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_clone_for_ref(err, expr, expr_ty, expected)
61 || self.suggest_into(err, expr, expr_ty, expected)
62 || self.suggest_floating_point_literal(err, expr, expected);
64 self.point_at_expr_source_of_inferred_type(err, expr, expr_ty, expected);
68 pub fn emit_coerce_suggestions(
71 expr: &hir::Expr<'tcx>,
74 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
75 error: Option<TypeError<'tcx>>,
77 if expr_ty == expected {
81 self.annotate_expected_due_to_let_ty(err, expr, error);
82 self.emit_type_mismatch_suggestions(err, expr, expr_ty, expected, expected_ty_expr, error);
83 self.note_type_is_not_clone(err, expected, expr_ty, expr);
84 self.note_need_for_fn_pointer(err, expected, expr_ty);
85 self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
86 self.check_for_range_as_method_call(err, expr, expr_ty, expected);
87 self.check_for_binding_assigned_block_without_tail_expression(err, expr, expr_ty, expected);
90 /// Requires that the two types unify, and prints an error message if
92 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
93 if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) {
98 pub fn demand_suptype_diag(
103 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
104 self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
107 #[instrument(skip(self), level = "debug")]
108 pub fn demand_suptype_with_origin(
110 cause: &ObligationCause<'tcx>,
113 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
114 match self.at(cause, self.param_env).sup(expected, actual) {
115 Ok(InferOk { obligations, value: () }) => {
116 self.register_predicates(obligations);
119 Err(e) => Some(self.err_ctxt().report_mismatched_types(&cause, expected, actual, e)),
123 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
124 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
129 pub fn demand_eqtype_diag(
134 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
135 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
138 pub fn demand_eqtype_with_origin(
140 cause: &ObligationCause<'tcx>,
143 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
144 match self.at(cause, self.param_env).eq(expected, actual) {
145 Ok(InferOk { obligations, value: () }) => {
146 self.register_predicates(obligations);
149 Err(e) => Some(self.err_ctxt().report_mismatched_types(cause, expected, actual, e)),
153 pub fn demand_coerce(
155 expr: &hir::Expr<'tcx>,
156 checked_ty: Ty<'tcx>,
158 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
159 allow_two_phase: AllowTwoPhase,
162 self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase);
163 if let Some(mut err) = err {
169 /// Checks that the type of `expr` can be coerced to `expected`.
171 /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!`
172 /// will be permitted if the diverges flag is currently "always".
173 #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))]
174 pub fn demand_coerce_diag(
176 expr: &hir::Expr<'tcx>,
177 checked_ty: Ty<'tcx>,
179 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
180 allow_two_phase: AllowTwoPhase,
181 ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
182 let expected = self.resolve_vars_with_obligations(expected);
184 let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) {
185 Ok(ty) => return (ty, None),
189 self.set_tainted_by_errors(self.tcx.sess.delay_span_bug(
191 "`TypeError` when attempting coercion but no error emitted",
193 let expr = expr.peel_drop_temps();
194 let cause = self.misc(expr.span);
195 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
196 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e);
198 let is_insufficiently_polymorphic =
199 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
201 // FIXME(#73154): For now, we do leak check when coercing function
202 // pointers in typeck, instead of only during borrowck. This can lead
203 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
204 if !is_insufficiently_polymorphic {
205 self.emit_coerce_suggestions(
215 (expected, Some(err))
218 pub fn point_at_expr_source_of_inferred_type(
220 err: &mut Diagnostic,
221 expr: &hir::Expr<'_>,
225 let map = self.tcx.hir();
227 let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = expr.kind else { return false; };
228 let [hir::PathSegment { ident, args: None, .. }] = p.segments else { return false; };
229 let hir::def::Res::Local(hir_id) = p.res else { return false; };
230 let Some(hir::Node::Pat(pat)) = map.find(hir_id) else { return false; };
231 let Some(hir::Node::Local(hir::Local {
235 })) = map.find_parent(pat.hir_id) else { return false; };
236 let Some(ty) = self.node_ty_opt(init.hir_id) else { return false; };
237 if ty.is_closure() || init.span.overlaps(expr.span) || pat.span.from_expansion() {
241 // Locate all the usages of the relevant binding.
242 struct FindExprs<'hir> {
244 uses: Vec<&'hir hir::Expr<'hir>>,
246 impl<'v> Visitor<'v> for FindExprs<'v> {
247 fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) {
248 if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = ex.kind
249 && let hir::def::Res::Local(hir_id) = path.res
250 && hir_id == self.hir_id
254 hir::intravisit::walk_expr(self, ex);
258 let mut expr_finder = FindExprs { hir_id, uses: vec![] };
259 let id = map.get_parent_item(hir_id);
260 let hir_id: hir::HirId = id.into();
262 let Some(node) = map.find(hir_id) else { return false; };
263 let Some(body_id) = node.body_id() else { return false; };
264 let body = map.body(body_id);
265 expr_finder.visit_expr(body.value);
266 // Hack to make equality checks on types with inference variables and regions useful.
267 let mut eraser = BottomUpFolder {
269 lt_op: |_| self.tcx.lifetimes.re_erased,
271 ty_op: |t| match *t.kind() {
272 ty::Infer(ty::TyVar(vid)) => self.tcx.mk_ty_infer(ty::TyVar(self.root_var(vid))),
273 ty::Infer(ty::IntVar(_)) => {
274 self.tcx.mk_ty_infer(ty::IntVar(ty::IntVid { index: 0 }))
276 ty::Infer(ty::FloatVar(_)) => {
277 self.tcx.mk_ty_infer(ty::FloatVar(ty::FloatVid { index: 0 }))
282 let mut prev = eraser.fold_ty(ty);
283 let mut prev_span = None;
285 for binding in expr_finder.uses {
286 // In every expression where the binding is referenced, we will look at that
287 // expression's type and see if it is where the incorrect found type was fully
288 // "materialized" and point at it. We will also try to provide a suggestion there.
