[core] typecheck: Disallow redeclaration of var shadowing global

nac3core/src/codegen/expr.rs

@@ -2886,7 +2886,31 @@ pub fn gen_expr<'ctx, G: CodeGenerator>(
             Some((_, Some(static_value), _)) => ValueEnum::Static(static_value.clone()),
             None => {
                 let resolver = ctx.resolver.clone();
-                resolver.get_symbol_value(*id, ctx, generator).unwrap()
+                let value = resolver.get_symbol_value(*id, ctx, generator).unwrap();
+
+                let globals = ctx
+                    .top_level
+                    .definitions
+                    .read()
+                    .iter()
+                    .filter_map(|def| {
+                        if let TopLevelDef::Variable { simple_name, ty, .. } = &*def.read() {
+                            Some((*simple_name, *ty))
+                        } else {
+                            None
+                        }
+                    })
+                    .collect_vec();
+
+                if let Some((_, ty)) = globals.iter().find(|(name, _)| name == id) {
+                    let ptr = value
+                        .to_basic_value_enum(ctx, generator, *ty)
+                        .map(BasicValueEnum::into_pointer_value)?;
+
+                    ctx.builder.build_load(ptr, id.to_string().as_str()).map(Into::into).unwrap()
+                } else {
+                    value
+                }
             }
         },
         ExprKind::List { elts, .. } => {

nac3core/src/toplevel/composer.rs

@@ -485,7 +485,7 @@ impl TopLevelComposer {
                     // things like `class A(Generic[T, V, ImportedModule.T])` is not supported
                     // i.e. only simple names are allowed in the subscript
                     // should update the TopLevelDef::Class.typevars and the TypeEnum::TObj.params
-                    ast::ExprKind::Subscript { value, slice, .. }
+                    ExprKind::Subscript { value, slice, .. }
                         if {
                             matches!(
                                 &value.node,
@@ -501,9 +501,9 @@ impl TopLevelComposer {
                         }
                         is_generic = true;
 
-                        let type_var_list: Vec<&ast::Expr<()>>;
+                        let type_var_list: Vec<&Expr<()>>;
                         // if `class A(Generic[T, V, G])`
-                        if let ast::ExprKind::Tuple { elts, .. } = &slice.node {
+                        if let ExprKind::Tuple { elts, .. } = &slice.node {
                             type_var_list = elts.iter().collect_vec();
                         // `class A(Generic[T])`
                         } else {
@@ -1014,18 +1014,18 @@ impl TopLevelComposer {
                     }
                 }
 
-                let arg_with_default: Vec<(&ast::Located<ast::ArgData<()>>, Option<&ast::Expr>)> =
+                let arg_with_default: Vec<(&ast::Located<ast::ArgData<()>>, Option<&Expr>)> = args
-                    args.args
+                    .args
-                        .iter()
+                    .iter()
-                        .rev()
+                    .rev()
-                        .zip(
+                    .zip(
-                            args.defaults
+                        args.defaults
-                                .iter()
+                            .iter()
-                                .rev()
+                            .rev()
-                                .map(|x| -> Option<&ast::Expr> { Some(x) })
+                            .map(|x| -> Option<&Expr> { Some(x) })
-                                .chain(std::iter::repeat(None)),
+                            .chain(std::iter::repeat(None)),
-                        )
+                    )
-                        .collect_vec();
+                    .collect_vec();
 
                 arg_with_default
                     .iter()
@@ -1283,7 +1283,7 @@ impl TopLevelComposer {
 
