core/typecheck/typedef: Add vararg to Unifier::stringify

nac3artiq/src/codegen.rs

@@ -386,7 +386,7 @@ fn gen_rpc_tag(
     } else {
         let ty_enum = ctx.unifier.get_ty(ty);
         match &*ty_enum {
-            TTuple { ty } => {
+            TTuple { ty, is_vararg_ctx: false } => {
                 buffer.push(b't');
                 buffer.push(ty.len() as u8);
                 for ty in ty {
@@ -700,6 +700,7 @@ pub fn attributes_writeback(
                     name: i.to_string().into(),
                     ty: *ty,
                     default_value: None,
+                    is_vararg: false,
                 })
                 .collect(),
             ret: ctx.primitives.none,

nac3artiq/src/lib.rs

@@ -264,7 +264,7 @@ impl Nac3 {
                     arg_names.len(),
                 ));
             }
-            for (i, FuncArg { ty, default_value, name }) in args.iter().enumerate() {
+            for (i, FuncArg { ty, default_value, name, .. }) in args.iter().enumerate() {
                 let in_name = match arg_names.get(i) {
                     Some(n) => n,
                     None if default_value.is_none() => {
@@ -863,6 +863,7 @@ impl Nac3 {
                         name: "t".into(),
                         ty: primitive.int64,
                         default_value: None,
+                        is_vararg: false,
                     }],
                     ret: primitive.none,
                     vars: VarMap::new(),
@@ -882,6 +883,7 @@ impl Nac3 {
                         name: "dt".into(),
                         ty: primitive.int64,
                         default_value: None,
+                        is_vararg: false,
                     }],
                     ret: primitive.none,
                     vars: VarMap::new(),

nac3artiq/src/symbol_resolver.rs

@@ -351,7 +351,7 @@ impl InnerResolver {
             Ok(Ok((ndarray, false)))
         } else if ty_id == self.primitive_ids.tuple {
             // do not handle type var param and concrete check here
-            Ok(Ok((unifier.add_ty(TypeEnum::TTuple { ty: vec![] }), false)))
+            Ok(Ok((unifier.add_ty(TypeEnum::TTuple { ty: vec![], is_vararg_ctx: false }), false)))
         } else if ty_id == self.primitive_ids.option {
             Ok(Ok((primitives.option, false)))
         } else if ty_id == self.primitive_ids.none {
@@ -555,7 +555,10 @@ impl InnerResolver {
                             Err(err) => return Ok(Err(err)),
                             _ => return Ok(Err("tuple type needs at least 1 type parameters".to_string()))
                         };
-                    Ok(Ok((unifier.add_ty(TypeEnum::TTuple { ty: args }), true)))
+                    Ok(Ok((
+                        unifier.add_ty(TypeEnum::TTuple { ty: args, is_vararg_ctx: false }),
+                        true,
+                    )))
                 }
                 TypeEnum::TObj { params, obj_id, .. } => {
                     let subst = {
@@ -797,7 +800,9 @@ impl InnerResolver {
                     .map(|elem| self.get_obj_type(py, elem, unifier, defs, primitives))
                     .collect();
                 let types = types?;
-                Ok(types.map(|types| unifier.add_ty(TypeEnum::TTuple { ty: types })))
+                Ok(types.map(|types| {
+                    unifier.add_ty(TypeEnum::TTuple { ty: types, is_vararg_ctx: false })
+                }))
             }
             // special handling for option type since its class member layout in python side
             // is special and cannot be mapped directly to a nac3 type as below
@@ -1196,7 +1201,9 @@ impl InnerResolver {
             Ok(Some(ndarray.as_pointer_value().into()))
         } else if ty_id == self.primitive_ids.tuple {
             let expected_ty_enum = ctx.unifier.get_ty_immutable(expected_ty);
-            let TypeEnum::TTuple { ty } = expected_ty_enum.as_ref() else { unreachable!() };
+            let TypeEnum::TTuple { ty, is_vararg_ctx: false } = expected_ty_enum.as_ref() else {
+                unreachable!()
+            };
 
             let tup_tys = ty.iter();
             let elements: &PyTuple = obj.downcast()?;

nac3core/src/codegen/builtin_fns.rs

@@ -1,15 +1,20 @@
 use inkwell::types::BasicTypeEnum;
-use inkwell::values::BasicValueEnum;
+use inkwell::values::{BasicValueEnum, IntValue};
 use inkwell::{FloatPredicate, IntPredicate, OptimizationLevel};
 use itertools::Itertools;
 
-use crate::codegen::classes::{NDArrayValue, ProxyValue, UntypedArrayLikeAccessor};
+use crate::codegen::classes::{
+    ArrayLikeValue, NDArrayValue, ProxyValue, RangeValue, TypedArrayLikeAccessor,
+    UntypedArrayLikeAccessor,
+};
+use crate::codegen::expr::destructure_range;
+use crate::codegen::irrt::calculate_len_for_slice_range;
 use crate::codegen::numpy::ndarray_elementwise_unaryop_impl;
 use crate::codegen::stmt::gen_for_callback_incrementing;
 use crate::codegen::{extern_fns, irrt, llvm_intrinsics, numpy, CodeGenContext, CodeGenerator};
 use crate::toplevel::helper::PrimDef;
 use crate::toplevel::numpy::unpack_ndarray_var_tys;
-use crate::typecheck::typedef::Type;
+use crate::typecheck::typedef::{Type, TypeEnum};
 
 /// Shorthand for [`unreachable!()`] when a type of argument is not supported.
 ///
@@ -21,6 +26,67 @@ fn unsupported_type(ctx: &CodeGenContext<'_, '_>, fn_name: &str, tys: &[Type]) -
     )
 }
 
+/// Invokes the `len` builtin function.
+pub fn call_len<'ctx, G: CodeGenerator + ?Sized>(
+    generator: &mut G,
+    ctx: &mut CodeGenContext<'ctx, '_>,
+    n: (Type, BasicValueEnum<'ctx>),
+) -> Result<IntValue<'ctx>, String> {
+    let llvm_i32 = ctx.ctx.i32_type();
+    let range_ty = ctx.primitives.range;
+    let (arg_ty, arg) = n;
+
+    Ok(if ctx.unifier.unioned(arg_ty, range_ty) {
+        let arg = RangeValue::from_ptr_val(arg.into_pointer_value(), Some("range"));
+        let (start, end, step) = destructure_range(ctx, arg);
+        calculate_len_for_slice_range(generator, ctx, start, end, step)
+    } else {
+        match &*ctx.unifier.get_ty_immutable(arg_ty) {
+            TypeEnum::TTuple { ty, .. } => llvm_i32.const_int(ty.len() as u64, false),
+            TypeEnum::TObj { obj_id, .. } if *obj_id == PrimDef::List.id() => {
+                let zero = llvm_i32.const_zero();
+                let len = ctx
+                    .build_gep_and_load(
+                        arg.into_pointer_value(),
+                        &[zero, llvm_i32.const_int(1, false)],
+                        None,
+                    )
+                    .into_int_value();
+                ctx.builder.build_int_truncate_or_bit_cast(len, llvm_i32, "len").unwrap()
+            }
+            TypeEnum::TObj { obj_id, .. } if *obj_id == PrimDef::NDArray.id() => {
+                let llvm_usize = generator.get_size_type(ctx.ctx);
+
+                let arg = NDArrayValue::from_ptr_val(arg.into_pointer_value(), llvm_usize, None);
+
+                let ndims = arg.dim_sizes().size(ctx, generator);
+                ctx.make_assert(
+                    generator,
+                    ctx.builder
+                        .build_int_compare(IntPredicate::NE, ndims, llvm_usize.const_zero(), "")
+                        .unwrap(),
+                    "0:TypeError",
+                    "len() of unsized object",
+                    [None, None, None],
+                    ctx.current_loc,
+                );
+
+                let len = unsafe {
+                    arg.dim_sizes().get_typed_unchecked(
+                        ctx,
+                        generator,
+                        &llvm_usize.const_zero(),
+                        None,
+                    )
+                };
+
+                ctx.builder.build_int_truncate_or_bit_cast(len, llvm_i32, "len").unwrap()
+            }
+            _ => unreachable!(),
+        }
+    })
+}
+
 /// Invokes the `int32` builtin function.
 pub fn call_int32<'ctx, G: CodeGenerator + ?Sized>(
     generator: &mut G,

nac3core/src/codegen/concrete_type.rs

@@ -25,6 +25,7 @@ pub struct ConcreteFuncArg {
     pub name: StrRef,
     pub ty: ConcreteType,
     pub default_value: Option<SymbolValue>,
+    pub is_vararg: bool,
 }
 
 #[derive(Clone, Debug)]
@@ -46,6 +47,7 @@ pub enum ConcreteTypeEnum {
     TPrimitive(Primitive),
     TTuple {
         ty: Vec<ConcreteType>,
+        is_vararg_ctx: bool,
     },
     TObj {
         obj_id: DefinitionId,
@@ -102,8 +104,16 @@ impl ConcreteTypeStore {
                 .iter()
                 .map(|arg| ConcreteFuncArg {
                     name: arg.name,
-                    ty: self.from_unifier_type(unifier, primitives, arg.ty, cache),
+                    ty: if arg.is_vararg {
+                        let tuple_ty = unifier
+                            .add_ty(TypeEnum::TTuple { ty: vec![arg.ty], is_vararg_ctx: true });
+
+                        self.from_unifier_type(unifier, primitives, tuple_ty, cache)
+                    } else {
+                        self.from_unifier_type(unifier, primitives, arg.ty, cache)
+                    },
                     default_value: arg.default_value.clone(),
+                    is_vararg: arg.is_vararg,
                 })
                 .collect(),
             ret: self.from_unifier_type(unifier, primitives, signature.ret, cache),
@@ -158,11 +168,12 @@ impl ConcreteTypeStore {
             cache.insert(ty, None);
             let ty_enum = unifier.get_ty(ty);
             let result = match &*ty_enum {
-                TypeEnum::TTuple { ty } => ConcreteTypeEnum::TTuple {
+                TypeEnum::TTuple { ty, is_vararg_ctx } => ConcreteTypeEnum::TTuple {
                     ty: ty
                         .iter()
                         .map(|t| self.from_unifier_type(unifier, primitives, *t, cache))
                         .collect(),
+                    is_vararg_ctx: *is_vararg_ctx,
                 },
                 TypeEnum::TObj { obj_id, fields, params } => ConcreteTypeEnum::TObj {
                     obj_id: *obj_id,
@@ -248,11 +259,12 @@ impl ConcreteTypeStore {
                 *cache.get_mut(&cty).unwrap() = Some(ty);
                 return ty;
             }
-            ConcreteTypeEnum::TTuple { ty } => TypeEnum::TTuple {
+            ConcreteTypeEnum::TTuple { ty, is_vararg_ctx } => TypeEnum::TTuple {
                 ty: ty
                     .iter()
                     .map(|cty| self.to_unifier_type(unifier, primitives, *cty, cache))
                     .collect(),
+                is_vararg_ctx: *is_vararg_ctx,
             },
             ConcreteTypeEnum::TVirtual { ty } => {
                 TypeEnum::TVirtual { ty: self.to_unifier_type(unifier, primitives, *ty, cache) }
@@ -277,6 +289,7 @@ impl ConcreteTypeStore {
                         name: arg.name,
                         ty: self.to_unifier_type(unifier, primitives, arg.ty, cache),
                         default_value: arg.default_value.clone(),
+                        is_vararg: false,
                     })
                     .collect(),
                 ret: self.to_unifier_type(unifier, primitives, *ret, cache),

nac3core/src/codegen/expr.rs

@@ -267,13 +267,16 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
             }
             Constant::Tuple(v) => {
                 let ty = self.unifier.get_ty(ty);
-                let types =
-                    if let TypeEnum::TTuple { ty } = &*ty { ty.clone() } else { unreachable!() };
+                let (types, is_vararg_ctx) = if let TypeEnum::TTuple { ty, is_vararg_ctx } = &*ty {
+                    (ty.clone(), *is_vararg_ctx)
+                } else {
+                    unreachable!()
+                };
                 let values = zip(types, v.iter())
                     .map_while(|(ty, v)| self.gen_const(generator, v, ty))
                     .collect_vec();
 
-                if values.len() == v.len() {
+                if is_vararg_ctx || values.len() == v.len() {
                     let types = values.iter().map(BasicValueEnum::get_type).collect_vec();
                     let ty = self.ctx.struct_type(&types, false);
                     Some(ty.const_named_struct(&values).into())
@@ -731,7 +734,15 @@ pub fn gen_func_instance<'ctx>(
         let zelf = store.from_unifier_type(&mut ctx.unifier, &ctx.primitives, obj.0, &mut cache);
         let ConcreteTypeEnum::TFunc { args, .. } = &mut signature else { unreachable!() };
 
-        args.insert(0, ConcreteFuncArg { name: "self".into(), ty: zelf, default_value: None });
+        args.insert(
+            0,
+            ConcreteFuncArg {
+                name: "self".into(),
+                ty: zelf,
+                default_value: None,
+                is_vararg: false,
+            },
+        );
     }
     let signature = store.add_cty(signature);
 
@@ -763,6 +774,9 @@ pub fn gen_call<'ctx, G: CodeGenerator>(
     let param_vals;
     let is_extern;
 
+    // Ensure that the function object only contains up to 1 vararg parameter
+    debug_assert!(fun.0.args.iter().filter(|arg| arg.is_vararg).count() <= 1);
+
     let symbol = {
         // make sure this lock guard is dropped at the end of this scope...
         let def = definition.read();
@@ -779,18 +793,46 @@ pub fn gen_call<'ctx, G: CodeGenerator>(
                 is_extern = instance_to_stmt.is_empty();
                 let old_key = ctx.get_subst_key(obj.as_ref().map(|a| a.0), fun.0, None);
                 let mut keys = fun.0.args.clone();
-                let mut mapping = HashMap::new();
+                let mut mapping = HashMap::<_, Vec<ValueEnum>>::new();
+
                 for (key, value) in params {
-                    mapping.insert(key.unwrap_or_else(|| keys.remove(0).name), value);
+                    // Find the matching argument
+                    let matching_param = fun
+                        .0
+                        .args
+                        .iter()
+                        .find_or_last(|p| key.is_some_and(|k| k == p.name))
+                        .unwrap();
+                    if matching_param.is_vararg {
+                        if key.is_none() && !keys.is_empty() {
+                            keys.remove(0);
+                        }
+
+                        if let Some(param) = mapping.get_mut(&matching_param.name) {
+                            param.push(value);
+                        } else {
+                            mapping.insert(key.unwrap_or(matching_param.name), vec![value]);
+                        }
+                    } else {
+                        mapping.insert(key.unwrap_or_else(|| keys.remove(0).name), vec![value]);
+                    }
                 }
+
                 // default value handling
                 for k in keys {
                     if mapping.contains_key(&k.name) {
                         continue;
                     }
+
                     mapping.insert(
                         k.name,
-                        ctx.gen_symbol_val(generator, &k.default_value.unwrap(), k.ty).into(),
+                        if k.is_vararg {
+                            Vec::default()
+                        } else {
+                            vec![ctx
+                                .gen_symbol_val(generator, &k.default_value.unwrap(), k.ty)
+                                .into()]
+                        },
                     );
                 }
                 // reorder the parameters
@@ -801,13 +843,15 @@ pub fn gen_call<'ctx, G: CodeGenerator>(
                     .map(|arg| (mapping.remove(&arg.name).unwrap(), arg.ty))
                     .collect_vec();
                 if let Some(obj) = &obj {
-                    real_params.insert(0, (obj.1.clone(), obj.0));
+                    real_params.insert(0, (vec![obj.1.clone()], obj.0));
                 }
                 let static_params = real_params
                     .iter()
                     .enumerate()
                     .filter_map(|(i, (v, _))| {
-                        if let ValueEnum::Static(s) = v {
+                        if v.len() != 1 {
+                            None
+                        } else if let ValueEnum::Static(s) = &v[0] {
                             Some((i, s.clone()))
                         } else {
                             None
@@ -837,8 +881,13 @@ pub fn gen_call<'ctx, G: CodeGenerator>(
                 };
                 param_vals = real_params
                     .into_iter()
-                    .map(|(p, t)| p.to_basic_value_enum(ctx, generator, t))
-                    .collect::<Result<Vec<_>, String>>()?;
+                    .map(|(ps, t)| {
+                        ps.into_iter().map(|p| p.to_basic_value_enum(ctx, generator, t)).collect()
+                    })
+                    .collect::<Result<Vec<Vec<_>>, _>>()?
+                    .into_iter()
+                    .flatten()
+                    .collect::<Vec<_>>();
                 instance_to_symbol.get(&key).cloned().ok_or_else(String::new)
             }
             TopLevelDef::Class { .. } => {
@@ -852,7 +901,10 @@ pub fn gen_call<'ctx, G: CodeGenerator>(
     let fun_val = ctx.module.get_function(&symbol).unwrap_or_else(|| {
         let mut args = fun.0.args.clone();
         if let Some(obj) = &obj {
-            args.insert(0, FuncArg { name: "self".into(), ty: obj.0, default_value: None });
+            args.insert(
+                0,
+                FuncArg { name: "self".into(), ty: obj.0, default_value: None, is_vararg: false },
+            );
         }
         let ret_type = if ctx.unifier.unioned(fun.0.ret, ctx.primitives.none) {
             None

