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();
158 let expr = expr.peel_drop_temps();
159 let cause = self.misc(expr.span);
160 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
161 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e.clone());
163 let is_insufficiently_polymorphic =
164 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
166 // FIXME(#73154): For now, we do leak check when coercing function
167 // pointers in typeck, instead of only during borrowck. This can lead
168 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
169 if !is_insufficiently_polymorphic {
170 self.emit_coerce_suggestions(
180 (expected, Some(err))
183 fn annotate_expected_due_to_let_ty(
185 err: &mut Diagnostic,
186 expr: &hir::Expr<'_>,
187 error: Option<TypeError<'_>>,
189 let parent = self.tcx.hir().get_parent_node(expr.hir_id);
190 match (self.tcx.hir().find(parent), error) {
191 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
192 if init.hir_id == expr.hir_id =>
194 // Point at `let` assignment type.
195 err.span_label(ty.span, "expected due to this");
198 Some(hir::Node::Expr(hir::Expr {
199 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
201 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
202 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
203 // We ignore closures explicitly because we already point at them elsewhere.
204 // Point at the assigned-to binding.
205 let mut primary_span = lhs.span;
206 let mut secondary_span = lhs.span;
207 let mut post_message = "";
209 hir::ExprKind::Path(hir::QPath::Resolved(
214 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
220 if let Some(hir::Node::Item(hir::Item {
222 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
224 })) = self.tcx.hir().get_if_local(*def_id)
226 primary_span = ty.span;
227 secondary_span = ident.span;
228 post_message = " type";
231 hir::ExprKind::Path(hir::QPath::Resolved(
233 hir::Path { res: hir::def::Res::Local(hir_id), .. },
235 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
236 let parent = self.tcx.hir().get_parent_node(pat.hir_id);
237 primary_span = pat.span;
238 secondary_span = pat.span;
239 match self.tcx.hir().find(parent) {
240 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
241 primary_span = ty.span;
242 post_message = " type";
244 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
245 primary_span = init.span;
246 post_message = " value";
248 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
249 primary_span = *ty_span;
250 post_message = " parameter type";
259 if primary_span != secondary_span
264 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
266 // We are pointing at the binding's type or initializer value, but it's pattern
267 // is in a different line, so we point at both.
268 err.span_label(secondary_span, "expected due to the type of this binding");
269 err.span_label(primary_span, &format!("expected due to this{post_message}"));
270 } else if post_message == "" {
271 // We are pointing at either the assignment lhs or the binding def pattern.
272 err.span_label(primary_span, "expected due to the type of this binding");
274 // We are pointing at the binding's type or initializer value.
275 err.span_label(primary_span, &format!("expected due to this{post_message}"));
278 if !lhs.is_syntactic_place_expr() {
279 // We already emitted E0070 "invalid left-hand side of assignment", so we
281 err.downgrade_to_delayed_bug();
288 /// If the expected type is an enum (Issue #55250) with any variants whose
289 /// sole field is of the found type, suggest such variants. (Issue #42764)
290 fn suggest_compatible_variants(
292 err: &mut Diagnostic,
293 expr: &hir::Expr<'_>,
297 if let ty::Adt(expected_adt, substs) = expected.kind() {
298 if let hir::ExprKind::Field(base, ident) = expr.kind {
299 let base_ty = self.typeck_results.borrow().expr_ty(base);
300 if self.can_eq(self.param_env, base_ty, expected).is_ok()
301 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
303 err.span_suggestion_verbose(
304 expr.span.with_lo(base_span.hi()),
305 format!("consider removing the tuple struct field `{ident}`"),
307 Applicability::MaybeIncorrect,
313 // If the expression is of type () and it's the return expression of a block,
314 // we suggest adding a separate return expression instead.
315 // (To avoid things like suggesting `Ok(while .. { .. })`.)
316 if expr_ty.is_unit() {
317 let mut id = expr.hir_id;
320 // Unroll desugaring, to make sure this works for `for` loops etc.
322 parent = self.tcx.hir().get_parent_node(id);
323 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
324 if parent_span.find_ancestor_inside(expr.span).is_some() {
325 // The parent node is part of the same span, so is the result of the
326 // same expansion/desugaring and not the 'real' parent node.
