This enforces the new constraint that templates expanding into an `Expr`
context must only inline a single `Expr`.
Perhaps in the future we'll support explicit splicing, like `,@` in
Lisp. But this new restriction is intended for two purposes:
- To make templates more predictable (if you have a list of expressions
inlined then they will act differently depending on the type of
expression that they are inlined into, which means that more defensive
programming would otherwise be required); and
- To make expansion easier, since we're going to have to set aside an
expansion workspace ahead of time to ensure ordering (Petgraph can't
replace edges in-place). If we support multi-expansion, we'd have to
handle associativity in all expression contexts.
This'll become more clear in future commits.
It's nice to see all this hard work coming together now, though; it's easy
now to perform static analysis on the system, and any part of the graph
construction can throw errors with rich diagnostic information and still
recover properly. And, importantly, the system enforces its own state, and
the compiler helps us with that (the previous commits).
DEV-13163
This produces a representation of abstract identifiers on the graph, for
`Expr`s at least. The next step will probably be to get this working
end-to-end in the xmli output before extending it to the other remaining
bindable contexts.
DEV-13163
This allows us to drop `AirIdent::IdentRef`, which in turn allows dropping
`AirIdent` entirely from `AirPkgAggregate`.
This is also a more appropriate abstraction; having to track all the ways in
which `IdentRef` was used can be confusing. This means that `AirIdent` is
true to its name---used only for identifiers. The new token type makes it
very clear where package imports are recognized, and it's also easier to
search for.
DEV-13162
The scope system works with the AIR stack frames, expecting all parent
environments to be on that stack. Since metavariables were (awkwardly) part
of the template parser, that didn't happen.
This change extracts metavariable parsing (with some remaining TODOs) into
its own parser, so that `AirTplAggregate` will be on the stack; then it's a
simple matter of using the existing `AirAggregateCtx` methods to define a
variable and index its shadow scope, which addresses TODOs in the existing
scope test cases.
This also involved separating the tokens from `AirTpl` into `AirMeta`; they
need to be renamed, which will happen in a following commit, since this is
large enough as it is.
Another change that had to be included here, which I wish I could have just
done separately if it wasn't too much work, was to permit overlapping
identifier shadows. Local variables have to cast a shadow so that we can
figure out if they would in turn shadow an identifier (which would be an
error), but they don't conflict with one-another if they don't have a
shared (visible) scope.
`AirAggregate` can be simplified even further, e.g. to eliminate the
expression stack and just use the ctx stack (which didn't previously exist),
but I need to continue; I'll return to it.
DEV-13162
This requires the name as part of the package definition, which in turn
removes a state (and all the combinations resulting from it) from
AirAggregate, which results in significant complexity reduction for a very
complex part of the system.
Pushing this complexity outward results in a reduction of overall
complexity, and obviates the question of where NIR will receive a generated
name.
DEV-13162
I had apparently forgotten about this, because I didn't benefit from the
exhaustiveness check; this needs to be eliminated so that this doesn't
happen again, and to provide a proper non-panicking error.
DEV-13162
This change requires every package to have a canonical name, and performs
namespec canonicalization on imports.
Since all package names are canonicalized, this opens the door to being able
to index package names at import, allowing the object to be shared on the
graph and properly reference a package after it has been resolved.
Note that the system tests' canonicalization is relative to the hard-coded
`/TODO` presently; that will change in the near future once `tamec`
generates names from the provided path.
DEV-13162
The previous commit introduced canonical names, and this uses them to index.
The next step will be to utilize those names to look up packages on
definition rather than creating a new package node, so that references to
yet-to-be-defined (or yet-to-be-imported) packages can be resolved on the
graph.
DEV-13162
This is already a concept in the XSLT-based compiler, where each package has
a `package/@name` generated from its path. The same will happen with tamec.
Before we can load packages into the graph, we need canonical identifiers so
that they can be indexed. The next commit will handle indexing using this
information.
DEV-13162
This introduces cycle detection, but it does not yet filter ontologically
permitted cycles, which will be needed prior to utilizing this in `tameld`.
There's a considerable amount of documentation here. While the
implementation is fairly simple, there are important algorithmic decisions,
both in the DFS construction and the derivation of the cycle path from data
that already exists.
This also supports recovery (by ignoring cycles), which can then be utilized
to find more cycles and other errors in the system.
DEV-13162
This supports arbitrary documentation as sibling text (mixed content, in XML
terms). The motivation behind this change is to permit existing system
tests to succeed when `Todo | TodoAttr` are both rejected, rather than
having to ignore this.
