1 //! Type checking expressions.
3 //! See `mod.rs` for more context on type checking in general.
5 use crate::astconv::AstConv as _;
6 use crate::check::cast;
7 use crate::check::coercion::CoerceMany;
8 use crate::check::fatally_break_rust;
9 use crate::check::method::SelfSource;
10 use crate::check::report_unexpected_variant_res;
11 use crate::check::BreakableCtxt;
12 use crate::check::Diverges;
13 use crate::check::DynamicCoerceMany;
14 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
15 use crate::check::FnCtxt;
16 use crate::check::Needs;
17 use crate::check::TupleArgumentsFlag::DontTupleArguments;
19 FieldMultiplySpecifiedInInitializer, FunctionalRecordUpdateOnNonStruct,
20 YieldExprOutsideOfGenerator,
22 use crate::type_error_struct;
24 use crate::errors::{AddressOfTemporaryTaken, ReturnStmtOutsideOfFnBody, StructExprNonExhaustive};
26 use rustc_data_structures::fx::FxHashMap;
27 use rustc_data_structures::stack::ensure_sufficient_stack;
28 use rustc_errors::ErrorReported;
29 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
31 use rustc_hir::def::{CtorKind, DefKind, Res};
32 use rustc_hir::def_id::DefId;
33 use rustc_hir::{ExprKind, QPath};
34 use rustc_infer::infer;
35 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
37 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
38 use rustc_middle::ty::subst::SubstsRef;
39 use rustc_middle::ty::Ty;
40 use rustc_middle::ty::TypeFoldable;
41 use rustc_middle::ty::{AdtKind, Visibility};
42 use rustc_span::edition::LATEST_STABLE_EDITION;
43 use rustc_span::hygiene::DesugaringKind;
44 use rustc_span::lev_distance::find_best_match_for_name;
45 use rustc_span::source_map::Span;
46 use rustc_span::symbol::{kw, sym, Ident, Symbol};
47 use rustc_trait_selection::traits::{self, ObligationCauseCode};
49 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
50 fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
51 let ty = self.check_expr_with_hint(expr, expected);
52 self.demand_eqtype(expr.span, expected, ty);
55 pub fn check_expr_has_type_or_error(
57 expr: &'tcx hir::Expr<'tcx>,
59 extend_err: impl Fn(&mut DiagnosticBuilder<'_>),
61 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
64 fn check_expr_meets_expectation_or_error(
66 expr: &'tcx hir::Expr<'tcx>,
67 expected: Expectation<'tcx>,
68 extend_err: impl Fn(&mut DiagnosticBuilder<'_>),
70 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
71 let mut ty = self.check_expr_with_expectation(expr, expected);
73 // While we don't allow *arbitrary* coercions here, we *do* allow
74 // coercions from ! to `expected`.
77 !self.typeck_results.borrow().adjustments().contains_key(expr.hir_id),
78 "expression with never type wound up being adjusted"
80 let adj_ty = self.next_ty_var(TypeVariableOrigin {
81 kind: TypeVariableOriginKind::AdjustmentType,
84 self.apply_adjustments(
86 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
91 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
92 let expr = expr.peel_drop_temps();
93 self.suggest_deref_ref_or_into(&mut err, expr, expected_ty, ty, None);
100 pub(super) fn check_expr_coercable_to_type(
102 expr: &'tcx hir::Expr<'tcx>,
104 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
106 let ty = self.check_expr_with_hint(expr, expected);
107 // checks don't need two phase
108 self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
111 pub(super) fn check_expr_with_hint(
113 expr: &'tcx hir::Expr<'tcx>,
116 self.check_expr_with_expectation(expr, ExpectHasType(expected))
119 fn check_expr_with_expectation_and_needs(
121 expr: &'tcx hir::Expr<'tcx>,
122 expected: Expectation<'tcx>,
125 let ty = self.check_expr_with_expectation(expr, expected);
127 // If the expression is used in a place whether mutable place is required
128 // e.g. LHS of assignment, perform the conversion.
129 if let Needs::MutPlace = needs {
130 self.convert_place_derefs_to_mutable(expr);
136 pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
137 self.check_expr_with_expectation(expr, NoExpectation)
140 pub(super) fn check_expr_with_needs(
142 expr: &'tcx hir::Expr<'tcx>,
145 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
149 /// If an expression has any sub-expressions that result in a type error,
150 /// inspecting that expression's type with `ty.references_error()` will return
151 /// true. Likewise, if an expression is known to diverge, inspecting its
152 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
153 /// strict, _|_ can appear in the type of an expression that does not,
154 /// itself, diverge: for example, fn() -> _|_.)
155 /// Note that inspecting a type's structure *directly* may expose the fact
156 /// that there are actually multiple representations for `Error`, so avoid
157 /// that when err needs to be handled differently.
158 #[instrument(skip(self, expr), level = "debug")]
159 pub(super) fn check_expr_with_expectation(
161 expr: &'tcx hir::Expr<'tcx>,
162 expected: Expectation<'tcx>,
164 self.check_expr_with_expectation_and_args(expr, expected, &[])
167 /// Same as `check_expr_with_expectation`, but allows us to pass in the arguments of a
168 /// `ExprKind::Call` when evaluating its callee when it is an `ExprKind::Path`.
169 pub(super) fn check_expr_with_expectation_and_args(
171 expr: &'tcx hir::Expr<'tcx>,
172 expected: Expectation<'tcx>,
173 args: &'tcx [hir::Expr<'tcx>],
175 if self.tcx().sess.verbose() {
176 // make this code only run with -Zverbose because it is probably slow
177 if let Ok(lint_str) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
178 if !lint_str.contains('\n') {
179 debug!("expr text: {}", lint_str);
181 let mut lines = lint_str.lines();
182 if let Some(line0) = lines.next() {
183 let remaining_lines = lines.count();
184 debug!("expr text: {}", line0);
185 debug!("expr text: ...(and {} more lines)", remaining_lines);
191 // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
192 // without the final expr (e.g. `try { return; }`). We don't want to generate an
193 // unreachable_code lint for it since warnings for autogenerated code are confusing.
194 let is_try_block_generated_unit_expr = match expr.kind {
195 ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
196 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
202 // Warn for expressions after diverging siblings.
203 if !is_try_block_generated_unit_expr {
204 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
207 // Hide the outer diverging and has_errors flags.
208 let old_diverges = self.diverges.replace(Diverges::Maybe);
209 let old_has_errors = self.has_errors.replace(false);
211 let ty = ensure_sufficient_stack(|| match &expr.kind {
213 qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
214 ) => self.check_expr_path(qpath, expr, args),
215 _ => self.check_expr_kind(expr, expected),
218 // Warn for non-block expressions with diverging children.
224 | ExprKind::Match(..) => {}
225 // If `expr` is a result of desugaring the try block and is an ok-wrapped
226 // diverging expression (e.g. it arose from desugaring of `try { return }`),
227 // we skip issuing a warning because it is autogenerated code.
228 ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
229 ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
230 ExprKind::MethodCall(_, ref span, _, _) => {
231 self.warn_if_unreachable(expr.hir_id, *span, "call")
233 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
236 // Any expression that produces a value of type `!` must have diverged
238 self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
241 // Record the type, which applies it effects.
