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 parent = map.get_parent_node(pat.hir_id);
230 let Some(hir::Node::Local(hir::Local {
234 })) = map.find(parent) 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 let parent = map.get_parent_node(binding.hir_id);
289 if let Some(hir::Node::Expr(expr))
290 | Some(hir::Node::Stmt(hir::Stmt {
291 kind: hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr),
293 })) = &map.find(parent)
294 && let hir::ExprKind::MethodCall(segment, rcvr, args, _span) = expr.kind
295 && rcvr.hir_id == binding.hir_id
296 && let Some(def_id) = self.typeck_results.borrow().type_dependent_def_id(expr.hir_id)
298 // We special case methods, because they can influence inference through the
299 // call's arguments and we can provide a more explicit span.
300 let sig = self.tcx.fn_sig(def_id);
301 let def_self_ty = sig.input(0).skip_binder();
302 let rcvr_ty = self.node_ty(rcvr.hir_id);
303 // Get the evaluated type *after* calling the method call, so that the influence
304 // of the arguments can be reflected in the receiver type. The receiver
305 // expression has the type *before* theis analysis is done.
306 let ty = match self.lookup_probe(
310 probe::ProbeScope::TraitsInScope,
312 Ok(pick) => pick.self_ty,
315 // Remove one layer of references to account for `&mut self` and
316 // `&self`, so that we can compare it against the binding.
317 let (ty, def_self_ty) = match (ty.kind(), def_self_ty.kind()) {
318 (ty::Ref(_, ty, a), ty::Ref(_, self_ty, b)) if a == b => (*ty, *self_ty),
319 _ => (ty, def_self_ty),
321 let mut param_args = FxHashMap::default();
322 let mut param_expected = FxHashMap::default();
323 let mut param_found = FxHashMap::default();
324 if self.can_eq(self.param_env, ty, found).is_ok() {
325 // We only point at the first place where the found type was inferred.
326 for (i, param_ty) in sig.inputs().skip_binder().iter().skip(1).enumerate() {
327 if def_self_ty.contains(*param_ty) && let ty::Param(_) = param_ty.kind() {
328 // We found an argument that references a type parameter in `Self`,
329 // so we assume that this is the argument that caused the found
330 // type, which we know already because of `can_eq` above was first
331 // inferred in this method call.
333 let arg_ty = self.node_ty(arg.hir_id);
337 "this is of type `{arg_ty}`, which causes `{ident}` to be \
341 param_args.insert(param_ty, (arg, arg_ty));
346 // Here we find, for a type param `T`, the type that `T` is in the current
347 // method call *and* in the original expected type. That way, we can see if we
348 // can give any structured suggestion for the function argument.
349 let mut c = CollectAllMismatches {
351 param_env: self.param_env,
354 let _ = c.relate(def_self_ty, ty);
355 for error in c.errors {
356 if let TypeError::Sorts(error) = error {
357 param_found.insert(error.expected, error.found);
361 let _ = c.relate(def_self_ty, expected);
362 for error in c.errors {
363 if let TypeError::Sorts(error) = error {
364 param_expected.insert(error.expected, error.found);
367 for (param, (arg, arg_ty)) in param_args.iter() {
368 let Some(expected) = param_expected.get(param) else { continue; };
369 let Some(found) = param_found.get(param) else { continue; };
370 if self.can_eq(self.param_env, *arg_ty, *found).is_err() { continue; }
371 self.emit_coerce_suggestions(err, arg, *found, *expected, None, None);
374 let ty = eraser.fold_ty(ty);
375 if ty.references_error() {
379 && param_args.is_empty()
380 && self.can_eq(self.param_env, ty, found).is_ok()
382 // We only point at the first place where the found type was inferred.
385 with_forced_trimmed_paths!(format!(
386 "here the type of `{ident}` is inferred to be `{ty}`",
390 } else if !param_args.is_empty() {
395 let ty = eraser.fold_ty(self.node_ty(binding.hir_id));
396 if ty.references_error() {
400 && let Some(span) = prev_span
401 && self.can_eq(self.param_env, ty, found).is_ok()
403 // We only point at the first place where the found type was inferred.
404 // We use the *previous* span because if the type is known *here* it means
405 // it was *evaluated earlier*. We don't do this for method calls because we
406 // evaluate the method's self type eagerly, but not in any other case.
409 with_forced_trimmed_paths!(format!(
410 "here the type of `{ident}` is inferred to be `{ty}`",
417 if binding.hir_id == expr.hir_id {
418 // Do not look at expressions that come after the expression we were originally
419 // evaluating and had a type error.
422 prev_span = Some(binding.span);
427 fn annotate_expected_due_to_let_ty(
429 err: &mut Diagnostic,
430 expr: &hir::Expr<'_>,
431 error: Option<TypeError<'tcx>>,
433 let parent = self.tcx.hir().parent_id(expr.hir_id);
434 match (self.tcx.hir().find(parent), error) {
435 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
436 if init.hir_id == expr.hir_id =>
438 // Point at `let` assignment type.
