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Add never_patterns feature gate

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This commit is contained in:
Nadrieril 2023-11-22 02:30:43 +01:00
parent 1bcbb7c93b
commit a3838c8550
40 changed files with 325 additions and 18 deletions
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4
compiler/rustc_ast/src/ast.rs
View file

@ -645,6 +645,7 @@ impl Pat {
// These patterns do not contain subpatterns, skip.
PatKind::Wild
| PatKind::Rest
| PatKind::Never
| PatKind::Lit(_)
| PatKind::Range(..)
| PatKind::Ident(..)
@ -795,6 +796,9 @@ pub enum PatKind {
/// only one rest pattern may occur in the pattern sequences.
Rest,
// A never pattern `!`
Never,
/// Parentheses in patterns used for grouping (i.e., `(PAT)`).
Paren(P<Pat>),

2
compiler/rustc_ast/src/mut_visit.rs
View file

@ -1249,7 +1249,7 @@ pub fn noop_visit_pat<T: MutVisitor>(pat: &mut P<Pat>, vis: &mut T) {
let Pat { id, kind, span, tokens } = pat.deref_mut();
vis.visit_id(id);
match kind {
PatKind::Wild | PatKind::Rest => {}
PatKind::Wild | PatKind::Rest | PatKind::Never => {}
PatKind::Ident(_binding_mode, ident, sub) => {
vis.visit_ident(ident);
visit_opt(sub, |sub| vis.visit_pat(sub));

2
compiler/rustc_ast/src/visit.rs
View file

@ -559,7 +559,7 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
walk_list!(visitor, visit_expr, lower_bound);
walk_list!(visitor, visit_expr, upper_bound);
}
PatKind::Wild | PatKind::Rest => {}
PatKind::Wild | PatKind::Rest | PatKind::Never => {}
PatKind::Tuple(elems) | PatKind::Slice(elems) | PatKind::Or(elems) => {
walk_list!(visitor, visit_pat, elems);
}

1
compiler/rustc_ast_lowering/src/pat.rs
View file

@ -24,6 +24,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let node = loop {
match &pattern.kind {
PatKind::Wild => break hir::PatKind::Wild,
PatKind::Never => break hir::PatKind::Never,
PatKind::Ident(binding_mode, ident, sub) => {
let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(s));
break self.lower_pat_ident(pattern, *binding_mode, *ident, lower_sub);

1
compiler/rustc_ast_passes/src/feature_gate.rs
View file

@ -555,6 +555,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
gate_all!(explicit_tail_calls, "`become` expression is experimental");
gate_all!(generic_const_items, "generic const items are experimental");
gate_all!(unnamed_fields, "unnamed fields are not yet fully implemented");
gate_all!(never_patterns, "`!` patterns are experimental");
if !visitor.features.negative_bounds {
for &span in spans.get(&sym::negative_bounds).iter().copied().flatten() {

1
compiler/rustc_ast_pretty/src/pprust/state.rs
View file

@ -1343,6 +1343,7 @@ impl<'a> State<'a> {
is that it doesn't matter */
match &pat.kind {
PatKind::Wild => self.word("_"),
PatKind::Never => self.word("!"),
PatKind::Ident(BindingAnnotation(by_ref, mutbl), ident, sub) => {
if *by_ref == ByRef::Yes {
self.word_nbsp("ref");

4
compiler/rustc_feature/src/unstable.rs
View file

@ -147,7 +147,7 @@ macro_rules! declare_features {
// was set.
//
// Note that the features are grouped into internal/user-facing and then
// sorted by version inside those groups. This is enforced with tidy.
// sorted alphabetically inside those groups. This is enforced with tidy.
//
// N.B., `tools/tidy/src/features.rs` parses this information directly out of the
// source, so take care when modifying it.
@ -512,6 +512,8 @@ declare_features! (
(unstable, native_link_modifiers_as_needed, "1.53.0", Some(81490), None),
/// Allow negative trait implementations.
(unstable, negative_impls, "1.44.0", Some(68318), None),
/// Allows the `!` pattern.
(incomplete, never_patterns, "CURRENT_RUSTC_VERSION", Some(118155), None),
/// Allows the `!` type. Does not imply 'exhaustive_patterns' (below) any more.
(unstable, never_type, "1.13.0", Some(35121), None),
/// Allows diverging expressions to fall back to `!` rather than `()`.