242 // We need to do this after the warning above, so that
243 // we don't warn for the diverging expression itself.
244 self.write_ty(expr.hir_id, ty);
246 // Combine the diverging and has_error flags.
247 self.diverges.set(self.diverges.get() | old_diverges);
248 self.has_errors.set(self.has_errors.get() | old_has_errors);
250 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
251 debug!("... {:?}, expected is {:?}", ty, expected);
256 #[instrument(skip(self, expr), level = "debug")]
259 expr: &'tcx hir::Expr<'tcx>,
260 expected: Expectation<'tcx>,
262 trace!("expr={:#?}", expr);
266 ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
267 ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
268 ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs),
269 ExprKind::Assign(lhs, rhs, ref span) => {
270 self.check_expr_assign(expr, expected, lhs, rhs, span)
272 ExprKind::AssignOp(op, lhs, rhs) => self.check_binop_assign(expr, op, lhs, rhs),
273 ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
274 ExprKind::AddrOf(kind, mutbl, oprnd) => {
275 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
277 ExprKind::Path(QPath::LangItem(lang_item, _)) => {
278 self.check_lang_item_path(lang_item, expr)
280 ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr, &[]),
281 ExprKind::InlineAsm(asm) => self.check_expr_asm(asm),
282 ExprKind::LlvmInlineAsm(asm) => {
283 for expr in asm.outputs_exprs.iter().chain(asm.inputs_exprs.iter()) {
284 self.check_expr(expr);
288 ExprKind::Break(destination, ref expr_opt) => {
289 self.check_expr_break(destination, expr_opt.as_deref(), expr)
291 ExprKind::Continue(destination) => {
292 if destination.target_id.is_ok() {
295 // There was an error; make type-check fail.
299 ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
300 ExprKind::Let(pat, let_expr, _) => self.check_expr_let(let_expr, pat),
301 ExprKind::Loop(body, _, source, _) => {
302 self.check_expr_loop(body, source, expected, expr)
304 ExprKind::Match(discrim, arms, match_src) => {
305 self.check_match(expr, &discrim, arms, expected, match_src)
307 ExprKind::Closure(capture, decl, body_id, _, gen) => {
308 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
310 ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
311 ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
312 ExprKind::MethodCall(segment, span, args, _) => {
313 self.check_method_call(expr, segment, span, args, expected)
315 ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
316 ExprKind::Type(e, t) => {
317 let ty = self.to_ty_saving_user_provided_ty(&t);
318 self.check_expr_eq_type(&e, ty);
321 ExprKind::If(cond, then_expr, opt_else_expr) => {
322 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
324 ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
325 ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
326 ExprKind::ConstBlock(ref anon_const) => self.to_const(anon_const).ty,
327 ExprKind::Repeat(element, ref count) => {
328 self.check_expr_repeat(element, count, expected, expr)
330 ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
331 ExprKind::Struct(qpath, fields, ref base_expr) => {
332 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
334 ExprKind::Field(base, field) => self.check_field(expr, &base, field),
335 ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
336 ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
337 hir::ExprKind::Err => tcx.ty_error(),
341 fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
342 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
343 ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
346 let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
347 self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
348 self.tcx.mk_box(referent_ty)
354 oprnd: &'tcx hir::Expr<'tcx>,
355 expected: Expectation<'tcx>,
356 expr: &'tcx hir::Expr<'tcx>,
359 let expected_inner = match unop {
360 hir::UnOp::Not | hir::UnOp::Neg => expected,
361 hir::UnOp::Deref => NoExpectation,
363 let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
365 if !oprnd_t.references_error() {
366 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
368 hir::UnOp::Deref => {
369 if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
372 let mut err = type_error_struct!(
377 "type `{}` cannot be dereferenced",
380 let sp = tcx.sess.source_map().start_point(expr.span);
382 tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
384 tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
387 oprnd_t = tcx.ty_error();
391 let result = self.check_user_unop(expr, oprnd_t, unop);
392 // If it's builtin, we can reuse the type, this helps inference.
393 if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
398 let result = self.check_user_unop(expr, oprnd_t, unop);
399 // If it's builtin, we can reuse the type, this helps inference.
400 if !oprnd_t.is_numeric() {
409 fn check_expr_addr_of(
411 kind: hir::BorrowKind,
412 mutbl: hir::Mutability,
413 oprnd: &'tcx hir::Expr<'tcx>,
414 expected: Expectation<'tcx>,
415 expr: &'tcx hir::Expr<'tcx>,
417 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
419 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
420 if oprnd.is_syntactic_place_expr() {
421 // Places may legitimately have unsized types.
422 // For example, dereferences of a fat pointer and
423 // the last field of a struct can be unsized.
426 Expectation::rvalue_hint(self, ty)
433 self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
435 let tm = ty::TypeAndMut { ty, mutbl };
437 _ if tm.ty.references_error() => self.tcx.ty_error(),
438 hir::BorrowKind::Raw => {
439 self.check_named_place_expr(oprnd);
442 hir::BorrowKind::Ref => {
443 // Note: at this point, we cannot say what the best lifetime
444 // is to use for resulting pointer. We want to use the
445 // shortest lifetime possible so as to avoid spurious borrowck
446 // errors. Moreover, the longest lifetime will depend on the
447 // precise details of the value whose address is being taken
448 // (and how long it is valid), which we don't know yet until
449 // type inference is complete.
451 // Therefore, here we simply generate a region variable. The
452 // region inferencer will then select a suitable value.
453 // Finally, borrowck will infer the value of the region again,
454 // this time with enough precision to check that the value
455 // whose address was taken can actually be made to live as long
456 // as it needs to live.
457 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
458 self.tcx.mk_ref(region, tm)
463 /// Does this expression refer to a place that either:
464 /// * Is based on a local or static.
465 /// * Contains a dereference
466 /// Note that the adjustments for the children of `expr` should already
467 /// have been resolved.
468 fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
469 let is_named = oprnd.is_place_expr(|base| {
470 // Allow raw borrows if there are any deref adjustments.
472 // const VAL: (i32,) = (0,);
473 // const REF: &(i32,) = &(0,);
475 // &raw const VAL.0; // ERROR
476 // &raw const REF.0; // OK, same as &raw const (*REF).0;
478 // This is maybe too permissive, since it allows
479 // `let u = &raw const Box::new((1,)).0`, which creates an
480 // immediately dangling raw pointer.
485 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
488 self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span })
492 fn check_lang_item_path(
494 lang_item: hir::LangItem,
495 expr: &'tcx hir::Expr<'tcx>,
497 self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id).1
500 pub(crate) fn check_expr_path(
502 qpath: &'tcx hir::QPath<'tcx>,
503 expr: &'tcx hir::Expr<'tcx>,
504 args: &'tcx [hir::Expr<'tcx>],
507 let (res, opt_ty, segs) =
508 self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
511 self.set_tainted_by_errors();
514 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
515 report_unexpected_variant_res(tcx, res, expr.span);
518 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
521 if let ty::FnDef(..) = ty.kind() {
522 let fn_sig = ty.fn_sig(tcx);
523 if !tcx.features().unsized_fn_params {
524 // We want to remove some Sized bounds from std functions,
525 // but don't want to expose the removal to stable Rust.
526 // i.e., we don't want to allow
532 // to work in stable even if the Sized bound on `drop` is relaxed.
533 for i in 0..fn_sig.inputs().skip_binder().len() {
534 // We just want to check sizedness, so instead of introducing
535 // placeholder lifetimes with probing, we just replace higher lifetimes
537 let span = args.get(i).map(|a| a.span).unwrap_or(expr.span);
539 .replace_bound_vars_with_fresh_vars(
541 infer::LateBoundRegionConversionTime::FnCall,
545 self.require_type_is_sized_deferred(
548 traits::SizedArgumentType(None),
552 // Here we want to prevent struct constructors from returning unsized types.
553 // There were two cases this happened: fn pointer coercion in stable
554 // and usual function call in presence of unsized_locals.
555 // Also, as we just want to check sizedness, instead of introducing
556 // placeholder lifetimes with probing, we just replace higher lifetimes
559 .replace_bound_vars_with_fresh_vars(
561 infer::LateBoundRegionConversionTime::FnCall,
565 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
568 // We always require that the type provided as the value for
569 // a type parameter outlives the moment of instantiation.
570 let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
571 self.add_wf_bounds(substs, expr);
578 destination: hir::Destination,
579 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
580 expr: &'tcx hir::Expr<'tcx>,
583 if let Ok(target_id) = destination.target_id {
585 if let Some(e) = expr_opt {
586 // If this is a break with a value, we need to type-check
587 // the expression. Get an expected type from the loop context.
588 let opt_coerce_to = {
589 // We should release `enclosing_breakables` before the `check_expr_with_hint`
590 // below, so can't move this block of code to the enclosing scope and share
591 // `ctxt` with the second `encloding_breakables` borrow below.
592 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
593 match enclosing_breakables.opt_find_breakable(target_id) {
594 Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
596 // Avoid ICE when `break` is inside a closure (#65383).
597 return tcx.ty_error_with_message(
599 "break was outside loop, but no error was emitted",
605 // If the loop context is not a `loop { }`, then break with
606 // a value is illegal, and `opt_coerce_to` will be `None`.
607 // Just set expectation to error in that case.
608 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
610 // Recurse without `enclosing_breakables` borrowed.
611 e_ty = self.check_expr_with_hint(e, coerce_to);
612 cause = self.misc(e.span);
614 // Otherwise, this is a break *without* a value. That's
615 // always legal, and is equivalent to `break ()`.
616 e_ty = tcx.mk_unit();
617 cause = self.misc(expr.span);
620 // Now that we have type-checked `expr_opt`, borrow
621 // the `enclosing_loops` field and let's coerce the
622 // type of `expr_opt` into what is expected.
623 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
624 let ctxt = match enclosing_breakables.opt_find_breakable(target_id) {
627 // Avoid ICE when `break` is inside a closure (#65383).
628 return tcx.ty_error_with_message(
630 "break was outside loop, but no error was emitted",
635 if let Some(ref mut coerce) = ctxt.coerce {
636 if let Some(ref e) = expr_opt {
637 coerce.coerce(self, &cause, e, e_ty);
639 assert!(e_ty.is_unit());
640 let ty = coerce.expected_ty();
641 coerce.coerce_forced_unit(
645 self.suggest_mismatched_types_on_tail(
646 &mut err, expr, ty, e_ty, target_id,
648 if let Some(val) = ty_kind_suggestion(ty) {
649 let label = destination
651 .map(|l| format!(" {}", l.ident))
652 .unwrap_or_else(String::new);
655 "give it a value of the expected type",
656 format!("break{} {}", label, val),
657 Applicability::HasPlaceholders,
665 // If `ctxt.coerce` is `None`, we can just ignore
666 // the type of the expression. This is because
667 // either this was a break *without* a value, in
668 // which case it is always a legal type (`()`), or
669 // else an error would have been flagged by the
670 // `loops` pass for using break with an expression
671 // where you are not supposed to.
672 assert!(expr_opt.is_none() || self.tcx.sess.has_errors());
675 // If we encountered a `break`, then (no surprise) it may be possible to break from the
676 // loop... unless the value being returned from the loop diverges itself, e.g.
677 // `break return 5` or `break loop {}`.
678 ctxt.may_break |= !self.diverges.get().is_always();
680 // the type of a `break` is always `!`, since it diverges
683 // Otherwise, we failed to find the enclosing loop;
684 // this can only happen if the `break` was not
685 // inside a loop at all, which is caught by the
686 // loop-checking pass.
687 let err = self.tcx.ty_error_with_message(
689 "break was outside loop, but no error was emitted",
692 // We still need to assign a type to the inner expression to
693 // prevent the ICE in #43162.
694 if let Some(e) = expr_opt {
695 self.check_expr_with_hint(e, err);
697 // ... except when we try to 'break rust;'.
698 // ICE this expression in particular (see #43162).
699 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
700 if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
701 fatally_break_rust(self.tcx.sess);
706 // There was an error; make type-check fail.
711 fn check_expr_return(
713 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
714 expr: &'tcx hir::Expr<'tcx>,
716 if self.ret_coercion.is_none() {
717 let mut err = ReturnStmtOutsideOfFnBody {
719 encl_body_span: None,
723 let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
725 if let Some(hir::Node::Item(hir::Item {
726 kind: hir::ItemKind::Fn(..),
730 | Some(hir::Node::TraitItem(hir::TraitItem {
731 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
735 | Some(hir::Node::ImplItem(hir::ImplItem {
736 kind: hir::ImplItemKind::Fn(..),
739 })) = self.tcx.hir().find(encl_item_id)
741 // We are inside a function body, so reporting "return statement
742 // outside of function body" needs an explanation.
744 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
746 // If this didn't hold, we would not have to report an error in
748 assert_ne!(encl_item_id, encl_body_owner_id);
750 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
751 let encl_body = self.tcx.hir().body(encl_body_id);
753 err.encl_body_span = Some(encl_body.value.span);
754 err.encl_fn_span = Some(*encl_fn_span);
757 self.tcx.sess.emit_err(err);
759 if let Some(e) = expr_opt {
760 // We still have to type-check `e` (issue #86188), but calling
761 // `check_return_expr` only works inside fn bodies.
764 } else if let Some(e) = expr_opt {
765 if self.ret_coercion_span.get().is_none() {
766 self.ret_coercion_span.set(Some(e.span));
768 self.check_return_expr(e, true);
770 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
771 if self.ret_coercion_span.get().is_none() {
772 self.ret_coercion_span.set(Some(expr.span));
774 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
775 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
776 coercion.coerce_forced_unit(
780 let span = fn_decl.output.span();
781 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
784 format!("expected `{}` because of this return type", snippet),
791 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
797 /// `explicit_return` is `true` if we're checkng an explicit `return expr`,
798 /// and `false` if we're checking a trailing expression.
