1 //! Type checking expressions.
3 //! See `mod.rs` for more context on type checking in general.
5 use crate::astconv::AstConv as _;
6 use crate::check::cast::{self, CastCheckResult};
7 use crate::check::coercion::CoerceMany;
8 use crate::check::fatally_break_rust;
9 use crate::check::method::SelfSource;
10 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
12 report_unexpected_variant_res, BreakableCtxt, Diverges, DynamicCoerceMany, FnCtxt, Needs,
13 TupleArgumentsFlag::DontTupleArguments,
16 FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
17 YieldExprOutsideOfGenerator,
19 use crate::type_error_struct;
21 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
23 use rustc_data_structures::fx::FxHashMap;
24 use rustc_data_structures::stack::ensure_sufficient_stack;
26 pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId,
27 ErrorGuaranteed, StashKey,
30 use rustc_hir::def::{CtorKind, DefKind, Res};
31 use rustc_hir::def_id::DefId;
32 use rustc_hir::intravisit::Visitor;
33 use rustc_hir::lang_items::LangItem;
34 use rustc_hir::{Closure, ExprKind, HirId, QPath};
35 use rustc_infer::infer;
36 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
37 use rustc_infer::infer::InferOk;
38 use rustc_infer::traits::ObligationCause;
39 use rustc_middle::middle::stability;
40 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
41 use rustc_middle::ty::error::TypeError::FieldMisMatch;
42 use rustc_middle::ty::subst::SubstsRef;
43 use rustc_middle::ty::{self, AdtKind, Ty, TypeVisitable};
44 use rustc_session::errors::ExprParenthesesNeeded;
45 use rustc_session::parse::feature_err;
46 use rustc_span::hygiene::DesugaringKind;
47 use rustc_span::lev_distance::find_best_match_for_name;
48 use rustc_span::source_map::{Span, Spanned};
49 use rustc_span::symbol::{kw, sym, Ident, Symbol};
50 use rustc_target::spec::abi::Abi::RustIntrinsic;
51 use rustc_trait_selection::infer::InferCtxtExt;
52 use rustc_trait_selection::traits::{self, ObligationCauseCode};
54 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
55 fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
56 let ty = self.check_expr_with_hint(expr, expected);
57 self.demand_eqtype(expr.span, expected, ty);
60 pub fn check_expr_has_type_or_error(
62 expr: &'tcx hir::Expr<'tcx>,
64 extend_err: impl FnMut(&mut Diagnostic),
66 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
69 fn check_expr_meets_expectation_or_error(
71 expr: &'tcx hir::Expr<'tcx>,
72 expected: Expectation<'tcx>,
73 mut extend_err: impl FnMut(&mut Diagnostic),
75 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
76 let mut ty = self.check_expr_with_expectation(expr, expected);
78 // While we don't allow *arbitrary* coercions here, we *do* allow
79 // coercions from ! to `expected`.
81 if let Some(adjustments) = self.typeck_results.borrow().adjustments().get(expr.hir_id) {
82 self.tcx().sess.delay_span_bug(
84 "expression with never type wound up being adjusted",
86 return if let [Adjustment { kind: Adjust::NeverToAny, target }] = &adjustments[..] {
93 let adj_ty = self.next_ty_var(TypeVariableOrigin {
94 kind: TypeVariableOriginKind::AdjustmentType,
97 self.apply_adjustments(
99 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
104 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
105 let expr = expr.peel_drop_temps();
106 self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
107 extend_err(&mut err);
113 pub(super) fn check_expr_coercable_to_type(
115 expr: &'tcx hir::Expr<'tcx>,
117 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
119 let ty = self.check_expr_with_hint(expr, expected);
120 // checks don't need two phase
121 self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
124 pub(super) fn check_expr_with_hint(
126 expr: &'tcx hir::Expr<'tcx>,
129 self.check_expr_with_expectation(expr, ExpectHasType(expected))
132 fn check_expr_with_expectation_and_needs(
134 expr: &'tcx hir::Expr<'tcx>,
135 expected: Expectation<'tcx>,
138 let ty = self.check_expr_with_expectation(expr, expected);
140 // If the expression is used in a place whether mutable place is required
141 // e.g. LHS of assignment, perform the conversion.
142 if let Needs::MutPlace = needs {
143 self.convert_place_derefs_to_mutable(expr);
149 pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
150 self.check_expr_with_expectation(expr, NoExpectation)
153 pub(super) fn check_expr_with_needs(
155 expr: &'tcx hir::Expr<'tcx>,
158 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
162 /// If an expression has any sub-expressions that result in a type error,
163 /// inspecting that expression's type with `ty.references_error()` will return
164 /// true. Likewise, if an expression is known to diverge, inspecting its
165 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
166 /// strict, _|_ can appear in the type of an expression that does not,
167 /// itself, diverge: for example, fn() -> _|_.)
168 /// Note that inspecting a type's structure *directly* may expose the fact
169 /// that there are actually multiple representations for `Error`, so avoid
170 /// that when err needs to be handled differently.
171 #[instrument(skip(self, expr), level = "debug")]
172 pub(super) fn check_expr_with_expectation(
174 expr: &'tcx hir::Expr<'tcx>,
175 expected: Expectation<'tcx>,
177 self.check_expr_with_expectation_and_args(expr, expected, &[])
180 /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
181 /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
182 pub(super) fn check_expr_with_expectation_and_args(
184 expr: &'tcx hir::Expr<'tcx>,
185 expected: Expectation<'tcx>,
186 args: &'tcx [hir::Expr<'tcx>],
188 if self.tcx().sess.verbose() {
189 // make this code only run with -Zverbose because it is probably slow
190 if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
191 if !lint_str.contains('\n') {
192 debug!("expr text: {lint_str}");
194 let mut lines = lint_str.lines();
195 if let Some(line0) = lines.next() {
196 let remaining_lines = lines.count();
197 debug!("expr text: {line0}");
198 debug!("expr text: ...(and {remaining_lines} more lines)");
204 // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
205 // without the final expr (e.g. `try { return; }`). We don't want to generate an
206 // unreachable_code lint for it since warnings for autogenerated code are confusing.
207 let is_try_block_generated_unit_expr = match expr.kind {
208 ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
209 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
215 // Warn for expressions after diverging siblings.
216 if !is_try_block_generated_unit_expr {
217 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
220 // Hide the outer diverging and has_errors flags.
221 let old_diverges = self.diverges.replace(Diverges::Maybe);
222 let old_has_errors = self.has_errors.replace(false);
224 let ty = ensure_sufficient_stack(|| match &expr.kind {
226 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
227 ) => self.check_expr_path(qpath, expr, args),
228 _ => self.check_expr_kind(expr, expected),
231 // Warn for non-block expressions with diverging children.
237 | ExprKind::Match(..) => {}
238 // If `expr` is a result of desugaring the try block and is an ok-wrapped
239 // diverging expression (e.g. it arose from desugaring of `try { return }`),
240 // we skip issuing a warning because it is autogenerated code.
241 ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
242 ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
243 ExprKind::MethodCall(segment, ..) => {
244 self.warn_if_unreachable(expr.hir_id, segment.ident.span, "call")
246 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
249 // Any expression that produces a value of type `!` must have diverged
251 self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
254 // Record the type, which applies it effects.
255 // We need to do this after the warning above, so that
256 // we don't warn for the diverging expression itself.
257 self.write_ty(expr.hir_id, ty);
259 // Combine the diverging and has_error flags.
260 self.diverges.set(self.diverges.get() | old_diverges);
261 self.has_errors.set(self.has_errors.get() | old_has_errors);
263 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
264 debug!("... {:?}, expected is {:?}", ty, expected);
269 #[instrument(skip(self, expr), level = "debug")]
272 expr: &'tcx hir::Expr<'tcx>,
273 expected: Expectation<'tcx>,
275 trace!("expr={:#?}", expr);
279 ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
280 ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
281 ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
282 ExprKind::Assign(lhs, rhs, span) => {
283 self.check_expr_assign(expr, expected, lhs, rhs, span)
285 ExprKind::AssignOp(op, lhs, rhs) => {
286 self.check_binop_assign(expr, op, lhs, rhs, expected)
288 ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
289 ExprKind::AddrOf(kind, mutbl, oprnd) => {
290 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
292 ExprKind::Path(QPath::LangItem(lang_item, _, hir_id)) => {
293 self.check_lang_item_path(lang_item, expr, hir_id)
295 ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
296 ExprKind::InlineAsm(asm) => {
297 // We defer some asm checks as we may not have resolved the input and output types yet (they may still be infer vars).