7
compiler/rustc_hir/src/hir.rs
View file

@ -1002,7 +1002,7 @@ impl<'hir> Pat<'hir> {
use PatKind::*;
match self.kind {
Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => true,
Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) => true,
Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
@ -1029,7 +1029,7 @@ impl<'hir> Pat<'hir> {
use PatKind::*;
match self.kind {
Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => {}
Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) => {}
Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
@ -1142,6 +1142,9 @@ pub enum PatKind<'hir> {
/// Invariant: `pats.len() >= 2`.
Or(&'hir [Pat<'hir>]),
/// A never pattern `!`.
Never,
/// A path pattern for a unit struct/variant or a (maybe-associated) constant.
Path(QPath<'hir>),

2
compiler/rustc_hir/src/intravisit.rs
View file

@ -660,7 +660,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) {
walk_list!(visitor, visit_expr, lower_bound);
walk_list!(visitor, visit_expr, upper_bound);
}
PatKind::Wild => (),
PatKind::Never | PatKind::Wild => (),
PatKind::Slice(prepatterns, ref slice_pattern, postpatterns) => {
walk_list!(visitor, visit_pat, prepatterns);
walk_list!(visitor, visit_pat, slice_pattern);

1
compiler/rustc_hir_analysis/src/check/region.rs
View file

@ -662,6 +662,7 @@ fn resolve_local<'tcx>(
PatKind::Ref(_, _)
| PatKind::Binding(hir::BindingAnnotation(hir::ByRef::No, _), ..)
| PatKind::Wild
| PatKind::Never
| PatKind::Path(_)
| PatKind::Lit(_)
| PatKind::Range(_, _, _) => false,

1
compiler/rustc_hir_pretty/src/lib.rs
View file

@ -1724,6 +1724,7 @@ impl<'a> State<'a> {
// is that it doesn't matter
match pat.kind {
PatKind::Wild => self.word("_"),
PatKind::Never => self.word("!"),
PatKind::Binding(BindingAnnotation(by_ref, mutbl), _, ident, sub) => {
if by_ref == ByRef::Yes {
self.word_nbsp("ref");

7
compiler/rustc_hir_typeck/src/expr_use_visitor.rs
View file

@ -401,12 +401,17 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
match &pat.kind {
PatKind::Binding(.., opt_sub_pat) => {
// If the opt_sub_pat is None, than the binding does not count as
// If the opt_sub_pat is None, then the binding does not count as
// a wildcard for the purpose of borrowing discr.
if opt_sub_pat.is_none() {
needs_to_be_read = true;
}
}
PatKind::Never => {
// A never pattern reads the value.
// FIXME(never_patterns): does this do what I expect?
needs_to_be_read = true;
}
PatKind::Path(qpath) => {
// A `Path` pattern is just a name like `Foo`. This is either a
// named constant or else it refers to an ADT variant

1
compiler/rustc_hir_typeck/src/mem_categorization.rs
View file

@ -766,6 +766,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
| PatKind::Binding(.., None)
| PatKind::Lit(..)
| PatKind::Range(..)
| PatKind::Never
| PatKind::Wild => {
// always ok
}

