fix: fix division by negative zero returning +Inf instead of -Inf

[andriibeee]

fixes VictoriaMetrics/VictoriaMetrics#10296

---

Summary by cubic

Fixes division by negative zero returning the wrong sign. Constant folding now preserves -0.0 so expressions like 1 / -0.0 yield -Inf.

• Bug Fixes
  • In simplifyConstantsInBinaryExpr, only rewrite 0 - x to -x when the left is literal +0.0; avoid rewriting -0 - x to keep signed-zero semantics.
  • Added tests for 1 / -0.0, (1) / (-0.0), -1 / 0, -1 / -0.0, (1 - 1) - 0, and (2 - 2) / -1.

^{Written for commit 4e0c0dc. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 2 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="parser.go">

<violation number="1" location="parser.go:197">
P2: Unary-minus preservation logic is overbroad and can rewrite ordinary `0 - x` constant-folded expressions, changing signed-zero semantics.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review, or fix all with cubic.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.69%. Comparing base (0dc0e2d) to head (4e0c0dc).
⚠️ Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #64      +/-   ##
==========================================
- Coverage   89.69%   89.69%   -0.01%     
==========================================
  Files          11       11              
  Lines        2969     2988      +19     
==========================================
+ Hits         2663     2680      +17     
- Misses        209      210       +1     
- Partials       97       98       +1     

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