Creates a RecType, normalizing its contents. This means:
Creates a RecType, normalizing its contents. This means:
Nested Rec types on the type's spine are merged with the outer one.
Any refinement of the form type T = z.T on the spine of the type where z refers to the created rec-type is replaced by type T. This avoids infinite recursions later when we try to follow these references.
Value parameters
parentExp
a function that takes the recursive type itself and returns its underlying type
