Rollup merge of #125168 - Jules-Bertholet:match-ergonomics-2024-align-with-rfc, r=Nadrieril

Match ergonomics 2024: align implementation with RFC

- Remove eat-two-layers (`ref_pat_everywhere`)
- Consolidate `mut_preserve_binding_mode_2024` into `ref_pat_eat_one_layer_2024`
- `&mut` no longer peels off `&`
- Apply "no `ref mut` behind `&`" rule on all editions with `ref_pat_eat_one_layer_2024`
- Require `mut_ref` feature gate for all mutable by-reference bindings

r? ``@Nadrieril``

cc https://github.com/rust-lang/rust/issues/123076

``@rustbot`` label A-edition-2024 A-patterns
This commit is contained in:
Matthias Krüger 2024-06-06 04:17:26 +02:00 committed by GitHub
commit 2611b292c4
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GPG Key ID: B5690EEEBB952194
18 changed files with 233 additions and 343 deletions

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@ -128,6 +128,8 @@ declare_features! (
/// Allows the use of type alias impl trait in function return positions
(removed, min_type_alias_impl_trait, "1.56.0", Some(63063),
Some("removed in favor of full type_alias_impl_trait")),
/// Make `mut` not reset the binding mode on edition >= 2024.
(removed, mut_preserve_binding_mode_2024, "1.79.0", Some(123076), Some("superseded by `ref_pat_eat_one_layer_2024`")),
(removed, needs_allocator, "1.4.0", Some(27389),
Some("subsumed by `#![feature(allocator_internals)]`")),
/// Allows use of unary negate on unsigned integers, e.g., -e for e: u8
@ -181,6 +183,7 @@ declare_features! (
(removed, pushpop_unsafe, "1.2.0", None, None),
(removed, quad_precision_float, "1.0.0", None, None),
(removed, quote, "1.33.0", Some(29601), None),
(removed, ref_pat_everywhere, "1.79.0", Some(123076), Some("superseded by `ref_pat_eat_one_layer_2024")),
(removed, reflect, "1.0.0", Some(27749), None),
/// Allows using the `#[register_attr]` attribute.
(removed, register_attr, "1.65.0", Some(66080),

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@ -529,8 +529,6 @@ declare_features! (
(unstable, more_qualified_paths, "1.54.0", Some(86935)),
/// Allows the `#[must_not_suspend]` attribute.
(unstable, must_not_suspend, "1.57.0", Some(83310)),
/// Make `mut` not reset the binding mode on edition >= 2024.
(incomplete, mut_preserve_binding_mode_2024, "1.79.0", Some(123076)),
/// Allows `mut ref` and `mut ref mut` identifier patterns.
(incomplete, mut_ref, "1.79.0", Some(123076)),
/// Allows using `#[naked]` on functions.
@ -573,8 +571,6 @@ declare_features! (
(unstable, raw_ref_op, "1.41.0", Some(64490)),
/// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024.
(incomplete, ref_pat_eat_one_layer_2024, "1.79.0", Some(123076)),
/// Allows `&` and `&mut` patterns to consume match-ergonomics-inserted references.
(incomplete, ref_pat_everywhere, "1.79.0", Some(123076)),
/// Allows using the `#[register_tool]` attribute.
(unstable, register_tool, "1.41.0", Some(66079)),
/// Allows the `#[repr(i128)]` attribute for enums.

