Add a test suite for the syntax collect.

collects/tests/syntax/run.rkt

@@ -0,0 +1,18 @@
+#lang racket/base
+
+(require rackunit rackunit/text-ui racket/runtime-path)
+
+;; Runs all the files in the tests subdirectory.
+;; A test fails if it throws an exception.
+
+(define-runtime-path tests-dir "./tests")
+
+(define tests
+  (make-test-suite
+   "syntax tests"
+   (for/list ([t (in-directory tests-dir)])
+     (test-suite
+      (path->string t)
+      (check-not-exn (lambda () (dynamic-require t #f)))))))
+
+(run-tests tests)

collects/tests/syntax/tests/pr12017.rkt

@@ -0,0 +1,20 @@
+#lang racket
+(require (for-syntax racket/struct-info racket/match))
+
+(define-signature sig2^
+  ((struct my-error (v))))
+
+
+(define-unit a-unit@
+  (import)
+  (export sig2^)
+  (define-struct my-error (v)))
+
+(define-values/invoke-unit/infer a-unit@)
+
+(begin-for-syntax
+  struct-info?
+  (match (extract-struct-info (syntax-local-value #'my-error))
+    [(list str m1 m? sels sets _)
+     (unless (= (length sels) (length sets))
+       (error "not the same number of selectors and setters"))]))