298 self.deferred_asm_checks.borrow_mut().push((asm, expr.hir_id));
299 self.check_expr_asm(asm)
301 ExprKind::Break(destination, ref expr_opt) => {
302 self.check_expr_break(destination, expr_opt.as_deref(), expr)
304 ExprKind::Continue(destination) => {
305 if destination.target_id.is_ok() {
308 // There was an error; make type-check fail.
312 ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
313 ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
314 ExprKind::Loop(body, _, source, _) => {
315 self.check_expr_loop(body, source, expected, expr)
317 ExprKind::Match(discrim, arms, match_src) => {
318 self.check_match(expr, &discrim, arms, expected, match_src)
320 ExprKind::Closure(&Closure { capture_clause, fn_decl, body, movability, .. }) => {
321 self.check_expr_closure(expr, capture_clause, &fn_decl, body, movability, expected)
323 ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
324 ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
325 ExprKind::MethodCall(segment, receiver, args, _) => {
326 self.check_method_call(expr, segment, receiver, args, expected)
328 ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
329 ExprKind::Type(e, t) => {
330 let ty = self.to_ty_saving_user_provided_ty(&t);
331 self.check_expr_eq_type(&e, ty);
334 ExprKind::If(cond, then_expr, opt_else_expr) => {
335 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
337 ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
338 ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
339 ExprKind::ConstBlock(ref anon_const) => {
340 self.check_expr_const_block(anon_const, expected, expr)
342 ExprKind::Repeat(element, ref count) => {
343 self.check_expr_repeat(element, count, expected, expr)
345 ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
346 ExprKind::Struct(qpath, fields, ref base_expr) => {
347 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
349 ExprKind::Field(base, field) => self.check_field(expr, &base, field),
350 ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
351 ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
352 hir::ExprKind::Err => tcx.ty_error(),
356 fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
357 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
358 ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
361 let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
362 self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
363 self.tcx.mk_box(referent_ty)
369 oprnd: &'tcx hir::Expr<'tcx>,
370 expected: Expectation<'tcx>,
371 expr: &'tcx hir::Expr<'tcx>,
374 let expected_inner = match unop {
375 hir::UnOp::Not | hir::UnOp::Neg => expected,
376 hir::UnOp::Deref => NoExpectation,
378 let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
380 if !oprnd_t.references_error() {
381 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
383 hir::UnOp::Deref => {
384 if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
387 let mut err = type_error_struct!(
392 "type `{oprnd_t}` cannot be dereferenced",
394 let sp = tcx.sess.source_map().start_point(expr.span);
396 tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
398 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
401 oprnd_t = tcx.ty_error();
405 let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
406 // If it's builtin, we can reuse the type, this helps inference.
407 if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
412 let result = self.check_user_unop(expr, oprnd_t, unop, expected_inner);
413 // If it's builtin, we can reuse the type, this helps inference.
414 if !oprnd_t.is_numeric() {
423 fn check_expr_addr_of(
425 kind: hir::BorrowKind,
426 mutbl: hir::Mutability,
427 oprnd: &'tcx hir::Expr<'tcx>,
428 expected: Expectation<'tcx>,
429 expr: &'tcx hir::Expr<'tcx>,
431 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
433 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
434 if oprnd.is_syntactic_place_expr() {
435 // Places may legitimately have unsized types.
436 // For example, dereferences of a fat pointer and
437 // the last field of a struct can be unsized.
440 Expectation::rvalue_hint(self, *ty)
447 self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
449 let tm = ty::TypeAndMut { ty, mutbl };
451 _ if tm.ty.references_error() => self.tcx.ty_error(),
452 hir::BorrowKind::Raw => {
453 self.check_named_place_expr(oprnd);
456 hir::BorrowKind::Ref => {
457 // Note: at this point, we cannot say what the best lifetime
458 // is to use for resulting pointer. We want to use the
459 // shortest lifetime possible so as to avoid spurious borrowck
460 // errors. Moreover, the longest lifetime will depend on the
461 // precise details of the value whose address is being taken
462 // (and how long it is valid), which we don't know yet until
463 // type inference is complete.
465 // Therefore, here we simply generate a region variable. The
466 // region inferencer will then select a suitable value.
467 // Finally, borrowck will infer the value of the region again,
468 // this time with enough precision to check that the value
469 // whose address was taken can actually be made to live as long
470 // as it needs to live.
471 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
472 self.tcx.mk_ref(region, tm)
477 /// Does this expression refer to a place that either:
478 /// * Is based on a local or static.
479 /// * Contains a dereference
480 /// Note that the adjustments for the children of `expr` should already
481 /// have been resolved.
482 fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
483 let is_named = oprnd.is_place_expr(|base| {
484 // Allow raw borrows if there are any deref adjustments.
486 // const VAL: (i32,) = (0,);
487 // const REF: &(i32,) = &(0,);
489 // &raw const VAL.0; // ERROR
490 // &raw const REF.0; // OK, same as &raw const (*REF).0;
492 // This is maybe too permissive, since it allows
493 // `let u = &raw const Box::new((1,)).0`, which creates an
494 // immediately dangling raw pointer.
499 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
502 self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span });
506 fn check_lang_item_path(
508 lang_item: hir::LangItem,
509 expr: &'tcx hir::Expr<'tcx>,
510 hir_id: Option<hir::HirId>,
512 self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id, hir_id).1
515 pub(crate) fn check_expr_path(
517 qpath: &'tcx hir::QPath<'tcx>,
518 expr: &'tcx hir::Expr<'tcx>,
519 args: &'tcx [hir::Expr<'tcx>],
522 let (res, opt_ty, segs) =
523 self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
526 self.set_tainted_by_errors();
529 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
530 report_unexpected_variant_res(tcx, res, qpath, expr.span);
533 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
536 if let ty::FnDef(did, ..) = *ty.kind() {
537 let fn_sig = ty.fn_sig(tcx);
538 if tcx.fn_sig(did).abi() == RustIntrinsic && tcx.item_name(did) == sym::transmute {
539 let from = fn_sig.inputs().skip_binder()[0];
540 let to = fn_sig.output().skip_binder();
541 // We defer the transmute to the end of typeck, once all inference vars have
542 // been resolved or we errored. This is important as we can only check transmute
543 // on concrete types, but the output type may not be known yet (it would only
544 // be known if explicitly specified via turbofish).
545 self.deferred_transmute_checks.borrow_mut().push((from, to, expr.hir_id));
547 if !tcx.features().unsized_fn_params {
548 // We want to remove some Sized bounds from std functions,
549 // but don't want to expose the removal to stable Rust.
550 // i.e., we don't want to allow
556 // to work in stable even if the Sized bound on `drop` is relaxed.
557 for i in 0..fn_sig.inputs().skip_binder().len() {
558 // We just want to check sizedness, so instead of introducing
559 // placeholder lifetimes with probing, we just replace higher lifetimes
561 let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
562 let input = self.replace_bound_vars_with_fresh_vars(
564 infer::LateBoundRegionConversionTime::FnCall,
567 self.require_type_is_sized_deferred(
570 traits::SizedArgumentType(None),
574 // Here we want to prevent struct constructors from returning unsized types.
575 // There were two cases this happened: fn pointer coercion in stable
576 // and usual function call in presence of unsized_locals.
577 // Also, as we just want to check sizedness, instead of introducing
578 // placeholder lifetimes with probing, we just replace higher lifetimes
580 let output = self.replace_bound_vars_with_fresh_vars(
582 infer::LateBoundRegionConversionTime::FnCall,
585 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
588 // We always require that the type provided as the value for
589 // a type parameter outlives the moment of instantiation.
590 let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
591 self.add_wf_bounds(substs, expr);
598 destination: hir::Destination,
599 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
600 expr: &'tcx hir::Expr<'tcx>,
603 if let Ok(target_id) = destination.target_id {
605 if let Some(e) = expr_opt {
606 // If this is a break with a value, we need to type-check
607 // the expression. Get an expected type from the loop context.
608 let opt_coerce_to = {
609 // We should release `enclosing_breakables` before the `check_expr_with_hint`
610 // below, so can't move this block of code to the enclosing scope and share
611 // `ctxt` with the second `enclosing_breakables` borrow below.
612 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
613 match enclosing_breakables.opt_find_breakable(target_id) {
614 Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
616 // Avoid ICE when `break` is inside a closure (#65383).
617 return tcx.ty_error_with_message(
619 "break was outside loop, but no error was emitted",
625 // If the loop context is not a `loop { }`, then break with
626 // a value is illegal, and `opt_coerce_to` will be `None`.
627 // Just set expectation to error in that case.
628 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
630 // Recurse without `enclosing_breakables` borrowed.
631 e_ty = self.check_expr_with_hint(e, coerce_to);
632 cause = self.misc(e.span);
634 // Otherwise, this is a break *without* a value. That's
635 // always legal, and is equivalent to `break ()`.
