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,
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_target::spec::abi::Abi::RustIntrinsic;
54 use rustc_trait_selection::infer::InferCtxtExt;
55 use rustc_trait_selection::traits::{self, ObligationCauseCode};
57 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
58 fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
59 let ty = self.check_expr_with_hint(expr, expected);
60 self.demand_eqtype(expr.span, expected, ty);
63 pub fn check_expr_has_type_or_error(
65 expr: &'tcx hir::Expr<'tcx>,
67 extend_err: impl FnMut(&mut Diagnostic),
69 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
72 fn check_expr_meets_expectation_or_error(
74 expr: &'tcx hir::Expr<'tcx>,
75 expected: Expectation<'tcx>,
76 mut extend_err: impl FnMut(&mut Diagnostic),
78 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
79 let mut ty = self.check_expr_with_expectation(expr, expected);
81 // While we don't allow *arbitrary* coercions here, we *do* allow
82 // coercions from ! to `expected`.
84 if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
85 self.tcx().sess.delay_span_bug(
87 "expression with never type wound up being adjusted",
89 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
96 let adj_ty = self.next_ty_var(TypeVariableOrigin {
97 kind: TypeVariableOriginKind::AdjustmentType,
100 self.apply_adjustments(
102 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
107 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
108 let expr = expr.peel_drop_temps();
109 self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
110 extend_err(&mut err);
116 pub(super) fn check_expr_coercable_to_type(
118 expr: &'tcx hir::Expr<'tcx>,
120 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
122 let ty = self.check_expr_with_hint(expr, expected);
123 // checks don't need two phase
124 self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
127 pub(super) fn check_expr_with_hint(
129 expr: &'tcx hir::Expr<'tcx>,
132 self.check_expr_with_expectation(expr, ExpectHasType(expected))
135 fn check_expr_with_expectation_and_needs(
137 expr: &'tcx hir::Expr<'tcx>,
138 expected: Expectation<'tcx>,
141 let ty = self.check_expr_with_expectation(expr, expected);
143 // If the expression is used in a place whether mutable place is required
144 // e.g. LHS of assignment, perform the conversion.
145 if let Needs::MutPlace = needs {
146 self.convert_place_derefs_to_mutable(expr);
152 pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
153 self.check_expr_with_expectation(expr, NoExpectation)
156 pub(super) fn check_expr_with_needs(
158 expr: &'tcx hir::Expr<'tcx>,
161 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
165 /// If an expression has any sub-expressions that result in a type error,
166 /// inspecting that expression's type with `ty.references_error()` will return
167 /// true. Likewise, if an expression is known to diverge, inspecting its
168 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
169 /// strict, _|_ can appear in the type of an expression that does not,
170 /// itself, diverge: for example, fn() -> _|_.)
171 /// Note that inspecting a type's structure *directly* may expose the fact
172 /// that there are actually multiple representations for `Error`, so avoid
173 /// that when err needs to be handled differently.
174 #[instrument(skip(self, expr), level = "debug")]
175 pub(super) fn check_expr_with_expectation(
177 expr: &'tcx hir::Expr<'tcx>,
178 expected: Expectation<'tcx>,
180 self.check_expr_with_expectation_and_args(expr, expected, &[])
183 /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
184 /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
185 pub(super) fn check_expr_with_expectation_and_args(
187 expr: &'tcx hir::Expr<'tcx>,
188 expected: Expectation<'tcx>,
189 args: &'tcx [hir::Expr<'tcx>],
191 if self.tcx().sess.verbose() {
192 // make this code only run with -Zverbose because it is probably slow
193 if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
194 if !lint_str.contains('\n') {
195 debug!("expr text: {lint_str}");
197 let mut lines = lint_str.lines();
198 if let Some(line0) = lines.next() {
199 let remaining_lines = lines.count();
200 debug!("expr text: {line0}");
201 debug!("expr text: ...(and {remaining_lines} more lines)");
207 // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
208 // without the final expr (e.g. `try { return; }`). We don't want to generate an
209 // unreachable_code lint for it since warnings for autogenerated code are confusing.
210 let is_try_block_generated_unit_expr = match expr.kind {
211 ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
212 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
218 // Warn for expressions after diverging siblings.
219 if !is_try_block_generated_unit_expr {
220 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
223 // Hide the outer diverging and has_errors flags.
224 let old_diverges = self.diverges.replace(Diverges::Maybe);
225 let old_has_errors = self.has_errors.replace(false);
227 let ty = ensure_sufficient_stack(|| match &expr.kind {
229 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
230 ) => self.check_expr_path(qpath, expr, args),
231 _ => self.check_expr_kind(expr, expected),
234 // Warn for non-block expressions with diverging children.
240 | ExprKind::Match(..) => {}
241 // If `expr` is a result of desugaring the try block and is an ok-wrapped
242 // diverging expression (e.g. it arose from desugaring of `try { return }`),
243 // we skip issuing a warning because it is autogenerated code.
244 ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
245 ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
246 ExprKind::MethodCall(segment, ..) => {
247 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
249 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
252 // Any expression that produces a value of type `!` must have diverged
254 self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
257 // Record the type, which applies it effects.
258 // We need to do this after the warning above, so that
259 // we don't warn for the diverging expression itself.
260 self.write_ty(expr.hir_id, ty);
262 // Combine the diverging and has_error flags.
263 self.diverges.set(self.diverges.get() | old_diverges);
264 self.has_errors.set(self.has_errors.get() | old_has_errors);
266 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
267 debug!("... {:?}, expected is {:?}", ty, expected);
272 #[instrument(skip(self, expr), level = "debug")]
275 expr: &'tcx hir::Expr<'tcx>,
276 expected: Expectation<'tcx>,
278 trace!("expr={:#?}", expr);
282 ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
283 ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
284 ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
285 ExprKind::Assign(lhs, rhs, span) => {
286 self.check_expr_assign(expr, expected, lhs, rhs, span)
288 ExprKind::AssignOp(op, lhs, rhs) => {
289 self.check_binop_assign(expr, op, lhs, rhs, expected)
291 ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
292 ExprKind::AddrOf(kind, mutbl, oprnd) => {
293 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
295 ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
296 self.check_lang_item_path(lang_item, expr, hir_id)
298 ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
299 ExprKind::InlineAsm(asm) => {
300 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
301 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
302 self.check_expr_asm(asm)
304 ExprKind::Break(destination, ref expr_opt) => {
305 self.check_expr_break(destination, expr_opt.as_deref(), expr)
307 ExprKind::Continue(destination) => {
308 if destination.target_id.is_ok() {
311 // There was an error; make type-check fail.
315 ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
316 ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
317 ExprKind::Loop(body, _, source, _) => {
318 self.check_expr_loop(body, source, expected, expr)
320 ExprKind::Match(discrim, arms, match_src) => {
321 self.check_match(expr, &discrim, arms, expected, match_src)
323 ExprKind::Closure(&Closure { capture_clause, fn_decl, body, movability, .. }) => {
324 self.check_expr_closure(expr, capture_clause, &fn_decl, body, movability, expected)
326 ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
327 ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
328 ExprKind::MethodCall(segment, args, _) => {
329 self.check_method_call(expr, segment, args, expected)
331 ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
332 ExprKind::Type(e, t) => {
333 let ty = self.to_ty_saving_user_provided_ty(&t);
334 self.check_expr_eq_type(&e, ty);
337 ExprKind::If(cond, then_expr, opt_else_expr) => {
338 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
340 ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
341 ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
342 ExprKind::ConstBlock(ref anon_const) => {
343 self.check_expr_const_block(anon_const, expected, expr)
345 ExprKind::Repeat(element, ref count) => {
346 self.check_expr_repeat(element, count, expected, expr)
348 ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
349 ExprKind::Struct(qpath, fields, ref base_expr) => {
350 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
352 ExprKind::Field(base, field) => self.check_field(expr, &base, field),
353 ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
354 ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
355 hir::ExprKind::Err => tcx.ty_error(),
359 fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
360 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
361 ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
364 let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
365 self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
366 self.tcx.mk_box(referent_ty)
372 oprnd: &'tcx hir::Expr<'tcx>,
373 expected: Expectation<'tcx>,
374 expr: &'tcx hir::Expr<'tcx>,
377 let expected_inner = match unop {
378 hir::UnOp::Not | hir::UnOp::Neg => expected,
379 hir::UnOp::Deref => NoExpectation,
381 let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
383 if !oprnd_t.references_error() {
384 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
386 hir::UnOp::Deref => {
387 if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
390 let mut err = type_error_struct!(
395 "type `{oprnd_t}` cannot be dereferenced",
397 let sp = tcx.sess.source_map().start_point(expr.span);
399 tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
401 tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
404 oprnd_t = tcx.ty_error();
408 let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
409 // If it's builtin, we can reuse the type, this helps inference.