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@ -12,7 +12,7 @@ use rustc_infer::infer;
use rustc_middle::mir::interpret::ErrorHandled;
use rustc_middle::ty::{self, Ty, TypeVisitableExt};
use rustc_middle::{bug, span_bug};
use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
use rustc_session::{lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS, parse::feature_err};
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::hygiene::DesugaringKind;
use rustc_span::source_map::Spanned;
@ -335,9 +335,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
match adjust_mode {
AdjustMode::Pass => (expected, def_br, max_ref_mutbl),
AdjustMode::Reset => (expected, ByRef::No, MutblCap::Mut),
AdjustMode::Peel => {
self.peel_off_references(pat, expected, def_br, Mutability::Mut, max_ref_mutbl)
}
AdjustMode::Peel => self.peel_off_references(pat, expected, def_br, max_ref_mutbl),
}
}
@ -408,8 +406,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
pat: &'tcx Pat<'tcx>,
expected: Ty<'tcx>,
mut def_br: ByRef,
max_peelable_mutability: Mutability,
mut max_ref_mutability: MutblCap,
mut max_ref_mutbl: MutblCap,
) -> (Ty<'tcx>, ByRef, MutblCap) {
let mut expected = self.try_structurally_resolve_type(pat.span, expected);
// Peel off as many `&` or `&mut` from the scrutinee type as possible. For example,
@ -421,9 +418,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
//
// See the examples in `ui/match-defbm*.rs`.
let mut pat_adjustments = vec![];
while let ty::Ref(_, inner_ty, inner_mutability) = *expected.kind()
&& inner_mutability <= max_peelable_mutability
{
while let ty::Ref(_, inner_ty, inner_mutability) = *expected.kind() {
debug!("inspecting {:?}", expected);
debug!("current discriminant is Ref, inserting implicit deref");
@ -443,10 +438,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
});
}
if pat.span.at_least_rust_2024() && self.tcx.features().ref_pat_eat_one_layer_2024 {
def_br = def_br.cap_ref_mutability(max_ref_mutability.as_mutbl());
if self.tcx.features().ref_pat_eat_one_layer_2024 {
def_br = def_br.cap_ref_mutability(max_ref_mutbl.as_mutbl());
if def_br == ByRef::Yes(Mutability::Not) {
max_ref_mutability = MutblCap::Not;
max_ref_mutbl = MutblCap::Not;
}
}
@ -458,7 +453,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
.insert(pat.hir_id, pat_adjustments);
}
(expected, def_br, max_ref_mutability)
(expected, def_br, max_ref_mutbl)
}
fn check_pat_lit(
@ -674,17 +669,27 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// Determine the binding mode...
let bm = match user_bind_annot {
// `mut` resets binding mode on edition <= 2021
BindingMode(ByRef::No, Mutability::Mut)
if !(pat.span.at_least_rust_2024()
&& self.tcx.features().mut_preserve_binding_mode_2024)
&& matches!(def_br, ByRef::Yes(_)) =>
{
self.typeck_results
.borrow_mut()
.rust_2024_migration_desugared_pats_mut()
.insert(pat_info.top_info.hir_id);
BindingMode(ByRef::No, Mutability::Mut)
BindingMode(ByRef::No, Mutability::Mut) if matches!(def_br, ByRef::Yes(_)) => {
if pat.span.at_least_rust_2024() && self.tcx.features().ref_pat_eat_one_layer_2024 {
if !self.tcx.features().mut_ref {
feature_err(
&self.tcx.sess,
sym::mut_ref,
pat.span.until(ident.span),
"binding cannot be both mutable and by-reference",
)
.emit();
}
BindingMode(def_br, Mutability::Mut)
} else {
// `mut` resets binding mode on edition <= 2021
self.typeck_results
.borrow_mut()
.rust_2024_migration_desugared_pats_mut()
.insert(pat_info.top_info.hir_id);
BindingMode(ByRef::No, Mutability::Mut)
}
}
BindingMode(ByRef::No, mutbl) => BindingMode(def_br, mutbl),
BindingMode(ByRef::Yes(_), _) => user_bind_annot,
@ -2126,57 +2131,47 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
mut expected: Ty<'tcx>,
mut pat_info: PatInfo<'tcx, '_>,
) -> Ty<'tcx> {
// FIXME: repace with `bool` once final decision on 1 vs 2 layers is made
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum MatchErgonomicsMode {
EatOneLayer,
EatTwoLayers,
Legacy,
}
