Allow marking free functions as suffixes

libsolidity/ast/AST.h

@@ -951,6 +951,7 @@ public:
 		bool _free,
 		Token _kind,
 		bool _isVirtual,
+		bool _usableAsSuffix,
 		ASTPointer<OverrideSpecifier> const& _overrides,
 		ASTPointer<StructuredDocumentation> const& _documentation,
 		ASTPointer<ParameterList> const& _parameters,
@@ -964,11 +965,14 @@ public:
 		m_stateMutability(_stateMutability),
 		m_free(_free),
 		m_kind(_kind),
+		m_usableAsSuffix(_usableAsSuffix),
 		m_functionModifiers(std::move(_modifiers)),
 		m_body(_body)
 	{
 		solAssert(_kind == Token::Constructor || _kind == Token::Function || _kind == Token::Fallback || _kind == Token::Receive, "");
 		solAssert(isOrdinary() == !name().empty(), "");
+		if (_usableAsSuffix)
+			solAssert(_free);
 	}
 
 	void accept(ASTVisitor& _visitor) override;
@@ -981,6 +985,7 @@ public:
 	bool isFallback() const { return m_kind == Token::Fallback; }
 	bool isReceive() const { return m_kind == Token::Receive; }
 	bool isFree() const { return m_free; }
+	bool usableAsSuffix() const { return m_usableAsSuffix; }
 	Token kind() const { return m_kind; }
 	bool isPayable() const { return m_stateMutability == StateMutability::Payable; }
 	std::vector<ASTPointer<ModifierInvocation>> const& modifiers() const { return m_functionModifiers; }
@@ -1027,9 +1032,10 @@ public:
 	) const override;
 
 private:
-	StateMutability m_stateMutability;
-	bool m_free;
-	Token const m_kind;
+	StateMutability m_stateMutability{};
+	bool m_free{};
+	Token const m_kind{};
+	bool m_usableAsSuffix{};
 	std::vector<ASTPointer<ModifierInvocation>> m_functionModifiers;
 	ASTPointer<Block> m_body;
 };

libsolidity/ast/ASTJsonExporter.cpp

@@ -458,6 +458,7 @@ bool ASTJsonExporter::visit(FunctionDefinition const& _node)
 		make_pair("kind", _node.isFree() ? "freeFunction" : TokenTraits::toString(_node.kind())),
 		make_pair("stateMutability", stateMutabilityToString(_node.stateMutability())),
 		make_pair("virtual", _node.markedVirtual()),
+		make_pair("suffix", _node.usableAsSuffix()),
 		make_pair("overrides", _node.overrides() ? toJson(*_node.overrides()) : Json::nullValue),
 		make_pair("parameters", toJson(_node.parameterList())),
 		make_pair("returnParameters", toJson(*_node.returnParameterList())),

libsolidity/ast/ASTJsonImporter.cpp

@@ -557,6 +557,7 @@ ASTPointer<FunctionDefinition> ASTJsonImporter::createFunctionDefinition(Json::V
 		freeFunction,
 		kind,
 		memberAsBool(_node, "virtual"),
+		memberAsBool(_node, "suffix"),
 		_node["overrides"].isNull() ? nullptr : createOverrideSpecifier(member(_node, "overrides")),
 		_node["documentation"].isNull() ? nullptr : createDocumentation(member(_node, "documentation")),
 		createParameterList(member(_node, "parameters")),