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);
88 self.check_wrong_return_type_due_to_generic_arg(err, expr, expr_ty);
91 /// Requires that the two types unify, and prints an error message if
93 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
94 if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) {
99 pub fn demand_suptype_diag(
104 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
105 self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
108 #[instrument(skip(self), level = "debug")]
109 pub fn demand_suptype_with_origin(
111 cause: &ObligationCause<'tcx>,
114 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
115 match self.at(cause, self.param_env).sup(expected, actual) {
116 Ok(InferOk { obligations, value: () }) => {
117 self.register_predicates(obligations);
120 Err(e) => Some(self.err_ctxt().report_mismatched_types(&cause, expected, actual, e)),
124 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
125 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
130 pub fn demand_eqtype_diag(
135 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
136 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
139 pub fn demand_eqtype_with_origin(
141 cause: &ObligationCause<'tcx>,
144 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
145 match self.at(cause, self.param_env).eq(expected, actual) {
146 Ok(InferOk { obligations, value: () }) => {
147 self.register_predicates(obligations);
150 Err(e) => Some(self.err_ctxt().report_mismatched_types(cause, expected, actual, e)),
154 pub fn demand_coerce(
156 expr: &hir::Expr<'tcx>,
157 checked_ty: Ty<'tcx>,
159 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
160 allow_two_phase: AllowTwoPhase,
163 self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase);
164 if let Some(mut err) = err {
170 /// Checks that the type of `expr` can be coerced to `expected`.
172 /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!`
173 /// will be permitted if the diverges flag is currently "always".
174 #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))]
175 pub fn demand_coerce_diag(
177 expr: &hir::Expr<'tcx>,
178 checked_ty: Ty<'tcx>,
180 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
181 allow_two_phase: AllowTwoPhase,
182 ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
183 let expected = self.resolve_vars_with_obligations(expected);
185 let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) {
186 Ok(ty) => return (ty, None),
190 self.set_tainted_by_errors(self.tcx.sess.delay_span_bug(
192 "`TypeError` when attempting coercion but no error emitted",
194 let expr = expr.peel_drop_temps();
195 let cause = self.misc(expr.span);
196 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
197 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e);
199 let is_insufficiently_polymorphic =
200 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
202 // FIXME(#73154): For now, we do leak check when coercing function
203 // pointers in typeck, instead of only during borrowck. This can lead
204 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
205 if !is_insufficiently_polymorphic {
206 self.emit_coerce_suggestions(
216 (expected, Some(err))
219 pub fn point_at_expr_source_of_inferred_type(
221 err: &mut Diagnostic,
222 expr: &hir::Expr<'_>,
226 let map = self.tcx.hir();
228 let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = expr.kind else { return false; };
229 let [hir::PathSegment { ident, args: None, .. }] = p.segments else { return false; };
230 let hir::def::Res::Local(hir_id) = p.res else { return false; };
231 let Some(hir::Node::Pat(pat)) = map.find(hir_id) else { return false; };
232 let Some(hir::Node::Local(hir::Local {
236 })) = map.find_parent(pat.hir_id) else { return false; };
237 let Some(ty) = self.node_ty_opt(init.hir_id) else { return false; };
238 if ty.is_closure() || init.span.overlaps(expr.span) || pat.span.from_expansion() {
242 // Locate all the usages of the relevant binding.
243 struct FindExprs<'hir> {
245 uses: Vec<&'hir hir::Expr<'hir>>,
247 impl<'v> Visitor<'v> for FindExprs<'v> {
248 fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) {
249 if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = ex.kind
250 && let hir::def::Res::Local(hir_id) = path.res
251 && hir_id == self.hir_id
255 hir::intravisit::walk_expr(self, ex);
259 let mut expr_finder = FindExprs { hir_id, uses: vec![] };
260 let id = map.get_parent_item(hir_id);
261 let hir_id: hir::HirId = id.into();
263 let Some(node) = map.find(hir_id) else { return false; };
264 let Some(body_id) = node.body_id() else { return false; };
265 let body = map.body(body_id);
266 expr_finder.visit_expr(body.value);
267 // Hack to make equality checks on types with inference variables and regions useful.
268 let mut eraser = BottomUpFolder {
270 lt_op: |_| self.tcx.lifetimes.re_erased,
272 ty_op: |t| match *t.kind() {
273 ty::Infer(ty::TyVar(vid)) => self.tcx.mk_ty_infer(ty::TyVar(self.root_var(vid))),
274 ty::Infer(ty::IntVar(_)) => {
275 self.tcx.mk_ty_infer(ty::IntVar(ty::IntVid { index: 0 }))
277 ty::Infer(ty::FloatVar(_)) => {
278 self.tcx.mk_ty_infer(ty::FloatVar(ty::FloatVid { index: 0 }))
283 let mut prev = eraser.fold_ty(ty);
284 let mut prev_span = None;
286 for binding in expr_finder.uses {
287 // In every expression where the binding is referenced, we will look at that
288 // expression's type and see if it is where the incorrect found type was fully
289 // "materialized" and point at it. We will also try to provide a suggestion there.
290 if let Some(hir::Node::Expr(expr)
291 | hir::Node::Stmt(hir::Stmt {
292 kind: hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr),
294 })) = &map.find_parent(binding.hir_id)
295 && let hir::ExprKind::MethodCall(segment, rcvr, args, _span) = expr.kind
296 && rcvr.hir_id == binding.hir_id
297 && let Some(def_id) = self.typeck_results.borrow().type_dependent_def_id(expr.hir_id)
299 // We special case methods, because they can influence inference through the
300 // call's arguments and we can provide a more explicit span.
301 let sig = self.tcx.fn_sig(def_id);
302 let def_self_ty = sig.input(0).skip_binder();
303 let rcvr_ty = self.node_ty(rcvr.hir_id);
304 // Get the evaluated type *after* calling the method call, so that the influence
305 // of the arguments can be reflected in the receiver type. The receiver
306 // expression has the type *before* theis analysis is done.
