Polyfill: Remove dead code

[jessealama]

After digging into code coverage following tc39/test262#4964, we found several unreachable code paths in the polyfill's non-ISO calendar and duration rounding logic, even after flossing for edge cases.

We verified this on Node only, so it's possible some of these paths are reachable in other engines. Happy to revert any individual removal if that turns out to be the case.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.64%. Comparing base (be4e0ef) to head (b6d60f2).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3289      +/-   ##
==========================================
+ Coverage   97.40%   97.64%   +0.23%     
==========================================
  Files          22       22              
  Lines       10771    10746      -25     
  Branches     1866     1855      -11     
==========================================
+ Hits        10492    10493       +1     
+ Misses        258      235      -23     
+ Partials       21       18       -3     

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[ptomato]

Thanks!

Good in principle, but needs a few adjustments. There are a few places where I think it'd be good to keep an assertion, and a few places where it looks like the /* c8 ignore next */ magic comments aren't working as intended so maybe those can get a closer look.

There are a couple of deletions that don't look obviously deleteable to me, so would appreciate hearing your analysis.

[ptomato]

Removing this looks wrong at first glance — as if it might be just happenstance that the bisection never overshoots in any of our tests.

(if removing it is correct, then the loop can be simplified a bit more — it looks like sign = 0 can become break, and the comment above the loop needs to be updated since it's no longer a bisection)

[jessealama]

Thanks!

Good in principle, but needs a few adjustments. There are a few places where I think it'd be good to keep an assertion, and a few places where it looks like the /* c8 ignore next */ magic comments aren't working as intended so maybe those can get a closer look.

There are a couple of deletions that don't look obviously deleteable to me, so would appreciate hearing your analysis.

Thanks for taking a look! The analysis of these was based on nothing deeper than looking at the coverage and noticing that they appear unused. I'm happy to take a more conservative approach and replace some of the deleted bits with assertions. I agree that some of these unused blocks are large enough to be better viewed as missing tests than as dead code. I'll take care of some of the lower-hanging fruit and try to turn those larger bits into tests. Until then, I'll mark this as a draft PR.

[ptomato]

@jessealama I realize now that Tim had looked at 2 of these and opened issues for them: #3235, #3217

[jessealama]

There are a couple of deletions that don't look obviously deleteable to me, so would appreciate hearing your analysis.

I've updated things a bit to use assertions in a couple places, and restored the code for the more aggressive deletions. Let's tackle those in separate issues.

[jessealama]

I'm marking this as ready for (re-)review. I made a couple of standalone PRs that track the aggressive deletions we originally had in this PR, thereby trimming down this PR.

[ptomato]

Thanks!