799 pub(super) fn check_return_expr(
801 return_expr: &'tcx hir::Expr<'tcx>,
802 explicit_return: bool,
804 let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
805 span_bug!(return_expr.span, "check_return_expr called outside fn body")
808 let ret_ty = ret_coercion.borrow().expected_ty();
809 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
810 let mut span = return_expr.span;
811 // Use the span of the trailing expression for our cause,
812 // not the span of the entire function
813 if !explicit_return {
814 if let ExprKind::Block(body, _) = return_expr.kind {
815 if let Some(last_expr) = body.expr {
816 span = last_expr.span;
820 ret_coercion.borrow_mut().coerce(
822 &self.cause(span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
828 pub(crate) fn check_lhs_assignable(
830 lhs: &'tcx hir::Expr<'tcx>,
831 err_code: &'static str,
834 if lhs.is_syntactic_place_expr() {
838 // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
839 let mut err = self.tcx.sess.struct_span_err_with_code(
841 "invalid left-hand side of assignment",
842 DiagnosticId::Error(err_code.into()),
844 err.span_label(lhs.span, "cannot assign to this expression");
848 // A generic function for checking the 'then' and 'else' clauses in an 'if'
849 // or 'if-else' expression.
852 cond_expr: &'tcx hir::Expr<'tcx>,
853 then_expr: &'tcx hir::Expr<'tcx>,
854 opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
856 orig_expected: Expectation<'tcx>,
858 let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
860 self.warn_if_unreachable(
863 "block in `if` or `while` expression",
866 let cond_diverges = self.diverges.get();
867 self.diverges.set(Diverges::Maybe);
869 let expected = orig_expected.adjust_for_branches(self);
870 let then_ty = self.check_expr_with_expectation(then_expr, expected);
871 let then_diverges = self.diverges.get();
872 self.diverges.set(Diverges::Maybe);
874 // We've already taken the expected type's preferences
875 // into account when typing the `then` branch. To figure
876 // out the initial shot at a LUB, we thus only consider
877 // `expected` if it represents a *hard* constraint
878 // (`only_has_type`); otherwise, we just go with a
879 // fresh type variable.
880 let coerce_to_ty = expected.coercion_target_type(self, sp);
881 let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
883 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
885 if let Some(else_expr) = opt_else_expr {
886 let else_ty = if sp.desugaring_kind() == Some(DesugaringKind::LetElse) {
887 // todo introduce `check_expr_with_expectation(.., Expectation::LetElse)`
888 // for errors that point to the offending expression rather than the entire block.
889 // We could use `check_expr_eq_type(.., tcx.types.never)`, but then there is no
890 // way to detect that the expected type originated from let-else and provide
891 // a customized error.
892 let else_ty = self.check_expr(else_expr);
893 let cause = self.cause(else_expr.span, ObligationCauseCode::LetElse);
895 if let Some(mut err) =
896 self.demand_eqtype_with_origin(&cause, self.tcx.types.never, else_ty)
904 self.check_expr_with_expectation(else_expr, expected)
906 let else_diverges = self.diverges.get();
908 let opt_suggest_box_span =
909 self.opt_suggest_box_span(else_expr.span, else_ty, orig_expected);
911 self.if_cause(sp, then_expr, else_expr, then_ty, else_ty, opt_suggest_box_span);
913 coerce.coerce(self, &if_cause, else_expr, else_ty);
915 // We won't diverge unless both branches do (or the condition does).
916 self.diverges.set(cond_diverges | then_diverges & else_diverges);
918 self.if_fallback_coercion(sp, then_expr, &mut coerce);
920 // If the condition is false we can't diverge.
921 self.diverges.set(cond_diverges);
924 let result_ty = coerce.complete(self);
925 if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
928 /// Type check assignment expression `expr` of form `lhs = rhs`.
929 /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
930 fn check_expr_assign(
932 expr: &'tcx hir::Expr<'tcx>,
933 expected: Expectation<'tcx>,
934 lhs: &'tcx hir::Expr<'tcx>,
935 rhs: &'tcx hir::Expr<'tcx>,
938 let expected_ty = expected.coercion_target_type(self, expr.span);
939 if expected_ty == self.tcx.types.bool {
940 // The expected type is `bool` but this will result in `()` so we can reasonably
941 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
942 // The likely cause of this is `if foo = bar { .. }`.
943 let actual_ty = self.tcx.mk_unit();
944 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
945 let lhs_ty = self.check_expr(&lhs);
946 let rhs_ty = self.check_expr(&rhs);
947 let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
948 (Applicability::MachineApplicable, true)
950 (Applicability::MaybeIncorrect, false)
952 if !lhs.is_syntactic_place_expr() {
953 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
954 let hir = self.tcx.hir();
955 if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
956 hir.get(hir.get_parent_node(hir.get_parent_node(expr.hir_id)))
958 err.span_suggestion_verbose(
959 expr.span.shrink_to_lo(),
960 "you might have meant to use pattern matching",
967 err.span_suggestion_verbose(
969 "you might have meant to compare for equality",
975 // If the assignment expression itself is ill-formed, don't
976 // bother emitting another error
977 if lhs_ty.references_error() || rhs_ty.references_error() {
982 return self.tcx.ty_error();
985 self.check_lhs_assignable(lhs, "E0070", span);
987 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
988 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty, Some(lhs));
990 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
992 if lhs_ty.references_error() || rhs_ty.references_error() {
999 fn check_expr_let(&self, expr: &'tcx hir::Expr<'tcx>, pat: &'tcx hir::Pat<'tcx>) -> Ty<'tcx> {
1000 self.warn_if_unreachable(expr.hir_id, expr.span, "block in `let` expression");
1001 let expr_ty = self.demand_scrutinee_type(expr, pat.contains_explicit_ref_binding(), false);
1002 self.check_pat_top(pat, expr_ty, Some(expr.span), true);
1008 body: &'tcx hir::Block<'tcx>,
1009 source: hir::LoopSource,
1010 expected: Expectation<'tcx>,
1011 expr: &'tcx hir::Expr<'tcx>,
1013 let coerce = match source {
1014 // you can only use break with a value from a normal `loop { }`
1015 hir::LoopSource::Loop => {
1016 let coerce_to = expected.coercion_target_type(self, body.span);
1017 Some(CoerceMany::new(coerce_to))
1020 hir::LoopSource::While | hir::LoopSource::ForLoop => None,
1023 let ctxt = BreakableCtxt {
1025 may_break: false, // Will get updated if/when we find a `break`.
1028 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
1029 self.check_block_no_value(&body);
1033 // No way to know whether it's diverging because
1034 // of a `break` or an outer `break` or `return`.
1035 self.diverges.set(Diverges::Maybe);
1038 // If we permit break with a value, then result type is
1039 // the LUB of the breaks (possibly ! if none); else, it
1040 // is nil. This makes sense because infinite loops
1041 // (which would have type !) are only possible iff we
1042 // permit break with a value [1].
1043 if ctxt.coerce.is_none() && !ctxt.may_break {
1045 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
1047 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
1050 /// Checks a method call.
1051 fn check_method_call(
1053 expr: &'tcx hir::Expr<'tcx>,
1054 segment: &hir::PathSegment<'_>,
1056 args: &'tcx [hir::Expr<'tcx>],
1057 expected: Expectation<'tcx>,
1059 let rcvr = &args[0];
1060 let rcvr_t = self.check_expr(&rcvr);
1061 // no need to check for bot/err -- callee does that
1062 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
1064 let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
1066 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
1067 // trigger this codepath causing `structuraly_resolved_type` to emit an error.