334 if let Some(hir::Node::Block(&hir::Block {
335 span: block_span, expr: Some(e), ..
336 })) = self.tcx.hir().find(parent)
339 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
340 let return_suggestions = if self
342 .is_diagnostic_item(sym::Result, expected_adt.did())
345 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
346 vec!["None", "Some(())"]
350 if let Some(indent) =
351 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
353 // Add a semicolon, except after `}`.
355 match self.tcx.sess.source_map().span_to_snippet(span) {
356 Ok(s) if s.ends_with('}') => "",
359 err.span_suggestions(
361 "try adding an expression at the end of the block",
364 .map(|r| format!("{semicolon}\n{indent}{r}")),
365 Applicability::MaybeIncorrect,
374 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
378 variant.fields.len() == 1
380 .filter_map(|variant| {
381 let sole_field = &variant.fields[0];
383 let field_is_local = sole_field.did.is_local();
384 let field_is_accessible =
385 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
386 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
387 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
389 if !field_is_local && !field_is_accessible {
393 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
394 .then(|| format!(" (its field is private, but it's local to this crate and its privacy can be changed)"));
396 let sole_field_ty = sole_field.ty(self.tcx, substs);
397 if self.can_coerce(expr_ty, sole_field_ty) {
399 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
400 // FIXME #56861: DRYer prelude filtering
401 if let Some(path) = variant_path.strip_prefix("std::prelude::")
402 && let Some((_, path)) = path.split_once("::")
404 return Some((path.to_string(), variant.ctor_kind, sole_field.name, note_about_variant_field_privacy));
406 Some((variant_path, variant.ctor_kind, sole_field.name, note_about_variant_field_privacy))
413 let suggestions_for = |variant: &_, ctor, field_name| {
414 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
415 Some(ident) => format!("{ident}: "),
416 None => String::new(),
419 let (open, close) = match ctor {
420 hir::def::CtorKind::Fn => ("(".to_owned(), ")"),
421 hir::def::CtorKind::Fictive => (format!(" {{ {field_name}: "), " }"),
423 // unit variants don't have fields
424 hir::def::CtorKind::Const => unreachable!(),
427 // Suggest constructor as deep into the block tree as possible.
428 // This fixes https://github.com/rust-lang/rust/issues/101065,
429 // and also just helps make the most minimal suggestions.
431 while let hir::ExprKind::Block(block, _) = &expr.kind
432 && let Some(expr_) = &block.expr
438 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
439 (expr.span.shrink_to_hi(), close.to_owned()),
443 match &compatible_variants[..] {
444 [] => { /* No variants to format */ }
445 [(variant, ctor_kind, field_name, note)] => {
446 // Just a single matching variant.
447 err.multipart_suggestion_verbose(
449 "try wrapping the expression in `{variant}`{note}",
450 note = note.as_deref().unwrap_or("")
452 suggestions_for(&**variant, *ctor_kind, *field_name),
453 Applicability::MaybeIncorrect,
458 // More than one matching variant.
459 err.multipart_suggestions(
461 "try wrapping the expression in a variant of `{}`",
462 self.tcx.def_path_str(expected_adt.did())
464 compatible_variants.into_iter().map(
465 |(variant, ctor_kind, field_name, _)| {
466 suggestions_for(&variant, ctor_kind, field_name)
469 Applicability::MaybeIncorrect,
479 fn suggest_non_zero_new_unwrap(
481 err: &mut Diagnostic,
482 expr: &hir::Expr<'_>,
487 let (adt, unwrap) = match expected.kind() {
488 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
489 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
491 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
495 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
496 ty::Adt(adt, _) => (adt, ".unwrap()"),
501 (sym::NonZeroU8, tcx.types.u8),
502 (sym::NonZeroU16, tcx.types.u16),
503 (sym::NonZeroU32, tcx.types.u32),
504 (sym::NonZeroU64, tcx.types.u64),
505 (sym::NonZeroU128, tcx.types.u128),
506 (sym::NonZeroI8, tcx.types.i8),
507 (sym::NonZeroI16, tcx.types.i16),
508 (sym::NonZeroI32, tcx.types.i32),
509 (sym::NonZeroI64, tcx.types.i64),
510 (sym::NonZeroI128, tcx.types.i128),
513 let Some((s, _)) = map
515 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
516 else { return false; };
518 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
520 err.multipart_suggestion(
521 format!("consider calling `{s}::new`"),
523 (expr.span.shrink_to_lo(), format!("{path}::new(")),
524 (expr.span.shrink_to_hi(), format!("){unwrap}")),
526 Applicability::MaybeIncorrect,
532 pub fn get_conversion_methods(
536 checked_ty: Ty<'tcx>,
538 ) -> Vec<AssocItem> {
539 let methods = self.probe_for_return_type(
541 probe::Mode::MethodCall,
546 self.has_only_self_parameter(m)
549 // This special internal attribute is used to permit
550 // "identity-like" conversion methods to be suggested here.
552 // FIXME (#46459 and #46460): ideally
553 // `std::convert::Into::into` and `std::borrow:ToOwned` would
554 // also be `#[rustc_conversion_suggestion]`, if not for
555 // method-probing false-positives and -negatives (respectively).
557 // FIXME? Other potential candidate methods: `as_ref` and
559 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
566 /// This function checks whether the method is not static and does not accept other parameters than `self`.
567 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
569 ty::AssocKind::Fn => {
570 method.fn_has_self_parameter
571 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
577 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
579 /// Given the following code:
580 /// ```compile_fail,E0308
582 /// fn takes_ref(_: &Foo) {}
583 /// let ref opt = Some(Foo);
585 /// opt.map(|param| takes_ref(param));
587 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
589 /// It only checks for `Option` and `Result` and won't work with
590 /// ```ignore (illustrative)
591 /// opt.map(|param| { takes_ref(param) });
593 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
594 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
598 let hir::def::Res::Local(local_id) = path.res else {
602 let local_parent = self.tcx.hir().get_parent_node(local_id);
603 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
607 let param_parent = self.tcx.hir().get_parent_node(*param_hir_id);
608 let Some(Node::Expr(hir::Expr {
610 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
612 })) = self.tcx.hir().find(param_parent) else {
616 let expr_parent = self.tcx.hir().get_parent_node(*expr_hir_id);
617 let hir = self.tcx.hir().find(expr_parent);
618 let closure_params_len = closure_fn_decl.inputs.len();
620 Some(Node::Expr(hir::Expr {
621 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
625 ) = (hir, closure_params_len) else {
629 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
630 let name = method_path.ident.name;
631 let is_as_ref_able = match self_ty.peel_refs().kind() {
633 (self.tcx.is_diagnostic_item(sym::Option, def.did())
634 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
635 && (name == sym::map || name == sym::and_then)
639 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
641 let suggestion = format!("as_ref().{}", src);
642 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
648 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
650 expr: &hir::Expr<'_>,
651 ) -> Option<Symbol> {
652 let hir = self.tcx.hir();
653 let local = match expr {
656 hir::ExprKind::Path(hir::QPath::Resolved(
659 res: hir::def::Res::Local(_),
660 segments: [hir::PathSegment { ident, .. }],
669 match hir.find(hir.get_parent_node(expr.hir_id))? {
670 Node::ExprField(field) => {
671 if field.ident.name == local.name && field.is_shorthand {
672 return Some(local.name);
681 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
682 pub(crate) fn maybe_get_block_expr(
684 expr: &hir::Expr<'tcx>,
685 ) -> Option<&'tcx hir::Expr<'tcx>> {
687 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
692 /// Returns whether the given expression is an `else if`.
693 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
694 if let hir::ExprKind::If(..) = expr.kind {
695 let parent_id = self.tcx.hir().get_parent_node(expr.hir_id);
696 if let Some(Node::Expr(hir::Expr {
697 kind: hir::ExprKind::If(_, _, Some(else_expr)),
699 })) = self.tcx.hir().find(parent_id)
701 return else_expr.hir_id == expr.hir_id;
707 /// This function is used to determine potential "simple" improvements or users' errors and
708 /// provide them useful help. For example:
710 /// ```compile_fail,E0308
711 /// fn some_fn(s: &str) {}
713 /// let x = "hey!".to_owned();
714 /// some_fn(x); // error
717 /// No need to find every potential function which could make a coercion to transform a
718 /// `String` into a `&str` since a `&` would do the trick!