636 e_ty = tcx.mk_unit();
637 cause = self.misc(expr.span);
640 // Now that we have type-checked `expr_opt`, borrow
641 // the `enclosing_loops` field and let's coerce the
642 // type of `expr_opt` into what is expected.
643 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
644 let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
645 // Avoid ICE when `break` is inside a closure (#65383).
646 return tcx.ty_error_with_message(
648 "break was outside loop, but no error was emitted",
652 if let Some(ref mut coerce) = ctxt.coerce {
653 if let Some(ref e) = expr_opt {
654 coerce.coerce(self, &cause, e, e_ty);
656 assert!(e_ty.is_unit());
657 let ty = coerce.expected_ty();
658 coerce.coerce_forced_unit(
662 self.suggest_mismatched_types_on_tail(
663 &mut err, expr, ty, e_ty, target_id,
665 if let Some(val) = ty_kind_suggestion(ty) {
666 let label = destination
668 .map(|l| format!(" {}", l.ident))
669 .unwrap_or_else(String::new);
672 "give it a value of the expected type",
673 format!("break{label} {val}"),
674 Applicability::HasPlaceholders,
682 // If `ctxt.coerce` is `None`, we can just ignore
683 // the type of the expression. This is because
684 // either this was a break *without* a value, in
685 // which case it is always a legal type (`()`), or
686 // else an error would have been flagged by the
687 // `loops` pass for using break with an expression
688 // where you are not supposed to.
689 assert!(expr_opt.is_none() || self.tcx.sess.has_errors().is_some());
692 // If we encountered a `break`, then (no surprise) it may be possible to break from the
693 // loop... unless the value being returned from the loop diverges itself, e.g.
694 // `break return 5` or `break loop {}`.
695 ctxt.may_break |= !self.diverges.get().is_always();
697 // the type of a `break` is always `!`, since it diverges
700 // Otherwise, we failed to find the enclosing loop;
701 // this can only happen if the `break` was not
702 // inside a loop at all, which is caught by the
703 // loop-checking pass.
704 let err = self.tcx.ty_error_with_message(
706 "break was outside loop, but no error was emitted",
709 // We still need to assign a type to the inner expression to
710 // prevent the ICE in #43162.
711 if let Some(e) = expr_opt {
712 self.check_expr_with_hint(e, err);
714 // ... except when we try to 'break rust;'.
715 // ICE this expression in particular (see #43162).
716 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
717 if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
718 fatally_break_rust(self.tcx.sess);
723 // There was an error; make type-check fail.
728 fn check_expr_return(
730 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
731 expr: &'tcx hir::Expr<'tcx>,
733 if self.ret_coercion.is_none() {
734 let mut err = ReturnStmtOutsideOfFnBody {
736 encl_body_span: None,
740 let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
742 if let Some(hir::Node::Item(hir::Item {
743 kind: hir::ItemKind::Fn(..),
747 | Some(hir::Node::TraitItem(hir::TraitItem {
748 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
752 | Some(hir::Node::ImplItem(hir::ImplItem {
753 kind: hir::ImplItemKind::Fn(..),
756 })) = self.tcx.hir().find_by_def_id(encl_item_id.def_id)
758 // We are inside a function body, so reporting "return statement
759 // outside of function body" needs an explanation.
761 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
763 // If this didn't hold, we would not have to report an error in
765 assert_ne!(encl_item_id.def_id, encl_body_owner_id);
767 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
768 let encl_body = self.tcx.hir().body(encl_body_id);
770 err.encl_body_span = Some(encl_body.value.span);
771 err.encl_fn_span = Some(*encl_fn_span);
774 self.tcx.sess.emit_err(err);
776 if let Some(e) = expr_opt {
777 // We still have to type-check `e` (issue #86188), but calling
778 // `check_return_expr` only works inside fn bodies.
781 } else if let Some(e) = expr_opt {
782 if self.ret_coercion_span.get().is_none() {
783 self.ret_coercion_span.set(Some(e.span));
785 self.check_return_expr(e, true);
787 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
788 if self.ret_coercion_span.get().is_none() {
789 self.ret_coercion_span.set(Some(expr.span));
791 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
792 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
793 coercion.coerce_forced_unit(
797 let span = fn_decl.output.span();
798 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
801 format!("expected `{snippet}` because of this return type"),
808 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
814 /// `explicit_return` is `true` if we're checking an explicit `return expr`,
815 /// and `false` if we're checking a trailing expression.
816 pub(super) fn check_return_expr(
818 return_expr: &'tcx hir::Expr<'tcx>,
819 explicit_return: bool,
821 let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
822 span_bug!(return_expr.span, "check_return_expr called outside fn body")
825 let ret_ty = ret_coercion.borrow().expected_ty();
826 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
827 let mut span = return_expr.span;
828 // Use the span of the trailing expression for our cause,
829 // not the span of the entire function
830 if !explicit_return {
831 if let ExprKind::Block(body, _) = return_expr.kind && let Some(last_expr) = body.expr {
832 span = last_expr.span;
835 ret_coercion.borrow_mut().coerce(
837 &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
842 if self.return_type_has_opaque {
843 // Point any obligations that were registered due to opaque type
844 // inference at the return expression.
845 self.select_obligations_where_possible(false, |errors| {
846 self.point_at_return_for_opaque_ty_error(errors, span, return_expr_ty);
851 fn point_at_return_for_opaque_ty_error(
853 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
855 return_expr_ty: Ty<'tcx>,
857 // Don't point at the whole block if it's empty
858 if span == self.tcx.hir().span(self.body_id) {
862 let cause = &mut err.obligation.cause;
863 if let ObligationCauseCode::OpaqueReturnType(None) = cause.code() {
864 let new_cause = ObligationCause::new(
867 ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
874 pub(crate) fn check_lhs_assignable(
876 lhs: &'tcx hir::Expr<'tcx>,
877 err_code: &'static str,
879 adjust_err: impl FnOnce(&mut Diagnostic),
881 if lhs.is_syntactic_place_expr() {
885 // FIXME: Make this use Diagnostic once error codes can be dynamically set.
886 let mut err = self.tcx.sess.struct_span_err_with_code(
888 "invalid left-hand side of assignment",
889 DiagnosticId::Error(err_code.into()),
891 err.span_label(lhs.span, "cannot assign to this expression");
893 self.comes_from_while_condition(lhs.hir_id, |expr| {
894 err.span_suggestion_verbose(
895 expr.span.shrink_to_lo(),
896 "you might have meant to use pattern destructuring",
898 Applicability::MachineApplicable,
902 adjust_err(&mut err);
907 // Check if an expression `original_expr_id` comes from the condition of a while loop,
908 // as opposed from the body of a while loop, which we can naively check by iterating
909 // parents until we find a loop...
910 pub(super) fn comes_from_while_condition(
912 original_expr_id: HirId,
913 then: impl FnOnce(&hir::Expr<'_>),
915 let mut parent = self.tcx.hir().get_parent_node(original_expr_id);
916 while let Some(node) = self.tcx.hir().find(parent) {
918 hir::Node::Expr(hir::Expr {
925 hir::ExprKind::Match(expr, ..) | hir::ExprKind::If(expr, ..),
931 hir::LoopSource::While,
936 // Check if our original expression is a child of the condition of a while loop
937 let expr_is_ancestor = std::iter::successors(Some(original_expr_id), |id| {
938 self.tcx.hir().find_parent_node(*id)
940 .take_while(|id| *id != parent)
941 .any(|id| id == expr.hir_id);
942 // if it is, then we have a situation like `while Some(0) = value.get(0) {`,
943 // where `while let` was more likely intended.
944 if expr_is_ancestor {
950 | hir::Node::ImplItem(_)
951 | hir::Node::TraitItem(_)
952 | hir::Node::Crate(_) => break,
954 parent = self.tcx.hir().get_parent_node(parent);
960 // A generic function for checking the 'then' and 'else' clauses in an 'if'
961 // or 'if-else' expression.
964 cond_expr: &'tcx hir::Expr<'tcx>,
965 then_expr: &'tcx hir::Expr<'tcx>,
966 opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
968 orig_expected: Expectation<'tcx>,
970 let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
972 self.warn_if_unreachable(
975 "block in `if` or `while` expression",
978 let cond_diverges = self.diverges.get();
979 self.diverges.set(Diverges::Maybe);
981 let expected = orig_expected.adjust_for_branches(self);
982 let then_ty = self.check_expr_with_expectation(then_expr, expected);
983 let then_diverges = self.diverges.get();
984 self.diverges.set(Diverges::Maybe);
986 // We've already taken the expected type's preferences
987 // into account when typing the `then` branch. To figure
988 // out the initial shot at a LUB, we thus only consider
989 // `expected` if it represents a *hard* constraint
990 // (`only_has_type`); otherwise, we just go with a
991 // fresh type variable.
