2 use rustc_ast::util::parser::PREC_POSTFIX;
3 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
5 use rustc_hir::lang_items::LangItem;
6 use rustc_hir::{is_range_literal, Node};
7 use rustc_infer::infer::InferOk;
8 use rustc_middle::lint::in_external_macro;
9 use rustc_middle::middle::stability::EvalResult;
10 use rustc_middle::ty::adjustment::AllowTwoPhase;
11 use rustc_middle::ty::error::{ExpectedFound, TypeError};
12 use rustc_middle::ty::print::with_no_trimmed_paths;
13 use rustc_middle::ty::{self, Article, AssocItem, Ty, TypeAndMut};
14 use rustc_span::symbol::{sym, Symbol};
15 use rustc_span::{BytePos, Span};
16 use rustc_trait_selection::infer::InferCtxtExt as _;
17 use rustc_trait_selection::traits::ObligationCause;
19 use super::method::probe;
23 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
24 pub fn emit_coerce_suggestions(
27 expr: &hir::Expr<'tcx>,
30 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
31 error: Option<TypeError<'tcx>>,
33 if expr_ty == expected {
37 self.annotate_expected_due_to_let_ty(err, expr, error);
39 // Use `||` to give these suggestions a precedence
40 let _ = self.suggest_missing_parentheses(err, expr)
41 || self.suggest_deref_ref_or_into(err, expr, expected, expr_ty, expected_ty_expr)
42 || self.suggest_compatible_variants(err, expr, expected, expr_ty)
43 || self.suggest_non_zero_new_unwrap(err, expr, expected, expr_ty)
44 || self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty)
45 || self.suggest_no_capture_closure(err, expected, expr_ty)
46 || self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty)
47 || self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected)
48 || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
49 || self.suggest_into(err, expr, expr_ty, expected)
50 || self.suggest_option_to_bool(err, expr, expr_ty, expected)
51 || self.suggest_floating_point_literal(err, expr, expected);
53 self.note_type_is_not_clone(err, expected, expr_ty, expr);
54 self.note_need_for_fn_pointer(err, expected, expr_ty);
55 self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
58 // Requires that the two types unify, and prints an error message if
60 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
61 if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) {
66 pub fn demand_suptype_diag(
71 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
72 self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
75 #[instrument(skip(self), level = "debug")]
76 pub fn demand_suptype_with_origin(
78 cause: &ObligationCause<'tcx>,
81 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
82 match self.at(cause, self.param_env).sup(expected, actual) {
83 Ok(InferOk { obligations, value: () }) => {
84 self.register_predicates(obligations);
87 Err(e) => Some(self.err_ctxt().report_mismatched_types(&cause, expected, actual, e)),
91 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
92 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
97 pub fn demand_eqtype_diag(
102 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
103 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
106 pub fn demand_eqtype_with_origin(
108 cause: &ObligationCause<'tcx>,
111 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
112 match self.at(cause, self.param_env).eq(expected, actual) {
113 Ok(InferOk { obligations, value: () }) => {
114 self.register_predicates(obligations);
117 Err(e) => Some(self.err_ctxt().report_mismatched_types(cause, expected, actual, e)),
121 pub fn demand_coerce(
123 expr: &hir::Expr<'tcx>,
124 checked_ty: Ty<'tcx>,
126 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
127 allow_two_phase: AllowTwoPhase,
130 self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase);
131 if let Some(mut err) = err {
137 /// Checks that the type of `expr` can be coerced to `expected`.
139 /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!`
140 /// will be permitted if the diverges flag is currently "always".
