1 //! Type checking expressions.
3 //! See `mod.rs` for more context on type checking in general.
5 use crate::astconv::AstConv as _;
6 use crate::check::cast;
7 use crate::check::coercion::CoerceMany;
8 use crate::check::fatally_break_rust;
9 use crate::check::method::SelfSource;
10 use crate::check::report_unexpected_variant_res;
11 use crate::check::BreakableCtxt;
12 use crate::check::Diverges;
13 use crate::check::DynamicCoerceMany;
14 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
15 use crate::check::FnCtxt;
16 use crate::check::Needs;
17 use crate::check::TupleArgumentsFlag::DontTupleArguments;
19 FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
20 YieldExprOutsideOfGenerator,
22 use crate::type_error_struct;
24 use super::suggest_call_constructor;
25 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
27 use rustc_data_structures::fx::FxHashMap;
28 use rustc_data_structures::stack::ensure_sufficient_stack;
30 pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId,
31 EmissionGuarantee, ErrorGuaranteed,
34 use rustc_hir::def::{CtorKind, DefKind, Res};
35 use rustc_hir::def_id::DefId;
36 use rustc_hir::intravisit::Visitor;
37 use rustc_hir::lang_items::LangItem;
38 use rustc_hir::{Closure, ExprKind, HirId, QPath};
39 use rustc_infer::infer;
40 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
41 use rustc_infer::infer::InferOk;
42 use rustc_infer::traits::ObligationCause;
43 use rustc_middle::middle::stability;
44 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
45 use rustc_middle::ty::error::TypeError::FieldMisMatch;
46 use rustc_middle::ty::subst::SubstsRef;
47 use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TypeVisitable};
48 use rustc_session::parse::feature_err;
49 use rustc_span::hygiene::DesugaringKind;
50 use rustc_span::lev_distance::find_best_match_for_name;
51 use rustc_span::source_map::{Span, Spanned};
52 use rustc_span::symbol::{kw, sym, Ident, Symbol};
53 use rustc_span::{BytePos, Pos};
54 use rustc_target::spec::abi::Abi::RustIntrinsic;
55 use rustc_trait_selection::infer::InferCtxtExt;
56 use rustc_trait_selection::traits::{self, ObligationCauseCode};
58 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
59 fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
60 let ty = self.check_expr_with_hint(expr, expected);
61 self.demand_eqtype(expr.span, expected, ty);
64 pub fn check_expr_has_type_or_error(
66 expr: &'tcx hir::Expr<'tcx>,
68 extend_err: impl FnMut(&mut Diagnostic),
70 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
73 fn check_expr_meets_expectation_or_error(
75 expr: &'tcx hir::Expr<'tcx>,
76 expected: Expectation<'tcx>,
77 mut extend_err: impl FnMut(&mut Diagnostic),
79 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
80 let mut ty = self.check_expr_with_expectation(expr, expected);
82 // While we don't allow *arbitrary* coercions here, we *do* allow
83 // coercions from ! to `expected`.
85 if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
86 self.tcx().sess.delay_span_bug(
88 "expression with never type wound up being adjusted",
90 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
97 let adj_ty = self.next_ty_var(TypeVariableOrigin {
98 kind: TypeVariableOriginKind::AdjustmentType,
101 self.apply_adjustments(
103 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
108 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
109 let expr = expr.peel_drop_temps();
110 self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
111 extend_err(&mut err);
117 pub(super) fn check_expr_coercable_to_type(
119 expr: &'tcx hir::Expr<'tcx>,
121 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
123 let ty = self.check_expr_with_hint(expr, expected);
124 // checks don't need two phase
125 self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
128 pub(super) fn check_expr_with_hint(
130 expr: &'tcx hir::Expr<'tcx>,
133 self.check_expr_with_expectation(expr, ExpectHasType(expected))
136 fn check_expr_with_expectation_and_needs(
138 expr: &'tcx hir::Expr<'tcx>,
139 expected: Expectation<'tcx>,
142 let ty = self.check_expr_with_expectation(expr, expected);
144 // If the expression is used in a place whether mutable place is required
145 // e.g. LHS of assignment, perform the conversion.
146 if let Needs::MutPlace = needs {
147 self.convert_place_derefs_to_mutable(expr);
153 pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
154 self.check_expr_with_expectation(expr, NoExpectation)
157 pub(super) fn check_expr_with_needs(
159 expr: &'tcx hir::Expr<'tcx>,
162 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
166 /// If an expression has any sub-expressions that result in a type error,
167 /// inspecting that expression's type with `ty.references_error()` will return
168 /// true. Likewise, if an expression is known to diverge, inspecting its
169 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
170 /// strict, _|_ can appear in the type of an expression that does not,
171 /// itself, diverge: for example, fn() -> _|_.)
172 /// Note that inspecting a type's structure *directly* may expose the fact
173 /// that there are actually multiple representations for `Error`, so avoid
174 /// that when err needs to be handled differently.
175 #[instrument(skip(self, expr), level = "debug")]
176 pub(super) fn check_expr_with_expectation(
178 expr: &'tcx hir::Expr<'tcx>,
179 expected: Expectation<'tcx>,
181 self.check_expr_with_expectation_and_args(expr, expected, &[])
184 /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
185 /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
186 pub(super) fn check_expr_with_expectation_and_args(
188 expr: &'tcx hir::Expr<'tcx>,
189 expected: Expectation<'tcx>,
190 args: &'tcx [hir::Expr<'tcx>],
192 if self.tcx().sess.verbose() {
193 // make this code only run with -Zverbose because it is probably slow
194 if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
195 if !lint_str.contains('\n') {
196 debug!("expr text: {lint_str}");
198 let mut lines = lint_str.lines();
199 if let Some(line0) = lines.next() {
200 let remaining_lines = lines.count();
201 debug!("expr text: {line0}");
202 debug!("expr text: ...(and {remaining_lines} more lines)");
208 // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
209 // without the final expr (e.g. `try { return; }`). We don't want to generate an
210 // unreachable_code lint for it since warnings for autogenerated code are confusing.
211 let is_try_block_generated_unit_expr = match expr.kind {
212 ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
213 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
219 // Warn for expressions after diverging siblings.
220 if !is_try_block_generated_unit_expr {
221 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
224 // Hide the outer diverging and has_errors flags.
225 let old_diverges = self.diverges.replace(Diverges::Maybe);
226 let old_has_errors = self.has_errors.replace(false);
228 let ty = ensure_sufficient_stack(|| match &expr.kind {
230 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
231 ) => self.check_expr_path(qpath, expr, args),
232 _ => self.check_expr_kind(expr, expected),
235 // Warn for non-block expressions with diverging children.
241 | ExprKind::Match(..) => {}
242 // If `expr` is a result of desugaring the try block and is an ok-wrapped
243 // diverging expression (e.g. it arose from desugaring of `try { return }`),
244 // we skip issuing a warning because it is autogenerated code.
245 ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
246 ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
247 ExprKind::MethodCall(segment, ..) => {
248 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
250 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
253 // Any expression that produces a value of type `!` must have diverged
255 self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
258 // Record the type, which applies it effects.
259 // We need to do this after the warning above, so that
260 // we don't warn for the diverging expression itself.
261 self.write_ty(expr.hir_id, ty);
263 // Combine the diverging and has_error flags.
264 self.diverges.set(self.diverges.get() | old_diverges);
265 self.has_errors.set(self.has_errors.get() | old_has_errors);
267 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
268 debug!("... {:?}, expected is {:?}", ty, expected);
273 #[instrument(skip(self, expr), level = "debug")]
276 expr: &'tcx hir::Expr<'tcx>,
277 expected: Expectation<'tcx>,
279 trace!("expr={:#?}", expr);
283 ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
284 ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
285 ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
286 ExprKind::Assign(lhs, rhs, span) => {
287 self.check_expr_assign(expr, expected, lhs, rhs, span)
289 ExprKind::AssignOp(op, lhs, rhs) => {
290 self.check_binop_assign(expr, op, lhs, rhs, expected)
292 ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
293 ExprKind::AddrOf(kind, mutbl, oprnd) => {
294 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
296 ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
297 self.check_lang_item_path(lang_item, expr, hir_id)
299 ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
300 ExprKind::InlineAsm(asm) => {
301 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
302 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
303 self.check_expr_asm(asm)
305 ExprKind::Break(destination, ref expr_opt) => {
306 self.check_expr_break(destination, expr_opt.as_deref(), expr)
308 ExprKind::Continue(destination) => {
309 if destination.target_id.is_ok() {
312 // There was an error; make type-check fail.
