2 use rustc_ast::util::parser::PREC_POSTFIX;
3 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
5 use rustc_hir::def::CtorKind;
6 use rustc_hir::lang_items::LangItem;
7 use rustc_hir::{is_range_literal, Node};
8 use rustc_infer::infer::InferOk;
9 use rustc_middle::lint::in_external_macro;
10 use rustc_middle::middle::stability::EvalResult;
11 use rustc_middle::ty::adjustment::AllowTwoPhase;
12 use rustc_middle::ty::error::{ExpectedFound, TypeError};
13 use rustc_middle::ty::print::with_no_trimmed_paths;
14 use rustc_middle::ty::{self, Article, AssocItem, Ty, TypeAndMut};
15 use rustc_span::symbol::{sym, Symbol};
16 use rustc_span::{BytePos, Span};
17 use rustc_trait_selection::infer::InferCtxtExt as _;
18 use rustc_trait_selection::traits::ObligationCause;
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 if expr_ty == expected {
38 self.annotate_expected_due_to_let_ty(err, expr, error);
40 // Use `||` to give these suggestions a precedence
41 let _ = self.suggest_missing_parentheses(err, expr)
42 || self.suggest_deref_ref_or_into(err, expr, expected, expr_ty, expected_ty_expr)
43 || self.suggest_compatible_variants(err, expr, expected, expr_ty)
44 || self.suggest_non_zero_new_unwrap(err, expr, expected, expr_ty)
45 || self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty)
46 || self.suggest_no_capture_closure(err, expected, expr_ty)
47 || self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty)
48 || self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected)
49 || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
50 || self.suggest_into(err, expr, expr_ty, expected)
51 || self.suggest_option_to_bool(err, expr, expr_ty, expected)
52 || self.suggest_floating_point_literal(err, expr, expected);
54 self.note_type_is_not_clone(err, expected, expr_ty, expr);
55 self.note_need_for_fn_pointer(err, expected, expr_ty);
56 self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
59 // Requires that the two types unify, and prints an error message if
61 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
62 if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) {
67 pub fn demand_suptype_diag(
72 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
73 self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
76 #[instrument(skip(self), level = "debug")]
77 pub fn demand_suptype_with_origin(
79 cause: &ObligationCause<'tcx>,
82 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
83 match self.at(cause, self.param_env).sup(expected, actual) {
84 Ok(InferOk { obligations, value: () }) => {
85 self.register_predicates(obligations);
88 Err(e) => Some(self.err_ctxt().report_mismatched_types(&cause, expected, actual, e)),
92 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
93 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
98 pub fn demand_eqtype_diag(
103 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
104 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
107 pub fn demand_eqtype_with_origin(
109 cause: &ObligationCause<'tcx>,
112 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
113 match self.at(cause, self.param_env).eq(expected, actual) {
114 Ok(InferOk { obligations, value: () }) => {
115 self.register_predicates(obligations);
118 Err(e) => Some(self.err_ctxt().report_mismatched_types(cause, expected, actual, e)),
122 pub fn demand_coerce(
124 expr: &hir::Expr<'tcx>,
125 checked_ty: Ty<'tcx>,
127 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
128 allow_two_phase: AllowTwoPhase,
131 self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase);
132 if let Some(mut err) = err {
138 /// Checks that the type of `expr` can be coerced to `expected`.
140 /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!`
141 /// will be permitted if the diverges flag is currently "always".
