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Rollup merge of #136584 - oli-obk:pattern-types-generic, r=BoxyUwU

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Prevent generic pattern types from being used in libstd

Pattern types should follow the same rules that patterns follow. So a pattern type range must not wrap and not be empty. While we reject such invalid ranges at layout computation time, that only happens during monomorphization in the case of const generics. This is the exact same issue as other const generic math has, and since there's no solution there yet, I put these pattern types behind a separate incomplete feature.

These are not necessary for the pattern types MVP (replacing the layout range attributes in libcore and rustc).

cc #136574 (new tracking issue for the `generic_pattern_types` feature gate)

r? ``@lcnr``

cc ``@scottmcm`` ``@joshtriplett``
This commit is contained in:
Matthias Krüger 2025-02-11 02:53:44 +01:00 • committed by GitHub
commit c92aae90e4
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7 changed files with 101 additions and 11 deletions
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2
compiler/rustc_feature/src/unstable.rs
View file

@ -513,6 +513,8 @@ declare_features! (
(incomplete, generic_const_exprs, "1.56.0", Some(76560)),
/// Allows generic parameters and where-clauses on free & associated const items.
(incomplete, generic_const_items, "1.73.0", Some(113521)),
/// Allows any generic constants being used as pattern type range ends
(incomplete, generic_pattern_types, "CURRENT_RUSTC_VERSION", Some(136574)),
/// Allows registering static items globally, possibly across crates, to iterate over at runtime.
(unstable, global_registration, "1.80.0", Some(125119)),
/// Allows using guards in patterns.

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

@ -1026,6 +1026,7 @@ symbols! {
generic_const_exprs,
generic_const_items,
generic_param_attrs,
generic_pattern_types,
get_context,
global_alloc_ty,
global_allocator,

44
compiler/rustc_trait_selection/src/traits/wf.rs
View file

@ -8,8 +8,9 @@ use rustc_middle::ty::{
self, GenericArg, GenericArgKind, GenericArgsRef, Ty, TyCtxt, TypeSuperVisitable,
TypeVisitable, TypeVisitableExt, TypeVisitor,
};
use rustc_span::Span;
use rustc_session::parse::feature_err;
use rustc_span::def_id::{DefId, LocalDefId};
use rustc_span::{Span, sym};
use tracing::{debug, instrument, trace};
use crate::infer::InferCtxt;
@ -704,8 +705,47 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
));
}
ty::Pat(subty, _) => {
ty::Pat(subty, pat) => {
self.require_sized(subty, ObligationCauseCode::Misc);
match *pat {
ty::PatternKind::Range { start, end, include_end: _ } => {
let mut check = |c| {
let cause = self.cause(ObligationCauseCode::Misc);
self.out.push(traits::Obligation::with_depth(
tcx,
cause.clone(),
self.recursion_depth,
self.param_env,
ty::Binder::dummy(ty::PredicateKind::Clause(
ty::ClauseKind::ConstArgHasType(c, subty),
)),
));
if !tcx.features().generic_pattern_types() {
if c.has_param() {
if self.span.is_dummy() {
self.tcx().dcx().delayed_bug(
"feature error should be reported elsewhere, too",
);
} else {
feature_err(
&self.tcx().sess,
sym::generic_pattern_types,
self.span,
"wraparound pattern type ranges cause monomorphization time errors",
)
.emit();
}
}
}
};
if let Some(start) = start {
check(start)
}
if let Some(end) = end {
check(end)
}
}
}
}
ty::Tuple(tys) => {