316 ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
317 ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
318 ExprKind::Loop(body, _, source, _) => {
319 self.check_expr_loop(body, source, expected, expr)
321 ExprKind::Match(discrim, arms, match_src) => {
322 self.check_match(expr, &discrim, arms, expected, match_src)
324 ExprKind::Closure(&Closure { capture_clause, fn_decl, body, movability, .. }) => {
325 self.check_expr_closure(expr, capture_clause, &fn_decl, body, movability, expected)
327 ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
328 ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
329 ExprKind::MethodCall(segment, args, _) => {
330 self.check_method_call(expr, segment, args, expected)
332 ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
333 ExprKind::Type(e, t) => {
334 let ty = self.to_ty_saving_user_provided_ty(&t);
335 self.check_expr_eq_type(&e, ty);
338 ExprKind::If(cond, then_expr, opt_else_expr) => {
339 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
341 ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
342 ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
343 ExprKind::ConstBlock(ref anon_const) => {
344 self.check_expr_const_block(anon_const, expected, expr)
346 ExprKind::Repeat(element, ref count) => {
347 self.check_expr_repeat(element, count, expected, expr)
349 ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
350 ExprKind::Struct(qpath, fields, ref base_expr) => {
351 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
353 ExprKind::Field(base, field) => self.check_field(expr, &base, field),
354 ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
355 ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
356 hir::ExprKind::Err => tcx.ty_error(),
360 fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
361 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
362 ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
365 let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
366 self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
367 self.tcx.mk_box(referent_ty)
373 oprnd: &'tcx hir::Expr<'tcx>,
374 expected: Expectation<'tcx>,
375 expr: &'tcx hir::Expr<'tcx>,
378 let expected_inner = match unop {
379 hir::UnOp::Not | hir::UnOp::Neg => expected,
380 hir::UnOp::Deref => NoExpectation,
382 let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
384 if !oprnd_t.references_error() {
385 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
387 hir::UnOp::Deref => {
388 if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
391 let mut err = type_error_struct!(
396 "type `{oprnd_t}` cannot be dereferenced",
398 let sp = tcx.sess.source_map().start_point(expr.span);
400 tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
402 tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
405 oprnd_t = tcx.ty_error();
409 let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
410 // If it's builtin, we can reuse the type, this helps inference.
411 if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
416 let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
417 // If it's builtin, we can reuse the type, this helps inference.
418 if !oprnd_t.is_numeric() {
427 fn check_expr_addr_of(
429 kind: hir::BorrowKind,
430 mutbl: hir::Mutability,
431 oprnd: &'tcx hir::Expr<'tcx>,
432 expected: Expectation<'tcx>,
433 expr: &'tcx hir::Expr<'tcx>,
435 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
437 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
438 if oprnd.is_syntactic_place_expr() {
439 // Places may legitimately have unsized types.
440 // For example, dereferences of a fat pointer and
441 // the last field of a struct can be unsized.
444 Expectation::rvalue_hint(self, *ty)
451 self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
453 let tm = ty::TypeAndMut { ty, mutbl };
455 _ if tm.ty.references_error() => self.tcx.ty_error(),
456 hir::BorrowKind::Raw => {
457 self.check_named_place_expr(oprnd);
460 hir::BorrowKind::Ref => {
461 // Note: at this point, we cannot say what the best lifetime
462 // is to use for resulting pointer. We want to use the
463 // shortest lifetime possible so as to avoid spurious borrowck
464 // errors. Moreover, the longest lifetime will depend on the
465 // precise details of the value whose address is being taken
466 // (and how long it is valid), which we don't know yet until
467 // type inference is complete.
469 // Therefore, here we simply generate a region variable. The
470 // region inferencer will then select a suitable value.
471 // Finally, borrowck will infer the value of the region again,
472 // this time with enough precision to check that the value
473 // whose address was taken can actually be made to live as long
474 // as it needs to live.
475 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
476 self.tcx.mk_ref(region, tm)
481 /// Does this expression refer to a place that either:
482 /// * Is based on a local or static.
483 /// * Contains a dereference
484 /// Note that the adjustments for the children of `expr` should already
485 /// have been resolved.
486 fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
487 let is_named = oprnd.is_place_expr(|base| {
488 // Allow raw borrows if there are any deref adjustments.
490 // const VAL: (i32,) = (0,);
491 // const REF: &(i32,) = &(0,);
493 // &raw const VAL.0; // ERROR
494 // &raw const REF.0; // OK, same as &raw const (*REF).0;
496 // This is maybe too permissive, since it allows
497 // `let u = &raw const Box::new((1,)).0`, which creates an
498 // immediately dangling raw pointer.
503 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
506 self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
510 fn check_lang_item_path(
512 lang_item: hir::LangItem,
513 expr: &'tcx hir::Expr<'tcx>,
514 hir_id: Option<hir::HirId>,
516 self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
519 pub(crate) fn check_expr_path(
521 qpath: &'tcx hir::QPath<'tcx>,
522 expr: &'tcx hir::Expr<'tcx>,
523 args: &'tcx [hir::Expr<'tcx>],
526 let (res, opt_ty, segs) =
527 self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
530 self.set_tainted_by_errors();
533 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
534 report_unexpected_variant_res(tcx, res, qpath, expr.span);
537 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
540 if let ty::FnDef(did, ..) = *ty.kind() {
541 let fn_sig = ty.fn_sig(tcx);
542 if tcx.fn_sig(did).abi() == RustIntrinsic && tcx.item_name(did) == sym::transmute {
543 let from = fn_sig.inputs().skip_binder()[0];
544 let to = fn_sig.output().skip_binder();
545 // We defer the transmute to the end of typeck, once all inference vars have
546 // been resolved or we errored. This is important as we can only check transmute
547 // on concrete types, but the output type may not be known yet (it would only
548 // be known if explicitly specified via turbofish).
549 self.deferred_transmute_checks.borrow_mut().push((from, to, expr.span));
551 if !tcx.features().unsized_fn_params {
552 // We want to remove some Sized bounds from std functions,
553 // but don't want to expose the removal to stable Rust.
554 // i.e., we don't want to allow
560 // to work in stable even if the Sized bound on `drop` is relaxed.
561 for i in 0..fn_sig.inputs().skip_binder().len() {
562 // We just want to check sizedness, so instead of introducing
563 // placeholder lifetimes with probing, we just replace higher lifetimes
565 let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
566 let input = self.replace_bound_vars_with_fresh_vars(
568 infer::LateBoundRegionConversionTime::FnCall,
571 self.require_type_is_sized_deferred(
574 traits::SizedArgumentType(None),
578 // Here we want to prevent struct constructors from returning unsized types.
579 // There were two cases this happened: fn pointer coercion in stable
580 // and usual function call in presence of unsized_locals.
581 // Also, as we just want to check sizedness, instead of introducing
582 // placeholder lifetimes with probing, we just replace higher lifetimes
584 let output = self.replace_bound_vars_with_fresh_vars(
586 infer::LateBoundRegionConversionTime::FnCall,
589 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
592 // We always require that the type provided as the value for
593 // a type parameter outlives the moment of instantiation.
594 let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
595 self.add_wf_bounds(substs, expr);
602 destination: hir::Destination,
603 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
604 expr: &'tcx hir::Expr<'tcx>,
607 if let Ok(target_id) = destination.target_id {
609 if let Some(e) = expr_opt {
610 // If this is a break with a value, we need to type-check
611 // the expression. Get an expected type from the loop context.
612 let opt_coerce_to = {
613 // We should release `enclosing_breakables` before the `check_expr_with_hint`
614 // below, so can't move this block of code to the enclosing scope and share
615 // `ctxt` with the second `enclosing_breakables` borrow below.
616 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
617 match enclosing_breakables.opt_find_breakable(target_id) {
618 Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
620 // Avoid ICE when `break` is inside a closure (#65383).
