From 70d7fb6a0358ed26f54d5b3c4b3f80500853d876 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 20 Feb 2023 00:39:57 +0100
Subject: [PATCH] LibCpp: Make C++ AST (mostly) const-correct

I cheated and used const_cast to avoid dealing with the strange pattern
where we sometimes do a delayed reparenting of an AST node.
---
 .../Cpp/CppComprehensionEngine.cpp            |  22 +-
 .../Cpp/CppComprehensionEngine.h              |  12 +-
 Userland/Libraries/LibCpp/AST.cpp             |  28 +-
 Userland/Libraries/LibCpp/AST.h               | 308 +++++++++---------
 Userland/Libraries/LibCpp/Parser.cpp          | 108 +++---
 Userland/Libraries/LibCpp/Parser.h            |  76 ++---
 6 files changed, 277 insertions(+), 277 deletions(-)

diff --git a/Userland/Libraries/LibCodeComprehension/Cpp/CppComprehensionEngine.cpp b/Userland/Libraries/LibCodeComprehension/Cpp/CppComprehensionEngine.cpp
index 5b6780da198..e298a3515e0 100644
--- a/Userland/Libraries/LibCodeComprehension/Cpp/CppComprehensionEngine.cpp
+++ b/Userland/Libraries/LibCodeComprehension/Cpp/CppComprehensionEngine.cpp
@@ -331,7 +331,7 @@ Vector<CppComprehensionEngine::Symbol> CppComprehensionEngine::properties_of_typ
     return properties;
 }
 
-CppComprehensionEngine::Symbol CppComprehensionEngine::Symbol::create(StringView name, Vector<StringView> const& scope, NonnullRefPtr<Cpp::Declaration> declaration, IsLocal is_local)
+CppComprehensionEngine::Symbol CppComprehensionEngine::Symbol::create(StringView name, Vector<StringView> const& scope, NonnullRefPtr<Cpp::Declaration const> declaration, IsLocal is_local)
 {
     return { { name, scope }, move(declaration), is_local == IsLocal::Yes };
 }
@@ -416,7 +416,7 @@ Optional<CodeComprehension::ProjectLocation> CppComprehensionEngine::find_declar
     return find_preprocessor_definition(document, identifier_position);
 }
 
-RefPtr<Cpp::Declaration> CppComprehensionEngine::find_declaration_of(DocumentData const& document, const GUI::TextPosition& identifier_position)
+RefPtr<Cpp::Declaration const> CppComprehensionEngine::find_declaration_of(DocumentData const& document, const GUI::TextPosition& identifier_position)
 {
     auto node = document.parser().node_at(Cpp::Position { identifier_position.line(), identifier_position.column() });
     if (!node) {
@@ -509,7 +509,7 @@ static Optional<TargetDeclaration> get_target_declaration(ASTNode const& node, D
 
     return TargetDeclaration { TargetDeclaration::Type::Variable, name };
 }
-RefPtr<Cpp::Declaration> CppComprehensionEngine::find_declaration_of(DocumentData const& document_data, ASTNode const& node) const
+RefPtr<Cpp::Declaration const> CppComprehensionEngine::find_declaration_of(DocumentData const& document_data, ASTNode const& node) const
 {
     dbgln_if(CPP_LANGUAGE_SERVER_DEBUG, "find_declaration_of: {} ({})", document_data.parser().text_of_node(node), node.class_name());
 
@@ -669,15 +669,15 @@ Vector<StringView> CppComprehensionEngine::scope_of_node(ASTNode const& node) co
     if (!parent->is_declaration())
         return parent_scope;
 
-    auto& parent_decl = static_cast<Cpp::Declaration&>(*parent);
+    auto& parent_decl = static_cast<Cpp::Declaration const&>(*parent);
 
     StringView containing_scope;
     if (parent_decl.is_namespace())
-        containing_scope = static_cast<NamespaceDeclaration&>(parent_decl).full_name();
+        containing_scope = static_cast<NamespaceDeclaration const&>(parent_decl).full_name();
     if (parent_decl.is_struct_or_class())
-        containing_scope = static_cast<StructOrClassDeclaration&>(parent_decl).full_name();
+        containing_scope = static_cast<StructOrClassDeclaration const&>(parent_decl).full_name();
     if (parent_decl.is_function())
-        containing_scope = static_cast<FunctionDeclaration&>(parent_decl).full_name();
+        containing_scope = static_cast<FunctionDeclaration const&>(parent_decl).full_name();
 
     parent_scope.append(containing_scope);
     return parent_scope;
@@ -751,9 +751,9 @@ Optional<Vector<CodeComprehension::AutocompleteResultEntry>> CppComprehensionEng
     return options;
 }
 
-RefPtr<Cpp::Declaration> CppComprehensionEngine::find_declaration_of(CppComprehensionEngine::DocumentData const& document, CppComprehensionEngine::SymbolName const& target_symbol_name) const
+RefPtr<Cpp::Declaration const> CppComprehensionEngine::find_declaration_of(CppComprehensionEngine::DocumentData const& document, CppComprehensionEngine::SymbolName const& target_symbol_name) const
 {
-    RefPtr<Cpp::Declaration> target_declaration;
+    RefPtr<Cpp::Declaration const> target_declaration;
     for_each_available_symbol(document, [&](Symbol const& symbol) {
         if (symbol.name == target_symbol_name) {
             target_declaration = symbol.declaration;
@@ -834,7 +834,7 @@ Optional<CodeComprehensionEngine::FunctionParamsHint> CppComprehensionEngine::ge
 
     dbgln_if(CPP_LANGUAGE_SERVER_DEBUG, "node type: {}", node->class_name());
 
-    FunctionCall* call_node { nullptr };
+    FunctionCall const* call_node { nullptr };
 
     if (node->is_function_call()) {
         call_node = verify_cast<FunctionCall>(node.ptr());
@@ -880,7 +880,7 @@ Optional<CodeComprehensionEngine::FunctionParamsHint> CppComprehensionEngine::ge
 
 Optional<CppComprehensionEngine::FunctionParamsHint> CppComprehensionEngine::get_function_params_hint(
     DocumentData const& document,
-    FunctionCall& call_node,
+    FunctionCall const& call_node,
     size_t argument_index)
 {
     Identifier const* callee = nullptr;
diff --git a/Userland/Libraries/LibCodeComprehension/Cpp/CppComprehensionEngine.h b/Userland/Libraries/LibCodeComprehension/Cpp/CppComprehensionEngine.h
index 8605540f079..e635afc2859 100644
--- a/Userland/Libraries/LibCodeComprehension/Cpp/CppComprehensionEngine.h
+++ b/Userland/Libraries/LibCodeComprehension/Cpp/CppComprehensionEngine.h
@@ -47,7 +47,7 @@ private:
 
     struct Symbol {
         SymbolName name;
-        NonnullRefPtr<Cpp::Declaration> declaration;
+        NonnullRefPtr<Cpp::Declaration const> declaration;
 
         // Local symbols are symbols that should not appear in a global symbol search.
         // For example, a variable that is declared inside a function will have is_local = true.
@@ -57,7 +57,7 @@ private:
             No,
             Yes
         };
-        static Symbol create(StringView name, Vector<StringView> const& scope, NonnullRefPtr<Cpp::Declaration>, IsLocal is_local);
+        static Symbol create(StringView name, Vector<StringView> const& scope, NonnullRefPtr<Cpp::Declaration const>, IsLocal is_local);
     };
 
     friend Traits<SymbolName>;
@@ -101,9 +101,9 @@ private:
     DeprecatedString type_of_property(DocumentData const&, Identifier const&) const;
     DeprecatedString type_of_variable(Identifier const&) const;
     bool is_property(ASTNode const&) const;
-    RefPtr<Cpp::Declaration> find_declaration_of(DocumentData const&, ASTNode const&) const;
-    RefPtr<Cpp::Declaration> find_declaration_of(DocumentData const&, SymbolName const&) const;
-    RefPtr<Cpp::Declaration> find_declaration_of(DocumentData const&, const GUI::TextPosition& identifier_position);
+    RefPtr<Cpp::Declaration const> find_declaration_of(DocumentData const&, ASTNode const&) const;
+    RefPtr<Cpp::Declaration const> find_declaration_of(DocumentData const&, SymbolName const&) const;
+    RefPtr<Cpp::Declaration const> find_declaration_of(DocumentData const&, const GUI::TextPosition& identifier_position);
 
     enum class RecurseIntoScopes {
         No,
@@ -134,7 +134,7 @@ private:
     Optional<Vector<CodeComprehension::AutocompleteResultEntry>> try_autocomplete_name(DocumentData const&, ASTNode const&, Optional<Token> containing_token) const;
     Optional<Vector<CodeComprehension::AutocompleteResultEntry>> try_autocomplete_include(DocumentData const&, Token include_path_token, Cpp::Position const& cursor_position) const;
     static bool is_symbol_available(Symbol const&, Vector<StringView> const& current_scope, Vector<StringView> const& reference_scope);
-    Optional<FunctionParamsHint> get_function_params_hint(DocumentData const&, FunctionCall&, size_t argument_index);
+    Optional<FunctionParamsHint> get_function_params_hint(DocumentData const&, FunctionCall const&, size_t argument_index);
 
     template<typename Func>
     void for_each_available_symbol(DocumentData const&, Func) const;
diff --git a/Userland/Libraries/LibCpp/AST.cpp b/Userland/Libraries/LibCpp/AST.cpp
index 36b2bd25f14..74c16851455 100644
--- a/Userland/Libraries/LibCpp/AST.cpp
+++ b/Userland/Libraries/LibCpp/AST.cpp
@@ -55,9 +55,9 @@ void FunctionDeclaration::dump(FILE* output, size_t indent) const
     }
 }
 
