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;
25 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
26 pub fn emit_coerce_suggestions(
29 expr: &hir::Expr<'tcx>,
32 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
33 error: Option<TypeError<'tcx>>,
35 if expr_ty == expected {
39 self.annotate_expected_due_to_let_ty(err, expr, error);
41 // Use `||` to give these suggestions a precedence
42 let _ = self.suggest_missing_parentheses(err, expr)
43 || self.suggest_deref_ref_or_into(err, expr, expected, expr_ty, expected_ty_expr)
44 || self.suggest_compatible_variants(err, expr, expected, expr_ty)
45 || self.suggest_non_zero_new_unwrap(err, expr, expected, expr_ty)
46 || self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty)
47 || self.suggest_no_capture_closure(err, expected, expr_ty)
48 || self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty)
49 || self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected)
50 || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
51 || self.suggest_into(err, expr, expr_ty, expected)
52 || self.suggest_option_to_bool(err, expr, expr_ty, expected)
53 || self.suggest_floating_point_literal(err, expr, expected);
55 self.note_type_is_not_clone(err, expected, expr_ty, expr);
56 self.note_need_for_fn_pointer(err, expected, expr_ty);
57 self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
60 // Requires that the two types unify, and prints an error message if
62 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
63 if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) {
68 pub fn demand_suptype_diag(
73 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
74 self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
77 #[instrument(skip(self), level = "debug")]
78 pub fn demand_suptype_with_origin(
80 cause: &ObligationCause<'tcx>,
83 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
84 match self.at(cause, self.param_env).sup(expected, actual) {
85 Ok(InferOk { obligations, value: () }) => {
86 self.register_predicates(obligations);
89 Err(e) => Some(self.err_ctxt().report_mismatched_types(&cause, expected, actual, e)),
93 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
94 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
99 pub fn demand_eqtype_diag(
104 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
105 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
108 pub fn demand_eqtype_with_origin(
110 cause: &ObligationCause<'tcx>,
113 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
114 match self.at(cause, self.param_env).eq(expected, actual) {
115 Ok(InferOk { obligations, value: () }) => {
116 self.register_predicates(obligations);
119 Err(e) => Some(self.err_ctxt().report_mismatched_types(cause, expected, actual, e)),
123 pub fn demand_coerce(
125 expr: &hir::Expr<'tcx>,
126 checked_ty: Ty<'tcx>,
128 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
129 allow_two_phase: AllowTwoPhase,
132 self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase);
133 if let Some(mut err) = err {
139 /// Checks that the type of `expr` can be coerced to `expected`.
141 /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!`
142 /// will be permitted if the diverges flag is currently "always".
143 #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))]
144 pub fn demand_coerce_diag(
146 expr: &hir::Expr<'tcx>,
147 checked_ty: Ty<'tcx>,
149 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
150 allow_two_phase: AllowTwoPhase,
151 ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
152 let expected = self.resolve_vars_with_obligations(expected);
154 let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) {
155 Ok(ty) => return (ty, None),
159 self.set_tainted_by_errors(self.tcx.sess.delay_span_bug(
161 "`TypeError` when attempting coercion but no error emitted",
163 let expr = expr.peel_drop_temps();
164 let cause = self.misc(expr.span);
165 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
166 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e.clone());
168 let is_insufficiently_polymorphic =
169 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
171 // FIXME(#73154): For now, we do leak check when coercing function
172 // pointers in typeck, instead of only during borrowck. This can lead
173 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
174 if !is_insufficiently_polymorphic {
175 self.emit_coerce_suggestions(
185 (expected, Some(err))
188 fn annotate_expected_due_to_let_ty(
190 err: &mut Diagnostic,
191 expr: &hir::Expr<'_>,
192 error: Option<TypeError<'_>>,
194 let parent = self.tcx.hir().get_parent_node(expr.hir_id);
195 match (self.tcx.hir().find(parent), error) {
196 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
197 if init.hir_id == expr.hir_id =>
199 // Point at `let` assignment type.
