Higher-ranked trait bounds for where clauses #6921
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crates/hir_def/src/generics.rs
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| bound: LifetimeRef, | ||
| }, | ||
| ForLifetime { | ||
| lifetimes: Box<[LifetimeRef]>, |
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these should just be Names, I think; they're not references to existing lifetimes, but defining new ones
crates/hir_def/src/generics.rs
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| .map_or_else(Name::missing, |lt| Name::new_lifetime(<)); | ||
| let param = LifetimeParamData { name: name.clone() }; | ||
| // FIXME: allocating the lifetime here means it looks like this lifetime belongs to the entire item | ||
| // but it only belongs to the bounded type-param |
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Yeah, I'm not sure giving these lifetimes a LifetimeParamId at all is the correct approach, since they're not parameters of the item. (There's another place where new lifetime names can be defined, namely for<'x> fn() function pointer types, and I think these two should work the same.)
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Also, while shadowing an existing lifetime is disallowed, you can easily have the same lifetime twice on an item this way:
fn foo<T, U>() where for<'b> U: 'b, for<'b> T: 'b {}There was a problem hiding this comment.
Well the main reason for giving them LifetimeParamIds is that for reference search we need to be able to address them as code_model::LifetimeParams, which is backed by a LifetimeParamId. And technically they are LifetimeParams right? Just with a smaller scope. Though I can't really think of a way to solve this problem, so I guess it's better to just not support reference search for these for the time being.
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Yeah, I don't really know how to model this yet either, and I think supporting reference search for these is probably not super important right now.
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Yea I agree, will remove those parts for now then. 👍
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r? @flodiebold |
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bors r+ |
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There is a slight problem with this which is also noted in a FIXME now but
LifetimeParametersof these ForLifetime where clauses allocate the lifetimes in the corresponding arena as if they were lifetimes of the item itself and not just the clause they belong to. I wasn't entirely sure what I could do about this but given nothing really uses lifetimes like that currently I figured it might be fine? Open to suggestions for that problem.