8
compiler/rustc_hir_typeck/src/pat.rs
View file

@ -178,6 +178,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let ty = match pat.kind {
PatKind::Wild => expected,
// FIXME(never_patterns): check the type is uninhabited. If that is not possible within
// typeck, do that in a later phase.
PatKind::Never => expected,
PatKind::Lit(lt) => self.check_pat_lit(pat.span, lt, expected, ti),
PatKind::Range(lhs, rhs, _) => self.check_pat_range(pat.span, lhs, rhs, expected, ti),
PatKind::Binding(ba, var_id, _, sub) => {
@ -287,9 +290,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
| PatKind::Box(_)
| PatKind::Range(..)
| PatKind::Slice(..) => AdjustMode::Peel,
// A never pattern behaves somewhat like a literal or unit variant.
PatKind::Never => AdjustMode::Peel,
// String and byte-string literals result in types `&str` and `&[u8]` respectively.
// All other literals result in non-reference types.
// As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo {}`.
// As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo" {}`.
//
// Call `resolve_vars_if_possible` here for inline const blocks.
PatKind::Lit(lt) => match self.resolve_vars_if_possible(self.check_expr(lt)).kind() {
@ -743,6 +748,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
| PatKind::Slice(..) => "binding",
PatKind::Wild
| PatKind::Never
| PatKind::Binding(..)
| PatKind::Path(..)
| PatKind::Box(..)

2
compiler/rustc_lint/src/unused.rs
View file

@ -1154,7 +1154,7 @@ impl EarlyLintPass for UnusedParens {
// Do not lint on `(..)` as that will result in the other arms being useless.
Paren(_)
// The other cases do not contain sub-patterns.
| Wild | Rest | Lit(..) | MacCall(..) | Range(..) | Ident(.., None) | Path(..) => {},
| Wild | Never | Rest | Lit(..) | MacCall(..) | Range(..) | Ident(.., None) | Path(..) => {},
// These are list-like patterns; parens can always be removed.
TupleStruct(_, _, ps) | Tuple(ps) | Slice(ps) | Or(ps) => for p in ps {
self.check_unused_parens_pat(cx, p, false, false, keep_space);

11
compiler/rustc_middle/src/thir.rs
View file

@ -635,7 +635,12 @@ impl<'tcx> Pat<'tcx> {
use PatKind::*;
match &self.kind {
Wild | Range(..) | Binding { subpattern: None, .. } | Constant { .. } | Error(_) => {}
Wild
| Never
| Range(..)
| Binding { subpattern: None, .. }
| Constant { .. }
| Error(_) => {}
AscribeUserType { subpattern, .. }
| Binding { subpattern: Some(subpattern), .. }
| Deref { subpattern }
@ -809,6 +814,9 @@ pub enum PatKind<'tcx> {
pats: Box<[Box<Pat<'tcx>>]>,
},
/// A never pattern `!`.
Never,
/// An error has been encountered during lowering. We probably shouldn't report more lints
/// related to this pattern.
Error(ErrorGuaranteed),
@ -1069,6 +1077,7 @@ impl<'tcx> fmt::Display for Pat<'tcx> {
match self.kind {
PatKind::Wild => write!(f, "_"),
PatKind::Never => write!(f, "!"),
PatKind::AscribeUserType { ref subpattern, .. } => write!(f, "{subpattern}: _"),
PatKind::Binding { mutability, name, mode, ref subpattern, .. } => {
let is_mut = match mode {

2
compiler/rustc_middle/src/thir/visit.rs
View file

@ -227,7 +227,7 @@ pub fn walk_pat<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, pat: &Pat<'
is_primary: _,
name: _,
} => visitor.visit_pat(subpattern),
Binding { .. } | Wild | Error(_) => {}
Binding { .. } | Wild | Never | Error(_) => {}
Variant { subpatterns, adt_def: _, args: _, variant_index: _ } | Leaf { subpatterns } => {
for subpattern in subpatterns {
visitor.visit_pat(&subpattern.pattern);

1
compiler/rustc_mir_build/src/build/matches/mod.rs
View file

@ -827,6 +827,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
PatKind::Constant { .. }
| PatKind::Range { .. }
| PatKind::Wild
| PatKind::Never
| PatKind::Error(_) => {}
PatKind::Deref { ref subpattern } => {

6
compiler/rustc_mir_build/src/build/matches/simplify.rs
View file

@ -194,6 +194,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
Ok(())
}
PatKind::Never => {
// A never pattern acts like a load from the place.
// FIXME(never_patterns): load from the place
Ok(())
}
PatKind::Constant { .. } => {
// FIXME normalize patterns when possible
Err(match_pair)

