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 crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
26 use rustc_data_structures::fx::FxHashMap;
27 use rustc_data_structures::stack::ensure_sufficient_stack;
29 pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId,
30 ErrorGuaranteed, StashKey,
33 use rustc_hir::def::{CtorKind, DefKind, Res};
34 use rustc_hir::def_id::DefId;
35 use rustc_hir::intravisit::Visitor;
36 use rustc_hir::lang_items::LangItem;
37 use rustc_hir::{Closure, ExprKind, HirId, QPath};
38 use rustc_infer::infer;
39 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
40 use rustc_infer::infer::InferOk;
41 use rustc_infer::traits::ObligationCause;
42 use rustc_middle::middle::stability;
43 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
44 use rustc_middle::ty::error::TypeError::FieldMisMatch;
45 use rustc_middle::ty::subst::SubstsRef;
46 use rustc_middle::ty::{self, AdtKind, Ty, TypeVisitable};
47 use rustc_session::parse::feature_err;
48 use rustc_span::hygiene::DesugaringKind;
49 use rustc_span::lev_distance::find_best_match_for_name;
50 use rustc_span::source_map::{Span, Spanned};
51 use rustc_span::symbol::{kw, sym, Ident, Symbol};
52 use rustc_target::spec::abi::Abi::RustIntrinsic;
53 use rustc_trait_selection::infer::InferCtxtExt;
54 use rustc_trait_selection::traits::{self, ObligationCauseCode};
56 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
57 fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
58 let ty = self.check_expr_with_hint(expr, expected);
59 self.demand_eqtype(expr.span, expected, ty);
62 pub fn check_expr_has_type_or_error(
64 expr: &'tcx hir::Expr<'tcx>,
66 extend_err: impl FnMut(&mut Diagnostic),
68 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
71 fn check_expr_meets_expectation_or_error(
73 expr: &'tcx hir::Expr<'tcx>,
74 expected: Expectation<'tcx>,
75 mut extend_err: impl FnMut(&mut Diagnostic),
77 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
78 let mut ty = self.check_expr_with_expectation(expr, expected);
80 // While we don't allow *arbitrary* coercions here, we *do* allow
81 // coercions from ! to `expected`.
83 if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
84 self.tcx().sess.delay_span_bug(
86 "expression with never type wound up being adjusted",
88 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
95 let adj_ty = self.next_ty_var(TypeVariableOrigin {
96 kind: TypeVariableOriginKind::AdjustmentType,
99 self.apply_adjustments(
101 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
106 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
107 let expr = expr.peel_drop_temps();
108 self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
109 extend_err(&mut err);
115 pub(super) fn check_expr_coercable_to_type(
117 expr: &'tcx hir::Expr<'tcx>,
119 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
121 let ty = self.check_expr_with_hint(expr, expected);
122 // checks don't need two phase
123 self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
126 pub(super) fn check_expr_with_hint(
128 expr: &'tcx hir::Expr<'tcx>,
131 self.check_expr_with_expectation(expr, ExpectHasType(expected))
134 fn check_expr_with_expectation_and_needs(
136 expr: &'tcx hir::Expr<'tcx>,
137 expected: Expectation<'tcx>,
140 let ty = self.check_expr_with_expectation(expr, expected);
142 // If the expression is used in a place whether mutable place is required
143 // e.g. LHS of assignment, perform the conversion.
144 if let Needs::MutPlace = needs {
145 self.convert_place_derefs_to_mutable(expr);
151 pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
152 self.check_expr_with_expectation(expr, NoExpectation)
155 pub(super) fn check_expr_with_needs(
157 expr: &'tcx hir::Expr<'tcx>,
160 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
164 /// If an expression has any sub-expressions that result in a type error,
165 /// inspecting that expression's type with `ty.references_error()` will return
166 /// true. Likewise, if an expression is known to diverge, inspecting its
167 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
168 /// strict, _|_ can appear in the type of an expression that does not,
169 /// itself, diverge: for example, fn() -> _|_.)
170 /// Note that inspecting a type's structure *directly* may expose the fact
171 /// that there are actually multiple representations for `Error`, so avoid
172 /// that when err needs to be handled differently.
173 #[instrument(skip(self, expr), level = "debug")]
174 pub(super) fn check_expr_with_expectation(
176 expr: &'tcx hir::Expr<'tcx>,
177 expected: Expectation<'tcx>,
179 self.check_expr_with_expectation_and_args(expr, expected, &[])
182 /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
183 /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
184 pub(super) fn check_expr_with_expectation_and_args(
186 expr: &'tcx hir::Expr<'tcx>,
187 expected: Expectation<'tcx>,
188 args: &'tcx [hir::Expr<'tcx>],
190 if self.tcx().sess.verbose() {
191 // make this code only run with -Zverbose because it is probably slow
192 if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
193 if !lint_str.contains('\n') {
194 debug!("expr text: {lint_str}");
196 let mut lines = lint_str.lines();
197 if let Some(line0) = lines.next() {
198 let remaining_lines = lines.count();
199 debug!("expr text: {line0}");
200 debug!("expr text: ...(and {remaining_lines} more lines)");
206 // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
207 // without the final expr (e.g. `try { return; }`). We don't want to generate an
208 // unreachable_code lint for it since warnings for autogenerated code are confusing.
209 let is_try_block_generated_unit_expr = match expr.kind {
210 ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
211 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
217 // Warn for expressions after diverging siblings.
218 if !is_try_block_generated_unit_expr {
219 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
222 // Hide the outer diverging and has_errors flags.
223 let old_diverges = self.diverges.replace(Diverges::Maybe);
224 let old_has_errors = self.has_errors.replace(false);
226 let ty = ensure_sufficient_stack(|| match &expr.kind {
228 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
229 ) => self.check_expr_path(qpath, expr, args),
230 _ => self.check_expr_kind(expr, expected),
233 // Warn for non-block expressions with diverging children.
239 | ExprKind::Match(..) => {}
240 // If `expr` is a result of desugaring the try block and is an ok-wrapped
241 // diverging expression (e.g. it arose from desugaring of `try { return }`),
242 // we skip issuing a warning because it is autogenerated code.
243 ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
244 ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
245 ExprKind::MethodCall(segment, ..) => {
246 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
248 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
251 // Any expression that produces a value of type `!` must have diverged
253 self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
256 // Record the type, which applies it effects.
257 // We need to do this after the warning above, so that
258 // we don't warn for the diverging expression itself.
259 self.write_ty(expr.hir_id, ty);
261 // Combine the diverging and has_error flags.
262 self.diverges.set(self.diverges.get() | old_diverges);
263 self.has_errors.set(self.has_errors.get() | old_has_errors);
265 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
266 debug!("... {:?}, expected is {:?}", ty, expected);
271 #[instrument(skip(self, expr), level = "debug")]
274 expr: &'tcx hir::Expr<'tcx>,
275 expected: Expectation<'tcx>,
277 trace!("expr={:#?}", expr);
281 ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
282 ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
283 ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
284 ExprKind::Assign(lhs, rhs, span) => {
285 self.check_expr_assign(expr, expected, lhs, rhs, span)
287 ExprKind::AssignOp(op, lhs, rhs) => {
288 self.check_binop_assign(expr, op, lhs, rhs, expected)
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(&Closure { capture_clause, fn_decl, body, movability, .. }) => {
323 self.check_expr_closure(expr, capture_clause, &fn_decl, body, movability, 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, receiver, args, _) => {
328 self.check_method_call(expr, segment, receiver, 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, expected_inner);
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, expected_inner);
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, qpath, 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);
564 let input = self.replace_bound_vars_with_fresh_vars(
566 infer::LateBoundRegionConversionTime::FnCall,
569 self.require_type_is_sized_deferred(
572 traits::SizedArgumentType(None),
576 // Here we want to prevent struct constructors from returning unsized types.
