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::{probe, MethodError, SelfSource};
10 use crate::check::report_unexpected_variant_res;
11 use crate::check::BreakableCtxt;
12 use crate::check::Diverges;
13 use crate::check::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
14 use crate::check::FnCtxt;
15 use crate::check::Needs;
16 use crate::check::TupleArgumentsFlag::DontTupleArguments;
17 use crate::type_error_struct;
18 use crate::util::common::ErrorReported;
21 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
22 use rustc::middle::lang_items;
23 use rustc::traits::{self, ObligationCauseCode};
25 use rustc::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
27 use rustc::ty::TypeFoldable;
28 use rustc::ty::{AdtKind, Visibility};
29 use rustc_data_structures::fx::FxHashMap;
30 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
32 use rustc_hir::def::{CtorKind, DefKind, Res};
33 use rustc_hir::def_id::DefId;
34 use rustc_hir::{ExprKind, QPath};
35 use rustc_span::hygiene::DesugaringKind;
36 use rustc_span::source_map::Span;
37 use rustc_span::symbol::{kw, sym, Symbol};
39 use syntax::util::lev_distance::find_best_match_for_name;
41 use std::fmt::Display;
43 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
44 fn check_expr_eq_type(&self, expr: &'tcx hir::Expr<'tcx>, expected: Ty<'tcx>) {
45 let ty = self.check_expr_with_hint(expr, expected);
46 self.demand_eqtype(expr.span, expected, ty);
49 pub fn check_expr_has_type_or_error(
51 expr: &'tcx hir::Expr<'tcx>,
53 extend_err: impl Fn(&mut DiagnosticBuilder<'_>),
55 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected), extend_err)
58 fn check_expr_meets_expectation_or_error(
60 expr: &'tcx hir::Expr<'tcx>,
61 expected: Expectation<'tcx>,
62 extend_err: impl Fn(&mut DiagnosticBuilder<'_>),
64 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
65 let mut ty = self.check_expr_with_expectation(expr, expected);
67 // While we don't allow *arbitrary* coercions here, we *do* allow
68 // coercions from ! to `expected`.
71 !self.tables.borrow().adjustments().contains_key(expr.hir_id),
72 "expression with never type wound up being adjusted"
74 let adj_ty = self.next_diverging_ty_var(TypeVariableOrigin {
75 kind: TypeVariableOriginKind::AdjustmentType,
78 self.apply_adjustments(
80 vec![Adjustment { kind: Adjust::NeverToAny, target: adj_ty }],
85 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
86 let expr = expr.peel_drop_temps();
87 self.suggest_ref_or_into(&mut err, expr, expected_ty, ty);
89 // Error possibly reported in `check_assign` so avoid emitting error again.
90 err.emit_unless(self.is_assign_to_bool(expr, expected_ty));
95 pub(super) fn check_expr_coercable_to_type(
97 expr: &'tcx hir::Expr<'tcx>,
100 let ty = self.check_expr_with_hint(expr, expected);
101 // checks don't need two phase
102 self.demand_coerce(expr, ty, expected, AllowTwoPhase::No)
105 pub(super) fn check_expr_with_hint(
107 expr: &'tcx hir::Expr<'tcx>,
110 self.check_expr_with_expectation(expr, ExpectHasType(expected))
113 pub(super) fn check_expr_with_expectation(
115 expr: &'tcx hir::Expr<'tcx>,
116 expected: Expectation<'tcx>,
118 self.check_expr_with_expectation_and_needs(expr, expected, Needs::None)
121 pub(super) fn check_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
122 self.check_expr_with_expectation(expr, NoExpectation)
125 pub(super) fn check_expr_with_needs(
127 expr: &'tcx hir::Expr<'tcx>,
130 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
134 /// If an expression has any sub-expressions that result in a type error,
135 /// inspecting that expression's type with `ty.references_error()` will return
136 /// true. Likewise, if an expression is known to diverge, inspecting its
137 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
138 /// strict, _|_ can appear in the type of an expression that does not,
139 /// itself, diverge: for example, fn() -> _|_.)
140 /// Note that inspecting a type's structure *directly* may expose the fact
141 /// that there are actually multiple representations for `Error`, so avoid
142 /// that when err needs to be handled differently.
143 fn check_expr_with_expectation_and_needs(
145 expr: &'tcx hir::Expr<'tcx>,
146 expected: Expectation<'tcx>,
149 debug!(">> type-checking: expr={:?} expected={:?}", expr, expected);
151 // True if `expr` is a `Try::from_ok(())` that is a result of desugaring a try block
152 // without the final expr (e.g. `try { return; }`). We don't want to generate an
153 // unreachable_code lint for it since warnings for autogenerated code are confusing.
154 let is_try_block_generated_unit_expr = match expr.kind {
155 ExprKind::Call(_, ref args) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {
156 args.len() == 1 && args[0].span.is_desugaring(DesugaringKind::TryBlock)
162 // Warn for expressions after diverging siblings.
163 if !is_try_block_generated_unit_expr {
164 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
167 // Hide the outer diverging and has_errors flags.
168 let old_diverges = self.diverges.get();
169 let old_has_errors = self.has_errors.get();
170 self.diverges.set(Diverges::Maybe);
171 self.has_errors.set(false);
173 let ty = self.check_expr_kind(expr, expected, needs);
175 // Warn for non-block expressions with diverging children.
177 ExprKind::Block(..) | ExprKind::Loop(..) | ExprKind::Match(..) => {}
178 // If `expr` is a result of desugaring the try block and is an ok-wrapped
179 // diverging expression (e.g. it arose from desugaring of `try { return }`),
180 // we skip issuing a warning because it is autogenerated code.
181 ExprKind::Call(..) if expr.span.is_desugaring(DesugaringKind::TryBlock) => {}
182 ExprKind::Call(ref callee, _) => {
183 self.warn_if_unreachable(expr.hir_id, callee.span, "call")
185 ExprKind::MethodCall(_, ref span, _) => {
186 self.warn_if_unreachable(expr.hir_id, *span, "call")
188 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression"),
191 // Any expression that produces a value of type `!` must have diverged
193 self.diverges.set(self.diverges.get() | Diverges::always(expr.span));
196 // Record the type, which applies it effects.
