Fix FP for MISRA-C RULE-13-4

[mbaluda]

This pull request addresses false positives in the ResultOfAnAssignmentOperatorShouldNotBeUsed rule by refining how assignment expressions are detected and reported.
Includes all types of Assignment (e.g. artihmetic assignments) and excludes the update section of for loops.
Improve tests to ensure that only genuine violations are flagged.

Motivated by this FP example:
https://github.com/mbaluda-org/judo-misra-c-autofix/security/code-scanning/690

Change request type

• Release or process automation (GitHub workflows, internal scripts)
• Internal documentation
• External documentation
• Query files (.ql, .qll, .qls or unit tests)
• External scripts (analysis report or other code shipped as part of a release)

Rules with added or modified queries

• No rules added
• Queries have been added for the following rules:
  • rule number here
• Queries have been modified for the following rules:
  • RULE-8-18-2
  • RULE-13-4

Release change checklist

A change note (development_handbook.md#change-notes) is required for any pull request which modifies:

• The structure or layout of the release artifacts.
• The evaluation performance (memory, execution time) of an existing query.
• The results of an existing query in any circumstance.

If you are only adding new rule queries, a change note is not required.

Author: Is a change note required?

• Yes
• No

🚨🚨🚨
Reviewer: Confirm that format of shared queries (not the .qll file, the
.ql file that imports it) is valid by running them within VS Code.

• Confirmed

Reviewer: Confirm that either a change note is not required or the change note is required and has been added.

• Confirmed

Query development review checklist

For PRs that add new queries or modify existing queries, the following checklist should be completed by both the author and reviewer:

Author

• Have all the relevant rule package description files been checked in?
• Have you verified that the metadata properties of each new query is set appropriately?
• Do all the unit tests contain both "COMPLIANT" and "NON_COMPLIANT" cases?
• Are the alert messages properly formatted and consistent with the style guide?
• Have you run the queries on OpenPilot and verified that the performance and results are acceptable?
  As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.
• Does the query have an appropriate level of in-query comments/documentation?
• Have you considered/identified possible edge cases?
• Does the query not reinvent features in the standard library?
• Can the query be simplified further (not golfed!)

Reviewer

• Have all the relevant rule package description files been checked in?
• Have you verified that the metadata properties of each new query is set appropriately?
• Do all the unit tests contain both "COMPLIANT" and "NON_COMPLIANT" cases?
• Are the alert messages properly formatted and consistent with the style guide?
• Have you run the queries on OpenPilot and verified that the performance and results are acceptable?
  As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.
• Does the query have an appropriate level of in-query comments/documentation?
• Have you considered/identified possible edge cases?
• Does the query not reinvent features in the standard library?
• Can the query be simplified further (not golfed!)

[Copilot]

Pull request overview

This PR refines the shared query for MISRA-C RULE-13-4 / MISRA C++ RULE-8-18-2 so assignment-operator result usage is detected more broadly while avoiding simple for-loop update false positives.

Changes:

• Changes the query from AssignExpr to Assignment to include compound assignments.
• Excludes direct assignment expressions used as for update expressions.
• Adds C/C++ test cases and a change note for the result change.

The change note is present, but review comments note that it needs to describe the newly reported compound-assignment results as well as the false-positive fix.

Show a summary per file

File	Description
cpp/common/src/codingstandards/cpp/rules/resultofanassignmentoperatorshouldnotbeused/ResultOfAnAssignmentOperatorShouldNotBeUsed.qll	Updates the shared query predicate logic.
c/common/test/rules/resultofanassignmentoperatorshouldnotbeused/test.c	Adds C test cases for compound assignment and loop updates.
c/common/test/rules/resultofanassignmentoperatorshouldnotbeused/ResultOfAnAssignmentOperatorShouldNotBeUsed.expected	Adds the expected C alert for compound assignment.
cpp/common/test/rules/resultofanassignmentoperatorshouldnotbeused/test.cpp	Adds matching C++ test cases.
change_notes/2026-05-18-fix-fp-misra-c-13-4.md	Adds a release change note for affected rules.

Copilot's findings

• Files reviewed: 5/5 changed files
• Comments generated: 3

[Copilot]

Copilot's findings

• Files reviewed: 5/5 changed files
• Comments generated: 1