410 if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
415 let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
416 // If it's builtin, we can reuse the type, this helps inference.
417 if !oprnd_t.is_numeric() {
426 fn check_expr_addr_of(
428 kind: hir::BorrowKind,
429 mutbl: hir::Mutability,
430 oprnd: &'tcx hir::Expr<'tcx>,
431 expected: Expectation<'tcx>,
432 expr: &'tcx hir::Expr<'tcx>,
434 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
436 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
437 if oprnd.is_syntactic_place_expr() {
438 // Places may legitimately have unsized types.
439 // For example, dereferences of a fat pointer and
440 // the last field of a struct can be unsized.
443 Expectation::rvalue_hint(self, *ty)
450 self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
452 let tm = ty::TypeAndMut { ty, mutbl };
454 _ if tm.ty.references_error() => self.tcx.ty_error(),
455 hir::BorrowKind::Raw => {
456 self.check_named_place_expr(oprnd);
459 hir::BorrowKind::Ref => {
460 // Note: at this point, we cannot say what the best lifetime
461 // is to use for resulting pointer. We want to use the
462 // shortest lifetime possible so as to avoid spurious borrowck
463 // errors. Moreover, the longest lifetime will depend on the
464 // precise details of the value whose address is being taken
465 // (and how long it is valid), which we don't know yet until
466 // type inference is complete.
468 // Therefore, here we simply generate a region variable. The
469 // region inferencer will then select a suitable value.
470 // Finally, borrowck will infer the value of the region again,
471 // this time with enough precision to check that the value
472 // whose address was taken can actually be made to live as long
473 // as it needs to live.
474 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
475 self.tcx.mk_ref(region, tm)
480 /// Does this expression refer to a place that either:
481 /// * Is based on a local or static.
482 /// * Contains a dereference
483 /// Note that the adjustments for the children of `expr` should already
484 /// have been resolved.
485 fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
486 let is_named = oprnd.is_place_expr(|base| {
487 // Allow raw borrows if there are any deref adjustments.
489 // const VAL: (i32,) = (0,);
490 // const REF: &(i32,) = &(0,);
492 // &raw const VAL.0; // ERROR
493 // &raw const REF.0; // OK, same as &raw const (*REF).0;
495 // This is maybe too permissive, since it allows
496 // `let u = &raw const Box::new((1,)).0`, which creates an
497 // immediately dangling raw pointer.
502 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
505 self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
509 fn check_lang_item_path(
511 lang_item: hir::LangItem,
512 expr: &'tcx hir::Expr<'tcx>,
513 hir_id: Option<hir::HirId>,
515 self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
518 pub(crate) fn check_expr_path(
520 qpath: &'tcx hir::QPath<'tcx>,
521 expr: &'tcx hir::Expr<'tcx>,
522 args: &'tcx [hir::Expr<'tcx>],
525 let (res, opt_ty, segs) =
526 self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
529 self.set_tainted_by_errors();
532 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
533 report_unexpected_variant_res(tcx, res, qpath, expr.span);
536 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
539 if let ty::FnDef(did, ..) = *ty.kind() {
540 let fn_sig = ty.fn_sig(tcx);
541 if tcx.fn_sig(did).abi() == RustIntrinsic && tcx.item_name(did) == sym::transmute {
542 let from = fn_sig.inputs().skip_binder()[0];
543 let to = fn_sig.output().skip_binder();
544 // We defer the transmute to the end of typeck, once all inference vars have
545 // been resolved or we errored. This is important as we can only check transmute
546 // on concrete types, but the output type may not be known yet (it would only
547 // be known if explicitly specified via turbofish).
548 self.deferred_transmute_checks.borrow_mut().push((from, to, expr.span));
550 if !tcx.features().unsized_fn_params {
551 // We want to remove some Sized bounds from std functions,
552 // but don't want to expose the removal to stable Rust.
553 // i.e., we don't want to allow
559 // to work in stable even if the Sized bound on `drop` is relaxed.
560 for i in 0..fn_sig.inputs().skip_binder().len() {
561 // We just want to check sizedness, so instead of introducing
562 // placeholder lifetimes with probing, we just replace higher lifetimes
564 let arg_span = args.get(i).map(|a| a.span);
565 let span = arg_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(
572 self.normalize_associated_types_in(span, input),
574 traits::SizedArgumentType(arg_span),
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(
590 self.normalize_associated_types_in(expr.span, output),
592 traits::SizedReturnType,
596 // We always require that the type provided as the value for
597 // a type parameter outlives the moment of instantiation.
598 let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
599 self.add_wf_bounds(substs, expr);
606 destination: hir::Destination,
607 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
608 expr: &'tcx hir::Expr<'tcx>,
611 if let Ok(target_id) = destination.target_id {
613 if let Some(e) = expr_opt {
614 // If this is a break with a value, we need to type-check
615 // the expression. Get an expected type from the loop context.
616 let opt_coerce_to = {
617 // We should release `enclosing_breakables` before the `check_expr_with_hint`
618 // below, so can't move this block of code to the enclosing scope and share
619 // `ctxt` with the second `enclosing_breakables` borrow below.
620 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
621 match enclosing_breakables.opt_find_breakable(target_id) {
622 Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
624 // Avoid ICE when `break` is inside a closure (#65383).
625 return tcx.ty_error_with_message(
627 "break was outside loop, but no error was emitted",
633 // If the loop context is not a `loop { }`, then break with
634 // a value is illegal, and `opt_coerce_to` will be `None`.
635 // Just set expectation to error in that case.
636 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
638 // Recurse without `enclosing_breakables` borrowed.
639 e_ty = self.check_expr_with_hint(e, coerce_to);
640 cause = self.misc(e.span);
642 // Otherwise, this is a break *without* a value. That's
643 // always legal, and is equivalent to `break ()`.
644 e_ty = tcx.mk_unit();
645 cause = self.misc(expr.span);
648 // Now that we have type-checked `expr_opt`, borrow
649 // the `enclosing_loops` field and let's coerce the
650 // type of `expr_opt` into what is expected.
651 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
652 let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
653 // Avoid ICE when `break` is inside a closure (#65383).
654 return tcx.ty_error_with_message(
656 "break was outside loop, but no error was emitted",
660 if let Some(ref mut coerce) = ctxt.coerce {
661 if let Some(ref e) = expr_opt {
662 coerce.coerce(self, &cause, e, e_ty);
664 assert!(e_ty.is_unit());
665 let ty = coerce.expected_ty();
666 coerce.coerce_forced_unit(
670 self.suggest_mismatched_types_on_tail(
671 &mut err, expr, ty, e_ty, target_id,
673 if let Some(val) = ty_kind_suggestion(ty) {
674 let label = destination
676 .map(|l| format!(" {}", l.ident))
677 .unwrap_or_else(String::new);
680 "give it a value of the expected type",
681 format!("break{label} {val}"),
682 Applicability::HasPlaceholders,
690 // If `ctxt.coerce` is `None`, we can just ignore
691 // the type of the expression. This is because
692 // either this was a break *without* a value, in
693 // which case it is always a legal type (`()`), or
694 // else an error would have been flagged by the
695 // `loops` pass for using break with an expression
696 // where you are not supposed to.
