Avoid panic from deserialized Uniform<char> where range == 0

[dhardy]

• Added a CHANGELOG.md entry

Summary

Fixes #1827. Closes #1829.

Details

Fixes the internal method UniformInt::max which previously ignored the special cases range == 0 and where low + range overflows.

[Copilot]

Pull request overview

This PR aims to prevent panics when sampling a Uniform<char> that has been deserialized from (potentially attacker-controlled) serde data, by tightening the internal maximum-value logic used by the UniformChar deserialization guard.

Changes:

• Update UniformInt::max to treat range == 0 (full-range marker) as having a maximum of $ty::MAX.
• Refactor and extend the Uniform<char> bad-deserialization test to cover the range == 0, low = 5 payload.
• Add a changelog entry documenting the fix.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/distr/uniform_other.rs	Refactors Uniform<char> serde failure test helper and adds coverage for an additional failing payload.
src/distr/uniform_int.rs	Adjusts UniformInt::max behavior when range == 0.
CHANGELOG.md	Documents the intended panic-avoidance fix.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

Suppressed comments (1)

Previously missed (1) — in code that hasn't changed since the last review.

src/distr/uniform_other.rs:324

• In builds with --no-default-features --features serde (i.e. without the alloc feature), the col parameter is unused because it’s only referenced inside #[cfg(feature = "alloc")], which can trigger an unused_variables warning in this test.

        fn do_test(json: &str, col: usize) {
            let result = serde_json::from_str::<Uniform<char>>(json);
            assert!(result.is_err());
            let err = result.unwrap_err();
            assert_eq!(err.classify(), serde_json::error::Category::Data);

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.