197 // We need to do this after the warning above, so that
198 // we don't warn for the diverging expression itself.
199 self.write_ty(expr.hir_id, ty);
201 // Combine the diverging and has_error flags.
202 self.diverges.set(self.diverges.get() | old_diverges);
203 self.has_errors.set(self.has_errors.get() | old_has_errors);
205 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.hir_id));
206 debug!("... {:?}, expected is {:?}", ty, expected);
213 expr: &'tcx hir::Expr<'tcx>,
214 expected: Expectation<'tcx>,
217 debug!("check_expr_kind(expr={:?}, expected={:?}, needs={:?})", expr, expected, needs,);
221 ExprKind::Box(ref subexpr) => self.check_expr_box(subexpr, expected),
222 ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
223 ExprKind::Binary(op, ref lhs, ref rhs) => self.check_binop(expr, op, lhs, rhs),
224 ExprKind::Assign(ref lhs, ref rhs, ref span) => {
225 self.check_expr_assign(expr, expected, lhs, rhs, span)
227 ExprKind::AssignOp(op, ref lhs, ref rhs) => self.check_binop_assign(expr, op, lhs, rhs),
228 ExprKind::Unary(unop, ref oprnd) => {
229 self.check_expr_unary(unop, oprnd, expected, needs, expr)
231 ExprKind::AddrOf(kind, mutbl, ref oprnd) => {
232 self.check_expr_addr_of(kind, mutbl, oprnd, expected, expr)
234 ExprKind::Path(ref qpath) => self.check_expr_path(qpath, expr),
235 ExprKind::InlineAsm(ref asm) => {
236 for expr in asm.outputs_exprs.iter().chain(asm.inputs_exprs.iter()) {
237 self.check_expr(expr);
241 ExprKind::Break(destination, ref expr_opt) => {
242 self.check_expr_break(destination, expr_opt.as_deref(), expr)
244 ExprKind::Continue(destination) => {
245 if destination.target_id.is_ok() {
248 // There was an error; make type-check fail.
252 ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
253 ExprKind::Loop(ref body, _, source) => {
254 self.check_expr_loop(body, source, expected, expr)
256 ExprKind::Match(ref discrim, ref arms, match_src) => {
257 self.check_match(expr, &discrim, arms, expected, match_src)
259 ExprKind::Closure(capture, ref decl, body_id, _, gen) => {
260 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
262 ExprKind::Block(ref body, _) => self.check_block_with_expected(&body, expected),
263 ExprKind::Call(ref callee, ref args) => self.check_call(expr, &callee, args, expected),
264 ExprKind::MethodCall(ref segment, span, ref args) => {
265 self.check_method_call(expr, segment, span, args, expected, needs)
267 ExprKind::Cast(ref e, ref t) => self.check_expr_cast(e, t, expr),
268 ExprKind::Type(ref e, ref t) => {
269 let ty = self.to_ty_saving_user_provided_ty(&t);
270 self.check_expr_eq_type(&e, ty);
273 ExprKind::DropTemps(ref e) => self.check_expr_with_expectation(e, expected),
274 ExprKind::Array(ref args) => self.check_expr_array(args, expected, expr),
275 ExprKind::Repeat(ref element, ref count) => {
276 self.check_expr_repeat(element, count, expected, expr)
278 ExprKind::Tup(ref elts) => self.check_expr_tuple(elts, expected, expr),
279 ExprKind::Struct(ref qpath, fields, ref base_expr) => {
280 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
282 ExprKind::Field(ref base, field) => self.check_field(expr, needs, &base, field),
283 ExprKind::Index(ref base, ref idx) => self.check_expr_index(base, idx, needs, expr),
284 ExprKind::Yield(ref value, ref src) => self.check_expr_yield(value, expr, src),
285 hir::ExprKind::Err => tcx.types.err,
289 fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
290 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind {
291 ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
294 let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
295 self.tcx.mk_box(referent_ty)
301 oprnd: &'tcx hir::Expr<'tcx>,
302 expected: Expectation<'tcx>,
304 expr: &'tcx hir::Expr<'tcx>,
307 let expected_inner = match unop {
308 hir::UnOp::UnNot | hir::UnOp::UnNeg => expected,
309 hir::UnOp::UnDeref => NoExpectation,
311 let needs = match unop {
312 hir::UnOp::UnDeref => needs,
315 let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd, expected_inner, needs);
317 if !oprnd_t.references_error() {
318 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
320 hir::UnOp::UnDeref => {
321 if let Some(mt) = oprnd_t.builtin_deref(true) {
323 } else if let Some(ok) = self.try_overloaded_deref(expr.span, oprnd_t, needs) {
324 let method = self.register_infer_ok_obligations(ok);
325 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].kind {
326 let mutbl = match mutbl {
327 hir::Mutability::Not => AutoBorrowMutability::Not,
328 hir::Mutability::Mut => AutoBorrowMutability::Mut {
329 // (It shouldn't actually matter for unary ops whether
330 // we enable two-phase borrows or not, since a unary
331 // op has no additional operands.)
332 allow_two_phase_borrow: AllowTwoPhase::No,
335 self.apply_adjustments(
338 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
339 target: method.sig.inputs()[0],
343 oprnd_t = self.make_overloaded_place_return_type(method).ty;
344 self.write_method_call(expr.hir_id, method);
346 let mut err = type_error_struct!(
351 "type `{}` cannot be dereferenced",
354 let sp = tcx.sess.source_map().start_point(expr.span);
356 tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
358 tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp, None);
361 oprnd_t = tcx.types.err;
364 hir::UnOp::UnNot => {
365 let result = self.check_user_unop(expr, oprnd_t, unop);
366 // If it's builtin, we can reuse the type, this helps inference.
367 if !(oprnd_t.is_integral() || oprnd_t.kind == ty::Bool) {
371 hir::UnOp::UnNeg => {
372 let result = self.check_user_unop(expr, oprnd_t, unop);
373 // If it's builtin, we can reuse the type, this helps inference.
374 if !oprnd_t.is_numeric() {
383 fn check_expr_addr_of(
385 kind: hir::BorrowKind,
386 mutbl: hir::Mutability,
387 oprnd: &'tcx hir::Expr<'tcx>,
388 expected: Expectation<'tcx>,
389 expr: &'tcx hir::Expr<'tcx>,
391 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
393 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
394 if oprnd.is_syntactic_place_expr() {
395 // Places may legitimately have unsized types.
396 // For example, dereferences of a fat pointer and
397 // the last field of a struct can be unsized.
400 Expectation::rvalue_hint(self, ty)
406 let needs = Needs::maybe_mut_place(mutbl);
407 let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs);
409 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
411 _ if tm.ty.references_error() => self.tcx.types.err,
412 hir::BorrowKind::Raw => {
413 self.check_named_place_expr(oprnd);
416 hir::BorrowKind::Ref => {
417 // Note: at this point, we cannot say what the best lifetime
418 // is to use for resulting pointer. We want to use the
419 // shortest lifetime possible so as to avoid spurious borrowck
420 // errors. Moreover, the longest lifetime will depend on the
421 // precise details of the value whose address is being taken
422 // (and how long it is valid), which we don't know yet until
423 // type inference is complete.
425 // Therefore, here we simply generate a region variable. The
426 // region inferencer will then select a suitable value.
427 // Finally, borrowck will infer the value of the region again,
428 // this time with enough precision to check that the value
429 // whose address was taken can actually be made to live as long
430 // as it needs to live.
431 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
432 self.tcx.mk_ref(region, tm)
437 /// Does this expression refer to a place that either:
438 /// * Is based on a local or static.
439 /// * Contains a dereference
440 /// Note that the adjustments for the children of `expr` should already
441 /// have been resolved.
442 fn check_named_place_expr(&self, oprnd: &'tcx hir::Expr<'tcx>) {
443 let is_named = oprnd.is_place_expr(|base| {
444 // Allow raw borrows if there are any deref adjustments.
446 // const VAL: (i32,) = (0,);
447 // const REF: &(i32,) = &(0,);
449 // &raw const VAL.0; // ERROR
450 // &raw const REF.0; // OK, same as &raw const (*REF).0;
452 // This is maybe too permissive, since it allows
453 // `let u = &raw const Box::new((1,)).0`, which creates an
454 // immediately dangling raw pointer.
455 self.tables.borrow().adjustments().get(base.hir_id).map_or(false, |x| {
456 x.iter().any(|adj| if let Adjust::Deref(_) = adj.kind { true } else { false })
464 "cannot take address of a temporary"
466 .span_label(oprnd.span, "temporary value")
471 fn check_expr_path(&self, qpath: &hir::QPath<'_>, expr: &'tcx hir::Expr<'tcx>) -> Ty<'tcx> {
473 let (res, opt_ty, segs) = self.resolve_ty_and_res_ufcs(qpath, expr.hir_id, expr.span);
476 self.set_tainted_by_errors();
479 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
480 report_unexpected_variant_res(tcx, res, expr.span, qpath);
483 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
486 if let ty::FnDef(..) = ty.kind {
487 let fn_sig = ty.fn_sig(tcx);
488 if !tcx.features().unsized_locals {
489 // We want to remove some Sized bounds from std functions,
490 // but don't want to expose the removal to stable Rust.
491 // i.e., we don't want to allow
497 // to work in stable even if the Sized bound on `drop` is relaxed.
498 for i in 0..fn_sig.inputs().skip_binder().len() {
499 // We just want to check sizedness, so instead of introducing
500 // placeholder lifetimes with probing, we just replace higher lifetimes
503 .replace_bound_vars_with_fresh_vars(
505 infer::LateBoundRegionConversionTime::FnCall,
509 self.require_type_is_sized_deferred(
512 traits::SizedArgumentType,
516 // Here we want to prevent struct constructors from returning unsized types.
517 // There were two cases this happened: fn pointer coercion in stable
518 // and usual function call in presence of unsized_locals.
519 // Also, as we just want to check sizedness, instead of introducing
520 // placeholder lifetimes with probing, we just replace higher lifetimes
523 .replace_bound_vars_with_fresh_vars(
525 infer::LateBoundRegionConversionTime::FnCall,
529 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
532 // We always require that the type provided as the value for
533 // a type parameter outlives the moment of instantiation.
534 let substs = self.tables.borrow().node_substs(expr.hir_id);
535 self.add_wf_bounds(substs, expr);
542 destination: hir::Destination,
543 expr_opt: Option<&'tcx hir::Expr<'tcx>>,
544 expr: &'tcx hir::Expr<'tcx>,
547 if let Ok(target_id) = destination.target_id {
549 if let Some(ref e) = expr_opt {
550 // If this is a break with a value, we need to type-check
551 // the expression. Get an expected type from the loop context.
552 let opt_coerce_to = {
553 // We should release `enclosing_breakables` before the `check_expr_with_hint`
554 // below, so can't move this block of code to the enclosing scope and share
555 // `ctxt` with the second `encloding_breakables` borrow below.
556 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
557 match enclosing_breakables.opt_find_breakable(target_id) {
558 Some(ctxt) => ctxt.coerce.as_ref().map(|coerce| coerce.expected_ty()),
560 // Avoid ICE when `break` is inside a closure (#65383).
561 self.tcx.sess.delay_span_bug(
563 "break was outside loop, but no error was emitted",
565 return tcx.types.err;
570 // If the loop context is not a `loop { }`, then break with
571 // a value is illegal, and `opt_coerce_to` will be `None`.
572 // Just set expectation to error in that case.
573 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
575 // Recurse without `enclosing_breakables` borrowed.
576 e_ty = self.check_expr_with_hint(e, coerce_to);
577 cause = self.misc(e.span);
579 // Otherwise, this is a break *without* a value. That's
580 // always legal, and is equivalent to `break ()`.