2
compiler/rustc_mir_build/src/build/matches/test.rs
View file

@ -75,6 +75,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
| PatKind::Array { .. }
| PatKind::Wild
| PatKind::Binding { .. }
| PatKind::Never
| PatKind::Leaf { .. }
| PatKind::Deref { .. }
| PatKind::Error(_) => self.error_simplifiable(match_pair),
@ -107,6 +108,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
PatKind::Slice { .. }
| PatKind::Array { .. }
| PatKind::Wild
| PatKind::Never
| PatKind::Or { .. }
| PatKind::Binding { .. }
| PatKind::AscribeUserType { .. }

3
compiler/rustc_mir_build/src/check_unsafety.rs
View file

@ -247,8 +247,9 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
self.requires_unsafe(pat.span, AccessToUnionField);
return; // we can return here since this already requires unsafe
}
// wildcard doesn't take anything
// wildcard/never don't take anything
PatKind::Wild |
PatKind::Never |
// these just wrap other patterns
PatKind::Or { .. } |
PatKind::InlineConstant { .. } |

6
compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
View file

@ -1557,6 +1557,12 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
let pats = expand_or_pat(pat);
fields = Fields::from_iter(cx, pats.into_iter().map(mkpat));
}
PatKind::Never => {
// FIXME(never_patterns): handle `!` in exhaustiveness. This is a sane default
// in the meantime.
ctor = Wildcard;
fields = Fields::empty();
}
PatKind::Error(_) => {
ctor = Opaque(OpaqueId::new());
fields = Fields::empty();

2
compiler/rustc_mir_build/src/thir/pattern/mod.rs
View file

@ -251,6 +251,8 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
let kind = match pat.kind {
hir::PatKind::Wild => PatKind::Wild,
hir::PatKind::Never => PatKind::Never,
hir::PatKind::Lit(value) => self.lower_lit(value),
hir::PatKind::Range(ref lo_expr, ref hi_expr, end) => {

3
compiler/rustc_mir_build/src/thir/print.rs
View file

@ -636,6 +636,9 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
PatKind::Wild => {
print_indented!(self, "Wild", depth_lvl + 1);
}
PatKind::Never => {
print_indented!(self, "Never", depth_lvl + 1);
}
PatKind::AscribeUserType { ascription, subpattern } => {
print_indented!(self, "AscribeUserType: {", depth_lvl + 1);
print_indented!(self, format!("ascription: {:?}", ascription), depth_lvl + 2);

6
compiler/rustc_parse/src/parser/pat.rs
View file

@ -368,8 +368,12 @@ impl<'a> Parser<'a> {
self.recover_dotdotdot_rest_pat(lo)
} else if let Some(form) = self.parse_range_end() {
self.parse_pat_range_to(form)? // `..=X`, `...X`, or `..X`.
} else if self.eat(&token::Not) {
// Parse `!`
self.sess.gated_spans.gate(sym::never_patterns, self.prev_token.span);
PatKind::Never
} else if self.eat_keyword(kw::Underscore) {
// Parse _
// Parse `_`
PatKind::Wild
} else if self.eat_keyword(kw::Mut) {
self.parse_pat_ident_mut(syntax_loc)?

17
compiler/rustc_passes/src/hir_stats.rs
View file

@ -286,7 +286,21 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
fn visit_pat(&mut self, p: &'v hir::Pat<'v>) {
record_variants!(
(self, p, p.kind, Id::Node(p.hir_id), hir, Pat, PatKind),
[Wild, Binding, Struct, TupleStruct, Or, Path, Tuple, Box, Ref, Lit, Range, Slice]
[
Wild,
Binding,
Struct,
TupleStruct,
Or,
Never,
Path,
Tuple,
Box,
Ref,
Lit,
Range,
Slice
]
);
hir_visit::walk_pat(self, p)
}
@ -554,6 +568,7 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
Range,
Slice,
Rest,
Never,
Paren,
MacCall
]

1
compiler/rustc_span/src/symbol.rs
View file

@ -1097,6 +1097,7 @@ symbols! {
negative_impls,
neon,
never,
never_patterns,
never_type,
never_type_fallback,
new,