200 err.span_label(ty.span, "expected due to this");
203 Some(hir::Node::Expr(hir::Expr {
204 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
206 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
207 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
208 // We ignore closures explicitly because we already point at them elsewhere.
209 // Point at the assigned-to binding.
210 let mut primary_span = lhs.span;
211 let mut secondary_span = lhs.span;
212 let mut post_message = "";
214 hir::ExprKind::Path(hir::QPath::Resolved(
219 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
225 if let Some(hir::Node::Item(hir::Item {
227 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
229 })) = self.tcx.hir().get_if_local(*def_id)
231 primary_span = ty.span;
232 secondary_span = ident.span;
233 post_message = " type";
236 hir::ExprKind::Path(hir::QPath::Resolved(
238 hir::Path { res: hir::def::Res::Local(hir_id), .. },
240 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
241 let parent = self.tcx.hir().get_parent_node(pat.hir_id);
242 primary_span = pat.span;
243 secondary_span = pat.span;
244 match self.tcx.hir().find(parent) {
245 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
246 primary_span = ty.span;
247 post_message = " type";
249 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
250 primary_span = init.span;
251 post_message = " value";
253 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
254 primary_span = *ty_span;
255 post_message = " parameter type";
264 if primary_span != secondary_span
269 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
271 // We are pointing at the binding's type or initializer value, but it's pattern
272 // is in a different line, so we point at both.
273 err.span_label(secondary_span, "expected due to the type of this binding");
274 err.span_label(primary_span, &format!("expected due to this{post_message}"));
275 } else if post_message == "" {
276 // We are pointing at either the assignment lhs or the binding def pattern.
277 err.span_label(primary_span, "expected due to the type of this binding");
279 // We are pointing at the binding's type or initializer value.
280 err.span_label(primary_span, &format!("expected due to this{post_message}"));
283 if !lhs.is_syntactic_place_expr() {
284 // We already emitted E0070 "invalid left-hand side of assignment", so we
286 err.downgrade_to_delayed_bug();
293 /// If the expected type is an enum (Issue #55250) with any variants whose
294 /// sole field is of the found type, suggest such variants. (Issue #42764)
295 fn suggest_compatible_variants(
297 err: &mut Diagnostic,
298 expr: &hir::Expr<'_>,
302 if let ty::Adt(expected_adt, substs) = expected.kind() {
303 if let hir::ExprKind::Field(base, ident) = expr.kind {
304 let base_ty = self.typeck_results.borrow().expr_ty(base);
305 if self.can_eq(self.param_env, base_ty, expected).is_ok()
306 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
308 err.span_suggestion_verbose(
309 expr.span.with_lo(base_span.hi()),
310 format!("consider removing the tuple struct field `{ident}`"),
312 Applicability::MaybeIncorrect,
318 // If the expression is of type () and it's the return expression of a block,
319 // we suggest adding a separate return expression instead.
320 // (To avoid things like suggesting `Ok(while .. { .. })`.)
321 if expr_ty.is_unit() {
322 let mut id = expr.hir_id;
325 // Unroll desugaring, to make sure this works for `for` loops etc.
327 parent = self.tcx.hir().get_parent_node(id);
328 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
329 if parent_span.find_ancestor_inside(expr.span).is_some() {
330 // The parent node is part of the same span, so is the result of the
331 // same expansion/desugaring and not the 'real' parent node.
339 if let Some(hir::Node::Block(&hir::Block {
340 span: block_span, expr: Some(e), ..
341 })) = self.tcx.hir().find(parent)
344 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
345 let return_suggestions = if self
347 .is_diagnostic_item(sym::Result, expected_adt.did())
350 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
351 vec!["None", "Some(())"]
355 if let Some(indent) =
356 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
358 // Add a semicolon, except after `}`.
