Add manual-display-to-file refactoring rules

[Copilot]

Detects manual file I/O patterns using call-with-output-file with display/displayln and suggests the more concise display-to-file/display-lines-to-file functions.

Changes

• Two new refactoring rules in file-io-suggestions.rkt:

  • manual-display-to-file: call-with-output-file + display → display-to-file
  • manual-displayln-to-file: call-with-output-file + displayln → display-lines-to-file

• Tests cover:

  • Both lambda and λ syntax
  • Both display and displayln variants
  • Negative cases (mismatched port identifiers, multiple expressions in lambda body)

Example

Before:

(define (f path s)
  (call-with-output-file path
    (lambda (out)
      (displayln s out))))

After:

(define (f path s)
  (display-lines-to-file (list s) path))

Original prompt

---

This section details on the original issue you should resolve

<issue_title>New rule: manual-display-to-file</issue_title>
<issue_description>### Rule summary

Code using call-with-output-file and display / displayln can use display-to-file / display-lines-to-file instead.

Test case

#lang resyntax/test

test: "original code should be refactorable to new code"
--------------------
#lang racket
(define (f path s)
  (call-with-output-file path
    (lambda (out)
      (displayln s out))))
====================
#lang racket
(define (f path s)
  (display-lines-to-file (list s) path))
--------------------

</issue_description>

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

• Fixes New rule: manual-display-to-file #673

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