feat: Implement slice_push_back in the comptime interpreter

compiler/noirc_frontend/src/hir/comptime/interpreter/builtin.rs

@@ -19,6 +19,7 @@ pub(super) fn call_builtin(
     match name {
         "array_len" => array_len(&arguments),
         "as_slice" => as_slice(arguments),
+        "slice_push_back" => slice_push_back(arguments),
         "type_def_as_type" => type_def_as_type(interner, arguments),
         "type_def_generics" => type_def_generics(interner, arguments),
         "type_def_fields" => type_def_fields(interner, arguments),
@@ -48,6 +49,20 @@ fn as_slice(mut arguments: Vec<(Value, Location)>) -> IResult<Value> {
     }
 }
 
+fn slice_push_back(mut arguments: Vec<(Value, Location)>) -> IResult<Value> {
+    assert_eq!(arguments.len(), 2, "ICE: `slice_push_back` should only receive two arguments");
+    let (element, _) = arguments.pop().unwrap();
+    let (slice, _) = arguments.pop().unwrap();
+    match slice {
+        Value::Slice(mut values, typ) => {
+            values.push_back(element);
+            Ok(Value::Slice(values, typ))
+        }
+        // Type checking should prevent this branch being taken.
+        _ => unreachable!("ICE: `slice_push_back` expects a slice as its first argument"),
+    }
+}
+
 /// fn as_type(self) -> Quoted
 fn type_def_as_type(
     interner: &NodeInterner,

test_programs/compile_success_empty/derive_impl/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "derive_impl"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.30.0"
+
+[dependencies]

test_programs/compile_success_empty/derive_impl/src/main.nr

@@ -0,0 +1,44 @@
+comptime fn derive_default(typ: TypeDefinition) -> Quoted {
+    let generics: [Quoted] = typ.generics();
+    assert_eq(
+        generics.len(), 0, "derive_default: Deriving Default on generic types is currently unimplemented"
+    );
+
+    let type_name = typ.as_type();
+    let fields = typ.fields();
+
+    let fields = join(make_field_exprs(fields));
+
+    quote {
+        impl Default for $type_name {
+            fn default() -> Self {
+                Self { $fields }
+            }
+        }
+    }
+}
+
+#[derive_default]
+struct Foo {
+    x: Field,
+    y: u32,
+}
+
+comptime fn make_field_exprs(fields: [(Quoted, Quoted)]) -> [Quoted] {
+    let mut result = &[];
+    for my_field in fields {
+        let name = my_field.0;
+        result = result.push_back(quote { $name: Default::default(), });
+    }
+    result
+}
+
+comptime fn join(slice: [Quoted]) -> Quoted {
+    let mut result = quote {};
+    for elem in slice {
+        result = quote { $result $elem };
+    }
+    result
+}
+
+fn main() {}