-NonnullRefPtrVector<Declaration> FunctionDeclaration::declarations() const
+NonnullRefPtrVector<Declaration const> FunctionDeclaration::declarations() const
 {
-    NonnullRefPtrVector<Declaration> declarations;
+    NonnullRefPtrVector<Declaration const> declarations;
     for (auto& arg : m_parameters) {
         declarations.append(arg);
     }
@@ -162,9 +162,9 @@ void FunctionDefinition::dump(FILE* output, size_t indent) const
     outln(output, "}}");
 }
 
-NonnullRefPtrVector<Declaration> FunctionDefinition::declarations() const
+NonnullRefPtrVector<Declaration const> FunctionDefinition::declarations() const
 {
-    NonnullRefPtrVector<Declaration> declarations;
+    NonnullRefPtrVector<Declaration const> declarations;
     for (auto& statement : m_statements) {
         declarations.extend(statement.declarations());
     }
@@ -350,9 +350,9 @@ void StructOrClassDeclaration::dump(FILE* output, size_t indent) const
         member.dump(output, indent + 1);
     }
 }
-NonnullRefPtrVector<Declaration> StructOrClassDeclaration::declarations() const
+NonnullRefPtrVector<Declaration const> StructOrClassDeclaration::declarations() const
 {
-    NonnullRefPtrVector<Declaration> declarations;
+    NonnullRefPtrVector<Declaration const> declarations;
     for (auto& member : m_members)
         declarations.append(member);
     return declarations;
@@ -458,10 +458,10 @@ void ForStatement::dump(FILE* output, size_t indent) const
         m_body->dump(output, indent + 1);
 }
 
-NonnullRefPtrVector<Declaration> Statement::declarations() const
+NonnullRefPtrVector<Declaration const> Statement::declarations() const
 {
     if (is_declaration()) {
-        NonnullRefPtrVector<Declaration> vec;
+        NonnullRefPtrVector<Declaration const> vec;
         auto const& decl = static_cast<Declaration const&>(*this);
         vec.empend(const_cast<Declaration&>(decl));
         return vec;
@@ -469,9 +469,9 @@ NonnullRefPtrVector<Declaration> Statement::declarations() const
     return {};
 }
 
-NonnullRefPtrVector<Declaration> ForStatement::declarations() const
+NonnullRefPtrVector<Declaration const> ForStatement::declarations() const
 {
-    NonnullRefPtrVector<Declaration> declarations;
+    NonnullRefPtrVector<Declaration const> declarations;
     if (m_init)
         declarations.extend(m_init->declarations());
     if (m_body)
@@ -479,9 +479,9 @@ NonnullRefPtrVector<Declaration> ForStatement::declarations() const
     return declarations;
 }
 
-NonnullRefPtrVector<Declaration> BlockStatement::declarations() const
+NonnullRefPtrVector<Declaration const> BlockStatement::declarations() const
 {
-    NonnullRefPtrVector<Declaration> declarations;
+    NonnullRefPtrVector<Declaration const> declarations;
     for (auto& statement : m_statements) {
         declarations.extend(statement.declarations());
     }
@@ -508,9 +508,9 @@ void IfStatement::dump(FILE* output, size_t indent) const
     }
 }
 
-NonnullRefPtrVector<Declaration> IfStatement::declarations() const
+NonnullRefPtrVector<Declaration const> IfStatement::declarations() const
 {
-    NonnullRefPtrVector<Declaration> declarations;
+    NonnullRefPtrVector<Declaration const> declarations;
     if (m_predicate)
         declarations.extend(m_predicate->declarations());
     if (m_then)
diff --git a/Userland/Libraries/LibCpp/AST.h b/Userland/Libraries/LibCpp/AST.h
index b0ec6c8de9c..0e8be683d3c 100644
--- a/Userland/Libraries/LibCpp/AST.h
+++ b/Userland/Libraries/LibCpp/AST.h
@@ -36,7 +36,7 @@ public:
     template<typename T>
     bool fast_is() const = delete;
 
-    ASTNode* parent() const { return m_parent; }
+    ASTNode const* parent() const { return m_parent; }
     Position start() const
     {
         VERIFY(m_start.has_value());
@@ -52,9 +52,9 @@ public:
         return m_filename;
     }
     void set_end(Position const& end) { m_end = end; }
-    void set_parent(ASTNode& parent) { m_parent = &parent; }
+    void set_parent(ASTNode const& parent) { m_parent = &parent; }
 
-    virtual NonnullRefPtrVector<Declaration> declarations() const { return {}; }
+    virtual NonnullRefPtrVector<Declaration const> declarations() const { return {}; }
 
     virtual bool is_identifier() const { return false; }
     virtual bool is_member_expression() const { return false; }
@@ -66,7 +66,7 @@ public:
     virtual bool is_dummy_node() const { return false; }
 
 protected:
-    ASTNode(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    ASTNode(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : m_parent(parent)
         , m_start(start)
         , m_end(end)
@@ -75,7 +75,7 @@ protected:
     }
 
 private:
-    ASTNode* m_parent { nullptr };
+    ASTNode const* m_parent { nullptr };
     Optional<Position> m_start;
     Optional<Position> m_end;
     DeprecatedFlyString m_filename;
@@ -87,17 +87,17 @@ public:
     virtual ~TranslationUnit() override = default;
     virtual StringView class_name() const override { return "TranslationUnit"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
-    virtual NonnullRefPtrVector<Declaration> declarations() const override { return m_declarations; }
+    virtual NonnullRefPtrVector<Declaration const> declarations() const override { return m_declarations; }
 
-    TranslationUnit(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    TranslationUnit(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : ASTNode(parent, start, end, filename)
     {
     }
 
-    void set_declarations(NonnullRefPtrVector<Declaration>&& declarations) { m_declarations = move(declarations); }
+    void set_declarations(NonnullRefPtrVector<Declaration const>&& declarations) { m_declarations = move(declarations); }
 
 private:
-    NonnullRefPtrVector<Declaration> m_declarations;
+    NonnullRefPtrVector<Declaration const> m_declarations;
 };
 
 class Statement : public ASTNode {
@@ -105,10 +105,10 @@ public:
     virtual ~Statement() override = default;
     virtual StringView class_name() const override { return "Statement"sv; }
 
-    virtual NonnullRefPtrVector<Declaration> declarations() const override;
+    virtual NonnullRefPtrVector<Declaration const> declarations() const override;
 
 protected:
-    Statement(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Statement(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : ASTNode(parent, start, end, filename)
     {
     }
@@ -129,15 +129,15 @@ public:
     bool is_member() const { return parent() != nullptr && parent()->is_declaration() && verify_cast<Declaration>(parent())->is_struct_or_class(); }
     Name const* name() const { return m_name; }
     StringView full_name() const;
-    void set_name(RefPtr<Name> name) { m_name = move(name); }
+    void set_name(RefPtr<Name const> name) { m_name = move(name); }
 
 protected:
-    Declaration(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Declaration(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Statement(parent, start, end, filename)
     {
     }
 
-    RefPtr<Name> m_name;
+    RefPtr<Name const> m_name;
     mutable Optional<DeprecatedString> m_full_name;
 };
 
@@ -146,7 +146,7 @@ class InvalidDeclaration : public Declaration {
 public:
     virtual ~InvalidDeclaration() override = default;
     virtual StringView class_name() const override { return "InvalidDeclaration"sv; }
-    InvalidDeclaration(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    InvalidDeclaration(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Declaration(parent, start, end, filename)
     {
     }
@@ -160,28 +160,28 @@ public:
     virtual bool is_function() const override { return true; }
     virtual bool is_constructor() const { return false; }
     virtual bool is_destructor() const { return false; }
-    RefPtr<FunctionDefinition> definition() { return m_definition; }
+    RefPtr<FunctionDefinition const> definition() { return m_definition; }
 
-    FunctionDeclaration(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    FunctionDeclaration(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Declaration(parent, start, end, filename)
     {
     }
 
-    virtual NonnullRefPtrVector<Declaration> declarations() const override;
+    virtual NonnullRefPtrVector<Declaration const> declarations() const override;
     Vector<StringView> const& qualifiers() const { return m_qualifiers; }
     void set_qualifiers(Vector<StringView> const& qualifiers) { m_qualifiers = qualifiers; }
     Type const* return_type() const { return m_return_type.ptr(); }
-    void set_return_type(RefPtr<Type> const& return_type) { m_return_type = return_type; }
-    NonnullRefPtrVector<Parameter> const& parameters() const { return m_parameters; }
-    void set_parameters(NonnullRefPtrVector<Parameter> const& parameters) { m_parameters = parameters; }
+    void set_return_type(RefPtr<Type const> const& return_type) { m_return_type = return_type; }
+    NonnullRefPtrVector<Parameter const> const& parameters() const { return m_parameters; }
+    void set_parameters(NonnullRefPtrVector<Parameter const> const& parameters) { m_parameters = parameters; }
     FunctionDefinition const* definition() const { return m_definition.ptr(); }
-    void set_definition(RefPtr<FunctionDefinition>&& definition) { m_definition = move(definition); }
+    void set_definition(RefPtr<FunctionDefinition const>&& definition) { m_definition = move(definition); }
 
 private:
     Vector<StringView> m_qualifiers;
-    RefPtr<Type> m_return_type;
-    NonnullRefPtrVector<Parameter> m_parameters;
-    RefPtr<FunctionDefinition> m_definition;
+    RefPtr<Type const> m_return_type;
+    NonnullRefPtrVector<Parameter const> m_parameters;
+    RefPtr<FunctionDefinition const> m_definition;
 };
 
 class VariableOrParameterDeclaration : public Declaration {
@@ -189,16 +189,16 @@ public:
     virtual ~VariableOrParameterDeclaration() override = default;
     virtual bool is_variable_or_parameter_declaration() const override { return true; }
 
-    void set_type(RefPtr<Type>&& type) { m_type = move(type); }
+    void set_type(RefPtr<Type const>&& type) { m_type = move(type); }
     Type const* type() const { return m_type.ptr(); }
 
 protected:
-    VariableOrParameterDeclaration(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    VariableOrParameterDeclaration(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Declaration(parent, start, end, filename)
     {
     }
 
-    RefPtr<Type> m_type;
+    RefPtr<Type const> m_type;
 };
 
 class Parameter : public VariableOrParameterDeclaration {
@@ -208,7 +208,7 @@ public:
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
     virtual bool is_parameter() const override { return true; }
 
-    Parameter(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, RefPtr<Name> name)
+    Parameter(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, RefPtr<Name const> name)
         : VariableOrParameterDeclaration(parent, start, end, filename)
     {
         m_name = name;
@@ -237,7 +237,7 @@ public:
     void set_qualifiers(Vector<StringView>&& qualifiers) { m_qualifiers = move(qualifiers); }
 
 protected:
-    Type(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Type(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : ASTNode(parent, start, end, filename)
     {
     }
@@ -254,16 +254,16 @@ public:
     virtual DeprecatedString to_deprecated_string() const override;
     virtual bool is_named_type() const override { return true; }
 
-    NamedType(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    NamedType(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Type(parent, start, end, filename)
     {
     }
 
     Name const* name() const { return m_name.ptr(); }
-    void set_name(RefPtr<Name>&& name) { m_name = move(name); }
+    void set_name(RefPtr<Name const>&& name) { m_name = move(name); }
 
 private:
-    RefPtr<Name> m_name;
+    RefPtr<Name const> m_name;
 };
 
 class Pointer : public Type {
@@ -273,16 +273,16 @@ public:
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
     virtual DeprecatedString to_deprecated_string() const override;
 
-    Pointer(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Pointer(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Type(parent, start, end, filename)
     {
     }
 
     Type const* pointee() const { return m_pointee.ptr(); }
-    void set_pointee(RefPtr<Type>&& pointee) { m_pointee = move(pointee); }
+    void set_pointee(RefPtr<Type const>&& pointee) { m_pointee = move(pointee); }
 
 private:
-    RefPtr<Type> m_pointee;
+    RefPtr<Type const> m_pointee;
 };
 
 class Reference : public Type {
@@ -297,14 +297,14 @@ public:
         Rvalue,
     };
 
-    Reference(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, Kind kind)
+    Reference(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, Kind kind)
         : Type(parent, start, end, filename)
         , m_kind(kind)
     {
     }
 
     Type const* referenced_type() const { return m_referenced_type.ptr(); }
-    void set_referenced_type(RefPtr<Type>&& pointee) { m_referenced_type = move(pointee); }
+    void set_referenced_type(RefPtr<Type const>&& pointee) { m_referenced_type = move(pointee); }
     Kind kind() const { return m_kind; }
 
 private:
@@ -319,17 +319,17 @@ public:
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
     virtual DeprecatedString to_deprecated_string() const override;
 
-    FunctionType(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    FunctionType(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Type(parent, start, end, filename)
     {
     }
 
     void set_return_type(Type& type) { m_return_type = type; }
-    void set_parameters(NonnullRefPtrVector<Parameter> parameters) { m_parameters = move(parameters); }
+    void set_parameters(NonnullRefPtrVector<Parameter const> parameters) { m_parameters = move(parameters); }
 
 private:
-    RefPtr<Type> m_return_type;
-    NonnullRefPtrVector<Parameter> m_parameters;
+    RefPtr<Type const> m_return_type;
+    NonnullRefPtrVector<Parameter const> m_parameters;
 };
 
 class FunctionDefinition : public ASTNode {
@@ -338,24 +338,24 @@ public:
     virtual StringView class_name() const override { return "FunctionDefinition"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    FunctionDefinition(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    FunctionDefinition(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : ASTNode(parent, start, end, filename)
     {
     }
 
-    virtual NonnullRefPtrVector<Declaration> declarations() const override;
-    NonnullRefPtrVector<Statement> const& statements() { return m_statements; }
-    void add_statement(NonnullRefPtr<Statement>&& statement) { m_statements.append(move(statement)); }
+    virtual NonnullRefPtrVector<Declaration const> declarations() const override;
+    NonnullRefPtrVector<Statement const> const& statements() { return m_statements; }
+    void add_statement(NonnullRefPtr<Statement const>&& statement) { m_statements.append(move(statement)); }
 
 private:
-    NonnullRefPtrVector<Statement> m_statements;
+    NonnullRefPtrVector<Statement const> m_statements;
 };
 
 class InvalidStatement : public Statement {
 public:
     virtual ~InvalidStatement() override = default;
     virtual StringView class_name() const override { return "InvalidStatement"sv; }
-    InvalidStatement(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    InvalidStatement(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Statement(parent, start, end, filename)
     {
     }
@@ -367,7 +367,7 @@ public:
     virtual StringView class_name() const override { return "Expression"sv; }
 
 protected:
-    Expression(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Expression(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Statement(parent, start, end, filename)
     {
     }
@@ -377,7 +377,7 @@ class InvalidExpression : public Expression {
 public:
     virtual ~InvalidExpression() override = default;
     virtual StringView class_name() const override { return "InvalidExpression"sv; }
-    InvalidExpression(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    InvalidExpression(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -389,7 +389,7 @@ public:
     virtual StringView class_name() const override { return "VariableDeclaration"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    VariableDeclaration(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    VariableDeclaration(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : VariableOrParameterDeclaration(parent, start, end, filename)
     {
     }
@@ -397,10 +397,10 @@ public:
     virtual bool is_variable_declaration() const override { return true; }
 
     Expression const* initial_value() const { return m_initial_value; }
-    void set_initial_value(RefPtr<Expression>&& initial_value) { m_initial_value = move(initial_value); }
+    void set_initial_value(RefPtr<Expression const>&& initial_value) { m_initial_value = move(initial_value); }
 
 private:
-    RefPtr<Expression> m_initial_value;
+    RefPtr<Expression const> m_initial_value;
 };
 
 class Identifier : public Expression {
@@ -409,12 +409,12 @@ public:
     virtual StringView class_name() const override { return "Identifier"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    Identifier(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, StringView name)
+    Identifier(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, StringView name)
         : Expression(parent, start, end, filename)
         , m_name(name)
     {
     }
-    Identifier(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Identifier(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Identifier(parent, start, end, filename, {})
     {
     }
@@ -436,21 +436,21 @@ public:
     virtual bool is_name() const override { return true; }
     virtual bool is_templatized() const { return false; }
 
-    Name(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Name(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
     virtual StringView full_name() const;
 
     Identifier const* name() const { return m_name.ptr(); }
-    void set_name(RefPtr<Identifier>&& name) { m_name = move(name); }
-    NonnullRefPtrVector<Identifier> const& scope() const { return m_scope; }
-    void set_scope(NonnullRefPtrVector<Identifier> scope) { m_scope = move(scope); }
-    void add_to_scope(NonnullRefPtr<Identifier>&& part) { m_scope.append(move(part)); }
+    void set_name(RefPtr<Identifier const>&& name) { m_name = move(name); }
+    NonnullRefPtrVector<Identifier const> const& scope() const { return m_scope; }
+    void set_scope(NonnullRefPtrVector<Identifier const> scope) { m_scope = move(scope); }
+    void add_to_scope(NonnullRefPtr<Identifier const>&& part) { m_scope.append(move(part)); }
 
 private:
-    RefPtr<Identifier> m_name;
-    NonnullRefPtrVector<Identifier> m_scope;
+    RefPtr<Identifier const> m_name;
+    NonnullRefPtrVector<Identifier const> m_scope;
     mutable Optional<DeprecatedString> m_full_name;
 };
 
@@ -461,15 +461,15 @@ public:
     virtual bool is_templatized() const override { return true; }
     virtual StringView full_name() const override;
 
-    TemplatizedName(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    TemplatizedName(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Name(parent, start, end, filename)
     {
     }
 
-    void add_template_argument(NonnullRefPtr<Type>&& type) { m_template_arguments.append(move(type)); }
+    void add_template_argument(NonnullRefPtr<Type const>&& type) { m_template_arguments.append(move(type)); }
 
 private:
-    NonnullRefPtrVector<Type> m_template_arguments;
+    NonnullRefPtrVector<Type const> m_template_arguments;
     mutable Optional<DeprecatedString> m_full_name;
 };
 
