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 self.annotate_expected_due_to_let_ty(err, expr, error);
35 // Use `||` to give these suggestions a precedence
36 let _ = self.suggest_missing_parentheses(err, expr)
37 || self.suggest_deref_ref_or_into(err, expr, expected, expr_ty, expected_ty_expr)
38 || self.suggest_compatible_variants(err, expr, expected, expr_ty)
39 || self.suggest_non_zero_new_unwrap(err, expr, expected, expr_ty)
40 || self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty)
41 || self.suggest_no_capture_closure(err, expected, expr_ty)
42 || self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty)
43 || self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected)
44 || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
45 || self.suggest_into(err, expr, expr_ty, expected);
47 self.note_type_is_not_clone(err, expected, expr_ty, expr);
48 self.note_need_for_fn_pointer(err, expected, expr_ty);
49 self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
52 // Requires that the two types unify, and prints an error message if
54 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
55 if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) {
60 pub fn demand_suptype_diag(
65 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
66 self.demand_suptype_with_origin(&self.misc(sp), expected, actual)
69 #[instrument(skip(self), level = "debug")]
70 pub fn demand_suptype_with_origin(
72 cause: &ObligationCause<'tcx>,
75 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
76 match self.at(cause, self.param_env).sup(expected, actual) {
77 Ok(InferOk { obligations, value: () }) => {
78 self.register_predicates(obligations);
81 Err(e) => Some(self.err_ctxt().report_mismatched_types(&cause, expected, actual, e)),
85 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
86 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
91 pub fn demand_eqtype_diag(
96 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
97 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
100 pub fn demand_eqtype_with_origin(
102 cause: &ObligationCause<'tcx>,
105 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
106 match self.at(cause, self.param_env).eq(expected, actual) {
107 Ok(InferOk { obligations, value: () }) => {
108 self.register_predicates(obligations);
111 Err(e) => Some(self.err_ctxt().report_mismatched_types(cause, expected, actual, e)),
115 pub fn demand_coerce(
117 expr: &hir::Expr<'tcx>,
118 checked_ty: Ty<'tcx>,
120 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
121 allow_two_phase: AllowTwoPhase,
124 self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase);
125 if let Some(mut err) = err {
131 /// Checks that the type of `expr` can be coerced to `expected`.
133 /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!`
134 /// will be permitted if the diverges flag is currently "always".
135 #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))]
136 pub fn demand_coerce_diag(
138 expr: &hir::Expr<'tcx>,
139 checked_ty: Ty<'tcx>,
141 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
142 allow_two_phase: AllowTwoPhase,
143 ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) {
144 let expected = self.resolve_vars_with_obligations(expected);
146 let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) {
147 Ok(ty) => return (ty, None),
151 self.set_tainted_by_errors();
152 let expr = expr.peel_drop_temps();
153 let cause = self.misc(expr.span);
154 let expr_ty = self.resolve_vars_with_obligations(checked_ty);
155 let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e.clone());
157 let is_insufficiently_polymorphic =
158 matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
160 // FIXME(#73154): For now, we do leak check when coercing function
161 // pointers in typeck, instead of only during borrowck. This can lead
162 // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
163 if !is_insufficiently_polymorphic {
164 self.emit_coerce_suggestions(
174 (expected, Some(err))
177 fn annotate_expected_due_to_let_ty(
179 err: &mut Diagnostic,
180 expr: &hir::Expr<'_>,
181 error: Option<TypeError<'_>>,
183 let parent = self.tcx.hir().get_parent_node(expr.hir_id);
184 match (self.tcx.hir().find(parent), error) {
185 (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _)
186 if init.hir_id == expr.hir_id =>
188 // Point at `let` assignment type.
189 err.span_label(ty.span, "expected due to this");
192 Some(hir::Node::Expr(hir::Expr {
193 kind: hir::ExprKind::Assign(lhs, rhs, _), ..
195 Some(TypeError::Sorts(ExpectedFound { expected, .. })),
196 ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => {
197 // We ignore closures explicitly because we already point at them elsewhere.
198 // Point at the assigned-to binding.
199 let mut primary_span = lhs.span;
200 let mut secondary_span = lhs.span;
201 let mut post_message = "";
203 hir::ExprKind::Path(hir::QPath::Resolved(
208 hir::def::DefKind::Static(_) | hir::def::DefKind::Const,
214 if let Some(hir::Node::Item(hir::Item {
216 kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..),
218 })) = self.tcx.hir().get_if_local(*def_id)
220 primary_span = ty.span;
221 secondary_span = ident.span;
222 post_message = " type";
225 hir::ExprKind::Path(hir::QPath::Resolved(
227 hir::Path { res: hir::def::Res::Local(hir_id), .. },
229 if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) {
230 let parent = self.tcx.hir().get_parent_node(pat.hir_id);
231 primary_span = pat.span;
232 secondary_span = pat.span;
233 match self.tcx.hir().find(parent) {
234 Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => {
235 primary_span = ty.span;
236 post_message = " type";
238 Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => {
239 primary_span = init.span;
240 post_message = " value";
242 Some(hir::Node::Param(hir::Param { ty_span, .. })) => {
243 primary_span = *ty_span;
244 post_message = " parameter type";
253 if primary_span != secondary_span
258 .is_multiline(secondary_span.shrink_to_hi().until(primary_span))
260 // We are pointing at the binding's type or initializer value, but it's pattern
261 // is in a different line, so we point at both.
262 err.span_label(secondary_span, "expected due to the type of this binding");
263 err.span_label(primary_span, &format!("expected due to this{post_message}"));
264 } else if post_message == "" {
265 // We are pointing at either the assignment lhs or the binding def pattern.
266 err.span_label(primary_span, "expected due to the type of this binding");
268 // We are pointing at the binding's type or initializer value.
269 err.span_label(primary_span, &format!("expected due to this{post_message}"));
272 if !lhs.is_syntactic_place_expr() {
273 // We already emitted E0070 "invalid left-hand side of assignment", so we
275 err.downgrade_to_delayed_bug();
282 /// If the expected type is an enum (Issue #55250) with any variants whose
283 /// sole field is of the found type, suggest such variants. (Issue #42764)
284 fn suggest_compatible_variants(
286 err: &mut Diagnostic,
287 expr: &hir::Expr<'_>,
291 if let ty::Adt(expected_adt, substs) = expected.kind() {
292 if let hir::ExprKind::Field(base, ident) = expr.kind {
293 let base_ty = self.typeck_results.borrow().expr_ty(base);
294 if self.can_eq(self.param_env, base_ty, expected).is_ok()
295 && let Some(base_span) = base.span.find_ancestor_inside(expr.span)
297 err.span_suggestion_verbose(
298 expr.span.with_lo(base_span.hi()),
299 format!("consider removing the tuple struct field `{ident}`"),
301 Applicability::MaybeIncorrect,
307 // If the expression is of type () and it's the return expression of a block,
308 // we suggest adding a separate return expression instead.
309 // (To avoid things like suggesting `Ok(while .. { .. })`.)
310 if expr_ty.is_unit() {
311 let mut id = expr.hir_id;
314 // Unroll desugaring, to make sure this works for `for` loops etc.
316 parent = self.tcx.hir().get_parent_node(id);
317 if let Some(parent_span) = self.tcx.hir().opt_span(parent) {
318 if parent_span.find_ancestor_inside(expr.span).is_some() {
319 // The parent node is part of the same span, so is the result of the
320 // same expansion/desugaring and not the 'real' parent node.
328 if let Some(hir::Node::Block(&hir::Block {
329 span: block_span, expr: Some(e), ..
330 })) = self.tcx.hir().find(parent)
333 if let Some(span) = expr.span.find_ancestor_inside(block_span) {
334 let return_suggestions = if self
336 .is_diagnostic_item(sym::Result, expected_adt.did())
339 } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) {
340 vec!["None", "Some(())"]
344 if let Some(indent) =
345 self.tcx.sess.source_map().indentation_before(span.shrink_to_lo())
347 // Add a semicolon, except after `}`.