289 if let Some(hir::Node::Expr(expr)
290 | hir::Node::Stmt(hir::Stmt {
291 kind: hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr),
293 })) = &map.find_parent(binding.hir_id)
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_for_diagnostic(
310 probe::ProbeScope::TraitsInScope,
313 Ok(pick) => pick.self_ty,
316 // Remove one layer of references to account for `&mut self` and
317 // `&self`, so that we can compare it against the binding.
318 let (ty, def_self_ty) = match (ty.kind(), def_self_ty.kind()) {
319 (ty::Ref(_, ty, a), ty::Ref(_, self_ty, b)) if a == b => (*ty, *self_ty),
320 _ => (ty, def_self_ty),
322 let mut param_args = FxHashMap::default();
323 let mut param_expected = FxHashMap::default();
324 let mut param_found = FxHashMap::default();
325 if self.can_eq(self.param_env, ty, found).is_ok() {
326 // We only point at the first place where the found type was inferred.
327 for (i, param_ty) in sig.inputs().skip_binder().iter().skip(1).enumerate() {
328 if def_self_ty.contains(*param_ty) && let ty::Param(_) = param_ty.kind() {
329 // We found an argument that references a type parameter in `Self`,
330 // so we assume that this is the argument that caused the found
331 // type, which we know already because of `can_eq` above was first
332 // inferred in this method call.
334 let arg_ty = self.node_ty(arg.hir_id);
338 "this is of type `{arg_ty}`, which causes `{ident}` to be \
342 param_args.insert(param_ty, (arg, arg_ty));
347 // Here we find, for a type param `T`, the type that `T` is in the current
348 // method call *and* in the original expected type. That way, we can see if we
349 // can give any structured suggestion for the function argument.
350 let mut c = CollectAllMismatches {
352 param_env: self.param_env,
355 let _ = c.relate(def_self_ty, ty);
356 for error in c.errors {
357 if let TypeError::Sorts(error) = error {
358 param_found.insert(error.expected, error.found);
362 let _ = c.relate(def_self_ty, expected);
363 for error in c.errors {
364 if let TypeError::Sorts(error) = error {
365 param_expected.insert(error.expected, error.found);
368 for (param, (arg, arg_ty)) in param_args.iter() {
369 let Some(expected) = param_expected.get(param) else { continue; };
370 let Some(found) = param_found.get(param) else { continue; };
371 if self.can_eq(self.param_env, *arg_ty, *found).is_err() { continue; }
372 self.emit_coerce_suggestions(err, arg, *found, *expected, None, None);
375 let ty = eraser.fold_ty(ty);
376 if ty.references_error() {
380 && param_args.is_empty()
381 && self.can_eq(self.param_env, ty, found).is_ok()
383 // We only point at the first place where the found type was inferred.
386 with_forced_trimmed_paths!(format!(
387 "here the type of `{ident}` is inferred to be `{ty}`",
391 } else if !param_args.is_empty() {
396 let ty = eraser.fold_ty(self.node_ty(binding.hir_id));
397 if ty.references_error() {
401 && let Some(span) = prev_span
402 && self.can_eq(self.param_env, ty, found).is_ok()
404 // We only point at the first place where the found type was inferred.
405 // We use the *previous* span because if the type is known *here* it means
406 // it was *evaluated earlier*. We don't do this for method calls because we
407 // evaluate the method's self type eagerly, but not in any other case.
410 with_forced_trimmed_paths!(format!(
411 "here the type of `{ident}` is inferred to be `{ty}`",
418 if binding.hir_id == expr.hir_id {
419 // Do not look at expressions that come after the expression we were originally
420 // evaluating and had a type error.
423 prev_span = Some(binding.span);
428 fn annotate_expected_due_to_let_ty(
430 err: &mut Diagnostic,
431 expr: &hir::Expr<'_>,
432 error: Option<TypeError<'tcx>>,
434 let parent = self.tcx.hir().parent_id(expr.hir_id);
435 match (self.tcx.hir().find(parent), error) {
436 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
437 if init.hir_id == expr.hir_id =>
439 // Point at `let` assignment type.
440 err.span_label(ty.span, "expected due to this");
443 Some(hir::Node::Expr(hir::Expr {
444 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
446 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
447 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
448 // We ignore closures explicitly because we already point at them elsewhere.
449 // Point at the assigned-to binding.
450 let mut primary_span = lhs.span;
451 let mut secondary_span = lhs.span;
452 let mut post_message = "";
454 hir::ExprKind::Path(hir::QPath::Resolved(
459 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
465 if let Some(hir::Node::Item(hir::Item {
467 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
469 })) = self.tcx.hir().get_if_local(*def_id)
471 primary_span = ty.span;
472 secondary_span = ident.span;
473 post_message = " type";
476 hir::ExprKind::Path(hir::QPath::Resolved(
478 hir::Path { res: hir::def::Res::Local(hir_id), .. },
480 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
481 primary_span = pat.span;
482 secondary_span = pat.span;
483 match self.tcx.hir().find_parent(pat.hir_id) {
484 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
485 primary_span = ty.span;
486 post_message = " type";
488 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
489 primary_span = init.span;
490 post_message = " value";
492 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
493 primary_span = *ty_span;
494 post_message = " parameter type";
503 if primary_span != secondary_span
508 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
510 // We are pointing at the binding's type or initializer value, but it's pattern
511 // is in a different line, so we point at both.
512 err.span_label(secondary_span, "expected due to the type of this binding");
513 err.span_label(primary_span, &format!("expected due to this{post_message}"));
514 } else if post_message == "" {
515 // We are pointing at either the assignment lhs or the binding def pattern.
516 err.span_label(primary_span, "expected due to the type of this binding");
518 // We are pointing at the binding's type or initializer value.
519 err.span_label(primary_span, &format!("expected due to this{post_message}"));
522 if !lhs.is_syntactic_place_expr() {
523 // We already emitted E0070 "invalid left-hand side of assignment", so we
525 err.downgrade_to_delayed_bug();
529 Some(hir::Node::Expr(hir::Expr {
530 kind: hir::ExprKind::Binary(_, lhs, rhs), ..
532 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
533 ) if rhs.hir_id == expr.hir_id
534 && self.typeck_results.borrow().expr_ty_adjusted_opt(lhs) == Some(expected) =>
536 err.span_label(lhs.span, &format!("expected because this is `{expected}`"));
542 fn annotate_alternative_method_deref(
544 err: &mut Diagnostic,
545 expr: &hir::Expr<'_>,
546 error: Option<TypeError<'tcx>>,
548 let parent = self.tcx.hir().parent_id(expr.hir_id);
549 let Some(TypeError::Sorts(ExpectedFound { expected, .. })) = error else {return;};
550 let Some(hir::Node::Expr(hir::Expr {
551 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
552 })) = self.tcx.hir().find(parent) else {return; };
553 if rhs.hir_id != expr.hir_id || expected.is_closure() {
556 let hir::ExprKind::Unary(hir::UnOp::Deref, deref) = lhs.kind else { return; };
557 let hir::ExprKind::MethodCall(path, base, args, _) = deref.kind else { return; };
558 let Some(self_ty) = self.typeck_results.borrow().expr_ty_adjusted_opt(base) else { return; };
561 .lookup_probe_for_diagnostic(
565 probe::ProbeScope::TraitsInScope,
570 let in_scope_methods = self.probe_for_name_many(
571 probe::Mode::MethodCall,
574 probe::IsSuggestion(true),
577 probe::ProbeScope::TraitsInScope,
579 let other_methods_in_scope: Vec<_> =
580 in_scope_methods.iter().filter(|c| c.item.def_id != pick.item.def_id).collect();
582 let all_methods = self.probe_for_name_many(
583 probe::Mode::MethodCall,
586 probe::IsSuggestion(true),
589 probe::ProbeScope::AllTraits,
591 let suggestions: Vec<_> = all_methods
593 .filter(|c| c.item.def_id != pick.item.def_id)
596 let substs = ty::InternalSubsts::for_item(self.tcx, m.def_id, |param, _| {
597 self.var_for_def(deref.span, param)
601 deref.span.until(base.span),
604 with_no_trimmed_paths!(
605 self.tcx.def_path_str_with_substs(m.def_id, substs,)
607 match self.tcx.fn_sig(m.def_id).input(0).skip_binder().kind() {
608 ty::Ref(_, _, hir::Mutability::Mut) => "&mut ",
609 ty::Ref(_, _, _) => "&",
615 [] => (base.span.shrink_to_hi().with_hi(deref.span.hi()), ")".to_string()),
616 [first, ..] => (base.span.between(first.span), ", ".to_string()),
621 if suggestions.is_empty() {
624 let mut path_span: MultiSpan = path.ident.span.into();
625 path_span.push_span_label(
627 with_no_trimmed_paths!(format!(
629 self.tcx.def_path_str(pick.item.def_id),
632 let container_id = pick.item.container_id(self.tcx);
633 let container = with_no_trimmed_paths!(self.tcx.def_path_str(container_id));
634 for def_id in pick.import_ids {
635 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
636 path_span.push_span_label(
637 self.tcx.hir().span(hir_id),
638 format!("`{container}` imported here"),
641 let tail = with_no_trimmed_paths!(match &other_methods_in_scope[..] {
643 [candidate] => format!(
644 "the method of the same name on {} `{}`",
645 match candidate.kind {
646 probe::CandidateKind::InherentImplCandidate(..) => "the inherent impl for",
649 self.tcx.def_path_str(candidate.item.container_id(self.tcx))
651 [.., last] if other_methods_in_scope.len() < 5 => {
653 "the methods of the same name on {} and `{}`",
654 other_methods_in_scope[..other_methods_in_scope.len() - 1]
658 self.tcx.def_path_str(c.item.container_id(self.tcx))
660 .collect::<Vec<String>>()
662 self.tcx.def_path_str(last.item.container_id(self.tcx))
666 "the methods of the same name on {} other traits",
667 other_methods_in_scope.len()
673 "the `{}` call is resolved to the method in `{container}`, shadowing {tail}",
677 if suggestions.len() > other_methods_in_scope.len() {
679 "additionally, there are {} other available methods that aren't in scope",
680 suggestions.len() - other_methods_in_scope.len()
683 err.multipart_suggestions(
685 "you might have meant to call {}; you can use the fully-qualified path to call {} \
687 if suggestions.len() == 1 {
690 "one of the other methods"
692 if suggestions.len() == 1 { "it" } else { "one of them" },
695 Applicability::MaybeIncorrect,
699 /// If the expected type is an enum (Issue #55250) with any variants whose
700 /// sole field is of the found type, suggest such variants. (Issue #42764)
701 fn suggest_compatible_variants(
703 err: &mut Diagnostic,
704 expr: &hir::Expr<'_>,
708 if let ty::Adt(expected_adt, substs) = expected.kind() {
709 if let hir::ExprKind::Field(base, ident) = expr.kind {
710 let base_ty = self.typeck_results.borrow().expr_ty(base);
711 if self.can_eq(self.param_env, base_ty, expected).is_ok()
712 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
714 err.span_suggestion_verbose(
715 expr.span.with_lo(base_span.hi()),
716 format!("consider removing the tuple struct field `{ident}`"),
718 Applicability::MaybeIncorrect,
724 // If the expression is of type () and it's the return expression of a block,
725 // we suggest adding a separate return expression instead.