141 #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))]
142 pub fn demand_coerce_diag(
144 expr: &hir::Expr<'tcx>,
145 checked_ty: Ty<'tcx>,
147 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
148 allow_two_phase: AllowTwoPhase,
149 ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
150 let expected = self.resolve_vars_with_obligations(expected);
152 let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) {
153 Ok(ty) => return (ty, None),
157 self.set_tainted_by_errors(self.tcx.sess.delay_span_bug(
159 "`TypeError` when attempting coercion but no error emitted",
161 let expr = expr.peel_drop_temps();
162 let cause = self.misc(expr.span);
163 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
164 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e.clone());
166 let is_insufficiently_polymorphic =
167 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
169 // FIXME(#73154): For now, we do leak check when coercing function
170 // pointers in typeck, instead of only during borrowck. This can lead
171 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
172 if !is_insufficiently_polymorphic {
173 self.emit_coerce_suggestions(
183 (expected, Some(err))
186 fn annotate_expected_due_to_let_ty(
188 err: &mut Diagnostic,
189 expr: &hir::Expr<'_>,
190 error: Option<TypeError<'_>>,
192 let parent = self.tcx.hir().get_parent_node(expr.hir_id);
193 match (self.tcx.hir().find(parent), error) {
194 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
195 if init.hir_id == expr.hir_id =>
197 // Point at `let` assignment type.
198 err.span_label(ty.span, "expected due to this");
201 Some(hir::Node::Expr(hir::Expr {
202 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
204 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
205 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
206 // We ignore closures explicitly because we already point at them elsewhere.
207 // Point at the assigned-to binding.
208 let mut primary_span = lhs.span;
209 let mut secondary_span = lhs.span;
210 let mut post_message = "";
212 hir::ExprKind::Path(hir::QPath::Resolved(
217 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
223 if let Some(hir::Node::Item(hir::Item {
225 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
227 })) = self.tcx.hir().get_if_local(*def_id)
229 primary_span = ty.span;
230 secondary_span = ident.span;
231 post_message = " type";
234 hir::ExprKind::Path(hir::QPath::Resolved(
236 hir::Path { res: hir::def::Res::Local(hir_id), .. },
238 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
239 let parent = self.tcx.hir().get_parent_node(pat.hir_id);
240 primary_span = pat.span;
241 secondary_span = pat.span;
242 match self.tcx.hir().find(parent) {
243 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
244 primary_span = ty.span;
245 post_message = " type";
247 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
248 primary_span = init.span;
249 post_message = " value";
251 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
252 primary_span = *ty_span;
253 post_message = " parameter type";
262 if primary_span != secondary_span
267 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
269 // We are pointing at the binding's type or initializer value, but it's pattern
270 // is in a different line, so we point at both.
271 err.span_label(secondary_span, "expected due to the type of this binding");
272 err.span_label(primary_span, &format!("expected due to this{post_message}"));
273 } else if post_message == "" {
274 // We are pointing at either the assignment lhs or the binding def pattern.
275 err.span_label(primary_span, "expected due to the type of this binding");
277 // We are pointing at the binding's type or initializer value.
278 err.span_label(primary_span, &format!("expected due to this{post_message}"));
281 if !lhs.is_syntactic_place_expr() {
282 // We already emitted E0070 "invalid left-hand side of assignment", so we
284 err.downgrade_to_delayed_bug();
291 /// If the expected type is an enum (Issue #55250) with any variants whose
292 /// sole field is of the found type, suggest such variants. (Issue #42764)
293 fn suggest_compatible_variants(
295 err: &mut Diagnostic,
296 expr: &hir::Expr<'_>,
300 if let ty::Adt(expected_adt, substs) = expected.kind() {
301 if let hir::ExprKind::Field(base, ident) = expr.kind {
302 let base_ty = self.typeck_results.borrow().expr_ty(base);
303 if self.can_eq(self.param_env, base_ty, expected).is_ok()
304 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
306 err.span_suggestion_verbose(
307 expr.span.with_lo(base_span.hi()),
308 format!("consider removing the tuple struct field `{ident}`"),
310 Applicability::MaybeIncorrect,
316 // If the expression is of type () and it's the return expression of a block,
317 // we suggest adding a separate return expression instead.
318 // (To avoid things like suggesting `Ok(while .. { .. })`.)
319 if expr_ty.is_unit() {
320 let mut id = expr.hir_id;
323 // Unroll desugaring, to make sure this works for `for` loops etc.