142 #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))]
143 pub fn demand_coerce_diag(
145 expr: &hir::Expr<'tcx>,
146 checked_ty: Ty<'tcx>,
148 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
149 allow_two_phase: AllowTwoPhase,
150 ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
151 let expected = self.resolve_vars_with_obligations(expected);
153 let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) {
154 Ok(ty) => return (ty, None),
158 self.set_tainted_by_errors(self.tcx.sess.delay_span_bug(
160 "`TypeError` when attempting coercion but no error emitted",
162 let expr = expr.peel_drop_temps();
163 let cause = self.misc(expr.span);
164 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
165 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e.clone());
167 let is_insufficiently_polymorphic =
168 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
170 // FIXME(#73154): For now, we do leak check when coercing function
171 // pointers in typeck, instead of only during borrowck. This can lead
172 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
173 if !is_insufficiently_polymorphic {
174 self.emit_coerce_suggestions(
184 (expected, Some(err))
187 fn annotate_expected_due_to_let_ty(
189 err: &mut Diagnostic,
190 expr: &hir::Expr<'_>,
191 error: Option<TypeError<'_>>,
193 let parent = self.tcx.hir().get_parent_node(expr.hir_id);
194 match (self.tcx.hir().find(parent), error) {
195 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
196 if init.hir_id == expr.hir_id =>
198 // Point at `let` assignment type.
199 err.span_label(ty.span, "expected due to this");
202 Some(hir::Node::Expr(hir::Expr {
203 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
205 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
206 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
207 // We ignore closures explicitly because we already point at them elsewhere.
208 // Point at the assigned-to binding.
209 let mut primary_span = lhs.span;
210 let mut secondary_span = lhs.span;
211 let mut post_message = "";
213 hir::ExprKind::Path(hir::QPath::Resolved(
218 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
224 if let Some(hir::Node::Item(hir::Item {
226 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
228 })) = self.tcx.hir().get_if_local(*def_id)
230 primary_span = ty.span;
231 secondary_span = ident.span;
232 post_message = " type";
235 hir::ExprKind::Path(hir::QPath::Resolved(
237 hir::Path { res: hir::def::Res::Local(hir_id), .. },
239 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
240 let parent = self.tcx.hir().get_parent_node(pat.hir_id);
241 primary_span = pat.span;
242 secondary_span = pat.span;
243 match self.tcx.hir().find(parent) {
244 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
245 primary_span = ty.span;
246 post_message = " type";
248 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
249 primary_span = init.span;
250 post_message = " value";
252 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
253 primary_span = *ty_span;
254 post_message = " parameter type";
263 if primary_span != secondary_span
268 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
270 // We are pointing at the binding's type or initializer value, but it's pattern
271 // is in a different line, so we point at both.
272 err.span_label(secondary_span, "expected due to the type of this binding");
273 err.span_label(primary_span, &format!("expected due to this{post_message}"));
274 } else if post_message == "" {
275 // We are pointing at either the assignment lhs or the binding def pattern.
276 err.span_label(primary_span, "expected due to the type of this binding");
278 // We are pointing at the binding's type or initializer value.
279 err.span_label(primary_span, &format!("expected due to this{post_message}"));
282 if !lhs.is_syntactic_place_expr() {
283 // We already emitted E0070 "invalid left-hand side of assignment", so we
285 err.downgrade_to_delayed_bug();
292 /// If the expected type is an enum (Issue #55250) with any variants whose
293 /// sole field is of the found type, suggest such variants. (Issue #42764)
294 fn suggest_compatible_variants(
296 err: &mut Diagnostic,
297 expr: &hir::Expr<'_>,
301 if let ty::Adt(expected_adt, substs) = expected.kind() {
302 if let hir::ExprKind::Field(base, ident) = expr.kind {
303 let base_ty = self.typeck_results.borrow().expr_ty(base);
304 if self.can_eq(self.param_env, base_ty, expected).is_ok()
305 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
307 err.span_suggestion_verbose(
308 expr.span.with_lo(base_span.hi()),
309 format!("consider removing the tuple struct field `{ident}`"),
311 Applicability::MaybeIncorrect,
317 // If the expression is of type () and it's the return expression of a block,
318 // we suggest adding a separate return expression instead.
319 // (To avoid things like suggesting `Ok(while .. { .. })`.)
320 if expr_ty.is_unit() {
321 let mut id = expr.hir_id;
324 // Unroll desugaring, to make sure this works for `for` loops etc.
326 parent = self.tcx.hir().get_parent_node(id);
327 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
328 if parent_span.find_ancestor_inside(expr.span).is_some() {
329 // The parent node is part of the same span, so is the result of the
330 // same expansion/desugaring and not the 'real' parent node.
