Remove dependence on specific Infos

[UnsignedByte]

@ethanuppal has mentioned issues that arise when every info is set to empty. This is something that arises from the info_cast macro defined in info.rs:

filament/crates/ir/src/info.rs

Lines 264 to 298 in 1f95254

	macro_rules! info_cast {
	($class:tt, $name:ident) => {
	impl Info {
	pub fn $name(&self) -> Option<&$class> {
	match self {
	Self::$class(v) => Some(v),
	Self::Empty(_) => None,
	_ => unreachable!(
	"Incorrect info type for {}.",
	stringify!($class)
	),
	}
	}
	}
	impl<'a> From<&'a Info> for &'a $class {
	fn from(info: &'a Info) -> Self {
	if let Info::$class(v) = info {
	v
	} else {
	unreachable!(
	"Incorrect info type for {}.",
	stringify!($class)
	);
	}
	}
	}
	impl<'a> From<&'a Info> for Option<&'a $class> {
	fn from(info: &'a Info) -> Self {
	info.$name()
	}
	}
	};
	}

It defines the From trait for infos, which panics if the incorrect info type is found. This is used in certain locations primarily to generate ir::Info::Reasons for constraints (some listed below). These should theoretically just return Info::Empty if either of the parents is missing, rather than panicking, so that we could remove the dependency on info entirely throughout the IR.

We should instead implement TryFrom or instead just directly force the user to use the as_type functions that are already defined.

Non-exhaustive examples

filament/crates/filament/src/ir_passes/type_check.rs

Lines 28 to 36 in 1f95254

	let &ir::info::Port { bind_loc, .. } = comp.get(*info).into();
	let wf = comp.add(
	ir::info::Reason::misc(
	"end of port access must greater than the start",
	loc,
	)
	.into(),
	);

filament/crates/filament/src/ir_passes/interval_check.rs

Lines 91 to 112 in 1f95254

	let &ir::info::EventBind {
	ev_delay_loc,
	bind_loc,
	} = comp.get(*info).into();
	let this_ev = &comp[comp[*arg].event];
	let this_delay = this_ev.delay.clone();
	let &ir::info::Event {
	delay_loc: ev_del_loc,
	..
	} = comp.get(this_ev.info).into();
	let reason = comp.add(
	ir::info::Reason::event_trig(
	ev_delay_loc,
	inv_delay.clone(),
	ev_del_loc,
	this_delay.clone(),
	bind_loc,
	)
	.into(),
	);

[rachitnigam]

Hm, some of these are tricky because they are not quite "info" (i.e., optional things that you are allowed to forget)...

[UnsignedByte]

What do you mean by this? I was under the assumption that the ir::Info::Reasons were used purely for pretty printing diagnostics if they occurred, and that the assumptions added could still be done with Info::Empty instead?

[rachitnigam]

The two examples you quoted have info::EventBind and info::Port

[UnsignedByte]

Yes but those are just used to get bind_locs to generate the other infos, so are not really necessary either (just propogate empties or loc::unknown)

[ethanuppal]

In my code I was pretty safe to just fill dummy infos with no location — that being said, I couldn't figure out how to actually get invocations working, so maybe invocations have a legitimate dependency on AST location info