577 // There were two cases this happened: fn pointer coercion in stable
578 // and usual function call in presence of unsized_locals.
579 // Also, as we just want to check sizedness, instead of introducing
580 // placeholder lifetimes with probing, we just replace higher lifetimes
582 let output = self.replace_bound_vars_with_fresh_vars(
584 infer::LateBoundRegionConversionTime::FnCall,
587 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
590 // We always require that the type provided as the value for
591 // a type parameter outlives the moment of instantiation.
592 let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
593 self.add_wf_bounds(substs, expr);
600 destination: hir::Destination,
601 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
602 expr: &'tcx hir::Expr<'tcx>,
605 if let Ok(target_id) = destination.target_id {
607 if let Some(e) = expr_opt {
608 // If this is a break with a value, we need to type-check
609 // the expression. Get an expected type from the loop context.
610 let opt_coerce_to = {
611 // We should release `enclosing_breakables` before the `check_expr_with_hint`
612 // below, so can't move this block of code to the enclosing scope and share
613 // `ctxt` with the second `enclosing_breakables` borrow below.
614 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
615 match enclosing_breakables.opt_find_breakable(target_id) {
616 Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
618 // Avoid ICE when `break` is inside a closure (#65383).
619 return tcx.ty_error_with_message(
621 "break was outside loop, but no error was emitted",
627 // If the loop context is not a `loop { }`, then break with
628 // a value is illegal, and `opt_coerce_to` will be `None`.
629 // Just set expectation to error in that case.
630 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
632 // Recurse without `enclosing_breakables` borrowed.
633 e_ty = self.check_expr_with_hint(e, coerce_to);
634 cause = self.misc(e.span);
636 // Otherwise, this is a break *without* a value. That's
637 // always legal, and is equivalent to `break ()`.
638 e_ty = tcx.mk_unit();
639 cause = self.misc(expr.span);
642 // Now that we have type-checked `expr_opt`, borrow
643 // the `enclosing_loops` field and let's coerce the
644 // type of `expr_opt` into what is expected.
645 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
646 let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
647 // Avoid ICE when `break` is inside a closure (#65383).
648 return tcx.ty_error_with_message(
650 "break was outside loop, but no error was emitted",
654 if let Some(ref mut coerce) = ctxt.coerce {
655 if let Some(ref e) = expr_opt {
656 coerce.coerce(self, &cause, e, e_ty);
658 assert!(e_ty.is_unit());
659 let ty = coerce.expected_ty();
660 coerce.coerce_forced_unit(
664 self.suggest_mismatched_types_on_tail(
665 &mut err, expr, ty, e_ty, target_id,
667 if let Some(val) = ty_kind_suggestion(ty) {
668 let label = destination
670 .map(|l| format!(" {}", l.ident))
671 .unwrap_or_else(String::new);
674 "give it a value of the expected type",
675 format!("break{label} {val}"),
676 Applicability::HasPlaceholders,
684 // If `ctxt.coerce` is `None`, we can just ignore
685 // the type of the expression. This is because
686 // either this was a break *without* a value, in
687 // which case it is always a legal type (`()`), or
688 // else an error would have been flagged by the
689 // `loops` pass for using break with an expression
690 // where you are not supposed to.
691 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
694 // If we encountered a `break`, then (no surprise) it may be possible to break from the
695 // loop... unless the value being returned from the loop diverges itself, e.g.
696 // `break return 5` or `break loop {}`.
697 ctxt.may_break |= !self.diverges.get().is_always();
699 // the type of a `break` is always `!`, since it diverges
702 // Otherwise, we failed to find the enclosing loop;
703 // this can only happen if the `break` was not
704 // inside a loop at all, which is caught by the
705 // loop-checking pass.
706 let err = self.tcx.ty_error_with_message(
708 "break was outside loop, but no error was emitted",
711 // We still need to assign a type to the inner expression to
712 // prevent the ICE in #43162.
713 if let Some(e) = expr_opt {
714 self.check_expr_with_hint(e, err);
716 // ... except when we try to 'break rust;'.
717 // ICE this expression in particular (see #43162).
718 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
719 if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
720 fatally_break_rust(self.tcx.sess);
725 // There was an error; make type-check fail.
730 fn check_expr_return(
732 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
733 expr: &'tcx hir::Expr<'tcx>,
735 if self.ret_coercion.is_none() {
736 let mut err = ReturnStmtOutsideOfFnBody {
738 encl_body_span: None,
742 let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
744 if let Some(hir::Node::Item(hir::Item {
745 kind: hir::ItemKind::Fn(..),
749 | Some(hir::Node::TraitItem(hir::TraitItem {
750 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
754 | Some(hir::Node::ImplItem(hir::ImplItem {
755 kind: hir::ImplItemKind::Fn(..),
758 })) = self.tcx.hir().find_by_def_id(encl_item_id)
760 // We are inside a function body, so reporting "return statement
761 // outside of function body" needs an explanation.
763 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
765 // If this didn't hold, we would not have to report an error in
767 assert_ne!(encl_item_id, encl_body_owner_id);
769 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
770 let encl_body = self.tcx.hir().body(encl_body_id);
772 err.encl_body_span = Some(encl_body.value.span);
773 err.encl_fn_span = Some(*encl_fn_span);
776 self.tcx.sess.emit_err(err);
778 if let Some(e) = expr_opt {
779 // We still have to type-check `e` (issue #86188), but calling
780 // `check_return_expr` only works inside fn bodies.
783 } else if let Some(e) = expr_opt {
784 if self.ret_coercion_span.get().is_none() {
785 self.ret_coercion_span.set(Some(e.span));
787 self.check_return_expr(e, true);
789 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
790 if self.ret_coercion_span.get().is_none() {
791 self.ret_coercion_span.set(Some(expr.span));
793 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
794 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
795 coercion.coerce_forced_unit(
799 let span = fn_decl.output.span();
800 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
803 format!("expected `{snippet}` because of this return type"),
810 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
816 /// `explicit_return` is `true` if we're checking an explicit `return expr`,
817 /// and `false` if we're checking a trailing expression.
818 pub(super) fn check_return_expr(
820 return_expr: &'tcx hir::Expr<'tcx>,
821 explicit_return: bool,
823 let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
824 span_bug!(return_expr.span, "check_return_expr called outside fn body")
827 let ret_ty = ret_coercion.borrow().expected_ty();
828 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
829 let mut span = return_expr.span;
830 // Use the span of the trailing expression for our cause,
831 // not the span of the entire function
832 if !explicit_return {
833 if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
834 span = last_expr.span;
837 ret_coercion.borrow_mut().coerce(
839 &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
844 if self.return_type_has_opaque {
845 // Point any obligations that were registered due to opaque type
846 // inference at the return expression.
