2 use rustc_ast::util::parser::PREC_POSTFIX;
3 use rustc_data_structures::fx::FxHashMap;
4 use rustc_errors::MultiSpan;
5 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
7 use rustc_hir::def::CtorKind;
8 use rustc_hir::intravisit::Visitor;
9 use rustc_hir::lang_items::LangItem;
10 use rustc_hir::{is_range_literal, Node};
11 use rustc_infer::infer::InferOk;
12 use rustc_middle::lint::in_external_macro;
13 use rustc_middle::middle::stability::EvalResult;
14 use rustc_middle::ty::adjustment::AllowTwoPhase;
15 use rustc_middle::ty::error::{ExpectedFound, TypeError};
16 use rustc_middle::ty::fold::{BottomUpFolder, TypeFolder};
17 use rustc_middle::ty::print::{with_forced_trimmed_paths, with_no_trimmed_paths};
18 use rustc_middle::ty::relate::TypeRelation;
19 use rustc_middle::ty::{self, Article, AssocItem, Ty, TypeAndMut, TypeVisitable};
20 use rustc_span::symbol::{sym, Symbol};
21 use rustc_span::{BytePos, Span};
22 use rustc_trait_selection::infer::InferCtxtExt as _;
23 use rustc_trait_selection::traits::error_reporting::method_chain::CollectAllMismatches;
24 use rustc_trait_selection::traits::ObligationCause;
26 use super::method::probe;
31 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
32 pub fn emit_type_mismatch_suggestions(
35 expr: &hir::Expr<'tcx>,
38 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
39 error: Option<TypeError<'tcx>>,
41 if expr_ty == expected {
45 self.annotate_alternative_method_deref(err, expr, error);
47 // Use `||` to give these suggestions a precedence
48 let suggested = self.suggest_missing_parentheses(err, expr)
49 || self.suggest_remove_last_method_call(err, expr, expected)
50 || self.suggest_associated_const(err, expr, expected)
51 || self.suggest_deref_ref_or_into(err, expr, expected, expr_ty, expected_ty_expr)
52 || self.suggest_option_to_bool(err, expr, expr_ty, expected)
53 || self.suggest_compatible_variants(err, expr, expected, expr_ty)
54 || self.suggest_non_zero_new_unwrap(err, expr, expected, expr_ty)
55 || self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty)
56 || self.suggest_no_capture_closure(err, expected, expr_ty)
57 || self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty)
58 || self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected)
59 || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
60 || self.suggest_into(err, expr, expr_ty, expected)
61 || self.suggest_floating_point_literal(err, expr, expected);
63 self.point_at_expr_source_of_inferred_type(err, expr, expr_ty, expected);
67 pub fn emit_coerce_suggestions(
70 expr: &hir::Expr<'tcx>,
73 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
74 error: Option<TypeError<'tcx>>,
76 if expr_ty == expected {
80 self.annotate_expected_due_to_let_ty(err, expr, error);
81 self.emit_type_mismatch_suggestions(err, expr, expr_ty, expected, expected_ty_expr, error);
82 self.note_type_is_not_clone(err, expected, expr_ty, expr);
83 self.note_need_for_fn_pointer(err, expected, expr_ty);
84 self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
85 self.check_for_range_as_method_call(err, expr, expr_ty, expected);
88 /// Requires that the two types unify, and prints an error message if
90 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
91 if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) {
96 pub fn demand_suptype_diag(
101 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
102 self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
105 #[instrument(skip(self), level = "debug")]
106 pub fn demand_suptype_with_origin(
108 cause: &ObligationCause<'tcx>,
111 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
112 match self.at(cause, self.param_env).sup(expected, actual) {
113 Ok(InferOk { obligations, value: () }) => {
114 self.register_predicates(obligations);
117 Err(e) => Some(self.err_ctxt().report_mismatched_types(&cause, expected, actual, e)),
121 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
122 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
127 pub fn demand_eqtype_diag(
132 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
133 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
136 pub fn demand_eqtype_with_origin(
138 cause: &ObligationCause<'tcx>,
141 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
142 match self.at(cause, self.param_env).eq(expected, actual) {
143 Ok(InferOk { obligations, value: () }) => {
144 self.register_predicates(obligations);
147 Err(e) => Some(self.err_ctxt().report_mismatched_types(cause, expected, actual, e)),
151 pub fn demand_coerce(
153 expr: &hir::Expr<'tcx>,
154 checked_ty: Ty<'tcx>,
156 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
157 allow_two_phase: AllowTwoPhase,
160 self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase);
161 if let Some(mut err) = err {
167 /// Checks that the type of `expr` can be coerced to `expected`.
169 /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!`
170 /// will be permitted if the diverges flag is currently "always".
171 #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))]
172 pub fn demand_coerce_diag(
174 expr: &hir::Expr<'tcx>,
175 checked_ty: Ty<'tcx>,
177 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
178 allow_two_phase: AllowTwoPhase,
179 ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
180 let expected = self.resolve_vars_with_obligations(expected);
182 let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) {
183 Ok(ty) => return (ty, None),
187 self.set_tainted_by_errors(self.tcx.sess.delay_span_bug(
189 "`TypeError` when attempting coercion but no error emitted",
191 let expr = expr.peel_drop_temps();
192 let cause = self.misc(expr.span);
193 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
194 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e);
196 let is_insufficiently_polymorphic =
197 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
199 // FIXME(#73154): For now, we do leak check when coercing function
200 // pointers in typeck, instead of only during borrowck. This can lead
201 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
202 if !is_insufficiently_polymorphic {
203 self.emit_coerce_suggestions(
213 (expected, Some(err))
216 pub fn point_at_expr_source_of_inferred_type(
218 err: &mut Diagnostic,
219 expr: &hir::Expr<'_>,
223 let map = self.tcx.hir();
225 let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = expr.kind else { return false; };
226 let [hir::PathSegment { ident, args: None, .. }] = p.segments else { return false; };
227 let hir::def::Res::Local(hir_id) = p.res else { return false; };
228 let Some(hir::Node::Pat(pat)) = map.find(hir_id) else { return false; };
229 let Some(hir::Node::Local(hir::Local {
233 })) = map.find_parent(pat.hir_id) else { return false; };
234 let Some(ty) = self.node_ty_opt(init.hir_id) else { return false; };
235 if ty.is_closure() || init.span.overlaps(expr.span) || pat.span.from_expansion() {
239 // Locate all the usages of the relevant binding.
