Merge pull request #4696 from ethereum/byteLiteralConversion

Disallow ambiguous implicit and explicit conversions from number literals to bytesXX

3 files changed, 46 insertions, 40 deletions

diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index bcc3757a..660bb828 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -2348,22 +2348,6 @@ void TypeChecker::expectType(Expression const& _expression, Type const& _expecte
 				"."
 			);
 	}
-
-	if (
-		type(_expression)->category() == Type::Category::RationalNumber &&
-		_expectedType.category() == Type::Category::FixedBytes
-	)
-	{
-		auto literal = dynamic_cast<Literal const*>(&_expression);
-
-		if (literal && !literal->isHexNumber())
-			m_errorReporter.warning(
-				_expression.location(),
-				"Decimal literal assigned to bytesXX variable will be left-aligned. "
-				"Use an explicit conversion to silence this warning."
-			);
-	}
-
 }
 
 void TypeChecker::requireLValue(Expression const& _expression)
diff --git a/libsolidity/ast/Types.cpp b/libsolidity/ast/Types.cpp
index 2dcfda42..349e4a02 100644
--- a/libsolidity/ast/Types.cpp
+++ b/libsolidity/ast/Types.cpp
@@ -355,13 +355,7 @@ TypePointer Type::forLiteral(Literal const& _literal)
 	case Token::FalseLiteral:
 		return make_shared<BoolType>();
 	case Token::Number:
-	{
-		tuple<bool, rational> validLiteral = RationalNumberType::isValidLiteral(_literal);
-		if (get<0>(validLiteral) == true)
-			return make_shared<RationalNumberType>(get<1>(validLiteral));
-		else
-			return TypePointer();
-	}
+		return RationalNumberType::forLiteral(_literal);
 	case Token::StringLiteral:
 		return make_shared<StringLiteralType>(_literal);
 	default:
@@ -779,6 +773,30 @@ tuple<bool, rational> RationalNumberType::parseRational(string const& _value)
 	}
 }
 
+TypePointer RationalNumberType::forLiteral(Literal const& _literal)
+{
+	solAssert(_literal.token() == Token::Number, "");
+	tuple<bool, rational> validLiteral = isValidLiteral(_literal);
+	if (get<0>(validLiteral))
+	{
+		TypePointer compatibleBytesType;
+		if (_literal.isHexNumber())
+		{
+			size_t digitCount = count_if(
+				_literal.value().begin() + 2, // skip "0x"
+				_literal.value().end(),
+				[](unsigned char _c) -> bool { return isxdigit(_c); }
+			);
+			// require even number of digits
+			if (!(digitCount & 1))
+				compatibleBytesType = make_shared<FixedBytesType>(digitCount / 2);
+		}
+
+		return make_shared<RationalNumberType>(get<1>(validLiteral), compatibleBytesType);
+	}
+	return TypePointer();
+}
+
 tuple<bool, rational> RationalNumberType::isValidLiteral(Literal const& _literal)
 {
 	rational value;
@@ -918,14 +936,7 @@ bool RationalNumberType::isImplicitlyConvertibleTo(Type const& _convertTo) const
 		return false;
 	}
 	case Category::FixedBytes:
-	{
-		FixedBytesType const& fixedBytes = dynamic_cast<FixedBytesType const&>(_convertTo);
-		if (isFractional())
-			return false;
-		if (integerType())
-			return fixedBytes.numBytes() * 8 >= integerType()->numBits();
-		return false;
-	}
+		return (m_value == rational(0)) || (m_compatibleBytesType && *m_compatibleBytesType == _convertTo);
 	default:
 		return false;
 	}
@@ -933,11 +944,15 @@ bool RationalNumberType::isImplicitlyConvertibleTo(Type const& _convertTo) const
 
 bool RationalNumberType::isExplicitlyConvertibleTo(Type const& _convertTo) const
 {
-	TypePointer mobType = mobileType();
-	return
-		(mobType && mobType->isExplicitlyConvertibleTo(_convertTo)) ||
-		(!isFractional() && _convertTo.category() == Category::FixedBytes)
-	;
+	if (isImplicitlyConvertibleTo(_convertTo))
+		return true;
+	else if (_convertTo.category() != Category::FixedBytes)
+	{
+		TypePointer mobType = mobileType();
+		return (mobType && mobType->isExplicitlyConvertibleTo(_convertTo));
+	}
+	else
+		return false;
 }
 
 TypePointer RationalNumberType::unaryOperatorResult(Token::Value _operator) const
diff --git a/libsolidity/ast/Types.h b/libsolidity/ast/Types.h
index 3b57109d..8bae3d41 100644
--- a/libsolidity/ast/Types.h
+++ b/libsolidity/ast/Types.h
@@ -423,12 +423,12 @@ public:
 
 	virtual Category category() const override { return Category::RationalNumber; }
 
-	/// @returns true if the literal is a valid integer.
-	static std::tuple<bool, rational> isValidLiteral(Literal const& _literal);
+	static TypePointer forLiteral(Literal const& _literal);
 
-	explicit RationalNumberType(rational const& _value):
-		m_value(_value)
+	explicit RationalNumberType(rational const& _value, TypePointer const& _compatibleBytesType = TypePointer()):
+		m_value(_value), m_compatibleBytesType(_compatibleBytesType)
 	{}
+
 	virtual bool isImplicitlyConvertibleTo(Type const& _convertTo) const override;
 	virtual bool isExplicitlyConvertibleTo(Type const& _convertTo) const override;
 	virtual TypePointer unaryOperatorResult(Token::Value _operator) const override;
@@ -462,6 +462,13 @@ public:
 private:
 	rational m_value;
 
+	/// Bytes type to which the rational can be explicitly converted.
+	/// Empty for all rationals that are not directly parsed from hex literals.
+	TypePointer m_compatibleBytesType;
+
+	/// @returns true if the literal is a valid integer.
+	static std::tuple<bool, rational> isValidLiteral(Literal const& _literal);
+
 	/// @returns true if the literal is a valid rational number.
 	static std::tuple<bool, rational> parseRational(std::string const& _value);