325 parent = self.tcx.hir().get_parent_node(id);
326 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
327 if parent_span.find_ancestor_inside(expr.span).is_some() {
328 // The parent node is part of the same span, so is the result of the
329 // same expansion/desugaring and not the 'real' parent node.
337 if let Some(hir::Node::Block(&hir::Block {
338 span: block_span, expr: Some(e), ..
339 })) = self.tcx.hir().find(parent)
342 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
343 let return_suggestions = if self
345 .is_diagnostic_item(sym::Result, expected_adt.did())
348 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
349 vec!["None", "Some(())"]
353 if let Some(indent) =
354 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
356 // Add a semicolon, except after `}`.
358 match self.tcx.sess.source_map().span_to_snippet(span) {
359 Ok(s) if s.ends_with('}') => "",
362 err.span_suggestions(
364 "try adding an expression at the end of the block",
367 .map(|r| format!("{semicolon}\n{indent}{r}")),
368 Applicability::MaybeIncorrect,
377 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
381 variant.fields.len() == 1
383 .filter_map(|variant| {
384 let sole_field = &variant.fields[0];
386 let field_is_local = sole_field.did.is_local();
387 let field_is_accessible =
388 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
389 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
390 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
392 if !field_is_local && !field_is_accessible {
396 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
397 .then(|| format!(" (its field is private, but it's local to this crate and its privacy can be changed)"));
399 let sole_field_ty = sole_field.ty(self.tcx, substs);
400 if self.can_coerce(expr_ty, sole_field_ty) {
402 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
403 // FIXME #56861: DRYer prelude filtering
404 if let Some(path) = variant_path.strip_prefix("std::prelude::")
405 && let Some((_, path)) = path.split_once("::")
407 return Some((path.to_string(), variant.ctor_kind, sole_field.name, note_about_variant_field_privacy));
409 Some((variant_path, variant.ctor_kind, sole_field.name, note_about_variant_field_privacy))
416 let suggestions_for = |variant: &_, ctor, field_name| {
417 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
418 Some(ident) => format!("{ident}: "),
419 None => String::new(),
422 let (open, close) = match ctor {
423 hir::def::CtorKind::Fn => ("(".to_owned(), ")"),
424 hir::def::CtorKind::Fictive => (format!(" {{ {field_name}: "), " }"),
426 // unit variants don't have fields
427 hir::def::CtorKind::Const => unreachable!(),
430 // Suggest constructor as deep into the block tree as possible.
431 // This fixes https://github.com/rust-lang/rust/issues/101065,
432 // and also just helps make the most minimal suggestions.
434 while let hir::ExprKind::Block(block, _) = &expr.kind
435 && let Some(expr_) = &block.expr
441 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
442 (expr.span.shrink_to_hi(), close.to_owned()),
446 match &compatible_variants[..] {
447 [] => { /* No variants to format */ }
448 [(variant, ctor_kind, field_name, note)] => {
449 // Just a single matching variant.
450 err.multipart_suggestion_verbose(
452 "try wrapping the expression in `{variant}`{note}",
453 note = note.as_deref().unwrap_or("")
455 suggestions_for(&**variant, *ctor_kind, *field_name),
456 Applicability::MaybeIncorrect,
461 // More than one matching variant.
462 err.multipart_suggestions(
464 "try wrapping the expression in a variant of `{}`",
465 self.tcx.def_path_str(expected_adt.did())
467 compatible_variants.into_iter().map(
468 |(variant, ctor_kind, field_name, _)| {
469 suggestions_for(&variant, ctor_kind, field_name)
472 Applicability::MaybeIncorrect,
482 fn suggest_non_zero_new_unwrap(
484 err: &mut Diagnostic,
485 expr: &hir::Expr<'_>,
490 let (adt, unwrap) = match expected.kind() {
491 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
492 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
494 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
498 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
499 ty::Adt(adt, _) => (adt, ".unwrap()"),
504 (sym::NonZeroU8, tcx.types.u8),
505 (sym::NonZeroU16, tcx.types.u16),
506 (sym::NonZeroU32, tcx.types.u32),
507 (sym::NonZeroU64, tcx.types.u64),
508 (sym::NonZeroU128, tcx.types.u128),
509 (sym::NonZeroI8, tcx.types.i8),
510 (sym::NonZeroI16, tcx.types.i16),
511 (sym::NonZeroI32, tcx.types.i32),
512 (sym::NonZeroI64, tcx.types.i64),
513 (sym::NonZeroI128, tcx.types.i128),
516 let Some((s, _)) = map
518 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
519 else { return false; };
521 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
523 err.multipart_suggestion(
524 format!("consider calling `{s}::new`"),
526 (expr.span.shrink_to_lo(), format!("{path}::new(")),
527 (expr.span.shrink_to_hi(), format!("){unwrap}")),
529 Applicability::MaybeIncorrect,
535 pub fn get_conversion_methods(
539 checked_ty: Ty<'tcx>,
541 ) -> Vec<AssocItem> {
542 let methods = self.probe_for_return_type(
544 probe::Mode::MethodCall,
549 self.has_only_self_parameter(m)
552 // This special internal attribute is used to permit
553 // "identity-like" conversion methods to be suggested here.
555 // FIXME (#46459 and #46460): ideally
556 // `std::convert::Into::into` and `std::borrow:ToOwned` would
557 // also be `#[rustc_conversion_suggestion]`, if not for
558 // method-probing false-positives and -negatives (respectively).
560 // FIXME? Other potential candidate methods: `as_ref` and
562 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
569 /// This function checks whether the method is not static and does not accept other parameters than `self`.
570 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
572 ty::AssocKind::Fn => {
573 method.fn_has_self_parameter
574 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
580 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
582 /// Given the following code:
583 /// ```compile_fail,E0308
585 /// fn takes_ref(_: &Foo) {}
586 /// let ref opt = Some(Foo);
588 /// opt.map(|param| takes_ref(param));
590 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
592 /// It only checks for `Option` and `Result` and won't work with
593 /// ```ignore (illustrative)
594 /// opt.map(|param| { takes_ref(param) });
596 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
597 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
601 let hir::def::Res::Local(local_id) = path.res else {
605 let local_parent = self.tcx.hir().get_parent_node(local_id);
606 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
610 let param_parent = self.tcx.hir().get_parent_node(*param_hir_id);
611 let Some(Node::Expr(hir::Expr {
613 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
615 })) = self.tcx.hir().find(param_parent) else {
619 let expr_parent = self.tcx.hir().get_parent_node(*expr_hir_id);
620 let hir = self.tcx.hir().find(expr_parent);
621 let closure_params_len = closure_fn_decl.inputs.len();
623 Some(Node::Expr(hir::Expr {
624 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
628 ) = (hir, closure_params_len) else {
632 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
633 let name = method_path.ident.name;
634 let is_as_ref_able = match self_ty.peel_refs().kind() {
636 (self.tcx.is_diagnostic_item(sym::Option, def.did())
637 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
638 && (name == sym::map || name == sym::and_then)
642 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
644 let suggestion = format!("as_ref().{}", src);
645 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
651 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
653 expr: &hir::Expr<'_>,
654 ) -> Option<Symbol> {
655 let hir = self.tcx.hir();
656 let local = match expr {
659 hir::ExprKind::Path(hir::QPath::Resolved(
662 res: hir::def::Res::Local(_),
663 segments: [hir::PathSegment { ident, .. }],
672 match hir.find(hir.get_parent_node(expr.hir_id))? {
673 Node::ExprField(field) => {
674 if field.ident.name == local.name && field.is_shorthand {
675 return Some(local.name);
684 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
685 pub(crate) fn maybe_get_block_expr(
687 expr: &hir::Expr<'tcx>,
688 ) -> Option<&'tcx hir::Expr<'tcx>> {
690 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
695 /// Returns whether the given expression is an `else if`.
696 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
697 if let hir::ExprKind::If(..) = expr.kind {
698 let parent_id = self.tcx.hir().get_parent_node(expr.hir_id);
699 if let Some(Node::Expr(hir::Expr {
700 kind: hir::ExprKind::If(_, _, Some(else_expr)),
702 })) = self.tcx.hir().find(parent_id)
704 return else_expr.hir_id == expr.hir_id;
710 /// This function is used to determine potential "simple" improvements or users' errors and
711 /// provide them useful help. For example:
713 /// ```compile_fail,E0308
714 /// fn some_fn(s: &str) {}
716 /// let x = "hey!".to_owned();
717 /// some_fn(x); // error
720 /// No need to find every potential function which could make a coercion to transform a
721 /// `String` into a `&str` since a `&` would do the trick!
723 /// In addition of this check, it also checks between references mutability state. If the
724 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
728 expr: &hir::Expr<'tcx>,
729 checked_ty: Ty<'tcx>,
737 bool, /* suggest `&` or `&mut` type annotation */
739 let sess = self.sess();
742 // If the span is from an external macro, there's no suggestion we can make.
743 if in_external_macro(sess, sp) {
747 let sm = sess.source_map();
749 let replace_prefix = |s: &str, old: &str, new: &str| {
750 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
753 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
754 let expr = expr.peel_drop_temps();
756 match (&expr.kind, expected.kind(), checked_ty.kind()) {
757 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
758 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
759 if let hir::ExprKind::Lit(_) = expr.kind
760 && let Ok(src) = sm.span_to_snippet(sp)
761 && replace_prefix(&src, "b\"", "\"").is_some()
763 let pos = sp.lo() + BytePos(1);
766 "consider removing the leading `b`".to_string(),
768 Applicability::MachineApplicable,
774 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
775 if let hir::ExprKind::Lit(_) = expr.kind
776 && let Ok(src) = sm.span_to_snippet(sp)
777 && replace_prefix(&src, "\"", "b\"").is_some()
781 "consider adding a leading `b`".to_string(),
783 Applicability::MachineApplicable,
791 (_, &ty::Ref(_, _, mutability), _) => {
792 // Check if it can work when put into a ref. For example:
795 // fn bar(x: &mut i32) {}
798 // bar(&x); // error, expected &mut
800 let ref_ty = match mutability {
801 hir::Mutability::Mut => {
802 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
804 hir::Mutability::Not => {
805 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
808 if self.can_coerce(ref_ty, expected) {
809 let mut sugg_sp = sp;
810 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
812 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
814 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
816 let ai = self.tcx.associated_item(did);
817 ai.trait_container(self.tcx) == Some(clone_trait)
820 && segment.ident.name == sym::clone
822 // If this expression had a clone call when suggesting borrowing
823 // we want to suggest removing it because it'd now be unnecessary.
824 sugg_sp = receiver.span;
827 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
828 let needs_parens = match expr.kind {
829 // parenthesize if needed (Issue #46756)
830 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
831 // parenthesize borrows of range literals (Issue #54505)
832 _ if is_range_literal(expr) => true,
836 if let Some(sugg) = self.can_use_as_ref(expr) {
841 Applicability::MachineApplicable,
847 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
848 Some(ident) => format!("{ident}: "),
849 None => String::new(),
852 if let Some(hir::Node::Expr(hir::Expr {
853 kind: hir::ExprKind::Assign(..),
855 })) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
857 if mutability == hir::Mutability::Mut {
858 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
863 let sugg_expr = if needs_parens { format!("({src})") } else { src };
864 return Some(match mutability {
865 hir::Mutability::Mut => (
867 "consider mutably borrowing here".to_string(),
868 format!("{prefix}&mut {sugg_expr}"),
869 Applicability::MachineApplicable,
873 hir::Mutability::Not => (
875 "consider borrowing here".to_string(),
876 format!("{prefix}&{sugg_expr}"),
877 Applicability::MachineApplicable,
886 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
888 &ty::Ref(_, checked, _),
889 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
890 // We have `&T`, check if what was expected was `T`. If so,
891 // we may want to suggest removing a `&`.
892 if sm.is_imported(expr.span) {
893 // Go through the spans from which this span was expanded,
894 // and find the one that's pointing inside `sp`.