307 let ty = match self.lookup_probe_for_diagnostic(
311 probe::ProbeScope::TraitsInScope,
314 Ok(pick) => pick.self_ty,
317 // Remove one layer of references to account for `&mut self` and
318 // `&self`, so that we can compare it against the binding.
319 let (ty, def_self_ty) = match (ty.kind(), def_self_ty.kind()) {
320 (ty::Ref(_, ty, a), ty::Ref(_, self_ty, b)) if a == b => (*ty, *self_ty),
321 _ => (ty, def_self_ty),
323 let mut param_args = FxHashMap::default();
324 let mut param_expected = FxHashMap::default();
325 let mut param_found = FxHashMap::default();
326 if self.can_eq(self.param_env, ty, found).is_ok() {
327 // We only point at the first place where the found type was inferred.
328 for (i, param_ty) in sig.inputs().skip_binder().iter().skip(1).enumerate() {
329 if def_self_ty.contains(*param_ty) && let ty::Param(_) = param_ty.kind() {
330 // We found an argument that references a type parameter in `Self`,
331 // so we assume that this is the argument that caused the found
332 // type, which we know already because of `can_eq` above was first
333 // inferred in this method call.
335 let arg_ty = self.node_ty(arg.hir_id);
339 "this is of type `{arg_ty}`, which causes `{ident}` to be \
343 param_args.insert(param_ty, (arg, arg_ty));
348 // Here we find, for a type param `T`, the type that `T` is in the current
349 // method call *and* in the original expected type. That way, we can see if we
350 // can give any structured suggestion for the function argument.
351 let mut c = CollectAllMismatches {
353 param_env: self.param_env,
356 let _ = c.relate(def_self_ty, ty);
357 for error in c.errors {
358 if let TypeError::Sorts(error) = error {
359 param_found.insert(error.expected, error.found);
363 let _ = c.relate(def_self_ty, expected);
364 for error in c.errors {
365 if let TypeError::Sorts(error) = error {
366 param_expected.insert(error.expected, error.found);
369 for (param, (arg, arg_ty)) in param_args.iter() {
370 let Some(expected) = param_expected.get(param) else { continue; };
371 let Some(found) = param_found.get(param) else { continue; };
372 if self.can_eq(self.param_env, *arg_ty, *found).is_err() { continue; }
373 self.emit_coerce_suggestions(err, arg, *found, *expected, None, None);
376 let ty = eraser.fold_ty(ty);
377 if ty.references_error() {
381 && param_args.is_empty()
382 && self.can_eq(self.param_env, ty, found).is_ok()
384 // We only point at the first place where the found type was inferred.
387 with_forced_trimmed_paths!(format!(
388 "here the type of `{ident}` is inferred to be `{ty}`",
392 } else if !param_args.is_empty() {
397 let ty = eraser.fold_ty(self.node_ty(binding.hir_id));
398 if ty.references_error() {
402 && let Some(span) = prev_span
403 && self.can_eq(self.param_env, ty, found).is_ok()
405 // We only point at the first place where the found type was inferred.
406 // We use the *previous* span because if the type is known *here* it means
407 // it was *evaluated earlier*. We don't do this for method calls because we
408 // evaluate the method's self type eagerly, but not in any other case.
411 with_forced_trimmed_paths!(format!(
412 "here the type of `{ident}` is inferred to be `{ty}`",
419 if binding.hir_id == expr.hir_id {
420 // Do not look at expressions that come after the expression we were originally
421 // evaluating and had a type error.
424 prev_span = Some(binding.span);
429 fn annotate_expected_due_to_let_ty(
431 err: &mut Diagnostic,
432 expr: &hir::Expr<'_>,
433 error: Option<TypeError<'tcx>>,
435 let parent = self.tcx.hir().parent_id(expr.hir_id);
436 match (self.tcx.hir().find(parent), error) {
437 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
438 if init.hir_id == expr.hir_id =>
440 // Point at `let` assignment type.
441 err.span_label(ty.span, "expected due to this");
444 Some(hir::Node::Expr(hir::Expr {
445 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
447 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
448 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
449 // We ignore closures explicitly because we already point at them elsewhere.
450 // Point at the assigned-to binding.
451 let mut primary_span = lhs.span;
452 let mut secondary_span = lhs.span;
453 let mut post_message = "";
455 hir::ExprKind::Path(hir::QPath::Resolved(
460 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
466 if let Some(hir::Node::Item(hir::Item {
468 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
470 })) = self.tcx.hir().get_if_local(*def_id)
472 primary_span = ty.span;
473 secondary_span = ident.span;
474 post_message = " type";
477 hir::ExprKind::Path(hir::QPath::Resolved(
479 hir::Path { res: hir::def::Res::Local(hir_id), .. },
481 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
482 primary_span = pat.span;
483 secondary_span = pat.span;
484 match self.tcx.hir().find_parent(pat.hir_id) {
485 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
486 primary_span = ty.span;
487 post_message = " type";
489 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
490 primary_span = init.span;
491 post_message = " value";
493 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
494 primary_span = *ty_span;
495 post_message = " parameter type";
504 if primary_span != secondary_span
509 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
511 // We are pointing at the binding's type or initializer value, but it's pattern
512 // is in a different line, so we point at both.
513 err.span_label(secondary_span, "expected due to the type of this binding");
514 err.span_label(primary_span, &format!("expected due to this{post_message}"));
515 } else if post_message == "" {
516 // We are pointing at either the assignment lhs or the binding def pattern.
517 err.span_label(primary_span, "expected due to the type of this binding");
519 // We are pointing at the binding's type or initializer value.
520 err.span_label(primary_span, &format!("expected due to this{post_message}"));
523 if !lhs.is_syntactic_place_expr() {
524 // We already emitted E0070 "invalid left-hand side of assignment", so we
526 err.downgrade_to_delayed_bug();
530 Some(hir::Node::Expr(hir::Expr {
531 kind: hir::ExprKind::Binary(_, lhs, rhs), ..
