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Filter out lookup_can_derive_copy for template type #2764

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Filter out lookup_can_derive_copy for template type #2764

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20 changes: 20 additions & 0 deletions bindgen/ir/context.rs
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Expand Up @@ -2767,6 +2767,7 @@ If you encounter an error missing from this list, please file an issue or a PR!"
let id = id.into();

!self.lookup_has_type_param_in_array(id) &&
!self.lookup_is_type_param_after_resolve(id) &&
!self.cannot_derive_copy.as_ref().unwrap().contains(&id)
}

Expand Down Expand Up @@ -2796,6 +2797,25 @@ If you encounter an error missing from this list, please file an issue or a PR!"
.contains(&id.into())
}

/// Look up whether the item with `id` is type parameter after resolve.
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This needs a test, but it seems to me this should happen in the can_derive_copy analysis.

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I will add test to verify regression.

As for can_derive_copy analysis, it makes sense to me as this can be analyzed before actual codegen. But it's not clear to me how. I skimmed over CannotDerive.constrain_type() and it's a bit hard where the code required.

image

This is graph from the problematic code. What I was trying is to make Item(2)(_Tp) CanDerive::No. From my undesrtanding, the basis is TypeParam which Union refers need to be CanDevice::No. But I saw it's bit hard because it's back edge from TypeParam.

Am I correctly understanding basic strategy? If then, how can I make _Tp CanDevice::No?

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@emilio Gentle reminder.

fn lookup_is_type_param_after_resolve<Id: Into<ItemId>>(
&self,
id: Id,
) -> bool {
if let Some(t) = id
.into()
.into_resolver()
.through_type_refs()
.resolve(self)
.kind()
.as_type()
{
t.is_type_param()
} else {
false
}
}

/// Compute whether the type has float.
fn compute_has_float(&mut self) {
let _t = self.timer("compute_has_float");
Expand Down