unimplemented semantic related errors

[jldav1d]

Unimplemented semantic related issues

• type checking for return types in function definition
• type checking for var assignment using function calls (ex. whole i = func()# | func() must return a value of the same type )
• type checking when assigning a value for array elements (ex. w_seq[0] = 1# )
• constant var checks for reassignment (reassigning a value for const var is not allowed)
• scope checks in nested code blocks