@@ -479,7 +479,7 @@ public:
     virtual StringView class_name() const override { return "NumericLiteral"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    NumericLiteral(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, StringView value)
+    NumericLiteral(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, StringView value)
         : Expression(parent, start, end, filename)
         , m_value(value)
     {
@@ -495,7 +495,7 @@ public:
     virtual StringView class_name() const override { return "NullPointerLiteral"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    NullPointerLiteral(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    NullPointerLiteral(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -507,7 +507,7 @@ public:
     virtual StringView class_name() const override { return "BooleanLiteral"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    BooleanLiteral(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, bool value)
+    BooleanLiteral(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, bool value)
         : Expression(parent, start, end, filename)
         , m_value(value)
     {
@@ -541,7 +541,7 @@ enum class BinaryOp {
 
 class BinaryExpression : public Expression {
 public:
-    BinaryExpression(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    BinaryExpression(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -553,14 +553,14 @@ public:
     BinaryOp op() const { return m_op; }
     void set_op(BinaryOp op) { m_op = op; }
     Expression const* lhs() const { return m_lhs.ptr(); }
-    void set_lhs(RefPtr<Expression>&& e) { m_lhs = move(e); }
+    void set_lhs(RefPtr<Expression const>&& e) { m_lhs = move(e); }
     Expression const* rhs() const { return m_rhs.ptr(); }
-    void set_rhs(RefPtr<Expression>&& e) { m_rhs = move(e); }
+    void set_rhs(RefPtr<Expression const>&& e) { m_rhs = move(e); }
 
 private:
     BinaryOp m_op;
-    RefPtr<Expression> m_lhs;
-    RefPtr<Expression> m_rhs;
+    RefPtr<Expression const> m_lhs;
+    RefPtr<Expression const> m_rhs;
 };
 
 enum class AssignmentOp {
@@ -571,7 +571,7 @@ enum class AssignmentOp {
 
 class AssignmentExpression : public Expression {
 public:
-    AssignmentExpression(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    AssignmentExpression(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -583,19 +583,19 @@ public:
     AssignmentOp op() const { return m_op; }
     void set_op(AssignmentOp op) { m_op = op; }
     Expression const* lhs() const { return m_lhs; }
-    void set_lhs(RefPtr<Expression>&& e) { m_lhs = move(e); }
+    void set_lhs(RefPtr<Expression const>&& e) { m_lhs = move(e); }
     Expression const* rhs() const { return m_rhs; }
-    void set_rhs(RefPtr<Expression>&& e) { m_rhs = move(e); }
+    void set_rhs(RefPtr<Expression const>&& e) { m_rhs = move(e); }
 
 private:
     AssignmentOp m_op {};
-    RefPtr<Expression> m_lhs;
-    RefPtr<Expression> m_rhs;
+    RefPtr<Expression const> m_lhs;
+    RefPtr<Expression const> m_rhs;
 };
 
 class FunctionCall : public Expression {
 public:
-    FunctionCall(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    FunctionCall(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -606,19 +606,19 @@ public:
     virtual bool is_function_call() const override { return true; }
 
     Expression const* callee() const { return m_callee.ptr(); }
-    void set_callee(RefPtr<Expression>&& callee) { m_callee = move(callee); }
+    void set_callee(RefPtr<Expression const>&& callee) { m_callee = move(callee); }
 
-    void add_argument(NonnullRefPtr<Expression>&& arg) { m_arguments.append(move(arg)); }
-    NonnullRefPtrVector<Expression> const& arguments() const { return m_arguments; }
+    void add_argument(NonnullRefPtr<Expression const>&& arg) { m_arguments.append(move(arg)); }
+    NonnullRefPtrVector<Expression const> const& arguments() const { return m_arguments; }
 
 private:
-    RefPtr<Expression> m_callee;
-    NonnullRefPtrVector<Expression> m_arguments;
+    RefPtr<Expression const> m_callee;
+    NonnullRefPtrVector<Expression const> m_arguments;
 };
 
 class StringLiteral final : public Expression {
 public:
-    StringLiteral(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    StringLiteral(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -639,17 +639,17 @@ public:
     virtual ~ReturnStatement() override = default;
     virtual StringView class_name() const override { return "ReturnStatement"sv; }
 
-    ReturnStatement(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    ReturnStatement(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Statement(parent, start, end, filename)
     {
     }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
     Expression const* value() const { return m_value.ptr(); }
-    void set_value(RefPtr<Expression>&& value) { m_value = move(value); }
+    void set_value(RefPtr<Expression const>&& value) { m_value = move(value); }
 
 private:
-    RefPtr<Expression> m_value;
+    RefPtr<Expression const> m_value;
 };
 
 class EnumDeclaration : public Declaration {
@@ -659,7 +659,7 @@ public:
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
     virtual bool is_enum() const override { return true; }
 
-    EnumDeclaration(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    EnumDeclaration(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Declaration(parent, start, end, filename)
     {
     }
@@ -670,13 +670,13 @@ public:
     };
 
     void set_type(Type type) { m_type = type; }
-    void add_entry(StringView entry, RefPtr<Expression> value = nullptr) { m_entries.append({ entry, move(value) }); }
+    void add_entry(StringView entry, RefPtr<Expression const> value = nullptr) { m_entries.append({ entry, move(value) }); }
 
 private:
     Type m_type { Type::RegularEnum };
     struct EnumerationEntry {
         StringView name;
-        RefPtr<Expression> value;
+        RefPtr<Expression const> value;
     };
     Vector<EnumerationEntry> m_entries;
 };
@@ -689,29 +689,29 @@ public:
     virtual bool is_struct_or_class() const override { return true; }
     virtual bool is_struct() const override { return m_type == Type::Struct; }
     virtual bool is_class() const override { return m_type == Type::Class; }
-    virtual NonnullRefPtrVector<Declaration> declarations() const override;
+    virtual NonnullRefPtrVector<Declaration const> declarations() const override;
 
     enum class Type {
         Struct,
         Class
     };
 
-    StructOrClassDeclaration(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, StructOrClassDeclaration::Type type)
+    StructOrClassDeclaration(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename, StructOrClassDeclaration::Type type)
         : Declaration(parent, start, end, filename)
         , m_type(type)
     {
     }
 
-    NonnullRefPtrVector<Declaration> const& members() const { return m_members; }
-    void set_members(NonnullRefPtrVector<Declaration>&& members) { m_members = move(members); }
+    NonnullRefPtrVector<Declaration const> const& members() const { return m_members; }
+    void set_members(NonnullRefPtrVector<Declaration const>&& members) { m_members = move(members); }
 
-    NonnullRefPtrVector<Name> const& baseclasses() const { return m_baseclasses; }
-    void set_baseclasses(NonnullRefPtrVector<Name>&& baseclasses) { m_baseclasses = move(baseclasses); }
+    NonnullRefPtrVector<Name const> const& baseclasses() const { return m_baseclasses; }
+    void set_baseclasses(NonnullRefPtrVector<Name const>&& baseclasses) { m_baseclasses = move(baseclasses); }
 
 private:
     StructOrClassDeclaration::Type m_type;
-    NonnullRefPtrVector<Declaration> m_members;
-    NonnullRefPtrVector<Name> m_baseclasses;
+    NonnullRefPtrVector<Declaration const> m_members;
+    NonnullRefPtrVector<Name const> m_baseclasses;
 };
 
 enum class UnaryOp {
@@ -726,7 +726,7 @@ enum class UnaryOp {
 
 class UnaryExpression : public Expression {
 public:
-    UnaryExpression(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    UnaryExpression(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -736,16 +736,16 @@ public:
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
     void set_op(UnaryOp op) { m_op = op; }
-    void set_lhs(RefPtr<Expression>&& e) { m_lhs = move(e); }
+    void set_lhs(RefPtr<Expression const>&& e) { m_lhs = move(e); }
 
 private:
     UnaryOp m_op;
-    RefPtr<Expression> m_lhs;
+    RefPtr<Expression const> m_lhs;
 };
 
 class MemberExpression : public Expression {
 public:
-    MemberExpression(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    MemberExpression(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -756,18 +756,18 @@ public:
     virtual bool is_member_expression() const override { return true; }
 
     Expression const* object() const { return m_object.ptr(); }
-    void set_object(RefPtr<Expression>&& object) { m_object = move(object); }
+    void set_object(RefPtr<Expression const>&& object) { m_object = move(object); }
     Expression const* property() const { return m_property.ptr(); }
-    void set_property(RefPtr<Expression>&& property) { m_property = move(property); }
+    void set_property(RefPtr<Expression const>&& property) { m_property = move(property); }
 
 private:
-    RefPtr<Expression> m_object;
-    RefPtr<Expression> m_property;
+    RefPtr<Expression const> m_object;
+    RefPtr<Expression const> m_property;
 };
 
 class ForStatement : public Statement {
 public:
-    ForStatement(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    ForStatement(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Statement(parent, start, end, filename)
     {
     }
@@ -776,24 +776,24 @@ public:
     virtual StringView class_name() const override { return "ForStatement"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    virtual NonnullRefPtrVector<Declaration> declarations() const override;
+    virtual NonnullRefPtrVector<Declaration const> declarations() const override;
 
-    void set_init(RefPtr<VariableDeclaration>&& init) { m_init = move(init); }
-    void set_test(RefPtr<Expression>&& test) { m_test = move(test); }
-    void set_update(RefPtr<Expression>&& update) { m_update = move(update); }
-    void set_body(RefPtr<Statement>&& body) { m_body = move(body); }
+    void set_init(RefPtr<VariableDeclaration const>&& init) { m_init = move(init); }
+    void set_test(RefPtr<Expression const>&& test) { m_test = move(test); }
+    void set_update(RefPtr<Expression const>&& update) { m_update = move(update); }
+    void set_body(RefPtr<Statement const>&& body) { m_body = move(body); }
     Statement const* body() const { return m_body.ptr(); }
 
 private:
-    RefPtr<VariableDeclaration> m_init;
-    RefPtr<Expression> m_test;
-    RefPtr<Expression> m_update;
-    RefPtr<Statement> m_body;
+    RefPtr<VariableDeclaration const> m_init;
+    RefPtr<Expression const> m_test;
+    RefPtr<Expression const> m_update;
+    RefPtr<Statement const> m_body;
 };
 
 class BlockStatement final : public Statement {
 public:
-    BlockStatement(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    BlockStatement(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Statement(parent, start, end, filename)
     {
     }
@@ -802,17 +802,17 @@ public:
     virtual StringView class_name() const override { return "BlockStatement"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    virtual NonnullRefPtrVector<Declaration> declarations() const override;
+    virtual NonnullRefPtrVector<Declaration const> declarations() const override;
 