621 return tcx.ty_error_with_message(
623 "break was outside loop, but no error was emitted",
629 // If the loop context is not a `loop { }`, then break with
630 // a value is illegal, and `opt_coerce_to` will be `None`.
631 // Just set expectation to error in that case.
632 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
634 // Recurse without `enclosing_breakables` borrowed.
635 e_ty = self.check_expr_with_hint(e, coerce_to);
636 cause = self.misc(e.span);
638 // Otherwise, this is a break *without* a value. That's
639 // always legal, and is equivalent to `break ()`.
640 e_ty = tcx.mk_unit();
641 cause = self.misc(expr.span);
644 // Now that we have type-checked `expr_opt`, borrow
645 // the `enclosing_loops` field and let's coerce the
646 // type of `expr_opt` into what is expected.
647 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
648 let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
649 // Avoid ICE when `break` is inside a closure (#65383).
650 return tcx.ty_error_with_message(
652 "break was outside loop, but no error was emitted",
656 if let Some(ref mut coerce) = ctxt.coerce {
657 if let Some(ref e) = expr_opt {
658 coerce.coerce(self, &cause, e, e_ty);
660 assert!(e_ty.is_unit());
661 let ty = coerce.expected_ty();
662 coerce.coerce_forced_unit(
666 self.suggest_mismatched_types_on_tail(
667 &mut err, expr, ty, e_ty, target_id,
669 if let Some(val) = ty_kind_suggestion(ty) {
670 let label = destination
672 .map(|l| format!(" {}", l.ident))
673 .unwrap_or_else(String::new);
676 "give it a value of the expected type",
677 format!("break{label} {val}"),
678 Applicability::HasPlaceholders,
686 // If `ctxt.coerce` is `None`, we can just ignore
687 // the type of the expression. This is because
688 // either this was a break *without* a value, in
689 // which case it is always a legal type (`()`), or
690 // else an error would have been flagged by the
691 // `loops` pass for using break with an expression
692 // where you are not supposed to.
693 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
696 // If we encountered a `break`, then (no surprise) it may be possible to break from the
697 // loop... unless the value being returned from the loop diverges itself, e.g.
698 // `break return 5` or `break loop {}`.
699 ctxt.may_break |= !self.diverges.get().is_always();
701 // the type of a `break` is always `!`, since it diverges
704 // Otherwise, we failed to find the enclosing loop;
705 // this can only happen if the `break` was not
706 // inside a loop at all, which is caught by the
707 // loop-checking pass.
708 let err = self.tcx.ty_error_with_message(
710 "break was outside loop, but no error was emitted",
713 // We still need to assign a type to the inner expression to
714 // prevent the ICE in #43162.
715 if let Some(e) = expr_opt {
716 self.check_expr_with_hint(e, err);
718 // ... except when we try to 'break rust;'.
719 // ICE this expression in particular (see #43162).
720 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
721 if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
722 fatally_break_rust(self.tcx.sess);
727 // There was an error; make type-check fail.
732 fn check_expr_return(
734 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
735 expr: &'tcx hir::Expr<'tcx>,
737 if self.ret_coercion.is_none() {
738 let mut err = ReturnStmtOutsideOfFnBody {
740 encl_body_span: None,
744 let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
746 if let Some(hir::Node::Item(hir::Item {
747 kind: hir::ItemKind::Fn(..),
751 | Some(hir::Node::TraitItem(hir::TraitItem {
752 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
756 | Some(hir::Node::ImplItem(hir::ImplItem {
757 kind: hir::ImplItemKind::Fn(..),
760 })) = self.tcx.hir().find_by_def_id(encl_item_id)
762 // We are inside a function body, so reporting "return statement
763 // outside of function body" needs an explanation.
765 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
767 // If this didn't hold, we would not have to report an error in
769 assert_ne!(hir::HirId::make_owner(encl_item_id), encl_body_owner_id);
771 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
772 let encl_body = self.tcx.hir().body(encl_body_id);
774 err.encl_body_span = Some(encl_body.value.span);
775 err.encl_fn_span = Some(*encl_fn_span);
778 self.tcx.sess.emit_err(err);
780 if let Some(e) = expr_opt {
781 // We still have to type-check `e` (issue #86188), but calling
782 // `check_return_expr` only works inside fn bodies.
785 } else if let Some(e) = expr_opt {
786 if self.ret_coercion_span.get().is_none() {
787 self.ret_coercion_span.set(Some(e.span));
789 self.check_return_expr(e, true);
791 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
792 if self.ret_coercion_span.get().is_none() {
793 self.ret_coercion_span.set(Some(expr.span));
795 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
796 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
797 coercion.coerce_forced_unit(
801 let span = fn_decl.output.span();
802 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
805 format!("expected `{snippet}` because of this return type"),
812 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
818 /// `explicit_return` is `true` if we're checking an explicit `return expr`,
819 /// and `false` if we're checking a trailing expression.
820 pub(super) fn check_return_expr(
822 return_expr: &'tcx hir::Expr<'tcx>,
823 explicit_return: bool,
825 let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
826 span_bug!(return_expr.span, "check_return_expr called outside fn body")
829 let ret_ty = ret_coercion.borrow().expected_ty();
830 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
831 let mut span = return_expr.span;
832 // Use the span of the trailing expression for our cause,
833 // not the span of the entire function
834 if !explicit_return {
835 if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
836 span = last_expr.span;
839 ret_coercion.borrow_mut().coerce(
841 &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
846 if self.return_type_has_opaque {
847 // Point any obligations that were registered due to opaque type
848 // inference at the return expression.
849 self.select_obligations_where_possible(false, |errors| {
850 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
855 fn point_at_return_for_opaque_ty_error(
857 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
859 return_expr_ty: Ty<'tcx>,
861 // Don't point at the whole block if it's empty
862 if span == self.tcx.hir().span(self.body_id) {
866 let cause = &mut err.obligation.cause;
867 if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
868 let new_cause = ObligationCause::new(
871 ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
878 pub(crate) fn check_lhs_assignable(
880 lhs: &'tcx hir::Expr<'tcx>,
881 err_code: &'static str,
883 adjust_err: impl FnOnce(&mut DiagnosticBuilder<'tcx, ErrorGuaranteed>),
885 if lhs.is_syntactic_place_expr() {
889 // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
890 let mut err = self.tcx.sess.struct_span_err_with_code(
892 "invalid left-hand side of assignment",
893 DiagnosticId::Error(err_code.into()),
895 err.span_label(lhs.span, "cannot assign to this expression");
897 self.comes_from_while_condition(lhs.hir_id, |expr| {
898 err.span_suggestion_verbose(
899 expr.span.shrink_to_lo(),
900 "you might have meant to use pattern destructuring",
902 Applicability::MachineApplicable,
906 adjust_err(&mut err);
911 // Check if an expression `original_expr_id` comes from the condition of a while loop,
912 // as opposed from the body of a while loop, which we can naively check by iterating
913 // parents until we find a loop...
914 pub(super) fn comes_from_while_condition(
916 original_expr_id: HirId,
917 then: impl FnOnce(&hir::Expr<'_>),
919 let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
920 while let Some(node) = self.tcx.hir().find(parent) {
922 hir::Node::Expr(hir::Expr {
929 hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
935 hir::LoopSource::While,
940 // Check if our original expression is a child of the condition of a while loop
941 let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
942 self.tcx.hir().find_parent_node(*id)
944 .take_while(|id| *id != parent)
945 .any(|id| id == expr.hir_id);
946 // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
947 // where `while let` was more likely intended.
948 if expr_is_ancestor {
954 | hir::Node::ImplItem(_)
955 | hir::Node::TraitItem(_)
956 | hir::Node::Crate(_) => break,
958 parent = self.tcx.hir().get_parent_node(parent);
964 // A generic function for checking the 'then' and 'else' clauses in an 'if'
965 // or 'if-else' expression.
