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commit 4dcb1230b895ba5dd896eb069c6ffebec05aa972
parent caeda2ff0dc5f370a8a7203817384c8ff10a1bd5
Author: Stephen Chang <stchang@ccs.neu.edu>
Date:   Fri, 15 Aug 2014 16:21:58 -0400

stlc: add extensibility note in define-type

Diffstat:
M
stlc.rkt
 | 
9
+++++++++

1 file changed, 9 insertions(+), 0 deletions(-)
diff --git a/stlc.rkt b/stlc.rkt
@@ -201,6 +201,15 @@
 
 
 (begin-for-syntax
+  ;; EXTENSIBILITY NOTE:
+  ;; Originally, define-type was a #:literal instead of a #:datum-literal, but
+  ;; this became a problem when sysf extended define-type (but not modul-begin).
+  ;; Putting define-type in the #:literals list makes it always expect the stlc
+  ;; version of define-type, so it wasnt getting properly parsed in sysf.
+  ;;
+  ;; Similarly, I had to define the define-type pattern below to avoid explicitly
+  ;; mentioning define-type on the rhs, otherwise it would again lock in the stlc
+  ;; version of define-type.
   (define-syntax-class maybe-def #:datum-literals (: define variant define-type)
     (pattern (define (f:id [x:id : τx] ...) body ...)
              #:with τ_result (generate-temporary #'f)