From 40fc2f4d7a4813e0b2a561565a3450a9e4ac0291 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 1 Nov 2025 23:59:04 +0000
Subject: [PATCH 1/5] Initial plan


From 09a6d1573e472e8148d4991be9ba3c1fcca24e36 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 2 Nov 2025 00:08:37 +0000
Subject: [PATCH 2/5] Add syntax-path->string and string->syntax-path functions

Co-authored-by: jackfirth <8175575+jackfirth@users.noreply.github.com>
---
 private/syntax-path.rkt | 111 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)

diff --git a/private/syntax-path.rkt b/private/syntax-path.rkt
index 4309838b..0e0ef73c 100644
--- a/private/syntax-path.rkt
+++ b/private/syntax-path.rkt
@@ -20,6 +20,8 @@
   [syntax-path-add (-> syntax-path? exact-nonnegative-integer? syntax-path?)]
   [syntax-path-remove-prefix (-> syntax-path? syntax-path? syntax-path?)]
   [syntax-path-neighbors? (-> syntax-path? syntax-path? boolean?)]
+  [syntax-path->string (-> syntax-path? string?)]
+  [string->syntax-path (-> string? syntax-path?)]
   [syntax-ref (-> syntax? syntax-path? syntax?)]
   [syntax-set (-> syntax? syntax-path? syntax? syntax?)]
   [syntax-remove-splice
@@ -37,6 +39,7 @@
          data/order
          guard
          racket/sequence
+         racket/string
          racket/struct
          racket/treelist
          racket/list
@@ -214,6 +217,114 @@
        (equal? leading (sub1 trailing))))
 
 
+(define (syntax-path->string path)
+  (if (empty-syntax-path? path)
+      "/"
+      (string-append
+       "/"
+       (string-join
+        (for/list ([elem (in-treelist (syntax-path-elements path))])
+          (number->string elem))
+        "/"))))
+
+
+(module+ test
+  (test-case "syntax-path->string"
+    (test-case "empty path"
+      (check-equal? (syntax-path->string empty-syntax-path) "/"))
+    
+    (test-case "single element"
+      (check-equal? (syntax-path->string (syntax-path (list 0))) "/0"))
+    
+    (test-case "multiple elements"
+      (check-equal? (syntax-path->string (syntax-path (list 0 1 2))) "/0/1/2"))
+    
+    (test-case "large numbers"
+      (check-equal? (syntax-path->string (syntax-path (list 42 99 1000))) "/42/99/1000"))))
+
+
+(define (string->syntax-path str)
+  (unless (string? str)
+    (raise-argument-error 'string->syntax-path "string?" str))
+  (unless (string-prefix? str "/")
+    (raise-arguments-error
+     'string->syntax-path
+     "syntax path string must start with /"
+     "given" str))
+  (when (and (> (string-length str) 1) (string-suffix? str "/"))
+    (raise-arguments-error
+     'string->syntax-path
+     "syntax path string must not end with / (except for root path)"
+     "given" str))
+  (if (equal? str "/")
+      empty-syntax-path
+      (let* ([parts (string-split (substring str 1) "/")]
+             [numbers (for/list ([part (in-list parts)])
+                        (define num (string->number part))
+                        (unless (and num (exact-nonnegative-integer? num))
+                          (raise-arguments-error
+                           'string->syntax-path
+                           "syntax path string contains invalid element (must be non-negative integer)"
+                           "given" str
+                           "invalid element" part))
+                        num)])
+        (syntax-path numbers))))
+
+
+(module+ test
+  (test-case "string->syntax-path"
+    (test-case "empty path"
+      (check-equal? (string->syntax-path "/") empty-syntax-path))
+    
+    (test-case "single element"
+      (check-equal? (string->syntax-path "/0") (syntax-path (list 0))))
+    
+    (test-case "multiple elements"
+      (check-equal? (string->syntax-path "/0/1/2") (syntax-path (list 0 1 2))))
+    
+    (test-case "large numbers"
+      (check-equal? (string->syntax-path "/42/99/1000") (syntax-path (list 42 99 1000))))
+    
+    (test-case "error on missing leading slash"
+      (check-exn exn:fail:contract?
+                 (λ () (string->syntax-path "0/1/2"))))
+    
+    (test-case "error on trailing slash"
+      (check-exn exn:fail:contract?
+                 (λ () (string->syntax-path "/0/1/"))))
+    
+    (test-case "error on invalid element"
+      (check-exn exn:fail:contract?
+                 (λ () (string->syntax-path "/0/abc/2"))))
+    
+    (test-case "error on negative number"
+      (check-exn exn:fail:contract?
+                 (λ () (string->syntax-path "/0/-1/2"))))
+    
+    (test-case "error on float"
+      (check-exn exn:fail:contract?
+                 (λ () (string->syntax-path "/0/1.5/2"))))))
+
+
+(module+ test
+  (test-case "round-trip conversion"
+    (test-case "empty path"
+      (check-equal? (string->syntax-path (syntax-path->string empty-syntax-path))
+                    empty-syntax-path))
+    
+    (test-case "single element path"
+      (define path (syntax-path (list 5)))
+      (check-equal? (string->syntax-path (syntax-path->string path)) path))
+    
+    (test-case "multiple element path"
+      (define path (syntax-path (list 1 2 3 4 5)))
+      (check-equal? (string->syntax-path (syntax-path->string path)) path))
+    
+    (test-case "path with large numbers"
+      (define path (syntax-path (list 0 100 999 1234567)))
+      (check-equal? (string->syntax-path (syntax-path->string path)) path))))
+
+
 (define (syntax-ref init-stx path)
   (define result
     (for/fold ([stx init-stx])