726 // (To avoid things like suggesting `Ok(while .. { .. })`.)
727 if expr_ty.is_unit() {
728 let mut id = expr.hir_id;
731 // Unroll desugaring, to make sure this works for `for` loops etc.
733 parent = self.tcx.hir().parent_id(id);
734 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
735 if parent_span.find_ancestor_inside(expr.span).is_some() {
736 // The parent node is part of the same span, so is the result of the
737 // same expansion/desugaring and not the 'real' parent node.
745 if let Some(hir::Node::Block(&hir::Block {
746 span: block_span, expr: Some(e), ..
747 })) = self.tcx.hir().find(parent)
750 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
751 let return_suggestions = if self
753 .is_diagnostic_item(sym::Result, expected_adt.did())
756 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
757 vec!["None", "Some(())"]
761 if let Some(indent) =
762 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
764 // Add a semicolon, except after `}`.
766 match self.tcx.sess.source_map().span_to_snippet(span) {
767 Ok(s) if s.ends_with('}') => "",
770 err.span_suggestions(
772 "try adding an expression at the end of the block",
775 .map(|r| format!("{semicolon}\n{indent}{r}")),
776 Applicability::MaybeIncorrect,
785 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
789 variant.fields.len() == 1
791 .filter_map(|variant| {
792 let sole_field = &variant.fields[0];
794 let field_is_local = sole_field.did.is_local();
795 let field_is_accessible =
796 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
797 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
798 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
800 if !field_is_local && !field_is_accessible {
804 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
805 .then(|| " (its field is private, but it's local to this crate and its privacy can be changed)".to_string());
807 let sole_field_ty = sole_field.ty(self.tcx, substs);
808 if self.can_coerce(expr_ty, sole_field_ty) {
810 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
811 // FIXME #56861: DRYer prelude filtering
812 if let Some(path) = variant_path.strip_prefix("std::prelude::")
813 && let Some((_, path)) = path.split_once("::")
815 return Some((path.to_string(), variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy));
817 Some((variant_path, variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy))
824 let suggestions_for = |variant: &_, ctor_kind, field_name| {
825 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
826 Some(ident) => format!("{ident}: "),
827 None => String::new(),
830 let (open, close) = match ctor_kind {
831 Some(CtorKind::Fn) => ("(".to_owned(), ")"),
832 None => (format!(" {{ {field_name}: "), " }"),
834 // unit variants don't have fields
835 Some(CtorKind::Const) => unreachable!(),
838 // Suggest constructor as deep into the block tree as possible.
839 // This fixes https://github.com/rust-lang/rust/issues/101065,
840 // and also just helps make the most minimal suggestions.
842 while let hir::ExprKind::Block(block, _) = &expr.kind
843 && let Some(expr_) = &block.expr
849 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
850 (expr.span.shrink_to_hi(), close.to_owned()),
854 match &compatible_variants[..] {
855 [] => { /* No variants to format */ }
856 [(variant, ctor_kind, field_name, note)] => {
857 // Just a single matching variant.
858 err.multipart_suggestion_verbose(
860 "try wrapping the expression in `{variant}`{note}",
861 note = note.as_deref().unwrap_or("")
863 suggestions_for(&**variant, *ctor_kind, *field_name),
864 Applicability::MaybeIncorrect,
869 // More than one matching variant.
870 err.multipart_suggestions(
872 "try wrapping the expression in a variant of `{}`",
873 self.tcx.def_path_str(expected_adt.did())
875 compatible_variants.into_iter().map(
876 |(variant, ctor_kind, field_name, _)| {
877 suggestions_for(&variant, ctor_kind, field_name)
880 Applicability::MaybeIncorrect,
890 fn suggest_non_zero_new_unwrap(
892 err: &mut Diagnostic,
893 expr: &hir::Expr<'_>,
898 let (adt, unwrap) = match expected.kind() {
899 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
900 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
902 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
906 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
907 ty::Adt(adt, _) => (adt, ".unwrap()"),
912 (sym::NonZeroU8, tcx.types.u8),
913 (sym::NonZeroU16, tcx.types.u16),
914 (sym::NonZeroU32, tcx.types.u32),
915 (sym::NonZeroU64, tcx.types.u64),
916 (sym::NonZeroU128, tcx.types.u128),
917 (sym::NonZeroI8, tcx.types.i8),
918 (sym::NonZeroI16, tcx.types.i16),
919 (sym::NonZeroI32, tcx.types.i32),
920 (sym::NonZeroI64, tcx.types.i64),
921 (sym::NonZeroI128, tcx.types.i128),
924 let Some((s, _)) = map
926 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
927 else { return false; };
929 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
931 err.multipart_suggestion(
932 format!("consider calling `{s}::new`"),
934 (expr.span.shrink_to_lo(), format!("{path}::new(")),
935 (expr.span.shrink_to_hi(), format!("){unwrap}")),
937 Applicability::MaybeIncorrect,
943 pub fn get_conversion_methods(
947 checked_ty: Ty<'tcx>,
949 ) -> Vec<AssocItem> {
950 let methods = self.probe_for_return_type(
952 probe::Mode::MethodCall,
957 self.has_only_self_parameter(m)
960 // This special internal attribute is used to permit
961 // "identity-like" conversion methods to be suggested here.
963 // FIXME (#46459 and #46460): ideally
964 // `std::convert::Into::into` and `std::borrow:ToOwned` would
965 // also be `#[rustc_conversion_suggestion]`, if not for
966 // method-probing false-positives and -negatives (respectively).