360 match self.tcx.sess.source_map().span_to_snippet(span) {
361 Ok(s) if s.ends_with('}') => "",
364 err.span_suggestions(
366 "try adding an expression at the end of the block",
369 .map(|r| format!("{semicolon}\n{indent}{r}")),
370 Applicability::MaybeIncorrect,
379 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
383 variant.fields.len() == 1
385 .filter_map(|variant| {
386 let sole_field = &variant.fields[0];
388 let field_is_local = sole_field.did.is_local();
389 let field_is_accessible =
390 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
391 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
392 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
394 if !field_is_local && !field_is_accessible {
398 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
399 .then(|| format!(" (its field is private, but it's local to this crate and its privacy can be changed)"));
401 let sole_field_ty = sole_field.ty(self.tcx, substs);
402 if self.can_coerce(expr_ty, sole_field_ty) {
404 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
405 // FIXME #56861: DRYer prelude filtering
406 if let Some(path) = variant_path.strip_prefix("std::prelude::")
407 && let Some((_, path)) = path.split_once("::")
409 return Some((path.to_string(), variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy));
411 Some((variant_path, variant.ctor_kind(), sole_field.name, note_about_variant_field_privacy))
418 let suggestions_for = |variant: &_, ctor_kind, field_name| {
419 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
420 Some(ident) => format!("{ident}: "),
421 None => String::new(),
424 let (open, close) = match ctor_kind {
425 Some(CtorKind::Fn) => ("(".to_owned(), ")"),
426 None => (format!(" {{ {field_name}: "), " }"),
428 // unit variants don't have fields
429 Some(CtorKind::Const) => unreachable!(),
432 // Suggest constructor as deep into the block tree as possible.
433 // This fixes https://github.com/rust-lang/rust/issues/101065,
434 // and also just helps make the most minimal suggestions.
436 while let hir::ExprKind::Block(block, _) = &expr.kind
437 && let Some(expr_) = &block.expr
443 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
444 (expr.span.shrink_to_hi(), close.to_owned()),
448 match &compatible_variants[..] {
449 [] => { /* No variants to format */ }
450 [(variant, ctor_kind, field_name, note)] => {
451 // Just a single matching variant.
452 err.multipart_suggestion_verbose(
454 "try wrapping the expression in `{variant}`{note}",
455 note = note.as_deref().unwrap_or("")
457 suggestions_for(&**variant, *ctor_kind, *field_name),
458 Applicability::MaybeIncorrect,
463 // More than one matching variant.
464 err.multipart_suggestions(
466 "try wrapping the expression in a variant of `{}`",
467 self.tcx.def_path_str(expected_adt.did())
469 compatible_variants.into_iter().map(
470 |(variant, ctor_kind, field_name, _)| {
471 suggestions_for(&variant, ctor_kind, field_name)
474 Applicability::MaybeIncorrect,
484 fn suggest_non_zero_new_unwrap(
486 err: &mut Diagnostic,
487 expr: &hir::Expr<'_>,
492 let (adt, unwrap) = match expected.kind() {
493 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
494 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
496 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
500 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
501 ty::Adt(adt, _) => (adt, ".unwrap()"),
506 (sym::NonZeroU8, tcx.types.u8),
507 (sym::NonZeroU16, tcx.types.u16),
508 (sym::NonZeroU32, tcx.types.u32),
509 (sym::NonZeroU64, tcx.types.u64),
510 (sym::NonZeroU128, tcx.types.u128),
511 (sym::NonZeroI8, tcx.types.i8),
512 (sym::NonZeroI16, tcx.types.i16),
513 (sym::NonZeroI32, tcx.types.i32),
514 (sym::NonZeroI64, tcx.types.i64),
515 (sym::NonZeroI128, tcx.types.i128),
518 let Some((s, _)) = map
520 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
521 else { return false; };
523 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
525 err.multipart_suggestion(
526 format!("consider calling `{s}::new`"),
528 (expr.span.shrink_to_lo(), format!("{path}::new(")),
529 (expr.span.shrink_to_hi(), format!("){unwrap}")),
531 Applicability::MaybeIncorrect,
537 pub fn get_conversion_methods(
541 checked_ty: Ty<'tcx>,
543 ) -> Vec<AssocItem> {
544 let methods = self.probe_for_return_type(
546 probe::Mode::MethodCall,
551 self.has_only_self_parameter(m)
554 // This special internal attribute is used to permit
555 // "identity-like" conversion methods to be suggested here.
