From 3fb0bd0cac8290d293baae3a8864a048d878d5d9 Mon Sep 17 00:00:00 2001
From: Jack Firth <jackhfirth@gmail.com>
Date: Tue, 14 Jul 2026 00:28:55 -0700
Subject: [PATCH] Test syntax-path error branches

Fixes #816

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 grimoire/syntax-path.rkt | 44 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/grimoire/syntax-path.rkt b/grimoire/syntax-path.rkt
index bd7eb4b7..93b1d262 100644
--- a/grimoire/syntax-path.rkt
+++ b/grimoire/syntax-path.rkt
@@ -214,6 +214,18 @@
       (check-equal? (syntax-path-remove-prefix path prefix) expected))))
 
 
+(module+ test
+  (test-case "syntax-path-remove-prefix errors"
+
+    (test-case "path shorter than prefix"
+      (check-exn #rx"path is shorter than prefix"
+                 (λ () (syntax-path-remove-prefix (syntax-path (list 1)) (syntax-path (list 1 2 3))))))
+
+    (test-case "path does not start with prefix"
+      (check-exn #rx"path does not start with given prefix"
+                 (λ () (syntax-path-remove-prefix (syntax-path (list 1 2 3)) (syntax-path (list 9))))))))
+
+
 (define (syntax-path-last-element path)
   (treelist-last (syntax-path-elements path)))
 
@@ -592,6 +604,30 @@
       (check-regexp-match #rx"path is inconsistent" (exn-message thrown)))))
 
 
+(module+ test
+  (test-case "syntax-ref errors"
+
+    (test-case "vector index out of bounds"
+      (check-exn #rx"path is inconsistent"
+                 (λ () (syntax-ref #'#[a b c] (syntax-path (list 5))))))
+
+    (test-case "box index out of bounds"
+      (check-exn #rx"path is inconsistent"
+                 (λ () (syntax-ref #'#&a (syntax-path (list 1))))))
+
+    (test-case "prefab field index out of bounds"
+      (check-exn #rx"path is inconsistent"
+                 (λ () (syntax-ref #'#s(point 10 20) (syntax-path (list 5))))))
+
+    (test-case "improper list index out of bounds"
+      (check-exn #rx"path is inconsistent"
+                 (λ () (syntax-ref #'(a b . c) (syntax-path (list 5))))))
+
+    (test-case "path into non-compound datum"
+      (check-exn #rx"path is inconsistent"
+                 (λ () (syntax-ref #'(a b c) (syntax-path (list 0 0))))))))
+
+
 (define (syntax-contains-path? init-stx path)
   (let/ec return
     (for/fold ([stx init-stx])
@@ -876,6 +912,14 @@
       (check-equal? (syntax->datum actual) '(a b c FOO e)))))
 
 
+(module+ test
+  (test-case "syntax-set errors"
+
+    (test-case "path into non-compound datum"
+      (check-exn #rx"path is inconsistent"
+                 (λ () (syntax-set #'(a b c) (syntax-path (list 0 0)) #'FOO))))))
+
+
 (define/guard (syntax-remove-splice stx path children-count)
   (unless (syntax-contains-path? stx path)
     (raise-arguments-error 'syntax-remove-splice