[ASL] Various features

[HadrienRenaud]

Major features

• [x] .item syntax to access tuple elements.
• [x] Case guards semantics and type-checking.

Type-checking and other safety features

• [x] Non overlapping slices on left-hand-side expressions.
• [x] Prevent empty enumerations.
• [x] Tuples are parameter-defining.
• [x] Ensure getters have corresponding setters.

And some bug fixes.

[HadrienRenaud]

Thanks for the review @Roman-Manevich and @jalglave, I'm merging.