1 use crate::check::FnCtxt;
2 use rustc_infer::infer::InferOk;
3 use rustc_middle::middle::stability::EvalResult;
4 use rustc_trait_selection::infer::InferCtxtExt as _;
5 use rustc_trait_selection::traits::ObligationCause;
7 use rustc_ast::util::parser::PREC_POSTFIX;
8 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
10 use rustc_hir::lang_items::LangItem;
11 use rustc_hir::{is_range_literal, Node};
12 use rustc_middle::lint::in_external_macro;
13 use rustc_middle::ty::adjustment::AllowTwoPhase;
14 use rustc_middle::ty::error::{ExpectedFound, TypeError};
15 use rustc_middle::ty::print::with_no_trimmed_paths;
16 use rustc_middle::ty::{self, Article, AssocItem, Ty, TypeAndMut};
17 use rustc_span::symbol::{sym, Symbol};
18 use rustc_span::{BytePos, Span};
20 use super::method::probe;
24 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
25 pub fn emit_coerce_suggestions(
28 expr: &hir::Expr<'tcx>,
31 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
32 error: Option<TypeError<'tcx>>,
34 self.annotate_expected_due_to_let_ty(err, expr, error);
36 // Use `||` to give these suggestions a precedence
37 let _ = self.suggest_missing_parentheses(err, expr)
38 || self.suggest_deref_ref_or_into(err, expr, expected, expr_ty, expected_ty_expr)
39 || self.suggest_compatible_variants(err, expr, expected, expr_ty)
40 || self.suggest_non_zero_new_unwrap(err, expr, expected, expr_ty)
41 || self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty)
42 || self.suggest_no_capture_closure(err, expected, expr_ty)
43 || self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty)
44 || self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected)
45 || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
46 || self.suggest_into(err, expr, expr_ty, expected);
48 self.note_type_is_not_clone(err, expected, expr_ty, expr);
49 self.note_need_for_fn_pointer(err, expected, expr_ty);
50 self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
53 // Requires that the two types unify, and prints an error message if
55 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
56 if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) {
61 pub fn demand_suptype_diag(
66 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
67 self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
70 #[instrument(skip(self), level = "debug")]
71 pub fn demand_suptype_with_origin(
73 cause: &ObligationCause<'tcx>,
76 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
77 match self.at(cause, self.param_env).sup(expected, actual) {
78 Ok(InferOk { obligations, value: () }) => {
79 self.register_predicates(obligations);
82 Err(e) => Some(self.err_ctxt().report_mismatched_types(&cause, expected, actual, e)),
86 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
87 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
92 pub fn demand_eqtype_diag(
97 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
98 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
101 pub fn demand_eqtype_with_origin(
103 cause: &ObligationCause<'tcx>,
106 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
107 match self.at(cause, self.param_env).eq(expected, actual) {
108 Ok(InferOk { obligations, value: () }) => {
109 self.register_predicates(obligations);
112 Err(e) => Some(self.err_ctxt().report_mismatched_types(cause, expected, actual, e)),
116 pub fn demand_coerce(
118 expr: &hir::Expr<'tcx>,
119 checked_ty: Ty<'tcx>,
121 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
122 allow_two_phase: AllowTwoPhase,
125 self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase);
126 if let Some(mut err) = err {
132 /// Checks that the type of `expr` can be coerced to `expected`.
134 /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!`
135 /// will be permitted if the diverges flag is currently "always".
136 #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))]
137 pub fn demand_coerce_diag(
139 expr: &hir::Expr<'tcx>,
140 checked_ty: Ty<'tcx>,
142 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
143 allow_two_phase: AllowTwoPhase,
144 ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
145 let expected = self.resolve_vars_with_obligations(expected);
147 let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) {
148 Ok(ty) => return (ty, None),
152 self.set_tainted_by_errors();
153 let expr = expr.peel_drop_temps();
154 let cause = self.misc(expr.span);
155 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
156 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e.clone());
158 let is_insufficiently_polymorphic =
159 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
161 // FIXME(#73154): For now, we do leak check when coercing function
162 // pointers in typeck, instead of only during borrowck. This can lead
163 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
164 if !is_insufficiently_polymorphic {
165 self.emit_coerce_suggestions(
175 (expected, Some(err))
178 fn annotate_expected_due_to_let_ty(
180 err: &mut Diagnostic,
181 expr: &hir::Expr<'_>,
182 error: Option<TypeError<'_>>,
184 let parent = self.tcx.hir().get_parent_node(expr.hir_id);
185 match (self.tcx.hir().find(parent), error) {
186 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
187 if init.hir_id == expr.hir_id =>
189 // Point at `let` assignment type.
190 err.span_label(ty.span, "expected due to this");
193 Some(hir::Node::Expr(hir::Expr {
194 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
196 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
197 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
198 // We ignore closures explicitly because we already point at them elsewhere.
199 // Point at the assigned-to binding.
200 let mut primary_span = lhs.span;
201 let mut secondary_span = lhs.span;
202 let mut post_message = "";
204 hir::ExprKind::Path(hir::QPath::Resolved(
209 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
215 if let Some(hir::Node::Item(hir::Item {
217 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
219 })) = self.tcx.hir().get_if_local(*def_id)
221 primary_span = ty.span;
222 secondary_span = ident.span;
223 post_message = " type";
226 hir::ExprKind::Path(hir::QPath::Resolved(
228 hir::Path { res: hir::def::Res::Local(hir_id), .. },
230 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
231 let parent = self.tcx.hir().get_parent_node(pat.hir_id);
232 primary_span = pat.span;
233 secondary_span = pat.span;
234 match self.tcx.hir().find(parent) {
235 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
236 primary_span = ty.span;
237 post_message = " type";
239 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
240 primary_span = init.span;
241 post_message = " value";
243 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
244 primary_span = *ty_span;
245 post_message = " parameter type";
254 if primary_span != secondary_span
259 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
261 // We are pointing at the binding's type or initializer value, but it's pattern
262 // is in a different line, so we point at both.
263 err.span_label(secondary_span, "expected due to the type of this binding");
264 err.span_label(primary_span, &format!("expected due to this{post_message}"));
265 } else if post_message == "" {
266 // We are pointing at either the assignment lhs or the binding def pattern.
267 err.span_label(primary_span, "expected due to the type of this binding");
269 // We are pointing at the binding's type or initializer value.
270 err.span_label(primary_span, &format!("expected due to this{post_message}"));
273 if !lhs.is_syntactic_place_expr() {
274 // We already emitted E0070 "invalid left-hand side of assignment", so we
276 err.downgrade_to_delayed_bug();
283 /// If the expected type is an enum (Issue #55250) with any variants whose
284 /// sole field is of the found type, suggest such variants. (Issue #42764)
285 fn suggest_compatible_variants(
287 err: &mut Diagnostic,
288 expr: &hir::Expr<'_>,
292 if let ty::Adt(expected_adt, substs) = expected.kind() {
293 if let hir::ExprKind::Field(base, ident) = expr.kind {
294 let base_ty = self.typeck_results.borrow().expr_ty(base);
295 if self.can_eq(self.param_env, base_ty, expected).is_ok()
296 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
298 err.span_suggestion_verbose(
299 expr.span.with_lo(base_span.hi()),
300 format!("consider removing the tuple struct field `{ident}`"),
302 Applicability::MaybeIncorrect,
308 // If the expression is of type () and it's the return expression of a block,
309 // we suggest adding a separate return expression instead.
310 // (To avoid things like suggesting `Ok(while .. { .. })`.)
311 if expr_ty.is_unit() {
312 let mut id = expr.hir_id;
315 // Unroll desugaring, to make sure this works for `for` loops etc.
317 parent = self.tcx.hir().get_parent_node(id);
318 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
319 if parent_span.find_ancestor_inside(expr.span).is_some() {
320 // The parent node is part of the same span, so is the result of the
321 // same expansion/desugaring and not the 'real' parent node.
329 if let Some(hir::Node::Block(&hir::Block {
330 span: block_span, expr: Some(e), ..