992 let coerce_to_ty = expected.coercion_target_type(self, sp);
993 let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
995 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
997 if let Some(else_expr) = opt_else_expr {
998 let else_ty = self.check_expr_with_expectation(else_expr, expected);
999 let else_diverges = self.diverges.get();
1001 let opt_suggest_box_span = self.opt_suggest_box_span(then_ty, else_ty, orig_expected);
1002 let if_cause = self.if_cause(
1009 opt_suggest_box_span,
1012 coerce.coerce(self, &if_cause, else_expr, else_ty);
1014 // We won't diverge unless both branches do (or the condition does).
1015 self.diverges.set(cond_diverges | then_diverges & else_diverges);
1017 self.if_fallback_coercion(sp, then_expr, &mut coerce);
1019 // If the condition is false we can't diverge.
1020 self.diverges.set(cond_diverges);
1023 let result_ty = coerce.complete(self);
1024 if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
1027 /// Type check assignment expression `expr` of form `lhs = rhs`.
1028 /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
1029 fn check_expr_assign(
1031 expr: &'tcx hir::Expr<'tcx>,
1032 expected: Expectation<'tcx>,
1033 lhs: &'tcx hir::Expr<'tcx>,
1034 rhs: &'tcx hir::Expr<'tcx>,
1037 let expected_ty = expected.coercion_target_type(self, expr.span);
1038 if expected_ty == self.tcx.types.bool {
1039 // The expected type is `bool` but this will result in `()` so we can reasonably
1040 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
1041 // The likely cause of this is `if foo = bar { .. }`.
1042 let actual_ty = self.tcx.mk_unit();
1043 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
1044 let lhs_ty = self.check_expr(&lhs);
1045 let rhs_ty = self.check_expr(&rhs);
1046 let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
1047 (Applicability::MachineApplicable, true)
1048 } else if let ExprKind::Binary(
1049 Spanned { node: hir::BinOpKind::And | hir::BinOpKind::Or, .. },
1054 let actual_lhs_ty = self.check_expr(&rhs_expr);
1055 (Applicability::MaybeIncorrect, self.can_coerce(rhs_ty, actual_lhs_ty))
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(
1078 span.shrink_to_hi(),
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 rcvr: &'tcx hir::Expr<'tcx>,
1205 args: &'tcx [hir::Expr<'tcx>],
1206 expected: Expectation<'tcx>,
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(rcvr.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(rcvr),
1238 // Call the generic checker.
1239 self.check_method_argument_types(span, expr, method, &args, DontTupleArguments, expected)
1244 e: &'tcx hir::Expr<'tcx>,
1245 t: &'tcx hir::Ty<'tcx>,
1246 expr: &'tcx hir::Expr<'tcx>,
1248 // Find the type of `e`. Supply hints based on the type we are casting to,
1250 let t_cast = self.to_ty_saving_user_provided_ty(t);
1251 let t_cast = self.resolve_vars_if_possible(t_cast);
1252 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1253 let t_expr = self.resolve_vars_if_possible(t_expr);
1255 // Eagerly check for some obvious errors.
1256 if t_expr.references_error() || t_cast.references_error() {
1259 // Defer other checks until we're done type checking.
1260 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1261 match cast::check_cast(self, e, t_expr, t_cast, t.span, expr.span) {
1262 CastCheckResult::Ok => t_cast,
1263 CastCheckResult::Deferred(cast_check) => {
1265 "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1266 t_cast, t_expr, cast_check,
1268 deferred_cast_checks.push(cast_check);
1271 CastCheckResult::Err(ErrorGuaranteed { .. }) => self.tcx.ty_error(),
1276 fn check_expr_array(
1278 args: &'tcx [hir::Expr<'tcx>],
1279 expected: Expectation<'tcx>,
1280 expr: &'tcx hir::Expr<'tcx>,
1282 let element_ty = if !args.is_empty() {
1283 let coerce_to = expected
1285 .and_then(|uty| match *uty.kind() {
1286 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1289 .unwrap_or_else(|| {
1290 self.next_ty_var(TypeVariableOrigin {
1291 kind: TypeVariableOriginKind::TypeInference,
1295 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1296 assert_eq!(self.diverges.get(), Diverges::Maybe);
1298 let e_ty = self.check_expr_with_hint(e, coerce_to);
1299 let cause = self.misc(e.span);
1300 coerce.coerce(self, &cause, e, e_ty);
1302 coerce.complete(self)
1304 self.next_ty_var(TypeVariableOrigin {
1305 kind: TypeVariableOriginKind::TypeInference,
1309 let array_len = args.len() as u64;
1310 self.suggest_array_len(expr, array_len);
1311 self.tcx.mk_array(element_ty, array_len)
1314 fn suggest_array_len(&self, expr: &'tcx hir::Expr<'tcx>, array_len: u64) {
1315 let parent_node = self.tcx.hir().parent_iter(expr.hir_id).find(|(_, node)| {
1316 !matches!(node, hir::Node::Expr(hir::Expr { kind: hir::ExprKind::AddrOf(..), .. }))
1319 hir::Node::Local(hir::Local { ty: Some(ty), .. })
1320 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _), .. }))
1321 ) = parent_node else {
1324 if let hir::TyKind::Array(_, length) = ty.peel_refs().kind
1325 && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
1326 && let Some(span) = self.tcx.hir().opt_span(hir_id)
1328 match self.tcx.sess.diagnostic().steal_diagnostic(span, StashKey::UnderscoreForArrayLengths) {
1330 err.span_suggestion(
1332 "consider specifying the array length",
1334 Applicability::MaybeIncorrect,
1343 fn check_expr_const_block(
1345 anon_const: &'tcx hir::AnonConst,
1346 expected: Expectation<'tcx>,
1347 _expr: &'tcx hir::Expr<'tcx>,
1349 let body = self.tcx.hir().body(anon_const.body);
1351 // Create a new function context.
1352 let fcx = FnCtxt::new(self, self.param_env.with_const(), body.value.hir_id);
1353 crate::check::GatherLocalsVisitor::new(&fcx).visit_body(body);
1355 let ty = fcx.check_expr_with_expectation(&body.value, expected);
1356 fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
1357 fcx.write_ty(anon_const.hir_id, ty);
1361 fn check_expr_repeat(
1363 element: &'tcx hir::Expr<'tcx>,
1364 count: &'tcx hir::ArrayLen,
1365 expected: Expectation<'tcx>,
1366 expr: &'tcx hir::Expr<'tcx>,
1369 let count = self.array_length_to_const(count);
1370 if let Some(count) = count.try_eval_usize(tcx, self.param_env) {
1371 self.suggest_array_len(expr, count);
1374 let uty = match expected {
1375 ExpectHasType(uty) => match *uty.kind() {
1376 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1382 let (element_ty, t) = match uty {
1384 self.check_expr_coercable_to_type(&element, uty, None);
1388 let ty = self.next_ty_var(TypeVariableOrigin {
1389 kind: TypeVariableOriginKind::MiscVariable,
1392 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1397 if element_ty.references_error() {
1398 return tcx.ty_error();
1401 self.check_repeat_element_needs_copy_bound(element, count, element_ty);
1403 tcx.mk_ty(ty::Array(t, count))
1406 fn check_repeat_element_needs_copy_bound(
1408 element: &hir::Expr<'_>,
1409 count: ty::Const<'tcx>,
1410 element_ty: Ty<'tcx>,
1413 // Actual constants as the repeat element get inserted repeatedly instead of getting copied via Copy.
1414 match &element.kind {
1415 hir::ExprKind::ConstBlock(..) => return,
1416 hir::ExprKind::Path(qpath) => {
1417 let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
1418 if let Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _) = res
1425 // If someone calls a const fn, they can extract that call out into a separate constant (or a const
1426 // block in the future), so we check that to tell them that in the diagnostic. Does not affect typeck.
1427 let is_const_fn = match element.kind {
1428 hir::ExprKind::Call(func, _args) => match *self.node_ty(func.hir_id).kind() {
1429 ty::FnDef(def_id, _) => tcx.is_const_fn(def_id),
1435 // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we
1436 // don't copy that one element, we move it. Only check for Copy if the length is larger.