968 // FIXME? Other potential candidate methods: `as_ref` and
970 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
977 /// This function checks whether the method is not static and does not accept other parameters than `self`.
978 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
980 ty::AssocKind::Fn => {
981 method.fn_has_self_parameter
982 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
988 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
990 /// Given the following code:
991 /// ```compile_fail,E0308
993 /// fn takes_ref(_: &Foo) {}
994 /// let ref opt = Some(Foo);
996 /// opt.map(|param| takes_ref(param));
998 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
1000 /// It only checks for `Option` and `Result` and won't work with
1001 /// ```ignore (illustrative)
1002 /// opt.map(|param| { takes_ref(param) });
1004 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
1005 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
1009 let hir::def::Res::Local(local_id) = path.res else {
1013 let local_parent = self.tcx.hir().parent_id(local_id);
1014 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
1018 let param_parent = self.tcx.hir().parent_id(*param_hir_id);
1019 let Some(Node::Expr(hir::Expr {
1020 hir_id: expr_hir_id,
1021 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
1023 })) = self.tcx.hir().find(param_parent) else {
1027 let expr_parent = self.tcx.hir().parent_id(*expr_hir_id);
1028 let hir = self.tcx.hir().find(expr_parent);
1029 let closure_params_len = closure_fn_decl.inputs.len();
1031 Some(Node::Expr(hir::Expr {
1032 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
1036 ) = (hir, closure_params_len) else {
1040 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
1041 let name = method_path.ident.name;
1042 let is_as_ref_able = match self_ty.peel_refs().kind() {
1043 ty::Adt(def, _) => {
1044 (self.tcx.is_diagnostic_item(sym::Option, def.did())
1045 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
1046 && (name == sym::map || name == sym::and_then)
1050 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
1051 (true, Ok(src)) => {
1052 let suggestion = format!("as_ref().{}", src);
1053 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
1059 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
1061 expr: &hir::Expr<'_>,
1062 ) -> Option<Symbol> {
1063 let hir = self.tcx.hir();
1064 let local = match expr {
1067 hir::ExprKind::Path(hir::QPath::Resolved(
1070 res: hir::def::Res::Local(_),
1071 segments: [hir::PathSegment { ident, .. }],
1080 match hir.find_parent(expr.hir_id)? {
1081 Node::ExprField(field) => {
1082 if field.ident.name == local.name && field.is_shorthand {
1083 return Some(local.name);
1092 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
1093 pub(crate) fn maybe_get_block_expr(
1095 expr: &hir::Expr<'tcx>,
1096 ) -> Option<&'tcx hir::Expr<'tcx>> {
1098 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
1103 /// Returns whether the given expression is an `else if`.
1104 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
1105 if let hir::ExprKind::If(..) = expr.kind {
1106 let parent_id = self.tcx.hir().parent_id(expr.hir_id);
1107 if let Some(Node::Expr(hir::Expr {
1108 kind: hir::ExprKind::If(_, _, Some(else_expr)),
1110 })) = self.tcx.hir().find(parent_id)
1112 return else_expr.hir_id == expr.hir_id;
1118 /// This function is used to determine potential "simple" improvements or users' errors and
1119 /// provide them useful help. For example:
1121 /// ```compile_fail,E0308
1122 /// fn some_fn(s: &str) {}
1124 /// let x = "hey!".to_owned();
1125 /// some_fn(x); // error
1128 /// No need to find every potential function which could make a coercion to transform a
1129 /// `String` into a `&str` since a `&` would do the trick!
1131 /// In addition of this check, it also checks between references mutability state. If the
1132 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
1136 expr: &hir::Expr<'tcx>,
1137 checked_ty: Ty<'tcx>,
1145 bool, /* suggest `&` or `&mut` type annotation */
1147 let sess = self.sess();
1150 // If the span is from an external macro, there's no suggestion we can make.
1151 if in_external_macro(sess, sp) {
1155 let sm = sess.source_map();
1157 let replace_prefix = |s: &str, old: &str, new: &str| {
1158 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
1161 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
1162 let expr = expr.peel_drop_temps();
1164 match (&expr.kind, expected.kind(), checked_ty.kind()) {
1165 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
1166 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
1167 if let hir::ExprKind::Lit(_) = expr.kind
1168 && let Ok(src) = sm.span_to_snippet(sp)
1169 && replace_prefix(&src, "b\"", "\"").is_some()
1171 let pos = sp.lo() + BytePos(1);
1174 "consider removing the leading `b`".to_string(),
1176 Applicability::MachineApplicable,
1182 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
1183 if let hir::ExprKind::Lit(_) = expr.kind
1184 && let Ok(src) = sm.span_to_snippet(sp)
1185 && replace_prefix(&src, "\"", "b\"").is_some()
1189 "consider adding a leading `b`".to_string(),
1191 Applicability::MachineApplicable,
1199 (_, &ty::Ref(_, _, mutability), _) => {
1200 // Check if it can work when put into a ref. For example:
1203 // fn bar(x: &mut i32) {}
1206 // bar(&x); // error, expected &mut
1208 let ref_ty = match mutability {
1209 hir::Mutability::Mut => {
1210 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1212 hir::Mutability::Not => {
1213 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1216 if self.can_coerce(ref_ty, expected) {
1217 let mut sugg_sp = sp;
1218 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
1220 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
1222 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
1224 let ai = self.tcx.associated_item(did);
1225 ai.trait_container(self.tcx) == Some(clone_trait)
1228 && segment.ident.name == sym::clone
1230 // If this expression had a clone call when suggesting borrowing
1231 // we want to suggest removing it because it'd now be unnecessary.
