Nonexistent types in function arguments aren't detected

[David Holland]

Consider the following otherwise useless script with a typo in it:

typedef FooType = {
   Thingy : (() -> ())
};

let foo_id (foo : FooTYpe) = foo;

It seems like this should not be allowed, because it names a type that doesn't exist. However, it's accepted silently.

This gets substantially more confusing if you try to access the members of the type:

typedef FooType = {
   Thingy : (() -> ())
};

let do_thingy (foo : FooTYpe) = foo.Thingy ();

because now it fails with the error Record lookup on non-record argument. If you can't spot the typo (or worse, you've got a name with multiple plausible spellings and you're using the wrong one, like Grey and Gray) this is horribly frustrating.

[Ryan Scott]

In the example above, FooTYpe is treated as a type variable. Type variables can begin with either lower or uppercase in SAWScript, and if a name does not refer to an existing identifier, then it is treated as a type variable:

sawscript> :type foo_id
{a.0} a.0 -> a.0

I can see why this would be confusing, although this is behaving as expected in some sense. Perhaps we could mention this in the SAW manual?

[David Holland]

Shouldn't (in the case where it's used at least, like in do_thingy) it then infer that it's a struct type, namely the same type that would be inferred for the function's return struct if there weren't an annotation? That would still produce somewhat unexpected behavior when there's a type conflict later on, but it wouldn't have the same flavor of "why is this just ignoring what I'm telling it and what do I even do about it?"

(also in the long run I would be all for moving to explicit declaration of type variables like Cryptol, but that's not a change one can just make arbitrarily)

[Ryan Scott]

Indeed, SAWScript's type inference could stand to be improved in this regard. See also #1995.

[David Holland]

Hmm in that case there's probably no need to keep this issue open

[David Holland]

Oops, wrong kind of close

[David Holland]

ok then, how about closing it as invalid?