1437 if count.try_eval_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
1438 let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
1439 let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
1440 self.require_type_meets(element_ty, element.span, code, lang_item);
1444 fn check_expr_tuple(
1446 elts: &'tcx [hir::Expr<'tcx>],
1447 expected: Expectation<'tcx>,
1448 expr: &'tcx hir::Expr<'tcx>,
1450 let flds = expected.only_has_type(self).and_then(|ty| {
1451 let ty = self.resolve_vars_with_obligations(ty);
1453 ty::Tuple(flds) => Some(&flds[..]),
1458 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1459 Some(fs) if i < fs.len() => {
1461 self.check_expr_coercable_to_type(&e, ety, None);
1464 _ => self.check_expr_with_expectation(&e, NoExpectation),
1466 let tuple = self.tcx.mk_tup(elt_ts_iter);
1467 if tuple.references_error() {
1470 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1475 fn check_expr_struct(
1477 expr: &hir::Expr<'_>,
1478 expected: Expectation<'tcx>,
1480 fields: &'tcx [hir::ExprField<'tcx>],
1481 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1483 // Find the relevant variant
1484 let Some((variant, adt_ty)) = self.check_struct_path(qpath, expr.hir_id) else {
1485 self.check_struct_fields_on_error(fields, base_expr);
1486 return self.tcx.ty_error();
1489 // Prohibit struct expressions when non-exhaustive flag is set.
1490 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1491 if !adt.did().is_local() && variant.is_field_list_non_exhaustive() {
1494 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1497 self.check_expr_struct_fields(
1508 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1512 fn check_expr_struct_fields(
1515 expected: Expectation<'tcx>,
1516 expr_id: hir::HirId,
1518 variant: &'tcx ty::VariantDef,
1519 ast_fields: &'tcx [hir::ExprField<'tcx>],
1520 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1525 let expected_inputs =
1526 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty]);
1527 let adt_ty_hint = if let Some(expected_inputs) = expected_inputs {
1528 expected_inputs.get(0).cloned().unwrap_or(adt_ty)
1532 // re-link the regions that EIfEO can erase.
1533 self.demand_eqtype(span, adt_ty_hint, adt_ty);
1535 let ty::Adt(adt, substs) = adt_ty.kind() else {
1536 span_bug!(span, "non-ADT passed to check_expr_struct_fields");
1538 let adt_kind = adt.adt_kind();
1540 let mut remaining_fields = variant
1544 .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
1545 .collect::<FxHashMap<_, _>>();
1547 let mut seen_fields = FxHashMap::default();
1549 let mut error_happened = false;
1551 // Type-check each field.
1552 for (idx, field) in ast_fields.iter().enumerate() {
1553 let ident = tcx.adjust_ident(field.ident, variant.def_id);
1554 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1555 seen_fields.insert(ident, field.span);
1556 self.write_field_index(field.hir_id, i);
1558 // We don't look at stability attributes on
1559 // struct-like enums (yet...), but it's definitely not
1560 // a bug to have constructed one.
1561 if adt_kind != AdtKind::Enum {
1562 tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1565 self.field_ty(field.span, v_field, substs)
1567 error_happened = true;
1568 if let Some(prev_span) = seen_fields.get(&ident) {
1569 tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1570 span: field.ident.span,
1571 prev_span: *prev_span,
1575 self.report_unknown_field(
1580 adt.variant_descr(),
1588 // Make sure to give a type to the field even if there's
1589 // an error, so we can continue type-checking.
1590 let ty = self.check_expr_with_hint(&field.expr, field_type);
1592 self.demand_coerce_diag(&field.expr, ty, field_type, None, AllowTwoPhase::No);
1594 if let Some(mut diag) = diag {
1595 if idx == ast_fields.len() - 1 && remaining_fields.is_empty() {
1596 self.suggest_fru_from_range(field, variant, substs, &mut diag);
1602 // Make sure the programmer specified correct number of fields.
1603 if adt_kind == AdtKind::Union {
1604 if ast_fields.len() != 1 {
1609 "union expressions should have exactly one field",
1615 // If check_expr_struct_fields hit an error, do not attempt to populate
1616 // the fields with the base_expr. This could cause us to hit errors later
1617 // when certain fields are assumed to exist that in fact do not.
1622 if let Some(base_expr) = base_expr {
1623 // FIXME: We are currently creating two branches here in order to maintain
1624 // consistency. But they should be merged as much as possible.
1625 let fru_tys = if self.tcx.features().type_changing_struct_update {
1626 if adt.is_struct() {
1627 // Make some fresh substitutions for our ADT type.
1628 let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
1629 // We do subtyping on the FRU fields first, so we can
1630 // learn exactly what types we expect the base expr
1631 // needs constrained to be compatible with the struct
1632 // type we expect from the expectation value.
1633 let fru_tys = variant
1637 let fru_ty = self.normalize_associated_types_in(
1639 self.field_ty(base_expr.span, f, fresh_substs),
1641 let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
1642 if let Some(_) = remaining_fields.remove(&ident) {
1643 let target_ty = self.field_ty(base_expr.span, f, substs);
1644 let cause = self.misc(base_expr.span);
1645 match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
1646 Ok(InferOk { obligations, value: () }) => {
1647 self.register_predicates(obligations)
1650 // This should never happen, since we're just subtyping the
1651 // remaining_fields, but it's fine to emit this, I guess.
1653 .report_mismatched_types(
1657 FieldMisMatch(variant.name, ident.name),
1663 self.resolve_vars_if_possible(fru_ty)
1666 // The use of fresh substs that we have subtyped against
1667 // our base ADT type's fields allows us to guide inference
1668 // along so that, e.g.
1670 // MyStruct<'a, F1, F2, const C: usize> {
1672 // // Other fields that reference `'a`, `F2`, and `C`
1675 // let x = MyStruct {
1680 // will have the `other_struct` expression constrained to
1681 // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
1682 // This is important to allow coercions to happen in
1683 // `other_struct` itself. See `coerce-in-base-expr.rs`.
1684 let fresh_base_ty = self.tcx.mk_adt(*adt, fresh_substs);
1685 self.check_expr_has_type_or_error(
1687 self.resolve_vars_if_possible(fresh_base_ty),
1692 // Check the base_expr, regardless of a bad expected adt_ty, so we can get
1693 // type errors on that expression, too.
1694 self.check_expr(base_expr);
1697 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1701 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {
1702 let base_ty = self.typeck_results.borrow().expr_ty(*base_expr);
1703 let same_adt = match (adt_ty.kind(), base_ty.kind()) {
1704 (ty::Adt(adt, _), ty::Adt(base_adt, _)) if adt == base_adt => true,
1707 if self.tcx.sess.is_nightly_build() && same_adt {
1709 &self.tcx.sess.parse_sess,
1710 sym::type_changing_struct_update,
1712 "type changing struct updating is experimental",
1717 match adt_ty.kind() {
1718 ty::Adt(adt, substs) if adt.is_struct() => variant
1722 self.normalize_associated_types_in(expr_span, f.ty(self.tcx, substs))
1728 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1733 self.typeck_results.borrow_mut().fru_field_types_mut().insert(expr_id, fru_tys);
1734 } else if adt_kind != AdtKind::Union && !remaining_fields.is_empty() {
1735 debug!(?remaining_fields);
1736 let private_fields: Vec<&ty::FieldDef> = variant
1739 .filter(|field| !field.vis.is_accessible_from(tcx.parent_module(expr_id), tcx))
1742 if !private_fields.is_empty() {
1743 self.report_private_fields(adt_ty, span, private_fields, ast_fields);
1745 self.report_missing_fields(
1757 fn check_struct_fields_on_error(
1759 fields: &'tcx [hir::ExprField<'tcx>],
1760 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1762 for field in fields {
1763 self.check_expr(&field.expr);
1765 if let Some(base) = *base_expr {
1766 self.check_expr(&base);
1770 /// Report an error for a struct field expression when there are fields which aren't provided.
1773 /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1774 /// --> src/main.rs:8:5
1776 /// 8 | foo::Foo {};
1777 /// | ^^^^^^^^ missing `you_can_use_this_field`
1779 /// error: aborting due to previous error
1781 fn report_missing_fields(
1785 remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1786 variant: &'tcx ty::VariantDef,
1787 ast_fields: &'tcx [hir::ExprField<'tcx>],
1788 substs: SubstsRef<'tcx>,
1790 let len = remaining_fields.len();
1792 let mut displayable_field_names: Vec<&str> =
1793 remaining_fields.keys().map(|ident| ident.as_str()).collect();
1794 // sorting &str primitives here, sort_unstable is ok
1795 displayable_field_names.sort_unstable();
1797 let mut truncated_fields_error = String::new();
1798 let remaining_fields_names = match &displayable_field_names[..] {
1799 [field1] => format!("`{}`", field1),
1800 [field1, field2] => format!("`{field1}` and `{field2}`"),
1801 [field1, field2, field3] => format!("`{field1}`, `{field2}` and `{field3}`"),
1803 truncated_fields_error =
1804 format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1805 displayable_field_names
1808 .map(|n| format!("`{n}`"))
1809 .collect::<Vec<_>>()
1814 let mut err = struct_span_err!(
1818 "missing field{} {}{} in initializer of `{}`",
1820 remaining_fields_names,
1821 truncated_fields_error,
1824 err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
1826 if let Some(last) = ast_fields.last() {
1827 self.suggest_fru_from_range(last, variant, substs, &mut err);
1833 /// If the last field is a range literal, but it isn't supposed to be, then they probably
1834 /// meant to use functional update syntax.