-    void add_statement(NonnullRefPtr<Statement>&& statement) { m_statements.append(move(statement)); }
+    void add_statement(NonnullRefPtr<Statement const>&& statement) { m_statements.append(move(statement)); }
 
 private:
-    NonnullRefPtrVector<Statement> m_statements;
+    NonnullRefPtrVector<Statement const> m_statements;
 };
 
 class Comment final : public Statement {
 public:
-    Comment(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Comment(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Statement(parent, start, end, filename)
     {
     }
@@ -823,7 +823,7 @@ public:
 
 class IfStatement : public Statement {
 public:
-    IfStatement(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    IfStatement(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Statement(parent, start, end, filename)
     {
     }
@@ -831,19 +831,19 @@ public:
     virtual ~IfStatement() override = default;
     virtual StringView class_name() const override { return "IfStatement"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
-    virtual NonnullRefPtrVector<Declaration> declarations() const override;
+    virtual NonnullRefPtrVector<Declaration const> declarations() const override;
 
-    void set_predicate(RefPtr<Expression>&& predicate) { m_predicate = move(predicate); }
-    void set_then_statement(RefPtr<Statement>&& then) { m_then = move(then); }
-    void set_else_statement(RefPtr<Statement>&& _else) { m_else = move(_else); }
+    void set_predicate(RefPtr<Expression const>&& predicate) { m_predicate = move(predicate); }
+    void set_then_statement(RefPtr<Statement const>&& then) { m_then = move(then); }
+    void set_else_statement(RefPtr<Statement const>&& _else) { m_else = move(_else); }
 
     Statement const* then_statement() const { return m_then.ptr(); }
     Statement const* else_statement() const { return m_else.ptr(); }
 
 private:
-    RefPtr<Expression> m_predicate;
-    RefPtr<Statement> m_then;
-    RefPtr<Statement> m_else;
+    RefPtr<Expression const> m_predicate;
+    RefPtr<Statement const> m_then;
+    RefPtr<Statement const> m_else;
 };
 
 class NamespaceDeclaration : public Declaration {
@@ -853,21 +853,21 @@ public:
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
     virtual bool is_namespace() const override { return true; }
 
-    NamespaceDeclaration(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    NamespaceDeclaration(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Declaration(parent, start, end, filename)
     {
     }
 
-    virtual NonnullRefPtrVector<Declaration> declarations() const override { return m_declarations; }
-    void add_declaration(NonnullRefPtr<Declaration>&& declaration) { m_declarations.append(move(declaration)); }
+    virtual NonnullRefPtrVector<Declaration const> declarations() const override { return m_declarations; }
+    void add_declaration(NonnullRefPtr<Declaration const>&& declaration) { m_declarations.append(move(declaration)); }
 
 private:
-    NonnullRefPtrVector<Declaration> m_declarations;
+    NonnullRefPtrVector<Declaration const> m_declarations;
 };
 
 class CppCastExpression : public Expression {
 public:
-    CppCastExpression(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    CppCastExpression(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -877,18 +877,18 @@ public:
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
     void set_cast_type(StringView cast_type) { m_cast_type = move(cast_type); }
-    void set_type(NonnullRefPtr<Type>&& type) { m_type = move(type); }
-    void set_expression(NonnullRefPtr<Expression>&& e) { m_expression = move(e); }
+    void set_type(NonnullRefPtr<Type const>&& type) { m_type = move(type); }
+    void set_expression(NonnullRefPtr<Expression const>&& e) { m_expression = move(e); }
 
 private:
     StringView m_cast_type;
-    RefPtr<Type> m_type;
-    RefPtr<Expression> m_expression;
+    RefPtr<Type const> m_type;
+    RefPtr<Expression const> m_expression;
 };
 
 class CStyleCastExpression : public Expression {
 public:
-    CStyleCastExpression(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    CStyleCastExpression(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -897,17 +897,17 @@ public:
     virtual StringView class_name() const override { return "CStyleCastExpression"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    void set_type(NonnullRefPtr<Type>&& type) { m_type = move(type); }
-    void set_expression(NonnullRefPtr<Expression>&& e) { m_expression = move(e); }
+    void set_type(NonnullRefPtr<Type const>&& type) { m_type = move(type); }
+    void set_expression(NonnullRefPtr<Expression const>&& e) { m_expression = move(e); }
 
 private:
-    RefPtr<Type> m_type;
-    RefPtr<Expression> m_expression;
+    RefPtr<Type const> m_type;
+    RefPtr<Expression const> m_expression;
 };
 
 class SizeofExpression : public Expression {
 public:
-    SizeofExpression(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    SizeofExpression(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -916,15 +916,15 @@ public:
     virtual StringView class_name() const override { return "SizeofExpression"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    void set_type(RefPtr<Type>&& type) { m_type = move(type); }
+    void set_type(RefPtr<Type const>&& type) { m_type = move(type); }
 
 private:
-    RefPtr<Type> m_type;
+    RefPtr<Type const> m_type;
 };
 
 class BracedInitList : public Expression {
 public:
-    BracedInitList(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    BracedInitList(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Expression(parent, start, end, filename)
     {
     }
@@ -933,15 +933,15 @@ public:
     virtual StringView class_name() const override { return "BracedInitList"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    void add_expression(NonnullRefPtr<Expression>&& exp) { m_expressions.append(move(exp)); }
+    void add_expression(NonnullRefPtr<Expression const>&& exp) { m_expressions.append(move(exp)); }
 
 private:
-    NonnullRefPtrVector<Expression> m_expressions;
+    NonnullRefPtrVector<Expression const> m_expressions;
 };
 
 class DummyAstNode : public ASTNode {
 public:
-    DummyAstNode(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    DummyAstNode(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : ASTNode(parent, start, end, filename)
     {
     }
@@ -957,7 +957,7 @@ public:
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
     virtual bool is_constructor() const override { return true; }
 
-    Constructor(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Constructor(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : FunctionDeclaration(parent, start, end, filename)
     {
     }
@@ -970,7 +970,7 @@ public:
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
     virtual bool is_destructor() const override { return true; }
 
-    Destructor(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    Destructor(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : FunctionDeclaration(parent, start, end, filename)
     {
     }
@@ -982,7 +982,7 @@ public:
     virtual StringView class_name() const override { return "UsingNamespaceDeclaration"sv; }
     virtual void dump(FILE* = stdout, size_t indent = 0) const override;
 
-    UsingNamespaceDeclaration(ASTNode* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
+    UsingNamespaceDeclaration(ASTNode const* parent, Optional<Position> start, Optional<Position> end, DeprecatedString const& filename)
         : Declaration(parent, start, end, filename)
     {
     }
diff --git a/Userland/Libraries/LibCpp/Parser.cpp b/Userland/Libraries/LibCpp/Parser.cpp
index 89ed2a79e27..a091b64085a 100644
--- a/Userland/Libraries/LibCpp/Parser.cpp
+++ b/Userland/Libraries/LibCpp/Parser.cpp
@@ -37,9 +37,9 @@ NonnullRefPtr<TranslationUnit> Parser::parse()
     return unit;
 }
 
-NonnullRefPtrVector<Declaration> Parser::parse_declarations_in_translation_unit(ASTNode& parent)
+NonnullRefPtrVector<Declaration const> Parser::parse_declarations_in_translation_unit(ASTNode const& parent)
 {
-    NonnullRefPtrVector<Declaration> declarations;
+    NonnullRefPtrVector<Declaration const> declarations;
     while (!eof()) {
         auto declaration = parse_single_declaration_in_translation_unit(parent);
         if (declaration) {
@@ -52,7 +52,7 @@ NonnullRefPtrVector<Declaration> Parser::parse_declarations_in_translation_unit(
     return declarations;
 }
 
-RefPtr<Declaration> Parser::parse_single_declaration_in_translation_unit(ASTNode& parent)
+RefPtr<Declaration const> Parser::parse_single_declaration_in_translation_unit(ASTNode const& parent)
 {
     while (!eof()) {
         if (match_comment()) {
@@ -74,7 +74,7 @@ RefPtr<Declaration> Parser::parse_single_declaration_in_translation_unit(ASTNode
     return {};
 }
 
-NonnullRefPtr<Declaration> Parser::parse_declaration(ASTNode& parent, DeclarationType declaration_type)
+NonnullRefPtr<Declaration const> Parser::parse_declaration(ASTNode const& parent, DeclarationType declaration_type)
 {
     switch (declaration_type) {
     case DeclarationType::Function:
@@ -99,7 +99,7 @@ NonnullRefPtr<Declaration> Parser::parse_declaration(ASTNode& parent, Declaratio
     }
 }
 
-NonnullRefPtr<FunctionDeclaration> Parser::parse_function_declaration(ASTNode& parent)
+NonnullRefPtr<FunctionDeclaration const> Parser::parse_function_declaration(ASTNode const& parent)
 {
     auto func = create_ast_node<FunctionDeclaration>(parent, position(), {});
 
@@ -120,7 +120,7 @@ NonnullRefPtr<FunctionDeclaration> Parser::parse_function_declaration(ASTNode& p
         // FIXME: Note that this function is supposed to be a class member, and `this` has to be const, somehow.
     }
 
-    RefPtr<FunctionDefinition> body;
+    RefPtr<FunctionDefinition const> body;
     Position func_end {};
     if (peek(Token::Type::LeftCurly).has_value()) {
         body = parse_function_definition(*func);
@@ -137,7 +137,7 @@ NonnullRefPtr<FunctionDeclaration> Parser::parse_function_declaration(ASTNode& p
     return func;
 }
 
-NonnullRefPtr<FunctionDefinition> Parser::parse_function_definition(ASTNode& parent)
+NonnullRefPtr<FunctionDefinition const> Parser::parse_function_definition(ASTNode const& parent)
 {
     LOG_SCOPE();
     auto func = create_ast_node<FunctionDefinition>(parent, position(), {});
@@ -151,7 +151,7 @@ NonnullRefPtr<FunctionDefinition> Parser::parse_function_definition(ASTNode& par
     return func;
 }
 
