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const forget tests #69645

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merged 3 commits into from
Mar 11, 2020
Merged

const forget tests #69645

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011fa91
const forget tests
DutchGhost Mar 2, 2020
5f4af54
An enter as last character pleases tidy it seems
DutchGhost Mar 2, 2020
a674e1c
remove unused mut, restructure the test
DutchGhost Mar 2, 2020
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1 change: 1 addition & 0 deletions src/libcore/tests/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@
#![feature(never_type)]
#![feature(unwrap_infallible)]
#![feature(leading_trailing_ones)]
#![feature(const_forget)]

extern crate test;

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18 changes: 18 additions & 0 deletions src/libcore/tests/mem.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -129,3 +129,21 @@ fn test_discriminant_send_sync() {
is_send_sync::<Discriminant<Regular>>();
is_send_sync::<Discriminant<NotSendSync>>();
}

#[test]
fn test_const_forget() {
const _: () = forget(0i32);
const _: () = forget(Vec::<Vec<Box<i32>>>::new());

// Writing this function signature without const-forget
// triggers compiler errors:
// 1) That we use a non-const fn inside a const fn
// 2) without the forget, it complains about the destructor of Box
const fn const_forget_box<T>(x: Box<T>) {
forget(x);
}

// Call the forget_box at runtime,
// as we can't const-construct a box yet.
const_forget_box(Box::new(0i32));
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@RalfJung RalfJung Mar 16, 2020 •
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This test fails in Miri due to a memory leak: it complains that there is a (run-time!) allocation that did not get freed, and that allocation is the Box being created here.

It almost looks like that is deliberate? Do we really want a leaking test in the test suite? Cc @oli-obk

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I don't entirely see the point of calling this function at run-time, as it tests nothing about CTFE. Sure, you can't test it at compile-time, but testing at run-time instead makes no sense, it just tests the entirely wrong thing. Am I missing something?

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Oh woops, I'm sory, I didn't thought of this failing miri. (Why did the CI still succeed, btw? no miri test?)
The runtime call was more like a 'Proof' it still works at runtime. It can be removed.

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Due to CI budget constraints, running Miri on the libcore test suite is a separate project. That's why CI here did not fail.

It can be removed.

I would prefer that. Can you submit a PR?

}