581 e_ty = tcx.mk_unit();
582 cause = self.misc(expr.span);
585 // Now that we have type-checked `expr_opt`, borrow
586 // the `enclosing_loops` field and let's coerce the
587 // type of `expr_opt` into what is expected.
588 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
589 let ctxt = match enclosing_breakables.opt_find_breakable(target_id) {
592 // Avoid ICE when `break` is inside a closure (#65383).
593 self.tcx.sess.delay_span_bug(
595 "break was outside loop, but no error was emitted",
597 return tcx.types.err;
601 if let Some(ref mut coerce) = ctxt.coerce {
602 if let Some(ref e) = expr_opt {
603 coerce.coerce(self, &cause, e, e_ty);
605 assert!(e_ty.is_unit());
606 let ty = coerce.expected_ty();
607 coerce.coerce_forced_unit(
611 self.suggest_mismatched_types_on_tail(
612 &mut err, expr, ty, e_ty, cause.span, target_id,
614 if let Some(val) = ty_kind_suggestion(ty) {
615 let label = destination
617 .map(|l| format!(" {}", l.ident))
618 .unwrap_or_else(String::new);
621 "give it a value of the expected type",
622 format!("break{} {}", label, val),
623 Applicability::HasPlaceholders,
631 // If `ctxt.coerce` is `None`, we can just ignore
632 // the type of the expression. This is because
633 // either this was a break *without* a value, in
634 // which case it is always a legal type (`()`), or
635 // else an error would have been flagged by the
636 // `loops` pass for using break with an expression
637 // where you are not supposed to.
638 assert!(expr_opt.is_none() || self.tcx.sess.has_errors());
641 ctxt.may_break = true;
643 // the type of a `break` is always `!`, since it diverges
646 // Otherwise, we failed to find the enclosing loop;
647 // this can only happen if the `break` was not
648 // inside a loop at all, which is caught by the
649 // loop-checking pass.
652 .delay_span_bug(expr.span, "break was outside loop, but no error was emitted");
654 // We still need to assign a type to the inner expression to
655 // prevent the ICE in #43162.
656 if let Some(ref e) = expr_opt {
657 self.check_expr_with_hint(e, tcx.types.err);
659 // ... except when we try to 'break rust;'.
660 // ICE this expression in particular (see #43162).
661 if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.kind {
662 if path.segments.len() == 1 && path.segments[0].ident.name == sym::rust {
663 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() {
682 "return statement outside of function body",
685 } else if let Some(ref e) = expr_opt {
686 if self.ret_coercion_span.borrow().is_none() {
687 *self.ret_coercion_span.borrow_mut() = Some(e.span);
689 self.check_return_expr(e);
691 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
692 if self.ret_coercion_span.borrow().is_none() {
693 *self.ret_coercion_span.borrow_mut() = Some(expr.span);
695 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
696 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
697 coercion.coerce_forced_unit(
702 fn_decl.output.span(),
703 format!("expected `{}` because of this return type", fn_decl.output,),
709 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
715 pub(super) fn check_return_expr(&self, return_expr: &'tcx hir::Expr<'tcx>) {
716 let ret_coercion = self.ret_coercion.as_ref().unwrap_or_else(|| {
717 span_bug!(return_expr.span, "check_return_expr called outside fn body")
720 let ret_ty = ret_coercion.borrow().expected_ty();
721 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty.clone());
722 ret_coercion.borrow_mut().coerce(
724 &self.cause(return_expr.span, ObligationCauseCode::ReturnValue(return_expr.hir_id)),
730 fn is_destructuring_place_expr(&self, expr: &'tcx hir::Expr<'tcx>) -> bool {
732 ExprKind::Array(comps) | ExprKind::Tup(comps) => {
733 comps.iter().all(|e| self.is_destructuring_place_expr(e))
735 ExprKind::Struct(_path, fields, rest) => {
736 rest.as_ref().map(|e| self.is_destructuring_place_expr(e)).unwrap_or(true)
737 && fields.iter().all(|f| self.is_destructuring_place_expr(&f.expr))
739 _ => expr.is_syntactic_place_expr(),
743 pub(crate) fn check_lhs_assignable(
745 lhs: &'tcx hir::Expr<'tcx>,
746 err_code: &'static str,
749 if !lhs.is_syntactic_place_expr() {
750 let mut err = self.tcx.sess.struct_span_err_with_code(
752 "invalid left-hand side of assignment",
753 DiagnosticId::Error(err_code.into()),
755 err.span_label(lhs.span, "cannot assign to this expression");
756 if self.is_destructuring_place_expr(lhs) {
757 err.note("destructuring assignments are not currently supported");
758 err.note("for more information, see https://github.com/rust-lang/rfcs/issues/372");
764 /// Type check assignment expression `expr` of form `lhs = rhs`.
765 /// The expected type is `()` and is passsed to the function for the purposes of diagnostics.
766 fn check_expr_assign(
768 expr: &'tcx hir::Expr<'tcx>,
769 expected: Expectation<'tcx>,
770 lhs: &'tcx hir::Expr<'tcx>,
771 rhs: &'tcx hir::Expr<'tcx>,
774 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
775 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
777 let expected_ty = expected.coercion_target_type(self, expr.span);
778 if expected_ty == self.tcx.types.bool {
779 // The expected type is `bool` but this will result in `()` so we can reasonably
780 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
781 // The likely cause of this is `if foo = bar { .. }`.
782 let actual_ty = self.tcx.mk_unit();
783 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
784 let msg = "try comparing for equality";
785 let left = self.tcx.sess.source_map().span_to_snippet(lhs.span);
786 let right = self.tcx.sess.source_map().span_to_snippet(rhs.span);
787 if let (Ok(left), Ok(right)) = (left, right) {
788 let help = format!("{} == {}", left, right);
789 err.span_suggestion(expr.span, msg, help, Applicability::MaybeIncorrect);
795 self.check_lhs_assignable(lhs, "E0070", span);
798 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
800 if lhs_ty.references_error() || rhs_ty.references_error() {
809 body: &'tcx hir::Block<'tcx>,
810 source: hir::LoopSource,
811 expected: Expectation<'tcx>,
812 expr: &'tcx hir::Expr<'tcx>,
814 let coerce = match source {
815 // you can only use break with a value from a normal `loop { }`
816 hir::LoopSource::Loop => {
817 let coerce_to = expected.coercion_target_type(self, body.span);
818 Some(CoerceMany::new(coerce_to))
821 hir::LoopSource::While | hir::LoopSource::WhileLet | hir::LoopSource::ForLoop => None,
824 let ctxt = BreakableCtxt {
826 may_break: false, // Will get updated if/when we find a `break`.