1232 sugg_sp = receiver.span;
1235 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
1236 let needs_parens = match expr.kind {
1237 // parenthesize if needed (Issue #46756)
1238 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
1239 // parenthesize borrows of range literals (Issue #54505)
1240 _ if is_range_literal(expr) => true,
1244 if let Some(sugg) = self.can_use_as_ref(expr) {
1249 Applicability::MachineApplicable,
1255 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1256 Some(ident) => format!("{ident}: "),
1257 None => String::new(),
1260 if let Some(hir::Node::Expr(hir::Expr {
1261 kind: hir::ExprKind::Assign(..),
1263 })) = self.tcx.hir().find_parent(expr.hir_id)
1265 if mutability.is_mut() {
1266 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
1271 let sugg_expr = if needs_parens { format!("({src})") } else { src };
1274 format!("consider {}borrowing here", mutability.mutably_str()),
1275 format!("{prefix}{}{sugg_expr}", mutability.ref_prefix_str()),
1276 Applicability::MachineApplicable,
1284 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
1286 &ty::Ref(_, checked, _),
1287 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
1288 // We have `&T`, check if what was expected was `T`. If so,
1289 // we may want to suggest removing a `&`.
1290 if sm.is_imported(expr.span) {
1291 // Go through the spans from which this span was expanded,
1292 // and find the one that's pointing inside `sp`.
1294 // E.g. for `&format!("")`, where we want the span to the
1295 // `format!()` invocation instead of its expansion.
1296 if let Some(call_span) =
1297 iter::successors(Some(expr.span), |s| s.parent_callsite())
1298 .find(|&s| sp.contains(s))
1299 && sm.is_span_accessible(call_span)
1302 sp.with_hi(call_span.lo()),
1303 "consider removing the borrow".to_string(),
1305 Applicability::MachineApplicable,
1312 if sp.contains(expr.span)
1313 && sm.is_span_accessible(expr.span)
1316 sp.with_hi(expr.span.lo()),
1317 "consider removing the borrow".to_string(),
1319 Applicability::MachineApplicable,
1327 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
1328 &ty::Ref(_, ty_a, mutbl_a),
1330 if let Some(steps) = self.deref_steps(ty_a, ty_b)
1331 // Only suggest valid if dereferencing needed.
1333 // The pointer type implements `Copy` trait so the suggestion is always valid.
1334 && let Ok(src) = sm.span_to_snippet(sp)
1336 let derefs = "*".repeat(steps);
1337 let old_prefix = mutbl_a.ref_prefix_str();
1338 let new_prefix = mutbl_b.ref_prefix_str().to_owned() + &derefs;
1340 let suggestion = replace_prefix(&src, old_prefix, &new_prefix).map(|_| {
1341 // skip `&` or `&mut ` if both mutabilities are mutable
1342 let lo = sp.lo() + BytePos(min(old_prefix.len(), mutbl_b.ref_prefix_str().len()) as _);
1343 // skip `&` or `&mut `
1344 let hi = sp.lo() + BytePos(old_prefix.len() as _);
1345 let sp = sp.with_lo(lo).with_hi(hi);
1349 format!("{}{derefs}", if mutbl_a != mutbl_b { mutbl_b.prefix_str() } else { "" }),
1350 if mutbl_b <= mutbl_a { Applicability::MachineApplicable } else { Applicability::MaybeIncorrect }
1354 if let Some((span, src, applicability)) = suggestion {
1357 "consider dereferencing".to_string(),
1366 _ if sp == expr.span => {
1367 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
1368 let mut expr = expr.peel_blocks();
1369 let mut prefix_span = expr.span.shrink_to_lo();
1370 let mut remove = String::new();
1372 // Try peeling off any existing `&` and `&mut` to reach our target type
1374 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
1375 // If the expression has `&`, removing it would fix the error
1376 prefix_span = prefix_span.with_hi(inner.span.lo());
1378 remove.push_str(mutbl.ref_prefix_str());
1384 // If we've reached our target type with just removing `&`, then just print now.
1385 if steps == 0 && !remove.trim().is_empty() {
1388 format!("consider removing the `{}`", remove.trim()),
1390 // Do not remove `&&` to get to bool, because it might be something like
1391 // { a } && b, which we have a separate fixup suggestion that is more
1392 // likely correct...
1393 if remove.trim() == "&&" && expected == self.tcx.types.bool {
1394 Applicability::MaybeIncorrect
1396 Applicability::MachineApplicable
1403 // For this suggestion to make sense, the type would need to be `Copy`,
1404 // or we have to be moving out of a `Box<T>`
1405 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1406 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1407 // `steps` layers of boxes, not just one, but this is easier and most likely.
1408 || (checked_ty.is_box() && steps == 1)
1410 let deref_kind = if checked_ty.is_box() {
1411 "unboxing the value"
1412 } else if checked_ty.is_region_ptr() {
1413 "dereferencing the borrow"
1415 "dereferencing the type"
1418 // Suggest removing `&` if we have removed any, otherwise suggest just
1419 // dereferencing the remaining number of steps.
1420 let message = if remove.is_empty() {
1421 format!("consider {deref_kind}")
1424 "consider removing the `{}` and {} instead",
1430 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1431 Some(ident) => format!("{ident}: "),
1432 None => String::new(),
1435 let (span, suggestion) = if self.is_else_if_block(expr) {
1436 // Don't suggest nonsense like `else *if`
1438 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1439 // prefix should be empty here..
1440 (expr.span.shrink_to_lo(), "*".to_string())
1442 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1444 if suggestion.trim().is_empty() {
1452 Applicability::MachineApplicable,
1464 pub fn check_for_cast(
1466 err: &mut Diagnostic,
1467 expr: &hir::Expr<'_>,
1468 checked_ty: Ty<'tcx>,
1469 expected_ty: Ty<'tcx>,
1470 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1472 if self.tcx.sess.source_map().is_imported(expr.span) {
1473 // Ignore if span is from within a macro.