720 /// In addition of this check, it also checks between references mutability state. If the
721 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
725 expr: &hir::Expr<'tcx>,
726 checked_ty: Ty<'tcx>,
734 bool, /* suggest `&` or `&mut` type annotation */
736 let sess = self.sess();
739 // If the span is from an external macro, there's no suggestion we can make.
740 if in_external_macro(sess, sp) {
744 let sm = sess.source_map();
746 let replace_prefix = |s: &str, old: &str, new: &str| {
747 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
750 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
751 let expr = expr.peel_drop_temps();
753 match (&expr.kind, expected.kind(), checked_ty.kind()) {
754 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
755 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
756 if let hir::ExprKind::Lit(_) = expr.kind
757 && let Ok(src) = sm.span_to_snippet(sp)
758 && replace_prefix(&src, "b\"", "\"").is_some()
760 let pos = sp.lo() + BytePos(1);
763 "consider removing the leading `b`".to_string(),
765 Applicability::MachineApplicable,
771 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
772 if let hir::ExprKind::Lit(_) = expr.kind
773 && let Ok(src) = sm.span_to_snippet(sp)
774 && replace_prefix(&src, "\"", "b\"").is_some()
778 "consider adding a leading `b`".to_string(),
780 Applicability::MachineApplicable,
788 (_, &ty::Ref(_, _, mutability), _) => {
789 // Check if it can work when put into a ref. For example:
792 // fn bar(x: &mut i32) {}
795 // bar(&x); // error, expected &mut
797 let ref_ty = match mutability {
798 hir::Mutability::Mut => {
799 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
801 hir::Mutability::Not => {
802 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
805 if self.can_coerce(ref_ty, expected) {
806 let mut sugg_sp = sp;
807 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
809 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
811 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
813 let ai = self.tcx.associated_item(did);
814 ai.trait_container(self.tcx) == Some(clone_trait)
817 && segment.ident.name == sym::clone
819 // If this expression had a clone call when suggesting borrowing
820 // we want to suggest removing it because it'd now be unnecessary.
821 sugg_sp = receiver.span;
824 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
825 let needs_parens = match expr.kind {
826 // parenthesize if needed (Issue #46756)
827 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
828 // parenthesize borrows of range literals (Issue #54505)
829 _ if is_range_literal(expr) => true,
833 if let Some(sugg) = self.can_use_as_ref(expr) {
838 Applicability::MachineApplicable,
844 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
845 Some(ident) => format!("{ident}: "),
846 None => String::new(),
849 if let Some(hir::Node::Expr(hir::Expr {
850 kind: hir::ExprKind::Assign(..),
852 })) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
854 if mutability == hir::Mutability::Mut {
855 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
860 let sugg_expr = if needs_parens { format!("({src})") } else { src };
861 return Some(match mutability {
862 hir::Mutability::Mut => (
864 "consider mutably borrowing here".to_string(),
865 format!("{prefix}&mut {sugg_expr}"),
866 Applicability::MachineApplicable,
870 hir::Mutability::Not => (
872 "consider borrowing here".to_string(),
873 format!("{prefix}&{sugg_expr}"),
874 Applicability::MachineApplicable,
883 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
885 &ty::Ref(_, checked, _),
886 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
887 // We have `&T`, check if what was expected was `T`. If so,
888 // we may want to suggest removing a `&`.
889 if sm.is_imported(expr.span) {
890 // Go through the spans from which this span was expanded,
891 // and find the one that's pointing inside `sp`.
893 // E.g. for `&format!("")`, where we want the span to the
894 // `format!()` invocation instead of its expansion.
895 if let Some(call_span) =
896 iter::successors(Some(expr.span), |s| s.parent_callsite())
897 .find(|&s| sp.contains(s))
898 && sm.is_span_accessible(call_span)
901 sp.with_hi(call_span.lo()),
902 "consider removing the borrow".to_string(),
904 Applicability::MachineApplicable,
911 if sp.contains(expr.span)
912 && sm.is_span_accessible(expr.span)
915 sp.with_hi(expr.span.lo()),
916 "consider removing the borrow".to_string(),
918 Applicability::MachineApplicable,
926 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
927 &ty::Ref(_, ty_a, mutbl_a),
929 if let Some(steps) = self.deref_steps(ty_a, ty_b)
930 // Only suggest valid if dereferencing needed.
932 // The pointer type implements `Copy` trait so the suggestion is always valid.
933 && let Ok(src) = sm.span_to_snippet(sp)
935 let derefs = "*".repeat(steps);
936 if let Some((span, src, applicability)) = match mutbl_b {
937 hir::Mutability::Mut => {
938 let new_prefix = "&mut ".to_owned() + &derefs;
940 hir::Mutability::Mut => {
941 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
942 let pos = sp.lo() + BytePos(5);
943 let sp = sp.with_lo(pos).with_hi(pos);
944 (sp, derefs, Applicability::MachineApplicable)
947 hir::Mutability::Not => {
948 replace_prefix(&src, "&", &new_prefix).map(|_| {
949 let pos = sp.lo() + BytePos(1);
950 let sp = sp.with_lo(pos).with_hi(pos);
953 format!("mut {derefs}"),
954 Applicability::Unspecified,
960 hir::Mutability::Not => {
961 let new_prefix = "&".to_owned() + &derefs;
963 hir::Mutability::Mut => {
964 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
965 let lo = sp.lo() + BytePos(1);
966 let hi = sp.lo() + BytePos(5);
967 let sp = sp.with_lo(lo).with_hi(hi);
968 (sp, derefs, Applicability::MachineApplicable)
971 hir::Mutability::Not => {
972 replace_prefix(&src, "&", &new_prefix).map(|_| {
973 let pos = sp.lo() + BytePos(1);
974 let sp = sp.with_lo(pos).with_hi(pos);
975 (sp, derefs, Applicability::MachineApplicable)
983 "consider dereferencing".to_string(),
992 _ if sp == expr.span => {
993 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
994 let mut expr = expr.peel_blocks();
995 let mut prefix_span = expr.span.shrink_to_lo();
996 let mut remove = String::new();
998 // Try peeling off any existing `&` and `&mut` to reach our target type
1000 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
1001 // If the expression has `&`, removing it would fix the error
1002 prefix_span = prefix_span.with_hi(inner.span.lo());
1004 remove += match mutbl {
1005 hir::Mutability::Not => "&",
1006 hir::Mutability::Mut => "&mut ",
1013 // If we've reached our target type with just removing `&`, then just print now.
1017 format!("consider removing the `{}`", remove.trim()),
1019 // Do not remove `&&` to get to bool, because it might be something like
1020 // { a } && b, which we have a separate fixup suggestion that is more
1021 // likely correct...
1022 if remove.trim() == "&&" && expected == self.tcx.types.bool {
1023 Applicability::MaybeIncorrect
1025 Applicability::MachineApplicable
1032 // For this suggestion to make sense, the type would need to be `Copy`,
1033 // or we have to be moving out of a `Box<T>`
1034 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1035 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1036 // `steps` layers of boxes, not just one, but this is easier and most likely.
1037 || (checked_ty.is_box() && steps == 1)
1039 let deref_kind = if checked_ty.is_box() {
1040 "unboxing the value"
1041 } else if checked_ty.is_region_ptr() {
1042 "dereferencing the borrow"
1044 "dereferencing the type"
1047 // Suggest removing `&` if we have removed any, otherwise suggest just
1048 // dereferencing the remaining number of steps.
1049 let message = if remove.is_empty() {
1050 format!("consider {deref_kind}")
1053 "consider removing the `{}` and {} instead",
1059 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1060 Some(ident) => format!("{ident}: "),
1061 None => String::new(),
1064 let (span, suggestion) = if self.is_else_if_block(expr) {
1065 // Don't suggest nonsense like `else *if`
1067 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1068 // prefix should be empty here..