533 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
534 ) if rhs.hir_id == expr.hir_id
535 && self.typeck_results.borrow().expr_ty_adjusted_opt(lhs) == Some(expected) =>
537 err.span_label(lhs.span, &format!("expected because this is `{expected}`"));
543 fn annotate_alternative_method_deref(
545 err: &mut Diagnostic,
546 expr: &hir::Expr<'_>,
547 error: Option<TypeError<'tcx>>,
549 let parent = self.tcx.hir().parent_id(expr.hir_id);
550 let Some(TypeError::Sorts(ExpectedFound { expected, .. })) = error else {return;};
551 let Some(hir::Node::Expr(hir::Expr {
552 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
553 })) = self.tcx.hir().find(parent) else {return; };
554 if rhs.hir_id != expr.hir_id || expected.is_closure() {
557 let hir::ExprKind::Unary(hir::UnOp::Deref, deref) = lhs.kind else { return; };
558 let hir::ExprKind::MethodCall(path, base, args, _) = deref.kind else { return; };
559 let Some(self_ty) = self.typeck_results.borrow().expr_ty_adjusted_opt(base) else { return; };
562 .lookup_probe_for_diagnostic(
566 probe::ProbeScope::TraitsInScope,
571 let in_scope_methods = self.probe_for_name_many(
572 probe::Mode::MethodCall,
575 probe::IsSuggestion(true),
578 probe::ProbeScope::TraitsInScope,
580 let other_methods_in_scope: Vec<_> =
581 in_scope_methods.iter().filter(|c| c.item.def_id != pick.item.def_id).collect();
583 let all_methods = self.probe_for_name_many(
584 probe::Mode::MethodCall,
587 probe::IsSuggestion(true),
590 probe::ProbeScope::AllTraits,
592 let suggestions: Vec<_> = all_methods
594 .filter(|c| c.item.def_id != pick.item.def_id)
597 let substs = ty::InternalSubsts::for_item(self.tcx, m.def_id, |param, _| {
598 self.var_for_def(deref.span, param)
602 deref.span.until(base.span),
605 with_no_trimmed_paths!(
606 self.tcx.def_path_str_with_substs(m.def_id, substs,)
608 match self.tcx.fn_sig(m.def_id).input(0).skip_binder().kind() {
609 ty::Ref(_, _, hir::Mutability::Mut) => "&mut ",
610 ty::Ref(_, _, _) => "&",
616 [] => (base.span.shrink_to_hi().with_hi(deref.span.hi()), ")".to_string()),
617 [first, ..] => (base.span.between(first.span), ", ".to_string()),
622 if suggestions.is_empty() {
625 let mut path_span: MultiSpan = path.ident.span.into();
626 path_span.push_span_label(
628 with_no_trimmed_paths!(format!(
630 self.tcx.def_path_str(pick.item.def_id),
633 let container_id = pick.item.container_id(self.tcx);
634 let container = with_no_trimmed_paths!(self.tcx.def_path_str(container_id));
635 for def_id in pick.import_ids {
636 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
637 path_span.push_span_label(
638 self.tcx.hir().span(hir_id),
639 format!("`{container}` imported here"),
642 let tail = with_no_trimmed_paths!(match &other_methods_in_scope[..] {
644 [candidate] => format!(
645 "the method of the same name on {} `{}`",
646 match candidate.kind {
647 probe::CandidateKind::InherentImplCandidate(..) => "the inherent impl for",
650 self.tcx.def_path_str(candidate.item.container_id(self.tcx))
652 [.., last] if other_methods_in_scope.len() < 5 => {
654 "the methods of the same name on {} and `{}`",
655 other_methods_in_scope[..other_methods_in_scope.len() - 1]
659 self.tcx.def_path_str(c.item.container_id(self.tcx))
661 .collect::<Vec<String>>()
663 self.tcx.def_path_str(last.item.container_id(self.tcx))
667 "the methods of the same name on {} other traits",
668 other_methods_in_scope.len()
674 "the `{}` call is resolved to the method in `{container}`, shadowing {tail}",
678 if suggestions.len() > other_methods_in_scope.len() {
680 "additionally, there are {} other available methods that aren't in scope",
681 suggestions.len() - other_methods_in_scope.len()
684 err.multipart_suggestions(
686 "you might have meant to call {}; you can use the fully-qualified path to call {} \
688 if suggestions.len() == 1 {
691 "one of the other methods"
693 if suggestions.len() == 1 { "it" } else { "one of them" },
696 Applicability::MaybeIncorrect,
700 /// If the expected type is an enum (Issue #55250) with any variants whose
701 /// sole field is of the found type, suggest such variants. (Issue #42764)
702 fn suggest_compatible_variants(
704 err: &mut Diagnostic,
705 expr: &hir::Expr<'_>,
709 if let ty::Adt(expected_adt, substs) = expected.kind() {
710 if let hir::ExprKind::Field(base, ident) = expr.kind {
711 let base_ty = self.typeck_results.borrow().expr_ty(base);
712 if self.can_eq(self.param_env, base_ty, expected).is_ok()
713 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
715 err.span_suggestion_verbose(
716 expr.span.with_lo(base_span.hi()),
717 format!("consider removing the tuple struct field `{ident}`"),
719 Applicability::MaybeIncorrect,
725 // If the expression is of type () and it's the return expression of a block,
726 // we suggest adding a separate return expression instead.
727 // (To avoid things like suggesting `Ok(while .. { .. })`.)
728 if expr_ty.is_unit() {
729 let mut id = expr.hir_id;
732 // Unroll desugaring, to make sure this works for `for` loops etc.
734 parent = self.tcx.hir().parent_id(id);
735 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
736 if parent_span.find_ancestor_inside(expr.span).is_some() {
737 // The parent node is part of the same span, so is the result of the
738 // same expansion/desugaring and not the 'real' parent node.
746 if let Some(hir::Node::Block(&hir::Block {
747 span: block_span, expr: Some(e), ..
748 })) = self.tcx.hir().find(parent)
751 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
752 let return_suggestions = if self
754 .is_diagnostic_item(sym::Result, expected_adt.did())
757 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
758 vec!["None", "Some(())"]
762 if let Some(indent) =
763 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
765 // Add a semicolon, except after `}`.
