fix: fix literal repr

[ascandone]

fixes: https://formance-team.atlassian.net/browse/TS-289?focusedCommentId=13805&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-13805

[coderabbitai]

Walkthrough

This pull request refactors numeric literal handling to support larger integers. It changes NumberLiteral.Number from int to *big.Int, updates the parser to use big.Int.SetString instead of strconv.Atoi, and adjusts downstream code to use pre-allocated big.Int values directly. A test case demonstrates the new bigint literal support.

Changes

Cohort / File(s)	Summary
Core Type Definition internal/parser/ast.go	Changed NumberLiteral.Number type from int to *big.Int to support arbitrary-precision integers.
Parser Parsing Logic internal/parser/parser.go	Replaced strconv.Atoi with big.Int.SetString for parsing numeric literals, enabling bigint support with panic-on-invalid semantics.
Downstream Consumers internal/analysis/check.go, internal/interpreter/evaluate_expr.go	Updated to use pre-allocated *big.Int from NumberLiteral.Number directly, eliminating unnecessary allocations.
Test Data internal/interpreter/testdata/script-tests/bigint-literal.num	Added test case demonstrating bigint literal transfer with large USDT amount.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Poem

🐰 Once bounded by the int so small,
Our numbers couldn't be that tall,
But big.Int came to save the day,
Now USDT amounts can stay,
In trillions, billions on display! ✨

🚥 Pre-merge checks | ✅ 1 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Title check	❓ Inconclusive	The title is vague and non-descriptive, using the generic term 'fix' without conveying what literal representation issue was addressed.	Use a more descriptive title like 'Support arbitrary-precision integers in number literals' or 'Replace int with big.Int for number literals' to clarify the actual change.

✅ Passed checks (1 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description references a Jira issue link but provides no additional context about the changes or their purpose in the pull request itself.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/handle-arbitrary-precision-number-literals

---

No actionable comments were generated in the recent review. 🎉

🧹 Recent nitpick comments

internal/analysis/check.go (1)

751-752: Returning expr.Number directly exposes the AST node's *big.Int to mutation by callers.

Currently all callers wrap the result in new allocations (new(big.Int).Neg(...), .Add(...), .Sub(...)), so this is safe today. But it's fragile — a future caller that mutates the returned value would silently corrupt the AST.

Consider whether the minor allocation saving is worth the risk, or document the "do not mutate" contract.

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[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 67.75%. Comparing base (aee5218) to head (ee167e1).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/parser/parser.go	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #113   +/-   ##
=======================================
  Coverage   67.75%   67.75%           
=======================================
  Files          45       45           
  Lines        4425     4425           
=======================================
  Hits         2998     2998           
  Misses       1264     1264           
  Partials      163      163           

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