829 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
830 self.check_block_no_value(&body);
834 // No way to know whether it's diverging because
835 // of a `break` or an outer `break` or `return`.
836 self.diverges.set(Diverges::Maybe);
839 // If we permit break with a value, then result type is
840 // the LUB of the breaks (possibly ! if none); else, it
841 // is nil. This makes sense because infinite loops
842 // (which would have type !) are only possible iff we
843 // permit break with a value [1].
844 if ctxt.coerce.is_none() && !ctxt.may_break {
846 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
848 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
851 /// Checks a method call.
852 fn check_method_call(
854 expr: &'tcx hir::Expr<'tcx>,
855 segment: &hir::PathSegment<'_>,
857 args: &'tcx [hir::Expr<'tcx>],
858 expected: Expectation<'tcx>,
862 let rcvr_t = self.check_expr_with_needs(&rcvr, needs);
863 // no need to check for bot/err -- callee does that
864 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
866 let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr) {
868 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
869 // trigger this codepath causing `structuraly_resolved_type` to emit an error.
871 self.write_method_call(expr.hir_id, method);
875 if segment.ident.name != kw::Invalid {
876 self.report_extended_method_error(segment, span, args, rcvr_t, error);
882 // Call the generic checker.
883 self.check_method_argument_types(
893 fn report_extended_method_error(
895 segment: &hir::PathSegment<'_>,
897 args: &'tcx [hir::Expr<'tcx>],
899 error: MethodError<'tcx>,
902 let try_alt_rcvr = |err: &mut DiagnosticBuilder<'_>, rcvr_t, lang_item| {
903 if let Some(new_rcvr_t) = self.tcx.mk_lang_item(rcvr_t, lang_item) {
904 if let Ok(pick) = self.lookup_probe(
909 probe::ProbeScope::AllTraits,
912 pick.item.ident.span,
913 &format!("the method is available for `{}` here", new_rcvr_t),
919 if let Some(mut err) = self.report_method_error(
923 SelfSource::MethodCall(rcvr),
927 if let ty::Adt(..) = rcvr_t.kind {
928 // Try alternative arbitrary self types that could fulfill this call.
929 // FIXME: probe for all types that *could* be arbitrary self-types, not
930 // just this whitelist.
931 try_alt_rcvr(&mut err, rcvr_t, lang_items::OwnedBoxLangItem);
932 try_alt_rcvr(&mut err, rcvr_t, lang_items::PinTypeLangItem);
933 try_alt_rcvr(&mut err, rcvr_t, lang_items::Arc);
934 try_alt_rcvr(&mut err, rcvr_t, lang_items::Rc);
942 e: &'tcx hir::Expr<'tcx>,
943 t: &'tcx hir::Ty<'tcx>,
944 expr: &'tcx hir::Expr<'tcx>,
946 // Find the type of `e`. Supply hints based on the type we are casting to,
948 let t_cast = self.to_ty_saving_user_provided_ty(t);
949 let t_cast = self.resolve_vars_if_possible(&t_cast);
950 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
951 let t_cast = self.resolve_vars_if_possible(&t_cast);
953 // Eagerly check for some obvious errors.
954 if t_expr.references_error() || t_cast.references_error() {
957 // Defer other checks until we're done type checking.
958 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
959 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
961 deferred_cast_checks.push(cast_check);
964 Err(ErrorReported) => self.tcx.types.err,
971 args: &'tcx [hir::Expr<'tcx>],
972 expected: Expectation<'tcx>,
973 expr: &'tcx hir::Expr<'tcx>,
975 let uty = expected.to_option(self).and_then(|uty| match uty.kind {
976 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
980 let element_ty = if !args.is_empty() {
981 let coerce_to = uty.unwrap_or_else(|| {
982 self.next_ty_var(TypeVariableOrigin {
983 kind: TypeVariableOriginKind::TypeInference,
987 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
988 assert_eq!(self.diverges.get(), Diverges::Maybe);
990 let e_ty = self.check_expr_with_hint(e, coerce_to);
991 let cause = self.misc(e.span);
992 coerce.coerce(self, &cause, e, e_ty);
994 coerce.complete(self)
996 self.next_ty_var(TypeVariableOrigin {
997 kind: TypeVariableOriginKind::TypeInference,
1001 self.tcx.mk_array(element_ty, args.len() as u64)
1004 fn check_expr_repeat(
1006 element: &'tcx hir::Expr<'tcx>,
1007 count: &'tcx hir::AnonConst,
1008 expected: Expectation<'tcx>,
1009 _expr: &'tcx hir::Expr<'tcx>,
1012 let count_def_id = tcx.hir().local_def_id(count.hir_id);
1013 let count = if self.const_param_def_id(count).is_some() {
1014 Ok(self.to_const(count, tcx.type_of(count_def_id)))
1016 tcx.const_eval_poly(count_def_id)
1019 let uty = match expected {
1020 ExpectHasType(uty) => match uty.kind {
1021 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
1027 let (element_ty, t) = match uty {
1029 self.check_expr_coercable_to_type(&element, uty);
1033 let ty = self.next_ty_var(TypeVariableOrigin {
1034 kind: TypeVariableOriginKind::MiscVariable,
1037 let element_ty = self.check_expr_has_type_or_error(&element, ty, |_| {});
1042 if element_ty.references_error() {
1044 } else if let Ok(count) = count {
1045 tcx.mk_ty(ty::Array(t, count))
1051 fn check_expr_tuple(
1053 elts: &'tcx [hir::Expr<'tcx>],
1054 expected: Expectation<'tcx>,
1055 expr: &'tcx hir::Expr<'tcx>,
1057 let flds = expected.only_has_type(self).and_then(|ty| {
1058 let ty = self.resolve_vars_with_obligations(ty);
1060 ty::Tuple(ref flds) => Some(&flds[..]),
1065 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
1066 let t = match flds {
1067 Some(ref fs) if i < fs.len() => {
1068 let ety = fs[i].expect_ty();
1069 self.check_expr_coercable_to_type(&e, ety);
1072 _ => self.check_expr_with_expectation(&e, NoExpectation),
1076 let tuple = self.tcx.mk_tup(elt_ts_iter);
1077 if tuple.references_error() {
1080 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
1085 fn check_expr_struct(
1087 expr: &hir::Expr<'_>,
1088 expected: Expectation<'tcx>,
1090 fields: &'tcx [hir::Field<'tcx>],
1091 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1093 // Find the relevant variant
1094 let (variant, adt_ty) = if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id)
1098 self.check_struct_fields_on_error(fields, base_expr);
1099 return self.tcx.types.err;
1102 let path_span = match *qpath {
1103 QPath::Resolved(_, ref path) => path.span,
1104 QPath::TypeRelative(ref qself, _) => qself.span,
1107 // Prohibit struct expressions when non-exhaustive flag is set.
