Fix overflowing length in Vec<ZST> to VecDeque #83244
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`Vec` can hold up to `usize::MAX` ZST items, but `VecDeque` has a lower
limit to keep its raw capacity as a power of two, so we should check
that in `From<Vec<T>> for VecDeque<T>`. We can also simplify the
capacity check for the remaining non-ZST case.
Before this fix, the new test would fail on the length:
```
thread 'collections::vec_deque::tests::test_from_vec_zst_overflow' panicked at 'assertion failed: `(left == right)`
left: `0`,
right: `9223372036854775808`', library/alloc/src/collections/vec_deque/tests.rs:474:5
note: panic did not contain expected string
panic message: `"assertion failed: `(left == right)`\n left: `0`,\n right: `9223372036854775808`"`,
expected substring: `"capacity overflow"`
```
That was a result of `len()` using a mask `& (size - 1)` with the
improper length. Now we do get a "capacity overflow" panic as soon as
that `VecDeque::from(vec)` is attempted.
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Rollup of 8 pull requests Successful merges: - rust-lang#79986 (Only build help popup when it's really needed) - rust-lang#82570 (Add `as_str` method for split whitespace str iterators) - rust-lang#83244 (Fix overflowing length in Vec<ZST> to VecDeque) - rust-lang#83254 (Include output stream in `panic!()` documentation) - rust-lang#83269 (Revert the second deprecation of collections::Bound) - rust-lang#83277 (Mark early otherwise optimization unsound) - rust-lang#83285 (Update LLVM to bring in SIMD updates for WebAssembly) - rust-lang#83297 (Do not ICE on ty::Error as an error must already have been reported) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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Veccan hold up tousize::MAXZST items, butVecDequehas a lowerlimit to keep its raw capacity as a power of two, so we should check
that in
From<Vec<T>> for VecDeque<T>. We can also simplify thecapacity check for the remaining non-ZST case.
Before this fix, the new test would fail on the length:
That was a result of
len()using a mask& (size - 1)with theimproper length. Now we do get a "capacity overflow" panic as soon as
that
VecDeque::from(vec)is attempted.Fixes #80167.