240 struct FindExprs<'hir> {
242 uses: Vec<&'hir hir::Expr<'hir>>,
244 impl<'v> Visitor<'v> for FindExprs<'v> {
245 fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) {
246 if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = ex.kind
247 && let hir::def::Res::Local(hir_id) = path.res
248 && hir_id == self.hir_id
252 hir::intravisit::walk_expr(self, ex);
256 let mut expr_finder = FindExprs { hir_id, uses: vec![] };
257 let id = map.get_parent_item(hir_id);
258 let hir_id: hir::HirId = id.into();
260 let Some(node) = map.find(hir_id) else { return false; };
261 let Some(body_id) = node.body_id() else { return false; };
262 let body = map.body(body_id);
263 expr_finder.visit_expr(body.value);
264 // Hack to make equality checks on types with inference variables and regions useful.
265 let mut eraser = BottomUpFolder {
267 lt_op: |_| self.tcx.lifetimes.re_erased,
269 ty_op: |t| match *t.kind() {
270 ty::Infer(ty::TyVar(vid)) => self.tcx.mk_ty_infer(ty::TyVar(self.root_var(vid))),
271 ty::Infer(ty::IntVar(_)) => {
272 self.tcx.mk_ty_infer(ty::IntVar(ty::IntVid { index: 0 }))
274 ty::Infer(ty::FloatVar(_)) => {
275 self.tcx.mk_ty_infer(ty::FloatVar(ty::FloatVid { index: 0 }))
280 let mut prev = eraser.fold_ty(ty);
281 let mut prev_span = None;
283 for binding in expr_finder.uses {
284 // In every expression where the binding is referenced, we will look at that
285 // expression's type and see if it is where the incorrect found type was fully
286 // "materialized" and point at it. We will also try to provide a suggestion there.
287 if let Some(hir::Node::Expr(expr)
288 | hir::Node::Stmt(hir::Stmt {
289 kind: hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr),
291 })) = &map.find_parent(binding.hir_id)
292 && let hir::ExprKind::MethodCall(segment, rcvr, args, _span) = expr.kind
293 && rcvr.hir_id == binding.hir_id
294 && let Some(def_id) = self.typeck_results.borrow().type_dependent_def_id(expr.hir_id)
296 // We special case methods, because they can influence inference through the
297 // call's arguments and we can provide a more explicit span.
298 let sig = self.tcx.fn_sig(def_id);
299 let def_self_ty = sig.input(0).skip_binder();
300 let rcvr_ty = self.node_ty(rcvr.hir_id);
301 // Get the evaluated type *after* calling the method call, so that the influence
302 // of the arguments can be reflected in the receiver type. The receiver
303 // expression has the type *before* theis analysis is done.
304 let ty = match self.lookup_probe(
308 probe::ProbeScope::TraitsInScope,
310 Ok(pick) => pick.self_ty,
313 // Remove one layer of references to account for `&mut self` and
314 // `&self`, so that we can compare it against the binding.
315 let (ty, def_self_ty) = match (ty.kind(), def_self_ty.kind()) {
316 (ty::Ref(_, ty, a), ty::Ref(_, self_ty, b)) if a == b => (*ty, *self_ty),
317 _ => (ty, def_self_ty),
319 let mut param_args = FxHashMap::default();
320 let mut param_expected = FxHashMap::default();
321 let mut param_found = FxHashMap::default();
322 if self.can_eq(self.param_env, ty, found).is_ok() {
323 // We only point at the first place where the found type was inferred.
324 for (i, param_ty) in sig.inputs().skip_binder().iter().skip(1).enumerate() {
325 if def_self_ty.contains(*param_ty) && let ty::Param(_) = param_ty.kind() {
326 // We found an argument that references a type parameter in `Self`,
327 // so we assume that this is the argument that caused the found
328 // type, which we know already because of `can_eq` above was first
329 // inferred in this method call.
331 let arg_ty = self.node_ty(arg.hir_id);
335 "this is of type `{arg_ty}`, which causes `{ident}` to be \
339 param_args.insert(param_ty, (arg, arg_ty));
344 // Here we find, for a type param `T`, the type that `T` is in the current
345 // method call *and* in the original expected type. That way, we can see if we
346 // can give any structured suggestion for the function argument.
347 let mut c = CollectAllMismatches {
349 param_env: self.param_env,
352 let _ = c.relate(def_self_ty, ty);
353 for error in c.errors {
354 if let TypeError::Sorts(error) = error {
355 param_found.insert(error.expected, error.found);
359 let _ = c.relate(def_self_ty, expected);
360 for error in c.errors {
361 if let TypeError::Sorts(error) = error {
362 param_expected.insert(error.expected, error.found);
365 for (param, (arg, arg_ty)) in param_args.iter() {
366 let Some(expected) = param_expected.get(param) else { continue; };
367 let Some(found) = param_found.get(param) else { continue; };
368 if self.can_eq(self.param_env, *arg_ty, *found).is_err() { continue; }
369 self.emit_coerce_suggestions(err, arg, *found, *expected, None, None);
372 let ty = eraser.fold_ty(ty);
373 if ty.references_error() {
377 && param_args.is_empty()
378 && self.can_eq(self.param_env, ty, found).is_ok()
380 // We only point at the first place where the found type was inferred.