767 match self.tcx.sess.source_map().span_to_snippet(span) {
768 Ok(s) if s.ends_with('}') => "",
771 err.span_suggestions(
773 "try adding an expression at the end of the block",
776 .map(|r| format!("{semicolon}\n{indent}{r}")),
777 Applicability::MaybeIncorrect,
786 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
790 variant.fields.len() == 1
792 .filter_map(|variant| {
793 let sole_field = &variant.fields[0];
795 let field_is_local = sole_field.did.is_local();
796 let field_is_accessible =
797 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
798 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
799 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
801 if !field_is_local && !field_is_accessible {
805 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
806 .then(|| " (its field is private, but it's local to this crate and its privacy can be changed)".to_string());
808 let sole_field_ty = sole_field.ty(self.tcx, substs);
809 if self.can_coerce(expr_ty, sole_field_ty) {
811 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
812 // FIXME #56861: DRYer prelude filtering
813 if let Some(path) = variant_path.strip_prefix("std::prelude::")
814 && let Some((_, path)) = path.split_once("::")
816 return Some((path.to_string(), variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy));
818 Some((variant_path, variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy))
825 let suggestions_for = |variant: &_, ctor_kind, field_name| {
826 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
827 Some(ident) => format!("{ident}: "),
828 None => String::new(),
831 let (open, close) = match ctor_kind {
832 Some(CtorKind::Fn) => ("(".to_owned(), ")"),
833 None => (format!(" {{ {field_name}: "), " }"),
835 // unit variants don't have fields
836 Some(CtorKind::Const) => unreachable!(),
839 // Suggest constructor as deep into the block tree as possible.
840 // This fixes https://github.com/rust-lang/rust/issues/101065,
841 // and also just helps make the most minimal suggestions.
843 while let hir::ExprKind::Block(block, _) = &expr.kind
844 && let Some(expr_) = &block.expr
850 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
851 (expr.span.shrink_to_hi(), close.to_owned()),
855 match &compatible_variants[..] {
856 [] => { /* No variants to format */ }
857 [(variant, ctor_kind, field_name, note)] => {
858 // Just a single matching variant.
859 err.multipart_suggestion_verbose(
861 "try wrapping the expression in `{variant}`{note}",
862 note = note.as_deref().unwrap_or("")
864 suggestions_for(&**variant, *ctor_kind, *field_name),
865 Applicability::MaybeIncorrect,
870 // More than one matching variant.
871 err.multipart_suggestions(
873 "try wrapping the expression in a variant of `{}`",
874 self.tcx.def_path_str(expected_adt.did())
876 compatible_variants.into_iter().map(
877 |(variant, ctor_kind, field_name, _)| {
878 suggestions_for(&variant, ctor_kind, field_name)
881 Applicability::MaybeIncorrect,
891 fn suggest_non_zero_new_unwrap(
893 err: &mut Diagnostic,
894 expr: &hir::Expr<'_>,
899 let (adt, unwrap) = match expected.kind() {
900 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
901 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
903 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
907 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
908 ty::Adt(adt, _) => (adt, ".unwrap()"),
913 (sym::NonZeroU8, tcx.types.u8),
914 (sym::NonZeroU16, tcx.types.u16),
915 (sym::NonZeroU32, tcx.types.u32),
916 (sym::NonZeroU64, tcx.types.u64),
917 (sym::NonZeroU128, tcx.types.u128),
918 (sym::NonZeroI8, tcx.types.i8),
919 (sym::NonZeroI16, tcx.types.i16),
920 (sym::NonZeroI32, tcx.types.i32),
921 (sym::NonZeroI64, tcx.types.i64),
922 (sym::NonZeroI128, tcx.types.i128),
925 let Some((s, _)) = map
927 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
928 else { return false; };
930 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
932 err.multipart_suggestion(
933 format!("consider calling `{s}::new`"),
935 (expr.span.shrink_to_lo(), format!("{path}::new(")),
936 (expr.span.shrink_to_hi(), format!("){unwrap}")),
938 Applicability::MaybeIncorrect,
944 pub fn get_conversion_methods(
948 checked_ty: Ty<'tcx>,
950 ) -> Vec<AssocItem> {
951 let methods = self.probe_for_return_type(
953 probe::Mode::MethodCall,
958 self.has_only_self_parameter(m)
961 // This special internal attribute is used to permit
962 // "identity-like" conversion methods to be suggested here.
964 // FIXME (#46459 and #46460): ideally
965 // `std::convert::Into::into` and `std::borrow:ToOwned` would
966 // also be `#[rustc_conversion_suggestion]`, if not for
967 // method-probing false-positives and -negatives (respectively).
969 // FIXME? Other potential candidate methods: `as_ref` and
971 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
978 /// This function checks whether the method is not static and does not accept other parameters than `self`.
