feat: Allow arguments to attribute functions (noir-lang#5494)

# Description

## Problem\*

Resolves noir-lang#5473
Resolves noir-lang#5476

## Summary\*

Allows arguments to attribute functions.
- These arguments are all quoted by default. This is to replicate
something like Rust's `#[derive(Foo, Bar)]` where `Foo` and `Bar` are
meant to be traits rather than values in scope.
- Varargs is also possible if the attribute accepts a slice of Quoted
values rather than individual Quoted arguments.

## Additional Context

## Documentation\*

Check one:
- [ ] No documentation needed.
- [ ] Documentation included in this PR.
- [x] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

compiler/noirc_frontend/src/elaborator/mod.rs

@@ -26,6 +26,7 @@ use crate::{
         traits::TraitConstraint,
         types::{Generics, Kind, ResolvedGeneric},
     },
+    lexer::Lexer,
     macros_api::{
         BlockExpression, Ident, NodeInterner, NoirFunction, NoirStruct, Pattern,
         SecondaryAttribute, StructId,
@@ -35,6 +36,7 @@ use crate::{
         TypeAliasId,
     },
     parser::TopLevelStatement,
+    token::Tokens,
     Shared, Type, TypeBindings, TypeVariable,
 };
 use crate::{
@@ -1284,18 +1286,24 @@ impl<'context> Elaborator<'context> {
         span: Span,
         generated_items: &mut CollectedItems,
     ) -> Result<(), (CompilationError, FileId)> {
+        let location = Location::new(span, self.file);
+        let (function_name, mut arguments) =
+            Self::parse_attribute(&attribute, location).unwrap_or((attribute, Vec::new()));
+
         let id = self
-            .lookup_global(Path::from_single(attribute, span))
+            .lookup_global(Path::from_single(function_name, span))
             .map_err(|_| (ResolverError::UnknownAnnotation { span }.into(), self.file))?;
 
         let definition = self.interner.definition(id);
         let DefinitionKind::Function(function) = definition.kind else {
             return Err((ResolverError::NonFunctionInAnnotation { span }.into(), self.file));
         };
-        let location = Location::new(span, self.file);
+
+        self.handle_varargs_attribute(function, &mut arguments, location);
+        arguments.insert(0, (Value::StructDefinition(struct_id), location));
+
         let mut interpreter_errors = vec![];
         let mut interpreter = self.setup_interpreter(&mut interpreter_errors);
-        let arguments = vec![(Value::StructDefinition(struct_id), location)];
 
         let value = interpreter
             .call_function(function, arguments, TypeBindings::new(), location)
@@ -1313,6 +1321,59 @@ impl<'context> Elaborator<'context> {
         Ok(())
     }
 
+    /// Parses an attribute in the form of a function call (e.g. `#[foo(a b, c d)]`) into
+    /// the function and quoted arguments called (e.g. `("foo", vec![(a b, location), (c d, location)])`)
+    fn parse_attribute(
+        annotation: &str,
+        location: Location,
+    ) -> Option<(String, Vec<(Value, Location)>)> {
+        let (tokens, errors) = Lexer::lex(annotation);
+        if !errors.is_empty() {
+            return None;
+        }
+
+        let mut tokens = tokens.0;
+        if tokens.len() >= 4 {
+            // Remove the outer  `ident ( )` wrapping the function arguments
+            let first = tokens.remove(0).into_token();
+            let second = tokens.remove(0).into_token();
+
+            // Last token is always an EndOfInput
+            let _ = tokens.pop().unwrap().into_token();
+            let last = tokens.pop().unwrap().into_token();
+
+            use crate::lexer::token::Token::*;
+            if let (Ident(name), LeftParen, RightParen) = (first, second, last) {
+                let args = tokens.split(|token| *token.token() == Comma);
+                let args =
+                    vecmap(args, |arg| (Value::Code(Rc::new(Tokens(arg.to_vec()))), location));
+                return Some((name, args));
+            }
+        }
+
+        None
+    }
+
+    /// Checks if the given attribute function is a varargs function.
+    /// If so, we should pass its arguments in one slice rather than as separate arguments.
+    fn handle_varargs_attribute(
+        &mut self,
+        function: FuncId,
+        arguments: &mut Vec<(Value, Location)>,
+        location: Location,
+    ) {
+        let meta = self.interner.function_meta(&function);
+        let parameters = &meta.parameters.0;
+
+        // If the last parameter is a slice, this is a varargs function.
+        if parameters.last().map_or(false, |(_, typ, _)| matches!(typ, Type::Slice(_))) {
+            let typ = Type::Slice(Box::new(Type::Quoted(crate::QuotedType::Quoted)));
+            let slice_elements = arguments.drain(..).map(|(value, _)| value);
+            let slice = Value::Slice(slice_elements.collect(), typ);
+            arguments.push((slice, location));
+        }
+    }
+
     pub fn resolve_struct_fields(
         &mut self,
         unresolved: NoirStruct,

compiler/noirc_frontend/src/hir/def_collector/dc_crate.rs

@@ -202,7 +202,7 @@ pub enum CompilationError {
 }
 
 impl CompilationError {
-    fn is_error(&self) -> bool {
+    pub fn is_error(&self) -> bool {
         let diagnostic = CustomDiagnostic::from(self);
         diagnostic.is_error()
     }

cspell.json

@@ -206,6 +206,8 @@
         "unoptimized",
         "urem",
         "USERPROFILE",
+        "vararg",
+        "varargs",
         "vecmap",
         "vitkov",
         "wasi",

test_programs/compile_success_empty/attribute_args/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "attribute_args"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.31.0"
+
+[dependencies]

test_programs/compile_success_empty/attribute_args/src/main.nr

@@ -0,0 +1,20 @@
+#[attr_with_args(a b, c d)]
+#[varargs(one, two)]
+#[varargs(one, two, three, four)]
+struct Foo {}
+
+comptime fn attr_with_args(s: StructDefinition, a: Quoted, b: Quoted) {
+    // Ensure all variables are in scope.
+    // We can't print them since that breaks the test runner.
+    let _ = s;
+    let _ = a;
+    let _ = b;
+}
+
+comptime fn varargs(s: StructDefinition, t: [Quoted]) {
+    let _ = s;
+    for _ in t {}
+    assert(t.len() < 5);
+}
+
+fn main() {}