Bug 7520: Eliminate redundant type checks for keyword arguments.

* sources/dfmc/harp-cg/harp-main.dylan
  (emit-check-type?): New method controlling when type checks are emitted.
  (emit-computation method on <keyword-check-type>): Remove.
  (emit-computation method on <check-type>): Use emit-check-type? to determine
   when to emit type checks.

sources/dfmc/harp-cg/harp-main.dylan

@@ -1286,18 +1286,23 @@ end method;
 
 // types
 
-define method emit-computation (back-end :: <harp-back-end>, c :: <keyword-check-type>) => ()
-  // MUST EMIT THESE CAUSE THEY CHECK FOR THINGS LIKE SIZE :: <INTEGER> FOR VECTOR
-  emit-type-check(back-end,
-		  emit-reference(back-end, #f, c.computation-value),
-		  c.type);
-  next-method();
-end method emit-computation;
+define method emit-check-type?
+    (back-end :: <harp-back-end>, c :: <check-type>)
+ => (well? :: <boolean>)
+  // Don't emit type checks for the Dylan library
+  ~compiling-dylan-library?()
+end method;
+
+define method emit-check-type?
+    (back-end :: <harp-back-end>, c :: <keyword-check-type>)
+ => (well? :: <boolean>)
+  // We must emit these cause they check for things like size :: <integer>
+  // for vector()
+  #t
+end method;
 
 define method emit-computation (back-end :: <harp-back-end>, c :: <check-type>) => ()
-  if (compiling-dylan-library?())
-    // don't emit type checks for the Dylan library
-  else
+  if (emit-check-type?(back-end, c))
     emit-type-check(back-end,
 		    emit-reference(back-end, #f, c.computation-value),
 		    c.type);