-NonnullRefPtr<Statement> Parser::parse_statement(ASTNode& parent)
+NonnullRefPtr<Statement const> Parser::parse_statement(ASTNode const& parent)
 {
     LOG_SCOPE();
     ArmedScopeGuard consume_semicolon([this]() {
@@ -190,7 +190,7 @@ NonnullRefPtr<Statement> Parser::parse_statement(ASTNode& parent)
     }
 }
 
-NonnullRefPtr<Comment> Parser::parse_comment(ASTNode& parent)
+NonnullRefPtr<Comment const> Parser::parse_comment(ASTNode const& parent)
 {
     auto comment = create_ast_node<Comment>(parent, position(), {});
     consume(Token::Type::Comment);
@@ -203,7 +203,7 @@ bool Parser::match_block_statement()
     return peek().type() == Token::Type::LeftCurly;
 }
 
-NonnullRefPtr<BlockStatement> Parser::parse_block_statement(ASTNode& parent)
+NonnullRefPtr<BlockStatement const> Parser::parse_block_statement(ASTNode const& parent)
 {
     LOG_SCOPE();
     auto block_statement = create_ast_node<BlockStatement>(parent, position(), {});
@@ -259,13 +259,13 @@ bool Parser::match_template_arguments()
     return peek().type() == Token::Type::Greater;
 }
 
-NonnullRefPtrVector<Type> Parser::parse_template_arguments(ASTNode& parent)
+NonnullRefPtrVector<Type const> Parser::parse_template_arguments(ASTNode const& parent)
 {
     LOG_SCOPE();
 
     consume(Token::Type::Less);
 
-    NonnullRefPtrVector<Type> template_arguments;
+    NonnullRefPtrVector<Type const> template_arguments;
     while (!eof() && peek().type() != Token::Type::Greater) {
         template_arguments.append(parse_type(parent));
     }
@@ -309,7 +309,7 @@ bool Parser::match_variable_declaration()
     return match(Token::Type::Semicolon);
 }
 
-NonnullRefPtr<VariableDeclaration> Parser::parse_variable_declaration(ASTNode& parent, bool expect_semicolon)
+NonnullRefPtr<VariableDeclaration const> Parser::parse_variable_declaration(ASTNode const& parent, bool expect_semicolon)
 {
     LOG_SCOPE();
     auto var = create_ast_node<VariableDeclaration>(parent, position(), {});
@@ -320,7 +320,7 @@ NonnullRefPtr<VariableDeclaration> Parser::parse_variable_declaration(ASTNode& p
     }
     var->set_type(parse_type(var));
     auto name = parse_name(*var);
-    RefPtr<Expression> initial_value;
+    RefPtr<Expression const> initial_value;
 
     if (match(Token::Type::Equals)) {
         consume(Token::Type::Equals);
@@ -341,7 +341,7 @@ NonnullRefPtr<VariableDeclaration> Parser::parse_variable_declaration(ASTNode& p
     return var;
 }
 
-NonnullRefPtr<Expression> Parser::parse_expression(ASTNode& parent)
+NonnullRefPtr<Expression const> Parser::parse_expression(ASTNode const& parent)
 {
     LOG_SCOPE();
     auto expression = parse_primary_expression(parent);
@@ -350,7 +350,7 @@ NonnullRefPtr<Expression> Parser::parse_expression(ASTNode& parent)
         return expression;
     }
 
-    NonnullRefPtrVector<Expression> secondary_expressions;
+    NonnullRefPtrVector<Expression const> secondary_expressions;
 
     while (match_secondary_expression()) {
         // FIXME: Handle operator precedence
@@ -359,7 +359,7 @@ NonnullRefPtr<Expression> Parser::parse_expression(ASTNode& parent)
     }
 
     for (size_t i = 0; secondary_expressions.size() != 0 && i < secondary_expressions.size() - 1; ++i) {
-        secondary_expressions[i].set_parent(secondary_expressions[i + 1]);
+        const_cast<Expression&>(secondary_expressions[i]).set_parent(secondary_expressions[i + 1]);
     }
 
     return expression;
@@ -402,7 +402,7 @@ bool Parser::match_secondary_expression()
         || type == Token::Type::LeftParen;
 }
 
-NonnullRefPtr<Expression> Parser::parse_primary_expression(ASTNode& parent)
+NonnullRefPtr<Expression const> Parser::parse_primary_expression(ASTNode const& parent)
 {
     LOG_SCOPE();
     // TODO: remove eof() logic, should still work without it
@@ -470,7 +470,7 @@ bool Parser::match_unary_expression()
         || type == Token::Type::And;
 }
 
-NonnullRefPtr<UnaryExpression> Parser::parse_unary_expression(ASTNode& parent)
+NonnullRefPtr<UnaryExpression const> Parser::parse_unary_expression(ASTNode const& parent)
 {
     auto unary_exp = create_ast_node<UnaryExpression>(parent, position(), {});
     auto op_token = consume();
@@ -504,7 +504,7 @@ NonnullRefPtr<UnaryExpression> Parser::parse_unary_expression(ASTNode& parent)
     return unary_exp;
 }
 
-NonnullRefPtr<Expression> Parser::parse_literal(ASTNode& parent)
+NonnullRefPtr<Expression const> Parser::parse_literal(ASTNode const& parent)
 {
     switch (peek().type()) {
     case Token::Type::Integer: {
@@ -532,7 +532,7 @@ NonnullRefPtr<Expression> Parser::parse_literal(ASTNode& parent)
     }
 }
 
-NonnullRefPtr<Expression> Parser::parse_secondary_expression(ASTNode& parent, NonnullRefPtr<Expression> lhs)
+NonnullRefPtr<Expression const> Parser::parse_secondary_expression(ASTNode const& parent, NonnullRefPtr<Expression const> lhs)
 {
     LOG_SCOPE();
     switch (peek().type()) {
@@ -559,7 +559,7 @@ NonnullRefPtr<Expression> Parser::parse_secondary_expression(ASTNode& parent, No
     case Token::Type::Dot: {
         consume();
         auto exp = create_ast_node<MemberExpression>(parent, lhs->start(), {});
-        lhs->set_parent(*exp);
+        const_cast<Expression&>(*lhs).set_parent(*exp);
         exp->set_object(move(lhs));
         auto identifier_token = consume(Token::Type::Identifier);
         exp->set_property(create_ast_node<Identifier>(*exp, identifier_token.start(), identifier_token.end(), identifier_token.text()));
@@ -569,7 +569,7 @@ NonnullRefPtr<Expression> Parser::parse_secondary_expression(ASTNode& parent, No
     case Token::Type::LeftParen: {
         consume();
         auto func = create_ast_node<FunctionCall>(parent, lhs->start(), {});
-        lhs->set_parent(*func);
+        const_cast<Expression&>(*lhs).set_parent(*func);
         func->set_callee(move(lhs));
         while (peek().type() != Token::Type::RightParen && !eof()) {
             func->add_argument(parse_expression(*func));
@@ -588,11 +588,11 @@ NonnullRefPtr<Expression> Parser::parse_secondary_expression(ASTNode& parent, No
     }
 }
 
-NonnullRefPtr<BinaryExpression> Parser::parse_binary_expression(ASTNode& parent, NonnullRefPtr<Expression> lhs, BinaryOp op)
+NonnullRefPtr<BinaryExpression const> Parser::parse_binary_expression(ASTNode const& parent, NonnullRefPtr<Expression const> lhs, BinaryOp op)
 {
     consume(); // Operator
     auto exp = create_ast_node<BinaryExpression>(parent, lhs->start(), {});
-    lhs->set_parent(*exp);
+    const_cast<Expression&>(*lhs).set_parent(*exp);
     exp->set_op(op);
     exp->set_lhs(move(lhs));
     auto rhs = parse_expression(exp);
@@ -601,11 +601,11 @@ NonnullRefPtr<BinaryExpression> Parser::parse_binary_expression(ASTNode& parent,
     return exp;
 }
 
-NonnullRefPtr<AssignmentExpression> Parser::parse_assignment_expression(ASTNode& parent, NonnullRefPtr<Expression> lhs, AssignmentOp op)
+NonnullRefPtr<AssignmentExpression const> Parser::parse_assignment_expression(ASTNode const& parent, NonnullRefPtr<Expression const> lhs, AssignmentOp op)
 {
     consume(); // Operator
     auto exp = create_ast_node<AssignmentExpression>(parent, lhs->start(), {});
-    lhs->set_parent(*exp);
+    const_cast<Expression&>(*lhs).set_parent(*exp);
     exp->set_op(op);
     exp->set_lhs(move(lhs));
     auto rhs = parse_expression(exp);
@@ -748,10 +748,10 @@ bool Parser::match_function_declaration()
     return false;
 }
 
-Optional<NonnullRefPtrVector<Parameter>> Parser::parse_parameter_list(ASTNode& parent)
+Optional<NonnullRefPtrVector<Parameter const>> Parser::parse_parameter_list(ASTNode const& parent)
 {
     LOG_SCOPE();
-    NonnullRefPtrVector<Parameter> parameters;
+    NonnullRefPtrVector<Parameter const> parameters;
     while (peek().type() != Token::Type::RightParen && !eof()) {
         if (match_ellipsis()) {
             auto param = create_ast_node<Parameter>(parent, position(), {}, RefPtr<Name> {});
@@ -764,13 +764,13 @@ Optional<NonnullRefPtrVector<Parameter>> Parser::parse_parameter_list(ASTNode& p
         } else {
             auto type = parse_type(parent);
 
-            RefPtr<Name> name;
+            RefPtr<Name const> name;
             if (match_name()) {
                 name = parse_name(parent);
             }
 
             auto param = create_ast_node<Parameter>(parent, type->start(), !name.is_null() ? name->end() : type->end(), name);
-            type->set_parent(*param.ptr());
+            const_cast<Type&>(*type).set_parent(*param.ptr());
 
             param->set_type(move(type));
             parameters.append(move(param));
@@ -958,7 +958,7 @@ Position Parser::previous_token_end() const
     return m_tokens[m_state.token_index - 1].end();
 }
 
