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_diverging_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);
95 // Error possibly reported in `check_assign` so avoid emitting error again.
96 err.emit_unless(self.is_assign_to_bool(expr, expected_ty));
101 pub(super) fn check_expr_coercable_to_type(
103 expr: &'tcx hir::Expr<'tcx>,
105 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
107 let ty = self.check_expr_with_hint(expr, expected);
108 // checks don't need two phase
109 self.demand_coerce(expr, ty, expected, expected_ty_expr, AllowTwoPhase::No)
112 pub(super) fn check_expr_with_hint(
114 expr: &'tcx hir::Expr<'tcx>,
117 self.check_expr_with_expectation(expr, ExpectHasType(expected))
120 fn check_expr_with_expectation_and_needs(
122 expr: &'tcx hir::Expr<'tcx>,
123 expected: Expectation<'tcx>,
126 let ty = self.check_expr_with_expectation(expr, expected);
128 // If the expression is used in a place whether mutable place is required
129 // e.g. LHS of assignment, perform the conversion.
130 if let Needs::MutPlace = needs {
131 self.convert_place_derefs_to_mutable(expr);
137 pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
138 self.check_expr_with_expectation(expr, NoExpectation)
141 pub(super) fn check_expr_with_needs(
143 expr: &'tcx hir::Expr<'tcx>,
146 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
150 /// If an expression has any sub-expressions that result in a type error,
151 /// inspecting that expression's type with `ty.references_error()` will return
152 /// true. Likewise, if an expression is known to diverge, inspecting its
153 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
154 /// strict, _|_ can appear in the type of an expression that does not,
155 /// itself, diverge: for example, fn() -> _|_.)
156 /// Note that inspecting a type's structure *directly* may expose the fact
157 /// that there are actually multiple representations for `Error`, so avoid
158 /// that when err needs to be handled differently.
159 pub(super) fn check_expr_with_expectation(
161 expr: &'tcx hir::Expr<'tcx>,
162 expected: Expectation<'tcx>,
164 debug!(">> type-checking: expected={:?}, expr={:?} ", expected, expr);
166 // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
167 // without the final expr (e.g. `try { return; }`). We don't want to generate an
168 // unreachable_code lint for it since warnings for autogenerated code are confusing.
169 let is_try_block_generated_unit_expr = match expr.kind {
170 ExprKind::Call(_, args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
171 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
177 // Warn for expressions after diverging siblings.
178 if !is_try_block_generated_unit_expr {
179 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
182 // Hide the outer diverging and has_errors flags.
183 let old_diverges = self.diverges.replace(Diverges::Maybe);
184 let old_has_errors = self.has_errors.replace(false);
186 let ty = ensure_sufficient_stack(|| self.check_expr_kind(expr, expected));
188 // Warn for non-block expressions with diverging children.
190 ExprKind::Block(..) | ExprKind::If(..) | ExprKind::Loop(..) | ExprKind::Match(..) => {}
191 // If `expr` is a result of desugaring the try block and is an ok-wrapped
192 // diverging expression (e.g. it arose from desugaring of `try { return }`),
193 // we skip issuing a warning because it is autogenerated code.
194 ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
195 ExprKind::Call(callee, _) => self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
196 ExprKind::MethodCall(_, ref span, _, _) => {
197 self.warn_if_unreachable(expr.hir_id, *span, "call")
199 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
202 // Any expression that produces a value of type `!` must have diverged
204 self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
207 // Record the type, which applies it effects.
208 // We need to do this after the warning above, so that
209 // we don't warn for the diverging expression itself.
210 self.write_ty(expr.hir_id, ty);
212 // Combine the diverging and has_error flags.
213 self.diverges.set(self.diverges.get() | old_diverges);
214 self.has_errors.set(self.has_errors.get() | old_has_errors);
216 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
217 debug!("... {:?}, expected is {:?}", ty, expected);
224 expr: &'tcx hir::Expr<'tcx>,
225 expected: Expectation<'tcx>,
227 debug!("check_expr_kind(expected={:?}, expr={:?})", expected, expr);
231 ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
232 ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
233 ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs),
234 ExprKind::Assign(lhs, rhs, ref span) => {
235 self.check_expr_assign(expr, expected, lhs, rhs, span)
237 ExprKind::AssignOp(op, lhs, rhs) => self.check_binop_assign(expr, op, lhs, rhs),
238 ExprKind::Unary(unop, oprnd) => self.check_expr_unary(unop, oprnd, expected, expr),
239 ExprKind::AddrOf(kind, mutbl, oprnd) => {
240 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
242 ExprKind::Path(QPath::LangItem(lang_item, _)) => {
243 self.check_lang_item_path(lang_item, expr)
245 ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr),
246 ExprKind::InlineAsm(asm) => self.check_expr_asm(asm),
247 ExprKind::LlvmInlineAsm(asm) => {
248 for expr in asm.outputs_exprs.iter().chain(asm.inputs_exprs.iter()) {
249 self.check_expr(expr);
253 ExprKind::Break(destination, ref expr_opt) => {
254 self.check_expr_break(destination, expr_opt.as_deref(), expr)
256 ExprKind::Continue(destination) => {
257 if destination.target_id.is_ok() {
260 // There was an error; make type-check fail.
264 ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
265 ExprKind::Loop(body, _, source, _) => {
266 self.check_expr_loop(body, source, expected, expr)
268 ExprKind::Match(discrim, arms, match_src) => {
269 self.check_match(expr, &discrim, arms, expected, match_src)
271 ExprKind::Closure(capture, decl, body_id, _, gen) => {
272 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
274 ExprKind::Block(body, _) => self.check_block_with_expected(&body, expected),
275 ExprKind::Call(callee, args) => self.check_call(expr, &callee, args, expected),
276 ExprKind::MethodCall(segment, span, args, _) => {
277 self.check_method_call(expr, segment, span, args, expected)
279 ExprKind::Cast(e, t) => self.check_expr_cast(e, t, expr),
280 ExprKind::Type(e, t) => {
281 let ty = self.to_ty_saving_user_provided_ty(&t);
282 self.check_expr_eq_type(&e, ty);
285 ExprKind::If(cond, then_expr, opt_else_expr) => {
286 self.check_then_else(cond, then_expr, opt_else_expr, expr.span, expected)
288 ExprKind::DropTemps(e) => self.check_expr_with_expectation(e, expected),
289 ExprKind::Array(args) => self.check_expr_array(args, expected, expr),
290 ExprKind::ConstBlock(ref anon_const) => self.to_const(anon_const).ty,
291 ExprKind::Repeat(element, ref count) => {
292 self.check_expr_repeat(element, count, expected, expr)
294 ExprKind::Tup(elts) => self.check_expr_tuple(elts, expected, expr),
295 ExprKind::Struct(qpath, fields, ref base_expr) => {
296 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
298 ExprKind::Field(base, field) => self.check_field(expr, &base, field),
299 ExprKind::Index(base, idx) => self.check_expr_index(base, idx, expr),
300 ExprKind::Yield(value, ref src) => self.check_expr_yield(value, expr, src),
301 hir::ExprKind::Err => tcx.ty_error(),
305 fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
306 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
307 ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
310 let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
311 self.tcx.mk_box(referent_ty)
317 oprnd: &'tcx hir::Expr<'tcx>,
318 expected: Expectation<'tcx>,
319 expr: &'tcx hir::Expr<'tcx>,
322 let expected_inner = match unop {
323 hir::UnOp::Not | hir::UnOp::Neg => expected,
324 hir::UnOp::Deref => NoExpectation,
326 let mut oprnd_t = self.check_expr_with_expectation(&oprnd, expected_inner);
328 if !oprnd_t.references_error() {
329 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
331 hir::UnOp::Deref => {
332 if let Some(ty) = self.lookup_derefing(expr, oprnd, oprnd_t) {
335 let mut err = type_error_struct!(
340 "type `{}` cannot be dereferenced",
343 let sp = tcx.sess.source_map().start_point(expr.span);
345 tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
347 tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
350 oprnd_t = tcx.ty_error();
354 let result = self.check_user_unop(expr, oprnd_t, unop);
355 // If it's builtin, we can reuse the type, this helps inference.