439 err.span_label(ty.span, "expected due to this");
442 Some(hir::Node::Expr(hir::Expr {
443 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
445 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
446 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
447 // We ignore closures explicitly because we already point at them elsewhere.
448 // Point at the assigned-to binding.
449 let mut primary_span = lhs.span;
450 let mut secondary_span = lhs.span;
451 let mut post_message = "";
453 hir::ExprKind::Path(hir::QPath::Resolved(
458 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
464 if let Some(hir::Node::Item(hir::Item {
466 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
468 })) = self.tcx.hir().get_if_local(*def_id)
470 primary_span = ty.span;
471 secondary_span = ident.span;
472 post_message = " type";
475 hir::ExprKind::Path(hir::QPath::Resolved(
477 hir::Path { res: hir::def::Res::Local(hir_id), .. },
479 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
480 primary_span = pat.span;
481 secondary_span = pat.span;
482 match self.tcx.hir().find_parent(pat.hir_id) {
483 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
484 primary_span = ty.span;
485 post_message = " type";
487 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
488 primary_span = init.span;
489 post_message = " value";
491 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
492 primary_span = *ty_span;
493 post_message = " parameter type";
502 if primary_span != secondary_span
507 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
509 // We are pointing at the binding's type or initializer value, but it's pattern
510 // is in a different line, so we point at both.
511 err.span_label(secondary_span, "expected due to the type of this binding");
512 err.span_label(primary_span, &format!("expected due to this{post_message}"));
513 } else if post_message == "" {
514 // We are pointing at either the assignment lhs or the binding def pattern.
515 err.span_label(primary_span, "expected due to the type of this binding");
517 // We are pointing at the binding's type or initializer value.
518 err.span_label(primary_span, &format!("expected due to this{post_message}"));
521 if !lhs.is_syntactic_place_expr() {
522 // We already emitted E0070 "invalid left-hand side of assignment", so we
524 err.downgrade_to_delayed_bug();
528 Some(hir::Node::Expr(hir::Expr {
529 kind: hir::ExprKind::Binary(_, lhs, rhs), ..
531 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
532 ) if rhs.hir_id == expr.hir_id
533 && self.typeck_results.borrow().expr_ty_adjusted_opt(lhs) == Some(expected) =>
535 err.span_label(lhs.span, &format!("expected because this is `{expected}`"));
541 fn annotate_alternative_method_deref(
543 err: &mut Diagnostic,
544 expr: &hir::Expr<'_>,
545 error: Option<TypeError<'tcx>>,
547 let parent = self.tcx.hir().parent_id(expr.hir_id);
548 let Some(TypeError::Sorts(ExpectedFound { expected, .. })) = error else {return;};
549 let Some(hir::Node::Expr(hir::Expr {
550 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
551 })) = self.tcx.hir().find(parent) else {return; };
552 if rhs.hir_id != expr.hir_id || expected.is_closure() {
555 let hir::ExprKind::Unary(hir::UnOp::Deref, deref) = lhs.kind else { return; };
556 let hir::ExprKind::MethodCall(path, base, args, _) = deref.kind else { return; };
557 let Some(self_ty) = self.typeck_results.borrow().expr_ty_adjusted_opt(base) else { return; };
561 probe::Mode::MethodCall,
563 probe::IsSuggestion(true),
566 probe::ProbeScope::TraitsInScope,
570 let in_scope_methods = self.probe_for_name_many(
571 probe::Mode::MethodCall,
573 probe::IsSuggestion(true),
576 probe::ProbeScope::TraitsInScope,
578 let other_methods_in_scope: Vec<_> =
579 in_scope_methods.iter().filter(|c| c.item.def_id != pick.item.def_id).collect();
581 let all_methods = self.probe_for_name_many(
582 probe::Mode::MethodCall,
584 probe::IsSuggestion(true),
587 probe::ProbeScope::AllTraits,
589 let suggestions: Vec<_> = all_methods
591 .filter(|c| c.item.def_id != pick.item.def_id)
594 let substs = ty::InternalSubsts::for_item(self.tcx, m.def_id, |param, _| {
595 self.var_for_def(deref.span, param)
599 deref.span.until(base.span),
602 with_no_trimmed_paths!(
603 self.tcx.def_path_str_with_substs(m.def_id, substs,)
605 match self.tcx.fn_sig(m.def_id).input(0).skip_binder().kind() {
606 ty::Ref(_, _, hir::Mutability::Mut) => "&mut ",
607 ty::Ref(_, _, _) => "&",
613 [] => (base.span.shrink_to_hi().with_hi(deref.span.hi()), ")".to_string()),
614 [first, ..] => (base.span.between(first.span), ", ".to_string()),
619 if suggestions.is_empty() {
622 let mut path_span: MultiSpan = path.ident.span.into();
623 path_span.push_span_label(
625 with_no_trimmed_paths!(format!(
627 self.tcx.def_path_str(pick.item.def_id),
630 let container_id = pick.item.container_id(self.tcx);
631 let container = with_no_trimmed_paths!(self.tcx.def_path_str(container_id));
632 for def_id in pick.import_ids {
633 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
634 path_span.push_span_label(
635 self.tcx.hir().span(hir_id),