979 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
981 ty::AssocKind::Fn => {
982 method.fn_has_self_parameter
983 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
989 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
991 /// Given the following code:
992 /// ```compile_fail,E0308
994 /// fn takes_ref(_: &Foo) {}
995 /// let ref opt = Some(Foo);
997 /// opt.map(|param| takes_ref(param));
999 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
1001 /// It only checks for `Option` and `Result` and won't work with
1002 /// ```ignore (illustrative)
1003 /// opt.map(|param| { takes_ref(param) });
1005 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
1006 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
1010 let hir::def::Res::Local(local_id) = path.res else {
1014 let local_parent = self.tcx.hir().parent_id(local_id);
1015 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
1019 let param_parent = self.tcx.hir().parent_id(*param_hir_id);
1020 let Some(Node::Expr(hir::Expr {
1021 hir_id: expr_hir_id,
1022 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
1024 })) = self.tcx.hir().find(param_parent) else {
1028 let expr_parent = self.tcx.hir().parent_id(*expr_hir_id);
1029 let hir = self.tcx.hir().find(expr_parent);
1030 let closure_params_len = closure_fn_decl.inputs.len();
1032 Some(Node::Expr(hir::Expr {
1033 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
1037 ) = (hir, closure_params_len) else {
1041 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
1042 let name = method_path.ident.name;
1043 let is_as_ref_able = match self_ty.peel_refs().kind() {
1044 ty::Adt(def, _) => {
1045 (self.tcx.is_diagnostic_item(sym::Option, def.did())
1046 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
1047 && (name == sym::map || name == sym::and_then)
1051 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
1052 (true, Ok(src)) => {
1053 let suggestion = format!("as_ref().{}", src);
1054 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
1060 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
1062 expr: &hir::Expr<'_>,
1063 ) -> Option<Symbol> {
1064 let hir = self.tcx.hir();
1065 let local = match expr {
1068 hir::ExprKind::Path(hir::QPath::Resolved(
1071 res: hir::def::Res::Local(_),
1072 segments: [hir::PathSegment { ident, .. }],
1081 match hir.find_parent(expr.hir_id)? {
1082 Node::ExprField(field) => {
1083 if field.ident.name == local.name && field.is_shorthand {
1084 return Some(local.name);
1093 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
1094 pub(crate) fn maybe_get_block_expr(
1096 expr: &hir::Expr<'tcx>,
1097 ) -> Option<&'tcx hir::Expr<'tcx>> {
1099 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
1104 /// Returns whether the given expression is an `else if`.
1105 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
1106 if let hir::ExprKind::If(..) = expr.kind {
1107 let parent_id = self.tcx.hir().parent_id(expr.hir_id);
1108 if let Some(Node::Expr(hir::Expr {
1109 kind: hir::ExprKind::If(_, _, Some(else_expr)),
1111 })) = self.tcx.hir().find(parent_id)
1113 return else_expr.hir_id == expr.hir_id;
1119 /// This function is used to determine potential "simple" improvements or users' errors and
1120 /// provide them useful help. For example:
1122 /// ```compile_fail,E0308
1123 /// fn some_fn(s: &str) {}
1125 /// let x = "hey!".to_owned();
1126 /// some_fn(x); // error
1129 /// No need to find every potential function which could make a coercion to transform a
1130 /// `String` into a `&str` since a `&` would do the trick!
1132 /// In addition of this check, it also checks between references mutability state. If the
1133 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
1137 expr: &hir::Expr<'tcx>,
1138 checked_ty: Ty<'tcx>,
1146 bool, /* suggest `&` or `&mut` type annotation */
1148 let sess = self.sess();
1151 // If the span is from an external macro, there's no suggestion we can make.
1152 if in_external_macro(sess, sp) {
1156 let sm = sess.source_map();
1158 let replace_prefix = |s: &str, old: &str, new: &str| {
1159 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
1162 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
1163 let expr = expr.peel_drop_temps();
1165 match (&expr.kind, expected.kind(), checked_ty.kind()) {
1166 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
1167 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
1168 if let hir::ExprKind::Lit(_) = expr.kind
1169 && let Ok(src) = sm.span_to_snippet(sp)
1170 && replace_prefix(&src, "b\"", "\"").is_some()
1172 let pos = sp.lo() + BytePos(1);
1175 "consider removing the leading `b`".to_string(),
1177 Applicability::MachineApplicable,
1183 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
1184 if let hir::ExprKind::Lit(_) = expr.kind
1185 && let Ok(src) = sm.span_to_snippet(sp)
1186 && replace_prefix(&src, "\"", "b\"").is_some()
1190 "consider adding a leading `b`".to_string(),
1192 Applicability::MachineApplicable,
1200 (_, &ty::Ref(_, _, mutability), _) => {
1201 // Check if it can work when put into a ref. For example:
1204 // fn bar(x: &mut i32) {}
1207 // bar(&x); // error, expected &mut
1209 let ref_ty = match mutability {
1210 hir::Mutability::Mut => {
1211 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1213 hir::Mutability::Not => {
1214 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
1217 if self.can_coerce(ref_ty, expected) {
1218 let mut sugg_sp = sp;
1219 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
1221 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
1223 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
1225 let ai = self.tcx.associated_item(did);
1226 ai.trait_container(self.tcx) == Some(clone_trait)
1229 && segment.ident.name == sym::clone
1231 // If this expression had a clone call when suggesting borrowing
1232 // we want to suggest removing it because it'd now be unnecessary.
1233 sugg_sp = receiver.span;
1236 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
1237 let needs_parens = match expr.kind {
1238 // parenthesize if needed (Issue #46756)
1239 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
1240 // parenthesize borrows of range literals (Issue #54505)
1241 _ if is_range_literal(expr) => true,
1245 if let Some(sugg) = self.can_use_as_ref(expr) {
1250 Applicability::MachineApplicable,
1256 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1257 Some(ident) => format!("{ident}: "),
1258 None => String::new(),
1261 if let Some(hir::Node::Expr(hir::Expr {
1262 kind: hir::ExprKind::Assign(..),
1264 })) = self.tcx.hir().find_parent(expr.hir_id)
1266 if mutability.is_mut() {
1267 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
1272 let sugg_expr = if needs_parens { format!("({src})") } else { src };
1275 format!("consider {}borrowing here", mutability.mutably_str()),
1276 format!("{prefix}{}{sugg_expr}", mutability.ref_prefix_str()),
1277 Applicability::MachineApplicable,
1285 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
1287 &ty::Ref(_, checked, _),
1288 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
1289 // We have `&T`, check if what was expected was `T`. If so,
1290 // we may want to suggest removing a `&`.
1291 if sm.is_imported(expr.span) {
1292 // Go through the spans from which this span was expanded,
1293 // and find the one that's pointing inside `sp`.
1295 // E.g. for `&format!("")`, where we want the span to the
1296 // `format!()` invocation instead of its expansion.
