcx>,
739 if self.ret_coercion.is_none() {
740 let mut err = ReturnStmtOutsideOfFnBody {
742 encl_body_span: None,
746 let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
748 if let Some(hir::Node::Item(hir::Item {
749 kind: hir::ItemKind::Fn(..),
753 | Some(hir::Node::TraitItem(hir::TraitItem {
754 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
758 | Some(hir::Node::ImplItem(hir::ImplItem {
759 kind: hir::ImplItemKind::Fn(..),
762 })) = self.tcx.hir().find_by_def_id(encl_item_id)
764 // We are inside a function body, so reporting "return statement
765 // outside of function body" needs an explanation.
767 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
769 // If this didn't hold, we would not have to report an error in
771 assert_ne!(hir::HirId::make_owner(encl_item_id), encl_body_owner_id);
773 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
774 let encl_body = self.tcx.hir().body(encl_body_id);
776 err.encl_body_span = Some(encl_body.value.span);
777 err.encl_fn_span = Some(*encl_fn_span);
780 self.tcx.sess.emit_err(err);
782 if let Some(e) = expr_opt {
783 // We still have to type-check `e` (issue #86188), but calling
784 // `check_return_expr` only works inside fn bodies.
787 } else if let Some(e) = expr_opt {
788 if self.ret_coercion_span.get().is_none() {
789 self.ret_coercion_span.set(Some(e.span));
791 self.check_return_expr(e, true);
793 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
794 if self.ret_coercion_span.get().is_none() {
795 self.ret_coercion_span.set(Some(expr.span));
797 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
798 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
799 coercion.coerce_forced_unit(
803 let span = fn_decl.output.span();
804 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
807 format!("expected `{snippet}` because of this return type"),
814 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
820 /// `explicit_return` is `true` if we're checking an explicit `return expr`,
821 /// and `false` if we're checking a trailing expression.
822 pub(super) fn check_return_expr(
824 return_expr: &'tcx hir::Expr<'tcx>,
825 explicit_return: bool,
827 let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
828 span_bug!(return_expr.span, "check_return_expr called outside fn body")
831 let ret_ty = ret_coercion.borrow().expected_ty();
832 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
833 let mut span = return_expr.span;
834 // Use the span of the trailing expression for our cause,
835 // not the span of the entire function
836 if !explicit_return {
837 if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
838 span = last_expr.span;
841 ret_coercion.borrow_mut().coerce(
843 &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
849 pub(crate) fn check_lhs_assignable(
851 lhs: &'tcx hir::Expr<'tcx>,
852 err_code: &'static str,
854 adjust_err: impl FnOnce(&mut DiagnosticBuilder<'tcx, ErrorGuaranteed>),
856 if lhs.is_syntactic_place_expr() {
860 // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
861 let mut err = self.tcx.sess.struct_span_err_with_code(
863 "invalid left-hand side of assignment",
864 DiagnosticId::Error(err_code.into()),
866 err.span_label(lhs.span, "cannot assign to this expression");
868 self.comes_from_while_condition(lhs.hir_id, |expr| {
869 err.span_suggestion_verbose(
870 expr.span.shrink_to_lo(),
871 "you might have meant to use pattern destructuring",
873 Applicability::MachineApplicable,
877 adjust_err(&mut err);
882 // Check if an expression `original_expr_id` comes from the condition of a while loop,
883 // as opposed from the body of a while loop, which we can naively check by iterating
884 // parents until we find a loop...
885 pub(super) fn comes_from_while_condition(
887 original_expr_id: HirId,
888 then: impl FnOnce(&hir::Expr<'_>),
890 let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
891 while let Some(node) = self.tcx.hir().find(parent) {
893 hir::Node::Expr(hir::Expr {
900 hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
906 hir::LoopSource::While,
911 // Check if our original expression is a child of the condition of a while loop
912 let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
913 self.tcx.hir().find_parent_node(*id)
915 .take_while(|id| *id != parent)
916 .any(|id| id == expr.hir_id);
917 // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
918 // where `while let` was more likely intended.
919 if expr_is_ancestor {
925 | hir::Node::ImplItem(_)
926 | hir::Node::TraitItem(_)
927 | hir::Node::Crate(_) => break,
929 parent = self.tcx.hir().get_parent_node(parent);
935 // A generic function for checking the 'then' and 'else' clauses in an 'if'
936 // or 'if-else' expression.
939 cond_expr: &'tcx hir::Expr<'tcx>,
940 then_expr: &'tcx hir::Expr<'tcx>,
941 opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
943 orig_expected: Expectation<'tcx>,
945 let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
947 self.warn_if_unreachable(
950 "block in `if` or `while` expression",
953 let cond_diverges = self.diverges.get();
954 self.diverges.set(Diverges::Maybe);
956 let expected = orig_expected.adjust_for_branches(self);
957 let then_ty = self.check_expr_with_expectation(then_expr, expected);
958 let then_diverges = self.diverges.get();
959 self.diverges.set(Diverges::Maybe);
961 // We've already taken the expected type's preferences
962 // into account when typing the `then` branch. To figure
963 // out the initial shot at a LUB, we thus only consider
964 // `expected` if it represents a *hard* constraint
965 // (`only_has_type`); otherwise, we just go with a
966 // fresh type variable.
967 let coerce_to_ty = expected.coercion_target_type(self, sp);
968 let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
970 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
972 if let Some(else_expr) = opt_else_expr {
973 let else_ty = if sp.desugaring_kind() == Some(DesugaringKind::LetElse) {
974 // todo introduce `check_expr_with_expectation(.., Expectation::LetElse)`
975 // for errors that point to the offending expression rather than the entire block.
