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Allow ~const bounds on non-const functions
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lilasta committed Sep 26, 2022
1 parent 17e8752 commit e4b08ab
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Showing 4 changed files with 43 additions and 32 deletions.
7 changes: 3 additions & 4 deletions compiler/rustc_ast_passes/src/ast_validation.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1415,7 +1415,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
if !self.is_tilde_const_allowed {
self.err_handler()
.struct_span_err(bound.span(), "`~const` is not allowed here")
.note("only allowed on bounds on traits' associated types and functions, const fns, const impls and its associated functions")
.note("only allowed on bounds on functions, traits' associated types and functions, const impls and its associated functions")
.emit();
}
}
Expand Down Expand Up @@ -1523,9 +1523,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
});
}

let tilde_const_allowed =
matches!(fk.header(), Some(FnHeader { constness: Const::Yes(_), .. }))
|| matches!(fk.ctxt(), Some(FnCtxt::Assoc(_)));
let tilde_const_allowed = matches!(fk.header(), Some(FnHeader { .. }))
|| matches!(fk.ctxt(), Some(FnCtxt::Assoc(_)));

self.with_tilde_const(tilde_const_allowed, |this| visit::walk_fn(this, fk));
}
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Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
// check-pass
#![feature(const_trait_impl)]
#![feature(generic_arg_infer)]
#![feature(generic_const_exprs)]
#![allow(incomplete_features)]

struct Foo<const N: usize>;

impl<const N: usize> Foo<N> {
fn add<A: ~const Add42>(self) -> Foo<{ A::add(N) }> {
Foo
}
}

#[const_trait]
trait Add42 {
fn add(a: usize) -> usize;
}

impl const Add42 for () {
fn add(a: usize) -> usize {
a + 42
}
}

fn bar<A: ~const Add42, const N: usize>(_: Foo<N>) -> Foo<{ A::add(N) }> {
Foo
}

fn main() {
let foo = Foo::<0>;
let foo = bar::<(), _>(foo);
let _foo = bar::<(), _>(foo);
}
Original file line number Diff line number Diff line change
Expand Up @@ -17,12 +17,6 @@ fn rpit_assoc_bound() -> impl IntoIterator<Item: ~const T> { Some(S) }
fn apit_assoc_bound(_: impl IntoIterator<Item: ~const T>) {}
//~^ ERROR `~const` is not allowed

fn generic<P: ~const T>() {}
//~^ ERROR `~const` is not allowed

fn where_clause<P>() where P: ~const T {}
//~^ ERROR `~const` is not allowed

struct TildeQuestion<T: ~const ?Sized>(std::marker::PhantomData<T>);
//~^ ERROR `~const` and `?` are mutually exclusive

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Original file line number Diff line number Diff line change
Expand Up @@ -4,53 +4,37 @@ error: `~const` is not allowed here
LL | fn rpit() -> impl ~const T { S }
| ^^^^^^^^
|
= note: only allowed on bounds on traits' associated types and functions, const fns, const impls and its associated functions
= note: only allowed on bounds on functions, traits' associated types and functions, const impls and its associated functions

error: `~const` is not allowed here
--> $DIR/tilde-const-invalid-places.rs:11:17
|
LL | fn apit(_: impl ~const T) {}
| ^^^^^^^^
|
= note: only allowed on bounds on traits' associated types and functions, const fns, const impls and its associated functions
= note: only allowed on bounds on functions, traits' associated types and functions, const impls and its associated functions

error: `~const` is not allowed here
--> $DIR/tilde-const-invalid-places.rs:14:50
|
LL | fn rpit_assoc_bound() -> impl IntoIterator<Item: ~const T> { Some(S) }
| ^^^^^^^^
|
= note: only allowed on bounds on traits' associated types and functions, const fns, const impls and its associated functions
= note: only allowed on bounds on functions, traits' associated types and functions, const impls and its associated functions

error: `~const` is not allowed here
--> $DIR/tilde-const-invalid-places.rs:17:48
|
LL | fn apit_assoc_bound(_: impl IntoIterator<Item: ~const T>) {}
| ^^^^^^^^
|
= note: only allowed on bounds on traits' associated types and functions, const fns, const impls and its associated functions

error: `~const` is not allowed here
--> $DIR/tilde-const-invalid-places.rs:20:15
|
LL | fn generic<P: ~const T>() {}
| ^^^^^^^^
|
= note: only allowed on bounds on traits' associated types and functions, const fns, const impls and its associated functions

error: `~const` is not allowed here
--> $DIR/tilde-const-invalid-places.rs:23:31
|
LL | fn where_clause<P>() where P: ~const T {}
| ^^^^^^^^
|
= note: only allowed on bounds on traits' associated types and functions, const fns, const impls and its associated functions
= note: only allowed on bounds on functions, traits' associated types and functions, const impls and its associated functions

error: `~const` and `?` are mutually exclusive
--> $DIR/tilde-const-invalid-places.rs:26:25
--> $DIR/tilde-const-invalid-places.rs:20:25
|
LL | struct TildeQuestion<T: ~const ?Sized>(std::marker::PhantomData<T>);
| ^^^^^^^^^^^^^

error: aborting due to 7 previous errors
error: aborting due to 5 previous errors

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