338 if let Some(hir::Node::Block(&hir::Block {
339 span: block_span, expr: Some(e), ..
340 })) = self.tcx.hir().find(parent)
343 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
344 let return_suggestions = if self
346 .is_diagnostic_item(sym::Result, expected_adt.did())
349 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
350 vec!["None", "Some(())"]
354 if let Some(indent) =
355 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
357 // Add a semicolon, except after `}`.
359 match self.tcx.sess.source_map().span_to_snippet(span) {
360 Ok(s) if s.ends_with('}') => "",
363 err.span_suggestions(
365 "try adding an expression at the end of the block",
368 .map(|r| format!("{semicolon}\n{indent}{r}")),
369 Applicability::MaybeIncorrect,
378 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
382 variant.fields.len() == 1
384 .filter_map(|variant| {
385 let sole_field = &variant.fields[0];
387 let field_is_local = sole_field.did.is_local();
388 let field_is_accessible =
389 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
390 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
391 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
393 if !field_is_local && !field_is_accessible {
397 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
398 .then(|| format!(" (its field is private, but it's local to this crate and its privacy can be changed)"));
400 let sole_field_ty = sole_field.ty(self.tcx, substs);
401 if self.can_coerce(expr_ty, sole_field_ty) {
403 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
404 // FIXME #56861: DRYer prelude filtering
405 if let Some(path) = variant_path.strip_prefix("std::prelude::")
406 && let Some((_, path)) = path.split_once("::")
408 return Some((path.to_string(), variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy));
410 Some((variant_path, variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy))
417 let suggestions_for = |variant: &_, ctor_kind, field_name| {
418 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
419 Some(ident) => format!("{ident}: "),
420 None => String::new(),
423 let (open, close) = match ctor_kind {
424 Some(CtorKind::Fn) => ("(".to_owned(), ")"),
425 None => (format!(" {{ {field_name}: "), " }"),
427 // unit variants don't have fields
428 Some(CtorKind::Const) => unreachable!(),
431 // Suggest constructor as deep into the block tree as possible.
432 // This fixes https://github.com/rust-lang/rust/issues/101065,
433 // and also just helps make the most minimal suggestions.
435 while let hir::ExprKind::Block(block, _) = &expr.kind
436 && let Some(expr_) = &block.expr
442 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
443 (expr.span.shrink_to_hi(), close.to_owned()),
447 match &compatible_variants[..] {
448 [] => { /* No variants to format */ }
449 [(variant, ctor_kind, field_name, note)] => {
450 // Just a single matching variant.
451 err.multipart_suggestion_verbose(
453 "try wrapping the expression in `{variant}`{note}",
454 note = note.as_deref().unwrap_or("")
456 suggestions_for(&**variant, *ctor_kind, *field_name),
457 Applicability::MaybeIncorrect,
462 // More than one matching variant.
463 err.multipart_suggestions(
465 "try wrapping the expression in a variant of `{}`",
466 self.tcx.def_path_str(expected_adt.did())
468 compatible_variants.into_iter().map(
469 |(variant, ctor_kind, field_name, _)| {
470 suggestions_for(&variant, ctor_kind, field_name)
473 Applicability::MaybeIncorrect,
483 fn suggest_non_zero_new_unwrap(
485 err: &mut Diagnostic,
486 expr: &hir::Expr<'_>,
491 let (adt, unwrap) = match expected.kind() {
492 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
493 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
495 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
499 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
500 ty::Adt(adt, _) => (adt, ".unwrap()"),
505 (sym::NonZeroU8, tcx.types.u8),
506 (sym::NonZeroU16, tcx.types.u16),
507 (sym::NonZeroU32, tcx.types.u32),
508 (sym::NonZeroU64, tcx.types.u64),
509 (sym::NonZeroU128, tcx.types.u128),
510 (sym::NonZeroI8, tcx.types.i8),
511 (sym::NonZeroI16, tcx.types.i16),
512 (sym::NonZeroI32, tcx.types.i32),
513 (sym::NonZeroI64, tcx.types.i64),
514 (sym::NonZeroI128, tcx.types.i128),
517 let Some((s, _)) = map
519 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
520 else { return false; };
522 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
524 err.multipart_suggestion(
525 format!("consider calling `{s}::new`"),
527 (expr.span.shrink_to_lo(), format!("{path}::new(")),
528 (expr.span.shrink_to_hi(), format!("){unwrap}")),
530 Applicability::MaybeIncorrect,
536 pub fn get_conversion_methods(
540 checked_ty: Ty<'tcx>,
542 ) -> Vec<AssocItem> {
543 let methods = self.probe_for_return_type(
545 probe::Mode::MethodCall,
550 self.has_only_self_parameter(m)
553 // This special internal attribute is used to permit
554 // "identity-like" conversion methods to be suggested here.
