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::{self, CastCheckResult};
7 use crate::check::coercion::CoerceMany;
8 use crate::check::fatally_break_rust;
9 use crate::check::method::SelfSource;
10 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
12 report_unexpected_variant_res, BreakableCtxt, Diverges, DynamicCoerceMany, FnCtxt, Needs,
13 TupleArgumentsFlag::DontTupleArguments,
16 FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
17 YieldExprOutsideOfGenerator,
19 use crate::type_error_struct;
21 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
23 use rustc_data_structures::fx::FxHashMap;
24 use rustc_data_structures::stack::ensure_sufficient_stack;
26 pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId,
27 ErrorGuaranteed, StashKey,
30 use rustc_hir::def::{CtorKind, DefKind, Res};
31 use rustc_hir::def_id::DefId;
32 use rustc_hir::intravisit::Visitor;
33 use rustc_hir::lang_items::LangItem;
34 use rustc_hir::{Closure, ExprKind, HirId, QPath};
35 use rustc_infer::infer;
36 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
37 use rustc_infer::infer::InferOk;
38 use rustc_infer::traits::ObligationCause;
39 use rustc_middle::middle::stability;
40 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
41 use rustc_middle::ty::error::TypeError::FieldMisMatch;
42 use rustc_middle::ty::subst::SubstsRef;
43 use rustc_middle::ty::{self, AdtKind, Ty, TypeVisitable};
44 use rustc_session::parse::feature_err;
45 use rustc_span::hygiene::DesugaringKind;
46 use rustc_span::lev_distance::find_best_match_for_name;
47 use rustc_span::source_map::{Span, Spanned};
48 use rustc_span::symbol::{kw, sym, Ident, Symbol};
49 use rustc_target::spec::abi::Abi::RustIntrinsic;
50 use rustc_trait_selection::infer::InferCtxtExt;
51 use rustc_trait_selection::traits::{self, ObligationCauseCode};
53 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
54 fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
55 let ty = self.check_expr_with_hint(expr, expected);
56 self.demand_eqtype(expr.span, expected, ty);
59 pub fn check_expr_has_type_or_error(
61 expr: &'tcx hir::Expr<'tcx>,
63 extend_err: impl FnMut(&mut Diagnostic),
65 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
68 fn check_expr_meets_expectation_or_error(
70 expr: &'tcx hir::Expr<'tcx>,
71 expected: Expectation<'tcx>,
72 mut extend_err: impl FnMut(&mut Diagnostic),
74 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
75 let mut ty = self.check_expr_with_expectation(expr, expected);
77 // While we don't allow *arbitrary* coercions here, we *do* allow
78 // coercions from ! to `expected`.
80 if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
81 self.tcx().sess.delay_span_bug(
83 "expression with never type wound up being adjusted",
85 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
92 let adj_ty = self.next_ty_var(TypeVariableOrigin {
93 kind: TypeVariableOriginKind::AdjustmentType,
96 self.apply_adjustments(
98 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
103 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
104 let expr = expr.peel_drop_temps();
105 self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
106 extend_err(&mut err);
112 pub(super) fn check_expr_coercable_to_type(
114 expr: &'tcx hir::Expr<'tcx>,
116 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
118 let ty = self.check_expr_with_hint(expr, expected);
119 // checks don't need two phase
120 self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
123 pub(super) fn check_expr_with_hint(
125 expr: &'tcx hir::Expr<'tcx>,
128 self.check_expr_with_expectation(expr, ExpectHasType(expected))
131 fn check_expr_with_expectation_and_needs(
133 expr: &'tcx hir::Expr<'tcx>,
134 expected: Expectation<'tcx>,
137 let ty = self.check_expr_with_expectation(expr, expected);
139 // If the expression is used in a place whether mutable place is required
140 // e.g. LHS of assignment, perform the conversion.
141 if let Needs::MutPlace = needs {
142 self.convert_place_derefs_to_mutable(expr);
148 pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
149 self.check_expr_with_expectation(expr, NoExpectation)
152 pub(super) fn check_expr_with_needs(
154 expr: &'tcx hir::Expr<'tcx>,
157 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
161 /// If an expression has any sub-expressions that result in a type error,
162 /// inspecting that expression's type with `ty.references_error()` will return
163 /// true. Likewise, if an expression is known to diverge, inspecting its
164 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
165 /// strict, _|_ can appear in the type of an expression that does not,
166 /// itself, diverge: for example, fn() -> _|_.)
167 /// Note that inspecting a type's structure *directly* may expose the fact
168 /// that there are actually multiple representations for `Error`, so avoid
169 /// that when err needs to be handled differently.
170 #[instrument(skip(self, expr), level = "debug")]
171 pub(super) fn check_expr_with_expectation(
173 expr: &'tcx hir::Expr<'tcx>,
174 expected: Expectation<'tcx>,
176 self.check_expr_with_expectation_and_args(expr, expected, &[])
179 /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
180 /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
181 pub(super) fn check_expr_with_expectation_and_args(
183 expr: &'tcx hir::Expr<'tcx>,
184 expected: Expectation<'tcx>,
185 args: &'tcx [hir::Expr<'tcx>],
187 if self.tcx().sess.verbose() {
188 // make this code only run with -Zverbose because it is probably slow
189 if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
190 if !lint_str.contains('\n') {
191 debug!("expr text: {lint_str}");
193 let mut lines = lint_str.lines();
194 if let Some(line0) = lines.next() {
195 let remaining_lines = lines.count();
196 debug!("expr text: {line0}");
197 debug!("expr text: ...(and {remaining_lines} more lines)");
203 // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
204 // without the final expr (e.g. `try { return; }`). We don't want to generate an
205 // unreachable_code lint for it since warnings for autogenerated code are confusing.
206 let is_try_block_generated_unit_expr = match expr.kind {
207 ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
208 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
214 // Warn for expressions after diverging siblings.
215 if !is_try_block_generated_unit_expr {
216 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
219 // Hide the outer diverging and has_errors flags.
220 let old_diverges = self.diverges.replace(Diverges::Maybe);
221 let old_has_errors = self.has_errors.replace(false);
223 let ty = ensure_sufficient_stack(|| match &expr.kind {
225 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
226 ) => self.check_expr_path(qpath, expr, args),
227 _ => self.check_expr_kind(expr, expected),
230 // Warn for non-block expressions with diverging children.
236 | ExprKind::Match(..) => {}
237 // If `expr` is a result of desugaring the try block and is an ok-wrapped
238 // diverging expression (e.g. it arose from desugaring of `try { return }`),
239 // we skip issuing a warning because it is autogenerated code.
240 ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
241 ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
242 ExprKind::MethodCall(segment, ..) => {
243 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
245 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
248 // Any expression that produces a value of type `!` must have diverged
250 self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
253 // Record the type, which applies it effects.
254 // We need to do this after the warning above, so that
255 // we don't warn for the diverging expression itself.
256 self.write_ty(expr.hir_id, ty);
258 // Combine the diverging and has_error flags.
259 self.diverges.set(self.diverges.get() | old_diverges);
260 self.has_errors.set(self.has_errors.get() | old_has_errors);
262 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
263 debug!("... {:?}, expected is {:?}", ty, expected);
268 #[instrument(skip(self, expr), level = "debug")]
271 expr: &'tcx hir::Expr<'tcx>,
272 expected: Expectation<'tcx>,
274 trace!("expr={:#?}", expr);
278 ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
279 ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
280 ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
281 ExprKind::Assign(lhs, rhs, span) => {
282 self.check_expr_assign(expr, expected, lhs, rhs, span)
284 ExprKind::AssignOp(op, lhs, rhs) => {
285 self.check_binop_assign(expr, op, lhs, rhs, expected)
287 ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
288 ExprKind::AddrOf(kind, mutbl, oprnd) => {
289 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
291 ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
292 self.check_lang_item_path(lang_item, expr, hir_id)
294 ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
295 ExprKind::InlineAsm(asm) => {
296 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
297 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
298 self.check_expr_asm(asm)
300 ExprKind::Break(destination, ref expr_opt) => {
301 self.check_expr_break(destination, expr_opt.as_deref(), expr)
303 ExprKind::Continue(destination) => {
304 if destination.target_id.is_ok() {
307 // There was an error; make type-check fail.
