function overload error

code:
```scala
def a(arg : int){}
def a(){}
```

exception:
```
[RedeclarationException] in test.ix[4:4]
Correct syntax errors before type checking can continue.
Redeclaration of variable `a`.
3: def a(arg : int){}
4: def a(){}
^^^^^^
5|
You cannot redeclare variables.
Logged from com.kingmang.ixion.api.Context:addVariableOrError@24
```