847 self.select_obligations_where_possible(false, |errors| {
848 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
853 fn point_at_return_for_opaque_ty_error(
855 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
857 return_expr_ty: Ty<'tcx>,
859 // Don't point at the whole block if it's empty
860 if span == self.tcx.hir().span(self.body_id) {
864 let cause = &mut err.obligation.cause;
865 if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
866 let new_cause = ObligationCause::new(
869 ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
876 pub(crate) fn check_lhs_assignable(
878 lhs: &'tcx hir::Expr<'tcx>,
879 err_code: &'static str,
881 adjust_err: impl FnOnce(&mut Diagnostic),
883 if lhs.is_syntactic_place_expr() {
887 // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
888 let mut err = self.tcx.sess.struct_span_err_with_code(
890 "invalid left-hand side of assignment",
891 DiagnosticId::Error(err_code.into()),
893 err.span_label(lhs.span, "cannot assign to this expression");
895 self.comes_from_while_condition(lhs.hir_id, |expr| {
896 err.span_suggestion_verbose(
897 expr.span.shrink_to_lo(),
898 "you might have meant to use pattern destructuring",
900 Applicability::MachineApplicable,
904 adjust_err(&mut err);
909 // Check if an expression `original_expr_id` comes from the condition of a while loop,
910 // as opposed from the body of a while loop, which we can naively check by iterating
911 // parents until we find a loop...
912 pub(super) fn comes_from_while_condition(
914 original_expr_id: HirId,
915 then: impl FnOnce(&hir::Expr<'_>),
917 let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
918 while let Some(node) = self.tcx.hir().find(parent) {
920 hir::Node::Expr(hir::Expr {
927 hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
933 hir::LoopSource::While,
938 // Check if our original expression is a child of the condition of a while loop
939 let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
940 self.tcx.hir().find_parent_node(*id)
942 .take_while(|id| *id != parent)
943 .any(|id| id == expr.hir_id);
944 // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
945 // where `while let` was more likely intended.
946 if expr_is_ancestor {
952 | hir::Node::ImplItem(_)
953 | hir::Node::TraitItem(_)
954 | hir::Node::Crate(_) => break,
956 parent = self.tcx.hir().get_parent_node(parent);
962 // A generic function for checking the 'then' and 'else' clauses in an 'if'
963 // or 'if-else' expression.
966 cond_expr: &'tcx hir::Expr<'tcx>,
967 then_expr: &'tcx hir::Expr<'tcx>,
968 opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
970 orig_expected: Expectation<'tcx>,
972 let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
974 self.warn_if_unreachable(
977 "block in `if` or `while` expression",
980 let cond_diverges = self.diverges.get();
981 self.diverges.set(Diverges::Maybe);
983 let expected = orig_expected.adjust_for_branches(self);
984 let then_ty = self.check_expr_with_expectation(then_expr, expected);
985 let then_diverges = self.diverges.get();
986 self.diverges.set(Diverges::Maybe);
988 // We've already taken the expected type's preferences
989 // into account when typing the `then` branch. To figure
990 // out the initial shot at a LUB, we thus only consider
991 // `expected` if it represents a *hard* constraint
992 // (`only_has_type`); otherwise, we just go with a
993 // fresh type variable.
994 let coerce_to_ty = expected.coercion_target_type(self, sp);
995 let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
997 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
999 if let Some(else_expr) = opt_else_expr {
1000 let else_ty = self.check_expr_with_expectation(else_expr, expected);
1001 let else_diverges = self.diverges.get();
1003 let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1004 let if_cause = self.if_cause(
1011 opt_suggest_box_span,
1014 coerce.coerce(self, &if_cause, else_expr, else_ty);
1016 // We won't diverge unless both branches do (or the condition does).
1017 self.diverges.set(cond_diverges | then_diverges & else_diverges);
1019 self.if_fallback_coercion(sp, then_expr, &mut coerce);
1021 // If the condition is false we can't diverge.
1022 self.diverges.set(cond_diverges);
1025 let result_ty = coerce.complete(self);
1026 if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1029 /// Type check assignment expression `expr` of form `lhs = rhs`.
1030 /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1031 fn check_expr_assign(
1033 expr: &'tcx hir::Expr<'tcx>,
1034 expected: Expectation<'tcx>,
1035 lhs: &'tcx hir::Expr<'tcx>,
1036 rhs: &'tcx hir::Expr<'tcx>,
1039 let expected_ty = expected.coercion_target_type(self, expr.span);
1040 if expected_ty == self.tcx.types.bool {
1041 // The expected type is `bool` but this will result in `()` so we can reasonably
1042 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1043 // The likely cause of this is `if foo = bar { .. }`.
1044 let actual_ty = self.tcx.mk_unit();
1045 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1046 let lhs_ty = self.check_expr(&lhs);
1047 let rhs_ty = self.check_expr(&rhs);
1048 let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1049 (Applicability::MachineApplicable, true)
1051 (Applicability::MaybeIncorrect, false)
1053 if !lhs.is_syntactic_place_expr()
1054 && lhs.is_approximately_pattern()
1055 && !matches!(lhs.kind, hir::ExprKind::Lit(_))
1057 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1058 let hir = self.tcx.hir();
1059 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1060 hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1062 err.span_suggestion_verbose(
1063 expr.span.shrink_to_lo(),
1064 "you might have meant to use pattern matching",
1071 err.span_suggestion_verbose(
1073 "you might have meant to compare for equality",
1079 // If the assignment expression itself is ill-formed, don't
1080 // bother emitting another error
1081 if lhs_ty.references_error() || rhs_ty.references_error() {
1086 return self.tcx.ty_error();
1089 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1091 let suggest_deref_binop = |err: &mut Diagnostic, rhs_ty: Ty<'tcx>| {
1092 if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1093 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1094 // unsized, do not suggest dereferencing it.
1095 let lhs_deref_ty_is_sized = self
1097 .type_implements_trait(
1098 self.tcx.lang_items().sized_trait().unwrap(),
1104 if lhs_deref_ty_is_sized && self.can_coerce(rhs_ty, lhs_deref_ty) {
1105 err.span_suggestion_verbose(
1106 lhs.span.shrink_to_lo(),
1107 "consider dereferencing here to assign to the mutably borrowed value",
1109 Applicability::MachineApplicable,
1115 self.check_lhs_assignable(lhs, "E0070", span, |err| {
1116 let rhs_ty = self.check_expr(&rhs);
1117 suggest_deref_binop(err, rhs_ty);
1120 // This is (basically) inlined `check_expr_coercable_to_type`, but we want
1121 // to suggest an additional fixup here in `suggest_deref_binop`.
1122 let rhs_ty = self.check_expr_with_hint(&rhs, lhs_ty);
1123 if let (_, Some(mut diag)) =
1124 self.demand_coerce_diag(rhs, rhs_ty, lhs_ty, Some(lhs), AllowTwoPhase::No)
1126 suggest_deref_binop(&mut diag, rhs_ty);
1130 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1132 if lhs_ty.references_error() || rhs_ty.references_error() {
1139 pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1140 // for let statements, this is done in check_stmt
1141 let init = let_expr.init;
1142 self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1143 // otherwise check exactly as a let statement
1144 self.check_decl(let_expr.into());
1145 // but return a bool, for this is a boolean expression
1151 body: &'tcx hir::Block<'tcx>,
1152 source: hir::LoopSource,
1153 expected: Expectation<'tcx>,
1154 expr: &'tcx hir::Expr<'tcx>,
1156 let coerce = match source {
1157 // you can only use break with a value from a normal `loop { }`
1158 hir::LoopSource::Loop => {
1159 let coerce_to = expected.coercion_target_type(self, body.span);
1160 Some(CoerceMany::new(coerce_to))
1163 hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1166 let ctxt = BreakableCtxt {
1168 may_break: false, // Will get updated if/when we find a `break`.
1171 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1172 self.check_block_no_value(&body);
1176 // No way to know whether it's diverging because
1177 // of a `break` or an outer `break` or `return`.