976 // We could use `check_expr_eq_type(.., tcx.types.never)`, but then there is no
977 // way to detect that the expected type originated from let-else and provide
978 // a customized error.
979 let else_ty = self.check_expr(else_expr);
980 let cause = self.cause(else_expr.span, ObligationCauseCode::LetElse);
982 if let Some(mut err) =
983 self.demand_eqtype_with_origin(&cause, self.tcx.types.never, else_ty)
991 self.check_expr_with_expectation(else_expr, expected)
993 let else_diverges = self.diverges.get();
995 let opt_suggest_box_span = self.opt_suggest_box_span(else_ty, orig_expected);
997 self.if_cause(sp, then_expr, else_expr, then_ty, else_ty, opt_suggest_box_span);
999 coerce.coerce(self, &if_cause, else_expr, else_ty);
1001 // We won't diverge unless both branches do (or the condition does).
1002 self.diverges.set(cond_diverges | then_diverges & else_diverges);
1004 self.if_fallback_coercion(sp, then_expr, &mut coerce);
1006 // If the condition is false we can't diverge.
1007 self.diverges.set(cond_diverges);
1010 let result_ty = coerce.complete(self);
1011 if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1014 /// Type check assignment expression `expr` of form `lhs = rhs`.
1015 /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1016 fn check_expr_assign(
1018 expr: &'tcx hir::Expr<'tcx>,
1019 expected: Expectation<'tcx>,
1020 lhs: &'tcx hir::Expr<'tcx>,
1021 rhs: &'tcx hir::Expr<'tcx>,
1024 let expected_ty = expected.coercion_target_type(self, expr.span);
1025 if expected_ty == self.tcx.types.bool {
1026 // The expected type is `bool` but this will result in `()` so we can reasonably
1027 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1028 // The likely cause of this is `if foo = bar { .. }`.
1029 let actual_ty = self.tcx.mk_unit();
1030 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1031 let lhs_ty = self.check_expr(&lhs);
1032 let rhs_ty = self.check_expr(&rhs);
1033 let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1034 (Applicability::MachineApplicable, true)
1036 (Applicability::MaybeIncorrect, false)
1038 if !lhs.is_syntactic_place_expr() && !matches!(lhs.kind, hir::ExprKind::Lit(_)) {
1039 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1040 let hir = self.tcx.hir();
1041 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1042 hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1044 err.span_suggestion_verbose(
1045 expr.span.shrink_to_lo(),
1046 "you might have meant to use pattern matching",
1053 err.span_suggestion_verbose(
1055 "you might have meant to compare for equality",
1061 // If the assignment expression itself is ill-formed, don't
1062 // bother emitting another error
1063 if lhs_ty.references_error() || rhs_ty.references_error() {
1068 return self.tcx.ty_error();
1071 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1073 let suggest_deref_binop = |err: &mut DiagnosticBuilder<'tcx, ErrorGuaranteed>,
1075 if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1076 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1077 // unsized, do not suggest dereferencing it.
1078 let lhs_deref_ty_is_sized = self
1080 .type_implements_trait(
1081 self.tcx.lang_items().sized_trait().unwrap(),
1087 if lhs_deref_ty_is_sized && self.can_coerce(rhs_ty, lhs_deref_ty) {
1088 err.span_suggestion_verbose(
1089 lhs.span.shrink_to_lo(),
1090 "consider dereferencing here to assign to the mutably borrowed value",
1092 Applicability::MachineApplicable,
1098 self.check_lhs_assignable(lhs, "E0070", span, |err| {
1099 let rhs_ty = self.check_expr(&rhs);
1100 suggest_deref_binop(err, rhs_ty);
1103 // This is (basically) inlined `check_expr_coercable_to_type`, but we want
1104 // to suggest an additional fixup here in `suggest_deref_binop`.
1105 let rhs_ty = self.check_expr_with_hint(&rhs, lhs_ty);
1106 if let (_, Some(mut diag)) =
1107 self.demand_coerce_diag(rhs, rhs_ty, lhs_ty, Some(lhs), AllowTwoPhase::No)
1109 suggest_deref_binop(&mut diag, rhs_ty);
1113 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1115 if lhs_ty.references_error() || rhs_ty.references_error() {
1122 pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1123 // for let statements, this is done in check_stmt
1124 let init = let_expr.init;
1125 self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1126 // otherwise check exactly as a let statement
1127 self.check_decl(let_expr.into());
1128 // but return a bool, for this is a boolean expression
1134 body: &'tcx hir::Block<'tcx>,
1135 source: hir::LoopSource,
1136 expected: Expectation<'tcx>,
1137 expr: &'tcx hir::Expr<'tcx>,
1139 let coerce = match source {
1140 // you can only use break with a value from a normal `loop { }`
1141 hir::LoopSource::Loop => {
1142 let coerce_to = expected.coercion_target_type(self, body.span);
1143 Some(CoerceMany::new(coerce_to))
1146 hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1149 let ctxt = BreakableCtxt {
1151 may_break: false, // Will get updated if/when we find a `break`.
1154 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1155 self.check_block_no_value(&body);
1159 // No way to know whether it's diverging because
1160 // of a `break` or an outer `break` or `return`.
1161 self.diverges.set(Diverges::Maybe);
1164 // If we permit break with a value, then result type is
1165 // the LUB of the breaks (possibly ! if none); else, it
1166 // is nil. This makes sense because infinite loops
1167 // (which would have type !) are only possible iff we
1168 // permit break with a value [1].
1169 if ctxt.coerce.is_none() && !ctxt.may_break {
1171 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1173 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1176 /// Checks a method call.
1177 fn check_method_call(
1179 expr: &'tcx hir::Expr<'tcx>,
1180 segment: &hir::PathSegment<'_>,
1181 args: &'tcx [hir::Expr<'tcx>],
1182 expected: Expectation<'tcx>,
1184 let rcvr = &args[0];
1185 let rcvr_t = self.check_expr(&rcvr);
1186 // no need to check for bot/err -- callee does that
1187 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
1188 let span = segment.ident.span;
1190 let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1192 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1193 // trigger this codepath causing `structurally_resolved_type` to emit an error.
1195 self.write_method_call(expr.hir_id, method);
1199 if segment.ident.name != kw::Empty {
1200 if let Some(mut err) = self.report_method_error(
1204 SelfSource::MethodCall(&args[0]),
1215 // Call the generic checker.
1216 self.check_method_argument_types(
1228 e: &'tcx hir::Expr<'tcx>,
1229 t: &'tcx hir::Ty<'tcx>,
1230 expr: &'tcx hir::Expr<'tcx>,
1232 // Find the type of `e`. Supply hints based on the type we are casting to,
1234 let t_cast = self.to_ty_saving_user_provided_ty(t);
1235 let t_cast = self.resolve_vars_if_possible(t_cast);
1236 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1237 let t_expr = self.resolve_vars_if_possible(t_expr);
1239 // Eagerly check for some obvious errors.
1240 if t_expr.references_error() || t_cast.references_error() {
1243 // Defer other checks until we're done type checking.
1244 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1245 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1248 "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1249 t_cast, t_expr, cast_check,
1251 deferred_cast_checks.push(cast_check);
1254 Err(_) => self.tcx.ty_error(),
1259 fn check_expr_array(
1261 args: &'tcx [hir::Expr<'tcx>],
1262 expected: Expectation<'tcx>,
1263 expr: &'tcx hir::Expr<'tcx>,
1265 let element_ty = if !args.is_empty() {
1266 let coerce_to = expected
1268 .and_then(|uty| match *uty.kind() {
1269 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1272 .unwrap_or_else(|| {
1273 self.next_ty_var(TypeVariableOrigin {
1274 kind: TypeVariableOriginKind::TypeInference,
1278 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1279 assert_eq!(self.diverges.get(), Diverges::Maybe);
1281 let e_ty = self.check_expr_with_hint(e, coerce_to);
1282 let cause = self.misc(e.span);
1283 coerce.coerce(self, &cause, e, e_ty);
1285 coerce.complete(self)
1287 self.next_ty_var(TypeVariableOrigin {
1288 kind: TypeVariableOriginKind::TypeInference,
1292 self.tcx.mk_array(element_ty, args.len() as u64)
1295 fn check_expr_const_block(
1297 anon_const: &'tcx hir::AnonConst,
1298 expected: Expectation<'tcx>,
1299 _expr: &'tcx hir::Expr<'tcx>,
1301 let body = self.tcx.hir().body(anon_const.body);
1303 // Create a new function context.
1304 let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1305 crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1307 let ty = fcx.check_expr_with_expectation(&body.value, expected);
1308 fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1309 fcx.write_ty(anon_const.hir_id, ty);
1313 fn check_expr_repeat(
1315 element: &'tcx hir::Expr<'tcx>,
1316 count: &'tcx hir::ArrayLen,
1317 expected: Expectation<'tcx>,
1318 _expr: &'tcx hir::Expr<'tcx>,
1321 let count = self.array_length_to_const(count);
1323 let uty = match expected {
1324 ExpectHasType(uty) => match *uty.kind() {
1325 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1331 let (element_ty, t) = match uty {
1333 self.check_expr_coercable_to_type(&element, uty, None);
1337 let ty = self.next_ty_var(TypeVariableOrigin {
1338 kind: TypeVariableOriginKind::MiscVariable,
1341 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1346 if element_ty.references_error() {
1347 return tcx.ty_error();
1350 self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1352 tcx.mk_ty(ty::Array(t, count))
1355 fn check_repeat_element_needs_copy_bound(
1357 element: &hir::Expr<'_>,
1358 count: ty::Const<'tcx>,
1359 element_ty: Ty<'tcx>,
1362 // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1363 match &element.kind {
1364 hir::ExprKind::ConstBlock(..) => return,
1365 hir::ExprKind::Path(qpath) => {
1366 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1367 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1374 // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1375 // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1376 let is_const_fn = match element.kind {
1377 hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1378 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1384 // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1385 // don't copy that one element, we move it. Only check for Copy if the length is larger.
1386 if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1387 let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1388 let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1389 self.require_type_meets(element_ty, element.span, code, lang_item);
1393 fn check_expr_tuple(
1395 elts: &'tcx [hir::Expr<'tcx>],
1396 expected: Expectation<'tcx>,
1397 expr: &'tcx hir::Expr<'tcx>,
1399 let flds = expected.only_has_type(self).and_then(|ty| {
1400 let ty = self.resolve_vars_with_obligations(ty);
1402 ty::Tuple(flds) => Some(&flds[..]),
1407 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1408 Some(fs) if i < fs.len() => {
1410 self.check_expr_coercable_to_type(&e, ety, None);
1413 _ => self.check_expr_with_expectation(&e, NoExpectation),
1415 let tuple = self.tcx.mk_tup(elt_ts_iter);
1416 if tuple.references_error() {
1419 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1424 fn check_expr_struct(
1426 expr: &hir::Expr<'_>,
1427 expected: Expectation<'tcx>,
1429 fields: &'tcx [hir::ExprField<'tcx>],
1430 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1432 // Find the relevant variant
1433 let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1434 self.check_struct_fields_on_error(fields, base_expr);
1435 return self.tcx.ty_error();
1438 // Prohibit struct expressions when non-exhaustive flag is set.
