Support rep.int() in subset indexing

[t-kalinowski]

Summary

• Support rep.int() when used as an index inside x[...] (e.g. x[rep.int(1L, 5L)]) by lowering it to a Fortran integer vector constructor.
• Scope support to subset indexing only; rep.int() used as a general value constructor errors to avoid silent type/semantic changes.
• Fail cleanly for invalid indexing args (e.g. NULL) with user-facing errors (no internal slot-access failures).

Tests

• Added tests/testthat/test-rep-int.R covering supported forms (positional, times=, non-literal times) and failure modes (outside indexing, NULL args).
• R -q -e 'devtools::test()'

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Use times value for rep.int length, not its size

The length you derive for the replicated index uses r2size(times_arg), which returns the size of the times expression (usually 1 for a scalar), not its runtime value. In x[rep.int(2L, n)] where n is a scalar integer (e.g., 4), this sets the index vector dims to length 1, so the subscript is treated as scalar during drop/shape inference in [ and the output shape becomes incorrect. The generated Fortran array constructor will still produce length n, so the wrapper’s metadata can disagree with the actual result. Consider propagating the actual times expression (or an unknown length) instead of r2size(times_arg).

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.78%. Comparing base (1de5107) to head (fe33d9b).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

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##             main      #95   +/-   ##
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  Coverage   92.78%   92.78%           
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  Files          27       27           
  Lines        5754     5754           
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  Hits         5339     5339           
  Misses        415      415           

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[t-kalinowski]

Re: len_expr <- r2size(times_arg, scope)

Here r2size() is used as a dims-expression helper: for scalar integer times it resolves to the runtime value expression (e.g. for x[rep.int(2L, n)] with n an integer scalar arg, r2size(n, scope) is n), not size(times).

This is exercised by tests/testthat/test-rep-int.R (the "rep.int supports non-literal times in subset indexing" test). If the handler were inferring length 1, [ would treat the index as scalar-like and the quick result would not match R (length would be wrong), so the test would fail.