356 if !(oprnd_t.is_integral() || *oprnd_t.kind() == ty::Bool) {
361 let result = self.check_user_unop(expr, oprnd_t, unop);
362 // If it's builtin, we can reuse the type, this helps inference.
363 if !oprnd_t.is_numeric() {
372 fn check_expr_addr_of(
374 kind: hir::BorrowKind,
375 mutbl: hir::Mutability,
376 oprnd: &'tcx hir::Expr<'tcx>,
377 expected: Expectation<'tcx>,
378 expr: &'tcx hir::Expr<'tcx>,
380 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
382 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
383 if oprnd.is_syntactic_place_expr() {
384 // Places may legitimately have unsized types.
385 // For example, dereferences of a fat pointer and
386 // the last field of a struct can be unsized.
389 Expectation::rvalue_hint(self, ty)
396 self.check_expr_with_expectation_and_needs(&oprnd, hint, Needs::maybe_mut_place(mutbl));
398 let tm = ty::TypeAndMut { ty, mutbl };
400 _ if tm.ty.references_error() => self.tcx.ty_error(),
401 hir::BorrowKind::Raw => {
402 self.check_named_place_expr(oprnd);
405 hir::BorrowKind::Ref => {
406 // Note: at this point, we cannot say what the best lifetime
407 // is to use for resulting pointer. We want to use the
408 // shortest lifetime possible so as to avoid spurious borrowck
409 // errors. Moreover, the longest lifetime will depend on the
410 // precise details of the value whose address is being taken
411 // (and how long it is valid), which we don't know yet until
412 // type inference is complete.
414 // Therefore, here we simply generate a region variable. The
415 // region inferencer will then select a suitable value.
416 // Finally, borrowck will infer the value of the region again,
417 // this time with enough precision to check that the value
418 // whose address was taken can actually be made to live as long
419 // as it needs to live.
420 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
421 self.tcx.mk_ref(region, tm)
426 /// Does this expression refer to a place that either:
427 /// * Is based on a local or static.
428 /// * Contains a dereference
429 /// Note that the adjustments for the children of `expr` should already
430 /// have been resolved.
431 fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
432 let is_named = oprnd.is_place_expr(|base| {
433 // Allow raw borrows if there are any deref adjustments.
435 // const VAL: (i32,) = (0,);
436 // const REF: &(i32,) = &(0,);
438 // &raw const VAL.0; // ERROR
439 // &raw const REF.0; // OK, same as &raw const (*REF).0;
441 // This is maybe too permissive, since it allows
442 // `let u = &raw const Box::new((1,)).0`, which creates an
443 // immediately dangling raw pointer.
448 .map_or(false, |x| x.iter().any(|adj| matches!(adj.kind, Adjust::Deref(_))))
451 self.tcx.sess.emit_err(AddressOfTemporaryTaken { span: oprnd.span })
455 fn check_lang_item_path(
457 lang_item: hir::LangItem,
458 expr: &'tcx hir::Expr<'tcx>,
460 self.resolve_lang_item_path(lang_item, expr.span, expr.hir_id).1
465 qpath: &'tcx hir::QPath<'tcx>,
466 expr: &'tcx hir::Expr<'tcx>,
469 let (res, opt_ty, segs) =
470 self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
473 self.set_tainted_by_errors();
476 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
477 report_unexpected_variant_res(tcx, res, expr.span);
480 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
483 if let ty::FnDef(..) = ty.kind() {
484 let fn_sig = ty.fn_sig(tcx);
485 if !tcx.features().unsized_fn_params {
486 // We want to remove some Sized bounds from std functions,
487 // but don't want to expose the removal to stable Rust.
488 // i.e., we don't want to allow
494 // to work in stable even if the Sized bound on `drop` is relaxed.
495 for i in 0..fn_sig.inputs().skip_binder().len() {
496 // We just want to check sizedness, so instead of introducing
497 // placeholder lifetimes with probing, we just replace higher lifetimes
500 .replace_bound_vars_with_fresh_vars(
502 infer::LateBoundRegionConversionTime::FnCall,
506 self.require_type_is_sized_deferred(
509 traits::SizedArgumentType(None),
513 // Here we want to prevent struct constructors from returning unsized types.
514 // There were two cases this happened: fn pointer coercion in stable
515 // and usual function call in presence of unsized_locals.
516 // Also, as we just want to check sizedness, instead of introducing
517 // placeholder lifetimes with probing, we just replace higher lifetimes
520 .replace_bound_vars_with_fresh_vars(
522 infer::LateBoundRegionConversionTime::FnCall,
526 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
529 // We always require that the type provided as the value for
530 // a type parameter outlives the moment of instantiation.
531 let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
532 self.add_wf_bounds(substs, expr);
539 destination: hir::Destination,
540 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
541 expr: &'tcx hir::Expr<'tcx>,
544 if let Ok(target_id) = destination.target_id {
546 if let Some(e) = expr_opt {
547 // If this is a break with a value, we need to type-check
548 // the expression. Get an expected type from the loop context.
549 let opt_coerce_to = {
550 // We should release `enclosing_breakables` before the `check_expr_with_hint`
551 // below, so can't move this block of code to the enclosing scope and share
552 // `ctxt` with the second `encloding_breakables` borrow below.
553 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
554 match enclosing_breakables.opt_find_breakable(target_id) {
555 Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
557 // Avoid ICE when `break` is inside a closure (#65383).
558 return tcx.ty_error_with_message(
560 "break was outside loop, but no error was emitted",
566 // If the loop context is not a `loop { }`, then break with
567 // a value is illegal, and `opt_coerce_to` will be `None`.