let no_ref_mut_behind_and = self.tcx.features().ref_pat_eat_one_layer_2024;
let new_match_ergonomics = pat.span.at_least_rust_2024() && no_ref_mut_behind_and;
let match_ergonomics_mode =
if pat.span.at_least_rust_2024() && self.tcx.features().ref_pat_eat_one_layer_2024 {
MatchErgonomicsMode::EatOneLayer
} else if self.tcx.features().ref_pat_everywhere {
MatchErgonomicsMode::EatTwoLayers
} else {
MatchErgonomicsMode::Legacy
};
let pat_prefix_span =
inner.span.find_ancestor_inside(pat.span).map(|end| pat.span.until(end));
let mut inherited_ref_mutbl_match = false;
if match_ergonomics_mode != MatchErgonomicsMode::Legacy {
if no_ref_mut_behind_and {
if pat_mutbl == Mutability::Not {
// Prevent the inner pattern from binding with `ref mut`.
pat_info.max_ref_mutbl = pat_info.max_ref_mutbl.cap_to_weakly_not(
inner.span.find_ancestor_inside(pat.span).map(|end| pat.span.until(end)),
);
pat_info.max_ref_mutbl = pat_info.max_ref_mutbl.cap_to_weakly_not(pat_prefix_span);
}
} else {
pat_info.max_ref_mutbl = MutblCap::Mut;
}
if new_match_ergonomics {
if let ByRef::Yes(inh_mut) = pat_info.binding_mode {
inherited_ref_mutbl_match = pat_mutbl <= inh_mut;
}
// ref pattern consumes inherited reference
if inherited_ref_mutbl_match {
pat_info.binding_mode = ByRef::No;
if match_ergonomics_mode == MatchErgonomicsMode::EatOneLayer {
self.typeck_results.borrow_mut().skipped_ref_pats_mut().insert(pat.hir_id);
self.check_pat(inner, expected, pat_info);
return expected;
if pat_mutbl > inh_mut {
// Tried to match inherited `ref` with `&mut`, which is an error
let err_msg = "cannot match inherited `&` with `&mut` pattern";
let err = if let Some(span) = pat_prefix_span {
let mut err = self.dcx().struct_span_err(span, err_msg);
err.span_suggestion_verbose(
span,
"replace this `&mut` pattern with `&`",
"&",
Applicability::MachineApplicable,
);
err
} else {
self.dcx().struct_span_err(pat.span, err_msg)
};
err.emit();
}
} else if match_ergonomics_mode == MatchErgonomicsMode::EatOneLayer
&& pat_mutbl == Mutability::Mut
{
// `&mut` patterns pell off `&` references
let (new_expected, new_bm, max_ref_mutbl) = self.peel_off_references(
pat,
expected,
pat_info.binding_mode,
Mutability::Not,
pat_info.max_ref_mutbl,
);
expected = new_expected;
pat_info.binding_mode = new_bm;
pat_info.max_ref_mutbl = max_ref_mutbl;
pat_info.binding_mode = ByRef::No;
self.typeck_results.borrow_mut().skipped_ref_pats_mut().insert(pat.hir_id);
self.check_pat(inner, expected, pat_info);
return expected;
}
} else {
// Reset binding mode on old editions
@ -2189,8 +2184,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
.rust_2024_migration_desugared_pats_mut()
.insert(pat_info.top_info.hir_id);
}
pat_info.max_ref_mutbl = MutblCap::Mut;
}
let tcx = self.tcx;
@ -2205,34 +2198,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// the bad interactions of the given hack detailed in (note_1).
debug!("check_pat_ref: expected={:?}", expected);
match *expected.kind() {
ty::Ref(_, r_ty, r_mutbl) if r_mutbl == pat_mutbl => {
if r_mutbl == Mutability::Not
&& match_ergonomics_mode != MatchErgonomicsMode::Legacy
{
ty::Ref(_, r_ty, r_mutbl)
if (new_match_ergonomics && r_mutbl >= pat_mutbl)
|| r_mutbl == pat_mutbl =>
{
if no_ref_mut_behind_and && r_mutbl == Mutability::Not {
pat_info.max_ref_mutbl = MutblCap::Not;
}
(expected, r_ty)
}
// `&` pattern eats `&mut` reference
ty::Ref(_, r_ty, Mutability::Mut)
if pat_mutbl == Mutability::Not
&& match_ergonomics_mode != MatchErgonomicsMode::Legacy =>
{
(expected, r_ty)
}
_ if inherited_ref_mutbl_match
&& match_ergonomics_mode == MatchErgonomicsMode::EatTwoLayers =>
{
// We already matched against a match-ergonmics inserted reference,
// so we don't need to match against a reference from the original type.
// Save this info for use in lowering later
self.typeck_results.borrow_mut().skipped_ref_pats_mut().insert(pat.hir_id);
(expected, expected)
}
_ => {
let inner_ty = self.next_ty_var(inner.span);
let ref_ty = self.new_ref_ty(pat.span, pat_mutbl, inner_ty);

