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Implement macro-based deref_pat!() syntax for deref patterns
Stop using `box PAT` syntax for deref patterns, as it's misleading and also causes their semantics being tangled up.
1 parent 1345c72 commit 7d50e10

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25 files changed

+107
-25
lines changed

25 files changed

+107
-25
lines changed

‎compiler/rustc_ast/src/ast.rs

+6-1
Original file line numberDiff line numberDiff line change
@@ -621,7 +621,9 @@ impl Pat {
621621
| PatKind::Or(s) => s.iter().for_each(|p| p.walk(it)),
622622

623623
// Trivial wrappers over inner patterns.
624-
PatKind::Box(s) | PatKind::Ref(s, _) | PatKind::Paren(s) => s.walk(it),
624+
PatKind::Box(s) | PatKind::Deref(s) | PatKind::Ref(s, _) | PatKind::Paren(s) => {
625+
s.walk(it)
626+
}
625627

626628
// These patterns do not contain subpatterns, skip.
627629
PatKind::Wild
@@ -792,6 +794,9 @@ pub enum PatKind {
792794
/// A `box` pattern.
793795
Box(P<Pat>),
794796

797+
/// A `deref` pattern (currently `deref_pat!()` macro-based syntax).
798+
Deref(P<Pat>),
799+
795800
/// A reference pattern (e.g., `&mut (a, b)`).
796801
Ref(P<Pat>, Mutability),
797802

‎compiler/rustc_ast/src/mut_visit.rs

+1
Original file line numberDiff line numberDiff line change
@@ -1295,6 +1295,7 @@ pub fn noop_visit_pat<T: MutVisitor>(pat: &mut P<Pat>, vis: &mut T) {
12951295
fields.flat_map_in_place(|field| vis.flat_map_pat_field(field));
12961296
}
12971297
PatKind::Box(inner) => vis.visit_pat(inner),
1298+
PatKind::Deref(inner) => vis.visit_pat(inner),
12981299
PatKind::Ref(inner, _mutbl) => vis.visit_pat(inner),
12991300
PatKind::Range(e1, e2, Spanned { span: _, node: _ }) => {
13001301
visit_opt(e1, |e| vis.visit_expr(e));

‎compiler/rustc_ast/src/visit.rs

+4-1
Original file line numberDiff line numberDiff line change
@@ -576,7 +576,10 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) -> V::Res
576576
try_visit!(visitor.visit_path(path, pattern.id));
577577
walk_list!(visitor, visit_pat_field, fields);
578578
}
579-
PatKind::Box(subpattern) | PatKind::Ref(subpattern, _) | PatKind::Paren(subpattern) => {
579+
PatKind::Box(subpattern)
580+
| PatKind::Deref(subpattern)
581+
| PatKind::Ref(subpattern, _)
582+
| PatKind::Paren(subpattern) => {
580583
try_visit!(visitor.visit_pat(subpattern));
581584
}
582585
PatKind::Ident(_, ident, optional_subpattern) => {

‎compiler/rustc_ast_lowering/src/pat.rs

+3
Original file line numberDiff line numberDiff line change
@@ -91,6 +91,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
9191
PatKind::Box(inner) => {
9292
break hir::PatKind::Box(self.lower_pat(inner));
9393
}
94+
PatKind::Deref(inner) => {
95+
break hir::PatKind::Deref(self.lower_pat(inner));
96+
}
9497
PatKind::Ref(inner, mutbl) => {
9598
break hir::PatKind::Ref(self.lower_pat(inner), *mutbl);
9699
}

