Add discard as an alias to empty outputs.

1 files changed, 5 insertions, 2 deletions

diff --git a/chickadee/graphics/seagull.scm b/chickadee/graphics/seagull.scm
index 515c9e1..c5452b0 100644
--- a/chickadee/graphics/seagull.scm
+++ b/chickadee/graphics/seagull.scm
@@ -39,9 +39,8 @@
 ;;
 ;; TODO:
 ;; - Loops
-;; - discard
 ;; - (define ...) form
-;; - struct field aliases (rgba for vec4, for example)
+;; - struct field aliases (rgba for vec4, for example) maybe a bad idea??
 ;; - Scheme shader type -> GLSL struct translation
 ;; - Dead code elimination (error when a uniform is eliminated)
 ;; - User defined structs
@@ -504,6 +503,10 @@
      (expand:cond clauses stage env))
     (('case key clauses ...)
      (expand:case key clauses stage env))
+    (('discard)
+     (if (eq? stage 'fragment)
+         '(outputs)
+         (seagull-syntax-error "discard not allowed in vertex shader" exp expand)))
     ;; Primitive calls:
     (((? primitive-call-for-stage? operator) args ...)
      (expand:primitive-call operator args stage env))