968 cond_expr: &'tcx hir::Expr<'tcx>,
969 then_expr: &'tcx hir::Expr<'tcx>,
970 opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
972 orig_expected: Expectation<'tcx>,
974 let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
976 self.warn_if_unreachable(
979 "block in `if` or `while` expression",
982 let cond_diverges = self.diverges.get();
983 self.diverges.set(Diverges::Maybe);
985 let expected = orig_expected.adjust_for_branches(self);
986 let then_ty = self.check_expr_with_expectation(then_expr, expected);
987 let then_diverges = self.diverges.get();
988 self.diverges.set(Diverges::Maybe);
990 // We've already taken the expected type's preferences
991 // into account when typing the `then` branch. To figure
992 // out the initial shot at a LUB, we thus only consider
993 // `expected` if it represents a *hard* constraint
994 // (`only_has_type`); otherwise, we just go with a
995 // fresh type variable.
996 let coerce_to_ty = expected.coercion_target_type(self, sp);
997 let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
999 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
1001 if let Some(else_expr) = opt_else_expr {
1002 let else_ty = self.check_expr_with_expectation(else_expr, expected);
1003 let else_diverges = self.diverges.get();
1005 let opt_suggest_box_span = self.opt_suggest_box_span(else_ty, orig_expected);
1007 self.if_cause(sp, then_expr, else_expr, then_ty, else_ty, opt_suggest_box_span);
1009 coerce.coerce(self, &if_cause, else_expr, else_ty);
1011 // We won't diverge unless both branches do (or the condition does).
1012 self.diverges.set(cond_diverges | then_diverges & else_diverges);
1014 self.if_fallback_coercion(sp, then_expr, &mut coerce);
1016 // If the condition is false we can't diverge.
1017 self.diverges.set(cond_diverges);
1020 let result_ty = coerce.complete(self);
1021 if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1024 /// Type check assignment expression `expr` of form `lhs = rhs`.
1025 /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1026 fn check_expr_assign(
1028 expr: &'tcx hir::Expr<'tcx>,
1029 expected: Expectation<'tcx>,
1030 lhs: &'tcx hir::Expr<'tcx>,
1031 rhs: &'tcx hir::Expr<'tcx>,
1034 let expected_ty = expected.coercion_target_type(self, expr.span);
1035 if expected_ty == self.tcx.types.bool {
1036 // The expected type is `bool` but this will result in `()` so we can reasonably
1037 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1038 // The likely cause of this is `if foo = bar { .. }`.
1039 let actual_ty = self.tcx.mk_unit();
1040 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1041 let lhs_ty = self.check_expr(&lhs);
1042 let rhs_ty = self.check_expr(&rhs);
1043 let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1044 (Applicability::MachineApplicable, true)
1046 (Applicability::MaybeIncorrect, false)
1048 if !lhs.is_syntactic_place_expr()
1049 && lhs.is_approximately_pattern()
1050 && !matches!(lhs.kind, hir::ExprKind::Lit(_))
1052 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1053 let hir = self.tcx.hir();
1054 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1055 hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1057 err.span_suggestion_verbose(
1058 expr.span.shrink_to_lo(),
1059 "you might have meant to use pattern matching",
1066 err.span_suggestion_verbose(
1068 "you might have meant to compare for equality",
1074 // If the assignment expression itself is ill-formed, don't
1075 // bother emitting another error
1076 if lhs_ty.references_error() || rhs_ty.references_error() {
1081 return self.tcx.ty_error();
1084 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1086 let suggest_deref_binop = |err: &mut DiagnosticBuilder<'tcx, ErrorGuaranteed>,
1088 if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1089 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1090 // unsized, do not suggest dereferencing it.
1091 let lhs_deref_ty_is_sized = self
1093 .type_implements_trait(
1094 self.tcx.lang_items().sized_trait().unwrap(),
1100 if lhs_deref_ty_is_sized && self.can_coerce(rhs_ty, lhs_deref_ty) {
1101 err.span_suggestion_verbose(
1102 lhs.span.shrink_to_lo(),
1103 "consider dereferencing here to assign to the mutably borrowed value",
1105 Applicability::MachineApplicable,
1111 self.check_lhs_assignable(lhs, "E0070", span, |err| {
1112 let rhs_ty = self.check_expr(&rhs);
1113 suggest_deref_binop(err, rhs_ty);
1116 // This is (basically) inlined `check_expr_coercable_to_type`, but we want
1117 // to suggest an additional fixup here in `suggest_deref_binop`.
1118 let rhs_ty = self.check_expr_with_hint(&rhs, lhs_ty);
1119 if let (_, Some(mut diag)) =
1120 self.demand_coerce_diag(rhs, rhs_ty, lhs_ty, Some(lhs), AllowTwoPhase::No)
1122 suggest_deref_binop(&mut diag, rhs_ty);
1126 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1128 if lhs_ty.references_error() || rhs_ty.references_error() {
1135 pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1136 // for let statements, this is done in check_stmt
1137 let init = let_expr.init;
1138 self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1139 // otherwise check exactly as a let statement
1140 self.check_decl(let_expr.into());
1141 // but return a bool, for this is a boolean expression
1147 body: &'tcx hir::Block<'tcx>,
1148 source: hir::LoopSource,
1149 expected: Expectation<'tcx>,
1150 expr: &'tcx hir::Expr<'tcx>,
1152 let coerce = match source {
1153 // you can only use break with a value from a normal `loop { }`
1154 hir::LoopSource::Loop => {
1155 let coerce_to = expected.coercion_target_type(self, body.span);
1156 Some(CoerceMany::new(coerce_to))
1159 hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1162 let ctxt = BreakableCtxt {
1164 may_break: false, // Will get updated if/when we find a `break`.
1167 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1168 self.check_block_no_value(&body);
1172 // No way to know whether it's diverging because
1173 // of a `break` or an outer `break` or `return`.
1174 self.diverges.set(Diverges::Maybe);
1177 // If we permit break with a value, then result type is
1178 // the LUB of the breaks (possibly ! if none); else, it
1179 // is nil. This makes sense because infinite loops
1180 // (which would have type !) are only possible iff we
1181 // permit break with a value [1].
1182 if ctxt.coerce.is_none() && !ctxt.may_break {
1184 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1186 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1189 /// Checks a method call.
1190 fn check_method_call(
1192 expr: &'tcx hir::Expr<'tcx>,
1193 segment: &hir::PathSegment<'_>,
1194 args: &'tcx [hir::Expr<'tcx>],
1195 expected: Expectation<'tcx>,
1197 let rcvr = &args[0];
1198 let rcvr_t = self.check_expr(&rcvr);
1199 // no need to check for bot/err -- callee does that
1200 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
1201 let span = segment.ident.span;
1203 let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1205 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1206 // trigger this codepath causing `structurally_resolved_type` to emit an error.
1208 self.write_method_call(expr.hir_id, method);
1212 if segment.ident.name != kw::Empty {
1213 if let Some(mut err) = self.report_method_error(
1217 SelfSource::MethodCall(&args[0]),
1228 // Call the generic checker.
1229 self.check_method_argument_types(
1241 e: &'tcx hir::Expr<'tcx>,
1242 t: &'tcx hir::Ty<'tcx>,
1243 expr: &'tcx hir::Expr<'tcx>,
1245 // Find the type of `e`. Supply hints based on the type we are casting to,
1247 let t_cast = self.to_ty_saving_user_provided_ty(t);
1248 let t_cast = self.resolve_vars_if_possible(t_cast);
1249 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1250 let t_expr = self.resolve_vars_if_possible(t_expr);
1252 // Eagerly check for some obvious errors.
1253 if t_expr.references_error() || t_cast.references_error() {
1256 // Defer other checks until we're done type checking.
1257 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1258 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1261 "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1262 t_cast, t_expr, cast_check,
1264 deferred_cast_checks.push(cast_check);
1267 Err(_) => self.tcx.ty_error(),
1272 fn check_expr_array(
1274 args: &'tcx [hir::Expr<'tcx>],
1275 expected: Expectation<'tcx>,
1276 expr: &'tcx hir::Expr<'tcx>,
1278 let element_ty = if !args.is_empty() {
1279 let coerce_to = expected
1281 .and_then(|uty| match *uty.kind() {
1282 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1285 .unwrap_or_else(|| {
1286 self.next_ty_var(TypeVariableOrigin {
1287 kind: TypeVariableOriginKind::TypeInference,
1291 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1292 assert_eq!(self.diverges.get(), Diverges::Maybe);
1294 let e_ty = self.check_expr_with_hint(e, coerce_to);
1295 let cause = self.misc(e.span);
1296 coerce.coerce(self, &cause, e, e_ty);
1298 coerce.complete(self)
1300 self.next_ty_var(TypeVariableOrigin {
1301 kind: TypeVariableOriginKind::TypeInference,
1305 self.tcx.mk_array(element_ty, args.len() as u64)
1308 fn check_expr_const_block(
1310 anon_const: &'tcx hir::AnonConst,
1311 expected: Expectation<'tcx>,
1312 _expr: &'tcx hir::Expr<'tcx>,
1314 let body = self.tcx.hir().body(anon_const.body);
1316 // Create a new function context.
