Make Tuple and NamedTuples .types to return tuples of metaclasses

[bcardiff]

Fixes #4737

Tuple#types return a tuple value now. Instead of a tuple type.
An analogous NamedTuple#types is added.
Since this methods depends only on the generic argument they can be class methods also/instead(?).

There is a small duplication hard to track in the compiler specs.
I am not sure if the specs should have some conditional like the one that was added before

[oprypin]

Tuple#types seems redundant
especially if you consider for an analogy that sizeof(obj) does not work

[bcardiff]

Another slightly inconsistency I found is that in macro interpreter given a generic type one can ask type_vars (that result in an ArrayLiteral, src-1 & src-2) and named_args (that result in an NamedTupleLiteral, src-3). The later matches NamedTuple.types, but the former maybe should return a TupleLiteral instead of an ArrayLiteral

[bcardiff]

I would prefer to remove the Tuple and NamedTuple types instance methods and leave only the class methods. 👍 / 👎 ? At most is a tuple.class.types vs tuple.types.

[asterite]

@bcardiff I don't think the semantic/codegen specs need to change, these don't require the prelude. They are testing that T is available as a tuple.

[bcardiff]

Ok @asterite I will rollback that but change slightly the compiled code in spec to avoid confusion with the stdlib implementation.

[bcardiff]

New shot with cleaned commit history. The commit c654908 is not actually regarding the NamedTuples.types method but is a missing piece to align the behavior of named tuples and tuples metaclasses. While doing it I enforce some checks in the semantic and codegen since the TupleIndexer ast node handling was assuming a tuple metaclass as the default case.

[luislavena]

Could we add another example accessing types from the instance?

tuple = {a: 1, b: "hello", c: 'x'}
tuple.class.types # => {a: Int32, b: String, c: Char}

That will avoid some people trying to do tuple.types by mistake.

😁

[bcardiff]

Sure. I will just change to your example. It's actually like the specs your suggestion.