TAME has always had a philosophy of literate documentation, however it was
never fully realized. This just maintains the status quo; the text is
unstructured, and maybe will be parsed in the future.
Unfortunately, this does _not_ include the output in the `xmli` file or the
system tests. The reason has nothing to do with TAMER---`xmllint` does not
format the output when there is mixed content, it seems, and I need to move
on for now; I'll consider my options in the future. But, it's available on
the graph and ready to go.
DEV-13708
There are no such invalid expansion contexts yet, but this gets rid of the
final remaining TODO from introducing the stack. With the existing feature
set, at least.
DEV-13708
This eliminates the TODOs that existed when looking for an OI for rooting an
identifier.
The change to `rooting_ci` is ridiculous, but I want to get other things
done before I jump down the rabbit hole of generalizing that (indexing local
identifiers). Though I have an approach in mind.
DEV-13708
`AirAggregate` now handles all delegation to `AirExprAggregate`. This is
possible because `AirAggregate` is now the superstate for each of these
parsers, so `AirTplAggregate` is able to transition to a state that is not
its own.
This does not go so far as reaching the ultimate objective---having nested
template support---even though it'd be fairly simple to do now; there's
going to be a number of interesting consequences to these changes, and a bit
of cleanup is still needed, and I want tests observing this functionality to
accompany those changes. That is: let's keep this a refactoring, to the
extent that it's possible.
Things are getting much easier to understand now, and much cleaner.
DEV-13708
This this a big change that's difficult to break up, and I don't have the
energy after it.
This introduces nullary template application, short- and long-form. Note
that a body of the short form is a `@values@` argument, so that's not
supported yet.
This continues to formalize the idea of what "template application" and
"template expansion" mean in TAMER. It makes a separate `TplApply`
unnecessary, because now application is simply a reference to a
template. Expansion and application are one and the same: when a template
expands, it'll re-bind metavariables to the parent context. So in a
template context, this amounts to application.
But applying a closed template will have nothing to bind, and so is
equivalent to expansion. And since `Meta` objects are not valid outside of
a `Tpl` context, applying a non-closed template outside of another template
will be invalid.
So we get all of this with a single primitive (getting the "value" of a
template).
The expansion is conceptually like `,@` in Lisp, where we're splicing trees.
It's a mess in some spots, but I want to get this committed before I do a
little bit of cleanup.
See the Air docblock for more information. I'm introducing new tokens for
the template system, which uses the terms "free" and "closed". I prefer
open/close for delimiters, as I've expressed elsewhere, but unfortunately it
conflicts too much (and too confusingly) with other standard terminology as
we get more into the formal side of the language.
DEV-13708
And finally we have tokens aggregated onto the ASG in the context of a
template. I expected to arrive here much more quickly, but there was a lot
of necessary refactoring. There's a lot more that could be done, but I need
to continue; I had wanted this done a week ago.
It is worth noting, though, that this finally achieves something I had been
wondering about since the inception of this project---how I'd represent
templates on the graph. I think this worked out rather nicely. It wasn't
even until a few months ago that I decided to use AIR instead of NIR for
that purpose (NIR wouldn't have worked).
And note how I didn't have to touch the program derivation at all---the
system test just works with the AIR change, because of the consistent
construction of the graph. Beautiful.
DEV-13708
This sets the stage for template parsing, and finally decides how we're
going to represent templates on the ASG. This is going to start simple,
since my original plans for improving how templates are
handled (conceptually) is going to have to wait.
This is the last difficult object type to figure out, with respect to graph
representation and derivation, so I wanted to get it out of the way.
DEV-13708
This does not yet create edges from identifiers to the package; just getting
this introduced was quite a bit of work, so I want to get this committed.
Note that this also includes a change to NIR so that `Close` contains the
entity so that we can pattern-match for AIR transformations rather than
retaining yet another stack with checks that are already going to be done by
AIR. This makes NIR stand less on its own from a self-validation point, but
that's okay, given that it's the language that the user entered and,
conceptually, they could enter invalid NIR the same as they enter invalid
XML (e.g. from a REPL).
In _practice_, of course, NIR is lowered from XML and the schema is enforced
during that lowering and so the validation does exist as part of that
parsing.
These concessions speak more to the verbosity of the language (Rust) than
anything.
DEV-13159
This adds support for identifier references, adding `Ident` as a valid edge
type for `Expr`.
There is nothing in the system yet to enforce ontology through levels of
indirection; that will come later on.
I'm testing these changes with a very minimal NIR parse, which I'll commit
shortly.
DEV-13597
This provides the initial implementation allowing an identifier to be
defined (bound to an object and made transparent).
I'm not yet entirely sure whether I'll stick with the "transparent" and
"opaque" terminology when there's also "declare" and "define", but a
`Missing` state is a type of declaration and so the distinction does still
seem to be important.
There is still work to be done on `ObjectIndex::<Ident>::bind_definition`,
which will follow. I'm going to be balancing work to provide type-level
guarantees, since I don't have the time to go as far as I'd like.
DEV-13597
This addresses the two outstanding `todo!` match arms representing errors in
lowering expressions into the graph. As noted in the comments, these errors
are unlikely to be hit when using TAME in the traditional way, since
e.g. XIR and NIR are going to catch the equivalent problems within their own
contexts (unbalanced tags and a valid expression grammar respectively).
_But_, the IR does need to stand on its own, and I further hope that some
tooling maybe can interact more directly with AIR in the future.
DEV-13160
This begins to place expressions on the graph---something that I've been
thinking about for a couple of years now, so it's interesting to finally be
doing it.
This is going to evolve; I want to get some things committed so that it's
clear how I'm moving forward. The ASG makes things a bit awkward for a
number of reasons:
1. I'm dealing with older code where I had a different model of doing
things;
2. It's mutable, rather than the mostly-functional lowering pipeline;
3. We're dealing with an aggregate ever-evolving blob of data (the graph)
rather than a stream of tokens; and
4. We don't have as many type guarantees.
I've shown with the lowering pipeline that I'm able to take a mutable
reference and convert it into something that's both functional and
performant, where I remove it from its container (an `Option`), create a new
version of it, and place it back. Rust is able to optimize away the memcpys
and such and just directly manipulate the underlying value, which is often a
register with all of the inlining.
_But_ this is a different scenario now. The lowering pipeline has a narrow
context. The graph has to keep hitting memory. So we'll see how this
goes. But it's most important to get this working and measure how it
performs; I'm not trying to prematurely optimize. My attempts right now are
for the way that I wish to develop.
Speaking to #4 above, it also sucks that I'm not able to type the
relationships between nodes on the graph. Rather, it's not that I _can't_,
but a project to created a typed graph library is beyond the scope of this
work and would take far too much time. I'll leave that to a personal,
non-work project. Instead, I'm going to have to narrow the type any time
the graph is accessed. And while that sucks, I'm going to do my best to
encapsulate those details to make it as seamless as possible API-wise. The
performance hit of performing the narrowing I'm hoping will be very small
relative to all the business logic going on (a single cache miss is bound to
be far more expensive than many narrowings which are just integer
comparisons and branching)...but we'll see. Introducing branching sucks,
but branch prediction is pretty damn good in modern CPUs.
DEV-13160
This finally uses `parse` all the way up to aggregation into the ASG, as can
be seen by the mess in `poc`. This will be further simplified---I just need
to get this committed so that I can mentally get it off my plate. I've been
separating this commit into smaller commits, but there's a point where it's
just not worth the effort anymore. I don't like making large changes such
as this one.
There is still work to do here. First, it's worth re-mentioning that
`poc` means "proof-of-concept", and represents things that still need a
proper home/abstraction.
Secondly, `poc` is retrieving the context of two parsers---`LowerContext`
and `Asg`. The latter is desirable, since it's the final aggregation point,
but the former needs to be eliminated; in particular, packages need to be
worked into the ASG so that `found` can be removed.
Recursively loading `xmlo` files still happens in `poc`, but the compiler
will need this as well. Once packages are on the ASG, along with their
state, that responsibility can be generalized as well.
That will then simplify lowering even further, to the point where hopefully
everything has the same shape (once final aggregation has an abstraction),
after which we can then create a final abstraction to concisely stitch
everything together. Right now, Rust isn't able to infer `S` for
`Lower<S, LS>`, which is unfortunate, but we'll be able to help it along
with a more explicit abstraction.
DEV-11864
This is the beginning of an incremental refactoring to remove generics, to
simplify the ASG. When I initially wrote the linker, I wasn't sure what
direction I was going in, but I was also negatively influenced by more
traditional approaches to both design and unit testing.
If we're going to call the ASG an IR, then it needs to be one---if the core
of the IR is generic, then it's more like an abstract data structure than
anything. We can abstract around the IR to slice it up into components that
are a little easier to reason about and understand how responsibilities are
segregated.
DEV-11864
Mike Gerwitz