fix(builder): clone MigratedClasses in cloneStateDiff

[infrmtcs-agent]

User description

Summary

• cloneStateDiff was missing a clone of MigratedClasses, so the cloned state diff shared the same underlying slice/backing array as the original
• Added the clone and covered it with a test

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PR Type

Bug fix, Tests

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Description

• Clone MigratedClasses to avoid shared state

• Add test covering full state diff fields

• Prevent clone mutations affecting original state

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File Walkthrough

	Relevant files
Bug fix	state.go Clone MigratedClasses in StateDiff clone                                  builder/state.go Adds MigratedClasses: maps.Clone(stateDiff.MigratedClasses) to cloneStateDiff +1/-0
Tests	state_test.go Add state diff clone coverage test                                              builder/state_test.go Adds TestCloneCopiesEveryStateDiffField validating all StateDiff fields clone Uses reflection fixture and mutation check to catch shared backing data +55/-0

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[github-actions]

Claude finished @infrmtcs-agent[bot]'s task in 2m 53s —— View job

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Reviewing PR #4032

• Gather context (diff, changed files, repo guidelines)
• Review builder/state.go change
• Review builder/state_test.go new test
• Post findings / summary

Summary

The PR is correct and clean — no issues found, no inline comments needed.

• MigratedClasses (map[felt.SierraClassHash]felt.CasmClassHash) is a value-typed map, so maps.Clone is the right and sufficient fix, consistent with how the other map fields (Nonces, DeployedContracts, DeclaredV1Classes, ReplacedClasses) are already cloned.
• The new test (TestCloneCopiesEveryStateDiffField) is well designed: it uses reflect to assert every StateDiff field is populated in the fixture (so a future field addition can't silently go unclonned/untested), then calls Merge on the original and asserts the clone is unaffected — this correctly exercises map aliasing for MigratedClasses (and all other map fields) via Merge's maps.Copy into the receiver's maps, and slice aliasing for DeclaredV0Classes.
• Verified go vet ./builder/... passes (type-checks the new test file cleanly). go test itself wasn't permitted to run in this sandbox, but the vet pass plus manual trace of Merge/cloneStateDiff confirms the fix and test are sound.

[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

⏱️ Estimated effort to review: 1 🔵⚪⚪⚪⚪

🏅 Score: 95

🧪 PR contains tests

🔒 No security concerns identified

⚡ No major issues detected

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.19%. Comparing base (121146c) to head (35bc8ec).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4032      +/-   ##
==========================================
- Coverage   79.31%   79.19%   -0.13%     
==========================================
  Files         464      464              
  Lines       35793    35788       -5     
==========================================
- Hits        28389    28341      -48     
- Misses       7395     7438      +43     
  Partials        9        9              

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