311 ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
312 ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
313 ExprKind::Loop(body, _, source, _) => {
314 self.check_expr_loop(body, source, expected, expr)
316 ExprKind::Match(discrim, arms, match_src) => {
317 self.check_match(expr, &discrim, arms, expected, match_src)
319 ExprKind::Closure(&Closure { capture_clause, fn_decl, body, movability, .. }) => {
320 self.check_expr_closure(expr, capture_clause, &fn_decl, body, movability, expected)
322 ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
323 ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
324 ExprKind::MethodCall(segment, receiver, args, _) => {
325 self.check_method_call(expr, segment, receiver, args, expected)
327 ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
328 ExprKind::Type(e, t) => {
329 let ty = self.to_ty_saving_user_provided_ty(&t);
330 self.check_expr_eq_type(&e, ty);
333 ExprKind::If(cond, then_expr, opt_else_expr) => {
334 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
336 ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
337 ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
338 ExprKind::ConstBlock(ref anon_const) => {
339 self.check_expr_const_block(anon_const, expected, expr)
341 ExprKind::Repeat(element, ref count) => {
342 self.check_expr_repeat(element, count, expected, expr)
344 ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
345 ExprKind::Struct(qpath, fields, ref base_expr) => {
346 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
348 ExprKind::Field(base, field) => self.check_field(expr, &base, field),
349 ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
350 ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
351 hir::ExprKind::Err => tcx.ty_error(),
355 fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
356 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
357 ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
360 let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
361 self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
362 self.tcx.mk_box(referent_ty)
368 oprnd: &'tcx hir::Expr<'tcx>,
369 expected: Expectation<'tcx>,
370 expr: &'tcx hir::Expr<'tcx>,
373 let expected_inner = match unop {
374 hir::UnOp::Not | hir::UnOp::Neg => expected,
375 hir::UnOp::Deref => NoExpectation,
377 let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
379 if !oprnd_t.references_error() {
380 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
382 hir::UnOp::Deref => {
383 if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
386 let mut err = type_error_struct!(
391 "type `{oprnd_t}` cannot be dereferenced",
393 let sp = tcx.sess.source_map().start_point(expr.span);
395 tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
397 tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
400 oprnd_t = tcx.ty_error();
404 let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
405 // If it's builtin, we can reuse the type, this helps inference.
406 if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
411 let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
412 // If it's builtin, we can reuse the type, this helps inference.
413 if !oprnd_t.is_numeric() {
422 fn check_expr_addr_of(
424 kind: hir::BorrowKind,
425 mutbl: hir::Mutability,
426 oprnd: &'tcx hir::Expr<'tcx>,
427 expected: Expectation<'tcx>,
428 expr: &'tcx hir::Expr<'tcx>,
430 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
432 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
433 if oprnd.is_syntactic_place_expr() {
434 // Places may legitimately have unsized types.
435 // For example, dereferences of a fat pointer and
436 // the last field of a struct can be unsized.
439 Expectation::rvalue_hint(self, *ty)
446 self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
448 let tm = ty::TypeAndMut { ty, mutbl };
450 _ if tm.ty.references_error() => self.tcx.ty_error(),
451 hir::BorrowKind::Raw => {
452 self.check_named_place_expr(oprnd);
455 hir::BorrowKind::Ref => {
456 // Note: at this point, we cannot say what the best lifetime
457 // is to use for resulting pointer. We want to use the
458 // shortest lifetime possible so as to avoid spurious borrowck
459 // errors. Moreover, the longest lifetime will depend on the
460 // precise details of the value whose address is being taken
461 // (and how long it is valid), which we don't know yet until
462 // type inference is complete.
464 // Therefore, here we simply generate a region variable. The
465 // region inferencer will then select a suitable value.
466 // Finally, borrowck will infer the value of the region again,
467 // this time with enough precision to check that the value
468 // whose address was taken can actually be made to live as long
469 // as it needs to live.
470 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
471 self.tcx.mk_ref(region, tm)
476 /// Does this expression refer to a place that either:
477 /// * Is based on a local or static.
478 /// * Contains a dereference
479 /// Note that the adjustments for the children of `expr` should already
480 /// have been resolved.
481 fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
482 let is_named = oprnd.is_place_expr(|base| {
483 // Allow raw borrows if there are any deref adjustments.
485 // const VAL: (i32,) = (0,);
486 // const REF: &(i32,) = &(0,);
488 // &raw const VAL.0; // ERROR
489 // &raw const REF.0; // OK, same as &raw const (*REF).0;
491 // This is maybe too permissive, since it allows
492 // `let u = &raw const Box::new((1,)).0`, which creates an
493 // immediately dangling raw pointer.
498 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
501 self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
505 fn check_lang_item_path(
507 lang_item: hir::LangItem,
508 expr: &'tcx hir::Expr<'tcx>,
509 hir_id: Option<hir::HirId>,
511 self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
514 pub(crate) fn check_expr_path(
516 qpath: &'tcx hir::QPath<'tcx>,
517 expr: &'tcx hir::Expr<'tcx>,
518 args: &'tcx [hir::Expr<'tcx>],
521 let (res, opt_ty, segs) =
522 self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
525 self.set_tainted_by_errors();
528 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
529 report_unexpected_variant_res(tcx, res, qpath, expr.span);
532 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
535 if let ty::FnDef(did, ..) = *ty.kind() {
536 let fn_sig = ty.fn_sig(tcx);
537 if tcx.fn_sig(did).abi() == RustIntrinsic && tcx.item_name(did) == sym::transmute {
538 let from = fn_sig.inputs().skip_binder()[0];
539 let to = fn_sig.output().skip_binder();
540 // We defer the transmute to the end of typeck, once all inference vars have
541 // been resolved or we errored. This is important as we can only check transmute
542 // on concrete types, but the output type may not be known yet (it would only
543 // be known if explicitly specified via turbofish).
544 self.deferred_transmute_checks.borrow_mut().push((from, to, expr.span));
546 if !tcx.features().unsized_fn_params {
547 // We want to remove some Sized bounds from std functions,
548 // but don't want to expose the removal to stable Rust.
549 // i.e., we don't want to allow
555 // to work in stable even if the Sized bound on `drop` is relaxed.
556 for i in 0..fn_sig.inputs().skip_binder().len() {
557 // We just want to check sizedness, so instead of introducing
558 // placeholder lifetimes with probing, we just replace higher lifetimes
560 let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
561 let input = self.replace_bound_vars_with_fresh_vars(
563 infer::LateBoundRegionConversionTime::FnCall,
566 self.require_type_is_sized_deferred(
569 traits::SizedArgumentType(None),
573 // Here we want to prevent struct constructors from returning unsized types.
574 // There were two cases this happened: fn pointer coercion in stable
575 // and usual function call in presence of unsized_locals.
576 // Also, as we just want to check sizedness, instead of introducing
577 // placeholder lifetimes with probing, we just replace higher lifetimes
579 let output = self.replace_bound_vars_with_fresh_vars(
581 infer::LateBoundRegionConversionTime::FnCall,
584 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
587 // We always require that the type provided as the value for
588 // a type parameter outlives the moment of instantiation.
589 let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
590 self.add_wf_bounds(substs, expr);
597 destination: hir::Destination,
598 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
599 expr: &'tcx hir::Expr<'tcx>,
602 if let Ok(target_id) = destination.target_id {
604 if let Some(e) = expr_opt {
605 // If this is a break with a value, we need to type-check
606 // the expression. Get an expected type from the loop context.
607 let opt_coerce_to = {
608 // We should release `enclosing_breakables` before the `check_expr_with_hint`
609 // below, so can't move this block of code to the enclosing scope and share
610 // `ctxt` with the second `enclosing_breakables` borrow below.
611 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
612 match enclosing_breakables.opt_find_breakable(target_id) {
613 Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
615 // Avoid ICE when `break` is inside a closure (#65383).
616 return tcx.ty_error_with_message(
618 "break was outside loop, but no error was emitted",
624 // If the loop context is not a `loop { }`, then break with
625 // a value is illegal, and `opt_coerce_to` will be `None`.
626 // Just set expectation to error in that case.
627 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
629 // Recurse without `enclosing_breakables` borrowed.
630 e_ty = self.check_expr_with_hint(e, coerce_to);
631 cause = self.misc(e.span);
633 // Otherwise, this is a break *without* a value. That's
634 // always legal, and is equivalent to `break ()`.
635 e_ty = tcx.mk_unit();
636 cause = self.misc(expr.span);
639 // Now that we have type-checked `expr_opt`, borrow
640 // the `enclosing_loops` field and let's coerce the
641 // type of `expr_opt` into what is expected.
642 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
643 let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
644 // Avoid ICE when `break` is inside a closure (#65383).