-RefPtr<ASTNode> Parser::node_at(Position pos) const
+RefPtr<ASTNode const> Parser::node_at(Position pos) const
 {
     VERIFY(m_saved_states.is_empty());
     auto index = index_of_node_at(pos);
@@ -1029,7 +1029,7 @@ Vector<CodeComprehension::TodoEntry> Parser::get_todo_entries() const
     return ret;
 }
 
-NonnullRefPtr<StringLiteral> Parser::parse_string_literal(ASTNode& parent)
+NonnullRefPtr<StringLiteral const> Parser::parse_string_literal(ASTNode const& parent)
 {
     LOG_SCOPE();
     Optional<size_t> start_token_index;
@@ -1063,7 +1063,7 @@ NonnullRefPtr<StringLiteral> Parser::parse_string_literal(ASTNode& parent)
     return string_literal;
 }
 
-NonnullRefPtr<ReturnStatement> Parser::parse_return_statement(ASTNode& parent)
+NonnullRefPtr<ReturnStatement const> Parser::parse_return_statement(ASTNode const& parent)
 {
     LOG_SCOPE();
     auto return_statement = create_ast_node<ReturnStatement>(parent, position(), {});
@@ -1075,7 +1075,7 @@ NonnullRefPtr<ReturnStatement> Parser::parse_return_statement(ASTNode& parent)
     return return_statement;
 }
 
-NonnullRefPtr<EnumDeclaration> Parser::parse_enum_declaration(ASTNode& parent)
+NonnullRefPtr<EnumDeclaration const> Parser::parse_enum_declaration(ASTNode const& parent)
 {
     LOG_SCOPE();
     auto enum_decl = create_ast_node<EnumDeclaration>(parent, position(), {});
@@ -1093,7 +1093,7 @@ NonnullRefPtr<EnumDeclaration> Parser::parse_enum_declaration(ASTNode& parent)
     consume(Token::Type::LeftCurly);
     while (!eof() && peek().type() != Token::Type::RightCurly) {
         auto name = text_of_token(consume(Token::Type::Identifier));
-        RefPtr<Expression> value;
+        RefPtr<Expression const> value;
         if (peek().type() == Token::Type::Equals) {
             consume();
             value = parse_expression(enum_decl);
@@ -1136,7 +1136,7 @@ bool Parser::match_keyword(DeprecatedString const& keyword)
     return true;
 }
 
-NonnullRefPtr<StructOrClassDeclaration> Parser::parse_class_declaration(ASTNode& parent)
+NonnullRefPtr<StructOrClassDeclaration const> Parser::parse_class_declaration(ASTNode const& parent)
 {
     LOG_SCOPE();
 
@@ -1155,7 +1155,7 @@ NonnullRefPtr<StructOrClassDeclaration> Parser::parse_class_declaration(ASTNode&
 
     auto has_final = match_keyword("final");
 
-    NonnullRefPtrVector<Name> baseclasses;
+    NonnullRefPtrVector<Name const> baseclasses;
 
     // FIXME: Don't ignore this.
     if (peek(has_final ? 1 : 0).type() == Token::Type::Colon) {
@@ -1186,7 +1186,7 @@ NonnullRefPtr<StructOrClassDeclaration> Parser::parse_class_declaration(ASTNode&
     return decl;
 }
 
-NonnullRefPtr<BooleanLiteral> Parser::parse_boolean_literal(ASTNode& parent)
+NonnullRefPtr<BooleanLiteral const> Parser::parse_boolean_literal(ASTNode const& parent)
 {
     LOG_SCOPE();
     auto token = consume(Token::Type::Keyword);
@@ -1205,7 +1205,7 @@ bool Parser::match_boolean_literal()
     return text == "true" || text == "false";
 }
 
-NonnullRefPtr<Type> Parser::parse_type(ASTNode& parent)
+NonnullRefPtr<Type const> Parser::parse_type(ASTNode const& parent)
 {
     LOG_SCOPE();
 
@@ -1284,7 +1284,7 @@ NonnullRefPtr<Type> Parser::parse_type(ASTNode& parent)
     return type;
 }
 
-NonnullRefPtr<ForStatement> Parser::parse_for_statement(ASTNode& parent)
+NonnullRefPtr<ForStatement const> Parser::parse_for_statement(ASTNode const& parent)
 {
     LOG_SCOPE();
     auto for_statement = create_ast_node<ForStatement>(parent, position(), {});
@@ -1308,7 +1308,7 @@ NonnullRefPtr<ForStatement> Parser::parse_for_statement(ASTNode& parent)
     return for_statement;
 }
 
-NonnullRefPtr<IfStatement> Parser::parse_if_statement(ASTNode& parent)
+NonnullRefPtr<IfStatement const> Parser::parse_if_statement(ASTNode const& parent)
 {
     LOG_SCOPE();
     auto if_statement = create_ast_node<IfStatement>(parent, position(), {});
@@ -1393,7 +1393,7 @@ bool Parser::match_ellipsis()
     return peek().type() == Token::Type::Dot && peek(1).type() == Token::Type::Dot && peek(2).type() == Token::Type::Dot;
 }
 
-NonnullRefPtr<NamespaceDeclaration> Parser::parse_namespace_declaration(ASTNode& parent, bool is_nested_namespace)
+NonnullRefPtr<NamespaceDeclaration const> Parser::parse_namespace_declaration(ASTNode const& parent, bool is_nested_namespace)
 {
     auto namespace_decl = create_ast_node<NamespaceDeclaration>(parent, position(), {});
 
@@ -1431,7 +1431,7 @@ bool Parser::match_name()
     return type == Token::Type::Identifier || type == Token::Type::KnownType;
 }
 
-NonnullRefPtr<Name> Parser::parse_name(ASTNode& parent)
+NonnullRefPtr<Name const> Parser::parse_name(ASTNode const& parent)
 {
     LOG_SCOPE();
     NonnullRefPtr<Name> name_node = create_ast_node<Name>(parent, position(), {});
@@ -1504,7 +1504,7 @@ bool Parser::match_c_style_cast_expression()
     return true;
 }
 
-NonnullRefPtr<CStyleCastExpression> Parser::parse_c_style_cast_expression(ASTNode& parent)
+NonnullRefPtr<CStyleCastExpression const> Parser::parse_c_style_cast_expression(ASTNode const& parent)
 {
     auto parse_exp = create_ast_node<CStyleCastExpression>(parent, position(), {});
 
@@ -1517,7 +1517,7 @@ NonnullRefPtr<CStyleCastExpression> Parser::parse_c_style_cast_expression(ASTNod
     return parse_exp;
 }
 
-NonnullRefPtr<CppCastExpression> Parser::parse_cpp_cast_expression(ASTNode& parent)
+NonnullRefPtr<CppCastExpression const> Parser::parse_cpp_cast_expression(ASTNode const& parent)
 {
     auto cast_expression = create_ast_node<CppCastExpression>(parent, position(), {});
 
@@ -1541,7 +1541,7 @@ bool Parser::match_sizeof_expression()
     return match_keyword("sizeof");
 }
 
-NonnullRefPtr<SizeofExpression> Parser::parse_sizeof_expression(ASTNode& parent)
+NonnullRefPtr<SizeofExpression const> Parser::parse_sizeof_expression(ASTNode const& parent)
 {
     auto exp = create_ast_node<SizeofExpression>(parent, position(), {});
     consume(Token::Type::Keyword);
@@ -1557,7 +1557,7 @@ bool Parser::match_braced_init_list()
     return match(Token::Type::LeftCurly);
 }
 
-NonnullRefPtr<BracedInitList> Parser::parse_braced_init_list(ASTNode& parent)
+NonnullRefPtr<BracedInitList const> Parser::parse_braced_init_list(ASTNode const& parent)
 {
     auto init_list = create_ast_node<BracedInitList>(parent, position(), {});
 
@@ -1569,11 +1569,11 @@ NonnullRefPtr<BracedInitList> Parser::parse_braced_init_list(ASTNode& parent)
     init_list->set_end(position());
     return init_list;
 }
-NonnullRefPtrVector<Declaration> Parser::parse_class_members(StructOrClassDeclaration& parent)
+NonnullRefPtrVector<Declaration const> Parser::parse_class_members(StructOrClassDeclaration& parent)
 {
     auto class_name = parent.full_name();
 
-    NonnullRefPtrVector<Declaration> members;
+    NonnullRefPtrVector<Declaration const> members;
     while (!eof() && peek().type() != Token::Type::RightCurly) {
         if (match_access_specifier())
             consume_access_specifier(); // FIXME: Do not ignore access specifiers
@@ -1677,7 +1677,7 @@ void Parser::parse_constructor_or_destructor_impl(FunctionDeclaration& func, Cto
 
     // TODO: Parse =default, =delete.
 
