test(extern): assert sub-parser honors overridden extern() address

[thedavidmeister]

`ERC4626SubParser.erc4626ConvertToAssetsSubParser` and its shares sibling call `extern()` — a virtual method — to obtain the extern contract address encoded into the emitted `ExternDispatchV2` constant. Any derived contract can override `extern()` to split the subparser and extern into separate deployments. Nothing tested that the sub-parser actually reads from the override rather than a hardcoded `address(this)`.

What

Adds `ERC4626SubParserSplitExternWrapper` — a test contract that overrides `extern()` to return `address(0xdead)` — and `testSubParserHonorsOverriddenExtern`, which:

1. Calls both `convertToAssetsSubParserPublic` and `convertToSharesSubParserPublic` on the split wrapper.
2. Asserts the emitted `ExternDispatchV2` constants encode `address(0xdead)`, not `address(splitWords)`.
3. Asserts the result differs from what `address(this)` would produce.

Mutation-validated: replacing `extern()` with `address(this)` in `ERC4626SubParser` causes the assertion to fail with the correct mismatch message.

Closes #42

Co-Authored-By: Claude noreply@anthropic.com

Summary by CodeRabbit

• Bug Fixes
  • Improved validation for sub-parser behavior when an external address is overridden, helping ensure results are generated from the correct source.
  • Added coverage for asset and share conversion paths to prevent regressions in encoded output handling.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: eb3ee565-d206-4e1e-b602-96f2e78d396d

📥 Commits

Reviewing files that changed from the base of the PR and between 14acd39 and f9b47a0.

📒 Files selected for processing (2)

• test/src/abstract/ERC4626SubParser.wordParsers.t.sol
• test/src/abstract/ERC4626SubParserSplitExtern.wrapper.sol

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Walkthrough

Adds a test-only derived wrapper that injects a custom extern() address, then verifies the sub-parser encodes both assets and shares dispatch constants against that overridden address instead of the contract address.

Changes

ERC4626 subparser extern override coverage

Layer / File(s)	Summary
Split extern wrapper and encoding test test/src/abstract/ERC4626SubParserSplitExtern.wrapper.sol, test/src/abstract/ERC4626SubParser.wordParsers.t.sol	ERC4626SubParserSplitExternWrapper overrides extern() with an injected address, and the new test asserts the parsed assets and shares dispatch constants encode that overridden extern target.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the added test for honoring an overridden extern() address.
Linked Issues check	✅ Passed	The changes add the requested coverage for a subclass overriding extern() and verify the emitted extern target matches the override.
Out of Scope Changes check	✅ Passed	The PR appears scoped to the requested test coverage and wrapper needed to validate extern() override behavior.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 2026-06-25-issue-42-extern-override-seam-test

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