1108 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
1109 if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
1114 "cannot create non-exhaustive {} using struct expression",
1120 let error_happened = self.check_expr_struct_fields(
1127 base_expr.is_none(),
1129 if let &Some(ref base_expr) = base_expr {
1130 // If check_expr_struct_fields hit an error, do not attempt to populate
1131 // the fields with the base_expr. This could cause us to hit errors later
1132 // when certain fields are assumed to exist that in fact do not.
1133 if !error_happened {
1134 self.check_expr_has_type_or_error(base_expr, adt_ty, |_| {});
1136 ty::Adt(adt, substs) if adt.is_struct() => {
1137 let fru_field_types = adt
1142 self.normalize_associated_types_in(
1144 &f.ty(self.tcx, substs),
1151 .fru_field_types_mut()
1152 .insert(expr.hir_id, fru_field_types);
1159 "functional record update syntax requires a struct"
1166 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
1170 fn check_expr_struct_fields(
1173 expected: Expectation<'tcx>,
1174 expr_id: hir::HirId,
1176 variant: &'tcx ty::VariantDef,
1177 ast_fields: &'tcx [hir::Field<'tcx>],
1178 check_completeness: bool,
1182 let adt_ty_hint = self
1183 .expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
1187 // re-link the regions that EIfEO can erase.
1188 self.demand_eqtype(span, adt_ty_hint, adt_ty);
1190 let (substs, adt_kind, kind_name) = match &adt_ty.kind {
1191 &ty::Adt(adt, substs) => (substs, adt.adt_kind(), adt.variant_descr()),
1192 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields"),
1195 let mut remaining_fields = variant
1199 .map(|(i, field)| (field.ident.modern(), (i, field)))
1200 .collect::<FxHashMap<_, _>>();
1202 let mut seen_fields = FxHashMap::default();
1204 let mut error_happened = false;
1206 // Type-check each field.
1207 for field in ast_fields {
1208 let ident = tcx.adjust_ident(field.ident, variant.def_id);
1209 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
1210 seen_fields.insert(ident, field.span);
1211 self.write_field_index(field.hir_id, i);
1213 // We don't look at stability attributes on
1214 // struct-like enums (yet...), but it's definitely not
1215 // a bug to have constructed one.
1216 if adt_kind != AdtKind::Enum {
1217 tcx.check_stability(v_field.did, Some(expr_id), field.span);
1220 self.field_ty(field.span, v_field, substs)
1222 error_happened = true;
1223 if let Some(prev_span) = seen_fields.get(&ident) {
1224 let mut err = struct_span_err!(
1228 "field `{}` specified more than once",
1232 err.span_label(field.ident.span, "used more than once");
1233 err.span_label(*prev_span, format!("first use of `{}`", ident));
1237 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name, span);
1243 // Make sure to give a type to the field even if there's
1244 // an error, so we can continue type-checking.
1245 self.check_expr_coercable_to_type(&field.expr, field_type);
1248 // Make sure the programmer specified correct number of fields.