568 // Just set expectation to error in that case.
569 let coerce_to = opt_coerce_to.unwrap_or_else(|| tcx.ty_error());
571 // Recurse without `enclosing_breakables` borrowed.
572 e_ty = self.check_expr_with_hint(e, coerce_to);
573 cause = self.misc(e.span);
575 // Otherwise, this is a break *without* a value. That's
576 // always legal, and is equivalent to `break ()`.
577 e_ty = tcx.mk_unit();
578 cause = self.misc(expr.span);
581 // Now that we have type-checked `expr_opt`, borrow
582 // the `enclosing_loops` field and let's coerce the
583 // type of `expr_opt` into what is expected.
584 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
585 let ctxt = match enclosing_breakables.opt_find_breakable(target_id) {
588 // Avoid ICE when `break` is inside a closure (#65383).
589 return tcx.ty_error_with_message(
591 "break was outside loop, but no error was emitted",
596 if let Some(ref mut coerce) = ctxt.coerce {
597 if let Some(ref e) = expr_opt {
598 coerce.coerce(self, &cause, e, e_ty);
600 assert!(e_ty.is_unit());
601 let ty = coerce.expected_ty();
602 coerce.coerce_forced_unit(
606 self.suggest_mismatched_types_on_tail(
607 &mut err, expr, ty, e_ty, target_id,
609 if let Some(val) = ty_kind_suggestion(ty) {
610 let label = destination
612 .map(|l| format!(" {}", l.ident))
613 .unwrap_or_else(String::new);
616 "give it a value of the expected type",
617 format!("break{} {}", label, val),
618 Applicability::HasPlaceholders,
626 // If `ctxt.coerce` is `None`, we can just ignore
627 // the type of the expression. This is because
628 // either this was a break *without* a value, in
629 // which case it is always a legal type (`()`), or
630 // else an error would have been flagged by the
631 // `loops` pass for using break with an expression
632 // where you are not supposed to.
633 assert!(expr_opt.is_none() || self.tcx.sess.has_errors());
636 // If we encountered a `break`, then (no surprise) it may be possible to break from the
637 // loop... unless the value being returned from the loop diverges itself, e.g.
638 // `break return 5` or `break loop {}`.
639 ctxt.may_break |= !self.diverges.get().is_always();
641 // the type of a `break` is always `!`, since it diverges
644 // Otherwise, we failed to find the enclosing loop;
645 // this can only happen if the `break` was not
646 // inside a loop at all, which is caught by the
647 // loop-checking pass.
648 let err = self.tcx.ty_error_with_message(
650 "break was outside loop, but no error was emitted",
653 // We still need to assign a type to the inner expression to
654 // prevent the ICE in #43162.
655 if let Some(e) = expr_opt {
656 self.check_expr_with_hint(e, err);
658 // ... except when we try to 'break rust;'.
659 // ICE this expression in particular (see #43162).
660 if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind {
661 if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
662 fatally_break_rust(self.tcx.sess);
667 // There was an error; make type-check fail.
672 fn check_expr_return(
674 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
675 expr: &'tcx hir::Expr<'tcx>,
677 if self.ret_coercion.is_none() {
678 let mut err = ReturnStmtOutsideOfFnBody {
680 encl_body_span: None,
684 let encl_item_id = self.tcx.hir().get_parent_item(expr.hir_id);
686 if let Some(hir::Node::Item(hir::Item {
687 kind: hir::ItemKind::Fn(..),
691 | Some(hir::Node::TraitItem(hir::TraitItem {
692 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
696 | Some(hir::Node::ImplItem(hir::ImplItem {
697 kind: hir::ImplItemKind::Fn(..),
700 })) = self.tcx.hir().find(encl_item_id)
702 // We are inside a function body, so reporting "return statement
703 // outside of function body" needs an explanation.
705 let encl_body_owner_id = self.tcx.hir().enclosing_body_owner(expr.hir_id);
707 // If this didn't hold, we would not have to report an error in
709 assert_ne!(encl_item_id, encl_body_owner_id);
711 let encl_body_id = self.tcx.hir().body_owned_by(encl_body_owner_id);
712 let encl_body = self.tcx.hir().body(encl_body_id);
714 err.encl_body_span = Some(encl_body.value.span);
715 err.encl_fn_span = Some(*encl_fn_span);
718 self.tcx.sess.emit_err(err);
720 if let Some(e) = expr_opt {
721 // We still have to type-check `e` (issue #86188), but calling
722 // `check_return_expr` only works inside fn bodies.
725 } else if let Some(e) = expr_opt {
726 if self.ret_coercion_span.get().is_none() {
727 self.ret_coercion_span.set(Some(e.span));
729 self.check_return_expr(e);
731 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
732 if self.ret_coercion_span.get().is_none() {
733 self.ret_coercion_span.set(Some(expr.span));
735 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
736 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
737 coercion.coerce_forced_unit(
741 let span = fn_decl.output.span();
742 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
745 format!("expected `{}` because of this return type", snippet),
752 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
758 pub(super) fn check_return_expr(&self, return_expr: &'tcx hir::Expr<'tcx>) {
759 let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
760 span_bug!(return_expr.span, "check_return_expr called outside fn body")
763 let ret_ty = ret_coercion.borrow().expected_ty();
764 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
765 ret_coercion.borrow_mut().coerce(
767 &self.cause(return_expr.span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
773 pub(crate) fn check_lhs_assignable(
775 lhs: &'tcx hir::Expr<'tcx>,
776 err_code: &'static str,
779 if lhs.is_syntactic_place_expr() {
783 // FIXME: Make this use SessionDiagnostic once error codes can be dynamically set.
784 let mut err = self.tcx.sess.struct_span_err_with_code(
786 "invalid left-hand side of assignment",
787 DiagnosticId::Error(err_code.into()),
789 err.span_label(lhs.span, "cannot assign to this expression");
793 // A generic function for checking the 'then' and 'else' clauses in an 'if'
794 // or 'if-else' expression.
797 cond_expr: &'tcx hir::Expr<'tcx>,
798 then_expr: &'tcx hir::Expr<'tcx>,
799 opt_else_expr: Option<&'tcx hir::Expr<'tcx>>,
801 orig_expected: Expectation<'tcx>,
803 let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool, |_| {});
805 self.warn_if_unreachable(cond_expr.hir_id, then_expr.span, "block in `if` expression");
807 let cond_diverges = self.diverges.get();
808 self.diverges.set(Diverges::Maybe);
810 let expected = orig_expected.adjust_for_branches(self);
811 let then_ty = self.check_expr_with_expectation(then_expr, expected);
812 let then_diverges = self.diverges.get();
813 self.diverges.set(Diverges::Maybe);
815 // We've already taken the expected type's preferences
816 // into account when typing the `then` branch. To figure
817 // out the initial shot at a LUB, we thus only consider
818 // `expected` if it represents a *hard* constraint
819 // (`only_has_type`); otherwise, we just go with a
820 // fresh type variable.