645 return tcx.ty_error_with_message(
647 "break was outside loop, but no error was emitted",
651 if let Some(ref mut coerce) = ctxt.coerce {
652 if let Some(ref e) = expr_opt {
653 coerce.coerce(self, &cause, e, e_ty);
655 assert!(e_ty.is_unit());
656 let ty = coerce.expected_ty();
657 coerce.coerce_forced_unit(
661 self.suggest_mismatched_types_on_tail(
662 &mut err, expr, ty, e_ty, target_id,
664 if let Some(val) = ty_kind_suggestion(ty) {
665 let label = destination
667 .map(|l| format!(" {}", l.ident))
668 .unwrap_or_else(String::new);
671 "give it a value of the expected type",
672 format!("break{label} {val}"),
673 Applicability::HasPlaceholders,
681 // If `ctxt.coerce` is `None`, we can just ignore
682 // the type of the expression. This is because
683 // either this was a break *without* a value, in
684 // which case it is always a legal type (`()`), or
685 // else an error would have been flagged by the
686 // `loops` pass for using break with an expression
687 // where you are not supposed to.
688 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
691 // If we encountered a `break`, then (no surprise) it may be possible to break from the
692 // loop... unless the value being returned from the loop diverges itself, e.g.
693 // `break return 5` or `break loop {}`.
694 ctxt.may_break |= !self.diverges.get().is_always();
696 // the type of a `break` is always `!`, since it diverges
699 // Otherwise, we failed to find the enclosing loop;
700 // this can only happen if the `break` was not
701 // inside a loop at all, which is caught by the
702 // loop-checking pass.
703 let err = self.tcx.ty_error_with_message(
705 "break was outside loop, but no error was emitted",
708 // We still need to assign a type to the inner expression to
709 // prevent the ICE in #43162.
710 if let Some(e) = expr_opt {
711 self.check_expr_with_hint(e, err);
713 // ... except when we try to 'break rust;'.
714 // ICE this expression in particular (see #43162).
715 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
716 if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
717 fatally_break_rust(self.tcx.sess);
722 // There was an error; make type-check fail.
727 fn check_expr_return(
729 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
730 expr: &'tcx hir::Expr<'tcx>,
732 if self.ret_coercion.is_none() {
733 let mut err = ReturnStmtOutsideOfFnBody {
735 encl_body_span: None,
739 let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
741 if let Some(hir::Node::Item(hir::Item {
742 kind: hir::ItemKind::Fn(..),
746 | Some(hir::Node::TraitItem(hir::TraitItem {
747 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
751 | Some(hir::Node::ImplItem(hir::ImplItem {
752 kind: hir::ImplItemKind::Fn(..),
755 })) = self.tcx.hir().find_by_def_id(encl_item_id.def_id)
757 // We are inside a function body, so reporting "return statement
758 // outside of function body" needs an explanation.
760 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
762 // If this didn't hold, we would not have to report an error in
764 assert_ne!(encl_item_id.def_id, encl_body_owner_id);
766 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
767 let encl_body = self.tcx.hir().body(encl_body_id);
769 err.encl_body_span = Some(encl_body.value.span);
770 err.encl_fn_span = Some(*encl_fn_span);
773 self.tcx.sess.emit_err(err);
775 if let Some(e) = expr_opt {
776 // We still have to type-check `e` (issue #86188), but calling
777 // `check_return_expr` only works inside fn bodies.
780 } else if let Some(e) = expr_opt {
781 if self.ret_coercion_span.get().is_none() {
782 self.ret_coercion_span.set(Some(e.span));
784 self.check_return_expr(e, true);
786 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
787 if self.ret_coercion_span.get().is_none() {
788 self.ret_coercion_span.set(Some(expr.span));
790 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
791 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
792 coercion.coerce_forced_unit(
796 let span = fn_decl.output.span();
797 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
800 format!("expected `{snippet}` because of this return type"),
807 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
813 /// `explicit_return` is `true` if we're checking an explicit `return expr`,
814 /// and `false` if we're checking a trailing expression.
815 pub(super) fn check_return_expr(
817 return_expr: &'tcx hir::Expr<'tcx>,
818 explicit_return: bool,
820 let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
821 span_bug!(return_expr.span, "check_return_expr called outside fn body")
824 let ret_ty = ret_coercion.borrow().expected_ty();
825 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
826 let mut span = return_expr.span;
827 // Use the span of the trailing expression for our cause,
828 // not the span of the entire function
829 if !explicit_return {
830 if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
831 span = last_expr.span;
834 ret_coercion.borrow_mut().coerce(
836 &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
841 if self.return_type_has_opaque {
842 // Point any obligations that were registered due to opaque type
843 // inference at the return expression.
844 self.select_obligations_where_possible(false, |errors| {
845 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
850 fn point_at_return_for_opaque_ty_error(
852 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
854 return_expr_ty: Ty<'tcx>,
856 // Don't point at the whole block if it's empty
857 if span == self.tcx.hir().span(self.body_id) {
861 let cause = &mut err.obligation.cause;
862 if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
863 let new_cause = ObligationCause::new(
866 ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
873 pub(crate) fn check_lhs_assignable(
875 lhs: &'tcx hir::Expr<'tcx>,
876 err_code: &'static str,
878 adjust_err: impl FnOnce(&mut Diagnostic),
880 if lhs.is_syntactic_place_expr() {
884 // FIXME: Make this use Diagnostic once error codes can be dynamically set.
885 let mut err = self.tcx.sess.struct_span_err_with_code(
887 "invalid left-hand side of assignment",
888 DiagnosticId::Error(err_code.into()),
890 err.span_label(lhs.span, "cannot assign to this expression");
892 self.comes_from_while_condition(lhs.hir_id, |expr| {
893 err.span_suggestion_verbose(
894 expr.span.shrink_to_lo(),
895 "you might have meant to use pattern destructuring",
897 Applicability::MachineApplicable,
901 adjust_err(&mut err);
906 // Check if an expression `original_expr_id` comes from the condition of a while loop,
907 // as opposed from the body of a while loop, which we can naively check by iterating
908 // parents until we find a loop...
909 pub(super) fn comes_from_while_condition(
911 original_expr_id: HirId,
912 then: impl FnOnce(&hir::Expr<'_>),
914 let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
915 while let Some(node) = self.tcx.hir().find(parent) {
917 hir::Node::Expr(hir::Expr {
924 hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
930 hir::LoopSource::While,
935 // Check if our original expression is a child of the condition of a while loop
936 let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
937 self.tcx.hir().find_parent_node(*id)
939 .take_while(|id| *id != parent)
940 .any(|id| id == expr.hir_id);
941 // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
942 // where `while let` was more likely intended.
943 if expr_is_ancestor {
949 | hir::Node::ImplItem(_)
950 | hir::Node::TraitItem(_)
951 | hir::Node::Crate(_) => break,
953 parent = self.tcx.hir().get_parent_node(parent);
959 // A generic function for checking the 'then' and 'else' clauses in an 'if'
960 // or 'if-else' expression.
963 cond_expr: &'tcx hir::Expr<'tcx>,
964 then_expr: &'tcx hir::Expr<'tcx>,
965 opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
967 orig_expected: Expectation<'tcx>,
969 let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
971 self.warn_if_unreachable(
974 "block in `if` or `while` expression",
977 let cond_diverges = self.diverges.get();
978 self.diverges.set(Diverges::Maybe);
980 let expected = orig_expected.adjust_for_branches(self);
981 let then_ty = self.check_expr_with_expectation(then_expr, expected);
982 let then_diverges = self.diverges.get();
983 self.diverges.set(Diverges::Maybe);
985 // We've already taken the expected type's preferences
986 // into account when typing the `then` branch. To figure
987 // out the initial shot at a LUB, we thus only consider
988 // `expected` if it represents a *hard* constraint
989 // (`only_has_type`); otherwise, we just go with a
990 // fresh type variable.
991 let coerce_to_ty = expected.coercion_target_type(self, sp);
992 let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
994 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
996 if let Some(else_expr) = opt_else_expr {
997 let else_ty = self.check_expr_with_expectation(else_expr, expected);
998 let else_diverges = self.diverges.get();
1000 let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1001 let if_cause = self.if_cause(
1008 opt_suggest_box_span,
1011 coerce.coerce(self, &if_cause, else_expr, else_ty);
1013 // We won't diverge unless both branches do (or the condition does).