349 match self.tcx.sess.source_map().span_to_snippet(span) {
350 Ok(s) if s.ends_with('}') => "",
353 err.span_suggestions(
355 "try adding an expression at the end of the block",
358 .map(|r| format!("{semicolon}\n{indent}{r}")),
359 Applicability::MaybeIncorrect,
368 let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt
372 variant.fields.len() == 1
374 .filter_map(|variant| {
375 let sole_field = &variant.fields[0];
377 let field_is_local = sole_field.did.is_local();
378 let field_is_accessible =
379 sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx)
380 // Skip suggestions for unstable public fields (for example `Pin::pointer`)
381 && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked);
383 if !field_is_local && !field_is_accessible {
387 let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
388 .then(|| format!(" (its field is private, but it's local to this crate and its privacy can be changed)"));
390 let sole_field_ty = sole_field.ty(self.tcx, substs);
391 if self.can_coerce(expr_ty, sole_field_ty) {
393 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
394 // FIXME #56861: DRYer prelude filtering
395 if let Some(path) = variant_path.strip_prefix("std::prelude::")
396 && let Some((_, path)) = path.split_once("::")
398 return Some((path.to_string(), variant.ctor_kind, sole_field.name, note_about_variant_field_privacy));
400 Some((variant_path, variant.ctor_kind, sole_field.name, note_about_variant_field_privacy))
407 let suggestions_for = |variant: &_, ctor, field_name| {
408 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
409 Some(ident) => format!("{ident}: "),
410 None => String::new(),
413 let (open, close) = match ctor {
414 hir::def::CtorKind::Fn => ("(".to_owned(), ")"),
415 hir::def::CtorKind::Fictive => (format!(" {{ {field_name}: "), " }"),
417 // unit variants don't have fields
418 hir::def::CtorKind::Const => unreachable!(),
421 // Suggest constructor as deep into the block tree as possible.
422 // This fixes https://github.com/rust-lang/rust/issues/101065,
423 // and also just helps make the most minimal suggestions.
425 while let hir::ExprKind::Block(block, _) = &expr.kind
426 && let Some(expr_) = &block.expr
432 (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")),
433 (expr.span.shrink_to_hi(), close.to_owned()),
437 match &compatible_variants[..] {
438 [] => { /* No variants to format */ }
439 [(variant, ctor_kind, field_name, note)] => {
440 // Just a single matching variant.
441 err.multipart_suggestion_verbose(
443 "try wrapping the expression in `{variant}`{note}",
444 note = note.as_deref().unwrap_or("")
446 suggestions_for(&**variant, *ctor_kind, *field_name),
447 Applicability::MaybeIncorrect,
452 // More than one matching variant.
453 err.multipart_suggestions(
455 "try wrapping the expression in a variant of `{}`",
456 self.tcx.def_path_str(expected_adt.did())
458 compatible_variants.into_iter().map(
459 |(variant, ctor_kind, field_name, _)| {
460 suggestions_for(&variant, ctor_kind, field_name)
463 Applicability::MaybeIncorrect,
473 fn suggest_non_zero_new_unwrap(
475 err: &mut Diagnostic,
476 expr: &hir::Expr<'_>,
481 let (adt, unwrap) = match expected.kind() {
482 // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
483 ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
485 let ty::Adt(adt, _) = substs.type_at(0).kind() else { return false; };
489 // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types
490 ty::Adt(adt, _) => (adt, ".unwrap()"),
495 (sym::NonZeroU8, tcx.types.u8),
496 (sym::NonZeroU16, tcx.types.u16),
497 (sym::NonZeroU32, tcx.types.u32),
498 (sym::NonZeroU64, tcx.types.u64),
499 (sym::NonZeroU128, tcx.types.u128),
500 (sym::NonZeroI8, tcx.types.i8),
501 (sym::NonZeroI16, tcx.types.i16),
502 (sym::NonZeroI32, tcx.types.i32),
503 (sym::NonZeroI64, tcx.types.i64),
504 (sym::NonZeroI128, tcx.types.i128),
507 let Some((s, _)) = map
509 .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t))
510 else { return false; };
512 let path = self.tcx.def_path_str(adt.non_enum_variant().def_id);
514 err.multipart_suggestion(
515 format!("consider calling `{s}::new`"),
517 (expr.span.shrink_to_lo(), format!("{path}::new(")),
518 (expr.span.shrink_to_hi(), format!("){unwrap}")),
520 Applicability::MaybeIncorrect,
526 pub fn get_conversion_methods(
530 checked_ty: Ty<'tcx>,
532 ) -> Vec<AssocItem> {
533 let methods = self.probe_for_return_type(
535 probe::Mode::MethodCall,
540 self.has_only_self_parameter(m)
543 // This special internal attribute is used to permit
544 // "identity-like" conversion methods to be suggested here.