                         let arg_with_default: Vec<(
                             &ast::Located<ast::ArgData<()>>,
-                            Option<&ast::Expr>,
+                            Option<&Expr>,
                         )> = args
                             .args
                             .iter()
@@ -1292,7 +1292,7 @@ impl TopLevelComposer {
                                 args.defaults
                                     .iter()
                                     .rev()
-                                    .map(|x| -> Option<&ast::Expr> { Some(x) })
+                                    .map(|x| -> Option<&Expr> { Some(x) })
                                     .chain(std::iter::repeat(None)),
                             )
                             .collect_vec();
@@ -1449,7 +1449,7 @@ impl TopLevelComposer {
                         .map_err(|e| HashSet::from([e.to_display(unifier).to_string()]))?;
                 }
                 ast::StmtKind::AnnAssign { target, annotation, value, .. } => {
-                    if let ast::ExprKind::Name { id: attr, .. } = &target.node {
+                    if let ExprKind::Name { id: attr, .. } = &target.node {
                         if defined_fields.insert(attr.to_string()) {
                             let dummy_field_type = unifier.get_dummy_var().ty;
 
@@ -1457,7 +1457,7 @@ impl TopLevelComposer {
                                 None => {
                                     // handle Kernel[T], KernelInvariant[T]
                                     let (annotation, mutable) = match &annotation.node {
-                                        ast::ExprKind::Subscript { value, slice, .. }
+                                        ExprKind::Subscript { value, slice, .. }
                                             if matches!(
                                                 &value.node,
                                                 ast::ExprKind::Name { id, .. } if id == &core_config.kernel_invariant_ann.into()
@@ -1465,7 +1465,7 @@ impl TopLevelComposer {
                                         {
                                             (slice, false)
                                         }
-                                        ast::ExprKind::Subscript { value, slice, .. }
+                                        ExprKind::Subscript { value, slice, .. }
                                             if matches!(
                                                 &value.node,
                                                 ast::ExprKind::Name { id, .. } if core_config.kernel_ann.map_or(false, |c| id == &c.into())
@@ -1483,13 +1483,13 @@ impl TopLevelComposer {
                                 Some(boxed_expr) => {
                                     // Class attributes are set as immutable regardless
                                     let (annotation, _) = match &annotation.node {
-                                        ast::ExprKind::Subscript { slice, .. } => (slice, false),
+                                        ExprKind::Subscript { slice, .. } => (slice, false),
                                         _ if core_config.kernel_ann.is_none() => (annotation, false),
                                         _ => continue,
                                     };
 
                                     match &**boxed_expr {
-                                        ast::Located {location: _, custom: (), node: ast::ExprKind::Constant { value: v, kind: _ }} => {
+                                        ast::Located {location: _, custom: (), node: ExprKind::Constant { value: v, kind: _ }} => {
                                             // Restricting the types allowed to be defined as class attributes
                                             match v {
                                                 ast::Constant::Bool(_) | ast::Constant::Str(_) | ast::Constant::Int(_) | ast::Constant::Float(_) => {}
@@ -1937,284 +1937,296 @@ impl TopLevelComposer {
             if ast.is_none() {
                 return Ok(());
             }
-            let mut function_def = def.write();
+
-            if let TopLevelDef::Function {
+            let (name, simple_name, signature, resolver) = {
-                instance_to_stmt,
+                let function_def = def.read();
-                instance_to_symbol,
+                let TopLevelDef::Function { name, simple_name, signature, resolver, .. } =
-                name,
+                    &*function_def
-                simple_name,
-                signature,
-                resolver,
-                ..
-            } = &mut *function_def
-            {
-                let signature_ty_enum = unifier.get_ty(*signature);
-                let TypeEnum::TFunc(FunSignature { args, ret, vars, .. }) =
-                    signature_ty_enum.as_ref()
                 else {
-                    unreachable!("must be typeenum::tfunc")
+                    return Ok(());
                 };
 