1014 self.diverges.set(cond_diverges | then_diverges & else_diverges);
1016 self.if_fallback_coercion(sp, then_expr, &mut coerce);
1018 // If the condition is false we can't diverge.
1019 self.diverges.set(cond_diverges);
1022 let result_ty = coerce.complete(self);
1023 if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1026 /// Type check assignment expression `expr` of form `lhs = rhs`.
1027 /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1028 fn check_expr_assign(
1030 expr: &'tcx hir::Expr<'tcx>,
1031 expected: Expectation<'tcx>,
1032 lhs: &'tcx hir::Expr<'tcx>,
1033 rhs: &'tcx hir::Expr<'tcx>,
1036 let expected_ty = expected.coercion_target_type(self, expr.span);
1037 if expected_ty == self.tcx.types.bool {
1038 // The expected type is `bool` but this will result in `()` so we can reasonably
1039 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1040 // The likely cause of this is `if foo = bar { .. }`.
1041 let actual_ty = self.tcx.mk_unit();
1042 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1043 let lhs_ty = self.check_expr(&lhs);
1044 let rhs_ty = self.check_expr(&rhs);
1045 let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1046 (Applicability::MachineApplicable, true)
1048 (Applicability::MaybeIncorrect, false)
1050 if !lhs.is_syntactic_place_expr()
1051 && lhs.is_approximately_pattern()
1052 && !matches!(lhs.kind, hir::ExprKind::Lit(_))
1054 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1055 let hir = self.tcx.hir();
1056 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1057 hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1059 err.span_suggestion_verbose(
1060 expr.span.shrink_to_lo(),
1061 "you might have meant to use pattern matching",
1068 err.span_suggestion_verbose(
1070 "you might have meant to compare for equality",
1076 // If the assignment expression itself is ill-formed, don't
1077 // bother emitting another error
1078 if lhs_ty.references_error() || rhs_ty.references_error() {
1083 return self.tcx.ty_error();
1086 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1088 let suggest_deref_binop = |err: &mut Diagnostic, rhs_ty: Ty<'tcx>| {
1089 if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1090 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1091 // unsized, do not suggest dereferencing it.
1092 let lhs_deref_ty_is_sized = self
1094 .type_implements_trait(
1095 self.tcx.lang_items().sized_trait().unwrap(),
1101 if lhs_deref_ty_is_sized && self.can_coerce(rhs_ty, lhs_deref_ty) {
1102 err.span_suggestion_verbose(
1103 lhs.span.shrink_to_lo(),
1104 "consider dereferencing here to assign to the mutably borrowed value",
1106 Applicability::MachineApplicable,
1112 self.check_lhs_assignable(lhs, "E0070", span, |err| {
1113 let rhs_ty = self.check_expr(&rhs);
1114 suggest_deref_binop(err, rhs_ty);
1117 // This is (basically) inlined `check_expr_coercable_to_type`, but we want
1118 // to suggest an additional fixup here in `suggest_deref_binop`.
1119 let rhs_ty = self.check_expr_with_hint(&rhs, lhs_ty);
1120 if let (_, Some(mut diag)) =
1121 self.demand_coerce_diag(rhs, rhs_ty, lhs_ty, Some(lhs), AllowTwoPhase::No)
1123 suggest_deref_binop(&mut diag, rhs_ty);
1127 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1129 if lhs_ty.references_error() || rhs_ty.references_error() {
1136 pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1137 // for let statements, this is done in check_stmt
1138 let init = let_expr.init;
1139 self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1140 // otherwise check exactly as a let statement
1141 self.check_decl(let_expr.into());
1142 // but return a bool, for this is a boolean expression
1148 body: &'tcx hir::Block<'tcx>,
1149 source: hir::LoopSource,
1150 expected: Expectation<'tcx>,
1151 expr: &'tcx hir::Expr<'tcx>,
1153 let coerce = match source {
1154 // you can only use break with a value from a normal `loop { }`
1155 hir::LoopSource::Loop => {
1156 let coerce_to = expected.coercion_target_type(self, body.span);
1157 Some(CoerceMany::new(coerce_to))
1160 hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1163 let ctxt = BreakableCtxt {
1165 may_break: false, // Will get updated if/when we find a `break`.
1168 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1169 self.check_block_no_value(&body);
1173 // No way to know whether it's diverging because
1174 // of a `break` or an outer `break` or `return`.
1175 self.diverges.set(Diverges::Maybe);
1178 // If we permit break with a value, then result type is
1179 // the LUB of the breaks (possibly ! if none); else, it
1180 // is nil. This makes sense because infinite loops
1181 // (which would have type !) are only possible iff we
1182 // permit break with a value [1].
1183 if ctxt.coerce.is_none() && !ctxt.may_break {
1185 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1187 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1190 /// Checks a method call.
1191 fn check_method_call(
1193 expr: &'tcx hir::Expr<'tcx>,
1194 segment: &hir::PathSegment<'_>,
1195 rcvr: &'tcx hir::Expr<'tcx>,
1196 args: &'tcx [hir::Expr<'tcx>],
1197 expected: Expectation<'tcx>,
1199 let rcvr_t = self.check_expr(&rcvr);
1200 // no need to check for bot/err -- callee does that
1201 let rcvr_t = self.structurally_resolved_type(rcvr.span, rcvr_t);
1202 let span = segment.ident.span;
1204 let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1206 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1207 // trigger this codepath causing `structurally_resolved_type` to emit an error.
1209 self.write_method_call(expr.hir_id, method);
1213 if segment.ident.name != kw::Empty {
1214 if let Some(mut err) = self.report_method_error(
1218 SelfSource::MethodCall(rcvr),
1229 // Call the generic checker.
1230 self.check_method_argument_types(span, expr, method, &args, DontTupleArguments, expected)
1235 e: &'tcx hir::Expr<'tcx>,
1236 t: &'tcx hir::Ty<'tcx>,
1237 expr: &'tcx hir::Expr<'tcx>,
1239 // Find the type of `e`. Supply hints based on the type we are casting to,
1241 let t_cast = self.to_ty_saving_user_provided_ty(t);
1242 let t_cast = self.resolve_vars_if_possible(t_cast);
1243 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1244 let t_expr = self.resolve_vars_if_possible(t_expr);
1246 // Eagerly check for some obvious errors.
1247 if t_expr.references_error() || t_cast.references_error() {
1250 // Defer other checks until we're done type checking.
1251 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1252 match cast::check_cast(self, e, t_expr, t_cast, t.span, expr.span) {
1253 CastCheckResult::Ok => t_cast,
1254 CastCheckResult::Deferred(cast_check) => {
1256 "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1257 t_cast, t_expr, cast_check,
1259 deferred_cast_checks.push(cast_check);
1262 CastCheckResult::Err(ErrorGuaranteed { .. }) => self.tcx.ty_error(),
1267 fn check_expr_array(
1269 args: &'tcx [hir::Expr<'tcx>],
1270 expected: Expectation<'tcx>,
1271 expr: &'tcx hir::Expr<'tcx>,
1273 let element_ty = if !args.is_empty() {
1274 let coerce_to = expected
1276 .and_then(|uty| match *uty.kind() {
1277 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1280 .unwrap_or_else(|| {
1281 self.next_ty_var(TypeVariableOrigin {
1282 kind: TypeVariableOriginKind::TypeInference,
1286 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1287 assert_eq!(self.diverges.get(), Diverges::Maybe);
1289 let e_ty = self.check_expr_with_hint(e, coerce_to);
1290 let cause = self.misc(e.span);
1291 coerce.coerce(self, &cause, e, e_ty);
1293 coerce.complete(self)
1295 self.next_ty_var(TypeVariableOrigin {
1296 kind: TypeVariableOriginKind::TypeInference,
1300 let array_len = args.len() as u64;
1301 self.suggest_array_len(expr, array_len);
1302 self.tcx.mk_array(element_ty, array_len)
1305 fn suggest_array_len(&self, expr: &'tcx hir::Expr<'tcx>, array_len: u64) {
1306 let parent_node = self.tcx.hir().parent_iter(expr.hir_id).find(|(_, node)| {
1307 !matches!(node, hir::Node::Expr(hir::Expr { kind: hir::ExprKind::AddrOf(..), .. }))
1310 hir::Node::Local(hir::Local { ty: Some(ty), .. })
1311 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _), .. }))
1312 ) = parent_node else {
1315 if let hir::TyKind::Array(_, length) = ty.peel_refs().kind
1316 && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
1317 && let Some(span) = self.tcx.hir().opt_span(hir_id)
1319 match self.tcx.sess.diagnostic().steal_diagnostic(span, StashKey::UnderscoreForArrayLengths) {
1321 err.span_suggestion(
1323 "consider specifying the array length",
1325 Applicability::MaybeIncorrect,
1334 fn check_expr_const_block(
1336 anon_const: &'tcx hir::AnonConst,
1337 expected: Expectation<'tcx>,
1338 _expr: &'tcx hir::Expr<'tcx>,
1340 let body = self.tcx.hir().body(anon_const.body);
1342 // Create a new function context.