636 format!("`{container}` imported here"),
639 let tail = with_no_trimmed_paths!(match &other_methods_in_scope[..] {
641 [candidate] => format!(
642 "the method of the same name on {} `{}`",
643 match candidate.kind {
644 probe::CandidateKind::InherentImplCandidate(..) => "the inherent impl for",
647 self.tcx.def_path_str(candidate.item.container_id(self.tcx))
649 [.., last] if other_methods_in_scope.len() < 5 => {
651 "the methods of the same name on {} and `{}`",
652 other_methods_in_scope[..other_methods_in_scope.len() - 1]
656 self.tcx.def_path_str(c.item.container_id(self.tcx))
658 .collect::<Vec<String>>()
660 self.tcx.def_path_str(last.item.container_id(self.tcx))
664 "the methods of the same name on {} other traits",
665 other_methods_in_scope.len()
671 "the `{}` call is resolved to the method in `{container}`, shadowing {tail}",
675 if suggestions.len() > other_methods_in_scope.len() {
677 "additionally, there are {} other available methods that aren't in scope",
678 suggestions.len() - other_methods_in_scope.len()
681 err.multipart_suggestions(
683 "you might have meant to call {}; you can use the fully-qualified path to call {} \
685 if suggestions.len() == 1 {
688 "one of the other methods"
690 if suggestions.len() == 1 { "it" } else { "one of them" },
693 Applicability::MaybeIncorrect,
697 /// If the expected type is an enum (Issue #55250) with any variants whose
698 /// sole field is of the found type, suggest such variants. (Issue #42764)
699 fn suggest_compatible_variants(
701 err: &mut Diagnostic,
702 expr: &hir::Expr<'_>,
706 if let ty::Adt(expected_adt, substs) = expected.kind() {
707 if let hir::ExprKind::Field(base, ident) = expr.kind {
708 let base_ty = self.typeck_results.borrow().expr_ty(base);
709 if self.can_eq(self.param_env, base_ty, expected).is_ok()
710 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
712 err.span_suggestion_verbose(
713 expr.span.with_lo(base_span.hi()),
714 format!("consider removing the tuple struct field `{ident}`"),
716 Applicability::MaybeIncorrect,
722 // If the expression is of type () and it's the return expression of a block,
723 // we suggest adding a separate return expression instead.
724 // (To avoid things like suggesting `Ok(while .. { .. })`.)
725 if expr_ty.is_unit() {
726 let mut id = expr.hir_id;
729 // Unroll desugaring, to make sure this works for `for` loops etc.
731 parent = self.tcx.hir().parent_id(id);
732 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
733 if parent_span.find_ancestor_inside(expr.span).is_some() {
734 // The parent node is part of the same span, so is the result of the
735 // same expansion/desugaring and not the 'real' parent node.
743 if let Some(hir::Node::Block(&hir::Block {
744 span: block_span, expr: Some(e), ..
745 })) = self.tcx.hir().find(parent)
748 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
749 let return_suggestions = if self
751 .is_diagnostic_item(sym::Result, expected_adt.did())
754 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
755 vec!["None", "Some(())"]
759 if let Some(indent) =
760 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
762 // Add a semicolon, except after `}`.
764 match self.tcx.sess.source_map().span_to_snippet(span) {
765 Ok(s) if s.ends_with('}') => "",
768 err.span_suggestions(
770 "try adding an expression at the end of the block",
773 .map(|r| format!("{semicolon}\n{indent}{r}")),
774 Applicability::MaybeIncorrect,
783 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
787 variant.fields.len() == 1
789 .filter_map(|variant| {
790 let sole_field = &variant.fields[0];
792 let field_is_local = sole_field.did.is_local();
793 let field_is_accessible =
794 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
795 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
796 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
798 if !field_is_local && !field_is_accessible {
802 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
803 .then(|| " (its field is private, but it's local to this crate and its privacy can be changed)".to_string());
805 let sole_field_ty = sole_field.ty(self.tcx, substs);
806 if self.can_coerce(expr_ty, sole_field_ty) {
808 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
809 // FIXME #56861: DRYer prelude filtering
810 if let Some(path) = variant_path.strip_prefix("std::prelude::")
811 && let Some((_, path)) = path.split_once("::")
813 return Some((path.to_string(), variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy));
815 Some((variant_path, variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy))
822 let suggestions_for = |variant: &_, ctor_kind, field_name| {
823 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
824 Some(ident) => format!("{ident}: "),
825 None => String::new(),
828 let (open, close) = match ctor_kind {
829 Some(CtorKind::Fn) => ("(".to_owned(), ")"),
830 None => (format!(" {{ {field_name}: "), " }"),
832 // unit variants don't have fields
833 Some(CtorKind::Const) => unreachable!(),
836 // Suggest constructor as deep into the block tree as possible.