-                let mut vars = vars.clone();
+                (name.clone(), *simple_name, *signature, resolver.clone())
-                // None if is not class method
+            };
-                let uninst_self_type = {
+
-                    if let Some(class_id) = method_class.get(&DefinitionId(id)) {
+            let signature_ty_enum = unifier.get_ty(signature);
-                        let class_def = definition_ast_list.get(class_id.0).unwrap();
+            let TypeEnum::TFunc(FunSignature { args, ret, vars, .. }) = signature_ty_enum.as_ref()
-                        let class_def = class_def.0.read();
+            else {
-                        let TopLevelDef::Class { type_vars, .. } = &*class_def else {
+                unreachable!("must be typeenum::tfunc")
-                            unreachable!("must be class def")
+            };
+
+            let mut vars = vars.clone();
+            // None if is not class method
+            let uninst_self_type = {
+                if let Some(class_id) = method_class.get(&DefinitionId(id)) {
+                    let class_def = definition_ast_list.get(class_id.0).unwrap();
+                    let class_def = class_def.0.read();
+                    let TopLevelDef::Class { type_vars, .. } = &*class_def else {
+                        unreachable!("must be class def")
+                    };
+
+                    let ty_ann = make_self_type_annotation(type_vars, *class_id);
+                    let self_ty = get_type_from_type_annotation_kinds(
+                        &def_list,
+                        unifier,
+                        primitives_ty,
+                        &ty_ann,
+                        &mut None,
+                    )?;
+                    vars.extend(type_vars.iter().map(|ty| {
+                        let TypeEnum::TVar { id, .. } = &*unifier.get_ty(*ty) else {
+                            unreachable!()
                         };
 
-                        let ty_ann = make_self_type_annotation(type_vars, *class_id);
+                        (*id, *ty)
-                        let self_ty = get_type_from_type_annotation_kinds(
+                    }));
-                            &def_list,
+                    Some((self_ty, type_vars.clone()))
-                            unifier,
+                } else {
-                            primitives_ty,
+                    None
-                            &ty_ann,
+                }
-                            &mut None,
+            };
-                        )?;
+            // carefully handle those with bounds, without bounds and no typevars
-                        vars.extend(type_vars.iter().map(|ty| {
+            // if class methods, `vars` also contains all class typevars here
-                            let TypeEnum::TVar { id, .. } = &*unifier.get_ty(*ty) else {
+            let (type_var_subst_comb, no_range_vars) = {
+                let mut no_ranges: Vec<Type> = Vec::new();
+                let var_combs = vars
+                    .values()
+                    .map(|ty| {
+                        unifier.get_instantiations(*ty).unwrap_or_else(|| {
+                            let TypeEnum::TVar { name, loc, is_const_generic: false, .. } =
+                                &*unifier.get_ty(*ty)
+                            else {
                                 unreachable!()
                             };
 