557 // FIXME (#46459 and #46460): ideally
558 // `std::convert::Into::into` and `std::borrow:ToOwned` would
559 // also be `#[rustc_conversion_suggestion]`, if not for
560 // method-probing false-positives and -negatives (respectively).
562 // FIXME? Other potential candidate methods: `as_ref` and
564 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
571 /// This function checks whether the method is not static and does not accept other parameters than `self`.
572 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
574 ty::AssocKind::Fn => {
575 method.fn_has_self_parameter
576 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
582 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
584 /// Given the following code:
585 /// ```compile_fail,E0308
587 /// fn takes_ref(_: &Foo) {}
588 /// let ref opt = Some(Foo);
590 /// opt.map(|param| takes_ref(param));
592 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
594 /// It only checks for `Option` and `Result` and won't work with
595 /// ```ignore (illustrative)
596 /// opt.map(|param| { takes_ref(param) });
598 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
599 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
603 let hir::def::Res::Local(local_id) = path.res else {
607 let local_parent = self.tcx.hir().get_parent_node(local_id);
608 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
612 let param_parent = self.tcx.hir().get_parent_node(*param_hir_id);
613 let Some(Node::Expr(hir::Expr {
615 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
617 })) = self.tcx.hir().find(param_parent) else {
621 let expr_parent = self.tcx.hir().get_parent_node(*expr_hir_id);
622 let hir = self.tcx.hir().find(expr_parent);
623 let closure_params_len = closure_fn_decl.inputs.len();
625 Some(Node::Expr(hir::Expr {
626 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
630 ) = (hir, closure_params_len) else {
634 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
635 let name = method_path.ident.name;
636 let is_as_ref_able = match self_ty.peel_refs().kind() {
638 (self.tcx.is_diagnostic_item(sym::Option, def.did())
639 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
640 && (name == sym::map || name == sym::and_then)
644 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
646 let suggestion = format!("as_ref().{}", src);
647 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
653 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
655 expr: &hir::Expr<'_>,
656 ) -> Option<Symbol> {
657 let hir = self.tcx.hir();
658 let local = match expr {
661 hir::ExprKind::Path(hir::QPath::Resolved(
664 res: hir::def::Res::Local(_),
665 segments: [hir::PathSegment { ident, .. }],
674 match hir.find(hir.get_parent_node(expr.hir_id))? {
675 Node::ExprField(field) => {
676 if field.ident.name == local.name && field.is_shorthand {
677 return Some(local.name);
686 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
687 pub(crate) fn maybe_get_block_expr(
689 expr: &hir::Expr<'tcx>,
690 ) -> Option<&'tcx hir::Expr<'tcx>> {
692 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
697 /// Returns whether the given expression is an `else if`.
698 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
699 if let hir::ExprKind::If(..) = expr.kind {
700 let parent_id = self.tcx.hir().get_parent_node(expr.hir_id);
701 if let Some(Node::Expr(hir::Expr {
702 kind: hir::ExprKind::If(_, _, Some(else_expr)),
704 })) = self.tcx.hir().find(parent_id)
706 return else_expr.hir_id == expr.hir_id;
712 /// This function is used to determine potential "simple" improvements or users' errors and
713 /// provide them useful help. For example:
715 /// ```compile_fail,E0308
716 /// fn some_fn(s: &str) {}
718 /// let x = "hey!".to_owned();
719 /// some_fn(x); // error
722 /// No need to find every potential function which could make a coercion to transform a
723 /// `String` into a `&str` since a `&` would do the trick!
725 /// In addition of this check, it also checks between references mutability state. If the
726 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
730 expr: &hir::Expr<'tcx>,
731 checked_ty: Ty<'tcx>,
739 bool, /* suggest `&` or `&mut` type annotation */
741 let sess = self.sess();
744 // If the span is from an external macro, there's no suggestion we can make.
745 if in_external_macro(sess, sp) {
749 let sm = sess.source_map();
751 let replace_prefix = |s: &str, old: &str, new: &str| {
752 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
755 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
756 let expr = expr.peel_drop_temps();
758 match (&expr.kind, expected.kind(), checked_ty.kind()) {
759 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
760 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
761 if let hir::ExprKind::Lit(_) = expr.kind
762 && let Ok(src) = sm.span_to_snippet(sp)
763 && replace_prefix(&src, "b\"", "\"").is_some()
765 let pos = sp.lo() + BytePos(1);
768 "consider removing the leading `b`".to_string(),
770 Applicability::MachineApplicable,
776 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
777 if let hir::ExprKind::Lit(_) = expr.kind
778 && let Ok(src) = sm.span_to_snippet(sp)
779 && replace_prefix(&src, "\"", "b\"").is_some()
783 "consider adding a leading `b`".to_string(),
785 Applicability::MachineApplicable,
793 (_, &ty::Ref(_, _, mutability), _) => {
794 // Check if it can work when put into a ref. For example:
797 // fn bar(x: &mut i32) {}
800 // bar(&x); // error, expected &mut
802 let ref_ty = match mutability {
803 hir::Mutability::Mut => {
804 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
806 hir::Mutability::Not => {
807 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
810 if self.can_coerce(ref_ty, expected) {
811 let mut sugg_sp = sp;
812 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
814 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
816 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
818 let ai = self.tcx.associated_item(did);
819 ai.trait_container(self.tcx) == Some(clone_trait)
822 && segment.ident.name == sym::clone
824 // If this expression had a clone call when suggesting borrowing
825 // we want to suggest removing it because it'd now be unnecessary.
826 sugg_sp = receiver.span;
829 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
830 let needs_parens = match expr.kind {
831 // parenthesize if needed (Issue #46756)
832 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
833 // parenthesize borrows of range literals (Issue #54505)
834 _ if is_range_literal(expr) => true,
838 if let Some(sugg) = self.can_use_as_ref(expr) {
843 Applicability::MachineApplicable,
849 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
850 Some(ident) => format!("{ident}: "),
851 None => String::new(),
854 if let Some(hir::Node::Expr(hir::Expr {
855 kind: hir::ExprKind::Assign(..),
857 })) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
859 if mutability.is_mut() {
860 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
865 let sugg_expr = if needs_parens { format!("({src})") } else { src };
868 format!("consider {}borrowing here", mutability.mutably_str()),
869 format!("{prefix}{}{sugg_expr}", mutability.ref_prefix_str()),
870 Applicability::MachineApplicable,
878 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
880 &ty::Ref(_, checked, _),
881 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
882 // We have `&T`, check if what was expected was `T`. If so,
883 // we may want to suggest removing a `&`.
884 if sm.is_imported(expr.span) {
885 // Go through the spans from which this span was expanded,
886 // and find the one that's pointing inside `sp`.
888 // E.g. for `&format!("")`, where we want the span to the
889 // `format!()` invocation instead of its expansion.
890 if let Some(call_span) =
891 iter::successors(Some(expr.span), |s| s.parent_callsite())
892 .find(|&s| sp.contains(s))
893 && sm.is_span_accessible(call_span)
896 sp.with_hi(call_span.lo()),
897 "consider removing the borrow".to_string(),
899 Applicability::MachineApplicable,
906 if sp.contains(expr.span)
907 && sm.is_span_accessible(expr.span)
910 sp.with_hi(expr.span.lo()),
911 "consider removing the borrow".to_string(),
913 Applicability::MachineApplicable,
921 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
922 &ty::Ref(_, ty_a, mutbl_a),
924 if let Some(steps) = self.deref_steps(ty_a, ty_b)
925 // Only suggest valid if dereferencing needed.
927 // The pointer type implements `Copy` trait so the suggestion is always valid.
928 && let Ok(src) = sm.span_to_snippet(sp)
930 let derefs = "*".repeat(steps);
931 let old_prefix = mutbl_a.ref_prefix_str();
932 let new_prefix = mutbl_b.ref_prefix_str().to_owned() + &derefs;
934 let suggestion = replace_prefix(&src, old_prefix, &new_prefix).map(|_| {
935 // skip `&` or `&mut ` if both mutabilities are mutable
936 let lo = sp.lo() + BytePos(min(old_prefix.len(), mutbl_b.ref_prefix_str().len()) as _);
937 // skip `&` or `&mut `
938 let hi = sp.lo() + BytePos(old_prefix.len() as _);
939 let sp = sp.with_lo(lo).with_hi(hi);
943 format!("{}{derefs}", if mutbl_a != mutbl_b { mutbl_b.prefix_str() } else { "" }),
944 if mutbl_b <= mutbl_a { Applicability::MachineApplicable } else { Applicability::MaybeIncorrect }
948 if let Some((span, src, applicability)) = suggestion {
951 "consider dereferencing".to_string(),
960 _ if sp == expr.span => {
961 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
962 let mut expr = expr.peel_blocks();
963 let mut prefix_span = expr.span.shrink_to_lo();
964 let mut remove = String::new();
966 // Try peeling off any existing `&` and `&mut` to reach our target type
968 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
969 // If the expression has `&`, removing it would fix the error
970 prefix_span = prefix_span.with_hi(inner.span.lo());
972 remove.push_str(mutbl.ref_prefix_str());
978 // If we've reached our target type with just removing `&`, then just print now.
982 format!("consider removing the `{}`", remove.trim()),
984 // Do not remove `&&` to get to bool, because it might be something like
985 // { a } && b, which we have a separate fixup suggestion that is more
987 if remove.trim() == "&&" && expected == self.tcx.types.bool {
988 Applicability::MaybeIncorrect
990 Applicability::MachineApplicable
997 // For this suggestion to make sense, the type would need to be `Copy`,
998 // or we have to be moving out of a `Box<T>`
999 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1000 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1001 // `steps` layers of boxes, not just one, but this is easier and most likely.
1002 || (checked_ty.is_box() && steps == 1)
1004 let deref_kind = if checked_ty.is_box() {
1005 "unboxing the value"
1006 } else if checked_ty.is_region_ptr() {
1007 "dereferencing the borrow"
1009 "dereferencing the type"
1012 // Suggest removing `&` if we have removed any, otherwise suggest just
1013 // dereferencing the remaining number of steps.
1014 let message = if remove.is_empty() {
1015 format!("consider {deref_kind}")
1018 "consider removing the `{}` and {} instead",
1024 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1025 Some(ident) => format!("{ident}: "),
1026 None => String::new(),
1029 let (span, suggestion) = if self.is_else_if_block(expr) {
1030 // Don't suggest nonsense like `else *if`
1032 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1033 // prefix should be empty here..
1034 (expr.span.shrink_to_lo(), "*".to_string())
1036 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1043 Applicability::MachineApplicable,
1055 pub fn check_for_cast(
1057 err: &mut Diagnostic,
1058 expr: &hir::Expr<'_>,
1059 checked_ty: Ty<'tcx>,
1060 expected_ty: Ty<'tcx>,
1061 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1063 if self.tcx.sess.source_map().is_imported(expr.span) {
1064 // Ignore if span is from within a macro.