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@ -1,14 +0,0 @@
pub fn main() {
if let Some(Some(&x)) = &Some(&Some(0)) {
//~^ ERROR: mismatched types [E0308]
let _: u32 = x;
}
if let Some(&Some(x)) = &Some(Some(0)) {
//~^ ERROR: mismatched types [E0308]
let _: u32 = x;
}
if let Some(Some(&mut x)) = &mut Some(&mut Some(0)) {
//~^ ERROR: mismatched types [E0308]
let _: u32 = x;
}
}

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@ -1,49 +0,0 @@
error[E0308]: mismatched types
--> $DIR/feature-gate-ref_pat_everywhere.rs:2:22
|
LL | if let Some(Some(&x)) = &Some(&Some(0)) {
| ^^ --------------- this expression has type `&Option<&Option<{integer}>>`
| |
| expected integer, found `&_`
|
= note: expected type `{integer}`
found reference `&_`
help: consider removing `&` from the pattern
|
LL | if let Some(Some(x)) = &Some(&Some(0)) {
| ~
error[E0308]: mismatched types
--> $DIR/feature-gate-ref_pat_everywhere.rs:6:17
|
LL | if let Some(&Some(x)) = &Some(Some(0)) {
| ^^^^^^^^ -------------- this expression has type `&Option<Option<{integer}>>`
| |
| expected `Option<{integer}>`, found `&_`
|
= note: expected enum `Option<{integer}>`
found reference `&_`
error[E0308]: mismatched types
--> $DIR/feature-gate-ref_pat_everywhere.rs:10:22
|
LL | if let Some(Some(&mut x)) = &mut Some(&mut Some(0)) {
| ^^^^^^ ----------------------- this expression has type `&mut Option<&mut Option<{integer}>>`
| |
| expected integer, found `&mut _`
|
= note: expected type `{integer}`
found mutable reference `&mut _`
note: to declare a mutable binding use: `mut x`
--> $DIR/feature-gate-ref_pat_everywhere.rs:10:22
|
LL | if let Some(Some(&mut x)) = &mut Some(&mut Some(0)) {
| ^^^^^^
help: consider removing `&mut` from the pattern
|
LL | if let Some(Some(x)) = &mut Some(&mut Some(0)) {
| ~
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0308`.

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@ -23,9 +23,6 @@ pub fn main() {
if let Some(Some(&x)) = &Some(&Some(0)) {
let _: u32 = x;
}
if let Some(&mut Some(&x)) = &Some(&mut Some(0)) {
let _: u32 = x;
}
if let Some(&Some(&x)) = &mut Some(&Some(0)) {
let _: u32 = x;
}
@ -35,9 +32,6 @@ pub fn main() {
if let Some(&Some(&mut ref x)) = Some(&Some(&mut 0)) {
let _: &u32 = x;
}
if let Some(Some(&mut x)) = &Some(Some(&mut 0)) {
let _: &u32 = x;
}
if let &Some(Some(x)) = &Some(&mut Some(0)) {
let _: &u32 = x;
}
@ -59,13 +53,4 @@ pub fn main() {
if let Some(&Some(x)) = &mut Some(Some(0)) {
let _: u32 = x;
}
let &mut x = &&mut 0;
let _: &u32 = x;
let &mut x = &&&&&&&&&&&&&&&&&&&&&&&&&&&&mut 0;
let _: &u32 = x;
let &mut &mut &mut &mut x = &mut &&&&mut &&&mut &mut 0;
let _: &u32 = x;
}