383 with_forced_trimmed_paths!(format!(
384 "here the type of `{ident}` is inferred to be `{ty}`",
388 } else if !param_args.is_empty() {
393 let ty = eraser.fold_ty(self.node_ty(binding.hir_id));
394 if ty.references_error() {
398 && let Some(span) = prev_span
399 && self.can_eq(self.param_env, ty, found).is_ok()
401 // We only point at the first place where the found type was inferred.
402 // We use the *previous* span because if the type is known *here* it means
403 // it was *evaluated earlier*. We don't do this for method calls because we
404 // evaluate the method's self type eagerly, but not in any other case.
407 with_forced_trimmed_paths!(format!(
408 "here the type of `{ident}` is inferred to be `{ty}`",
415 if binding.hir_id == expr.hir_id {
416 // Do not look at expressions that come after the expression we were originally
417 // evaluating and had a type error.
420 prev_span = Some(binding.span);
425 fn annotate_expected_due_to_let_ty(
427 err: &mut Diagnostic,
428 expr: &hir::Expr<'_>,
429 error: Option<TypeError<'tcx>>,
431 let parent = self.tcx.hir().parent_id(expr.hir_id);
432 match (self.tcx.hir().find(parent), error) {
433 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
434 if init.hir_id == expr.hir_id =>
436 // Point at `let` assignment type.
437 err.span_label(ty.span, "expected due to this");
440 Some(hir::Node::Expr(hir::Expr {
441 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
443 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
444 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
445 // We ignore closures explicitly because we already point at them elsewhere.
446 // Point at the assigned-to binding.
447 let mut primary_span = lhs.span;
448 let mut secondary_span = lhs.span;
449 let mut post_message = "";
451 hir::ExprKind::Path(hir::QPath::Resolved(
456 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
462 if let Some(hir::Node::Item(hir::Item {
464 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
466 })) = self.tcx.hir().get_if_local(*def_id)
468 primary_span = ty.span;
469 secondary_span = ident.span;
470 post_message = " type";
473 hir::ExprKind::Path(hir::QPath::Resolved(
475 hir::Path { res: hir::def::Res::Local(hir_id), .. },
477 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
478 primary_span = pat.span;
479 secondary_span = pat.span;
480 match self.tcx.hir().find_parent(pat.hir_id) {
481 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
482 primary_span = ty.span;
483 post_message = " type";
485 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
486 primary_span = init.span;
487 post_message = " value";
489 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
490 primary_span = *ty_span;
491 post_message = " parameter type";
500 if primary_span != secondary_span
505 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
507 // We are pointing at the binding's type or initializer value, but it's pattern
508 // is in a different line, so we point at both.
509 err.span_label(secondary_span, "expected due to the type of this binding");
510 err.span_label(primary_span, &format!("expected due to this{post_message}"));
511 } else if post_message == "" {
512 // We are pointing at either the assignment lhs or the binding def pattern.
513 err.span_label(primary_span, "expected due to the type of this binding");
515 // We are pointing at the binding's type or initializer value.
516 err.span_label(primary_span, &format!("expected due to this{post_message}"));
519 if !lhs.is_syntactic_place_expr() {
520 // We already emitted E0070 "invalid left-hand side of assignment", so we
522 err.downgrade_to_delayed_bug();
526 Some(hir::Node::Expr(hir::Expr {
527 kind: hir::ExprKind::Binary(_, lhs, rhs), ..
529 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
530 ) if rhs.hir_id == expr.hir_id
531 && self.typeck_results.borrow().expr_ty_adjusted_opt(lhs) == Some(expected) =>
533 err.span_label(lhs.span, &format!("expected because this is `{expected}`"));
539 fn annotate_alternative_method_deref(
541 err: &mut Diagnostic,
542 expr: &hir::Expr<'_>,
543 error: Option<TypeError<'tcx>>,
545 let parent = self.tcx.hir().parent_id(expr.hir_id);
546 let Some(TypeError::Sorts(ExpectedFound { expected, .. })) = error else {return;};
547 let Some(hir::Node::Expr(hir::Expr {
548 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
549 })) = self.tcx.hir().find(parent) else {return; };
550 if rhs.hir_id != expr.hir_id || expected.is_closure() {
553 let hir::ExprKind::Unary(hir::UnOp::Deref, deref) = lhs.kind else { return; };
554 let hir::ExprKind::MethodCall(path, base, args, _) = deref.kind else { return; };
555 let Some(self_ty) = self.typeck_results.borrow().expr_ty_adjusted_opt(base) else { return; };
559 probe::Mode::MethodCall,
561 probe::IsSuggestion(true),
564 probe::ProbeScope::TraitsInScope,
568 let in_scope_methods = self.probe_for_name_many(
569 probe::Mode::MethodCall,
571 probe::IsSuggestion(true),
574 probe::ProbeScope::TraitsInScope,
576 let other_methods_in_scope: Vec<_> =
577 in_scope_methods.iter().filter(|c| c.item.def_id != pick.item.def_id).collect();
579 let all_methods = self.probe_for_name_many(
580 probe::Mode::MethodCall,
582 probe::IsSuggestion(true),
585 probe::ProbeScope::AllTraits,
587 let suggestions: Vec<_> = all_methods
589 .filter(|c| c.item.def_id != pick.item.def_id)
592 let substs = ty::InternalSubsts::for_item(self.tcx, m.def_id, |param, _| {
593 self.var_for_def(deref.span, param)
597 deref.span.until(base.span),
600 with_no_trimmed_paths!(
601 self.tcx.def_path_str_with_substs(m.def_id, substs,)
603 match self.tcx.fn_sig(m.def_id).input(0).skip_binder().kind() {
604 ty::Ref(_, _, hir::Mutability::Mut) => "&mut ",
605 ty::Ref(_, _, _) => "&",
611 [] => (base.span.shrink_to_hi().with_hi(deref.span.hi()), ")".to_string()),
612 [first, ..] => (base.span.between(first.span), ", ".to_string()),
617 if suggestions.is_empty() {
620 let mut path_span: MultiSpan = path.ident.span.into();
621 path_span.push_span_label(
623 with_no_trimmed_paths!(format!(
625 self.tcx.def_path_str(pick.item.def_id),
628 let container_id = pick.item.container_id(self.tcx);
629 let container = with_no_trimmed_paths!(self.tcx.def_path_str(container_id));
630 for def_id in pick.import_ids {
631 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
632 path_span.push_span_label(
633 self.tcx.hir().span(hir_id),
634 format!("`{container}` imported here"),
637 let tail = with_no_trimmed_paths!(match &other_methods_in_scope[..] {
639 [candidate] => format!(
640 "the method of the same name on {} `{}`",
641 match candidate.kind {
642 probe::CandidateKind::InherentImplCandidate(..) => "the inherent impl for",
645 self.tcx.def_path_str(candidate.item.container_id(self.tcx))
647 [.., last] if other_methods_in_scope.len() < 5 => {
649 "the methods of the same name on {} and `{}`",
650 other_methods_in_scope[..other_methods_in_scope.len() - 1]
654 self.tcx.def_path_str(c.item.container_id(self.tcx))
656 .collect::<Vec<String>>()
658 self.tcx.def_path_str(last.item.container_id(self.tcx))
662 "the methods of the same name on {} other traits",
663 other_methods_in_scope.len()
669 "the `{}` call is resolved to the method in `{container}`, shadowing {tail}",
673 if suggestions.len() > other_methods_in_scope.len() {
675 "additionally, there are {} other available methods that aren't in scope",
676 suggestions.len() - other_methods_in_scope.len()
679 err.multipart_suggestions(
681 "you might have meant to call {}; you can use the fully-qualified path to call {} \
683 if suggestions.len() == 1 {
686 "one of the other methods"
688 if suggestions.len() == 1 { "it" } else { "one of them" },
691 Applicability::MaybeIncorrect,
695 /// If the expected type is an enum (Issue #55250) with any variants whose
696 /// sole field is of the found type, suggest such variants. (Issue #42764)
697 fn suggest_compatible_variants(
699 err: &mut Diagnostic,
700 expr: &hir::Expr<'_>,
704 if let ty::Adt(expected_adt, substs) = expected.kind() {
705 if let hir::ExprKind::Field(base, ident) = expr.kind {
706 let base_ty = self.typeck_results.borrow().expr_ty(base);
707 if self.can_eq(self.param_env, base_ty, expected).is_ok()
708 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
710 err.span_suggestion_verbose(
711 expr.span.with_lo(base_span.hi()),
712 format!("consider removing the tuple struct field `{ident}`"),
714 Applicability::MaybeIncorrect,
720 // If the expression is of type () and it's the return expression of a block,
721 // we suggest adding a separate return expression instead.
722 // (To avoid things like suggesting `Ok(while .. { .. })`.)
723 if expr_ty.is_unit() {
724 let mut id = expr.hir_id;
727 // Unroll desugaring, to make sure this works for `for` loops etc.
729 parent = self.tcx.hir().parent_id(id);
730 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
731 if parent_span.find_ancestor_inside(expr.span).is_some() {
732 // The parent node is part of the same span, so is the result of the
733 // same expansion/desugaring and not the 'real' parent node.
741 if let Some(hir::Node::Block(&hir::Block {
742 span: block_span, expr: Some(e), ..
743 })) = self.tcx.hir().find(parent)
746 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
747 let return_suggestions = if self
749 .is_diagnostic_item(sym::Result, expected_adt.did())
752 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
753 vec!["None", "Some(())"]
757 if let Some(indent) =
758 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
760 // Add a semicolon, except after `}`.
762 match self.tcx.sess.source_map().span_to_snippet(span) {
763 Ok(s) if s.ends_with('}') => "",
766 err.span_suggestions(
768 "try adding an expression at the end of the block",
771 .map(|r| format!("{semicolon}\n{indent}{r}")),
772 Applicability::MaybeIncorrect,
781 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
785 variant.fields.len() == 1
787 .filter_map(|variant| {
788 let sole_field = &variant.fields[0];
790 let field_is_local = sole_field.did.is_local();
791 let field_is_accessible =
792 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
793 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
794 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
796 if !field_is_local && !field_is_accessible {
800 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
801 .then(|| " (its field is private, but it's local to this crate and its privacy can be changed)".to_string());
803 let sole_field_ty = sole_field.ty(self.tcx, substs);
804 if self.can_coerce(expr_ty, sole_field_ty) {
806 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
807 // FIXME #56861: DRYer prelude filtering
808 if let Some(path) = variant_path.strip_prefix("std::prelude::")
809 && let Some((_, path)) = path.split_once("::")
811 return Some((path.to_string(), variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy));
813 Some((variant_path, variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy))
820 let suggestions_for = |variant: &_, ctor_kind, field_name| {
821 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
822 Some(ident) => format!("{ident}: "),
823 None => String::new(),
826 let (open, close) = match ctor_kind {
827 Some(CtorKind::Fn) => ("(".to_owned(), ")"),
828 None => (format!(" {{ {field_name}: "), " }"),
830 // unit variants don't have fields
831 Some(CtorKind::Const) => unreachable!(),
834 // Suggest constructor as deep into the block tree as possible.
835 // This fixes https://github.com/rust-lang/rust/issues/101065,
836 // and also just helps make the most minimal suggestions.
838 while let hir::ExprKind::Block(block, _) = &expr.kind
839 && let Some(expr_) = &block.expr
845 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
846 (expr.span.shrink_to_hi(), close.to_owned()),
850 match &compatible_variants[..] {
851 [] => { /* No variants to format */ }
852 [(variant, ctor_kind, field_name, note)] => {
853 // Just a single matching variant.
854 err.multipart_suggestion_verbose(
856 "try wrapping the expression in `{variant}`{note}",
857 note = note.as_deref().unwrap_or("")
859 suggestions_for(&**variant, *ctor_kind, *field_name),
860 Applicability::MaybeIncorrect,
865 // More than one matching variant.
866 err.multipart_suggestions(
868 "try wrapping the expression in a variant of `{}`",
869 self.tcx.def_path_str(expected_adt.did())
871 compatible_variants.into_iter().map(
872 |(variant, ctor_kind, field_name, _)| {
873 suggestions_for(&variant, ctor_kind, field_name)
876 Applicability::MaybeIncorrect,
886 fn suggest_non_zero_new_unwrap(
888 err: &mut Diagnostic,
889 expr: &hir::Expr<'_>,
894 let (adt, unwrap) = match expected.kind() {
895 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
896 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
898 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
902 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
903 ty::Adt(adt, _) => (adt, ".unwrap()"),
908 (sym::NonZeroU8, tcx.types.u8),
909 (sym::NonZeroU16, tcx.types.u16),
910 (sym::NonZeroU32, tcx.types.u32),
911 (sym::NonZeroU64, tcx.types.u64),
912 (sym::NonZeroU128, tcx.types.u128),
913 (sym::NonZeroI8, tcx.types.i8),
914 (sym::NonZeroI16, tcx.types.i16),
915 (sym::NonZeroI32, tcx.types.i32),
916 (sym::NonZeroI64, tcx.types.i64),
917 (sym::NonZeroI128, tcx.types.i128),
920 let Some((s, _)) = map
922 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
923 else { return false; };
925 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
927 err.multipart_suggestion(
928 format!("consider calling `{s}::new`"),
930 (expr.span.shrink_to_lo(), format!("{path}::new(")),
931 (expr.span.shrink_to_hi(), format!("){unwrap}")),
933 Applicability::MaybeIncorrect,
939 pub fn get_conversion_methods(
943 checked_ty: Ty<'tcx>,
945 ) -> Vec<AssocItem> {
946 let methods = self.probe_for_return_type(
948 probe::Mode::MethodCall,
953 self.has_only_self_parameter(m)
956 // This special internal attribute is used to permit
957 // "identity-like" conversion methods to be suggested here.
959 // FIXME (#46459 and #46460): ideally
960 // `std::convert::Into::into` and `std::borrow:ToOwned` would
961 // also be `#[rustc_conversion_suggestion]`, if not for
962 // method-probing false-positives and -negatives (respectively).
964 // FIXME? Other potential candidate methods: `as_ref` and
966 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
973 /// This function checks whether the method is not static and does not accept other parameters than `self`.
974 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
976 ty::AssocKind::Fn => {
977 method.fn_has_self_parameter
978 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
984 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
986 /// Given the following code:
987 /// ```compile_fail,E0308
989 /// fn takes_ref(_: &Foo) {}
990 /// let ref opt = Some(Foo);
992 /// opt.map(|param| takes_ref(param));
994 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
996 /// It only checks for `Option` and `Result` and won't work with
997 /// ```ignore (illustrative)
998 /// opt.map(|param| { takes_ref(param) });
1000 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
1001 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
1005 let hir::def::Res::Local(local_id) = path.res else {
1009 let local_parent = self.tcx.hir().parent_id(local_id);
1010 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
1014 let param_parent = self.tcx.hir().parent_id(*param_hir_id);
1015 let Some(Node::Expr(hir::Expr {
1016 hir_id: expr_hir_id,
1017 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
1019 })) = self.tcx.hir().find(param_parent) else {
1023 let expr_parent = self.tcx.hir().parent_id(*expr_hir_id);
1024 let hir = self.tcx.hir().find(expr_parent);
1025 let closure_params_len = closure_fn_decl.inputs.len();
1027 Some(Node::Expr(hir::Expr {
1028 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
1032 ) = (hir, closure_params_len) else {
1036 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
1037 let name = method_path.ident.name;
1038 let is_as_ref_able = match self_ty.peel_refs().kind() {
1039 ty::Adt(def, _) => {
1040 (self.tcx.is_diagnostic_item(sym::Option, def.did())
1041 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
1042 && (name == sym::map || name == sym::and_then)
1046 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
1047 (true, Ok(src)) => {
1048 let suggestion = format!("as_ref().{}", src);
1049 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
1055 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
1057 expr: &hir::Expr<'_>,
1058 ) -> Option<Symbol> {
1059 let hir = self.tcx.hir();
1060 let local = match expr {
1063 hir::ExprKind::Path(hir::QPath::Resolved(
1066 res: hir::def::Res::Local(_),
1067 segments: [hir::PathSegment { ident, .. }],
1076 match hir.find_parent(expr.hir_id)? {
1077 Node::ExprField(field) => {
1078 if field.ident.name == local.name && field.is_shorthand {
1079 return Some(local.name);
1088 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
1089 pub(crate) fn maybe_get_block_expr(
1091 expr: &hir::Expr<'tcx>,
1092 ) -> Option<&'tcx hir::Expr<'tcx>> {
1094 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
1099 /// Returns whether the given expression is an `else if`.
1100 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
1101 if let hir::ExprKind::If(..) = expr.kind {
1102 let parent_id = self.tcx.hir().parent_id(expr.hir_id);
1103 if let Some(Node::Expr(hir::Expr {
1104 kind: hir::ExprKind::If(_, _, Some(else_expr)),
1106 })) = self.tcx.hir().find(parent_id)
1108 return else_expr.hir_id == expr.hir_id;
1114 /// This function is used to determine potential "simple" improvements or users' errors and
1115 /// provide them useful help. For example:
1117 /// ```compile_fail,E0308
1118 /// fn some_fn(s: &str) {}
1120 /// let x = "hey!".to_owned();
1121 /// some_fn(x); // error
1124 /// No need to find every potential function which could make a coercion to transform a
1125 /// `String` into a `&str` since a `&` would do the trick!