1069 (expr.span.shrink_to_lo(), "*".to_string())
1071 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1078 Applicability::MachineApplicable,
1090 pub fn check_for_cast(
1092 err: &mut Diagnostic,
1093 expr: &hir::Expr<'_>,
1094 checked_ty: Ty<'tcx>,
1095 expected_ty: Ty<'tcx>,
1096 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1098 if self.tcx.sess.source_map().is_imported(expr.span) {
1099 // Ignore if span is from within a macro.
1103 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1107 // If casting this expression to a given numeric type would be appropriate in case of a type
1110 // We want to minimize the amount of casting operations that are suggested, as it can be a
1111 // lossy operation with potentially bad side effects, so we only suggest when encountering
1112 // an expression that indicates that the original type couldn't be directly changed.
1114 // For now, don't suggest casting with `as`.
1115 let can_cast = false;
1117 let mut sugg = vec![];
1119 if let Some(hir::Node::ExprField(field)) =
1120 self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
1122 // `expr` is a literal field for a struct, only suggest if appropriate
1123 if field.is_shorthand {
1124 // This is a field literal
1125 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1127 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1132 if let hir::ExprKind::Call(path, args) = &expr.kind
1133 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1134 (&path.kind, args.len())
1135 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1136 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1137 (&base_ty.kind, path_segment.ident.name)
1139 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1153 if base_ty_path.segments.len() == 1 =>
1163 "you can convert {} `{}` to {} `{}`",
1164 checked_ty.kind().article(),
1166 expected_ty.kind().article(),
1169 let cast_msg = format!(
1170 "you can cast {} `{}` to {} `{}`",
1171 checked_ty.kind().article(),
1173 expected_ty.kind().article(),
1176 let lit_msg = format!(
1177 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1180 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1181 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1187 let mut cast_suggestion = sugg.clone();
1188 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1189 let mut into_suggestion = sugg.clone();
1190 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1191 let mut suffix_suggestion = sugg.clone();
1192 suffix_suggestion.push((
1194 (&expected_ty.kind(), &checked_ty.kind()),
1195 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1197 // Remove fractional part from literal, for example `42.0f32` into `42`
1198 let src = src.trim_end_matches(&checked_ty.to_string());
1199 let len = src.split('.').next().unwrap().len();
1200 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1202 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1203 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1205 if expr.precedence().order() < PREC_POSTFIX {
1207 format!("{expected_ty})")
1209 expected_ty.to_string()
1212 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1213 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1215 let is_negative_int =
1216 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1217 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1219 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1221 let suggest_fallible_into_or_lhs_from =
1222 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1223 // If we know the expression the expected type is derived from, we might be able
1224 // to suggest a widening conversion rather than a narrowing one (which may
1225 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1227 // can be given the suggestion "u32::from(x) > y" rather than
1228 // "x > y.try_into().unwrap()".
1229 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1233 .span_to_snippet(expr.span)
1235 .map(|src| (expr, src))
1237 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1238 (lhs_expr_and_src, exp_to_found_is_fallible)
1241 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1243 let suggestion = vec![
1244 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1245 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1249 let msg = format!("{msg} and panic if the converted value doesn't fit");
1250 let mut suggestion = sugg.clone();
1252 expr.span.shrink_to_hi(),
1253 format!("{close_paren}.try_into().unwrap()"),
1257 err.multipart_suggestion_verbose(
1260 Applicability::MachineApplicable,
1264 let suggest_to_change_suffix_or_into =
1265 |err: &mut Diagnostic,
1266 found_to_exp_is_fallible: bool,
1267 exp_to_found_is_fallible: bool| {
1269 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1275 let always_fallible = found_to_exp_is_fallible
1276 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1277 let msg = if literal_is_ty_suffixed(expr) {
1279 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1280 // We now know that converting either the lhs or rhs is fallible. Before we
1281 // suggest a fallible conversion, check if the value can never fit in the
1283 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1286 } else if in_const_context {
1287 // Do not recommend `into` or `try_into` in const contexts.
