Rollup merge of rust-lang#102273 - woppopo:relax_const_bound, r=fee1-dead

Allow `~const` bounds on non-const functions Makes the behavior of bound of trait-associated functions and non-associated functions consistent.

Author: matthiaskrgr

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -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();
  }
  }
@@ -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));
  }

src/test/ui/rfc-2632-const-trait-impl/tilde-const-and-const-params.rs

@@ -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);
+}

src/test/ui/rfc-2632-const-trait-impl/tilde-const-invalid-places.rs

@@ -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
 

src/test/ui/rfc-2632-const-trait-impl/tilde-const-invalid-places.stderr

@@ -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