1 use crate::check
::FnCtxt
;
2 use rustc_infer
::infer
::InferOk
;
3 use rustc_trait_selection
::infer
::InferCtxtExt
as _
;
4 use rustc_trait_selection
::traits
::ObligationCause
;
6 use rustc_ast
::util
::parser
::PREC_POSTFIX
;
7 use rustc_errors
::{Applicability, DiagnosticBuilder}
;
9 use rustc_hir
::lang_items
::CloneTraitLangItem
;
10 use rustc_hir
::{is_range_literal, Node}
;
11 use rustc_middle
::ty
::adjustment
::AllowTwoPhase
;
12 use rustc_middle
::ty
::{self, AssocItem, Ty, TypeAndMut}
;
13 use rustc_span
::symbol
::sym
;
16 use super::method
::probe
;
20 impl<'a
, 'tcx
> FnCtxt
<'a
, 'tcx
> {
21 pub fn emit_coerce_suggestions(
23 err
: &mut DiagnosticBuilder
<'_
>,
27 expected_ty_expr
: Option
<&'tcx hir
::Expr
<'tcx
>>,
29 self.annotate_expected_due_to_let_ty(err
, expr
);
30 self.suggest_compatible_variants(err
, expr
, expected
, expr_ty
);
31 self.suggest_deref_ref_or_into(err
, expr
, expected
, expr_ty
, expected_ty_expr
);
32 if self.suggest_calling_boxed_future_when_appropriate(err
, expr
, expected
, expr_ty
) {
35 self.suggest_boxing_when_appropriate(err
, expr
, expected
, expr_ty
);
36 self.suggest_missing_await(err
, expr
, expected
, expr_ty
);
37 self.note_need_for_fn_pointer(err
, expected
, expr_ty
);
40 // Requires that the two types unify, and prints an error message if
42 pub fn demand_suptype(&self, sp
: Span
, expected
: Ty
<'tcx
>, actual
: Ty
<'tcx
>) {
43 if let Some(mut e
) = self.demand_suptype_diag(sp
, expected
, actual
) {
48 pub fn demand_suptype_diag(
53 ) -> Option
<DiagnosticBuilder
<'tcx
>> {
54 self.demand_suptype_with_origin(&self.misc(sp
), expected
, actual
)
57 pub fn demand_suptype_with_origin(
59 cause
: &ObligationCause
<'tcx
>,
62 ) -> Option
<DiagnosticBuilder
<'tcx
>> {
63 match self.at(cause
, self.param_env
).sup(expected
, actual
) {
64 Ok(InferOk { obligations, value: () }
) => {
65 self.register_predicates(obligations
);
68 Err(e
) => Some(self.report_mismatched_types(&cause
, expected
, actual
, e
)),
72 pub fn demand_eqtype(&self, sp
: Span
, expected
: Ty
<'tcx
>, actual
: Ty
<'tcx
>) {
73 if let Some(mut err
) = self.demand_eqtype_diag(sp
, expected
, actual
) {
78 pub fn demand_eqtype_diag(
83 ) -> Option
<DiagnosticBuilder
<'tcx
>> {
84 self.demand_eqtype_with_origin(&self.misc(sp
), expected
, actual
)
87 pub fn demand_eqtype_with_origin(
89 cause
: &ObligationCause
<'tcx
>,
92 ) -> Option
<DiagnosticBuilder
<'tcx
>> {
93 match self.at(cause
, self.param_env
).eq(expected
, actual
) {
94 Ok(InferOk { obligations, value: () }
) => {
95 self.register_predicates(obligations
);
98 Err(e
) => Some(self.report_mismatched_types(cause
, expected
, actual
, e
)),
102 pub fn demand_coerce(
104 expr
: &hir
::Expr
<'_
>,
105 checked_ty
: Ty
<'tcx
>,
107 expected_ty_expr
: Option
<&'tcx hir
::Expr
<'tcx
>>,
108 allow_two_phase
: AllowTwoPhase
,
111 self.demand_coerce_diag(expr
, checked_ty
, expected
, expected_ty_expr
, allow_two_phase
);
112 if let Some(mut err
) = err
{
118 // Checks that the type of `expr` can be coerced to `expected`.