nac3core/src/codegen/mod.rs

@@ -520,8 +520,10 @@ fn get_llvm_type<'ctx, G: CodeGenerator + ?Sized>(
                 };
                 return ty;
             }
-            TTuple { ty } => {
+            TTuple { ty, is_vararg_ctx } => {
                 // a struct with fields in the order present in the tuple
+                assert!(!is_vararg_ctx, "Tuples in vararg context must be instantiated with the correct number of arguments before calling get_llvm_type");
+
                 let fields = ty
                     .iter()
                     .map(|ty| {
@@ -700,6 +702,7 @@ pub fn gen_func_impl<
                 name: arg.name,
                 ty: task.store.to_unifier_type(&mut unifier, &primitives, arg.ty, &mut cache),
                 default_value: arg.default_value.clone(),
+                is_vararg: arg.is_vararg,
             })
             .collect_vec(),
         task.store.to_unifier_type(&mut unifier, &primitives, *ret, &mut cache),
@@ -723,6 +726,19 @@ pub fn gen_func_impl<
     let mut params = args
         .iter()
         .map(|arg| {
+            let base_ty = if arg.is_vararg {
+                let TypeEnum::TTuple { ty, is_vararg_ctx: true, .. } =
+                    &*unifier.get_ty_immutable(arg.ty)
+                else {
+                    unreachable!()
+                };
+                debug_assert_eq!(ty.len(), 1);
+
+                ty[0]
+            } else {
+                arg.ty
+            };
+
             get_llvm_abi_type(
                 context,
                 &module,
@@ -731,7 +747,7 @@ pub fn gen_func_impl<
                 top_level_ctx.as_ref(),
                 &mut type_cache,
                 &primitives,
-                arg.ty,
+                base_ty,
             )
             .into()
         })
@@ -741,9 +757,11 @@ pub fn gen_func_impl<
         params.insert(0, ret_type.unwrap().ptr_type(AddressSpace::default()).into());
     }
 
+    let is_vararg = args.iter().any(|arg| arg.is_vararg);
+
     let fn_type = match ret_type {
-        Some(ret_type) if !has_sret => ret_type.fn_type(&params, false),
-        _ => context.void_type().fn_type(&params, false),
+        Some(ret_type) if !has_sret => ret_type.fn_type(&params, is_vararg),
+        _ => context.void_type().fn_type(&params, is_vararg),
     };
 
     let symbol = &task.symbol_name;

nac3core/src/codegen/test.rs

@@ -109,8 +109,18 @@ fn test_primitives() {
     let threads = vec![DefaultCodeGenerator::new("test".into(), 32).into()];
     let signature = FunSignature {
         args: vec![
-            FuncArg { name: "a".into(), ty: primitives.int32, default_value: None },
-            FuncArg { name: "b".into(), ty: primitives.int32, default_value: None },
+            FuncArg {
+                name: "a".into(),
+                ty: primitives.int32,
+                default_value: None,
+                is_vararg: false,
+            },
+            FuncArg {
+                name: "b".into(),
+                ty: primitives.int32,
+                default_value: None,
+                is_vararg: false,
+            },
         ],
         ret: primitives.int32,
         vars: VarMap::new(),
@@ -253,7 +263,12 @@ fn test_simple_call() {
     unifier.top_level = Some(top_level.clone());
 
     let signature = FunSignature {
-        args: vec![FuncArg { name: "a".into(), ty: primitives.int32, default_value: None }],
+        args: vec![FuncArg {
+            name: "a".into(),
+            ty: primitives.int32,
+            default_value: None,
+            is_vararg: false,
+        }],
         ret: primitives.int32,
         vars: VarMap::new(),
     };

nac3core/src/symbol_resolver.rs

@@ -78,14 +78,14 @@ impl SymbolValue {
             }
             Constant::Tuple(t) => {
                 let expected_ty = unifier.get_ty(expected_ty);
-                let TypeEnum::TTuple { ty } = expected_ty.as_ref() else {
+                let TypeEnum::TTuple { ty, is_vararg_ctx } = expected_ty.as_ref() else {
                     return Err(format!(
                         "Expected {:?}, but got Tuple",
                         expected_ty.get_type_name()
                     ));
                 };
 
-                assert_eq!(ty.len(), t.len());
+                assert!(*is_vararg_ctx || ty.len() == t.len());
 
                 let elems = t
                     .iter()
@@ -155,7 +155,7 @@ impl SymbolValue {
             SymbolValue::Bool(_) => primitives.bool,
             SymbolValue::Tuple(vs) => {
                 let vs_tys = vs.iter().map(|v| v.get_type(primitives, unifier)).collect::<Vec<_>>();
-                unifier.add_ty(TypeEnum::TTuple { ty: vs_tys })
+                unifier.add_ty(TypeEnum::TTuple { ty: vs_tys, is_vararg_ctx: false })
             }
             SymbolValue::OptionSome(_) | SymbolValue::OptionNone => primitives.option,
         }
@@ -482,7 +482,7 @@ pub fn parse_type_annotation<T>(
                         parse_type_annotation(resolver, top_level_defs, unifier, primitives, elt)
                     })
                     .collect::<Result<Vec<_>, _>>()?;
-                Ok(unifier.add_ty(TypeEnum::TTuple { ty }))
+                Ok(unifier.add_ty(TypeEnum::TTuple { ty, is_vararg_ctx: false }))
             } else {
                 Err(HashSet::from(["Expected multiple elements for tuple".into()]))
             }

