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Rollup merge of rust-lang#139035 - nnethercote:PatKind-Missing, r=oli-obk
Add new `PatKind::Missing` variants To avoid some ugly uses of `kw::Empty` when handling "missing" patterns, e.g. in bare fn tys. Helps with rust-lang#137978. Details in the individual commits. r? `@oli-obk`
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‎compiler/rustc_ast/src/ast.rs

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -563,6 +563,7 @@ impl Pat {
563563
/// This is intended for use by diagnostics.
564564
pub fn to_ty(&self) -> Option<P<Ty>> {
565565
let kind = match &self.kind {
566+
PatKind::Missing => unreachable!(),
566567
// In a type expression `_` is an inference variable.
567568
PatKind::Wild => TyKind::Infer,
568569
// An IDENT pattern with no binding mode would be valid as path to a type. E.g. `u32`.
@@ -625,7 +626,8 @@ impl Pat {
625626
| PatKind::Guard(s, _) => s.walk(it),
626627

627628
// These patterns do not contain subpatterns, skip.
628-
PatKind::Wild
629+
PatKind::Missing
630+
| PatKind::Wild
629631
| PatKind::Rest
630632
| PatKind::Never
631633
| PatKind::Expr(_)
@@ -676,6 +678,7 @@ impl Pat {
676678
/// Return a name suitable for diagnostics.
677679
pub fn descr(&self) -> Option<String> {
678680
match &self.kind {
681+
PatKind::Missing => unreachable!(),
679682
PatKind::Wild => Some("_".to_string()),
680683
PatKind::Ident(BindingMode::NONE, ident, None) => Some(format!("{ident}")),
681684
PatKind::Ref(pat, mutbl) => pat.descr().map(|d| format!("&{}{d}", mutbl.prefix_str())),
@@ -769,6 +772,9 @@ pub enum RangeSyntax {
769772
// Adding a new variant? Please update `test_pat` in `tests/ui/macros/stringify.rs`.
770773
#[derive(Clone, Encodable, Decodable, Debug)]
771774
pub enum PatKind {
775+
/// A missing pattern, e.g. for an anonymous param in a bare fn like `fn f(u32)`.
776+
Missing,
777+
772778
/// Represents a wildcard pattern (`_`).
773779
Wild,
774780

‎compiler/rustc_ast/src/mut_visit.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1587,7 +1587,7 @@ pub fn walk_pat<T: MutVisitor>(vis: &mut T, pat: &mut P<Pat>) {
15871587
vis.visit_id(id);
15881588
match kind {
15891589
PatKind::Err(_guar) => {}
1590-
PatKind::Wild | PatKind::Rest | PatKind::Never => {}
1590+
PatKind::Missing | PatKind::Wild | PatKind::Rest | PatKind::Never => {}
15911591
PatKind::Ident(_binding_mode, ident, sub) => {
15921592
vis.visit_ident(ident);
15931593
visit_opt(sub, |sub| vis.visit_pat(sub));

‎compiler/rustc_ast/src/visit.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -750,7 +750,7 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) -> V::Res
750750
try_visit!(visitor.visit_pat(subpattern));
751751
try_visit!(visitor.visit_expr(guard_condition));
752752
}
753-
PatKind::Wild | PatKind::Rest | PatKind::Never => {}
753+
PatKind::Missing | PatKind::Wild | PatKind::Rest | PatKind::Never => {}
754754
PatKind::Err(_guar) => {}
755755
PatKind::Tuple(elems) | PatKind::Slice(elems) | PatKind::Or(elems) => {
756756
walk_list!(visitor, visit_pat, elems);

‎compiler/rustc_ast_lowering/src/lib.rs

Lines changed: 3 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -1496,18 +1496,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
14961496

14971497
fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> &'hir [Option<Ident>] {
14981498
self.arena.alloc_from_iter(decl.inputs.iter().map(|param| match param.pat.kind {
1499-
PatKind::Ident(_, ident, _) => {
1500-
if ident.name != kw::Empty {
1501-
Some(self.lower_ident(ident))
1502-
} else {
1503-
None
1504-
}
1505-
}
1499+
PatKind::Missing => None,
1500+
PatKind::Ident(_, ident, _) => Some(self.lower_ident(ident)),
15061501
PatKind::Wild => Some(Ident::new(kw::Underscore, self.lower_span(param.pat.span))),
15071502
_ => {
15081503
self.dcx().span_delayed_bug(
15091504
param.pat.span,
1510-
"non-ident/wild param pat must trigger an error",
1505+
"non-missing/ident/wild param pat must trigger an error",
15111506
);
15121507
None
15131508
}