120 // N.B., this code relies on `self.diverges` to be accurate. In
121 // particular, assignments to `!` will be permitted if the
122 // diverges flag is currently "always".
123 pub fn demand_coerce_diag(
125 expr
: &hir
::Expr
<'_
>,
126 checked_ty
: Ty
<'tcx
>,
128 expected_ty_expr
: Option
<&'tcx hir
::Expr
<'tcx
>>,
129 allow_two_phase
: AllowTwoPhase
,
130 ) -> (Ty
<'tcx
>, Option
<DiagnosticBuilder
<'tcx
>>) {
131 let expected
= self.resolve_vars_with_obligations(expected
);
133 let e
= match self.try_coerce(expr
, checked_ty
, expected
, allow_two_phase
) {
134 Ok(ty
) => return (ty
, None
),
138 let expr
= expr
.peel_drop_temps();
139 let cause
= self.misc(expr
.span
);
140 let expr_ty
= self.resolve_vars_with_obligations(checked_ty
);
141 let mut err
= self.report_mismatched_types(&cause
, expected
, expr_ty
, e
);
143 if self.is_assign_to_bool(expr
, expected
) {
144 // Error reported in `check_assign` so avoid emitting error again.
146 return (expected
, None
);
149 self.emit_coerce_suggestions(&mut err
, expr
, expr_ty
, expected
, expected_ty_expr
);
151 (expected
, Some(err
))
154 fn annotate_expected_due_to_let_ty(
156 err
: &mut DiagnosticBuilder
<'_
>,
157 expr
: &hir
::Expr
<'_
>,
159 let parent
= self.tcx
.hir().get_parent_node(expr
.hir_id
);
160 if let Some(hir
::Node
::Local(hir
::Local { ty: Some(ty), init: Some(init), .. }
)) =
161 self.tcx
.hir().find(parent
)
163 if init
.hir_id
== expr
.hir_id
{
164 // Point at `let` assignment type.
165 err
.span_label(ty
.span
, "expected due to this");
170 /// Returns whether the expected type is `bool` and the expression is `x = y`.
171 pub fn is_assign_to_bool(&self, expr
: &hir
::Expr
<'_
>, expected
: Ty
<'tcx
>) -> bool
{
172 if let hir
::ExprKind
::Assign(..) = expr
.kind
{
173 return expected
== self.tcx
.types
.bool
;
178 /// If the expected type is an enum (Issue #55250) with any variants whose
179 /// sole field is of the found type, suggest such variants. (Issue #42764)
180 fn suggest_compatible_variants(
182 err
: &mut DiagnosticBuilder
<'_
>,
183 expr
: &hir
::Expr
<'_
>,
187 if let ty
::Adt(expected_adt
, substs
) = expected
.kind
{
188 if !expected_adt
.is_enum() {
192 let mut compatible_variants
= expected_adt
195 .filter(|variant
| variant
.fields
.len() == 1)
196 .filter_map(|variant
| {
197 let sole_field
= &variant
.fields
[0];
198 let sole_field_ty
= sole_field
.ty(self.tcx
, substs
);
199 if self.can_coerce(expr_ty
, sole_field_ty
) {
200 let variant_path
= self.tcx
.def_path_str(variant
.def_id
);
201 // FIXME #56861: DRYer prelude filtering
202 Some(variant_path
.trim_start_matches("std::prelude::v1::").to_string())
209 if compatible_variants
.peek().is_some() {
210 if let Ok(expr_text
) = self.tcx
.sess
.source_map().span_to_snippet(expr
.span
) {
211 let suggestions
= compatible_variants
.map(|v
| format
!("{}({})", v
, expr_text
));
212 let msg
= "try using a variant of the expected enum";
213 err
.span_suggestions(
217 Applicability
::MaybeIncorrect
,
224 pub fn get_conversion_methods(
228 checked_ty
: Ty
<'tcx
>,
230 ) -> Vec
<AssocItem
> {
232 self.probe_for_return_type(span
, probe
::Mode
::MethodCall
, expected
, checked_ty
, hir_id
);
234 self.has_only_self_parameter(m
)
239 // This special internal attribute is used to permit
240 // "identity-like" conversion methods to be suggested here.
242 // FIXME (#46459 and #46460): ideally
243 // `std::convert::Into::into` and `std::borrow:ToOwned` would
244 // also be `#[rustc_conversion_suggestion]`, if not for
245 // method-probing false-positives and -negatives (respectively).
