[WIP] Make statement lists have a scope

Note that this doesn't actually properly execute shadowing, it simply
makes it not error. And introduces a bunch of other problems.

The reason this doesn't shadow variables is that locals are created at
parse time (hence why a scope is needed in both `Stmt.cc` and `parse.y`
for the statement lists), but locals are used at execution time
(obviously). This means that executing the local will just grab the
outer scope one every time - the inner scope one goes to die.

So the next step *could* be to move locals to getting created at
execution time, which seems like it's what should happen. But that may
be a lot of work.

Optionally, we can alse just add a scope counter and "append" that in
some way to the variable's name. That seems pretty easy.

Not that shadowing is that important to do anyway, I just wanted to try.

src/Expr.cc

@@ -4321,7 +4321,7 @@ void LambdaExpr::BuildName() {
 
         my_name = "lambda_<" + std::to_string(h[0]) + ">";
         auto fullname = make_full_var_name(current_module.data(), my_name.data());
-        const auto& id = current_scope()->Find(fullname);
+        const auto& id = current_function_scope()->Find(fullname);
 
         if ( id )
             // Just try again to make a unique lambda name.

src/Scope.cc

@@ -90,7 +90,7 @@ TraversalCode Scope::Traverse(TraversalCallback* cb) const {
 }
 
 const IDPtr& lookup_ID(const char* name, const char* curr_module, bool no_global, bool same_module_only,
-                       bool check_export) {
+                       bool check_export, bool same_scope_only) {
     bool explicit_global = zeek::util::starts_with(name, "::");
 
     static std::string global_prefix = util::fmt("%s::", GLOBAL_MODULE_NAME);
@@ -123,6 +123,9 @@ const IDPtr& lookup_ID(const char* name, const char* curr_module, bool no_global
 
                 return id;
             }
+
+            if ( same_scope_only )
+                break;
         }
     }
 
@@ -170,20 +173,39 @@ void push_scope(IDPtr id, std::unique_ptr<std::vector<AttrPtr>> attrs) {
     scopes.push_back(top_scope);
 }
 
+void pop_local_scope() {
+    scopes.pop_back();
+    top_scope = scopes.empty() ? nullptr : scopes.back();
+}
+
 ScopePtr pop_scope() {
     if ( scopes.empty() )
         reporter->InternalError("scope underflow");
+
+    while ( scopes.back()->GetID() == nullptr )
+        scopes.pop_back();
+
+    auto old_top = scopes.back();
+
     scopes.pop_back();
 
-    auto old_top = top_scope;
-
-    top_scope = scopes.empty() ? nullptr : scopes.back();
+    top_scope = scopes.back();
 
     return old_top;
 }
 
 ScopePtr current_scope() { return top_scope; }
 
+ScopePtr current_function_scope() {
+    for ( auto s_i = scopes.rbegin(); s_i != scopes.rend(); ++s_i ) {
+        if ( (*s_i)->GetID() != nullptr ) {
+            return *s_i;
+        }
+    }
+
+    return top_scope;
+}
+
 ScopePtr global_scope() { return scopes.empty() ? 0 : scopes.front(); }
 
 } // namespace zeek::detail

src/Scope.h

@@ -81,7 +81,7 @@ protected:
 
 // If no_global is true, don't search in the default "global" namespace.
 extern const IDPtr& lookup_ID(const char* name, const char* module, bool no_global = false,
-                              bool same_module_only = false, bool check_export = true);
+                              bool same_module_only = false, bool check_export = true, bool same_scope_only = false);
 
 extern IDPtr install_ID(const char* name, const char* module_name, bool is_global, bool is_export);
 
@@ -91,7 +91,10 @@ extern void push_existing_scope(ScopePtr scope);
 // Returns the one popped off.
 extern ScopePtr pop_scope();
 
+extern void pop_local_scope();
+
 extern ScopePtr current_scope();
+extern ScopePtr current_function_scope();
 extern ScopePtr global_scope();
 
 // Current module (identified by its name).

src/Stmt.cc

@@ -1355,9 +1355,9 @@ TraversalCode FallthroughStmt::Traverse(TraversalCallback* cb) const {
 }
 
 ReturnStmt::ReturnStmt(ExprPtr arg_e) : ExprStmt(STMT_RETURN, std::move(arg_e)) {
-    auto s = current_scope();
+    auto s = current_function_scope();
 
-    if ( ! s || ! s->GetID() ) {
+    if ( ! s ) {
         Error("return statement outside of function/event");
         return;
     }
@@ -1419,6 +1419,7 @@ void ReturnStmt::StmtDescribe(ODesc* d) const {
 StmtList::StmtList() : Stmt(STMT_LIST) {}
 
 ValPtr StmtList::Exec(Frame* f, StmtFlowType& flow) {
+    push_scope(nullptr, nullptr);
     RegisterAccess();
     flow = FLOW_NEXT;
 
@@ -1439,6 +1440,7 @@ ValPtr StmtList::Exec(Frame* f, StmtFlowType& flow) {
             return result;
     }
 