1178 self.diverges.set(Diverges::Maybe);
1181 // If we permit break with a value, then result type is
1182 // the LUB of the breaks (possibly ! if none); else, it
1183 // is nil. This makes sense because infinite loops
1184 // (which would have type !) are only possible iff we
1185 // permit break with a value [1].
1186 if ctxt.coerce.is_none() && !ctxt.may_break {
1188 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1190 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1193 /// Checks a method call.
1194 fn check_method_call(
1196 expr: &'tcx hir::Expr<'tcx>,
1197 segment: &hir::PathSegment<'_>,
1198 rcvr: &'tcx hir::Expr<'tcx>,
1199 args: &'tcx [hir::Expr<'tcx>],
1200 expected: Expectation<'tcx>,
1202 let rcvr_t = self.check_expr(&rcvr);
1203 // no need to check for bot/err -- callee does that
1204 let rcvr_t = self.structurally_resolved_type(rcvr.span, rcvr_t);
1205 let span = segment.ident.span;
1207 let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1209 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1210 // trigger this codepath causing `structurally_resolved_type` to emit an error.
1212 self.write_method_call(expr.hir_id, method);
1216 if segment.ident.name != kw::Empty {
1217 if let Some(mut err) = self.report_method_error(
1221 SelfSource::MethodCall(rcvr),
1232 // Call the generic checker.
1233 self.check_method_argument_types(span, expr, method, &args, DontTupleArguments, expected)
1238 e: &'tcx hir::Expr<'tcx>,
1239 t: &'tcx hir::Ty<'tcx>,
1240 expr: &'tcx hir::Expr<'tcx>,
1242 // Find the type of `e`. Supply hints based on the type we are casting to,
1244 let t_cast = self.to_ty_saving_user_provided_ty(t);
1245 let t_cast = self.resolve_vars_if_possible(t_cast);
1246 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1247 let t_expr = self.resolve_vars_if_possible(t_expr);
1249 // Eagerly check for some obvious errors.
1250 if t_expr.references_error() || t_cast.references_error() {
1253 // Defer other checks until we're done type checking.
1254 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1255 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1258 "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1259 t_cast, t_expr, cast_check,
1261 deferred_cast_checks.push(cast_check);
1264 Err(_) => self.tcx.ty_error(),
1269 fn check_expr_array(
1271 args: &'tcx [hir::Expr<'tcx>],
1272 expected: Expectation<'tcx>,
1273 expr: &'tcx hir::Expr<'tcx>,
1275 let element_ty = if !args.is_empty() {
1276 let coerce_to = expected
1278 .and_then(|uty| match *uty.kind() {
1279 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1282 .unwrap_or_else(|| {
1283 self.next_ty_var(TypeVariableOrigin {
1284 kind: TypeVariableOriginKind::TypeInference,
1288 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1289 assert_eq!(self.diverges.get(), Diverges::Maybe);
1291 let e_ty = self.check_expr_with_hint(e, coerce_to);
1292 let cause = self.misc(e.span);
1293 coerce.coerce(self, &cause, e, e_ty);
1295 coerce.complete(self)
1297 self.next_ty_var(TypeVariableOrigin {
1298 kind: TypeVariableOriginKind::TypeInference,
1302 let array_len = args.len() as u64;
1303 self.suggest_array_len(expr, array_len);
1304 self.tcx.mk_array(element_ty, array_len)
1307 fn suggest_array_len(&self, expr: &'tcx hir::Expr<'tcx>, array_len: u64) {
1308 let parent_node = self.tcx.hir().parent_iter(expr.hir_id).find(|(_, node)| {
1309 !matches!(node, hir::Node::Expr(hir::Expr { kind: hir::ExprKind::AddrOf(..), .. }))
1312 hir::Node::Local(hir::Local { ty: Some(ty), .. })
1313 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _), .. }))
1314 ) = parent_node else {
1317 if let hir::TyKind::Array(_, length) = ty.peel_refs().kind
1318 && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
1319 && let Some(span) = self.tcx.hir().opt_span(hir_id)
1321 match self.tcx.sess.diagnostic().steal_diagnostic(span, StashKey::UnderscoreForArrayLengths) {
1323 err.span_suggestion(
1325 "consider specifying the array length",
1327 Applicability::MaybeIncorrect,
1336 fn check_expr_const_block(
1338 anon_const: &'tcx hir::AnonConst,
1339 expected: Expectation<'tcx>,
1340 _expr: &'tcx hir::Expr<'tcx>,
1342 let body = self.tcx.hir().body(anon_const.body);
1344 // Create a new function context.
1345 let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1346 crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1348 let ty = fcx.check_expr_with_expectation(&body.value, expected);
1349 fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1350 fcx.write_ty(anon_const.hir_id, ty);
1354 fn check_expr_repeat(
1356 element: &'tcx hir::Expr<'tcx>,
1357 count: &'tcx hir::ArrayLen,
1358 expected: Expectation<'tcx>,
1359 expr: &'tcx hir::Expr<'tcx>,
1362 let count = self.array_length_to_const(count);
1363 if let Some(count) = count.try_eval_usize(tcx, self.param_env) {
1364 self.suggest_array_len(expr, count);
1367 let uty = match expected {
1368 ExpectHasType(uty) => match *uty.kind() {
1369 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1375 let (element_ty, t) = match uty {
1377 self.check_expr_coercable_to_type(&element, uty, None);
1381 let ty = self.next_ty_var(TypeVariableOrigin {
1382 kind: TypeVariableOriginKind::MiscVariable,
1385 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1390 if element_ty.references_error() {
1391 return tcx.ty_error();
1394 self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1396 tcx.mk_ty(ty::Array(t, count))
1399 fn check_repeat_element_needs_copy_bound(
1401 element: &hir::Expr<'_>,
1402 count: ty::Const<'tcx>,
1403 element_ty: Ty<'tcx>,
1406 // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1407 match &element.kind {
1408 hir::ExprKind::ConstBlock(..) => return,
1409 hir::ExprKind::Path(qpath) => {
1410 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1411 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1418 // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1419 // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1420 let is_const_fn = match element.kind {
1421 hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1422 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1428 // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1429 // don't copy that one element, we move it. Only check for Copy if the length is larger.
1430 if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1431 let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1432 let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1433 self.require_type_meets(element_ty, element.span, code, lang_item);
1437 fn check_expr_tuple(
1439 elts: &'tcx [hir::Expr<'tcx>],
1440 expected: Expectation<'tcx>,
1441 expr: &'tcx hir::Expr<'tcx>,
1443 let flds = expected.only_has_type(self).and_then(|ty| {
1444 let ty = self.resolve_vars_with_obligations(ty);
1446 ty::Tuple(flds) => Some(&flds[..]),
1451 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1452 Some(fs) if i < fs.len() => {
1454 self.check_expr_coercable_to_type(&e, ety, None);
1457 _ => self.check_expr_with_expectation(&e, NoExpectation),
1459 let tuple = self.tcx.mk_tup(elt_ts_iter);
1460 if tuple.references_error() {
1463 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1468 fn check_expr_struct(
1470 expr: &hir::Expr<'_>,
1471 expected: Expectation<'tcx>,
1473 fields: &'tcx [hir::ExprField<'tcx>],
1474 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1476 // Find the relevant variant
1477 let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1478 self.check_struct_fields_on_error(fields, base_expr);
1479 return self.tcx.ty_error();
1482 // Prohibit struct expressions when non-exhaustive flag is set.