546 // FIXME (#46459 and #46460): ideally
547 // `std::convert::Into::into` and `std::borrow:ToOwned` would
548 // also be `#[rustc_conversion_suggestion]`, if not for
549 // method-probing false-positives and -negatives (respectively).
551 // FIXME? Other potential candidate methods: `as_ref` and
553 .has_attr(m.def_id, sym::rustc_conversion_suggestion)
560 /// This function checks whether the method is not static and does not accept other parameters than `self`.
561 fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
563 ty::AssocKind::Fn => {
564 method.fn_has_self_parameter
565 && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1
571 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
573 /// Given the following code:
574 /// ```compile_fail,E0308
576 /// fn takes_ref(_: &Foo) {}
577 /// let ref opt = Some(Foo);
579 /// opt.map(|param| takes_ref(param));
581 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
583 /// It only checks for `Option` and `Result` and won't work with
584 /// ```ignore (illustrative)
585 /// opt.map(|param| { takes_ref(param) });
587 fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
588 let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
592 let hir::def::Res::Local(local_id) = path.res else {
596 let local_parent = self.tcx.hir().get_parent_node(local_id);
597 let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
601 let param_parent = self.tcx.hir().get_parent_node(*param_hir_id);
602 let Some(Node::Expr(hir::Expr {
604 kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }),
606 })) = self.tcx.hir().find(param_parent) else {
610 let expr_parent = self.tcx.hir().get_parent_node(*expr_hir_id);
611 let hir = self.tcx.hir().find(expr_parent);
612 let closure_params_len = closure_fn_decl.inputs.len();
614 Some(Node::Expr(hir::Expr {
615 kind: hir::ExprKind::MethodCall(method_path, receiver, ..),
619 ) = (hir, closure_params_len) else {
623 let self_ty = self.typeck_results.borrow().expr_ty(receiver);
624 let name = method_path.ident.name;
625 let is_as_ref_able = match self_ty.peel_refs().kind() {
627 (self.tcx.is_diagnostic_item(sym::Option, def.did())
628 || self.tcx.is_diagnostic_item(sym::Result, def.did()))
629 && (name == sym::map || name == sym::and_then)
633 match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) {
635 let suggestion = format!("as_ref().{}", src);
636 Some((method_path.ident.span, "consider using `as_ref` instead", suggestion))
642 pub(crate) fn maybe_get_struct_pattern_shorthand_field(
644 expr: &hir::Expr<'_>,
645 ) -> Option<Symbol> {
646 let hir = self.tcx.hir();
647 let local = match expr {
650 hir::ExprKind::Path(hir::QPath::Resolved(
653 res: hir::def::Res::Local(_),
654 segments: [hir::PathSegment { ident, .. }],
663 match hir.find(hir.get_parent_node(expr.hir_id))? {
664 Node::ExprField(field) => {
665 if field.ident.name == local.name && field.is_shorthand {
666 return Some(local.name);
675 /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
676 pub(crate) fn maybe_get_block_expr(
678 expr: &hir::Expr<'tcx>,
679 ) -> Option<&'tcx hir::Expr<'tcx>> {
681 hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr,
686 /// Returns whether the given expression is an `else if`.
687 pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool {
688 if let hir::ExprKind::If(..) = expr.kind {
689 let parent_id = self.tcx.hir().get_parent_node(expr.hir_id);
690 if let Some(Node::Expr(hir::Expr {
691 kind: hir::ExprKind::If(_, _, Some(else_expr)),
693 })) = self.tcx.hir().find(parent_id)
695 return else_expr.hir_id == expr.hir_id;
701 /// This function is used to determine potential "simple" improvements or users' errors and
702 /// provide them useful help. For example:
704 /// ```compile_fail,E0308
705 /// fn some_fn(s: &str) {}
707 /// let x = "hey!".to_owned();
708 /// some_fn(x); // error
711 /// No need to find every potential function which could make a coercion to transform a
712 /// `String` into a `&str` since a `&` would do the trick!
714 /// In addition of this check, it also checks between references mutability state. If the
715 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
719 expr: &hir::Expr<'tcx>,
720 checked_ty: Ty<'tcx>,
728 bool, /* suggest `&` or `&mut` type annotation */
730 let sess = self.sess();
733 // If the span is from an external macro, there's no suggestion we can make.
734 if in_external_macro(sess, sp) {
738 let sm = sess.source_map();
740 let replace_prefix = |s: &str, old: &str, new: &str| {
741 s.strip_prefix(old).map(|stripped| new.to_string() + stripped)
744 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
745 let expr = expr.peel_drop_temps();
747 match (&expr.kind, expected.kind(), checked_ty.kind()) {
748 (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
749 (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
750 if let hir::ExprKind::Lit(_) = expr.kind
751 && let Ok(src) = sm.span_to_snippet(sp)
752 && replace_prefix(&src, "b\"", "\"").is_some()
754 let pos = sp.lo() + BytePos(1);
757 "consider removing the leading `b`".to_string(),
759 Applicability::MachineApplicable,
765 (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
766 if let hir::ExprKind::Lit(_) = expr.kind
767 && let Ok(src) = sm.span_to_snippet(sp)
768 && replace_prefix(&src, "\"", "b\"").is_some()
772 "consider adding a leading `b`".to_string(),
774 Applicability::MachineApplicable,
782 (_, &ty::Ref(_, _, mutability), _) => {
783 // Check if it can work when put into a ref. For example:
786 // fn bar(x: &mut i32) {}
789 // bar(&x); // error, expected &mut
791 let ref_ty = match mutability {
792 hir::Mutability::Mut => {
793 self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
795 hir::Mutability::Not => {
796 self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
799 if self.can_coerce(ref_ty, expected) {
800 let mut sugg_sp = sp;
801 if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind {
803 self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span));
805 && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
807 let ai = self.tcx.associated_item(did);
808 ai.trait_container(self.tcx) == Some(clone_trait)
811 && segment.ident.name == sym::clone
813 // If this expression had a clone call when suggesting borrowing
814 // we want to suggest removing it because it'd now be unnecessary.
815 sugg_sp = receiver.span;
818 if let Ok(src) = sm.span_to_snippet(sugg_sp) {
819 let needs_parens = match expr.kind {
820 // parenthesize if needed (Issue #46756)
821 hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
822 // parenthesize borrows of range literals (Issue #54505)
823 _ if is_range_literal(expr) => true,
827 if let Some(sugg) = self.can_use_as_ref(expr) {
832 Applicability::MachineApplicable,
838 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
839 Some(ident) => format!("{ident}: "),
840 None => String::new(),
843 if let Some(hir::Node::Expr(hir::Expr {
844 kind: hir::ExprKind::Assign(..),
846 })) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
848 if mutability == hir::Mutability::Mut {
849 // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
854 let sugg_expr = if needs_parens { format!("({src})") } else { src };
855 return Some(match mutability {
856 hir::Mutability::Mut => (
858 "consider mutably borrowing here".to_string(),
859 format!("{prefix}&mut {sugg_expr}"),
860 Applicability::MachineApplicable,
864 hir::Mutability::Not => (
866 "consider borrowing here".to_string(),
867 format!("{prefix}&{sugg_expr}"),
868 Applicability::MachineApplicable,
877 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
879 &ty::Ref(_, checked, _),
880 ) if self.can_sub(self.param_env, checked, expected).is_ok() => {
881 // We have `&T`, check if what was expected was `T`. If so,
882 // we may want to suggest removing a `&`.
883 if sm.is_imported(expr.span) {
884 // Go through the spans from which this span was expanded,
885 // and find the one that's pointing inside `sp`.
887 // E.g. for `&format!("")`, where we want the span to the
888 // `format!()` invocation instead of its expansion.
889 if let Some(call_span) =
890 iter::successors(Some(expr.span), |s| s.parent_callsite())
891 .find(|&s| sp.contains(s))
892 && sm.is_span_accessible(call_span)
895 sp.with_hi(call_span.lo()),
896 "consider removing the borrow".to_string(),
898 Applicability::MachineApplicable,
905 if sp.contains(expr.span)
906 && sm.is_span_accessible(expr.span)
909 sp.with_hi(expr.span.lo()),
910 "consider removing the borrow".to_string(),
912 Applicability::MachineApplicable,
920 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
921 &ty::Ref(_, ty_a, mutbl_a),
923 if let Some(steps) = self.deref_steps(ty_a, ty_b)
924 // Only suggest valid if dereferencing needed.
926 // The pointer type implements `Copy` trait so the suggestion is always valid.