697 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
700 // If we encountered a `break`, then (no surprise) it may be possible to break from the
701 // loop... unless the value being returned from the loop diverges itself, e.g.
702 // `break return 5` or `break loop {}`.
703 ctxt.may_break |= !self.diverges.get().is_always();
705 // the type of a `break` is always `!`, since it diverges
708 // Otherwise, we failed to find the enclosing loop;
709 // this can only happen if the `break` was not
710 // inside a loop at all, which is caught by the
711 // loop-checking pass.
712 let err = self.tcx.ty_error_with_message(
714 "break was outside loop, but no error was emitted",
717 // We still need to assign a type to the inner expression to
718 // prevent the ICE in #43162.
719 if let Some(e) = expr_opt {
720 self.check_expr_with_hint(e, err);
722 // ... except when we try to 'break rust;'.
723 // ICE this expression in particular (see #43162).
724 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
725 if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
726 fatally_break_rust(self.tcx.sess);
731 // There was an error; make type-check fail.
736 fn check_expr_return(
738 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
739 expr: &'tcx hir::Expr<'tcx>,
741 if self.ret_coercion.is_none() {
742 let mut err = ReturnStmtOutsideOfFnBody {
744 encl_body_span: None,
748 let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
750 if let Some(hir::Node::Item(hir::Item {
751 kind: hir::ItemKind::Fn(..),
755 | Some(hir::Node::TraitItem(hir::TraitItem {
756 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
760 | Some(hir::Node::ImplItem(hir::ImplItem {
761 kind: hir::ImplItemKind::Fn(..),
764 })) = self.tcx.hir().find_by_def_id(encl_item_id)
766 // We are inside a function body, so reporting "return statement
767 // outside of function body" needs an explanation.
769 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
771 // If this didn't hold, we would not have to report an error in
773 assert_ne!(encl_item_id, encl_body_owner_id);
775 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
776 let encl_body = self.tcx.hir().body(encl_body_id);
778 err.encl_body_span = Some(encl_body.value.span);
779 err.encl_fn_span = Some(*encl_fn_span);
782 self.tcx.sess.emit_err(err);
784 if let Some(e) = expr_opt {
785 // We still have to type-check `e` (issue #86188), but calling
786 // `check_return_expr` only works inside fn bodies.
789 } else if let Some(e) = expr_opt {
790 if self.ret_coercion_span.get().is_none() {
791 self.ret_coercion_span.set(Some(e.span));
793 self.check_return_expr(e, true);
795 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
796 if self.ret_coercion_span.get().is_none() {
797 self.ret_coercion_span.set(Some(expr.span));
799 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
800 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
801 coercion.coerce_forced_unit(
805 let span = fn_decl.output.span();
806 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
809 format!("expected `{snippet}` because of this return type"),
816 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
822 /// `explicit_return` is `true` if we're checking an explicit `return expr`,
823 /// and `false` if we're checking a trailing expression.
824 pub(super) fn check_return_expr(
826 return_expr: &'tcx hir::Expr<'tcx>,
827 explicit_return: bool,
829 let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
830 span_bug!(return_expr.span, "check_return_expr called outside fn body")
833 let ret_ty = ret_coercion.borrow().expected_ty();
834 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
835 let mut span = return_expr.span;
836 // Use the span of the trailing expression for our cause,
837 // not the span of the entire function
838 if !explicit_return {
839 if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
840 span = last_expr.span;
843 ret_coercion.borrow_mut().coerce(
845 &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
850 if self.return_type_has_opaque {
851 // Point any obligations that were registered due to opaque type
852 // inference at the return expression.
853 self.select_obligations_where_possible(false, |errors| {
854 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
859 fn point_at_return_for_opaque_ty_error(
861 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
863 return_expr_ty: Ty<'tcx>,
865 // Don't point at the whole block if it's empty
866 if span == self.tcx.hir().span(self.body_id) {
870 let cause = &mut err.obligation.cause;
871 if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
872 let new_cause = ObligationCause::new(
875 ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
882 pub(crate) fn check_lhs_assignable(
884 lhs: &'tcx hir::Expr<'tcx>,
885 err_code: &'static str,
887 adjust_err: impl FnOnce(&mut Diagnostic),
889 if lhs.is_syntactic_place_expr() {
893 // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
894 let mut err = self.tcx.sess.struct_span_err_with_code(
896 "invalid left-hand side of assignment",
897 DiagnosticId::Error(err_code.into()),
899 err.span_label(lhs.span, "cannot assign to this expression");
901 self.comes_from_while_condition(lhs.hir_id, |expr| {
902 err.span_suggestion_verbose(
903 expr.span.shrink_to_lo(),
904 "you might have meant to use pattern destructuring",
906 Applicability::MachineApplicable,
910 adjust_err(&mut err);
915 // Check if an expression `original_expr_id` comes from the condition of a while loop,
916 // as opposed from the body of a while loop, which we can naively check by iterating
917 // parents until we find a loop...
918 pub(super) fn comes_from_while_condition(
920 original_expr_id: HirId,
921 then: impl FnOnce(&hir::Expr<'_>),
923 let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
924 while let Some(node) = self.tcx.hir().find(parent) {
926 hir::Node::Expr(hir::Expr {
933 hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
939 hir::LoopSource::While,
944 // Check if our original expression is a child of the condition of a while loop
945 let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
946 self.tcx.hir().find_parent_node(*id)
948 .take_while(|id| *id != parent)
949 .any(|id| id == expr.hir_id);
950 // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
951 // where `while let` was more likely intended.
952 if expr_is_ancestor {
958 | hir::Node::ImplItem(_)
959 | hir::Node::TraitItem(_)
960 | hir::Node::Crate(_) => break,
962 parent = self.tcx.hir().get_parent_node(parent);
968 // A generic function for checking the 'then' and 'else' clauses in an 'if'
969 // or 'if-else' expression.
972 cond_expr: &'tcx hir::Expr<'tcx>,
973 then_expr: &'tcx hir::Expr<'tcx>,
974 opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
976 orig_expected: Expectation<'tcx>,
978 let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
980 self.warn_if_unreachable(
983 "block in `if` or `while` expression",
986 let cond_diverges = self.diverges.get();
987 self.diverges.set(Diverges::Maybe);
989 let expected = orig_expected.adjust_for_branches(self);
990 let then_ty = self.check_expr_with_expectation(then_expr, expected);
991 let then_diverges = self.diverges.get();
992 self.diverges.set(Diverges::Maybe);
994 // We've already taken the expected type's preferences
995 // into account when typing the `then` branch. To figure
996 // out the initial shot at a LUB, we thus only consider
997 // `expected` if it represents a *hard* constraint
998 // (`only_has_type`); otherwise, we just go with a
999 // fresh type variable.
1000 let coerce_to_ty = expected.coercion_target_type(self, sp);
1001 let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
1003 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
1005 if let Some(else_expr) = opt_else_expr {
1006 let else_ty = self.check_expr_with_expectation(else_expr, expected);
1007 let else_diverges = self.diverges.get();
1009 let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1010 let if_cause = self.if_cause(
1017 opt_suggest_box_span,
1020 coerce.coerce(self, &if_cause, else_expr, else_ty);
1022 // We won't diverge unless both branches do (or the condition does).
1023 self.diverges.set(cond_diverges | then_diverges & else_diverges);
1025 self.if_fallback_coercion(sp, then_expr, &mut coerce);
1027 // If the condition is false we can't diverge.
1028 self.diverges.set(cond_diverges);
1031 let result_ty = coerce.complete(self);
1032 if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1035 /// Type check assignment expression `expr` of form `lhs = rhs`.
