syntax/module-reader: make language name after meta-reader syntax-original?

Thanks to Robby for the test.

pkgs/racket-test/tests/syntax/meta-reader-original.rkt

@@ -0,0 +1,13 @@
+#lang racket/base
+(define p (open-input-string "#lang at-exp racket/base\n"))
+(port-count-lines! p)
+(define stx
+  (parameterize ([read-accept-reader #t]
+                 [current-namespace (make-base-namespace)])
+    (expand (read-syntax "x.rkt" p))))
+(define r/b
+  (syntax-case stx ()
+    [(_1 _2 r/b _3 ...) #'r/b]))
+(unless (syntax-original? r/b)
+  (error "module name after `at-exp` is not `syntax-original?`"))
+

racket/collects/syntax/module-reader.rkt

@@ -260,7 +260,11 @@
                              (datum->syntax #f
                                             guarded-spec
                                             (vector src spec-line spec-col spec-pos
-                                                    (max 0 (- spec-end-pos spec-pos))))
+                                                    (max 0 (- spec-end-pos spec-pos)))
+                                            ;; get syntax with `syntax-original?` property:
+                                            (call-with-default-reading-parameterization
+                                             (lambda ()
+                                               (read-syntax 'orig (open-input-bytes #"x")))))
                              guarded-spec))
                         (loop (cdr specs))))
                   (bad spec #f))))))