896 // E.g. for `&format!("")`, where we want the span to the
897 // `format!()` invocation instead of its expansion.
898 if let Some(call_span) =
899 iter::successors(Some(expr.span), |s| s.parent_callsite())
900 .find(|&s| sp.contains(s))
901 && sm.is_span_accessible(call_span)
904 sp.with_hi(call_span.lo()),
905 "consider removing the borrow".to_string(),
907 Applicability::MachineApplicable,
914 if sp.contains(expr.span)
915 && sm.is_span_accessible(expr.span)
918 sp.with_hi(expr.span.lo()),
919 "consider removing the borrow".to_string(),
921 Applicability::MachineApplicable,
929 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
930 &ty::Ref(_, ty_a, mutbl_a),
932 if let Some(steps) = self.deref_steps(ty_a, ty_b)
933 // Only suggest valid if dereferencing needed.
935 // The pointer type implements `Copy` trait so the suggestion is always valid.
936 && let Ok(src) = sm.span_to_snippet(sp)
938 let derefs = "*".repeat(steps);
939 if let Some((span, src, applicability)) = match mutbl_b {
940 hir::Mutability::Mut => {
941 let new_prefix = "&mut ".to_owned() + &derefs;
943 hir::Mutability::Mut => {
944 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
945 let pos = sp.lo() + BytePos(5);
946 let sp = sp.with_lo(pos).with_hi(pos);
947 (sp, derefs, Applicability::MachineApplicable)
950 hir::Mutability::Not => {
951 replace_prefix(&src, "&", &new_prefix).map(|_| {
952 let pos = sp.lo() + BytePos(1);
953 let sp = sp.with_lo(pos).with_hi(pos);
956 format!("mut {derefs}"),
957 Applicability::Unspecified,
963 hir::Mutability::Not => {
964 let new_prefix = "&".to_owned() + &derefs;
966 hir::Mutability::Mut => {
967 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
968 let lo = sp.lo() + BytePos(1);
969 let hi = sp.lo() + BytePos(5);
970 let sp = sp.with_lo(lo).with_hi(hi);
971 (sp, derefs, Applicability::MachineApplicable)
974 hir::Mutability::Not => {
975 replace_prefix(&src, "&", &new_prefix).map(|_| {
976 let pos = sp.lo() + BytePos(1);
977 let sp = sp.with_lo(pos).with_hi(pos);
978 (sp, derefs, Applicability::MachineApplicable)
986 "consider dereferencing".to_string(),
995 _ if sp == expr.span => {
996 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
997 let mut expr = expr.peel_blocks();
998 let mut prefix_span = expr.span.shrink_to_lo();
999 let mut remove = String::new();
1001 // Try peeling off any existing `&` and `&mut` to reach our target type
1003 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
1004 // If the expression has `&`, removing it would fix the error
1005 prefix_span = prefix_span.with_hi(inner.span.lo());
1007 remove += match mutbl {
1008 hir::Mutability::Not => "&",
1009 hir::Mutability::Mut => "&mut ",
1016 // If we've reached our target type with just removing `&`, then just print now.
1020 format!("consider removing the `{}`", remove.trim()),
1022 // Do not remove `&&` to get to bool, because it might be something like
1023 // { a } && b, which we have a separate fixup suggestion that is more
1024 // likely correct...
1025 if remove.trim() == "&&" && expected == self.tcx.types.bool {
1026 Applicability::MaybeIncorrect
1028 Applicability::MachineApplicable
1035 // For this suggestion to make sense, the type would need to be `Copy`,
1036 // or we have to be moving out of a `Box<T>`
1037 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1038 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1039 // `steps` layers of boxes, not just one, but this is easier and most likely.
1040 || (checked_ty.is_box() && steps == 1)
1042 let deref_kind = if checked_ty.is_box() {
1043 "unboxing the value"
1044 } else if checked_ty.is_region_ptr() {
1045 "dereferencing the borrow"
1047 "dereferencing the type"
1050 // Suggest removing `&` if we have removed any, otherwise suggest just
1051 // dereferencing the remaining number of steps.