1127 /// In addition of this check, it also checks between references mutability state. If the
1128 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
1132 expr: &hir::Expr<'tcx>,
1133 checked_ty: Ty<'tcx>,
1141 bool, /* suggest `&` or `&mut` type annotation */
1143 let sess = self.sess();
1146 // If the span is from an external macro, there's no suggestion we can make.
1147 if in_external_macro(sess, sp) {
1151 let sm = sess.source_map();
1153 let replace_prefix = |s: &str, old: &str, new: &str| {
1154 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
1157 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
1158 let expr = expr.peel_drop_temps();
1160 match (&expr.kind, expected.kind(), checked_ty.kind()) {
1161 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
1162 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
1163 if let hir::ExprKind::Lit(_) = expr.kind
1164 && let Ok(src) = sm.span_to_snippet(sp)
1165 && replace_prefix(&src, "b\"", "\"").is_some()
1167 let pos = sp.lo() + BytePos(1);
1170 "consider removing the leading `b`".to_string(),
1172 Applicability::MachineApplicable,
1178 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
1179 if let hir::ExprKind::Lit(_) = expr.kind
1180 && let Ok(src) = sm.span_to_snippet(sp)
1181 && replace_prefix(&src, "\"", "b\"").is_some()
1185 "consider adding a leading `b`".to_string(),
1187 Applicability::MachineApplicable,
1195 (_, &ty::Ref(_, _, mutability), _) => {
1196 // Check if it can work when put into a ref. For example:
1199 // fn bar(x: &mut i32) {}
1202 // bar(&x); // error, expected &mut
1204 let ref_ty = match mutability {
1205 hir::Mutability::Mut => {
1206 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1208 hir::Mutability::Not => {
1209 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1212 if self.can_coerce(ref_ty, expected) {
1213 let mut sugg_sp = sp;
1214 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
1216 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
1218 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
1220 let ai = self.tcx.associated_item(did);
1221 ai.trait_container(self.tcx) == Some(clone_trait)
1224 && segment.ident.name == sym::clone
1226 // If this expression had a clone call when suggesting borrowing
1227 // we want to suggest removing it because it'd now be unnecessary.
1228 sugg_sp = receiver.span;
1231 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
1232 let needs_parens = match expr.kind {
1233 // parenthesize if needed (Issue #46756)
1234 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
1235 // parenthesize borrows of range literals (Issue #54505)
1236 _ if is_range_literal(expr) => true,
1240 if let Some(sugg) = self.can_use_as_ref(expr) {
1245 Applicability::MachineApplicable,
1251 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1252 Some(ident) => format!("{ident}: "),
1253 None => String::new(),
1256 if let Some(hir::Node::Expr(hir::Expr {
1257 kind: hir::ExprKind::Assign(..),
1259 })) = self.tcx.hir().find_parent(expr.hir_id)
1261 if mutability.is_mut() {
1262 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
1267 let sugg_expr = if needs_parens { format!("({src})") } else { src };
1270 format!("consider {}borrowing here", mutability.mutably_str()),
1271 format!("{prefix}{}{sugg_expr}", mutability.ref_prefix_str()),
1272 Applicability::MachineApplicable,
1280 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
1282 &ty::Ref(_, checked, _),
1283 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
1284 // We have `&T`, check if what was expected was `T`. If so,
1285 // we may want to suggest removing a `&`.
1286 if sm.is_imported(expr.span) {
1287 // Go through the spans from which this span was expanded,
1288 // and find the one that's pointing inside `sp`.
1290 // E.g. for `&format!("")`, where we want the span to the
1291 // `format!()` invocation instead of its expansion.
1292 if let Some(call_span) =
1293 iter::successors(Some(expr.span), |s| s.parent_callsite())
1294 .find(|&s| sp.contains(s))
1295 && sm.is_span_accessible(call_span)
1298 sp.with_hi(call_span.lo()),
1299 "consider removing the borrow".to_string(),
1301 Applicability::MachineApplicable,
1308 if sp.contains(expr.span)
1309 && sm.is_span_accessible(expr.span)
1312 sp.with_hi(expr.span.lo()),
1313 "consider removing the borrow".to_string(),
1315 Applicability::MachineApplicable,
1323 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
1324 &ty::Ref(_, ty_a, mutbl_a),
1326 if let Some(steps) = self.deref_steps(ty_a, ty_b)
1327 // Only suggest valid if dereferencing needed.
1329 // The pointer type implements `Copy` trait so the suggestion is always valid.
1330 && let Ok(src) = sm.span_to_snippet(sp)
1332 let derefs = "*".repeat(steps);
1333 let old_prefix = mutbl_a.ref_prefix_str();
1334 let new_prefix = mutbl_b.ref_prefix_str().to_owned() + &derefs;
1336 let suggestion = replace_prefix(&src, old_prefix, &new_prefix).map(|_| {
1337 // skip `&` or `&mut ` if both mutabilities are mutable
1338 let lo = sp.lo() + BytePos(min(old_prefix.len(), mutbl_b.ref_prefix_str().len()) as _);
1339 // skip `&` or `&mut `
1340 let hi = sp.lo() + BytePos(old_prefix.len() as _);
1341 let sp = sp.with_lo(lo).with_hi(hi);
1345 format!("{}{derefs}", if mutbl_a != mutbl_b { mutbl_b.prefix_str() } else { "" }),
1346 if mutbl_b <= mutbl_a { Applicability::MachineApplicable } else { Applicability::MaybeIncorrect }
1350 if let Some((span, src, applicability)) = suggestion {
1353 "consider dereferencing".to_string(),
1362 _ if sp == expr.span => {
1363 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
1364 let mut expr = expr.peel_blocks();
1365 let mut prefix_span = expr.span.shrink_to_lo();
1366 let mut remove = String::new();
1368 // Try peeling off any existing `&` and `&mut` to reach our target type
1370 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
1371 // If the expression has `&`, removing it would fix the error
1372 prefix_span = prefix_span.with_hi(inner.span.lo());
1374 remove.push_str(mutbl.ref_prefix_str());
1380 // If we've reached our target type with just removing `&`, then just print now.