1249 if kind_name == "union" {
1250 if ast_fields.len() != 1 {
1251 tcx.sess.span_err(span, "union expressions should have exactly one field");
1253 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
1254 let len = remaining_fields.len();
1256 let mut displayable_field_names =
1257 remaining_fields.keys().map(|ident| ident.as_str()).collect::<Vec<_>>();
1259 displayable_field_names.sort();
1261 let truncated_fields_error = if len <= 3 {
1264 format!(" and {} other field{}", (len - 3), if len - 3 == 1 { "" } else { "s" })
1267 let remaining_fields_names = displayable_field_names
1270 .map(|n| format!("`{}`", n))
1271 .collect::<Vec<_>>()
1278 "missing field{} {}{} in initializer of `{}`",
1279 pluralize!(remaining_fields.len()),
1280 remaining_fields_names,
1281 truncated_fields_error,
1286 format!("missing {}{}", remaining_fields_names, truncated_fields_error),
1293 fn check_struct_fields_on_error(
1295 fields: &'tcx [hir::Field<'tcx>],
1296 base_expr: &'tcx Option<&'tcx hir::Expr<'tcx>>,
1298 for field in fields {
1299 self.check_expr(&field.expr);
1301 if let Some(ref base) = *base_expr {
1302 self.check_expr(&base);
1306 fn report_unknown_field(
1309 variant: &'tcx ty::VariantDef,
1310 field: &hir::Field<'_>,
1311 skip_fields: &[hir::Field<'_>],
1315 if variant.recovered {
1318 let mut err = self.type_error_struct_with_diag(
1320 |actual| match ty.kind {
1321 ty::Adt(adt, ..) if adt.is_enum() => struct_span_err!(
1325 "{} `{}::{}` has no field named `{}`",
1331 _ => struct_span_err!(
1335 "{} `{}` has no field named `{}`",
1343 match variant.ctor_kind {
1345 err.span_label(variant.ident.span, format!("`{adt}` defined here", adt = ty));
1346 err.span_label(field.ident.span, "field does not exist");
1350 "`{adt}` is a tuple {kind_name}, \
1351 use the appropriate syntax: `{adt}(/* fields */)`",
1353 kind_name = kind_name
1358 // prevent all specified fields from being suggested
1359 let skip_fields = skip_fields.iter().map(|ref x| x.ident.name);
1360 if let Some(field_name) =
1361 Self::suggest_field_name(variant, &field.ident.as_str(), skip_fields.collect())
1363 err.span_suggestion(
1365 "a field with a similar name exists",
1366 field_name.to_string(),
1367 Applicability::MaybeIncorrect,
1371 ty::Adt(adt, ..) => {
1375 format!("`{}::{}` does not have this field", ty, variant.ident),
1380 format!("`{}` does not have this field", ty),
1383 let available_field_names = self.available_field_names(variant);
1384 if !available_field_names.is_empty() {
1386 "available fields are: {}",
1387 self.name_series_display(available_field_names)
1391 _ => bug!("non-ADT passed to report_unknown_field"),
1399 // Return an hint about the closest match in field names
1400 fn suggest_field_name(
1401 variant: &'tcx ty::VariantDef,
1404 ) -> Option<Symbol> {
1405 let names = variant.fields.iter().filter_map(|field| {
1406 // ignore already set fields and private fields from non-local crates
1407 if skip.iter().any(|&x| x == field.ident.name)
1408 || (!variant.def_id.is_local() && field.vis != Visibility::Public)
1412 Some(&field.ident.name)
1416 find_best_match_for_name(names, field, None)
1419 fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<ast::Name> {
1424 let def_scope = self
1426 .adjust_ident_and_get_scope(field.ident, variant.def_id, self.body_id)
1428 field.vis.is_accessible_from(def_scope, self.tcx)
1430 .map(|field| field.ident.name)
1434 fn name_series_display(&self, names: Vec<ast::Name>) -> String {
1435 // dynamic limit, to never omit just one field
1436 let limit = if names.len() == 6 { 6 } else { 5 };
1438 names.iter().take(limit).map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
1439 if names.len() > limit {
1440 display = format!("{} ... and {} others", display, names.len() - limit);
1445 // Check field access expressions
1448 expr: &'tcx hir::Expr<'tcx>,
1450 base: &'tcx hir::Expr<'tcx>,
1453 let expr_t = self.check_expr_with_needs(base, needs);
1454 let expr_t = self.structurally_resolved_type(base.span, expr_t);
1455 let mut private_candidate = None;
1456 let mut autoderef = self.autoderef(expr.span, expr_t);
1457 while let Some((base_t, _)) = autoderef.next() {
1459 ty::Adt(base_def, substs) if !base_def.is_enum() => {
1460 debug!("struct named {:?}", base_t);
1461 let (ident, def_scope) =
1462 self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
1463 let fields = &base_def.non_enum_variant().fields;
1464 if let Some(index) = fields.iter().position(|f| f.ident.modern() == ident) {
1465 let field = &fields[index];
1466 let field_ty = self.field_ty(expr.span, field, substs);
1467 // Save the index of all fields regardless of their visibility in case
1468 // of error recovery.
1469 self.write_field_index(expr.hir_id, index);
1470 if field.vis.is_accessible_from(def_scope, self.tcx) {
1471 let adjustments = autoderef.adjust_steps(self, needs);
1472 self.apply_adjustments(base, adjustments);
1473 autoderef.finalize(self);
1475 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span);
1478 private_candidate = Some((base_def.did, field_ty));
1481 ty::Tuple(ref tys) => {
1482 let fstr = field.as_str();
1483 if let Ok(index) = fstr.parse::<usize>() {
1484 if fstr == index.to_string() {
1485 if let Some(field_ty) = tys.get(index) {
1486 let adjustments = autoderef.adjust_steps(self, needs);
1487 self.apply_adjustments(base, adjustments);
1488 autoderef.finalize(self);
1490 self.write_field_index(expr.hir_id, index);
1491 return field_ty.expect_ty();
1499 autoderef.unambiguous_final_ty(self);
1501 if let Some((did, field_ty)) = private_candidate {
1502 self.ban_private_field_access(expr, expr_t, field, did);
1506 if field.name == kw::Invalid {
1507 } else if self.method_exists(field, expr_t, expr.hir_id, true) {
1508 self.ban_take_value_of_method(expr, expr_t, field);
1509 } else if !expr_t.is_primitive_ty() {
1510 self.ban_nonexisting_field(field, base, expr, expr_t);
1517 "`{}` is a primitive type and therefore doesn't have fields",
1523 self.tcx().types.err
1526 fn ban_nonexisting_field(
1529 base: &'tcx hir::Expr<'tcx>,
1530 expr: &'tcx hir::Expr<'tcx>,
1533 let mut err = self.no_such_field_err(field.span, field, expr_t);
1535 match expr_t.peel_refs().kind {
1536 ty::Array(_, len) => {
1537 self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
1540 self.suggest_first_deref_field(&mut err, expr, base, field);
1542 ty::Adt(def, _) if !def.is_enum() => {
1543 self.suggest_fields_on_recordish(&mut err, def, field);
1545 ty::Param(param_ty) => {
1546 self.point_at_param_definition(&mut err, param_ty);
1551 if field.name == kw::Await {
1552 // We know by construction that `<expr>.await` is either on Rust 2015
1553 // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
1554 err.note("to `.await` a `Future`, switch to Rust 2018");
1555 err.help("set `edition = \"2018\"` in `Cargo.toml`");
1556 err.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
1562 fn ban_private_field_access(
1564 expr: &hir::Expr<'_>,
1569 let struct_path = self.tcx().def_path_str(base_did);
1570 let kind_name = match self.tcx().def_kind(base_did) {
1571 Some(def_kind) => def_kind.descr(base_did),
1574 let mut err = struct_span_err!(
1578 "field `{}` of {} `{}` is private",
1583 // Also check if an accessible method exists, which is often what is meant.