1835 fn suggest_fru_from_range(
1837 last_expr_field: &hir::ExprField<'tcx>,
1838 variant: &ty::VariantDef,
1839 substs: SubstsRef<'tcx>,
1840 err: &mut Diagnostic,
1842 // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
1843 if let ExprKind::Struct(
1844 QPath::LangItem(LangItem::Range, ..),
1845 &[ref range_start, ref range_end],
1847 ) = last_expr_field.expr.kind
1848 && let variant_field =
1849 variant.fields.iter().find(|field| field.ident(self.tcx) == last_expr_field.ident)
1850 && let range_def_id = self.tcx.lang_items().range_struct()
1852 .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
1853 .map(|adt| adt.did())
1860 .span_to_snippet(range_end.expr.span)
1861 .map(|s| format!(" from `{s}`"))
1862 .unwrap_or_default();
1863 err.span_suggestion(
1864 range_start.span.shrink_to_hi(),
1865 &format!("to set the remaining fields{instead}, separate the last named field with a comma"),
1867 Applicability::MaybeIncorrect,
1872 /// Report an error for a struct field expression when there are invisible fields.
1875 /// error: cannot construct `Foo` with struct literal syntax due to private fields
1876 /// --> src/main.rs:8:5
1878 /// 8 | foo::Foo {};
1881 /// error: aborting due to previous error
1883 fn report_private_fields(
1887 private_fields: Vec<&ty::FieldDef>,
1888 used_fields: &'tcx [hir::ExprField<'tcx>],
1890 let mut err = self.tcx.sess.struct_span_err(
1893 "cannot construct `{adt_ty}` with struct literal syntax due to private fields",
1896 let (used_private_fields, remaining_private_fields): (
1897 Vec<(Symbol, Span, bool)>,
1898 Vec<(Symbol, Span, bool)>,
1902 match used_fields.iter().find(|used_field| field.name == used_field.ident.name) {
1903 Some(used_field) => (field.name, used_field.span, true),
1904 None => (field.name, self.tcx.def_span(field.did), false),
1907 .partition(|field| field.2);
1908 err.span_labels(used_private_fields.iter().map(|(_, span, _)| *span), "private field");
1909 if !remaining_private_fields.is_empty() {
1910 let remaining_private_fields_len = remaining_private_fields.len();
1911 let names = match &remaining_private_fields
1913 .map(|(name, _, _)| name)
1914 .collect::<Vec<_>>()[..]
1916 _ if remaining_private_fields_len > 6 => String::new(),
1917 [name] => format!("`{name}` "),
1918 [names @ .., last] => {
1919 let names = names.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
1920 format!("{} and `{last}` ", names.join(", "))
1922 [] => unreachable!(),
1925 "... and other private field{s} {names}that {were} not provided",
1926 s = pluralize!(remaining_private_fields_len),
1927 were = pluralize!("was", remaining_private_fields_len),
1933 fn report_unknown_field(
1936 variant: &'tcx ty::VariantDef,
1937 field: &hir::ExprField<'_>,
1938 skip_fields: &[hir::ExprField<'_>],
1942 if variant.is_recovered() {
1943 self.set_tainted_by_errors();
1946 let mut err = self.err_ctxt().type_error_struct_with_diag(
1948 |actual| match ty.kind() {
1949 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1953 "{} `{}::{}` has no field named `{}`",
1959 _ => struct_span_err!(
1963 "{} `{}` has no field named `{}`",
1972 let variant_ident_span = self.tcx.def_ident_span(variant.def_id).unwrap();
1973 match variant.ctor_kind {
1974 CtorKind::Fn => match ty.kind() {
1975 ty::Adt(adt, ..) if adt.is_enum() => {
1979 "`{adt}::{variant}` defined here",
1981 variant = variant.name,
1984 err.span_label(field.ident.span, "field does not exist");
1985 err.span_suggestion_verbose(
1988 "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1990 variant = variant.name,
1993 "{adt}::{variant}(/* fields */)",
1995 variant = variant.name,
1997 Applicability::HasPlaceholders,
2001 err.span_label(variant_ident_span, format!("`{adt}` defined here", adt = ty));
2002 err.span_label(field.ident.span, "field does not exist");
2003 err.span_suggestion_verbose(
2006 "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
2008 kind_name = kind_name,
2010 format!("{adt}(/* fields */)", adt = ty),
2011 Applicability::HasPlaceholders,
2016 // prevent all specified fields from being suggested
2017 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
2018 if let Some(field_name) = self.suggest_field_name(
2021 skip_fields.collect(),
2024 err.span_suggestion(
2026 "a field with a similar name exists",
2028 Applicability::MaybeIncorrect,
2032 ty::Adt(adt, ..) => {
2036 format!("`{}::{}` does not have this field", ty, variant.name),
2041 format!("`{ty}` does not have this field"),
2044 let available_field_names =
2045 self.available_field_names(variant, expr_span);
2046 if !available_field_names.is_empty() {
2048 "available fields are: {}",
2049 self.name_series_display(available_field_names)
2053 _ => bug!("non-ADT passed to report_unknown_field"),
2061 // Return a hint about the closest match in field names
2062 fn suggest_field_name(
2064 variant: &'tcx ty::VariantDef,
2067 // The span where stability will be checked
2069 ) -> Option<Symbol> {
2073 .filter_map(|field| {
2074 // ignore already set fields and private fields from non-local crates
2075 // and unstable fields.
2076 if skip.iter().any(|&x| x == field.name)
2077 || (!variant.def_id.is_local() && !field.vis.is_public())
2079 self.tcx.eval_stability(field.did, None, span, None),
2080 stability::EvalResult::Deny { .. }
2088 .collect::<Vec<Symbol>>();
2090 find_best_match_for_name(&names, field, None)
2093 fn available_field_names(
2095 variant: &'tcx ty::VariantDef,
2102 let def_scope = self
2104 .adjust_ident_and_get_scope(field.ident(self.tcx), variant.def_id, self.body_id)
2106 field.vis.is_accessible_from(def_scope, self.tcx)
2108 self.tcx.eval_stability(field.did, None, access_span, None),
2109 stability::EvalResult::Deny { .. }
2112 .filter(|field| !self.tcx.is_doc_hidden(field.did))
2113 .map(|field| field.name)
2117 fn name_series_display(&self, names: Vec<Symbol>) -> String {
2118 // dynamic limit, to never omit just one field
2119 let limit = if names.len() == 6 { 6 } else { 5 };
2121 names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
2122 if names.len() > limit {
2123 display = format!("{} ... and {} others", display, names.len() - limit);
2128 // Check field access expressions
2131 expr: &'tcx hir::Expr<'tcx>,
2132 base: &'tcx hir::Expr<'tcx>,
2135 debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
2136 let base_ty = self.check_expr(base);
2137 let base_ty = self.structurally_resolved_type(base.span, base_ty);
2138 let mut private_candidate = None;
2139 let mut autoderef = self.autoderef(expr.span, base_ty);
2140 while let Some((deref_base_ty, _)) = autoderef.next() {
2141 debug!("deref_base_ty: {:?}", deref_base_ty);
2142 match deref_base_ty.kind() {
2143 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2144 debug!("struct named {:?}", deref_base_ty);
2145 let (ident, def_scope) =
2146 self.tcx.adjust_ident_and_get_scope(field, base_def.did(), self.body_id);
2147 let fields = &base_def.non_enum_variant().fields;
2148 if let Some(index) = fields
2150 .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
2152 let field = &fields[index];
2153 let field_ty = self.field_ty(expr.span, field, substs);
2154 // Save the index of all fields regardless of their visibility in case
2155 // of error recovery.