‎compiler/rustc_ast_passes/src/feature_gate.rs

+2-8
Original file line numberDiff line numberDiff line change
@@ -413,10 +413,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
413413
}
414414
}
415415
PatKind::Box(..) => {
416-
if !self.features.deref_patterns {
417-
// Allow box patterns under `deref_patterns`.
418-
gate!(&self, box_patterns, pattern.span, "box pattern syntax is experimental");
419-
}
416+
gate!(&self, box_patterns, pattern.span, "box pattern syntax is experimental");
420417
}
421418
PatKind::Range(_, Some(_), Spanned { node: RangeEnd::Excluded, .. }) => {
422419
gate!(
@@ -610,10 +607,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
610607
};
611608
}
612609

613-
if !visitor.features.deref_patterns {
614-
// Allow box patterns under `deref_patterns`.
615-
gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental");
616-
}
610+
gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental");
617611
gate_all_legacy_dont_use!(trait_alias, "trait aliases are experimental");
618612
// Despite being a new feature, `where T: Trait<Assoc(): Sized>`, which is RTN syntax now,
619613
// used to be gated under associated_type_bounds, which are right above, so RTN needs to

‎compiler/rustc_ast_pretty/src/pprust/state.rs

+6
Original file line numberDiff line numberDiff line change
@@ -1626,6 +1626,12 @@ impl<'a> State<'a> {
16261626
self.word("box ");
16271627
self.print_pat(inner);
16281628
}
1629+
PatKind::Deref(inner) => {
1630+
self.word("deref_pat!");
1631+
self.popen();
1632+
self.print_pat(inner);
1633+
self.pclose();
1634+
}
16291635
PatKind::Ref(inner, mutbl) => {
16301636
self.word("&");
16311637
if mutbl.is_mut() {

‎compiler/rustc_builtin_macros/src/deref_pat.rs

+23
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
1+
use rustc_ast as ast;
2+
use rustc_ast::tokenstream::TokenStream;
3+
use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
4+
use rustc_parse::parser::{CommaRecoveryMode, RecoverColon, RecoverComma};
5+
use rustc_span::Span;
6+
7+
pub fn expand_deref_pat(
8+
cx: &mut ExtCtxt<'_>,
9+
span: Span,
10+
tts: TokenStream,
11+
) -> MacroExpanderResult<'static> {
12+
ExpandResult::Ready(
13+
match cx.new_parser_from_tts(tts).parse_pat_allow_top_alt(
14+
None,
15+
RecoverComma::Yes,
16+
RecoverColon::Yes,
17+
CommaRecoveryMode::LikelyTuple,
18+
) {
19+
Ok(parsed) => MacEager::pat(cx.pat(span, ast::PatKind::Deref(parsed))),
20+
Err(err) => DummyResult::any(span, err.emit()),
21+
},
22+
)
23+
}

‎compiler/rustc_builtin_macros/src/lib.rs

+2
Original file line numberDiff line numberDiff line change
@@ -37,6 +37,7 @@ mod compile_error;
3737
mod concat;
3838
mod concat_bytes;
3939
mod concat_idents;
40+
mod deref_pat;
4041
mod derive;
4142
mod deriving;
4243
mod edition_panic;
@@ -84,6 +85,7 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
8485
concat_idents: concat_idents::expand_concat_idents,
8586
const_format_args: format::expand_format_args,
8687
core_panic: edition_panic::expand_panic,
88+
deref_pat: deref_pat::expand_deref_pat,
8789
env: env::expand_env,
8890
file: source_util::expand_file,
8991
format_args: format::expand_format_args,

‎compiler/rustc_hir/src/hir.rs

+5-2
Original file line numberDiff line numberDiff line change
@@ -1003,7 +1003,7 @@ impl<'hir> Pat<'hir> {
10031003
use PatKind::*;
10041004
match self.kind {
10051005
Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => true,
1006-
Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
1006+
Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
10071007
Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
10081008
TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
10091009
Slice(before, slice, after) => {
@@ -1030,7 +1030,7 @@ impl<'hir> Pat<'hir> {
10301030
use PatKind::*;
10311031
match self.kind {
10321032
Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => {}
1033-
Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
1033+
Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
10341034
Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
10351035
TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
10361036
Slice(before, slice, after) => {
@@ -1173,6 +1173,9 @@ pub enum PatKind<'hir> {
11731173
/// A `box` pattern.
11741174
Box(&'hir Pat<'hir>),
11751175