331 })) = self.tcx.hir().find(parent)
334 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
335 let return_suggestions = if self
337 .is_diagnostic_item(sym::Result, expected_adt.did())
340 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
341 vec!["None", "Some(())"]
345 if let Some(indent) =
346 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
348 // Add a semicolon, except after `}`.
350 match self.tcx.sess.source_map().span_to_snippet(span) {
351 Ok(s) if s.ends_with('}') => "",
354 err.span_suggestions(
356 "try adding an expression at the end of the block",
359 .map(|r| format!("{semicolon}\n{indent}{r}")),
360 Applicability::MaybeIncorrect,
369 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
373 variant.fields.len() == 1
375 .filter_map(|variant| {
376 let sole_field = &variant.fields[0];
378 let field_is_local = sole_field.did.is_local();
379 let field_is_accessible =
380 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
381 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
382 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
384 if !field_is_local && !field_is_accessible {
388 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
389 .then(|| format!(" (its field is private, but it's local to this crate and its privacy can be changed)"));
391 let sole_field_ty = sole_field.ty(self.tcx, substs);
392 if self.can_coerce(expr_ty, sole_field_ty) {
394 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
395 // FIXME #56861: DRYer prelude filtering
396 if let Some(path) = variant_path.strip_prefix("std::prelude::")
397 && let Some((_, path)) = path.split_once("::")
399 return Some((path.to_string(), variant.ctor_kind, sole_field.name, note_about_variant_field_privacy));
401 Some((variant_path, variant.ctor_kind, sole_field.name, note_about_variant_field_privacy))
408 let suggestions_for = |variant: &_, ctor, field_name| {
409 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
410 Some(ident) => format!("{ident}: "),
411 None => String::new(),
414 let (open, close) = match ctor {
415 hir::def::CtorKind::Fn => ("(".to_owned(), ")"),
416 hir::def::CtorKind::Fictive => (format!(" {{ {field_name}: "), " }"),
418 // unit variants don't have fields
419 hir::def::CtorKind::Const => unreachable!(),
422 // Suggest constructor as deep into the block tree as possible.
423 // This fixes https://github.com/rust-lang/rust/issues/101065,
424 // and also just helps make the most minimal suggestions.
426 while let hir::ExprKind::Block(block, _) = &expr.kind
427 && let Some(expr_) = &block.expr
433 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
434 (expr.span.shrink_to_hi(), close.to_owned()),
438 match &compatible_variants[..] {
439 [] => { /* No variants to format */ }
440 [(variant, ctor_kind, field_name, note)] => {
441 // Just a single matching variant.
442 err.multipart_suggestion_verbose(
444 "try wrapping the expression in `{variant}`{note}",
445 note = note.as_deref().unwrap_or("")
447 suggestions_for(&**variant, *ctor_kind, *field_name),
448 Applicability::MaybeIncorrect,
453 // More than one matching variant.
454 err.multipart_suggestions(
456 "try wrapping the expression in a variant of `{}`",
457 self.tcx.def_path_str(expected_adt.did())
459 compatible_variants.into_iter().map(
460 |(variant, ctor_kind, field_name, _)| {
461 suggestions_for(&variant, ctor_kind, field_name)
464 Applicability::MaybeIncorrect,
474 fn suggest_non_zero_new_unwrap(
476 err: &mut Diagnostic,
477 expr: &hir::Expr<'_>,
482 let (adt, unwrap) = match expected.kind() {
483 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
484 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
486 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
490 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
491 ty::Adt(adt, _) => (adt, ".unwrap()"),
496 (sym::NonZeroU8, tcx.types.u8),
497 (sym::NonZeroU16, tcx.types.u16),
498 (sym::NonZeroU32, tcx.types.u32),
499 (sym::NonZeroU64, tcx.types.u64),
500 (sym::NonZeroU128, tcx.types.u128),
501 (sym::NonZeroI8, tcx.types.i8),
502 (sym::NonZeroI16, tcx.types.i16),
503 (sym::NonZeroI32, tcx.types.i32),
504 (sym::NonZeroI64, tcx.types.i64),
505 (sym::NonZeroI128, tcx.types.i128),
508 let Some((s, _)) = map
510 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
511 else { return false; };
513 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
515 err.multipart_suggestion(
516 format!("consider calling `{s}::new`"),
518 (expr.span.shrink_to_lo(), format!("{path}::new(")),
519 (expr.span.shrink_to_hi(), format!("){unwrap}")),
521 Applicability::MaybeIncorrect,
527 pub fn get_conversion_methods(
531 checked_ty: Ty<'tcx>,
533 ) -> Vec<AssocItem> {
535 self.probe_for_return_type(span, probe::Mode::MethodCall, expected, checked_ty, hir_id);
537 self.has_only_self_parameter(m)
540 // This special internal attribute is used to permit
541 // "identity-like" conversion methods to be suggested here.