1069 self.write_method_call(expr.hir_id, method);
1073 if segment.ident.name != kw::Empty {
1074 if let Some(mut err) = self.report_method_error(
1078 SelfSource::MethodCall(&args[0]),
1089 // Call the generic checker.
1090 self.check_method_argument_types(
1102 e: &'tcx hir::Expr<'tcx>,
1103 t: &'tcx hir::Ty<'tcx>,
1104 expr: &'tcx hir::Expr<'tcx>,
1106 // Find the type of `e`. Supply hints based on the type we are casting to,
1108 let t_cast = self.to_ty_saving_user_provided_ty(t);
1109 let t_cast = self.resolve_vars_if_possible(t_cast);
1110 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1111 let t_expr = self.resolve_vars_if_possible(t_expr);
1113 // Eagerly check for some obvious errors.
1114 if t_expr.references_error() || t_cast.references_error() {
1117 // Defer other checks until we're done type checking.
1118 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1119 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1122 "check_expr_cast: deferring cast from {:?} to {:?}: {:?}",
1123 t_cast, t_expr, cast_check,
1125 deferred_cast_checks.push(cast_check);
1128 Err(ErrorReported) => self.tcx.ty_error(),
1133 fn check_expr_array(
1135 args: &'tcx [hir::Expr<'tcx>],
1136 expected: Expectation<'tcx>,
1137 expr: &'tcx hir::Expr<'tcx>,
1139 let element_ty = if !args.is_empty() {
1140 let coerce_to = expected
1142 .and_then(|uty| match *uty.kind() {
1143 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1146 .unwrap_or_else(|| {
1147 self.next_ty_var(TypeVariableOrigin {
1148 kind: TypeVariableOriginKind::TypeInference,
1152 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1153 assert_eq!(self.diverges.get(), Diverges::Maybe);
1155 let e_ty = self.check_expr_with_hint(e, coerce_to);
1156 let cause = self.misc(e.span);
1157 coerce.coerce(self, &cause, e, e_ty);
1159 coerce.complete(self)
1161 self.next_ty_var(TypeVariableOrigin {
1162 kind: TypeVariableOriginKind::TypeInference,
1166 self.tcx.mk_array(element_ty, args.len() as u64)
1169 fn check_expr_repeat(
1171 element: &'tcx hir::Expr<'tcx>,
1172 count: &'tcx hir::AnonConst,
1173 expected: Expectation<'tcx>,
1174 _expr: &'tcx hir::Expr<'tcx>,
1177 let count = self.to_const(count);
1179 let uty = match expected {
1180 ExpectHasType(uty) => match *uty.kind() {
1181 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1187 let (element_ty, t) = match uty {
1189 self.check_expr_coercable_to_type(&element, uty, None);
1193 let ty = self.next_ty_var(TypeVariableOrigin {
1194 kind: TypeVariableOriginKind::MiscVariable,
1197 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1202 if element_ty.references_error() {
1203 return tcx.ty_error();
1206 tcx.mk_ty(ty::Array(t, count))
1209 fn check_expr_tuple(
1211 elts: &'tcx [hir::Expr<'tcx>],
1212 expected: Expectation<'tcx>,
1213 expr: &'tcx hir::Expr<'tcx>,
1215 let flds = expected.only_has_type(self).and_then(|ty| {
1216 let ty = self.resolve_vars_with_obligations(ty);
1218 ty::Tuple(flds) => Some(&flds[..]),
1223 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1224 Some(fs) if i < fs.len() => {
1225 let ety = fs[i].expect_ty();
1226 self.check_expr_coercable_to_type(&e, ety, None);
1229 _ => self.check_expr_with_expectation(&e, NoExpectation),
1231 let tuple = self.tcx.mk_tup(elt_ts_iter);
1232 if tuple.references_error() {
1235 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1240 fn check_expr_struct(
1242 expr: &hir::Expr<'_>,
1243 expected: Expectation<'tcx>,
1245 fields: &'tcx [hir::ExprField<'tcx>],
1246 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1248 // Find the relevant variant
1249 let (variant, adt_ty) = if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id)
1253 self.check_struct_fields_on_error(fields, base_expr);
1254 return self.tcx.ty_error();
1257 // Prohibit struct expressions when non-exhaustive flag is set.
1258 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1259 if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
1262 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1265 let error_happened = self.check_expr_struct_fields(
1272 base_expr.is_none(),
1275 if let Some(base_expr) = base_expr {
1276 // If check_expr_struct_fields hit an error, do not attempt to populate
1277 // the fields with the base_expr. This could cause us to hit errors later
1278 // when certain fields are assumed to exist that in fact do not.
1279 if !error_happened {
1280 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {});
1281 match adt_ty.kind() {
1282 ty::Adt(adt, substs) if adt.is_struct() => {
1283 let fru_field_types = adt
1288 self.normalize_associated_types_in(
1290 f.ty(self.tcx, substs),
1297 .fru_field_types_mut()
1298 .insert(expr.hir_id, fru_field_types);
1303 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1308 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1312 fn check_expr_struct_fields(
1315 expected: Expectation<'tcx>,
1316 expr_id: hir::HirId,
1318 variant: &'tcx ty::VariantDef,
1319 ast_fields: &'tcx [hir::ExprField<'tcx>],
1320 check_completeness: bool,
1325 let adt_ty_hint = self
1326 .expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
1330 // re-link the regions that EIfEO can erase.
1331 self.demand_eqtype(span, adt_ty_hint, adt_ty);
1333 let (substs, adt_kind, kind_name) = match adt_ty.kind() {
1334 ty::Adt(adt, substs) => (substs, adt.adt_kind(), adt.variant_descr()),
1335 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields"),
1338 let mut remaining_fields = variant
1342 .map(|(i, field)| (field.ident.normalize_to_macros_2_0(), (i, field)))
1343 .collect::<FxHashMap<_, _>>();
1345 let mut seen_fields = FxHashMap::default();
1347 let mut error_happened = false;
1349 // Type-check each field.
1350 for field in ast_fields {
1351 let ident = tcx.adjust_ident(field.ident, variant.def_id);
1352 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1353 seen_fields.insert(ident, field.span);
1354 self.write_field_index(field.hir_id, i);
1356 // We don't look at stability attributes on
1357 // struct-like enums (yet...), but it's definitely not
1358 // a bug to have constructed one.
1359 if adt_kind != AdtKind::Enum {
1360 tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1363 self.field_ty(field.span, v_field, substs)
1365 error_happened = true;
1366 if let Some(prev_span) = seen_fields.get(&ident) {
1367 tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1368 span: field.ident.span,
1369 prev_span: *prev_span,
1373 self.report_unknown_field(
1374 adt_ty, variant, field, ast_fields, kind_name, expr_span,
1381 // Make sure to give a type to the field even if there's
1382 // an error, so we can continue type-checking.
