- Clearly distinguish Exceptions from Errors. The only catchable exception
available in our AST is `EmptyError`, so the corresponding nodes are made less
generic, and a node `FatalError` is added
- Runtime errors are defined as a specific type in the OCaml runtime, with a
carrier exception and printing functions. These are used throughout, and
consistently by the interpreter. They always carry a position, that can be
converted to be printed with the fancy compiler location printer, or in a
simpler way from the backends.
- All operators that might be subject to an error take a position as argument,
in order to print an informative message without relying on backtraces from
the backend
Closes#592
A new node is added in `desugared`, and translated into an exploded structure
literal during translation to `scopelang`. The main reason to put it there is
that it needs to be after disambiguation, since that is used to discover the
type of the structure that is being updated.
They are to become citizens of the same class if we want to allow
output-subscopes (without unnecessary complications like deconstructing and
reconstructing the same structure). And it's reasonable to assume that they
share the same namespace.
With this we should shortly collapse the (internal) ambiguity between
- `subscope.subvar`: access to a variable within a subscope
- `subscope.subfield`: access to a field of the output structure contained in a
subscope variable
With the subscope a variable, these should now become strictly equivalent, so
the plan is that the first could be removed.
The primary use-case for this was to be able to run computations on a list of
structures, then return an updated list with some fields in the structures
modified : that is what we need for distribution of tax amounts among household
members, for example.
This patch has a few components:
- Addition of a test as an example for tax distributions
- Added a transformation, performed during desugaring, that -- where lists are
syntactically expected, i.e. after the `among` keyword -- turns a (syntactic)
tuple of lists into a list of tuples ("zipping" the lists)
- Arg-extremum transformation was also fixed to use an intermediate list instead
of computing the predicate twice
- For convenience, allow to bind multiple variables in most* list
operations (previously only `let in` and functions allowed it)
- Fixed the printer for tuples to differentiate them from lists
*Note: tuples are not yet allowed on the left-hand side of filters and
arg-extremums for annoying syntax conflict reasons.
As part of making tuples first-class citizens, expliciting the arity upon
function application was needed (so that a function of two args can
transparently -- in the surface language -- be applied to either two arguments
or a pair).
It was decided to actually explicit the whole type of arguments because the cost
is the same, and this is consistent with lambda definitions.
A related change done here is the replacement of the `EOp` node for operators by
an "operator application" `EAppOp` node, enforcing a pervasive invariant that
operators are always directly applied. This makes matches terser, and highlights
the fact that the treatment of operator application is almost always different
from function application in practice.
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).
rather than scattered in structures
The context is still hierarchical for defs though, so one needs to retrieve the
path to lookup in the correct context for info. Exceptions are enums and struct
defs, which are re-exposed at toplevel.
This makes sure `catala module` finds the local runtime when run from the catala
source tree; and fixes lookup of the catala exec on custom uses of `clerk runtest`.
This patch functorises the generic expression printer, in order to be able to
re-use it for end-user printing.
It makes it possible to have an end-user, localised printer that shares the code
for e.g. priority and automatic parens handling.
A generic AST rewriting that disambiguates variables (very simple to write with
bindlib) is also added and used in the OCaml backend for something safer than
just appending `_user` (-- this also handles clashing variables that could be
introduced during compilation which would have generated wrong code before this)
Finally, the `explain` plugin is adapted to use the new printer.
Ah, and `String.format_t` was tweaked to correctly print strings that might
contain unicode without breaking alignment, and should be used instead of
`format_string` or `%s` whenever unicode can be expected.
- Use separate functions for successive passes in module `Driver.Passes`
- Use other functions for end results printing in module `Driver.Commands`
As a consequence, it is much more flexible to use by plugins or libs and we no
longer need the complex polymorphic variant parameter.
This patch leverages previous changes to use Cmdliner subcommands and
effectively specialises the flags of each Catala subcommand.
Other changes include:
- an attempt to normalise the generic options and reduce the number of global
references. Some are ok, like `debug` ; some would better be further cleaned up,
e.g. the ones used by Proof backend were moved to a `Proof.globals` module and
need discussion. The printer no longer relies on the global languages and prints
money amounts in an agnostic way.
- the plugin directory is automatically guessed and loaded even in dev setups.
Plugins are shown by the main `catala` command and listed in `catala --help`
- exception catching at the toplevel has been refactored a bit as well; return
codes are normalised to follow the manpage and avoid codes >= 128 that are
generally reserved for shells.
Update tests
(first working dynload test with compilation done by manual calls to ocaml)
A few pieces of the puzzle:
* Loading of interfaces only from Catala files
* Registration of toplevel values in modules compiled to OCaml, to allow access
using dynlink
* Shady conversion from OCaml runtime values to/from Catala expressions, to
allow interop (ffi) of compiled modules and the interpreter