1317 let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1318 crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1320 let ty = fcx.check_expr_with_expectation(&body.value, expected);
1321 fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1322 fcx.write_ty(anon_const.hir_id, ty);
1326 fn check_expr_repeat(
1328 element: &'tcx hir::Expr<'tcx>,
1329 count: &'tcx hir::ArrayLen,
1330 expected: Expectation<'tcx>,
1331 _expr: &'tcx hir::Expr<'tcx>,
1334 let count = self.array_length_to_const(count);
1336 let uty = match expected {
1337 ExpectHasType(uty) => match *uty.kind() {
1338 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1344 let (element_ty, t) = match uty {
1346 self.check_expr_coercable_to_type(&element, uty, None);
1350 let ty = self.next_ty_var(TypeVariableOrigin {
1351 kind: TypeVariableOriginKind::MiscVariable,
1354 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1359 if element_ty.references_error() {
1360 return tcx.ty_error();
1363 self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1365 tcx.mk_ty(ty::Array(t, count))
1368 fn check_repeat_element_needs_copy_bound(
1370 element: &hir::Expr<'_>,
1371 count: ty::Const<'tcx>,
1372 element_ty: Ty<'tcx>,
1375 // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1376 match &element.kind {
1377 hir::ExprKind::ConstBlock(..) => return,
1378 hir::ExprKind::Path(qpath) => {
1379 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1380 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1387 // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1388 // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1389 let is_const_fn = match element.kind {
1390 hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1391 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1397 // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1398 // don't copy that one element, we move it. Only check for Copy if the length is larger.
1399 if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1400 let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1401 let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1402 self.require_type_meets(element_ty, element.span, code, lang_item);
1406 fn check_expr_tuple(
1408 elts: &'tcx [hir::Expr<'tcx>],
1409 expected: Expectation<'tcx>,
1410 expr: &'tcx hir::Expr<'tcx>,
1412 let flds = expected.only_has_type(self).and_then(|ty| {
1413 let ty = self.resolve_vars_with_obligations(ty);
1415 ty::Tuple(flds) => Some(&flds[..]),
1420 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1421 Some(fs) if i < fs.len() => {
1423 self.check_expr_coercable_to_type(&e, ety, None);
1426 _ => self.check_expr_with_expectation(&e, NoExpectation),
1428 let tuple = self.tcx.mk_tup(elt_ts_iter);
1429 if tuple.references_error() {
1432 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1437 fn check_expr_struct(
1439 expr: &hir::Expr<'_>,
1440 expected: Expectation<'tcx>,
1442 fields: &'tcx [hir::ExprField<'tcx>],
1443 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1445 // Find the relevant variant
1446 let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1447 self.check_struct_fields_on_error(fields, base_expr);
1448 return self.tcx.ty_error();
1451 // Prohibit struct expressions when non-exhaustive flag is set.
1452 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1453 if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1456 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1459 self.check_expr_struct_fields(
1470 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1474 fn check_expr_struct_fields(
1477 expected: Expectation<'tcx>,
1478 expr_id: hir::HirId,
1480 variant: &'tcx ty::VariantDef,
1481 ast_fields: &'tcx [hir::ExprField<'tcx>],
1482 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1487 let expected_inputs =
1488 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1489 let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1490 expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1494 // re-link the regions that EIfEO can erase.
1495 self.demand_eqtype(span, adt_ty_hint, adt_ty);
1497 let ty::Adt(adt, substs) = adt_ty.kind() else {
1498 span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1500 let adt_kind = adt.adt_kind();
1502 let mut remaining_fields = variant
1506 .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1507 .collect::<FxHashMap<_, _>>();
1509 let mut seen_fields = FxHashMap::default();
1511 let mut error_happened = false;
1513 // Type-check each field.
1514 for field in ast_fields {
1515 let ident = tcx.adjust_ident(field.ident, variant.def_id);
1516 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1517 seen_fields.insert(ident, field.span);
1518 self.write_field_index(field.hir_id, i);
1520 // We don't look at stability attributes on
1521 // struct-like enums (yet...), but it's definitely not
1522 // a bug to have constructed one.
1523 if adt_kind != AdtKind::Enum {
1524 tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1527 self.field_ty(field.span, v_field, substs)
1529 error_happened = true;
1530 if let Some(prev_span) = seen_fields.get(&ident) {
1531 tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1532 span: field.ident.span,
1533 prev_span: *prev_span,
1537 self.report_unknown_field(
1542 adt.variant_descr(),
1550 // Make sure to give a type to the field even if there's
1551 // an error, so we can continue type-checking.
1552 self.check_expr_coercable_to_type(&field.expr, field_type, None);
1555 // Make sure the programmer specified correct number of fields.
1556 if adt_kind == AdtKind::Union {
1557 if ast_fields.len() != 1 {
1562 "union expressions should have exactly one field",
1568 // If check_expr_struct_fields hit an error, do not attempt to populate
1569 // the fields with the base_expr. This could cause us to hit errors later
1570 // when certain fields are assumed to exist that in fact do not.
1575 if let Some(base_expr) = base_expr {
1576 // FIXME: We are currently creating two branches here in order to maintain
1577 // consistency. But they should be merged as much as possible.
1578 let fru_tys = if self.tcx.features().type_changing_struct_update {
1579 if adt.is_struct() {
1580 // Make some fresh substitutions for our ADT type.
1581 let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1582 // We do subtyping on the FRU fields first, so we can
1583 // learn exactly what types we expect the base expr
1584 // needs constrained to be compatible with the struct
1585 // type we expect from the expectation value.
1586 let fru_tys = variant
1590 let fru_ty = self.normalize_associated_types_in(
1592 self.field_ty(base_expr.span, f, fresh_substs),
1594 let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1595 if let Some(_) = remaining_fields.remove(&ident) {
1596 let target_ty = self.field_ty(base_expr.span, f, substs);
1597 let cause = self.misc(base_expr.span);
1598 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1599 Ok(InferOk { obligations, value: () }) => {
1600 self.register_predicates(obligations)
1603 // This should never happen, since we're just subtyping the
1604 // remaining_fields, but it's fine to emit this, I guess.
1605 self.report_mismatched_types(
1609 FieldMisMatch(variant.name, ident.name),
1615 self.resolve_vars_if_possible(fru_ty)
1618 // The use of fresh substs that we have subtyped against
1619 // our base ADT type's fields allows us to guide inference
1620 // along so that, e.g.
1622 // MyStruct<'a, F1, F2, const C: usize> {
1624 // // Other fields that reference `'a`, `F2`, and `C`
1627 // let x = MyStruct {
1632 // will have the `other_struct` expression constrained to
1633 // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1634 // This is important to allow coercions to happen in
1635 // `other_struct` itself. See `coerce-in-base-expr.rs`.
1636 let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1637 self.check_expr_has_type_or_error(
1639 self.resolve_vars_if_possible(fresh_base_ty),
1644 // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1645 // type errors on that expression, too.
1646 self.check_expr(base_expr);
1649 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1653 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1654 let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1655 let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1656 (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1659 if self.tcx.sess.is_nightly_build() && same_adt {
1661 &self.tcx.sess.parse_sess,
1662 sym::type_changing_struct_update,
1664 "type changing struct updating is experimental",
1669 match adt_ty.kind() {
1670 ty::Adt(adt, substs) if adt.is_struct() => variant
1674 self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1680 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1685 self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1686 } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1687 debug!(?remaining_fields);
1688 let private_fields: Vec<&ty::FieldDef> = variant
1692 !field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1696 if !private_fields.is_empty() {
1697 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1699 self.report_missing_fields(
1711 fn check_struct_fields_on_error(
1713 fields: &'tcx [hir::ExprField<'tcx>],
1714 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1716 for field in fields {
1717 self.check_expr(&field.expr);
1719 if let Some(base) = *base_expr {
1720 self.check_expr(&base);
1724 /// Report an error for a struct field expression when there are fields which aren't provided.