821 let coerce_to_ty = expected.coercion_target_type(self, sp);
822 let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
824 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
826 if let Some(else_expr) = opt_else_expr {
827 let else_ty = self.check_expr_with_expectation(else_expr, expected);
828 let else_diverges = self.diverges.get();
830 let opt_suggest_box_span =
831 self.opt_suggest_box_span(else_expr.span, else_ty, orig_expected);
833 self.if_cause(sp, then_expr, else_expr, then_ty, else_ty, opt_suggest_box_span);
835 coerce.coerce(self, &if_cause, else_expr, else_ty);
837 // We won't diverge unless both branches do (or the condition does).
838 self.diverges.set(cond_diverges | then_diverges & else_diverges);
840 self.if_fallback_coercion(sp, then_expr, &mut coerce, |hir_id, span| {
841 self.maybe_get_coercion_reason_if(hir_id, span)
844 // If the condition is false we can't diverge.
845 self.diverges.set(cond_diverges);
848 let result_ty = coerce.complete(self);
849 if cond_ty.references_error() { self.tcx.ty_error() } else { result_ty }
852 /// Type check assignment expression `expr` of form `lhs = rhs`.
853 /// The expected type is `()` and is passed to the function for the purposes of diagnostics.
854 fn check_expr_assign(
856 expr: &'tcx hir::Expr<'tcx>,
857 expected: Expectation<'tcx>,
858 lhs: &'tcx hir::Expr<'tcx>,
859 rhs: &'tcx hir::Expr<'tcx>,
862 let expected_ty = expected.coercion_target_type(self, expr.span);
863 if expected_ty == self.tcx.types.bool {
864 // The expected type is `bool` but this will result in `()` so we can reasonably
865 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
866 // The likely cause of this is `if foo = bar { .. }`.
867 let actual_ty = self.tcx.mk_unit();
868 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
869 let lhs_ty = self.check_expr(&lhs);
870 let rhs_ty = self.check_expr(&rhs);
871 let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
872 (Applicability::MachineApplicable, true)
874 (Applicability::MaybeIncorrect, false)
876 if !lhs.is_syntactic_place_expr() {
877 // Do not suggest `if let x = y` as `==` is way more likely to be the intention.
878 let mut span_err = || {
879 // Likely `if let` intended.
880 err.span_suggestion_verbose(
881 expr.span.shrink_to_lo(),
882 "you might have meant to use pattern matching",
887 if let hir::Node::Expr(hir::Expr {
888 kind: ExprKind::Match(_, _, hir::MatchSource::WhileDesugar),
890 }) = self.tcx.hir().get(
891 self.tcx.hir().get_parent_node(self.tcx.hir().get_parent_node(expr.hir_id)),
894 } else if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) =
895 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr.hir_id))
901 err.span_suggestion_verbose(
903 "you might have meant to compare for equality",
909 if self.sess().if_let_suggestions.borrow().get(&expr.span).is_some() {
910 // We already emitted an `if let` suggestion due to an identifier not found.
915 return self.tcx.ty_error();
918 self.check_lhs_assignable(lhs, "E0070", span);
920 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
921 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty, Some(lhs));
923 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
925 if lhs_ty.references_error() || rhs_ty.references_error() {
934 body: &'tcx hir::Block<'tcx>,
935 source: hir::LoopSource,
936 expected: Expectation<'tcx>,
937 expr: &'tcx hir::Expr<'tcx>,
939 let coerce = match source {
940 // you can only use break with a value from a normal `loop { }`
941 hir::LoopSource::Loop => {
942 let coerce_to = expected.coercion_target_type(self, body.span);
943 Some(CoerceMany::new(coerce_to))
946 hir::LoopSource::While | hir::LoopSource::WhileLet | hir::LoopSource::ForLoop => None,
949 let ctxt = BreakableCtxt {
951 may_break: false, // Will get updated if/when we find a `break`.
954 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
955 self.check_block_no_value(&body);
959 // No way to know whether it's diverging because
960 // of a `break` or an outer `break` or `return`.
961 self.diverges.set(Diverges::Maybe);
964 // If we permit break with a value, then result type is
965 // the LUB of the breaks (possibly ! if none); else, it
966 // is nil. This makes sense because infinite loops
967 // (which would have type !) are only possible iff we
968 // permit break with a value [1].
969 if ctxt.coerce.is_none() && !ctxt.may_break {
971 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
973 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
976 /// Checks a method call.
977 fn check_method_call(
979 expr: &'tcx hir::Expr<'tcx>,
980 segment: &hir::PathSegment<'_>,
982 args: &'tcx [hir::Expr<'tcx>],
983 expected: Expectation<'tcx>,
986 let rcvr_t = self.check_expr(&rcvr);
987 // no need to check for bot/err -- callee does that
988 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
990 let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr, args) {
992 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
993 // trigger this codepath causing `structuraly_resolved_type` to emit an error.
995 self.write_method_call(expr.hir_id, method);
999 if segment.ident.name != kw::Empty {
1000 if let Some(mut err) = self.report_method_error(
1004 SelfSource::MethodCall(&args[0]),
1015 // Call the generic checker.
1016 self.check_method_argument_types(
1028 e: &'tcx hir::Expr<'tcx>,
1029 t: &'tcx hir::Ty<'tcx>,
1030 expr: &'tcx hir::Expr<'tcx>,
1032 // Find the type of `e`. Supply hints based on the type we are casting to,
1034 let t_cast = self.to_ty_saving_user_provided_ty(t);
1035 let t_cast = self.resolve_vars_if_possible(t_cast);
1036 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
1037 let t_cast = self.resolve_vars_if_possible(t_cast);
1039 // Eagerly check for some obvious errors.
1040 if t_expr.references_error() || t_cast.references_error() {
1043 // Defer other checks until we're done type checking.
