Opportunistically split != to successfully parse never type
#145536
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r? petrochenkov or reassign |
fmease
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Aug 17, 2025
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| #[cfg(false)] struct W<const X: ! = { loop {} }>; | ||
| #[cfg(false)] struct S<const X: != { loop {} }>; | ||
| } |
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Maybe add this, too:
#![feature(default_field_values)]
struct X<T> {
w: fn(T) -> ! = |_| loop {},
s: fn(T) -> != |_| loop {},
}Doesn't really matter tho.
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Yeah, let's add this one too.
fmease
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Aug 17, 2025
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| // Parse `!` | ||
| // Ideally we'd use `eat_bang` here to allow us to parse `!=>` as `! =>`. However, | ||
| // `break_and_eat` doesn't "reglue" the split-off `=` with any following `>` (since | ||
| // that would likely be super fragile and complex). |
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It will probably work if the support is added to break_two_token_op.
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Accept code like
let _: != loop {};orlet _: fn() -> != || loop {};(previously: syntax error). Similar to sth. like #51068.There's no inherent need to update
can_begin_typefrom what I can tell, since macro matcher$ty:ty =already accepts!=and since no other current direct/transitive callers would 'benefit' from doing that either, so I didn't do it. It's a conservative choice to avoid odd consequences (concrete example: it would widen the follow set of:visto include!=).