1439 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1440 if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1443 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1446 self.check_expr_struct_fields(
1457 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1461 fn check_expr_struct_fields(
1464 expected: Expectation<'tcx>,
1465 expr_id: hir::HirId,
1467 variant: &'tcx ty::VariantDef,
1468 ast_fields: &'tcx [hir::ExprField<'tcx>],
1469 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1474 let expected_inputs =
1475 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1476 let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1477 expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1481 // re-link the regions that EIfEO can erase.
1482 self.demand_eqtype(span, adt_ty_hint, adt_ty);
1484 let (substs, adt_kind, kind_name) = match adt_ty.kind() {
1485 ty::Adt(adt, substs) => (substs, adt.adt_kind(), adt.variant_descr()),
1486 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields"),
1489 let mut remaining_fields = variant
1493 .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1494 .collect::<FxHashMap<_, _>>();
1496 let mut seen_fields = FxHashMap::default();
1498 let mut error_happened = false;
1500 // Type-check each field.
1501 for field in ast_fields {
1502 let ident = tcx.adjust_ident(field.ident, variant.def_id);
1503 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1504 seen_fields.insert(ident, field.span);
1505 self.write_field_index(field.hir_id, i);
1507 // We don't look at stability attributes on
1508 // struct-like enums (yet...), but it's definitely not
1509 // a bug to have constructed one.
1510 if adt_kind != AdtKind::Enum {
1511 tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1514 self.field_ty(field.span, v_field, substs)
1516 error_happened = true;
1517 if let Some(prev_span) = seen_fields.get(&ident) {
1518 tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1519 span: field.ident.span,
1520 prev_span: *prev_span,
1524 self.report_unknown_field(
1525 adt_ty, variant, field, ast_fields, kind_name, expr_span,
1532 // Make sure to give a type to the field even if there's
1533 // an error, so we can continue type-checking.
1534 self.check_expr_coercable_to_type(&field.expr, field_type, None);
1537 // Make sure the programmer specified correct number of fields.
1538 if kind_name == "union" {
1539 if ast_fields.len() != 1 {
1544 "union expressions should have exactly one field",
1550 // If check_expr_struct_fields hit an error, do not attempt to populate
1551 // the fields with the base_expr. This could cause us to hit errors later
1552 // when certain fields are assumed to exist that in fact do not.
1557 if let Some(base_expr) = base_expr {
1558 // FIXME: We are currently creating two branches here in order to maintain
1559 // consistency. But they should be merged as much as possible.
1560 let fru_tys = if self.tcx.features().type_changing_struct_update {
1561 let base_ty = self.check_expr(base_expr);
1562 match adt_ty.kind() {
1563 ty::Adt(adt, substs) if adt.is_struct() => {
1564 match base_ty.kind() {
1565 ty::Adt(base_adt, base_subs) if adt == base_adt => {
1570 let fru_ty = self.normalize_associated_types_in(
1572 self.field_ty(base_expr.span, f, base_subs),
1576 .adjust_ident(f.ident(self.tcx), variant.def_id);
1577 if let Some(_) = remaining_fields.remove(&ident) {
1579 self.field_ty(base_expr.span, f, substs);
1580 let cause = self.misc(base_expr.span);
1582 .at(&cause, self.param_env)
1583 .sup(target_ty, fru_ty)
1585 Ok(InferOk { obligations, value: () }) => {
1586 self.register_predicates(obligations)
1588 // FIXME: Need better diagnostics for `FieldMisMatch` error
1590 self.report_mismatched_types(
1594 FieldMisMatch(variant.name, ident.name),
1605 self.report_mismatched_types(
1606 &self.misc(base_expr.span),
1609 Sorts(ExpectedFound::new(true, adt_ty, base_ty)),
1619 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1624 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1625 let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1626 let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1627 (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1630 if self.tcx.sess.is_nightly_build() && same_adt {
1632 &self.tcx.sess.parse_sess,
1633 sym::type_changing_struct_update,
1635 "type changing struct updating is experimental",
1640 match adt_ty.kind() {
1641 ty::Adt(adt, substs) if adt.is_struct() => variant
1645 self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1651 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1656 self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1657 } else if kind_name != "union" && !remaining_fields.is_empty() {
1658 let inaccessible_remaining_fields = remaining_fields.iter().any(|(_, (_, field))| {
1659 !field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1662 if inaccessible_remaining_fields {
1663 self.report_inaccessible_fields(adt_ty, span);
1665 self.report_missing_fields(
1677 fn check_struct_fields_on_error(
1679 fields: &'tcx [hir::ExprField<'tcx>],
1680 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1682 for field in fields {
1683 self.check_expr(&field.expr);
1685 if let Some(base) = *base_expr {
1686 self.check_expr(&base);
1690 /// Report an error for a struct field expression when there are fields which aren't provided.