1297 if let Some(call_span) =
1298 iter::successors(Some(expr.span), |s| s.parent_callsite())
1299 .find(|&s| sp.contains(s))
1300 && sm.is_span_accessible(call_span)
1303 sp.with_hi(call_span.lo()),
1304 "consider removing the borrow".to_string(),
1306 Applicability::MachineApplicable,
1313 if sp.contains(expr.span)
1314 && sm.is_span_accessible(expr.span)
1317 sp.with_hi(expr.span.lo()),
1318 "consider removing the borrow".to_string(),
1320 Applicability::MachineApplicable,
1328 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
1329 &ty::Ref(_, ty_a, mutbl_a),
1331 if let Some(steps) = self.deref_steps(ty_a, ty_b)
1332 // Only suggest valid if dereferencing needed.
1334 // The pointer type implements `Copy` trait so the suggestion is always valid.
1335 && let Ok(src) = sm.span_to_snippet(sp)
1337 let derefs = "*".repeat(steps);
1338 let old_prefix = mutbl_a.ref_prefix_str();
1339 let new_prefix = mutbl_b.ref_prefix_str().to_owned() + &derefs;
1341 let suggestion = replace_prefix(&src, old_prefix, &new_prefix).map(|_| {
1342 // skip `&` or `&mut ` if both mutabilities are mutable
1343 let lo = sp.lo() + BytePos(min(old_prefix.len(), mutbl_b.ref_prefix_str().len()) as _);
1344 // skip `&` or `&mut `
1345 let hi = sp.lo() + BytePos(old_prefix.len() as _);
1346 let sp = sp.with_lo(lo).with_hi(hi);
1350 format!("{}{derefs}", if mutbl_a != mutbl_b { mutbl_b.prefix_str() } else { "" }),
1351 if mutbl_b <= mutbl_a { Applicability::MachineApplicable } else { Applicability::MaybeIncorrect }
1355 if let Some((span, src, applicability)) = suggestion {
1358 "consider dereferencing".to_string(),
1367 _ if sp == expr.span => {
1368 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
1369 let mut expr = expr.peel_blocks();
1370 let mut prefix_span = expr.span.shrink_to_lo();
1371 let mut remove = String::new();
1373 // Try peeling off any existing `&` and `&mut` to reach our target type
1375 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
1376 // If the expression has `&`, removing it would fix the error
1377 prefix_span = prefix_span.with_hi(inner.span.lo());
1379 remove.push_str(mutbl.ref_prefix_str());
1385 // If we've reached our target type with just removing `&`, then just print now.
1386 if steps == 0 && !remove.trim().is_empty() {
1389 format!("consider removing the `{}`", remove.trim()),
1391 // Do not remove `&&` to get to bool, because it might be something like
1392 // { a } && b, which we have a separate fixup suggestion that is more
1393 // likely correct...
1394 if remove.trim() == "&&" && expected == self.tcx.types.bool {
1395 Applicability::MaybeIncorrect
1397 Applicability::MachineApplicable
1404 // For this suggestion to make sense, the type would need to be `Copy`,
1405 // or we have to be moving out of a `Box<T>`
1406 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1407 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1408 // `steps` layers of boxes, not just one, but this is easier and most likely.
1409 || (checked_ty.is_box() && steps == 1)
1411 let deref_kind = if checked_ty.is_box() {
1412 "unboxing the value"
1413 } else if checked_ty.is_region_ptr() {
1414 "dereferencing the borrow"
1416 "dereferencing the type"
1419 // Suggest removing `&` if we have removed any, otherwise suggest just
1420 // dereferencing the remaining number of steps.
1421 let message = if remove.is_empty() {
1422 format!("consider {deref_kind}")
1425 "consider removing the `{}` and {} instead",
1431 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1432 Some(ident) => format!("{ident}: "),
1433 None => String::new(),
1436 let (span, suggestion) = if self.is_else_if_block(expr) {
1437 // Don't suggest nonsense like `else *if`
1439 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1440 // prefix should be empty here..
1441 (expr.span.shrink_to_lo(), "*".to_string())
1443 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1445 if suggestion.trim().is_empty() {
1453 Applicability::MachineApplicable,
1465 pub fn check_for_cast(
1467 err: &mut Diagnostic,
1468 expr: &hir::Expr<'_>,
1469 checked_ty: Ty<'tcx>,
1470 expected_ty: Ty<'tcx>,
1471 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1473 if self.tcx.sess.source_map().is_imported(expr.span) {
1474 // Ignore if span is from within a macro.
1478 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1482 // If casting this expression to a given numeric type would be appropriate in case of a type
1485 // We want to minimize the amount of casting operations that are suggested, as it can be a
1486 // lossy operation with potentially bad side effects, so we only suggest when encountering
1487 // an expression that indicates that the original type couldn't be directly changed.
1489 // For now, don't suggest casting with `as`.
1490 let can_cast = false;
1492 let mut sugg = vec![];
1494 if let Some(hir::Node::ExprField(field)) = self.tcx.hir().find_parent(expr.hir_id) {
1495 // `expr` is a literal field for a struct, only suggest if appropriate
1496 if field.is_shorthand {
1497 // This is a field literal
1498 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1500 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1505 if let hir::ExprKind::Call(path, args) = &expr.kind
1506 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1507 (&path.kind, args.len())
1508 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1509 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1510 (&base_ty.kind, path_segment.ident.name)
1512 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1526 if base_ty_path.segments.len() == 1 =>
1536 "you can convert {} `{}` to {} `{}`",
1537 checked_ty.kind().article(),
1539 expected_ty.kind().article(),
1542 let cast_msg = format!(
1543 "you can cast {} `{}` to {} `{}`",
1544 checked_ty.kind().article(),
1546 expected_ty.kind().article(),
1549 let lit_msg = format!(
1550 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1553 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1554 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1560 let mut cast_suggestion = sugg.clone();
1561 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1562 let mut into_suggestion = sugg.clone();
1563 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1564 let mut suffix_suggestion = sugg.clone();
1565 suffix_suggestion.push((
1567 (&expected_ty.kind(), &checked_ty.kind()),
1568 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1570 // Remove fractional part from literal, for example `42.0f32` into `42`
1571 let src = src.trim_end_matches(&checked_ty.to_string());
1572 let len = src.split('.').next().unwrap().len();
1573 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1575 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1576 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1578 if expr.precedence().order() < PREC_POSTFIX {
1580 format!("{expected_ty})")
1582 expected_ty.to_string()
1585 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1586 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1588 let is_negative_int =
1589 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1590 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1592 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1594 let suggest_fallible_into_or_lhs_from =
1595 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1596 // If we know the expression the expected type is derived from, we might be able
1597 // to suggest a widening conversion rather than a narrowing one (which may
1598 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1600 // can be given the suggestion "u32::from(x) > y" rather than
1601 // "x > y.try_into().unwrap()".