1727 /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1728 /// --> src/main.rs:8:5
1730 /// 8 | foo::Foo {};
1731 /// | ^^^^^^^^ missing `you_can_use_this_field`
1733 /// error: aborting due to previous error
1735 fn report_missing_fields(
1739 remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1740 variant: &'tcx ty::VariantDef,
1741 ast_fields: &'tcx [hir::ExprField<'tcx>],
1742 substs: SubstsRef<'tcx>,
1744 let len = remaining_fields.len();
1746 let mut displayable_field_names: Vec<&str> =
1747 remaining_fields.keys().map(|ident| ident.as_str()).collect();
1748 // sorting &str primitives here, sort_unstable is ok
1749 displayable_field_names.sort_unstable();
1751 let mut truncated_fields_error = String::new();
1752 let remaining_fields_names = match &displayable_field_names[..] {
1753 [field1] => format!("`{}`", field1),
1754 [field1, field2] => format!("`{field1}` and `{field2}`"),
1755 [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1757 truncated_fields_error =
1758 format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1759 displayable_field_names
1762 .map(|n| format!("`{n}`"))
1763 .collect::<Vec<_>>()
1768 let mut err = struct_span_err!(
1772 "missing field{} {}{} in initializer of `{}`",
1774 remaining_fields_names,
1775 truncated_fields_error,
1778 err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1780 // If the last field is a range literal, but it isn't supposed to be, then they probably
1781 // meant to use functional update syntax.
1783 // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1787 QPath::LangItem(LangItem::Range, ..),
1788 &[ref range_start, ref range_end],
1791 )) = ast_fields.last().map(|last| (last, &last.expr.kind)) &&
1793 variant.fields.iter().find(|field| field.ident(self.tcx) == last.ident) &&
1794 let range_def_id = self.tcx.lang_items().range_struct() &&
1796 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1797 .map(|adt| adt.did())
1804 .span_to_snippet(range_end.expr.span)
1805 .map(|s| format!(" from `{s}`"))
1806 .unwrap_or_default();
1807 err.span_suggestion(
1808 range_start.span.shrink_to_hi(),
1809 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1811 Applicability::MaybeIncorrect,
1818 /// Report an error for a struct field expression when there are invisible fields.
1821 /// error: cannot construct `Foo` with struct literal syntax due to private fields
1822 /// --> src/main.rs:8:5
1824 /// 8 | foo::Foo {};
1827 /// error: aborting due to previous error
1829 fn report_private_fields(
1833 private_fields: Vec<&ty::FieldDef>,
1834 used_fields: &'tcx [hir::ExprField<'tcx>],
1836 let mut err = self.tcx.sess.struct_span_err(
1839 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1842 let (used_private_fields, remaining_private_fields): (
1843 Vec<(Symbol, Span, bool)>,
1844 Vec<(Symbol, Span, bool)>,
1848 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1849 Some(used_field) => (field.name, used_field.span, true),
1850 None => (field.name, self.tcx.def_span(field.did), false),
1853 .partition(|field| field.2);
1854 err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1855 if !remaining_private_fields.is_empty() {
1856 let remaining_private_fields_len = remaining_private_fields.len();
1857 let names = match &remaining_private_fields
1859 .map(|(name, _, _)| name)
1860 .collect::<Vec<_>>()[..]
1862 _ if remaining_private_fields_len > 6 => String::new(),
1863 [name] => format!("`{name}` "),
1864 [names @ .., last] => {
1865 let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1866 format!("{} and `{last}` ", names.join(", "))
1868 [] => unreachable!(),
1871 "... and other private field{s} {names}that {were} not provided",
1872 s = pluralize!(remaining_private_fields_len),
1873 were = pluralize!("was", remaining_private_fields_len),
1879 fn report_unknown_field(
1882 variant: &'tcx ty::VariantDef,
1883 field: &hir::ExprField<'_>,
1884 skip_fields: &[hir::ExprField<'_>],
1888 if variant.is_recovered() {
1889 self.set_tainted_by_errors();
1892 let mut err = self.type_error_struct_with_diag(
1894 |actual| match ty.kind() {
1895 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1899 "{} `{}::{}` has no field named `{}`",
1905 _ => struct_span_err!(
1909 "{} `{}` has no field named `{}`",
1918 let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1919 match variant.ctor_kind {
1920 CtorKind::Fn => match ty.kind() {
1921 ty::Adt(adt, ..) if adt.is_enum() => {
1925 "`{adt}::{variant}` defined here",
1927 variant = variant.name,
1930 err.span_label(field.ident.span, "field does not exist");
1931 err.span_suggestion_verbose(
1934 "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1936 variant = variant.name,
1939 "{adt}::{variant}(/* fields */)",
1941 variant = variant.name,
1943 Applicability::HasPlaceholders,
1947 err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1948 err.span_label(field.ident.span, "field does not exist");
1949 err.span_suggestion_verbose(
1952 "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1954 kind_name = kind_name,
1956 format!("{adt}(/* fields */)", adt = ty),
1957 Applicability::HasPlaceholders,
1962 // prevent all specified fields from being suggested
1963 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
1964 if let Some(field_name) = self.suggest_field_name(
1967 skip_fields.collect(),
1970 err.span_suggestion(
1972 "a field with a similar name exists",
1974 Applicability::MaybeIncorrect,
1978 ty::Adt(adt, ..) => {
1982 format!("`{}::{}` does not have this field", ty, variant.name),
1987 format!("`{ty}` does not have this field"),
1990 let available_field_names =
1991 self.available_field_names(variant, expr_span);
1992 if !available_field_names.is_empty() {
1994 "available fields are: {}",
1995 self.name_series_display(available_field_names)
1999 _ => bug!("non-ADT passed to report_unknown_field"),
2007 // Return a hint about the closest match in field names
2008 fn suggest_field_name(
2010 variant: &'tcx ty::VariantDef,
2013 // The span where stability will be checked
2015 ) -> Option<Symbol> {
2019 .filter_map(|field| {
2020 // ignore already set fields and private fields from non-local crates
2021 // and unstable fields.
2022 if skip.iter().any(|&x| x == field.name)
2023 || (!variant.def_id.is_local() && !field.vis.is_public())
2025 self.tcx.eval_stability(field.did, None, span, None),
2026 stability::EvalResult::Deny { .. }
2034 .collect::<Vec<Symbol>>();
2036 find_best_match_for_name(&names, field, None)
2039 fn available_field_names(
2041 variant: &'tcx ty::VariantDef,
2048 let def_scope = self
2050 .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2052 field.vis.is_accessible_from(def_scope, self.tcx)
2054 self.tcx.eval_stability(field.did, None, access_span, None),
2055 stability::EvalResult::Deny { .. }
2058 .filter(|field| !self.tcx.is_doc_hidden(field.did))
2059 .map(|field| field.name)
2063 fn name_series_display(&self, names: Vec<Symbol>) -> String {
2064 // dynamic limit, to never omit just one field
2065 let limit = if names.len() == 6 { 6 } else { 5 };
2067 names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2068 if names.len() > limit {
2069 display = format!("{} ... and {} others", display, names.len() - limit);
2074 // Check field access expressions
2077 expr: &'tcx hir::Expr<'tcx>,
2078 base: &'tcx hir::Expr<'tcx>,
2081 debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2082 let expr_t = self.check_expr(base);
2083 let expr_t = self.structurally_resolved_type(base.span, expr_t);
2084 let mut private_candidate = None;
2085 let mut autoderef = self.autoderef(expr.span, expr_t);
2086 while let Some((base_t, _)) = autoderef.next() {
2087 debug!("base_t: {:?}", base_t);
2088 match base_t.kind() {
2089 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2090 debug!("struct named {:?}", base_t);
2091 let (ident, def_scope) =
2092 self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2093 let fields = &base_def.non_enum_variant().fields;
2094 if let Some(index) = fields
2096 .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2098 let field = &fields[index];
2099 let field_ty = self.field_ty(expr.span, field, substs);
2100 // Save the index of all fields regardless of their visibility in case
2101 // of error recovery.