1483 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1484 if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1487 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1490 self.check_expr_struct_fields(
1501 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1505 fn check_expr_struct_fields(
1508 expected: Expectation<'tcx>,
1509 expr_id: hir::HirId,
1511 variant: &'tcx ty::VariantDef,
1512 ast_fields: &'tcx [hir::ExprField<'tcx>],
1513 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1518 let expected_inputs =
1519 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1520 let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1521 expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1525 // re-link the regions that EIfEO can erase.
1526 self.demand_eqtype(span, adt_ty_hint, adt_ty);
1528 let ty::Adt(adt, substs) = adt_ty.kind() else {
1529 span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1531 let adt_kind = adt.adt_kind();
1533 let mut remaining_fields = variant
1537 .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1538 .collect::<FxHashMap<_, _>>();
1540 let mut seen_fields = FxHashMap::default();
1542 let mut error_happened = false;
1544 // Type-check each field.
1545 for (idx, field) in ast_fields.iter().enumerate() {
1546 let ident = tcx.adjust_ident(field.ident, variant.def_id);
1547 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1548 seen_fields.insert(ident, field.span);
1549 self.write_field_index(field.hir_id, i);
1551 // We don't look at stability attributes on
1552 // struct-like enums (yet...), but it's definitely not
1553 // a bug to have constructed one.
1554 if adt_kind != AdtKind::Enum {
1555 tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1558 self.field_ty(field.span, v_field, substs)
1560 error_happened = true;
1561 if let Some(prev_span) = seen_fields.get(&ident) {
1562 tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1563 span: field.ident.span,
1564 prev_span: *prev_span,
1568 self.report_unknown_field(
1573 adt.variant_descr(),
1581 // Make sure to give a type to the field even if there's
1582 // an error, so we can continue type-checking.
1583 let ty = self.check_expr_with_hint(&field.expr, field_type);
1585 self.demand_coerce_diag(&field.expr, ty, field_type, None, AllowTwoPhase::No);
1587 if let Some(mut diag) = diag {
1588 if idx == ast_fields.len() - 1 && remaining_fields.is_empty() {
1589 self.suggest_fru_from_range(field, variant, substs, &mut diag);
1595 // Make sure the programmer specified correct number of fields.
1596 if adt_kind == AdtKind::Union {
1597 if ast_fields.len() != 1 {
1602 "union expressions should have exactly one field",
1608 // If check_expr_struct_fields hit an error, do not attempt to populate
1609 // the fields with the base_expr. This could cause us to hit errors later
1610 // when certain fields are assumed to exist that in fact do not.
1615 if let Some(base_expr) = base_expr {
1616 // FIXME: We are currently creating two branches here in order to maintain
1617 // consistency. But they should be merged as much as possible.
1618 let fru_tys = if self.tcx.features().type_changing_struct_update {
1619 if adt.is_struct() {
1620 // Make some fresh substitutions for our ADT type.
1621 let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1622 // We do subtyping on the FRU fields first, so we can
1623 // learn exactly what types we expect the base expr
1624 // needs constrained to be compatible with the struct
1625 // type we expect from the expectation value.
1626 let fru_tys = variant
1630 let fru_ty = self.normalize_associated_types_in(
1632 self.field_ty(base_expr.span, f, fresh_substs),
1634 let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1635 if let Some(_) = remaining_fields.remove(&ident) {
1636 let target_ty = self.field_ty(base_expr.span, f, substs);
1637 let cause = self.misc(base_expr.span);
1638 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1639 Ok(InferOk { obligations, value: () }) => {
1640 self.register_predicates(obligations)
1643 // This should never happen, since we're just subtyping the
1644 // remaining_fields, but it's fine to emit this, I guess.
1645 self.report_mismatched_types(
1649 FieldMisMatch(variant.name, ident.name),
1655 self.resolve_vars_if_possible(fru_ty)
1658 // The use of fresh substs that we have subtyped against
1659 // our base ADT type's fields allows us to guide inference
1660 // along so that, e.g.
1662 // MyStruct<'a, F1, F2, const C: usize> {
1664 // // Other fields that reference `'a`, `F2`, and `C`
1667 // let x = MyStruct {
1672 // will have the `other_struct` expression constrained to
1673 // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1674 // This is important to allow coercions to happen in
1675 // `other_struct` itself. See `coerce-in-base-expr.rs`.
1676 let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1677 self.check_expr_has_type_or_error(
1679 self.resolve_vars_if_possible(fresh_base_ty),
1684 // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1685 // type errors on that expression, too.
1686 self.check_expr(base_expr);
1689 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1693 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1694 let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1695 let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1696 (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1699 if self.tcx.sess.is_nightly_build() && same_adt {
1701 &self.tcx.sess.parse_sess,
1702 sym::type_changing_struct_update,
1704 "type changing struct updating is experimental",
1709 match adt_ty.kind() {
1710 ty::Adt(adt, substs) if adt.is_struct() => variant
1714 self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1720 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1725 self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1726 } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1727 debug!(?remaining_fields);
1728 let private_fields: Vec<&ty::FieldDef> = variant
1731 .filter(|field| !field.vis.is_accessible_from(tcx.parent_module(expr_id), tcx))
1734 if !private_fields.is_empty() {
1735 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1737 self.report_missing_fields(
1749 fn check_struct_fields_on_error(
1751 fields: &'tcx [hir::ExprField<'tcx>],
1752 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1754 for field in fields {
1755 self.check_expr(&field.expr);
1757 if let Some(base) = *base_expr {
1758 self.check_expr(&base);
1762 /// Report an error for a struct field expression when there are fields which aren't provided.
1765 /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1766 /// --> src/main.rs:8:5
1768 /// 8 | foo::Foo {};
1769 /// | ^^^^^^^^ missing `you_can_use_this_field`
1771 /// error: aborting due to previous error
1773 fn report_missing_fields(
1777 remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1778 variant: &'tcx ty::VariantDef,
1779 ast_fields: &'tcx [hir::ExprField<'tcx>],
1780 substs: SubstsRef<'tcx>,
1782 let len = remaining_fields.len();
1784 let mut displayable_field_names: Vec<&str> =
1785 remaining_fields.keys().map(|ident| ident.as_str()).collect();
1786 // sorting &str primitives here, sort_unstable is ok
1787 displayable_field_names.sort_unstable();
1789 let mut truncated_fields_error = String::new();
1790 let remaining_fields_names = match &displayable_field_names[..] {
1791 [field1] => format!("`{}`", field1),
1792 [field1, field2] => format!("`{field1}` and `{field2}`"),
1793 [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1795 truncated_fields_error =
1796 format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1797 displayable_field_names
1800 .map(|n| format!("`{n}`"))
1801 .collect::<Vec<_>>()
1806 let mut err = struct_span_err!(
1810 "missing field{} {}{} in initializer of `{}`",
1812 remaining_fields_names,
1813 truncated_fields_error,
1816 err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1818 if let Some(last) = ast_fields.last() {
1819 self.suggest_fru_from_range(last, variant, substs, &mut err);
1825 /// If the last field is a range literal, but it isn't supposed to be, then they probably
1826 /// meant to use functional update syntax.
1827 fn suggest_fru_from_range(
1829 last_expr_field: &hir::ExprField<'tcx>,
1830 variant: &ty::VariantDef,
1831 substs: SubstsRef<'tcx>,
1832 err: &mut Diagnostic,
1834 // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1835 if let ExprKind::Struct(
1836 QPath::LangItem(LangItem::Range, ..),
1837 &[ref range_start, ref range_end],
1839 ) = last_expr_field.expr.kind
1840 && let variant_field =
1841 variant.fields.iter().find(|field| field.ident(self.tcx) == last_expr_field.ident)
1842 && let range_def_id = self.tcx.lang_items().range_struct()
1844 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1845 .map(|adt| adt.did())
1852 .span_to_snippet(range_end.expr.span)
1853 .map(|s| format!(" from `{s}`"))
1854 .unwrap_or_default();
1855 err.span_suggestion(
1856 range_start.span.shrink_to_hi(),
1857 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1859 Applicability::MaybeIncorrect,
1864 /// Report an error for a struct field expression when there are invisible fields.
1867 /// error: cannot construct `Foo` with struct literal syntax due to private fields
1868 /// --> src/main.rs:8:5
1870 /// 8 | foo::Foo {};
1873 /// error: aborting due to previous error
1875 fn report_private_fields(
1879 private_fields: Vec<&ty::FieldDef>,
1880 used_fields: &'tcx [hir::ExprField<'tcx>],
1882 let mut err = self.tcx.sess.struct_span_err(
1885 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1888 let (used_private_fields, remaining_private_fields): (
1889 Vec<(Symbol, Span, bool)>,
1890 Vec<(Symbol, Span, bool)>,
1894 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1895 Some(used_field) => (field.name, used_field.span, true),
1896 None => (field.name, self.tcx.def_span(field.did), false),
1899 .partition(|field| field.2);
1900 err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1901 if !remaining_private_fields.is_empty() {
1902 let remaining_private_fields_len = remaining_private_fields.len();
1903 let names = match &remaining_private_fields
1905 .map(|(name, _, _)| name)
1906 .collect::<Vec<_>>()[..]
1908 _ if remaining_private_fields_len > 6 => String::new(),
1909 [name] => format!("`{name}` "),
1910 [names @ .., last] => {
1911 let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1912 format!("{} and `{last}` ", names.join(", "))
1914 [] => unreachable!(),
1917 "... and other private field{s} {names}that {were} not provided",
1918 s = pluralize!(remaining_private_fields_len),
1919 were = pluralize!("was", remaining_private_fields_len),
1925 fn report_unknown_field(
1928 variant: &'tcx ty::VariantDef,
1929 field: &hir::ExprField<'_>,
1930 skip_fields: &[hir::ExprField<'_>],
1934 if variant.is_recovered() {
1935 self.set_tainted_by_errors();
1938 let mut err = self.type_error_struct_with_diag(
1940 |actual| match ty.kind() {
1941 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1945 "{} `{}::{}` has no field named `{}`",
1951 _ => struct_span_err!(
1955 "{} `{}` has no field named `{}`",
1964 let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1965 match variant.ctor_kind {
1966 CtorKind::Fn => match ty.kind() {
1967 ty::Adt(adt, ..) if adt.is_enum() => {
1971 "`{adt}::{variant}` defined here",
1973 variant = variant.name,
1976 err.span_label(field.ident.span, "field does not exist");
1977 err.span_suggestion_verbose(
1980 "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1982 variant = variant.name,
1985 "{adt}::{variant}(/* fields */)",
1987 variant = variant.name,
1989 Applicability::HasPlaceholders,
1993 err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1994 err.span_label(field.ident.span, "field does not exist");
1995 err.span_suggestion_verbose(
1998 "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
2000 kind_name = kind_name,
2002 format!("{adt}(/* fields */)", adt = ty),
2003 Applicability::HasPlaceholders,
2008 // prevent all specified fields from being suggested
2009 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
2010 if let Some(field_name) = self.suggest_field_name(
2013 skip_fields.collect(),
2016 err.span_suggestion(
2018 "a field with a similar name exists",
2020 Applicability::MaybeIncorrect,
2024 ty::Adt(adt, ..) => {
2028 format!("`{}::{}` does not have this field", ty, variant.name),
2033 format!("`{ty}` does not have this field"),
2036 let available_field_names =
2037 self.available_field_names(variant, expr_span);
2038 if !available_field_names.is_empty() {
2040 "available fields are: {}",
2041 self.name_series_display(available_field_names)
2045 _ => bug!("non-ADT passed to report_unknown_field"),
2053 // Return a hint about the closest match in field names
2054 fn suggest_field_name(
2056 variant: &'tcx ty::VariantDef,
2059 // The span where stability will be checked
2061 ) -> Option<Symbol> {
2065 .filter_map(|field| {
2066 // ignore already set fields and private fields from non-local crates
2067 // and unstable fields.
2068 if skip.iter().any(|&x| x == field.name)
2069 || (!variant.def_id.is_local() && !field.vis.is_public())
2071 self.tcx.eval_stability(field.did, None, span, None),
2072 stability::EvalResult::Deny { .. }
2080 .collect::<Vec<Symbol>>();
2082 find_best_match_for_name(&names, field, None)
2085 fn available_field_names(
2087 variant: &'tcx ty::VariantDef,
2094 let def_scope = self
2096 .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2098 field.vis.is_accessible_from(def_scope, self.tcx)
2100 self.tcx.eval_stability(field.did, None, access_span, None),
2101 stability::EvalResult::Deny { .. }
2104 .filter(|field| !self.tcx.is_doc_hidden(field.did))
2105 .map(|field| field.name)
2109 fn name_series_display(&self, names: Vec<Symbol>) -> String {
2110 // dynamic limit, to never omit just one field
2111 let limit = if names.len() == 6 { 6 } else { 5 };
2113 names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2114 if names.len() > limit {
2115 display = format!("{} ... and {} others", display, names.len() - limit);
2120 // Check field access expressions
2123 expr: &'tcx hir::Expr<'tcx>,
2124 base: &'tcx hir::Expr<'tcx>,
2127 debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2128 let base_ty = self.check_expr(base);
2129 let base_ty = self.structurally_resolved_type(base.span, base_ty);
2130 let mut private_candidate = None;
2131 let mut autoderef = self.autoderef(expr.span, base_ty);
2132 while let Some((deref_base_ty, _)) = autoderef.next() {
2133 debug!("deref_base_ty: {:?}", deref_base_ty);
2134 match deref_base_ty.kind() {
2135 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2136 debug!("struct named {:?}", deref_base_ty);
2137 let (ident, def_scope) =
2138 self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2139 let fields = &base_def.non_enum_variant().fields;
2140 if let Some(index) = fields
2142 .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2144 let field = &fields[index];
2145 let field_ty = self.field_ty(expr.span, field, substs);
2146 // Save the index of all fields regardless of their visibility in case
2147 // of error recovery.
2148 self.write_field_index(expr.hir_id, index);
2149 let adjustments = self.adjust_steps(&autoderef);
2150 if field.vis.is_accessible_from(def_scope, self.tcx) {
2151 self.apply_adjustments(base, adjustments);
2152 self.register_predicates(autoderef.into_obligations());
2154 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2157 private_candidate = Some((adjustments, base_def.did(), field_ty));
2161 let fstr = field.as_str();
2162 if let Ok(index) = fstr.parse::<usize>() {
2163 if fstr == index.to_string() {
2164 if let Some(&field_ty) = tys.get(index) {
2165 let adjustments = self.adjust_steps(&autoderef);
2166 self.apply_adjustments(base, adjustments);
2167 self.register_predicates(autoderef.into_obligations());
2169 self.write_field_index(expr.hir_id, index);
2178 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2180 if let Some((adjustments, did, field_ty)) = private_candidate {
2181 // (#90483) apply adjustments to avoid ExprUseVisitor from
2182 // creating erroneous projection.