1584 if self.method_exists(field, expr_t, expr.hir_id, false) && !self.expr_in_place(expr.hir_id)
1586 self.suggest_method_call(
1588 &format!("a method `{}` also exists, call it with parentheses", field),
1597 fn ban_take_value_of_method(&self, expr: &hir::Expr<'_>, expr_t: Ty<'tcx>, field: ast::Ident) {
1598 let mut err = type_error_struct!(
1603 "attempted to take value of method `{}` on type `{}`",
1608 if !self.expr_in_place(expr.hir_id) {
1609 self.suggest_method_call(
1611 "use parentheses to call the method",
1617 err.help("methods are immutable and cannot be assigned to");
1623 fn point_at_param_definition(&self, err: &mut DiagnosticBuilder<'_>, param: ty::ParamTy) {
1624 let generics = self.tcx.generics_of(self.body_id.owner_def_id());
1625 let generic_param = generics.type_param(¶m, self.tcx);
1626 if let ty::GenericParamDefKind::Type { synthetic: Some(..), .. } = generic_param.kind {
1629 let param_def_id = generic_param.def_id;
1630 let param_hir_id = match self.tcx.hir().as_local_hir_id(param_def_id) {
1634 let param_span = self.tcx.hir().span(param_hir_id);
1635 let param_name = self.tcx.hir().ty_param_name(param_hir_id);
1637 err.span_label(param_span, &format!("type parameter '{}' declared here", param_name));
1640 fn suggest_fields_on_recordish(
1642 err: &mut DiagnosticBuilder<'_>,
1643 def: &'tcx ty::AdtDef,
1646 if let Some(suggested_field_name) =
1647 Self::suggest_field_name(def.non_enum_variant(), &field.as_str(), vec![])
1649 err.span_suggestion(
1651 "a field with a similar name exists",
1652 suggested_field_name.to_string(),
1653 Applicability::MaybeIncorrect,
1656 err.span_label(field.span, "unknown field");
1657 let struct_variant_def = def.non_enum_variant();
1658 let field_names = self.available_field_names(struct_variant_def);
1659 if !field_names.is_empty() {
1661 "available fields are: {}",
1662 self.name_series_display(field_names),
1668 fn maybe_suggest_array_indexing(
1670 err: &mut DiagnosticBuilder<'_>,
1671 expr: &hir::Expr<'_>,
1672 base: &hir::Expr<'_>,
1674 len: &ty::Const<'tcx>,
1676 if let (Some(len), Ok(user_index)) =
1677 (len.try_eval_usize(self.tcx, self.param_env), field.as_str().parse::<u64>())
1683 .span_to_snippet(base.span)
1684 .unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
1685 let help = "instead of using tuple indexing, use array indexing";
1686 let suggestion = format!("{}[{}]", base, field);
1687 let applicability = if len < user_index {
1688 Applicability::MachineApplicable
1690 Applicability::MaybeIncorrect
1692 err.span_suggestion(expr.span, help, suggestion, applicability);
1696 fn suggest_first_deref_field(
1698 err: &mut DiagnosticBuilder<'_>,
1699 expr: &hir::Expr<'_>,
1700 base: &hir::Expr<'_>,
1707 .span_to_snippet(base.span)
1708 .unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
1709 let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
1710 let suggestion = format!("(*{}).{}", base, field);
1711 err.span_suggestion(expr.span, &msg, suggestion, Applicability::MaybeIncorrect);
1714 fn no_such_field_err<T: Display>(
1718 expr_t: &ty::TyS<'_>,
1719 ) -> DiagnosticBuilder<'_> {
1725 "no field `{}` on type `{}`",
1731 fn check_expr_index(
1733 base: &'tcx hir::Expr<'tcx>,
1734 idx: &'tcx hir::Expr<'tcx>,
1736 expr: &'tcx hir::Expr<'tcx>,
1738 let base_t = self.check_expr_with_needs(&base, needs);
1739 let idx_t = self.check_expr(&idx);
1741 if base_t.references_error() {
1743 } else if idx_t.references_error() {
1746 let base_t = self.structurally_resolved_type(base.span, base_t);
1747 match self.lookup_indexing(expr, base, base_t, idx_t, needs) {
1748 Some((index_ty, element_ty)) => {
1749 // two-phase not needed because index_ty is never mutable
1750 self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No);
1754 let mut err = type_error_struct!(
1759 "cannot index into a value of type `{}`",
1762 // Try to give some advice about indexing tuples.
1763 if let ty::Tuple(..) = base_t.kind {
1764 let mut needs_note = true;
1765 // If the index is an integer, we can show the actual
1766 // fixed expression:
1767 if let ExprKind::Lit(ref lit) = idx.kind {
1768 if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
1769 let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
1770 if let Ok(snip) = snip {
1771 err.span_suggestion(
1773 "to access tuple elements, use",
1774 format!("{}.{}", snip, i),
1775 Applicability::MachineApplicable,
1783 "to access tuple elements, use tuple indexing \
1784 syntax (e.g., `tuple.0`)",
1795 fn check_expr_yield(
1797 value: &'tcx hir::Expr<'tcx>,
1798 expr: &'tcx hir::Expr<'tcx>,
1799 src: &'tcx hir::YieldSource,
1801 match self.yield_ty {
1803 self.check_expr_coercable_to_type(&value, ty);
1805 // Given that this `yield` expression was generated as a result of lowering a `.await`,
1806 // we know that the yield type must be `()`; however, the context won't contain this
1807 // information. Hence, we check the source of the yield expression here and check its
1808 // value's type against `()` (this check should always hold).
1809 None if src == &hir::YieldSource::Await => {
1810 self.check_expr_coercable_to_type(&value, self.tcx.mk_unit());
1817 "yield expression outside of generator literal"
1826 pub(super) fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> {
1827 Some(match ty.kind {
1830 ty::Int(_) | ty::Uint(_) => "42",
1831 ty::Float(_) => "3.14159",
1832 ty::Error | ty::Never => return None,