Fix expression evaluation method used for generatebiome

#32

worldedit-core/src/main/java/com/sk89q/worldedit/EditSession.java

@@ -3566,7 +3566,7 @@ public class EditSession extends PassthroughExtent implements AutoCloseable {
                 double scaledZ = (z - zero.getZ()) / unit.getZ();
 
                 try {
-                    if (expression.evaluate(timeout, scaledX, scaledY, scaledZ) <= 0) {
+                    if (expression.evaluate(new double[]{scaledX, scaledY, scaledZ}, timeout) <= 0) {
                         return null;
                     }
 

worldedit-core/src/main/java/com/sk89q/worldedit/command/GenerationCommands.java

@@ -443,7 +443,8 @@ public class GenerationCommands {
             @Selection Region region,
             @Arg(desc = "The biome type to set")
                     BiomeType target,
-            @Arg(desc = "Expression to test block placement locations and set biome type", variable = true)
+            @Arg(desc = "Expression to test block placement locations and set biome type. Requires x,y,z variables be present",
+                    variable = true)
                     List<String> expression,
             @Switch(name = 'h', desc = "Generate a hollow shape")
                     boolean hollow,