2183 self.apply_adjustments(base, adjustments);
2184 self.ban_private_field_access(expr, base_ty, field, did);
2188 if field.name == kw::Empty {
2189 } else if self.method_exists(field, base_ty, expr.hir_id, true) {
2190 self.ban_take_value_of_method(expr, base_ty, field);
2191 } else if !base_ty.is_primitive_ty() {
2192 self.ban_nonexisting_field(field, base, expr, base_ty);
2194 let field_name = field.to_string();
2195 let mut err = type_error_struct!(
2200 "`{base_ty}` is a primitive type and therefore doesn't have fields",
2202 let is_valid_suffix = |field: &str| {
2203 if field == "f32" || field == "f64" {
2206 let mut chars = field.chars().peekable();
2207 match chars.peek() {
2208 Some('e') | Some('E') => {
2210 if let Some(c) = chars.peek()
2211 && !c.is_numeric() && *c != '-' && *c != '+'
2215 while let Some(c) = chars.peek() {
2216 if !c.is_numeric() {
2224 let suffix = chars.collect::<String>();
2225 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2227 let maybe_partial_suffix = |field: &str| -> Option<&str> {
2228 let first_chars = ['f', 'l'];
2230 && field.to_lowercase().starts_with(first_chars)
2231 && field[1..].chars().all(|c| c.is_ascii_digit())
2233 if field.to_lowercase().starts_with(['f']) { Some("f32") } else { Some("f64") }
2238 if let ty::Infer(ty::IntVar(_)) = base_ty.kind()
2239 && let ExprKind::Lit(Spanned {
2240 node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2243 && !base.span.from_expansion()
2245 if is_valid_suffix(&field_name) {
2246 err.span_suggestion_verbose(
2247 field.span.shrink_to_lo(),
2248 "if intended to be a floating point literal, consider adding a `0` after the period",
2250 Applicability::MaybeIncorrect,
2252 } else if let Some(correct_suffix) = maybe_partial_suffix(&field_name) {
2253 err.span_suggestion_verbose(
2255 format!("if intended to be a floating point literal, consider adding a `0` after the period and a `{correct_suffix}` suffix"),
2256 format!("0{correct_suffix}"),
2257 Applicability::MaybeIncorrect,
2264 self.tcx().ty_error()
2267 fn suggest_await_on_field_access(
2269 err: &mut Diagnostic,
2271 base: &'tcx hir::Expr<'tcx>,
2274 let output_ty = match self.get_impl_future_output_ty(ty) {
2275 Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2278 let mut add_label = true;
2279 if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2280 // no field access on enum type
2286 .any(|field| field.ident(self.tcx) == field_ident)
2291 "field not available in `impl Future`, but it is available in its `Output`",
2293 err.span_suggestion_verbose(
2294 base.span.shrink_to_hi(),
2295 "consider `await`ing on the `Future` and access the field of its `Output`",
2297 Applicability::MaybeIncorrect,
2303 err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2307 fn ban_nonexisting_field(
2310 base: &'tcx hir::Expr<'tcx>,
2311 expr: &'tcx hir::Expr<'tcx>,
2315 "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, base_ty={:?}",
2316 ident, base, expr, base_ty
2318 let mut err = self.no_such_field_err(ident, base_ty, base.hir_id);
2320 match *base_ty.peel_refs().kind() {
2321 ty::Array(_, len) => {
2322 self.maybe_suggest_array_indexing(&mut err, expr, base, ident, len);
2325 self.suggest_first_deref_field(&mut err, expr, base, ident);
2327 ty::Adt(def, _) if !def.is_enum() => {
2328 self.suggest_fields_on_recordish(&mut err, def, ident, expr.span);
2330 ty::Param(param_ty) => {
2331 self.point_at_param_definition(&mut err, param_ty);
2333 ty::Opaque(_, _) => {
2334 self.suggest_await_on_field_access(&mut err, ident, base, base_ty.peel_refs());
2339 self.suggest_fn_call(&mut err, base, base_ty, |output_ty| {
2340 if let ty::Adt(def, _) = output_ty.kind() && !def.is_enum() {
2341 def.non_enum_variant().fields.iter().any(|field| {
2342 field.ident(self.tcx) == ident
2343 && field.vis.is_accessible_from(expr.hir_id.owner, self.tcx)
2345 } else if let ty::Tuple(tys) = output_ty.kind()
2346 && let Ok(idx) = ident.as_str().parse::<usize>()
2354 if ident.name == kw::Await {
2355 // We know by construction that `<expr>.await` is either on Rust 2015
2356 // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2357 err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2358 err.help_use_latest_edition();
2364 fn ban_private_field_access(
2366 expr: &hir::Expr<'_>,
2371 let struct_path = self.tcx().def_path_str(base_did);
2372 let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2373 let mut err = struct_span_err!(
2377 "field `{field}` of {kind_name} `{struct_path}` is private",
2379 err.span_label(field.span, "private field");
2380 // Also check if an accessible method exists, which is often what is meant.
2381 if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2383 self.suggest_method_call(
2385 &format!("a method `{field}` also exists, call it with parentheses"),
2395 fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2396 let mut err = type_error_struct!(
2401 "attempted to take value of method `{field}` on type `{expr_t}`",
2403 err.span_label(field.span, "method, not a field");
2405 if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2406 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2408 expr.hir_id == callee.hir_id
2413 self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2414 let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2415 let after_open = expr.span.lo() + rustc_span::BytePos(1);
2416 let before_close = expr.span.hi() - rustc_span::BytePos(1);
2418 if expr_is_call && is_wrapped {
2419 err.multipart_suggestion(
2420 "remove wrapping parentheses to call the method",
2422 (expr.span.with_hi(after_open), String::new()),
2423 (expr.span.with_lo(before_close), String::new()),
2425 Applicability::MachineApplicable,
2427 } else if !self.expr_in_place(expr.hir_id) {
2428 // Suggest call parentheses inside the wrapping parentheses
2429 let span = if is_wrapped {
2430 expr.span.with_lo(after_open).with_hi(before_close)
2434 self.suggest_method_call(
2436 "use parentheses to call the method",
2442 } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2443 && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2444 && let ExprKind::Field(base_expr, _) = expr.kind
2445 && adt_def.variants().len() == 1
2453 .any(|f| f.ident(self.tcx) == field)
2455 err.multipart_suggestion(
2456 "to access the field, dereference first",
2458 (base_expr.span.shrink_to_lo(), "(*".to_string()),
2459 (base_expr.span.shrink_to_hi(), ")".to_string()),
2461 Applicability::MaybeIncorrect,
2464 err.help("methods are immutable and cannot be assigned to");
2470 fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2471 let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2472 let generic_param = generics.type_param(¶m, self.tcx);
2473 if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2476 let param_def_id = generic_param.def_id;
2477 let param_hir_id = match param_def_id.as_local() {
2478 Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2481 let param_span = self.tcx.hir().span(param_hir_id);
2482 let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2484 err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2487 fn suggest_fields_on_recordish(
2489 err: &mut Diagnostic,
2490 def: ty::AdtDef<'tcx>,
2494 if let Some(suggested_field_name) =
2495 self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2497 err.span_suggestion(
2499 "a field with a similar name exists",
2500 suggested_field_name,
2501 Applicability::MaybeIncorrect,
2504 err.span_label(field.span, "unknown field");
2505 let struct_variant_def = def.non_enum_variant();
2506 let field_names = self.available_field_names(struct_variant_def, access_span);
2507 if !field_names.is_empty() {
2509 "available fields are: {}",
2510 self.name_series_display(field_names),
2516 fn maybe_suggest_array_indexing(
2518 err: &mut Diagnostic,
2519 expr: &hir::Expr<'_>,
2520 base: &hir::Expr<'_>,
2522 len: ty::Const<'tcx>,
2524 if let (Some(len), Ok(user_index)) =
2525 (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2526 && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2528 let help = "instead of using tuple indexing, use array indexing";
2529 let suggestion = format!("{base}[{field}]");
2530 let applicability = if len < user_index {
2531 Applicability::MachineApplicable
2533 Applicability::MaybeIncorrect
2535 err.span_suggestion(expr.span, help, suggestion, applicability);
2539 fn suggest_first_deref_field(
2541 err: &mut Diagnostic,
2542 expr: &hir::Expr<'_>,
2543 base: &hir::Expr<'_>,
2546 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2547 let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2548 let suggestion = format!("(*{base}).{field}");
2549 err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2553 fn no_such_field_err(
2558 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2559 let span = field.span;
2560 debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2562 let mut err = type_error_struct!(
2567 "no field `{field}` on type `{expr_t}`",
2570 // try to add a suggestion in case the field is a nested field of a field of the Adt
2571 let mod_id = self.tcx.parent_module(id).to_def_id();
2572 if let Some((fields, substs)) =
2573 self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2575 let candidate_fields: Vec<_> = fields
2576 .filter_map(|candidate_field| {
2577 self.check_for_nested_field_satisfying(
2579 &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2586 .map(|mut field_path| {
2590 .map(|id| id.name.to_ident_string())
2591 .collect::<Vec<String>>()
2594 .collect::<Vec<_>>();
2596 let len = candidate_fields.len();
2598 err.span_suggestions(
2599 field.span.shrink_to_lo(),
2601 "{} of the expressions' fields {} a field of the same name",
2602 if len > 1 { "some" } else { "one" },
2603 if len > 1 { "have" } else { "has" },
2605 candidate_fields.iter().map(|path| format!("{path}.")),
2606 Applicability::MaybeIncorrect,
2613 pub(crate) fn get_field_candidates_considering_privacy(
2618 ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2619 debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2621 for (base_t, _) in self.autoderef(span, base_ty) {
2622 match base_t.kind() {
2623 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2625 let fields = &base_def.non_enum_variant().fields;
2626 // Some struct, e.g. some that impl `Deref`, have all private fields
2627 // because you're expected to deref them to access the _real_ fields.
