Added a new type safety invariant to ensure that the type `TDefault` can only appear in certain positions,
* On the left-hand side of an arrow with arity 1, as the type of a scope (for scope calls).
* At the root of the type tree (outside a default).
* On the right-hand side of the arrow at the root of the type (occurs for rentrant variables).
This is crucial to maintain the safety of the type system, as demonstrated in the formal development.
The invariant was checked on all tests cases and on family and housing benefits.
Adjusted inversion invariant about app to handle external objects as well.
This changes the `decl_ctx` to be toplevel only, with flattened references to
uids for most elements. The module hierarchy, which is still useful in a few
places, is kept separately.
Module names are also changed to UIDs early on, and support for module aliases
has been added (needs testing).
This resolves some issues with lookup, and should be much more robust, as well
as more convenient for most lookups.
The `decl_ctx` was also extended for string ident lookups, which avoids having
to keep the desugared resolution structure available throughout the compilation
chain.
- Add a `-I` option that allows defined modules to be available from other
directories
- Add reporting of the number of successful / failed tests
- Locate the project root, and always run the commands from there
The way nested priorities are encoded use `< < excs | true :- nested > :- x >`,
which imply that `nested` can actually be ∅ ; to cope with this, the typing of
default terms is made more generic (the return type is now the same as the
`cons` type `'a`, rather than `<'a>`). For the general case, we add an explicit
`EPureDefault` node which just encapsulates its argument (a `return`, in monad
terminology).