1036 /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1037 fn check_expr_assign(
1039 expr: &'tcx hir::Expr<'tcx>,
1040 expected: Expectation<'tcx>,
1041 lhs: &'tcx hir::Expr<'tcx>,
1042 rhs: &'tcx hir::Expr<'tcx>,
1045 let expected_ty = expected.coercion_target_type(self, expr.span);
1046 if expected_ty == self.tcx.types.bool {
1047 // The expected type is `bool` but this will result in `()` so we can reasonably
1048 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1049 // The likely cause of this is `if foo = bar { .. }`.
1050 let actual_ty = self.tcx.mk_unit();
1051 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1052 let lhs_ty = self.check_expr(&lhs);
1053 let rhs_ty = self.check_expr(&rhs);
1054 let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1055 (Applicability::MachineApplicable, true)
1057 (Applicability::MaybeIncorrect, false)
1059 if !lhs.is_syntactic_place_expr()
1060 && lhs.is_approximately_pattern()
1061 && !matches!(lhs.kind, hir::ExprKind::Lit(_))
1063 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
1064 let hir = self.tcx.hir();
1065 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
1066 hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
1068 err.span_suggestion_verbose(
1069 expr.span.shrink_to_lo(),
1070 "you might have meant to use pattern matching",
1077 err.span_suggestion_verbose(
1079 "you might have meant to compare for equality",
1085 // If the assignment expression itself is ill-formed, don't
1086 // bother emitting another error
1087 if lhs_ty.references_error() || rhs_ty.references_error() {
1092 return self.tcx.ty_error();
1095 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
1097 let suggest_deref_binop = |err: &mut Diagnostic, rhs_ty: Ty<'tcx>| {
1098 if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
1099 // Can only assign if the type is sized, so if `DerefMut` yields a type that is
1100 // unsized, do not suggest dereferencing it.
1101 let lhs_deref_ty_is_sized = self
1103 .type_implements_trait(
1104 self.tcx.lang_items().sized_trait().unwrap(),
1110 if lhs_deref_ty_is_sized && self.can_coerce(rhs_ty, lhs_deref_ty) {
1111 err.span_suggestion_verbose(
1112 lhs.span.shrink_to_lo(),
1113 "consider dereferencing here to assign to the mutably borrowed value",
1115 Applicability::MachineApplicable,
1121 self.check_lhs_assignable(lhs, "E0070", span, |err| {
1122 let rhs_ty = self.check_expr(&rhs);
1123 suggest_deref_binop(err, rhs_ty);
1126 // This is (basically) inlined `check_expr_coercable_to_type`, but we want
1127 // to suggest an additional fixup here in `suggest_deref_binop`.
1128 let rhs_ty = self.check_expr_with_hint(&rhs, lhs_ty);
1129 if let (_, Some(mut diag)) =
1130 self.demand_coerce_diag(rhs, rhs_ty, lhs_ty, Some(lhs), AllowTwoPhase::No)
1132 suggest_deref_binop(&mut diag, rhs_ty);
1136 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
1138 if lhs_ty.references_error() || rhs_ty.references_error() {
1145 pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
1146 // for let statements, this is done in check_stmt
1147 let init = let_expr.init;
1148 self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
1149 // otherwise check exactly as a let statement
1150 self.check_decl(let_expr.into());
1151 // but return a bool, for this is a boolean expression
1157 body: &'tcx hir::Block<'tcx>,
1158 source: hir::LoopSource,
1159 expected: Expectation<'tcx>,
1160 expr: &'tcx hir::Expr<'tcx>,
1162 let coerce = match source {
1163 // you can only use break with a value from a normal `loop { }`
1164 hir::LoopSource::Loop => {
1165 let coerce_to = expected.coercion_target_type(self, body.span);
1166 Some(CoerceMany::new(coerce_to))
1169 hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1172 let ctxt = BreakableCtxt {
1174 may_break: false, // Will get updated if/when we find a `break`.
1177 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1178 self.check_block_no_value(&body);
1182 // No way to know whether it's diverging because
1183 // of a `break` or an outer `break` or `return`.
1184 self.diverges.set(Diverges::Maybe);
1187 // If we permit break with a value, then result type is
1188 // the LUB of the breaks (possibly ! if none); else, it
1189 // is nil. This makes sense because infinite loops
1190 // (which would have type !) are only possible iff we
1191 // permit break with a value [1].
1192 if ctxt.coerce.is_none() && !ctxt.may_break {
1194 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1196 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1199 /// Checks a method call.
1200 fn check_method_call(
1202 expr: &'tcx hir::Expr<'tcx>,
1203 segment: &hir::PathSegment<'_>,
1204 args: &'tcx [hir::Expr<'tcx>],
1205 expected: Expectation<'tcx>,
1207 let rcvr = &args[0];
1208 let rcvr_t = self.check_expr(&rcvr);
1209 // no need to check for bot/err -- callee does that
1210 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
1211 let span = segment.ident.span;
1213 let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1215 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1216 // trigger this codepath causing `structurally_resolved_type` to emit an error.
1218 self.write_method_call(expr.hir_id, method);
1222 if segment.ident.name != kw::Empty {
1223 if let Some(mut err) = self.report_method_error(
1227 SelfSource::MethodCall(&args[0]),
1238 // Call the generic checker.
1239 self.check_method_argument_types(
1251 e: &'tcx hir::Expr<'tcx>,
1252 t: &'tcx hir::Ty<'tcx>,
1253 expr: &'tcx hir::Expr<'tcx>,
1255 // Find the type of `e`. Supply hints based on the type we are casting to,
1257 let t_cast = self.to_ty_saving_user_provided_ty(t);
1258 let t_cast = self.resolve_vars_if_possible(t_cast);
1259 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1260 let t_expr = self.resolve_vars_if_possible(t_expr);
1262 // Eagerly check for some obvious errors.
1263 if t_expr.references_error() || t_cast.references_error() {
1266 // Defer other checks until we're done type checking.
1267 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1268 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1271 "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1272 t_cast, t_expr, cast_check,
1274 deferred_cast_checks.push(cast_check);
1277 Err(_) => self.tcx.ty_error(),
1282 fn check_expr_array(
1284 args: &'tcx [hir::Expr<'tcx>],
1285 expected: Expectation<'tcx>,
1286 expr: &'tcx hir::Expr<'tcx>,
1288 let element_ty = if !args.is_empty() {
1289 let coerce_to = expected
1291 .and_then(|uty| match *uty.kind() {
1292 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1295 .unwrap_or_else(|| {
1296 self.next_ty_var(TypeVariableOrigin {
1297 kind: TypeVariableOriginKind::TypeInference,
1301 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1302 assert_eq!(self.diverges.get(), Diverges::Maybe);
1304 let e_ty = self.check_expr_with_hint(e, coerce_to);
1305 let cause = self.misc(e.span);
1306 coerce.coerce(self, &cause, e, e_ty);
1308 coerce.complete(self)
1310 self.next_ty_var(TypeVariableOrigin {
1311 kind: TypeVariableOriginKind::TypeInference,
1315 self.tcx.mk_array(element_ty, args.len() as u64)
1318 fn check_expr_const_block(
1320 anon_const: &'tcx hir::AnonConst,
1321 expected: Expectation<'tcx>,
1322 _expr: &'tcx hir::Expr<'tcx>,
1324 let body = self.tcx.hir().body(anon_const.body);
1326 // Create a new function context.
1327 let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1328 crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1330 let ty = fcx.check_expr_with_expectation(&body.value, expected);
1331 fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1332 fcx.write_ty(anon_const.hir_id, ty);
1336 fn check_expr_repeat(
1338 element: &'tcx hir::Expr<'tcx>,
1339 count: &'tcx hir::ArrayLen,
1340 expected: Expectation<'tcx>,
1341 _expr: &'tcx hir::Expr<'tcx>,
1344 let count = self.array_length_to_const(count);
1346 let uty = match expected {
1347 ExpectHasType(uty) => match *uty.kind() {
1348 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1354 let (element_ty, t) = match uty {
1356 self.check_expr_coercable_to_type(&element, uty, None);
1360 let ty = self.next_ty_var(TypeVariableOrigin {
1361 kind: TypeVariableOriginKind::MiscVariable,
1364 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1369 if element_ty.references_error() {
1370 return tcx.ty_error();
1373 self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1375 tcx.mk_ty(ty::Array(t, count))
1378 fn check_repeat_element_needs_copy_bound(
1380 element: &hir::Expr<'_>,
1381 count: ty::Const<'tcx>,
1382 element_ty: Ty<'tcx>,
1385 // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1386 match &element.kind {
1387 hir::ExprKind::ConstBlock(..) => return,
1388 hir::ExprKind::Path(qpath) => {
1389 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1390 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1397 // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1398 // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1399 let is_const_fn = match element.kind {
1400 hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1401 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1407 // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1408 // don't copy that one element, we move it. Only check for Copy if the length is larger.
1409 if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1410 let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1411 let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1412 self.require_type_meets(element_ty, element.span, code, lang_item);
1416 fn check_expr_tuple(
1418 elts: &'tcx [hir::Expr<'tcx>],
1419 expected: Expectation<'tcx>,
1420 expr: &'tcx hir::Expr<'tcx>,
1422 let flds = expected.only_has_type(self).and_then(|ty| {
1423 let ty = self.resolve_vars_with_obligations(ty);
1425 ty::Tuple(flds) => Some(&flds[..]),
1430 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1431 Some(fs) if i < fs.len() => {
1433 self.check_expr_coercable_to_type(&e, ety, None);
1436 _ => self.check_expr_with_expectation(&e, NoExpectation),
1438 let tuple = self.tcx.mk_tup(elt_ts_iter);
1439 if tuple.references_error() {
1442 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1447 fn check_expr_struct(
1449 expr: &hir::Expr<'_>,
1450 expected: Expectation<'tcx>,
1452 fields: &'tcx [hir::ExprField<'tcx>],
1453 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1455 // Find the relevant variant
1456 let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1457 self.check_struct_fields_on_error(fields, base_expr);
1458 return self.tcx.ty_error();
1461 // Prohibit struct expressions when non-exhaustive flag is set.
1462 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1463 if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1466 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1469 self.check_expr_struct_fields(
1480 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1484 fn check_expr_struct_fields(
1487 expected: Expectation<'tcx>,
1488 expr_id: hir::HirId,
1490 variant: &'tcx ty::VariantDef,
1491 ast_fields: &'tcx [hir::ExprField<'tcx>],
1492 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1497 let expected_inputs =
1498 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1499 let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1500 expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1504 // re-link the regions that EIfEO can erase.
1505 self.demand_eqtype(span, adt_ty_hint, adt_ty);
1507 let ty::Adt(adt, substs) = adt_ty.kind() else {
1508 span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1510 let adt_kind = adt.adt_kind();
1512 let mut remaining_fields = variant
1516 .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1517 .collect::<FxHashMap<_, _>>();
1519 let mut seen_fields = FxHashMap::default();
1521 let mut error_happened = false;
1523 // Type-check each field.
1524 for field in ast_fields {
1525 let ident = tcx.adjust_ident(field.ident, variant.def_id);
1526 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1527 seen_fields.insert(ident, field.span);
1528 self.write_field_index(field.hir_id, i);
1530 // We don't look at stability attributes on
1531 // struct-like enums (yet...), but it's definitely not
1532 // a bug to have constructed one.
1533 if adt_kind != AdtKind::Enum {
1534 tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1537 self.field_ty(field.span, v_field, substs)
1539 error_happened = true;
1540 if let Some(prev_span) = seen_fields.get(&ident) {
1541 tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1542 span: field.ident.span,
1543 prev_span: *prev_span,
1547 self.report_unknown_field(
1552 adt.variant_descr(),
1560 // Make sure to give a type to the field even if there's
1561 // an error, so we can continue type-checking.
1562 self.check_expr_coercable_to_type(&field.expr, field_type, None);
1565 // Make sure the programmer specified correct number of fields.
1566 if adt_kind == AdtKind::Union {
1567 if ast_fields.len() != 1 {
1572 "union expressions should have exactly one field",
1578 // If check_expr_struct_fields hit an error, do not attempt to populate
1579 // the fields with the base_expr. This could cause us to hit errors later
1580 // when certain fields are assumed to exist that in fact do not.
1585 if let Some(base_expr) = base_expr {
1586 // FIXME: We are currently creating two branches here in order to maintain
1587 // consistency. But they should be merged as much as possible.
1588 let fru_tys = if self.tcx.features().type_changing_struct_update {
1589 if adt.is_struct() {
1590 // Make some fresh substitutions for our ADT type.
1591 let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1592 // We do subtyping on the FRU fields first, so we can
1593 // learn exactly what types we expect the base expr
1594 // needs constrained to be compatible with the struct
1595 // type we expect from the expectation value.
1596 let fru_tys = variant
1600 let fru_ty = self.normalize_associated_types_in(
1602 self.field_ty(base_expr.span, f, fresh_substs),
1604 let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1605 if let Some(_) = remaining_fields.remove(&ident) {
1606 let target_ty = self.field_ty(base_expr.span, f, substs);
1607 let cause = self.misc(base_expr.span);
1608 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1609 Ok(InferOk { obligations, value: () }) => {
1610 self.register_predicates(obligations)
1613 // This should never happen, since we're just subtyping the
1614 // remaining_fields, but it's fine to emit this, I guess.
1615 self.report_mismatched_types(
1619 FieldMisMatch(variant.name, ident.name),
1625 self.resolve_vars_if_possible(fru_ty)
1628 // The use of fresh substs that we have subtyped against
1629 // our base ADT type's fields allows us to guide inference
1630 // along so that, e.g.
1632 // MyStruct<'a, F1, F2, const C: usize> {
1634 // // Other fields that reference `'a`, `F2`, and `C`
1637 // let x = MyStruct {
1642 // will have the `other_struct` expression constrained to
1643 // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1644 // This is important to allow coercions to happen in
1645 // `other_struct` itself. See `coerce-in-base-expr.rs`.
1646 let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1647 self.check_expr_has_type_or_error(
1649 self.resolve_vars_if_possible(fresh_base_ty),
1654 // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1655 // type errors on that expression, too.
1656 self.check_expr(base_expr);
1659 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1663 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1664 let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1665 let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1666 (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1669 if self.tcx.sess.is_nightly_build() && same_adt {
1671 &self.tcx.sess.parse_sess,
1672 sym::type_changing_struct_update,
1674 "type changing struct updating is experimental",
1679 match adt_ty.kind() {
1680 ty::Adt(adt, substs) if adt.is_struct() => variant
1684 self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1690 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1695 self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1696 } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1697 debug!(?remaining_fields);
1698 let private_fields: Vec<&ty::FieldDef> = variant
1702 !field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1706 if !private_fields.is_empty() {
1707 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1709 self.report_missing_fields(
1721 fn check_struct_fields_on_error(
1723 fields: &'tcx [hir::ExprField<'tcx>],
1724 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1726 for field in fields {
1727 self.check_expr(&field.expr);
1729 if let Some(base) = *base_expr {
1730 self.check_expr(&base);
1734 /// Report an error for a struct field expression when there are fields which aren't provided.