556 // FIXME (#46459 and #46460): ideally
557 // `std::convert::Into::into` and `std::borrow:ToOwned` would
558 // also be `#[rustc_conversion_suggestion]`, if not for
559 // method-probing false-positives and -negatives (respectively).
561 // FIXME? Other potential candidate methods: `as_ref` and
563 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
570 /// This function checks whether the method is not static and does not accept other parameters than `self`.
571 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
573 ty::AssocKind::Fn => {
574 method.fn_has_self_parameter
575 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
581 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
583 /// Given the following code:
584 /// ```compile_fail,E0308
586 /// fn takes_ref(_: &Foo) {}
587 /// let ref opt = Some(Foo);
589 /// opt.map(|param| takes_ref(param));
591 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
593 /// It only checks for `Option` and `Result` and won't work with
594 /// ```ignore (illustrative)
595 /// opt.map(|param| { takes_ref(param) });
597 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
598 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
602 let hir::def::Res::Local(local_id) = path.res else {
606 let local_parent = self.tcx.hir().get_parent_node(local_id);
607 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
611 let param_parent = self.tcx.hir().get_parent_node(*param_hir_id);
612 let Some(Node::Expr(hir::Expr {
614 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
616 })) = self.tcx.hir().find(param_parent) else {
620 let expr_parent = self.tcx.hir().get_parent_node(*expr_hir_id);
621 let hir = self.tcx.hir().find(expr_parent);
622 let closure_params_len = closure_fn_decl.inputs.len();
624 Some(Node::Expr(hir::Expr {
625 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
629 ) = (hir, closure_params_len) else {
633 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
634 let name = method_path.ident.name;
635 let is_as_ref_able = match self_ty.peel_refs().kind() {
637 (self.tcx.is_diagnostic_item(sym::Option, def.did())
638 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
639 && (name == sym::map || name == sym::and_then)
643 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
645 let suggestion = format!("as_ref().{}", src);
646 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
652 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
654 expr: &hir::Expr<'_>,
655 ) -> Option<Symbol> {
656 let hir = self.tcx.hir();
657 let local = match expr {
660 hir::ExprKind::Path(hir::QPath::Resolved(
663 res: hir::def::Res::Local(_),
664 segments: [hir::PathSegment { ident, .. }],
673 match hir.find(hir.get_parent_node(expr.hir_id))? {
674 Node::ExprField(field) => {
675 if field.ident.name == local.name && field.is_shorthand {
676 return Some(local.name);
685 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
686 pub(crate) fn maybe_get_block_expr(
688 expr: &hir::Expr<'tcx>,
689 ) -> Option<&'tcx hir::Expr<'tcx>> {
691 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
696 /// Returns whether the given expression is an `else if`.
697 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
698 if let hir::ExprKind::If(..) = expr.kind {
699 let parent_id = self.tcx.hir().get_parent_node(expr.hir_id);
700 if let Some(Node::Expr(hir::Expr {
701 kind: hir::ExprKind::If(_, _, Some(else_expr)),
703 })) = self.tcx.hir().find(parent_id)
705 return else_expr.hir_id == expr.hir_id;
711 /// This function is used to determine potential "simple" improvements or users' errors and
712 /// provide them useful help. For example:
714 /// ```compile_fail,E0308
715 /// fn some_fn(s: &str) {}
717 /// let x = "hey!".to_owned();
718 /// some_fn(x); // error
721 /// No need to find every potential function which could make a coercion to transform a
722 /// `String` into a `&str` since a `&` would do the trick!
724 /// In addition of this check, it also checks between references mutability state. If the
725 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
729 expr: &hir::Expr<'tcx>,
730 checked_ty: Ty<'tcx>,
738 bool, /* suggest `&` or `&mut` type annotation */
740 let sess = self.sess();
743 // If the span is from an external macro, there's no suggestion we can make.
744 if in_external_macro(sess, sp) {
748 let sm = sess.source_map();
750 let replace_prefix = |s: &str, old: &str, new: &str| {
751 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
754 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
755 let expr = expr.peel_drop_temps();
757 match (&expr.kind, expected.kind(), checked_ty.kind()) {
758 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
759 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
760 if let hir::ExprKind::Lit(_) = expr.kind
761 && let Ok(src) = sm.span_to_snippet(sp)
762 && replace_prefix(&src, "b\"", "\"").is_some()
764 let pos = sp.lo() + BytePos(1);
767 "consider removing the leading `b`".to_string(),
769 Applicability::MachineApplicable,
775 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
776 if let hir::ExprKind::Lit(_) = expr.kind
777 && let Ok(src) = sm.span_to_snippet(sp)
778 && replace_prefix(&src, "\"", "b\"").is_some()
782 "consider adding a leading `b`".to_string(),
784 Applicability::MachineApplicable,
792 (_, &ty::Ref(_, _, mutability), _) => {
793 // Check if it can work when put into a ref. For example:
796 // fn bar(x: &mut i32) {}
799 // bar(&x); // error, expected &mut
801 let ref_ty = match mutability {
802 hir::Mutability::Mut => {
803 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
805 hir::Mutability::Not => {
806 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
809 if self.can_coerce(ref_ty, expected) {
810 let mut sugg_sp = sp;
811 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
813 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
815 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
817 let ai = self.tcx.associated_item(did);
818 ai.trait_container(self.tcx) == Some(clone_trait)
821 && segment.ident.name == sym::clone
823 // If this expression had a clone call when suggesting borrowing
824 // we want to suggest removing it because it'd now be unnecessary.
825 sugg_sp = receiver.span;
828 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
829 let needs_parens = match expr.kind {
830 // parenthesize if needed (Issue #46756)
831 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
832 // parenthesize borrows of range literals (Issue #54505)
833 _ if is_range_literal(expr) => true,
837 if let Some(sugg) = self.can_use_as_ref(expr) {
842 Applicability::MachineApplicable,
848 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
849 Some(ident) => format!("{ident}: "),
850 None => String::new(),
853 if let Some(hir::Node::Expr(hir::Expr {
854 kind: hir::ExprKind::Assign(..),
856 })) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
858 if mutability == hir::Mutability::Mut {
859 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
864 let sugg_expr = if needs_parens { format!("({src})") } else { src };
865 return Some(match mutability {
866 hir::Mutability::Mut => (
868 "consider mutably borrowing here".to_string(),
869 format!("{prefix}&mut {sugg_expr}"),
870 Applicability::MachineApplicable,
874 hir::Mutability::Not => (
876 "consider borrowing here".to_string(),
877 format!("{prefix}&{sugg_expr}"),
878 Applicability::MachineApplicable,
887 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
889 &ty::Ref(_, checked, _),
890 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
891 // We have `&T`, check if what was expected was `T`. If so,
892 // we may want to suggest removing a `&`.
893 if sm.is_imported(expr.span) {
894 // Go through the spans from which this span was expanded,
895 // and find the one that's pointing inside `sp`.
897 // E.g. for `&format!("")`, where we want the span to the
898 // `format!()` invocation instead of its expansion.