1052 let message = if remove.is_empty() {
1053 format!("consider {deref_kind}")
1056 "consider removing the `{}` and {} instead",
1062 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1063 Some(ident) => format!("{ident}: "),
1064 None => String::new(),
1067 let (span, suggestion) = if self.is_else_if_block(expr) {
1068 // Don't suggest nonsense like `else *if`
1070 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1071 // prefix should be empty here..
1072 (expr.span.shrink_to_lo(), "*".to_string())
1074 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1081 Applicability::MachineApplicable,
1093 pub fn check_for_cast(
1095 err: &mut Diagnostic,
1096 expr: &hir::Expr<'_>,
1097 checked_ty: Ty<'tcx>,
1098 expected_ty: Ty<'tcx>,
1099 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1101 if self.tcx.sess.source_map().is_imported(expr.span) {
1102 // Ignore if span is from within a macro.
1106 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1110 // If casting this expression to a given numeric type would be appropriate in case of a type
1113 // We want to minimize the amount of casting operations that are suggested, as it can be a
1114 // lossy operation with potentially bad side effects, so we only suggest when encountering
1115 // an expression that indicates that the original type couldn't be directly changed.
1117 // For now, don't suggest casting with `as`.
1118 let can_cast = false;
1120 let mut sugg = vec![];
1122 if let Some(hir::Node::ExprField(field)) =
1123 self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
1125 // `expr` is a literal field for a struct, only suggest if appropriate
1126 if field.is_shorthand {
1127 // This is a field literal
1128 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1130 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1135 if let hir::ExprKind::Call(path, args) = &expr.kind
1136 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1137 (&path.kind, args.len())
1138 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1139 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1140 (&base_ty.kind, path_segment.ident.name)
1142 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1156 if base_ty_path.segments.len() == 1 =>
1166 "you can convert {} `{}` to {} `{}`",
1167 checked_ty.kind().article(),
1169 expected_ty.kind().article(),
1172 let cast_msg = format!(
1173 "you can cast {} `{}` to {} `{}`",
1174 checked_ty.kind().article(),
1176 expected_ty.kind().article(),
1179 let lit_msg = format!(
1180 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1183 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1184 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1190 let mut cast_suggestion = sugg.clone();
1191 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1192 let mut into_suggestion = sugg.clone();
1193 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1194 let mut suffix_suggestion = sugg.clone();
1195 suffix_suggestion.push((
1197 (&expected_ty.kind(), &checked_ty.kind()),
1198 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1200 // Remove fractional part from literal, for example `42.0f32` into `42`
1201 let src = src.trim_end_matches(&checked_ty.to_string());
1202 let len = src.split('.').next().unwrap().len();
1203 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1205 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1206 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1208 if expr.precedence().order() < PREC_POSTFIX {
1210 format!("{expected_ty})")
1212 expected_ty.to_string()
1215 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1216 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1218 let is_negative_int =
1219 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1220 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1222 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1224 let suggest_fallible_into_or_lhs_from =
1225 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1226 // If we know the expression the expected type is derived from, we might be able
1227 // to suggest a widening conversion rather than a narrowing one (which may
1228 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1230 // can be given the suggestion "u32::from(x) > y" rather than
1231 // "x > y.try_into().unwrap()".
1232 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1236 .span_to_snippet(expr.span)
1238 .map(|src| (expr, src))
1240 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1241 (lhs_expr_and_src, exp_to_found_is_fallible)
1244 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1246 let suggestion = vec![
1247 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1248 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1252 let msg = format!("{msg} and panic if the converted value doesn't fit");
1253 let mut suggestion = sugg.clone();
1255 expr.span.shrink_to_hi(),
1256 format!("{close_paren}.try_into().unwrap()"),
1260 err.multipart_suggestion_verbose(
1263 Applicability::MachineApplicable,
1267 let suggest_to_change_suffix_or_into =
1268 |err: &mut Diagnostic,
1269 found_to_exp_is_fallible: bool,
1270 exp_to_found_is_fallible: bool| {
1272 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1278 let always_fallible = found_to_exp_is_fallible
1279 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1280 let msg = if literal_is_ty_suffixed(expr) {
1282 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1283 // We now know that converting either the lhs or rhs is fallible. Before we
1284 // suggest a fallible conversion, check if the value can never fit in the
1286 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1289 } else if in_const_context {
1290 // Do not recommend `into` or `try_into` in const contexts.