1383 self.check_expr_coercable_to_type(&field.expr, field_type, None);
1386 // Make sure the programmer specified correct number of fields.
1387 if kind_name == "union" {
1388 if ast_fields.len() != 1 {
1393 "union expressions should have exactly one field",
1397 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
1398 let inaccessible_remaining_fields = remaining_fields.iter().any(|(_, (_, field))| {
1399 !field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1402 if inaccessible_remaining_fields {
1403 self.report_inaccessible_fields(adt_ty, span);
1405 self.report_missing_fields(adt_ty, span, remaining_fields);
1412 fn check_struct_fields_on_error(
1414 fields: &'tcx [hir::ExprField<'tcx>],
1415 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1417 for field in fields {
1418 self.check_expr(&field.expr);
1420 if let Some(base) = *base_expr {
1421 self.check_expr(&base);
1425 /// Report an error for a struct field expression when there are fields which aren't provided.
1428 /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1429 /// --> src/main.rs:8:5
1431 /// 8 | foo::Foo {};
1432 /// | ^^^^^^^^ missing `you_can_use_this_field`
1434 /// error: aborting due to previous error
1436 fn report_missing_fields(
1440 remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1442 let len = remaining_fields.len();
1444 let mut displayable_field_names =
1445 remaining_fields.keys().map(|ident| ident.as_str()).collect::<Vec<_>>();
1447 displayable_field_names.sort();
1449 let mut truncated_fields_error = String::new();
1450 let remaining_fields_names = match &displayable_field_names[..] {
1451 [field1] => format!("`{}`", field1),
1452 [field1, field2] => format!("`{}` and `{}`", field1, field2),
1453 [field1, field2, field3] => format!("`{}`, `{}` and `{}`", field1, field2, field3),
1455 truncated_fields_error =
1456 format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1457 displayable_field_names
1460 .map(|n| format!("`{}`", n))
1461 .collect::<Vec<_>>()
1470 "missing field{} {}{} in initializer of `{}`",
1472 remaining_fields_names,
1473 truncated_fields_error,
1476 .span_label(span, format!("missing {}{}", remaining_fields_names, truncated_fields_error))
1480 /// Report an error for a struct field expression when there are invisible fields.
1483 /// error: cannot construct `Foo` with struct literal syntax due to inaccessible fields
1484 /// --> src/main.rs:8:5
1486 /// 8 | foo::Foo {};
1489 /// error: aborting due to previous error
1491 fn report_inaccessible_fields(&self, adt_ty: Ty<'tcx>, span: Span) {
1492 self.tcx.sess.span_err(
1495 "cannot construct `{}` with struct literal syntax due to inaccessible fields",
1501 fn report_unknown_field(
1504 variant: &'tcx ty::VariantDef,
1505 field: &hir::ExprField<'_>,
1506 skip_fields: &[hir::ExprField<'_>],
1510 if variant.is_recovered() {
1511 self.set_tainted_by_errors();
1514 let mut err = self.type_error_struct_with_diag(
1516 |actual| match ty.kind() {
1517 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1521 "{} `{}::{}` has no field named `{}`",
1527 _ => struct_span_err!(
1531 "{} `{}` has no field named `{}`",
1539 match variant.ctor_kind {
1540 CtorKind::Fn => match ty.kind() {
1541 ty::Adt(adt, ..) if adt.is_enum() => {
1545 "`{adt}::{variant}` defined here",
1547 variant = variant.ident,
1550 err.span_label(field.ident.span, "field does not exist");
1551 err.span_suggestion_verbose(
1554 "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1556 variant = variant.ident,
1559 "{adt}::{variant}(/* fields */)",
1561 variant = variant.ident,
1563 Applicability::HasPlaceholders,
1567 err.span_label(variant.ident.span, format!("`{adt}` defined here", adt = ty));
1568 err.span_label(field.ident.span, "field does not exist");
1569 err.span_suggestion_verbose(
1572 "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1574 kind_name = kind_name,
1576 format!("{adt}(/* fields */)", adt = ty),
1577 Applicability::HasPlaceholders,
1582 // prevent all specified fields from being suggested
1583 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
1584 if let Some(field_name) =
1585 Self::suggest_field_name(variant, field.ident.name, skip_fields.collect())
1587 err.span_suggestion(
1589 "a field with a similar name exists",
1590 field_name.to_string(),
1591 Applicability::MaybeIncorrect,
1595 ty::Adt(adt, ..) => {
1599 format!("`{}::{}` does not have this field", ty, variant.ident),
1604 format!("`{}` does not have this field", ty),
1607 let available_field_names = self.available_field_names(variant);
1608 if !available_field_names.is_empty() {
1610 "available fields are: {}",
1611 self.name_series_display(available_field_names)
1615 _ => bug!("non-ADT passed to report_unknown_field"),
1623 // Return an hint about the closest match in field names
1624 fn suggest_field_name(
1625 variant: &'tcx ty::VariantDef,
1628 ) -> Option<Symbol> {
1632 .filter_map(|field| {
1633 // ignore already set fields and private fields from non-local crates
1634 if skip.iter().any(|&x| x == field.ident.name)
1635 || (!variant.def_id.is_local() && field.vis != Visibility::Public)
1639 Some(field.ident.name)
1642 .collect::<Vec<Symbol>>();
1644 find_best_match_for_name(&names, field, None)
1647 fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<Symbol> {
1652 let def_scope = self
1654 .adjust_ident_and_get_scope(field.ident, variant.def_id, self.body_id)
1656 field.vis.is_accessible_from(def_scope, self.tcx)
1658 .map(|field| field.ident.name)
1662 fn name_series_display(&self, names: Vec<Symbol>) -> String {
1663 // dynamic limit, to never omit just one field
1664 let limit = if names.len() == 6 { 6 } else { 5 };
1666 names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
1667 if names.len() > limit {
1668 display = format!("{} ... and {} others", display, names.len() - limit);
1673 // Check field access expressions
1676 expr: &'tcx hir::Expr<'tcx>,
1677 base: &'tcx hir::Expr<'tcx>,
1680 debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
1681 let expr_t = self.check_expr(base);
1682 let expr_t = self.structurally_resolved_type(base.span, expr_t);
1683 let mut private_candidate = None;
1684 let mut autoderef = self.autoderef(expr.span, expr_t);
1685 while let Some((base_t, _)) = autoderef.next() {
1686 debug!("base_t: {:?}", base_t);
1687 match base_t.kind() {
1688 ty::Adt(base_def, substs) if !base_def.is_enum() => {
1689 debug!("struct named {:?}", base_t);
1690 let (ident, def_scope) =
1691 self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
1692 let fields = &base_def.non_enum_variant().fields;
1693 if let Some(index) =
1694 fields.iter().position(|f| f.ident.normalize_to_macros_2_0() == ident)
1696 let field = &fields[index];
1697 let field_ty = self.field_ty(expr.span, field, substs);
1698 // Save the index of all fields regardless of their visibility in case
1699 // of error recovery.