3
src/librustdoc/clean/utils.rs
View file

@ -303,7 +303,8 @@ pub(crate) fn name_from_pat(p: &hir::Pat<'_>) -> Symbol {
debug!("trying to get a name from pattern: {p:?}");
Symbol::intern(&match p.kind {
PatKind::Wild | PatKind::Struct(..) => return kw::Underscore,
// FIXME(never_patterns): does this make sense?
PatKind::Wild | PatKind::Never | PatKind::Struct(..) => return kw::Underscore,
PatKind::Binding(_, _, ident, _) => return ident.name,
PatKind::TupleStruct(ref p, ..) | PatKind::Path(ref p) => qpath_to_string(p),
PatKind::Or(pats) => {

2
src/tools/clippy/clippy_lints/src/equatable_if_let.rs
View file

@ -46,7 +46,7 @@ fn unary_pattern(pat: &Pat<'_>) -> bool {
pats.iter().all(unary_pattern)
}
match &pat.kind {
PatKind::Slice(_, _, _) | PatKind::Range(_, _, _) | PatKind::Binding(..) | PatKind::Wild | PatKind::Or(_) => {
PatKind::Slice(_, _, _) | PatKind::Range(_, _, _) | PatKind::Binding(..) | PatKind::Wild | PatKind::Never | PatKind::Or(_) => {
false
},
PatKind::Struct(_, a, etc) => !etc && a.iter().all(|x| unary_pattern(x.pat)),

3
src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs
View file

@ -150,6 +150,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
#[derive(Clone, Copy)]
enum NormalizedPat<'a> {
Wild,
Never,
Struct(Option<DefId>, &'a [(Symbol, Self)]),
Tuple(Option<DefId>, &'a [Self]),
Or(&'a [Self]),
@ -229,6 +230,7 @@ impl<'a> NormalizedPat<'a> {
PatKind::Binding(.., Some(pat)) | PatKind::Box(pat) | PatKind::Ref(pat, _) => {
Self::from_pat(cx, arena, pat)
},
PatKind::Never => Self::Never,
PatKind::Struct(ref path, fields, _) => {
let fields =
arena.alloc_from_iter(fields.iter().map(|f| (f.ident.name, Self::from_pat(cx, arena, f.pat))));
@ -333,6 +335,7 @@ impl<'a> NormalizedPat<'a> {
fn has_overlapping_values(&self, other: &Self) -> bool {
match (*self, *other) {
(Self::Wild, _) | (_, Self::Wild) => true,
(Self::Never, Self::Never) => true,
(Self::Or(pats), ref other) | (ref other, Self::Or(pats)) => {
pats.iter().any(|pat| pat.has_overlapping_values(other))
},

2
src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs
View file

@ -226,7 +226,7 @@ fn transform_with_focus_on_idx(alternatives: &mut ThinVec<P<Pat>>, focus_idx: us
// Therefore they are not some form of constructor `C`,
// with which a pattern `C(p_0)` may be formed,
// which we would want to join with other `C(p_j)`s.
Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_)
Ident(.., None) | Lit(_) | Wild | Never | Path(..) | Range(..) | Rest | MacCall(_)
// Skip immutable refs, as grouping them saves few characters,
// and almost always requires adding parens (increasing noisiness).
// In the case of only two patterns, replacement adds net characters.

1
src/tools/clippy/clippy_lints/src/utils/author.rs
View file

@ -629,6 +629,7 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
match pat.value.kind {
PatKind::Wild => kind!("Wild"),
PatKind::Never => kind!("Never"),
PatKind::Binding(ann, _, name, sub) => {
bind!(self, name);
opt_bind!(self, sub);

1
src/tools/clippy/clippy_utils/src/hir_utils.rs
View file

@ -1017,6 +1017,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
}
e.hash(&mut self.s);
},
PatKind::Never => {},
PatKind::Wild => {},
}
}