837 // This fixes https://github.com/rust-lang/rust/issues/101065,
838 // and also just helps make the most minimal suggestions.
840 while let hir::ExprKind::Block(block, _) = &expr.kind
841 && let Some(expr_) = &block.expr
847 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
848 (expr.span.shrink_to_hi(), close.to_owned()),
852 match &compatible_variants[..] {
853 [] => { /* No variants to format */ }
854 [(variant, ctor_kind, field_name, note)] => {
855 // Just a single matching variant.
856 err.multipart_suggestion_verbose(
858 "try wrapping the expression in `{variant}`{note}",
859 note = note.as_deref().unwrap_or("")
861 suggestions_for(&**variant, *ctor_kind, *field_name),
862 Applicability::MaybeIncorrect,
867 // More than one matching variant.
868 err.multipart_suggestions(
870 "try wrapping the expression in a variant of `{}`",
871 self.tcx.def_path_str(expected_adt.did())
873 compatible_variants.into_iter().map(
874 |(variant, ctor_kind, field_name, _)| {
875 suggestions_for(&variant, ctor_kind, field_name)
878 Applicability::MaybeIncorrect,
888 fn suggest_non_zero_new_unwrap(
890 err: &mut Diagnostic,
891 expr: &hir::Expr<'_>,
896 let (adt, unwrap) = match expected.kind() {
897 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
898 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
900 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
904 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
905 ty::Adt(adt, _) => (adt, ".unwrap()"),
910 (sym::NonZeroU8, tcx.types.u8),
911 (sym::NonZeroU16, tcx.types.u16),
912 (sym::NonZeroU32, tcx.types.u32),
913 (sym::NonZeroU64, tcx.types.u64),
914 (sym::NonZeroU128, tcx.types.u128),
915 (sym::NonZeroI8, tcx.types.i8),
916 (sym::NonZeroI16, tcx.types.i16),
917 (sym::NonZeroI32, tcx.types.i32),
918 (sym::NonZeroI64, tcx.types.i64),
919 (sym::NonZeroI128, tcx.types.i128),
922 let Some((s, _)) = map
924 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
925 else { return false; };
927 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
929 err.multipart_suggestion(
930 format!("consider calling `{s}::new`"),
932 (expr.span.shrink_to_lo(), format!("{path}::new(")),
933 (expr.span.shrink_to_hi(), format!("){unwrap}")),
935 Applicability::MaybeIncorrect,
941 pub fn get_conversion_methods(
945 checked_ty: Ty<'tcx>,
947 ) -> Vec<AssocItem> {
948 let methods = self.probe_for_return_type(
950 probe::Mode::MethodCall,
955 self.has_only_self_parameter(m)
958 // This special internal attribute is used to permit
959 // "identity-like" conversion methods to be suggested here.
961 // FIXME (#46459 and #46460): ideally
962 // `std::convert::Into::into` and `std::borrow:ToOwned` would
963 // also be `#[rustc_conversion_suggestion]`, if not for
964 // method-probing false-positives and -negatives (respectively).
966 // FIXME? Other potential candidate methods: `as_ref` and
968 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
975 /// This function checks whether the method is not static and does not accept other parameters than `self`.
976 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
978 ty::AssocKind::Fn => {
979 method.fn_has_self_parameter
980 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
986 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
988 /// Given the following code:
989 /// ```compile_fail,E0308
991 /// fn takes_ref(_: &Foo) {}
992 /// let ref opt = Some(Foo);
994 /// opt.map(|param| takes_ref(param));
996 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
998 /// It only checks for `Option` and `Result` and won't work with
999 /// ```ignore (illustrative)
1000 /// opt.map(|param| { takes_ref(param) });
1002 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
1003 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
1007 let hir::def::Res::Local(local_id) = path.res else {
1011 let local_parent = self.tcx.hir().parent_id(local_id);
1012 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
1016 let param_parent = self.tcx.hir().parent_id(*param_hir_id);
1017 let Some(Node::Expr(hir::Expr {
1018 hir_id: expr_hir_id,
1019 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
1021 })) = self.tcx.hir().find(param_parent) else {
1025 let expr_parent = self.tcx.hir().parent_id(*expr_hir_id);
1026 let hir = self.tcx.hir().find(expr_parent);
1027 let closure_params_len = closure_fn_decl.inputs.len();
1029 Some(Node::Expr(hir::Expr {
1030 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
1034 ) = (hir, closure_params_len) else {
1038 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
1039 let name = method_path.ident.name;
1040 let is_as_ref_able = match self_ty.peel_refs().kind() {
1041 ty::Adt(def, _) => {
1042 (self.tcx.is_diagnostic_item(sym::Option, def.did())
1043 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
1044 && (name == sym::map || name == sym::and_then)
1048 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
1049 (true, Ok(src)) => {
1050 let suggestion = format!("as_ref().{}", src);
1051 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
1057 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
1059 expr: &hir::Expr<'_>,
1060 ) -> Option<Symbol> {
1061 let hir = self.tcx.hir();
1062 let local = match expr {
1065 hir::ExprKind::Path(hir::QPath::Resolved(
1068 res: hir::def::Res::Local(_),
1069 segments: [hir::PathSegment { ident, .. }],
1078 match hir.find_parent(expr.hir_id)? {
1079 Node::ExprField(field) => {
1080 if field.ident.name == local.name && field.is_shorthand {
1081 return Some(local.name);
1090 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
1091 pub(crate) fn maybe_get_block_expr(
1093 expr: &hir::Expr<'tcx>,
1094 ) -> Option<&'tcx hir::Expr<'tcx>> {
1096 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
1101 /// Returns whether the given expression is an `else if`.