2156 self.write_field_index(expr.hir_id, index);
2157 let adjustments = self.adjust_steps(&autoderef);
2158 if field.vis.is_accessible_from(def_scope, self.tcx) {
2159 self.apply_adjustments(base, adjustments);
2160 self.register_predicates(autoderef.into_obligations());
2162 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
2165 private_candidate = Some((adjustments, base_def.did(), field_ty));
2169 let fstr = field.as_str();
2170 if let Ok(index) = fstr.parse::<usize>() {
2171 if fstr == index.to_string() {
2172 if let Some(&field_ty) = tys.get(index) {
2173 let adjustments = self.adjust_steps(&autoderef);
2174 self.apply_adjustments(base, adjustments);
2175 self.register_predicates(autoderef.into_obligations());
2177 self.write_field_index(expr.hir_id, index);
2186 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
2188 if let Some((adjustments, did, field_ty)) = private_candidate {
2189 // (#90483) apply adjustments to avoid ExprUseVisitor from
2190 // creating erroneous projection.
2191 self.apply_adjustments(base, adjustments);
2192 self.ban_private_field_access(expr, base_ty, field, did);
2196 if field.name == kw::Empty {
2197 } else if self.method_exists(field, base_ty, expr.hir_id, true) {
2198 self.ban_take_value_of_method(expr, base_ty, field);
2199 } else if !base_ty.is_primitive_ty() {
2200 self.ban_nonexisting_field(field, base, expr, base_ty);
2202 let field_name = field.to_string();
2203 let mut err = type_error_struct!(
2208 "`{base_ty}` is a primitive type and therefore doesn't have fields",
2210 let is_valid_suffix = |field: &str| {
2211 if field == "f32" || field == "f64" {
2214 let mut chars = field.chars().peekable();
2215 match chars.peek() {
2216 Some('e') | Some('E') => {
2218 if let Some(c) = chars.peek()
2219 && !c.is_numeric() && *c != '-' && *c != '+'
2223 while let Some(c) = chars.peek() {
2224 if !c.is_numeric() {
2232 let suffix = chars.collect::<String>();
2233 suffix.is_empty() || suffix == "f32" || suffix == "f64"
2235 let maybe_partial_suffix = |field: &str| -> Option<&str> {
2236 let first_chars = ['f', 'l'];
2238 && field.to_lowercase().starts_with(first_chars)
2239 && field[1..].chars().all(|c| c.is_ascii_digit())
2241 if field.to_lowercase().starts_with(['f']) { Some("f32") } else { Some("f64") }
2246 if let ty::Infer(ty::IntVar(_)) = base_ty.kind()
2247 && let ExprKind::Lit(Spanned {
2248 node: ast::LitKind::Int(_, ast::LitIntType::Unsuffixed),
2251 && !base.span.from_expansion()
2253 if is_valid_suffix(&field_name) {
2254 err.span_suggestion_verbose(
2255 field.span.shrink_to_lo(),
2256 "if intended to be a floating point literal, consider adding a `0` after the period",
2258 Applicability::MaybeIncorrect,
2260 } else if let Some(correct_suffix) = maybe_partial_suffix(&field_name) {
2261 err.span_suggestion_verbose(
2263 format!("if intended to be a floating point literal, consider adding a `0` after the period and a `{correct_suffix}` suffix"),
2264 format!("0{correct_suffix}"),
2265 Applicability::MaybeIncorrect,
2272 self.tcx().ty_error()
2275 fn suggest_await_on_field_access(
2277 err: &mut Diagnostic,
2279 base: &'tcx hir::Expr<'tcx>,
2282 let output_ty = match self.get_impl_future_output_ty(ty) {
2283 Some(output_ty) => self.resolve_vars_if_possible(output_ty),
2286 let mut add_label = true;
2287 if let ty::Adt(def, _) = output_ty.skip_binder().kind() {
2288 // no field access on enum type
2294 .any(|field| field.ident(self.tcx) == field_ident)
2299 "field not available in `impl Future`, but it is available in its `Output`",
2301 err.span_suggestion_verbose(
2302 base.span.shrink_to_hi(),
2303 "consider `await`ing on the `Future` and access the field of its `Output`",
2305 Applicability::MaybeIncorrect,
2311 err.span_label(field_ident.span, &format!("field not found in `{ty}`"));
2315 fn ban_nonexisting_field(
2318 base: &'tcx hir::Expr<'tcx>,
2319 expr: &'tcx hir::Expr<'tcx>,
2323 "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, base_ty={:?}",
2324 ident, base, expr, base_ty
2326 let mut err = self.no_such_field_err(ident, base_ty, base.hir_id);
2328 match *base_ty.peel_refs().kind() {
2329 ty::Array(_, len) => {
2330 self.maybe_suggest_array_indexing(&mut err, expr, base, ident, len);
2333 self.suggest_first_deref_field(&mut err, expr, base, ident);
2335 ty::Adt(def, _) if !def.is_enum() => {
2336 self.suggest_fields_on_recordish(&mut err, def, ident, expr.span);
2338 ty::Param(param_ty) => {
2339 self.point_at_param_definition(&mut err, param_ty);
2341 ty::Opaque(_, _) => {
2342 self.suggest_await_on_field_access(&mut err, ident, base, base_ty.peel_refs());
2347 self.suggest_fn_call(&mut err, base, base_ty, |output_ty| {
2348 if let ty::Adt(def, _) = output_ty.kind() && !def.is_enum() {
2349 def.non_enum_variant().fields.iter().any(|field| {
2350 field.ident(self.tcx) == ident
2351 && field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
2353 } else if let ty::Tuple(tys) = output_ty.kind()
2354 && let Ok(idx) = ident.as_str().parse::<usize>()
2362 if ident.name == kw::Await {
2363 // We know by construction that `<expr>.await` is either on Rust 2015
2364 // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
2365 err.note("to `.await` a `Future`, switch to Rust 2018 or later");
2366 err.help_use_latest_edition();
2372 fn ban_private_field_access(
2374 expr: &hir::Expr<'_>,
2379 let struct_path = self.tcx().def_path_str(base_did);
2380 let kind_name = self.tcx().def_kind(base_did).descr(base_did);
2381 let mut err = struct_span_err!(
2385 "field `{field}` of {kind_name} `{struct_path}` is private",
2387 err.span_label(field.span, "private field");
2388 // Also check if an accessible method exists, which is often what is meant.
2389 if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
2391 self.suggest_method_call(
2393 &format!("a method `{field}` also exists, call it with parentheses"),
2403 fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
2404 let mut err = type_error_struct!(
2409 "attempted to take value of method `{field}` on type `{expr_t}`",
2411 err.span_label(field.span, "method, not a field");
2413 if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
2414 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
2416 expr.hir_id == callee.hir_id
2421 self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or_default();
2422 let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
2423 let after_open = expr.span.lo() + rustc_span::BytePos(1);
2424 let before_close = expr.span.hi() - rustc_span::BytePos(1);
2426 if expr_is_call && is_wrapped {
2427 err.multipart_suggestion(
2428 "remove wrapping parentheses to call the method",
2430 (expr.span.with_hi(after_open), String::new()),
2431 (expr.span.with_lo(before_close), String::new()),
2433 Applicability::MachineApplicable,
2435 } else if !self.expr_in_place(expr.hir_id) {
2436 // Suggest call parentheses inside the wrapping parentheses
2437 let span = if is_wrapped {
2438 expr.span.with_lo(after_open).with_hi(before_close)
2442 self.suggest_method_call(
2444 "use parentheses to call the method",
2450 } else if let ty::RawPtr(ty_and_mut) = expr_t.kind()
2451 && let ty::Adt(adt_def, _) = ty_and_mut.ty.kind()
2452 && let ExprKind::Field(base_expr, _) = expr.kind
2453 && adt_def.variants().len() == 1
2461 .any(|f| f.ident(self.tcx) == field)
2463 err.multipart_suggestion(
2464 "to access the field, dereference first",
2466 (base_expr.span.shrink_to_lo(), "(*".to_string()),
2467 (base_expr.span.shrink_to_hi(), ")".to_string()),
2469 Applicability::MaybeIncorrect,
2472 err.help("methods are immutable and cannot be assigned to");
2478 fn point_at_param_definition(&self, err: &mut Diagnostic, param: ty::ParamTy) {
2479 let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
2480 let generic_param = generics.type_param(¶m, self.tcx);
2481 if let ty::GenericParamDefKind::Type { synthetic: true, .. } = generic_param.kind {
2484 let param_def_id = generic_param.def_id;
2485 let param_hir_id = match param_def_id.as_local() {
2486 Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
2489 let param_span = self.tcx.hir().span(param_hir_id);
2490 let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
2492 err.span_label(param_span, &format!("type parameter '{param_name}' declared here"));
2495 fn suggest_fields_on_recordish(
2497 err: &mut Diagnostic,
2498 def: ty::AdtDef<'tcx>,
2502 if let Some(suggested_field_name) =
2503 self.suggest_field_name(def.non_enum_variant(), field.name, vec![], access_span)
2505 err.span_suggestion(
2507 "a field with a similar name exists",
2508 suggested_field_name,
2509 Applicability::MaybeIncorrect,
2512 err.span_label(field.span, "unknown field");
2513 let struct_variant_def = def.non_enum_variant();
2514 let field_names = self.available_field_names(struct_variant_def, access_span);
2515 if !field_names.is_empty() {
2517 "available fields are: {}",
2518 self.name_series_display(field_names),
2524 fn maybe_suggest_array_indexing(
2526 err: &mut Diagnostic,
2527 expr: &hir::Expr<'_>,
