change `define-type' to use #:reflection-name instead of prop:custom-write

collects/plai/datatype.rkt

@@ -143,14 +143,7 @@
                 #:transparent
                 #:omit-define-syntaxes
                 #:mutable
-                #:property
-                prop:custom-write
-                (lambda (v port write?)
-                  ((if write? write display)
-                   (list 'variant
-                         (variant-field v)
-                         ...)
-                   port)))
+                #:reflection-name 'variant)
               ...
               (define variant? 
                 (flat-named-contract 'variant? variant*?))

collects/tests/plai/printer.rkt

@@ -0,0 +1,23 @@
+#lang racket/base
+(require (only-in plai define-type)
+         racket/contract)
+
+(define-type Foo
+  [bar (v any/c)
+       (v2 any/c)])
+
+(define (to-string print v)
+  (let ([s (open-output-string)])
+    (print v s)
+    (get-output-string s)))
+
+(define (check a b) 
+  (unless (equal? a b) (error 'check "failed: ~s vs. ~s" a b)))
+
+(check (to-string print (bar "a" 'b)) "(bar \"a\" 'b)")
+(check (to-string write (bar "a" 'b)) "#(struct:bar \"a\" b)")
+(check (to-string display (bar "a" 'b)) "#(struct:bar a b)")
+
+(check (to-string print (list (bar "a" (list 'b)))) "(list (bar \"a\" '(b)))")
+(check (to-string write (list (bar "a" (list 'b)))) "(#(struct:bar \"a\" (b)))")
+(check (to-string display (list (bar "a" (list 'b)))) "(#(struct:bar a (b)))")