Add implicit convertibility to function pointer with higher state mutability

2 files changed, 65 insertions, 21 deletions

diff --git a/libsolidity/ast/Types.cpp b/libsolidity/ast/Types.cpp
index 0d69ae1a..9e815ca8 100644
--- a/libsolidity/ast/Types.cpp
+++ b/libsolidity/ast/Types.cpp
@@ -2569,28 +2569,10 @@ bool FunctionType::operator==(Type const& _other) const
 {
 	if (_other.category() != category())
 		return false;
-
 	FunctionType const& other = dynamic_cast<FunctionType const&>(_other);
-	if (
-		m_kind != other.m_kind ||
-		m_stateMutability != other.stateMutability() ||
-		m_parameterTypes.size() != other.m_parameterTypes.size() ||
-		m_returnParameterTypes.size() != other.m_returnParameterTypes.size()
-	)
-		return false;
-
-	auto typeCompare = [](TypePointer const& _a, TypePointer const& _b) -> bool { return *_a == *_b; };
-	if (
-		!equal(m_parameterTypes.cbegin(), m_parameterTypes.cend(), other.m_parameterTypes.cbegin(), typeCompare) ||
-		!equal(m_returnParameterTypes.cbegin(), m_returnParameterTypes.cend(), other.m_returnParameterTypes.cbegin(), typeCompare)
-	)
-		return false;
-	//@todo this is ugly, but cannot be prevented right now
-	if (m_gasSet != other.m_gasSet || m_valueSet != other.m_valueSet)
-		return false;
-	if (bound() != other.bound())
+	if (!equalExcludingStateMutability(other))
 		return false;
-	if (bound() && *selfType() != *other.selfType())
+	if (m_stateMutability != other.stateMutability())
 		return false;
 	return true;
 }
@@ -2606,6 +2588,31 @@ bool FunctionType::isExplicitlyConvertibleTo(Type const& _convertTo) const
 	return _convertTo.category() == category();
 }
 
+bool FunctionType::isImplicitlyConvertibleTo(Type const& _convertTo) const
+{
+	if (_convertTo.category() != category())
+		return false;
+
+	FunctionType const& convertTo = dynamic_cast<FunctionType const&>(_convertTo);
+
+	if (!equalExcludingStateMutability(convertTo))
+		return false;
+
+	// non-payable should not be convertible to payable
+	if (m_stateMutability != StateMutability::Payable && convertTo.stateMutability() == StateMutability::Payable)
+		return false;
+
+	// payable should be convertible to non-payable, because you are free to pay 0 ether
+	if (m_stateMutability == StateMutability::Payable && convertTo.stateMutability() == StateMutability::NonPayable)
+		return true;
+
+	// e.g. pure should be convertible to view, but not the other way around.
+	if (m_stateMutability > convertTo.stateMutability())
+		return false;
+
+	return true;
+}
+
 TypePointer FunctionType::unaryOperatorResult(Token::Value _operator) const
 {
 	if (_operator == Token::Value::Delete)
@@ -2863,6 +2870,38 @@ bool FunctionType::hasEqualParameterTypes(FunctionType const& _other) const
 	);
 }
 
+bool FunctionType::hasEqualReturnTypes(FunctionType const& _other) const
+{
+	if (m_returnParameterTypes.size() != _other.m_returnParameterTypes.size())
+		return false;
+	return equal(
+		m_returnParameterTypes.cbegin(),
+		m_returnParameterTypes.cend(),
+		_other.m_returnParameterTypes.cbegin(),
+		[](TypePointer const& _a, TypePointer const& _b) -> bool { return *_a == *_b; }
+	);
+}
+
+bool FunctionType::equalExcludingStateMutability(FunctionType const& _other) const
+{
+	if (m_kind != _other.m_kind)
+		return false;
+
+	if (!hasEqualParameterTypes(_other) || !hasEqualReturnTypes(_other))
+		return false;
+
+	//@todo this is ugly, but cannot be prevented right now
+	if (m_gasSet != _other.m_gasSet || m_valueSet != _other.m_valueSet)
+		return false;
+
+	if (bound() != _other.bound())
+		return false;
+
+	solAssert(!bound() || *selfType() == *_other.selfType(), "");
+
+	return true;
+}
+
 bool FunctionType::isBareCall() const
 {
 	switch (m_kind)
diff --git a/libsolidity/ast/Types.h b/libsolidity/ast/Types.h
index 8bae3d41..cc96ac4b 100644
--- a/libsolidity/ast/Types.h
+++ b/libsolidity/ast/Types.h
@@ -1012,6 +1012,7 @@ public:
 
 	virtual std::string richIdentifier() const override;
 	virtual bool operator==(Type const& _other) const override;
+	virtual bool isImplicitlyConvertibleTo(Type const& _convertTo) const override;
 	virtual bool isExplicitlyConvertibleTo(Type const& _convertTo) const override;
 	virtual TypePointer unaryOperatorResult(Token::Value _operator) const override;
 	virtual TypePointer binaryOperatorResult(Token::Value, TypePointer const&) const override;
@@ -1041,8 +1042,12 @@ public:
 	/// @param _selfType if the function is bound, this has to be supplied and is the type of the
 	/// expression the function is called on.
 	bool canTakeArguments(TypePointers const& _arguments, TypePointer const& _selfType = TypePointer()) const;
-	/// @returns true if the types of parameters are equal (doesn't check return parameter types)
+	/// @returns true if the types of parameters are equal (does not check return parameter types)
 	bool hasEqualParameterTypes(FunctionType const& _other) const;
+	/// @returns true iff the return types are equal (does not check parameter types)
+	bool hasEqualReturnTypes(FunctionType const& _other) const;
+	/// @returns true iff the function type is equal to the given type, ignoring state mutability differences.
+	bool equalExcludingStateMutability(FunctionType const& _other) const;
 
 	/// @returns true if the ABI is used for this call (only meaningful for external calls)
 	bool isBareCall() const;