1384 format!("consider removing the `{}`", remove.trim()),
1386 // Do not remove `&&` to get to bool, because it might be something like
1387 // { a } && b, which we have a separate fixup suggestion that is more
1388 // likely correct...
1389 if remove.trim() == "&&" && expected == self.tcx.types.bool {
1390 Applicability::MaybeIncorrect
1392 Applicability::MachineApplicable
1399 // For this suggestion to make sense, the type would need to be `Copy`,
1400 // or we have to be moving out of a `Box<T>`
1401 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1402 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1403 // `steps` layers of boxes, not just one, but this is easier and most likely.
1404 || (checked_ty.is_box() && steps == 1)
1406 let deref_kind = if checked_ty.is_box() {
1407 "unboxing the value"
1408 } else if checked_ty.is_region_ptr() {
1409 "dereferencing the borrow"
1411 "dereferencing the type"
1414 // Suggest removing `&` if we have removed any, otherwise suggest just
1415 // dereferencing the remaining number of steps.
1416 let message = if remove.is_empty() {
1417 format!("consider {deref_kind}")
1420 "consider removing the `{}` and {} instead",
1426 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1427 Some(ident) => format!("{ident}: "),
1428 None => String::new(),
1431 let (span, suggestion) = if self.is_else_if_block(expr) {
1432 // Don't suggest nonsense like `else *if`
1434 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1435 // prefix should be empty here..
1436 (expr.span.shrink_to_lo(), "*".to_string())
1438 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1445 Applicability::MachineApplicable,
1457 pub fn check_for_cast(
1459 err: &mut Diagnostic,
1460 expr: &hir::Expr<'_>,
1461 checked_ty: Ty<'tcx>,
1462 expected_ty: Ty<'tcx>,
1463 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1465 if self.tcx.sess.source_map().is_imported(expr.span) {
1466 // Ignore if span is from within a macro.
1470 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1474 // If casting this expression to a given numeric type would be appropriate in case of a type
1477 // We want to minimize the amount of casting operations that are suggested, as it can be a
1478 // lossy operation with potentially bad side effects, so we only suggest when encountering
1479 // an expression that indicates that the original type couldn't be directly changed.
1481 // For now, don't suggest casting with `as`.
1482 let can_cast = false;
1484 let mut sugg = vec![];
1486 if let Some(hir::Node::ExprField(field)) = self.tcx.hir().find_parent(expr.hir_id) {
1487 // `expr` is a literal field for a struct, only suggest if appropriate
1488 if field.is_shorthand {
1489 // This is a field literal
1490 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1492 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1497 if let hir::ExprKind::Call(path, args) = &expr.kind
1498 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1499 (&path.kind, args.len())
1500 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1501 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1502 (&base_ty.kind, path_segment.ident.name)
1504 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1518 if base_ty_path.segments.len() == 1 =>
1528 "you can convert {} `{}` to {} `{}`",
1529 checked_ty.kind().article(),
1531 expected_ty.kind().article(),
1534 let cast_msg = format!(
1535 "you can cast {} `{}` to {} `{}`",
1536 checked_ty.kind().article(),
1538 expected_ty.kind().article(),
1541 let lit_msg = format!(
1542 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1545 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1546 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1552 let mut cast_suggestion = sugg.clone();
1553 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1554 let mut into_suggestion = sugg.clone();
1555 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1556 let mut suffix_suggestion = sugg.clone();
1557 suffix_suggestion.push((
1559 (&expected_ty.kind(), &checked_ty.kind()),
1560 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1562 // Remove fractional part from literal, for example `42.0f32` into `42`
1563 let src = src.trim_end_matches(&checked_ty.to_string());
1564 let len = src.split('.').next().unwrap().len();
1565 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1567 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1568 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1570 if expr.precedence().order() < PREC_POSTFIX {
1572 format!("{expected_ty})")
1574 expected_ty.to_string()
1577 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1578 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1580 let is_negative_int =
1581 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1582 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1584 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1586 let suggest_fallible_into_or_lhs_from =
1587 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1588 // If we know the expression the expected type is derived from, we might be able
1589 // to suggest a widening conversion rather than a narrowing one (which may
1590 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1592 // can be given the suggestion "u32::from(x) > y" rather than
1593 // "x > y.try_into().unwrap()".
1594 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1598 .span_to_snippet(expr.span)
1600 .map(|src| (expr, src))
1602 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1603 (lhs_expr_and_src, exp_to_found_is_fallible)
1606 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1608 let suggestion = vec![
1609 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1610 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1614 let msg = format!("{msg} and panic if the converted value doesn't fit");
1615 let mut suggestion = sugg.clone();
1617 expr.span.shrink_to_hi(),
1618 format!("{close_paren}.try_into().unwrap()"),
1622 err.multipart_suggestion_verbose(
1625 Applicability::MachineApplicable,
1629 let suggest_to_change_suffix_or_into =
1630 |err: &mut Diagnostic,
1631 found_to_exp_is_fallible: bool,
1632 exp_to_found_is_fallible: bool| {
1634 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1640 let always_fallible = found_to_exp_is_fallible
1641 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1642 let msg = if literal_is_ty_suffixed(expr) {
1644 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1645 // We now know that converting either the lhs or rhs is fallible. Before we
1646 // suggest a fallible conversion, check if the value can never fit in the
1648 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1651 } else if in_const_context {
1652 // Do not recommend `into` or `try_into` in const contexts.
