Made combine more consistent for all numeric types

For all boxed primitive numeric types, combine now adds them instead of just integers

Author: SerenaLynas

src/main/java/com/mojang/brigadier/results/CommandResult.java

@@ -18,22 +18,48 @@ public interface CommandResult {
      * @return The combined result
      */
     default Object combine(Object other) {
-        ListCommandResult list = new ListCommandResult();
-        list.combine(this);
-        list.combine(other);
-        return list;
+        return ListCommandResult.from(this, other);
     }
 
+    /**
+     * <p>Combine any objects, even if they are not Command Results.
+     * Target is the object which will be mutated to contain
+     * the combined target and source.
+     * 
+     * <p>If either of the supplied objects are EmptyCommandResult, the
+     * non-empty result will be returned.
+     * 
+     * <p>If the target implements CommandResult, the `combine` method
+     * will be called on the target: `target.combine(source)`
+     * 
+     * <p>If the target and source are the same type of boxed primitive
+     * number (ie Integer, Long, Double, etc.), they will be added together.
+     * 
+     * <p>Otherwise, a new ListCommandResult containing both target and source
+     * will be returned.
+     * 
+     * @param target the object which the source will be combined into
+     * @param source the object to combine into the target
+     */
     static Object combine(Object target, Object source) {
         if (target instanceof CommandResult) {
             return ((CommandResult)target).combine(source);
-        } else if (target instanceof Integer && source instanceof Integer) {
-            // Backwards compatability
-            return (Integer)target + (Integer)source;
         } else if (source instanceof EmptyCommandResult) {
             return target;
+        } else if (target instanceof Byte && source instanceof Byte) {
+            return (byte) target + (byte) source;
+        } else if (target instanceof Short && source instanceof Short) {
+            return (short) target + (short) source;
+        } else if (target instanceof Integer && source instanceof Integer) {
+            return (int) target + (int) source;
+        } else if (target instanceof Long && source instanceof Long) {
+            return (long) source + (long) source;
+        } else if (source instanceof Float && source instanceof Float) {
+            return (float) source + (float) source;
+        } else if (source instanceof Double && target instanceof Double) {
+            return (double) source + (double) target;
         } else {
-            return source;
+            return ListCommandResult.from(target, source);
         }
     }
 }

src/main/java/com/mojang/brigadier/results/ListCommandResult.java

@@ -21,4 +21,11 @@ public ListCommandResult combine(Object other) {
 
         return this;
     }
+
+    public static ListCommandResult from(Object a, Object b) {
+        ListCommandResult list = new ListCommandResult();
+        list = list.combine(a);
+        list = list.combine(b);
+        return list;
+    }
 }