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`)
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 !