1343 let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1344 crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1346 let ty = fcx.check_expr_with_expectation(&body.value, expected);
1347 fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1348 fcx.write_ty(anon_const.hir_id, ty);
1352 fn check_expr_repeat(
1354 element: &'tcx hir::Expr<'tcx>,
1355 count: &'tcx hir::ArrayLen,
1356 expected: Expectation<'tcx>,
1357 expr: &'tcx hir::Expr<'tcx>,
1360 let count = self.array_length_to_const(count);
1361 if let Some(count) = count.try_eval_usize(tcx, self.param_env) {
1362 self.suggest_array_len(expr, count);
1365 let uty = match expected {
1366 ExpectHasType(uty) => match *uty.kind() {
1367 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1373 let (element_ty, t) = match uty {
1375 self.check_expr_coercable_to_type(&element, uty, None);
1379 let ty = self.next_ty_var(TypeVariableOrigin {
1380 kind: TypeVariableOriginKind::MiscVariable,
1383 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1388 if element_ty.references_error() {
1389 return tcx.ty_error();
1392 self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1394 tcx.mk_ty(ty::Array(t, count))
1397 fn check_repeat_element_needs_copy_bound(
1399 element: &hir::Expr<'_>,
1400 count: ty::Const<'tcx>,
1401 element_ty: Ty<'tcx>,
1404 // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1405 match &element.kind {
1406 hir::ExprKind::ConstBlock(..) => return,
1407 hir::ExprKind::Path(qpath) => {
1408 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1409 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1416 // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1417 // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1418 let is_const_fn = match element.kind {
1419 hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1420 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1426 // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1427 // don't copy that one element, we move it. Only check for Copy if the length is larger.
1428 if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1429 let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1430 let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1431 self.require_type_meets(element_ty, element.span, code, lang_item);
1435 fn check_expr_tuple(
1437 elts: &'tcx [hir::Expr<'tcx>],
1438 expected: Expectation<'tcx>,
1439 expr: &'tcx hir::Expr<'tcx>,
1441 let flds = expected.only_has_type(self).and_then(|ty| {
1442 let ty = self.resolve_vars_with_obligations(ty);
1444 ty::Tuple(flds) => Some(&flds[..]),
1449 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1450 Some(fs) if i < fs.len() => {
1452 self.check_expr_coercable_to_type(&e, ety, None);
1455 _ => self.check_expr_with_expectation(&e, NoExpectation),
1457 let tuple = self.tcx.mk_tup(elt_ts_iter);
1458 if tuple.references_error() {
1461 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1466 fn check_expr_struct(
1468 expr: &hir::Expr<'_>,
1469 expected: Expectation<'tcx>,
1471 fields: &'tcx [hir::ExprField<'tcx>],
1472 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1474 // Find the relevant variant
1475 let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1476 self.check_struct_fields_on_error(fields, base_expr);
1477 return self.tcx.ty_error();
1480 // Prohibit struct expressions when non-exhaustive flag is set.
1481 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1482 if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1485 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1488 self.check_expr_struct_fields(
1499 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1503 fn check_expr_struct_fields(
1506 expected: Expectation<'tcx>,
1507 expr_id: hir::HirId,
1509 variant: &'tcx ty::VariantDef,
1510 ast_fields: &'tcx [hir::ExprField<'tcx>],
1511 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1516 let expected_inputs =
1517 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1518 let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1519 expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1523 // re-link the regions that EIfEO can erase.
1524 self.demand_eqtype(span, adt_ty_hint, adt_ty);
1526 let ty::Adt(adt, substs) = adt_ty.kind() else {
1527 span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1529 let adt_kind = adt.adt_kind();
1531 let mut remaining_fields = variant
1535 .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1536 .collect::<FxHashMap<_, _>>();
1538 let mut seen_fields = FxHashMap::default();
1540 let mut error_happened = false;
1542 // Type-check each field.
1543 for (idx, field) in ast_fields.iter().enumerate() {
1544 let ident = tcx.adjust_ident(field.ident, variant.def_id);
1545 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1546 seen_fields.insert(ident, field.span);
1547 self.write_field_index(field.hir_id, i);
1549 // We don't look at stability attributes on
1550 // struct-like enums (yet...), but it's definitely not
1551 // a bug to have constructed one.
1552 if adt_kind != AdtKind::Enum {
1553 tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1556 self.field_ty(field.span, v_field, substs)
1558 error_happened = true;
1559 if let Some(prev_span) = seen_fields.get(&ident) {
1560 tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1561 span: field.ident.span,
1562 prev_span: *prev_span,
1566 self.report_unknown_field(
1571 adt.variant_descr(),
1579 // Make sure to give a type to the field even if there's
1580 // an error, so we can continue type-checking.
1581 let ty = self.check_expr_with_hint(&field.expr, field_type);
1583 self.demand_coerce_diag(&field.expr, ty, field_type, None, AllowTwoPhase::No);
1585 if let Some(mut diag) = diag {
1586 if idx == ast_fields.len() - 1 && remaining_fields.is_empty() {
1587 self.suggest_fru_from_range(field, variant, substs, &mut diag);
1593 // Make sure the programmer specified correct number of fields.
1594 if adt_kind == AdtKind::Union {
1595 if ast_fields.len() != 1 {
1600 "union expressions should have exactly one field",
1606 // If check_expr_struct_fields hit an error, do not attempt to populate
1607 // the fields with the base_expr. This could cause us to hit errors later
1608 // when certain fields are assumed to exist that in fact do not.
1613 if let Some(base_expr) = base_expr {
1614 // FIXME: We are currently creating two branches here in order to maintain
1615 // consistency. But they should be merged as much as possible.
1616 let fru_tys = if self.tcx.features().type_changing_struct_update {
1617 if adt.is_struct() {
1618 // Make some fresh substitutions for our ADT type.
1619 let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1620 // We do subtyping on the FRU fields first, so we can
1621 // learn exactly what types we expect the base expr
1622 // needs constrained to be compatible with the struct
1623 // type we expect from the expectation value.
1624 let fru_tys = variant
1628 let fru_ty = self.normalize_associated_types_in(
1630 self.field_ty(base_expr.span, f, fresh_substs),
1632 let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1633 if let Some(_) = remaining_fields.remove(&ident) {
1634 let target_ty = self.field_ty(base_expr.span, f, substs);
1635 let cause = self.misc(base_expr.span);
1636 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1637 Ok(InferOk { obligations, value: () }) => {
1638 self.register_predicates(obligations)
1641 // This should never happen, since we're just subtyping the
1642 // remaining_fields, but it's fine to emit this, I guess.
1643 self.report_mismatched_types(
1647 FieldMisMatch(variant.name, ident.name),
1653 self.resolve_vars_if_possible(fru_ty)
1656 // The use of fresh substs that we have subtyped against
1657 // our base ADT type's fields allows us to guide inference
1658 // along so that, e.g.
1660 // MyStruct<'a, F1, F2, const C: usize> {
1662 // // Other fields that reference `'a`, `F2`, and `C`
1665 // let x = MyStruct {
1670 // will have the `other_struct` expression constrained to
1671 // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1672 // This is important to allow coercions to happen in
1673 // `other_struct` itself. See `coerce-in-base-expr.rs`.
1674 let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1675 self.check_expr_has_type_or_error(
1677 self.resolve_vars_if_possible(fresh_base_ty),
1682 // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1683 // type errors on that expression, too.