543 // FIXME (#46459 and #46460): ideally
544 // `std::convert::Into::into` and `std::borrow:ToOwned` would
545 // also be `#[rustc_conversion_suggestion]`, if not for
546 // method-probing false-positives and -negatives (respectively).
548 // FIXME? Other potential candidate methods: `as_ref` and
550 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
556 /// This function checks whether the method is not static and does not accept other parameters than `self`.
557 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
559 ty::AssocKind::Fn => {
560 method.fn_has_self_parameter
561 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
567 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
569 /// Given the following code:
570 /// ```compile_fail,E0308
572 /// fn takes_ref(_: &Foo) {}
573 /// let ref opt = Some(Foo);
575 /// opt.map(|param| takes_ref(param));
577 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
579 /// It only checks for `Option` and `Result` and won't work with
580 /// ```ignore (illustrative)
581 /// opt.map(|param| { takes_ref(param) });
583 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
584 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
588 let hir::def::Res::Local(local_id) = path.res else {
592 let local_parent = self.tcx.hir().get_parent_node(local_id);
593 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
597 let param_parent = self.tcx.hir().get_parent_node(*param_hir_id);
598 let Some(Node::Expr(hir::Expr {
600 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
602 })) = self.tcx.hir().find(param_parent) else {
606 let expr_parent = self.tcx.hir().get_parent_node(*expr_hir_id);
607 let hir = self.tcx.hir().find(expr_parent);
608 let closure_params_len = closure_fn_decl.inputs.len();
610 Some(Node::Expr(hir::Expr {
611 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
615 ) = (hir, closure_params_len) else {
619 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
620 let name = method_path.ident.name;
621 let is_as_ref_able = match self_ty.peel_refs().kind() {
623 (self.tcx.is_diagnostic_item(sym::Option, def.did())
624 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
625 && (name == sym::map || name == sym::and_then)
629 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
631 let suggestion = format!("as_ref().{}", src);
632 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
638 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
640 expr: &hir::Expr<'_>,
641 ) -> Option<Symbol> {
642 let hir = self.tcx.hir();
643 let local = match expr {
646 hir::ExprKind::Path(hir::QPath::Resolved(
649 res: hir::def::Res::Local(_),
650 segments: [hir::PathSegment { ident, .. }],
659 match hir.find(hir.get_parent_node(expr.hir_id))? {
660 Node::ExprField(field) => {
661 if field.ident.name == local.name && field.is_shorthand {
662 return Some(local.name);
671 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
672 pub(crate) fn maybe_get_block_expr(
674 expr: &hir::Expr<'tcx>,
675 ) -> Option<&'tcx hir::Expr<'tcx>> {
677 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
682 /// Returns whether the given expression is an `else if`.
683 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
684 if let hir::ExprKind::If(..) = expr.kind {
685 let parent_id = self.tcx.hir().get_parent_node(expr.hir_id);
686 if let Some(Node::Expr(hir::Expr {
687 kind: hir::ExprKind::If(_, _, Some(else_expr)),
689 })) = self.tcx.hir().find(parent_id)
691 return else_expr.hir_id == expr.hir_id;
697 /// This function is used to determine potential "simple" improvements or users' errors and
698 /// provide them useful help. For example:
700 /// ```compile_fail,E0308
701 /// fn some_fn(s: &str) {}
703 /// let x = "hey!".to_owned();
704 /// some_fn(x); // error
707 /// No need to find every potential function which could make a coercion to transform a
708 /// `String` into a `&str` since a `&` would do the trick!