nac3core/src/toplevel/builtins.rs

@@ -14,9 +14,7 @@ use strum::IntoEnumIterator;
 use crate::{
     codegen::{
         builtin_fns,
-        classes::{ArrayLikeValue, NDArrayValue, ProxyValue, RangeValue, TypedArrayLikeAccessor},
-        expr::destructure_range,
-        irrt::*,
+        classes::{ProxyValue, RangeValue},
         numpy::*,
         stmt::exn_constructor,
     },
@@ -45,10 +43,26 @@ pub fn get_exn_constructor(
             name: "msg".into(),
             ty: string,
             default_value: Some(SymbolValue::Str(String::new())),
+            is_vararg: false,
+        },
+        FuncArg {
+            name: "param0".into(),
+            ty: int64,
+            default_value: Some(SymbolValue::I64(0)),
+            is_vararg: false,
+        },
+        FuncArg {
+            name: "param1".into(),
+            ty: int64,
+            default_value: Some(SymbolValue::I64(0)),
+            is_vararg: false,
+        },
+        FuncArg {
+            name: "param2".into(),
+            ty: int64,
+            default_value: Some(SymbolValue::I64(0)),
+            is_vararg: false,
         },
-        FuncArg { name: "param0".into(), ty: int64, default_value: Some(SymbolValue::I64(0)) },
-        FuncArg { name: "param1".into(), ty: int64, default_value: Some(SymbolValue::I64(0)) },
-        FuncArg { name: "param2".into(), ty: int64, default_value: Some(SymbolValue::I64(0)) },
     ];
     let exn_type = unifier.add_ty(TypeEnum::TObj {
         obj_id: DefinitionId(class_id),
@@ -114,7 +128,12 @@ fn create_fn_by_codegen(
         signature: unifier.add_ty(TypeEnum::TFunc(FunSignature {
             args: param_ty
                 .iter()
-                .map(|p| FuncArg { name: p.1.into(), ty: p.0, default_value: None })
+                .map(|p| FuncArg {
+                    name: p.1.into(),
+                    ty: p.0,
+                    default_value: None,
+                    is_vararg: false,
+                })
                 .collect(),
             ret: ret_ty,
             vars: var_map.clone(),
@@ -613,17 +632,24 @@ impl<'a> BuiltinBuilder<'a> {
         let make_ctor_signature = |unifier: &mut Unifier| {
             unifier.add_ty(TypeEnum::TFunc(FunSignature {
                 args: vec![
-                    FuncArg { name: "start".into(), ty: int32, default_value: None },
+                    FuncArg {
+                        name: "start".into(),
+                        ty: int32,
+                        default_value: None,
+                        is_vararg: false,
+                    },
                     FuncArg {
                         name: "stop".into(),
                         ty: int32,
                         // placeholder
                         default_value: Some(SymbolValue::I32(0)),
+                        is_vararg: false,
                     },
                     FuncArg {
                         name: "step".into(),
                         ty: int32,
                         default_value: Some(SymbolValue::I32(1)),
+                        is_vararg: false,
                     },
                 ],
                 ret: range,
@@ -879,6 +905,7 @@ impl<'a> BuiltinBuilder<'a> {
                         name: "n".into(),
                         ty: self.option_tvar.ty,
                         default_value: None,
+                        is_vararg: false,
                     }],
                     ret: self.primitives.option,
                     vars: into_var_map([self.option_tvar]),
@@ -1013,6 +1040,7 @@ impl<'a> BuiltinBuilder<'a> {
                     name: "n".into(),
                     ty: self.num_or_ndarray_ty.ty,
                     default_value: None,
+                    is_vararg: false,
                 }],
                 ret: self.num_or_ndarray_ty.ty,
                 vars: self.num_or_ndarray_var_map.clone(),
@@ -1232,16 +1260,23 @@ impl<'a> BuiltinBuilder<'a> {
                     simple_name: prim.simple_name().into(),
                     signature: self.unifier.add_ty(TypeEnum::TFunc(FunSignature {
                         args: vec![
-                            FuncArg { name: "object".into(), ty: tv.ty, default_value: None },
+                            FuncArg {
+                                name: "object".into(),
+                                ty: tv.ty,
+                                default_value: None,
+                                is_vararg: false,
+                            },
                             FuncArg {
                                 name: "copy".into(),
                                 ty: bool,
                                 default_value: Some(SymbolValue::Bool(true)),
+                                is_vararg: false,
                             },
                             FuncArg {
                                 name: "ndmin".into(),
                                 ty: int32,
                                 default_value: Some(SymbolValue::U32(0)),
+                                is_vararg: false,
                             },
                         ],
                         ret: ndarray,
@@ -1283,17 +1318,24 @@ impl<'a> BuiltinBuilder<'a> {
                     simple_name: prim.simple_name().into(),
                     signature: self.unifier.add_ty(TypeEnum::TFunc(FunSignature {
                         args: vec![
-                            FuncArg { name: "N".into(), ty: int32, default_value: None },
+                            FuncArg {
+                                name: "N".into(),
+                                ty: int32,
+                                default_value: None,
+                                is_vararg: false,
+                            },
                             // TODO(Derppening): Default values current do not work?
                             FuncArg {
                                 name: "M".into(),
                                 ty: int32,
                                 default_value: Some(SymbolValue::OptionNone),
+                                is_vararg: false,
                             },
                             FuncArg {
                                 name: "k".into(),
                                 ty: int32,
                                 default_value: Some(SymbolValue::I32(0)),
+                                is_vararg: false,
                             },
                         ],
                         ret: self.ndarray_float_2d,
@@ -1337,7 +1379,12 @@ impl<'a> BuiltinBuilder<'a> {
             name: prim.name().into(),
             simple_name: prim.simple_name().into(),
             signature: self.unifier.add_ty(TypeEnum::TFunc(FunSignature {
-                args: vec![FuncArg { name: "s".into(), ty: str, default_value: None }],
+                args: vec![FuncArg {
+                    name: "s".into(),
+                    ty: str,
+                    default_value: None,
+                    is_vararg: false,
+                }],
                 ret: str,
                 vars: VarMap::default(),
             })),
@@ -1423,7 +1470,12 @@ impl<'a> BuiltinBuilder<'a> {
             name: prim.name().into(),
             simple_name: prim.simple_name().into(),
             signature: self.unifier.add_ty(TypeEnum::TFunc(FunSignature {
-                args: vec![FuncArg { name: "ls".into(), ty: arg_ty.ty, default_value: None }],
+                args: vec![FuncArg {
+                    name: "ls".into(),
+                    ty: arg_ty.ty,
+                    default_value: None,
+                    is_vararg: false,
+                }],
                 ret: int32,
                 vars: into_var_map([tvar, arg_ty]),
             })),
@@ -1433,86 +1485,10 @@ impl<'a> BuiltinBuilder<'a> {
             resolver: None,
             codegen_callback: Some(Arc::new(GenCall::new(Box::new(
                 move |ctx, _, fun, args, generator| {
-                    let range_ty = ctx.primitives.range;
                     let arg_ty = fun.0.args[0].ty;
                     let arg = args[0].1.clone().to_basic_value_enum(ctx, generator, arg_ty)?;
-                    Ok(if ctx.unifier.unioned(arg_ty, range_ty) {
-                        let arg = RangeValue::from_ptr_val(arg.into_pointer_value(), Some("range"));
-                        let (start, end, step) = destructure_range(ctx, arg);
-                        Some(calculate_len_for_slice_range(generator, ctx, start, end, step).into())
-                    } else {
-                        match &*ctx.unifier.get_ty_immutable(arg_ty) {
-                            TypeEnum::TObj { obj_id, .. } if *obj_id == PrimDef::List.id() => {
-                                let int32 = ctx.ctx.i32_type();
-                                let zero = int32.const_zero();
-                                let len = ctx
-                                    .build_gep_and_load(
-                                        arg.into_pointer_value(),
-                                        &[zero, int32.const_int(1, false)],
-                                        None,
-                                    )
-                                    .into_int_value();
-                                if len.get_type().get_bit_width() == 32 {
-                                    Some(len.into())
-                                } else {
-                                    Some(
-                                        ctx.builder
-                                            .build_int_truncate(len, int32, "len2i32")
-                                            .map(Into::into)
-                                            .unwrap(),
-                                    )
-                                }
-                            }
-                            TypeEnum::TObj { obj_id, .. } if *obj_id == PrimDef::NDArray.id() => {
-                                let llvm_i32 = ctx.ctx.i32_type();
-                                let llvm_usize = generator.get_size_type(ctx.ctx);
 
-                                let arg = NDArrayValue::from_ptr_val(
-                                    arg.into_pointer_value(),
-                                    llvm_usize,
-                                    None,
-                                );
-
-                                let ndims = arg.dim_sizes().size(ctx, generator);
-                                ctx.make_assert(
-                                    generator,
-                                    ctx.builder
-                                        .build_int_compare(
-                                            IntPredicate::NE,
-                                            ndims,
-                                            llvm_usize.const_zero(),
-                                            "",
-                                        )
-                                        .unwrap(),
-                                    "0:TypeError",
-                                    &format!("{name}() of unsized object", name = prim.name()),
-                                    [None, None, None],
-                                    ctx.current_loc,
-                                );
-
-                                let len = unsafe {
-                                    arg.dim_sizes().get_typed_unchecked(
-                                        ctx,
-                                        generator,
-                                        &llvm_usize.const_zero(),
-                                        None,
-                                    )
-                                };
-
-                                if len.get_type().get_bit_width() == 32 {
-                                    Some(len.into())
-                                } else {
-                                    Some(
-                                        ctx.builder
-                                            .build_int_truncate(len, llvm_i32, "len")
-                                            .map(Into::into)
-                                            .unwrap(),
-                                    )
-                                }
-                            }
-                            _ => unreachable!(),
-                        }
-                    })
+                    builtin_fns::call_len(generator, ctx, (arg_ty, arg)).map(|ret| Some(ret.into()))
                 },
             )))),
             loc: None,
@@ -1528,8 +1504,18 @@ impl<'a> BuiltinBuilder<'a> {
             simple_name: prim.simple_name().into(),
             signature: self.unifier.add_ty(TypeEnum::TFunc(FunSignature {
                 args: vec![
-                    FuncArg { name: "m".into(), ty: self.num_ty.ty, default_value: None },
-                    FuncArg { name: "n".into(), ty: self.num_ty.ty, default_value: None },
+                    FuncArg {
+                        name: "m".into(),
+                        ty: self.num_ty.ty,
+                        default_value: None,
+                        is_vararg: false,
+                    },
+                    FuncArg {
+                        name: "n".into(),
+                        ty: self.num_ty.ty,
+                        default_value: None,
+                        is_vararg: false,
+                    },
                 ],
                 ret: self.num_ty.ty,
                 vars: self.num_var_map.clone(),
@@ -1611,7 +1597,12 @@ impl<'a> BuiltinBuilder<'a> {
             signature: self.unifier.add_ty(TypeEnum::TFunc(FunSignature {
                 args: param_ty
                     .iter()
-                    .map(|p| FuncArg { name: p.1.into(), ty: p.0, default_value: None })
+                    .map(|p| FuncArg {
+                        name: p.1.into(),
+                        ty: p.0,
+                        default_value: None,
+                        is_vararg: false,
+                    })
                     .collect(),
                 ret: ret_ty.ty,
                 vars: into_var_map([x1_ty, x2_ty, ret_ty]),
@@ -1652,6 +1643,7 @@ impl<'a> BuiltinBuilder<'a> {
                     name: "n".into(),
                     ty: self.num_or_ndarray_ty.ty,
                     default_value: None,
+                    is_vararg: false,
                 }],
                 ret: self.num_or_ndarray_ty.ty,
                 vars: self.num_or_ndarray_var_map.clone(),
@@ -1840,7 +1832,12 @@ impl<'a> BuiltinBuilder<'a> {
             signature: self.unifier.add_ty(TypeEnum::TFunc(FunSignature {
                 args: param_ty
                     .iter()
-                    .map(|p| FuncArg { name: p.1.into(), ty: p.0, default_value: None })
+                    .map(|p| FuncArg {
+                        name: p.1.into(),
+                        ty: p.0,
+                        default_value: None,
+                        is_vararg: false,
+                    })
                     .collect(),
                 ret: ret_ty.ty,
                 vars: into_var_map([x1_ty, x2_ty, ret_ty]),

nac3core/src/toplevel/composer.rs

@@ -859,7 +859,72 @@ impl TopLevelComposer {
             let resolver = &**resolver;
 
             let mut function_var_map = VarMap::new();
-            let arg_types = {
+
+            let vararg = args
+                .vararg
+                .as_ref()
+                .map(|vararg| -> Result<_, HashSet<String>> {
+                    let vararg = vararg.as_ref();
+
+                    let annotation = vararg
+                        .node
+                        .annotation
+                        .as_ref()
+                        .ok_or_else(|| {
+                            HashSet::from([format!(
+                                "function parameter `{}` needs type annotation at {}",
+                                vararg.node.arg, vararg.location
+                            )])
+                        })?
+                        .as_ref();
+
+                    let type_annotation = parse_ast_to_type_annotation_kinds(
+                        resolver,
+                        temp_def_list.as_slice(),
+                        unifier,
+                        primitives_store,
+                        annotation,
+                        // NOTE: since only class need this, for function
+                        // it should be fine to be empty map
+                        HashMap::new(),
+                    )?;
+
+                    let type_vars_within =
+                        get_type_var_contained_in_type_annotation(&type_annotation)
+                            .into_iter()
+                            .map(|x| -> Result<TypeVar, HashSet<String>> {
+                                let TypeAnnotation::TypeVar(ty) = x else {
+                                    unreachable!("must be type var annotation kind")
+                                };
+
+                                let id = Self::get_var_id(ty, unifier)?;
+                                Ok(TypeVar { id, ty })
+                            })
+                            .collect::<Result<Vec<_>, _>>()?;
+                    for var in type_vars_within {
+                        if let Some(prev_ty) = function_var_map.insert(var.id, var.ty) {
+                            // if already have the type inserted, make sure they are the same thing
+                            assert_eq!(prev_ty, var.ty);
+                        }
+                    }
+
+                    let ty = get_type_from_type_annotation_kinds(
+                        temp_def_list.as_ref(),
+                        unifier,
+                        &type_annotation,
+                        &mut None,
+                    )?;
+
+                    Ok(FuncArg {
+                        name: vararg.node.arg,
+                        ty,
+                        default_value: Some(SymbolValue::Tuple(Vec::default())),
+                        is_vararg: true,
+                    })
+                })
+                .transpose()?;
+
+            let mut arg_types = {
                 // make sure no duplicate parameter
                 let mut defined_parameter_name: HashSet<_> = HashSet::new();
                 for x in &args.args {
@@ -959,11 +1024,18 @@ impl TopLevelComposer {
                                     v
                                 }),
                             },
+                            is_vararg: false,
                         })
                     })
                     .collect::<Result<Vec<_>, _>>()?
             };
 
+            if let Some(vararg) = vararg {
+                arg_types.push(vararg);
+            };
+
+            let arg_types = arg_types;
+
             let return_ty = {
                 if let Some(returns) = returns {
                     let return_ty_annotation = {
@@ -1214,6 +1286,7 @@ impl TopLevelComposer {
                                             })
                                         }
                                     },
+                                    is_vararg: false,
                                 };
                                 // push the dummy type and the type annotation
                                 // into the list for later unification
@@ -1638,21 +1711,25 @@ impl TopLevelComposer {
                                 name: "msg".into(),
                                 ty: string,
                                 default_value: Some(SymbolValue::Str(String::new())),
+                                is_vararg: false,
                             },
                             FuncArg {
                                 name: "param0".into(),
                                 ty: int64,
                                 default_value: Some(SymbolValue::I64(0)),
+                                is_vararg: false,
                             },
                             FuncArg {
                                 name: "param1".into(),
                                 ty: int64,
                                 default_value: Some(SymbolValue::I64(0)),
+                                is_vararg: false,
                             },
                             FuncArg {
                                 name: "param2".into(),
                                 ty: int64,
                                 default_value: Some(SymbolValue::I64(0)),
+                                is_vararg: false,
                             },
                         ],
                         ret: self_type,
@@ -1858,6 +1935,7 @@ impl TopLevelComposer {
                                 name: a.name,
                                 ty: unifier.subst(a.ty, &subst).unwrap_or(a.ty),
                                 default_value: a.default_value.clone(),
+                                is_vararg: false,
                             })
                             .collect_vec()
                     };

nac3core/src/toplevel/helper.rs

@@ -448,6 +448,7 @@ impl TopLevelComposer {
                 name: "value".into(),
                 ty: ndarray_dtype_tvar.ty,
                 default_value: None,
+                is_vararg: false,
             }],
             ret: none,
             vars: into_var_map([ndarray_dtype_tvar, ndarray_ndims_tvar]),