1044 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
1045 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
1047 deferred_cast_checks.push(cast_check);
1050 Err(ErrorReported) => self.tcx.ty_error(),
1055 fn check_expr_array(
1057 args: &'tcx [hir::Expr<'tcx>],
1058 expected: Expectation<'tcx>,
1059 expr: &'tcx hir::Expr<'tcx>,
1061 let element_ty = if !args.is_empty() {
1062 let coerce_to = expected
1064 .and_then(|uty| match *uty.kind() {
1065 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1068 .unwrap_or_else(|| {
1069 self.next_ty_var(TypeVariableOrigin {
1070 kind: TypeVariableOriginKind::TypeInference,
1074 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
1075 assert_eq!(self.diverges.get(), Diverges::Maybe);
1077 let e_ty = self.check_expr_with_hint(e, coerce_to);
1078 let cause = self.misc(e.span);
1079 coerce.coerce(self, &cause, e, e_ty);
1081 coerce.complete(self)
1083 self.next_ty_var(TypeVariableOrigin {
1084 kind: TypeVariableOriginKind::TypeInference,
1088 self.tcx.mk_array(element_ty, args.len() as u64)
1091 fn check_expr_repeat(
1093 element: &'tcx hir::Expr<'tcx>,
1094 count: &'tcx hir::AnonConst,
1095 expected: Expectation<'tcx>,
1096 _expr: &'tcx hir::Expr<'tcx>,
1099 let count = self.to_const(count);
1101 let uty = match expected {
1102 ExpectHasType(uty) => match *uty.kind() {
1103 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1109 let (element_ty, t) = match uty {
1111 self.check_expr_coercable_to_type(&element, uty, None);
1115 let ty = self.next_ty_var(TypeVariableOrigin {
1116 kind: TypeVariableOriginKind::MiscVariable,
1119 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1124 if element_ty.references_error() {
1125 return tcx.ty_error();
1128 tcx.mk_ty(ty::Array(t, count))
1131 fn check_expr_tuple(
1133 elts: &'tcx [hir::Expr<'tcx>],
1134 expected: Expectation<'tcx>,
1135 expr: &'tcx hir::Expr<'tcx>,
1137 let flds = expected.only_has_type(self).and_then(|ty| {
1138 let ty = self.resolve_vars_with_obligations(ty);
1140 ty::Tuple(flds) => Some(&flds[..]),
1145 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
1146 Some(fs) if i < fs.len() => {
1147 let ety = fs[i].expect_ty();
1148 self.check_expr_coercable_to_type(&e, ety, None);
1151 _ => self.check_expr_with_expectation(&e, NoExpectation),
1153 let tuple = self.tcx.mk_tup(elt_ts_iter);
1154 if tuple.references_error() {
1157 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1162 fn check_expr_struct(
1164 expr: &hir::Expr<'_>,
1165 expected: Expectation<'tcx>,
1167 fields: &'tcx [hir::ExprField<'tcx>],
1168 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1170 // Find the relevant variant
1171 let (variant, adt_ty) = if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id)
1175 self.check_struct_fields_on_error(fields, base_expr);
1176 return self.tcx.ty_error();
1179 // Prohibit struct expressions when non-exhaustive flag is set.
1180 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1181 if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
1184 .emit_err(StructExprNonExhaustive { span: expr.span, what: adt.variant_descr() });
1187 let error_happened = self.check_expr_struct_fields(
1194 base_expr.is_none(),
1196 if let Some(base_expr) = base_expr {
1197 // If check_expr_struct_fields hit an error, do not attempt to populate
1198 // the fields with the base_expr. This could cause us to hit errors later
1199 // when certain fields are assumed to exist that in fact do not.
1200 if !error_happened {
1201 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {});
1202 match adt_ty.kind() {
1203 ty::Adt(adt, substs) if adt.is_struct() => {
1204 let fru_field_types = adt
1209 self.normalize_associated_types_in(
1211 f.ty(self.tcx, substs),
1218 .fru_field_types_mut()
1219 .insert(expr.hir_id, fru_field_types);
1224 .emit_err(FunctionalRecordUpdateOnNonStruct { span: base_expr.span });
1229 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1233 fn check_expr_struct_fields(
1236 expected: Expectation<'tcx>,
1237 expr_id: hir::HirId,
1239 variant: &'tcx ty::VariantDef,
1240 ast_fields: &'tcx [hir::ExprField<'tcx>],
1241 check_completeness: bool,
1245 let adt_ty_hint = self
1246 .expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
1250 // re-link the regions that EIfEO can erase.
1251 self.demand_eqtype(span, adt_ty_hint, adt_ty);
1253 let (substs, adt_kind, kind_name) = match adt_ty.kind() {
1254 ty::Adt(adt, substs) => (substs, adt.adt_kind(), adt.variant_descr()),
1255 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields"),
1258 let mut remaining_fields = variant
1262 .map(|(i, field)| (field.ident.normalize_to_macros_2_0(), (i, field)))
1263 .collect::<FxHashMap<_, _>>();
1265 let mut seen_fields = FxHashMap::default();
1267 let mut error_happened = false;
1269 // Type-check each field.
1270 for field in ast_fields {
1271 let ident = tcx.adjust_ident(field.ident, variant.def_id);
1272 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1273 seen_fields.insert(ident, field.span);
1274 self.write_field_index(field.hir_id, i);
1276 // We don't look at stability attributes on
1277 // struct-like enums (yet...), but it's definitely not
1278 // a bug to have constructed one.
1279 if adt_kind != AdtKind::Enum {
1280 tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
1283 self.field_ty(field.span, v_field, substs)
1285 error_happened = true;
1286 if let Some(prev_span) = seen_fields.get(&ident) {
1287 tcx.sess.emit_err(FieldMultiplySpecifiedInInitializer {
1288 span: field.ident.span,
1289 prev_span: *prev_span,
1293 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name, span);
1299 // Make sure to give a type to the field even if there's
1300 // an error, so we can continue type-checking.
1301 self.check_expr_coercable_to_type(&field.expr, field_type, None);
1304 // Make sure the programmer specified correct number of fields.
1305 if kind_name == "union" {
1306 if ast_fields.len() != 1 {
1311 "union expressions should have exactly one field",
1315 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
1316 let no_accessible_remaining_fields = remaining_fields
1318 .find(|(_, (_, field))| {
1319 field.vis.is_accessible_from(tcx.parent_module(expr_id).to_def_id(), tcx)
1323 if no_accessible_remaining_fields {
1324 self.report_no_accessible_fields(adt_ty, span);
1326 self.report_missing_fields(adt_ty, span, remaining_fields);
1333 fn check_struct_fields_on_error(
1335 fields: &'tcx [hir::ExprField<'tcx>],
1336 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1338 for field in fields {
1339 self.check_expr(&field.expr);
1341 if let Some(base) = *base_expr {
1342 self.check_expr(&base);
1346 /// Report an error for a struct field expression when there are fields which aren't provided.
1349 /// error: missing field `you_can_use_this_field` in initializer of `foo::Foo`
1350 /// --> src/main.rs:8:5
1352 /// 8 | foo::Foo {};
1353 /// | ^^^^^^^^ missing `you_can_use_this_field`
1355 /// error: aborting due to previous error
1357 fn report_missing_fields(
1361 remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
1363 let len = remaining_fields.len();
1365 let mut displayable_field_names =
1366 remaining_fields.keys().map(|ident| ident.as_str()).collect::<Vec<_>>();
1368 displayable_field_names.sort();
1370 let mut truncated_fields_error = String::new();
1371 let remaining_fields_names = match &displayable_field_names[..] {
1372 [field1] => format!("`{}`", field1),
1373 [field1, field2] => format!("`{}` and `{}`", field1, field2),
1374 [field1, field2, field3] => format!("`{}`, `{}` and `{}`", field1, field2, field3),
1376 truncated_fields_error =
1377 format!(" and {} other field{}", len - 3, pluralize!(len - 3));
1378 displayable_field_names
1381 .map(|n| format!("`{}`", n))
1382 .collect::<Vec<_>>()
1391 "missing field{} {}{} in initializer of `{}`",
1393 remaining_fields_names,
1394 truncated_fields_error,
1397 .span_label(span, format!("missing {}{}", remaining_fields_names, truncated_fields_error))
1401 /// Report an error for a struct field expression when there are no visible fields.
