find-repetition

name	find-repetition
description	Scan file(s) for repeated code patterns and suggest functions to encapsulate them
argument-hint	<file or glob>

Scan $ARGUMENTS for two kinds of issues:

1. Repeated constructs worth extracting

For each pattern found, show the locations where it appears, explain what the shared logic is doing, and suggest a function signature that would encapsulate it. Only flag repetition that is genuinely worth extracting -- three or more occurrences, or two that are complex enough that a helper would meaningfully reduce the maintenance surface. Do not suggest abstractions for simple one-liners or cases where the repetition is coincidental rather than structural.

2. Manual implementations of existing helpers

Read .claude/helpers.md first. Then scan the target files for code that manually implements logic already covered by a helper in the index. For each instance found, cite the helper from .claude/helpers.md that should replace it and show a before/after sketch.

Common patterns to watch for in this codebase:

• Shimmer boilerplate -- Code that does var new: OptionalHandle = .none; try shimmerToX(...); handle.swapIfNew(new); when an in-place wrapper like getInteger, getFloat, getBoolean, getIndex, shimmerToList, getListLength, getCodepointLength, or resolveHash already exists on Interp.
• Dict access patterns -- Manual key lookups followed by dictLookupFollowRefs or dictGetTable when Interp.getDictValue, getDictValueOrError, getDictValueRecursively, getDictValueRecursivelyOrError, putDictValue, putDictValueRecursively, removeDictValue, removeDictValueRecursively, getDictValueInPlace, or putDictValueInPlace would handle the shimmer and error plumbing.
• List construction -- createObject + manual field initialization when newList, newListWithCapacity, or listAppendAssumeCapacity would suffice.
• String allocation -- createString + setNormalString when newString, newStringFmt, newStringToFill, or setStringOwning would work.
• Ref-count dance -- Manual incrRefCount/decrRefCount pairs when takeReference(), dupOrRef(), reference(), or referenceTakeOwnership() express the intent more directly.
• Error-details plumbing -- Creating a local ErrorDetails and passing it through multiple layers when interp.wrapError or interp.wrapShimmerFn could collapse the boilerplate.
• Range/index resolution -- Manual index arithmetic when Heap.ListIndex.asAbsoluteIndex, Range.fromIndexes, getRange, or getRangeInPlace already exists.
• Expression evaluation -- Manual tokenization or AST walking when evalExpression, evalExpressionInPlace, or getBoolFromExpression should be used.
• Scope capture -- Manual dict construction from call frames when captureScope or captureCurrentScope already does it.

When reporting a subsumed pattern, include:

1. The helper name from .claude/helpers.md.
2. The file and line range of the manual implementation.
3. A one-line explanation of what the manual code is doing.
4. A brief replacement sketch showing how the helper simplifies it.

Be conservative: only flag cases where the replacement is clearly equivalent and actually shorter or clearer. Do not suggest replacing code that uses the helper's internals intentionally or that has subtle behavioral differences.