1693 /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1694 /// --> src/main.rs:8:5
1696 /// 8 | foo::Foo {};
1697 /// | ^^^^^^^^ missing `you_can_use_this_field`
1699 /// error: aborting due to previous error
1701 fn report_missing_fields(
1705 remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1706 variant: &'tcx ty::VariantDef,
1707 ast_fields: &'tcx [hir::ExprField<'tcx>],
1708 substs: SubstsRef<'tcx>,
1710 let len = remaining_fields.len();
1712 let mut displayable_field_names: Vec<&str> =
1713 remaining_fields.keys().map(|ident| ident.as_str()).collect();
1714 // sorting &str primitives here, sort_unstable is ok
1715 displayable_field_names.sort_unstable();
1717 let mut truncated_fields_error = String::new();
1718 let remaining_fields_names = match &displayable_field_names[..] {
1719 [field1] => format!("`{}`", field1),
1720 [field1, field2] => format!("`{field1}` and `{field2}`"),
1721 [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1723 truncated_fields_error =
1724 format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1725 displayable_field_names
1728 .map(|n| format!("`{n}`"))
1729 .collect::<Vec<_>>()
1734 let mut err = struct_span_err!(
1738 "missing field{} {}{} in initializer of `{}`",
1740 remaining_fields_names,
1741 truncated_fields_error,
1744 err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1746 // If the last field is a range literal, but it isn't supposed to be, then they probably
1747 // meant to use functional update syntax.
1749 // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1753 QPath::LangItem(LangItem::Range, ..),
1754 &[ref range_start, ref range_end],
1757 )) = ast_fields.last().map(|last| (last, &last.expr.kind)) &&
1759 variant.fields.iter().find(|field| field.ident(self.tcx) == last.ident) &&
1760 let range_def_id = self.tcx.lang_items().range_struct() &&
1762 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1763 .map(|adt| adt.did())
1770 .span_to_snippet(range_end.expr.span)
1771 .map(|s| format!(" from `{s}`"))
1772 .unwrap_or(String::new());
1773 err.span_suggestion(
1774 range_start.span.shrink_to_hi(),
1775 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1777 Applicability::MaybeIncorrect,
1784 /// Report an error for a struct field expression when there are invisible fields.
1787 /// error: cannot construct `Foo` with struct literal syntax due to inaccessible fields
1788 /// --> src/main.rs:8:5
1790 /// 8 | foo::Foo {};
1793 /// error: aborting due to previous error
1795 fn report_inaccessible_fields(&self, adt_ty: Ty<'tcx>, span: Span) {
1796 self.tcx.sess.span_err(
1799 "cannot construct `{adt_ty}` with struct literal syntax due to inaccessible fields",
1804 fn report_unknown_field(
1807 variant: &'tcx ty::VariantDef,
1808 field: &hir::ExprField<'_>,
1809 skip_fields: &[hir::ExprField<'_>],
1813 if variant.is_recovered() {
1814 self.set_tainted_by_errors();
1817 let mut err = self.type_error_struct_with_diag(
1819 |actual| match ty.kind() {
1820 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1824 "{} `{}::{}` has no field named `{}`",
1830 _ => struct_span_err!(
1834 "{} `{}` has no field named `{}`",
1843 let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1844 match variant.ctor_kind {
1845 CtorKind::Fn => match ty.kind() {
1846 ty::Adt(adt, ..) if adt.is_enum() => {
1850 "`{adt}::{variant}` defined here",
1852 variant = variant.name,
1855 err.span_label(field.ident.span, "field does not exist");
1856 err.span_suggestion_verbose(
1859 "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1861 variant = variant.name,
1864 "{adt}::{variant}(/* fields */)",
1866 variant = variant.name,
1868 Applicability::HasPlaceholders,
1872 err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1873 err.span_label(field.ident.span, "field does not exist");
1874 err.span_suggestion_verbose(
1877 "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1879 kind_name = kind_name,
1881 format!("{adt}(/* fields */)", adt = ty),
1882 Applicability::HasPlaceholders,
1887 // prevent all specified fields from being suggested
1888 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
1889 if let Some(field_name) = self.suggest_field_name(
1892 skip_fields.collect(),
1895 err.span_suggestion(
1897 "a field with a similar name exists",
1898 field_name.to_string(),
1899 Applicability::MaybeIncorrect,
1903 ty::Adt(adt, ..) => {
1907 format!("`{}::{}` does not have this field", ty, variant.name),
1912 format!("`{ty}` does not have this field"),
1915 let available_field_names =
1916 self.available_field_names(variant, expr_span);
1917 if !available_field_names.is_empty() {
1919 "available fields are: {}",
1920 self.name_series_display(available_field_names)
1924 _ => bug!("non-ADT passed to report_unknown_field"),
1932 // Return a hint about the closest match in field names
1933 fn suggest_field_name(
1935 variant: &'tcx ty::VariantDef,
1938 // The span where stability will be checked
1940 ) -> Option<Symbol> {
1944 .filter_map(|field| {
1945 // ignore already set fields and private fields from non-local crates
1946 // and unstable fields.