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@ -5,26 +5,26 @@
pub fn main() {
if let Some(&mut Some(&_)) = &Some(&Some(0)) {
//~^ ERROR: mismatched types
//~^ ERROR: cannot match inherited `&` with `&mut` pattern
}
if let Some(&Some(&mut _)) = &Some(&mut Some(0)) {
//~^ ERROR: mismatched types
//~^ ERROR: cannot match inherited `&` with `&mut` pattern
}
if let Some(&Some(x)) = &mut Some(&Some(0)) {
let _: &mut u32 = x;
//~^ ERROR: mismatched types
}
if let Some(&Some(&mut _)) = &mut Some(&Some(0)) {
//~^ ERROR: mismatched types
//~^ ERROR: cannot match inherited `&` with `&mut` pattern
}
if let Some(&Some(Some((&mut _)))) = &Some(Some(&mut Some(0))) {
//~^ ERROR: mismatched types
//~^ ERROR: cannot match inherited `&` with `&mut` pattern
}
if let Some(&mut Some(x)) = &Some(Some(0)) {
//~^ ERROR: mismatched types
//~^ ERROR: cannot match inherited `&` with `&mut` pattern
}
if let Some(&mut Some(x)) = &Some(Some(0)) {
//~^ ERROR: mismatched types
//~^ ERROR: cannot match inherited `&` with `&mut` pattern
}
let &mut _ = &&0;
@ -32,4 +32,31 @@ pub fn main() {
let &mut _ = &&&&&&&&&&&&&&&&&&&&&&&&&&&&0;
//~^ ERROR: mismatched types
if let Some(&mut Some(&_)) = &Some(&mut Some(0)) {
//~^ ERROR: cannot match inherited `&` with `&mut` pattern
}
if let Some(Some(&mut x)) = &Some(Some(&mut 0)) {
//~^ ERROR: cannot match inherited `&` with `&mut` pattern
}
let &mut _ = &&mut 0;
//~^ ERROR: mismatched types
let &mut _ = &&&&&&&&&&&&&&&&&&&&&&&&&&&&mut 0;
//~^ ERROR: mismatched types
let &mut &mut &mut &mut _ = &mut &&&&mut &&&mut &mut 0;
//~^ ERROR: mismatched types
struct Foo(u8);
let Foo(mut a) = &Foo(0);
//~^ ERROR: binding cannot be both mutable and by-reference
a = &42;
let Foo(mut a) = &mut Foo(0);
//~^ ERROR: binding cannot be both mutable and by-reference
a = &mut 42;
}