1102 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
1103 if let hir::ExprKind::If(..) = expr.kind {
1104 let parent_id = self.tcx.hir().parent_id(expr.hir_id);
1105 if let Some(Node::Expr(hir::Expr {
1106 kind: hir::ExprKind::If(_, _, Some(else_expr)),
1108 })) = self.tcx.hir().find(parent_id)
1110 return else_expr.hir_id == expr.hir_id;
1116 /// This function is used to determine potential "simple" improvements or users' errors and
1117 /// provide them useful help. For example:
1119 /// ```compile_fail,E0308
1120 /// fn some_fn(s: &str) {}
1122 /// let x = "hey!".to_owned();
1123 /// some_fn(x); // error
1126 /// No need to find every potential function which could make a coercion to transform a
1127 /// `String` into a `&str` since a `&` would do the trick!
1129 /// In addition of this check, it also checks between references mutability state. If the
1130 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
1134 expr: &hir::Expr<'tcx>,
1135 checked_ty: Ty<'tcx>,
1143 bool, /* suggest `&` or `&mut` type annotation */
1145 let sess = self.sess();
1148 // If the span is from an external macro, there's no suggestion we can make.
1149 if in_external_macro(sess, sp) {
1153 let sm = sess.source_map();
1155 let replace_prefix = |s: &str, old: &str, new: &str| {
1156 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
1159 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
1160 let expr = expr.peel_drop_temps();
1162 match (&expr.kind, expected.kind(), checked_ty.kind()) {
1163 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
1164 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
1165 if let hir::ExprKind::Lit(_) = expr.kind
1166 && let Ok(src) = sm.span_to_snippet(sp)
1167 && replace_prefix(&src, "b\"", "\"").is_some()
1169 let pos = sp.lo() + BytePos(1);
1172 "consider removing the leading `b`".to_string(),
1174 Applicability::MachineApplicable,
1180 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
1181 if let hir::ExprKind::Lit(_) = expr.kind
1182 && let Ok(src) = sm.span_to_snippet(sp)
1183 && replace_prefix(&src, "\"", "b\"").is_some()
1187 "consider adding a leading `b`".to_string(),
1189 Applicability::MachineApplicable,
1197 (_, &ty::Ref(_, _, mutability), _) => {
1198 // Check if it can work when put into a ref. For example:
1201 // fn bar(x: &mut i32) {}
1204 // bar(&x); // error, expected &mut
1206 let ref_ty = match mutability {
1207 hir::Mutability::Mut => {
1208 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1210 hir::Mutability::Not => {
1211 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1214 if self.can_coerce(ref_ty, expected) {
1215 let mut sugg_sp = sp;
1216 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
1218 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
1220 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
1222 let ai = self.tcx.associated_item(did);
1223 ai.trait_container(self.tcx) == Some(clone_trait)
1226 && segment.ident.name == sym::clone
1228 // If this expression had a clone call when suggesting borrowing
1229 // we want to suggest removing it because it'd now be unnecessary.
1230 sugg_sp = receiver.span;
1233 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
1234 let needs_parens = match expr.kind {
1235 // parenthesize if needed (Issue #46756)
1236 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
1237 // parenthesize borrows of range literals (Issue #54505)
1238 _ if is_range_literal(expr) => true,
1242 if let Some(sugg) = self.can_use_as_ref(expr) {
1247 Applicability::MachineApplicable,
1253 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1254 Some(ident) => format!("{ident}: "),
1255 None => String::new(),
1258 if let Some(hir::Node::Expr(hir::Expr {
1259 kind: hir::ExprKind::Assign(..),
1261 })) = self.tcx.hir().find_parent(expr.hir_id)
1263 if mutability.is_mut() {
1264 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
1269 let sugg_expr = if needs_parens { format!("({src})") } else { src };
1272 format!("consider {}borrowing here", mutability.mutably_str()),
1273 format!("{prefix}{}{sugg_expr}", mutability.ref_prefix_str()),
1274 Applicability::MachineApplicable,
1282 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
1284 &ty::Ref(_, checked, _),
1285 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
1286 // We have `&T`, check if what was expected was `T`. If so,
1287 // we may want to suggest removing a `&`.
