From d68c526eaacc1072e8c0ddb4b3513897cce352b7 Mon Sep 17 00:00:00 2001
From: Daniel Kirchner <daniel@ekpyron.org>
Date: Fri, 3 Apr 2020 11:56:51 +0200
Subject: [PATCH] Disallow external function pointers as immutables.

---
 libsolidity/analysis/TypeChecker.cpp          |  8 ++++++++
 .../semanticTests/immutable/complexGetter.sol | 12 -----------
 .../immutable/external_function_pointer.sol   | 20 -------------------
 .../immutable/external_function_pointer.sol   |  5 +++++
 4 files changed, 13 insertions(+), 32 deletions(-)
 delete mode 100644 test/libsolidity/semanticTests/immutable/complexGetter.sol
 delete mode 100644 test/libsolidity/semanticTests/immutable/external_function_pointer.sol
 create mode 100644 test/libsolidity/syntaxTests/immutable/external_function_pointer.sol

diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index 8e7bef338..2bdc706a2 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -481,8 +481,16 @@ bool TypeChecker::visit(VariableDeclaration const& _variable)
 			);
 	}
 	else if (_variable.immutable())
+	{
 		if (!_variable.type()->isValueType())
 			m_errorReporter.typeError(_variable.location(), "Immutable variables cannot have a non-value type.");
+		if (
+			auto const* functionType = dynamic_cast<FunctionType const*>(_variable.type());
+			functionType && functionType->kind() == FunctionType::Kind::External
+		)
+			m_errorReporter.typeError(_variable.location(), "Immutable variables of external function type are not yet supported.");
+		solAssert(_variable.type()->sizeOnStack() == 1 || m_errorReporter.hasErrors(), "");
+	}
 
 	if (!_variable.isStateVariable())
 	{
diff --git a/test/libsolidity/semanticTests/immutable/complexGetter.sol b/test/libsolidity/semanticTests/immutable/complexGetter.sol
deleted file mode 100644
index 851120847..000000000
--- a/test/libsolidity/semanticTests/immutable/complexGetter.sol
+++ /dev/null
@@ -1,12 +0,0 @@
-contract C {
-    function() external returns (uint, uint) immutable public x = this.f;
-    function f() external pure returns (uint, uint) {
-        return (1, 2);
-    }
-
-    function test() external returns (uint, uint) {
-        return this.x()();
-    }
-}
-// ----
-// test() -> 1, 2
diff --git a/test/libsolidity/semanticTests/immutable/external_function_pointer.sol b/test/libsolidity/semanticTests/immutable/external_function_pointer.sol
deleted file mode 100644
index c815a18c3..000000000
--- a/test/libsolidity/semanticTests/immutable/external_function_pointer.sol
+++ /dev/null
@@ -1,20 +0,0 @@
-contract D {
-	function f() external view returns (uint256) {
-		return 42;
-	}
-}
-contract C {
-	D d;
-	function() external view returns(uint256) immutable z;
-	constructor() public {
-		d = new D();
-		z = d.f;
-	}
-	function f() public view returns (uint256) {
-	assert(z.address == address(d));
-	assert(z.selector == D.f.selector);
-		return z();
-	}
-}
-// ----
-// f() -> 42
diff --git a/test/libsolidity/syntaxTests/immutable/external_function_pointer.sol b/test/libsolidity/syntaxTests/immutable/external_function_pointer.sol
new file mode 100644
index 000000000..7ab8393cf
--- /dev/null
+++ b/test/libsolidity/syntaxTests/immutable/external_function_pointer.sol
@@ -0,0 +1,5 @@
+contract C {
+    function() external immutable f;
+}
+// ----
+// TypeError: (17-48): Immutable variables of external function type are not yet supported.