927 && let Ok(src) = sm.span_to_snippet(sp)
929 let derefs = "*".repeat(steps);
930 if let Some((span, src, applicability)) = match mutbl_b {
931 hir::Mutability::Mut => {
932 let new_prefix = "&mut ".to_owned() + &derefs;
934 hir::Mutability::Mut => {
935 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
936 let pos = sp.lo() + BytePos(5);
937 let sp = sp.with_lo(pos).with_hi(pos);
938 (sp, derefs, Applicability::MachineApplicable)
941 hir::Mutability::Not => {
942 replace_prefix(&src, "&", &new_prefix).map(|_| {
943 let pos = sp.lo() + BytePos(1);
944 let sp = sp.with_lo(pos).with_hi(pos);
947 format!("mut {derefs}"),
948 Applicability::Unspecified,
954 hir::Mutability::Not => {
955 let new_prefix = "&".to_owned() + &derefs;
957 hir::Mutability::Mut => {
958 replace_prefix(&src, "&mut ", &new_prefix).map(|_| {
959 let lo = sp.lo() + BytePos(1);
960 let hi = sp.lo() + BytePos(5);
961 let sp = sp.with_lo(lo).with_hi(hi);
962 (sp, derefs, Applicability::MachineApplicable)
965 hir::Mutability::Not => {
966 replace_prefix(&src, "&", &new_prefix).map(|_| {
967 let pos = sp.lo() + BytePos(1);
968 let sp = sp.with_lo(pos).with_hi(pos);
969 (sp, derefs, Applicability::MachineApplicable)
977 "consider dereferencing".to_string(),
986 _ if sp == expr.span => {
987 if let Some(mut steps) = self.deref_steps(checked_ty, expected) {
988 let mut expr = expr.peel_blocks();
989 let mut prefix_span = expr.span.shrink_to_lo();
990 let mut remove = String::new();
992 // Try peeling off any existing `&` and `&mut` to reach our target type
994 if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind {
995 // If the expression has `&`, removing it would fix the error
996 prefix_span = prefix_span.with_hi(inner.span.lo());
998 remove += match mutbl {
999 hir::Mutability::Not => "&",
1000 hir::Mutability::Mut => "&mut ",
1007 // If we've reached our target type with just removing `&`, then just print now.
1011 format!("consider removing the `{}`", remove.trim()),
1013 // Do not remove `&&` to get to bool, because it might be something like
1014 // { a } && b, which we have a separate fixup suggestion that is more
1015 // likely correct...
1016 if remove.trim() == "&&" && expected == self.tcx.types.bool {
1017 Applicability::MaybeIncorrect
1019 Applicability::MachineApplicable
1026 // For this suggestion to make sense, the type would need to be `Copy`,
1027 // or we have to be moving out of a `Box<T>`
1028 if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
1029 // FIXME(compiler-errors): We can actually do this if the checked_ty is
1030 // `steps` layers of boxes, not just one, but this is easier and most likely.
1031 || (checked_ty.is_box() && steps == 1)
1033 let deref_kind = if checked_ty.is_box() {
1034 "unboxing the value"
1035 } else if checked_ty.is_region_ptr() {
1036 "dereferencing the borrow"
1038 "dereferencing the type"
1041 // Suggest removing `&` if we have removed any, otherwise suggest just
1042 // dereferencing the remaining number of steps.
1043 let message = if remove.is_empty() {
1044 format!("consider {deref_kind}")
1047 "consider removing the `{}` and {} instead",
1053 let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
1054 Some(ident) => format!("{ident}: "),
1055 None => String::new(),
1058 let (span, suggestion) = if self.is_else_if_block(expr) {
1059 // Don't suggest nonsense like `else *if`
1061 } else if let Some(expr) = self.maybe_get_block_expr(expr) {
1062 // prefix should be empty here..
1063 (expr.span.shrink_to_lo(), "*".to_string())
1065 (prefix_span, format!("{}{}", prefix, "*".repeat(steps)))
1072 Applicability::MachineApplicable,
1084 pub fn check_for_cast(
1086 err: &mut Diagnostic,
1087 expr: &hir::Expr<'_>,
1088 checked_ty: Ty<'tcx>,
1089 expected_ty: Ty<'tcx>,
1090 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
1092 if self.tcx.sess.source_map().is_imported(expr.span) {
1093 // Ignore if span is from within a macro.