1477 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1481 // If casting this expression to a given numeric type would be appropriate in case of a type
1484 // We want to minimize the amount of casting operations that are suggested, as it can be a
1485 // lossy operation with potentially bad side effects, so we only suggest when encountering
1486 // an expression that indicates that the original type couldn't be directly changed.
1488 // For now, don't suggest casting with `as`.
1489 let can_cast = false;
1491 let mut sugg = vec![];
1493 if let Some(hir::Node::ExprField(field)) = self.tcx.hir().find_parent(expr.hir_id) {
1494 // `expr` is a literal field for a struct, only suggest if appropriate
1495 if field.is_shorthand {
1496 // This is a field literal
1497 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1499 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1504 if let hir::ExprKind::Call(path, args) = &expr.kind
1505 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1506 (&path.kind, args.len())
1507 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1508 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1509 (&base_ty.kind, path_segment.ident.name)
1511 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1525 if base_ty_path.segments.len() == 1 =>
1535 "you can convert {} `{}` to {} `{}`",
1536 checked_ty.kind().article(),
1538 expected_ty.kind().article(),
1541 let cast_msg = format!(
1542 "you can cast {} `{}` to {} `{}`",
1543 checked_ty.kind().article(),
1545 expected_ty.kind().article(),
1548 let lit_msg = format!(
1549 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1552 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1553 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1559 let mut cast_suggestion = sugg.clone();
1560 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1561 let mut into_suggestion = sugg.clone();
1562 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1563 let mut suffix_suggestion = sugg.clone();
1564 suffix_suggestion.push((
1566 (&expected_ty.kind(), &checked_ty.kind()),
1567 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1569 // Remove fractional part from literal, for example `42.0f32` into `42`
1570 let src = src.trim_end_matches(&checked_ty.to_string());
1571 let len = src.split('.').next().unwrap().len();
1572 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1574 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1575 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1577 if expr.precedence().order() < PREC_POSTFIX {
1579 format!("{expected_ty})")
1581 expected_ty.to_string()
1584 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1585 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1587 let is_negative_int =
1588 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1589 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1591 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1593 let suggest_fallible_into_or_lhs_from =
1594 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1595 // If we know the expression the expected type is derived from, we might be able
1596 // to suggest a widening conversion rather than a narrowing one (which may
1597 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1599 // can be given the suggestion "u32::from(x) > y" rather than
1600 // "x > y.try_into().unwrap()".
1601 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1605 .span_to_snippet(expr.span)
1607 .map(|src| (expr, src))
1609 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1610 (lhs_expr_and_src, exp_to_found_is_fallible)
1613 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1615 let suggestion = vec![
1616 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1617 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1621 let msg = format!("{msg} and panic if the converted value doesn't fit");
1622 let mut suggestion = sugg.clone();
1624 expr.span.shrink_to_hi(),
1625 format!("{close_paren}.try_into().unwrap()"),
1629 err.multipart_suggestion_verbose(
1632 Applicability::MachineApplicable,
1636 let suggest_to_change_suffix_or_into =
1637 |err: &mut Diagnostic,
1638 found_to_exp_is_fallible: bool,
1639 exp_to_found_is_fallible: bool| {
1641 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1647 let always_fallible = found_to_exp_is_fallible
1648 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1649 let msg = if literal_is_ty_suffixed(expr) {
1651 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1652 // We now know that converting either the lhs or rhs is fallible. Before we
1653 // suggest a fallible conversion, check if the value can never fit in the
1655 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1658 } else if in_const_context {
1659 // Do not recommend `into` or `try_into` in const contexts.
1661 } else if found_to_exp_is_fallible {
1662 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1666 let suggestion = if literal_is_ty_suffixed(expr) {
1667 suffix_suggestion.clone()
1669 into_suggestion.clone()
1671 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1674 match (&expected_ty.kind(), &checked_ty.kind()) {
1675 (ty::Int(exp), ty::Int(found)) => {
1676 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1678 (Some(exp), Some(found)) if exp < found => (true, false),
1679 (Some(exp), Some(found)) if exp > found => (false, true),
1680 (None, Some(8 | 16)) => (false, true),
1681 (Some(8 | 16), None) => (true, false),
1682 (None, _) | (_, None) => (true, true),
1683 _ => (false, false),
1685 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1688 (ty::Uint(exp), ty::Uint(found)) => {
1689 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1691 (Some(exp), Some(found)) if exp < found => (true, false),
1692 (Some(exp), Some(found)) if exp > found => (false, true),
1693 (None, Some(8 | 16)) => (false, true),
1694 (Some(8 | 16), None) => (true, false),
1695 (None, _) | (_, None) => (true, true),
1696 _ => (false, false),
1698 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1701 (&ty::Int(exp), &ty::Uint(found)) => {
1702 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1704 (Some(exp), Some(found)) if found < exp => (false, true),
1705 (None, Some(8)) => (false, true),
1708 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1711 (&ty::Uint(exp), &ty::Int(found)) => {