2102 self.write_field_index(expr.hir_id, index);
2103 let adjustments = self.adjust_steps(&autoderef);
2104 if field.vis.is_accessible_from(def_scope, self.tcx) {
2105 self.apply_adjustments(base, adjustments);
2106 self.register_predicates(autoderef.into_obligations());
2108 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2111 private_candidate = Some((adjustments, base_def.did(), field_ty));
2115 let fstr = field.as_str();
2116 if let Ok(index) = fstr.parse::<usize>() {
2117 if fstr == index.to_string() {
2118 if let Some(&field_ty) = tys.get(index) {
2119 let adjustments = self.adjust_steps(&autoderef);
2120 self.apply_adjustments(base, adjustments);
2121 self.register_predicates(autoderef.into_obligations());
2123 self.write_field_index(expr.hir_id, index);
2132 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2134 if let Some((adjustments, did, field_ty)) = private_candidate {
2135 // (#90483) apply adjustments to avoid ExprUseVisitor from
2136 // creating erroneous projection.
2137 self.apply_adjustments(base, adjustments);
2138 self.ban_private_field_access(expr, expr_t, field, did);
2142 if field.name == kw::Empty {
2143 } else if self.method_exists(field, expr_t, expr.hir_id, true) {
2144 self.ban_take_value_of_method(expr, expr_t, field);
2145 } else if !expr_t.is_primitive_ty() {
2146 self.ban_nonexisting_field(field, base, expr, expr_t);
2148 let field_name = field.to_string();
2149 let mut err = type_error_struct!(
2154 "`{expr_t}` is a primitive type and therefore doesn't have fields",
2156 let is_valid_suffix = |field: String| {
2157 if field == "f32" || field == "f64" {
2160 let mut chars = field.chars().peekable();
2161 match chars.peek() {
2162 Some('e') | Some('E') => {
2164 if let Some(c) = chars.peek()
2165 && !c.is_numeric() && *c != '-' && *c != '+'
2169 while let Some(c) = chars.peek() {
2170 if !c.is_numeric() {
2178 let suffix = chars.collect::<String>();
2179 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2181 if let ty::Infer(ty::IntVar(_)) = expr_t.kind()
2182 && let ExprKind::Lit(Spanned {
2183 node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2186 && !base.span.from_expansion()
2187 && is_valid_suffix(field_name)
2189 err.span_suggestion_verbose(
2190 field.span.shrink_to_lo(),
2191 "If the number is meant to be a floating point number, consider adding a `0` after the period",
2193 Applicability::MaybeIncorrect,
2199 self.tcx().ty_error()
2202 fn check_call_constructor<G: EmissionGuarantee>(
2204 err: &mut DiagnosticBuilder<'_, G>,
2205 base: &'tcx hir::Expr<'tcx>,
2208 if let Some(local_id) = def_id.as_local() {
2209 let hir_id = self.tcx.hir().local_def_id_to_hir_id(local_id);
2210 let node = self.tcx.hir().get(hir_id);
2212 if let Some(fields) = node.tuple_fields() {
2213 let kind = match self.tcx.opt_def_kind(local_id) {
2214 Some(DefKind::Ctor(of, _)) => of,
2218 suggest_call_constructor(base.span, kind, fields.len(), err);
2221 // The logic here isn't smart but `associated_item_def_ids`
2222 // doesn't work nicely on local.
2223 if let DefKind::Ctor(of, _) = self.tcx.def_kind(def_id) {
2224 let parent_def_id = self.tcx.parent(def_id);
2225 let fields = self.tcx.associated_item_def_ids(parent_def_id);
2226 suggest_call_constructor(base.span, of, fields.len(), err);
2231 fn suggest_await_on_field_access(
2233 err: &mut Diagnostic,
2235 base: &'tcx hir::Expr<'tcx>,
2238 let output_ty = match self.get_impl_future_output_ty(ty) {
2239 Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2242 let mut add_label = true;
2243 if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2244 // no field access on enum type
2250 .any(|field| field.ident(self.tcx) == field_ident)
2255 "field not available in `impl Future`, but it is available in its `Output`",
2257 err.span_suggestion_verbose(
2258 base.span.shrink_to_hi(),
2259 "consider `await`ing on the `Future` and access the field of its `Output`",
2261 Applicability::MaybeIncorrect,
2267 err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2271 fn ban_nonexisting_field(
2274 base: &'tcx hir::Expr<'tcx>,
2275 expr: &'tcx hir::Expr<'tcx>,
2279 "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
2280 field, base, expr, expr_t
2282 let mut err = self.no_such_field_err(field, expr_t, base.hir_id);
2284 match *expr_t.peel_refs().kind() {
2285 ty::Array(_, len) => {
2286 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
2289 self.suggest_first_deref_field(&mut err, expr, base, field);
2291 ty::Adt(def, _) if !def.is_enum() => {
2292 self.suggest_fields_on_recordish(&mut err, def, field, expr.span);
2294 ty::Param(param_ty) => {
2295 self.point_at_param_definition(&mut err, param_ty);
2297 ty::Opaque(_, _) => {
2298 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
2300 ty::FnDef(def_id, _) => {
2301 self.check_call_constructor(&mut err, base, def_id);
2306 if field.name == kw::Await {
2307 // We know by construction that `<expr>.await` is either on Rust 2015
2308 // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2309 err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2310 err.help_use_latest_edition();
2316 fn ban_private_field_access(
2318 expr: &hir::Expr<'_>,
2323 let struct_path = self.tcx().def_path_str(base_did);
2324 let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2325 let mut err = struct_span_err!(
2329 "field `{field}` of {kind_name} `{struct_path}` is private",
2331 err.span_label(field.span, "private field");
2332 // Also check if an accessible method exists, which is often what is meant.
2333 if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2335 self.suggest_method_call(
2337 &format!("a method `{field}` also exists, call it with parentheses"),
2347 fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2348 let mut err = type_error_struct!(
2353 "attempted to take value of method `{field}` on type `{expr_t}`",
2355 err.span_label(field.span, "method, not a field");
2357 if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2358 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2360 expr.hir_id == callee.hir_id
2365 self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2366 let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2367 let after_open = expr.span.lo() + rustc_span::BytePos(1);
2368 let before_close = expr.span.hi() - rustc_span::BytePos(1);
2370 if expr_is_call && is_wrapped {
2371 err.multipart_suggestion(
2372 "remove wrapping parentheses to call the method",
2374 (expr.span.with_hi(after_open), String::new()),
2375 (expr.span.with_lo(before_close), String::new()),
2377 Applicability::MachineApplicable,
2379 } else if !self.expr_in_place(expr.hir_id) {
2380 // Suggest call parentheses inside the wrapping parentheses
2381 let span = if is_wrapped {
2382 expr.span.with_lo(after_open).with_hi(before_close)
2386 self.suggest_method_call(
2388 "use parentheses to call the method",
2395 let mut found = false;
2397 if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2398 && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2400 if adt_def.variants().len() == 1
2408 .any(|f| f.ident(self.tcx) == field)
2410 if let Some(dot_loc) = expr_snippet.rfind('.') {
2412 err.span_suggestion(
2413 expr.span.with_hi(expr.span.lo() + BytePos::from_usize(dot_loc)),
2414 "to access the field, dereference first",
2415 format!("(*{})", &expr_snippet[0..dot_loc]),
2416 Applicability::MaybeIncorrect,
2423 err.help("methods are immutable and cannot be assigned to");
2430 fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2431 let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2432 let generic_param = generics.type_param(¶m, self.tcx);
2433 if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2436 let param_def_id = generic_param.def_id;
2437 let param_hir_id = match param_def_id.as_local() {
2438 Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2441 let param_span = self.tcx.hir().span(param_hir_id);
2442 let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2444 err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2447 fn suggest_fields_on_recordish(
2449 err: &mut Diagnostic,
2450 def: ty::AdtDef<'tcx>,
2454 if let Some(suggested_field_name) =
2455 self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2457 err.span_suggestion(
2459 "a field with a similar name exists",
2460 suggested_field_name,
2461 Applicability::MaybeIncorrect,
2464 err.span_label(field.span, "unknown field");
2465 let struct_variant_def = def.non_enum_variant();
2466 let field_names = self.available_field_names(struct_variant_def, access_span);
2467 if !field_names.is_empty() {
2469 "available fields are: {}",
2470 self.name_series_display(field_names),
2476 fn maybe_suggest_array_indexing(
2478 err: &mut Diagnostic,
2479 expr: &hir::Expr<'_>,
2480 base: &hir::Expr<'_>,
2482 len: ty::Const<'tcx>,
2484 if let (Some(len), Ok(user_index)) =
2485 (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2486 && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2488 let help = "instead of using tuple indexing, use array indexing";
2489 let suggestion = format!("{base}[{field}]");
2490 let applicability = if len < user_index {
2491 Applicability::MachineApplicable
2493 Applicability::MaybeIncorrect
2495 err.span_suggestion(expr.span, help, suggestion, applicability);
2499 fn suggest_first_deref_field(
2501 err: &mut Diagnostic,
2502 expr: &hir::Expr<'_>,
2503 base: &hir::Expr<'_>,
2506 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2507 let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2508 let suggestion = format!("(*{base}).{field}");
2509 err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2513 fn no_such_field_err(
2518 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2519 let span = field.span;
2520 debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2522 let mut err = type_error_struct!(
2527 "no field `{field}` on type `{expr_t}`",
2530 // try to add a suggestion in case the field is a nested field of a field of the Adt
2531 if let Some((fields, substs)) = self.get_field_candidates(span, expr_t) {
2532 for candidate_field in fields.iter() {
2533 if let Some(mut field_path) = self.check_for_nested_field_satisfying(
2535 &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2539 self.tcx.parent_module(id).to_def_id(),
2541 // field_path includes `field` that we're looking for, so pop it.