1700 self.write_field_index(expr.hir_id, index);
1701 let adjustments = self.adjust_steps(&autoderef);
1702 if field.vis.is_accessible_from(def_scope, self.tcx) {
1703 self.apply_adjustments(base, adjustments);
1704 self.register_predicates(autoderef.into_obligations());
1706 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
1709 private_candidate = Some((adjustments, base_def.did, field_ty));
1713 let fstr = field.as_str();
1714 if let Ok(index) = fstr.parse::<usize>() {
1715 if fstr == index.to_string() {
1716 if let Some(field_ty) = tys.get(index) {
1717 let adjustments = self.adjust_steps(&autoderef);
1718 self.apply_adjustments(base, adjustments);
1719 self.register_predicates(autoderef.into_obligations());
1721 self.write_field_index(expr.hir_id, index);
1722 return field_ty.expect_ty();
1730 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
1732 if let Some((adjustments, did, field_ty)) = private_candidate {
1733 // (#90483) apply adjustments to avoid ExprUseVisitor from
1734 // creating erroneous projection.
1735 self.apply_adjustments(base, adjustments);
1736 self.ban_private_field_access(expr, expr_t, field, did);
1740 if field.name == kw::Empty {
1741 } else if self.method_exists(field, expr_t, expr.hir_id, true) {
1742 self.ban_take_value_of_method(expr, expr_t, field);
1743 } else if !expr_t.is_primitive_ty() {
1744 self.ban_nonexisting_field(field, base, expr, expr_t);
1751 "`{}` is a primitive type and therefore doesn't have fields",
1757 self.tcx().ty_error()
1760 fn suggest_await_on_field_access(
1762 err: &mut DiagnosticBuilder<'_>,
1764 base: &'tcx hir::Expr<'tcx>,
1767 let output_ty = match self.infcx.get_impl_future_output_ty(ty) {
1768 Some(output_ty) => self.resolve_vars_if_possible(output_ty),
1771 let mut add_label = true;
1772 if let ty::Adt(def, _) = output_ty.kind() {
1773 // no field access on enum type
1775 if def.non_enum_variant().fields.iter().any(|field| field.ident == field_ident) {
1779 "field not available in `impl Future`, but it is available in its `Output`",
1781 err.span_suggestion_verbose(
1782 base.span.shrink_to_hi(),
1783 "consider `await`ing on the `Future` and access the field of its `Output`",
1784 ".await".to_string(),
1785 Applicability::MaybeIncorrect,
1791 err.span_label(field_ident.span, &format!("field not found in `{}`", ty));
1795 fn ban_nonexisting_field(
1798 base: &'tcx hir::Expr<'tcx>,
1799 expr: &'tcx hir::Expr<'tcx>,
1803 "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
1804 field, base, expr, expr_t
1806 let mut err = self.no_such_field_err(field, expr_t);
1808 match *expr_t.peel_refs().kind() {
1809 ty::Array(_, len) => {
1810 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
1813 self.suggest_first_deref_field(&mut err, expr, base, field);
1815 ty::Adt(def, _) if !def.is_enum() => {
1816 self.suggest_fields_on_recordish(&mut err, def, field);
1818 ty::Param(param_ty) => {
1819 self.point_at_param_definition(&mut err, param_ty);
1821 ty::Opaque(_, _) => {
1822 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
1827 if field.name == kw::Await {
1828 // We know by construction that `<expr>.await` is either on Rust 2015
1829 // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
1830 err.note("to `.await` a `Future`, switch to Rust 2018 or later");
1831 err.help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION));
1832 err.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
1838 fn ban_private_field_access(
1840 expr: &hir::Expr<'_>,
1845 let struct_path = self.tcx().def_path_str(base_did);
1846 let kind_name = self.tcx().def_kind(base_did).descr(base_did);
1847 let mut err = struct_span_err!(
1851 "field `{}` of {} `{}` is private",
1856 err.span_label(field.span, "private field");
1857 // Also check if an accessible method exists, which is often what is meant.
1858 if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
1860 self.suggest_method_call(
1862 &format!("a method `{}` also exists, call it with parentheses", field),
1872 fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
1873 let mut err = type_error_struct!(
1878 "attempted to take value of method `{}` on type `{}`",
1882 err.span_label(field.span, "method, not a field");
1884 if let hir::Node::Expr(hir::Expr { kind: ExprKind::Call(callee, _args), .. }) =
1885 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
1887 expr.hir_id == callee.hir_id
1892 self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap_or(String::new());
1893 let is_wrapped = expr_snippet.starts_with('(') && expr_snippet.ends_with(')');
1894 let after_open = expr.span.lo() + rustc_span::BytePos(1);
1895 let before_close = expr.span.hi() - rustc_span::BytePos(1);
1897 if expr_is_call && is_wrapped {
1898 err.multipart_suggestion(
1899 "remove wrapping parentheses to call the method",
1901 (expr.span.with_hi(after_open), String::new()),
1902 (expr.span.with_lo(before_close), String::new()),
1904 Applicability::MachineApplicable,
1906 } else if !self.expr_in_place(expr.hir_id) {
1907 // Suggest call parentheses inside the wrapping parentheses
1908 let span = if is_wrapped {
1909 expr.span.with_lo(after_open).with_hi(before_close)
1913 self.suggest_method_call(
1915 "use parentheses to call the method",
1922 err.help("methods are immutable and cannot be assigned to");
1928 fn point_at_param_definition(&self, err: &mut DiagnosticBuilder<'_>, param: ty::ParamTy) {
1929 let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
1930 let generic_param = generics.type_param(¶m, self.tcx);
1931 if let ty::GenericParamDefKind::Type { synthetic: Some(..), .. } = generic_param.kind {
1934 let param_def_id = generic_param.def_id;
1935 let param_hir_id = match param_def_id.as_local() {
1936 Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
1939 let param_span = self.tcx.hir().span(param_hir_id);
1940 let param_name = self.tcx.hir().ty_param_name(param_hir_id);
1942 err.span_label(param_span, &format!("type parameter '{}' declared here", param_name));
1945 fn suggest_fields_on_recordish(
1947 err: &mut DiagnosticBuilder<'_>,
1948 def: &'tcx ty::AdtDef,
1951 if let Some(suggested_field_name) =
1952 Self::suggest_field_name(def.non_enum_variant(), field.name, vec![])
1954 err.span_suggestion(
1956 "a field with a similar name exists",
1957 suggested_field_name.to_string(),
1958 Applicability::MaybeIncorrect,
1961 err.span_label(field.span, "unknown field");
1962 let struct_variant_def = def.non_enum_variant();
1963 let field_names = self.available_field_names(struct_variant_def);
1964 if !field_names.is_empty() {
1966 "available fields are: {}",
1967 self.name_series_display(field_names),
1973 fn maybe_suggest_array_indexing(
1975 err: &mut DiagnosticBuilder<'_>,
1976 expr: &hir::Expr<'_>,
1977 base: &hir::Expr<'_>,
1979 len: &ty::Const<'tcx>,
1981 if let (Some(len), Ok(user_index)) =
1982 (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
1984 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
1985 let help = "instead of using tuple indexing, use array indexing";
1986 let suggestion = format!("{}[{}]", base, field);
1987 let applicability = if len < user_index {
1988 Applicability::MachineApplicable
1990 Applicability::MaybeIncorrect
1992 err.span_suggestion(expr.span, help, suggestion, applicability);
1997 fn suggest_first_deref_field(