1712 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1714 (Some(exp), Some(found)) if found > exp => (true, false),
1715 (Some(8), None) => (true, false),
1718 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1721 (ty::Float(exp), ty::Float(found)) => {
1722 if found.bit_width() < exp.bit_width() {
1723 suggest_to_change_suffix_or_into(err, false, true);
1724 } else if literal_is_ty_suffixed(expr) {
1725 err.multipart_suggestion_verbose(
1728 Applicability::MachineApplicable,
1730 } else if can_cast {
1731 // Missing try_into implementation for `f64` to `f32`
1732 err.multipart_suggestion_verbose(
1733 &format!("{cast_msg}, producing the closest possible value"),
1735 Applicability::MaybeIncorrect, // lossy conversion
1740 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1741 if literal_is_ty_suffixed(expr) {
1742 err.multipart_suggestion_verbose(
1745 Applicability::MachineApplicable,
1747 } else if can_cast {
1748 // Missing try_into implementation for `{float}` to `{integer}`
1749 err.multipart_suggestion_verbose(
1750 &format!("{msg}, rounding the float towards zero"),
1752 Applicability::MaybeIncorrect, // lossy conversion
1757 (ty::Float(exp), ty::Uint(found)) => {
1758 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1759 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1760 err.multipart_suggestion_verbose(
1762 "{msg}, producing the floating point representation of the integer",
1765 Applicability::MachineApplicable,
1767 } else if literal_is_ty_suffixed(expr) {
1768 err.multipart_suggestion_verbose(
1771 Applicability::MachineApplicable,
1774 // Missing try_into implementation for `{integer}` to `{float}`
1775 err.multipart_suggestion_verbose(
1777 "{cast_msg}, producing the floating point representation of the integer, \
1778 rounded if necessary",
1781 Applicability::MaybeIncorrect, // lossy conversion
1786 (ty::Float(exp), ty::Int(found)) => {
1787 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1788 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1789 err.multipart_suggestion_verbose(
1791 "{}, producing the floating point representation of the integer",
1795 Applicability::MachineApplicable,
1797 } else if literal_is_ty_suffixed(expr) {
1798 err.multipart_suggestion_verbose(
1801 Applicability::MachineApplicable,
1804 // Missing try_into implementation for `{integer}` to `{float}`
1805 err.multipart_suggestion_verbose(
1807 "{}, producing the floating point representation of the integer, \
1808 rounded if necessary",
1812 Applicability::MaybeIncorrect, // lossy conversion
1818 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1819 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1822 err.multipart_suggestion_verbose(
1823 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1825 Applicability::MachineApplicable,
1833 /// Identify when the user has written `foo..bar()` instead of `foo.bar()`.
1834 pub fn check_for_range_as_method_call(
1836 err: &mut Diagnostic,
1837 expr: &hir::Expr<'tcx>,
1838 checked_ty: Ty<'tcx>,
1839 expected_ty: Ty<'tcx>,
1841 if !hir::is_range_literal(expr) {
1844 let hir::ExprKind::Struct(
1845 hir::QPath::LangItem(LangItem::Range, ..),
1848 ) = expr.kind else { return; };
1849 let parent = self.tcx.hir().parent_id(expr.hir_id);
1850 if let Some(hir::Node::ExprField(_)) = self.tcx.hir().find(parent) {
1851 // Ignore `Foo { field: a..Default::default() }`
1854 let mut expr = end.expr;
1855 let mut expectation = Some(expected_ty);
1856 while let hir::ExprKind::MethodCall(_, rcvr, ..) = expr.kind {
1857 // Getting to the root receiver and asserting it is a fn call let's us ignore cases in
1858 // `src/test/ui/methods/issues/issue-90315.stderr`.
1860 // If we have more than one layer of calls, then the expected ty
1861 // cannot guide the method probe.
1864 let hir::ExprKind::Call(method_name, _) = expr.kind else { return; };
1865 let ty::Adt(adt, _) = checked_ty.kind() else { return; };
1866 if self.tcx.lang_items().range_struct() != Some(adt.did()) {
1869 if let ty::Adt(adt, _) = expected_ty.kind()
1870 && self.tcx.lang_items().range_struct() == Some(adt.did())
1874 // Check if start has method named end.
1875 let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = method_name.kind else { return; };
1876 let [hir::PathSegment { ident, .. }] = p.segments else { return; };
1877 let self_ty = self.typeck_results.borrow().expr_ty(start.expr);
1878 let Ok(_pick) = self.lookup_probe_for_diagnostic(
1882 probe::ProbeScope::AllTraits,
1886 let mut span = start.expr.span.between(end.expr.span);
1887 if span.lo() + BytePos(2) == span.hi() {
1888 // There's no space between the start, the range op and the end, suggest removal which
1889 // will be more noticeable than the replacement of `..` with `.`.
1890 span = span.with_lo(span.lo() + BytePos(1));
1893 err.span_suggestion_verbose(
1895 "you likely meant to write a method call instead of a range",
1897 Applicability::MachineApplicable,
1901 /// Identify when the type error is because `()` is found in a binding that was assigned a
1902 /// block without a tail expression.
1903 fn check_for_binding_assigned_block_without_tail_expression(
1905 err: &mut Diagnostic,
1906 expr: &hir::Expr<'_>,
1907 checked_ty: Ty<'tcx>,
1908 expected_ty: Ty<'tcx>,
1910 if !checked_ty.is_unit() {
1913 let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = expr.kind else { return; };
1914 let hir::def::Res::Local(hir_id) = path.res else { return; };
1915 let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(hir_id) else {
1918 let Some(hir::Node::Local(hir::Local {
1922 })) = self.tcx.hir().find_parent(pat.hir_id) else { return; };
1923 let hir::ExprKind::Block(block, None) = init.kind else { return; };
1924 if block.expr.is_some() {
1927 let [.., stmt] = block.stmts else {
1928 err.span_label(block.span, "this empty block is missing a tail expression");
1931 let hir::StmtKind::Semi(tail_expr) = stmt.kind else { return; };
1932 let Some(ty) = self.node_ty_opt(tail_expr.hir_id) else { return; };
1933 if self.can_eq(self.param_env, expected_ty, ty).is_ok() {
1934 err.span_suggestion_short(
1935 stmt.span.with_lo(tail_expr.span.hi()),
1936 "remove this semicolon",
1938 Applicability::MachineApplicable,
1941 err.span_label(block.span, "this block is missing a tail expression");