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);
86 self.check_for_binding_assigned_block_without_tail_expression(err, expr, expr_ty, expected);
89 /// Requires that the two types unify, and prints an error message if
91 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
92 if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) {
97 pub fn demand_suptype_diag(
102 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
103 self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
106 #[instrument(skip(self), level = "debug")]
107 pub fn demand_suptype_with_origin(
109 cause: &ObligationCause<'tcx>,
112 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
113 match self.at(cause, self.param_env).sup(expected, actual) {
114 Ok(InferOk { obligations, value: () }) => {
115 self.register_predicates(obligations);
118 Err(e) => Some(self.err_ctxt().report_mismatched_types(&cause, expected, actual, e)),
122 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
123 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
128 pub fn demand_eqtype_diag(
133 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
134 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
137 pub fn demand_eqtype_with_origin(
139 cause: &ObligationCause<'tcx>,
142 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
143 match self.at(cause, self.param_env).eq(expected, actual) {
144 Ok(InferOk { obligations, value: () }) => {
145 self.register_predicates(obligations);
148 Err(e) => Some(self.err_ctxt().report_mismatched_types(cause, expected, actual, e)),
152 pub fn demand_coerce(
154 expr: &hir::Expr<'tcx>,
155 checked_ty: Ty<'tcx>,
157 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
158 allow_two_phase: AllowTwoPhase,
161 self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase);
162 if let Some(mut err) = err {
168 /// Checks that the type of `expr` can be coerced to `expected`.
170 /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!`
171 /// will be permitted if the diverges flag is currently "always".
172 #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))]
173 pub fn demand_coerce_diag(
175 expr: &hir::Expr<'tcx>,
176 checked_ty: Ty<'tcx>,
178 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
179 allow_two_phase: AllowTwoPhase,
180 ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
181 let expected = self.resolve_vars_with_obligations(expected);
183 let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) {
184 Ok(ty) => return (ty, None),
188 self.set_tainted_by_errors(self.tcx.sess.delay_span_bug(
190 "`TypeError` when attempting coercion but no error emitted",
192 let expr = expr.peel_drop_temps();
193 let cause = self.misc(expr.span);
194 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
195 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e);
197 let is_insufficiently_polymorphic =
198 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
200 // FIXME(#73154): For now, we do leak check when coercing function
201 // pointers in typeck, instead of only during borrowck. This can lead
202 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
203 if !is_insufficiently_polymorphic {
204 self.emit_coerce_suggestions(
214 (expected, Some(err))
217 pub fn point_at_expr_source_of_inferred_type(
219 err: &mut Diagnostic,
220 expr: &hir::Expr<'_>,
224 let map = self.tcx.hir();
226 let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = expr.kind else { return false; };
227 let [hir::PathSegment { ident, args: None, .. }] = p.segments else { return false; };
228 let hir::def::Res::Local(hir_id) = p.res else { return false; };
229 let Some(hir::Node::Pat(pat)) = map.find(hir_id) else { return false; };
230 let Some(hir::Node::Local(hir::Local {
234 })) = map.find_parent(pat.hir_id) else { return false; };
235 let Some(ty) = self.node_ty_opt(init.hir_id) else { return false; };
236 if ty.is_closure() || init.span.overlaps(expr.span) || pat.span.from_expansion() {
240 // Locate all the usages of the relevant binding.
241 struct FindExprs<'hir> {
243 uses: Vec<&'hir hir::Expr<'hir>>,
245 impl<'v> Visitor<'v> for FindExprs<'v> {
246 fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) {
247 if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = ex.kind
248 && let hir::def::Res::Local(hir_id) = path.res
249 && hir_id == self.hir_id
253 hir::intravisit::walk_expr(self, ex);
257 let mut expr_finder = FindExprs { hir_id, uses: vec![] };
258 let id = map.get_parent_item(hir_id);
259 let hir_id: hir::HirId = id.into();
261 let Some(node) = map.find(hir_id) else { return false; };
262 let Some(body_id) = node.body_id() else { return false; };
263 let body = map.body(body_id);
264 expr_finder.visit_expr(body.value);
265 // Hack to make equality checks on types with inference variables and regions useful.
266 let mut eraser = BottomUpFolder {
268 lt_op: |_| self.tcx.lifetimes.re_erased,
270 ty_op: |t| match *t.kind() {
271 ty::Infer(ty::TyVar(vid)) => self.tcx.mk_ty_infer(ty::TyVar(self.root_var(vid))),
272 ty::Infer(ty::IntVar(_)) => {
273 self.tcx.mk_ty_infer(ty::IntVar(ty::IntVid { index: 0 }))
275 ty::Infer(ty::FloatVar(_)) => {
276 self.tcx.mk_ty_infer(ty::FloatVar(ty::FloatVid { index: 0 }))
281 let mut prev = eraser.fold_ty(ty);
282 let mut prev_span = None;
284 for binding in expr_finder.uses {
285 // In every expression where the binding is referenced, we will look at that
286 // expression's type and see if it is where the incorrect found type was fully
287 // "materialized" and point at it. We will also try to provide a suggestion there.
288 if let Some(hir::Node::Expr(expr)
289 | hir::Node::Stmt(hir::Stmt {
290 kind: hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr),
292 })) = &map.find_parent(binding.hir_id)
293 && let hir::ExprKind::MethodCall(segment, rcvr, args, _span) = expr.kind
294 && rcvr.hir_id == binding.hir_id
295 && let Some(def_id) = self.typeck_results.borrow().type_dependent_def_id(expr.hir_id)
297 // We special case methods, because they can influence inference through the
298 // call's arguments and we can provide a more explicit span.