1602 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1606 .span_to_snippet(expr.span)
1608 .map(|src| (expr, src))
1610 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1611 (lhs_expr_and_src, exp_to_found_is_fallible)
1614 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1616 let suggestion = vec![
1617 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1618 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1622 let msg = format!("{msg} and panic if the converted value doesn't fit");
1623 let mut suggestion = sugg.clone();
1625 expr.span.shrink_to_hi(),
1626 format!("{close_paren}.try_into().unwrap()"),
1630 err.multipart_suggestion_verbose(
1633 Applicability::MachineApplicable,
1637 let suggest_to_change_suffix_or_into =
1638 |err: &mut Diagnostic,
1639 found_to_exp_is_fallible: bool,
1640 exp_to_found_is_fallible: bool| {
1642 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1648 let always_fallible = found_to_exp_is_fallible
1649 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1650 let msg = if literal_is_ty_suffixed(expr) {
1652 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1653 // We now know that converting either the lhs or rhs is fallible. Before we
1654 // suggest a fallible conversion, check if the value can never fit in the
1656 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1659 } else if in_const_context {
1660 // Do not recommend `into` or `try_into` in const contexts.
1662 } else if found_to_exp_is_fallible {
1663 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1667 let suggestion = if literal_is_ty_suffixed(expr) {
1668 suffix_suggestion.clone()
1670 into_suggestion.clone()
1672 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1675 match (&expected_ty.kind(), &checked_ty.kind()) {
1676 (ty::Int(exp), ty::Int(found)) => {
1677 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1679 (Some(exp), Some(found)) if exp < found => (true, false),
1680 (Some(exp), Some(found)) if exp > found => (false, true),
1681 (None, Some(8 | 16)) => (false, true),
1682 (Some(8 | 16), None) => (true, false),
1683 (None, _) | (_, None) => (true, true),
1684 _ => (false, false),
1686 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1689 (ty::Uint(exp), ty::Uint(found)) => {
1690 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1692 (Some(exp), Some(found)) if exp < found => (true, false),
1693 (Some(exp), Some(found)) if exp > found => (false, true),
1694 (None, Some(8 | 16)) => (false, true),
1695 (Some(8 | 16), None) => (true, false),
1696 (None, _) | (_, None) => (true, true),
1697 _ => (false, false),
1699 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1702 (&ty::Int(exp), &ty::Uint(found)) => {
1703 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1705 (Some(exp), Some(found)) if found < exp => (false, true),
1706 (None, Some(8)) => (false, true),
1709 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1712 (&ty::Uint(exp), &ty::Int(found)) => {
1713 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1715 (Some(exp), Some(found)) if found > exp => (true, false),
1716 (Some(8), None) => (true, false),
1719 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1722 (ty::Float(exp), ty::Float(found)) => {
1723 if found.bit_width() < exp.bit_width() {
1724 suggest_to_change_suffix_or_into(err, false, true);
1725 } else if literal_is_ty_suffixed(expr) {
1726 err.multipart_suggestion_verbose(
1729 Applicability::MachineApplicable,
1731 } else if can_cast {
1732 // Missing try_into implementation for `f64` to `f32`
1733 err.multipart_suggestion_verbose(
1734 &format!("{cast_msg}, producing the closest possible value"),
1736 Applicability::MaybeIncorrect, // lossy conversion
1741 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1742 if literal_is_ty_suffixed(expr) {
1743 err.multipart_suggestion_verbose(
1746 Applicability::MachineApplicable,
1748 } else if can_cast {
1749 // Missing try_into implementation for `{float}` to `{integer}`
1750 err.multipart_suggestion_verbose(
1751 &format!("{msg}, rounding the float towards zero"),
1753 Applicability::MaybeIncorrect, // lossy conversion
1758 (ty::Float(exp), ty::Uint(found)) => {
1759 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1760 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1761 err.multipart_suggestion_verbose(
1763 "{msg}, producing the floating point representation of the integer",
1766 Applicability::MachineApplicable,
1768 } else if literal_is_ty_suffixed(expr) {
1769 err.multipart_suggestion_verbose(
1772 Applicability::MachineApplicable,
1775 // Missing try_into implementation for `{integer}` to `{float}`
1776 err.multipart_suggestion_verbose(
1778 "{cast_msg}, producing the floating point representation of the integer, \
1779 rounded if necessary",
1782 Applicability::MaybeIncorrect, // lossy conversion
1787 (ty::Float(exp), ty::Int(found)) => {
1788 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1789 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1790 err.multipart_suggestion_verbose(
1792 "{}, producing the floating point representation of the integer",
1796 Applicability::MachineApplicable,
1798 } else if literal_is_ty_suffixed(expr) {
1799 err.multipart_suggestion_verbose(
1802 Applicability::MachineApplicable,
1805 // Missing try_into implementation for `{integer}` to `{float}`
1806 err.multipart_suggestion_verbose(
1808 "{}, producing the floating point representation of the integer, \
1809 rounded if necessary",
1813 Applicability::MaybeIncorrect, // lossy conversion
1819 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1820 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1823 err.multipart_suggestion_verbose(
1824 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1826 Applicability::MachineApplicable,
1834 /// Identify when the user has written `foo..bar()` instead of `foo.bar()`.
