Add Challenge 25: VecDeque (#269)

This PR adds Challenge 25 for VecDeque

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under the terms of the Apache 2.0 and MIT licenses.

---------

Co-authored-by: Michael Tautschnig <[email protected]>

Author: thanhnguyen-aws

doc/src/SUMMARY.md

@@ -35,3 +35,4 @@
   - [20: Verify the safety of char-related functions in str::pattern](./challenges/0020-str-pattern-pt1.md)
   - [21: Verify the safety of substring-related functions in str::pattern](./challenges/0021-str-pattern-pt2.md)
   - [22: Verify the safety of str iter functions](./challenges/0022-str-iter.md)
+  - [25: Verify the safety of `VecDeque` functions](./challenges/0025-vecdeque.md)

doc/src/challenges/0025-vecdeque.md

@@ -0,0 +1,87 @@
+# Challenge 25: Verify the safety of `VecDeque` functions
+
+- **Status:** Open
+- **Tracking Issue:** [#286](https://github.com/model-checking/verify-rust-std/issues/286)
+- **Start date:** *2025-03-07*
+- **End date:** *2025-10-17*
+- **Reward:** *10000 USD*
+
+-------------------
+
+
+## Goal
+
+Verify the safety of `VecDeque` functions in (library/alloc/src/collections/vec_deque/mod.rs).
+
+
+### Success Criteria
+
+Verify the safety of the following functions in (library/alloc/src/collections/vec_deque/mod.rs):
+
+Write and prove the contract for the safety of the following unsafe functions:
+
+| Function |
+|---------|
+|push_unchecked|
+|buffer_read|
+|buffer_write|
+|buffer_range|
+|copy|
+|copy_nonoverlapping|
+|wrap_copy|
+|copy_slice|
+|write_iter|
+|write_iter_wrapping|
+|handle_capacity_increase|
+|from_contiguous_raw_parts_in|
+|abort_shrink|
+
+Prove the absence of undefined behavior for following safe abstractions:
+
+|get|
+|get_mut|
+|swap|
+|reserve_exact|
+|reserve|
+|try_reserve_exact|
+|try_reserve|
+|shrink_to|
+|truncate|
+|as_slices|
+|as_mut_slices|
+|range|
+|range_mut|
+|drain|
+|pop_front|
+|pop_back|
+|push_front|
+|push_back|
+|insert|
+|remove|
+|split_off|
+|append|
+|retain_mut|
+|grow|
+|resize_with|
+|make_contiguous|
+|rotate_left|
+|rotate_right|
+|rotate_left_inner|
+|rotate_right_inner|
+
+The verification must be unbounded---it must hold for slices of arbitrary length.
+
+The verification must hold for generic type `T` (no monomorphization).
+
+### List of UBs
+
+All proofs must automatically ensure the absence of the following undefined behaviors [ref](https://github.com/rust-lang/reference/blob/142b2ed77d33f37a9973772bd95e6144ed9dce43/src/behavior-considered-undefined.md):
+
+* Accessing (loading from or storing to) a place that is dangling or based on a misaligned pointer.
+* Reading from uninitialized memory except for padding or unions.
+* Mutating immutable bytes.
+* Producing an invalid value
+
+
+Note: All solutions to verification challenges need to satisfy the criteria established in the [challenge book](../general-rules.md)
+in addition to the ones listed above.