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@ -1,24 +1,24 @@
error[E0308]: mismatched types
error: cannot match inherited `&` with `&mut` pattern
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:7:17
|
LL | if let Some(&mut Some(&_)) = &Some(&Some(0)) {
| ^^^^^^^^^^^^^ --------------- this expression has type `&Option<&Option<{integer}>>`
| |
| expected `Option<{integer}>`, found `&mut _`
| ^^^^^
|
= note: expected enum `Option<{integer}>`
found mutable reference `&mut _`
help: replace this `&mut` pattern with `&`
|
LL | if let Some(&Some(&_)) = &Some(&Some(0)) {
| ~
error[E0308]: mismatched types
error: cannot match inherited `&` with `&mut` pattern
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:10:23
|
LL | if let Some(&Some(&mut _)) = &Some(&mut Some(0)) {
| ^^^^^^ ------------------- this expression has type `&Option<&mut Option<{integer}>>`
| |
| expected integer, found `&mut _`
| ^^^^^
|
= note: expected type `{integer}`
found mutable reference `&mut _`
help: replace this `&mut` pattern with `&`
|
LL | if let Some(&Some(&_)) = &Some(&mut Some(0)) {
| ~
error[E0308]: mismatched types
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:14:27
@ -31,49 +31,49 @@ LL | let _: &mut u32 = x;
= note: expected mutable reference `&mut u32`
found reference `&{integer}`
error[E0308]: mismatched types
error: cannot match inherited `&` with `&mut` pattern
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:17:23
|
LL | if let Some(&Some(&mut _)) = &mut Some(&Some(0)) {
| ^^^^^^ ------------------- this expression has type `&mut Option<&Option<{integer}>>`
| |
| expected integer, found `&mut _`
| ^^^^^
|
= note: expected type `{integer}`
found mutable reference `&mut _`
help: replace this `&mut` pattern with `&`
|
LL | if let Some(&Some(&_)) = &mut Some(&Some(0)) {
| ~
error[E0308]: mismatched types
error: cannot match inherited `&` with `&mut` pattern
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:20:29
|
LL | if let Some(&Some(Some((&mut _)))) = &Some(Some(&mut Some(0))) {
| ^^^^^^ ------------------------- this expression has type `&Option<Option<&mut Option<{integer}>>>`
| |
| expected integer, found `&mut _`
| ^^^^^
|
= note: expected type `{integer}`
found mutable reference `&mut _`
help: replace this `&mut` pattern with `&`
|
LL | if let Some(&Some(Some((&_)))) = &Some(Some(&mut Some(0))) {
| ~
error[E0308]: mismatched types
error: cannot match inherited `&` with `&mut` pattern
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:23:17
|
LL | if let Some(&mut Some(x)) = &Some(Some(0)) {
| ^^^^^^^^^^^^ -------------- this expression has type `&Option<Option<{integer}>>`
| |
| expected `Option<{integer}>`, found `&mut _`
| ^^^^^
|
= note: expected enum `Option<{integer}>`
found mutable reference `&mut _`
help: replace this `&mut` pattern with `&`
|
LL | if let Some(&Some(x)) = &Some(Some(0)) {
| ~
error[E0308]: mismatched types
error: cannot match inherited `&` with `&mut` pattern
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:26:17
|
LL | if let Some(&mut Some(x)) = &Some(Some(0)) {
| ^^^^^^^^^^^^ -------------- this expression has type `&Option<Option<{integer}>>`
| |
| expected `Option<{integer}>`, found `&mut _`
| ^^^^^
|
= note: expected enum `Option<{integer}>`
found mutable reference `&mut _`
help: replace this `&mut` pattern with `&`
|
LL | if let Some(&Some(x)) = &Some(Some(0)) {
| ~
error[E0308]: mismatched types
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:30:9
@ -81,9 +81,9 @@ error[E0308]: mismatched types
LL | let &mut _ = &&0;
| ^^^^^^ --- this expression has type `&&{integer}`
| |
| expected integer, found `&mut _`
| types differ in mutability
|
= note: expected type `{integer}`
= note: expected reference `&&{integer}`
found mutable reference `&mut _`
error[E0308]: mismatched types
@ -92,11 +92,87 @@ error[E0308]: mismatched types
LL | let &mut _ = &&&&&&&&&&&&&&&&&&&&&&&&&&&&0;
| ^^^^^^ ----------------------------- this expression has type `&&&&&&&&&&&&&&&&&&&&&&&&&&&&{integer}`
| |
| expected integer, found `&mut _`
| types differ in mutability
|
= note: expected type `{integer}`
= note: expected reference `&&&&&&&&&&&&&&&&&&&&&&&&&&&&{integer}`
found mutable reference `&mut _`
error: aborting due to 9 previous errors
error: cannot match inherited `&` with `&mut` pattern
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:36:17
|
LL | if let Some(&mut Some(&_)) = &Some(&mut Some(0)) {
| ^^^^^
|
help: replace this `&mut` pattern with `&`
|
LL | if let Some(&Some(&_)) = &Some(&mut Some(0)) {
| ~
For more information about this error, try `rustc --explain E0308`.
error: cannot match inherited `&` with `&mut` pattern
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:40:22
|
LL | if let Some(Some(&mut x)) = &Some(Some(&mut 0)) {
| ^^^^^
|
help: replace this `&mut` pattern with `&`
|
LL | if let Some(Some(&x)) = &Some(Some(&mut 0)) {
| ~
error[E0308]: mismatched types
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:44:9
|
LL | let &mut _ = &&mut 0;
| ^^^^^^ ------- this expression has type `&&mut {integer}`
| |
| types differ in mutability
|
= note: expected reference `&&mut {integer}`
found mutable reference `&mut _`
error[E0308]: mismatched types
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:47:9
|
LL | let &mut _ = &&&&&&&&&&&&&&&&&&&&&&&&&&&&mut 0;
| ^^^^^^ --------------------------------- this expression has type `&&&&&&&&&&&&&&&&&&&&&&&&&&&&mut {integer}`
| |
| types differ in mutability
|
= note: expected reference `&&&&&&&&&&&&&&&&&&&&&&&&&&&&mut {integer}`
found mutable reference `&mut _`
error[E0308]: mismatched types
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:50:14
|
LL | let &mut &mut &mut &mut _ = &mut &&&&mut &&&mut &mut 0;
| ^^^^^^^^^^^^^^^^ -------------------------- this expression has type `&mut &&&&mut &&&mut &mut {integer}`
| |
| types differ in mutability
|
= note: expected reference `&&&&mut &&&mut &mut {integer}`
found mutable reference `&mut _`
error[E0658]: binding cannot be both mutable and by-reference
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:55:13
|
LL | let Foo(mut a) = &Foo(0);
| ^^^^
|
= note: see issue #123076 <https://github.com/rust-lang/rust/issues/123076> for more information
= help: add `#![feature(mut_ref)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error[E0658]: binding cannot be both mutable and by-reference
--> $DIR/ref_pat_eat_one_layer_2024_fail.rs:59:13
|
LL | let Foo(mut a) = &mut Foo(0);
| ^^^^
|
= note: see issue #123076 <https://github.com/rust-lang/rust/issues/123076> for more information
= help: add `#![feature(mut_ref)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error: aborting due to 16 previous errors
Some errors have detailed explanations: E0308, E0658.
For more information about an error, try `rustc --explain E0308`.