49
tests/ui/type/pattern_types/assoc_const.default.stderr
View file

@ -1,3 +1,24 @@
error[E0658]: wraparound pattern type ranges cause monomorphization time errors
--> $DIR/assoc_const.rs:17:19
|
LL | fn foo<T: Foo>(_: pattern_type!(u32 is <T as Foo>::START..=<T as Foo>::END)) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #136574 <https://github.com/rust-lang/rust/issues/136574> for more information
= help: add `#![feature(generic_pattern_types)]` 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]: wraparound pattern type ranges cause monomorphization time errors
--> $DIR/assoc_const.rs:17:19
|
LL | fn foo<T: Foo>(_: pattern_type!(u32 is <T as Foo>::START..=<T as Foo>::END)) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #136574 <https://github.com/rust-lang/rust/issues/136574> for more information
= help: add `#![feature(generic_pattern_types)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
error: constant expression depends on a generic parameter
--> $DIR/assoc_const.rs:17:19
|
@ -15,8 +36,29 @@ LL | fn foo<T: Foo>(_: pattern_type!(u32 is <T as Foo>::START..=<T as Foo>::END)
= note: this may fail depending on what value the parameter takes
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
error[E0658]: wraparound pattern type ranges cause monomorphization time errors
--> $DIR/assoc_const.rs:22:19
|
LL | fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #136574 <https://github.com/rust-lang/rust/issues/136574> for more information
= help: add `#![feature(generic_pattern_types)]` 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]: wraparound pattern type ranges cause monomorphization time errors
--> $DIR/assoc_const.rs:22:19
|
LL | fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #136574 <https://github.com/rust-lang/rust/issues/136574> for more information
= help: add `#![feature(generic_pattern_types)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
error: constant expression depends on a generic parameter
--> $DIR/assoc_const.rs:20:19
--> $DIR/assoc_const.rs:22:19
|
LL | fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -24,7 +66,7 @@ LL | fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
= note: this may fail depending on what value the parameter takes
error: constant expression depends on a generic parameter
--> $DIR/assoc_const.rs:20:19
--> $DIR/assoc_const.rs:22:19
|
LL | fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -32,5 +74,6 @@ LL | fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
= note: this may fail depending on what value the parameter takes
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
error: aborting due to 4 previous errors
error: aborting due to 8 previous errors
For more information about this error, try `rustc --explain E0658`.

8
tests/ui/type/pattern_types/assoc_const.rs
View file

@ -1,8 +1,8 @@
#![feature(pattern_types)]
#![feature(pattern_type_macro)]
#![cfg_attr(const_arg, feature(generic_const_exprs))]
#![cfg_attr(const_arg, feature(generic_const_exprs, generic_pattern_types))]
#![expect(incomplete_features)]
// gate-test-generic_pattern_types line to the test file.
//@ revisions: default const_arg
//@[const_arg] check-pass
@ -17,8 +17,12 @@ trait Foo {
fn foo<T: Foo>(_: pattern_type!(u32 is <T as Foo>::START..=<T as Foo>::END)) {}
//[default]~^ ERROR: constant expression depends on a generic parameter
//[default]~| ERROR: constant expression depends on a generic parameter
//[default]~| ERROR: wraparound pattern type ranges cause monomorphization time errors
//[default]~| ERROR: wraparound pattern type ranges cause monomorphization time errors
fn bar<T: Foo>(_: pattern_type!(u32 is T::START..=T::END)) {}
//[default]~^ ERROR: constant expression depends on a generic parameter
//[default]~| ERROR: constant expression depends on a generic parameter
//[default]~| ERROR: wraparound pattern type ranges cause monomorphization time errors
//[default]~| ERROR: wraparound pattern type ranges cause monomorphization time errors
fn main() {}

4
tests/ui/type/pattern_types/const_generics.rs
View file

@ -1,7 +1,7 @@
//@ check-pass
#![feature(pattern_types)]
#![feature(pattern_type_macro)]
#![feature(pattern_types, generic_pattern_types, pattern_type_macro)]
#![expect(incomplete_features)]
use std::pat::pattern_type;

4
tests/ui/type/pattern_types/transmute.rs
View file

@ -1,5 +1,5 @@
#![feature(pattern_types)]
#![feature(pattern_type_macro)]
#![feature(pattern_types, pattern_type_macro, generic_pattern_types)]
#![expect(incomplete_features)]
use std::pat::pattern_type;