1289 } else if found_to_exp_is_fallible {
1290 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1294 let suggestion = if literal_is_ty_suffixed(expr) {
1295 suffix_suggestion.clone()
1297 into_suggestion.clone()
1299 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1302 match (&expected_ty.kind(), &checked_ty.kind()) {
1303 (&ty::Int(ref exp), &ty::Int(ref found)) => {
1304 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1306 (Some(exp), Some(found)) if exp < found => (true, false),
1307 (Some(exp), Some(found)) if exp > found => (false, true),
1308 (None, Some(8 | 16)) => (false, true),
1309 (Some(8 | 16), None) => (true, false),
1310 (None, _) | (_, None) => (true, true),
1311 _ => (false, false),
1313 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1316 (&ty::Uint(ref exp), &ty::Uint(ref found)) => {
1317 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1319 (Some(exp), Some(found)) if exp < found => (true, false),
1320 (Some(exp), Some(found)) if exp > found => (false, true),
1321 (None, Some(8 | 16)) => (false, true),
1322 (Some(8 | 16), None) => (true, false),
1323 (None, _) | (_, None) => (true, true),
1324 _ => (false, false),
1326 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1329 (&ty::Int(exp), &ty::Uint(found)) => {
1330 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1332 (Some(exp), Some(found)) if found < exp => (false, true),
1333 (None, Some(8)) => (false, true),
1336 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1339 (&ty::Uint(exp), &ty::Int(found)) => {
1340 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1342 (Some(exp), Some(found)) if found > exp => (true, false),
1343 (Some(8), None) => (true, false),
1346 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1349 (&ty::Float(ref exp), &ty::Float(ref found)) => {
1350 if found.bit_width() < exp.bit_width() {
1351 suggest_to_change_suffix_or_into(err, false, true);
1352 } else if literal_is_ty_suffixed(expr) {
1353 err.multipart_suggestion_verbose(
1356 Applicability::MachineApplicable,
1358 } else if can_cast {
1359 // Missing try_into implementation for `f64` to `f32`
1360 err.multipart_suggestion_verbose(
1361 &format!("{cast_msg}, producing the closest possible value"),
1363 Applicability::MaybeIncorrect, // lossy conversion
1368 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1369 if literal_is_ty_suffixed(expr) {
1370 err.multipart_suggestion_verbose(
1373 Applicability::MachineApplicable,
1375 } else if can_cast {
1376 // Missing try_into implementation for `{float}` to `{integer}`
1377 err.multipart_suggestion_verbose(
1378 &format!("{msg}, rounding the float towards zero"),
1380 Applicability::MaybeIncorrect, // lossy conversion
1385 (&ty::Float(ref exp), &ty::Uint(ref found)) => {
1386 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1387 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1388 err.multipart_suggestion_verbose(
1390 "{msg}, producing the floating point representation of the integer",
1393 Applicability::MachineApplicable,
1395 } else if literal_is_ty_suffixed(expr) {
1396 err.multipart_suggestion_verbose(
1399 Applicability::MachineApplicable,
1402 // Missing try_into implementation for `{integer}` to `{float}`
1403 err.multipart_suggestion_verbose(
1405 "{cast_msg}, producing the floating point representation of the integer, \
1406 rounded if necessary",
1409 Applicability::MaybeIncorrect, // lossy conversion
1414 (&ty::Float(ref exp), &ty::Int(ref found)) => {
1415 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1416 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1417 err.multipart_suggestion_verbose(
1419 "{}, producing the floating point representation of the integer",
1423 Applicability::MachineApplicable,
1425 } else if literal_is_ty_suffixed(expr) {
1426 err.multipart_suggestion_verbose(
1429 Applicability::MachineApplicable,
1432 // Missing try_into implementation for `{integer}` to `{float}`
1433 err.multipart_suggestion_verbose(
1435 "{}, producing the floating point representation of the integer, \
1436 rounded if necessary",
1440 Applicability::MaybeIncorrect, // lossy conversion
1446 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1447 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1450 err.multipart_suggestion_verbose(
1451 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1453 Applicability::MachineApplicable,