update rounding behavior in `calculateSolvencyAfterShort`

[dpaiton]

Resolved Issues

working towards https://github.com/delvtech/hyperdrive-rs/issues/29

Description

The solvency after short check used divDown to convert from base to shares, but the open short function uses divUp. Therefore it was possible to have the solvency check say "all good" and then open short reverts. This fixes that problem.

I also added some intermediate checks so that the function fails gracefully in more situations.

Review Checklists

Please check each item before approving the pull request. While going through the checklist, it is recommended to leave comments on items that are referenced in the checklist to make sure that they are reviewed. If there are multiple reviewers, copy the checklists into sections titled ## [Reviewer Name]. If the PR doesn't touch Solidity, the corresponding checklist can be removed.

[[Reviewer Name]]

• [ ] Tokens
  • [ ] Do all approve calls use forceApprove?
  • [ ] Do all transfer calls use safeTransfer?
  • [ ] Do all transferFrom calls use msg.sender as the from address?
    • [ ] If not, is the function access restricted to prevent unauthorized token spend?
• [ ] Low-level calls (call, delegatecall, staticcall, transfer, send)
  • [ ] Is the returned success boolean checked to handle failed calls?
  • [ ] If using delegatecall, are there strict access controls on the addresses that can be called? It shouldn't be possible to delegatecall arbitrary addresses, so the list of possible targets should either be immutable or tightly controlled by an admin.
• [ ] Reentrancy
  • [ ] Are functions that make external calls or transfer ether marked as nonReentrant?
    • [ ] If not, is there documentation that explains why reentrancy is not a concern or how it's mitigated?
• [ ] Gas Optimizations
  • [ ] Is the logic as simple as possible?
  • [ ] Are the storage values that are used repeatedly cached in stack or memory variables?
  • [ ] If loops are used, are there guards in place to avoid out-of-gas issues?
• [ ] Visibility
  • [ ] Are all payable functions restricted to avoid stuck ether?
• [ ] Math
  • [ ] Is all of the arithmetic checked or guarded by if-statements that will catch underflows?
  • [ ] If Safe functions are altered, are potential underflows and overflows caught so that a failure flag can be thrown?
  • [ ] Are all of the rounding directions clearly documented?
• [ ] Testing
  • [ ] Are there new or updated unit or integration tests?
  • [ ] Do the tests cover the happy paths?
  • [ ] Do the tests cover the unhappy paths?
  • [ ] Are there an adequate number of fuzz tests to ensure that we are covering the full input space?

[coveralls]

Pull Request Test Coverage Report for Build 9555621955

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.124%

---

Totals
Change from base Build 9523138246:	0.0%
Covered Lines:	1965
Relevant Lines:	2133

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9555779516

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.124%

---

Totals
Change from base Build 9523138246:	0.0%
Covered Lines:	1965
Relevant Lines:	2133

---

💛 - Coveralls

[github-actions[bot]]

Hyperdrive Gas Benchmark

Benchmark suite	Current: 57240de0d00d783dd7a8fd8324f749dc74bced06	Previous: e5525e96fea5bc61e0eec7fe694049aa6722aa1c	Deviation	Status
addLiquidity: min	33937 gas	33937 gas	0%	🟰
addLiquidity: avg	156470 gas	155877 gas	0.3804%	🚨
addLiquidity: max	429437 gas	429437 gas	0%	🟰
checkpoint: min	40316 gas	40316 gas	0%	🟰
checkpoint: avg	144612 gas	144636 gas	-0.0166%	✅
checkpoint: max	255830 gas	255830 gas	0%	🟰
closeLong: min	31361 gas	31361 gas	0%	🟰
closeLong: avg	136498 gas	136439 gas	0.0432%	🚨
closeLong: max	2621435 gas	2621435 gas	0%	🟰
closeShort: min	31327 gas	31327 gas	0%	🟰
closeShort: avg	132281 gas	132305 gas	-0.0181%	✅
closeShort: max	402622 gas	272530 gas	47.7349%	🚨
initialize: min	31349 gas	31349 gas	0%	🟰
initialize: avg	333288 gas	333352 gas	-0.0192%	✅
initialize: max	399922 gas	399922 gas	0%	🟰
openLong: min	33370 gas	33370 gas	0%	🟰
openLong: avg	174259 gas	174248 gas	0.0063%	🚨
openLong: max	335241 gas	335241 gas	0%	🟰
openShort: min	33936 gas	33936 gas	0%	🟰
openShort: avg	169132 gas	168925 gas	0.1225%	🚨
openShort: max	416115 gas	415870 gas	0.0589%	🚨
redeemWithdrawalShares: min	31251 gas	31251 gas	0%	🟰
redeemWithdrawalShares: avg	74764 gas	75830 gas	-1.4058%	✅
redeemWithdrawalShares: max	305633 gas	305633 gas	0%	🟰
removeLiquidity: min	31301 gas	31301 gas	0%	🟰
removeLiquidity: avg	215692 gas	214933 gas	0.3531%	🚨
removeLiquidity: max	404194 gas	404194 gas	0%	🟰

This comment was automatically generated by workflow using github-action-benchmark.

[coveralls]

Pull Request Test Coverage Report for Build 9555912671

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.124%

---

Totals
Change from base Build 9523138246:	0.0%
Covered Lines:	1965
Relevant Lines:	2133

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9555967822

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.124%

---

Totals
Change from base Build 9523138246:	0.0%
Covered Lines:	1965
Relevant Lines:	2133

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9556234202

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.124%

---

Totals
Change from base Build 9523138246:	0.0%
Covered Lines:	1965
Relevant Lines:	2133

---

💛 - Coveralls