1684 self.check_expr(base_expr);
1687 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1691 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1692 let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1693 let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1694 (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1697 if self.tcx.sess.is_nightly_build() && same_adt {
1699 &self.tcx.sess.parse_sess,
1700 sym::type_changing_struct_update,
1702 "type changing struct updating is experimental",
1707 match adt_ty.kind() {
1708 ty::Adt(adt, substs) if adt.is_struct() => variant
1712 self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1718 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1723 self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1724 } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1725 debug!(?remaining_fields);
1726 let private_fields: Vec<&ty::FieldDef> = variant
1729 .filter(|field| !field.vis.is_accessible_from(tcx.parent_module(expr_id), tcx))
1732 if !private_fields.is_empty() {
1733 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1735 self.report_missing_fields(
1747 fn check_struct_fields_on_error(
1749 fields: &'tcx [hir::ExprField<'tcx>],
1750 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1752 for field in fields {
1753 self.check_expr(&field.expr);
1755 if let Some(base) = *base_expr {
1756 self.check_expr(&base);
1760 /// Report an error for a struct field expression when there are fields which aren't provided.
1763 /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1764 /// --> src/main.rs:8:5
1766 /// 8 | foo::Foo {};
1767 /// | ^^^^^^^^ missing `you_can_use_this_field`
1769 /// error: aborting due to previous error
1771 fn report_missing_fields(
1775 remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1776 variant: &'tcx ty::VariantDef,
1777 ast_fields: &'tcx [hir::ExprField<'tcx>],
1778 substs: SubstsRef<'tcx>,
1780 let len = remaining_fields.len();
1782 let mut displayable_field_names: Vec<&str> =
1783 remaining_fields.keys().map(|ident| ident.as_str()).collect();
1784 // sorting &str primitives here, sort_unstable is ok
1785 displayable_field_names.sort_unstable();
1787 let mut truncated_fields_error = String::new();
1788 let remaining_fields_names = match &displayable_field_names[..] {
1789 [field1] => format!("`{}`", field1),
1790 [field1, field2] => format!("`{field1}` and `{field2}`"),
1791 [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1793 truncated_fields_error =
1794 format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1795 displayable_field_names
1798 .map(|n| format!("`{n}`"))
1799 .collect::<Vec<_>>()
1804 let mut err = struct_span_err!(
1808 "missing field{} {}{} in initializer of `{}`",
1810 remaining_fields_names,
1811 truncated_fields_error,
1814 err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1816 if let Some(last) = ast_fields.last() {
1817 self.suggest_fru_from_range(last, variant, substs, &mut err);
1823 /// If the last field is a range literal, but it isn't supposed to be, then they probably
1824 /// meant to use functional update syntax.
1825 fn suggest_fru_from_range(
1827 last_expr_field: &hir::ExprField<'tcx>,
1828 variant: &ty::VariantDef,
1829 substs: SubstsRef<'tcx>,
1830 err: &mut Diagnostic,
1832 // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1833 if let ExprKind::Struct(
1834 QPath::LangItem(LangItem::Range, ..),
1835 &[ref range_start, ref range_end],
1837 ) = last_expr_field.expr.kind
1838 && let variant_field =
1839 variant.fields.iter().find(|field| field.ident(self.tcx) == last_expr_field.ident)
1840 && let range_def_id = self.tcx.lang_items().range_struct()
1842 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1843 .map(|adt| adt.did())
1850 .span_to_snippet(range_end.expr.span)
1851 .map(|s| format!(" from `{s}`"))
1852 .unwrap_or_default();
1853 err.span_suggestion(
1854 range_start.span.shrink_to_hi(),
1855 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1857 Applicability::MaybeIncorrect,
1862 /// Report an error for a struct field expression when there are invisible fields.
1865 /// error: cannot construct `Foo` with struct literal syntax due to private fields
1866 /// --> src/main.rs:8:5
1868 /// 8 | foo::Foo {};
1871 /// error: aborting due to previous error
1873 fn report_private_fields(
1877 private_fields: Vec<&ty::FieldDef>,
1878 used_fields: &'tcx [hir::ExprField<'tcx>],
1880 let mut err = self.tcx.sess.struct_span_err(
1883 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1886 let (used_private_fields, remaining_private_fields): (
1887 Vec<(Symbol, Span, bool)>,
1888 Vec<(Symbol, Span, bool)>,
1892 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1893 Some(used_field) => (field.name, used_field.span, true),
1894 None => (field.name, self.tcx.def_span(field.did), false),
1897 .partition(|field| field.2);
1898 err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1899 if !remaining_private_fields.is_empty() {
1900 let remaining_private_fields_len = remaining_private_fields.len();
1901 let names = match &remaining_private_fields
1903 .map(|(name, _, _)| name)
1904 .collect::<Vec<_>>()[..]
1906 _ if remaining_private_fields_len > 6 => String::new(),
1907 [name] => format!("`{name}` "),
1908 [names @ .., last] => {
1909 let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1910 format!("{} and `{last}` ", names.join(", "))
1912 [] => unreachable!(),
1915 "... and other private field{s} {names}that {were} not provided",
1916 s = pluralize!(remaining_private_fields_len),
1917 were = pluralize!("was", remaining_private_fields_len),
1923 fn report_unknown_field(
1926 variant: &'tcx ty::VariantDef,
1927 field: &hir::ExprField<'_>,
1928 skip_fields: &[hir::ExprField<'_>],
1932 if variant.is_recovered() {
1933 self.set_tainted_by_errors();
1936 let mut err = self.type_error_struct_with_diag(
1938 |actual| match ty.kind() {
1939 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1943 "{} `{}::{}` has no field named `{}`",
1949 _ => struct_span_err!(
1953 "{} `{}` has no field named `{}`",
1962 let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1963 match variant.ctor_kind {
1964 CtorKind::Fn => match ty.kind() {
1965 ty::Adt(adt, ..) if adt.is_enum() => {
1969 "`{adt}::{variant}` defined here",
1971 variant = variant.name,
1974 err.span_label(field.ident.span, "field does not exist");
1975 err.span_suggestion_verbose(
1978 "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1980 variant = variant.name,
1983 "{adt}::{variant}(/* fields */)",
1985 variant = variant.name,
1987 Applicability::HasPlaceholders,
1991 err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1992 err.span_label(field.ident.span, "field does not exist");
1993 err.span_suggestion_verbose(
1996 "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1998 kind_name = kind_name,
2000 format!("{adt}(/* fields */)", adt = ty),
2001 Applicability::HasPlaceholders,
2006 // prevent all specified fields from being suggested
2007 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
2008 if let Some(field_name) = self.suggest_field_name(
2011 skip_fields.collect(),
2014 err.span_suggestion(
2016 "a field with a similar name exists",
2018 Applicability::MaybeIncorrect,
2022 ty::Adt(adt, ..) => {
2026 format!("`{}::{}` does not have this field", ty, variant.name),
2031 format!("`{ty}` does not have this field"),
2034 let available_field_names =
2035 self.available_field_names(variant, expr_span);
2036 if !available_field_names.is_empty() {
2038 "available fields are: {}",
2039 self.name_series_display(available_field_names)
2043 _ => bug!("non-ADT passed to report_unknown_field"),
2051 // Return a hint about the closest match in field names
2052 fn suggest_field_name(
2054 variant: &'tcx ty::VariantDef,
2057 // The span where stability will be checked
2059 ) -> Option<Symbol> {
2063 .filter_map(|field| {
2064 // ignore already set fields and private fields from non-local crates
2065 // and unstable fields.
2066 if skip.iter().any(|&x| x == field.name)
2067 || (!variant.def_id.is_local() && !field.vis.is_public())
2069 self.tcx.eval_stability(field.did, None, span, None),
2070 stability::EvalResult::Deny { .. }
2078 .collect::<Vec<Symbol>>();
2080 find_best_match_for_name(&names, field, None)
2083 fn available_field_names(
2085 variant: &'tcx ty::VariantDef,
2092 let def_scope = self
2094 .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2096 field.vis.is_accessible_from(def_scope, self.tcx)
2098 self.tcx.eval_stability(field.did, None, access_span, None),
2099 stability::EvalResult::Deny { .. }
2102 .filter(|field| !self.tcx.is_doc_hidden(field.did))
2103 .map(|field| field.name)
2107 fn name_series_display(&self, names: Vec<Symbol>) -> String {
2108 // dynamic limit, to never omit just one field
2109 let limit = if names.len() == 6 { 6 } else { 5 };
2111 names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2112 if names.len() > limit {
2113 display = format!("{} ... and {} others", display, names.len() - limit);
2118 // Check field access expressions
2121 expr: &'tcx hir::Expr<'tcx>,
2122 base: &'tcx hir::Expr<'tcx>,
2125 debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2126 let base_ty = self.check_expr(base);
2127 let base_ty = self.structurally_resolved_type(base.span, base_ty);
2128 let mut private_candidate = None;
2129 let mut autoderef = self.autoderef(expr.span, base_ty);
2130 while let Some((deref_base_ty, _)) = autoderef.next() {
2131 debug!("deref_base_ty: {:?}", deref_base_ty);
2132 match deref_base_ty.kind() {
2133 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2134 debug!("struct named {:?}", deref_base_ty);
2135 let (ident, def_scope) =
2136 self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2137 let fields = &base_def.non_enum_variant().fields;
2138 if let Some(index) = fields
2140 .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2142 let field = &fields[index];
2143 let field_ty = self.field_ty(expr.span, field, substs);
2144 // Save the index of all fields regardless of their visibility in case
2145 // of error recovery.