-    RefPtr<FunctionDefinition> body;
+    RefPtr<FunctionDefinition const> body;
     Position ctor_end {};
     if (peek(Token::Type::LeftCurly).has_value()) {
         body = parse_function_definition(func);
@@ -1693,14 +1693,14 @@ void Parser::parse_constructor_or_destructor_impl(FunctionDeclaration& func, Cto
     func.set_end(ctor_end);
 }
 
-NonnullRefPtr<Constructor> Parser::parse_constructor(ASTNode& parent)
+NonnullRefPtr<Constructor const> Parser::parse_constructor(ASTNode const& parent)
 {
     auto ctor = create_ast_node<Constructor>(parent, position(), {});
     parse_constructor_or_destructor_impl(*ctor, CtorOrDtor::Ctor);
     return ctor;
 }
 
-NonnullRefPtr<Destructor> Parser::parse_destructor(ASTNode& parent)
+NonnullRefPtr<Destructor const> Parser::parse_destructor(ASTNode const& parent)
 {
     auto ctor = create_ast_node<Destructor>(parent, position(), {});
     parse_constructor_or_destructor_impl(*ctor, CtorOrDtor::Dtor);
@@ -1723,7 +1723,7 @@ bool Parser::match_using_namespace_declaration()
     return true;
 }
 
-NonnullRefPtr<UsingNamespaceDeclaration> Parser::parse_using_namespace_declaration(ASTNode& parent)
+NonnullRefPtr<UsingNamespaceDeclaration const> Parser::parse_using_namespace_declaration(ASTNode const& parent)
 {
     auto decl = create_ast_node<UsingNamespaceDeclaration>(parent, position(), {});
 
diff --git a/Userland/Libraries/LibCpp/Parser.h b/Userland/Libraries/LibCpp/Parser.h
index 41684f08e9c..349d2eb0b13 100644
--- a/Userland/Libraries/LibCpp/Parser.h
+++ b/Userland/Libraries/LibCpp/Parser.h
@@ -25,7 +25,7 @@ public:
     NonnullRefPtr<TranslationUnit> parse();
     bool eof() const;
 
-    RefPtr<ASTNode> node_at(Position) const;
+    RefPtr<ASTNode const> node_at(Position) const;
     Optional<size_t> index_of_node_at(Position) const;
     Optional<Token> token_at(Position) const;
     Optional<size_t> index_of_token_at(Position) const;
@@ -83,45 +83,45 @@ private:
     bool match_destructor(StringView class_name);
     bool match_using_namespace_declaration();
 
-    Optional<NonnullRefPtrVector<Parameter>> parse_parameter_list(ASTNode& parent);
+    Optional<NonnullRefPtrVector<Parameter const>> parse_parameter_list(ASTNode const& parent);
     Optional<Token> consume_whitespace();
     void consume_preprocessor();
 
-    NonnullRefPtr<Declaration> parse_declaration(ASTNode& parent, DeclarationType);
-    NonnullRefPtr<FunctionDeclaration> parse_function_declaration(ASTNode& parent);
-    NonnullRefPtr<FunctionDefinition> parse_function_definition(ASTNode& parent);
-    NonnullRefPtr<Statement> parse_statement(ASTNode& parent);
-    NonnullRefPtr<VariableDeclaration> parse_variable_declaration(ASTNode& parent, bool expect_semicolon = true);
-    NonnullRefPtr<Expression> parse_expression(ASTNode& parent);
-    NonnullRefPtr<Expression> parse_primary_expression(ASTNode& parent);
-    NonnullRefPtr<Expression> parse_secondary_expression(ASTNode& parent, NonnullRefPtr<Expression> lhs);
-    NonnullRefPtr<StringLiteral> parse_string_literal(ASTNode& parent);
-    NonnullRefPtr<ReturnStatement> parse_return_statement(ASTNode& parent);
-    NonnullRefPtr<EnumDeclaration> parse_enum_declaration(ASTNode& parent);
-    NonnullRefPtr<StructOrClassDeclaration> parse_class_declaration(ASTNode& parent);
-    NonnullRefPtr<Expression> parse_literal(ASTNode& parent);
-    NonnullRefPtr<UnaryExpression> parse_unary_expression(ASTNode& parent);
-    NonnullRefPtr<BooleanLiteral> parse_boolean_literal(ASTNode& parent);
-    NonnullRefPtr<Type> parse_type(ASTNode& parent);
-    NonnullRefPtr<BinaryExpression> parse_binary_expression(ASTNode& parent, NonnullRefPtr<Expression> lhs, BinaryOp);
-    NonnullRefPtr<AssignmentExpression> parse_assignment_expression(ASTNode& parent, NonnullRefPtr<Expression> lhs, AssignmentOp);
-    NonnullRefPtr<ForStatement> parse_for_statement(ASTNode& parent);
-    NonnullRefPtr<BlockStatement> parse_block_statement(ASTNode& parent);
-    NonnullRefPtr<Comment> parse_comment(ASTNode& parent);
-    NonnullRefPtr<IfStatement> parse_if_statement(ASTNode& parent);
-    NonnullRefPtr<NamespaceDeclaration> parse_namespace_declaration(ASTNode& parent, bool is_nested_namespace = false);
-    NonnullRefPtrVector<Declaration> parse_declarations_in_translation_unit(ASTNode& parent);
-    RefPtr<Declaration> parse_single_declaration_in_translation_unit(ASTNode& parent);
-    NonnullRefPtrVector<Type> parse_template_arguments(ASTNode& parent);
-    NonnullRefPtr<Name> parse_name(ASTNode& parent);
-    NonnullRefPtr<CppCastExpression> parse_cpp_cast_expression(ASTNode& parent);
-    NonnullRefPtr<SizeofExpression> parse_sizeof_expression(ASTNode& parent);
-    NonnullRefPtr<BracedInitList> parse_braced_init_list(ASTNode& parent);
-    NonnullRefPtr<CStyleCastExpression> parse_c_style_cast_expression(ASTNode& parent);
-    NonnullRefPtrVector<Declaration> parse_class_members(StructOrClassDeclaration& parent);
-    NonnullRefPtr<Constructor> parse_constructor(ASTNode& parent);
-    NonnullRefPtr<Destructor> parse_destructor(ASTNode& parent);
-    NonnullRefPtr<UsingNamespaceDeclaration> parse_using_namespace_declaration(ASTNode& parent);
+    NonnullRefPtr<Declaration const> parse_declaration(ASTNode const& parent, DeclarationType);
+    NonnullRefPtr<FunctionDeclaration const> parse_function_declaration(ASTNode const& parent);
+    NonnullRefPtr<FunctionDefinition const> parse_function_definition(ASTNode const& parent);
+    NonnullRefPtr<Statement const> parse_statement(ASTNode const& parent);
+    NonnullRefPtr<VariableDeclaration const> parse_variable_declaration(ASTNode const& parent, bool expect_semicolon = true);
+    NonnullRefPtr<Expression const> parse_expression(ASTNode const& parent);
+    NonnullRefPtr<Expression const> parse_primary_expression(ASTNode const& parent);
+    NonnullRefPtr<Expression const> parse_secondary_expression(ASTNode const& parent, NonnullRefPtr<Expression const> lhs);
+    NonnullRefPtr<StringLiteral const> parse_string_literal(ASTNode const& parent);
+    NonnullRefPtr<ReturnStatement const> parse_return_statement(ASTNode const& parent);
+    NonnullRefPtr<EnumDeclaration const> parse_enum_declaration(ASTNode const& parent);
+    NonnullRefPtr<StructOrClassDeclaration const> parse_class_declaration(ASTNode const& parent);
+    NonnullRefPtr<Expression const> parse_literal(ASTNode const& parent);
+    NonnullRefPtr<UnaryExpression const> parse_unary_expression(ASTNode const& parent);
+    NonnullRefPtr<BooleanLiteral const> parse_boolean_literal(ASTNode const& parent);
+    NonnullRefPtr<Type const> parse_type(ASTNode const& parent);
+    NonnullRefPtr<BinaryExpression const> parse_binary_expression(ASTNode const& parent, NonnullRefPtr<Expression const> lhs, BinaryOp);
+    NonnullRefPtr<AssignmentExpression const> parse_assignment_expression(ASTNode const& parent, NonnullRefPtr<Expression const> lhs, AssignmentOp);
+    NonnullRefPtr<ForStatement const> parse_for_statement(ASTNode const& parent);
+    NonnullRefPtr<BlockStatement const> parse_block_statement(ASTNode const& parent);
+    NonnullRefPtr<Comment const> parse_comment(ASTNode const& parent);
+    NonnullRefPtr<IfStatement const> parse_if_statement(ASTNode const& parent);
+    NonnullRefPtr<NamespaceDeclaration const> parse_namespace_declaration(ASTNode const& parent, bool is_nested_namespace = false);
+    NonnullRefPtrVector<Declaration const> parse_declarations_in_translation_unit(ASTNode const& parent);
+    RefPtr<Declaration const> parse_single_declaration_in_translation_unit(ASTNode const& parent);
+    NonnullRefPtrVector<Type const> parse_template_arguments(ASTNode const& parent);
+    NonnullRefPtr<Name const> parse_name(ASTNode const& parent);
+    NonnullRefPtr<CppCastExpression const> parse_cpp_cast_expression(ASTNode const& parent);
+    NonnullRefPtr<SizeofExpression const> parse_sizeof_expression(ASTNode const& parent);
+    NonnullRefPtr<BracedInitList const> parse_braced_init_list(ASTNode const& parent);
+    NonnullRefPtr<CStyleCastExpression const> parse_c_style_cast_expression(ASTNode const& parent);
+    NonnullRefPtrVector<Declaration const> parse_class_members(StructOrClassDeclaration& parent);
+    NonnullRefPtr<Constructor const> parse_constructor(ASTNode const& parent);
+    NonnullRefPtr<Destructor const> parse_destructor(ASTNode const& parent);
+    NonnullRefPtr<UsingNamespaceDeclaration const> parse_using_namespace_declaration(ASTNode const& parent);
 
     bool match(Token::Type);
     Token consume(Token::Type);
@@ -145,7 +145,7 @@ private:
 
     template<class T, class... Args>
     NonnullRefPtr<T>
-    create_ast_node(ASTNode& parent, Position const& start, Optional<Position> end, Args&&... args)
+    create_ast_node(ASTNode const& parent, Position const& start, Optional<Position> end, Args&&... args)
     {
         auto node = adopt_ref(*new T(&parent, start, end, m_filename, forward<Args>(args)...));