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@ -1,12 +0,0 @@
#![allow(incomplete_features)]
#![feature(ref_pat_everywhere)]
pub fn main() {
if let Some(&x) = Some(0) {
//~^ ERROR: mismatched types [E0308]
let _: u32 = x;
}
if let Some(&mut x) = Some(&0) {
//~^ ERROR: mismatched types [E0308]
let _: u32 = x;
}
}

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@ -1,38 +0,0 @@
error[E0308]: mismatched types
--> $DIR/ref_pat_everywhere-fail.rs:4:17
|
LL | if let Some(&x) = Some(0) {
| ^^ ------- this expression has type `Option<{integer}>`
| |
| expected integer, found `&_`
|
= note: expected type `{integer}`
found reference `&_`
help: consider removing `&` from the pattern
|
LL | if let Some(x) = Some(0) {
| ~
error[E0308]: mismatched types
--> $DIR/ref_pat_everywhere-fail.rs:8:17
|
LL | if let Some(&mut x) = Some(&0) {
| ^^^^^^ -------- this expression has type `Option<&{integer}>`
| |
| types differ in mutability
|
= note: expected reference `&{integer}`
found mutable reference `&mut _`
note: to declare a mutable binding use: `mut x`
--> $DIR/ref_pat_everywhere-fail.rs:8:17
|
LL | if let Some(&mut x) = Some(&0) {
| ^^^^^^
help: consider removing `&mut` from the pattern
|
LL | if let Some(x) = Some(&0) {
| ~
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0308`.