899 if let Some(call_span) =
900 iter::successors(Some(expr.span), |s| s.parent_callsite())
901 .find(|&s| sp.contains(s))
902 && sm.is_span_accessible(call_span)
905 sp.with_hi(call_span.lo()),
906 "consider removing the borrow".to_string(),
908 Applicability::MachineApplicable,
915 if sp.contains(expr.span)
916 && sm.is_span_accessible(expr.span)
919 sp.with_hi(expr.span.lo()),
920 "consider removing the borrow".to_string(),
922 Applicability::MachineApplicable,
930 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
931 &ty::Ref(_, ty_a, mutbl_a),
933 if let Some(steps) = self.deref_steps(ty_a, ty_b)
934 // Only suggest valid if dereferencing needed.
936 // The pointer type implements `Copy` trait so the suggestion is always valid.
937 && let Ok(src) = sm.span_to_snippet(sp)
939 let derefs = "*".repeat(steps);
940 if let Some((span, src, applicability)) = match mutbl_b {
941 hir::Mutability::Mut => {
942 let new_prefix = "&mut ".to_owned() + &derefs;
944 hir::Mutability::Mut => {
945 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
946 let pos = sp.lo() + BytePos(5);
947 let sp = sp.with_lo(pos).with_hi(pos);
948 (sp, derefs, Applicability::MachineApplicable)
951 hir::Mutability::Not => {
952 replace_prefix(&src, "&", &new_prefix).map(|_| {
953 let pos = sp.lo() + BytePos(1);
954 let sp = sp.with_lo(pos).with_hi(pos);
957 format!("mut {derefs}"),
958 Applicability::Unspecified,
964 hir::Mutability::Not => {
965 let new_prefix = "&".to_owned() + &derefs;
967 hir::Mutability::Mut => {
968 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
969 let lo = sp.lo() + BytePos(1);
970 let hi = sp.lo() + BytePos(5);
971 let sp = sp.with_lo(lo).with_hi(hi);
972 (sp, derefs, Applicability::MachineApplicable)
975 hir::Mutability::Not => {
976 replace_prefix(&src, "&", &new_prefix).map(|_| {
977 let pos = sp.lo() + BytePos(1);
978 let sp = sp.with_lo(pos).with_hi(pos);
979 (sp, derefs, Applicability::MachineApplicable)
987 "consider dereferencing".to_string(),
996 _ if sp == expr.span => {
997 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
998 let mut expr = expr.peel_blocks();
999 let mut prefix_span = expr.span.shrink_to_lo();
1000 let mut remove = String::new();
1002 // Try peeling off any existing `&` and `&mut` to reach our target type
1004 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
1005 // If the expression has `&`, removing it would fix the error
1006 prefix_span = prefix_span.with_hi(inner.span.lo());
1008 remove += match mutbl {
1009 hir::Mutability::Not => "&",
1010 hir::Mutability::Mut => "&mut ",
1017 // If we've reached our target type with just removing `&`, then just print now.
1021 format!("consider removing the `{}`", remove.trim()),
1023 // Do not remove `&&` to get to bool, because it might be something like
1024 // { a } && b, which we have a separate fixup suggestion that is more
1025 // likely correct...
1026 if remove.trim() == "&&" && expected == self.tcx.types.bool {
1027 Applicability::MaybeIncorrect
1029 Applicability::MachineApplicable
1036 // For this suggestion to make sense, the type would need to be `Copy`,
1037 // or we have to be moving out of a `Box<T>`
1038 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1039 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1040 // `steps` layers of boxes, not just one, but this is easier and most likely.
1041 || (checked_ty.is_box() && steps == 1)
1043 let deref_kind = if checked_ty.is_box() {
1044 "unboxing the value"
1045 } else if checked_ty.is_region_ptr() {
1046 "dereferencing the borrow"
1048 "dereferencing the type"
1051 // Suggest removing `&` if we have removed any, otherwise suggest just
1052 // dereferencing the remaining number of steps.
1053 let message = if remove.is_empty() {
1054 format!("consider {deref_kind}")
1057 "consider removing the `{}` and {} instead",
1063 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1064 Some(ident) => format!("{ident}: "),
1065 None => String::new(),
1068 let (span, suggestion) = if self.is_else_if_block(expr) {
1069 // Don't suggest nonsense like `else *if`
1071 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1072 // prefix should be empty here..
1073 (expr.span.shrink_to_lo(), "*".to_string())
1075 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1082 Applicability::MachineApplicable,
1094 pub fn check_for_cast(
1096 err: &mut Diagnostic,
1097 expr: &hir::Expr<'_>,
1098 checked_ty: Ty<'tcx>,
1099 expected_ty: Ty<'tcx>,
1100 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1102 if self.tcx.sess.source_map().is_imported(expr.span) {
1103 // Ignore if span is from within a macro.
1107 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1111 // If casting this expression to a given numeric type would be appropriate in case of a type
1114 // We want to minimize the amount of casting operations that are suggested, as it can be a
1115 // lossy operation with potentially bad side effects, so we only suggest when encountering
1116 // an expression that indicates that the original type couldn't be directly changed.
1118 // For now, don't suggest casting with `as`.
1119 let can_cast = false;
1121 let mut sugg = vec![];
1123 if let Some(hir::Node::ExprField(field)) =
1124 self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
1126 // `expr` is a literal field for a struct, only suggest if appropriate
1127 if field.is_shorthand {
1128 // This is a field literal
1129 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1131 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1136 if let hir::ExprKind::Call(path, args) = &expr.kind
1137 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1138 (&path.kind, args.len())
1139 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1140 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1141 (&base_ty.kind, path_segment.ident.name)
1143 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1157 if base_ty_path.segments.len() == 1 =>
1167 "you can convert {} `{}` to {} `{}`",
1168 checked_ty.kind().article(),
1170 expected_ty.kind().article(),
1173 let cast_msg = format!(
1174 "you can cast {} `{}` to {} `{}`",
1175 checked_ty.kind().article(),
1177 expected_ty.kind().article(),
1180 let lit_msg = format!(
1181 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1184 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1185 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1191 let mut cast_suggestion = sugg.clone();
1192 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1193 let mut into_suggestion = sugg.clone();
1194 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1195 let mut suffix_suggestion = sugg.clone();
1196 suffix_suggestion.push((
1198 (&expected_ty.kind(), &checked_ty.kind()),
1199 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1201 // Remove fractional part from literal, for example `42.0f32` into `42`
1202 let src = src.trim_end_matches(&checked_ty.to_string());
1203 let len = src.split('.').next().unwrap().len();
1204 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1206 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1207 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1209 if expr.precedence().order() < PREC_POSTFIX {
1211 format!("{expected_ty})")
1213 expected_ty.to_string()
1216 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1217 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1219 let is_negative_int =
1220 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1221 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1223 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1225 let suggest_fallible_into_or_lhs_from =
1226 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1227 // If we know the expression the expected type is derived from, we might be able
1228 // to suggest a widening conversion rather than a narrowing one (which may
1229 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1231 // can be given the suggestion "u32::from(x) > y" rather than
1232 // "x > y.try_into().unwrap()".
1233 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1237 .span_to_snippet(expr.span)
1239 .map(|src| (expr, src))
1241 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1242 (lhs_expr_and_src, exp_to_found_is_fallible)
1245 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1247 let suggestion = vec![
1248 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1249 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1253 let msg = format!("{msg} and panic if the converted value doesn't fit");
1254 let mut suggestion = sugg.clone();
1256 expr.span.shrink_to_hi(),
1257 format!("{close_paren}.try_into().unwrap()"),
1261 err.multipart_suggestion_verbose(
1264 Applicability::MachineApplicable,
1268 let suggest_to_change_suffix_or_into =
1269 |err: &mut Diagnostic,
1270 found_to_exp_is_fallible: bool,
1271 exp_to_found_is_fallible: bool| {
1273 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1279 let always_fallible = found_to_exp_is_fallible
1280 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1281 let msg = if literal_is_ty_suffixed(expr) {
1283 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1284 // We now know that converting either the lhs or rhs is fallible. Before we
1285 // suggest a fallible conversion, check if the value can never fit in the
1287 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1290 } else if in_const_context {
1291 // Do not recommend `into` or `try_into` in const contexts.