1947 if skip.iter().any(|&x| x == field.name)
1948 || (!variant.def_id.is_local() && !field.vis.is_public())
1950 self.tcx.eval_stability(field.did, None, span, None),
1951 stability::EvalResult::Deny { .. }
1959 .collect::<Vec<Symbol>>();
1961 find_best_match_for_name(&names, field, None)
1964 fn available_field_names(
1966 variant: &'tcx ty::VariantDef,
1973 let def_scope = self
1975 .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
1977 field.vis.is_accessible_from(def_scope, self.tcx)
1979 self.tcx.eval_stability(field.did, None, access_span, None),
1980 stability::EvalResult::Deny { .. }
1983 .filter(|field| !self.tcx.is_doc_hidden(field.did))
1984 .map(|field| field.name)
1988 fn name_series_display(&self, names: Vec<Symbol>) -> String {
1989 // dynamic limit, to never omit just one field
1990 let limit = if names.len() == 6 { 6 } else { 5 };
1992 names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
1993 if names.len() > limit {
1994 display = format!("{} ... and {} others", display, names.len() - limit);
1999 // Check field access expressions
2002 expr: &'tcx hir::Expr<'tcx>,
2003 base: &'tcx hir::Expr<'tcx>,
2006 debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2007 let expr_t = self.check_expr(base);
2008 let expr_t = self.structurally_resolved_type(base.span, expr_t);
2009 let mut private_candidate = None;
2010 let mut autoderef = self.autoderef(expr.span, expr_t);
2011 while let Some((base_t, _)) = autoderef.next() {
2012 debug!("base_t: {:?}", base_t);
2013 match base_t.kind() {
2014 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2015 debug!("struct named {:?}", base_t);
2016 let (ident, def_scope) =
2017 self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2018 let fields = &base_def.non_enum_variant().fields;
2019 if let Some(index) = fields
2021 .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2023 let field = &fields[index];
2024 let field_ty = self.field_ty(expr.span, field, substs);
2025 // Save the index of all fields regardless of their visibility in case
2026 // of error recovery.
2027 self.write_field_index(expr.hir_id, index);
2028 let adjustments = self.adjust_steps(&autoderef);
2029 if field.vis.is_accessible_from(def_scope, self.tcx) {
2030 self.apply_adjustments(base, adjustments);
2031 self.register_predicates(autoderef.into_obligations());
2033 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2036 private_candidate = Some((adjustments, base_def.did(), field_ty));
2040 let fstr = field.as_str();
2041 if let Ok(index) = fstr.parse::<usize>() {
2042 if fstr == index.to_string() {
2043 if let Some(&field_ty) = tys.get(index) {
2044 let adjustments = self.adjust_steps(&autoderef);
2045 self.apply_adjustments(base, adjustments);
2046 self.register_predicates(autoderef.into_obligations());
2048 self.write_field_index(expr.hir_id, index);
2057 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2059 if let Some((adjustments, did, field_ty)) = private_candidate {
2060 // (#90483) apply adjustments to avoid ExprUseVisitor from
2061 // creating erroneous projection.
2062 self.apply_adjustments(base, adjustments);
2063 self.ban_private_field_access(expr, expr_t, field, did);
2067 if field.name == kw::Empty {
2068 } else if self.method_exists(field, expr_t, expr.hir_id, true) {
2069 self.ban_take_value_of_method(expr, expr_t, field);
2070 } else if !expr_t.is_primitive_ty() {
2071 self.ban_nonexisting_field(field, base, expr, expr_t);
2078 "`{expr_t}` is a primitive type and therefore doesn't have fields",
2083 self.tcx().ty_error()
2086 fn check_call_constructor<G: EmissionGuarantee>(
2088 err: &mut DiagnosticBuilder<'_, G>,
2089 base: &'tcx hir::Expr<'tcx>,
2092 if let Some(local_id) = def_id.as_local() {
2093 let hir_id = self.tcx.hir().local_def_id_to_hir_id(local_id);
2094 let node = self.tcx.hir().get(hir_id);
2096 if let Some(fields) = node.tuple_fields() {
2097 let kind = match self.tcx.opt_def_kind(local_id) {
2098 Some(DefKind::Ctor(of, _)) => of,
2102 suggest_call_constructor(base.span, kind, fields.len(), err);
2105 // The logic here isn't smart but `associated_item_def_ids`
2106 // doesn't work nicely on local.
2107 if let DefKind::Ctor(of, _) = self.tcx.def_kind(def_id) {
2108 let parent_def_id = self.tcx.parent(def_id);
2109 let fields = self.tcx.associated_item_def_ids(parent_def_id);
2110 suggest_call_constructor(base.span, of, fields.len(), err);
2115 fn suggest_await_on_field_access(
2117 err: &mut Diagnostic,
2119 base: &'tcx hir::Expr<'tcx>,
2122 let output_ty = match self.infcx.get_impl_future_output_ty(ty) {
2123 Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2126 let mut add_label = true;
2127 if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2128 // no field access on enum type
2134 .any(|field| field.ident(self.tcx) == field_ident)
2139 "field not available in `impl Future`, but it is available in its `Output`",
2141 err.span_suggestion_verbose(
2142 base.span.shrink_to_hi(),
2143 "consider `await`ing on the `Future` and access the field of its `Output`",
2144 ".await".to_string(),
2145 Applicability::MaybeIncorrect,
2151 err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2155 fn ban_nonexisting_field(
2158 base: &'tcx hir::Expr<'tcx>,
2159 expr: &'tcx hir::Expr<'tcx>,
2163 "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
2164 field, base, expr, expr_t
2166 let mut err = self.no_such_field_err(field, expr_t, base.hir_id);
2168 match *expr_t.peel_refs().kind() {
2169 ty::Array(_, len) => {
2170 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
2173 self.suggest_first_deref_field(&mut err, expr, base, field);
2175 ty::Adt(def, _) if !def.is_enum() => {
2176 self.suggest_fields_on_recordish(&mut err, def, field, expr.span);
2178 ty::Param(param_ty) => {
2179 self.point_at_param_definition(&mut err, param_ty);
2181 ty::Opaque(_, _) => {
2182 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
2184 ty::FnDef(def_id, _) => {
2185 self.check_call_constructor(&mut err, base, def_id);
2190 if field.name == kw::Await {
2191 // We know by construction that `<expr>.await` is either on Rust 2015
2192 // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2193 err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2194 err.help_use_latest_edition();
2200 fn ban_private_field_access(
2202 expr: &hir::Expr<'_>,
2207 let struct_path = self.tcx().def_path_str(base_did);
2208 let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2209 let mut err = struct_span_err!(
2213 "field `{field}` of {kind_name} `{struct_path}` is private",
2215 err.span_label(field.span, "private field");
2216 // Also check if an accessible method exists, which is often what is meant.
