Check whether the closure's owner is an ADT in thir-unsafeck

[FabianWolff]

This pull request fixes #85871. The code in rustc_mir_build/src/check_unsafety.rs incorrectly assumes that a closure's owner always has a body, but only functions, closures, and constants have bodies, whereas a closure can also appear inside a struct or enum:

struct S {
    arr: [(); match || 1 { _ => 42 }]
}

enum E {
    A([(); { || 1; 42 }])
}

This pull request fixes the resulting ICE by checking whether the closure's owner is an ADT and only deferring to thir_check_unsafety(owner) if it isn't.

[rust-highfive]

r? @petrochenkov

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[petrochenkov]

r? @nikomatsakis

[nikomatsakis]

I'm not sure if this is adequate. For example, what about type Foo = [...; || ...];?

We probably want to identify the cases where we should check the owner instead and enumerate those.

[FabianWolff]

You are right, .is_adt() is not comprehensive enough (although it is not a regression from the current behavior either).

I have used .maybe_body_owned_by(...).is_some() now, which should be more robust, and expanded the test case; could you have another look?

[nikomatsakis]

The concept of body owner is a bit confusing, but this does seem right. Nice.

[nikomatsakis]

@bors r+

[bors]

📌 Commit 433c1ae has been approved by nikomatsakis

[bors]

⌛ Testing commit 433c1ae with merge f1e691d...

[bors]

☀️ Test successful - checks-actions
Approved by: nikomatsakis
Pushing f1e691d to master...