-                            (*id, *ty)
+                            let rigid = unifier.get_fresh_rigid_var(*name, *loc).ty;
-                        }));
+                            no_ranges.push(rigid);
-                        Some((self_ty, type_vars.clone()))
+                            vec![rigid]
-                    } else {
-                        None
-                    }
-                };
-                // carefully handle those with bounds, without bounds and no typevars
-                // if class methods, `vars` also contains all class typevars here
-                let (type_var_subst_comb, no_range_vars) = {
-                    let mut no_ranges: Vec<Type> = Vec::new();
-                    let var_combs = vars
-                        .values()
-                        .map(|ty| {
-                            unifier.get_instantiations(*ty).unwrap_or_else(|| {
-                                let TypeEnum::TVar { name, loc, is_const_generic: false, .. } =
-                                    &*unifier.get_ty(*ty)
-                                else {
-                                    unreachable!()
-                                };
-
-                                let rigid = unifier.get_fresh_rigid_var(*name, *loc).ty;
-                                no_ranges.push(rigid);
-                                vec![rigid]
-                            })
                         })
-                        .multi_cartesian_product()
+                    })
-                        .collect_vec();
+                    .multi_cartesian_product()
-                    let mut result: Vec<VarMap> = Vec::default();
+                    .collect_vec();
-                    for comb in var_combs {
+                let mut result: Vec<VarMap> = Vec::default();
-                        result.push(vars.keys().copied().zip(comb).collect());
+                for comb in var_combs {
+                    result.push(vars.keys().copied().zip(comb).collect());
+                }
+                // NOTE: if is empty, means no type var, append a empty subst, ok to do this?
+                if result.is_empty() {
+                    result.push(VarMap::new());
+                }
+                (result, no_ranges)
+            };
+
+            for subst in type_var_subst_comb {
+                // for each instance
+                let inst_ret = unifier.subst(*ret, &subst).unwrap_or(*ret);
+                let inst_args = {
+                    args.iter()
+                        .map(|a| FuncArg {
+                            name: a.name,
+                            ty: unifier.subst(a.ty, &subst).unwrap_or(a.ty),
+                            default_value: a.default_value.clone(),
+                            is_vararg: false,
+                        })
+                        .collect_vec()
+                };
+                let self_type = {
+                    uninst_self_type.clone().map(|(self_type, type_vars)| {
+                        let subst_for_self = {
+                            let class_ty_var_ids = type_vars
+                                .iter()
+                                .map(|x| {
+                                    if let TypeEnum::TVar { id, .. } = &*unifier.get_ty(*x) {
+                                        *id
+                                    } else {
+                                        unreachable!("must be type var here");
+                                    }
+                                })
+                                .collect::<HashSet<_>>();
+                            subst
+                                .iter()
+                                .filter_map(|(ty_var_id, ty_var_target)| {
+                                    if class_ty_var_ids.contains(ty_var_id) {
+                                        Some((*ty_var_id, *ty_var_target))
+                                    } else {
+                                        None
+                                    }
+                                })
+                                .collect::<VarMap>()
+                        };
+                        unifier.subst(self_type, &subst_for_self).unwrap_or(self_type)
+                    })
+                };
+                let mut identifiers = {
+                    let mut result = HashMap::new();
+                    if self_type.is_some() {
+                        result.insert("self".into(), IdentifierInfo::default());
                     }
-                    // NOTE: if is empty, means no type var, append a empty subst, ok to do this?
+                    result.extend(inst_args.iter().map(|x| (x.name, IdentifierInfo::default())));
-                    if result.is_empty() {
+                    result
-                        result.push(VarMap::new());
+                };
-                    }
+                let mut calls: HashMap<CodeLocation, CallId> = HashMap::new();
-                    (result, no_ranges)
+                let mut inferencer = Inferencer {
+                    top_level: ctx.as_ref(),
+                    defined_identifiers: identifiers.clone(),
+                    function_data: &mut FunctionData {
+                        resolver: resolver.as_ref().unwrap().clone(),
+                        return_type: if unifier.unioned(inst_ret, primitives_ty.none) {
+                            None
+                        } else {
+                            Some(inst_ret)
+                        },
+                        // NOTE: allowed type vars
+                        bound_variables: no_range_vars.clone(),
+                    },
+                    unifier,
+                    variable_mapping: {
+                        let mut result: HashMap<StrRef, Type> = HashMap::new();
+                        if let Some(self_ty) = self_type {
+                            result.insert("self".into(), self_ty);
+                        }
+                        result.extend(inst_args.iter().map(|x| (x.name, x.ty)));
+                        result
+                    },
+                    primitives: primitives_ty,
+                    virtual_checks: &mut Vec::new(),
+                    calls: &mut calls,
+                    in_handler: false,
                 };
 