2528 base: &hir::Expr<'_>,
2530 len: ty::Const<'tcx>,
2532 if let (Some(len), Ok(user_index)) =
2533 (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
2534 && let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span)
2536 let help = "instead of using tuple indexing, use array indexing";
2537 let suggestion = format!("{base}[{field}]");
2538 let applicability = if len < user_index {
2539 Applicability::MachineApplicable
2541 Applicability::MaybeIncorrect
2543 err.span_suggestion(expr.span, help, suggestion, applicability);
2547 fn suggest_first_deref_field(
2549 err: &mut Diagnostic,
2550 expr: &hir::Expr<'_>,
2551 base: &hir::Expr<'_>,
2554 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2555 let msg = format!("`{base}` is a raw pointer; try dereferencing it");
2556 let suggestion = format!("(*{base}).{field}");
2557 err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2561 fn no_such_field_err(
2566 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
2567 let span = field.span;
2568 debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2570 let mut err = type_error_struct!(
2575 "no field `{field}` on type `{expr_t}`",
2578 // try to add a suggestion in case the field is a nested field of a field of the Adt
2579 let mod_id = self.tcx.parent_module(id).to_def_id();
2580 if let Some((fields, substs)) =
2581 self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
2583 let candidate_fields: Vec<_> = fields
2584 .filter_map(|candidate_field| {
2585 self.check_for_nested_field_satisfying(
2587 &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
2594 .map(|mut field_path| {
2598 .map(|id| id.name.to_ident_string())
2599 .collect::<Vec<String>>()
2602 .collect::<Vec<_>>();
2604 let len = candidate_fields.len();
2606 err.span_suggestions(
2607 field.span.shrink_to_lo(),
2609 "{} of the expressions' fields {} a field of the same name",
2610 if len > 1 { "some" } else { "one" },
2611 if len > 1 { "have" } else { "has" },
2613 candidate_fields.iter().map(|path| format!("{path}.")),
2614 Applicability::MaybeIncorrect,
2621 pub(crate) fn get_field_candidates_considering_privacy(
2626 ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
2627 debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
2629 for (base_t, _) in self.autoderef(span, base_ty) {
2630 match base_t.kind() {
2631 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2633 let fields = &base_def.non_enum_variant().fields;
2634 // Some struct, e.g. some that impl `Deref`, have all private fields
2635 // because you're expected to deref them to access the _real_ fields.
2636 // This, for example, will help us suggest accessing a field through a `Box<T>`.
2637 if fields.iter().all(|field| !field.vis.is_accessible_from(mod_id, tcx)) {
2643 .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
2644 // For compile-time reasons put a limit on number of fields we search
2655 /// This method is called after we have encountered a missing field error to recursively
2656 /// search for the field
2657 pub(crate) fn check_for_nested_field_satisfying(
2660 matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
2661 candidate_field: &ty::FieldDef,
2662 subst: SubstsRef<'tcx>,
2663 mut field_path: Vec<Ident>,
2665 ) -> Option<Vec<Ident>> {
2667 "check_for_nested_field_satisfying(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2668 span, candidate_field, field_path
2671 if field_path.len() > 3 {
2672 // For compile-time reasons and to avoid infinite recursion we only check for fields
2673 // up to a depth of three
2676 field_path.push(candidate_field.ident(self.tcx).normalize_to_macros_2_0());
2677 let field_ty = candidate_field.ty(self.tcx, subst);
2678 if matches(candidate_field, field_ty) {
2679 return Some(field_path);
2680 } else if let Some((nested_fields, subst)) =
2681 self.get_field_candidates_considering_privacy(span, field_ty, mod_id)
2683 // recursively search fields of `candidate_field` if it's a ty::Adt
2684 for field in nested_fields {
2685 if let Some(field_path) = self.check_for_nested_field_satisfying(
2693 return Some(field_path);
2701 fn check_expr_index(
2703 base: &'tcx hir::Expr<'tcx>,
2704 idx: &'tcx hir::Expr<'tcx>,
2705 expr: &'tcx hir::Expr<'tcx>,
2707 let base_t = self.check_expr(&base);
2708 let idx_t = self.check_expr(&idx);
2710 if base_t.references_error() {
2712 } else if idx_t.references_error() {
2715 let base_t = self.structurally_resolved_type(base.span, base_t);
2716 match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2717 Some((index_ty, element_ty)) => {
2718 // two-phase not needed because index_ty is never mutable
2719 self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2720 self.select_obligations_where_possible(false, |errors| {
2721 self.point_at_index_if_possible(errors, idx.span)
2726 let mut err = type_error_struct!(
2731 "cannot index into a value of type `{base_t}`",
2733 // Try to give some advice about indexing tuples.
2734 if let ty::Tuple(..) = base_t.kind() {
2735 let mut needs_note = true;
2736 // If the index is an integer, we can show the actual
2737 // fixed expression:
2738 if let ExprKind::Lit(ref lit) = idx.kind {
2739 if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2740 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2741 if let Ok(snip) = snip {
2742 err.span_suggestion(
2744 "to access tuple elements, use",
2745 format!("{snip}.{i}"),
2746 Applicability::MachineApplicable,
2754 "to access tuple elements, use tuple indexing \
2755 syntax (e.g., `tuple.0`)",
2766 fn point_at_index_if_possible(
2768 errors: &mut Vec<traits::FulfillmentError<'tcx>>,
2771 for error in errors {
2772 match error.obligation.predicate.kind().skip_binder() {
2773 ty::PredicateKind::Trait(predicate)
2774 if self.tcx.is_diagnostic_item(sym::SliceIndex, predicate.trait_ref.def_id) => {
2778 error.obligation.cause.span = span;
2782 fn check_expr_yield(
2784 value: &'tcx hir::Expr<'tcx>,
2785 expr: &'tcx hir::Expr<'tcx>,
2786 src: &'tcx hir::YieldSource,
2788 match self.resume_yield_tys {
2789 Some((resume_ty, yield_ty)) => {
2790 self.check_expr_coercable_to_type(&value, yield_ty, None);
2794 // Given that this `yield` expression was generated as a result of lowering a `.await`,
2795 // we know that the yield type must be `()`; however, the context won't contain this
2796 // information. Hence, we check the source of the yield expression here and check its
2797 // value's type against `()` (this check should always hold).
2798 None if src.is_await() => {
2799 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2803 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2804 // Avoid expressions without types during writeback (#78653).
2805 self.check_expr(value);
2811 fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2812 let needs = if is_input { Needs::None } else { Needs::MutPlace };
2813 let ty = self.check_expr_with_needs(expr, needs);
2814 self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2816 if !is_input && !expr.is_syntactic_place_expr() {
2817 let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2818 err.span_label(expr.span, "cannot assign to this expression");
2822 // If this is an input value, we require its type to be fully resolved
2823 // at this point. This allows us to provide helpful coercions which help
2824 // pass the type candidate list in a later pass.
2826 // We don't require output types to be resolved at this point, which
2827 // allows them to be inferred based on how they are used later in the
2830 let ty = self.structurally_resolved_type(expr.span, ty);
2833 let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2834 self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2836 ty::Ref(_, base_ty, mutbl) => {
2837 let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2838 self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2845 fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2846 for (op, _op_sp) in asm.operands {
2848 hir::InlineAsmOperand::In { expr, .. } => {
2849 self.check_expr_asm_operand(expr, true);
2851 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2852 | hir::InlineAsmOperand::InOut { expr, .. } => {
2853 self.check_expr_asm_operand(expr, false);
2855 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2856 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2857 self.check_expr_asm_operand(in_expr, true);
2858 if let Some(out_expr) = out_expr {
2859 self.check_expr_asm_operand(out_expr, false);
2862 // `AnonConst`s have their own body and is type-checked separately.
2863 // As they don't flow into the type system we don't need them to
2865 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } => {}
2866 hir::InlineAsmOperand::SymStatic { .. } => {}
2869 if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2870 self.tcx.types.never
2877 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2878 Some(match ty.kind() {
2881 ty::Int(_) | ty::Uint(_) => "42",
2882 ty::Float(_) => "3.14159",
2883 ty::Error(_) | ty::Never => return None,