Add const and unsafe block suport to bsn! macro#24336
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| let braced = braced_tokens(input)?; | ||
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| BsnValue::Expr(quote! {#unsafe_token {#braced}}) | ||
| } else if input.peek(Token![async]) && input.peek2(Brace) { |
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Given the difficulties you noted with supporting async blocks, it may be better to leave this out until it's supported
You can't really make it work properly without limits.
The problem is that async futures produce unnamable types.
You'd have to box them but the `.into()` call we use doesn't
work for that.
```rust
fn what_we_do() -> Box<dyn Future<Output = ()>> {
{async {}}.into()
}
// This wouldn't be generic over the container though
fn what_we_need_to_do() -> Box<dyn Future<Output = ()>> {
Box::new({async {}})
}
```
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|
I've ripped out support for async blocks. More detailed reasoning is in the commit description but tl;dr there's just no way to type a struct field that would make it work. If somebody really needs it they can do |
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Objective
Closes #24121
Solution
Add
const,unsafeandasyncblock support to bsn expressions.Testing
I've added a compile test for
constandunsafeblocks. I couldn't figure out how to test or even use the async blocks. The macro needs to construct a struct that holds a future, butasyncblocks produce voldemort (unnameable) types. UsingBox<dyn Future>fixes this problem but then you run into the problem that the struct needs to be clone-able and have a default value.asyncblock futures have neither of those properties.Showcase
The
bsn!macro now supportsconstandunsafeblocks.