1292 } else if found_to_exp_is_fallible {
1293 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1297 let suggestion = if literal_is_ty_suffixed(expr) {
1298 suffix_suggestion.clone()
1300 into_suggestion.clone()
1302 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1305 match (&expected_ty.kind(), &checked_ty.kind()) {
1306 (&ty::Int(ref exp), &ty::Int(ref found)) => {
1307 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1309 (Some(exp), Some(found)) if exp < found => (true, false),
1310 (Some(exp), Some(found)) if exp > found => (false, true),
1311 (None, Some(8 | 16)) => (false, true),
1312 (Some(8 | 16), None) => (true, false),
1313 (None, _) | (_, None) => (true, true),
1314 _ => (false, false),
1316 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1319 (&ty::Uint(ref exp), &ty::Uint(ref found)) => {
1320 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1322 (Some(exp), Some(found)) if exp < found => (true, false),
1323 (Some(exp), Some(found)) if exp > found => (false, true),
1324 (None, Some(8 | 16)) => (false, true),
1325 (Some(8 | 16), None) => (true, false),
1326 (None, _) | (_, None) => (true, true),
1327 _ => (false, false),
1329 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1332 (&ty::Int(exp), &ty::Uint(found)) => {
1333 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1335 (Some(exp), Some(found)) if found < exp => (false, true),
1336 (None, Some(8)) => (false, true),
1339 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1342 (&ty::Uint(exp), &ty::Int(found)) => {
1343 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1345 (Some(exp), Some(found)) if found > exp => (true, false),
1346 (Some(8), None) => (true, false),
1349 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1352 (&ty::Float(ref exp), &ty::Float(ref found)) => {
1353 if found.bit_width() < exp.bit_width() {
1354 suggest_to_change_suffix_or_into(err, false, true);
1355 } else if literal_is_ty_suffixed(expr) {
1356 err.multipart_suggestion_verbose(
1359 Applicability::MachineApplicable,
1361 } else if can_cast {
1362 // Missing try_into implementation for `f64` to `f32`
1363 err.multipart_suggestion_verbose(
1364 &format!("{cast_msg}, producing the closest possible value"),
1366 Applicability::MaybeIncorrect, // lossy conversion
1371 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1372 if literal_is_ty_suffixed(expr) {
1373 err.multipart_suggestion_verbose(
1376 Applicability::MachineApplicable,
1378 } else if can_cast {
1379 // Missing try_into implementation for `{float}` to `{integer}`
1380 err.multipart_suggestion_verbose(
1381 &format!("{msg}, rounding the float towards zero"),
1383 Applicability::MaybeIncorrect, // lossy conversion
1388 (&ty::Float(ref exp), &ty::Uint(ref found)) => {
1389 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1390 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1391 err.multipart_suggestion_verbose(
1393 "{msg}, 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 "{cast_msg}, producing the floating point representation of the integer, \
1409 rounded if necessary",
1412 Applicability::MaybeIncorrect, // lossy conversion
1417 (&ty::Float(ref exp), &ty::Int(ref found)) => {
1418 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1419 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1420 err.multipart_suggestion_verbose(
1422 "{}, producing the floating point representation of the integer",
1426 Applicability::MachineApplicable,
1428 } else if literal_is_ty_suffixed(expr) {
1429 err.multipart_suggestion_verbose(
1432 Applicability::MachineApplicable,
1435 // Missing try_into implementation for `{integer}` to `{float}`
1436 err.multipart_suggestion_verbose(
1438 "{}, producing the floating point representation of the integer, \
1439 rounded if necessary",
1443 Applicability::MaybeIncorrect, // lossy conversion
1449 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1450 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1453 err.multipart_suggestion_verbose(
1454 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1456 Applicability::MachineApplicable,