1654 } else if found_to_exp_is_fallible {
1655 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1659 let suggestion = if literal_is_ty_suffixed(expr) {
1660 suffix_suggestion.clone()
1662 into_suggestion.clone()
1664 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1667 match (&expected_ty.kind(), &checked_ty.kind()) {
1668 (ty::Int(exp), ty::Int(found)) => {
1669 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1671 (Some(exp), Some(found)) if exp < found => (true, false),
1672 (Some(exp), Some(found)) if exp > found => (false, true),
1673 (None, Some(8 | 16)) => (false, true),
1674 (Some(8 | 16), None) => (true, false),
1675 (None, _) | (_, None) => (true, true),
1676 _ => (false, false),
1678 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1681 (ty::Uint(exp), ty::Uint(found)) => {
1682 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1684 (Some(exp), Some(found)) if exp < found => (true, false),
1685 (Some(exp), Some(found)) if exp > found => (false, true),
1686 (None, Some(8 | 16)) => (false, true),
1687 (Some(8 | 16), None) => (true, false),
1688 (None, _) | (_, None) => (true, true),
1689 _ => (false, false),
1691 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1694 (&ty::Int(exp), &ty::Uint(found)) => {
1695 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1697 (Some(exp), Some(found)) if found < exp => (false, true),
1698 (None, Some(8)) => (false, true),
1701 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1704 (&ty::Uint(exp), &ty::Int(found)) => {
1705 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1707 (Some(exp), Some(found)) if found > exp => (true, false),
1708 (Some(8), None) => (true, false),
1711 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1714 (ty::Float(exp), ty::Float(found)) => {
1715 if found.bit_width() < exp.bit_width() {
1716 suggest_to_change_suffix_or_into(err, false, true);
1717 } else if literal_is_ty_suffixed(expr) {
1718 err.multipart_suggestion_verbose(
1721 Applicability::MachineApplicable,
1723 } else if can_cast {
1724 // Missing try_into implementation for `f64` to `f32`
1725 err.multipart_suggestion_verbose(
1726 &format!("{cast_msg}, producing the closest possible value"),
1728 Applicability::MaybeIncorrect, // lossy conversion
1733 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1734 if literal_is_ty_suffixed(expr) {
1735 err.multipart_suggestion_verbose(
1738 Applicability::MachineApplicable,
1740 } else if can_cast {
1741 // Missing try_into implementation for `{float}` to `{integer}`
1742 err.multipart_suggestion_verbose(
1743 &format!("{msg}, rounding the float towards zero"),
1745 Applicability::MaybeIncorrect, // lossy conversion
1750 (ty::Float(exp), ty::Uint(found)) => {
1751 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1752 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1753 err.multipart_suggestion_verbose(
1755 "{msg}, producing the floating point representation of the integer",
1758 Applicability::MachineApplicable,
1760 } else if literal_is_ty_suffixed(expr) {
1761 err.multipart_suggestion_verbose(
1764 Applicability::MachineApplicable,
1767 // Missing try_into implementation for `{integer}` to `{float}`
1768 err.multipart_suggestion_verbose(
1770 "{cast_msg}, producing the floating point representation of the integer, \
1771 rounded if necessary",
1774 Applicability::MaybeIncorrect, // lossy conversion
1779 (ty::Float(exp), ty::Int(found)) => {
1780 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1781 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1782 err.multipart_suggestion_verbose(
1784 "{}, producing the floating point representation of the integer",
1788 Applicability::MachineApplicable,
1790 } else if literal_is_ty_suffixed(expr) {
1791 err.multipart_suggestion_verbose(
1794 Applicability::MachineApplicable,
1797 // Missing try_into implementation for `{integer}` to `{float}`
1798 err.multipart_suggestion_verbose(
1800 "{}, producing the floating point representation of the integer, \
1801 rounded if necessary",
1805 Applicability::MaybeIncorrect, // lossy conversion
1811 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1812 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1815 err.multipart_suggestion_verbose(
1816 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1818 Applicability::MachineApplicable,
1826 /// Identify when the user has written `foo..bar()` instead of `foo.bar()`.
1827 pub fn check_for_range_as_method_call(
1829 err: &mut Diagnostic,
1830 expr: &hir::Expr<'_>,
1831 checked_ty: Ty<'tcx>,
1832 expected_ty: Ty<'tcx>,
1834 if !hir::is_range_literal(expr) {
1837 let hir::ExprKind::Struct(
1838 hir::QPath::LangItem(LangItem::Range, ..),
1841 ) = expr.kind else { return; };
1842 let parent = self.tcx.hir().parent_id(expr.hir_id);
1843 if let Some(hir::Node::ExprField(_)) = self.tcx.hir().find(parent) {
1844 // Ignore `Foo { field: a..Default::default() }`
1847 let mut expr = end.expr;
1848 while let hir::ExprKind::MethodCall(_, rcvr, ..) = expr.kind {
1849 // Getting to the root receiver and asserting it is a fn call let's us ignore cases in
1850 // `src/test/ui/methods/issues/issue-90315.stderr`.
1853 let hir::ExprKind::Call(method_name, _) = expr.kind else { return; };
1854 let ty::Adt(adt, _) = checked_ty.kind() else { return; };
1855 if self.tcx.lang_items().range_struct() != Some(adt.did()) {
1858 if let ty::Adt(adt, _) = expected_ty.kind()
1859 && self.tcx.lang_items().range_struct() == Some(adt.did())
1863 // Check if start has method named end.
1864 let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = method_name.kind else { return; };
1865 let [hir::PathSegment { ident, .. }] = p.segments else { return; };
1866 let self_ty = self.typeck_results.borrow().expr_ty(start.expr);
1867 let Ok(_pick) = self.probe_for_name(
1868 probe::Mode::MethodCall,
1870 probe::IsSuggestion(true),
1873 probe::ProbeScope::AllTraits,
1876 let mut span = start.expr.span.between(end.expr.span);
1877 if span.lo() + BytePos(2) == span.hi() {
1878 // There's no space between the start, the range op and the end, suggest removal which
1879 // will be more noticeable than the replacement of `..` with `.`.
1880 span = span.with_lo(span.lo() + BytePos(1));
1883 err.span_suggestion_verbose(
1885 "you likely meant to write a method call instead of a range",
1887 Applicability::MachineApplicable,