1404 /// error: cannot construct `Foo` with struct literal syntax due to inaccessible fields
1405 /// --> src/main.rs:8:5
1407 /// 8 | foo::Foo {};
1410 /// error: aborting due to previous error
1412 fn report_no_accessible_fields(&self, adt_ty: Ty<'tcx>, span: Span) {
1413 self.tcx.sess.span_err(
1416 "cannot construct `{}` with struct literal syntax due to inaccessible fields",
1422 fn report_unknown_field(
1425 variant: &'tcx ty::VariantDef,
1426 field: &hir::ExprField<'_>,
1427 skip_fields: &[hir::ExprField<'_>],
1431 if variant.is_recovered() {
1432 self.set_tainted_by_errors();
1435 let mut err = self.type_error_struct_with_diag(
1437 |actual| match ty.kind() {
1438 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1442 "{} `{}::{}` has no field named `{}`",
1448 _ => struct_span_err!(
1452 "{} `{}` has no field named `{}`",
1460 match variant.ctor_kind {
1461 CtorKind::Fn => match ty.kind() {
1462 ty::Adt(adt, ..) if adt.is_enum() => {
1466 "`{adt}::{variant}` defined here",
1468 variant = variant.ident,
1471 err.span_label(field.ident.span, "field does not exist");
1472 err.span_suggestion(
1475 "`{adt}::{variant}` is a tuple {kind_name}, use the appropriate syntax",
1477 variant = variant.ident,
1480 "{adt}::{variant}(/* fields */)",
1482 variant = variant.ident,
1484 Applicability::HasPlaceholders,
1488 err.span_label(variant.ident.span, format!("`{adt}` defined here", adt = ty));
1489 err.span_label(field.ident.span, "field does not exist");
1490 err.span_suggestion(
1493 "`{adt}` is a tuple {kind_name}, use the appropriate syntax",
1495 kind_name = kind_name,
1497 format!("{adt}(/* fields */)", adt = ty),
1498 Applicability::HasPlaceholders,
1503 // prevent all specified fields from being suggested
1504 let skip_fields = skip_fields.iter().map(|x| x.ident.name);
1505 if let Some(field_name) =
1506 Self::suggest_field_name(variant, field.ident.name, skip_fields.collect())
1508 err.span_suggestion(
1510 "a field with a similar name exists",
1511 field_name.to_string(),
1512 Applicability::MaybeIncorrect,
1516 ty::Adt(adt, ..) => {
1520 format!("`{}::{}` does not have this field", ty, variant.ident),
1525 format!("`{}` does not have this field", ty),
1528 let available_field_names = self.available_field_names(variant);
1529 if !available_field_names.is_empty() {
1531 "available fields are: {}",
1532 self.name_series_display(available_field_names)
1536 _ => bug!("non-ADT passed to report_unknown_field"),
1544 // Return an hint about the closest match in field names
1545 fn suggest_field_name(
1546 variant: &'tcx ty::VariantDef,
1549 ) -> Option<Symbol> {
1553 .filter_map(|field| {
1554 // ignore already set fields and private fields from non-local crates
1555 if skip.iter().any(|&x| x == field.ident.name)
1556 || (!variant.def_id.is_local() && field.vis != Visibility::Public)
1560 Some(field.ident.name)
1563 .collect::<Vec<Symbol>>();
1565 find_best_match_for_name(&names, field, None)
1568 fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<Symbol> {
1573 let def_scope = self
1575 .adjust_ident_and_get_scope(field.ident, variant.def_id, self.body_id)
1577 field.vis.is_accessible_from(def_scope, self.tcx)
1579 .map(|field| field.ident.name)
1583 fn name_series_display(&self, names: Vec<Symbol>) -> String {
1584 // dynamic limit, to never omit just one field
1585 let limit = if names.len() == 6 { 6 } else { 5 };
1587 names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
1588 if names.len() > limit {
1589 display = format!("{} ... and {} others", display, names.len() - limit);
1594 // Check field access expressions
1597 expr: &'tcx hir::Expr<'tcx>,
1598 base: &'tcx hir::Expr<'tcx>,
1601 debug!("check_field(expr: {:?}, base: {:?}, field: {:?})", expr, base, field);
1602 let expr_t = self.check_expr(base);
1603 let expr_t = self.structurally_resolved_type(base.span, expr_t);
1604 let mut private_candidate = None;
1605 let mut autoderef = self.autoderef(expr.span, expr_t);
1606 while let Some((base_t, _)) = autoderef.next() {
1607 debug!("base_t: {:?}", base_t);
1608 match base_t.kind() {
1609 ty::Adt(base_def, substs) if !base_def.is_enum() => {
1610 debug!("struct named {:?}", base_t);
1611 let (ident, def_scope) =
1612 self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
1613 let fields = &base_def.non_enum_variant().fields;
1614 if let Some(index) =
1615 fields.iter().position(|f| f.ident.normalize_to_macros_2_0() == ident)
1617 let field = &fields[index];
1618 let field_ty = self.field_ty(expr.span, field, substs);
1619 // Save the index of all fields regardless of their visibility in case
1620 // of error recovery.