710 /// In addition of this check, it also checks between references mutability state. If the
711 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
715 expr: &hir::Expr<'tcx>,
716 checked_ty: Ty<'tcx>,
718 ) -> Option<(Span, String, String, Applicability, bool /* verbose */)> {
719 let sess = self.sess();
722 // If the span is from an external macro, there's no suggestion we can make.
723 if in_external_macro(sess, sp) {
727 let sm = sess.source_map();
729 let replace_prefix = |s: &str, old: &str, new: &str| {
730 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
733 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
734 let expr = expr.peel_drop_temps();
736 match (&expr.kind, expected.kind(), checked_ty.kind()) {
737 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
738 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
739 if let hir::ExprKind::Lit(_) = expr.kind
740 && let Ok(src) = sm.span_to_snippet(sp)
741 && replace_prefix(&src, "b\"", "\"").is_some()
743 let pos = sp.lo() + BytePos(1);
746 "consider removing the leading `b`".to_string(),
748 Applicability::MachineApplicable,
753 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
754 if let hir::ExprKind::Lit(_) = expr.kind
755 && let Ok(src) = sm.span_to_snippet(sp)
756 && replace_prefix(&src, "\"", "b\"").is_some()
760 "consider adding a leading `b`".to_string(),
762 Applicability::MachineApplicable,
769 (_, &ty::Ref(_, _, mutability), _) => {
770 // Check if it can work when put into a ref. For example:
773 // fn bar(x: &mut i32) {}
776 // bar(&x); // error, expected &mut
778 let ref_ty = match mutability {
779 hir::Mutability::Mut => {
780 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
782 hir::Mutability::Not => {
783 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
786 if self.can_coerce(ref_ty, expected) {
787 let mut sugg_sp = sp;
788 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
790 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
792 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
794 let ai = self.tcx.associated_item(did);
795 ai.trait_container(self.tcx) == Some(clone_trait)
798 && segment.ident.name == sym::clone
800 // If this expression had a clone call when suggesting borrowing
801 // we want to suggest removing it because it'd now be unnecessary.
802 sugg_sp = receiver.span;
805 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
806 let needs_parens = match expr.kind {
807 // parenthesize if needed (Issue #46756)
808 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
809 // parenthesize borrows of range literals (Issue #54505)
810 _ if is_range_literal(expr) => true,
814 if let Some(sugg) = self.can_use_as_ref(expr) {
819 Applicability::MachineApplicable,
824 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
825 Some(ident) => format!("{ident}: "),
826 None => String::new(),
829 if let Some(hir::Node::Expr(hir::Expr {
830 kind: hir::ExprKind::Assign(..),
832 })) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
834 if mutability == hir::Mutability::Mut {
835 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
840 let sugg_expr = if needs_parens { format!("({src})") } else { src };
841 return Some(match mutability {
842 hir::Mutability::Mut => (
844 "consider mutably borrowing here".to_string(),
845 format!("{prefix}&mut {sugg_expr}"),
846 Applicability::MachineApplicable,
849 hir::Mutability::Not => (
851 "consider borrowing here".to_string(),
852 format!("{prefix}&{sugg_expr}"),
853 Applicability::MachineApplicable,
861 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
863 &ty::Ref(_, checked, _),
864 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
865 // We have `&T`, check if what was expected was `T`. If so,
866 // we may want to suggest removing a `&`.
867 if sm.is_imported(expr.span) {
868 // Go through the spans from which this span was expanded,
869 // and find the one that's pointing inside `sp`.
871 // E.g. for `&format!("")`, where we want the span to the
872 // `format!()` invocation instead of its expansion.