nac3core/src/toplevel/type_annotation.rs

@@ -502,7 +502,7 @@ pub fn get_type_from_type_annotation_kinds(
                     get_type_from_type_annotation_kinds(top_level_defs, unifier, x, subst_list)
                 })
                 .collect::<Result<Vec<_>, _>>()?;
-            Ok(unifier.add_ty(TypeEnum::TTuple { ty: tys }))
+            Ok(unifier.add_ty(TypeEnum::TTuple { ty: tys, is_vararg_ctx: false }))
         }
     }
 }

nac3core/src/typecheck/function_check.rs

@@ -218,7 +218,7 @@ impl<'a> Inferencer<'a> {
             ]
             .iter()
             .any(|allowed_ty| self.unifier.unioned(ret_ty, *allowed_ty)),
-            TypeEnum::TTuple { ty } => ty.iter().all(|t| self.check_return_value_ty(*t)),
+            TypeEnum::TTuple { ty, .. } => ty.iter().all(|t| self.check_return_value_ty(*t)),
             _ => false,
         }
     }

nac3core/src/typecheck/magic_methods.rs

@@ -197,6 +197,7 @@ pub fn impl_binop(
                             ty: other_ty,
                             default_value: None,
                             name: "other".into(),
+                            is_vararg: false,
                         }],
                     })),
                     false,
@@ -261,6 +262,7 @@ pub fn impl_cmpop(
                             ty: other_ty,
                             default_value: None,
                             name: "other".into(),
+                            is_vararg: false,
                         }],
                     })),
                     false,

nac3core/src/typecheck/type_error.rs

@@ -183,9 +183,10 @@ impl<'a> Display for DisplayTypeError<'a> {
                         }
                         result
                     }
-                    (TypeEnum::TTuple { ty: ty1 }, TypeEnum::TTuple { ty: ty2 })
-                        if ty1.len() != ty2.len() =>
-                    {
+                    (
+                        TypeEnum::TTuple { ty: ty1, is_vararg_ctx: is_vararg1 },
+                        TypeEnum::TTuple { ty: ty2, is_vararg_ctx: is_vararg2 },
+                    ) if !is_vararg1 && !is_vararg2 && ty1.len() != ty2.len() => {
                         let t1 = self.unifier.stringify_with_notes(*t1, &mut notes);
                         let t2 = self.unifier.stringify_with_notes(*t2, &mut notes);
                         write!(f, "Tuple length mismatch: got {t1} and {t2}")

nac3core/src/typecheck/type_inferencer/mod.rs

@@ -763,7 +763,7 @@ impl<'a> Inferencer<'a> {
         let fun = FunSignature {
             args: fn_args
                 .iter()
-                .map(|(k, ty)| FuncArg { name: *k, ty: *ty, default_value: None })
+                .map(|(k, ty)| FuncArg { name: *k, ty: *ty, default_value: None, is_vararg: false })
                 .collect(),
             ret,
             vars: VarMap::default(),
@@ -977,13 +977,14 @@ impl<'a> Inferencer<'a> {
                     ]));
                 }
             }
-            TypeEnum::TTuple { ty: tuple_element_types } => {
+            TypeEnum::TTuple { ty: tuple_element_types, .. } => {
                 // Handle 2. A tuple of int32s
 
                 // Typecheck
                 // The expected type is just the tuple but with all its elements being int32.
                 let expected_ty = self.unifier.add_ty(TypeEnum::TTuple {
                     ty: tuple_element_types.iter().map(|_| self.primitives.int32).collect_vec(),
+                    is_vararg_ctx: false,
                 });
                 self.unifier.unify(shape_ty, expected_ty).map_err(|err| {
                     HashSet::from([err
@@ -1110,6 +1111,7 @@ impl<'a> Inferencer<'a> {
                     name: "n".into(),
                     ty: arg0.custom.unwrap(),
                     default_value: None,
+                    is_vararg: false,
                 }],
                 ret,
                 vars: VarMap::new(),
@@ -1148,6 +1150,7 @@ impl<'a> Inferencer<'a> {
                     name: "a".into(),
                     ty: arg0.custom.unwrap(),
                     default_value: None,
+                    is_vararg: false,
                 }],
                 ret,
                 vars: VarMap::new(),
@@ -1248,8 +1251,18 @@ impl<'a> Inferencer<'a> {
 
             let custom = self.unifier.add_ty(TypeEnum::TFunc(FunSignature {
                 args: vec![
-                    FuncArg { name: "x1".into(), ty: arg0.custom.unwrap(), default_value: None },
-                    FuncArg { name: "x2".into(), ty: arg1.custom.unwrap(), default_value: None },
+                    FuncArg {
+                        name: "x1".into(),
+                        ty: arg0.custom.unwrap(),
+                        default_value: None,
+                        is_vararg: false,
+                    },
+                    FuncArg {
+                        name: "x2".into(),
+                        ty: arg1.custom.unwrap(),
+                        default_value: None,
+                        is_vararg: false,
+                    },
                 ],
                 ret,
                 vars: VarMap::new(),
@@ -1329,6 +1342,7 @@ impl<'a> Inferencer<'a> {
                     name: "n".into(),
                     ty: arg0.custom.unwrap(),
                     default_value: None,
+                    is_vararg: false,
                 }],
                 ret,
                 vars: VarMap::new(),
@@ -1370,6 +1384,7 @@ impl<'a> Inferencer<'a> {
                     name: "shape".into(),
                     ty: shape.custom.unwrap(),
                     default_value: None,
+                    is_vararg: false,
                 }],
                 ret,
                 vars: VarMap::new(),
@@ -1413,11 +1428,17 @@ impl<'a> Inferencer<'a> {
             let ret = make_ndarray_ty(self.unifier, self.primitives, Some(ty), Some(ndims));
             let custom = self.unifier.add_ty(TypeEnum::TFunc(FunSignature {
                 args: vec![
-                    FuncArg { name: "shape".into(), ty: arg0.custom.unwrap(), default_value: None },
+                    FuncArg {
+                        name: "shape".into(),
+                        ty: arg0.custom.unwrap(),
+                        default_value: None,
+                        is_vararg: false,
+                    },
                     FuncArg {
                         name: "fill_value".into(),
                         ty: arg1.custom.unwrap(),
                         default_value: None,
+                        is_vararg: false,
                     },
                 ],
                 ret,
@@ -1472,16 +1493,19 @@ impl<'a> Inferencer<'a> {
                         name: "object".into(),
                         ty: arg0.custom.unwrap(),
                         default_value: None,
+                        is_vararg: false,
                     },
                     FuncArg {
                         name: "copy".into(),
                         ty: self.primitives.bool,
                         default_value: Some(SymbolValue::Bool(true)),
+                        is_vararg: false,
                     },
                     FuncArg {
                         name: "ndmin".into(),
                         ty: self.primitives.int32,
                         default_value: Some(SymbolValue::U32(0)),
+                        is_vararg: false,
                     },
                 ],
                 ret,
@@ -1539,6 +1563,7 @@ impl<'a> Inferencer<'a> {
                     loc: Some(location),
                     operator_info: None,
                 };
+                println!("{}", self.unifier.stringify(func.custom.unwrap()));
                 self.unifier.unify_call(&call, func.custom.unwrap(), sign).map_err(|e| {
                     HashSet::from([e.at(Some(location)).to_display(self.unifier).to_string()])
                 })?;
@@ -1603,7 +1628,7 @@ impl<'a> Inferencer<'a> {
             ast::Constant::Tuple(vals) => {
                 let ty: Result<Vec<_>, _> =
                     vals.iter().map(|x| self.infer_constant(x, loc)).collect();
-                Ok(self.unifier.add_ty(TypeEnum::TTuple { ty: ty? }))
+                Ok(self.unifier.add_ty(TypeEnum::TTuple { ty: ty?, is_vararg_ctx: false }))
             }
             ast::Constant::Str(_) => Ok(self.primitives.str),
             ast::Constant::None => {
@@ -1637,7 +1662,7 @@ impl<'a> Inferencer<'a> {
     #[allow(clippy::unnecessary_wraps)]
     fn infer_tuple(&mut self, elts: &[ast::Expr<Option<Type>>]) -> InferenceResult {
         let ty = elts.iter().map(|x| x.custom.unwrap()).collect();
-        Ok(self.unifier.add_ty(TypeEnum::TTuple { ty }))
+        Ok(self.unifier.add_ty(TypeEnum::TTuple { ty, is_vararg_ctx: false }))
     }
 
