Enable the -Wconversion warning

libsolidity/ast/ASTJsonConverter.h

@@ -156,14 +156,14 @@ private:
 	static std::string literalTokenKind(Token _token);
 	static std::string type(Expression const& _expression);
 	static std::string type(VariableDeclaration const& _varDecl);
-	static int nodeId(ASTNode const& _node)
+	static int64_t nodeId(ASTNode const& _node)
 	{
 		return _node.id();
 	}
 	template<class Container>
 	static Json::Value getContainerIds(Container const& _container, bool _order = false)
 	{
-		std::vector<int> tmp;
+		std::vector<int64_t> tmp;
 
 		for (auto const& element: _container)
 		{
@@ -174,7 +174,7 @@ private:
 			std::sort(tmp.begin(), tmp.end());
 		Json::Value json(Json::arrayValue);
 
-		for (int val: tmp)
+		for (int64_t val: tmp)
 			json.append(val);
 
 		return json;

libsolidity/ast/TypeProvider.cpp

@@ -368,7 +368,7 @@ RationalNumberType const* TypeProvider::rationalNumber(Literal const& _literal)
 		{
 			size_t const digitCount = _literal.valueWithoutUnderscores().length() - 2;
 			if (digitCount % 2 == 0 && (digitCount / 2) <= 32)
-				compatibleBytesType = fixedBytes(digitCount / 2);
+				compatibleBytesType = fixedBytes(static_cast<unsigned>(digitCount / 2));
 		}
 
 		return rationalNumber(std::get<1>(validLiteral), compatibleBytesType);

libsolidity/ast/Types.cpp

@@ -811,7 +811,7 @@ tuple<bool, rational> RationalNumberType::parseRational(string const& _value)
 			denominator = bigint(string(fractionalBegin, _value.end()));
 			denominator /= boost::multiprecision::pow(
 				bigint(10),
-				static_cast<size_t>(distance(radixPoint + 1, _value.end()))
+				static_cast<unsigned>(distance(radixPoint + 1, _value.end()))
 			);
 			numerator = bigint(string(_value.begin(), radixPoint));
 			value = numerator + denominator;

libsolidity/ast/Types.h

@@ -294,6 +294,7 @@ public:
 		return *m_stackItems;
 	}
 	/// Total number of stack slots occupied by this type. This is the sum of ``sizeOnStack`` of all ``stackItems()``.
+	// TODO: consider changing the return type to be size_t
 	unsigned sizeOnStack() const
 	{
 		if (!m_stackSize)
@@ -306,7 +307,7 @@ public:
 					++sizeOnStack;
 			m_stackSize = sizeOnStack;
 		}
-		return *m_stackSize;
+		return static_cast<unsigned>(*m_stackSize);
 	}
 	/// If it is possible to initialize such a value in memory by just writing zeros
 	/// of the size memoryHeadSize().