Fix for #577

This was a simple problem where the count component of an array
generator expression was not being checked as an int.

modules/wyc/src/wyc/builder/FlowTypeChecker.java

@@ -1739,10 +1739,11 @@ private Expr propagate(Expr.ArrayInitialiser expr, Environment environment, Cont
 		return expr;
 	}
 
-	private Expr propagate(Expr.ArrayGenerator expr, Environment environment, Context context) {
+	private Expr propagate(Expr.ArrayGenerator expr, Environment environment, Context context) {		
 		expr.element = propagate(expr.element, environment, context);
-		expr.count = propagate(expr.count, environment, context);
+		expr.count = propagate(expr.count, environment, context);		
 		expr.type = Nominal.Array(expr.element.result(), true);
+		checkIsSubtype(Type.T_INT, expr.count);
 		return expr;
 	}
 

tests/invalid/ListGenerator_Invalid_4.sysout

@@ -1,3 +1,3 @@
-../../tests/invalid/ListGenerator_Invalid_4.whiley:0: operand types are not compatible (bool vs int)
-
-^
+../../tests/invalid/ListGenerator_Invalid_4.whiley:2: expected type int, found byte
+    return [0; n]
+               ^