1621 self.write_field_index(expr.hir_id, index);
1622 if field.vis.is_accessible_from(def_scope, self.tcx) {
1623 let adjustments = self.adjust_steps(&autoderef);
1624 self.apply_adjustments(base, adjustments);
1625 self.register_predicates(autoderef.into_obligations());
1627 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
1630 private_candidate = Some((base_def.did, field_ty));
1634 let fstr = field.as_str();
1635 if let Ok(index) = fstr.parse::<usize>() {
1636 if fstr == index.to_string() {
1637 if let Some(field_ty) = tys.get(index) {
1638 let adjustments = self.adjust_steps(&autoderef);
1639 self.apply_adjustments(base, adjustments);
1640 self.register_predicates(autoderef.into_obligations());
1642 self.write_field_index(expr.hir_id, index);
1643 return field_ty.expect_ty();
1651 self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
1653 if let Some((did, field_ty)) = private_candidate {
1654 self.ban_private_field_access(expr, expr_t, field, did);
1658 if field.name == kw::Empty {
1659 } else if self.method_exists(field, expr_t, expr.hir_id, true) {
1660 self.ban_take_value_of_method(expr, expr_t, field);
1661 } else if !expr_t.is_primitive_ty() {
1662 self.ban_nonexisting_field(field, base, expr, expr_t);
1669 "`{}` is a primitive type and therefore doesn't have fields",
1675 self.tcx().ty_error()
1678 fn suggest_await_on_field_access(
1680 err: &mut DiagnosticBuilder<'_>,
1682 base: &'tcx hir::Expr<'tcx>,
1685 let output_ty = match self.infcx.get_impl_future_output_ty(ty) {
1686 Some(output_ty) => self.resolve_vars_if_possible(output_ty),
1689 let mut add_label = true;
1690 if let ty::Adt(def, _) = output_ty.kind() {
1691 // no field access on enum type
1693 if def.non_enum_variant().fields.iter().any(|field| field.ident == field_ident) {
1697 "field not available in `impl Future`, but it is available in its `Output`",
1699 err.span_suggestion_verbose(
1700 base.span.shrink_to_hi(),
1701 "consider `await`ing on the `Future` and access the field of its `Output`",
1702 ".await".to_string(),
1703 Applicability::MaybeIncorrect,
1709 err.span_label(field_ident.span, &format!("field not found in `{}`", ty));
1713 fn ban_nonexisting_field(
1716 base: &'tcx hir::Expr<'tcx>,
1717 expr: &'tcx hir::Expr<'tcx>,
1721 "ban_nonexisting_field: field={:?}, base={:?}, expr={:?}, expr_ty={:?}",
1722 field, base, expr, expr_t
1724 let mut err = self.no_such_field_err(field, expr_t);
1726 match *expr_t.peel_refs().kind() {
1727 ty::Array(_, len) => {
1728 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
1731 self.suggest_first_deref_field(&mut err, expr, base, field);
1733 ty::Adt(def, _) if !def.is_enum() => {
1734 self.suggest_fields_on_recordish(&mut err, def, field);
1736 ty::Param(param_ty) => {
1737 self.point_at_param_definition(&mut err, param_ty);
1739 ty::Opaque(_, _) => {
1740 self.suggest_await_on_field_access(&mut err, field, base, expr_t.peel_refs());
1745 if field.name == kw::Await {
1746 // We know by construction that `<expr>.await` is either on Rust 2015
1747 // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
1748 err.note("to `.await` a `Future`, switch to Rust 2018 or later");
1749 err.help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION));
1750 err.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
1756 fn ban_private_field_access(
1758 expr: &hir::Expr<'_>,
1763 let struct_path = self.tcx().def_path_str(base_did);
1764 let kind_name = self.tcx().def_kind(base_did).descr(base_did);
1765 let mut err = struct_span_err!(
1769 "field `{}` of {} `{}` is private",
1774 err.span_label(field.span, "private field");
1775 // Also check if an accessible method exists, which is often what is meant.
1776 if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
1778 self.suggest_method_call(
1780 &format!("a method `{}` also exists, call it with parentheses", field),
1789 fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: Ident) {
1790 let mut err = type_error_struct!(
1795 "attempted to take value of method `{}` on type `{}`",
1799 err.span_label(field.span, "method, not a field");
1800 if !self.expr_in_place(expr.hir_id) {
1801 self.suggest_method_call(
1803 "use parentheses to call the method",
1809 err.help("methods are immutable and cannot be assigned to");
1815 fn point_at_param_definition(&self, err: &mut DiagnosticBuilder<'_>, param: ty::ParamTy) {
1816 let generics = self.tcx.generics_of(self.body_id.owner.to_def_id());
1817 let generic_param = generics.type_param(¶m, self.tcx);
1818 if let ty::GenericParamDefKind::Type { synthetic: Some(..), .. } = generic_param.kind {
1821 let param_def_id = generic_param.def_id;
1822 let param_hir_id = match param_def_id.as_local() {
1823 Some(x) => self.tcx.hir().local_def_id_to_hir_id(x),
1826 let param_span = self.tcx.hir().span(param_hir_id);
1827 let param_name = self.tcx.hir().ty_param_name(param_hir_id);
1829 err.span_label(param_span, &format!("type parameter '{}' declared here", param_name));
1832 fn suggest_fields_on_recordish(
1834 err: &mut DiagnosticBuilder<'_>,
1835 def: &'tcx ty::AdtDef,
1838 if let Some(suggested_field_name) =
1839 Self::suggest_field_name(def.non_enum_variant(), field.name, vec![])
1841 err.span_suggestion(
1843 "a field with a similar name exists",
1844 suggested_field_name.to_string(),
1845 Applicability::MaybeIncorrect,
1848 err.span_label(field.span, "unknown field");
1849 let struct_variant_def = def.non_enum_variant();
1850 let field_names = self.available_field_names(struct_variant_def);
1851 if !field_names.is_empty() {
1853 "available fields are: {}",
1854 self.name_series_display(field_names),
1860 fn maybe_suggest_array_indexing(
1862 err: &mut DiagnosticBuilder<'_>,
1863 expr: &hir::Expr<'_>,
1864 base: &hir::Expr<'_>,
1866 len: &ty::Const<'tcx>,
1868 if let (Some(len), Ok(user_index)) =
1869 (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
1871 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
1872 let help = "instead of using tuple indexing, use array indexing";
1873 let suggestion = format!("{}[{}]", base, field);
1874 let applicability = if len < user_index {
1875 Applicability::MachineApplicable
1877 Applicability::MaybeIncorrect
1879 err.span_suggestion(expr.span, help, suggestion, applicability);
1884 fn suggest_first_deref_field(
1886 err: &mut DiagnosticBuilder<'_>,
1887 expr: &hir::Expr<'_>,
1888 base: &hir::Expr<'_>,
1891 if let Ok(base) = self.tcx.sess.source_map().span_to_snippet(base.span) {
1892 let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
1893 let suggestion = format!("(*{}).{}", base, field);
1894 err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
1898 fn no_such_field_err(
1901 expr_t: &'tcx ty::TyS<'tcx>,
1902 ) -> DiagnosticBuilder<'_> {
1903 let span = field.span;
1904 debug!("no_such_field_err(span: {:?}, field: {:?}, expr_t: {:?})", span, field, expr_t);
1906 let mut err = type_error_struct!(
1911 "no field `{}` on type `{}`",
