Warn/enforce single bytes argument for certain builtins (hashing functions).

In 0.5.0 mode, only accept a single bytes argument for ``.call``,
``keccak256`` and others and do not pad when encoding.

libsolidity/analysis/TypeChecker.cpp

@@ -1760,6 +1760,33 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
 		}
 	}
 
+	if (functionType->takesSinglePackedBytesParameter())
+	{
+		string generalMessage =
+			"This function only accepts a single \"bytes\" argument. Please use "
+			"\"abi.encodePacked(...)\" or a similar function to encode the data.";
+
+		if (arguments.size() > 1)
+		{
+			if (v050)
+				m_errorReporter.typeError(_functionCall.location(), generalMessage);
+			else
+				m_errorReporter.warning(_functionCall.location(), generalMessage);
+		}
+		else if (arguments.size() == 1 && !type(*arguments.front())->isImplicitlyConvertibleTo(ArrayType(DataLocation::Memory)))
+		{
+			string msg =
+				generalMessage +
+				" The provided argument of type " +
+				type(*arguments.front())->toString() +
+				" is not implicitly convertible to expected type bytes memory.";
+			if (v050)
+				m_errorReporter.typeError(_functionCall.location(), msg);
+			else
+				m_errorReporter.warning(_functionCall.location(), msg);
+		}
+	}
+
 	if (functionType->takesArbitraryParameters() && arguments.size() < parameterTypes.size())
 	{
 		solAssert(_functionCall.annotation().kind == FunctionCallKind::FunctionCall, "");

libsolidity/ast/Types.h

@@ -1058,6 +1058,22 @@ public:
 	/// true iff arguments are to be padded to multiples of 32 bytes for external calls
 	bool padArguments() const { return !(m_kind == Kind::SHA3 || m_kind == Kind::SHA256 || m_kind == Kind::RIPEMD160 || m_kind == Kind::ABIEncodePacked); }
 	bool takesArbitraryParameters() const { return m_arbitraryParameters; }
+	/// true iff the function takes a single bytes parameter and it is passed on without padding.
+	/// @todo until 0.5.0, this is just a "recommendation".
+	bool takesSinglePackedBytesParameter() const
+	{
+		// @todo add the call kinds here with 0.5.0 and perhaps also log0.
+		switch (m_kind)
+		{
+		case FunctionType::Kind::SHA3:
+		case FunctionType::Kind::SHA256:
+		case FunctionType::Kind::RIPEMD160:
+			return true;
+		default:
+			return false;
+		}
+	}
+
 	bool gasSet() const { return m_gasSet; }
 	bool valueSet() const { return m_valueSet; }
 	bool bound() const { return m_bound; }