1
src/tools/clippy/clippy_utils/src/lib.rs
View file

@ -1707,6 +1707,7 @@ pub fn is_refutable(cx: &LateContext<'_>, pat: &Pat<'_>) -> bool {
match pat.kind {
PatKind::Wild => false,
PatKind::Never => false, // If `!` typechecked then the type is empty, so not refutable.
PatKind::Binding(_, _, _, pat) => pat.map_or(false, |pat| is_refutable(cx, pat)),
PatKind::Box(pat) | PatKind::Ref(pat, _) => is_refutable(cx, pat),
PatKind::Lit(..) | PatKind::Range(..) => true,

5
src/tools/rustfmt/src/patterns.rs
View file

@ -40,7 +40,9 @@ pub(crate) fn is_short_pattern(pat: &ast::Pat, pat_str: &str) -> bool {
fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
match pat.kind {
ast::PatKind::Rest | ast::PatKind::Wild | ast::PatKind::Lit(_) => true,
ast::PatKind::Rest | ast::PatKind::Never | ast::PatKind::Wild | ast::PatKind::Lit(_) => {
true
}
ast::PatKind::Ident(_, _, ref pat) => pat.is_none(),
ast::PatKind::Struct(..)
| ast::PatKind::MacCall(..)
@ -193,6 +195,7 @@ impl Rewrite for Pat {
None
}
}
PatKind::Never => None,
PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
let infix = match end_kind.node {
RangeEnd::Included(RangeSyntax::DotDotDot) => "...",

27
tests/ui/feature-gates/feature-gate-never_patterns.rs Normal file
View file

@ -0,0 +1,27 @@
// Check that never patterns require the feature gate.
use std::ptr::NonNull;
enum Void {}
fn main() {
let res: Result<u32, Void> = Ok(0);
let (Ok(_x) | Err(&!)) = res.as_ref();
//~^ ERROR `!` patterns are experimental
//~| ERROR: is not bound in all patterns
unsafe {
let ptr: *const Void = NonNull::dangling().as_ptr();
match *ptr {
! => {} //~ ERROR `!` patterns are experimental
}
}
// Check that the gate operates even behind `cfg`.
#[cfg(FALSE)]
unsafe {
let ptr: *const Void = NonNull::dangling().as_ptr();
match *ptr {
! => {} //~ ERROR `!` patterns are experimental
}
}
}

39
tests/ui/feature-gates/feature-gate-never_patterns.stderr Normal file
View file

@ -0,0 +1,39 @@
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/feature-gate-never_patterns.rs:8:19
|
LL | let (Ok(_x) | Err(&!)) = res.as_ref();
| -- ^^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
error[E0658]: `!` patterns are experimental
--> $DIR/feature-gate-never_patterns.rs:8:24
|
LL | let (Ok(_x) | Err(&!)) = res.as_ref();
| ^
|
= note: see issue #118155 <https://github.com/rust-lang/rust/issues/118155> for more information
= help: add `#![feature(never_patterns)]` to the crate attributes to enable
error[E0658]: `!` patterns are experimental
--> $DIR/feature-gate-never_patterns.rs:15:13
|
LL | ! => {}
| ^
|
= note: see issue #118155 <https://github.com/rust-lang/rust/issues/118155> for more information
= help: add `#![feature(never_patterns)]` to the crate attributes to enable
error[E0658]: `!` patterns are experimental
--> $DIR/feature-gate-never_patterns.rs:24:13
|
LL | ! => {}
| ^
|
= note: see issue #118155 <https://github.com/rust-lang/rust/issues/118155> for more information
= help: add `#![feature(never_patterns)]` to the crate attributes to enable
error: aborting due to 4 previous errors
Some errors have detailed explanations: E0408, E0658.
For more information about an error, try `rustc --explain E0408`.