1068 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1072 // If casting this expression to a given numeric type would be appropriate in case of a type
1075 // We want to minimize the amount of casting operations that are suggested, as it can be a
1076 // lossy operation with potentially bad side effects, so we only suggest when encountering
1077 // an expression that indicates that the original type couldn't be directly changed.
1079 // For now, don't suggest casting with `as`.
1080 let can_cast = false;
1082 let mut sugg = vec![];
1084 if let Some(hir::Node::ExprField(field)) =
1085 self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
1087 // `expr` is a literal field for a struct, only suggest if appropriate
1088 if field.is_shorthand {
1089 // This is a field literal
1090 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1092 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1097 if let hir::ExprKind::Call(path, args) = &expr.kind
1098 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1099 (&path.kind, args.len())
1100 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1101 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1102 (&base_ty.kind, path_segment.ident.name)
1104 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1118 if base_ty_path.segments.len() == 1 =>
1128 "you can convert {} `{}` to {} `{}`",
1129 checked_ty.kind().article(),
1131 expected_ty.kind().article(),
1134 let cast_msg = format!(
1135 "you can cast {} `{}` to {} `{}`",
1136 checked_ty.kind().article(),
1138 expected_ty.kind().article(),
1141 let lit_msg = format!(
1142 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1145 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1146 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1152 let mut cast_suggestion = sugg.clone();
1153 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1154 let mut into_suggestion = sugg.clone();
1155 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1156 let mut suffix_suggestion = sugg.clone();
1157 suffix_suggestion.push((
1159 (&expected_ty.kind(), &checked_ty.kind()),
1160 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1162 // Remove fractional part from literal, for example `42.0f32` into `42`
1163 let src = src.trim_end_matches(&checked_ty.to_string());
1164 let len = src.split('.').next().unwrap().len();
1165 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1167 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1168 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1170 if expr.precedence().order() < PREC_POSTFIX {
1172 format!("{expected_ty})")
1174 expected_ty.to_string()
1177 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1178 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1180 let is_negative_int =
1181 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1182 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1184 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1186 let suggest_fallible_into_or_lhs_from =
1187 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1188 // If we know the expression the expected type is derived from, we might be able
1189 // to suggest a widening conversion rather than a narrowing one (which may
1190 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1192 // can be given the suggestion "u32::from(x) > y" rather than
1193 // "x > y.try_into().unwrap()".
1194 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1198 .span_to_snippet(expr.span)
1200 .map(|src| (expr, src))
1202 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1203 (lhs_expr_and_src, exp_to_found_is_fallible)
1206 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1208 let suggestion = vec![
1209 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1210 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1214 let msg = format!("{msg} and panic if the converted value doesn't fit");
1215 let mut suggestion = sugg.clone();
1217 expr.span.shrink_to_hi(),
1218 format!("{close_paren}.try_into().unwrap()"),
1222 err.multipart_suggestion_verbose(
1225 Applicability::MachineApplicable,
1229 let suggest_to_change_suffix_or_into =
1230 |err: &mut Diagnostic,
1231 found_to_exp_is_fallible: bool,
1232 exp_to_found_is_fallible: bool| {
1234 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1240 let always_fallible = found_to_exp_is_fallible
1241 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1242 let msg = if literal_is_ty_suffixed(expr) {
1244 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1245 // We now know that converting either the lhs or rhs is fallible. Before we
1246 // suggest a fallible conversion, check if the value can never fit in the
1248 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1251 } else if in_const_context {
1252 // Do not recommend `into` or `try_into` in const contexts.