1737 /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1738 /// --> src/main.rs:8:5
1740 /// 8 | foo::Foo {};
1741 /// | ^^^^^^^^ missing `you_can_use_this_field`
1743 /// error: aborting due to previous error
1745 fn report_missing_fields(
1749 remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1750 variant: &'tcx ty::VariantDef,
1751 ast_fields: &'tcx [hir::ExprField<'tcx>],
1752 substs: SubstsRef<'tcx>,
1754 let len = remaining_fields.len();
1756 let mut displayable_field_names: Vec<&str> =
1757 remaining_fields.keys().map(|ident| ident.as_str()).collect();
1758 // sorting &str primitives here, sort_unstable is ok
1759 displayable_field_names.sort_unstable();
1761 let mut truncated_fields_error = String::new();
1762 let remaining_fields_names = match &displayable_field_names[..] {
1763 [field1] => format!("`{}`", field1),
1764 [field1, field2] => format!("`{field1}` and `{field2}`"),
1765 [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1767 truncated_fields_error =
1768 format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1769 displayable_field_names
1772 .map(|n| format!("`{n}`"))
1773 .collect::<Vec<_>>()
1778 let mut err = struct_span_err!(
1782 "missing field{} {}{} in initializer of `{}`",
1784 remaining_fields_names,
1785 truncated_fields_error,
1788 err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1790 // If the last field is a range literal, but it isn't supposed to be, then they probably
1791 // meant to use functional update syntax.
1793 // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1797 QPath::LangItem(LangItem::Range, ..),
1798 &[ref range_start, ref range_end],
1801 )) = ast_fields.last().map(|last| (last, &last.expr.kind)) &&
1803 variant.fields.iter().find(|field| field.ident(self.tcx) == last.ident) &&
1804 let range_def_id = self.tcx.lang_items().range_struct() &&
1806 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1807 .map(|adt| adt.did())
1814 .span_to_snippet(range_end.expr.span)
1815 .map(|s| format!(" from `{s}`"))
1816 .unwrap_or_default();
1817 err.span_suggestion(
1818 range_start.span.shrink_to_hi(),
1819 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1821 Applicability::MaybeIncorrect,
1828 /// Report an error for a struct field expression when there are invisible fields.
1831 /// error: cannot construct `Foo` with struct literal syntax due to private fields
1832 /// --> src/main.rs:8:5
1834 /// 8 | foo::Foo {};
1837 /// error: aborting due to previous error
1839 fn report_private_fields(
1843 private_fields: Vec<&ty::FieldDef>,
1844 used_fields: &'tcx [hir::ExprField<'tcx>],
1846 let mut err = self.tcx.sess.struct_span_err(
1849 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1852 let (used_private_fields, remaining_private_fields): (
1853 Vec<(Symbol, Span, bool)>,
1854 Vec<(Symbol, Span, bool)>,
1858 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1859 Some(used_field) => (field.name, used_field.span, true),
1860 None => (field.name, self.tcx.def_span(field.did), false),
1863 .partition(|field| field.2);
1864 err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1865 if !remaining_private_fields.is_empty() {
1866 let remaining_private_fields_len = remaining_private_fields.len();
1867 let names = match &remaining_private_fields
1869 .map(|(name, _, _)| name)
1870 .collect::<Vec<_>>()[..]
1872 _ if remaining_private_fields_len > 6 => String::new(),
1873 [name] => format!("`{name}` "),
1874 [names @ .., last] => {
1875 let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1876 format!("{} and `{last}` ", names.join(", "))
1878 [] => unreachable!(),
1881 "... and other private field{s} {names}that {were} not provided",
1882 s = pluralize!(remaining_private_fields_len),
1883 were = pluralize!("was", remaining_private_fields_len),
1889 fn report_unknown_field(
1892 variant: &'tcx ty::VariantDef,
1893 field: &hir::ExprField<'_>,
1894 skip_fields: &[hir::ExprField<'_>],
1898 if variant.is_recovered() {
1899 self.set_tainted_by_errors();
1902 let mut err = self.type_error_struct_with_diag(
1904 |actual| match ty.kind() {
1905 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1909 "{} `{}::{}` has no field named `{}`",
1915 _ => struct_span_err!(
1919 "{} `{}` has no field named `{}`",
1928 let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1929 match variant.ctor_kind {
1930 CtorKind::Fn => match ty.kind() {
1931 ty::Adt(adt, ..) if adt.is_enum() => {
1935 "`{adt}::{variant}` defined here",
1937 variant = variant.name,
1940 err.span_label(field.ident.span, "field does not exist");
1941 err.span_suggestion_verbose(
1944 "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1946 variant = variant.name,
1949 "{adt}::{variant}(/* fields */)",
1951 variant = variant.name,
1953 Applicability::HasPlaceholders,
1957 err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
1958 err.span_label(field.ident.span, "field does not exist");
1959 err.span_suggestion_verbose(
1962 "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1964 kind_name = kind_name,
1966 format!("{adt}(/* fields */)", adt = ty),
1967 Applicability::HasPlaceholders,
1972 // prevent all specified fields from being suggested
1973 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
1974 if let Some(field_name) = self.suggest_field_name(
1977 skip_fields.collect(),
1980 err.span_suggestion(
1982 "a field with a similar name exists",
1984 Applicability::MaybeIncorrect,
1988 ty::Adt(adt, ..) => {
1992 format!("`{}::{}` does not have this field", ty, variant.name),
1997 format!("`{ty}` does not have this field"),
2000 let available_field_names =
2001 self.available_field_names(variant, expr_span);
2002 if !available_field_names.is_empty() {
2004 "available fields are: {}",
2005 self.name_series_display(available_field_names)
2009 _ => bug!("non-ADT passed to report_unknown_field"),
2017 // Return a hint about the closest match in field names
2018 fn suggest_field_name(
2020 variant: &'tcx ty::VariantDef,
2023 // The span where stability will be checked
2025 ) -> Option<Symbol> {
2029 .filter_map(|field| {
2030 // ignore already set fields and private fields from non-local crates
2031 // and unstable fields.
2032 if skip.iter().any(|&x| x == field.name)
2033 || (!variant.def_id.is_local() && !field.vis.is_public())
2035 self.tcx.eval_stability(field.did, None, span, None),
2036 stability::EvalResult::Deny { .. }
2044 .collect::<Vec<Symbol>>();
2046 find_best_match_for_name(&names, field, None)
2049 fn available_field_names(
2051 variant: &'tcx ty::VariantDef,
2058 let def_scope = self
2060 .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2062 field.vis.is_accessible_from(def_scope, self.tcx)
2064 self.tcx.eval_stability(field.did, None, access_span, None),
2065 stability::EvalResult::Deny { .. }
2068 .filter(|field| !self.tcx.is_doc_hidden(field.did))
2069 .map(|field| field.name)
2073 fn name_series_display(&self, names: Vec<Symbol>) -> String {
2074 // dynamic limit, to never omit just one field
2075 let limit = if names.len() == 6 { 6 } else { 5 };
2077 names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2078 if names.len() > limit {
2079 display = format!("{} ... and {} others", display, names.len() - limit);
2084 // Check field access expressions
2087 expr: &'tcx hir::Expr<'tcx>,
2088 base: &'tcx hir::Expr<'tcx>,
2091 debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2092 let expr_t = self.check_expr(base);
2093 let expr_t = self.structurally_resolved_type(base.span, expr_t);
2094 let mut private_candidate = None;
2095 let mut autoderef = self.autoderef(expr.span, expr_t);
2096 while let Some((base_t, _)) = autoderef.next() {
2097 debug!("base_t: {:?}", base_t);
2098 match base_t.kind() {
2099 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2100 debug!("struct named {:?}", base_t);
2101 let (ident, def_scope) =
2102 self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2103 let fields = &base_def.non_enum_variant().fields;
2104 if let Some(index) = fields
2106 .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2108 let field = &fields[index];
2109 let field_ty = self.field_ty(expr.span, field, substs);
2110 // Save the index of all fields regardless of their visibility in case
2111 // of error recovery.