2217 if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2219 self.suggest_method_call(
2221 &format!("a method `{field}` also exists, call it with parentheses"),
2231 fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2232 let mut err = type_error_struct!(
2237 "attempted to take value of method `{field}` on type `{expr_t}`",
2239 err.span_label(field.span, "method, not a field");
2241 if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2242 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2244 expr.hir_id == callee.hir_id
2249 self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or(String::new());
2250 let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2251 let after_open = expr.span.lo() + rustc_span::BytePos(1);
2252 let before_close = expr.span.hi() - rustc_span::BytePos(1);
2254 if expr_is_call && is_wrapped {
2255 err.multipart_suggestion(
2256 "remove wrapping parentheses to call the method",
2258 (expr.span.with_hi(after_open), String::new()),
2259 (expr.span.with_lo(before_close), String::new()),
2261 Applicability::MachineApplicable,
2263 } else if !self.expr_in_place(expr.hir_id) {
2264 // Suggest call parentheses inside the wrapping parentheses
2265 let span = if is_wrapped {
2266 expr.span.with_lo(after_open).with_hi(before_close)
2270 self.suggest_method_call(
2272 "use parentheses to call the method",
2279 let mut found = false;
2281 if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2282 && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2284 if adt_def.variants().len() == 1
2292 .any(|f| f.ident(self.tcx) == field)
2294 if let Some(dot_loc) = expr_snippet.rfind('.') {
2296 err.span_suggestion(
2297 expr.span.with_hi(expr.span.lo() + BytePos::from_usize(dot_loc)),
2298 "to access the field, dereference first",
2299 format!("(*{})", &expr_snippet[0..dot_loc]),
2300 Applicability::MaybeIncorrect,
2307 err.help("methods are immutable and cannot be assigned to");
2314 fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2315 let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2316 let generic_param = generics.type_param(¶m, self.tcx);
2317 if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2320 let param_def_id = generic_param.def_id;
2321 let param_hir_id = match param_def_id.as_local() {
2322 Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2325 let param_span = self.tcx.hir().span(param_hir_id);
2326 let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2328 err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2331 fn suggest_fields_on_recordish(
2333 err: &mut Diagnostic,
2334 def: ty::AdtDef<'tcx>,
2338 if let Some(suggested_field_name) =
2339 self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2341 err.span_suggestion(
2343 "a field with a similar name exists",
2344 suggested_field_name.to_string(),
2345 Applicability::MaybeIncorrect,
2348 err.span_label(field.span, "unknown field");
2349 let struct_variant_def = def.non_enum_variant();
2350 let field_names = self.available_field_names(struct_variant_def, access_span);
2351 if !field_names.is_empty() {
2353 "available fields are: {}",
2354 self.name_series_display(field_names),
2360 fn maybe_suggest_array_indexing(
2362 err: &mut Diagnostic,
2363 expr: &hir::Expr<'_>,
2364 base: &hir::Expr<'_>,
2366 len: ty::Const<'tcx>,
2368 if let (Some(len), Ok(user_index)) =
2369 (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2370 && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2372 let help = "instead of using tuple indexing, use array indexing";
2373 let suggestion = format!("{base}[{field}]");
2374 let applicability = if len < user_index {
2375 Applicability::MachineApplicable
2377 Applicability::MaybeIncorrect
2379 err.span_suggestion(expr.span, help, suggestion, applicability);
2383 fn suggest_first_deref_field(
2385 err: &mut Diagnostic,
2386 expr: &hir::Expr<'_>,
2387 base: &hir::Expr<'_>,
2390 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2391 let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2392 let suggestion = format!("(*{base}).{field}");
2393 err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2397 fn no_such_field_err(
2402 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2403 let span = field.span;
2404 debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2406 let mut err = type_error_struct!(
2411 "no field `{field}` on type `{expr_t}`",
2414 // try to add a suggestion in case the field is a nested field of a field of the Adt
2415 if let Some((fields, substs)) = self.get_field_candidates(span, expr_t) {
2416 for candidate_field in fields.iter() {
2417 if let Some(mut field_path) = self.check_for_nested_field_satisfying(
2419 &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2423 self.tcx.parent_module(id).to_def_id(),
2425 // field_path includes `field` that we're looking for, so pop it.