299 let sig = self.tcx.fn_sig(def_id);
300 let def_self_ty = sig.input(0).skip_binder();
301 let rcvr_ty = self.node_ty(rcvr.hir_id);
302 // Get the evaluated type *after* calling the method call, so that the influence
303 // of the arguments can be reflected in the receiver type. The receiver
304 // expression has the type *before* theis analysis is done.
305 let ty = match self.lookup_probe(
309 probe::ProbeScope::TraitsInScope,
311 Ok(pick) => pick.self_ty,
314 // Remove one layer of references to account for `&mut self` and
315 // `&self`, so that we can compare it against the binding.
316 let (ty, def_self_ty) = match (ty.kind(), def_self_ty.kind()) {
317 (ty::Ref(_, ty, a), ty::Ref(_, self_ty, b)) if a == b => (*ty, *self_ty),
318 _ => (ty, def_self_ty),
320 let mut param_args = FxHashMap::default();
321 let mut param_expected = FxHashMap::default();
322 let mut param_found = FxHashMap::default();
323 if self.can_eq(self.param_env, ty, found).is_ok() {
324 // We only point at the first place where the found type was inferred.
325 for (i, param_ty) in sig.inputs().skip_binder().iter().skip(1).enumerate() {
326 if def_self_ty.contains(*param_ty) && let ty::Param(_) = param_ty.kind() {
327 // We found an argument that references a type parameter in `Self`,
328 // so we assume that this is the argument that caused the found
329 // type, which we know already because of `can_eq` above was first
330 // inferred in this method call.
332 let arg_ty = self.node_ty(arg.hir_id);
336 "this is of type `{arg_ty}`, which causes `{ident}` to be \
340 param_args.insert(param_ty, (arg, arg_ty));
345 // Here we find, for a type param `T`, the type that `T` is in the current
346 // method call *and* in the original expected type. That way, we can see if we
347 // can give any structured suggestion for the function argument.
348 let mut c = CollectAllMismatches {
350 param_env: self.param_env,
353 let _ = c.relate(def_self_ty, ty);
354 for error in c.errors {
355 if let TypeError::Sorts(error) = error {
356 param_found.insert(error.expected, error.found);
360 let _ = c.relate(def_self_ty, expected);
361 for error in c.errors {
362 if let TypeError::Sorts(error) = error {
363 param_expected.insert(error.expected, error.found);
366 for (param, (arg, arg_ty)) in param_args.iter() {
367 let Some(expected) = param_expected.get(param) else { continue; };
368 let Some(found) = param_found.get(param) else { continue; };
369 if self.can_eq(self.param_env, *arg_ty, *found).is_err() { continue; }
370 self.emit_coerce_suggestions(err, arg, *found, *expected, None, None);
373 let ty = eraser.fold_ty(ty);
374 if ty.references_error() {
378 && param_args.is_empty()
379 && self.can_eq(self.param_env, ty, found).is_ok()
381 // We only point at the first place where the found type was inferred.
384 with_forced_trimmed_paths!(format!(
385 "here the type of `{ident}` is inferred to be `{ty}`",
389 } else if !param_args.is_empty() {
394 let ty = eraser.fold_ty(self.node_ty(binding.hir_id));
395 if ty.references_error() {
399 && let Some(span) = prev_span
400 && self.can_eq(self.param_env, ty, found).is_ok()
402 // We only point at the first place where the found type was inferred.
403 // We use the *previous* span because if the type is known *here* it means
404 // it was *evaluated earlier*. We don't do this for method calls because we
405 // evaluate the method's self type eagerly, but not in any other case.
408 with_forced_trimmed_paths!(format!(
409 "here the type of `{ident}` is inferred to be `{ty}`",
416 if binding.hir_id == expr.hir_id {
417 // Do not look at expressions that come after the expression we were originally
418 // evaluating and had a type error.
421 prev_span = Some(binding.span);
426 fn annotate_expected_due_to_let_ty(
428 err: &mut Diagnostic,
429 expr: &hir::Expr<'_>,
430 error: Option<TypeError<'tcx>>,
432 let parent = self.tcx.hir().parent_id(expr.hir_id);
433 match (self.tcx.hir().find(parent), error) {
434 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
435 if init.hir_id == expr.hir_id =>
437 // Point at `let` assignment type.
438 err.span_label(ty.span, "expected due to this");
441 Some(hir::Node::Expr(hir::Expr {
442 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
444 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
445 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
446 // We ignore closures explicitly because we already point at them elsewhere.
447 // Point at the assigned-to binding.
448 let mut primary_span = lhs.span;
449 let mut secondary_span = lhs.span;
450 let mut post_message = "";
452 hir::ExprKind::Path(hir::QPath::Resolved(
457 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
463 if let Some(hir::Node::Item(hir::Item {
465 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
467 })) = self.tcx.hir().get_if_local(*def_id)
469 primary_span = ty.span;
470 secondary_span = ident.span;
471 post_message = " type";
474 hir::ExprKind::Path(hir::QPath::Resolved(
476 hir::Path { res: hir::def::Res::Local(hir_id), .. },
478 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
479 primary_span = pat.span;
480 secondary_span = pat.span;
481 match self.tcx.hir().find_parent(pat.hir_id) {
482 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
483 primary_span = ty.span;
484 post_message = " type";
486 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
487 primary_span = init.span;
488 post_message = " value";
490 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
491 primary_span = *ty_span;
492 post_message = " parameter type";
501 if primary_span != secondary_span
506 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
508 // We are pointing at the binding's type or initializer value, but it's pattern
509 // is in a different line, so we point at both.
510 err.span_label(secondary_span, "expected due to the type of this binding");
511 err.span_label(primary_span, &format!("expected due to this{post_message}"));
512 } else if post_message == "" {
513 // We are pointing at either the assignment lhs or the binding def pattern.
514 err.span_label(primary_span, "expected due to the type of this binding");
516 // We are pointing at the binding's type or initializer value.
517 err.span_label(primary_span, &format!("expected due to this{post_message}"));
520 if !lhs.is_syntactic_place_expr() {
521 // We already emitted E0070 "invalid left-hand side of assignment", so we
523 err.downgrade_to_delayed_bug();
527 Some(hir::Node::Expr(hir::Expr {
528 kind: hir::ExprKind::Binary(_, lhs, rhs), ..
530 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
531 ) if rhs.hir_id == expr.hir_id
532 && self.typeck_results.borrow().expr_ty_adjusted_opt(lhs) == Some(expected) =>
534 err.span_label(lhs.span, &format!("expected because this is `{expected}`"));
540 fn annotate_alternative_method_deref(
542 err: &mut Diagnostic,
543 expr: &hir::Expr<'_>,
544 error: Option<TypeError<'tcx>>,
546 let parent = self.tcx.hir().parent_id(expr.hir_id);
547 let Some(TypeError::Sorts(ExpectedFound { expected, .. })) = error else {return;};
548 let Some(hir::Node::Expr(hir::Expr {
549 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
550 })) = self.tcx.hir().find(parent) else {return; };
551 if rhs.hir_id != expr.hir_id || expected.is_closure() {
554 let hir::ExprKind::Unary(hir::UnOp::Deref, deref) = lhs.kind else { return; };
555 let hir::ExprKind::MethodCall(path, base, args, _) = deref.kind else { return; };
556 let Some(self_ty) = self.typeck_results.borrow().expr_ty_adjusted_opt(base) else { return; };
560 probe::Mode::MethodCall,
562 probe::IsSuggestion(true),
565 probe::ProbeScope::TraitsInScope,
569 let in_scope_methods = self.probe_for_name_many(
570 probe::Mode::MethodCall,
572 probe::IsSuggestion(true),
575 probe::ProbeScope::TraitsInScope,
577 let other_methods_in_scope: Vec<_> =
578 in_scope_methods.iter().filter(|c| c.item.def_id != pick.item.def_id).collect();
580 let all_methods = self.probe_for_name_many(
581 probe::Mode::MethodCall,
583 probe::IsSuggestion(true),
586 probe::ProbeScope::AllTraits,
588 let suggestions: Vec<_> = all_methods
590 .filter(|c| c.item.def_id != pick.item.def_id)
593 let substs = ty::InternalSubsts::for_item(self.tcx, m.def_id, |param, _| {
594 self.var_for_def(deref.span, param)
598 deref.span.until(base.span),
601 with_no_trimmed_paths!(
602 self.tcx.def_path_str_with_substs(m.def_id, substs,)
604 match self.tcx.fn_sig(m.def_id).input(0).skip_binder().kind() {
605 ty::Ref(_, _, hir::Mutability::Mut) => "&mut ",
606 ty::Ref(_, _, _) => "&",
612 [] => (base.span.shrink_to_hi().with_hi(deref.span.hi()), ")".to_string()),
613 [first, ..] => (base.span.between(first.span), ", ".to_string()),
618 if suggestions.is_empty() {
621 let mut path_span: MultiSpan = path.ident.span.into();
622 path_span.push_span_label(
624 with_no_trimmed_paths!(format!(
626 self.tcx.def_path_str(pick.item.def_id),
629 let container_id = pick.item.container_id(self.tcx);
630 let container = with_no_trimmed_paths!(self.tcx.def_path_str(container_id));
631 for def_id in pick.import_ids {
632 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
633 path_span.push_span_label(
634 self.tcx.hir().span(hir_id),
635 format!("`{container}` imported here"),
638 let tail = with_no_trimmed_paths!(match &other_methods_in_scope[..] {
640 [candidate] => format!(
641 "the method of the same name on {} `{}`",
642 match candidate.kind {
643 probe::CandidateKind::InherentImplCandidate(..) => "the inherent impl for",
646 self.tcx.def_path_str(candidate.item.container_id(self.tcx))
648 [.., last] if other_methods_in_scope.len() < 5 => {
650 "the methods of the same name on {} and `{}`",
651 other_methods_in_scope[..other_methods_in_scope.len() - 1]
655 self.tcx.def_path_str(c.item.container_id(self.tcx))
657 .collect::<Vec<String>>()
659 self.tcx.def_path_str(last.item.container_id(self.tcx))
663 "the methods of the same name on {} other traits",
664 other_methods_in_scope.len()
670 "the `{}` call is resolved to the method in `{container}`, shadowing {tail}",
674 if suggestions.len() > other_methods_in_scope.len() {
676 "additionally, there are {} other available methods that aren't in scope",
677 suggestions.len() - other_methods_in_scope.len()
680 err.multipart_suggestions(
682 "you might have meant to call {}; you can use the fully-qualified path to call {} \
684 if suggestions.len() == 1 {
687 "one of the other methods"
689 if suggestions.len() == 1 { "it" } else { "one of them" },
692 Applicability::MaybeIncorrect,
696 /// If the expected type is an enum (Issue #55250) with any variants whose
697 /// sole field is of the found type, suggest such variants. (Issue #42764)
698 fn suggest_compatible_variants(
700 err: &mut Diagnostic,
701 expr: &hir::Expr<'_>,
705 if let ty::Adt(expected_adt, substs) = expected.kind() {
706 if let hir::ExprKind::Field(base, ident) = expr.kind {
707 let base_ty = self.typeck_results.borrow().expr_ty(base);
708 if self.can_eq(self.param_env, base_ty, expected).is_ok()
709 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
711 err.span_suggestion_verbose(
712 expr.span.with_lo(base_span.hi()),
713 format!("consider removing the tuple struct field `{ident}`"),
715 Applicability::MaybeIncorrect,
721 // If the expression is of type () and it's the return expression of a block,
722 // we suggest adding a separate return expression instead.
723 // (To avoid things like suggesting `Ok(while .. { .. })`.)
724 if expr_ty.is_unit() {
725 let mut id = expr.hir_id;
728 // Unroll desugaring, to make sure this works for `for` loops etc.
730 parent = self.tcx.hir().parent_id(id);
731 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
732 if parent_span.find_ancestor_inside(expr.span).is_some() {
733 // The parent node is part of the same span, so is the result of the
734 // same expansion/desugaring and not the 'real' parent node.
742 if let Some(hir::Node::Block(&hir::Block {
743 span: block_span, expr: Some(e), ..
744 })) = self.tcx.hir().find(parent)
747 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
748 let return_suggestions = if self
750 .is_diagnostic_item(sym::Result, expected_adt.did())
753 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
754 vec!["None", "Some(())"]
758 if let Some(indent) =
759 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
761 // Add a semicolon, except after `}`.
763 match self.tcx.sess.source_map().span_to_snippet(span) {
764 Ok(s) if s.ends_with('}') => "",
767 err.span_suggestions(
769 "try adding an expression at the end of the block",
772 .map(|r| format!("{semicolon}\n{indent}{r}")),
773 Applicability::MaybeIncorrect,
782 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
786 variant.fields.len() == 1
788 .filter_map(|variant| {
789 let sole_field = &variant.fields[0];
791 let field_is_local = sole_field.did.is_local();
792 let field_is_accessible =
793 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
794 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
795 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
797 if !field_is_local && !field_is_accessible {
801 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
802 .then(|| " (its field is private, but it's local to this crate and its privacy can be changed)".to_string());
804 let sole_field_ty = sole_field.ty(self.tcx, substs);
805 if self.can_coerce(expr_ty, sole_field_ty) {
807 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
808 // FIXME #56861: DRYer prelude filtering
809 if let Some(path) = variant_path.strip_prefix("std::prelude::")
810 && let Some((_, path)) = path.split_once("::")
812 return Some((path.to_string(), variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy));
814 Some((variant_path, variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy))
821 let suggestions_for = |variant: &_, ctor_kind, field_name| {
822 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
823 Some(ident) => format!("{ident}: "),
824 None => String::new(),
827 let (open, close) = match ctor_kind {
828 Some(CtorKind::Fn) => ("(".to_owned(), ")"),
829 None => (format!(" {{ {field_name}: "), " }"),
831 // unit variants don't have fields
832 Some(CtorKind::Const) => unreachable!(),
835 // Suggest constructor as deep into the block tree as possible.
836 // This fixes https://github.com/rust-lang/rust/issues/101065,
837 // and also just helps make the most minimal suggestions.
839 while let hir::ExprKind::Block(block, _) = &expr.kind
840 && let Some(expr_) = &block.expr
846 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
847 (expr.span.shrink_to_hi(), close.to_owned()),
851 match &compatible_variants[..] {
852 [] => { /* No variants to format */ }
853 [(variant, ctor_kind, field_name, note)] => {
854 // Just a single matching variant.
855 err.multipart_suggestion_verbose(
857 "try wrapping the expression in `{variant}`{note}",
858 note = note.as_deref().unwrap_or("")
860 suggestions_for(&**variant, *ctor_kind, *field_name),
861 Applicability::MaybeIncorrect,
866 // More than one matching variant.
867 err.multipart_suggestions(
869 "try wrapping the expression in a variant of `{}`",
870 self.tcx.def_path_str(expected_adt.did())
872 compatible_variants.into_iter().map(
873 |(variant, ctor_kind, field_name, _)| {
874 suggestions_for(&variant, ctor_kind, field_name)
877 Applicability::MaybeIncorrect,
887 fn suggest_non_zero_new_unwrap(
889 err: &mut Diagnostic,
890 expr: &hir::Expr<'_>,
895 let (adt, unwrap) = match expected.kind() {
896 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
897 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
899 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
903 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
904 ty::Adt(adt, _) => (adt, ".unwrap()"),
909 (sym::NonZeroU8, tcx.types.u8),
910 (sym::NonZeroU16, tcx.types.u16),
911 (sym::NonZeroU32, tcx.types.u32),
912 (sym::NonZeroU64, tcx.types.u64),
913 (sym::NonZeroU128, tcx.types.u128),
914 (sym::NonZeroI8, tcx.types.i8),
915 (sym::NonZeroI16, tcx.types.i16),
916 (sym::NonZeroI32, tcx.types.i32),
917 (sym::NonZeroI64, tcx.types.i64),
918 (sym::NonZeroI128, tcx.types.i128),
921 let Some((s, _)) = map
923 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
924 else { return false; };
926 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
928 err.multipart_suggestion(
929 format!("consider calling `{s}::new`"),
931 (expr.span.shrink_to_lo(), format!("{path}::new(")),
932 (expr.span.shrink_to_hi(), format!("){unwrap}")),
934 Applicability::MaybeIncorrect,
940 pub fn get_conversion_methods(
944 checked_ty: Ty<'tcx>,
946 ) -> Vec<AssocItem> {
947 let methods = self.probe_for_return_type(
949 probe::Mode::MethodCall,
954 self.has_only_self_parameter(m)
957 // This special internal attribute is used to permit
958 // "identity-like" conversion methods to be suggested here.
960 // FIXME (#46459 and #46460): ideally
961 // `std::convert::Into::into` and `std::borrow:ToOwned` would
962 // also be `#[rustc_conversion_suggestion]`, if not for
963 // method-probing false-positives and -negatives (respectively).
965 // FIXME? Other potential candidate methods: `as_ref` and
967 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
974 /// This function checks whether the method is not static and does not accept other parameters than `self`.
975 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
977 ty::AssocKind::Fn => {
978 method.fn_has_self_parameter
979 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
985 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
987 /// Given the following code:
988 /// ```compile_fail,E0308
990 /// fn takes_ref(_: &Foo) {}
991 /// let ref opt = Some(Foo);
993 /// opt.map(|param| takes_ref(param));
995 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
997 /// It only checks for `Option` and `Result` and won't work with
998 /// ```ignore (illustrative)
999 /// opt.map(|param| { takes_ref(param) });
1001 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
1002 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
1006 let hir::def::Res::Local(local_id) = path.res else {
1010 let local_parent = self.tcx.hir().parent_id(local_id);
1011 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
1015 let param_parent = self.tcx.hir().parent_id(*param_hir_id);
1016 let Some(Node::Expr(hir::Expr {
1017 hir_id: expr_hir_id,
1018 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
1020 })) = self.tcx.hir().find(param_parent) else {
1024 let expr_parent = self.tcx.hir().parent_id(*expr_hir_id);
1025 let hir = self.tcx.hir().find(expr_parent);
1026 let closure_params_len = closure_fn_decl.inputs.len();
1028 Some(Node::Expr(hir::Expr {
1029 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
1033 ) = (hir, closure_params_len) else {
1037 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
1038 let name = method_path.ident.name;
1039 let is_as_ref_able = match self_ty.peel_refs().kind() {
1040 ty::Adt(def, _) => {
1041 (self.tcx.is_diagnostic_item(sym::Option, def.did())
1042 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
1043 && (name == sym::map || name == sym::and_then)
1047 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
1048 (true, Ok(src)) => {
1049 let suggestion = format!("as_ref().{}", src);
1050 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
1056 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
1058 expr: &hir::Expr<'_>,
1059 ) -> Option<Symbol> {
1060 let hir = self.tcx.hir();
1061 let local = match expr {
1064 hir::ExprKind::Path(hir::QPath::Resolved(
1067 res: hir::def::Res::Local(_),
1068 segments: [hir::PathSegment { ident, .. }],
1077 match hir.find_parent(expr.hir_id)? {
1078 Node::ExprField(field) => {
1079 if field.ident.name == local.name && field.is_shorthand {
1080 return Some(local.name);
1089 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
1090 pub(crate) fn maybe_get_block_expr(
1092 expr: &hir::Expr<'tcx>,
1093 ) -> Option<&'tcx hir::Expr<'tcx>> {
1095 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
1100 /// Returns whether the given expression is an `else if`.
1101 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
1102 if let hir::ExprKind::If(..) = expr.kind {
1103 let parent_id = self.tcx.hir().parent_id(expr.hir_id);
1104 if let Some(Node::Expr(hir::Expr {
1105 kind: hir::ExprKind::If(_, _, Some(else_expr)),
1107 })) = self.tcx.hir().find(parent_id)
1109 return else_expr.hir_id == expr.hir_id;
1115 /// This function is used to determine potential "simple" improvements or users' errors and
1116 /// provide them useful help. For example:
1118 /// ```compile_fail,E0308
1119 /// fn some_fn(s: &str) {}
1121 /// let x = "hey!".to_owned();
1122 /// some_fn(x); // error
1125 /// No need to find every potential function which could make a coercion to transform a
1126 /// `String` into a `&str` since a `&` would do the trick!
1128 /// In addition of this check, it also checks between references mutability state. If the
1129 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
1133 expr: &hir::Expr<'tcx>,
1134 checked_ty: Ty<'tcx>,
1142 bool, /* suggest `&` or `&mut` type annotation */
1144 let sess = self.sess();
1147 // If the span is from an external macro, there's no suggestion we can make.
1148 if in_external_macro(sess, sp) {
1152 let sm = sess.source_map();
1154 let replace_prefix = |s: &str, old: &str, new: &str| {
1155 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
1158 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
1159 let expr = expr.peel_drop_temps();
1161 match (&expr.kind, expected.kind(), checked_ty.kind()) {
1162 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
1163 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
1164 if let hir::ExprKind::Lit(_) = expr.kind
1165 && let Ok(src) = sm.span_to_snippet(sp)
1166 && replace_prefix(&src, "b\"", "\"").is_some()
1168 let pos = sp.lo() + BytePos(1);
1171 "consider removing the leading `b`".to_string(),
1173 Applicability::MachineApplicable,
1179 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
1180 if let hir::ExprKind::Lit(_) = expr.kind
1181 && let Ok(src) = sm.span_to_snippet(sp)
1182 && replace_prefix(&src, "\"", "b\"").is_some()
1186 "consider adding a leading `b`".to_string(),
1188 Applicability::MachineApplicable,
1196 (_, &ty::Ref(_, _, mutability), _) => {
1197 // Check if it can work when put into a ref. For example:
1200 // fn bar(x: &mut i32) {}
1203 // bar(&x); // error, expected &mut
1205 let ref_ty = match mutability {
1206 hir::Mutability::Mut => {
1207 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1209 hir::Mutability::Not => {
1210 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1213 if self.can_coerce(ref_ty, expected) {
1214 let mut sugg_sp = sp;
1215 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
1217 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
1219 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
1221 let ai = self.tcx.associated_item(did);
1222 ai.trait_container(self.tcx) == Some(clone_trait)
1225 && segment.ident.name == sym::clone
1227 // If this expression had a clone call when suggesting borrowing
1228 // we want to suggest removing it because it'd now be unnecessary.
1229 sugg_sp = receiver.span;
1232 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
1233 let needs_parens = match expr.kind {
1234 // parenthesize if needed (Issue #46756)
1235 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
1236 // parenthesize borrows of range literals (Issue #54505)
1237 _ if is_range_literal(expr) => true,
1241 if let Some(sugg) = self.can_use_as_ref(expr) {
1246 Applicability::MachineApplicable,
1252 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1253 Some(ident) => format!("{ident}: "),
1254 None => String::new(),
1257 if let Some(hir::Node::Expr(hir::Expr {
1258 kind: hir::ExprKind::Assign(..),
1260 })) = self.tcx.hir().find_parent(expr.hir_id)
1262 if mutability.is_mut() {
1263 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
1268 let sugg_expr = if needs_parens { format!("({src})") } else { src };
1271 format!("consider {}borrowing here", mutability.mutably_str()),
1272 format!("{prefix}{}{sugg_expr}", mutability.ref_prefix_str()),
1273 Applicability::MachineApplicable,
1281 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
1283 &ty::Ref(_, checked, _),
1284 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
1285 // We have `&T`, check if what was expected was `T`. If so,
1286 // we may want to suggest removing a `&`.
1287 if sm.is_imported(expr.span) {
1288 // Go through the spans from which this span was expanded,
1289 // and find the one that's pointing inside `sp`.
1291 // E.g. for `&format!("")`, where we want the span to the
1292 // `format!()` invocation instead of its expansion.
1293 if let Some(call_span) =
1294 iter::successors(Some(expr.span), |s| s.parent_callsite())
1295 .find(|&s| sp.contains(s))
1296 && sm.is_span_accessible(call_span)
1299 sp.with_hi(call_span.lo()),
1300 "consider removing the borrow".to_string(),
1302 Applicability::MachineApplicable,
1309 if sp.contains(expr.span)
1310 && sm.is_span_accessible(expr.span)
1313 sp.with_hi(expr.span.lo()),
1314 "consider removing the borrow".to_string(),
1316 Applicability::MachineApplicable,
1324 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
1325 &ty::Ref(_, ty_a, mutbl_a),
1327 if let Some(steps) = self.deref_steps(ty_a, ty_b)
1328 // Only suggest valid if dereferencing needed.
1330 // The pointer type implements `Copy` trait so the suggestion is always valid.
1331 && let Ok(src) = sm.span_to_snippet(sp)
1333 let derefs = "*".repeat(steps);
1334 let old_prefix = mutbl_a.ref_prefix_str();
1335 let new_prefix = mutbl_b.ref_prefix_str().to_owned() + &derefs;
1337 let suggestion = replace_prefix(&src, old_prefix, &new_prefix).map(|_| {
1338 // skip `&` or `&mut ` if both mutabilities are mutable
1339 let lo = sp.lo() + BytePos(min(old_prefix.len(), mutbl_b.ref_prefix_str().len()) as _);
1340 // skip `&` or `&mut `
1341 let hi = sp.lo() + BytePos(old_prefix.len() as _);
1342 let sp = sp.with_lo(lo).with_hi(hi);
1346 format!("{}{derefs}", if mutbl_a != mutbl_b { mutbl_b.prefix_str() } else { "" }),
1347 if mutbl_b <= mutbl_a { Applicability::MachineApplicable } else { Applicability::MaybeIncorrect }
1351 if let Some((span, src, applicability)) = suggestion {
1354 "consider dereferencing".to_string(),
1363 _ if sp == expr.span => {
1364 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
1365 let mut expr = expr.peel_blocks();
1366 let mut prefix_span = expr.span.shrink_to_lo();
1367 let mut remove = String::new();
1369 // Try peeling off any existing `&` and `&mut` to reach our target type
1371 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
1372 // If the expression has `&`, removing it would fix the error
1373 prefix_span = prefix_span.with_hi(inner.span.lo());
1375 remove.push_str(mutbl.ref_prefix_str());
1381 // If we've reached our target type with just removing `&`, then just print now.
1385 format!("consider removing the `{}`", remove.trim()),
1387 // Do not remove `&&` to get to bool, because it might be something like
1388 // { a } && b, which we have a separate fixup suggestion that is more
1389 // likely correct...
1390 if remove.trim() == "&&" && expected == self.tcx.types.bool {
1391 Applicability::MaybeIncorrect
1393 Applicability::MachineApplicable
1400 // For this suggestion to make sense, the type would need to be `Copy`,
1401 // or we have to be moving out of a `Box<T>`
1402 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1403 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1404 // `steps` layers of boxes, not just one, but this is easier and most likely.
1405 || (checked_ty.is_box() && steps == 1)
1407 let deref_kind = if checked_ty.is_box() {
1408 "unboxing the value"
1409 } else if checked_ty.is_region_ptr() {
1410 "dereferencing the borrow"
1412 "dereferencing the type"
1415 // Suggest removing `&` if we have removed any, otherwise suggest just
1416 // dereferencing the remaining number of steps.
1417 let message = if remove.is_empty() {
1418 format!("consider {deref_kind}")
1421 "consider removing the `{}` and {} instead",
1427 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1428 Some(ident) => format!("{ident}: "),
1429 None => String::new(),
1432 let (span, suggestion) = if self.is_else_if_block(expr) {
1433 // Don't suggest nonsense like `else *if`
1435 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1436 // prefix should be empty here..
1437 (expr.span.shrink_to_lo(), "*".to_string())
1439 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1446 Applicability::MachineApplicable,
1458 pub fn check_for_cast(
1460 err: &mut Diagnostic,
1461 expr: &hir::Expr<'_>,
1462 checked_ty: Ty<'tcx>,
1463 expected_ty: Ty<'tcx>,
1464 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1466 if self.tcx.sess.source_map().is_imported(expr.span) {
1467 // Ignore if span is from within a macro.
1471 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1475 // If casting this expression to a given numeric type would be appropriate in case of a type
1478 // We want to minimize the amount of casting operations that are suggested, as it can be a
1479 // lossy operation with potentially bad side effects, so we only suggest when encountering
1480 // an expression that indicates that the original type couldn't be directly changed.
1482 // For now, don't suggest casting with `as`.
1483 let can_cast = false;
1485 let mut sugg = vec![];
1487 if let Some(hir::Node::ExprField(field)) = self.tcx.hir().find_parent(expr.hir_id) {
1488 // `expr` is a literal field for a struct, only suggest if appropriate
1489 if field.is_shorthand {
1490 // This is a field literal
1491 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1493 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1498 if let hir::ExprKind::Call(path, args) = &expr.kind
1499 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1500 (&path.kind, args.len())
1501 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1502 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1503 (&base_ty.kind, path_segment.ident.name)
1505 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1519 if base_ty_path.segments.len() == 1 =>
1529 "you can convert {} `{}` to {} `{}`",
1530 checked_ty.kind().article(),
1532 expected_ty.kind().article(),
1535 let cast_msg = format!(
1536 "you can cast {} `{}` to {} `{}`",
1537 checked_ty.kind().article(),
1539 expected_ty.kind().article(),
1542 let lit_msg = format!(
1543 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1546 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1547 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1553 let mut cast_suggestion = sugg.clone();
1554 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1555 let mut into_suggestion = sugg.clone();
1556 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1557 let mut suffix_suggestion = sugg.clone();
1558 suffix_suggestion.push((
1560 (&expected_ty.kind(), &checked_ty.kind()),
1561 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1563 // Remove fractional part from literal, for example `42.0f32` into `42`
1564 let src = src.trim_end_matches(&checked_ty.to_string());
1565 let len = src.split('.').next().unwrap().len();
1566 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1568 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1569 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1571 if expr.precedence().order() < PREC_POSTFIX {
1573 format!("{expected_ty})")
1575 expected_ty.to_string()
1578 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1579 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1581 let is_negative_int =
1582 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1583 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1585 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1587 let suggest_fallible_into_or_lhs_from =
1588 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1589 // If we know the expression the expected type is derived from, we might be able
1590 // to suggest a widening conversion rather than a narrowing one (which may
1591 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1593 // can be given the suggestion "u32::from(x) > y" rather than
1594 // "x > y.try_into().unwrap()".
1595 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1599 .span_to_snippet(expr.span)
1601 .map(|src| (expr, src))
1603 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1604 (lhs_expr_and_src, exp_to_found_is_fallible)
1607 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1609 let suggestion = vec![
1610 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1611 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1615 let msg = format!("{msg} and panic if the converted value doesn't fit");
1616 let mut suggestion = sugg.clone();
1618 expr.span.shrink_to_hi(),
1619 format!("{close_paren}.try_into().unwrap()"),
1623 err.multipart_suggestion_verbose(
1626 Applicability::MachineApplicable,
1630 let suggest_to_change_suffix_or_into =
1631 |err: &mut Diagnostic,
1632 found_to_exp_is_fallible: bool,
1633 exp_to_found_is_fallible: bool| {
1635 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1641 let always_fallible = found_to_exp_is_fallible
1642 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1643 let msg = if literal_is_ty_suffixed(expr) {
1645 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1646 // We now know that converting either the lhs or rhs is fallible. Before we
1647 // suggest a fallible conversion, check if the value can never fit in the
1649 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1652 } else if in_const_context {
1653 // Do not recommend `into` or `try_into` in const contexts.
1655 } else if found_to_exp_is_fallible {
1656 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1660 let suggestion = if literal_is_ty_suffixed(expr) {
1661 suffix_suggestion.clone()
1663 into_suggestion.clone()
1665 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1668 match (&expected_ty.kind(), &checked_ty.kind()) {
1669 (ty::Int(exp), ty::Int(found)) => {
1670 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1672 (Some(exp), Some(found)) if exp < found => (true, false),
1673 (Some(exp), Some(found)) if exp > found => (false, true),
1674 (None, Some(8 | 16)) => (false, true),
1675 (Some(8 | 16), None) => (true, false),
1676 (None, _) | (_, None) => (true, true),
1677 _ => (false, false),
1679 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1682 (ty::Uint(exp), ty::Uint(found)) => {
1683 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1685 (Some(exp), Some(found)) if exp < found => (true, false),
1686 (Some(exp), Some(found)) if exp > found => (false, true),
1687 (None, Some(8 | 16)) => (false, true),
1688 (Some(8 | 16), None) => (true, false),
1689 (None, _) | (_, None) => (true, true),
1690 _ => (false, false),
1692 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1695 (&ty::Int(exp), &ty::Uint(found)) => {
1696 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1698 (Some(exp), Some(found)) if found < exp => (false, true),
1699 (None, Some(8)) => (false, true),
