Disallow enums in interfaces

docs/contracts.rst

@@ -933,6 +933,7 @@ Interfaces are similar to abstract contracts, but they cannot have any functions
 #. Cannot inherit other contracts or interfaces.
 #. Cannot define variables.
 #. Cannot define structs.
+#. Cannot define enums.
 
 Some of these restrictions might be lifted in the future.
 

libsolidity/analysis/TypeChecker.cpp

@@ -517,6 +517,13 @@ bool TypeChecker::visit(VariableDeclaration const& _variable)
 	return false;
 }
 
+bool TypeChecker::visit(EnumDefinition const& _enum)
+{
+	if (m_scope->contractKind() == ContractDefinition::ContractKind::Interface)
+		typeError(_enum.location(), "Enumerable cannot be declared in interfaces.");
+	return false;
+}
+
 void TypeChecker::visitManually(
 	ModifierInvocation const& _modifier,
 	vector<ContractDefinition const*> const& _bases

libsolidity/analysis/TypeChecker.h

@@ -83,6 +83,7 @@ class TypeChecker: private ASTConstVisitor
 	virtual bool visit(StructDefinition const& _struct) override;
 	virtual bool visit(FunctionDefinition const& _function) override;
 	virtual bool visit(VariableDeclaration const& _variable) override;
+	virtual bool visit(EnumDefinition const& _enum) override;
 	/// We need to do this manually because we want to pass the bases of the current contract in
 	/// case this is a base constructor call.
 	void visitManually(ModifierInvocation const& _modifier, std::vector<ContractDefinition const*> const& _bases);

test/libsolidity/SolidityNameAndTypeResolution.cpp

@@ -5411,6 +5411,16 @@ BOOST_AUTO_TEST_CASE(interface_variables)
 	CHECK_ERROR(text, TypeError, "Variables cannot be declared in interfaces");
 }
 
+BOOST_AUTO_TEST_CASE(interface_enums)
+{
+	char const* text = R"(
+		interface I {
+			enum A { B, C }
+		}
+	)";
+	CHECK_ERROR(text, TypeError, "Enumerable cannot be declared in interfaces");
+}
+
 BOOST_AUTO_TEST_CASE(using_interface)
 {
 	char const* text = R"(