2112 self.write_field_index(expr.hir_id, index);
2113 let adjustments = self.adjust_steps(&autoderef);
2114 if field.vis.is_accessible_from(def_scope, self.tcx) {
2115 self.apply_adjustments(base, adjustments);
2116 self.register_predicates(autoderef.into_obligations());
2118 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2121 private_candidate = Some((adjustments, base_def.did(), field_ty));
2125 let fstr = field.as_str();
2126 if let Ok(index) = fstr.parse::<usize>() {
2127 if fstr == index.to_string() {
2128 if let Some(&field_ty) = tys.get(index) {
2129 let adjustments = self.adjust_steps(&autoderef);
2130 self.apply_adjustments(base, adjustments);
2131 self.register_predicates(autoderef.into_obligations());
2133 self.write_field_index(expr.hir_id, index);
2142 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2144 if let Some((adjustments, did, field_ty)) = private_candidate {
2145 // (#90483) apply adjustments to avoid ExprUseVisitor from
2146 // creating erroneous projection.
2147 self.apply_adjustments(base, adjustments);
2148 self.ban_private_field_access(expr, expr_t, field, did);
2152 if field.name == kw::Empty {
2153 } else if self.method_exists(field, expr_t, expr.hir_id, true) {
2154 self.ban_take_value_of_method(expr, expr_t, field);
2155 } else if !expr_t.is_primitive_ty() {
2156 self.ban_nonexisting_field(field, base, expr, expr_t);
2158 let field_name = field.to_string();
2159 let mut err = type_error_struct!(
2164 "`{expr_t}` is a primitive type and therefore doesn't have fields",
2166 let is_valid_suffix = |field: String| {
2167 if field == "f32" || field == "f64" {
2170 let mut chars = field.chars().peekable();
2171 match chars.peek() {
2172 Some('e') | Some('E') => {
2174 if let Some(c) = chars.peek()
2175 && !c.is_numeric() && *c != '-' && *c != '+'
2179 while let Some(c) = chars.peek() {
2180 if !c.is_numeric() {
2188 let suffix = chars.collect::<String>();
2189 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2191 if let ty::Infer(ty::IntVar(_)) = expr_t.kind()
2192 && let ExprKind::Lit(Spanned {
2193 node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2196 && !base.span.from_expansion()
2197 && is_valid_suffix(field_name)
2199 err.span_suggestion_verbose(
2200 field.span.shrink_to_lo(),
2201 "If the number is meant to be a floating point number, consider adding a `0` after the period",
2203 Applicability::MaybeIncorrect,
2209 self.tcx().ty_error()
2212 fn check_call_constructor(
2214 err: &mut Diagnostic,
2215 base: &'tcx hir::Expr<'tcx>,
2218 if let Some(local_id) = def_id.as_local() {
2219 let hir_id = self.tcx.hir().local_def_id_to_hir_id(local_id);
2220 let node = self.tcx.hir().get(hir_id);
2222 if let Some(fields) = node.tuple_fields() {
2223 let kind = match self.tcx.opt_def_kind(local_id) {
2224 Some(DefKind::Ctor(of, _)) => of,
2228 suggest_call_constructor(base.span, kind, fields.len(), err);
2231 // The logic here isn't smart but `associated_item_def_ids`
2232 // doesn't work nicely on local.
2233 if let DefKind::Ctor(of, _) = self.tcx.def_kind(def_id) {
2234 let parent_def_id = self.tcx.parent(def_id);
2235 let fields = self.tcx.associated_item_def_ids(parent_def_id);
2236 suggest_call_constructor(base.span, of, fields.len(), err);
2241 fn suggest_await_on_field_access(
2243 err: &mut Diagnostic,
2245 base: &'tcx hir::Expr<'tcx>,
2248 let output_ty = match self.get_impl_future_output_ty(ty) {
2249 Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2252 let mut add_label = true;
2253 if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2254 // no field access on enum type
2260 .any(|field| field.ident(self.tcx) == field_ident)
2265 "field not available in `impl Future`, but it is available in its `Output`",
2267 err.span_suggestion_verbose(
2268 base.span.shrink_to_hi(),
2269 "consider `await`ing on the `Future` and access the field of its `Output`",
2271 Applicability::MaybeIncorrect,
2277 err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2281 fn ban_nonexisting_field(
2284 base: &'tcx hir::Expr<'tcx>,
2285 expr: &'tcx hir::Expr<'tcx>,
2289 "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
2290 field, base, expr, expr_t
2292 let mut err = self.no_such_field_err(field, expr_t, base.hir_id);
2294 match *expr_t.peel_refs().kind() {
2295 ty::Array(_, len) => {
2296 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
2299 self.suggest_first_deref_field(&mut err, expr, base, field);
2301 ty::Adt(def, _) if !def.is_enum() => {
2302 self.suggest_fields_on_recordish(&mut err, def, field, expr.span);
2304 ty::Param(param_ty) => {
2305 self.point_at_param_definition(&mut err, param_ty);
2307 ty::Opaque(_, _) => {
2308 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
2310 ty::FnDef(def_id, _) => {
2311 self.check_call_constructor(&mut err, base, def_id);
2316 if field.name == kw::Await {
2317 // We know by construction that `<expr>.await` is either on Rust 2015
2318 // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2319 err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2320 err.help_use_latest_edition();
2326 fn ban_private_field_access(
2328 expr: &hir::Expr<'_>,
2333 let struct_path = self.tcx().def_path_str(base_did);
2334 let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2335 let mut err = struct_span_err!(
2339 "field `{field}` of {kind_name} `{struct_path}` is private",
2341 err.span_label(field.span, "private field");
2342 // Also check if an accessible method exists, which is often what is meant.
2343 if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2345 self.suggest_method_call(
2347 &format!("a method `{field}` also exists, call it with parentheses"),
2357 fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2358 let mut err = type_error_struct!(
2363 "attempted to take value of method `{field}` on type `{expr_t}`",
2365 err.span_label(field.span, "method, not a field");
2367 if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2368 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2370 expr.hir_id == callee.hir_id
2375 self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2376 let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2377 let after_open = expr.span.lo() + rustc_span::BytePos(1);
2378 let before_close = expr.span.hi() - rustc_span::BytePos(1);
2380 if expr_is_call && is_wrapped {
2381 err.multipart_suggestion(
2382 "remove wrapping parentheses to call the method",
2384 (expr.span.with_hi(after_open), String::new()),
2385 (expr.span.with_lo(before_close), String::new()),
2387 Applicability::MachineApplicable,
2389 } else if !self.expr_in_place(expr.hir_id) {
2390 // Suggest call parentheses inside the wrapping parentheses
2391 let span = if is_wrapped {
2392 expr.span.with_lo(after_open).with_hi(before_close)
2396 self.suggest_method_call(
2398 "use parentheses to call the method",
2404 } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2405 && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2406 && let ExprKind::Field(base_expr, _) = expr.kind
2407 && adt_def.variants().len() == 1
2415 .any(|f| f.ident(self.tcx) == field)
2417 err.multipart_suggestion(
2418 "to access the field, dereference first",
2420 (base_expr.span.shrink_to_lo(), "(*".to_string()),
2421 (base_expr.span.shrink_to_hi(), ")".to_string()),
2423 Applicability::MaybeIncorrect,
2426 err.help("methods are immutable and cannot be assigned to");
2432 fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2433 let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2434 let generic_param = generics.type_param(¶m, self.tcx);
2435 if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2438 let param_def_id = generic_param.def_id;
2439 let param_hir_id = match param_def_id.as_local() {
2440 Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2443 let param_span = self.tcx.hir().span(param_hir_id);
2444 let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2446 err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2449 fn suggest_fields_on_recordish(
2451 err: &mut Diagnostic,
2452 def: ty::AdtDef<'tcx>,
2456 if let Some(suggested_field_name) =
2457 self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2459 err.span_suggestion(
2461 "a field with a similar name exists",
2462 suggested_field_name,
2463 Applicability::MaybeIncorrect,
2466 err.span_label(field.span, "unknown field");
2467 let struct_variant_def = def.non_enum_variant();
2468 let field_names = self.available_field_names(struct_variant_def, access_span);
2469 if !field_names.is_empty() {
2471 "available fields are: {}",
2472 self.name_series_display(field_names),
2478 fn maybe_suggest_array_indexing(
2480 err: &mut Diagnostic,
2481 expr: &hir::Expr<'_>,
2482 base: &hir::Expr<'_>,
2484 len: ty::Const<'tcx>,
2486 if let (Some(len), Ok(user_index)) =
2487 (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2488 && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2490 let help = "instead of using tuple indexing, use array indexing";
2491 let suggestion = format!("{base}[{field}]");
2492 let applicability = if len < user_index {
2493 Applicability::MachineApplicable
2495 Applicability::MaybeIncorrect
2497 err.span_suggestion(expr.span, help, suggestion, applicability);
2501 fn suggest_first_deref_field(
2503 err: &mut Diagnostic,
2504 expr: &hir::Expr<'_>,
2505 base: &hir::Expr<'_>,
2508 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2509 let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2510 let suggestion = format!("(*{base}).{field}");
2511 err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2515 fn no_such_field_err(
2520 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2521 let span = field.span;
2522 debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2524 let mut err = type_error_struct!(
2529 "no field `{field}` on type `{expr_t}`",
2532 // try to add a suggestion in case the field is a nested field of a field of the Adt
2533 let mod_id = self.tcx.parent_module(id).to_def_id();
2534 if let Some((fields, substs)) =
2535 self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2537 for candidate_field in fields {
2538 if let Some(mut field_path) = self.check_for_nested_field_satisfying(
2540 &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2546 // field_path includes `field` that we're looking for, so pop it.