1702 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1705 (&ty::Uint(exp), &ty::Int(found)) => {
1706 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1708 (Some(exp), Some(found)) if found > exp => (true, false),
1709 (Some(8), None) => (true, false),
1712 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1715 (ty::Float(exp), ty::Float(found)) => {
1716 if found.bit_width() < exp.bit_width() {
1717 suggest_to_change_suffix_or_into(err, false, true);
1718 } else if literal_is_ty_suffixed(expr) {
1719 err.multipart_suggestion_verbose(
1722 Applicability::MachineApplicable,
1724 } else if can_cast {
1725 // Missing try_into implementation for `f64` to `f32`
1726 err.multipart_suggestion_verbose(
1727 &format!("{cast_msg}, producing the closest possible value"),
1729 Applicability::MaybeIncorrect, // lossy conversion
1734 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1735 if literal_is_ty_suffixed(expr) {
1736 err.multipart_suggestion_verbose(
1739 Applicability::MachineApplicable,
1741 } else if can_cast {
1742 // Missing try_into implementation for `{float}` to `{integer}`
1743 err.multipart_suggestion_verbose(
1744 &format!("{msg}, rounding the float towards zero"),
1746 Applicability::MaybeIncorrect, // lossy conversion
1751 (ty::Float(exp), ty::Uint(found)) => {
1752 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1753 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1754 err.multipart_suggestion_verbose(
1756 "{msg}, producing the floating point representation of the integer",
1759 Applicability::MachineApplicable,
1761 } else if literal_is_ty_suffixed(expr) {
1762 err.multipart_suggestion_verbose(
1765 Applicability::MachineApplicable,
1768 // Missing try_into implementation for `{integer}` to `{float}`
1769 err.multipart_suggestion_verbose(
1771 "{cast_msg}, producing the floating point representation of the integer, \
1772 rounded if necessary",
1775 Applicability::MaybeIncorrect, // lossy conversion
1780 (ty::Float(exp), ty::Int(found)) => {
1781 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1782 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1783 err.multipart_suggestion_verbose(
1785 "{}, producing the floating point representation of the integer",
1789 Applicability::MachineApplicable,
1791 } else if literal_is_ty_suffixed(expr) {
1792 err.multipart_suggestion_verbose(
1795 Applicability::MachineApplicable,
1798 // Missing try_into implementation for `{integer}` to `{float}`
1799 err.multipart_suggestion_verbose(
1801 "{}, producing the floating point representation of the integer, \
1802 rounded if necessary",
1806 Applicability::MaybeIncorrect, // lossy conversion
1812 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1813 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1816 err.multipart_suggestion_verbose(
1817 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1819 Applicability::MachineApplicable,
1827 /// Identify when the user has written `foo..bar()` instead of `foo.bar()`.
1828 pub fn check_for_range_as_method_call(
1830 err: &mut Diagnostic,
1831 expr: &hir::Expr<'_>,
1832 checked_ty: Ty<'tcx>,
1833 expected_ty: Ty<'tcx>,
1835 if !hir::is_range_literal(expr) {
1838 let hir::ExprKind::Struct(
1839 hir::QPath::LangItem(LangItem::Range, ..),
1842 ) = expr.kind else { return; };
1843 let parent = self.tcx.hir().parent_id(expr.hir_id);
1844 if let Some(hir::Node::ExprField(_)) = self.tcx.hir().find(parent) {
1845 // Ignore `Foo { field: a..Default::default() }`
1848 let mut expr = end.expr;
1849 while let hir::ExprKind::MethodCall(_, rcvr, ..) = expr.kind {
1850 // Getting to the root receiver and asserting it is a fn call let's us ignore cases in
1851 // `src/test/ui/methods/issues/issue-90315.stderr`.
1854 let hir::ExprKind::Call(method_name, _) = expr.kind else { return; };
1855 let ty::Adt(adt, _) = checked_ty.kind() else { return; };
1856 if self.tcx.lang_items().range_struct() != Some(adt.did()) {
1859 if let ty::Adt(adt, _) = expected_ty.kind()
1860 && self.tcx.lang_items().range_struct() == Some(adt.did())
1864 // Check if start has method named end.
1865 let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = method_name.kind else { return; };
1866 let [hir::PathSegment { ident, .. }] = p.segments else { return; };
1867 let self_ty = self.typeck_results.borrow().expr_ty(start.expr);
1868 let Ok(_pick) = self.probe_for_name(
1869 probe::Mode::MethodCall,
1871 probe::IsSuggestion(true),
1874 probe::ProbeScope::AllTraits,
1877 let mut span = start.expr.span.between(end.expr.span);
1878 if span.lo() + BytePos(2) == span.hi() {
1879 // There's no space between the start, the range op and the end, suggest removal which
1880 // will be more noticeable than the replacement of `..` with `.`.
1881 span = span.with_lo(span.lo() + BytePos(1));
1884 err.span_suggestion_verbose(
1886 "you likely meant to write a method call instead of a range",
1888 Applicability::MachineApplicable,
1892 /// Identify when the type error is because `()` is found in a binding that was assigned a
1893 /// block without a tail expression.
1894 fn check_for_binding_assigned_block_without_tail_expression(
1896 err: &mut Diagnostic,
1897 expr: &hir::Expr<'_>,
1898 checked_ty: Ty<'tcx>,
1899 expected_ty: Ty<'tcx>,
1901 if !checked_ty.is_unit() {
1904 let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = expr.kind else { return; };
1905 let hir::def::Res::Local(hir_id) = path.res else { return; };
1906 let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(hir_id) else {
1909 let Some(hir::Node::Local(hir::Local {
1913 })) = self.tcx.hir().find_parent(pat.hir_id) else { return; };
1914 let hir::ExprKind::Block(block, None) = init.kind else { return; };
1915 if block.expr.is_some() {
1918 let [.., stmt] = block.stmts else {
1919 err.span_label(block.span, "this empty block is missing a tail expression");
1922 let hir::StmtKind::Semi(tail_expr) = stmt.kind else { return; };
1923 let Some(ty) = self.node_ty_opt(tail_expr.hir_id) else { return; };
1924 if self.can_eq(self.param_env, expected_ty, ty).is_ok() {
1925 err.span_suggestion_short(
1926 stmt.span.with_lo(tail_expr.span.hi()),
1927 "remove this semicolon",
1929 Applicability::MachineApplicable,
1932 err.span_label(block.span, "this block is missing a tail expression");