+    pop_local_scope();
     return nullptr;
 }
 
@@ -1729,7 +1731,7 @@ WhenInfo::WhenInfo(ExprPtr arg_cond, FuncType::CaptureList* arg_cl, bool arg_is_
 
     lambda_ft->SetCaptures(*cl);
 
-    auto id = current_scope()->GenerateTemporary("when-internal");
+    auto id = current_function_scope()->GenerateTemporary("when-internal");
     id->SetType(lambda_ft);
     push_scope(std::move(id), nullptr);
 
@@ -1848,7 +1850,7 @@ void WhenInfo::Build(StmtPtr ws) {
 
     auto shebang = make_intrusive<StmtList>(do_test, do_bodies, dummy_return);
 
-    auto ingredients = std::make_shared<FunctionIngredients>(current_scope(), shebang, current_module);
+    auto ingredients = std::make_shared<FunctionIngredients>(current_function_scope(), shebang, current_module);
     auto outer_ids = gather_outer_ids(pop_scope(), ingredients->Body());
 
     lambda = make_intrusive<LambdaExpr>(std::move(ingredients), std::move(outer_ids), "", ws);

src/Var.cc

@@ -644,8 +644,8 @@ void begin_func(IDPtr id, const char* module_name, FunctionFlavor flavor, bool i
         if ( ! check_params(i, prototype, args, canon_args, module_name) )
             break;
 
-    if ( Attr* depr_attr = find_attr(current_scope()->Attrs().get(), ATTR_DEPRECATED) )
-        current_scope()->GetID()->MakeDeprecated(depr_attr->GetExpr());
+    if ( Attr* depr_attr = find_attr(current_function_scope()->Attrs().get(), ATTR_DEPRECATED) )
+        current_function_scope()->GetID()->MakeDeprecated(depr_attr->GetExpr());
 
     // Reset the AST node statistics to track afresh for this function.
     Stmt::ResetNumStmts();

src/parse.y

@@ -154,9 +154,6 @@ bool defining_global_ID = false;
 std::vector<int> saved_in_init;
 static int expr_list_has_opt_comma = 0;
 
-std::vector<std::set<const ID*>> locals_at_this_scope;
-static std::unordered_set<const ID*> out_of_scope_locals;
-
 static Location func_hdr_location;
 static int func_hdr_cond_epoch = 0;
 EnumType* cur_enum_type = nullptr;
@@ -772,8 +769,6 @@ expr:
 	|	TOK_WHEN_LOCAL local_id '=' rhs
 			{
 			set_location(@2, @4);
-			if ( ! locals_at_this_scope.empty() )
-			       locals_at_this_scope.back().insert($2);
 			$$ = add_and_assign_local({AdoptRef{}, $2}, {AdoptRef{}, $4},
 			                                        val_mgr->True()).release();
 			}
@@ -1012,9 +1007,6 @@ expr:
 					}
 				else
 					{
-					if ( out_of_scope_locals.count(id.get()) > 0 )
-						id->Error("use of out-of-scope local; move declaration to outer scope");
-
 					$$ = new NameExpr(std::move(id));
 					}
 				}
@@ -1545,9 +1537,6 @@ func_body:
 			{
 			saved_in_init.push_back(in_init);
 			in_init = 0;
-
-			locals_at_this_scope.clear();
-			out_of_scope_locals.clear();
 			}
 
 		stmt_list
@@ -1832,19 +1821,18 @@ attr:
 stmt:
 		'{'
 			{
+            push_scope(nullptr, nullptr);
 			std::set<const ID*> id_set;
-			locals_at_this_scope.emplace_back(id_set);
 			}
 		opt_no_test_block stmt_list '}'
 			{
-			auto& scope_locals = locals_at_this_scope.back();
-			out_of_scope_locals.insert(scope_locals.begin(), scope_locals.end());
-			locals_at_this_scope.pop_back();
 
 			set_location(@1, @5);
 			$$ = $4;
 			if ( $3 )
 			    script_coverage_mgr.DecIgnoreDepth();
+
+            pop_local_scope();
 			}
 
 	|	TOK_ASSERT expr opt_assert_msg ';'
@@ -1949,8 +1937,6 @@ stmt:
 	|	TOK_LOCAL local_id opt_type init_class opt_init opt_attr ';' opt_no_test
 			{
 			set_location(@1, @7);
-			if ( ! locals_at_this_scope.empty() )
-			       locals_at_this_scope.back().insert($2);
 			$$ = build_local($2, $3, $4, $5, $6, VAR_REGULAR, ! $8).release();
 			}
 
@@ -2174,7 +2160,7 @@ local_id:
 		TOK_ID
 			{
 			set_location(@1);
-			auto id = lookup_ID($1, current_module.c_str());
+			auto id = lookup_ID($1, current_module.c_str(), false, false, true, true);
 			$$ = id.release();
 
 			if ( $$ )

src/zeek-setup.cc

@@ -406,7 +406,7 @@ static void terminate_zeek() {
 #endif
 
     // free the global scope
-    pop_scope();
+    pop_local_scope();
 
     reporter = nullptr;
 }