1176+
/// A `deref` pattern (currently `deref_pat!()` macro-based syntax).
1177+
Deref(&'hir Pat<'hir>),
1178+
11761179
/// A reference pattern (e.g., `&mut (a, b)`).
11771180
Ref(&'hir Pat<'hir>, Mutability),
11781181

‎compiler/rustc_hir/src/intravisit.rs

+3-1
Original file line numberDiff line numberDiff line change
@@ -660,7 +660,9 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) -> V:
660660
PatKind::Tuple(tuple_elements, _) => {
661661
walk_list!(visitor, visit_pat, tuple_elements);
662662
}
663-
PatKind::Box(ref subpattern) | PatKind::Ref(ref subpattern, _) => {
663+
PatKind::Box(ref subpattern)
664+
| PatKind::Deref(ref subpattern)
665+
| PatKind::Ref(ref subpattern, _) => {
664666
try_visit!(visitor.visit_pat(subpattern));
665667
}
666668
PatKind::Binding(_, _hir_id, ident, ref optional_subpattern) => {

‎compiler/rustc_hir_analysis/src/check/region.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -668,7 +668,7 @@ fn resolve_local<'tcx>(
668668
| PatKind::TupleStruct(_, subpats, _)
669669
| PatKind::Tuple(subpats, _) => subpats.iter().any(|p| is_binding_pat(p)),
670670

671-
PatKind::Box(subpat) => is_binding_pat(subpat),
671+
PatKind::Box(subpat) | PatKind::Deref(subpat) => is_binding_pat(subpat),
672672

673673
PatKind::Ref(_, _)
674674
| PatKind::Binding(hir::BindingAnnotation(hir::ByRef::No, _), ..)

‎compiler/rustc_hir_pretty/src/lib.rs

+6
Original file line numberDiff line numberDiff line change
@@ -1808,6 +1808,12 @@ impl<'a> State<'a> {
18081808
self.pclose();
18091809
}
18101810
}
1811+
PatKind::Deref(inner) => {
1812+
self.word("deref_pat!");
1813+
self.popen();
1814+
self.print_pat(inner);
1815+
self.pclose();
1816+
}
18111817
PatKind::Ref(inner, mutbl) => {
18121818
let is_range_inner = matches!(inner.kind, PatKind::Range(..));
18131819
self.word("&");

‎compiler/rustc_hir_typeck/src/expr_use_visitor.rs

+1
Original file line numberDiff line numberDiff line change
@@ -463,6 +463,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
463463
}
464464
PatKind::Or(_)
465465
| PatKind::Box(_)
466+
| PatKind::Deref(_)
466467
| PatKind::Ref(..)
467468
| PatKind::Wild
468469
| PatKind::Err(_) => {

‎compiler/rustc_hir_typeck/src/mem_categorization.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -719,7 +719,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
719719
self.cat_pattern_(place_with_id, subpat, op)?;
720720
}
721721

722-
PatKind::Box(subpat) | PatKind::Ref(subpat, _) => {
722+
PatKind::Box(subpat) | PatKind::Ref(subpat, _) | PatKind::Deref(subpat) => {
723723
// box p1, &p1, &mut p1. we can ignore the mutability of
724724
// PatKind::Ref since that information is already contained
725725
// in the type.