2428 let field_path_str = field_path
2430 .map(|id| id.name.to_ident_string())
2431 .collect::<Vec<String>>()
2433 debug!("field_path_str: {:?}", field_path_str);
2435 err.span_suggestion_verbose(
2436 field.span.shrink_to_lo(),
2437 "one of the expressions' fields has a field of the same name",
2438 format!("{field_path_str}."),
2439 Applicability::MaybeIncorrect,
2447 pub(crate) fn get_field_candidates(
2451 ) -> Option<(&[ty::FieldDef], SubstsRef<'tcx>)> {
2452 debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_t);
2454 for (base_t, _) in self.autoderef(span, base_t) {
2455 match base_t.kind() {
2456 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2457 let fields = &base_def.non_enum_variant().fields;
2458 // For compile-time reasons put a limit on number of fields we search
2459 if fields.len() > 100 {
2462 return Some((fields, substs));
2470 /// This method is called after we have encountered a missing field error to recursively
2471 /// search for the field
2472 pub(crate) fn check_for_nested_field_satisfying(
2475 matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2476 candidate_field: &ty::FieldDef,
2477 subst: SubstsRef<'tcx>,
2478 mut field_path: Vec<Ident>,
2480 ) -> Option<Vec<Ident>> {
2482 "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2483 span, candidate_field, field_path
2486 if field_path.len() > 3 {
2487 // For compile-time reasons and to avoid infinite recursion we only check for fields
2488 // up to a depth of three
2491 // recursively search fields of `candidate_field` if it's a ty::Adt
2492 field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2493 let field_ty = candidate_field.ty(self.tcx, subst);
2494 if let Some((nested_fields, subst)) = self.get_field_candidates(span, field_ty) {
2495 for field in nested_fields.iter() {
2496 if field.vis.is_accessible_from(id, self.tcx) {
2497 if matches(candidate_field, field_ty) {
2498 return Some(field_path);
2499 } else if let Some(field_path) = self.check_for_nested_field_satisfying(
2507 return Some(field_path);
2516 fn check_expr_index(
2518 base: &'tcx hir::Expr<'tcx>,
2519 idx: &'tcx hir::Expr<'tcx>,
2520 expr: &'tcx hir::Expr<'tcx>,
2522 let base_t = self.check_expr(&base);
2523 let idx_t = self.check_expr(&idx);
2525 if base_t.references_error() {
2527 } else if idx_t.references_error() {
2530 let base_t = self.structurally_resolved_type(base.span, base_t);
2531 match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2532 Some((index_ty, element_ty)) => {
2533 // two-phase not needed because index_ty is never mutable
2534 self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2538 let mut err = type_error_struct!(
2543 "cannot index into a value of type `{base_t}`",
2545 // Try to give some advice about indexing tuples.
2546 if let ty::Tuple(..) = base_t.kind() {
2547 let mut needs_note = true;
2548 // If the index is an integer, we can show the actual
2549 // fixed expression:
2550 if let ExprKind::Lit(ref lit) = idx.kind {
2551 if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2552 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2553 if let Ok(snip) = snip {
2554 err.span_suggestion(
2556 "to access tuple elements, use",
2557 format!("{snip}.{i}"),
2558 Applicability::MachineApplicable,
2566 "to access tuple elements, use tuple indexing \
2567 syntax (e.g., `tuple.0`)",
2578 fn check_expr_yield(
2580 value: &'tcx hir::Expr<'tcx>,
2581 expr: &'tcx hir::Expr<'tcx>,
2582 src: &'tcx hir::YieldSource,
2584 match self.resume_yield_tys {
2585 Some((resume_ty, yield_ty)) => {
2586 self.check_expr_coercable_to_type(&value, yield_ty, None);
2590 // Given that this `yield` expression was generated as a result of lowering a `.await`,
2591 // we know that the yield type must be `()`; however, the context won't contain this
2592 // information. Hence, we check the source of the yield expression here and check its
2593 // value's type against `()` (this check should always hold).
2594 None if src.is_await() => {
2595 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2599 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2600 // Avoid expressions without types during writeback (#78653).
2601 self.check_expr(value);
2607 fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2608 let needs = if is_input { Needs::None } else { Needs::MutPlace };
2609 let ty = self.check_expr_with_needs(expr, needs);
2610 self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2612 if !is_input && !expr.is_syntactic_place_expr() {
2613 let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2614 err.span_label(expr.span, "cannot assign to this expression");
2618 // If this is an input value, we require its type to be fully resolved
2619 // at this point. This allows us to provide helpful coercions which help
2620 // pass the type candidate list in a later pass.
2622 // We don't require output types to be resolved at this point, which
2623 // allows them to be inferred based on how they are used later in the
2626 let ty = self.structurally_resolved_type(expr.span, ty);
2629 let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2630 self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2632 ty::Ref(_, base_ty, mutbl) => {
2633 let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2634 self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2641 fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2642 for (op, _op_sp) in asm.operands {
2644 hir::InlineAsmOperand::In { expr, .. } => {
2645 self.check_expr_asm_operand(expr, true);
2647 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2648 | hir::InlineAsmOperand::InOut { expr, .. } => {
2649 self.check_expr_asm_operand(expr, false);
2651 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2652 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2653 self.check_expr_asm_operand(in_expr, true);
2654 if let Some(out_expr) = out_expr {
2655 self.check_expr_asm_operand(out_expr, false);
2658 // `AnonConst`s have their own body and is type-checked separately.
2659 // As they don't flow into the type system we don't need them to
2661 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2662 hir::InlineAsmOperand::SymStatic { .. } => {}
2665 if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2666 self.tcx.types.never
2673 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2674 Some(match ty.kind() {
2677 ty::Int(_) | ty::Uint(_) => "42",
2678 ty::Float(_) => "3.14159",
2679 ty::Error(_) | ty::Never => return None,