2549 let field_path_str = field_path
2551 .map(|id| id.name.to_ident_string())
2552 .collect::<Vec<String>>()
2554 debug!("field_path_str: {:?}", field_path_str);
2556 err.span_suggestion_verbose(
2557 field.span.shrink_to_lo(),
2558 "one of the expressions' fields has a field of the same name",
2559 format!("{field_path_str}."),
2560 Applicability::MaybeIncorrect,
2568 pub(crate) fn get_field_candidates_considering_privacy(
2573 ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2574 debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2576 for (base_t, _) in self.autoderef(span, base_ty) {
2577 match base_t.kind() {
2578 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2580 let fields = &base_def.non_enum_variant().fields;
2581 // Some struct, e.g. some that impl `Deref`, have all private fields
2582 // because you're expected to deref them to access the _real_ fields.
2583 // This, for example, will help us suggest accessing a field through a `Box<T>`.
2584 if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2590 .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2591 // For compile-time reasons put a limit on number of fields we search
2602 /// This method is called after we have encountered a missing field error to recursively
2603 /// search for the field
2604 pub(crate) fn check_for_nested_field_satisfying(
2607 matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2608 candidate_field: &ty::FieldDef,
2609 subst: SubstsRef<'tcx>,
2610 mut field_path: Vec<Ident>,
2612 ) -> Option<Vec<Ident>> {
2614 "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2615 span, candidate_field, field_path
2618 if field_path.len() > 3 {
2619 // For compile-time reasons and to avoid infinite recursion we only check for fields
2620 // up to a depth of three
2623 field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2624 let field_ty = candidate_field.ty(self.tcx, subst);
2625 if matches(candidate_field, field_ty) {
2626 return Some(field_path);
2627 } else if let Some((nested_fields, subst)) =
2628 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2630 // recursively search fields of `candidate_field` if it's a ty::Adt
2631 for field in nested_fields {
2632 if let Some(field_path) = self.check_for_nested_field_satisfying(
2640 return Some(field_path);
2648 fn check_expr_index(
2650 base: &'tcx hir::Expr<'tcx>,
2651 idx: &'tcx hir::Expr<'tcx>,
2652 expr: &'tcx hir::Expr<'tcx>,
2654 let base_t = self.check_expr(&base);
2655 let idx_t = self.check_expr(&idx);
2657 if base_t.references_error() {
2659 } else if idx_t.references_error() {
2662 let base_t = self.structurally_resolved_type(base.span, base_t);
2663 match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2664 Some((index_ty, element_ty)) => {
2665 // two-phase not needed because index_ty is never mutable
2666 self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2667 self.select_obligations_where_possible(false, |errors| {
2668 self.point_at_index_if_possible(errors, idx.span)
2673 let mut err = type_error_struct!(
2678 "cannot index into a value of type `{base_t}`",
2680 // Try to give some advice about indexing tuples.
2681 if let ty::Tuple(..) = base_t.kind() {
2682 let mut needs_note = true;
2683 // If the index is an integer, we can show the actual
2684 // fixed expression:
2685 if let ExprKind::Lit(ref lit) = idx.kind {
2686 if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2687 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2688 if let Ok(snip) = snip {
2689 err.span_suggestion(
2691 "to access tuple elements, use",
2692 format!("{snip}.{i}"),
2693 Applicability::MachineApplicable,
2701 "to access tuple elements, use tuple indexing \
2702 syntax (e.g., `tuple.0`)",
2713 fn point_at_index_if_possible(
2715 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2718 for error in errors {
2719 match error.obligation.predicate.kind().skip_binder() {
2720 ty::PredicateKind::Trait(predicate)
2721 if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2725 error.obligation.cause.span = span;
2729 fn check_expr_yield(
2731 value: &'tcx hir::Expr<'tcx>,
2732 expr: &'tcx hir::Expr<'tcx>,
2733 src: &'tcx hir::YieldSource,
2735 match self.resume_yield_tys {
2736 Some((resume_ty, yield_ty)) => {
2737 self.check_expr_coercable_to_type(&value, yield_ty, None);
2741 // Given that this `yield` expression was generated as a result of lowering a `.await`,
2742 // we know that the yield type must be `()`; however, the context won't contain this
2743 // information. Hence, we check the source of the yield expression here and check its
2744 // value's type against `()` (this check should always hold).
2745 None if src.is_await() => {
2746 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2750 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2751 // Avoid expressions without types during writeback (#78653).
2752 self.check_expr(value);
2758 fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2759 let needs = if is_input { Needs::None } else { Needs::MutPlace };
2760 let ty = self.check_expr_with_needs(expr, needs);
2761 self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2763 if !is_input && !expr.is_syntactic_place_expr() {
2764 let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2765 err.span_label(expr.span, "cannot assign to this expression");
2769 // If this is an input value, we require its type to be fully resolved
2770 // at this point. This allows us to provide helpful coercions which help
2771 // pass the type candidate list in a later pass.
2773 // We don't require output types to be resolved at this point, which
2774 // allows them to be inferred based on how they are used later in the
2777 let ty = self.structurally_resolved_type(expr.span, ty);
2780 let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2781 self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2783 ty::Ref(_, base_ty, mutbl) => {
2784 let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2785 self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2792 fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2793 for (op, _op_sp) in asm.operands {
2795 hir::InlineAsmOperand::In { expr, .. } => {
2796 self.check_expr_asm_operand(expr, true);
2798 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2799 | hir::InlineAsmOperand::InOut { expr, .. } => {
2800 self.check_expr_asm_operand(expr, false);
2802 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2803 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2804 self.check_expr_asm_operand(in_expr, true);
2805 if let Some(out_expr) = out_expr {
2806 self.check_expr_asm_operand(out_expr, false);
2809 // `AnonConst`s have their own body and is type-checked separately.
2810 // As they don't flow into the type system we don't need them to
2812 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2813 hir::InlineAsmOperand::SymStatic { .. } => {}
2816 if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2817 self.tcx.types.never
2824 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2825 Some(match ty.kind() {
2828 ty::Int(_) | ty::Uint(_) => "42",
2829 ty::Float(_) => "3.14159",
2830 ty::Error(_) | ty::Never => return None,