1916 // try to add a suggestion in case the field is a nested field of a field of the Adt
1917 if let Some((fields, substs)) = self.get_field_candidates(span, &expr_t) {
1918 for candidate_field in fields.iter() {
1919 if let Some(field_path) =
1920 self.check_for_nested_field(span, field, candidate_field, substs, vec![])
1922 let field_path_str = field_path
1924 .map(|id| id.name.to_ident_string())
1925 .collect::<Vec<String>>()
1927 debug!("field_path_str: {:?}", field_path_str);
1929 err.span_suggestion_verbose(
1930 field.span.shrink_to_lo(),
1931 "one of the expressions' fields has a field of the same name",
1932 format!("{}.", field_path_str),
1933 Applicability::MaybeIncorrect,
1941 fn get_field_candidates(
1945 ) -> Option<(&Vec<ty::FieldDef>, SubstsRef<'tcx>)> {
1946 debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_t);
1948 let mut autoderef = self.autoderef(span, base_t);
1949 while let Some((base_t, _)) = autoderef.next() {
1950 match base_t.kind() {
1951 ty::Adt(base_def, substs) if !base_def.is_enum() => {
1952 let fields = &base_def.non_enum_variant().fields;
1953 // For compile-time reasons put a limit on number of fields we search
1954 if fields.len() > 100 {
1957 return Some((fields, substs));
1965 /// This method is called after we have encountered a missing field error to recursively
1966 /// search for the field
1967 fn check_for_nested_field(
1970 target_field: Ident,
1971 candidate_field: &ty::FieldDef,
1972 subst: SubstsRef<'tcx>,
1973 mut field_path: Vec<Ident>,
1974 ) -> Option<Vec<Ident>> {
1976 "check_for_nested_field(span: {:?}, candidate_field: {:?}, field_path: {:?}",
1977 span, candidate_field, field_path
1980 if candidate_field.ident == target_field {
1982 } else if field_path.len() > 3 {
1983 // For compile-time reasons and to avoid infinite recursion we only check for fields
1984 // up to a depth of three
1987 // recursively search fields of `candidate_field` if it's a ty::Adt
1989 field_path.push(candidate_field.ident.normalize_to_macros_2_0());
1990 let field_ty = candidate_field.ty(self.tcx, subst);
1991 if let Some((nested_fields, subst)) = self.get_field_candidates(span, &field_ty) {
1992 for field in nested_fields.iter() {
1993 let ident = field.ident.normalize_to_macros_2_0();
1994 if ident == target_field {
1995 return Some(field_path);
1997 let field_path = field_path.clone();
1998 if let Some(path) = self.check_for_nested_field(
2014 fn check_expr_index(
2016 base: &'tcx hir::Expr<'tcx>,
2017 idx: &'tcx hir::Expr<'tcx>,
2018 expr: &'tcx hir::Expr<'tcx>,
2020 let base_t = self.check_expr(&base);
2021 let idx_t = self.check_expr(&idx);
2023 if base_t.references_error() {
2025 } else if idx_t.references_error() {
2028 let base_t = self.structurally_resolved_type(base.span, base_t);
2029 match self.lookup_indexing(expr, base, base_t, idx_t) {
2030 Some((index_ty, element_ty)) => {
2031 // two-phase not needed because index_ty is never mutable
2032 self.demand_coerce(idx, idx_t, index_ty, None, AllowTwoPhase::No);
2036 let mut err = type_error_struct!(
2041 "cannot index into a value of type `{}`",
2044 // Try to give some advice about indexing tuples.
2045 if let ty::Tuple(..) = base_t.kind() {
2046 let mut needs_note = true;
2047 // If the index is an integer, we can show the actual
2048 // fixed expression:
2049 if let ExprKind::Lit(ref lit) = idx.kind {
2050 if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
2051 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
2052 if let Ok(snip) = snip {
2053 err.span_suggestion(
2055 "to access tuple elements, use",
2056 format!("{}.{}", snip, i),
2057 Applicability::MachineApplicable,
2065 "to access tuple elements, use tuple indexing \
2066 syntax (e.g., `tuple.0`)",
2077 fn check_expr_yield(
2079 value: &'tcx hir::Expr<'tcx>,
2080 expr: &'tcx hir::Expr<'tcx>,
2081 src: &'tcx hir::YieldSource,
2083 match self.resume_yield_tys {
2084 Some((resume_ty, yield_ty)) => {
2085 self.check_expr_coercable_to_type(&value, yield_ty, None);
2089 // Given that this `yield` expression was generated as a result of lowering a `.await`,
2090 // we know that the yield type must be `()`; however, the context won't contain this
2091 // information. Hence, we check the source of the yield expression here and check its
2092 // value's type against `()` (this check should always hold).
2093 None if src.is_await() => {
2094 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
2098 self.tcx.sess.emit_err(YieldExprOutsideOfGenerator { span: expr.span });
2099 // Avoid expressions without types during writeback (#78653).
2100 self.check_expr(value);
2106 fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
2107 let needs = if is_input { Needs::None } else { Needs::MutPlace };
2108 let ty = self.check_expr_with_needs(expr, needs);
2109 self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
2111 if !is_input && !expr.is_syntactic_place_expr() {
2112 let mut err = self.tcx.sess.struct_span_err(expr.span, "invalid asm output");
2113 err.span_label(expr.span, "cannot assign to this expression");
2117 // If this is an input value, we require its type to be fully resolved
2118 // at this point. This allows us to provide helpful coercions which help
2119 // pass the type candidate list in a later pass.
2121 // We don't require output types to be resolved at this point, which
2122 // allows them to be inferred based on how they are used later in the
2125 let ty = self.structurally_resolved_type(expr.span, &ty);
2128 let fnptr_ty = self.tcx.mk_fn_ptr(ty.fn_sig(self.tcx));
2129 self.demand_coerce(expr, ty, fnptr_ty, None, AllowTwoPhase::No);
2131 ty::Ref(_, base_ty, mutbl) => {
2132 let ptr_ty = self.tcx.mk_ptr(ty::TypeAndMut { ty: base_ty, mutbl });
2133 self.demand_coerce(expr, ty, ptr_ty, None, AllowTwoPhase::No);
2140 fn check_expr_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>) -> Ty<'tcx> {
2141 for (op, _op_sp) in asm.operands {
2143 hir::InlineAsmOperand::In { expr, .. } => {
2144 self.check_expr_asm_operand(expr, true);
2146 hir::InlineAsmOperand::Out { expr, .. } => {
2147 if let Some(expr) = expr {
2148 self.check_expr_asm_operand(expr, false);
2151 hir::InlineAsmOperand::InOut { expr, .. } => {
2152 self.check_expr_asm_operand(expr, false);
2154 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
2155 self.check_expr_asm_operand(in_expr, true);
2156 if let Some(out_expr) = out_expr {
2157 self.check_expr_asm_operand(out_expr, false);
2160 hir::InlineAsmOperand::Const { anon_const } => {
2161 self.to_const(anon_const);
2163 hir::InlineAsmOperand::Sym { expr } => {
2164 self.check_expr(expr);
2168 if asm.options.contains(ast::InlineAsmOptions::NORETURN) {
2169 self.tcx.types.never
2176 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
2177 Some(match ty.kind() {
2180 ty::Int(_) | ty::Uint(_) => "42",
2181 ty::Float(_) => "3.14159",
2182 ty::Error(_) | ty::Never => return None,