List of all permitted operations on scope function parameters.

[Loara]

Documentation page 
https://dlang.org/spec/function.html#scope-parameters about 
`scope` function parameters says simply that a scoped parameter 
"can't escape that function's scope". This concept can be very 
tricky with some non-trivial algebra of struct's members and 
pointers, so I think it's better to provide a general algorithm 
to state if an expression/statement involving one or more `scope` 
function parameters is valid or not.