247 // FIXME? Other potential candidate methods: `as_ref` and
249 .any(|a
| a
.check_name(sym
::rustc_conversion_suggestion
))
255 /// This function checks whether the method is not static and does not accept other parameters than `self`.
256 fn has_only_self_parameter(&self, method
: &AssocItem
) -> bool
{
258 ty
::AssocKind
::Fn
=> {
259 method
.fn_has_self_parameter
260 && self.tcx
.fn_sig(method
.def_id
).inputs().skip_binder().len() == 1
266 /// Identify some cases where `as_ref()` would be appropriate and suggest it.
268 /// Given the following code:
271 /// fn takes_ref(_: &Foo) {}
272 /// let ref opt = Some(Foo);
274 /// opt.map(|param| takes_ref(param));
276 /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead.
278 /// It only checks for `Option` and `Result` and won't work with
280 /// opt.map(|param| { takes_ref(param) });
282 fn can_use_as_ref(&self, expr
: &hir
::Expr
<'_
>) -> Option
<(Span
, &'
static str, String
)> {
283 let path
= match expr
.kind
{
284 hir
::ExprKind
::Path(hir
::QPath
::Resolved(_
, ref path
)) => path
,
288 let local_id
= match path
.res
{
289 hir
::def
::Res
::Local(id
) => id
,
293 let local_parent
= self.tcx
.hir().get_parent_node(local_id
);
294 let param_hir_id
= match self.tcx
.hir().find(local_parent
) {
295 Some(Node
::Param(hir
::Param { hir_id, .. }
)) => hir_id
,
299 let param_parent
= self.tcx
.hir().get_parent_node(*param_hir_id
);
300 let (expr_hir_id
, closure_fn_decl
) = match self.tcx
.hir().find(param_parent
) {
301 Some(Node
::Expr(hir
::Expr
{
303 kind
: hir
::ExprKind
::Closure(_
, decl
, ..),
305 })) => (hir_id
, decl
),
309 let expr_parent
= self.tcx
.hir().get_parent_node(*expr_hir_id
);
310 let hir
= self.tcx
.hir().find(expr_parent
);
311 let closure_params_len
= closure_fn_decl
.inputs
.len();
312 let (method_path
, method_span
, method_expr
) = match (hir
, closure_params_len
) {
314 Some(Node
::Expr(hir
::Expr
{
315 kind
: hir
::ExprKind
::MethodCall(path
, span
, expr
, _
),
319 ) => (path
, span
, expr
),
323 let self_ty
= self.tables
.borrow().node_type(method_expr
[0].hir_id
);
324 let self_ty
= format
!("{:?}", self_ty
);
325 let name
= method_path
.ident
.as_str();
326 let is_as_ref_able
= (self_ty
.starts_with("&std::option::Option")
327 || self_ty
.starts_with("&std::result::Result")
328 || self_ty
.starts_with("std::option::Option")
329 || self_ty
.starts_with("std::result::Result"))
330 && (name
== "map" || name
== "and_then");
331 match (is_as_ref_able
, self.sess().source_map().span_to_snippet(*method_span
)) {
333 let suggestion
= format
!("as_ref().{}", src
);
334 Some((*method_span
, "consider using `as_ref` instead", suggestion
))
340 crate fn is_hir_id_from_struct_pattern_shorthand_field(
345 let sm
= self.sess().source_map();
346 let parent_id
= self.tcx
.hir().get_parent_node(hir_id
);
347 if let Some(parent
) = self.tcx
.hir().find(parent_id
) {
348 // Account for fields
349 if let Node
::Expr(hir
::Expr { kind: hir::ExprKind::Struct(_, fields, ..), .. }
) = parent
351 if let Ok(src
) = sm
.span_to_snippet(sp
) {
352 for field
in *fields
{
353 if field
.ident
.as_str() == src
&& field
.is_shorthand
{
363 fn replace_prefix
<A
, B
, C
>(&self, s
: A
, old
: B
, new
: C
) -> Option
<String
>
370 let old
= old
.as_ref();
371 if s
.starts_with(old
) { Some(new.as_ref().to_owned() + &s[old.len()..]) }
else { None }
374 /// This function is used to determine potential "simple" improvements or users' errors and
375 /// provide them useful help. For example:
378 /// fn some_fn(s: &str) {}
380 /// let x = "hey!".to_owned();
381 /// some_fn(x); // error
384 /// No need to find every potential function which could make a coercion to transform a
385 /// `String` into a `&str` since a `&` would do the trick!
387 /// In addition of this check, it also checks between references mutability state. If the
388 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
392 expr
: &hir
::Expr
<'_
>,
393 checked_ty
: Ty
<'tcx
>,
395 ) -> Option
<(Span
, &'
static str, String
, Applicability
)> {
396 let sm
= self.sess().source_map();
398 if sm
.is_imported(sp
) {
399 // Ignore if span is from within a macro #41858, #58298. We previously used the macro
400 // call span, but that breaks down when the type error comes from multiple calls down.
404 let is_struct_pat_shorthand_field
=
405 self.is_hir_id_from_struct_pattern_shorthand_field(expr
.hir_id
, sp
);
407 // If the span is from a macro, then it's hard to extract the text
408 // and make a good suggestion, so don't bother.
409 let is_macro
= sp
.from_expansion() && sp
.desugaring_kind().is_none();
411 // `ExprKind::DropTemps` is semantically irrelevant for these suggestions.
412 let expr
= expr
.peel_drop_temps();
414 match (&expr
.kind
, &expected
.kind
, &checked_ty
.kind
) {
415 (_
, &ty
::Ref(_
, exp
, _
), &ty
::Ref(_
, check
, _
)) => match (&exp
.kind
, &check
.kind
) {
416 (&ty
::Str
, &ty
::Array(arr
, _
) | &ty
::Slice(arr
)) if arr
== self.tcx
.types
.u8 => {
417 if let hir
::ExprKind
::Lit(_
) = expr
.kind
{
418 if let Ok(src
) = sm
.span_to_snippet(sp
) {
419 if let Some(src
) = self.replace_prefix(src
, "b\"", "\"") {
422 "consider removing the leading `b`",
424 Applicability
::MachineApplicable
,
430 (&ty
::Array(arr
, _
) | &ty
::Slice(arr
), &ty
::Str
) if arr
== self.tcx
.types
.u8 => {
431 if let hir
::ExprKind
::Lit(_
) = expr
.kind
{
432 if let Ok(src
) = sm
.span_to_snippet(sp
) {
433 if let Some(src
) = self.replace_prefix(src
, "\"", "b\"") {
436 "consider adding a leading `b`",
438 Applicability
::MachineApplicable
,
446 (_
, &ty
::Ref(_
, _
, mutability
), _
) => {
447 // Check if it can work when put into a ref. For example:
450 // fn bar(x: &mut i32) {}
453 // bar(&x); // error, expected &mut
455 let ref_ty
= match mutability
{
456 hir
::Mutability
::Mut
=> {
457 self.tcx
.mk_mut_ref(self.tcx
.mk_region(ty
::ReStatic
), checked_ty
)
459 hir
::Mutability
::Not
=> {
460 self.tcx
.mk_imm_ref(self.tcx
.mk_region(ty
::ReStatic
), checked_ty
)
463 if self.can_coerce(ref_ty
, expected
) {
464 let mut sugg_sp
= sp
;
465 if let hir
::ExprKind
::MethodCall(ref segment
, sp
, ref args
, _
) = expr
.kind
{
466 let clone_trait
= self.tcx
.require_lang_item(CloneTraitLangItem
, Some(sp
));
467 if let ([arg
], Some(true), sym
::clone
) = (
469 self.tables
.borrow().type_dependent_def_id(expr
.hir_id
).map(|did
| {
470 let ai
= self.tcx
.associated_item(did
);
471 ai
.container
== ty
::TraitContainer(clone_trait
)
475 // If this expression had a clone call when suggesting borrowing
476 // we want to suggest removing it because it'd now be unnecessary.
480 if let Ok(src
) = sm
.span_to_snippet(sugg_sp
) {
481 let needs_parens
= match expr
.kind
{
482 // parenthesize if needed (Issue #46756)
483 hir
::ExprKind
::Cast(_
, _
) | hir
::ExprKind
::Binary(_
, _
, _
) => true,
484 // parenthesize borrows of range literals (Issue #54505)
485 _
if is_range_literal(self.tcx
.sess
.source_map(), expr
) => true,
488 let sugg_expr
= if needs_parens { format!("({}
)", src) } else { src };
490 if let Some(sugg) = self.can_use_as_ref(expr) {
495 Applicability::MachineApplicable,
498 let field_name = if is_struct_pat_shorthand_field {
499 format!("{}
: ", sugg_expr)
503 if let Some(hir::Node::Expr(hir::Expr {
504 kind: hir::ExprKind::Assign(left_expr, ..),
506 })) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
508 if mutability == hir::Mutability::Mut {
509 // Found the following case:
510 // fn foo(opt: &mut Option<String>){ opt = None }
513 // consider dereferencing here: `*opt` |
514 // expected mutable reference, found enum `Option`
515 if let Ok(src) = sm.span_to_snippet(left_expr.span) {
518 "consider dereferencing here to assign to the mutable
\
519 borrowed piece of memory
",
521 Applicability::MachineApplicable,
527 return Some(match mutability {
528 hir::Mutability::Mut => (
530 "consider mutably borrowing here
",
531 format!("{}
&mut {}
", field_name, sugg_expr),
532 Applicability::MachineApplicable,
534 hir::Mutability::Not => (
536 "consider borrowing here
",
537 format!("{}
&{}
", field_name, sugg_expr),
538 Applicability::MachineApplicable,
545 hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr),
547 &ty::Ref(_, checked, _),
549 self.infcx.can_sub(self.param_env, checked, &expected).is_ok() && !is_macro
552 // We have `&T`, check if what was expected was `T`. If so,
553 // we may want to suggest removing a `&`.
554 if sm.is_imported(expr.span) {
555 if let Ok(src) = sm.span_to_snippet(sp) {
556 if let Some(src) = self.replace_prefix(src, "&", "") {
559 "consider removing the borrow
",
561 Applicability::MachineApplicable,
567 if let Ok(code) = sm.span_to_snippet(expr.span) {
570 "consider removing the borrow
",
572 Applicability::MachineApplicable,
578 &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }),
579 &ty::Ref(_, ty_a, mutbl_a),
581 if let Some(steps) = self.deref_steps(ty_a, ty_b) {
582 // Only suggest valid if dereferencing needed.
584 // The pointer type implements `Copy` trait so the suggestion is always valid.
585 if let Ok(src) = sm.span_to_snippet(sp) {
586 let derefs = &"*".repeat(steps);
587 if let Some((src, applicability)) = match mutbl_b {
588 hir::Mutability::Mut => {
589 let new_prefix = "&mut ".to_owned() + derefs;
591 hir::Mutability::Mut => {
593 self.replace_prefix(src, "&mut ", new_prefix)
595 Some((s, Applicability::MachineApplicable))
600 hir::Mutability::Not => {
602 self.replace_prefix(src, "&", new_prefix)
604 Some((s, Applicability::Unspecified))
611 hir::Mutability::Not => {
612 let new_prefix = "&".to_owned() + derefs;
614 hir::Mutability::Mut => {
616 self.replace_prefix(src, "&mut ", new_prefix)
618 Some((s, Applicability::MachineApplicable))
623 hir::Mutability::Not => {
625 self.replace_prefix(src, "&", new_prefix)
627 Some((s, Applicability::MachineApplicable))
635 return Some((sp, "consider dereferencing
", src, applicability));
641 _ if sp == expr.span && !is_macro => {
642 if let Some(steps) = self.deref_steps(checked_ty, expected) {
644 // For a suggestion to make sense, the type would need to be `Copy`.
645 if self.infcx.type_is_copy_modulo_regions(self.param_env, expected, sp) {
646 if let Ok(code) = sm.span_to_snippet(sp) {
647 let message = if checked_ty.is_region_ptr() {
648 "consider dereferencing the borrow
"
650 "consider dereferencing the
type"
652 let suggestion = if is_struct_pat_shorthand_field {
653 format!("{}
: *{}
", code, code)
661 Applicability::MachineApplicable,
673 pub fn check_for_cast(
675 err: &mut DiagnosticBuilder<'_>,
676 expr: &hir::Expr<'_>,
677 checked_ty: Ty<'tcx>,
678 expected_ty: Ty<'tcx>,
679 expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
681 if self.tcx.sess.source_map().is_imported(expr.span) {
682 // Ignore if span is from within a macro.
686 let src = if let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) {
692 // If casting this expression to a given numeric type would be appropriate in case of a type
695 // We want to minimize the amount of casting operations that are suggested, as it can be a
696 // lossy operation with potentially bad side effects, so we only suggest when encountering
697 // an expression that indicates that the original type couldn't be directly changed.
699 // For now, don't suggest casting with `as`.
700 let can_cast = false;
702 let prefix = if let Some(hir::Node::Expr(hir::Expr {
703 kind: hir::ExprKind::Struct(_, fields, _),
705 })) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id))
707 // `expr` is a literal field for a struct, only suggest if appropriate
710 .find(|field| field.expr.hir_id == expr.hir_id && field.is_shorthand)
712 // This is a field literal
713 Some(field) => format!("{}
: ", field.ident),
714 // Likely a field was meant, but this field wasn't found. Do not suggest anything.
715 None => return false,
721 if let hir::ExprKind::Call(path, args) = &expr.kind {
722 if let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) =
723 (&path.kind, args.len())
725 // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697).
726 if let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) =
727 (&base_ty.kind, path_segment.ident.name)
729 if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() {
743 if base_ty_path.segments.len() == 1 =>
754 let msg = format!("you can convert an `{}` to `{}`
", checked_ty, expected_ty);
755 let cast_msg = format!("you can cast an `{} to `{}`
", checked_ty, expected_ty);
756 let lit_msg = format!(
757 "change the
type of the numeric literal from `{}` to `{}`
",
758 checked_ty, expected_ty,
761 let with_opt_paren: fn(&dyn fmt::Display) -> String =
762 if expr.precedence().order() < PREC_POSTFIX {
763 |s| format!("({}
)", s)
768 let cast_suggestion = format!("{}{}
as {}
", prefix, with_opt_paren(&src), expected_ty);
769 let into_suggestion = format!("{}{}
.into()", prefix, with_opt_paren(&src));
770 let suffix_suggestion = with_opt_paren(&format_args!(
773 (&expected_ty.kind, &checked_ty.kind),
774 (ty::Int(_) | ty::Uint(_), ty::Float(_))
776 // Remove fractional part from literal, for example `42.0f32` into `42`
777 let src = src.trim_end_matches(&checked_ty.to_string());
778 src.split('.').next().unwrap()
780 src.trim_end_matches(&checked_ty.to_string())
784 let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| {
785 if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false }
787 let is_negative_int =
788 |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::UnNeg, ..));
789 let is_uint = |ty: Ty<'_>| matches!(ty.kind, ty::Uint(..));
791 let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id);
793 let suggest_fallible_into_or_lhs_from =
794 |err: &mut DiagnosticBuilder<'_>, exp_to_found_is_fallible: bool| {
795 // If we know the expression the expected type is derived from, we might be able
796 // to suggest a widening conversion rather than a narrowing one (which may
797 // panic). For example, given x: u8 and y: u32, if we know the span of "x
",
799 // can be given the suggestion "u32::from(x
) > y
" rather than
800 // "x
> y
.try_into().unwrap()".
801 let lhs_expr_and_src = expected_ty_expr.and_then(|expr| {
802 match self.tcx.sess.source_map().span_to_snippet(expr.span).ok() {
803 Some(src) => Some((expr, src)),
807 let (span, msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) =
808 (lhs_expr_and_src, exp_to_found_is_fallible)
811 "you can convert `{}` from `{}` to `{}`
, matching the
type of `{}`
",
812 lhs_src, expected_ty, checked_ty, src
814 let suggestion = format!("{}
::from({}
)", checked_ty, lhs_src);
815 (lhs_expr.span, msg, suggestion)
817 let msg = format!("{} and panic
if the converted value wouldn't fit
", msg);
819 format!("{}{}
.try_into().unwrap()", prefix, with_opt_paren(&src));
820 (expr.span, msg, suggestion)
822 err.span_suggestion(span, &msg, suggestion, Applicability::MachineApplicable);
825 let suggest_to_change_suffix_or_into =
826 |err: &mut DiagnosticBuilder<'_>,
827 found_to_exp_is_fallible: bool,
828 exp_to_found_is_fallible: bool| {
829 let always_fallible = found_to_exp_is_fallible
830 && (exp_to_found_is_fallible || expected_ty_expr.is_none());
831 let msg = if literal_is_ty_suffixed(expr) {
833 } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) {
834 // We now know that converting either the lhs or rhs is fallible. Before we
835 // suggest a fallible conversion, check if the value can never fit in the
837 let msg = format!("`{}` cannot fit into
type `{}`
", src, expected_ty);
840 } else if in_const_context {
841 // Do not recommend `into` or `try_into` in const contexts.
843 } else if found_to_exp_is_fallible {
844 return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible);
848 let suggestion = if literal_is_ty_suffixed(expr) {
849 suffix_suggestion.clone()
851 into_suggestion.clone()
853 err.span_suggestion(expr.span, msg, suggestion, Applicability::MachineApplicable);
856 match (&expected_ty.kind, &checked_ty.kind) {
857 (&ty::Int(ref exp), &ty::Int(ref found)) => {
858 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
860 (Some(exp), Some(found)) if exp < found => (true, false),
861 (Some(exp), Some(found)) if exp > found => (false, true),
862 (None, Some(8 | 16)) => (false, true),
863 (Some(8 | 16), None) => (true, false),
864 (None, _) | (_, None) => (true, true),
867 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
870 (&ty::Uint(ref exp), &ty::Uint(ref found)) => {
871 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
873 (Some(exp), Some(found)) if exp < found => (true, false),
874 (Some(exp), Some(found)) if exp > found => (false, true),
875 (None, Some(8 | 16)) => (false, true),
876 (Some(8 | 16), None) => (true, false),
877 (None, _) | (_, None) => (true, true),
880 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
883 (&ty::Int(exp), &ty::Uint(found)) => {
884 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
886 (Some(exp), Some(found)) if found < exp => (false, true),
887 (None, Some(8)) => (false, true),
890 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
893 (&ty::Uint(exp), &ty::Int(found)) => {
894 let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width())
896 (Some(exp), Some(found)) if found > exp => (true, false),
897 (Some(8), None) => (true, false),
900 suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible);
903 (&ty::Float(ref exp), &ty::Float(ref found)) => {
904 if found.bit_width() < exp.bit_width() {
905 suggest_to_change_suffix_or_into(err, false, true);
906 } else if literal_is_ty_suffixed(expr) {
911 Applicability::MachineApplicable,
914 // Missing try_into implementation for `f64` to `f32`
917 &format!("{}
, producing the closest possible value
", cast_msg),
919 Applicability::MaybeIncorrect, // lossy conversion
924 (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => {
925 if literal_is_ty_suffixed(expr) {
930 Applicability::MachineApplicable,
933 // Missing try_into implementation for `{float}` to `{integer}`
936 &format!("{}
, rounding the float towards zero
", msg),
938 Applicability::MaybeIncorrect, // lossy conversion
943 (&ty::Float(ref exp), &ty::Uint(ref found)) => {
944 // if `found` is `None` (meaning found is `usize`), don't suggest `.into()`
945 if exp.bit_width() > found.bit_width().unwrap_or(256) {
949 "{}
, producing the floating point representation of the integer
",
953 Applicability::MachineApplicable,
955 } else if literal_is_ty_suffixed(expr) {
960 Applicability::MachineApplicable,
963 // Missing try_into implementation for `{integer}` to `{float}`
967 "{}
, producing the floating point representation of the integer
,
968 rounded
if necessary
",
972 Applicability::MaybeIncorrect, // lossy conversion
977 (&ty::Float(ref exp), &ty::Int(ref found)) => {
978 // if `found` is `None` (meaning found is `isize`), don't suggest `.into()`
979 if exp.bit_width() > found.bit_width().unwrap_or(256) {
983 "{}
, producing the floating point representation of the integer
",
987 Applicability::MachineApplicable,
989 } else if literal_is_ty_suffixed(expr) {
994 Applicability::MachineApplicable,
997 // Missing try_into implementation for `{integer}` to `{float}`
1001 "{}
, producing the floating point representation of the integer
, \
1002 rounded
if necessary
",
1006 Applicability::MaybeIncorrect, // lossy conversion