1288 if sm.is_imported(expr.span) {
1289 // Go through the spans from which this span was expanded,
1290 // and find the one that's pointing inside `sp`.
1292 // E.g. for `&format!("")`, where we want the span to the
1293 // `format!()` invocation instead of its expansion.
1294 if let Some(call_span) =
1295 iter::successors(Some(expr.span), |s| s.parent_callsite())
1296 .find(|&s| sp.contains(s))
1297 && sm.is_span_accessible(call_span)
1300 sp.with_hi(call_span.lo()),
1301 "consider removing the borrow".to_string(),
1303 Applicability::MachineApplicable,
1310 if sp.contains(expr.span)
1311 && sm.is_span_accessible(expr.span)
1314 sp.with_hi(expr.span.lo()),
1315 "consider removing the borrow".to_string(),
1317 Applicability::MachineApplicable,
1325 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
1326 &ty::Ref(_, ty_a, mutbl_a),
1328 if let Some(steps) = self.deref_steps(ty_a, ty_b)
1329 // Only suggest valid if dereferencing needed.
1331 // The pointer type implements `Copy` trait so the suggestion is always valid.
1332 && let Ok(src) = sm.span_to_snippet(sp)
1334 let derefs = "*".repeat(steps);
1335 let old_prefix = mutbl_a.ref_prefix_str();
1336 let new_prefix = mutbl_b.ref_prefix_str().to_owned() + &derefs;
1338 let suggestion = replace_prefix(&src, old_prefix, &new_prefix).map(|_| {
1339 // skip `&` or `&mut ` if both mutabilities are mutable
1340 let lo = sp.lo() + BytePos(min(old_prefix.len(), mutbl_b.ref_prefix_str().len()) as _);
1341 // skip `&` or `&mut `
1342 let hi = sp.lo() + BytePos(old_prefix.len() as _);
1343 let sp = sp.with_lo(lo).with_hi(hi);
1347 format!("{}{derefs}", if mutbl_a != mutbl_b { mutbl_b.prefix_str() } else { "" }),
1348 if mutbl_b <= mutbl_a { Applicability::MachineApplicable } else { Applicability::MaybeIncorrect }
1352 if let Some((span, src, applicability)) = suggestion {
1355 "consider dereferencing".to_string(),
1364 _ if sp == expr.span => {
1365 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
1366 let mut expr = expr.peel_blocks();
1367 let mut prefix_span = expr.span.shrink_to_lo();
1368 let mut remove = String::new();
1370 // Try peeling off any existing `&` and `&mut` to reach our target type
1372 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
1373 // If the expression has `&`, removing it would fix the error
1374 prefix_span = prefix_span.with_hi(inner.span.lo());
1376 remove.push_str(mutbl.ref_prefix_str());
1382 // If we've reached our target type with just removing `&`, then just print now.
1386 format!("consider removing the `{}`", remove.trim()),
1388 // Do not remove `&&` to get to bool, because it might be something like
1389 // { a } && b, which we have a separate fixup suggestion that is more
1390 // likely correct...
1391 if remove.trim() == "&&" && expected == self.tcx.types.bool {
1392 Applicability::MaybeIncorrect
1394 Applicability::MachineApplicable
1401 // For this suggestion to make sense, the type would need to be `Copy`,
1402 // or we have to be moving out of a `Box<T>`
1403 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1404 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1405 // `steps` layers of boxes, not just one, but this is easier and most likely.
1406 || (checked_ty.is_box() && steps == 1)
1408 let deref_kind = if checked_ty.is_box() {
1409 "unboxing the value"
1410 } else if checked_ty.is_region_ptr() {
1411 "dereferencing the borrow"
1413 "dereferencing the type"
1416 // Suggest removing `&` if we have removed any, otherwise suggest just
1417 // dereferencing the remaining number of steps.
1418 let message = if remove.is_empty() {
1419 format!("consider {deref_kind}")
1422 "consider removing the `{}` and {} instead",
1428 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1429 Some(ident) => format!("{ident}: "),
1430 None => String::new(),
1433 let (span, suggestion) = if self.is_else_if_block(expr) {
1434 // Don't suggest nonsense like `else *if`
1436 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1437 // prefix should be empty here..
1438 (expr.span.shrink_to_lo(), "*".to_string())
1440 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1447 Applicability::MachineApplicable,
1459 pub fn check_for_cast(
1461 err: &mut Diagnostic,
1462 expr: &hir::Expr<'_>,
1463 checked_ty: Ty<'tcx>,
1464 expected_ty: Ty<'tcx>,
1465 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1467 if self.tcx.sess.source_map().is_imported(expr.span) {
1468 // Ignore if span is from within a macro.