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@ -1,24 +0,0 @@
//@ run-pass
#![allow(incomplete_features)]
#![feature(ref_pat_everywhere)]
pub fn main() {
if let Some(Some(&x)) = &Some(&Some(0)) {
let _: u32 = x;
}
if let Some(&Some(x)) = &Some(Some(0)) {
let _: u32 = x;
}
if let Some(Some(&mut x)) = &mut Some(&mut Some(0)) {
let _: u32 = x;
}
if let Some(Some(&x)) = &Some(&mut Some(0)) {
let _: u32 = x;
}
if let &Some(x) = &mut Some(0) {
let _: u32 = x;
}
if let Some(&x) = &mut Some(0) {
let _: u32 = x;
}
}

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@ -1,14 +0,0 @@
//@ edition: 2024
//@ compile-flags: -Zunstable-options
struct Foo(u8);
fn main() {
let Foo(mut a) = &Foo(0);
a = &42;
//~^ ERROR: mismatched types
let Foo(mut a) = &mut Foo(0);
a = &mut 42;
//~^ ERROR: mismatched types
}

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@ -1,31 +0,0 @@
error[E0308]: mismatched types
--> $DIR/feature-gate-mut_preserve_binding_mode_2024.rs:8:9
|
LL | let Foo(mut a) = &Foo(0);
| ----- expected due to the type of this binding
LL | a = &42;
| ^^^ expected `u8`, found `&{integer}`
|
help: consider removing the borrow
|
LL - a = &42;
LL + a = 42;
|
error[E0308]: mismatched types
--> $DIR/feature-gate-mut_preserve_binding_mode_2024.rs:12:9
|
LL | let Foo(mut a) = &mut Foo(0);
| ----- expected due to the type of this binding
LL | a = &mut 42;
| ^^^^^^^ expected `u8`, found `&mut {integer}`
|
help: consider removing the borrow
|
LL - a = &mut 42;
LL + a = 42;
|
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0308`.

View File

@ -2,7 +2,7 @@
//@ run-rustfix
//@ rustfix-only-machine-applicable
//@ aux-build:match_ergonomics_2024_macros.rs
#![feature(mut_preserve_binding_mode_2024, ref_pat_eat_one_layer_2024)]
#![feature(mut_ref, ref_pat_eat_one_layer_2024)]
#![allow(incomplete_features, unused)]
#![deny(rust_2024_incompatible_pat)]

View File

@ -2,7 +2,7 @@
//@ run-rustfix
//@ rustfix-only-machine-applicable
//@ aux-build:match_ergonomics_2024_macros.rs
#![feature(mut_preserve_binding_mode_2024, ref_pat_eat_one_layer_2024)]
#![feature(mut_ref, ref_pat_eat_one_layer_2024)]
#![allow(incomplete_features, unused)]
#![deny(rust_2024_incompatible_pat)]

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@ -1,6 +1,6 @@
//@ edition: 2021
//@ compile-flags: -Zunstable-options
#![feature(mut_preserve_binding_mode_2024)]
#![feature(ref_pat_eat_one_layer_2024)]
#![allow(incomplete_features)]
struct Foo(u8);

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@ -1,7 +1,7 @@
//@ run-pass
//@ edition: 2024
//@ compile-flags: -Zunstable-options
#![feature(mut_preserve_binding_mode_2024)]
#![feature(mut_ref, ref_pat_eat_one_layer_2024)]
#![allow(incomplete_features, unused)]
struct Foo(u8);

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@ -0,0 +1,9 @@
//@ edition: 2021
//@ run-pass
#![allow(incomplete_features)]
#![feature(ref_pat_eat_one_layer_2024)]
fn main() {
let &[[x]] = &[&mut [42]];
let _: &i32 = x;
}