Force fallback to be external (experimental 0.5.0 change)

3 files changed, 39 insertions, 1 deletions

diff --git a/Changelog.md b/Changelog.md
index 0b9295d0..26a4862a 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,7 +1,7 @@
 ### 0.4.17 (unreleased)
 
 Features:
- * Support ``pragma experimental v0.5.0;`` to turn on upcoming breaking changes.
+ * Support ``pragma experimental "v0.5.0";`` to turn on upcoming breaking changes.
  * Code Generator: Added ``.selector`` member on external function types to retrieve their signature.
  * Code Generator: Keep a single copy of encoding functions when using the experimental "ABIEncoderV2".
  * Optimizer: Add new optimization step to remove unused ``JUMPDEST``s.
@@ -12,6 +12,7 @@ Features:
  * Type Checker: Warn on using literals as tight packing parameters in ``keccak256``, ``sha3``, ``sha256`` and ``ripemd160``.
  * Type Checker: Enforce ``view`` and ``pure``.
  * Type Checker: Enforce ``view`` / ``constant`` with error as experimental 0.5.0 feature.
+ * Type Checker: Enforce fallback functions to be ``external`` as experimental 0.5.0 feature.
 
 Bugfixes:
  * ABI JSON: Include all overloaded events.
diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index 26529c22..529a4f8d 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -120,6 +120,11 @@ bool TypeChecker::visit(ContractDefinition const& _contract)
 					m_errorReporter.typeError(fallbackFunction->parameterList().location(), "Fallback function cannot take parameters.");
 				if (!fallbackFunction->returnParameters().empty())
 					m_errorReporter.typeError(fallbackFunction->returnParameterList()->location(), "Fallback function cannot return values.");
+				if (
+					_contract.sourceUnit().annotation().experimentalFeatures.count(ExperimentalFeature::V050) &&
+					fallbackFunction->visibility() != FunctionDefinition::Visibility::External
+				)
+					m_errorReporter.typeError(fallbackFunction->location(), "Fallback function must be defined as \"external\".");
 			}
 		}
 	}
diff --git a/test/libsolidity/SolidityNameAndTypeResolution.cpp b/test/libsolidity/SolidityNameAndTypeResolution.cpp
index 8c271fe1..be3b56f3 100644
--- a/test/libsolidity/SolidityNameAndTypeResolution.cpp
+++ b/test/libsolidity/SolidityNameAndTypeResolution.cpp
@@ -6691,6 +6691,38 @@ BOOST_AUTO_TEST_CASE(tight_packing_literals)
 	CHECK_WARNING(text, "The type of \"int_const 1\" was inferred as uint8.");
 }
 
+BOOST_AUTO_TEST_CASE(non_external_fallback)
+{
+	char const* text = R"(
+		pragma experimental "v0.5.0";
+		contract C {
+			function () external { }
+		}
+	)";
+	CHECK_WARNING(text, "Experimental features are turned on.");
+	text = R"(
+		pragma experimental "v0.5.0";
+		contract C {
+			function () internal { }
+		}
+	)";
+	CHECK_ERROR(text, TypeError, "Fallback function must be defined as \"external\".");
+	text = R"(
+		pragma experimental "v0.5.0";
+		contract C {
+			function () private { }
+		}
+	)";
+	CHECK_ERROR(text, TypeError, "Fallback function must be defined as \"external\".");
+	text = R"(
+		pragma experimental "v0.5.0";
+		contract C {
+			function () public { }
+		}
+	)";
+	CHECK_ERROR(text, TypeError, "Fallback function must be defined as \"external\".");
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }