Implement first version of the custom sigil functionality by enricobolzonello · Pull Request #158 · arialang/aria

enricobolzonello · 2025-09-01T20:00:18Z

Part of #7. In the first version, it allows defining custom sigils, but only with alphabetic characters for now (using identifier created ambiguity in the grammar). Basically, sigils are syntactic sugar around functions: they are stored and called just like functions, but are prefixed with _sigil. However it creates the issue that _sigil is effectively a reserved keyword.
I'm not particularly fond of the use of a separate global register for sigils, but I couldn't come up with anything better: directly translating to functions means that probably using sigils from other modules would be a pain, while registering them as built-ins didn't feel right. I'm open to other possibilities that I have missed.
Next on the todo list is to implement some sigils for the stdlib

egranata · 2025-09-03T17:36:39Z

Hey. This is neat. I may take longer to review than usual. I am on a business trip in Europe and jetlagged right now since I just landed today from the US. I should get to it next week though, once I'm back home. I'll take a look but would rather not merge just yet on account of my limited brain power this week :)

egranata

Some feedback - as I mentioned earlier, I'd rather wait to merge until I am a bit more available, but some early thinks to think about :)

parser-lib/src/grammar/grammar.pest

egranata · 2025-09-04T08:24:38Z

parser-lib/src/grammar/grammar.pest

+postfix_term_object_write =  { "{" ~ postfix_term_write_list ~ "}" }
+postfix_term_enum_case    =  { "::" ~ identifier ~ ("(" ~ expression ~ ")")? }
+postfix_term_sigil        = @{ "_" ~ ASCII_ALPHA+ }
+postfix_term              =  {


If I understand correctly, doing this via a postfix means that - in theory - you can apply sigils to function calls, attribute reads, ... - instead of just a literal? Is that intentional? Do you have use cases in mind?

compiler-lib/src/do_compile/postfix.rs

egranata · 2025-09-04T08:25:55Z

compiler-lib/src/do_compile/postfix.rs

+            PostfixValue::Sigil(base, sigil, loc) => {
+                base.emit_read(params)?;
+
+                let internal_name = format!("__sigil_{sigil}");


IIRC, __ is a reserved prefix, which means you cannot use it as an identifier

wdym? because it seems like that the grammar forbids __ prefixed identifiers in user code, but compiler and vm can create this names (for example __repl_chunk)

Right, right, the VM can do whatever. But it does mean that if you have sigil-A that wants to reuse the code from sigil-B, you can't do it directly, without defining a helper function in the middle. I ran into the same problem when I did the whole operator overloading thing. Initially, I had __op_this_op_that and it meant that if you had operator + and reverse operator +, you couldn't just have one call the other because user code could not use the __ identifier. I fixed it by making the operator functions be _op (single _)

Maybe this is less of a problem for sigils?

docs/manual.md

egranata · 2025-09-04T08:31:53Z

vm-lib/src/builtins/register_sigil.rs

+        vm: &mut crate::vm::VirtualMachine,
+    ) -> crate::vm::ExecutionResult<RunloopExit> {
+        let sigil_name_val = cur_frame.stack.pop();
+        let function = cur_frame.stack.pop();


What happens if I pass a non-function thing here? In theory, I should be able to pass:

a closure

a function

an object with operator call defined

and it should all work, but if I say

register_sigil(foo, 3) then it should fail? Or do you think you should be able to pass anything and then it gets validated at runtime?

Also, what happens if I redefine a sigil? Is that allowed? Should it fail?

it makes more sense to catch errors early, and also to not redefine them. Changed

vm-lib/src/vm.rs

vm-lib/src/sigil_registry.rs

egranata · 2025-09-04T12:19:20Z

I had one thought - say that I have

func foo(x) { ... }
[...]
register_sigil("blah", foo);

val x = 1;
val x_blah = 1;
val y = x_blah; # ???

does x_blah mean x with the blah sigil, or does it mean the variable x_blah? I suspect there is a fundamental ambiguity because _ is a valid character anywhere in identifiers and sigils are allowed on any identifier

A few options I can think of, in no particular order of preference (yet):

we only allow sigils on literal numbers (so 3.14_blah is a sigil valid but x_blah is an identfiier);
we pick a different symbol to mark sigils that is not allowed on identifiers (e.g. how about we only allow $ at the start of an identifier and then do x$blah to mean "x with sigil blah")

Anything I am missing here? Either in terms of possible resolutions or maybe I am wrong about this problem entirely?

egranata · 2025-09-23T04:01:52Z

@enricobolzonello friendly ping if you're still interested in merging this - if not, let me know & I can keep working on it

enricobolzonello · 2025-09-24T08:57:07Z

hey, sorry for the inactivity, got stuck with work. I'm going to work on it this weekend :)

egranata · 2025-09-24T21:22:24Z

hey, sorry for the inactivity, got stuck with work. I'm going to work on it this weekend :)

no worries at all - just checking what you wanted done with this PR :)

egranata

Few questions, but getting closer. Thanks for hacking at this!

egranata · 2025-09-29T16:34:37Z

docs/manual.md

+register_sigil("sigil_name", function_to_call);
+```
+
+Complete example:


am I missing something, or does this code never call register_sigil?

egranata · 2025-09-29T16:35:22Z

parser-lib/src/ast/nodes/postfix_term_sigil.rs

+    fn from_parse_tree(p: pest::iterators::Pair<'_, Rule>, source: &SourceBuffer) -> Self {
+        assert!(p.as_rule() == Rule::postfix_term_sigil);
+        let loc = From::from(&p.as_span());
+        let sigil = p.as_str().strip_prefix("@").unwrap().to_string();


maybe expect instead of unwrap so it crashes with some kind of readable-ish error?

egranata · 2025-09-29T16:36:19Z

tests/sigils.aria

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: Apache-2.0


suggest adding tests for a few things:

free function

method (you do that)

closure

not a callable thing at all

and checking what each does?

egranata · 2025-09-29T16:37:12Z

vm-lib/src/builtins/register_sigil.rs

+        let sigil_name = sigil_name_val.prettyprint(cur_frame, vm);
+
+        let internal_name = format!("__sigil_{sigil_name}");
+        if function.as_function().is_some()


not your problem, but I should probably centralize this code somewhere; once we merge your PR we have 3 places that do this exact resolution

egranata · 2025-09-29T16:39:13Z

vm-lib/src/builtins/register_sigil.rs

+                .is_ok()
+        {
+            if vm.sigil_registry.read(&internal_name).is_some() {
+                return Err(VmErrorReason::OperationFailed(format!(


I am a bit torn on this - on the one hand, most things in Aria can freely be redefined, e.g.

〉struct Foo { ::: type func new() = alloc(This); ::: func bar() = 42; ::: } 〉val f = Foo.new(); 〉f.bar(); 42 〉extension Foo { ::: func bar() = 44; ::: } 〉f.bar(); 44

on the other hand, maybe if your literals break horribly that's a step too far?

egranata · 2025-09-29T16:41:16Z

vm-lib/src/builtins/register_sigil.rs

+}
+
+pub(super) fn insert_builtins(builtins: &mut VmBuiltins) {
+    builtins.insert_builtin::<RegisterSigil>();


should there be a way to read all registered sigils? unregister one? wdyt?

Implement first version of the custom sigil functionality

be6390d

enricobolzonello requested a review from egranata as a code owner September 1, 2025 20:00

egranata requested changes Sep 4, 2025

View reviewed changes

enricobolzonello added 3 commits September 28, 2025 22:06

Change sigil symbol and other fixes

3102fae

Merge branch 'master' into issue-7-custom-sigils

5c5c52f

Do some cleanup

72232b2

egranata requested changes Sep 29, 2025

View reviewed changes

Conversation

enricobolzonello commented Sep 1, 2025

Uh oh!

egranata commented Sep 3, 2025

Uh oh!

egranata left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

egranata commented Sep 4, 2025

Uh oh!

egranata commented Sep 23, 2025

Uh oh!

enricobolzonello commented Sep 24, 2025

Uh oh!

egranata commented Sep 24, 2025

Uh oh!

egranata left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants