Add fuse-map-with-for refactoring rule

[Copilot]

• Explore and understand the existing refactoring rule structure
• Create test file for fuse-map-with-for rule
• Implement the fuse-map-with-for refactoring rule
• Add the new rule to default-recommendations
• Run tests to verify implementation - all tests passing
• Code review - addressed feedback
• Security check - no issues found
• Address PR comments - fixed rule logic and added missing tests

Summary

Implemented the fuse-map-with-for refactoring rule that fuses map expressions with for loops when the intermediate list is only used once. The rule now correctly:

• For loops*: Fuses with ANY for* loop (single or multi-clause) by adding nested clauses
• For loops: Only fuses with SINGLE-clause for loops using internal definitions (multi-clause for loops iterate in parallel and cannot be fused)

All test cases pass including the newly added tests for single-clause for* loops and multi-clause for loops.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>New rule: fuse-map-with-for</issue_title>
<issue_description>### Rule summary

A map expression that produces a list which is immediately iterated over by a for* loop can be fused with the for* loop, if the intermediate list isn't used elsewhere. This avoids constructing the intermediate list and is usually more readable. This should only be applied when the map expression is given a short lambda.

Test case

#lang resyntax/test

test: "original code should be refactorable to new code"
--------------------
#lang racket
(define (f xs g h)
  (define ys (map (λ (x) (g x)) xs))
  (for* ([y (in-list ys)]
         [z (in-list (h y))])
    (displayln z)))
====================
#lang racket
(define (f xs g h)
  (for* ([x (in-list xs)]
         [y (in-list (g x))]
         [z (in-list (h y))])
    (displayln z)))
--------------------

No-change test case

#lang resyntax/test

no-change-test: "code not refactorable"
--------------------
#lang racket
(define (f xs g h)
  (define ys (map (λ (x) (g x)) xs))
  (for* ([y (in-list ys)]
         [z (in-list (h y))])
    (displayln z))
  (displayln ys))
--------------------

Additional context

Spotted this here in racket/drracket#783.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes New rule: fuse-map-with-for #764

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[github-actions]

Resyntax analyzed 3 files in this pull request and found no issues.

[jackfirth]

@copilot

[coveralls]

coverage: 93.676% (+0.01%) from 93.662%
when pulling 9580e5e on copilot/add-fuse-map-with-for-rule
into 9dbfa96 on master.