Enhancing error message

[renuccif]

Feature Request

Description of Problem:

When defining a lambda function without typing its arguments, the error message is cryptic: {x|fooBarFunction($x)} // fails with "Function type is not fully defined in {NULL[NULL], NULL[NULL]->NULL[NULL]}". The fooBarFunction has already been defined with appropriate signature, like: fooBarFunction (Argument: Type[n]):ReturnType[m]

Potential Solutions:

Either infer that x is of type Type, or (much simpler) return an error message such as "argument types not defined".