5
tests/ui/macros/stringify.rs
View file

@ -11,6 +11,7 @@
#![feature(decl_macro)]
#![feature(explicit_tail_calls)]
#![feature(more_qualified_paths)]
#![feature(never_patterns)]
#![feature(raw_ref_op)]
#![feature(trait_alias)]
#![feature(try_blocks)]
@ -635,6 +636,10 @@ fn test_pat() {
// PatKind::Rest
c1!(pat, [ .. ], "..");
// PatKind::Never
c1!(pat, [ Some(!) ], "Some(!)");
c1!(pat, [ None | Some(!) ], "None | Some(!)");
// PatKind::Paren
c1!(pat, [ (pat) ], "(pat)");

99
tests/ui/pattern/never_patterns.rs Normal file
View file

@ -0,0 +1,99 @@
#![feature(never_patterns)]
#![allow(incomplete_features)]
enum Void {}
fn main() {}
// The classic use for empty types.
fn safe_unwrap_result<T>(res: Result<T, Void>) {
let Ok(_x) = res;
// FIXME(never_patterns): These should be allowed
let (Ok(_x) | Err(!)) = &res;
//~^ ERROR: is not bound in all patterns
let (Ok(_x) | Err(&!)) = res.as_ref();
//~^ ERROR: is not bound in all patterns
}
// Check we only accept `!` where we want to.
fn never_pattern_location(void: Void) {
// FIXME(never_patterns): Don't accept on a non-empty type.
match Some(0) {
None => {}
Some(!) => {}
}
// FIXME(never_patterns): Don't accept on an arbitrary type, even if there are no more branches.
match () {
() => {}
! => {}
}
// FIXME(never_patterns): Don't accept even on an empty branch.
match None::<Void> {
None => {}
! => {}
}
// FIXME(never_patterns): Let alone if the emptiness is behind a reference.
match None::<&Void> {
None => {}
! => {}
}
// Participate in match ergonomics.
match &void {
! => {}
}
match &&void {
! => {}
}
match &&void {
&! => {}
}
match &None::<Void> {
None => {}
Some(!) => {}
}
match None::<&Void> {
None => {}
Some(!) => {}
}
// Accept on a composite empty type.
match None::<&(u32, Void)> {
None => {}
Some(&!) => {}
}
// Accept on an simple empty type.
match None::<Void> {
None => {}
Some(!) => {}
}
match None::<&Void> {
None => {}
Some(&!) => {}
}
match None::<&(u32, Void)> {
None => {}
Some(&(_, !)) => {}
}
}
fn never_and_bindings() {
let x: Result<bool, &(u32, Void)> = Ok(false);
// FIXME(never_patterns): Never patterns in or-patterns don't need to share the same bindings.
match x {
Ok(_x) | Err(&!) => {}
//~^ ERROR: is not bound in all patterns
}
let (Ok(_x) | Err(&!)) = x;
//~^ ERROR: is not bound in all patterns
// FIXME(never_patterns): A never pattern mustn't have bindings.
match x {
Ok(_) => {}
Err(&(_b, !)) => {}
}
match x {
Ok(_a) | Err(&(_b, !)) => {}
//~^ ERROR: is not bound in all patterns
//~| ERROR: is not bound in all patterns
}
}

51
tests/ui/pattern/never_patterns.stderr Normal file
View file

@ -0,0 +1,51 @@
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/never_patterns.rs:12:19
|
LL | let (Ok(_x) | Err(!)) = &res;
| -- ^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/never_patterns.rs:14:19
|
LL | let (Ok(_x) | Err(&!)) = res.as_ref();
| -- ^^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/never_patterns.rs:83:18
|
LL | Ok(_x) | Err(&!) => {}
| -- ^^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
error[E0408]: variable `_x` is not bound in all patterns
--> $DIR/never_patterns.rs:86:19
|
LL | let (Ok(_x) | Err(&!)) = x;
| -- ^^^^^^^ pattern doesn't bind `_x`
| |
| variable not in all patterns
error[E0408]: variable `_b` is not bound in all patterns
--> $DIR/never_patterns.rs:95:9
|
LL | Ok(_a) | Err(&(_b, !)) => {}
| ^^^^^^ -- variable not in all patterns
| |
| pattern doesn't bind `_b`
error[E0408]: variable `_a` is not bound in all patterns
--> $DIR/never_patterns.rs:95:18
|
LL | Ok(_a) | Err(&(_b, !)) => {}
| -- ^^^^^^^^^^^^^ pattern doesn't bind `_a`
| |
| variable not in all patterns
error: aborting due to 6 previous errors
For more information about this error, try `rustc --explain E0408`.