`unbounded-vec-growth`'s length-check detection is satisfied by any `.len()` call anywhere in the function

[unrealtim-tech]

Labels: bug, checks-crate
Crate: checks

Description
crates/checks/src/vec_growth.rs (lines ~69-89) sets has_len_check = true on any .len() method call found anywhere in the method body, with no correlation to the receiver or to whether it actually gates the push/push_back call:

if method == "len" {
    self.has_len_check = true;
}

A .len() call on an unrelated collection (e.g. logging other_vec.len()) suppresses the finding even when the actual storage-backed Vec being grown has no cap at all. This is the same "presence, not gating condition" defect class already tracked for unchecked-arithmetic (issue #278), recurring independently in this check.

Acceptance Criteria

• Require the .len() call to be on the same receiver/variable as the vector being pushed to (or otherwise demonstrably gate the push), not just present anywhere in the function.
• Add a test with an unrelated .len() call plus a genuinely unbounded push, asserting a finding is still produced.

Difficulty: intermediate

[kosisochukwu1234]

@kosisochukwu1234 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I am confident that I can implement this having worked on something similar in the past

ℹ️ Repo Maintainers: To accept this application, review their application or assign @kosisochukwu1234 to this issue.

[Ebby46]

@Ebby46 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello, pls i will like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Ebby46 to this issue.

[Abyy8]

@Abyy8 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I would like to work on this issue. I will refine the analysis so that a length check is associated with the specific vector being modified rather than any len() call within the function. I will also add a regression test covering an unrelated len() call alongside an unbounded push to ensure the check only passes when the correct vector is actually guarded.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Abyy8 to this issue.