2544 let field_path_str = field_path
2546 .map(|id| id.name.to_ident_string())
2547 .collect::<Vec<String>>()
2549 debug!("field_path_str: {:?}", field_path_str);
2551 err.span_suggestion_verbose(
2552 field.span.shrink_to_lo(),
2553 "one of the expressions' fields has a field of the same name",
2554 format!("{field_path_str}."),
2555 Applicability::MaybeIncorrect,
2563 pub(crate) fn get_field_candidates(
2567 ) -> Option<(&[ty::FieldDef], SubstsRef<'tcx>)> {
2568 debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_t);
2570 for (base_t, _) in self.autoderef(span, base_t) {
2571 match base_t.kind() {
2572 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2573 let fields = &base_def.non_enum_variant().fields;
2574 // For compile-time reasons put a limit on number of fields we search
2575 if fields.len() > 100 {
2578 return Some((fields, substs));
2586 /// This method is called after we have encountered a missing field error to recursively
2587 /// search for the field
2588 pub(crate) fn check_for_nested_field_satisfying(
2591 matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2592 candidate_field: &ty::FieldDef,
2593 subst: SubstsRef<'tcx>,
2594 mut field_path: Vec<Ident>,
2596 ) -> Option<Vec<Ident>> {
2598 "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2599 span, candidate_field, field_path
2602 if field_path.len() > 3 {
2603 // For compile-time reasons and to avoid infinite recursion we only check for fields
2604 // up to a depth of three
2607 // recursively search fields of `candidate_field` if it's a ty::Adt
2608 field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2609 let field_ty = candidate_field.ty(self.tcx, subst);
2610 if let Some((nested_fields, subst)) = self.get_field_candidates(span, field_ty) {
2611 for field in nested_fields.iter() {
2612 if field.vis.is_accessible_from(id, self.tcx) {
2613 if matches(candidate_field, field_ty) {
2614 return Some(field_path);
2615 } else if let Some(field_path) = self.check_for_nested_field_satisfying(
2623 return Some(field_path);
2632 fn check_expr_index(
2634 base: &'tcx hir::Expr<'tcx>,
2635 idx: &'tcx hir::Expr<'tcx>,
2636 expr: &'tcx hir::Expr<'tcx>,
2638 let base_t = self.check_expr(&base);
2639 let idx_t = self.check_expr(&idx);
2641 if base_t.references_error() {
2643 } else if idx_t.references_error() {
2646 let base_t = self.structurally_resolved_type(base.span, base_t);
2647 match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2648 Some((index_ty, element_ty)) => {
2649 // two-phase not needed because index_ty is never mutable
2650 self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2651 self.select_obligations_where_possible(false, |errors| {
2652 self.point_at_index_if_possible(errors, idx.span)
2657 let mut err = type_error_struct!(
2662 "cannot index into a value of type `{base_t}`",
2664 // Try to give some advice about indexing tuples.
2665 if let ty::Tuple(..) = base_t.kind() {
2666 let mut needs_note = true;
2667 // If the index is an integer, we can show the actual
2668 // fixed expression:
2669 if let ExprKind::Lit(ref lit) = idx.kind {
2670 if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2671 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2672 if let Ok(snip) = snip {
2673 err.span_suggestion(
2675 "to access tuple elements, use",
2676 format!("{snip}.{i}"),
2677 Applicability::MachineApplicable,
2685 "to access tuple elements, use tuple indexing \
2686 syntax (e.g., `tuple.0`)",
2697 fn point_at_index_if_possible(
2699 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2702 for error in errors {
2703 match error.obligation.predicate.kind().skip_binder() {
2704 ty::PredicateKind::Trait(predicate)
2705 if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2709 error.obligation.cause.span = span;
2713 fn check_expr_yield(
2715 value: &'tcx hir::Expr<'tcx>,
2716 expr: &'tcx hir::Expr<'tcx>,
2717 src: &'tcx hir::YieldSource,
2719 match self.resume_yield_tys {
2720 Some((resume_ty, yield_ty)) => {
2721 self.check_expr_coercable_to_type(&value, yield_ty, None);
2725 // Given that this `yield` expression was generated as a result of lowering a `.await`,
2726 // we know that the yield type must be `()`; however, the context won't contain this
2727 // information. Hence, we check the source of the yield expression here and check its
2728 // value's type against `()` (this check should always hold).
2729 None if src.is_await() => {
2730 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2734 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2735 // Avoid expressions without types during writeback (#78653).
2736 self.check_expr(value);
2742 fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2743 let needs = if is_input { Needs::None } else { Needs::MutPlace };
2744 let ty = self.check_expr_with_needs(expr, needs);
2745 self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2747 if !is_input && !expr.is_syntactic_place_expr() {
2748 let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2749 err.span_label(expr.span, "cannot assign to this expression");
2753 // If this is an input value, we require its type to be fully resolved
2754 // at this point. This allows us to provide helpful coercions which help
2755 // pass the type candidate list in a later pass.
2757 // We don't require output types to be resolved at this point, which
2758 // allows them to be inferred based on how they are used later in the
2761 let ty = self.structurally_resolved_type(expr.span, ty);
2764 let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2765 self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2767 ty::Ref(_, base_ty, mutbl) => {
2768 let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2769 self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2776 fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2777 for (op, _op_sp) in asm.operands {
2779 hir::InlineAsmOperand::In { expr, .. } => {
2780 self.check_expr_asm_operand(expr, true);
2782 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2783 | hir::InlineAsmOperand::InOut { expr, .. } => {
2784 self.check_expr_asm_operand(expr, false);
2786 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2787 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2788 self.check_expr_asm_operand(in_expr, true);
2789 if let Some(out_expr) = out_expr {
2790 self.check_expr_asm_operand(out_expr, false);
2793 // `AnonConst`s have their own body and is type-checked separately.
2794 // As they don't flow into the type system we don't need them to
2796 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2797 hir::InlineAsmOperand::SymStatic { .. } => {}
2800 if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2801 self.tcx.types.never
2808 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2809 Some(match ty.kind() {
2812 ty::Int(_) | ty::Uint(_) => "42",
2813 ty::Float(_) => "3.14159",
2814 ty::Error(_) | ty::Never => return None,