873 if let Some(call_span) =
874 iter::successors(Some(expr.span), |s| s.parent_callsite())
875 .find(|&s| sp.contains(s))
876 && sm.is_span_accessible(call_span)
879 sp.with_hi(call_span.lo()),
880 "consider removing the borrow".to_string(),
882 Applicability::MachineApplicable,
888 if sp.contains(expr.span)
889 && sm.is_span_accessible(expr.span)
892 sp.with_hi(expr.span.lo()),
893 "consider removing the borrow".to_string(),
895 Applicability::MachineApplicable,
902 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
903 &ty::Ref(_, ty_a, mutbl_a),
905 if let Some(steps) = self.deref_steps(ty_a, ty_b)
906 // Only suggest valid if dereferencing needed.
908 // The pointer type implements `Copy` trait so the suggestion is always valid.
909 && let Ok(src) = sm.span_to_snippet(sp)
911 let derefs = "*".repeat(steps);
912 if let Some((span, src, applicability)) = match mutbl_b {
913 hir::Mutability::Mut => {
914 let new_prefix = "&mut ".to_owned() + &derefs;
916 hir::Mutability::Mut => {
917 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
918 let pos = sp.lo() + BytePos(5);
919 let sp = sp.with_lo(pos).with_hi(pos);
920 (sp, derefs, Applicability::MachineApplicable)
923 hir::Mutability::Not => {
924 replace_prefix(&src, "&", &new_prefix).map(|_| {
925 let pos = sp.lo() + BytePos(1);
926 let sp = sp.with_lo(pos).with_hi(pos);
929 format!("mut {derefs}"),
930 Applicability::Unspecified,
936 hir::Mutability::Not => {
937 let new_prefix = "&".to_owned() + &derefs;
939 hir::Mutability::Mut => {
940 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
941 let lo = sp.lo() + BytePos(1);
942 let hi = sp.lo() + BytePos(5);
943 let sp = sp.with_lo(lo).with_hi(hi);
944 (sp, derefs, Applicability::MachineApplicable)
947 hir::Mutability::Not => {
948 replace_prefix(&src, "&", &new_prefix).map(|_| {
949 let pos = sp.lo() + BytePos(1);
950 let sp = sp.with_lo(pos).with_hi(pos);
951 (sp, derefs, Applicability::MachineApplicable)
959 "consider dereferencing".to_string(),
967 _ if sp == expr.span => {
968 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
969 let mut expr = expr.peel_blocks();
970 let mut prefix_span = expr.span.shrink_to_lo();
971 let mut remove = String::new();
973 // Try peeling off any existing `&` and `&mut` to reach our target type
975 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
976 // If the expression has `&`, removing it would fix the error
977 prefix_span = prefix_span.with_hi(inner.span.lo());
979 remove += match mutbl {
980 hir::Mutability::Not => "&",
981 hir::Mutability::Mut => "&mut ",
988 // If we've reached our target type with just removing `&`, then just print now.
992 format!("consider removing the `{}`", remove.trim()),
994 // Do not remove `&&` to get to bool, because it might be something like
995 // { a } && b, which we have a separate fixup suggestion that is more
997 if remove.trim() == "&&" && expected == self.tcx.types.bool {
998 Applicability::MaybeIncorrect
1000 Applicability::MachineApplicable
1006 // For this suggestion to make sense, the type would need to be `Copy`,
1007 // or we have to be moving out of a `Box<T>`
1008 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1009 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1010 // `steps` layers of boxes, not just one, but this is easier and most likely.
1011 || (checked_ty.is_box() && steps == 1)
1013 let deref_kind = if checked_ty.is_box() {
1014 "unboxing the value"
1015 } else if checked_ty.is_region_ptr() {
1016 "dereferencing the borrow"
1018 "dereferencing the type"
1021 // Suggest removing `&` if we have removed any, otherwise suggest just
1022 // dereferencing the remaining number of steps.
1023 let message = if remove.is_empty() {
1024 format!("consider {deref_kind}")
1027 "consider removing the `{}` and {} instead",
1033 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1034 Some(ident) => format!("{ident}: "),
1035 None => String::new(),
1038 let (span, suggestion) = if self.is_else_if_block(expr) {
1039 // Don't suggest nonsense like `else *if`
1041 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1042 // prefix should be empty here..
1043 (expr.span.shrink_to_lo(), "*".to_string())
1045 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1052 Applicability::MachineApplicable,
1063 pub fn check_for_cast(
1065 err: &mut Diagnostic,
1066 expr: &hir::Expr<'_>,
1067 checked_ty: Ty<'tcx>,
1068 expected_ty: Ty<'tcx>,
1069 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1071 if self.tcx.sess.source_map().is_imported(expr.span) {
1072 // Ignore if span is from within a macro.
1076 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1080 // If casting this expression to a given numeric type would be appropriate in case of a type
1083 // We want to minimize the amount of casting operations that are suggested, as it can be a
1084 // lossy operation with potentially bad side effects, so we only suggest when encountering
1085 // an expression that indicates that the original type couldn't be directly changed.
1087 // For now, don't suggest casting with `as`.
1088 let can_cast = false;
1090 let mut sugg = vec![];
1092 if let Some(hir::Node::ExprField(field)) =
1093 self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
1095 // `expr` is a literal field for a struct, only suggest if appropriate
1096 if field.is_shorthand {
1097 // This is a field literal
1098 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1100 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1105 if let hir::ExprKind::Call(path, args) = &expr.kind
1106 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1107 (&path.kind, args.len())
1108 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1109 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1110 (&base_ty.kind, path_segment.ident.name)
1112 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1126 if base_ty_path.segments.len() == 1 =>
1136 "you can convert {} `{}` to {} `{}`",
1137 checked_ty.kind().article(),
1139 expected_ty.kind().article(),
1142 let cast_msg = format!(
1143 "you can cast {} `{}` to {} `{}`",
1144 checked_ty.kind().article(),
1146 expected_ty.kind().article(),
1149 let lit_msg = format!(
1150 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1153 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1154 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1160 let mut cast_suggestion = sugg.clone();
1161 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1162 let mut into_suggestion = sugg.clone();
1163 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1164 let mut suffix_suggestion = sugg.clone();
1165 suffix_suggestion.push((
1167 (&expected_ty.kind(), &checked_ty.kind()),
1168 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1170 // Remove fractional part from literal, for example `42.0f32` into `42`
1171 let src = src.trim_end_matches(&checked_ty.to_string());
1172 let len = src.split('.').next().unwrap().len();
1173 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1175 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1176 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1178 if expr.precedence().order() < PREC_POSTFIX {
1180 format!("{expected_ty})")
1182 expected_ty.to_string()
1185 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1186 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1188 let is_negative_int =
1189 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1190 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1192 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1194 let suggest_fallible_into_or_lhs_from =
1195 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1196 // If we know the expression the expected type is derived from, we might be able
1197 // to suggest a widening conversion rather than a narrowing one (which may
1198 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1200 // can be given the suggestion "u32::from(x) > y" rather than
1201 // "x > y.try_into().unwrap()".
1202 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1206 .span_to_snippet(expr.span)
1208 .map(|src| (expr, src))
1210 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1211 (lhs_expr_and_src, exp_to_found_is_fallible)
1214 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1216 let suggestion = vec![
1217 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1218 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1222 let msg = format!("{msg} and panic if the converted value doesn't fit");
1223 let mut suggestion = sugg.clone();
1225 expr.span.shrink_to_hi(),
1226 format!("{close_paren}.try_into().unwrap()"),
1230 err.multipart_suggestion_verbose(
1233 Applicability::MachineApplicable,
1237 let suggest_to_change_suffix_or_into =
1238 |err: &mut Diagnostic,
1239 found_to_exp_is_fallible: bool,
1240 exp_to_found_is_fallible: bool| {
1242 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1248 let always_fallible = found_to_exp_is_fallible
1249 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1250 let msg = if literal_is_ty_suffixed(expr) {
1252 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1253 // We now know that converting either the lhs or rhs is fallible. Before we
1254 // suggest a fallible conversion, check if the value can never fit in the
1256 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1259 } else if in_const_context {
1260 // Do not recommend `into` or `try_into` in const contexts.