     /// Checks for non-class attributes

nac3core/src/typecheck/type_inferencer/test.rs

@@ -83,7 +83,12 @@ impl TestEnvironment {
         });
         with_fields(&mut unifier, int32, |unifier, fields| {
             let add_ty = unifier.add_ty(TypeEnum::TFunc(FunSignature {
-                args: vec![FuncArg { name: "other".into(), ty: int32, default_value: None }],
+                args: vec![FuncArg {
+                    name: "other".into(),
+                    ty: int32,
+                    default_value: None,
+                    is_vararg: false,
+                }],
                 ret: int32,
                 vars: VarMap::new(),
             }));
@@ -224,7 +229,12 @@ impl TestEnvironment {
         });
         with_fields(&mut unifier, int32, |unifier, fields| {
             let add_ty = unifier.add_ty(TypeEnum::TFunc(FunSignature {
-                args: vec![FuncArg { name: "other".into(), ty: int32, default_value: None }],
+                args: vec![FuncArg {
+                    name: "other".into(),
+                    ty: int32,
+                    default_value: None,
+                    is_vararg: false,
+                }],
                 ret: int32,
                 vars: VarMap::new(),
             }));

nac3core/src/typecheck/typedef/mod.rs

@@ -1,15 +1,14 @@
 use indexmap::IndexMap;
-use itertools::Itertools;
+use itertools::{repeat_n, Itertools};
+use nac3parser::ast::{Cmpop, Location, StrRef, Unaryop};
 use std::cell::RefCell;
 use std::collections::HashMap;
 use std::fmt::{self, Display};
-use std::iter::zip;
+use std::iter::{repeat_with, zip};
 use std::rc::Rc;
 use std::sync::{Arc, Mutex};
 use std::{borrow::Cow, collections::HashSet};
 
-use nac3parser::ast::{Cmpop, Location, StrRef, Unaryop};
-
 use super::magic_methods::Binop;
 use super::type_error::{TypeError, TypeErrorKind};
 use super::unification_table::{UnificationKey, UnificationTable};
@@ -115,6 +114,7 @@ pub struct FuncArg {
     pub name: StrRef,
     pub ty: Type,
     pub default_value: Option<SymbolValue>,
+    pub is_vararg: bool,
 }
 
 impl FuncArg {
@@ -233,6 +233,12 @@ pub enum TypeEnum {
     TTuple {
         /// The types of elements present in this tuple.
         ty: Vec<Type>,
+
+        /// Whether this tuple is used in a vararg context.
+        ///
+        /// If `true`, `ty` must only contain one type, and the tuple is assumed to contain any
+        /// number of `ty`-typed values.
+        is_vararg_ctx: bool,
     },
 
     /// An object type.
@@ -527,7 +533,7 @@ impl Unifier {
             TypeEnum::TVirtual { ty } => self.get_instantiations(*ty).map(|ty| {
                 ty.iter().map(|&ty| self.add_ty(TypeEnum::TVirtual { ty })).collect_vec()
             }),
-            TypeEnum::TTuple { ty } => {
+            TypeEnum::TTuple { ty, is_vararg_ctx } => {
                 let tuples = ty
                     .iter()
                     .map(|ty| self.get_instantiations(*ty).unwrap_or_else(|| vec![*ty]))
@@ -537,7 +543,12 @@ impl Unifier {
                     None
                 } else {
                     Some(
-                        tuples.into_iter().map(|ty| self.add_ty(TypeEnum::TTuple { ty })).collect(),
+                        tuples
+                            .into_iter()
+                            .map(|ty| {
+                                self.add_ty(TypeEnum::TTuple { ty, is_vararg_ctx: *is_vararg_ctx })
+                            })
+                            .collect(),
                     )
                 }
             }
@@ -581,7 +592,7 @@ impl Unifier {
             TVar { .. } => allowed_typevars.iter().any(|b| self.unification_table.unioned(a, *b)),
             TCall { .. } => false,
             TVirtual { ty } => self.is_concrete(*ty, allowed_typevars),
-            TTuple { ty } => ty.iter().all(|ty| self.is_concrete(*ty, allowed_typevars)),
+            TTuple { ty, .. } => ty.iter().all(|ty| self.is_concrete(*ty, allowed_typevars)),
             TObj { params: vars, .. } => {
                 vars.values().all(|ty| self.is_concrete(*ty, allowed_typevars))
             }
@@ -649,6 +660,7 @@ impl Unifier {
 
         // Get details about the function signature/parameters.
         let num_params = signature.args.len();
+        let is_vararg = signature.args.iter().any(|arg| arg.is_vararg);
 
         // Force the type vars in `b` and `signature' to be up-to-date.
         let b = self.instantiate_fun(b, signature);
@@ -737,7 +749,7 @@ impl Unifier {
                 };
 
                 // Check for "too many arguments"
-                if num_params < posargs.len() {
+                if !is_vararg && num_params < posargs.len() {
                     let expected_min_count =
                         signature.args.iter().filter(|param| param.is_required()).count();
                     let expected_max_count = num_params;
@@ -761,7 +773,7 @@ impl Unifier {
                     .collect();
 
                 // Now consume all positional arguments and typecheck them.
-                for (&arg_ty, param) in zip(posargs, signature.args.iter()) {
+                for (param, &arg_ty) in zip(signature.args.iter().chain(repeat_with(|| signature.args.iter().last().unwrap())), posargs) {
                     // We will also use this opportunity to mark the corresponding `param_info` as having been supplied.
                     let param_info = param_info_by_name.get_mut(&param.name).unwrap();
                     param_info.has_been_supplied = true;
@@ -959,7 +971,10 @@ impl Unifier {
                 self.unify_impl(x, b, false)?;
                 self.set_a_to_b(a, x);
             }
-            (TVar { fields: Some(fields), range, is_const_generic: false, .. }, TTuple { ty }) => {
+            (
+                TVar { fields: Some(fields), range, is_const_generic: false, .. },
+                TTuple { ty, .. },
+            ) => {
                 let len = i32::try_from(ty.len()).unwrap();
                 for (k, v) in fields {
                     match *k {
@@ -1056,15 +1071,43 @@ impl Unifier {
                 self.set_a_to_b(a, b);
             }
 