2146 self.write_field_index(expr.hir_id, index);
2147 let adjustments = self.adjust_steps(&autoderef);
2148 if field.vis.is_accessible_from(def_scope, self.tcx) {
2149 self.apply_adjustments(base, adjustments);
2150 self.register_predicates(autoderef.into_obligations());
2152 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2155 private_candidate = Some((adjustments, base_def.did(), field_ty));
2159 let fstr = field.as_str();
2160 if let Ok(index) = fstr.parse::<usize>() {
2161 if fstr == index.to_string() {
2162 if let Some(&field_ty) = tys.get(index) {
2163 let adjustments = self.adjust_steps(&autoderef);
2164 self.apply_adjustments(base, adjustments);
2165 self.register_predicates(autoderef.into_obligations());
2167 self.write_field_index(expr.hir_id, index);
2176 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2178 if let Some((adjustments, did, field_ty)) = private_candidate {
2179 // (#90483) apply adjustments to avoid ExprUseVisitor from
2180 // creating erroneous projection.
2181 self.apply_adjustments(base, adjustments);
2182 self.ban_private_field_access(expr, base_ty, field, did);
2186 if field.name == kw::Empty {
2187 } else if self.method_exists(field, base_ty, expr.hir_id, true) {
2188 self.ban_take_value_of_method(expr, base_ty, field);
2189 } else if !base_ty.is_primitive_ty() {
2190 self.ban_nonexisting_field(field, base, expr, base_ty);
2192 let field_name = field.to_string();
2193 let mut err = type_error_struct!(
2198 "`{base_ty}` is a primitive type and therefore doesn't have fields",
2200 let is_valid_suffix = |field: &str| {
2201 if field == "f32" || field == "f64" {
2204 let mut chars = field.chars().peekable();
2205 match chars.peek() {
2206 Some('e') | Some('E') => {
2208 if let Some(c) = chars.peek()
2209 && !c.is_numeric() && *c != '-' && *c != '+'
2213 while let Some(c) = chars.peek() {
2214 if !c.is_numeric() {
2222 let suffix = chars.collect::<String>();
2223 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2225 let maybe_partial_suffix = |field: &str| -> Option<&str> {
2226 let first_chars = ['f', 'l'];
2228 && field.to_lowercase().starts_with(first_chars)
2229 && field[1..].chars().all(|c| c.is_ascii_digit())
2231 if field.to_lowercase().starts_with(['f']) { Some("f32") } else { Some("f64") }
2236 if let ty::Infer(ty::IntVar(_)) = base_ty.kind()
2237 && let ExprKind::Lit(Spanned {
2238 node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2241 && !base.span.from_expansion()
2243 if is_valid_suffix(&field_name) {
2244 err.span_suggestion_verbose(
2245 field.span.shrink_to_lo(),
2246 "if intended to be a floating point literal, consider adding a `0` after the period",
2248 Applicability::MaybeIncorrect,
2250 } else if let Some(correct_suffix) = maybe_partial_suffix(&field_name) {
2251 err.span_suggestion_verbose(
2253 format!("if intended to be a floating point literal, consider adding a `0` after the period and a `{correct_suffix}` suffix"),
2254 format!("0{correct_suffix}"),
2255 Applicability::MaybeIncorrect,
2262 self.tcx().ty_error()
2265 fn suggest_await_on_field_access(
2267 err: &mut Diagnostic,
2269 base: &'tcx hir::Expr<'tcx>,
2272 let output_ty = match self.get_impl_future_output_ty(ty) {
2273 Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2276 let mut add_label = true;
2277 if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2278 // no field access on enum type
2284 .any(|field| field.ident(self.tcx) == field_ident)
2289 "field not available in `impl Future`, but it is available in its `Output`",
2291 err.span_suggestion_verbose(
2292 base.span.shrink_to_hi(),
2293 "consider `await`ing on the `Future` and access the field of its `Output`",
2295 Applicability::MaybeIncorrect,
2301 err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2305 fn ban_nonexisting_field(
2308 base: &'tcx hir::Expr<'tcx>,
2309 expr: &'tcx hir::Expr<'tcx>,
2313 "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, base_ty={:?}",
2314 ident, base, expr, base_ty
2316 let mut err = self.no_such_field_err(ident, base_ty, base.hir_id);
2318 match *base_ty.peel_refs().kind() {
2319 ty::Array(_, len) => {
2320 self.maybe_suggest_array_indexing(&mut err, expr, base, ident, len);
2323 self.suggest_first_deref_field(&mut err, expr, base, ident);
2325 ty::Adt(def, _) if !def.is_enum() => {
2326 self.suggest_fields_on_recordish(&mut err, def, ident, expr.span);
2328 ty::Param(param_ty) => {
2329 self.point_at_param_definition(&mut err, param_ty);
2331 ty::Opaque(_, _) => {
2332 self.suggest_await_on_field_access(&mut err, ident, base, base_ty.peel_refs());
2337 self.suggest_fn_call(&mut err, base, base_ty, |output_ty| {
2338 if let ty::Adt(def, _) = output_ty.kind() && !def.is_enum() {
2339 def.non_enum_variant().fields.iter().any(|field| {
2340 field.ident(self.tcx) == ident
2341 && field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
2343 } else if let ty::Tuple(tys) = output_ty.kind()
2344 && let Ok(idx) = ident.as_str().parse::<usize>()
2352 if ident.name == kw::Await {
2353 // We know by construction that `<expr>.await` is either on Rust 2015
2354 // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2355 err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2356 err.help_use_latest_edition();
2362 fn ban_private_field_access(
2364 expr: &hir::Expr<'_>,
2369 let struct_path = self.tcx().def_path_str(base_did);
2370 let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2371 let mut err = struct_span_err!(
2375 "field `{field}` of {kind_name} `{struct_path}` is private",
2377 err.span_label(field.span, "private field");
2378 // Also check if an accessible method exists, which is often what is meant.
2379 if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2381 self.suggest_method_call(
2383 &format!("a method `{field}` also exists, call it with parentheses"),
2393 fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2394 let mut err = type_error_struct!(
2399 "attempted to take value of method `{field}` on type `{expr_t}`",
2401 err.span_label(field.span, "method, not a field");
2403 if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2404 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2406 expr.hir_id == callee.hir_id
2411 self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2412 let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2413 let after_open = expr.span.lo() + rustc_span::BytePos(1);
2414 let before_close = expr.span.hi() - rustc_span::BytePos(1);
2416 if expr_is_call && is_wrapped {
2417 err.multipart_suggestion(
2418 "remove wrapping parentheses to call the method",
2420 (expr.span.with_hi(after_open), String::new()),
2421 (expr.span.with_lo(before_close), String::new()),
2423 Applicability::MachineApplicable,
2425 } else if !self.expr_in_place(expr.hir_id) {
2426 // Suggest call parentheses inside the wrapping parentheses
2427 let span = if is_wrapped {
2428 expr.span.with_lo(after_open).with_hi(before_close)
2432 self.suggest_method_call(
2434 "use parentheses to call the method",
2440 } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2441 && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2442 && let ExprKind::Field(base_expr, _) = expr.kind
2443 && adt_def.variants().len() == 1
2451 .any(|f| f.ident(self.tcx) == field)
2453 err.multipart_suggestion(
2454 "to access the field, dereference first",
2456 (base_expr.span.shrink_to_lo(), "(*".to_string()),
2457 (base_expr.span.shrink_to_hi(), ")".to_string()),
2459 Applicability::MaybeIncorrect,
2462 err.help("methods are immutable and cannot be assigned to");
2468 fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2469 let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2470 let generic_param = generics.type_param(¶m, self.tcx);
2471 if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2474 let param_def_id = generic_param.def_id;
2475 let param_hir_id = match param_def_id.as_local() {
2476 Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2479 let param_span = self.tcx.hir().span(param_hir_id);
2480 let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2482 err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2485 fn suggest_fields_on_recordish(
2487 err: &mut Diagnostic,
2488 def: ty::AdtDef<'tcx>,
2492 if let Some(suggested_field_name) =
2493 self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2495 err.span_suggestion(
2497 "a field with a similar name exists",
2498 suggested_field_name,
2499 Applicability::MaybeIncorrect,
2502 err.span_label(field.span, "unknown field");
2503 let struct_variant_def = def.non_enum_variant();
2504 let field_names = self.available_field_names(struct_variant_def, access_span);
2505 if !field_names.is_empty() {
2507 "available fields are: {}",
2508 self.name_series_display(field_names),
2514 fn maybe_suggest_array_indexing(
2516 err: &mut Diagnostic,
2517 expr: &hir::Expr<'_>,
2518 base: &hir::Expr<'_>,
2520 len: ty::Const<'tcx>,
2522 if let (Some(len), Ok(user_index)) =
2523 (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2524 && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2526 let help = "instead of using tuple indexing, use array indexing";
2527 let suggestion = format!("{base}[{field}]");
2528 let applicability = if len < user_index {
2529 Applicability::MachineApplicable
2531 Applicability::MaybeIncorrect
2533 err.span_suggestion(expr.span, help, suggestion, applicability);
2537 fn suggest_first_deref_field(
2539 err: &mut Diagnostic,
2540 expr: &hir::Expr<'_>,
2541 base: &hir::Expr<'_>,
2544 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2545 let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2546 let suggestion = format!("(*{base}).{field}");
2547 err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2551 fn no_such_field_err(
2556 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2557 let span = field.span;
2558 debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2560 let mut err = type_error_struct!(
2565 "no field `{field}` on type `{expr_t}`",
2568 // try to add a suggestion in case the field is a nested field of a field of the Adt
2569 let mod_id = self.tcx.parent_module(id).to_def_id();
2570 if let Some((fields, substs)) =
2571 self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2573 let candidate_fields: Vec<_> = fields
2574 .filter_map(|candidate_field| {
2575 self.check_for_nested_field_satisfying(
2577 &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2584 .map(|mut field_path| {
2588 .map(|id| id.name.to_ident_string())
2589 .collect::<Vec<String>>()
2592 .collect::<Vec<_>>();
2594 let len = candidate_fields.len();
2596 err.span_suggestions(
2597 field.span.shrink_to_lo(),
2599 "{} of the expressions' fields {} a field of the same name",
2600 if len > 1 { "some" } else { "one" },
2601 if len > 1 { "have" } else { "has" },
2603 candidate_fields.iter().map(|path| format!("{path}.")),
2604 Applicability::MaybeIncorrect,
2611 pub(crate) fn get_field_candidates_considering_privacy(
2616 ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2617 debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2619 for (base_t, _) in self.autoderef(span, base_ty) {
2620 match base_t.kind() {
2621 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2623 let fields = &base_def.non_enum_variant().fields;
2624 // Some struct, e.g. some that impl `Deref`, have all private fields
2625 // because you're expected to deref them to access the _real_ fields.
2626 // This, for example, will help us suggest accessing a field through a `Box<T>`.
2627 if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2633 .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2634 // For compile-time reasons put a limit on number of fields we search
2645 /// This method is called after we have encountered a missing field error to recursively
2646 /// search for the field
2647 pub(crate) fn check_for_nested_field_satisfying(
2650 matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2651 candidate_field: &ty::FieldDef,
2652 subst: SubstsRef<'tcx>,
2653 mut field_path: Vec<Ident>,
2655 ) -> Option<Vec<Ident>> {
2657 "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2658 span, candidate_field, field_path
2661 if field_path.len() > 3 {
2662 // For compile-time reasons and to avoid infinite recursion we only check for fields
2663 // up to a depth of three
2666 field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2667 let field_ty = candidate_field.ty(self.tcx, subst);
2668 if matches(candidate_field, field_ty) {
2669 return Some(field_path);
2670 } else if let Some((nested_fields, subst)) =
2671 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2673 // recursively search fields of `candidate_field` if it's a ty::Adt
2674 for field in nested_fields {
2675 if let Some(field_path) = self.check_for_nested_field_satisfying(
2683 return Some(field_path);
2691 fn check_expr_index(
2693 base: &'tcx hir::Expr<'tcx>,
2694 idx: &'tcx hir::Expr<'tcx>,
2695 expr: &'tcx hir::Expr<'tcx>,
2697 let base_t = self.check_expr(&base);
2698 let idx_t = self.check_expr(&idx);
2700 if base_t.references_error() {
2702 } else if idx_t.references_error() {
2705 let base_t = self.structurally_resolved_type(base.span, base_t);
2706 match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2707 Some((index_ty, element_ty)) => {
2708 // two-phase not needed because index_ty is never mutable
2709 self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2710 self.select_obligations_where_possible(false, |errors| {
2711 self.point_at_index_if_possible(errors, idx.span)
2716 let mut err = type_error_struct!(
2721 "cannot index into a value of type `{base_t}`",
2723 // Try to give some advice about indexing tuples.
2724 if let ty::Tuple(..) = base_t.kind() {
2725 let mut needs_note = true;
2726 // If the index is an integer, we can show the actual
2727 // fixed expression:
2728 if let ExprKind::Lit(ref lit) = idx.kind {
2729 if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2730 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2731 if let Ok(snip) = snip {
2732 err.span_suggestion(
2734 "to access tuple elements, use",
2735 format!("{snip}.{i}"),
2736 Applicability::MachineApplicable,
2744 "to access tuple elements, use tuple indexing \
2745 syntax (e.g., `tuple.0`)",
2756 fn point_at_index_if_possible(
2758 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2761 for error in errors {
2762 match error.obligation.predicate.kind().skip_binder() {
2763 ty::PredicateKind::Trait(predicate)
2764 if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2768 error.obligation.cause.span = span;
2772 fn check_expr_yield(
2774 value: &'tcx hir::Expr<'tcx>,
2775 expr: &'tcx hir::Expr<'tcx>,
2776 src: &'tcx hir::YieldSource,
2778 match self.resume_yield_tys {
2779 Some((resume_ty, yield_ty)) => {
2780 self.check_expr_coercable_to_type(&value, yield_ty, None);
2784 // Given that this `yield` expression was generated as a result of lowering a `.await`,
2785 // we know that the yield type must be `()`; however, the context won't contain this
2786 // information. Hence, we check the source of the yield expression here and check its
2787 // value's type against `()` (this check should always hold).
2788 None if src.is_await() => {
2789 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2793 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2794 // Avoid expressions without types during writeback (#78653).
2795 self.check_expr(value);
2801 fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2802 let needs = if is_input { Needs::None } else { Needs::MutPlace };
2803 let ty = self.check_expr_with_needs(expr, needs);
2804 self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2806 if !is_input && !expr.is_syntactic_place_expr() {
2807 let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2808 err.span_label(expr.span, "cannot assign to this expression");
2812 // If this is an input value, we require its type to be fully resolved
2813 // at this point. This allows us to provide helpful coercions which help
2814 // pass the type candidate list in a later pass.
2816 // We don't require output types to be resolved at this point, which
2817 // allows them to be inferred based on how they are used later in the
2820 let ty = self.structurally_resolved_type(expr.span, ty);
2823 let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2824 self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2826 ty::Ref(_, base_ty, mutbl) => {
2827 let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2828 self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2835 fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2836 for (op, _op_sp) in asm.operands {
2838 hir::InlineAsmOperand::In { expr, .. } => {
2839 self.check_expr_asm_operand(expr, true);
2841 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2842 | hir::InlineAsmOperand::InOut { expr, .. } => {
2843 self.check_expr_asm_operand(expr, false);
2845 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2846 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2847 self.check_expr_asm_operand(in_expr, true);
2848 if let Some(out_expr) = out_expr {
2849 self.check_expr_asm_operand(out_expr, false);
2852 // `AnonConst`s have their own body and is type-checked separately.
2853 // As they don't flow into the type system we don't need them to
2855 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2856 hir::InlineAsmOperand::SymStatic { .. } => {}
2859 if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2860 self.tcx.types.never
2867 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2868 Some(match ty.kind() {
2871 ty::Int(_) | ty::Uint(_) => "42",
2872 ty::Float(_) => "3.14159",
2873 ty::Error(_) | ty::Never => return None,