1097 let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else {
1101 // If casting this expression to a given numeric type would be appropriate in case of a type
1104 // We want to minimize the amount of casting operations that are suggested, as it can be a
1105 // lossy operation with potentially bad side effects, so we only suggest when encountering
1106 // an expression that indicates that the original type couldn't be directly changed.
1108 // For now, don't suggest casting with `as`.
1109 let can_cast = false;
1111 let mut sugg = vec![];
1113 if let Some(hir::Node::ExprField(field)) =
1114 self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
1116 // `expr` is a literal field for a struct, only suggest if appropriate
1117 if field.is_shorthand {
1118 // This is a field literal
1119 sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident)));
1121 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
1126 if let hir::ExprKind::Call(path, args) = &expr.kind
1127 && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
1128 (&path.kind, args.len())
1129 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
1130 && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
1131 (&base_ty.kind, path_segment.ident.name)
1133 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
1147 if base_ty_path.segments.len() == 1 =>
1157 "you can convert {} `{}` to {} `{}`",
1158 checked_ty.kind().article(),
1160 expected_ty.kind().article(),
1163 let cast_msg = format!(
1164 "you can cast {} `{}` to {} `{}`",
1165 checked_ty.kind().article(),
1167 expected_ty.kind().article(),
1170 let lit_msg = format!(
1171 "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`",
1174 let close_paren = if expr.precedence().order() < PREC_POSTFIX {
1175 sugg.push((expr.span.shrink_to_lo(), "(".to_string()));
1181 let mut cast_suggestion = sugg.clone();
1182 cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}")));
1183 let mut into_suggestion = sugg.clone();
1184 into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()")));
1185 let mut suffix_suggestion = sugg.clone();
1186 suffix_suggestion.push((
1188 (&expected_ty.kind(), &checked_ty.kind()),
1189 (ty::Int(_) | ty::Uint(_), ty::Float(_))
1191 // Remove fractional part from literal, for example `42.0f32` into `42`
1192 let src = src.trim_end_matches(&checked_ty.to_string());
1193 let len = src.split('.').next().unwrap().len();
1194 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1196 let len = src.trim_end_matches(&checked_ty.to_string()).len();
1197 expr.span.with_lo(expr.span.lo() + BytePos(len as u32))
1199 if expr.precedence().order() < PREC_POSTFIX {
1201 format!("{expected_ty})")
1203 expected_ty.to_string()
1206 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
1207 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
1209 let is_negative_int =
1210 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..));
1211 let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..));
1213 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
1215 let suggest_fallible_into_or_lhs_from =
1216 |err: &mut Diagnostic, exp_to_found_is_fallible: bool| {
1217 // If we know the expression the expected type is derived from, we might be able
1218 // to suggest a widening conversion rather than a narrowing one (which may
1219 // panic). For example, given x: u8 and y: u32, if we know the span of "x",
1221 // can be given the suggestion "u32::from(x) > y" rather than
1222 // "x > y.try_into().unwrap()".
1223 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
1227 .span_to_snippet(expr.span)
1229 .map(|src| (expr, src))
1231 let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
1232 (lhs_expr_and_src, exp_to_found_is_fallible)
1235 "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`",
1237 let suggestion = vec![
1238 (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")),
1239 (lhs_expr.span.shrink_to_hi(), ")".to_string()),
1243 let msg = format!("{msg} and panic if the converted value doesn't fit");
1244 let mut suggestion = sugg.clone();
1246 expr.span.shrink_to_hi(),
1247 format!("{close_paren}.try_into().unwrap()"),
1251 err.multipart_suggestion_verbose(
1254 Applicability::MachineApplicable,
1258 let suggest_to_change_suffix_or_into =
1259 |err: &mut Diagnostic,
1260 found_to_exp_is_fallible: bool,
1261 exp_to_found_is_fallible: bool| {
1263 expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false);
1269 let always_fallible = found_to_exp_is_fallible
1270 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
1271 let msg = if literal_is_ty_suffixed(expr) {
1273 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
1274 // We now know that converting either the lhs or rhs is fallible. Before we
1275 // suggest a fallible conversion, check if the value can never fit in the
1277 let msg = format!("`{src}` cannot fit into type `{expected_ty}`");
1280 } else if in_const_context {
1281 // Do not recommend `into` or `try_into` in const contexts.
1283 } else if found_to_exp_is_fallible {
1284 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
1288 let suggestion = if literal_is_ty_suffixed(expr) {
1289 suffix_suggestion.clone()
1291 into_suggestion.clone()
1293 err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable);
1296 match (&expected_ty.kind(), &checked_ty.kind()) {
1297 (&ty::Int(ref exp), &ty::Int(ref found)) => {
1298 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1300 (Some(exp), Some(found)) if exp < found => (true, false),
1301 (Some(exp), Some(found)) if exp > found => (false, true),
1302 (None, Some(8 | 16)) => (false, true),
1303 (Some(8 | 16), None) => (true, false),
1304 (None, _) | (_, None) => (true, true),
1305 _ => (false, false),
1307 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1310 (&ty::Uint(ref exp), &ty::Uint(ref found)) => {
1311 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1313 (Some(exp), Some(found)) if exp < found => (true, false),
1314 (Some(exp), Some(found)) if exp > found => (false, true),
1315 (None, Some(8 | 16)) => (false, true),
1316 (Some(8 | 16), None) => (true, false),
1317 (None, _) | (_, None) => (true, true),
1318 _ => (false, false),
1320 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1323 (&ty::Int(exp), &ty::Uint(found)) => {
1324 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1326 (Some(exp), Some(found)) if found < exp => (false, true),
1327 (None, Some(8)) => (false, true),
1330 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1333 (&ty::Uint(exp), &ty::Int(found)) => {
1334 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
1336 (Some(exp), Some(found)) if found > exp => (true, false),
1337 (Some(8), None) => (true, false),
1340 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
1343 (&ty::Float(ref exp), &ty::Float(ref found)) => {
1344 if found.bit_width() < exp.bit_width() {
1345 suggest_to_change_suffix_or_into(err, false, true);
1346 } else if literal_is_ty_suffixed(expr) {
1347 err.multipart_suggestion_verbose(
1350 Applicability::MachineApplicable,
1352 } else if can_cast {
1353 // Missing try_into implementation for `f64` to `f32`
1354 err.multipart_suggestion_verbose(
1355 &format!("{cast_msg}, producing the closest possible value"),
1357 Applicability::MaybeIncorrect, // lossy conversion
1362 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
1363 if literal_is_ty_suffixed(expr) {
1364 err.multipart_suggestion_verbose(
1367 Applicability::MachineApplicable,
1369 } else if can_cast {
1370 // Missing try_into implementation for `{float}` to `{integer}`
1371 err.multipart_suggestion_verbose(
1372 &format!("{msg}, rounding the float towards zero"),
1374 Applicability::MaybeIncorrect, // lossy conversion
1379 (&ty::Float(ref exp), &ty::Uint(ref found)) => {
1380 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
1381 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1382 err.multipart_suggestion_verbose(
1384 "{msg}, producing the floating point representation of the integer",
1387 Applicability::MachineApplicable,
1389 } else if literal_is_ty_suffixed(expr) {
1390 err.multipart_suggestion_verbose(
1393 Applicability::MachineApplicable,
1396 // Missing try_into implementation for `{integer}` to `{float}`
1397 err.multipart_suggestion_verbose(
1399 "{cast_msg}, producing the floating point representation of the integer, \
1400 rounded if necessary",
1403 Applicability::MaybeIncorrect, // lossy conversion
1408 (&ty::Float(ref exp), &ty::Int(ref found)) => {
1409 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
1410 if exp.bit_width() > found.bit_width().unwrap_or(256) {
1411 err.multipart_suggestion_verbose(
1413 "{}, producing the floating point representation of the integer",
1417 Applicability::MachineApplicable,
1419 } else if literal_is_ty_suffixed(expr) {
1420 err.multipart_suggestion_verbose(
1423 Applicability::MachineApplicable,
1426 // Missing try_into implementation for `{integer}` to `{float}`
1427 err.multipart_suggestion_verbose(
1429 "{}, producing the floating point representation of the integer, \
1430 rounded if necessary",
1434 Applicability::MaybeIncorrect, // lossy conversion
1440 &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128)
1441 | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128),
1444 err.multipart_suggestion_verbose(
1445 &format!("{cast_msg}, since a `char` always occupies 4 bytes"),
1447 Applicability::MachineApplicable,