-            (TTuple { ty: ty1 }, TTuple { ty: ty2 }) => {
-                if ty1.len() != ty2.len() {
-                    return Err(TypeError::new(TypeErrorKind::IncompatibleTypes(a, b), None));
-                }
-                for (x, y) in ty1.iter().zip(ty2.iter()) {
-                    if self.unify_impl(*x, *y, false).is_err() {
-                        return Err(TypeError::new(TypeErrorKind::IncompatibleTypes(a, b), None));
+            (
+                TTuple { ty: ty1, is_vararg_ctx: is_vararg1 },
+                TTuple { ty: ty2, is_vararg_ctx: is_vararg2 },
+            ) => {
+                // Rules for Tuples:
+                // - ty1: is_vararg && ty2: is_vararg -> ty1[0] == ty2[0]
+                // - ty1: is_vararg && ty2: !is_vararg -> type error (not enough info to infer the correct number of arguments)
+                // - ty1: !is_vararg && ty2: is_vararg -> ty1[..] == ty2[0]
+                // - ty1: !is_vararg && ty2: !is_vararg -> ty1.len() == ty2.len() && ty1[i] == ty2[i]
+
+                debug_assert!(!is_vararg1 || ty1.len() == 1);
+                debug_assert!(!is_vararg2 || ty2.len() == 1);
+
+                match (*is_vararg1, *is_vararg2) {
+                    (true, true) => {
+                        if self.unify_impl(ty1[0], ty2[0], false).is_err() {
+                            return Self::incompatible_types(a, b);
+                        }
+                    }
+                    (true, false) => return Self::incompatible_types(a, b),
+
+                    (false, true) => {
+                        for y in ty2 {
+                            if self.unify_impl(ty1[0], *y, false).is_err() {
+                                return Self::incompatible_types(a, b);
+                            }
+                        }
+                    }
+                    (false, false) => {
+                        for (x, y) in ty1.iter().zip(ty2.iter()) {
+                            if self.unify_impl(*x, *y, false).is_err() {
+                                return Self::incompatible_types(a, b);
+                            }
+                        }
                     }
                 }
+
                 self.set_a_to_b(a, b);
             }
             (TVar { fields: Some(map), range, .. }, TObj { obj_id, fields, params }) => {
@@ -1307,10 +1350,22 @@ impl Unifier {
             TypeEnum::TLiteral { values, .. } => {
                 format!("const({})", values.iter().map(|v| format!("{v:?}")).join(", "))
             }
-            TypeEnum::TTuple { ty } => {
-                let mut fields =
-                    ty.iter().map(|v| self.internal_stringify(*v, obj_to_name, var_to_name, notes));
-                format!("tuple[{}]", fields.join(", "))
+            TypeEnum::TTuple { ty, is_vararg_ctx } => {
+                if *is_vararg_ctx {
+                    debug_assert_eq!(ty.len(), 1);
+                    let field = self.internal_stringify(
+                        *ty.iter().next().unwrap(),
+                        obj_to_name,
+                        var_to_name,
+                        notes,
+                    );
+                    format!("tuple[*{field}]")
+                } else {
+                    let mut fields = ty
+                        .iter()
+                        .map(|v| self.internal_stringify(*v, obj_to_name, var_to_name, notes));
+                    format!("tuple[{}]", fields.join(", "))
+                }
             }
             TypeEnum::TVirtual { ty } => {
                 format!(
@@ -1335,17 +1390,21 @@ impl Unifier {
                     .args
                     .iter()
                     .map(|arg| {
+                        let vararg_prefix = if arg.is_vararg { "*" } else { "" };
+
                         if let Some(dv) = &arg.default_value {
                             format!(
-                                "{}:{}={}",
+                                "{}:{}{}={}",
                                 arg.name,
+                                vararg_prefix,
                                 self.internal_stringify(arg.ty, obj_to_name, var_to_name, notes),
                                 dv
                             )
                         } else {
                             format!(
-                                "{}:{}",
+                                "{}:{}{}",
                                 arg.name,
+                                vararg_prefix,
                                 self.internal_stringify(arg.ty, obj_to_name, var_to_name, notes)
                             )
                         }
@@ -1431,7 +1490,7 @@ impl Unifier {
         match &*ty {
             TypeEnum::TRigidVar { .. } | TypeEnum::TLiteral { .. } => None,
             TypeEnum::TVar { id, .. } => mapping.get(id).copied(),
-            TypeEnum::TTuple { ty } => {
+            TypeEnum::TTuple { ty, is_vararg_ctx } => {
                 let mut new_ty = Cow::from(ty);
                 for (i, t) in ty.iter().enumerate() {
                     if let Some(t1) = self.subst_impl(*t, mapping, cache) {
@@ -1439,7 +1498,10 @@ impl Unifier {
                     }
                 }
                 if matches!(new_ty, Cow::Owned(_)) {
-                    Some(self.add_ty(TypeEnum::TTuple { ty: new_ty.into_owned() }))
+                    Some(self.add_ty(TypeEnum::TTuple {
+                        ty: new_ty.into_owned(),
+                        is_vararg_ctx: *is_vararg_ctx,
+                    }))
                 } else {
                     None
                 }
@@ -1599,16 +1661,37 @@ impl Unifier {
                 }
             }
             (TVar { range, .. }, _) => self.check_var_compatibility(b, range).or(Err(())),
-            (TTuple { ty: ty1 }, TTuple { ty: ty2 }) if ty1.len() == ty2.len() => {
-                let ty: Vec<_> = zip(ty1.iter(), ty2.iter())
-                    .map(|(a, b)| self.get_intersection(*a, *b))
-                    .try_collect()?;
-                if ty.iter().any(Option::is_some) {
-                    Ok(Some(self.add_ty(TTuple {
-                        ty: zip(ty, ty1.iter()).map(|(a, b)| a.unwrap_or(*b)).collect(),
-                    })))
+            (
+                TTuple { ty: ty1, is_vararg_ctx: is_vararg1 },
+                TTuple { ty: ty2, is_vararg_ctx: is_vararg2 },
+            ) => {
+                if *is_vararg1 && *is_vararg2 {
+                    let isect_ty = self.get_intersection(ty1[0], ty2[0])?;
+                    Ok(isect_ty.map(|ty| self.add_ty(TTuple { ty: vec![ty], is_vararg_ctx: true })))
                 } else {
-                    Ok(None)
+                    let zip_iter: Box<dyn Iterator<Item = (&Type, &Type)>> =
+                        match (*is_vararg1, *is_vararg2) {
+                            (true, _) => Box::new(repeat_n(&ty1[0], ty2.len()).zip(ty2.iter())),
+                            (_, false) => Box::new(ty1.iter().zip(repeat_n(&ty2[0], ty1.len()))),
+                            _ => {
+                                if ty1.len() != ty2.len() {
+                                    return Err(());
+                                }
+
+                                Box::new(ty1.iter().zip(ty2.iter()))
+                            }
+                        };
+
+                    let ty: Vec<_> =
+                        zip_iter.map(|(a, b)| self.get_intersection(*a, *b)).try_collect()?;
+                    Ok(if ty.iter().any(Option::is_some) {
+                        Some(self.add_ty(TTuple {
+                            ty: zip(ty, ty1.iter()).map(|(a, b)| a.unwrap_or(*b)).collect(),
+                            is_vararg_ctx: false,
+                        }))
+                    } else {
+                        None
+                    })
                 }
             }
             // TODO(Derppening): #444

nac3core/src/typecheck/typedef/test.rs

@@ -28,7 +28,10 @@ impl Unifier {
                 TypeEnum::TVar { fields: Some(map1), .. },
                 TypeEnum::TVar { fields: Some(map2), .. },
             ) => self.map_eq2(map1, map2),
-            (TypeEnum::TTuple { ty: ty1 }, TypeEnum::TTuple { ty: ty2 }) => {
+            (
+                TypeEnum::TTuple { ty: ty1, is_vararg_ctx: false },
+                TypeEnum::TTuple { ty: ty2, is_vararg_ctx: false },
+            ) => {
                 ty1.len() == ty2.len()
                     && ty1.iter().zip(ty2.iter()).all(|(t1, t2)| self.eq(*t1, *t2))
             }
@@ -178,7 +181,7 @@ impl TestEnvironment {
                     ty.push(result.0);
                     s = result.1;
                 }
-                (self.unifier.add_ty(TypeEnum::TTuple { ty }), &s[1..])
+                (self.unifier.add_ty(TypeEnum::TTuple { ty, is_vararg_ctx: false }), &s[1..])
             }
             "Record" => {
                 let mut s = &typ[end..];
@@ -608,7 +611,7 @@ fn test_instantiation() {
     let v1 = env.unifier.get_fresh_var_with_range(&[list_v, int], None, None).ty;
     let v2 = env.unifier.get_fresh_var_with_range(&[list_int, float], None, None).ty;
     let t = env.unifier.get_dummy_var().ty;
-    let tuple = env.unifier.add_ty(TypeEnum::TTuple { ty: vec![v, v1, v2] });
+    let tuple = env.unifier.add_ty(TypeEnum::TTuple { ty: vec![v, v1, v2], is_vararg_ctx: false });
     let v3 = env.unifier.get_fresh_var_with_range(&[tuple, t], None, None).ty;
     // t = TypeVar('t')
     // v = TypeVar('v', int, bool)

nac3standalone/demo/src/vararg.py

@@ -0,0 +1,11 @@
+def f(*args: int32):
+    pass
+
+
+def run() -> int32:
+    f()
+    f(1)
+    f(1, 2)
+    f(1, 2, 3)
+
+    return 0