‎compiler/rustc_hir_typeck/src/pat.rs

+3-3
Original file line numberDiff line numberDiff line change
@@ -210,10 +210,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
210210
PatKind::Tuple(elements, ddpos) => {
211211
self.check_pat_tuple(pat.span, elements, ddpos, expected, pat_info)
212212
}
213-
PatKind::Box(inner) if self.tcx.features().deref_patterns => {
214-
self.check_pat_deref(pat.span, inner, expected, pat_info)
215-
}
216213
PatKind::Box(inner) => self.check_pat_box(pat.span, inner, expected, pat_info),
214+
PatKind::Deref(inner) => self.check_pat_deref(pat.span, inner, expected, pat_info),
217215
PatKind::Ref(inner, mutbl) => self.check_pat_ref(pat, inner, mutbl, expected, pat_info),
218216
PatKind::Slice(before, slice, after) => {
219217
self.check_pat_slice(pat.span, before, slice, after, expected, pat_info)
@@ -297,6 +295,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
297295
| PatKind::TupleStruct(..)
298296
| PatKind::Tuple(..)
299297
| PatKind::Box(_)
298+
| PatKind::Deref(_)
300299
| PatKind::Range(..)
301300
| PatKind::Slice(..) => AdjustMode::Peel,
302301
// A never pattern behaves somewhat like a literal or unit variant.
@@ -762,6 +761,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
762761
| PatKind::Binding(..)
763762
| PatKind::Path(..)
764763
| PatKind::Box(..)
764+
| PatKind::Deref(_)
765765
| PatKind::Ref(..)
766766
| PatKind::Lit(..)
767767
| PatKind::Range(..)

‎compiler/rustc_lint/src/unused.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -1181,7 +1181,7 @@ impl EarlyLintPass for UnusedParens {
11811181
self.check_unused_parens_pat(cx, &f.pat, false, false, keep_space);
11821182
},
11831183
// Avoid linting on `i @ (p0 | .. | pn)` and `box (p0 | .. | pn)`, #64106.
1184-
Ident(.., Some(p)) | Box(p) => self.check_unused_parens_pat(cx, p, true, false, keep_space),
1184+
Ident(.., Some(p)) | Box(p) | Deref(p) => self.check_unused_parens_pat(cx, p, true, false, keep_space),
11851185
// Avoid linting on `&(mut x)` as `&mut x` has a different meaning, #55342.
11861186
// Also avoid linting on `& mut? (p0 | .. | pn)`, #64106.
11871187
Ref(p, m) => self.check_unused_parens_pat(cx, p, true, *m == Mutability::Not, keep_space),

‎compiler/rustc_middle/src/thir.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -1179,7 +1179,7 @@ impl<'tcx> fmt::Display for Pat<'tcx> {
11791179
write!(f, "{subpattern}")
11801180
}
11811181
PatKind::DerefPattern { ref subpattern } => {
1182-
write!(f, "k#deref {subpattern}")
1182+
write!(f, "deref_pat!({subpattern})")
11831183
}
11841184
PatKind::Constant { value } => write!(f, "{value}"),
11851185
PatKind::InlineConstant { def: _, ref subpattern } => {

‎compiler/rustc_mir_build/src/thir/pattern/mod.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -257,7 +257,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
257257
return self.lower_path(qpath, pat.hir_id, pat.span);
258258
}
259259

260-
hir::PatKind::Box(subpattern) if self.tcx.features().deref_patterns => {
260+
hir::PatKind::Deref(subpattern) => {
261261
PatKind::DerefPattern { subpattern: self.lower_pattern(subpattern) }
262262
}
263263
hir::PatKind::Ref(subpattern, _) | hir::PatKind::Box(subpattern) => {

‎compiler/rustc_passes/src/hir_stats.rs

+2
Original file line numberDiff line numberDiff line change
@@ -300,6 +300,7 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
300300
Path,
301301
Tuple,
302302
Box,
303+
Deref,
303304
Ref,
304305
Lit,
305306
Range,
@@ -566,6 +567,7 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
566567
Path,
567568
Tuple,
568569
Box,
570+
Deref,
569571
Ref,
570572
Lit,
571573
Range,

