lazy functions with set parameter sizes will report an error if no properly specced. Fixes #1064

src/main/java/carpet/script/Expression.java

@@ -489,6 +489,39 @@ public class Expression
                 return false;
             }
 
+            @Override
+            public LazyValue lazyEval(Context c, Context.Type i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
+            {
+                ILazyFunction.checkInterrupts();
+                if (num_params >= 0 && lazyParams.size() != num_params)
+                    throw new InternalExpressionException("'"+name+"' requires "+num_params+" parameters, "+lazyParams.size()+" provided.");
+
+                try
+                {
+                    return fun.apply(c, i, lazyParams);
+                }
+                catch (RuntimeException exc)
+                {
+                    throw handleCodeException(c, exc, e, t);
+                }
+            }
+        });
+    }
+
+    public void addLazyFunction(String name, TriFunction<Context, Context.Type, List<LazyValue>, LazyValue> fun)
+    {
+        functions.put(name, new AbstractLazyFunction(-1, name)
+        {
+            @Override
+            public boolean pure() {
+                return false;
+            }
+
+            @Override
+            public boolean transitive() {
+                return false;
+            }
+
             @Override
             public LazyValue lazyEval(Context c, Context.Type i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
             {