1254 } else if found_to_exp_is_fallible {
1255 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1259 let suggestion = if literal_is_ty_suffixed(expr) {
1260 suffix_suggestion.clone()
1262 into_suggestion.clone()
1264 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1267 match (&expected_ty.kind(), &checked_ty.kind()) {
1268 (&ty::Int(ref exp), &ty::Int(ref found)) => {
1269 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1271 (Some(exp), Some(found)) if exp < found => (true, false),
1272 (Some(exp), Some(found)) if exp > found => (false, true),
1273 (None, Some(8 | 16)) => (false, true),
1274 (Some(8 | 16), None) => (true, false),
1275 (None, _) | (_, None) => (true, true),
1276 _ => (false, false),
1278 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1281 (&ty::Uint(ref exp), &ty::Uint(ref found)) => {
1282 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1284 (Some(exp), Some(found)) if exp < found => (true, false),
1285 (Some(exp), Some(found)) if exp > found => (false, true),
1286 (None, Some(8 | 16)) => (false, true),
1287 (Some(8 | 16), None) => (true, false),
1288 (None, _) | (_, None) => (true, true),
1289 _ => (false, false),
1291 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1294 (&ty::Int(exp), &ty::Uint(found)) => {
1295 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1297 (Some(exp), Some(found)) if found < exp => (false, true),
1298 (None, Some(8)) => (false, true),
1301 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1304 (&ty::Uint(exp), &ty::Int(found)) => {
1305 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1307 (Some(exp), Some(found)) if found > exp => (true, false),
1308 (Some(8), None) => (true, false),
1311 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1314 (&ty::Float(ref exp), &ty::Float(ref found)) => {
1315 if found.bit_width() < exp.bit_width() {
1316 suggest_to_change_suffix_or_into(err, false, true);
1317 } else if literal_is_ty_suffixed(expr) {
1318 err.multipart_suggestion_verbose(
1321 Applicability::MachineApplicable,
1323 } else if can_cast {
1324 // Missing try_into implementation for `f64` to `f32`
1325 err.multipart_suggestion_verbose(
1326 &format!("{cast_msg}, producing the closest possible value"),
1328 Applicability::MaybeIncorrect, // lossy conversion
1333 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1334 if literal_is_ty_suffixed(expr) {
1335 err.multipart_suggestion_verbose(
1338 Applicability::MachineApplicable,
1340 } else if can_cast {
1341 // Missing try_into implementation for `{float}` to `{integer}`
1342 err.multipart_suggestion_verbose(
1343 &format!("{msg}, rounding the float towards zero"),
1345 Applicability::MaybeIncorrect, // lossy conversion
1350 (&ty::Float(ref exp), &ty::Uint(ref found)) => {
1351 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1352 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1353 err.multipart_suggestion_verbose(
1355 "{msg}, producing the floating point representation of the integer",
1358 Applicability::MachineApplicable,
1360 } else if literal_is_ty_suffixed(expr) {
1361 err.multipart_suggestion_verbose(
1364 Applicability::MachineApplicable,
1367 // Missing try_into implementation for `{integer}` to `{float}`
1368 err.multipart_suggestion_verbose(
1370 "{cast_msg}, producing the floating point representation of the integer, \
1371 rounded if necessary",
1374 Applicability::MaybeIncorrect, // lossy conversion
1379 (&ty::Float(ref exp), &ty::Int(ref found)) => {
1380 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1381 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1382 err.multipart_suggestion_verbose(
1384 "{}, producing the floating point representation of the integer",
1388 Applicability::MachineApplicable,
1390 } else if literal_is_ty_suffixed(expr) {
1391 err.multipart_suggestion_verbose(
1394 Applicability::MachineApplicable,
1397 // Missing try_into implementation for `{integer}` to `{float}`
1398 err.multipart_suggestion_verbose(
1400 "{}, producing the floating point representation of the integer, \
1401 rounded if necessary",
1405 Applicability::MaybeIncorrect, // lossy conversion
1411 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1412 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1415 err.multipart_suggestion_verbose(
1416 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1418 Applicability::MachineApplicable,