-                for subst in type_var_subst_comb {
+                let ast::StmtKind::FunctionDef { body, decorator_list, .. } =
-                    // for each instance
+                    ast.clone().unwrap().node
-                    let inst_ret = unifier.subst(*ret, &subst).unwrap_or(*ret);
+                else {
-                    let inst_args = {
+                    unreachable!("must be function def ast")
-                        args.iter()
+                };
-                            .map(|a| FuncArg {
+
-                                name: a.name,
+                if !decorator_list.is_empty() {
-                                ty: unifier.subst(a.ty, &subst).unwrap_or(a.ty),
+                    if matches!(&decorator_list[0].node, ExprKind::Name { id, .. } if id == &"extern".into())
-                                default_value: a.default_value.clone(),
+                    {
-                                is_vararg: false,
+                        let TopLevelDef::Function { instance_to_symbol, .. } = &mut *def.write()
-                            })
+                        else {
-                            .collect_vec()
+                            unreachable!()
-                    };
+                        };
-                    let self_type = {
+                        instance_to_symbol.insert(String::new(), simple_name.to_string());
-                        uninst_self_type.clone().map(|(self_type, type_vars)| {
+                        continue;
-                            let subst_for_self = {
+                    }
-                                let class_ty_var_ids = type_vars
+
-                                    .iter()
+                    if matches!(&decorator_list[0].node, ExprKind::Name { id, .. } if id == &"rpc".into())
-                                    .map(|x| {
+                    {
-                                        if let TypeEnum::TVar { id, .. } = &*unifier.get_ty(*x) {
+                        let TopLevelDef::Function { instance_to_symbol, .. } = &mut *def.write()
-                                            *id
+                        else {
-                                        } else {
+                            unreachable!()
-                                            unreachable!("must be type var here");
+                        };
-                                        }
+                        instance_to_symbol.insert(String::new(), simple_name.to_string());
-                                    })
+                        continue;
-                                    .collect::<HashSet<_>>();
+                    }
-                                subst
+
-                                    .iter()
+                    if let ExprKind::Call { func, .. } = &decorator_list[0].node {
-                                    .filter_map(|(ty_var_id, ty_var_target)| {
+                        if matches!(&func.node, ExprKind::Name { id, .. } if id == &"rpc".into()) {
-                                        if class_ty_var_ids.contains(ty_var_id) {
+                            let TopLevelDef::Function { instance_to_symbol, .. } =
-                                            Some((*ty_var_id, *ty_var_target))
+                                &mut *def.write()
-                                        } else {
+                            else {
-                                            None
+                                unreachable!()
-                                        }
-                                    })
-                                    .collect::<VarMap>()
                             };
-                            unifier.subst(self_type, &subst_for_self).unwrap_or(self_type)
+                            instance_to_symbol.insert(String::new(), simple_name.to_string());
-                        })
+                            continue;
-                    };
-                    let mut identifiers = {
-                        let mut result = HashMap::new();
-                        if self_type.is_some() {
-                            result.insert("self".into(), IdentifierInfo::default());
-                        }
-                        result
-                            .extend(inst_args.iter().map(|x| (x.name, IdentifierInfo::default())));
-                        result
-                    };
-                    let mut calls: HashMap<CodeLocation, CallId> = HashMap::new();
-                    let mut inferencer = Inferencer {
-                        top_level: ctx.as_ref(),
-                        defined_identifiers: identifiers.clone(),
-                        function_data: &mut FunctionData {
-                            resolver: resolver.as_ref().unwrap().clone(),
-                            return_type: if unifier.unioned(inst_ret, primitives_ty.none) {
-                                None
-                            } else {
-                                Some(inst_ret)
-                            },
-                            // NOTE: allowed type vars
-                            bound_variables: no_range_vars.clone(),
-                        },
-                        unifier,
-                        variable_mapping: {
-                            let mut result: HashMap<StrRef, Type> = HashMap::new();
-                            if let Some(self_ty) = self_type {
-                                result.insert("self".into(), self_ty);
-                            }
-                            result.extend(inst_args.iter().map(|x| (x.name, x.ty)));
-                            result
-                        },
-                        primitives: primitives_ty,
-                        virtual_checks: &mut Vec::new(),
-                        calls: &mut calls,
-                        in_handler: false,
-                    };
-
-                    let ast::StmtKind::FunctionDef { body, decorator_list, .. } =
-                        ast.clone().unwrap().node
-                    else {
-                        unreachable!("must be function def ast")
-                    };
-                    if !decorator_list.is_empty()
-                        && matches!(&decorator_list[0].node,
-                            ast::ExprKind::Name{ id, .. } if id == &"extern".into())
-                    {
-                        instance_to_symbol.insert(String::new(), simple_name.to_string());
-                        continue;
-                    }
-                    if !decorator_list.is_empty()
-                        && matches!(&decorator_list[0].node,
-                            ast::ExprKind::Name{ id, .. } if id == &"rpc".into())
-                    {
-                        instance_to_symbol.insert(String::new(), simple_name.to_string());
-                        continue;
-                    }
-                    if !decorator_list.is_empty() {
-                        if let ast::ExprKind::Call { func, .. } = &decorator_list[0].node {
-                            if matches!(&func.node,
-                                ast::ExprKind::Name{ id, .. } if id == &"rpc".into())
-                            {
-                                instance_to_symbol.insert(String::new(), simple_name.to_string());
-                                continue;
-                            }
                         }
                     }
+                }
 
-                    let fun_body = body
+                let fun_body =
-                        .into_iter()
+                    body.into_iter()
                         .map(|b| inferencer.fold_stmt(b))
                         .collect::<Result<Vec<_>, _>>()?;
 
-                    let returned = inferencer.check_block(fun_body.as_slice(), &mut identifiers)?;
+                let returned = inferencer.check_block(fun_body.as_slice(), &mut identifiers)?;
-                    {
+                {
-                        // check virtuals
+                    // check virtuals
-                        let defs = ctx.definitions.read();
+                    let defs = ctx.definitions.read();
-                        for (subtype, base, loc) in &*inferencer.virtual_checks {
+                    for (subtype, base, loc) in &*inferencer.virtual_checks {
-                            let base_id = {
+                        let base_id = {
-                                let base = inferencer.unifier.get_ty(*base);
+                            let base = inferencer.unifier.get_ty(*base);
-                                if let TypeEnum::TObj { obj_id, .. } = &*base {
+                            if let TypeEnum::TObj { obj_id, .. } = &*base {
-                                    *obj_id
+                                *obj_id
-                                } else {
+                            } else {
-                                    return Err(HashSet::from([format!(
+                                return Err(HashSet::from([format!(
-                                        "Base type should be a class (at {loc})"
+                                    "Base type should be a class (at {loc})"
-                                    )]));
+                                )]));
-                                }
+                            }
-                            };
+                        };
-                            let subtype_id = {
+                        let subtype_id = {
-                                let ty = inferencer.unifier.get_ty(*subtype);
+                            let ty = inferencer.unifier.get_ty(*subtype);
-                                if let TypeEnum::TObj { obj_id, .. } = &*ty {
+                            if let TypeEnum::TObj { obj_id, .. } = &*ty {
-                                    *obj_id
+                                *obj_id
-                                } else {
+                            } else {
-                                    let base_repr = inferencer.unifier.stringify(*base);
-                                    let subtype_repr = inferencer.unifier.stringify(*subtype);
-                                    return Err(HashSet::from([format!(
-                                        "Expected a subtype of {base_repr}, but got {subtype_repr} (at {loc})"),
-                                    ]));
-                                }
-                            };
-                            let subtype_entry = defs[subtype_id.0].read();
-                            let TopLevelDef::Class { ancestors, .. } = &*subtype_entry else {
-                                unreachable!()
-                            };
-
-                            let m = ancestors.iter()
-                                .find(|kind| matches!(kind, TypeAnnotation::CustomClass { id, .. } if *id == base_id));
-                            if m.is_none() {
                                 let base_repr = inferencer.unifier.stringify(*base);
                                 let subtype_repr = inferencer.unifier.stringify(*subtype);
                                 return Err(HashSet::from([format!(
                                     "Expected a subtype of {base_repr}, but got {subtype_repr} (at {loc})"),
                                 ]));
                             }
+                        };
+                        let subtype_entry = defs[subtype_id.0].read();
+                        let TopLevelDef::Class { ancestors, .. } = &*subtype_entry else {
+                            unreachable!()
+                        };
+
+                        let m = ancestors.iter()
+                            .find(|kind| matches!(kind, TypeAnnotation::CustomClass { id, .. } if *id == base_id));
+                        if m.is_none() {
+                            let base_repr = inferencer.unifier.stringify(*base);
+                            let subtype_repr = inferencer.unifier.stringify(*subtype);
+                            return Err(HashSet::from([format!(
+                                "Expected a subtype of {base_repr}, but got {subtype_repr} (at {loc})"),
+                            ]));
                         }
                     }
-                    if !unifier.unioned(inst_ret, primitives_ty.none) && !returned {
-                        let def_ast_list = &definition_ast_list;
-                        let ret_str = unifier.internal_stringify(
-                            inst_ret,
-                            &mut |id| {
-                                let TopLevelDef::Class { name, .. } = &*def_ast_list[id].0.read()
-                                else {
-                                    unreachable!("must be class id here")
-                                };
-
-                                name.to_string()
-                            },
-                            &mut |id| format!("typevar{id}"),
-                            &mut None,
-                        );
-                        return Err(HashSet::from([format!(
-                            "expected return type of `{}` in function `{}` (at {})",
-                            ret_str,
-                            name,
-                            ast.as_ref().unwrap().location
-                        )]));
-                    }
-
-                    instance_to_stmt.insert(
-                        get_subst_key(
-                            unifier,
-                            self_type,
-                            &subst,
-                            Some(&vars.keys().copied().collect()),
-                        ),
-                        FunInstance {
-                            body: Arc::new(fun_body),
-                            unifier_id: 0,
-                            calls: Arc::new(calls),
-                            subst,
-                        },
-                    );
                 }
+                if !unifier.unioned(inst_ret, primitives_ty.none) && !returned {
+                    let def_ast_list = &definition_ast_list;
+                    let ret_str = unifier.internal_stringify(
+                        inst_ret,
+                        &mut |id| {
+                            let TopLevelDef::Class { name, .. } = &*def_ast_list[id].0.read()
+                            else {
+                                unreachable!("must be class id here")
+                            };
+
+                            name.to_string()
+                        },
+                        &mut |id| format!("typevar{id}"),
+                        &mut None,
+                    );
+                    return Err(HashSet::from([format!(
+                        "expected return type of `{}` in function `{}` (at {})",
+                        ret_str,
+                        name,
+                        ast.as_ref().unwrap().location
+                    )]));
+                }
+
+                let TopLevelDef::Function { instance_to_stmt, .. } = &mut *def.write() else {
+                    unreachable!()
+                };
+                instance_to_stmt.insert(
+                    get_subst_key(
+                        unifier,
+                        self_type,
+                        &subst,
+                        Some(&vars.keys().copied().collect()),
+                    ),
+                    FunInstance {
+                        body: Arc::new(fun_body),
+                        unifier_id: 0,
+                        calls: Arc::new(calls),
+                        subst,
+                    },
+                );
             }
 