1293 } else if found_to_exp_is_fallible {
1294 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1298 let suggestion = if literal_is_ty_suffixed(expr) {
1299 suffix_suggestion.clone()
1301 into_suggestion.clone()
1303 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1306 match (&expected_ty.kind(), &checked_ty.kind()) {
1307 (&ty::Int(ref exp), &ty::Int(ref found)) => {
1308 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1310 (Some(exp), Some(found)) if exp < found => (true, false),
1311 (Some(exp), Some(found)) if exp > found => (false, true),
1312 (None, Some(8 | 16)) => (false, true),
1313 (Some(8 | 16), None) => (true, false),
1314 (None, _) | (_, None) => (true, true),
1315 _ => (false, false),
1317 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1320 (&ty::Uint(ref exp), &ty::Uint(ref found)) => {
1321 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1323 (Some(exp), Some(found)) if exp < found => (true, false),
1324 (Some(exp), Some(found)) if exp > found => (false, true),
1325 (None, Some(8 | 16)) => (false, true),
1326 (Some(8 | 16), None) => (true, false),
1327 (None, _) | (_, None) => (true, true),
1328 _ => (false, false),
1330 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1333 (&ty::Int(exp), &ty::Uint(found)) => {
1334 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1336 (Some(exp), Some(found)) if found < exp => (false, true),
1337 (None, Some(8)) => (false, true),
1340 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1343 (&ty::Uint(exp), &ty::Int(found)) => {
1344 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1346 (Some(exp), Some(found)) if found > exp => (true, false),
1347 (Some(8), None) => (true, false),
1350 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1353 (&ty::Float(ref exp), &ty::Float(ref found)) => {
1354 if found.bit_width() < exp.bit_width() {
1355 suggest_to_change_suffix_or_into(err, false, true);
1356 } else if literal_is_ty_suffixed(expr) {
1357 err.multipart_suggestion_verbose(
1360 Applicability::MachineApplicable,
1362 } else if can_cast {
1363 // Missing try_into implementation for `f64` to `f32`
1364 err.multipart_suggestion_verbose(
1365 &format!("{cast_msg}, producing the closest possible value"),
1367 Applicability::MaybeIncorrect, // lossy conversion
1372 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1373 if literal_is_ty_suffixed(expr) {
1374 err.multipart_suggestion_verbose(
1377 Applicability::MachineApplicable,
1379 } else if can_cast {
1380 // Missing try_into implementation for `{float}` to `{integer}`
1381 err.multipart_suggestion_verbose(
1382 &format!("{msg}, rounding the float towards zero"),
1384 Applicability::MaybeIncorrect, // lossy conversion
1389 (&ty::Float(ref exp), &ty::Uint(ref found)) => {
1390 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1391 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1392 err.multipart_suggestion_verbose(
1394 "{msg}, producing the floating point representation of the integer",
1397 Applicability::MachineApplicable,
1399 } else if literal_is_ty_suffixed(expr) {
1400 err.multipart_suggestion_verbose(
1403 Applicability::MachineApplicable,
1406 // Missing try_into implementation for `{integer}` to `{float}`
1407 err.multipart_suggestion_verbose(
1409 "{cast_msg}, producing the floating point representation of the integer, \
1410 rounded if necessary",
1413 Applicability::MaybeIncorrect, // lossy conversion
1418 (&ty::Float(ref exp), &ty::Int(ref found)) => {
1419 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1420 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1421 err.multipart_suggestion_verbose(
1423 "{}, producing the floating point representation of the integer",
1427 Applicability::MachineApplicable,
1429 } else if literal_is_ty_suffixed(expr) {
1430 err.multipart_suggestion_verbose(
1433 Applicability::MachineApplicable,
1436 // Missing try_into implementation for `{integer}` to `{float}`
1437 err.multipart_suggestion_verbose(
1439 "{}, producing the floating point representation of the integer, \
1440 rounded if necessary",
1444 Applicability::MaybeIncorrect, // lossy conversion
1450 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1451 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1454 err.multipart_suggestion_verbose(
1455 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1457 Applicability::MachineApplicable,