Normalize raw pointers

[samueltardieu]

Consider raw pointers fields as normalizable.

This is only used to determine the layout, and the layout of a raw pointer is known, whatever the designated type is. As a side effect, this makes the layout of Box<T> known, even inside T, and enables recursive types.

Would there be a drawback in doing this?

I have included the new tests in a separate commit, so that the effect of the change can be seen in the second commit. It can also be seen on the lintcheck diff result.

Close #9798.

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changelog: none

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[llogiq]

Thank you!

[Jarcho]

This is only used to determine the layout, and the layout of a raw pointer is known, whatever the designated type is.

This is wrong. The size of both references and raw pointers depend on whether the pointee is Sized.

[samueltardieu]

This is only used to determine the layout, and the layout of a raw pointer is known, whatever the designated type is.
This is wrong. The size of both references and raw pointers depend on whether the pointee is Sized.

This is what I meant by "known" instead of "constant", because I thought that at this stage the sizedness of the pointee type would be known. I will try to double-check this.

[Jarcho]

The sizedness of pointee types is the reason layout_of caused ICEs in the first place. For most cases it returns an error, but for pointers and references it sometimes caused a delayed bug to be issued.

[samueltardieu]

@llogiq I haven't checked, but it probably fails because of the missing changelog entry. Anyhow, I don't know if we should merge it right now given @Jarcho's comments. I'll set the PR to draft, even if I couldn't notice crashes in lintchecks for example, I'll have to double-check that this cannot happen.

[y21]

For reference (maybe this helps), a concrete repro that starts ICE-ing with this change (taken from #12550 which also intends to fix the same issue)

#![warn(clippy::zero_sized_map_values)]

trait Foo { type Foo; }

struct Bar<T: Foo>(T::Foo);

type Bad<T> = std::collections::HashMap<u32, *const Bar<T>>;

fn main() {}

[samueltardieu]

Thanks @y21 that will be useful