*Disclaimer*: This is intended for discussion
My impression is that the with-exceptions backend is to be superseded by the
without-exception backend, which is more general and more efficient. Therefore,
seeing the added complexity of maintaining the two in parallel, I see no good
reason to keep the with-exceptions version now that the equivalence of their
semantics have been proved.
It will also be nice to reduce divergences between the different backends ; and
this should make further simplifications possible (e.g. some thunkings may no
longer be needed)
Of course I am ready to hear arguments in favor of keeping it, be it in the mid-
or long-term.
This patch removes the `--avoid-exceptions` flag, making it the only option, and
the corresponding `with_exceptions` variant of the dcalc->lcalc translation. It
doesn't do further simplifications.
This is a first step into unifying trace handling. This patch only affects the
interpreter, by delegating trace recording to the already existing runtime
functions.
At end of interpretation, it recovers the registered trace from the runtime, and
prints it.
NOTE: there are some limitations due to this approach, as runtime values going
through this interface have to be converted to the "runtime embedded" type. In
particular, functions can no longer be printed (which makes full sense if we
want it to happen in the same way in compiled code) ; some information, like
types, is lost, but it didn't appear to be used.
Also, a specific printer had to be added for runtime values (but it's very
simple so that shouldn't be a problem).
@denismerigoux I'd like your input on how well this goes for your use-cases.
Further work should probably be cleanup and unification of the runtime logging
interfaces ; there is already code for re-structuring the traces, printing to
JSON, etc. which could be common to runtime and interpreter.
mostly reverting to the ones the interpreter was printing ; for the case of
divisions, we choose to point to the denominator instead of the operator as it's
where the only possible error (division by zero) comes from.
Positions within the Default terms are specially important since they can come
from separate definitions in the source (before this, we would be falling back
to the single declaration).
- 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
Ensuring messages don't print overlong lines still requires some manual work:
- if they don't contain any `Format` directives (`%` or `@`), use `"%a"
Format.pp_print_text` to turn word-wrapping on.
- otherwise replace spaces with `@ ` to mark possible cutting points, as soon
that it's possible the line will get over 80 chars (most often, this means
starting before the first `%a`)
Thanks @denismerigoux
This renames the "ScopeDef" variant from `SubScope` to `SubScopeInput`, which is
much clearer and avoids confusion with the `SubScope` elements in the surface
AST (which are really subscopes and not variables at this point).
And improves some error message by specialising depending on whether we are
dealing with a subscope or an explicit structure.
Lots of tests have a new warning because they were calling subscopes without
using their outputs. A better solution could be to mark these subscopes as
`output`, now that it's possible !