1835 pub fn check_for_range_as_method_call(
1837 err: &mut Diagnostic,
1838 expr: &hir::Expr<'tcx>,
1839 checked_ty: Ty<'tcx>,
1840 expected_ty: Ty<'tcx>,
1842 if !hir::is_range_literal(expr) {
1845 let hir::ExprKind::Struct(
1846 hir::QPath::LangItem(LangItem::Range, ..),
1849 ) = expr.kind else { return; };
1850 let parent = self.tcx.hir().parent_id(expr.hir_id);
1851 if let Some(hir::Node::ExprField(_)) = self.tcx.hir().find(parent) {
1852 // Ignore `Foo { field: a..Default::default() }`
1855 let mut expr = end.expr;
1856 let mut expectation = Some(expected_ty);
1857 while let hir::ExprKind::MethodCall(_, rcvr, ..) = expr.kind {
1858 // Getting to the root receiver and asserting it is a fn call let's us ignore cases in
1859 // `tests/ui/methods/issues/issue-90315.stderr`.
1861 // If we have more than one layer of calls, then the expected ty
1862 // cannot guide the method probe.
1865 let hir::ExprKind::Call(method_name, _) = expr.kind else { return; };
1866 let ty::Adt(adt, _) = checked_ty.kind() else { return; };
1867 if self.tcx.lang_items().range_struct() != Some(adt.did()) {
1870 if let ty::Adt(adt, _) = expected_ty.kind()
1871 && self.tcx.lang_items().range_struct() == Some(adt.did())
1875 // Check if start has method named end.
1876 let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = method_name.kind else { return; };
1877 let [hir::PathSegment { ident, .. }] = p.segments else { return; };
1878 let self_ty = self.typeck_results.borrow().expr_ty(start.expr);
1879 let Ok(_pick) = self.lookup_probe_for_diagnostic(
1883 probe::ProbeScope::AllTraits,
1887 let mut span = start.expr.span.between(end.expr.span);
1888 if span.lo() + BytePos(2) == span.hi() {
1889 // There's no space between the start, the range op and the end, suggest removal which
1890 // will be more noticeable than the replacement of `..` with `.`.
1891 span = span.with_lo(span.lo() + BytePos(1));
1894 err.span_suggestion_verbose(
1896 "you likely meant to write a method call instead of a range",
1898 Applicability::MachineApplicable,
1902 /// Identify when the type error is because `()` is found in a binding that was assigned a
1903 /// block without a tail expression.
1904 fn check_for_binding_assigned_block_without_tail_expression(
1906 err: &mut Diagnostic,
1907 expr: &hir::Expr<'_>,
1908 checked_ty: Ty<'tcx>,
1909 expected_ty: Ty<'tcx>,
1911 if !checked_ty.is_unit() {
1914 let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = expr.kind else { return; };
1915 let hir::def::Res::Local(hir_id) = path.res else { return; };
1916 let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(hir_id) else {
1919 let Some(hir::Node::Local(hir::Local {
1923 })) = self.tcx.hir().find_parent(pat.hir_id) else { return; };
1924 let hir::ExprKind::Block(block, None) = init.kind else { return; };
1925 if block.expr.is_some() {
1928 let [.., stmt] = block.stmts else {
1929 err.span_label(block.span, "this empty block is missing a tail expression");
1932 let hir::StmtKind::Semi(tail_expr) = stmt.kind else { return; };
1933 let Some(ty) = self.node_ty_opt(tail_expr.hir_id) else { return; };
1934 if self.can_eq(self.param_env, expected_ty, ty).is_ok() {
1935 err.span_suggestion_short(
1936 stmt.span.with_lo(tail_expr.span.hi()),
1937 "remove this semicolon",
1939 Applicability::MachineApplicable,
1942 err.span_label(block.span, "this block is missing a tail expression");
1946 fn check_wrong_return_type_due_to_generic_arg(
1948 err: &mut Diagnostic,
1949 expr: &hir::Expr<'_>,
1950 checked_ty: Ty<'tcx>,
1952 let Some(hir::Node::Expr(parent_expr)) = self.tcx.hir().find_parent(expr.hir_id) else { return; };
1958 let mut maybe_emit_help = |def_id: hir::def_id::DefId,
1959 callable: rustc_span::symbol::Ident,
1960 args: &[hir::Expr<'_>],
1961 kind: CallableKind| {
1962 let arg_idx = args.iter().position(|a| a.hir_id == expr.hir_id).unwrap();
1963 let fn_ty = self.tcx.bound_type_of(def_id).0;
1967 let fn_sig = fn_ty.fn_sig(self.tcx).skip_binder();
1968 let Some(&arg) = fn_sig.inputs().get(arg_idx + if matches!(kind, CallableKind::Method) { 1 } else { 0 }) else { return; };
1969 if matches!(arg.kind(), ty::Param(_))
1970 && fn_sig.output().contains(arg)
1971 && self.node_ty(args[arg_idx].hir_id) == checked_ty
1973 let mut multi_span: MultiSpan = parent_expr.span.into();
1974 multi_span.push_span_label(
1977 "this argument influences the {} of `{}`",
1978 if matches!(kind, CallableKind::Constructor) {
1989 "the {} `{}` due to the type of the argument passed",
1991 CallableKind::Function => "return type of this call is",
1992 CallableKind::Method => "return type of this call is",
1993 CallableKind::Constructor => "type constructed contains",
2000 match parent_expr.kind {
2001 hir::ExprKind::Call(fun, args) => {
2002 let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = fun.kind else { return; };
2003 let hir::def::Res::Def(kind, def_id) = path.res else { return; };
2004 let callable_kind = if matches!(kind, hir::def::DefKind::Ctor(_, _)) {
2005 CallableKind::Constructor
2007 CallableKind::Function
2009 maybe_emit_help(def_id, path.segments[0].ident, args, callable_kind);
2011 hir::ExprKind::MethodCall(method, _receiver, args, _span) => {
2012 let Some(def_id) = self.typeck_results.borrow().type_dependent_def_id(parent_expr.hir_id) else { return; };
2013 maybe_emit_help(def_id, method.ident, args, CallableKind::Method)