‎compiler/rustc_ast_lowering/src/pat.rs

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -26,6 +26,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
2626
let pat_hir_id = self.lower_node_id(pattern.id);
2727
let node = loop {
2828
match &pattern.kind {
29+
PatKind::Missing => break hir::PatKind::Missing,
2930
PatKind::Wild => break hir::PatKind::Wild,
3031
PatKind::Never => break hir::PatKind::Never,
3132
PatKind::Ident(binding_mode, ident, sub) => {

‎compiler/rustc_ast_passes/src/ast_validation.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -244,7 +244,7 @@ impl<'a> AstValidator<'a> {
244244
fn check_decl_no_pat(decl: &FnDecl, mut report_err: impl FnMut(Span, Option<Ident>, bool)) {
245245
for Param { pat, .. } in &decl.inputs {
246246
match pat.kind {
247-
PatKind::Ident(BindingMode::NONE, _, None) | PatKind::Wild => {}
247+
PatKind::Missing | PatKind::Ident(BindingMode::NONE, _, None) | PatKind::Wild => {}
248248
PatKind::Ident(BindingMode::MUT, ident, None) => {
249249
report_err(pat.span, Some(ident), true)
250250
}

‎compiler/rustc_ast_pretty/src/pprust/state.rs

Lines changed: 3 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -1622,9 +1622,9 @@ impl<'a> State<'a> {
16221622
fn print_pat(&mut self, pat: &ast::Pat) {
16231623
self.maybe_print_comment(pat.span.lo());
16241624
self.ann.pre(self, AnnNode::Pat(pat));
1625-
/* Pat isn't normalized, but the beauty of it
1626-
is that it doesn't matter */
1625+
/* Pat isn't normalized, but the beauty of it is that it doesn't matter */
16271626
match &pat.kind {
1627+
PatKind::Missing => unreachable!(),
16281628
PatKind::Wild => self.word("_"),
16291629
PatKind::Never => self.word("!"),
16301630
PatKind::Ident(BindingMode(by_ref, mutbl), ident, sub) => {
@@ -1946,12 +1946,7 @@ impl<'a> State<'a> {
19461946
if let Some(eself) = input.to_self() {
19471947
self.print_explicit_self(&eself);
19481948
} else {
1949-
let invalid = if let PatKind::Ident(_, ident, _) = input.pat.kind {
1950-
ident.name == kw::Empty
1951-
} else {
1952-
false
1953-
};
1954-
if !invalid {
1949+
if !matches!(input.pat.kind, PatKind::Missing) {
19551950
self.print_pat(&input.pat);
19561951
self.word(":");
19571952
self.space();

‎compiler/rustc_hir/src/hir.rs

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1555,6 +1555,7 @@ impl<'hir> Pat<'hir> {
15551555

15561556
use PatKind::*;
15571557
match self.kind {
1558+
Missing => unreachable!(),
15581559
Wild | Never | Expr(_) | Range(..) | Binding(.., None) | Err(_) => true,
15591560
Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) | Guard(s, _) => s.walk_short_(it),
15601561
Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
@@ -1582,7 +1583,7 @@ impl<'hir> Pat<'hir> {
15821583

15831584
use PatKind::*;
15841585
match self.kind {
1585-
Wild | Never | Expr(_) | Range(..) | Binding(.., None) | Err(_) => {}
1586+
Missing | Wild | Never | Expr(_) | Range(..) | Binding(.., None) | Err(_) => {}
15861587
Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) | Guard(s, _) => s.walk_(it),
15871588
Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
15881589
TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
@@ -1720,6 +1721,9 @@ pub enum TyPatKind<'hir> {
17201721

17211722
#[derive(Debug, Clone, Copy, HashStable_Generic)]
17221723
pub enum PatKind<'hir> {
1724+
/// A missing pattern, e.g. for an anonymous param in a bare fn like `fn f(u32)`.
1725+
Missing,
1726+
17231727
/// Represents a wildcard pattern (i.e., `_`).
17241728
Wild,
17251729

‎compiler/rustc_hir/src/intravisit.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -744,7 +744,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) -> V:
744744
visit_opt!(visitor, visit_pat_expr, lower_bound);
745745
visit_opt!(visitor, visit_pat_expr, upper_bound);
746746
}
747-
PatKind::Never | PatKind::Wild | PatKind::Err(_) => (),
747+
PatKind::Missing | PatKind::Never | PatKind::Wild | PatKind::Err(_) => (),
748748
PatKind::Slice(prepatterns, ref slice_pattern, postpatterns) => {
749749
walk_list!(visitor, visit_pat, prepatterns);
750750
visit_opt!(visitor, visit_pat, slice_pattern);

‎compiler/rustc_hir_analysis/src/check/region.rs

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -623,6 +623,7 @@ fn resolve_local<'tcx>(
623623

624624
PatKind::Ref(_, _)
625625
| PatKind::Binding(hir::BindingMode(hir::ByRef::No, _), ..)
626+
| PatKind::Missing
626627
| PatKind::Wild
627628
| PatKind::Never
628629
| PatKind::Expr(_)

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