             Ok(())
         };
+
         for (id, (def, ast)) in self.definition_ast_list.iter().enumerate().skip(self.builtin_num) {
             if ast.is_none() {
                 continue;

nac3core/src/typecheck/function_check.rs

@@ -10,7 +10,7 @@ use nac3parser::ast::{
 };
 
 use super::{
-    type_inferencer::{IdentifierInfo, Inferencer},
+    type_inferencer::{DeclarationSource, IdentifierInfo, Inferencer},
     typedef::{Type, TypeEnum},
 };
 use crate::toplevel::helper::PrimDef;
@@ -34,6 +34,20 @@ impl<'a> Inferencer<'a> {
                 Err(HashSet::from([format!("cannot assign to a `none` (at {})", pattern.location)]))
             }
             ExprKind::Name { id, .. } => {
+                // If `id` refers to a declared symbol, reject this assignment if it is used in the
+                // context of an (implicit) global variable
+                if let Some(id_info) = self.defined_identifiers.get(id) {
+                    if matches!(
+                        id_info.source,
+                        DeclarationSource::Global { is_explicit: Some(false) }
+                    ) {
+                        return Err(HashSet::from([format!(
+                            "cannot access local variable '{id}' before it is declared (at {})",
+                            pattern.location
+                        )]));
+                    }
+                }
+
                 if !defined_identifiers.contains_key(id) {
                     defined_identifiers.insert(*id, IdentifierInfo::default());
                 }
@@ -104,7 +118,7 @@ impl<'a> Inferencer<'a> {
                         *id,
                     ) {
                         Ok(_) => {
-                            self.defined_identifiers.insert(*id, IdentifierInfo::default());
+                            defined_identifiers.insert(*id, IdentifierInfo::default());
                         }
                         Err(e) => {
                             return Err(HashSet::from([format!(
@@ -368,9 +382,9 @@ impl<'a> Inferencer<'a> {
             StmtKind::Global { names, .. } => {
                 for id in names {
                     if let Some(id_info) = defined_identifiers.get(id) {
-                        if !id_info.is_global {
+                        if id_info.source == DeclarationSource::Local {
                             return Err(HashSet::from([format!(
-                                "name '{id}' is assigned to before global declaration at {}",
+                                "name '{id}' is used prior to global declaration at {}",
                                 stmt.location,
                             )]));
                         }
@@ -385,8 +399,12 @@ impl<'a> Inferencer<'a> {
                         *id,
                     ) {
                         Ok(_) => {
-                            self.defined_identifiers
+                            self.defined_identifiers.insert(
-                                .insert(*id, IdentifierInfo { is_global: true });
+                                *id,
+                                IdentifierInfo {
+                                    source: DeclarationSource::Global { is_explicit: Some(true) },
+                                },
+                            );
                         }
                         Err(e) => {
                             return Err(HashSet::from([format!(

nac3core/src/typecheck/type_inferencer/mod.rs

@@ -88,11 +88,31 @@ impl PrimitiveStore {
     }
 }
 
+/// The location where an identifier declaration refers to.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum DeclarationSource {
+    /// Local scope.
+    Local,
+
+    /// Global scope.
+    Global {
+        /// Whether the identifier is declared by the use of `global` statement. This field is
+        /// [`None`] if the identifier does not refer to a variable.
+        is_explicit: Option<bool>,
+    },
+}
+
 /// Information regarding a defined identifier.
-#[derive(Clone, Copy, Debug, Default)]
+#[derive(Clone, Copy, Debug)]
 pub struct IdentifierInfo {
     /// Whether this identifier refers to a global variable.
-    pub is_global: bool,
+    pub source: DeclarationSource,
+}
+
+impl Default for IdentifierInfo {
+    fn default() -> Self {
+        IdentifierInfo { source: DeclarationSource::Local }
+    }
 }
 
 impl IdentifierInfo {
@@ -566,15 +586,45 @@ impl<'a> Fold<()> for Inferencer<'a> {
                         unreachable!("must be tobj")
                     }
                 } else {
+                    let top_level_defs = &self.top_level.definitions.read();
+
                     if !self.defined_identifiers.contains_key(id) {
                         match self.function_data.resolver.get_symbol_type(
                             self.unifier,
-                            &self.top_level.definitions.read(),
+                            top_level_defs,
                             self.primitives,
                             *id,
                         ) {
                             Ok(_) => {
-                                self.defined_identifiers.insert(*id, IdentifierInfo::default());
+                                // Determine if the referenced id refers to a global symbol
+                                let is_explicit = top_level_defs
+                                    .iter()
+                                    .map(|def| match *def.read() {
+                                        TopLevelDef::Class { name, .. } => (name, false),
+                                        TopLevelDef::Function { simple_name, .. } => {
+                                            (simple_name, false)
+                                        }
+                                        TopLevelDef::Variable { simple_name, .. } => {
+                                            (simple_name, true)
+                                        }
+                                    })
+                                    .find(|(global, _)| global == id)
+                                    .map(|(_, has_explicit_prop)| has_explicit_prop);
+
+                                self.defined_identifiers.insert(
+                                    *id,
+                                    IdentifierInfo {
+                                        source: match is_explicit {
+                                            Some(true) => DeclarationSource::Global {
+                                                is_explicit: Some(false),
+                                            },
+                                            Some(false) => {
+                                                DeclarationSource::Global { is_explicit: None }
+                                            }
+                                            None => DeclarationSource::Local,
+                                        },
+                                    },
+                                );
                             }
                             Err(e) => {
                                 return report_error(