‎compiler/rustc_pattern_analysis/src/rustc.rs

+1
Original file line numberDiff line numberDiff line change
@@ -465,6 +465,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
465465
PatKind::DerefPattern { .. } => {
466466
// FIXME(deref_patterns): At least detect that `box _` is irrefutable.
467467
fields = vec![];
468+
arity = 0;
468469
ctor = Opaque(OpaqueId::new());
469470
}
470471
PatKind::Leaf { subpatterns } | PatKind::Variant { subpatterns, .. } => {

‎compiler/rustc_span/src/symbol.rs

+1
Original file line numberDiff line numberDiff line change
@@ -674,6 +674,7 @@ symbols! {
674674
deref_method,
675675
deref_mut,
676676
deref_mut_method,
677+
deref_pat,
677678
deref_patterns,
678679
deref_target,
679680
derive,

‎library/core/src/macros/mod.rs

+12
Original file line numberDiff line numberDiff line change
@@ -1714,6 +1714,18 @@ pub(crate) mod builtin {
17141714
/* compiler built-in */
17151715
}
17161716

1717+
#[cfg(not(bootstrap))]
1718+
/// Unstable placeholder for type ascription.
1719+
#[rustc_builtin_macro]
1720+
#[unstable(
1721+
feature = "deref_patterns",
1722+
issue = "87121",
1723+
reason = "placeholder syntax for deref patterns"
1724+
)]
1725+
pub macro deref_pat($pat:pat) {
1726+
/* compiler built-in */
1727+
}
1728+
17171729
/// Unstable implementation detail of the `rustc` compiler, do not use.
17181730
#[rustc_builtin_macro]
17191731
#[stable(feature = "rust1", since = "1.0.0")]

‎library/core/src/prelude/v1.rs

+8
Original file line numberDiff line numberDiff line change
@@ -103,3 +103,11 @@ pub use crate::macros::builtin::cfg_eval;
103103
reason = "placeholder syntax for type ascription"
104104
)]
105105
pub use crate::macros::builtin::type_ascribe;
106+
107+
#[cfg(not(bootstrap))]
108+
#[unstable(
109+
feature = "deref_patterns",
110+
issue = "87121",
111+
reason = "placeholder syntax for deref patterns"
112+
)]
113+
pub use crate::macros::builtin::deref_pat;

‎library/std/src/prelude/v1.rs

+9
Original file line numberDiff line numberDiff line change
@@ -91,6 +91,15 @@ pub use core::prelude::v1::cfg_eval;
9191
)]
9292
pub use core::prelude::v1::type_ascribe;
9393

94+
#[cfg(not(bootstrap))]
95+
// Do not `doc(no_inline)` either.
96+
#[unstable(
97+
feature = "deref_patterns",
98+
issue = "87121",
99+
reason = "placeholder syntax for deref patterns"
100+
)]
101+
pub use core::prelude::v1::deref_pat;
102+
94103
// The file so far is equivalent to core/src/prelude/v1.rs. It is duplicated
95104
// rather than glob imported because we want docs to show these re-exports as
96105
// pointing to within `std`.

‎tests/ui/pattern/deref-patterns/typeck.rs

+4-4
Original file line numberDiff line numberDiff line change
@@ -7,19 +7,19 @@ use std::rc::Rc;
77
fn main() {
88
let vec: Vec<u32> = Vec::new();
99
match vec {
10-
box [..] => {}
10+
deref_pat!([..]) => {}
1111
_ => {}
1212
}
1313
match Box::new(true) {
14-
box true => {}
14+
deref_pat!(true) => {}
1515
_ => {}
1616
}
1717
match &Box::new(true) {
18-
box true => {}
18+
deref_pat!(true) => {}
1919
_ => {}
2020
}
2121
match &Rc::new(0) {
22-
box (1..) => {}
22+
deref_pat!(1..) => {}
2323
_ => {}
2424
}
2525
// FIXME(deref_patterns): fails to typecheck because `"foo"` has type &str but deref creates a

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