.grep propagates .is-lazy

RT#128773

Author: zoffixznet

S32-list/grep.t

@@ -9,7 +9,7 @@ built-in grep tests
 
 =end pod
 
-plan 37;
+plan 39;
 
 my @list = (1 .. 10);
 
@@ -132,4 +132,10 @@ my @list = (1 .. 10);
         'grep is rw-like, can chain it to modify elements of grepped list/array';
 }
 
+# RT #128773
+{
+    is (^∞).grep(*.is-prime).is-lazy, True, '.grep propagates .is-lazy';
+    is (grep *.is-prime, ^∞).is-lazy, True, 'grep() propagates .is-lazy';
+}
+
 # vim: ft=perl6