The dependent eliminator for an inductive predicate C is called C.drec
TODO: construct dcases_on and drec_on using C.drec
We need this recursor for implementing dependent elimination for
inductive predicates.
We don't need to define acc.drec and eq.drec in the standard library anymore.
(Type u) is the old (Type (u+1))
(PType u) is the old (Type u)
Type* is the old (Type (_+1))
PType* is the old Type*
The stdlib can be compiled, but we still have > 70 broken tests
See discussion at #1341
Before this commit, we were inferring whether an
inductive/structure/class were meta or not. This was bad since the user
had no clue whether the type was trusted (non meta) or not.
Moreover, users could get confused by this behavior and assume the
kernel was allowing trusted code to rely on untrusted one.
Now, eta and impredicativity are assumed to be always true.
Motivation: the rest of the system assumes eta.
Regarding impredicativity, we decided to support only the standard library.