From 2045eee606892ba4ae097e62717a39d039b77f15 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 2 Nov 2025 00:10:16 +0000
Subject: [PATCH 3/5] Address code review feedback

Co-authored-by: jackfirth <8175575+jackfirth@users.noreply.github.com>
---
 private/syntax-path.rkt | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/private/syntax-path.rkt b/private/syntax-path.rkt
index 0e0ef73c..641dced7 100644
--- a/private/syntax-path.rkt
+++ b/private/syntax-path.rkt
@@ -244,8 +244,6 @@
 
 
 (define (string->syntax-path str)
-  (unless (string? str)
-    (raise-argument-error 'string->syntax-path "string?" str))
   (unless (string-prefix? str "/")
     (raise-arguments-error
      'string->syntax-path
@@ -264,7 +262,7 @@
                         (unless (and num (exact-nonnegative-integer? num))
                           (raise-arguments-error
                            'string->syntax-path
-                           "syntax path string contains invalid element (must be non-negative integer)"
+                           "syntax path string contains invalid element (must be nonnegative integer)"
                            "given" str
                            "invalid element" part))
                         num)])

From 6d4cb05e6beacf2f132681ef4b207abba12bf057 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 2 Nov 2025 00:37:05 +0000
Subject: [PATCH 4/5] Simplify syntax-path->string and enhance error test
 assertions

Co-authored-by: jackfirth <8175575+jackfirth@users.noreply.github.com>
---
 private/syntax-path.rkt | 71 ++++++++++++++++++++++++++++++-----------
 1 file changed, 53 insertions(+), 18 deletions(-)

diff --git a/private/syntax-path.rkt b/private/syntax-path.rkt
index 641dced7..7272a445 100644
--- a/private/syntax-path.rkt
+++ b/private/syntax-path.rkt
@@ -218,14 +218,11 @@
 
 
 (define (syntax-path->string path)
-  (if (empty-syntax-path? path)
-      "/"
-      (string-append
-       "/"
-       (string-join
-        (for/list ([elem (in-treelist (syntax-path-elements path))])
-          (number->string elem))
-        "/"))))
+  (string-join
+   (for/list ([elem (in-treelist (syntax-path-elements path))])
+     (number->string elem))
+   "/"
+   #:before-first "/"))
 
 
 (module+ test
@@ -284,24 +281,62 @@
       (check-equal? (string->syntax-path "/42/99/1000") (syntax-path (list 42 99 1000))))
     
     (test-case "error on missing leading slash"
-      (check-exn exn:fail:contract?
-                 (λ () (string->syntax-path "0/1/2"))))
+      (define input "0/1/2")
+      (define thrown
+        (with-handlers ([(λ (_) #true) values])
+          (string->syntax-path input)
+          #false))
+      (check-pred exn:fail:contract? thrown)
+      (check-regexp-match #rx"string->syntax-path:" (exn-message thrown))
+      (check-regexp-match #rx"given: \"0/1/2\"" (exn-message thrown))
+      (check-regexp-match #rx"syntax path string must start with /" (exn-message thrown)))
     
     (test-case "error on trailing slash"
-      (check-exn exn:fail:contract?
-                 (λ () (string->syntax-path "/0/1/"))))
+      (define input "/0/1/")
+      (define thrown
+        (with-handlers ([(λ (_) #true) values])
+          (string->syntax-path input)
+          #false))
+      (check-pred exn:fail:contract? thrown)
+      (check-regexp-match #rx"string->syntax-path:" (exn-message thrown))
+      (check-regexp-match #rx"given: \"/0/1/\"" (exn-message thrown))
+      (check-regexp-match #rx"syntax path string must not end with /" (exn-message thrown)))
     
     (test-case "error on invalid element"
-      (check-exn exn:fail:contract?
-                 (λ () (string->syntax-path "/0/abc/2"))))
+      (define input "/0/abc/2")
+      (define thrown
+        (with-handlers ([(λ (_) #true) values])
+          (string->syntax-path input)
+          #false))
+      (check-pred exn:fail:contract? thrown)
+      (check-regexp-match #rx"string->syntax-path:" (exn-message thrown))
+      (check-regexp-match #rx"given: \"/0/abc/2\"" (exn-message thrown))
+      (check-regexp-match #rx"syntax path string contains invalid element" (exn-message thrown))
+      (check-regexp-match #rx"invalid element: \"abc\"" (exn-message thrown)))
     
     (test-case "error on negative number"
-      (check-exn exn:fail:contract?
-                 (λ () (string->syntax-path "/0/-1/2"))))
+      (define input "/0/-1/2")
+      (define thrown
+        (with-handlers ([(λ (_) #true) values])
+          (string->syntax-path input)
+          #false))
+      (check-pred exn:fail:contract? thrown)
+      (check-regexp-match #rx"string->syntax-path:" (exn-message thrown))
+      (check-regexp-match #rx"given: \"/0/-1/2\"" (exn-message thrown))
+      (check-regexp-match #rx"syntax path string contains invalid element" (exn-message thrown))
+      (check-regexp-match #rx"invalid element: \"-1\"" (exn-message thrown)))
     
     (test-case "error on float"
-      (check-exn exn:fail:contract?
-                 (λ () (string->syntax-path "/0/1.5/2"))))))
+      (define input "/0/1.5/2")
+      (define thrown
+        (with-handlers ([(λ (_) #true) values])
+          (string->syntax-path input)
+          #false))
+      (check-pred exn:fail:contract? thrown)
+      (check-regexp-match #rx"string->syntax-path:" (exn-message thrown))
+      (check-regexp-match #rx"given: \"/0/1.5/2\"" (exn-message thrown))
+      (check-regexp-match #rx"syntax path string contains invalid element" (exn-message thrown))
+      (check-regexp-match #rx"invalid element: \"1.5\"" (exn-message thrown)))))
 
 
 (module+ test

From 47718c48ae932feab972d0982b2254b577bf9654 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 2 Nov 2025 00:53:07 +0000
Subject: [PATCH 5/5] Change syntax-path->string to return immutable-string?

Co-authored-by: jackfirth <8175575+jackfirth@users.noreply.github.com>
---
 private/syntax-path.rkt | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/private/syntax-path.rkt b/private/syntax-path.rkt
index 7272a445..428882f5 100644
--- a/private/syntax-path.rkt
+++ b/private/syntax-path.rkt
@@ -20,7 +20,7 @@
   [syntax-path-add (-> syntax-path? exact-nonnegative-integer? syntax-path?)]
   [syntax-path-remove-prefix (-> syntax-path? syntax-path? syntax-path?)]
   [syntax-path-neighbors? (-> syntax-path? syntax-path? boolean?)]
-  [syntax-path->string (-> syntax-path? string?)]
+  [syntax-path->string (-> syntax-path? immutable-string?)]
   [string->syntax-path (-> string? syntax-path?)]
   [syntax-ref (-> syntax? syntax-path? syntax?)]
   [syntax-set (-> syntax? syntax-path? syntax? syntax?)]
@@ -38,6 +38,7 @@
                      racket/syntax)
          data/order
          guard
+         racket/mutability
          racket/sequence
          racket/string
          racket/struct
@@ -218,11 +219,12 @@
 
 
 (define (syntax-path->string path)
-  (string-join
-   (for/list ([elem (in-treelist (syntax-path-elements path))])
-     (number->string elem))
-   "/"
-   #:before-first "/"))
+  (string->immutable-string
+   (string-join
+    (for/list ([elem (in-treelist (syntax-path-elements path))])
+      (number->string elem))
+    "/"
+    #:before-first "/")))
 
 
 (module+ test