1262 } else if found_to_exp_is_fallible {
1263 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1267 let suggestion = if literal_is_ty_suffixed(expr) {
1268 suffix_suggestion.clone()
1270 into_suggestion.clone()
1272 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1275 match (&expected_ty.kind(), &checked_ty.kind()) {
1276 (&ty::Int(ref exp), &ty::Int(ref found)) => {
1277 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1279 (Some(exp), Some(found)) if exp < found => (true, false),
1280 (Some(exp), Some(found)) if exp > found => (false, true),
1281 (None, Some(8 | 16)) => (false, true),
1282 (Some(8 | 16), None) => (true, false),
1283 (None, _) | (_, None) => (true, true),
1284 _ => (false, false),
1286 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1289 (&ty::Uint(ref exp), &ty::Uint(ref found)) => {
1290 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1292 (Some(exp), Some(found)) if exp < found => (true, false),
1293 (Some(exp), Some(found)) if exp > found => (false, true),
1294 (None, Some(8 | 16)) => (false, true),
1295 (Some(8 | 16), None) => (true, false),
1296 (None, _) | (_, None) => (true, true),
1297 _ => (false, false),
1299 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1302 (&ty::Int(exp), &ty::Uint(found)) => {
1303 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1305 (Some(exp), Some(found)) if found < exp => (false, true),
1306 (None, Some(8)) => (false, true),
1309 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1312 (&ty::Uint(exp), &ty::Int(found)) => {
1313 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1315 (Some(exp), Some(found)) if found > exp => (true, false),
1316 (Some(8), None) => (true, false),
1319 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1322 (&ty::Float(ref exp), &ty::Float(ref found)) => {
1323 if found.bit_width() < exp.bit_width() {
1324 suggest_to_change_suffix_or_into(err, false, true);
1325 } else if literal_is_ty_suffixed(expr) {
1326 err.multipart_suggestion_verbose(
1329 Applicability::MachineApplicable,
1331 } else if can_cast {
1332 // Missing try_into implementation for `f64` to `f32`
1333 err.multipart_suggestion_verbose(
1334 &format!("{cast_msg}, producing the closest possible value"),
1336 Applicability::MaybeIncorrect, // lossy conversion
1341 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1342 if literal_is_ty_suffixed(expr) {
1343 err.multipart_suggestion_verbose(
1346 Applicability::MachineApplicable,
1348 } else if can_cast {
1349 // Missing try_into implementation for `{float}` to `{integer}`
1350 err.multipart_suggestion_verbose(
1351 &format!("{msg}, rounding the float towards zero"),
1353 Applicability::MaybeIncorrect, // lossy conversion
1358 (&ty::Float(ref exp), &ty::Uint(ref found)) => {
1359 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1360 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1361 err.multipart_suggestion_verbose(
1363 "{msg}, producing the floating point representation of the integer",
1366 Applicability::MachineApplicable,
1368 } else if literal_is_ty_suffixed(expr) {
1369 err.multipart_suggestion_verbose(
1372 Applicability::MachineApplicable,
1375 // Missing try_into implementation for `{integer}` to `{float}`
1376 err.multipart_suggestion_verbose(
1378 "{cast_msg}, producing the floating point representation of the integer, \
1379 rounded if necessary",
1382 Applicability::MaybeIncorrect, // lossy conversion
1387 (&ty::Float(ref exp), &ty::Int(ref found)) => {
1388 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1389 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1390 err.multipart_suggestion_verbose(
1392 "{}, producing the floating point representation of the integer",
1396 Applicability::MachineApplicable,
1398 } else if literal_is_ty_suffixed(expr) {
1399 err.multipart_suggestion_verbose(
1402 Applicability::MachineApplicable,
1405 // Missing try_into implementation for `{integer}` to `{float}`
1406 err.multipart_suggestion_verbose(
1408 "{}, producing the floating point representation of the integer, \
1409 rounded if necessary",
1413 Applicability::MaybeIncorrect, // lossy conversion
1419 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1420 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1423 err.multipart_suggestion_verbose(
1424 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1426 Applicability::MachineApplicable,