1472 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1476 // If casting this expression to a given numeric type would be appropriate in case of a type
1479 // We want to minimize the amount of casting operations that are suggested, as it can be a
1480 // lossy operation with potentially bad side effects, so we only suggest when encountering
1481 // an expression that indicates that the original type couldn't be directly changed.
1483 // For now, don't suggest casting with `as`.
1484 let can_cast = false;
1486 let mut sugg = vec![];
1488 if let Some(hir::Node::ExprField(field)) = self.tcx.hir().find_parent(expr.hir_id) {
1489 // `expr` is a literal field for a struct, only suggest if appropriate
1490 if field.is_shorthand {
1491 // This is a field literal
1492 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1494 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1499 if let hir::ExprKind::Call(path, args) = &expr.kind
1500 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1501 (&path.kind, args.len())
1502 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1503 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1504 (&base_ty.kind, path_segment.ident.name)
1506 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1520 if base_ty_path.segments.len() == 1 =>
1530 "you can convert {} `{}` to {} `{}`",
1531 checked_ty.kind().article(),
1533 expected_ty.kind().article(),
1536 let cast_msg = format!(
1537 "you can cast {} `{}` to {} `{}`",
1538 checked_ty.kind().article(),
1540 expected_ty.kind().article(),
1543 let lit_msg = format!(
1544 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1547 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1548 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1554 let mut cast_suggestion = sugg.clone();
1555 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1556 let mut into_suggestion = sugg.clone();
1557 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1558 let mut suffix_suggestion = sugg.clone();
1559 suffix_suggestion.push((
1561 (&expected_ty.kind(), &checked_ty.kind()),
1562 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1564 // Remove fractional part from literal, for example `42.0f32` into `42`
1565 let src = src.trim_end_matches(&checked_ty.to_string());
1566 let len = src.split('.').next().unwrap().len();
1567 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1569 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1570 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1572 if expr.precedence().order() < PREC_POSTFIX {
1574 format!("{expected_ty})")
1576 expected_ty.to_string()
1579 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1580 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1582 let is_negative_int =
1583 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1584 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1586 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1588 let suggest_fallible_into_or_lhs_from =
1589 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1590 // If we know the expression the expected type is derived from, we might be able
1591 // to suggest a widening conversion rather than a narrowing one (which may
1592 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1594 // can be given the suggestion "u32::from(x) > y" rather than
1595 // "x > y.try_into().unwrap()".
1596 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1600 .span_to_snippet(expr.span)
1602 .map(|src| (expr, src))
1604 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1605 (lhs_expr_and_src, exp_to_found_is_fallible)
1608 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1610 let suggestion = vec![
1611 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1612 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1616 let msg = format!("{msg} and panic if the converted value doesn't fit");
1617 let mut suggestion = sugg.clone();
1619 expr.span.shrink_to_hi(),
1620 format!("{close_paren}.try_into().unwrap()"),
1624 err.multipart_suggestion_verbose(
1627 Applicability::MachineApplicable,
1631 let suggest_to_change_suffix_or_into =
1632 |err: &mut Diagnostic,
1633 found_to_exp_is_fallible: bool,
1634 exp_to_found_is_fallible: bool| {
1636 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1642 let always_fallible = found_to_exp_is_fallible
1643 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1644 let msg = if literal_is_ty_suffixed(expr) {
1646 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1647 // We now know that converting either the lhs or rhs is fallible. Before we
1648 // suggest a fallible conversion, check if the value can never fit in the
1650 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1653 } else if in_const_context {
1654 // Do not recommend `into` or `try_into` in const contexts.