2628 // This, for example, will help us suggest accessing a field through a `Box<T>`.
2629 if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2635 .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2636 // For compile-time reasons put a limit on number of fields we search
2647 /// This method is called after we have encountered a missing field error to recursively
2648 /// search for the field
2649 pub(crate) fn check_for_nested_field_satisfying(
2652 matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2653 candidate_field: &ty::FieldDef,
2654 subst: SubstsRef<'tcx>,
2655 mut field_path: Vec<Ident>,
2657 ) -> Option<Vec<Ident>> {
2659 "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2660 span, candidate_field, field_path
2663 if field_path.len() > 3 {
2664 // For compile-time reasons and to avoid infinite recursion we only check for fields
2665 // up to a depth of three
2668 field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2669 let field_ty = candidate_field.ty(self.tcx, subst);
2670 if matches(candidate_field, field_ty) {
2671 return Some(field_path);
2672 } else if let Some((nested_fields, subst)) =
2673 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2675 // recursively search fields of `candidate_field` if it's a ty::Adt
2676 for field in nested_fields {
2677 if let Some(field_path) = self.check_for_nested_field_satisfying(
2685 return Some(field_path);
2693 fn check_expr_index(
2695 base: &'tcx hir::Expr<'tcx>,
2696 idx: &'tcx hir::Expr<'tcx>,
2697 expr: &'tcx hir::Expr<'tcx>,
2699 let base_t = self.check_expr(&base);
2700 let idx_t = self.check_expr(&idx);
2702 if base_t.references_error() {
2704 } else if idx_t.references_error() {
2707 let base_t = self.structurally_resolved_type(base.span, base_t);
2708 match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2709 Some((index_ty, element_ty)) => {
2710 // two-phase not needed because index_ty is never mutable
2711 self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2712 self.select_obligations_where_possible(false, |errors| {
2713 self.point_at_index_if_possible(errors, idx.span)
2718 let mut err = type_error_struct!(
2723 "cannot index into a value of type `{base_t}`",
2725 // Try to give some advice about indexing tuples.
2726 if let ty::Tuple(..) = base_t.kind() {
2727 let mut needs_note = true;
2728 // If the index is an integer, we can show the actual
2729 // fixed expression:
2730 if let ExprKind::Lit(ref lit) = idx.kind {
2731 if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2732 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2733 if let Ok(snip) = snip {
2734 err.span_suggestion(
2736 "to access tuple elements, use",
2737 format!("{snip}.{i}"),
2738 Applicability::MachineApplicable,
2746 "to access tuple elements, use tuple indexing \
2747 syntax (e.g., `tuple.0`)",
2758 fn point_at_index_if_possible(
2760 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2763 for error in errors {
2764 match error.obligation.predicate.kind().skip_binder() {
2765 ty::PredicateKind::Trait(predicate)
2766 if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2770 error.obligation.cause.span = span;
2774 fn check_expr_yield(
2776 value: &'tcx hir::Expr<'tcx>,
2777 expr: &'tcx hir::Expr<'tcx>,
2778 src: &'tcx hir::YieldSource,
2780 match self.resume_yield_tys {
2781 Some((resume_ty, yield_ty)) => {
2782 self.check_expr_coercable_to_type(&value, yield_ty, None);
2786 // Given that this `yield` expression was generated as a result of lowering a `.await`,
2787 // we know that the yield type must be `()`; however, the context won't contain this
2788 // information. Hence, we check the source of the yield expression here and check its
2789 // value's type against `()` (this check should always hold).
2790 None if src.is_await() => {
2791 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2795 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2796 // Avoid expressions without types during writeback (#78653).
2797 self.check_expr(value);
2803 fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2804 let needs = if is_input { Needs::None } else { Needs::MutPlace };
2805 let ty = self.check_expr_with_needs(expr, needs);
2806 self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2808 if !is_input && !expr.is_syntactic_place_expr() {
2809 let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2810 err.span_label(expr.span, "cannot assign to this expression");
2814 // If this is an input value, we require its type to be fully resolved
2815 // at this point. This allows us to provide helpful coercions which help
2816 // pass the type candidate list in a later pass.
2818 // We don't require output types to be resolved at this point, which
2819 // allows them to be inferred based on how they are used later in the
2822 let ty = self.structurally_resolved_type(expr.span, ty);
2825 let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2826 self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2828 ty::Ref(_, base_ty, mutbl) => {
2829 let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2830 self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2837 fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2838 for (op, _op_sp) in asm.operands {
2840 hir::InlineAsmOperand::In { expr, .. } => {
2841 self.check_expr_asm_operand(expr, true);
2843 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2844 | hir::InlineAsmOperand::InOut { expr, .. } => {
2845 self.check_expr_asm_operand(expr, false);
2847 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2848 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2849 self.check_expr_asm_operand(in_expr, true);
2850 if let Some(out_expr) = out_expr {
2851 self.check_expr_asm_operand(out_expr, false);
2854 // `AnonConst`s have their own body and is type-checked separately.
2855 // As they don't flow into the type system we don't need them to
2857 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2858 hir::InlineAsmOperand::SymStatic { .. } => {}
2861 if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2862 self.tcx.types.never
2869 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2870 Some(match ty.kind() {
2873 ty::Int(_) | ty::Uint(_) => "42",
2874 ty::Float(_) => "3.14159",
2875 ty::Error(_) | ty::Never => return None,