1999 err: &mut DiagnosticBuilder<'_>,
2000 expr: &hir::Expr<'_>,
2001 base: &hir::Expr<'_>,
2004 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
2005 let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
2006 let suggestion = format!("(*{}).{}", base, field);
2007 err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
2011 fn no_such_field_err(
2014 expr_t: &'tcx ty::TyS<'tcx>,
2015 ) -> DiagnosticBuilder<'_> {
2016 let span = field.span;
2017 debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
2019 let mut err = type_error_struct!(
2024 "no field `{}` on type `{}`",
2029 // try to add a suggestion in case the field is a nested field of a field of the Adt
2030 if let Some((fields, substs)) = self.get_field_candidates(span, &expr_t) {
2031 for candidate_field in fields.iter() {
2032 if let Some(field_path) =
2033 self.check_for_nested_field(span, field, candidate_field, substs, vec![])
2035 let field_path_str = field_path
2037 .map(|id| id.name.to_ident_string())
2038 .collect::<Vec<String>>()
2040 debug!("field_path_str: {:?}", field_path_str);
2042 err.span_suggestion_verbose(
2043 field.span.shrink_to_lo(),
2044 "one of the expressions' fields has a field of the same name",
2045 format!("{}.", field_path_str),
2046 Applicability::MaybeIncorrect,
2054 fn get_field_candidates(
2058 ) -> Option<(&Vec<ty::FieldDef>, SubstsRef<'tcx>)> {
2059 debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_t);
2061 for (base_t, _) in self.autoderef(span, base_t) {
2062 match base_t.kind() {
2063 ty::Adt(base_def, substs) if !base_def.is_enum() => {
2064 let fields = &base_def.non_enum_variant().fields;
2065 // For compile-time reasons put a limit on number of fields we search
2066 if fields.len() > 100 {
2069 return Some((fields, substs));
2077 /// This method is called after we have encountered a missing field error to recursively
2078 /// search for the field
2079 fn check_for_nested_field(
2082 target_field: Ident,
2083 candidate_field: &ty::FieldDef,
2084 subst: SubstsRef<'tcx>,
2085 mut field_path: Vec<Ident>,
2086 ) -> Option<Vec<Ident>> {
2088 "check_for_nested_field(span: {:?}, candidate_field: {:?}, field_path: {:?}",
2089 span, candidate_field, field_path
2092 if candidate_field.ident == target_field {
2094 } else if field_path.len() > 3 {
2095 // For compile-time reasons and to avoid infinite recursion we only check for fields
2096 // up to a depth of three
2099 // recursively search fields of `candidate_field` if it's a ty::Adt
2101 field_path.push(candidate_field.ident.normalize_to_macros_2_0());
2102 let field_ty = candidate_field.ty(self.tcx, subst);
2103 if let Some((nested_fields, subst)) = self.get_field_candidates(span, &field_ty) {
2104 for field in nested_fields.iter() {
2105 let ident = field.ident.normalize_to_macros_2_0();
2106 if ident == target_field {
2107 return Some(field_path);
2109 let field_path = field_path.clone();
2110 if let Some(path) = self.check_for_nested_field(
2126 fn check_expr_index(
2128 base: &'tcx hir::Expr<'tcx>,
2129 idx: &'tcx hir::Expr<'tcx>,
2130 expr: &'tcx hir::Expr<'tcx>,
2132 let base_t = self.check_expr(&base);
2133 let idx_t = self.check_expr(&idx);
2135 if base_t.references_error() {
2137 } else if idx_t.references_error() {
2140 let base_t = self.structurally_resolved_type(base.span, base_t);
2141 match self.lookup_indexing(expr, base, base_t, idx, idx_t) {
2142 Some((index_ty, element_ty)) => {
2143 // two-phase not needed because index_ty is never mutable
2144 self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2148 let mut err = type_error_struct!(
2153 "cannot index into a value of type `{}`",
2156 // Try to give some advice about indexing tuples.
2157 if let ty::Tuple(..) = base_t.kind() {
2158 let mut needs_note = true;
2159 // If the index is an integer, we can show the actual
2160 // fixed expression:
2161 if let ExprKind::Lit(ref lit) = idx.kind {
2162 if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2163 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2164 if let Ok(snip) = snip {
2165 err.span_suggestion(
2167 "to access tuple elements, use",
2168 format!("{}.{}", snip, i),
2169 Applicability::MachineApplicable,
2177 "to access tuple elements, use tuple indexing \
2178 syntax (e.g., `tuple.0`)",
2189 fn check_expr_yield(
2191 value: &'tcx hir::Expr<'tcx>,
2192 expr: &'tcx hir::Expr<'tcx>,
2193 src: &'tcx hir::YieldSource,
2195 match self.resume_yield_tys {
2196 Some((resume_ty, yield_ty)) => {
2197 self.check_expr_coercable_to_type(&value, yield_ty, None);
2201 // Given that this `yield` expression was generated as a result of lowering a `.await`,
2202 // we know that the yield type must be `()`; however, the context won't contain this
2203 // information. Hence, we check the source of the yield expression here and check its
2204 // value's type against `()` (this check should always hold).
2205 None if src.is_await() => {
2206 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2210 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2211 // Avoid expressions without types during writeback (#78653).
2212 self.check_expr(value);
2218 fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2219 let needs = if is_input { Needs::None } else { Needs::MutPlace };
2220 let ty = self.check_expr_with_needs(expr, needs);
2221 self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2223 if !is_input && !expr.is_syntactic_place_expr() {
2224 let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2225 err.span_label(expr.span, "cannot assign to this expression");
2229 // If this is an input value, we require its type to be fully resolved
2230 // at this point. This allows us to provide helpful coercions which help
2231 // pass the type candidate list in a later pass.
2233 // We don't require output types to be resolved at this point, which
2234 // allows them to be inferred based on how they are used later in the
2237 let ty = self.structurally_resolved_type(expr.span, &ty);
2240 let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2241 self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2243 ty::Ref(_, base_ty, mutbl) => {
2244 let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2245 self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2252 fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2253 for (op, _op_sp) in asm.operands {
2255 hir::InlineAsmOperand::In { expr, .. } => {
2256 self.check_expr_asm_operand(expr, true);
2258 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
2259 | hir::InlineAsmOperand::InOut { expr, .. } => {
2260 self.check_expr_asm_operand(expr, false);
2262 hir::InlineAsmOperand::Out { expr: None, .. } => {}
2263 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2264 self.check_expr_asm_operand(in_expr, true);
2265 if let Some(out_expr) = out_expr {
2266 self.check_expr_asm_operand(out_expr, false);
2269 hir::InlineAsmOperand::Const { anon_const } => {
2270 self.to_const(anon_const);
2272 hir::InlineAsmOperand::Sym { expr } => {
2273 self.check_expr(expr);
2277 if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2278 self.tcx.types.never
2285 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2286 Some(match ty.kind() {
2289 ty::Int(_) | ty::Uint(_) => "42",
2290 ty::Float(_) => "3.14159",
2291 ty::Error(_) | ty::Never => return None,