1656 } else if found_to_exp_is_fallible {
1657 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1661 let suggestion = if literal_is_ty_suffixed(expr) {
1662 suffix_suggestion.clone()
1664 into_suggestion.clone()
1666 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1669 match (&expected_ty.kind(), &checked_ty.kind()) {
1670 (ty::Int(exp), ty::Int(found)) => {
1671 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1673 (Some(exp), Some(found)) if exp < found => (true, false),
1674 (Some(exp), Some(found)) if exp > found => (false, true),
1675 (None, Some(8 | 16)) => (false, true),
1676 (Some(8 | 16), None) => (true, false),
1677 (None, _) | (_, None) => (true, true),
1678 _ => (false, false),
1680 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1683 (ty::Uint(exp), ty::Uint(found)) => {
1684 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1686 (Some(exp), Some(found)) if exp < found => (true, false),
1687 (Some(exp), Some(found)) if exp > found => (false, true),
1688 (None, Some(8 | 16)) => (false, true),
1689 (Some(8 | 16), None) => (true, false),
1690 (None, _) | (_, None) => (true, true),
1691 _ => (false, false),
1693 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1696 (&ty::Int(exp), &ty::Uint(found)) => {
1697 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1699 (Some(exp), Some(found)) if found < exp => (false, true),
1700 (None, Some(8)) => (false, true),
1703 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1706 (&ty::Uint(exp), &ty::Int(found)) => {
1707 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1709 (Some(exp), Some(found)) if found > exp => (true, false),
1710 (Some(8), None) => (true, false),
1713 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1716 (ty::Float(exp), ty::Float(found)) => {
1717 if found.bit_width() < exp.bit_width() {
1718 suggest_to_change_suffix_or_into(err, false, true);
1719 } else if literal_is_ty_suffixed(expr) {
1720 err.multipart_suggestion_verbose(
1723 Applicability::MachineApplicable,
1725 } else if can_cast {
1726 // Missing try_into implementation for `f64` to `f32`
1727 err.multipart_suggestion_verbose(
1728 &format!("{cast_msg}, producing the closest possible value"),
1730 Applicability::MaybeIncorrect, // lossy conversion
1735 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1736 if literal_is_ty_suffixed(expr) {
1737 err.multipart_suggestion_verbose(
1740 Applicability::MachineApplicable,
1742 } else if can_cast {
1743 // Missing try_into implementation for `{float}` to `{integer}`
1744 err.multipart_suggestion_verbose(
1745 &format!("{msg}, rounding the float towards zero"),
1747 Applicability::MaybeIncorrect, // lossy conversion
1752 (ty::Float(exp), ty::Uint(found)) => {
1753 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1754 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1755 err.multipart_suggestion_verbose(
1757 "{msg}, producing the floating point representation of the integer",
1760 Applicability::MachineApplicable,
1762 } else if literal_is_ty_suffixed(expr) {
1763 err.multipart_suggestion_verbose(
1766 Applicability::MachineApplicable,
1769 // Missing try_into implementation for `{integer}` to `{float}`
1770 err.multipart_suggestion_verbose(
1772 "{cast_msg}, producing the floating point representation of the integer, \
1773 rounded if necessary",
1776 Applicability::MaybeIncorrect, // lossy conversion
1781 (ty::Float(exp), ty::Int(found)) => {
1782 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1783 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1784 err.multipart_suggestion_verbose(
1786 "{}, producing the floating point representation of the integer",
1790 Applicability::MachineApplicable,
1792 } else if literal_is_ty_suffixed(expr) {
1793 err.multipart_suggestion_verbose(
1796 Applicability::MachineApplicable,
1799 // Missing try_into implementation for `{integer}` to `{float}`
1800 err.multipart_suggestion_verbose(
1802 "{}, producing the floating point representation of the integer, \
1803 rounded if necessary",
1807 Applicability::MaybeIncorrect, // lossy conversion
1813 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1814 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1817 err.multipart_suggestion_verbose(
1818 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1820 Applicability::MachineApplicable,
1828 /// Identify when the user has written `foo..bar()` instead of `foo.bar()`.
1829 pub fn check_for_range_as_method_call(
1831 err: &mut Diagnostic,
1832 expr: &hir::Expr<'_>,
1833 checked_ty: Ty<'tcx>,
1834 expected_ty: Ty<'tcx>,
1836 if !hir::is_range_literal(expr) {
1839 let hir::ExprKind::Struct(
1840 hir::QPath::LangItem(LangItem::Range, ..),
1843 ) = expr.kind else { return; };
1844 let parent = self.tcx.hir().parent_id(expr.hir_id);
1845 if let Some(hir::Node::ExprField(_)) = self.tcx.hir().find(parent) {
1846 // Ignore `Foo { field: a..Default::default() }`
1849 let mut expr = end.expr;
1850 while let hir::ExprKind::MethodCall(_, rcvr, ..) = expr.kind {
1851 // Getting to the root receiver and asserting it is a fn call let's us ignore cases in
1852 // `src/test/ui/methods/issues/issue-90315.stderr`.
1855 let hir::ExprKind::Call(method_name, _) = expr.kind else { return; };
1856 let ty::Adt(adt, _) = checked_ty.kind() else { return; };
1857 if self.tcx.lang_items().range_struct() != Some(adt.did()) {
1860 if let ty::Adt(adt, _) = expected_ty.kind()
1861 && self.tcx.lang_items().range_struct() == Some(adt.did())
1865 // Check if start has method named end.
1866 let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = method_name.kind else { return; };
1867 let [hir::PathSegment { ident, .. }] = p.segments else { return; };
1868 let self_ty = self.typeck_results.borrow().expr_ty(start.expr);
1869 let Ok(_pick) = self.probe_for_name(
1870 probe::Mode::MethodCall,
1872 probe::IsSuggestion(true),
1875 probe::ProbeScope::AllTraits,
1878 let mut span = start.expr.span.between(end.expr.span);
1879 if span.lo() + BytePos(2) == span.hi() {
1880 // There's no space between the start, the range op and the end, suggest removal which
1881 // will be more noticeable than the replacement of `..` with `.`.
1882 span = span.with_lo(span.lo() + BytePos(1));
1885 err.span_suggestion_verbose(
1887 "you likely meant to write a method call instead of a range",
1889 Applicability::MachineApplicable,